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The annealing of pyrolyzed paper (PP) under isopropanol vapor leads to the formation of highly graphitic nanolayers (∼15 nm) on the material surface. PP electrodes with a resistivity as low as 7 mΩ cm could be achieved for sensing applications.

The same electrochemical process drives the preparation of supported and free-standing molybdenum disulfide monolayers.

Functionalization of carbon nanotubes through protein corona formation with bovine plasma is a novel waste-to-wealth approach in agri-environmental nanoscience towards remediation of pollutants from water.

The design of solid-state materials whose properties and functions can be manipulated in a controlled manner by the application of electron beam irradiation is important in modern materials chemistry and physics. In this paper, we present a progress in the development of scalable electron beam irradiation platform to obtain innovative materials for technological and industrial applications, since one of the problems to be solved in this research area is the scalability of these new nanomaterials induced by electron beam irradiation (EBI). In particular, we focus on carbon structures due to its excellent and exciting properties applied in the technological area in the last years, where we show for the first time a new strategy for carbon allotropic transformation through the portable EBI. This new platform is particularly effective, fast, versatile, clean and easy-to-use, facilitating the preparation of many types of nanomaterials that cannot be obtained by conventional chemical and physical methods. The EBI on flat graphite pellets resulted in a covering of it surface with rod-like particles composed of different allotropic forms of carbon. Furthermore, the developed system allowed the implantation of the Fe as a catalytic material through steel sputtering of the high voltage acceleration anode during the EBI process. It was observed by HRTEM analyses that the rod-like particles are preferentially composed of highly oriented graphite in its bottom, polycrystalline graphite in its middle and magnetite nanoparticles in its top.

Herein, a novel silver and chromium nanostructured N-doped carbonaceous material has been synthesized by a biomass-annealing approach using readily available chitosan as a raw material. The resulting catalyst AgCr@CN-800 has been applied for the dehydrogenative coupling reaction of various silanes with different alcohols to obtain the corresponding silyl ethers under aerobic and mild conditions. Besides excellent activity and selectivity, the as-prepared catalyst exhibits good stability and reusability. Characterization by X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometry, and high-resolution transmission electron microscopy (TEM) in combination with careful examination of the structure with Cs-corrected high-angle annular dark-field scanning TEM revealed that the catalyst AgCr@CN-800 comprises Ag- and CrN-aggregated particles, as well as highly dispersed Ag–Nx and Cr–Nx sites embedded in N-doped graphitic structures. A comparative catalytic study using structure-related catalysts in combination with acid-leaching treatments has shown that the most active species are the Ag particles and that their activity is boosted by the presence of Cr-derived species. By in situ Raman spectroscopy experiments, it has been found that the dehydrogenative coupling of silanes with alcohols in the presence of catalyst AgCr@CN-800 takes place through an oxygen-assisted mechanism., The authors thank the financial support from MICIU/AEI/FEDER (PGC2018-094417-B-I00 and RTI2018-098237-B-C22) and Universitat Jaume I (UJI-A2019-16, UJI-B2019-30, and UJI-B2018-23). I.S. thanks the Spanish Ministerio de Economía, Industria y Competitividad (MINECO) for a postdoctoral “Juan de la Cierva-Incorporación” fellowship (IJCI-2016-30590), and the financial support from the “José Castillejo” Mobility Program (CAS19/00339) of the Ministerio de Ciencia, Innovación y Universidades (MICIU). S.M. acknowledges DGA/fondos FEDER (construyendo Europa desde Aragón) for funding the research group Platón (E31_17R). D.V.-E. thanks the MICIU for a FPU grant (FPU15/03011). E.L. and M.A. thank the financial support from FAPESP (2013/07296-2), CNPq (166281/2017-4), CAPES, and FINEP. The authors also thank the “Servei Central d’Instrumentació Científica (SCIC)” of the Universitat Jaume I, as well as Dr. G. Antorrena for technical support in XPS studies.

