228 results on '"Heinz Frei"'
Search Results
2. Polynuclear Photocatalysts in Nanoporous Silica for Artificial Photosynthesis
- Author
-
Heinz Frei
- Subjects
Artificial photosynthesis ,Carbon dioxide reduction ,Metal-to-metal charge-transfer ,Nanoporous silica ,Water oxidation ,Chemistry ,QD1-999 - Abstract
In this article, recent progress towards robust photocatalysts for the visible light-driven reduction of CO2 by H2O is presented. All-inorganic polynuclear photocatalysts consisting of an oxo-bridged binuclear charge-transfer chromophore (metal-to-metal charge-transfer) coupled to a multi-electron transfer catalyst anchored in a nanoporous silica scaffold have been developed. Mild synthetic methods afford assembly, on silica nanopore surfaces, of heterobinuclear units with donor and acceptor metal centers selected for optimum solar coverage and photon to chemical energy conversion efficiency. A photocatalyst featuring a TiOCrIII group coupled to an IrO2 nanocluster on MCM-41 silica support is shown to function as an efficient visible light water oxidation unit. Nanostructured Co3O4 clusters in mesoporous silica SBA-15 constitute the first example of a nanometer-sized multi-electron catalyst made of an earth-abundant metal oxide that evolves oxygen from water efficiently. For carbon dioxide reduction, a binuclear unit consisting of a Zr acceptor and a CuI donor (ZrOCuI) acts as light absorber as well as redox site, splitting CO2 to CO and H2O upon excitation of the charge-transfer transition. Structural and mechanistic insights of the photocatalytic units based on static and time-resolved optical, FT-infrared, FT-Raman, EPR, X-ray absorption spectroscopy and transmission electron microscopy are critical for improving designs. The photocatalytic units presented here form the basis for developing robust and efficient artificial photosynthetic systems for the conversion of carbon dioxide and water to a liquid fuel.
- Published
- 2009
- Full Text
- View/download PDF
3. Chemistry with Red and Near Infrared Light
- Author
-
Heinz Frei
- Subjects
Chemistry ,QD1-999 - Abstract
Opportunities are explored to initiate controlled chemistry by photolysis with long-wavelength visible and near infrared light. In one direction, bimolecular reactions are induced by exciting collisional pairs in a solid matrix to energy surfaces well below reactant dissociation limits. Examples discussed include product specific (including stereospecific) photo-oxidation of small alkenes and alkynes by NO2, and cycloaddition reactions of singlet SO and singlet O2. Conducting the chemistry in rare gas matrices allows us to elucidate elementary reaction steps by FT-IR spectroscopy of trapped intermediates, and to gain insight into the dynamics of transients by wavelength-dependent laser photochemistry. In the case of olefin epoxidations, stereochemical details of reaction paths are uncovered by chemical trapping of transient oxirane biradicals in their nascent conformation. State-specific reactions of singlet excited SO and singlet O2 with hydrocarbons illustrate how photons deep in the near infrared can be used for controlled chemical synthesis. In parallel work, excited state redox reactions in homogeneous and colloidal semiconductor solutions are explored that pertain to chemical storage of near infrared quanta and conversion into electrical energy. Examples are studies on chemical storage of singlet delta molecular oxygen (O2(1?), a metastable near infrared energy carrier, its excited state redox chemistry in aqueous solution, and direct reduction Of (O2(1?) at a semiconductor electrode. Using very sensitive time resolved optical techniques, new mechanistic insight is gained on singlet O2 reactions, and on photo-oxidation of halide at the semiconductor-solution interface.
- Published
- 1991
4. Ultrathin Oxide Layers for Solar and Electrocatalytic Systems
- Author
-
Heinz Frei, Daniel Esposito, Heinz Frei, Daniel Esposito and Heinz Frei, Daniel Esposito, Heinz Frei, Daniel Esposito
- Published
- 2022
5. Self-Assembled Monolayers for Improved Charge Injection of Silver Back Electrodes in Inverted Organic Electronic Devices
- Author
-
Sneha Sreekumar, Marzieh Heidari, Zhongkai Cheng, Hemanth Maddali, Krystal House, Heinz Frei, Elena Galoppini, and Deirdre M. O’Carroll
- Subjects
General Materials Science - Abstract
Self-assembled monolayers (SAMs) formed from thiol compounds bound to Ag and Au electrodes have been used as an important strategy in improving the stability and efficiency of optoelectronic devices. Thiol compounds provide only one binding site with the metal electrode which limits their influence. Dithiolane/dithiol compounds can provide multiple binding sites and could be useful in enhancing the performance of the device. In this study, inverted organic semiconducting hole-only devices were fabricated by using Ag back electrodes in conjunction with SAMs formed from disulfide lipoic acid-based compounds and were compared to a long aliphatic chain thiol. The binding and the electronic properties as well as electrical characteristics of the SAMs on silver were studied to look at the influence of their structure on charge injection in the organic semiconductor devices. It was found that the SAMs formed with (±)-α-lipoic acid, isolipoic acid, and (±)-4-phenylbutyl 5-(1,2-dithiolan-3-yl) pentanoate significantly improved the charge injection by either changing the work function of the Ag or altering the physical interaction between the polymer and the metal surface. This study may lead to an understanding of how the nature of the functional groups of the SAM and the number of bonds formed between each SAM molecule and the metal electrode influence the contact resistance and the performance of organic semiconductor devices.
- Published
- 2022
6. Diurnal timing of physical activity and risk of colorectal cancer in the UK Biobank
- Author
-
Michael J. Stein, Hansjörg Baurecht, Patricia Bohmann, Béatrice Fervers, Emma Fontvieille, Heinz Freisling, Christine M. Friedenreich, Julian Konzok, Laia Peruchet-Noray, Anja M. Sedlmeier, Michael F. Leitzmann, and Andrea Weber
- Subjects
Physical activity patterns ,Colorectal cancer ,UK Biobank ,Raw accelerometry ,Medicine - Abstract
Abstract Background Physical activity reduces colorectal cancer risk, yet the diurnal timing of physical activity in colorectal cancer etiology remains unclear. Methods This study used 24-h accelerometry time series from UK Biobank participants aged 42 to 79 years to derive circadian physical activity patterns using functional principal component analysis. Multivariable Cox proportional hazard models were used to examine associations with colorectal cancer risk. Results Among 86,252 participants (56% women), 529 colorectal cancer cases occurred during a median 5.3-year follow-up. We identified four physical activity patterns that explained almost 100% of the data variability during the day. A pattern of continuous day-long activity was inversely associated with colorectal cancer risk (hazard ratio (HR) = 0.94, 95% confidence interval (CI) = 0.89–0.99). A second pattern of late-day activity was suggestively inversely related to risk (HR = 0.93, 95% CI = 0.85–1.02). A third pattern of early- plus late-day activity was associated with decreased risk (HR = 0.89, 95% CI = 0.80–0.99). A fourth pattern of mid-day plus night-time activity showed no relation (HR = 1.02, 95% CI = 0.88–1.19). Our results were consistent across various sensitivity analyses, including the restriction to never smokers, the exclusion of the first 2 years of follow-up, and the adjustment for shift work. Conclusions A pattern of early- plus late-day activity is related to reduced colorectal cancer risk, beyond the benefits of overall activity. Further research is needed to confirm the role of activity timing in colorectal cancer prevention.
- Published
- 2024
- Full Text
- View/download PDF
7. Association of body shape phenotypes and body fat distribution indexes with inflammatory biomarkers in the European Prospective Investigation into Cancer and Nutrition (EPIC) and UK Biobank
- Author
-
Esther M. González-Gil, Laia Peruchet-Noray, Anja M. Sedlmeier, Sofia Christakoudi, Carine Biessy, Anne-Sophie Navionis, Yahya Mahamat-Saleh, Rola F. Jaafar, Hansjörg Baurecht, Marcela Guevara, Pilar Amiano Etxezarreta, W. M. Monique Verschuren, Jolanda M. A. Boer, Anja Olsen, Anne Tjønneland, Vittorio Simeon, Carlota Castro-Espin, Dagfinn Aune, Alicia K. Heath, Marc Gunter, Sandra M. Colorado-Yohar, Nuno R. Zilhão, Christina C. Dahm, Erand Llanaj, Matthias B. Schulze, Dafina Petrova, Sabina Sieri, Fulvio Ricceri, Giovanna Masala, Tim Key, Vivian Viallon, Sabina Rinaldi, Heinz Freisling, and Laure Dossus
- Subjects
Body shape ,Height ,Anthropometric indicators ,Inflammation ,C-reactive protein ,Medicine - Abstract
Abstract Background The allometric body shape index (ABSI) and hip index (HI), as well as multi-trait body shape phenotypes, have not yet been compared in their associations with inflammatory markers. The aim of this study was to examine the relationship between novel and traditional anthropometric indexes with inflammation using data from the European Prospective Investigation into Cancer and Nutrition (EPIC) and UK Biobank cohorts. Methods Participants from EPIC (n = 17,943, 69.1% women) and UK Biobank (n = 426,223, 53.2% women) with data on anthropometric indexes and C-reactive protein (CRP) were included in this cross-sectional analysis. A subset of women in EPIC also had at least one measurement for interleukins, tumour necrosis factor alpha, interferon gamma, leptin, and adiponectin. Four distinct body shape phenotypes were derived by a principal component (PC) analysis on height, weight, body mass index (BMI), waist (WC) and hip circumferences (HC), and waist-to-hip ratio (WHR). PC1 described overall adiposity, PC2 tall with low WHR, PC3 tall and centrally obese, and PC4 high BMI and weight with low WC and HC, suggesting an athletic phenotype. ABSI, HI, waist-to-height ratio and waist-to-hip index (WHI) were also calculated. Linear regression models were carried out separately in EPIC and UK Biobank stratified by sex and adjusted for age, smoking status, education, and physical activity. Results were additionally combined in a random-effects meta-analysis. Results Traditional anthropometric indexes, particularly BMI, WC, and weight were positively associated with CRP levels, in men and women. Body shape phenotypes also showed distinct associations with CRP. Specifically, PC2 showed inverse associations with CRP in EPIC and UK Biobank in both sexes, similarly to height. PC3 was inversely associated with CRP among women, whereas positive associations were observed among men. Conclusions Specific indexes of body size and body fat distribution showed differential associations with inflammation in adults. Notably, our results suggest that in women, height may mitigate the impact of a higher WC and HC on inflammation. This suggests that subtypes of adiposity exhibit substantial variation in their inflammatory potential, which may have implications for inflammation-related chronic diseases.
