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Optical Pressure Sensor Based on the Emission and Excitation Band Width (FWHM) and Luminescence Shift of Ce3+ Doped Fluorapatite – High-Pressure Sensing
摘要： A novel, contactless optical sensor of pressure based on the luminescence red-shift and band width (full width at half maximum - FWHM) of the Ce3+-doped fluorapatite - Y6Ba4(SiO4)6F2 powder, has been successfully synthesized via a facile solid-state method. The obtained material exhibits a bright blue emission under UV light excitation. It was characterized using powder X-ray diffraction, scanning electron microscopy and luminescence spectroscopy, including high-pressure measurements of excitation and emission spectra, up to above ≈30 GPa. Compression of the material resulted in a significant red-shift of the allowed 4f→5d and 5d→4f transitions of Ce3+ in the excitation and emission spectra, respectively. The pressure-induced monotonic shift of the emission band, as well as changes in the excitation/emission band widths, have been correlated with pressure for sensing purposes. The material exhibits a high pressure sensitivity (dλ/dP ≈0.63 nm/GPa), and outstanding signal intensity at high-pressure conditions (≈90% of the initial intensity at around 20 GPa) with minimal pressure-induced quenching of luminescence.
关键词： Ce3+ doping,Contactless pressure gauge,Y6Ba4(SiO4)6F2 apatite phosphors,Lanthanide ions (Ln3+),Compression in DAC,Luminescent functional materials
更新于2025-09-23 15:23:52
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One-Step Solvothermal Formation of Pt Nanoparticles Decorated Pt <sup>2+</sup> -Doped α-Fe <sub/>2</sub> O <sub/>3</sub> Nanoplates with Enhanced Photocatalytic O <sub/>2</sub> Evolution
摘要： The photooxidation of water into O2 has been identified as the barrier of water-splitting, and light-driven water oxidation catalysts have been intensively explored to develop highly active water splitting materials. Despite the fascinating advantages for photocatalytic water oxidation, such as abundance in nature, inexpensiveness, low toxicity, thermo/photo-stability, and suitable electronic band structures, hematite α-Fe2O3 is a poor photocatalyst for water oxidation due to its short exciton lifetime and hole diffusion length, weak carrier mobility and shallow sunlight penetration depth. In this work, we have synthesized Pt nanoparticles decorated Pt2+-doped α-Fe2O3 nanoplates (Pt/Pt-Fe2O3 NPs) by a one-step solvothermal route, which exhibit the enhanced photoactivity and photostablity for water oxidation. The introduction of the Pt into the α-Fe2O3 by the means of elemental doping and nanoparticle decoration accounts for the enhanced performance. The doping of Pt2+ into α-Fe2O3 improves the isolation efficiency of the photo-induced carriers which remarkably increases the lifespan of hole carriers, and the adherence of metal Pt nanoparticles to the surface of α-Fe2O3 leads to formation of schottky barriers at the interface which effectively impedes the combination of photo-generated electrons and holes.
关键词： photocatalytic O2 evolution,Pt nanoparticles decoration,Pt2+ doping,schottky barrier,α-Fe2O3 nanoplates
更新于2025-09-23 15:23:52
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La-doped p-type ZnO nanowire with enhanced piezoelectric performance for flexible nanogenerators
摘要： In recent years, energy harvesting has attracted considerable attention as a promising method to convert waste energy to useful energy. In particular, piezoelectric energy harvesters are of significant interest, because they have a simple structure and can be used to harvest energy regardless of weather or other environmental conditions. In accordance with the miniaturization trend of electronic devices driven by low power, piezoelectric nanogenerators (PENGs) using various nanostructured materials are being developed. Among them, ZnO nanowires (NWs) are most widely used for the use of PENGs. However, while research on n-type ZnO NWs is extensive, studies on p-type ZnO NWs are insufficient owing to their poor stability. In this study, La-doped p-type ZnO (La:ZnO) NWs were synthesized by a hydrothermal method to expand the applications of p-type ZnO and determine their potential as PENGs. XRD analysis showed that La3+ ions was well doped without the formation of any secondary phases and caused a change in the lattice parameter when compared to that of undoped ZnO. XPS analysis was performed to investigate the surface elemental compositions of La:ZnO NWs, and the morphology of La:ZnO NWs was investigated using SEM and TEM. We further studied the piezoelectric output performance of undoped and La-doped ZnO NWs, and found that La:ZnO NWs showed improved piezoelectric output performance as a result of electron screening effect of the p-type semiconductor.