Summary Atomic-scale structure determination is crucial to the understanding of nanomaterial properties and development of new technologies. Although pair distribution function (PDF) analysis by neutrons and X-ray scattering profile has been used to study materials, electron diffraction can offer advantages to characterize the atomic structure of clusters, amorphous samples, and nanomaterials. Electrons have higher scattering power than X-rays, allowing the acquirement of PDF from electron diffraction (ePDF) for small sample amounts and with time-efficient data acquisition. Compared with synchrotron X-rays and neutrons as sources for PDF, the availability of electron microscopes worldwide is advantageous. Nowadays, with the rise of methodologies and specific software for ePDF data analysis, the scientific community can benefit from advanced transmission electron microscopy (TEM) structure determination integrating commonly available TEM analyses—size, distribution, shape, and high-resolution TEM atomic visualization—with ePDF atomic structure determination, both for bulk and surface configurations. Therefore, ePDF has the potential to become a routine and advanced characterization tool for nanomaterials science.

Copper indium sulfide quantum dots (QDs) have attracted substantial attention in recent years due to environmental issues and diverse applications. We report the synthesis and characterization of c...

International audience; Hard and strong transparent glass-ceramics (TGCs) can be used as cooktop plates, telescope mirrors, armor materials, and screens for smartphones and tablets. In this work, transparent glass-ceramics from the MgO-Al2O3-SiO2 (MAS) system were obtained after a refined heat-treatment protocol. The evolution in fracture toughness, KIC (Single Edge Precracked Beam), and Vickers hardness (H-V) were characterized as a function of the crystallization progress. The K-IC of the parent glass was 0.6 MPa m(1/2), whereas the TGC samples present values around 1.1 MPa m(1/2). The average glass hardness was 8.5 and PLUSMN; 0.8 GPa for loads of 0.6-5 N, whereas the H-V of the TGC samples varied from 9 to 10 GPa, for indentation loads ranging from 4.9 to 9.8 N. These results are discussed in light of our previous findings on the evolution of elastic modulus in the same glass-ceramics.

Annealing of sugarcane bagasse cellulose or lignin biocarbons under isopropanol vapor has induced an improvement on electrical conductivity of these materials. Remarkably, the sheet resistance drop...

One of the main drawbacks of welding dissimilar metal alloys is the potential massive precipitation of deleterious intermetallic compounds that occurs at the interface joint. Solid-state welding processes are therefore attractive, given the lower temperatures involved. In this work, dissimilar high strength aluminum and titanium alloys were friction-stir-welded using the spindle power control mode to reduce the heat input at the joint as much as possible. A microstructural characterization indicated that the chosen parameters (heat input of ~0.5 kJ/mm) produced welded joints without spatially continuous layers of deleterious intermetallic compounds.

Using a combination of in situ high-resolution transmission electron microscopy and density functional theory, we report the formation and rupture of ZrO_{2} atomic ionic wires. Near rupture, under tensile stress, the system favors the spontaneous formation of oxygen vacancies, a critical step in the formation of the monatomic bridge. In this length scale, vacancies provide ductilelike behavior, an unexpected mechanical behavior for ionic systems. Our results add an ionic compound to the very selective list of materials that can form monatomic wires and they contribute to the fundamental understanding of the mechanical properties of ceramic materials at the nanoscale.

Multifunctional quantum dots (QDs) of Co3O4 were fabricated using cobalt II nitrate hexahydrate with tomato (Solanum lycopersicum L.) seed extract and were efficiently applied as a virucidal additive in cotton fabric. The low-dimensional semiconductor, exhibiting a quantum confinement regime along with charge carrier confinement, resulted in superior antiviral characteristics. The QDs were characterized by UV-visible spectrophotometry, high-resolution transmission electron microscopy, X-ray excited photoelectron spectrometry, Fourier transform infrared spectroscopy, and magnetic properties using a superconductor quantum interference device. Co3O4 QDs exhibit chirality, as evidenced by the magnetic circular dichroism spectrum in the spectral region in which the material absorbs. The high ferritin content in tomato seeds, as evidenced by electron paramagnetic resonance, suggested that this protein acts as a nanocage for the growth of Co3O4. Commercially purified horse spleen ferritin was equally efficient in producing Co3O4 QDs. Based on these results, it can be concluded that the multifunctional platform of Co3O4 QDs satisfactorily meets the requirements to be an efficient photocatalyst and exhibits the potential to be employed as a semiconductor textile-based to combat/ to prevent coronavirus disease as a sustainable personal protective clothing.