- Published
- 2024
- Full Text
- View/download PDF
8. Time-Resolved Vibrational and Electronic Spectroscopy for Understanding How Charges Drive Metal Oxide Catalysts for Water Oxidation
- Author
-
Heinz Frei
- Subjects
Spectrum Analysis ,Water ,General Materials Science ,Oxides ,Physical and Theoretical Chemistry ,Electronics ,Catalysis - Abstract
Temporally resolved spectroscopy is a powerful approach for gaining detailed mechanistic understanding of water oxidation at robust Earth-abundant metal oxide catalysts for guiding efficiency improvement of solar fuel conversion systems. Beyond detecting and structurally identifying surface intermediates by vibrational and accompanying optical spectroscopy, knowledge of how charges, sequentially delivered to the metal oxide surface, drive the four-electron water oxidation cycle is critical for enhancing catalytic efficiency. Key issues addressed in this Perspective are the experimental requirements for establishing the kinetic relevancy of observed surface species and the discovery of the rate-boosting role of encounters of two or more one-electron surface hole charges, often in the form of randomly hopping metal oxo or oxyl moieties, for accessing very low-barrier O-O bond-forming pathways. Recent spectroscopic breakthroughs of metal oxide photo- and electrocatalysts inspire future research poised to take advantage of new highly sensitive spectroscopic tools and of methods for fast catalysis triggering.
- Published
- 2022
9. On the use of the healthy lifestyle index to investigate specific disease outcomes
- Author
-
Vivian Viallon, Heinz Freisling, Komodo Matta, Anne Østergaard Nannsen, Christina C. Dahm, Anne Tjønneland, Anne Kirstine Eriksen, Rudolf Kaaks, Verena A. Katzke, Matthias B. Schulze, Giovanna Masala, Giovanna Tagliabue, Vittorio Simeon, Rosario Tumino, Lorenzo Milani, Jeroen W. G. Derksen, Yvonne T. van der Schouw, Therese Haugdahl Nøst, Kristin Benjaminsen Borch, Torkjel M. Sandanger, J. Ramón Quirós, Miguel Rodriguez-Barranco, Catalina Bonet, Amaia Aizpurua-Atxega, Lluís Cirera, Marcela Guevara, Björn Sundström, Anna Winkvist, Alicia K. Heath, Marc J. Gunter, Elisabete Weiderpass, Mattias Johansson, and Pietro Ferrari
- Subjects
Healthy lifestyle index ,Lifestyle factors ,Mortality ,Type 2 diabetes ,Cardiovascular diseases ,Cancer ,Medicine ,Science - Abstract
Abstract The healthy lifestyle index (HLI), defined as the unweighted sum of individual lifestyle components, was used to investigate the combined role of lifestyle factors on health-related outcomes. We introduced weighted outcome-specific versions of the HLI, where individual lifestyle components were weighted according to their associations with disease outcomes. Within the European Prospective Investigation into Cancer and Nutrition (EPIC), we examined the association between the standard and the outcome-specific HLIs and the risk of T2D, CVD, cancer, and all-cause premature mortality. Estimates of the hazard ratios (HRs), the Harrell’s C-index and the population attributable fractions (PAFs) were compared. For T2D, the HR for 1-SD increase of the standard and T2D-specific HLI were 0.66 (95% CI: 0.64, 0.67) and 0.43 (0.42, 0.44), respectively, and the C-index were 0.63 (0.62, 0.64) and 0.72 (0.72, 0.73). Similar, yet less pronounced differences in HR and C-index were observed for standard and outcome-specific estimates for cancer, CVD and all-cause mortality. PAF estimates for mortality before age 80 were 57% (55%, 58%) and 33% (32%, 34%) for standard and mortality-specific HLI, respectively. The use of outcome-specific HLI could improve the assessment of the role of lifestyle factors on disease outcomes, thus enhancing the definition of public health recommendations.
- Published
- 2024
- Full Text
- View/download PDF
10. Hepatic steatosis, metabolic dysfunction and risk of mortality: findings from a multinational prospective cohort study
- Author
-
Ana-Lucia Mayén, Mirna Sabra, Elom K. Aglago, Gabriel Perlemuter, Cosmin Voican, Ines Ramos, Charlotte Debras, Jessica Blanco, Vivian Viallon, Pietro Ferrari, Anja Olsen, Anne Tjønneland, Fie Langmann, Christina C. Dahm, Joseph Rothwell, Nasser Laouali, Chloé Marques, Matthias B. Schulze, Verena Katzke, Rudolf Kaaks, Domenico Palli, Alessandra Macciotta, Salvatore Panico, Rosario Tumino, Claudia Agnoli, Marta Farràs, Esther Molina-Montes, Pilar Amiano, María-Dolores Chirlaque, Jesús Castilla, Mårten Werner, Stina Bodén, Alicia K. Heath, Kostas Tsilidis, Dagfinn Aune, Elisabete Weiderpass, Heinz Freisling, Marc J. Gunter, and Mazda Jenab
- Subjects
Hepatic steatosis ,Metabolic syndrome ,Mortality ,Phenotypic NASH ,MAFLD ,Medicine - Abstract
Abstract Background Non-alcoholic fatty liver disease (NAFLD) and metabolic syndrome (MetS) are implicated in the aetiology of non-communicable diseases. Our study aimed to evaluate associations between NAFLD and MetS with overall and cause-specific mortality. Methods We used dietary, lifestyle, anthropometric and metabolic biomarker data from a random subsample of 15,784 EPIC cohort participants. NAFLD was assessed using the fatty liver index (FLI) and MetS using the revised definition. Indices for metabolic dysfunction–associated fatty liver disease (MAFLD) were calculated. The individual associations of these indices with overall and cause-specific mortality were assessed using multivariable Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (95%CIs). As a subobjective, risk associations with adaptations of new classifications of metabolic dysfunction–associated steatotic liver disease (MASLD) and metabolic and alcohol-related liver disease (MetALD) were also assessed. Results Among the 15,784 sub-cohort participants, a total of 1997 deaths occurred (835 due to cancer, 520 to CVD, 642 to other causes) over a median 15.6 (IQR, 12.3–17.1) years of follow-up. Compared to an FLI
- Published
- 2024
- Full Text
- View/download PDF
11. Healthy lifestyle change and all-cause and cancer mortality in the European Prospective Investigation into Cancer and Nutrition cohort
- Author
-
Komodo Matta, Vivian Viallon, Edoardo Botteri, Giulia Peveri, Christina Dahm, Anne Østergaard Nannsen, Anja Olsen, Anne Tjønneland, Alexis Elbaz, Fanny Artaud, Chloé Marques, Rudolf Kaaks, Verena Katzke, Matthias B. Schulze, Erand Llanaj, Giovanna Masala, Valeria Pala, Salvatore Panico, Rosario Tumino, Fulvio Ricceri, Jeroen W. G. Derksen, Therese Haugdahl Nøst, Torkjel M. Sandanger, Kristin Benjaminsen Borch, J. Ramón Quirós, Carlota Castro-Espin, Maria-José Sánchez, Amaia Aizpurua Atxega, Lluís Cirera, Marcela Guevara, Jonas Manjer, Sandar Tin Tin, Alicia Heath, Mathilde Touvier, Marcel Goldberg, Elisabete Weiderpass, Marc J. Gunter, Heinz Freisling, Elio Riboli, and Pietro Ferrari
- Subjects
Healthy lifestyle index ,Composite score ,Change score ,Mortality ,Cancer ,Longitudinal ,Medicine - Abstract
Abstract Background Healthy lifestyles are inversely associated with the risk of noncommunicable diseases, which are leading causes of death. However, few studies have used longitudinal data to assess the impact of changing lifestyle behaviours on all-cause and cancer mortality. Methods Within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, lifestyle profiles of 308,497 cancer-free adults (71% female) aged 35–70 years at recruitment across nine countries were assessed with baseline and follow-up questionnaires administered on average of 7 years apart. A healthy lifestyle index (HLI), assessed at two time points, combined information on smoking status, alcohol intake, body mass index, and physical activity, and ranged from 0 to 16 units. A change score was calculated as the difference between HLI at baseline and follow-up. Associations between HLI change and all-cause and cancer mortality were modelled with Cox regression, and the impact of changing HLI on accelerating mortality rate was estimated by rate advancement periods (RAP, in years). Results After the follow-up questionnaire, participants were followed for an average of 9.9 years, with 21,696 deaths (8407 cancer deaths) documented. Compared to participants whose HLIs remained stable (within one unit), improving HLI by more than one unit was inversely associated with all-cause and cancer mortality (hazard ratio [HR]: 0.84; 95% confidence interval [CI]: 0.81, 0.88; and HR: 0.87; 95% CI: 0.82, 0.92; respectively), while worsening HLI by more than one unit was associated with an increase in mortality (all-cause mortality HR: 1.26; 95% CI: 1.20, 1.33; cancer mortality HR: 1.19; 95% CI: 1.09, 1.29). Participants who worsened HLI by more than one advanced their risk of death by 1.62 (1.44, 1.96) years, while participants who improved HLI by the same amount delayed their risk of death by 1.19 (0.65, 2.32) years, compared to those with stable HLI. Conclusions Making healthier lifestyle changes during adulthood was inversely associated with all-cause and cancer mortality and delayed risk of death. Conversely, making unhealthier lifestyle changes was positively associated with mortality and an accelerated risk of death.
