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Fabrication of Fe-doped SrTiO3 photocatalyst with enhanced dinitrogen photofixation performance
摘要： SrTiO3 as semiconducting photocatalyst has been extensively investigated due to its band edges meeting the thermodynamic requirements for water splitting, but a few attention has been concentrated on its application in the NH3 synthesis via N2 photofixation process. Herein, Fe-doped SrTiO3 (FexSr1-xTiO3) products (0 ≤ x ≤ 0.20) were synthesized via a hydrothermal process followed by calcination at 700oC. All FexSr1-xTiO3 products (0.03 ≤ x ≤ 0.20) deliver an enhanced N2 fixation ability, and FexSr1-xTiO3 (x = 0.10) achieves the best NH3 production activity of 30.1 μmol g-1 h-1, which is 3.2-hold higher than that of SrTiO3 alone. Once the x value is higher than 0.10, FexSr1-xTiO3 will transform into composites containing Fe-doped SrTiO3 and α-Fe2O3, which acts as charge recombination sites, thus causes a decreased N2 fixation activity. Further investigations demonstrate that the surface Fe3+-doped sites can not only chemisorb and activate N2 molecules, but also promote the interfacial electron transfer from Fe-doped SrTiO3 to N2 molecules, and thus significantly improve the N2 fixation ability. The present Fe-doped SrTiO3 products exhibit characteristic features such as stable and efficient N2 fixation ability as well as simultaneous realization of N2 reduction and H2O oxidation without co-catalyst, which are of significance in artificial photosynthesis with H2O as electron and proton sources.
关键词： Photocatalysis,Fe-doped SrTiO3,Dinitrogen photofixation,N2 molecule activation
更新于2025-11-21 11:01:37
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Correlation between the morphology and the opto-electronic and electrical properties of organometallic halide perovskite (CH<sub>3</sub>NH<sub>3</sub>MH<sub>3</sub>) thin films
摘要： Organometallic halide perovskites are emerging as a promising class of materials for optoelectronic applications. Crystal morphology is important for improving the organic-inorganic lead halide perovskite semiconductor property in optoelectronic, electrical and photovoltaic devices. It is thus important to investigate how the changes in crystal morphology affect the semiconductor behavior. This work presents a study that was carried out to assess the relationship between different deposition methodologies and the opto-electronic and electrical properties of the resultant organometallic halide perovskite thin films. Herein, single step solution deposition method and two step solution deposition methods have been used to deposit perovskite thin films. The structure and morphology of perovskite was controlled by changing concentration, annealing temperatures and dip coating times. From the study, prepared films showed different morphologies as the concentration, annealing temperatures and dip coating times were varied. Optical band gap energies of 2.23 eV, 2.13 eV and 2.09 eV were obtained for samples prepared by single step solution deposition method and 1.57 eV, 1.55 eV and 1.52 eV for two step solution deposition method. The sheet resistance values decreased with an increase in concentration, annealing temperatures and dip coating times. The decrease in optical band gap energy and sheet resistances are excellent properties for high performance photovoltaic devices.
关键词： Perovskite,sheet resistivity,activation energy,band gap,sheet resistance,spectroscopy
更新于2025-11-19 16:56:35
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Photocatalytic Activation of C-H Bonds by Spatially Controlled Chlorine and Titanium on the Silicate Layer
摘要： Owing to the economic and environmental benefits, photocatalytic organic transformation via C-H activation is a crucially important, while still challenging area. We report photocatalytic process for partial cyclohexane oxidation with enhanced catalytic activity that exploits chlorine and titanium atoms spatially arranged on a silica substrate. Silica-based catalysts bearing grafted titanium that effectively interacts with photochemically adsorbed chlorine were prepared. The catalysts were synthesized by reacting a layered silicate with titanium(IV) acetylacetonate and subsequent chlorination treatment. Characterization by a variety of techniques revealed that the organic ligand of the titanium species that is grafted onto the silicate layer surface is converted into chlorine while maintaining its coordination state. However, upon subsequent hydration, the chlorine existed as HCl. We investigated the performance of the catalyst for the production of cyclohexanol and cyclohexanone from cyclohexane with molecular oxygen under solar light irradiation. The chlorinated layered silicate photocatalyst exhibited a remarkably high production rate (0.7 mmol g-1 h-1) and large amount of product formed (0.8 mmol), while the over-oxidation of cyclohexane was inhibited. The enhanced catalytic ability could be explained by the presence of a radical mediator (chlorine) located at a position neighboring an isolated titanium atom. The high surface density of these active species (both titanium and chlorine) on the silicate layer provided suitable electron transfer to form chlorine radicals.