Lead halide perovskites have emerged as promising materials for light-emitting devices. Here, we report the preparation of colloidal CsPbBr3 nanoplatelets (3 × 4 × 23 nm3) experiencing a strong qua...

Made available in DSpace on 2022-04-28T19:47:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Ministerio de Ciencia, Innovación y Universidades Universitat Jaume I This work elucidates the morphology-photoluminescence (PL) emission relationships, based on experimental and calculated results, on β-Ag2MoO4 samples synthesized by microwave-assisted hydrothermal method. It was shown that the solvent (water and ammonia) and temperature (120, 130, 140, and 150 °C) play a crucial role in the morphology and PL emissions. A crystal structure model, composed by the local coordination of both Ag and Mo atoms at bulk and exposed surfaces, was built, and the possible mechanism along the synthesis progress was proposed and analyzed. This study provides an idea for the preparation and development of β-Ag2MoO4 based materials with desirable properties. CDMF Federal University of São Carlos, P.O. Box 676 Institute of Chemistry State University of Campinas, Campinas Universidade Estadual Paulista Laboratório Interdisciplinary de Eletroquímica e Cerâmica Department of Physics Federal University of São Carlos, P.O. Box 676 Department of Analytical and Physical Chemistry University Jaume I Brazilian Nanotechnology National Laboratory (LNNano)/CNPEM, Campinas Universidade Estadual Paulista Laboratório Interdisciplinary de Eletroquímica e Cerâmica CAPES: 001 CNPq: 142035/2017-3 FAPESP: 2013/07296-2 FAPESP: 2016/23891-6 FAPESP: 2017/26105-4 FAPESP: 2019/01732-1 CNPq: 305792/2020-2 Ministerio de Ciencia, Innovación y Universidades: PGC2018-094417-B-I00 Universitat Jaume I: UJI-B2019-30

Mn5Si3 nanowires are believed to be the building blocks of the newest trends of flexible and stretchable devices in nanoelectronics. In this context , growing Mn5Si3 nanowires, as well as characterizing their electronic transport properties provide insight into their phenomenology. In this work, we report on the growth mechanism of Mn5Si3 nanowires produced by the metallic flux nanonucleation method, as well as the resistivity measurements of these nanostructures. Our calculation allows us, by using the Washburn equation for pore infiltration, to give a guess on why we obtain Mn-rich nanowires. In addition, some morphological aspects of the diameter-modulated Mn5Si3 nanowires were discussed based on the classical nucleation theory. From the resistivity measurements for the smallest diameter among the nanowires, we observed a significant reduction of around 37% of the phonons characteristic temperature by fitting the Bloch–Grünesein formula with other sources of scattering. Our results lead to a better understanding on the recent metallic flux nanonucleation growth method, as well as going a step further into the electronic transport properties of the Mn5Si3 nanowires.

CdTe/CdS core/shell quantum dots (QDs) are formed in aqueous synthesis via the partial decomposition of hydrophilic thiols, used as surface ligands. In this work, we investigate the influence of the chemical nature (functional group and chain length) of the used surface ligands on the shell formation. Four different surface ligands are compared: 3-mercaptopropionic acid, MPA, thioglycolic acid, TGA, sodium 3-mercaptopropanesulfonate, MPS, and sodium 2-mercaptoethanesulfonate, MES. The QD growth rate increases when the ligand aliphatic chain length decreases due to steric reasons. At the same time, the QDs stabilized with carboxylate ligands grow faster and achieve higher photoluminescence quantum yields compared to those containing sulfonate ligands. The average PL lifetime of TGA and MPA capped QDs is similar (≈20 ns) while in the case of MPS shorter (≈15 ns) and for MES significantly longer (≈30 ns) values are measured. A detailed structural analysis combining powder X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) indicates the existence of two novel regimes of band alignment: in the case of the mercaptocarboxylate ligands the classic type I band alignment between the core and shell materials is predominant, while the mercaptosulfonate ligands induce a quasi-type II alignment (MES) or an inverted type I alignment (MPS). Finally, the effect of the pH value on the optical properties was evaluated: using a ligand excess in solution allows achieving better stability of the QDs while maintaining high photoluminescence intensity at low pH.