- Published
- 2024
- Full Text
- View/download PDF
12. Impact of pre‐existing cardiometabolic diseases on metastatic cancer stage at diagnosis: a prospective multinational cohort study
- Author
-
Anna Jansana, Aviane Auguste, Marina Kvaskoff, Agnès Fournier, Emma Fontvieille, Laia Peruchet‐Noray, Carine Biessy, Reynalda Cordova, Kristina Elin Nielsen Petersen, Anne Tjønneland, Verena Katzke, Rudolf Kaaks, Fulvio Ricceri, Salvatore Panico, Paolo Contiero, Maria‐Jose Sánchez, Jesus Castilla, Marta Crous‐Bou, Alicia Heath, Elom Kouassivi Aglago, Elisabete Weiderpass, Marc James Gunter, Pietro Ferrari, Elio Riboli, Vivian Viallon, and Heinz Freisling
- Subjects
Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Published
- 2024
- Full Text
- View/download PDF
13. Selective CO2 electrocatalysis at the pseudocapacitive nanoparticle/ordered-ligand interlayer
- Author
-
Peidong Yang, Lin-Wang Wang, Heinz Frei, Sheena Louisia, Sunmoon Yu, Gabor A. Somorjai, Inwhan Roh, Yifan Li, Zhiyuan Qi, Dohyung Kim, and Fan Zheng
- Subjects
Aqueous solution ,Materials science ,biology ,Renewable Energy, Sustainability and the Environment ,Ligand ,Energy Engineering and Power Technology ,Nanoparticle ,Active site ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Catalysis ,Metal ,Fuel Technology ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,biology.protein ,0210 nano-technology ,Selectivity - Abstract
Enzymes feature the concerted operation of multiple components around an active site, leading to exquisite catalytic specificity. Realizing such configurations on synthetic catalyst surfaces remains elusive. Here, we report a nanoparticle/ordered-ligand interlayer that contains a multi-component catalytic pocket for high-specificity CO2 electrocatalysis. The nanoparticle/ordered-ligand interlayer comprises a metal nanoparticle surface and a detached layer of ligands in its vicinity. This interlayer possesses unique pseudocapacitive characteristics where desolvated cations are intercalated, creating an active-site configuration that enhances catalytic turnover by two orders and one order of magnitude against a pristine metal surface and nanoparticle with tethered ligands, respectively. The nanoparticle/ordered-ligand interlayer is demonstrated across several metals with up to 99% CO selectivity at marginal overpotentials and onset overpotentials of as low as 27 mV, in aqueous conditions. Furthermore, in a gas-diffusion environment with neutral media, the nanoparticle/ordered-ligand interlayer achieves nearly unit CO selectivity at high current densities (98.1% at 400 mA cm−2). The complex, multi-component environments found in enzymes induce high catalytic specificity, but are difficult to achieve in synthetic catalysts. Now, researchers report a catalyst comprising a dynamic, ordered layer of ligands above a nanoparticle surface that creates a pocket to facilitate CO2 electroreduction.
- Published
- 2020
14. Precise Colloidal Plasmonic Photocatalysts Constructed by Multistep Photodepositions
- Author
-
Ivan A. Moreno-Hernandez, Heinz Frei, Gaurav A. Kamat, Hyun Dong Ha, Georgios Katsoukis, Chang Yan, and A. Paul Alivisatos
- Subjects
Titanium ,Fabrication ,Aqueous solution ,Nanostructure ,Materials science ,Light ,Mechanical Engineering ,Oxygen evolution ,Bioengineering ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Surface Plasmon Resonance ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Catalysis ,Photocatalysis ,General Materials Science ,Charge carrier ,Gold ,Surface plasmon resonance ,0210 nano-technology ,Plasmon - Abstract
Natural photosynthesis relies on a sophisticated charge transfer pathway among multiple components with precise spatial, energetic, and temporal organizations in the aqueous environment. It continues to inspire and challenge the design and fabrication of artificial multicomponent colloidal nanostructures for solar-to-fuel conversion. Herein, we introduce a plasmonic photocatalyst synthesized with colloidal methods with five integrated components including cocatalysts installed in orthogonal locations. The precise deposition of individual inorganic components on an Au/TiO2 nanodumbell nanostructure is enabled by photoreduction and photo-oxidation, which selectively occurs at the TiO2 tip sites and Au lateral sites, respectively. Under visible-light irradiation, the photocatalyst exhibited activity of oxygen evolution from water without scavengers. We demonstrate that each component is essential for improving the photocatalytic performance. In addition, mechanistic studies suggest that the photocatalytic reaction requires combining the hot charge carriers derived from exciting both the d-sp interband transition and the localized surface plasmon resonance of Au.
- Published
- 2020
15. Observation of O–O Bond Forming Step of Molecular Co4O4 Cubane Catalyst for Water Oxidation by Rapid-Scan FT-IR Spectroscopy
- Author
-
Hongfei Liu and Heinz Frei
- Subjects
Rapid scan ,Materials science ,010405 organic chemistry ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,3. Good health ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Cubane ,Polymer chemistry ,Pyridine ,Ft ir spectroscopy ,Spectroscopy ,Cobalt oxide - Abstract
Monitoring of water oxidation by the established Co cubane catalyst Co4O4(OAc)4(py)4 (abbrev. Co4O4, OAc = acetate, py = pyridine) by time-resolved rapid-scan ATR FT-IR spectroscopy revealed the O–...
- Published
- 2020
16. Multi-Trait Body Shape Phenotypes and Breast Cancer Risk in Postmenopausal Women: A Causal Mediation Analysis in the UK Biobank Cohort
- Author
-
Amina Amadou, Heinz Freisling, Anja M. Sedlmeier, Patricia Bohmann, Emma Fontvieille, Andrea Weber, Julian Konzok, Michael J. Stein, Laia Peruchet-Noray, Anna Jansana, Hwayoung Noh, Mathilde His, Quan Gan, Hansjörg Baurecht, and Béatrice Fervers
- Subjects
Breast cancer ,Anthropometry ,Body shape ,Biomarker ,Mediation ,Interaction ,Public aspects of medicine ,RA1-1270 - Abstract
Abstract Body shape phenotypes combining multiple anthropometric traits have been linked to postmenopausal breast cancer (BC). However, underlying biological pathways remain poorly understood. This study investigated to what extent the associations of body shapes with postmenopausal BC risk is mediated by biochemical markers. The study included 176,686 postmenopausal women from UK Biobank. Four body shape phenotypes were derived from principal component (PC) analysis of height, weight, body mass index, waist and hip circumferences, and waist-to-hip ratio (WHR). The four-way decomposition of the total effect was used to estimate mediation and interaction effects simultaneously as well as the mediated proportions. After 10.9 years median follow-up, 6,396 incident postmenopausal BC were diagnosed. There was strong evidence of positive associations between PC1 (general obesity) and PC2 (tall, low WHR), and BC risk. The association of PC1 with BC risk was positively mediated by testosterone and negatively by insulin-like growth factor-1 (IGF-1), with the overall proportion mediated (sum of the mediated interaction and pure indirect effect (PIE)) accounting for 11.4% (95% confidence intervals: 5.1 to 17.8%) and -12.2% (-20.5% to -4.0%) of the total effect, respectively. Small proportions of the association between PC2 and BC were mediated by IGF-1 (PIE: 2.8% (0.6 to 4.9%)), and sex hormone-binding globulin (SHBG) (PIE: -6.1% (-10.9% to -1.3%)). Our findings are consistent with differential pathways linking different body shapes with BC risk, with a suggestive mediation through testosterone and IGF-1 in the relationship of a generally obese body shape and BC risk, while IGF-1 and SHBG may mediate a tall/lean body shape-BC risk association.
- Published
- 2024
- Full Text
- View/download PDF
17. Controlling and Optimizing Photoinduced Charge Transfer across Ultrathin Silica Separation Membrane with Embedded Molecular Wires for Artificial Photosynthesis
- Author
-
Indranil Rudra, Elena Galoppini, Hongna Zhang, Won Jun Jo, Ian Weiss, Heinz Frei, Georgios Katsoukis, and Simon Kellner
- Subjects
Materials science ,molecular wires ,FT-IRRAS spectroscopy ,02 engineering and technology ,Conductivity ,010402 general chemistry ,01 natural sciences ,Artificial photosynthesis ,Molecular wire ,Electron transfer ,Engineering ,photocurrent measurements ,General Materials Science ,Nanoscience & Nanotechnology ,HOMO/LUMO ,Photocurrent ,021001 nanoscience & nanotechnology ,electron transfer ,0104 chemical sciences ,Membrane ,charge flux ,Chemical physics ,artificial photosynthesis ,Chemical Sciences ,Density functional theory ,0210 nano-technology ,ultrathin silica membrane - Abstract
Ultrathin amorphous silica membranes with embedded organic molecular wires (oligo(p-phenylenevinylene), three aryl units) provide chemical separation of incompatible catalytic environments of CO2 reduction and H2O oxidation while maintaining electronic and protonic coupling between them. For an efficient nanoscale artificial photosystem, important performance criteria are high rate and directionality of charge flow. Here, the visible-light-induced charge flow from an anchored Ru bipyridyl light absorber across the silica nanomembrane to Co3O4 water oxidation catalyst is quantitatively evaluated by photocurrent measurements. Charge transfer rates increase linearly with wire density, with 5 nm-2 identified as an optimal target. Accurate measurement of wire and light absorber densities is accomplished by the polarized FT-IRRAS method. Guided by density functional theory (DFT) calculations, four wire derivatives featuring electron-donating (methoxy) and -withdrawing groups (sulfonate, perfluorophenyl) with highest occupied molecular orbital (HOMO) potentials ranging from 1.48 to 0.64 V vs NHE were synthesized and photocurrents evaluated. Charge transfer rates increase sharply with increasing driving force for hole transfer from the excited light absorber to the embedded wire, followed by a decrease as the HOMO potential of the wire moves beyond the Co3O4 valence band level toward more negative values, pointing to an optimal wire HOMO potential around 1.3 V vs NHE. Comparison with photocurrents of samples without nanomembrane indicates that silica layers with optimized wires are able to approach undiminished electron flux at typical solar intensities. Combined with the established high proton conductivity and small-molecule blocking property, the charge transfer measurements demonstrate that oxidation and reduction catalysis can be efficiently integrated on the nanoscale under separation by an ultrathin silica membrane.
- Published
- 2021
18. Spectroscopic Characterization of μ-η1:η1-Peroxo Ligands Formed by Reaction of Dioxygen with Electron-Rich Iridium Clusters
- Author
-
Christian Schöttle, Andrew Palermo, Shengjie Zhang, Bruce C. Gates, David A. Dixon, Heinz Frei, Alexander Katz, Nicolás A. Grosso-Giordano, and Alexander Okrut
- Subjects
Isosbestic point ,Ligand ,Infrared spectroscopy ,chemistry.chemical_element ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,symbols.namesake ,chemistry ,symbols ,Cluster (physics) ,Iridium ,Physical and Theoretical Chemistry ,Raman spectroscopy ,Phosphine - Abstract
Although oxygen is a common ligand in supported metal catalysts, its coordination has been challenging to elucidate. We now characterize a diiridium complex that has been previously shown by X-ray diffraction crystallography to incorporate a μ-η1:η1-peroxo ligand. We observe markedly enhanced intensity at 788 cm-1 in the Raman spectrum of this complex, which is a consequence of bonding of the peroxo ligand but does not shift upon 18O labeling. Electronic structure calculations at the density functional theory level suggest that this increase in Raman intensity results from bands associated with rocking of CH2 substituents directly attached to P(Ph)2 groups coupling with the O-O band. These results provide part of the foundation for understanding oxygen ligands on a silica-supported tetrairidium carbonyl cluster stabilized with bulky electron-donating phosphine ligands [p-tert-butyl-calix[4]arene(OPr)3(OCH2PPh2) (Ph = phenyl; Pr = propyl)]. Reaction of the cluster with O2 also led to the growing in of a Raman band at 788 cm-1, similar to that in the diiridium complex and also assigned to the bonding of a bridging peroxo ligand. Infrared spectra recorded as the supported cluster reacted in sequential exposures to (i) H2, (ii) O2, (iii) H2, and (iv) CO indicate that two bridging peroxo ligands were bonded irreversibly per tetrairidium cluster, replacing bridging carbonyl ligands without altering either the cluster frame or the phosphine ligands. X-ray absorption near edge and infrared spectra include isosbestic points signifying a stoichiometrically simple reaction of the cluster with O2, and mass spectra of the effluent gas show that CO2 formed by oxidation of one terminal CO ligand per cluster as H2 (and not H2O) formed, evidence that hydride ligands had been present on the cluster following treatment (i). The understanding of how O2 reacts with the metal polyhedron provides a foundation for understanding of how oxidation catalysis may proceed on the surfaces of noble metals.