关键词： Photocatalysis,partial oxidation,C-H activation,KA oil,layered silicate,titanosilicate,chlorine,cyclohexane oxidation
更新于2025-11-19 16:51:07
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Temperature-dependent dielectric response of (1-x)PVDF/(x)BaTiO3 nanocomposite films
摘要： The PVDF/BaTiO3 nanocomposite films were prepared by solution casting method by using dimethylformamide as solvent. The dielectric constant and loss tangent of the PVDF and PVDF/BaTiO3 composites have been determined as functions of frequency (20 Hz to 2 MHz) and temperature (80 to 425 K). A significant enhancement in dielectric constant ε' is observed in composite samples. Tangent loss factor (tan δ) is maximum at lower frequencies due to interfacial polarization. In composite samples owing to the synthesis process, there is a phase transition in PVDF from α to β which results in the formation of dipolar relaxation. The dipolar nature of both the PVDF and PVDF/BaTiO3 nanocomposites is arrested below 200 K. The activation energy values (0.43- 0.69 eV) associated with tan δ peak in the region 200 – 270 K are in agreement with the activation energy associated with a dipolar relaxation process. The relaxation time (τ) decreases with increasing BaTiO3 filler content while the number density of dipoles increases from 4.06×1021 cm-3 for pristine PVDF to 6.62×1023 cm-3 for (0.5)PVDF/(0.5)BaTiO3 composite and confirms a significant amount of dipolar relaxation in PVDF/BaTiO3 composites.
关键词： dielectric relaxation,activation energy,dielectric constant,PVDF/BaTiO3 nanocomposites
更新于2025-11-14 17:28:48
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High-efficiency synthesis of high-performance K0.5Na0.5NbO3 ceramics
摘要： Pure (K0.5Na0.5)NbO3 (KNN) ceramics with high density, fine and uniform-size grains were prepared by mechanochemical activation-assisted process. The time of synthesis is only 100 min, which is 72% - 93% shorter than the 6-24h of the conventional solid-state method. Compared to samples prepared by conventional solid-state method, both the microstructure evolvement and electric properties were explored in detail. Results show the electric properties was significantly improved. Moreover, the dielectric and ferroelectric properties of obtained KNN ceramics exhibit strong dependence on the crystal size of the initial powders. The optimized ceramics HKNN100 showed a quite high energy storage performance, i.e., large electric energy storage density (Wtol=1.612 J/cm3) and recoverable energy storage density (Wrec=0.431 J/cm3), which can be mainly ascribed to the large dielectric breakdown strength (DBS=110 kV/cm). Our works demonstrated that mechanochemical activation-assisted method possesses advantages for high-efficiency preparation of KNN or KNN-based ceramics.
关键词： Dielectric properties,Ferroelectricity,(K0.5Na0.5)NbO3 Ceramics,Mechanochemical activation,Microstructure
更新于2025-11-14 17:04:02
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A spark discharge generator for scalable aerosol CVD synthesis of single-walled carbon nanotubes with tailored characteristics
摘要： We have designed and built an exhaust-free spark discharge generator for robust aerosol CVD synthesis of single-walled carbon nanotubes. The systematic study has shown the generator to provide a facile and repeatable route to precisely control the size of the catalyst particle and, therefore, carbon nanotube growth. Using a comprehensive set of methods (the analysis of differential mobility of the aerosol particles, optical spectroscopy, scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy) we have revealed the relation between the defectiveness, length, diameter distribution of carbon nanotubes and specific features of a generator such as electrode characteristics (breakdown voltage, composition, and current) as well as the nature of the surrounding media (carrier gas nature, flow rate). The design used has resulted in separation of the nanoparticle formation and carbon nanotube nucleation processes. This provides a mutual independence of the growth parameters and the diameter distribution of the single-walled carbon nanotubes enhancing the scalability of the process. For instance, the breakdown voltage has been shown to have nearly zero effect on diameter and length distribution of carbon nanotubes produced while strictly governing the yield. We focus here on producing specifically short carbon nanotubes (l < 500nm) of pronounced defectiveness for drug delivery and transistor applications.