Nanoparticle stability against coarsening is one of the keys to allow better exploitation of the properties of nanoscale materials. The intrinsically high interfacial energies of nanoparticles constitute the driving force for coarsening, and therefore can serve as targets to design materials with improved thermal stability. In this study, we discuss the surface engineering of TiO2 nanocatalysts for artificial photosynthesis by exploiting the spontaneous segregation of Ba2+ ions to the interfaces of TiO2 nanocrystals. Ba2+ is a strong candidate for photoelectrocatalytic reduction of CO2 and its effects on interfacial energies lead to a remarkable increase in thermal stability. By using a systematic lixiviation method, we quantified the Ba2+ content located at both the surface and at grain boundary interfaces and combined with direct calorimetric measurements of surface energies and microstructural studies to demonstrate that Ba2+ excess quantities directly impact coarsening of TiO2 nanocatalysts by creatin...

Observation of relevant phenomena related with dynamical redox process in a plasmonic heterogeneous-photocatalyst system composed by silver nanoparticles (NPs) around and in contact with amorphous silver chloride NPs are reported by in situ transmission electron microscopy. During this process, nanobubbles are initially produced inside the silver chloride NPs, which immediately begin to move within the amorphous phase. Besides, silver atoms inside the silver chloride NPs start to migrate out the occupied volume leaving a space behind, which is filled by crystalline regions of silver chloride located between the pre-existing silver NPs. During the observation time, fast-nucleation, movement, growth, and fast-dissolution of silver NPs take place. Specific space correlation with silver mass loss (or gain) when a new NP is formed (or dissolved), was detected in different regions during the reaction. This mass loss (or gain) takes place on certain places of pre-existing silver NPs. All these phenomena were observed for a configuration comprising at least two silver NPs separated few nanometers apart by a silver chloride NP., Facultad de Ingeniería, Centro de Investigaciones Ópticas

Aim: This work is focused on obtaining degradable mesoporous silica nanoparticles (DMSNs) which are able to maintain their colloidal stability in complex biological media. Materials & methods: DMSNs were synthesized using different ratios of disulfide organosilane (degradable structural moiety) and further functionalized with sulfobetaine silane (SBS) to enhance colloidal stability and improve biological compatibility. Results: There was a clear trade-off between nanoparticle degradability and colloidal stability, since full optimization of the degradation process generated unstable particles, while enhancing colloidal stability resulted in poor DMSNs degradation. It was also shown that acidic pH improved particle degradation which is commonly triggered by reduction stimulus. Conclusion: A chemical composition window was found where DMSNs presented satisfactory colloidal stability in biologically relevant medium, meaningful degradation profiles and high biocompatibility.

Made available in DSpace on 2022-04-28T19:46:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-16 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Ministerio de Ciencia, Innovación y Universidades Universitat Jaume I In this study, we have demonstrated that Bi2S3 semiconductor under ultrasound behaves as a piezoelectric material, facilitating the transfer of electrons and holes, thus enabling the formation of oxidizing agents. In the presence of light, Bi2S3 showed no photocatalytic activity, resulting in Rhodamine B (RhB) degradation of 2.5%, while the ultrasound application led to a degradation of 40.6%. Herein, we propose a possible mechanism to explain this behavior based on the local charge polarization in [BiS7] clusters. LIEC – CDMF - Department of Chemistry Universidade Federal de São Carlos - UFSCar, P.O. Box 676 Department of Chemistry Universidade Estadual Paulista - Unesp, P.O. Box 473 Institute of Chemistry - São Paulo State University - UNESP Departament de Química Inorgànica I Orgànica Universitat Jaume I (UJI) Department of Analytical and Physical Chemistry University Jaume I Brazilian Nanotechnology National Laboratory (LNNano)/CNPEM Department of Chemistry Universidade Estadual Paulista - Unesp, P.O. Box 473 Institute of Chemistry - São Paulo State University - UNESP CNPq: 142035/2017-3 FAPESP: 2013/07296-2 Ministerio de Ciencia, Innovación y Universidades: PGC2018094417-B-I00 Universitat Jaume I: UJI-B2019-30