关键词： p-type ZnO,La-doping,Flexible device,ZnO nanowires,Nanogenerators
更新于2025-09-23 15:23:52
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Doping modulation of quasi-free-standing monolayer graphene formed on SiC(0001) through Sn1-Ge intercalation
摘要： In order to modulate the transfer doping of quasi-free-standing monolayer graphene (QFMLG) formed on SiC(0001), Ge atoms were intercalated additionally into QFMLG already formed by Sn intercalation between ZL and 6H-SiC(0001). By postannealing the Ge-deposited surface at 600 °C, the Sn1-xGex film with the 4 × √3 structure, composed of a bilayer and adatoms with dangling bonds under QFMLG, has been formed. It turns out that, in this Sn1-xGex film, Ge atoms preferentially occupy the bottom layer bound to the top Si atoms of the substrate, while Sn atoms occupy the top adatom sites. Strong correlation among the electrons localized at these adatom sites induces a semiconducting alloy film. As the postannealing temperature is increased up to 800 °C, the concentration of Ge in the intercalated film of the same 4 × √3 structure is gradually increased and the Dirac point also shifts gradually from ?0.16 eV to +0.20 eV relative to the Fermi level. Such a result confirms that the transfer doping of QFMLG on SiC(0001) has been modulated by varying the alloy composition of the Sn1-xGex interfacial film.
关键词： Scanning tunneling microscopy,Quasi-free-standing graphene,SnGe alloy intercalation,Hubbard band,Doping modulation,Photoemission spectroscopy,SiC(0001)
更新于2025-09-23 15:23:52
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Elucidation of the structural and charge separation properties of titanium-doped hematite films deposited by electrospray method for photoelectrochemical water oxidation
摘要： Elemental doping is considered to be an effective strategy to improve the photoelectrochemical (PEC) activity of hematite (a-Fe2O3) as a photoanode for water splitting, but the precise function(s) of the dopant remains unclear. In this study, we report on the structural and charge separation properties of titanium-doped hematite (Ti doped Fe2O3) films prepared by a simple electrospray technique for PEC water oxidation. The effect of Ti doping on the structure, morphology, light absorption, and electrical and photoelectrochemical properties was investigated on a-Fe2O3 films. SEM images revealed a reduction in particle sizes for 2% Ti doped a-Fe2O3, while an increase in particle size was observed for higher Ti content. XRD confirmed the presence of a-Fe2O3 without any impurity or other phases. From XPS spectra, the incorporation of Ti was confirmed in the form of Ti4+ as predominant species while no impurities from the substrate were detected. When the Ti doped Fe2O3 (2% Ti) film was used as a photoanode in a PEC cell, it delivered the best performance with a maximum photocurrent density of 1.09 mA cm-2 (at 1.8 V vs. RHE and under standard 1 sun illumination conditions (AM 1.5 G, 100 mW cm-2)), which is 2 times higher than that of the un-doped a-Fe2O3 (0.51 mA cm-2). The photoelectrode also showed a superior incident photon to current efficiency (IPCE) as compared to an un-doped a-Fe2O3. This enhancement in performance was attributed to the better charge separation and transport properties of a-Fe2O3 due to Ti doping, as revealed by an electrochemical impedance spectroscopy (EIS) analysis.
关键词： Electrospray deposition,PEC,a-Fe2O3,Ti doping,Water splitting
更新于2025-09-23 15:23:52
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Role of carbon-rings in polycrystalline GeSb2Te4 phase-change material
摘要： Carbon (C) is used to increase the overall performance of Ge-Sb-Te (GST) phase-change memory material. Yet the C configuration in polycrystalline GST and its microscopic role is unclear. Using the well-studied GeSb2Te4 as an example, this work unravels the microscopic C doping role based on ab initio calculations. Our results reveal that carbon prefers occupying the interstitials at very low C concentrations, while with a roughly critical C concentration of over 2%, carbon atoms will cluster at the grain boundaries, with very few carbon atoms might exist at the interstitials. With further increasing the C concentrations, C atoms tend to form ring-like configurations in the grain boundaries rather than chain-like configurations. This is due to that the covalent bonds in ring-like configurations are stronger than that in chain-like configurations. Further analysis on the lone-pair electrons and electronic densities of states show that C dopants significantly change the number of lone-pair electrons of surrounding atoms, thus affecting the electronic structure. Finally, the diffusion coefficient of C is estimated to be of the order of 10^-13 m^2/s at 400 K, indicating the good stability of C dopants in GeSb2Te4. Our work provides fundamental understanding on the microscopic role of C doping in GST phase-change materials and benefits for improving the properties of the recording materials by controlling the doping concentration.
