139 results on '"Ying, Li"'
Search Results
2. Multi-Förster Resonance Energy Transfer-Based Fluorescent Probe for Spatiotemporal Matrix Metalloproteinase-2 and Caspase-3 Imaging.
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Hong Cheng, Shi-Ying Li, Hao-Ran Zheng, Chu-Xin Li, Bo-Ru Xie, Ke-Wei Chen, Bin Li, and Xian-Zheng Zhang
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FLUORESCENCE resonance energy transfer , *CANCER diagnosis , *FLUORESCENT probes , *MATRIX metalloproteinases , *CASPASES , *CANCER cells - Abstract
A novel single-molecular fluorescent probe was developed for spatiotemporal matrix metalloproteinase-2 (MMP-2) and caspase-3 imaging with distinct fluorescence signals. Due to the multi-Förster resonance energy transfer (FRET) processes, the probe could respond to MMP-2 and caspase-3 independently with high signal-to-noise ratio. Moreover, the overexpression of MMP-2 in cancer cell lines and the cisplatin induced cell apoptosis were spatiotemporal imaged with distinct fluorescence emissions. Because of the independent process of the probe for MMP-2 and caspase-3 imaging, the probe could meet the demands for precise disease diagnosis and cancer theranostic applications, which could extensively simplify the processes for precise cancer diagnosis and imaging. [ABSTRACT FROM AUTHOR]
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- 2017
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3. Aqueous Photochemistry of Secondary Organic Aerosol of α-Pinene and α-Humulene Oxidized with Ozone, Hydroxyl Radical, and Nitrate Radical.
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Romonosky, Dian E., Ying Li, Manabu Shiraiwa, Laskin, Alexander, Laskin, Julia, and Nizkorodov, Sergey A.
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VOLATILE organic compounds , *PYROLYSIS , *SESQUITERPENES , *PHOTOCHEMISTRY , *PINENE , *HUMULENE , *HYDROXYL group , *NITRATES - Abstract
Formation of secondary organic aerosols (SOA) from biogenic volatile organic compounds (BVOC) occurs via O3- and OH-initiated reactions during the day and reactions with NO3 during the night. We explored the effect of these three oxidation conditions on the molecular composition and aqueous photochemistry of model SOA prepared from two common BVOC. A common monoterpene, α-pinene, and sesquiterpene, α-humulene, were used to form SOA in a smog chamber via BVOC + O3, BVOC + NO3, and BVOC + OH + NOx oxidation. Samples of SOA were collected on filters, water-soluble compounds from SOA were extracted in water, and the resulting aqueous solutions were photolyzed to simulate the photochemical aqueous processing of SOA. The extent of change in the molecular level composition of SOA over 4 h of photolysis (approximately equivalent to 64 h of photolysis under ambient conditions) was assessed with high-resolution electrospray ionization mass spectrometry. The analysis revealed significant differences in the molecular composition between SOA formed by the different oxidation pathways. The composition further evolved during photolysis with the most notable change corresponding to the nearly complete removal of nitrogen-containing organic compounds. Hydrolysis of SOA compounds also occurred in parallel with photolysis. The preferential loss of larger SOA compounds during photolysis and hydrolysis made the SOA compounds more volatile on average. This study suggests that aqueous processes may under certain conditions lead to a reduction in the SOA loading as opposed to an increase in SOA loading commonly assumed in the literature. [ABSTRACT FROM AUTHOR]
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- 2017
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4. High-Efficiency and Air-Stable Perovskite Quantum Dots Light-Emitting Diodes with an All-Inorganic Heterostructure.
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Zhifeng Shi, Ying Li, Yuantao Zhang, Yongsheng Chen, Xinjian Li, Di Wu, Tingting Xu, Chongxin Shan, and Guotong Du
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PEROVSKITE , *LIGHT emitting diodes , *QUANTUM dots - Abstract
Perovskite light-emitting diodes (PeLEDs), because of its fundamental scientific importance and practical applications in the fields of low-cost light source or display applications, have drawn worldwide attention in recent years. However, PeLEDs available today suffer from a compromise in their emission efficiency and operation stability. In this study, we designed and fabricated a stacking all-inorganic multilayer structure by using inorganic perovskite CsPbBr3 quantum dots (QDs) as the emissive layer and inorganic n-type MgZnO and p-type MgNiO as the carrier injectors, respectively. Through energy band engineering of carrier injectors by Mg incorporation and their thickness optimization, PeLEDs with maximum luminance of 3809 cd/m2, luminous efficiency of 2.25 cd/A, and external quantum efficiency of 2.39% have been realized, which are much better than most PeLEDs from CH3NH3PbBr3 films, and comparable with the highest results reported on CsPbBr3 QDs LEDs. More importantly, the unencapsulated PeLEDs in a continuous current mode demonstrate a remarkable operation stability against water and oxygen degradation. After a continuous operation for 10 h under a dc bias (10.0 V), nearly 80% of the original efficiency of the PeLEDs has been retained, greatly superior to reference and other previously reported devices constructed with conventional organic carrier injectors. Our results obtained open possibilities for the design and development of high-efficiency and air-stable PeLEDs that are not dependent on expensive and less-stable organic carrier injectors. [ABSTRACT FROM AUTHOR]
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- 2017
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5. Fluorescent Biosensors Based on Single-Molecule Counting.
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Fei Ma, Ying Li, Bo Tang, and Chun-yang Zhang
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FLUORESCENCE , *MOLECULAR diagnosis , *BIOMOLECULE analysis , *BIOCHEMISTRY , *SIGNAL processing - Abstract
Conspectus: Biosensors for highly sensitive, selective, and rapid quantification of specific biomolecules make great contributions to biomedical research, especially molecular diagnostics. However, conventional methods for biomolecular assays often suffer from insufficient sensitivity and poor specificity. In some case (e.g., early disease diagnostics), the concentration of target biomolecules is too low to be detected by these routine approaches, and cumbersome procedures are needed to improve the detection sensitivity. Therefore, there is an urgent need for rapid and ultrasensitive analytical tools. In this respect, single-molecule fluorescence approaches may well satisfy the requirement and hold promising potential for the development of ultrasensitive biosensors. Encouragingly, owing to the advances in single-molecule microscopy and spectroscopy over past decades, the detection of single fluorescent molecule comes true, greatly boosting the development of highly sensitive biosensors. By in vitro/in vivo labeling of target biomolecules with proper fluorescent tags, the quantification of certain biomolecule at the single-molecule level is achieved. In comparison with conventional ensemble measurements, single-molecule detection-based analytical methods possess the advantages of ultrahigh sensitivity, good selectivity, rapid analysis time, and low sample consumption. Consequently, single-molecule detection may be potentially employed as an ideal analytical approach to quantify low-abundant biomolecules with rapidity and simplicity. In this Account, we will summarize our efforts for developing a series of ultrasensitive biosensors based on single-molecule counting. Single-molecule counting is a member of single-molecule detection technologies and may be used as a very simple and ultrasensitive method to quantify target molecules by simply counting the individual fluorescent bursts. In the fluorescent sensors, the signals of target biomolecules may be translated to the fluorescence signals by specific in vitro/in vivo fluorescent labeling, and consequently, the fluorescent molecules indicate the presence of target molecules. The resultant fluorescence signals may be simply counted by either microfluidic device-integrated confocal microscopy or total internal reflection fluorescence-based single-molecule imaging. We have developed a series of single-molecule counting-based biosensors which can be classified as separation-free and separation-assisted assays. As a proof-of-concept, we demonstrate the applications of single-molecule counting-based biosensors for sensitive detection of various target biomolecules such as DNAs, miRNAs, proteins, enzymes, and intact cells, which may function as the disease-related biomarkers. Moreover, we give a summary of future directions to expand the usability of single-molecule counting-based biosensors including (1) the development of more user-friendly and automated instruments, (2) the discovery of new fluorescent labels and labeling strategies, and (3) the introduction of new concepts for the design of novel biosensors. Due to their high sensitivity, good selectivity, rapidity, and simplicity, we believe that the single-molecule counting-based fluorescent biosensors will indubitably find wide applications in biological research, clinical diagnostics, and drug discovery. [ABSTRACT FROM AUTHOR]
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- 2016
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6. Silk Sericin-Functionalized Bacterial Cellulose as a Potential Wound-Healing Biomaterial.