关键词： single-walled carbon nanotubes,differential mobility analyzer,catalyst activation,spark-discharge generator,aerosol CVD,floating bed reactor
更新于2025-11-14 17:03:37
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Photo-physical properties of substituted 2,3-distyryl indoles: Spectroscopic, computational and biological insights
摘要： The structural dependence of the photo-physical properties of substituted 2,3-distyryl (23DSI) indoles were studied using several spectroscopic techniques including steady-state UV-VIS spectroscopy, steady-state fluorescence spectroscopy, steady-state excitation spectroscopy, time correlated single photon counting (TCSPC) spectroscopy, and time-resolved fluorescence upconversion spectroscopy (TRFLS). Each of 23DSI derivatives investigated showed distinct fluorescence emission and UV-VIS spectra, indicating strong structural dependence of the emission and the excitation. The UV-VIS spectra of the 23DSI derivatives showed three main identical absorption bands with minor deviations in the absorbance caused by substituent groups on the distyryl rings. The time-resolved fluorescence up-conversion studies indicated that the fluorescence undergoes a mono-exponential decay whereas the calculated fluorescence lifetime showed relatively short fluorescence lifetimes of approximately 1 ns. All of the 23DSI derivatives showed two-photon absorption upon direct excitation of 1.6 W laser pulses at 800 nm. These studies suggest that the substituents, attached to distyryl core, are capable of boosting or hindering fluorescence intensities by distorting the π-conjugation of the 23DSI molecule. Our studies showed that 23DSI (p-F) has the highest fluorescence emission quantum yield. Theoretical calculations for the ground state of 23DSI derivatives confirmed differences in electron densities in 23DSI derivatives in the presence of different substituent attachments. The excellent fluorescence emission, high fluorescence quantum yield and two-photon absorption properties of these 23DSI molecules make them attractive candidates for potential applications in the fields of biological imaging, biomedicine, fluorescent probes, and photodynamic inactivation (PDI). B. subtilis samples, treated with micro molar solutions of 23DSI (p-OCH3) and 23DSI (p-CH3), showed very effective photodynamic inactivation (PDI) upon irradiation with white light.
关键词： Two photon absorption,Time-resolved fluorescence upconversion laser spectroscopy,Photodynamic inactivation,Gaussian calculations,Photo-physical properties,Light-activation
更新于2025-11-14 15:26:12
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Spectroscopic Compton imaging of prompt gamma emission at the MeV energy range
摘要： This work explores a novel tomographic approach to PGAA that is both quantitative and spatially resolved, adapted from a clinical "proton beam range finder" in which MeV gamma rays are imaged by coincidence measurements of Compton scattered gamma rays with multi-detector arrays. We performed preliminary measurements using a Compton camera made with CdZnTe detector arrays on a series of test samples with high-energy (> 1 MeV) gamma emission lines. 3D image reconstructions were performed on the 2.2 MeV peak from H. The image reconstruction methods were also evaluated using the emission data generated by Monte Carlo simulations under ideal conditions.
关键词： 3D elemental distribution,Compton imaging,Prompt gamma activation analysis
更新于2025-09-23 15:23:52
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Sn-doped and porogen-modified TiO2 photocatalyst for solar light elimination of sulfure diethyle as a model for chemical warfare agent
摘要： In the context of the increase in chemical threat due to warfare agents, the development of efficient methods for destruction of Chemical Warfare Agents are of first importance both for civilian and military purposes. Here, we demonstrate that optimized Sn-TiO2 doped and PEG-modified photocatalysts allow increased and high performances under UV-A and solar-light irradiations leading to total elimination of highly contaminated environments containing Diethylsulfide (DES) used as a model molecule mimicking Yperite (Mustard Gas). It has been shown that Sn doping induces significant modifications on the structural, morphological, surface, electronic and optical properties of TiO2. For example, the addition of 1% Sn increases significantly the surface area from 30 to 80 m2/g and decreases the particle size, while Sn-doping results in a reduction of the anatase band-gap from 3.2 to 2.95 eV. Total DES elimination could be reached for 90 and 120 min under continuous contaminant flux under UV-A and solar light activation, respectively accompanied with limited deactivation phenomenon. Correlations between the resulting physico-chemical properties of the doped and PEG-modified materials and the photocatalytic activities were carried out. The results open up extremely promising way for the decontamination of highly contaminated environments containing real warfare agents under UV-A but also under solar light illumination.
关键词： DES elimination,PEG-modified TiO2,UV-A and solar light activation,Sn-doped TiO2
更新于2025-09-23 15:23:52
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C5-Selective Trifluoromethylation of 8-Amino quinolines via Photoredox Catalysis
摘要： A new protocol for C5-selective C–H trifluoromethylation of 8-aminoquinolines via photoredox catalysis was developed. It allows rapid access to various C5-trifluoromethyl 8-amino quinoline derivatives in MeCN/H2O enabled by Eosin Y as photocatalysts.
关键词： para-selective C-H activation,Photoredox catalysis,Trifluoromethylation,8-Aminoquinolines
更新于2025-09-23 15:23:52