Recently, core–shell nanowires have been proposed as potential electrical connectors for nanoelectronics components. A promising candidate is Mn5Si3 nanowires encapsulated in an oxide shell, due to their low reactivity and large flexibility. In this work, we investigate the use of the one-step metallic flux nanonucleation method to easily grow manganese silicide single crystal oxide-protected nanowires by performing their structural and electrical characterization. We find that the fabrication method yields a room-temperature hexagonal crystalline structure with the c-axis along the nanowire. Moreover, the obtained nanowires are metallic at low temperature and low sensitive to a strong external magnetic field. Finally, we observe an unknown electron scattering mechanism for small diameters. In conclusion, the one-step metallic flux nanonucleation method yields intermetallic nanowires suitable for both integration in flexible nanoelectronics as well as low-dimensionality transport experiments.

Zwitterionic molecules are known to resist nonspecific protein adsorption and have been proposed as an alternative to the widely used polyethylene glycol. Recently, zwitterionic-like nanoparticles were created from the coimmobilization of positive and negative ligands, resulting in surfaces that also prevent protein corona formation while keeping available sites for bioconjugation. However, it is unclear if they are able to keep their original properties when immersed in biological environments while retaining a toxicity-free profile, indispensable features before considering these structures for clinics. Herein, we obtained optimized zwitterionic-like silica nanoparticles from the functionalization with varying ratios of THPMP and DETAPTMS organosilanes and investigated their behavior in realistic biological milieu. The generated zwitterionic-like particle was able to resist single-protein adsorption, while the interaction with a myriad of serum proteins led to significant loss of colloidal stability. Moreover, the zwitterionic particles presented poor hemocompatibility, causing considerable disruption of red blood cells. Our findings suggest that the exposure of ionic groups allows these structures to directly engage with the environment and that electrostatic neutrality is not enough to grant low-fouling and stealth properties.

A facile hydrothermal method to synthesize water-soluble copper indium sulfide (CIS) nanocrystals (NCs) at 150 &deg, C is presented. The obtained samples exhibited three distinct photoluminescence peaks in the red, green and blue spectral regions, corresponding to three size fractions, which could be separated by means of size-selective precipitation. While the red and green emitting fractions consist of 4.5 and 2.5 nm CIS NCs, the blue fraction was identified as in situ formed carbon nanodots showing excitation wavelength dependent emission. When used as light absorbers in quantum dot sensitized solar cells, the individual green and red fractions yielded power conversion efficiencies of 2.9% and 2.6%, respectively. With the unfractionated samples, the efficiency values approaching 5% were obtained. This improvement was mainly due to a significantly enhanced photocurrent arising from complementary panchromatic absorption.

Present theoretical and experimental work provides an in-depth understanding of the morphological, structural, electronic, and optical properties of hexagonal and monoclinic polymorphs of bismuth phosphate (BiPO

Novel magnetic metals and metal oxides that use both the spin and charge of an electron offer exciting technological applications. Their discovery could boost research on functional nanoscale materials. Here, for the first time, we report the magnetization of α-Ag2WO4 under electron beam and femtosecond laser irradiation. The formation and growth of silver oxides (AgO, Ag2O, and Ag3O4) and Ag nanofilaments can be observed on the surface of α-Ag2WO4 crystals. These features were also present in the composition of an extruded material and could open new avenues for surface magnetism studies. In order to understand these results, we used first-principles density functional theory calculations. This allowed us to investigate several potential scenarios for controlling magnetic properties. The effect of electron addition on the crystalline structures of α-Ag2WO4, Ag3O4, Ag2O, and AgO has been analyzed in detail. The creation of Ag and O vacancies on these compounds was also analyzed. Based on structural and electronic changes at the local coordination site of Ag, a mechanism was proposed. The mechanism illustrates the processes responsible for the formation and growth of metallic Ag and the magnetic response to electron beam irradiation.