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Lamboni, Lallepak, Ying Li, Jianfeng Liu, and Guang Yang
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SERICIN , *CELLULOSE , *BIOMATERIALS , *WOUND healing , *CYTOPROTECTION , *HYDROGEN bonding - Abstract
Bacterial cellulose (BC) is a polysaccharide known as a suitable matrix for proper wound healing. To improve this ability, BC was functionalized with silk sericin (SS) that has cytoprotective and mitogenic effects. The composites obtained by solution impregnation were stabilized by hydrogen bonds, and SS could be released in a controlled manner. The constructs were highly porous with interconnected pores allowing for high water uptake that varied with the SS concentration used for sample preparation. While SS did not disrupt the stability of the BC network, soluble SS diffusing from the composites did not influence keratinocyte growth but enhanced fibroblast proliferation, which would further optimize the wound healing process and improve extracellular matrix production, accelerating healing. Further, improved cell viability was observed upon the composites. Because of their attractive structure and properties, these BC-SS biomaterials represent potential candidates not only for wound dressing applications but also for tissue engineering. [ABSTRACT FROM AUTHOR]
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- 2016
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7. Tuning the Colors of the Dark Isomers of Photochromic Boron Compounds with Fluoride Ions: Four-State Color Switching.
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Mellerup, Soren K., Ying-Li Rao, Amarne, Hazem, and Suning Wang
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BORON compounds , *FUNCTIONAL groups , *PHOTOCHROMIC materials , *ORGANOBORON compounds , *COLOR change sensors - Abstract
Combining a three-coordinated boron (BMes2) moiety with a four-coordinated photochromic organoboron unit leads to a series of new diboron compounds that undergo four-state reversible color switching in response to stimuli of light, heat, and fluoride ions. Thus, these hybrid diboron systems allow both convenient color tuning/switching of such photochromic systems, as well as visual fluoride sensing by color or fluorescent emission color change. [ABSTRACT FROM AUTHOR]
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- 2016
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8. α-Regioselective Barbier Reaction of Carbonyl Compounds and Allyl Halides Mediated by Praseodymium.
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San Wu, Ying Li, and Songlin Zhang
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The first utility of praseodymium as a mediating metal in the Barbier reaction of carbonyl compounds with allyl halides was reported in this paper. In contrast to the traditional metal-mediated or catalyzed Barbier reactions, exclusive α-adducts were obtained in this one-pot reaction with a broad scope of substrates and feasible reaction conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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9. Enantiomeric Excess-Tuned 2D Structural Transition: From Heterochiral to Homochiral Supramolecular Assemblies.
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Shu-Ying Li, Ting Chen, Lin Wang, Bing Sun, Dong Wang, and Li-Jun Wan
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SUPRAMOLECULES , *ENANTIOMERS , *CHIRALITY , *SOLUTION (Chemistry) , *DIMERS - Abstract
Spontaneous resolution of enantiomers is an intriguing and important phenomenon in surface chirality studies. Herein, we report on a two-dimensional (2D) structural transition from the heterochiral to homochiral assembly tuned by changing the enantiomeric excess (ee) of enantiomers in the solution phase. Enantiomers cocrystallize as racemates on the surface when the ee of the R-enantiomer (or S-enantiomer) remains below a critical value, whereas chiral segregation is achieved, and globally homochiral surfaces composed of exclusively one enantiomer are obtained as the critical ee is exceeded. The heterochiral-homochiral transition is ascribed to the formation of energetically unfavored homochiral molecular dimers under the control of the majority-rules principle at high ee values. Such results present an intriguing phenomenon in chiral ordering at surfaces, promising a new enlightenment toward understanding chiral resolution and the evolution of chirality. [ABSTRACT FROM AUTHOR]
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- 2016
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10. One-Pot Sequential Aldol Condensation and Hydrogenation of n-Butyraldehyde to 2-Ethylhexanol.
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Ying Li, Xiaohong Liu, Hualiang An, Xinqiang Zhao, and Yanji Wang
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ALDOL condensation , *HYDROGENATION , *BUTYRALDEHYDE , *ETHYLHEXANOL , *PROPENE , *HYDROFORMYLATION - Abstract
2-Ethylhexanol (2EHO) is an important organic chemical. The industrial production of 2EHO comprises three units: propylene hydroformylation to n-butyraldehyde, n-butyraldehyde self-condensation to 2-ethyl-2-hexenal (2E2H), and 2E2H hydrogenation to 2EHO. In the present work, 2EHO was synthesized by one-pot sequential aldol condensation and hydrogenation of n-butyraldehyde. Among a series of metal-solid acid bifunctional catalysts, Ni/La-Al2O3 showed a better catalytic performance. The effect of reaction conditions on the one-pot sequential synthesis of 2EHO catalyzed by Ni/La-Al2O3 was investigated, and the suitable reaction conditions were obtained as follows: weight percentage of Ni/La-Al2O3 = 15%, self-condensation reaction conducted at 180 °C for 8 h, and then hydrogenation reaction conducted at 180 °C for 6 h under 4 MPa H2 pressure. Under the above reaction conditions, n-butyraldehyde conversion attained 100% at a 2EHO selectivity of 67.0%. The inhibition of Ni to n-butyraldehyde self-condensation reaction is responsible for the low selectivity of 2EHO. On the basis of the analysis of the reaction system, some side reactions in the one-pot sequential synthesis of 2EHO were proposed. The deactivation of Ni/La-Al2O3 was due to the agglomeration of Ni and La2O3 particles and the occurrence of γ-Al2O3 hydration. Introduction of some hydrophobic groups on the surface of γ-Al2O3 could effectively inhibit the hydration of γ-Al2O3. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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11. Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal--Ligand Coordination.
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Ying-Li Rao, Chortos, Alex, Pfattner, Raphael, Lissel, Franziska, Yu-Cheng Chiu, Feig, Vivian, Jie Xu, Tadanori Kurosawa, Xiaodan Gu, Chao Wang, Mingqian He, Jong Won Chung, and Zhenan Bao
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DIELECTRICS research , *ELASTOMERS , *POLYDIMETHYLSILOXANE , *CROSSLINKING site (Polymers) , *CROSSLINKED polymers - Abstract
A self-healing dielectric elastomer is achieved by the incorporation of metal--ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'- bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe2+ and Zn2+ with various counteranions. The kinetically labile coordination between Zn2+ and bipyridine endows the polymer fast selfhealing ability at ambient condition. When integrated into organic fieldeffect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl- anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4,- CIO4-, CF3SO3-) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal--ligand cross-linked polymers. [ABSTRACT FROM AUTHOR]
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- 2016
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12. Tube-graft-Sheet Nano-Objects Created by A Stepwise Self-Assembly of Polymer-Polyoxometalate Hybrids.
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Jing Tang, Xue-Ying Li, Han Wu, Li-Jun Ren, Yu-Qi Zhang, Hai-Xia Yao, Min-Biao Hu, and Wei Wang
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MOLECULAR self-assembly , *POLYOXOMETALATES , *CHEMICAL sample preparation , *COMPLEX compounds , *NANOPARTICLE synthesis , *SOLUTION (Chemistry) - Abstract
In this work, we report the preparation of complex nano-objects by means of a stepwise self-assembly of two polymer-polyoxometalate hybrids (PPHs) in solution. The PPHs are designed and synthesized by tethering two linear poly(e-caprolactone)s (PCL) of different molecular weights (MW) on a complex of a Wells-Dawson-type polyoxometalate (POM) cluster and its countraions. The higher MW PCL-POM self-assembled into nanosheets, while the lower MW PCL-POM assembled into nanotubes just by altering the ratio of water in the DMF-water mixed solvent system. The two nano-objects have a similar membrane structure in which a PCL layer is sandwiched by the two POM-based complex layers. The PCL layer in the nanosheets is semicrystalline, while the PCL layer in the nanotubes is amorphous. We further exploited this MW-dependence to self-assemble the nanotubes on the nanosheet edges to create complex tube-graft-sheet nano-objects. We found that the nanotubes nucleate on the four {110} faces of the PCL crystal and then further grow along the crystallographic b-axis of the PCL crystal. Our findings offer hope for the further development of nano-objects with increasing complexity. [ABSTRACT FROM AUTHOR]
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- 2016
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13. Photoresponsive Molecular Switch for Regulating Transmembrane Proton-Transfer Kinetics.
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Ying Li, Tse, Edmund C. M., Barile, Christopher J., Gewirth, Andrew A., and Zimmerman, Steven C.
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BILAYER lipid membranes , *PROTON transfer reactions , *ELECTROCATALYSIS , *OXIDATION-reduction reaction , *ISOMERS , *IRRADIATION , *MOLECULAR switches - Abstract
To control proton delivery across biological membranes, we synthesized a photoresponsive molecular switch and incorporated it in a lipid layer. This proton gate was reversibly activated with 390 nm light (Z-isomer) and then deactivated by 360 nm irradiation (E-isomer). In a lipid layer this stimuli responsive proton gate allowed the regulation of proton flux with irradiation to a lipid-buried O2 reduction electrocatalyst. Thus, the catalyst was turned on and off with the E-to-Z interconversion. This light-induced membrane proton delivery system may be useful in developing any functional device that performs proton-coupled electron-transfer reactions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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14. Diastereoisomers of Ruthenium Dyes with Unsymmetric Ligands for DSC: Fundamental Chemistry and Photovoltaic Performance.