- Published
- 2019
19. Factors and Dynamics of Cu Nanocrystal Reconstruction under CO2 Reduction
- Author
-
Georgios Katsoukis, Jasper J. Nussbaum, Heinz Frei, Gaurav A. Kamat, Wojciech T. Osowiecki, A. Paul Alivisatos, Marc Ledendecker, and Alexis T. Bell
- Subjects
Reduction (complexity) ,Materials science ,Nanocrystal ,Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Nanotechnology ,Electrical and Electronic Engineering - Abstract
Cu nanocrystals as catalysts for CO2 reduction are a subject of considerable contemporary interest, but their stability has not been considered as extensively. Herein, we report on the reconstructi...
- Published
- 2019
20. Interfacial charge transfer in Pt-loaded TiO2 P25 photocatalysts studied by in-situ diffuse reflectance FTIR spectroscopy of adsorbed CO
- Author
-
A Anton Litke, Emiel J. M. Hensen, Heinz Frei, Jan P. Hofmann, and Inorganic Materials & Catalysis
- Subjects
Titania ,General Chemical Engineering ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,chemistry.chemical_compound ,Adsorption ,Engineering ,Charge transfer ,Fourier transform infrared spectroscopy ,Photocatalysis ,Carbon monoxide ,Aqueous solution ,Chemical Physics ,Chemistry ,business.industry ,General Chemistry ,Biological Sciences ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,FTIR spectroscopy ,Semiconductor ,Chemical Sciences ,Charge carrier ,Diffuse reflection ,0210 nano-technology ,business - Abstract
The efficiency of photocatalytic systems is strongly depending on the charge carrier transfer from the excited semiconductor to co-catalyst particles attached on its surface. In this study, we investigated the influence of photo-induced charge transfer in photoplatinized TiO 2 P25 photocatalysts by diffuse reflectance FTIR spectroscopy of CO molecules adsorbed on the Pt co-catalyst under well-defined gas phase conditions. In contrast to aqueous conditions, where shifts of the CO stretching vibration of up to 50 cm −1 have been reported, the observed shifts under gas phase conditions are very small (−1). This demonstrates that the difference in dielectric properties between aqueous electrolytes and vacuum are critical for the development of prominent shifts of adsorbed CO bands upon trapping of photogenerated charge carriers on co-catalyst particles. The experimental findings are discussed in terms of an electrostatic Stark effect, charge screening, co-adsorption, coverage-dependent shifts of the vibrational bands of adsorbed CO and photocatalytic surface reactions.
- Published
- 2019
21. Efficiency and mechanism for driving ultrathin membrane-separated catalysts for H2O oxidation and CO2 reduction by visible light
- Author
-
Heinz Frei, Hongna Zhang, and Georgios Katsoukis
- Published
- 2020
22. Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid‐to‐Solid Interfaces of Stacked Metal Oxide Nanolayers While Blocking Oxygen
- Author
-
Won Jun Jo, Georgios Katsoukis, and Heinz Frei
- Subjects
Materials science ,Proton ,Absorption spectroscopy ,Oxide ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Metal ,Biomaterials ,chemistry.chemical_compound ,Atomic layer deposition ,Engineering ,Proton transport ,Electrochemistry ,Materials ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Dielectric spectroscopy ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical engineering ,visual_art ,Physical Sciences ,Chemical Sciences ,visual_art.visual_art_medium ,0210 nano-technology ,Layer (electronics) - Abstract
Author(s): Jo, WJ; Katsoukis, G; Frei, H | Abstract: A large jump of proton transfer rates across solid-to-solid interfaces by inserting an ultrathin amorphous silica layer into stacked metal oxide nanolayers is discovered using electrochemical impedance spectroscopy and Fourier-transform infrared reflection absorption spectroscopy (FT-IRRAS). The triple stacked nanolayers of Co3O4, SiO2, and TiO2 prepared by atomic layer deposition (ALD) enable a proton flux of 2400 ± 60 s−1 nm−2 (pH 4, room temperature), while a single TiO2 (5 nm) layer exhibits a threefold lower flux of 830 s−1 nm−2. Based on FT-IRRAS measurements, this remarkable enhancement is proposed to originate from the sandwiched silica layer forming interfacial SiOTi and SiOCo linkages to TiO2 and Co3O4 nanolayers, respectively, with the O bridges providing fast H+ hopping pathways across the solid-to-solid interfaces. Together with the complete O2 impermeability of a 2 nm ALD-grown SiO2 layer, the high flux for proton transport across multi-stack metal oxide layers opens up the integration of incompatible catalytic environments to form functional nanoscale assemblies such as artificial photosystems for CO2 reduction by H2O.
- Published
- 2022
23. Body mass index and cancer risk among adults with and without cardiometabolic diseases: evidence from the EPIC and UK Biobank prospective cohort studies
- Author
-
Emma Fontvieille, Vivian Viallon, Martina Recalde, Reynalda Cordova, Anna Jansana, Laia Peruchet-Noray, Hannah Lennon, Alicia K. Heath, Dagfinn Aune, Sofia Christakoudi, Verena Katzke, Rudolf Kaaks, Elif Inan-Eroglu, Matthias B. Schulze, Lene Mellemkjær, Anne Tjønneland, Kim Overvad, Marta Farràs, Dafina Petrova, Pilar Amiano, María-Dolores Chirlaque, Conchi Moreno-Iribas, Sandar Tin Tin, Giovanna Masala, Sabina Sieri, Fulvio Ricceri, Salvatore Panico, Anne M. May, Evelyn M. Monninkhof, Elisabete Weiderpass, Marc J. Gunter, Pietro Ferrari, and Heinz Freisling
- Subjects
Obesity ,Type 2 diabetes ,Cardiovascular diseases ,Comorbidities ,Obesity-related cancers ,Multimorbidity ,Medicine - Abstract
Abstract Background Whether cancer risk associated with a higher body mass index (BMI), a surrogate measure of adiposity, differs among adults with and without cardiovascular diseases (CVD) and/or type 2 diabetes (T2D) is unclear. The primary aim of this study was to evaluate separate and joint associations of BMI and CVD/T2D with the risk of cancer. Methods This is an individual participant data meta-analysis of two prospective cohort studies, the UK Biobank (UKB) and the European Prospective Investigation into Cancer and nutrition (EPIC), with a total of 577,343 adults, free of cancer, T2D, and CVD at recruitment. We used Cox proportional hazard regressions to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between BMI and incidence of obesity-related cancer and in turn overall cancer with a multiplicative interaction between BMI and the two cardiometabolic diseases (CMD). HRs and 95% CIs for separate and joint associations for categories of overweight/obesity and CMD status were estimated, and additive interaction was quantified through relative excess risk due to interaction (RERI). Results In the meta-analysis of both cohorts, BMI (per ~ 5 kg/m2) was positively associated with the risk of obesity-related cancer among participants without a CMD (HR: 1.11, 95%CI: 1.07,1.16), among participants with T2D (HR: 1.11, 95% CI: 1.05,1.18), among participants with CVD (HR: 1.17, 95% CI: 1.11,1.24), and suggestively positive among those with both T2D and CVD (HR: 1.09, 95% CI: 0.94,1.25). An additive interaction between obesity (BMI ≥ 30 kg/m2) and CVD with the risk of overall cancer translated into a meta-analytical RERI of 0.28 (95% CI: 0.09–0.47). Conclusions Irrespective of CMD status, higher BMI increased the risk of obesity-related cancer among European adults. The additive interaction between obesity and CVD suggests that obesity prevention would translate into a greater cancer risk reduction among population groups with CVD than among the general population.
- Published
- 2023
- Full Text
- View/download PDF
24. Carbon Dioxide Dimer Radical Anion as Surface Intermediate of Photoinduced CO2 Reduction at Aqueous Cu and CdSe Nanoparticle Catalysts by Rapid-Scan FT-IR Spectroscopy
- Author
-
Hua Sheng, Myoung Hwan Oh, Wooyul Kim, A. Paul Alivisatos, Wojciech T. Osowiecki, and Heinz Frei
- Subjects
Tafel equation ,Aqueous solution ,Dimer ,Photodissociation ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Biochemistry ,Porphyrin ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,0210 nano-technology ,Spectroscopy ,Carbon - Abstract
Monitoring of visible light sensitized reduction of CO2 at Cu nanoparticles in aqueous solution by rapid-scan ATR FT-IR spectroscopy on the time scale of seconds allowed structural identification of a one-electron intermediate and demonstrated its kinetic relevancy for the first time. Isotopic labeling (12C: 1632, 1358, 1346 cm–1; 13C: 1588, 1326, 1316 cm–1) revealed a species of carbon dioxide dimer radical anion structure, most likely bound to the catalyst surface through carbon. Intermediacy of Cu—C(═O)OCO2– surface species is in agreement with a recently proposed mechanism for electrocatalytic CO2 reduction at Cu metal nanoparticles based on Tafel slope analysis. Spontaneous decrease of the intermediate after termination of the photosensitization pulse (Sn porphyrin excited at 405 nm) was accompanied by the growth of HCO3–. CO was produced as well, but sensitive detection required photolysis for tens of minutes. A direct kinetic link between a C2O4– surface intermediate and the CO product was also dem...