In recent years, cryogenic electron microscopy (Cryo-EM) has revolutionized the structure determination of wet samples and especially that of biological macromolecules. The glassy-water medium in which the molecules are embedded is considered an almost

Made available in DSpace on 2020-12-12T01:25:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-06-01 Present theoretical and experimental work provides an in-depth understanding of the morphological, structural, electronic, and optical properties of hexagonal and monoclinic polymorphs of bismuth phosphate (BiPO4). Herein, we demonstrate how microwave irradiation induces the transformation of a hexagonal phase to a monoclinic phase in a short period of time and, thus, the photocatalytic performance of BiPO4. To complement and rationalize the experimental results, first-principles calculations have been performed within the framework of density functional theory. This was aimed at obtaining the geometric, energetic, and structural parameters as well as vibrational frequencies; further, the electronic properties (band structure diagram and density of states) of the bulk and corresponding surfaces of both the hexagonal and monoclinic phases of BiPO4 were also acquired. A detailed characterization of the low vibrational modes of both the hexagonal and monoclinic polymorphs is key to explaining the irreversible phase transformation from hexagonal to monoclinic. On the basis of the calculated values of the surface energies, a map of the available morphologies of both phases was obtained by using Wulff construction and compared to the observed scanning electron microscopy images. The BiPO4 crystals obtained after 16-32 min of microwave irradiation provided excellent photodegradation of Rhodamine B under visible-light irradiation. This enhancement was found to be related to the surface energy and the types of clusters formed on the exposed surfaces of the morphology. These findings provide details of the hexagonal-to-monoclinic phase transition in BiPO4 during microwave irradiation; further, the results will assist in the design of electronic devices with higher efficiency and reliability. Chemistry Department CDMF LIEC Federal University of São Carlos, P.O. Box 676 Instituto de Química de São Carlos Universidade de São Paulo, P.O. Box 780 CDMF LIEC Chemistry Institute of the Paulista State University UNESP, P.O. Box 1680 Department of Physical and Analytical Chemistry University Jaume i Physics Department Federal University of São Carlos, P.O. Box 676 Brazilian Nanotechnology National Laboratory, Rua Giuseppe Maximo Scolfa no. 10000 CDMF LIEC Chemistry Institute of the Paulista State University UNESP, P.O. Box 1680

Lead halide perovskites have emerged as promising materials for light-emitting devices. Here, we report the preparation of colloidal CsPbBr

The search for efficient, stable electrocatalysts for the oxygen reduction reaction (ORR) has received increased attention, given the need to speed up this reaction in fuel cells. This article reports the one-pot synthesis of novel metal nanodendrites (MNDs) of Pt or Pt–Pd alloy surface-covering patterns that, supported on Vulcan Carbon XC-72, effectively catalyzed the ORR. The surface of Vulcan Carbon XC-72 exhibits raised plains interspersed with ribbed troughs, in a pattern energetically favorable to metal precipitation (deposition) into the ribbed troughs. This produces MND/C structures that are strongly catalytic toward the ORR. Mass-specific activity (MSA) of 0.56 mA μg−1 and specific activity (SA) in the 1.17–1.35 mA cm−2 range are noteworthy findings for Pt/C, Pt@Au′/C, and Pt–Pd/C MND electrocatalysts at 0.9 ViR-free, using platinum-group metal (PGM) loadings as low as 26 μg cm−2—better values, therefore, than the United States Department of Energy (DOE) targets for MSA (0.44 A mgPt−1) and SA (0.72 mA cm−2 at 0.9 ViR-free) for electrocatalysts used in portable applications to be marketed in 2017, and for cathode areal PGM loadings (

Structural improvements of efficient and abundant photocatalysts and the employment of less expensive co-catalysts are appealing routes to promote the development of economically viable solar fuel production. We herein report a significant enhancement of the H2 production from photocatalytic water splitting over K2Ti4O9 after pillaring with TiO2 pillars and loading of NiOx as a co-catalyst. The pillaring favored the charge carrier separation within the photocatalyst framework under illumination, whereas the NiOx co-catalyst, composed of nickel metal nanoparticles and nanostructured NiO, intensified the electron–hole separation at the surface. These are unprecedented results indicated by surface photovoltage spectroscopy, which was applied for the first time in this kind of photocatalyst composite. All modifications enhanced the H2 evolution from 14.9 μmol, for the pristine K2Ti4O9, to 982.0 μmol, for the final product, after 7 h of irradiation tests using methanol as a hole scavenger. This boost was also favored by the mesoporosity and high surface area created by the pillaring process. Moreover, NiOx as the co-catalyst proved to be as effective as platinum and more effective than Ag and Au in this particular system.