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Jheng-Ying Li, Chia Lee, Chia-Yuan Chen, Wen-Long Lee, Ren Ma, and Chun-Guey Wu
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RUTHENIUM , *LIGANDS (Chemistry) , *DIASTEREOISOMERS , *PHOTOVOLTAIC effect , *ISOMERS - Abstract
A new thiocyanic acid-free ruthenium sensitizer, CYC-B29, containing two unsymmetrical ancillary ligands, was synthesized, and its three diastereoisomers CYC-B29-CC, CYC-B29-TT, and CYC-B29-CT with significantly different optical, electronic, and electrochemical properties were carefully separated. CYC-B29-TT with the smallest size has the strongest absorption coefficient of the MLCT band, the shortest λmax, the lowest highest occupied molecular orbital level and the highest dye loading. Therefore, dye-sensitized solar cell based on CYC-B29-TT has the highest efficiency, which is two times higher than that of CYC-B29-CC-sensitized device and 10% higher than that of N719-based cell. Time-dependent density functional theory-calculated transition bands for the three isomers are not identical, and only CYC-B29-TT has the calculated transition bands close to the experimental absorption profile. Although the calculated transition bands for CYC-B29-CC and CYC-B29-CT are not consistent with the experimental data, the ground-state vertical excitation energy with oscillator strength and electron-density difference map data combining with the dye loading predict correctly the order of the photocurrent for the three isomers sensitized devices. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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15. Assessing Long-Term Trend of Particulate Matter Pollution in the Pearl River Delta Region Using Satellite Remote Sensing.
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Ying Li, Changqing Lin, Lau, Alexis K. H., Chenghao Liao, Yongbo Zhang, Wutao Zeng, Chengcai Li, Fung, Jimmy C. H., and Tse, Tim K. T.
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PARTICULATE matter , *REMOTE sensing , *ADVERSE health care events , *AIR pollution - Abstract
Serious particulate matter (PM) pollution problems in many polluted regions of China have been frequently reported in recent years. Long-term exposure to ambient PM pollution is significantly associated with adverse health effects. Characterizing the long-term trends and variation in PM pollution is a basic requirement for evaluating long-term exposure and for guiding future policies to reduce the effects of air pollution on health. However, long-term, ground-based PM measurements are only available at a few fixed stations. In this study, an algorithm is developed and validated to estimate PM concentrations based on the satellite atmospheric optical depth with 1 km spatial resolution. The long-term trends of PM10 concentrations in the entire Pearl River Delta (PRD) region and different cities are quantified and discussed. From 2001 to 2013, the PM10 pollution of the entire PRD region was dominated by a decreasing trend of -0.15 ± 0.23 µg/m³·yr. This decreasing PM10 trend was apparent over 75% of the PRD area, with the most significant decreases observed in the center of the region. However, the remaining 25%, mostly located in the outskirts of the region, showed an increasing PM10 trend. This overall decreasing trend indicates the effectiveness of the control measures applied in the past decade for the primary pollutants. [ABSTRACT FROM AUTHOR]
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- 2015
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16. Competitive Volumetric Bar-Chart Chip with Real-Time Internal Control for Point-of-Care Diagnostics.
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Ying Li, Jie Xuan, Tom Xia, Xin Han, Yujun Song, Zheng Cao, Xin jiang, Yi Guo, Ping Wang, and Lidong Qin
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VOLUMETRIC analysis , *ENZYME-linked immunosorbent assay , *CHORIONIC gonadotropins , *GLYCOPROTEIN hormones , *IMMUNOENZYME technique - Abstract
Point-of-care (POC) testing has become widely used in clinical analysis because of its speed and portability; however, POC tools, such as lateral flow assays, suffer from low specificity, unclear readouts, and susceptibility to environmental and user errors. Herein, we report an ELISA-based competitive volumetric bar-chart chip (CV-chip) that eliminates these limitations. The CV-chip displays the readout in the form of ink bar charts based on direct competition between gases generated by the sample and the internal control. By employing a "competition mode", this platform decreases the potential influence of background resulting from environmental factors and provides visually clear positive or negative results without the requirement of calibration. In addition, the on-chip comparison enables the device to distinguish imperceptible differences (less than 1.3-fold) in human chorionic gonadotropin (hCG) concentrations that are near the cutoff value for pregnancy (∼1.4 ng/mL). We also utilized the ELISA-based CV-chip to successfully detect biomarkers from cancer cells. As a proof-of-concept application in a clinical setting, the CV-chip was employed to evaluate the status of drugs of abuse in 18 patients. For six different drugs, zerofalse-positive and very few false-negative (<2%) results were reported in more than 100 tests. This new ELISA platform offers a clinical diagnostics tool that is portable and easy to use, and provides improved clarity and sensitivity due to the inclusion of a real-time internal control. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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17. Evaluation of the Effect of the Structure of Bacterial Cellulose on Full Thickness Skin Wound Repair on a Microfluidic Chip.
- Author
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Ying Li, Shiwen Wang, Rong Huang, Zhuo Huang, Binfeng Hu, Wenfu Zheng, Guang Yang, and Xingyu Jiang
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BACTERIAL cells , *CELLULOSE , *CHEMICAL structure , *SKIN wound treatment , *MICROFLUIDIC analytical techniques , *TISSUE engineering - Abstract
Bacterial cellulose (BC) is a kind of nanobiomaterial for tissue engineering. How the nanoscale structure of BC affects skin wound repair is unexplored. Here, the hierarchical structure of BC films and their different effects on skin wound healing were studied both in vitro and in vivo. The bottom side of the BC film had a larger pore size, and a looser and rougher structure than that of the top side. By using a microfluidics-based in vitro wound healing model, we revealed that the bottom side of the BC film can better promote the migration of cells to facilitate wound healing. Furthermore, the full-thickness skin wounds on Wistar rats demonstrated that, compared with gauze and the top side of the BC film, the wound covered by the bottom side of the BC film showed faster recovery rate and less inflammatory response. The results indicate that the platform based on the microfluidic chip provide a rapid, reliable, and repeatable method for wound dressing screening. As an excellent biomaterial for wound healing, the BC film displays different properties on different sides, which not only provides a method to optimize the biocompatibility of wound dressings but also paves a new way to building heterogeneous BC-based biomaterials for complex tissue engineering. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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18. Reaction of Arynes with Sulfoxides.
- Author
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Hong-Ying Li, Li-Juan Xing, Mei-Mei Lou, Han Wang, Rui-Hua Liu, and Bin Wang
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CHEMICAL reactions , *ARYNE , *SULFOXIDES , *CHEMICAL bonds , *SULFUR compounds , *YLIDES , *METHYLENE group , *CARBONYL compounds - Abstract
A S-O bond insertion reaction of sulfoxides with arynes is reported. This reaction represents a rare instance of semipolar single bond insertion in aryne chemistry. The study of mechanism indicates that a sulfur ylide triggered by aryne is the key intermediate, which further transfers its methylene group to carbonyl compounds to give epoxides and thioethers through a sequential process. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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19. Ultrafast Microfluidic Mixer for Tracking the Early Folding Kinetics of Human Telomere G-Quadruplex.
- Author
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Ying Li, Chao Liu, Xiaojun Feng, Youzhi Xu, and Bi-Feng Liu
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MICROFLUIDIC devices , *ANALYTICAL mechanics , *MACROMOLECULES , *TELOMERES , *MOLECULES - Abstract
The folding of G-quadruplex is hypothesized to undergo a complex process, from the formation of a hairpin structure to a triplex intermediate and to the final G-quadruplex. Currently, no experimental evidence has been found for the hairpin formation, because it folds in the time regime of 10-100 μs, entailing the development of microfluidic mixers with a mixing time of less than 10 fts. In this paper, we reported an ultrarapid micromixer with a mixing time of S.5 μs, which represents the fastest turbulent micromixer to our best knowledge. Evaluations of the micromixer were conducted to confirm its mixing efficiency for small molecules and macromolecules. This new micromixer enabled us to interrogate the hairpin formation in the early folding process of human telomere G-quadruplex The experimental kinetic evidence for the formation of hairpin was obtained for the first time. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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20. Reactivity and ElectronicProperties of a FerroceneMolecule Bearing an N,C-Chelated BMes2Unit.