- Published
- 2018
25. Ultra processed foods and cancer-authors' reply
- Author
-
Heinz Freisling, Reynalda Córdova, Dagfinn Aune, and Karl-Heinz Wagner
- Subjects
Public aspects of medicine ,RA1-1270 - Published
- 2024
- Full Text
- View/download PDF
26. Body mass index and incident cardiometabolic conditions in relation to obesity‐related cancer risk: A population‐based cohort study in Catalonia, Spain
- Author
-
Martina Recalde, Andrea Pistillo, Vivian Viallon, Emma Fontvieille, Talita Duarte‐Salles, and Heinz Freisling
- Subjects
adiposity ,cancer ,cardiovascular disease ,electronic health record ,hypertension ,type 2 diabetes ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Abstract
Abstract Background We investigated the association between body mass index (BMI) and obesity‐related cancer risk among individuals with/without incident hypertension (HTN), type 2 diabetes mellitus (T2DM), and cardiovascular disease (CVD) and the joint associations of overweight/obesity (BMI ≥25 kg/m2) and each cardiometabolic condition with obesity‐related cancer risk Methods We conducted a population‐based cohort (n = 1,774,904 individuals aged ≥40 years and free of cancer and cardiometabolic conditions at baseline) study between 2010 and 2018 with electronic health records from Spain. Our main outcome measures were hazard ratios (HRs) for incident obesity‐related cancers and relative excess risk due to interaction (RERI). Results A total of 38,082 individuals developed obesity‐related cancers after a median of 8 years of follow‐up. The positive association between BMI and obesity‐related cancer risk was similar among individuals free of cardiometabolic conditions (hazard ratio, HR per 5 kg/m2: 1.08, 95% confidence interval, CI: 1.06–1.10) and with incident HTN (1.05, 1.01–1.08). The association among those with incident T2DM was null (0.98, 0.93–1.03). There was a positive additive interaction between overweight/obesity and CVD (relative excess risk due to interaction [RERI]: 0.19 [0.09, 0.30]), meaning that the combined association was 0.19 more than the sum of the individual associations. In contrast, a RERI of −0.24 (−0.28, −0.20) was observed for the combined association between overweight/obesity and T2DM. Conclusions Public health strategies to reduce overweight can help prevent cancer cases among the general population and individuals with incident HTN/CVD. Further, weight‐loss interventions seem to lead to a greater cancer risk reduction among individuals with CVD.
- Published
- 2023
- Full Text
- View/download PDF
27. Association between circadian physical activity patterns and mortality in the UK Biobank
- Author
-
Michael J. Stein, Hansjörg Baurecht, Anja M. Sedlmeier, Julian Konzok, Patricia Bohmann, Emma Fontvieille, Laia Peruchet-Noray, Jack Bowden, Christine M. Friedenreich, Béatrice Fervers, Pietro Ferrari, Marc J. Gunter, Heinz Freisling, Michael F. Leitzmann, Vivian Viallon, and Andrea Weber
- Subjects
Physical activity patterns ,All-cause mortality ,UK Biobank ,Raw accelerometry ,Nutritional diseases. Deficiency diseases ,RC620-627 ,Public aspects of medicine ,RA1-1270 - Abstract
Abstract Background The benefit of physical activity (PA) for increasing longevity is well-established, however, the impact of diurnal timing of PA on mortality remains poorly understood. We aimed to derive circadian PA patterns and investigate their associations with all-cause mortality. Methods We used 24 h PA time series from 96,351 UK Biobank participants aged between 42 and 79 years at accelerometry in 2013–2015. Functional principal component analysis (fPCA) was applied to obtain circadian PA patterns. Using multivariable Cox proportional hazard models, we related the loading scores of these fPCs to estimate risk of mortality. Results During 6.9 years of follow-up, 2,850 deaths occurred. Four distinct fPCs accounted for 96% of the variation of the accelerometry data. Using a loading score of zero (i.e., average overall PA during the day) as the reference, a fPC1 score of + 2 (high overall PA) was inversely associated with mortality (Hazard ratio, HR = 0.91; 95% CI: 0.84–0.99), whereas a score of -2 (low overall PA) was associated with higher mortality (1.69; 95% CI: 1.57–1.81; p for non-linearity
- Published
- 2023
- Full Text
- View/download PDF
28. Ultrafast Charge Transfer between Light Absorber and Co3O4 Water Oxidation Catalyst across Molecular Wires Embedded in Silica Membrane
- Author
-
Heinz Frei, Dirk M. Guldi, Ian D. Sharp, Jason K. Cooper, and Eran Edri
- Subjects
Aqueous solution ,Chemistry ,Nanoparticle ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Biochemistry ,Porphyrin ,Catalysis ,0104 chemical sciences ,Molecular wire ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Adsorption ,Picosecond ,Ultrafast laser spectroscopy ,0210 nano-technology ,Spectroscopy - Abstract
© 2017 American Chemical Society. The mechanism of visible light-induced hole transfer from a molecular light absorber, in the form of a free-base porphyrin, coupled to a Co3O4nanoparticle catalyst for water oxidation by a molecular wire (p-oligo(phenylenevinylene) featuring three aryl units) is investigated by transient absorption spectroscopy. The wires are covalently anchored on the Co3O4surface and embedded in a dense, yet ultrathin (2 nm), silica layer that separates light absorber and catalyst. The porphyrin is electrostatically adsorbed on the silica surface, and aqueous colloidal solutions of the core-shell particles are used for transient optical measurements. Pulsed optical excitation of the porphyrin results in rapid injection of the photogenerated hole onto the molecular wire and concurrent formation of reduced light absorber in less than 1 picosecond (ps). Ultrafast charge separation was monitored by transient absorption of the wire radical cation, which is given by bands in the 500 to 600 nm region and at 1130 nm, while formation of reduced porphyrin was characterized by absorption at 700 nm. Forward transfer of the hole to Co3O4catalyst proceeds in 255 ± 23 ps. Ultrafast transfer of positive charge from the molecular assembly to a metal oxide nanoparticle catalyst for water oxidation is unprecedented. Holes on Co3O4recombined with electrons of the reduced sensitizer with biphasic kinetics on a much longer time scale of ten to several hundred nanoseconds. The unusually efficient hole transfer coupling of a molecular light absorber with an Earth-abundant metal oxide catalyst by silica-embedded p-oligo(phenylenevinylene) offers an approach for integrated artificial photosystems featuring product separation on the nanoscale.
- Published
- 2017
29. Photocatalytic fuel production
- Author
-
Heinz Frei
- Subjects
Materials science ,Oxide ,New materials ,Nanotechnology ,02 engineering and technology ,Chromophore ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Catalysis ,chemistry.chemical_compound ,chemistry ,Coupling (computer programming) ,Artificial systems ,Electrochemistry ,Photocatalysis ,0210 nano-technology ,Photosystem - Abstract
The conversion of carbon dioxide and water to fuel in artificial systems requires efficient coupling of light absorbers and catalysts, and assembly of the components into hierarchical structures to close the photocatalytic cycle. Recent breakthroughs in the embodiment of molecular photoactive components in ultrathin oxide layers, and the introduction of new materials approaches for interfacial charge transfer have led to substantially improved coupling of chromophores and catalysts. These advances are accelerating the exploration of novel architectures for reducing CO2 by H2O in scalable, single integrated photosystems to reach the high power efficiencies recently demonstrated with photovoltaic-assisted approaches.
- Published
- 2017
30. Coupling metal oxide nanoparticle catalysts for water oxidation to molecular light absorbers
- Author
-
Heinz Frei
- Subjects
Materials science ,Oxide ,Energy Engineering and Power Technology ,Nanoparticle ,chemistry.chemical_element ,Bioengineering ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,Physical Chemistry ,01 natural sciences ,Oxygen ,Catalysis ,Artificial photosynthesis ,Metal ,chemistry.chemical_compound ,Electrochemistry ,Coupling ,Organic Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Fuel Technology ,chemistry ,visual_art ,Photocatalysis ,visual_art.visual_art_medium ,0210 nano-technology ,Energy (miscellaneous) - Abstract
Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to achieve high efficiency. Molecular light absorbers offer flexibility in fine tuning of orbital energetics, and metal oxide nanoparticles have emerged as robust oxygen evolving catalysts. Hence, these material choices offer a promising approach for the development of photocatalytic systems for water oxidation. However, efficient charge transfer coupling of molecular light absorbers and metal oxide nanoparticle catalysts has proven a challenge. Recent new approaches toward the efficient coupling of these components based on synthetic design improvements combined with direct spectroscopic observation and kinetic evaluation of charge transfer processes are discussed.
- Published
- 2017
31. Spectroscopic Characterization of μ-η
- Author
-
Andrew P, Palermo, Christian, Schöttle, Shengjie, Zhang, Nicolás A, Grosso-Giordano, Alexander, Okrut, David A, Dixon, Heinz, Frei, Bruce C, Gates, and Alexander, Katz
- Abstract
Although oxygen is a common ligand in supported metal catalysts, its coordination has been challenging to elucidate. We now characterize a diiridium complex that has been previously shown by X-ray diffraction crystallography to incorporate a μ-η
- Published
- 2019
32. Structure and Orientation of Molecular Wires Embedded in Ultrathin Silica Membrane for Artificial Photosynthesis Elucidated by Polarized FT-IRRAS
- Author
-
Heinz Frei, Won Jun Jo, and Georgios Katsoukis
- Subjects
Technology ,Materials science ,Infrared ,Bioengineering ,02 engineering and technology ,Orientation (graph theory) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Physical Chemistry ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Artificial photosynthesis ,Molecular wire ,General Energy ,Engineering ,Chemical engineering ,Covalent bond ,Chemical Sciences ,Silica membrane ,Nanotechnology ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Surface sensitive infrared spectroscopic methods are employed for elucidating the structure and orientation of charge conducting molecular wires of type oligo(p-phenylenevinylene) covalently anchored on an ultrathin planar Co oxide catalyst surface and embedded in a few nanometer thick amorphous silica membrane. Comparison of polarized FT-IRRAS with nonpolarized grazing angle ATR FT-IR spectra of nanolayer samples supported on a flat Pt surface and transmission spectra of powder samples showed distinct intensity differences for molecular in-plane and out-of-plane modes that reveal the spatial orientation with respect to the oxide surface. All observations support an upright orientation of the molecular wire axis, which is further confirmed by comparison with IRRAS measurements of physisorbed, horizontally positioned wire molecules. The structural integrity of the molecules is maintained after embedding in the silica membrane by plasma-enhanced atomic layer deposition at 40 °C. The results provide the first spectroscopic evidence of perpendicular orientation of the wire molecules. The complementary surface sensitive infrared measurements by FT-IRRAS and grazing angle ATR FT-IR constitute a powerful approach for elucidating the structure and orientation of surface-anchored molecules and the integrity upon casting into oxide layers such as silica for developing artificial photosystems. Use of the nanolayer construct in IRRAS spectroelectrochemical cell configuration will enable in situ monitoring of the structural and orientation integrity of the silica embedded molecular wires under the sustained electron and proton flux conditions of photocatalytic operation.