Here we show a new nanowire growth procedure, exploring the thermally activated motion of Au droplets on III-V surfaces. We show that by setting a single growth parameter we can activate the crawling motion of Au droplets in vacuum and locally modify surface composition in order to enhance vapor-solid (VS) growth along oxide-free areas on the trail of the metal particle. Asymmetric VS growth rates are comparable in magnitude to the vapor-liquid-solid growth, producing unconventional wurtzite GaP morphologies, which shows negligible defect density as well as optical signal in the green spectral region. Finally, we demonstrate that this effect can also be explored in different substrate compositions and orientations with the final shape finely tuned by group III flow and nanoparticle size. This distinct morphology for wurtzite GaP nanomaterials can be interesting for the design of nanophotonics devices.

The design of the hierarchically tailored 4.4 nm nanoparticles was based on the alternation between un-doped and Ln(III)-doped layers (Ln(III) = Eu(III), Tb(III)), ensuring the isolation of different Ln(III) ions in order to prevent energy transfers between them, which may lead to long term loss of quality of the emission due to one-sided cascading of the excitation energy to a single emitter. Photoluminescence emission and excitation spectra have shown the importance of this design in obtaining white light: for the alternating layer design there are no energy transfer between Tb(III) and Eu(III) ions, and emission spectra with exc = 260 nm of Tb(III),Eu(III)-codoped ZrO2 nanoparticles over a ZnO-coated silica host show a combination of Tb(III) green, Eu(III) red, and silica defects blue emissions resulting in pure white emission, and warm white with an additional Eu(III)-doped layer. While the ZnO coating layer was vital in improving Eu(III) emission intensity by suppresion of SiO2 surface (-OH) oscilla...

In this work were synthesized highly luminescent carbon dots for use as fluorescence sensor for Cr(VI). Carbon dots (CDots) were prepared by pyrolysis of the mixture of molecular precursors as citric acid and reduced glutathione. Pyrolysis revealed to be a simple procedure that afforded CDots with a photoluminescence quantum yield of 69.4%, and particle size of about 2.5 nm. To explore the analytical potentiality of the nanomaterial produced, the CDots were applied as fluorescent sensors to determine Cr(VI) in water and soil samples. The interaction mechanism between CDots and Cr(VI) is associated with both inner filter effect and static quenching. After optimization of the main analytical parameters, the method showed a linear range of 0.10–12 μg mL −1 with limit of detection (LOD) of 0.03 μg mL −1 (pH 7), and recoveries of 90–105% and 99.5–107% for samples of water and soil, respectively. Thus, the method proved to be sensitive, fast and versatile for applications in different environmental samples.

We report the synthesis of novel multicolor photoluminescent carbon quantum dots (CQDs) from multi-wall carbon nanotubes, and their covalent functionalization with amines by peptide bonds. The resulting CQDs consisted of quasi-spherical graphite nanocrystals around 10 nm diameter, which were capped by amines with different hydrocarbon chains such as propylamine, octylamine, dodecylamine and octadecylamine. The introduction of nitrogen atoms and the hydrocarbon chains in the surface of the CQDs dramatically affected their photoluminescence profiles, quantum yields and solubility. The photoluminescence emission wavelength of these novel organic-soluble CQDs depended on the excitation wavelength and their quantum yields varied with the chain length of the hydrocarbon chain attached to the surface of the carbon dots.

Herein, the fine-scaled α phase precipitation during step-quench heat treatments in Ti‐15Nb‐3.0Fe and Ti‐11Nb‐3.5Fe (wt%) alloys was evaluated. Thermodynamic analyses suggest that Ti‐11Nb‐3.5Fe alloy should present homogenous α phase formation via the pseudospinodal mechanism when solution-treated and step-quenched at 450 °C, which is confirmed in this work. STEM-EDX measurements confirm the non-equilibrium state of the α phase precipitates, whose Nb content is significantly higher than that of the α phase laths obtained after solution heat treatment followed by furnace cooling. Fe seems to play an important role in the precipitation mechanism, and is depleted from α phase laths in a short aging time.