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Ying-Li Rao, Tetsuro Kusamoto, Ryota Sakamoto, Hiroshi Nishihara, and Suning Wang
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CHEMICAL synthesis , *FERROCENE , *FERROCENE derivatives , *ORGANIC compound derivatives , *CHELATE physiology , *COORDINATION polymers synthesis , *NITROGEN spectra - Abstract
A dimesitylboron-functionalizedbenzimidazolylferrocene, B(2-ferrocenyl-N-Me-benzimidazolyl)Mes2(1), hasbeen synthesized and fully characterized. The B–N bond in 1was found to undergo a dynamic dissociation/associationprocess in solution, leading to a dynamic exchange of the two mesitylsbound to the boron atom and slow hydrolysis of 1underambient conditions. The hydrolyzed product 2-BMes(OH)-1-(N-methylbenzimidazol-2-yl)ferrocene (2) was isolatedand characterized, in which the boron center has a trigonal-planargeometry with one of the mesityls being replaced by an OH–group. The photoisomerization process of the boron unit in 1was fully inhibited by the low lying d–d/MLCT statesof the ferrocene unit. Compound 1can be oxidized readilyby I2, forming the ferrocenium species [1+]I3-(3). NMR and EPR data for 3indicated a notable spin delocalization through space fromthe Fe(III) center to a flanking mesityl group. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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21. Isothermally Sensitive Detection of Serum Circulating miRNAs for Lung Cancer Diagnosis.
- Author
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Ying Li, Li Liang, and Chun-yang Zhang
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LUNG cancer diagnosis , *MICRORNA , *BIOMARKERS , *DNA polymerases , *SEQUENCE alignment , *POLYMERASE chain reaction - Abstract
Tumor-derived miRNAs in serum are emerging as the new noninvasive biomarkers for the diagnosis of human cancers, especially at their early stage. An ideal method with high sensitivity, excellent selectivity, a simple procedure, and small amounts of starting materials is imperative for the detection of clinic circulating miRNAs. Here, we develop a new method for isothermally sensitive detection of serum miRNAs using hairpin probe-based rolling circle amplification (HP-RCA). This method exhibits ultrahigh sensitivity toward lung cancer-related miR-486-5p with a detection limit of as low as 10 fM and a large dynamic range of 6 orders of magnitude, and it can even discriminate miR-486-5p from both miRNAs with high sequence homology and its precursors (pre-miRNAs). More importantly, this method can directly and accurately distinguish the expression of serum miR-486-5p among six nonsmall-cell lung carcinoma (NSCLC) patients and six healthy persons, holding a great potential for further applications in the clinical diagnosis of lung cancers. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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22. Photo- and Thermal-Induced Multistructural Transformation of 2-Phenylazolyl Chelate Boron Compounds.
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Ying-Li Rao, Amarne, Hazem, Chen, Leanne D., Brown, Matthew L., Mosey, Nicholas J., and Suning Wang
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CHELATES , *BORON compounds , *ISOMERS , *IRRADIATION , *HEATING , *PHOTOISOMERIZATION , *DIASTEREOISOMERS , *AZOLES - Abstract
The new N,C-chelate boron compounds B(2-phenylazolyl)Mes2 [Mes = mesityl; azolyl = benzothiazolyl (1a), 4-methylthiazolyl (2a), benzoxazolyl (3a), benzimidazolyl (4a)] undergo an unprecedented multistructural transformation upon light irradiation or heating, sequentially producing isomers b, c, d, and e. The dark isomers b generated by photoisomerization of a undergo a rare thermal intramolecular H-atom transfer (HAT), reducing the azole ring and generating new isomers c, which are further transformed into isomers d. Remarkably, isomers d can be converted to their diastereomers e quantitatively by heating, and e can be converted back to d by irradiation at 300 nm. The structures of isomers 1d and 1e were established by X-ray diffraction. The unusual HAT reactivity can be attributed to the geometry of the highly energetic isomers b and the relatively low aromaticity of the azole rings. The boryl unit plays a key role in the reversible interconversion of d and e, as shown by mechanistic pathways established through DFT and TD-DFT calculations. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
23. A Rapid Microfluidic Mixer for High-Viscosity Fluids To Track Ultrafast Early Folding Kinetics of G-Quadruplex under Molecular Crowding Conditions.
- Author
-
Ying Li, Youzhi Xu, Xiaojun Feng, and Bi-Feng Liu
- Subjects
- *
MICROFLUIDIC analytical techniques , *VISCOSITY , *TELOMERES , *MACROMOLECULES , *MOLECULAR conformation , *MIXING machinery - Abstract
Tracking the folding kinetics of macromolecules under molecular crowding conditions represents a tremendous challenge due to the high viscosity of the solution. In this paper, we report a unique T-type microfluidic mixer with seven consecutive ω-shaped baffles for fast mixing of high-viscosity fluids. Numerical simulations and experimental characterizations proved that the micromixer could achieve a mixing time of 579.4 μs for solutions with viscosities about 33.6 times that of pure water. Over a 1000-fold improvement in mixing dead time was accomplished in comparison to those reported previously. We further used this highly efficient micromixer to track the early folding kinetics of human telomere G-quadruplex under molecular crowding conditions. Results indicated an exponential process in the initial folding phase of G-quadruplex, and the G-quadruplex formed a more compact structure under higher degrees of molecular crowding conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
24. Inverse-Micelle-Encapsulated Water-Enabled Bond Breaking of Dialkyl Diselenide/Disulfide: A Critical Step for Synthesizing High-Quality Gold Nanoparticles.
- Author
-
Zaluzhna, Oksana, Ying Li, Allison, Thomas C., and Tong, YuYe J.
- Subjects
- *
REVERSED micelles , *GOLD nanoparticle synthesis , *SCISSION (Chemistry) , *WATER , *MICROENCAPSULATION , *SELENIDES , *DISULFIDES - Abstract
Inverse-micelle-encapsulated water formed in the two-phase Brust-Schiffrin method (BSM) synthesis of Au nanoparticles (NPs) is identified as essential for dialkyl diselenide/disulfide to react with the Au(III) complex in which the Se-Se/S-S bond is broken leading to formation of higher-quality Au NPs. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
25. Allylic Amination and N-Arylation-Based Domino Reactions Providing Rapid Three-Component Strategies to Fused Pyrroles with Different Substituted Patterns.
- Author
-
Bo Jiang, Ying Li, Man-Su Tu, Shu-Liang Wang, Shu-Jiang Tu, and Guigen Li
- Subjects
- *
ALLYLIC amination , *ARYLATION , *PYRROLES , *SUBSTITUTION reactions , *ACETIC acid , *AMINO acids - Abstract
New three-component domino reaction providing divergent approaches to multifunctionalized fused pyrroles with different substituted patterns have been established (40 examples). The direct C(sp³)-N bond formation was achieved through intermolecular allylic amination in a one-pot operation, and N-arylation of amines was realized by varying N-amino acid enaminones. The reaction is easy to perform simply by mixing three common reactants in acetic acid under microwave heating. The reaction proceeds at fast rates and can be finished within 30 min, which makes workup convenient to give good chemical yields. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
26. Stepwise Intramolecular Photoisomerization of NHC-Chelate Dimesitylboron Compounds with C—C Bond Formation and C—H Bond Insertion.
- Author
-
Ying-Li Rao, Chen, Leanne D., Mosey, Nicholas J., and Suning Wang
- Subjects
- *
PHOTOISOMERIZATION , *BORON compounds , *CARBON-carbon bonds , *INSERTION reactions (Chemistry) , *CARBON-hydrogen bonds , *X-ray diffraction measurement , *MOLECULAR structure of heterocyclic compounds , *MOLECULAR structure of carbenes - Abstract
C,C-chelate dimesitylboron (BMes2) compounds containing an N-heterocyclic carbene (NHC) donor have been obtained. Single-crystal X-ray diffraction analyses established that the boron atom in these compounds is bound by four carbon atoms in a distorted tetrahedral geometry. Compared to previously reported N,C-chelate dimesitylboron compounds, the new C,C-chelate boron compounds have a much larger HOMO-LUMO energy gap (>3.60 eV). They do, however, respond to UV irradiation (300 nm) in the same manner as N,C-chelate BMes2 compounds do, undergoing photoisomerization and converting to an intensely colored (yellow or orange) isomer A quantitatively, with a high quantum efficiency (0.60-0.75). NMR and single-crystal X-ray diffraction analyses established that the structure of A is similar to the dark isomers obtained from N,C-chelate BMes2 compounds. However, unlike the N,C-chelate dark isomers that have the tendency to thermally reverse back to the light colored isomers, the isomers A of the C,C-chelate BMes2 are thermally stable and no reverse isomerization was observed even when heated to 80 °C (or 110 °C) for hours. The most unusual finding is that isomers A undergo further photoisomerization when irradiated at 350 nm, forming a new colorless species B nearly quantitatively. NMR and single-crystal X-ray diffraction analyses established the structure of isomer B, which may be considered as an intramolecular C-H insertion product via a borylene intermediate. Mechanistic aspects of this unusual two-step photoisomerization process have been examined by DFT computational studies. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
27. Analysis of MicroRNA-Induced Silencing Complex-Involved MicroRNA-Target Recognition by Single-Molecule Fluorescence Resonance Energy Transfer.