- Published
- 2019
33. Nanoscale membranes that chemically isolate and electronically wire up the abiotic/biotic interface
- Author
-
Hua Sheng, Jose A. Cornejo, Caroline M. Ajo-Franklin, Heinz Frei, and Eran Edri
- Subjects
Shewanella ,Trimethylsilyl Compounds ,Science ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Redox ,Article ,Catalysis ,General Biochemistry, Genetics and Molecular Biology ,law.invention ,Electron Transport ,Affordable and Clean Energy ,law ,Nanotechnology ,Shewanella oneidensis ,lcsh:Science ,Platinum ,Electrolysis ,Multidisciplinary ,Fouling ,biology ,Nanowires ,Chemistry ,Microbial electrosynthesis ,Tin Compounds ,Electrochemical Techniques ,General Chemistry ,021001 nanoscience & nanotechnology ,biology.organism_classification ,0104 chemical sciences ,Anode ,Membrane ,Chemical engineering ,lcsh:Q ,0210 nano-technology ,Oxidation-Reduction - Abstract
By electrochemically coupling microbial and abiotic catalysts, bioelectrochemical systems such as microbial electrolysis cells and microbial electrosynthesis systems synthesize energy-rich chemicals from energy-poor precursors with unmatched efficiency. However, to circumvent chemical incompatibilities between the microbial cells and inorganic materials that result in toxicity, corrosion, fouling, and efficiency-degrading cross-reactions between oxidation and reduction environments, bioelectrochemical systems physically separate the microbial and inorganic catalysts by macroscopic distances, thus introducing ohmic losses, rendering these systems impractical at scale. Here we electrochemically couple an inorganic catalyst, a SnO2 anode, with a microbial catalyst, Shewanella oneidensis, via a 2-nm-thick silica membrane containing -CN and -NO2 functionalized p-oligo(phenylene vinylene) molecular wires. This membrane enables electron flow at 0.51 μA cm−2 from microbial catalysts to the inorganic anode, while blocking small molecule transport. Thus the modular architecture avoids chemical incompatibilities without ohmic losses and introduces an immense design space for scale up of bioelectrochemical systems., Bioelectrochemical cells have huge potential, yet incompatibilities between the microbe and abiotic catalysts can affect efficiency. Here, the authors report the development of thin silica membranes with bridging molecular wires that chemically separate yet electrically connect the two components.
- Published
- 2018
34. A body shape index (ABSI) is associated inversely with post-menopausal progesterone-receptor-negative breast cancer risk in a large European cohort
- Author
-
Sofia Christakoudi, Konstantinos K. Tsilidis, Laure Dossus, Sabina Rinaldi, Elisabete Weiderpass, Christian S. Antoniussen, Christina C. Dahm, Anne Tjønneland, Lene Mellemkjær, Verena Katzke, Rudolf Kaaks, Matthias B. Schulze, Giovanna Masala, Sara Grioni, Salvatore Panico, Rosario Tumino, Carlotta Sacerdote, Anne M. May, Evelyn M. Monninkhof, J. Ramón Quirós, Catalina Bonet, Maria-Jose Sánchez, Pilar Amiano, María-Dolores Chirlaque, Marcela Guevara, Ann H. Rosendahl, Tanja Stocks, Aurora Perez-Cornago, Sandar Tin Tin, Alicia K. Heath, Elom K. Aglago, Laia Peruchet-Noray, Heinz Freisling, and Elio Riboli
- Subjects
Obesity ,Body shape ,Waist size ,ABSI ,Hip size ,Breast cancer ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Abstract
Abstract Background Associations of body shape with breast cancer risk, independent of body size, are unclear because waist and hip circumferences are correlated strongly positively with body mass index (BMI). Methods We evaluated body shape with the allometric “a body shape index” (ABSI) and hip index (HI), which compare waist and hip circumferences, correspondingly, among individuals with the same weight and height. We examined associations of ABSI, HI, and BMI (per one standard deviation increment) with breast cancer overall, and according to menopausal status at baseline, age at diagnosis, and oestrogen and progesterone receptor status (ER+/-PR+/-) in multivariable Cox proportional hazards models using data from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Results During a mean follow-up of 14.0 years, 9011 incident breast cancers were diagnosed among 218,276 women. Although there was little evidence for association of ABSI with breast cancer overall (hazard ratio HR = 0.984; 95% confidence interval: 0.961–1.007), we found borderline inverse associations for post-menopausal women (HR = 0.971; 0.942-1.000; n = 5268 cases) and breast cancers diagnosed at age ≥ 55 years (HR = 0.976; 0.951–1.002; n = 7043) and clear inverse associations for ER + PR- subtypes (HR = 0.894; 0.822–0.971; n = 726) and ER-PR- subtypes (HR = 0.906; 0.835–0.983 n = 759). There were no material associations with HI. BMI was associated strongly positively with breast cancer overall (HR = 1.074; 1.049–1.098), for post-menopausal women (HR = 1.117; 1.085–1.150), for cancers diagnosed at age ≥ 55 years (HR = 1.104; 1.076–1.132), and for ER + PR + subtypes (HR = 1.122; 1.080–1.165; n = 3101), but not for PR- subtypes. Conclusions In the EPIC cohort, abdominal obesity evaluated with ABSI was not associated with breast cancer risk overall but was associated inversely with the risk of post-menopausal PR- breast cancer. Our findings require validation in other cohorts and with a larger number of PR- breast cancer cases.
- Published
- 2023
- Full Text
- View/download PDF
35. Longitudinal body mass index and cancer risk: a cohort study of 2.6 million Catalan adults
- Author
-
Martina Recalde, Andrea Pistillo, Veronica Davila-Batista, Michael Leitzmann, Isabelle Romieu, Vivian Viallon, Heinz Freisling, and Talita Duarte-Salles
- Subjects
Science - Abstract
Abstract Single body mass index (BMI) measurements have been associated with increased risk of 13 cancers. Whether life course adiposity-related exposures are more relevant cancer risk factors than baseline BMI (ie, at start of follow-up for disease outcome) remains unclear. We conducted a cohort study from 2009 until 2018 with population-based electronic health records in Catalonia, Spain. We included 2,645,885 individuals aged ≥40 years and free of cancer in 2009. After 9 years of follow-up, 225,396 participants were diagnosed with cancer. This study shows that longer duration, greater degree, and younger age of onset of overweight and obesity during early adulthood are positively associated with risk of 18 cancers, including leukemia, non-Hodgkin lymphoma, and among never-smokers, head and neck, and bladder cancers which are not yet considered as obesity-related cancers in the literature. Our findings support public health strategies for cancer prevention focussing on preventing and reducing early overweight and obesity.
- Published
- 2023
- Full Text
- View/download PDF
36. Surface Proton Hopping and Fast-Kinetics Pathway of Water Oxidation on Co3O4 (001) Surface
- Author
-
Heinz Frei, Hieu H. Pham, Mu Jeng Cheng, and Lin-Wang Wang
- Subjects
biology ,Chemistry ,Kinetics ,Oxygen evolution ,Active site ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Deprotonation ,Catalytic cycle ,Nucleophile ,biology.protein ,Water splitting ,Molecule ,0210 nano-technology - Abstract
We propose a mechanism of water splitting on cobalt oxide surface with atomistic thermodynamic and kinetic details. The density-functional theory studies suggest that the oxidation process could proceed with several nonelectrochemical (spontaneous) intermediate steps, following the initial electrochemical hydroxyl-to-oxo conversion. More specifically, the single oxo sites CoIV═O can hop (via surface proton/electron hopping) to form oxo pair CoIV(═O)-O-CoIV═O, which will undergo nucleophilic attack by a water molecule and form the hydroperoxide CoIII–OOH. Encounter with another oxo would generate a superoxo CoIII–OO, followed by the O2 release. Finally the addition and deprotonation of a fresh water molecule will restart the catalytic cycle by forming the hydroxyl CoIII–OH at this active site. Our theoretical investigations indicate that all nonelectrochemical reactions are kinetically fast and thermodynamically downhill. This hypothesis is supported by recent in situ spectroscopic observations of surface ...
- Published
- 2016
37. Direct Observation by Rapid-Scan FT-IR Spectroscopy of Two-Electron-Reduced Intermediate of Tetraaza Catalyst [CoIIN4H(MeCN)]2+ Converting CO2 to CO
- Author
-
Heinz Frei and Hua Sheng
- Subjects
Ligand ,Infrared spectroscopy ,02 engineering and technology ,General Chemistry ,Electron ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Adduct ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,chemistry ,Carboxylate ,0210 nano-technology ,Spectroscopy ,Acetonitrile - Abstract
In the search for the two-electron-reduced intermediate of the tetraaza catalyst [Co(II)N4H(MeCN)](2+) (N4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene) for CO2 reduction and elementary steps that result in the formation of CO product, rapid-scan FT-IR spectroscopy of the visible-light-sensitized catalysis, using Ir(ppy)3 in wet acetonitrile (CD3CN) solution, led to the observation of two sequential intermediates. The initially formed one-electron-reduced [Co(I)N4H](+)-CO2 adduct was converted by the second electron to a transient [Co(I)N4H](+)-CO2(-) complex that spontaneously converted CO2 to CO in a rate-limiting step on the second time scale in the dark under regeneration of the catalyst (room temperature). The macrocycle IR spectra of the [Co(I)N4H](+)-CO2(-) complex and the preceding one-electron [Co(I)N4H](+)-CO2 intermediate show close similarity but distinct differences in the carboxylate modes, indicating that the second electron resides mainly on the CO2 ligand. Vibrational assignments are corroborated by (13)C isotopic labeling. The structure and stability of the two-electron-reduced intermediate derived from the time-resolved IR study are in good agreement with recent predictions by DFT electronic structure calculations. This is the first observation of an intermediate of a molecular catalyst for CO2 reduction during the bond-breaking step producing CO. The reaction pathway for the Co tetraaza catalyst uncovered here suggests that the competition between CO2 reduction and proton reduction of a macrocyclic multi-electron catalyst is steered toward CO2 activation if the second electron is directly captured by an adduct of CO2 and the one-electron-reduced catalyst intermediate.