- Author
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Ying Li and Chun-yang Zhang
- Subjects
- *
MICRORNA , *GENE silencing , *SINGLE molecules , *FLUORESCENCE resonance energy transfer , *GENE targeting - Abstract
MicroRNAs (miRNAs) are important regulators of gene expression that control almost every physiological and pathological process. Although the complementarity between the seed region of a miRNA and its target mRNA is usually deemed as the key determinant in the miRNA-target recognition in animals, the mechanism of their recognition still remains enigmatic as more and more exceptions challenge the seed rule. Herein, we employ single-molecule fluorescence resonance energy transfer (smFRET) to investigate human miRNA-induced silencing complex (miRISC)-involved miRNA-target recognition with either perfect base pairing or poor seed match in real time. Our results demonstrate that the recognition between mammalian mIRNA and its target with perfect base pairing proceeds in a two-state model as prokaryotic guide DNA-mediated recognition, suggesting a conserved pattern of guide RNA/DNA strand recognition. In addition to the general rule of mIRNA-target recognition, our results reveal that annealing between miRNA and its target with poor seed match proceeds in a stepwise way, which is in accordance with the increase in the number of conformational states of miRNA-target duplex accommodated by the miRJSC, suggesting the structural plasticity of human miRISC to conciliate the mismatches m seed region. This new dynamic information revealed by smPRET has an important implication for comprehensive understanding of the role of m1RJSC in the target recognition in mammals. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
28. Theoretical Study on Polynuclear Superalkali Cations with Various Functional Groups as the Central Core.
- Author
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Jing Tong, Ying Li, Di Wu, and Zhi-Jian Wu
- Subjects
- *
CATIONS , *ELECTRON affinity , *FUNCTIONAL groups , *LITHIUM , *ALKALI metals , *COORDINATION compounds , *ATOMS - Abstract
A new series of polynuclear superalkali cations YLi3+ (Y = CO3, SO3, SO4, O4, and O5) has been created when the central group is surrounded by alkali atoms. The structural characteristics and stabilities of these systems are provided on the basis of ab initio methods. In the lowest-energy structure of the CO3Li3+, SO3Li3+, and SO4Li3+ cations, the central Y (Y = CO3, SO3, and SO4 ) group features a slight distortion. The global minima of O4Li3+ and O5Li3+ are of the forms O2-(Li+)3O2- and O2-(Li+)3O3-, respectively, both of which contain two monovalent ion units. The structural integrity of the central Y group and the arrangement of the Hthium ligands are two influencing factors on the vertical electron affinities (EAvert) for the YLi3+ species. The YLi3+ cation, with its lithium ligands being distributed evenly or far from each other, tends to exhibit a low EAvert value, whereas a greater extent of cleavage of the central Y group leads to a higher EAvert value and even makes some species lose their superalkali nature. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
29. Four-Coordinate Organoboron Compounds with a π-Conjugated Chelate Ligand for Optoelectronic Applications.
- Author
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Ying-Li Rao and Suning Wang
- Subjects
- *
ORGANOBORON compounds , *CHELATES , *OPTOELECTRONICS , *ELECTRON transport , *LIGHT emitting diodes , *TRANSISTORS , *PHOTOCHROMIC materials - Abstract
Four-coordinate organoboron compounds with a π-conjugated chelate backbone have emerged recently as highly attractive materials for a number of applications including use as emitters and electron-transport materials for organic light-emitting diodes (OLEDs) or organic field transistors, photoresponsive materials, and sensory and imaging materials. Many applications of this class of boron compounds stem from the electronic properties of the π-conjugated chelate backbone. Charge-transfer transitions from an aromatic substituent attached to the boron center of the p-conjugated chelate backbone and steric congestion have also been found to play important roles in the luminescent and photochromic properties of the four-coordinate boron compounds. This article provides an update-to-date account on the application aspects of this important class of compounds in materials science with the emphasis on OLED applications and photochromic switching. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
30. Synthesis of a Redox-Responsive Quadruple Hydrogen-Bonding Unit for Applications in Supramolecular Chemistry.
- Author
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Ying Li, Park, Taiho, Kwansima Quansah, J., and Zimmerman, Steven C.
- Subjects
- *
OXIDATION-reduction reaction , *HYDROGEN bonding , *SUPRAMOLECULAR chemistry , *POLYMER networks , *VOLTAMMETRY - Abstract
A redox-responsive quadruple hydrogen-bonding module (eDAN) has been developed. The strong binding between the reduced form and its partner (DeUG) can be significantly decreased upon oxidation but restored upon subsequent reduction. This on-off switch was successfully applied to provide reversible control of macroscopic supramolecular polymer networks. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
31. Mechanisms for the Reaction of Water, Butadiene, and Palladium Complex with 1,2-Dimetallacyclohexene (R2MMR2, M = C, Si, Ge, Sn, Pb). A Theoretical Study.
- Author
-
Bo-Ying Li, Jeng-Horng Sheu, and Ming-Der Su
- Subjects
- *
REACTION mechanisms (Chemistry) , *WATER , *BUTADIENE , *TRANSITION metal complexes , *DENSITY functionals , *RING formation (Chemistry) , *REACTIVITY (Chemistry) , *ACTIVATION (Chemistry) , *ATOMIC weights - Abstract
The potential energy surfaces for the chemical reactions of six-membered cyclic dimetallaalkenes containing the MM doubly bonded species Rea-MM, where M = C, Si, Ge, Sn, and Pb, were studied, using the density functional theory (B3LYP/LANL2DZ) method. Three kinds of chemical reaction, water addition, [2+4] Diels–Alder cycloaddition, and palladium complexation, were also used to study the chemical reactivity of these group 14 Rea-MMmolecules. In principle, our present theoretical work suggests that the smaller the singlet–triplet splitting of the Rea-MM, the lower are its activation barriers and, in turn, the more rapid are its chemical reactions with other molecules. These theoretical investigations indicate that the relative chemical reactivity increases in the order Rea-MM-C< Rea-MM-Si< Rea-MM-Ge< Rea-MM-Sn< Rea-MM-Pb. That is, the smaller the atomic weight of the group 14 atom (M), the more stable is its Rea-MMto chemical reaction. As a result, we predict that the group 14 Rea-MM(M = C and Si) compounds should be stable and readily synthesized and isolated at room temperature. Our computational results are in good agreement with the available experimental observations. The present explanation for the reactivity of six-membered cyclic Rea-MMcompounds promises a deeper understanding and may have a future application in main group chemistry. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
32. Impact of Cyclometalation and π-Conjugation on Photoisomerization of an N,C-Chelate Organoboron Compound.
- Author
-
Ying-Li Rao and Suning Wang
- Subjects
- *
ORGANOMETALLIC chemistry , *PHOTOISOMERIZATION , *CHELATES , *ORGANOBORON compounds , *COORDINATION compounds , *PHOTOCHROMIC materials , *FUNCTIONAL groups , *X-ray diffraction , *PHOSPHORESCENCE - Abstract
N,C-Chelate four-coordinate boron compounds that contain a B(ppy)Mes2unit (ppy = 2-phenylpyridyl, Mes = mesityl) are a new class of photochromic molecules discovered recently by our group that undergo photoisomerization upon exposure to light. To examine the influence of a covalently bound transition metal ion on the photochromic properties of this class of boron compounds, a new molecule (L1) that contains two linearly conjugated ppy units has been synthesized. A BMes2group was attached to L1via chelation with one of the ppy units, producing a new four-coordinate boron compound, B1. The reactions of B1with PtPh2(DMSO)2produced a Pt(II) cyclometalated compound, Pt1, where a PtPh(DMSO) unit is bound to the second ppy unit of B1. Replacement of DMSO in Pt1by p-t-Bu-pyridine provided a new compound, Pt2. A third Pt(II) compound, Pt3, where a Pt(dpm) group (dpm = dipivaloylmethane) is chelated to the second ppy site of B1, was also synthesized successfully. The crystal structures of B1and Pt3have been determined by single-crystal X-ray diffraction analyses. The photophysical and photochromic properties of B1and Pt1–Pt3have been examined. Experimental and computational studies established that Pt(II) cyclometalation to B1stabilizes a 3LC state that involves π→π* transitions localized on the ppy–ppy conjugated backbone. This 3LC state of the Pt(II) compounds is highly phosphorescent, with quantum efficiencies being 0.16, 0.13, and 0.45 for Pt1, Pt2, and Pt3, respectively, in toluene and at ambient temperature. The B(ppy)Mes2chromophore in all three Pt(II) compounds has been found to undergo photoisomerization in a similar manner to that of B1, but with a much lower quantum efficiency than B1. Deactivation of the photoisomerization process by the 3LC state has been found to be most likely responsible for the low photoisomerization quantum efficiency of the Pt(II) compounds. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
33. Hexaazatriphenylene Derivatives with Tunable Lowest Unoccupied Molecular Orbital Levels.
- Author
-
Ming Wang, Ying Li, Hui Tong, Yanxiang Cheng, Lixiang Wang, Xiabin Jing, and Fosong Wang
- Subjects
- *
PHENYL compounds , *MOLECULAR orbitals , *CONDENSATION , *ORGANIC synthesis , *PHOTOCHEMISTRY , *ELECTROCHEMICAL analysis , *PYRAZINES , *ENERGY levels (Quantum mechanics) - Abstract
A series of n-type hexaazatriphenylene derivatives were synthesized by condensation coupling of 1,2-diamines and 1,2-diketones. The study of their photophysical and electrochemical properties showed that their lowest unoccupied molecular orbital (LUMO) energy levels could be effectively tuned from â3.54 to â4.02 eV simply by increasing the number of pyrazine units in their molecular structures. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
34. Critical Role of Water and the Structure of Inverse Micelles in the Brust–Schiffrin Synthesis of Metal Nanoparticles.