- Published
- 2016
38. Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs
- Author
-
E. Goggins, T-C Weng, K. Nagaya, Tetsuo Katayama, Dimosthenis Sokaras, B. A. McClure, Kazuki Asa, Nicholas K. Sauter, Roberto Alonso-Mori, Walter W. Weare, Kiyoshi Ueda, Sheraz Gul, Tadashi Togashi, Vittal K. Yachandra, Junko Yano, Toshiyuki Nishiyama, Thomas Kroll, Mohamed Ibrahim, Iris D. Young, Claudio Saracini, Yoshiaki Kumagai, Ruchira Chatterjee, Johannes Messinger, Franklin D. Fuller, Tsukasa Takanashi, Athina Zouni, Koji Motomura, Aaron S. Brewster, Y. Sato, Heinz Frei, D. Iablonskyi, Uwe Bergmann, Hironobu Fukuzawa, Jan Kern, Jason K. Cooper, and Makina Yabashi
- Subjects
Free electron model ,Astrophysics::High Energy Astrophysical Phenomena ,Electrons ,Nanotechnology ,Crystallography, X-Ray ,010402 general chemistry ,01 natural sciences ,Catalysis ,Article ,law.invention ,law ,0103 physical sciences ,Artificial systems ,Physical and Theoretical Chemistry ,010306 general physics ,Physics ,Crystallography ,Chemical Physics ,Lasers ,X-Rays ,Laser ,0104 chemical sciences ,Characterization (materials science) ,Excited state ,Chemical Sciences ,Femtosecond ,X-Ray - Abstract
This journal is © The Royal Society of Chemistry. The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.
- Published
- 2016
39. Heterobinuclear Light Absorber Coupled to Molecular Wire for Charge Transport across Ultrathin Silica Membrane for Artificial Photosynthesis
- Author
-
Georgios Katsoukis and Heinz Frei
- Subjects
Materials science ,Absorption spectroscopy ,silica membrane ,Oxide ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,transient optical spectroscopy ,surface anchoring ,Artificial photosynthesis ,chemistry.chemical_compound ,Molecular wire ,Engineering ,Phenylene ,molecular wire ,Molecule ,General Materials Science ,Nanoscience & Nanotechnology ,Photodissociation ,charge transfer ,Chromophore ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Chemical engineering ,chemistry ,artificial photosynthesis ,Chemical Sciences ,0210 nano-technology - Abstract
Coupling of robust, all-inorganic heterobinuclear light absorbers to metal oxide catalysts for water oxidation across an ultrathin product-separating silica membrane requires charge transfer through organic molecular wires embedded in the silica. A synthetic approach for assembling the bimetallic units on the silica surface is introduced that is compatible with the presence of encapsulated organic molecules. Accurate selection and fine tuning of the concentration of embedded conducting wires are enabled by a two-step method consisting of surface attachment of a tripodal anchor, trimethoxysilyl aniline, followed by attachment of p-oligo(phenylene vinylene) through amide linkage. Each step of the assembly process was monitored and characterized by a combination of Fourier transform infrared, Fourier transform-Raman, and UV-vis spectroscopy techniques. Hole transfer was observed from transient CoIII, formed by TiIVOCoII → TiIIIOCoIII charge transfer excitation of the chromophore, to p-oligo(phenylene vinylene) molecule within the 8 ns width of the photolysis laser pulse by transient optical absorption spectroscopy of the wire radical cation. The rectifying property of the light absorber-wire assembly enabled by appropriate selection of redox potentials of metals and embedded wire obviates the need for a molecularly defined linkage between the components. Combined with the previously observed ultrafast hole injection from the embedded wires to Co oxide catalyst, the result implies visible-light-induced hole transfer from visible-light-excited binuclear light absorber to water oxidation catalyst across the silica separation membrane in a few nanoseconds or faster. Demonstration and understanding of this interfacial charge-transfer step is critical for developing nanoscale core-shell architectures for complete photosynthetic cycles.
- Published
- 2018
40. Photoinduced Electron Transfer from ZrOCo Binuclear Light Absorber to Pyridine Elucidated by Transient Optical and Infrared Spectroscopy
- Author
-
Adam D. Hill, Georgios Katsoukis, and Heinz Frei
- Subjects
Technology ,Materials science ,Absorption spectroscopy ,010405 organic chemistry ,Infrared ,Infrared spectroscopy ,Bioengineering ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Physical Chemistry ,Photoinduced electron transfer ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Electron transfer ,General Energy ,Engineering ,Excited state ,Chemical Sciences ,Ultraviolet light ,Physical and Theoretical Chemistry ,Spectroscopy - Abstract
All-inorganic heterobinculear units can be excited to a metal-to-metal charge transfer (MMCT) state by visible and ultraviolet light and form the core of multicomponent artificial photosystems that rely on conjugated molecular wires to transmit electrons and holes across ultrathin silica separation membranes to catalytic sites. To understand electron transfer from a heterobinuclear unit to an organic molecule, model systems consisting of pyridine interacting with ZrIVOCoII or TiIVOCoII sites on silica nanoparticles were assembled and spectroscopically characterized. Transient optical absorption spectroscopy combined with infrared analysis revealed that visible light excitation of assemblies in which pyridine interacts with the Zr center of the ZrOCo unit results in sub-10 ns separation by electron transfer to the organic moiety. Rapid-scan FT-IR spectroscopy supported by density functional theory confirmed the identity of the pyridine radical anion charge-separated state. This state shows a lifetime of 220 (±60) ms prior to complete recovery of the initial state, suggesting spin crossover along the electron transfer path. No hole transfer from excited ZrIVOCoII ZrIIIOCoIII to pyridine is observed. The rectifying charge transfer behavior is an important design aspect for developing efficient artificial photosystems.
- Published
- 2018
41. Fabrication of Core-Shell Nanotube Array for Artificial Photosynthesis Featuring an Ultrathin Composite Separation Membrane
- Author
-
Shaul Aloni, Heinz Frei, and Eran Edri
- Subjects
Nanotube ,Materials science ,Fabrication ,molecular wires ,General Physics and Astronomy ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Molecular wire ,Atomic layer deposition ,X-ray photoelectron spectroscopy ,Nanotechnology ,General Materials Science ,Nanoscience & Nanotechnology ,Nanoscopic scale ,General Engineering ,021001 nanoscience & nanotechnology ,core−shell ,0104 chemical sciences ,core-shell ,Membrane ,Chemical engineering ,artificial photosynthesis ,Nanorod ,nanotube array ,0210 nano-technology ,ultrathin silica membrane - Abstract
Macroscale arrays of cobalt oxide-silica core-shell nanotubes with high aspect ratio and ultrathin walls of less than 20 nm have been fabricated. The silica shells feature embedded oligo-para(phenylenevinylene) molecules for charge transport across the insulating silica layer, which is tightly controlled by their electronic properties. The assembly is based on the use of a sacrificial Si nanorod array template combined with atomic layer deposition, covalent anchoring of organic wire molecules, and dry cryo-etching. High-resolution TEM imaging of samples prepared by microtome affords structural details of single core-shell nanotubes. The integrity of silica-embedded organic wire molecules exposed to atomic layer deposition, thermal treatment, and harsh etching procedures is demonstrated by grazing angle ATR FT-IR, FT-Raman, and XPS spectroscopy. The inorganic oxide-based core-shell nanotubes with ultrathin gas-impermeable, proton-conducting silica shells functionalized by molecular wires enable complete nanoscale photosynthetic units for CO2 reduction by H2O under membrane separation. Arrays of massive numbers of such core-shell nanotube units afford a design that extends the separation of the incompatible H2O oxidation and CO2 reduction catalysis environments across the continuum of length scales from nanometers to centimeters.
- Published
- 2018
42. Directed Assembly of Cuprous Oxide Nanocatalyst for CO2 Reduction Coupled to Heterobinuclear ZrOCoII Light Absorber in Mesoporous Silica
- Author
-
Heinz Frei and Wooyul Kim
- Subjects
Chemistry ,Inorganic chemistry ,Oxide ,Electron donor ,General Chemistry ,Mesoporous silica ,Chromophore ,Photochemistry ,Catalysis ,law.invention ,chemistry.chemical_compound ,law ,Oxidation state ,Photocatalysis ,Calcination ,Visible spectrum - Abstract
Hierarchical assembly of an oxo-bridged binuclear ZrOCoII light absorber unit coupled to a cuprous oxide nanocluster catalyst for CO2 reduction on mesoporous silica support is demonstrated. The proper positioning of the Cu oxide cluster was achieved by photodeposition of a [Cu(NCCH3)4]2+precursor by visible light excitation of the ZrOCo charge transfer chromophore, followed by mild calcination at 350 C. Illumination of the CuxOy-ZrOCo unit so formed in the presence of a diethylamine electron donor resulted in the reduction of surface Cu centers to Cu0 as demonstrated by the characteristic infrared band of adsorbed 13CO probe molecules at 2056 cm–1. For analogous CuxOy-TiOCoII units, the oxidation state makeup of the surface Cu centers was dominated by CuI, and the Cu0, CuI, and CuII composition was found to depend on the wavelength of MMCT excitation. The observed strong dependence of the CO2 photoreduction yield on the oxidation state of the surface Cu centers directly proves that CO2 is reduced on the C...
- Published
- 2015
43. Determinants of handbike use in persons with spinal cord injury: results of a community survey in Switzerland
- Author
-
Ursina, Arnet, Timo, Hinrichs, Veronika, Lay, Sue, Bertschy, Heinz, Frei, Martin W G, Brinkhof, Christine, Thyrian, University of Zurich, and Arnet, Ursina
- Subjects
Adult ,Male ,030506 rehabilitation ,medicine.medical_specialty ,Adolescent ,Population ,Physical fitness ,Poison control ,610 Medicine & health ,Quadriplegia ,Occupational safety and health ,Young Adult ,03 medical and health sciences ,0302 clinical medicine ,Surveys and Questionnaires ,Activities of Daily Living ,Injury prevention ,medicine ,Humans ,Disabled Persons ,education ,Tetraplegia ,Spinal cord injury ,Spinal Cord Injuries ,Aged ,Paraplegia ,education.field_of_study ,business.industry ,Rehabilitation ,Middle Aged ,medicine.disease ,2742 Rehabilitation ,Cross-Sectional Studies ,Logistic Models ,Socioeconomic Factors ,Wheelchairs ,Multivariate Analysis ,Quality of Life ,Physical therapy ,Female ,10046 Balgrist University Hospital, Swiss Spinal Cord Injury Center ,0305 other medical science ,business ,Switzerland ,030217 neurology & neurosurgery - Abstract
To examine the prevalence and determinants of handbike use in persons living with spinal cord injury in Switzerland.A population-based cross-sectional survey in Switzerland.The crude prevalence of handbike use among the 1549 participants was 22.6%, varying between 25.3% in men and 17.7% in women. Prevalence was higher in complete than in incomplete spinal cord injury (SCI) (41.5% versus 11.9% in paraplegia, 25.6% versus 11.1% in tetraplegia). Multivariable analysis of handbike use confirmed differences with lesion characteristics and gender and showed a decline with age, lowest rates in the low-income group, variation with language, but no association with level of education or cause of spinal cord injury. In total, 45.8% of users reported to engage in handcycling at least once a week. Frequent contextual reasons for refraining from handcycling were: no interest (26%); inability due to disability (20%); unfamiliarity with the handbike (19%) and financial constraints (14%).Conditional on the major determinants that include demographic factors and lesion characteristics, main barriers involve contextual factors that can principally be overcome. Our findings thus suggest scope for promoting handcycling as a means towards a healthy and more physically active lifestyle in persons living with SCI.Handcycling is an effective means of improving health and quality of life of persons with a spinal cord injury. Persons with the following traits are most likely to use the handbike: persons younger than 62 years, with a complete paraplegia, who are German-speaking (vs. French/Italian) and having a middle or high net income. Indicated reasons for not using a handbike varied by SCI characteristics and included disinterest, inability related to the level of impairment, unfamiliarity and financial costs. Barriers that involve the above mentioned contextual factors can principally be overcome by targeted policy or information campaigns.