- Author
-
Ying Li, Oksana Zaluzhna, and YuYe J. Tong
- Subjects
- *
MOLECULAR structure , *WATER , *MICELLES , *ORGANIC synthesis , *LIGANDS (Chemistry) , *COLLOIDAL gold , *MIXTURES , *THIOLS , *NUCLEAR magnetic resonance spectroscopy , *CHEMICAL reactions - Abstract
Although Brust–Schiffrin two-phase synthesis is a popular method for synthesizing ligand-protected metal nanoparticles with an average size of less than 5 nm, the details on how the reactions can be controlled from a mechanistic point of view are still unclear, therefore hindering efforts to synthesize monodisperse metal nanoparticles. It was recently discovered that this method is basically an inverse-micelle-based synthesis (Li, Y.; Zaluzhna, O.; Xu, B.; Gao, Y.; Modest, J. M.; Tong, Y. Y. J. J. Am. Chem. Soc.2011, 133, 2092). In this letter, the critical role of water and the structure of inverse micelles in typical synthesis of gold nanoparticles were further investigated. We found that (1) water encapsulated in the inverse micelles of [TOA]+that also hosted metal ions formed a hydrophilic microenvironment that acted as a reaction-enabling proton-accepting medium for the thiol protons (RS–H) and (2) not only the presence but also the amount of water in the reaction medium has a profound effect on the Au(I) precursor species (a pure [TOA][AuX2] complex or a mixture of a [TOA][AuX2] complex and polymeric [AuISR]nspecies), the reduction of Au(III) by thiols, and the formation of uniform small metal nanoparticles. A quantitative analysis of the 1H NMR of the encapsulated water enabled an estimation of the size and composition of the involved inverse micelles. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
35. Mechanistic Insights into the Brust–Schiffrin Two-Phase Synthesis of Organo-chalcogenate-Protected Metal Nanoparticles.
- Author
-
Ying Li, Zaluzhna, Oksana, Bolian Xu, Yuan Gao, Modest, Jacob M., and Tong, YuYe J.
- Subjects
- *
CHALCOGENS , *NANOPARTICLES , *MICELLES , *NUCLEATION , *METAL research - Abstract
New insights into the formation chemistry of chalcogenate-protected metal nanoparticles (NPs) synthesized via the well-known Brust-Schiffrin two-phase method are presented here. On the basis of Raman, NMR, and surface plasmon resonance characterizations, it is concluded that, before the formation of any metal-chalcogen bonds, metal nucleation centers/NPs are first formed inside the inverse micelles of the tetrabutylammonium bromide in the organic solvent, where the metal ions are reduced by NaBH4. The ensuing formation of the metal-chalcogen bonds between the naked metal NPs inside the micelles and the organochalcogen ligands in the organic solvent is the mechanism by which the further growth of the metal core can be controlled. This proposed mechanism is further examined in the formation of Ag and Cu NPs. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
36. Unsymmetrical Squaraines Incorporating the Thiophene Unit for Panchromatic Dye-Sensitized Solar Cells.
- Author
-
Jheng-Ying Li, Chia-Yuan Chen, Chuan-Pei Lee, Szu-Chien Chen, Tsu-Han Lin, Hui-Hsu Tsai, Kuo-Chuan Ho, and Chun-Guey Wu
- Subjects
- *
THIOPHENES , *DYE-sensitized solar cells , *ELECTRONS , *ETHYLENE , *BIOCONJUGATES , *PHENYL compounds , *AMINO acids , *PHOTONS , *ELECTRICITY - Abstract
Two unsymmetrical squaraines, where the electron-rich 3,4-ethylenedioxythiophene or bithiophene conjugated fragment was used to link unconventionally the squaraine core and the hexyloxyphenyl amino group, were applied for DSCs. The corresponding photovoltaic devices exhibit an attractively panchromatic response and also convert a portion of the near-infrared photons into electricity. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
37. Fractal Dimensions of Macroporous and Hypercrosslinked Polymeric Adsorbents from Nitrogen Adsorption Data.
- Author
-
Ying Li, Chao Long, Weihua Tao, Aimin Li, and Quanxing Zhang
- Subjects
- *
POROUS materials , *CROSSLINKED polymers , *NITROGEN absorption & adsorption , *SURFACE area , *PARTICLE size distribution , *TRANSMISSION electron microscopy , *PRESSURE , *ATMOSPHERIC temperature - Abstract
The nitrogen adsorption data of macroporous and hypercrosslinked adsorbents at 77 K were measured in the relative pressure range of 10â6to 0.99. The BrunauerâEmmettâTeller (BET) surface area, micropore volume, pore size distribution, and fractal dimension of two adsorbents were evaluated from analysis of N2gas adsorption isotherms. The estimated surface fractal dimensions Dof macroporous and hypercrosslinked adsorbents using the modified fractal FrenkelâHalseyâHill (FHH) model were 2.471 and 2.709, respectively. Compared with the results of N2adsorption isotherm analysis, it should be noted that the surface fractal dimension Dwas related to the pore size distribution of the adsorbents. The more well-developed the microporous structure of a polymeric adsorbent, the larger the fractal dimension D. Moreover, the adsorbents were also analyzed by transmission electron microscopy (TEM), confirming the surface irregularities and more sophisticated microporous structure of the hypercrosslinked adsorbent as compared to the macroporous adsorbent. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
38. Effect of Divalent Cationic Ions on the Adsorption Behavior of Zwitterionic Surfactant at Silica/Solution Interface.
- Author
-
Xiaoying Hu, Ying Li, Huanquan Sun, Xinwang Song, Quanwei Li, Xulong Cao, and Zhenquan Li
- Subjects
- *
CATIONS , *ADSORPTION (Chemistry) , *POLYZWITTERIONS , *SURFACE active agents , *SILICA , *SOLUTION (Chemistry) , *SURFACE chemistry , *MOLECULAR dynamics - Abstract
The adsorption behavior of zwitterionic surfactant dodecyl sulfobetaine (DBS) on a silica/solution interface with Ca2+, Mg2+existing in aqueous solution is explored by atomistic molecular simulations. The interaction energy contribution of van der Waals and electrostatic potentials in the surfactants/water/silica system are respectively calculated, from which the electrical interaction can be found to play a decisive role in the adsorption tendency of DBS on the silica surface with or without inorganic ions, despite different mechanisms. The distinct decrease of energy has been found to be derived from electrical interaction when DBS adsorb on the silica surface covered by Ca2+or Mg2+. Therefore, it can be predicted that the cationic ions combined on the negatively charged silica surface in a mineral water medium might decrease the adsorption trend of DBS on the silica surface, which has been experimentally proven by TOC measurement. Structural information of the close interface layer and the distribution of water molecules are analyzed after the complete molecular dynamics simulation using a ternary model. Ca2+and Mg2+combined on the silica surface can reduce the adsorption amount of DBS by preventing the direct interaction between DBS and surface, and bringing about the orientation reversal of DBS molecules to break the order of adsorption interface layer. Furthermore, changes in the status of the water spreading on the silica surface caused by the complexation of cations are also an important reason in the adsorption reduction. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
39. Shell-Cross-Linked Micelles from PNIPAM-b-(PLL)2Y-Shaped Miktoarm Star Copolymer as Drug Carriers.
- Author
-
Li-Ying Li, Wei-Dong He, Jian Li, Bo-Yu Zhang, Ting-Ting Pan, Xiao-Li Sun, and Zong-Lei Ding
- Subjects
- *
CROSSLINKED polymers , *MICELLES , *COPOLYMERS , *DRUG carriers , *BIOMOLECULES , *CROSSLINKING (Polymerization) - Abstract
Well-defined AB2Y-shaped miktoarm star copolymers of PNIPAM-b-(PZLL)2and PNIPAM-b-(PLL)2were synthesized through the combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and click chemistry, where PNIPAM, PZLL, and PLL are poly(N-isopropylacrylamide), poly(ε-benzyloxy-carbonyl-l-lysine), and poly(l-lysine), respectively. Propargyl amine was employed as ROP initiator for the preparation of alkynyl-terminated PZLL. Diazide-terminated PNIPAM was obtained with an azide-containing ATRP initiator. The subsequent click reaction led to the formation of PNIPAM-b-(PZLL)2. After the removal of the benzyloxycarbonyl group, water-soluble PNIPAM-b-(PLL)2was obtained. The core−shell micelles of PNIPAM-b-(PLL)2were formed above lower critical solution temperature of PNIPAM block. At this temperature, the shell cross-linking was performed through the reaction between glutaraldehyde and the primary amine groups of the PLL shell, affording the micelles with the endurance to temperature and pH changes. These shell-cross-linked micelles were used as drug nanocarriers and the release profile was dually controlled by the solution temperature and the cross-linking degree. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
40. An Extremely Facile Synthesis of Furans, Pyrroles, and Thiophenes by the Dehydrative Cyclization of Propargyl Alcohols.
- Author
-
Aaron Aponick, Chuan-Ying Li, Jeremy Malinge, and Emerson Finco Marques
- Subjects
- *
FURANS , *PYRROLES , *ORGANIC synthesis , *THIOPHENES , *RING formation (Chemistry) , *ALCOHOLS (Chemical class) , *METAL catalysts , *GOLD - Abstract
Furans, pyrroles, and thiophenes are efficiently prepared by gold-catalyzed dehydrative cyclizations of readily available, heteroatom-substituted propargylic alcohols. The reactions are rapid, high-yielding, and procedurally simple, giving essentially pure aromatic heterocycles in minutes under open-flask conditions with catalyst loadings as low as 0.05 mol %. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
41. Evaluation on Pore Structures of Organosilicate Thin Films by Grazing Incidence Small-Angle X-ray Scattering.
- Author
-
Hong-Ji Chen, Sheng-Ying Li, Xiao-Jun Liu, Rui-Peng Li, Detlef-M. Smilgies, Zhong-Hua Wu, and Zhihong Li
- Subjects
- *
MOLECULAR structure , *SILICATES , *THIN films , *GRAZING incidence , *MICROFABRICATION , *SURFACE active agents , *MOLECULAR weights , *SMALL-angle X-ray scattering , *PARTICLE size distribution - Abstract
Nanoporous thin films fabricated by both a core−shell-shaped organic−inorganic hybrid sphere (octa(2,4-dinitrophenyl)silsesquioxane, ODNPSQ) and a four-leg-numbered surfactant (polyoxyethylene sorbitan monolaurate, Tween-20) for porogens in a higher molecular weight precursor (polyphenylsilsesquioxane, PPSQ) were characterized, respectively, by grazing incidence small-angle X-ray scattering (GISAXS), and the measured 2D GISAXS profiles were analyzed quantitatively by using a GISAXS formula based on the distorted wave Born approximation (DWBA). The fitted 2D GISAXS data show that the PPSQ porous thin films imprinted with ODNPSQ porogen exhibit sphere-shaped closed pores with the average pore size within a range of 1.18−3.12 nm and pore size distribution widths about 3.0 nm when the porogen loadings increase from 10 to 40 wt % and those imprinted with Tween-20 porogen give out an average pore size of 1.07−1.29 nm and pore size distribution widths about 2.0 nm with the porogen loading varying from 5 to 30 wt %. The nanoporous dielectric thin films imprinted with ODNPSQ porogen show a reducing to the molecular aggregation of porogens and significant antiphase separation behavior in the cross-linked matrix. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
42. Synthesis of CuO Perpendicularly Cross-Bedded Microstructure via a Precursor-Based Route.
- Author
-
Jiang-Ying Li, Shenglin Xiong, Baojuan Xi, Xin-Gui Li, and Yi-Tai Qian
- Subjects
- *
INORGANIC synthesis , *COPPER oxide , *MICROSTRUCTURE , *TEMPERATURE effect , *BROMIDES , *SOLUTION (Chemistry) , *GAS detectors - Abstract
Perpendicularly cross-bedded CuO microstructure has been prepared via a precursor-based route. First, Cu2(OH)3Br, as the precursor, was hydrothermally synthesized in 0.1 M hexadecyl trimethyl ammonium bromide (CTAB) solution. Then the precursor was treated with 1 M NaOH solution at room temperature, and finally after heating treatment at 200 °C in furnace it transformed to CuO with a perpendicularly cross-bedded microstructure. The gas sensor property investigation shows that the sensitivities to ethanol and acetone of the as-prepared CuO are two times higher than those of CuO particles(about 100 nm in size) in the gas concentration from 50 to 500 ppm. In particular, the linear response to the ethanol can be used as an operating curve to detect the ethanol concentration in this range. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
43. Impact of Constitutional Isomers of (BMes2)phenylpyridine on Structure, Stability, Phosphorescenc, and Lewis Acidity of Mononuclear and Dinuclear Pt(II) Complexes.
- Author
-
Ying-Li Rao and Suning Wang
- Subjects
- *
NUCLEAR isomers , *CHELATES , *LEWIS acids , *BINDING sites , *CHEMICAL reactions - Abstract
The impact of two constitutional isomers, 2-(4-BMes2-Ph)-pyridine (p-B-ppy, 1) and 5-Mes2-2-ph0pyridine (p-ppy-B, 2), as N,C-chelate ligands on the structures, stabilities, electronic na dphtophysical properties, and Lewis acidities of Pt(II) complexes has been investigated. SIx Pt(II) complexes, Pt(p-B-ppy)Ph(DMSO) (1a), Pt(p-B-ppy)Ph(py)Ph(py) (1b), [Pt(p-B-ppy)Ph]2(4,4'-bipy) (1c), Pt(p-ppy-B)Ph(DMSO) (2a), Pt(p-ppy-B)Ph(py) (2b), and [Pt(p-ppy-B)Ph]2(4,4'-bipy) (2c), have been synthesized and fully characterized. The structures of 1a, 1c, 2a, and 2c were established by sing;e-crystal X-ray diffraction analysis. All complexes adopt a cis geometry with the phenyk ligand being cis to the phenyl ring of the chelate. The dinuclear complexes 2a and 2c were found to exist in two isomeric forms in solution, syn and anti, with respect to the relative orientation of the two BMes2 groups in the molecule. While all complexes are stable in solution under ambient air, acompound 2a was found to react wtih H2O slowly in solution and form complex 2a-OH, where one of the mesityl groups on the boron center was replaced by an OH group. This instability of 2a is attributed to an internal dimethylsulfoxide-directed hydrolysis process via hydrogen bonds. The electron-accepting ability of the free ligands and the complexes were examined by cyclic voltammetry, establishing that, for p-ppy-B, Pt(II) chelation enhances the elctron-accepting ability while, for p-B-ppy, Pt(II) chelation has little impact. All Pt(II) complexes display oxygen-sensitive phosphorescence in solution at ambient temperature, dominated by B-ppy or ppy-B centered π→π* transitions. The Lewis acidity of the complexes was examined by fluoride titration experiments using UV—vis, phosphorescence, and NMR spectroscopic methods, establishing that the p-ppy-B complexes have similar and strong binding constants while the p-B-ppy complexes have a much lower affinity toward F—, compared to the tree ligands. In the dinuclear complexes, weak electronic communication between the two Pt(II) units is evident in 1c but absent in 2c, attributable to the different steric interactions in the two molecules. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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44. Models of Single-Molecule Experiments with Periodic Perturbations Reveal Hidden Dynamics in RNA Folding.
- Author
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Ying Li, Xiaohui Qu, Ao Ma, Glenna J. Smith, Norbert F. Scherer, and Aaron R. Dinner
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RNA , *QUANTUM perturbations , *MOLECULAR dynamics , *STRUCTURAL analysis (Science) , *HIDDEN Markov models , *DEGREES of freedom , *SCIENTIFIC experimentation - Abstract
Traditionally, microscopic fluctuations of molecules have been probed by measuring responses of an ensemble to perturbations. Now, single-molecule experiments are capable of following fluctuations without introducing perturbations. However, dynamics not readily sampled at equilibrium should be accessible to nonequilibrium single-molecule measurements. In a recent study [Qu, X.et al. Proc. Natl. Acad. Sci. U.S.A.2008, 105, 6602â6607], the efficiency of fluorescence resonance energy transfer (FRET) between probes on the L18 loop and 3â² terminus of the 260 nucleotide RNase P RNA from Bacillus stearothermophiluswas found to exhibit complex kinetics that depended on the (periodically alternating) concentration of magnesium ions ([Mg2]) in solution. Specifically, this time series was found to exhibit a quasi-periodic response to a square-wave pattern of [Mg2] changes. Because these experiments directly probe only one of the many degrees of freedom in the macromolecule, models are needed to interpret these data. We find that Hidden Markov Models are inadequate for describing the nonequilibrium dynamics, but they serve as starting points for the construction of models in which a discrete observable degree of freedom is coupled to a continuously evolving (hidden) variable. Consideration of several models of this general form indicates that the quasi-periodic response in the nonequilibrium experiments results from the switching (back and forth) in positions of the minima of the effective potential for the hidden variable. This switching drives oscillation of that variable and synchronizes the population to the changing [Mg2]. We set the models in the context of earlier theoretical and experimental studies and conclude that single-molecule experiments with periodic peturbations can indeed yield qualitatively new information beyond that obtained at equilibrium. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
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45. How Focal Adhesion Size Depends on Integrin Affinity.