- Published
- 2015
44. Water Oxidation Mechanisms of Metal Oxide Catalysts by Vibrational Spectroscopy of Transient Intermediates
- Author
-
Miao Zhang and Heinz Frei
- Subjects
transients ,Infrared ,Oxide ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Physical Chemistry ,Catalysis ,Artificial photosynthesis ,Metal ,chemistry.chemical_compound ,symbols.namesake ,water oxidation catalysis ,Theoretical and Computational Chemistry ,metal oxides ,Physical and Theoretical Chemistry ,Chemical Physics ,Chemistry ,surface intermediates ,021001 nanoscience & nanotechnology ,Solar fuel ,0104 chemical sciences ,artificial photosynthesis ,visual_art ,visual_art.visual_art_medium ,symbols ,0210 nano-technology ,Raman spectroscopy ,infrared and Raman spectroscopy ,Physical Chemistry (incl. Structural) - Abstract
©2017 by Annual Reviews. All rights reserved. Water oxidation is an essential reaction of an artificial photosystem for solar fuel generation because it provides electrons needed to reduce carbon dioxide or protons to a fuel. Earth-abundant metal oxides are among the most attractive catalytic materials for this reaction because of their robustness and scalability, but their efficiency poses a challenge. Knowledge of catalytic surface intermediates gained by vibrational spectroscopy under reaction conditions plays a key role in uncovering kinetic bottlenecks and provides a basis for catalyst design improvements. Recent dynamic infrared and Raman studies reveal the molecular identity of transient surface intermediates of water oxidation on metal oxides. Combined with ultrafast infrared observations of how charges are delivered to active sites of the metal oxide catalyst and drive the multielectron reaction, spectroscopic advances are poised to play a key role in accelerating progress toward improved catalysts for artificial photosynthesis.
- Published
- 2017
45. Ultrafast Charge Transfer between Light Absorber and Co
- Author
-
Eran, Edri, Jason K, Cooper, Ian D, Sharp, Dirk M, Guldi, and Heinz, Frei
- Abstract
The mechanism of visible light-induced hole transfer from a molecular light absorber, in the form of a free-base porphyrin, coupled to a Co
- Published
- 2017
46. Excited State Electron Transfer of All-Inorganic Heterobinuclear TiOMn2+ Chromophore Anchored on Silica Nanoparticle Surface
- Author
-
Beth Anne McClure and Heinz Frei
- Subjects
Coupling constant ,Materials science ,Analytical chemistry ,Activation energy ,Chromophore ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Electron transfer ,General Energy ,Absorption band ,Excited state ,Yield (chemistry) ,Ultrafast laser spectroscopy ,Physical and Theoretical Chemistry - Abstract
The oxo-bridged heterobinuclear chromophore TiOMn2+ has been covalently anchored onto a silica nanoparticle surface, allowing for the preparation of optically transparent solid state samples. Optical spectra of the material yield a broad metal-to-metal charge-transfer (MMCT) transition in the UV with a tail extending to 550 nm. Fitting the absorption band to a Gaussian curve gives a maximum at 44 610 (±230) cm–1 (587 (±20) M–1 cm–1) with a full width at half-maximum of 17 320 (±160) cm–1, and yields an electronic coupling constant, HABopt, of 4200 cm–1 by Hush analysis. Transient absorption measurements of transparent pressed pellets in vacuum yield a 2.43 (±0.20) μs lifetime at room temperature. The temperature dependence of the lifetime in the range of 10–40 °C gives an activation energy of 1.67 (±0.36) kcal/mol and pre-exponential factor A of 7.3 (±4.4) × 106 s–1. This temperature dependence results in an electronic coupling constant HABkin of less than 1 cm–1. The disparity between the large electroni...
- Published
- 2014
47. Binuclear ZrOCo Metal-to-Metal Charge-Transfer Unit in Mesoporous Silica for Light-Driven CO2 Reduction to CO and Formate
- Author
-
Heinz Frei, Han Sen Soo, and Marisa Macnaughtan
- Subjects
Materials science ,Extended X-ray absorption fine structure ,Mesoporous silica ,Photochemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,chemistry.chemical_compound ,General Energy ,Adsorption ,chemistry ,visual_art ,visual_art.visual_art_medium ,Formate ,Physical and Theoretical Chemistry ,Visible spectrum ,Coordination geometry ,Carbon monoxide - Abstract
Oxo-bridged heterobinuclear units of the type Zr(IV)OCo(II) covalently anchored on the pore surface of mesoporous silica SBA-15 have been synthesized with high selectivity. The unit exhibits a visible light absorbing metal-to-metal charge-transfer absorption (MMCT) extending to about 550 nm. The oxo-bridged structure of the binuclear moiety is manifested by spectral blue-shifts of the optical Co(II) spin–orbit bands due to reduced π-electron donating ability of the bridging oxygen caused by the electron-withdrawing Zr center. EXAFS measurements of the Zr and Co K-edges and curve fitting analysis revealed a Zr to Co distance of 3.4 A. The coordination geometry of the Zr and Co metal centers in monometallic Zr and Co-SBA-15 samples is closely preserved in the ZrOCo unit. Illumination of the MMCT absorption at 420 nm and shorter wavelengths resulted in the reduction of CO2 to gas phase CO and HCO2–, the latter adsorbed on the silica pore surface. The branching between carbon monoxide and formate was found to...
- Published
- 2014
48. Solar cells and photocatalytic systems: general discussion
- Author
-
Galen D. Stucky, Xile Hu, Zhong-Qun Tian, Gang Chen, Fei Li, Licheng Sun, Peng Fei Liu, Lulu Long, Yicheng Zhao, Jingshan Luo, Wei Han, Baohua Wang, Dong Ryeol Whang, Takashi Hisatomi, Joachim Maier, Erwin Reisner, Yu Li, Andrew R. Mount, Zhonghua Li, Liang Chen, Jian He, Huiqiong Wang, Ram Seshadri, Can Li, Nam-Gyu Park, Kai Zhu, Shi-Gang Sun, Fuping Pan, Chao Zhan, Heinz Frei, Shihe Yang, Pingwu Du, Hong Liu, Michael Grätzel, Xudong Yang, and Lee Cronin
- Subjects
Materials science ,Photocatalysis ,Nanotechnology ,Physical and Theoretical Chemistry - Published
- 2014
49. Ultrathin oxide layers for nanoscale integration of molecular light absorbers, catalysts, and complete artificial photosystems
- Author
-
Georgios Katsoukis and Heinz Frei
- Subjects
Chemical Physics ,Materials science ,010304 chemical physics ,Oxide ,General Physics and Astronomy ,Nanotechnology ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Artificial photosynthesis ,chemistry.chemical_compound ,Engineering ,Membrane ,chemistry ,Physical Sciences ,Chemical Sciences ,0103 physical sciences ,Nanometre ,Physical and Theoretical Chemistry ,Nanoscopic scale ,Electrochemical reduction of carbon dioxide ,Photosystem - Abstract
Artificial photosynthesis is an attractive approach for the generation of renewable fuels because such systems will be suitable for deployment on highly abundant, non-arable land. Recently emerged methods of nanoscience to create conformal, ultrathin oxide layers enable the hierarchical integration of light absorbers, catalysts, and membranes into systems with far simpler synthetic approaches than available till now. This holds in particular for the coupling of molecular light absorbers and catalysts for sunlight to fuel conversion, providing photoelectrodes with greatly improved stability. Moreover, the use of ultrathin inert oxides as proton conducting, molecule impermeable membranes has opened up the integration of reduction and oxidation half reactions into complete photosynthetic systems on the shortest possible length scale-the nanometer scale. This capability affords minimization of energy-degrading resistance losses caused by ion transport over macroscale distances while separating the incompatible water oxidation and carbon dioxide reduction catalysis environments on the nanoscale. Understanding of charge transport between molecular components embedded in the oxide layers is critical for guiding synthetic design improvements of the light absorber-catalyst units to optimize performance and integrate them into complete artificial photosystems. Recent results and insights from transient optical, vibrational, and photoelectrochemical studies are presented, and future challenges and opportunities for engaging dynamic spectroscopies to accelerate the development of nanoscale integrated artificial photosystems are discussed.
- Published
- 2019
50. Dietary intake of advanced glycation endproducts (AGEs) and cancer risk across more than 20 anatomical sites: A multinational cohort study
- Author
-
Reynalda Córdova, Ana‐Lucia Mayén, Viktoria Knaze, Elom Kouassivi Aglago, Casper Schalkwijk, Karl‐Heinz Wagner, Kim Overvad, Anne Tjønneland, Cecilie Kyrø, Verena Andrea Katzke, Charlotte Le Cornet, Matthias Bernd Schulze, Anna Birukov, Domenico Palli, Sara Grioni, Fabrizio Pasanisi, Alberto Catalano, Torkjel Manning Sandanger, Inger Torhild Gram, Guri Skeie, Marta Crous‐Bou, Esther Molina‐Montes, Pilar Amiano, Sandra Milena Colorado‐Yohar, Eva Ardanaz, Isabel Drake, Jonas Manjer, Ingegerd Johansson, Anders Esberg, Aurora Perez‐Cornago, Elisabete Weiderpass, Mazda Jenab, and Heinz Freisling
- Subjects
Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Published
- 2022
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.