- Author
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Tong Zhao, Ying Li, and Aaron R. Dinner
- Subjects
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INTEGRINS , *ADHESION , *CHEMICAL affinity , *THERMODYNAMICS , *SURFACE chemistry , *CELL physiology , *MONTE Carlo method - Abstract
Understanding how the thermodynamics and kinetics of integrin receptor binding and clustering impact the formation of focal adhesions is important for understanding the mechanisms cells use to sense and respond to physical cues in their environment. Cells on chemically well-defined surfaces were observed to have distributions of focal adhesions shifted toward smaller sizes when presented with higher affinity ligands (Kato, M.; Mrksich, M. Biochemistry2004, 43, 2699). In this paper, we account for this trend with a simple model in which integrins are treated as particles on a lattice, and their stochastic dynamics are simulated with a kinetic Monte Carlo algorithm. How the trend depends on force-coupled growth, membrane fluctuations, and heterogeneity of receptor−ligand interactions is analyzed. Predictions are made for substrates in which the ligands presented can vary in either space or time, so that the model can be validated experimentally. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
46. Au-Catalyzed Cyclization of Monopropargylic Triols: An Expedient Synthesis of Monounsaturated Spiroketals.
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Aaron Aponick, Chuan-Ying Li, and Jean A. Palmes
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ORGANIC synthesis , *ALKENES , *RING formation (Chemistry) , *GOLD , *CATALYSTS , *CHEMICAL reactions - Abstract
The gold-catalyzed cyclization of monopropargylic triols to form olefin-containing spiroketals is reported. The reactions are rapid and high yielding when 2 mol % of the catalyst generated in situ from Au[P(t-Bu)2(o-biphenyl)]Cl and AgOTf is employed in THF at 0 °C. A range of differentially substituted triols leading to substituted 5- and 6-membered ring spiroketals were prepared and function well in the reaction. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
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47. Compounds of Superatom Clusters: Preferred Structures and Significant Nonlinear Optical Properties of the BLi[sub6]-X (X = F, LiF[sub2], BeF[sub3], BF[sub4]) Motifs.
- Author
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Ying Li, Di Wu, and Zhi-Ru Li
- Subjects
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ATOMS , *ALKALIES , *HALOGENS , *HALOGEN compounds , *NONLINEAR optics , *MICROCLUSTERS , *CHEMICAL bonds - Abstract
A new type of superalkali-(super)halogen compound, BLi6-X (X = F, LiF2, BeF3, BF4), is theoretically predicted. The interaction between superalkali BLi6 and different shaped superhalogen X is found to be strong and ionic in nature. Bond energies of these BLi6-X species are in the range of 151.3-220.6 kcal/mol at the CCSD(T)/aug-cc- pVDZ level, which are much larger than the traditional ionic bond energy of 130.1 kcal/mol for LiF. Furthermore, because of their delocalized electron character, these superalkali-(super)halogen species exhibit extraordinarily large first hyperpolarizabilities with βo ranging from 5166.5 to 17791.0 au. Besides, the examination of the variation of nonlinear optical (NLO) properties with the size of (BLi6-BeF3)n assemblies shows the dependence of NLO properties on the chain length of (BLi6-BeF3)n. The present investigation gives hints to scientists in extending the research in atomic dimension to direct the interaction between superatoms, and using superatoms as building blocks to synthesize novel meaningful materials with unusual properties such as nonlinear optical properties. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
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48. Development of Silica/Vanadia/ Titania Catalysts for Removal of Elemental Mercury from Coal-Combustion Flue Gas.
- Author
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Ying Li, Murphy, Patrick D., Chang-Yu Wu, Powers, Kevin W., and Bonzongo, Jean-Claude J.
- Subjects
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SILICA , *TITANIUM dioxide , *CATALYSTS , *MERCURY , *COAL combustion , *PURIFICATION of flue gases , *OXIDATION , *MICROSTRUCTURE , *POWER plants , *ULTRAVIOLET radiation - Abstract
SiO2/V2O5/TiO2 catalysts were synthesized for removing elemental mercury (Hg0) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO2—TiO2 composites developed in previous studies, the V2O5 based catalysts do not need ultraviolet light activation and have higher Hg0 oxidation efficiencies. For Hg0 removal by SiO2—V2O5 catalysts, the optimal V2O5 loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg0 oxidation follows an Eley—Rideal mechanism where HCI, NO, and NO2 are first adsorbed on the V2O5 active sites and then react with gas-phase Hg0. HCI, NO, and NO2 promote Hg oxidation, while SO2 has an insignificant effect and water vapor inhibits Hg0 oxidation. The SiO2—TiO2—V2O5 catalysts exhibit greater Hg0 oxidation efficiencies than SiO2—V2O5, may be because the V—O—Ti bonds are more active than the V—O—Si bonds. This superior oxidation capability is advantageous to power plants equipped with wet-scrubbers where oxidized Hg can be easily captured. The findings in this work revealed the importance of optimizing the composition and microstructures of SCR (selective catalytic reduction) catalysts for Hg0 oxidation in coal-combustion flue gas. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
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49. Alkanetelluroxide-Protected Gold Nanoparticles.
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Ying Li, Latoya C. Silverton, Richard Haasch, and Yu Ye Tong
- Subjects
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NANOPARTICLES , *GOLD , *LIGANDS (Chemistry) , *TELLURIUM - Abstract
The synthesis and characterization of the first air-stable tellurium-containing ligand-protected gold nanoparticles (NPs) are reported. Although the synthesis largely followed the well-known Brust two-phase approach, the starting ligand was dioctyl ditelluride rather than alkanetellurol, which is an analogue of the widely used alkanethiol. Dioctyl ditelluride was used because alkanetellurol is unstable. The 1H and 13C NMR spectra, as well as infrared spectra (IR) of the formed Au NPs, indicated that the Te−Te bond in the starting ligand was broken but the octyl group was intact. This was further corroborated by the solid-state 125Te NMR spectrum that displayed a very broad and significantly downfield-shifted peak, indicating that tellurium was directly bound to the Au core. Furthermore, the O 1s and Te 3d XPS spectra of the Au NPs indicated that the capping ligands were octanetelluroxide. An average particle size of 2.7 nm diameter as measured by transmission electron microscopy (TEM) corresponded to an Au 607core. A two-step weight loss of ∼22.2% in total was observed in the thermogravimetric analysis, which indicated about 53% ligand monolayer coverage (i.e., Au 607(Te(O)C 8H 17) 133). Additionally, dioctyl ditelluride demonstrated an intriguing reductive power that led to a more sophisticated chemistry of forming the air-stable octanetelluroxide-protected gold NPs. It has been found that (1) when the ratio of Au to Te was about 1.5 a colorless intermediate state similar to Au(I)-SR (the intermediate state widely accepted in the synthesis of thiolate-protected Au NPs) could be obtained and (2) this kind of intermediate state played a key role in the formation of stable Au NPs. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
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50. Study on the Extent of Folding Back Conformation in Poly(aryl ether) Dendrimers by Intramolecular Electron Transfer and Exciplex Formation.
- Author
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Ying-Ying Li, Lei Han, Jinping Chen, Shaojun Zheng, Yi Zen, Yi Li, Shayu Li, and Guoqiang Yang
- Subjects
- *
PARTICLES (Nuclear physics) , *ORGANIC compounds , *GENERATIONS , *MACROMOLECULES - Abstract
A series of poly(aryl ether) dendrimers (Py−Gn−NHPh, n1−4) with only one pyrene chromophore at the periphery and an aniline group at the core were synthesized and the extent of folding back conformation was given by the intramolecular electron transfer and exciplex formation. Selective excitation of the periphery pyrene moiety of Py−Gn−NHPh in dichloromethane resulted in an electron-transfer process from aniline to pyrene, and as a consequence of the electron transfer, an intramolecular exciplex was formed. Since the exciplex formation requires a direct orbital overlap between the donor and the acceptor groups, this gives us a direct experimental observation for the folding back conformation of poly(aryl ether) dendrimers. The efficiencies and the rate constants of electron transfer in dichloromethane are measured to be 0.90, 0.83, 0.78, 0.68, and 3.6 × 108, 1.7 × 108, 1.2 × 108, and 6.6 × 107s-1for generations 1−4, respectively. The separations (center to center) between the core donor group and the periphery acceptor chromophore are estimated from the rate constants of electron transfer, which are 7.7, 8.0, 8.2, and 8.5 Å for generations 1−4, respectively. This means that the periphery chromophores can fold inward and reach to the core vicinity for all four generations. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
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