关键词： Ab initio molecular dynamic simulations,Ab initio calculations,Phase-change materials,Grain boundary,GeSb2Te4,Carbon doping
更新于2025-09-23 15:23:52
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Facile synthesis of N/B double-doped Mn <sub/>2</sub> O <sub/>3</sub> and WO <sub/>3</sub> nanoparticles for dye degradation under visible light
摘要： In the present work, Nitrogen-doped and Nitrogen-Boron double doped manganese oxide (Mn2O3) and tungsten oxide (WO3) nanoparticles were synthesized using precipitation-hydrothermal method for methylene blue degradation under visible light. Materials were characterized using X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and UV-Vis spectroscopy. Results showed that N and B were successfully incorporated into the crystal lattices of Mn2O3 and WO3. XRD showed that WO3 was crystallized in the form of a monoclinic lattice, while cubic Mn2O3 was produced in the cubic form. The crystallite size was found to be decreased due to the substitution of N and B elements which reveals their roles to accelerate the crystal nucleation rate resulting in the decreased size. On the other hand, single and double doping has successfully narrowed the bandgaps of the as-synthesised metal oxide photocatalysts resulting in better absorption in the visible light. Bandgaps obtained were as follows: 3.02, 2.50, 1.73 and 1.77 eV for N-WO3 N/B-WO3, N-Mn2O3 and N/B-Mn2O3 respectively. Photocatalytic experiments showed that all as-synthesised materials exhibited a photocatalytic efficiency under visible light ≥420 nm. The degradation efficiency of MB was in the following order: N-B-co-doped metal oxides > N-doped metal oxides > metal oxides. The presence of scavenger molecules such as isopropanol (IPA), EDTA-2Na and benzoquinone inhibited MB degradation. Finally, the results showed that these materials can be reused several times without a notable decrease in efficiency.
关键词： Photocatalytic degradation,Visible light,Double-doping,Metal oxides
更新于2025-09-23 15:23:52
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Preparation and photocatalytic performance of Cu-doped CeO <sub/>2</sub> by citrate combustion method
摘要： Cu-doped cerium oxides were successfully prepared by nitrate combustion method. The crysatlline phase evolution, micro morphology and photocatalytic performance of the products are systematically studied by XRD, SEM/EDX and degradation rate of methylene blue. The results show that at relative low temperature (<600°C), 20 mol% copper can be dissolved into CeO2 fluorite type cubic structure, however, at high temperature of 700°C, CuO phase desolution from CeO2 solid solution is detected by XRD, and confirmed by DTA for 5% Cu-doped sample. The as prepared photocatalysts show agglomeration of ultra fine particles with porous structure. Degradation results of methylene blue indicate that better photocatalytic performance is obtained for 5% Cu-doped CeO2 under the stimulated visible light than UV light irradiation (both 254 nm and 365 nm), even the power of former is half of the later. The loss of photocatalytic activity for higher doping samples (>5% Cu) is believed to be the serious agglomeration of the particles and desolution of CuO from CeO2 solid solution.
关键词： doping,citrate combustion method,copper,photocatalytic,Ceria
更新于2025-09-23 15:23:52
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Cation disorder and epitaxial strain modulated Drude–Smith type terahertz conductivity and Hall-carrier switching in Ca <sub/> 1? <i>x</i> </sub> Ce <sub/><i>x</i> </sub> RuO <sub/>3</sub> thin films
摘要： The CaRuO3 is a non-Fermi liquid pseudo-cubic perovskite with a magnetic ground state on the verge of phase transition and it lies in the vicinity of the quantum critical point. To understand the sensitivity of its ground state, the effects of subtle aliovalent chemical disorder on the static and high frequency dynamic conductivity in the coherently strained structures were explored. The Ce-doped Ca1?xCexRuO3 (0 ? x ? 0.1) thin films were deposited on LaAlO3 (1 0 0) and SrTiO3 (1 0 0) substrates and studies for low-energy terahertz (THz) carrier dynamics, dc transport and Hall effect. These compositions exhibited a very effective and unusual Hall-carrier switching in both compressive and tensile strain induced epitaxial thin films. The dc resistivity depicts a switching from a non-Fermi liquid to a Fermi liquid behavior without any magnetic phase transition. A discernible and gradual crossover from Drude to Drude–Smith THz dynamic optical conductivity was observed while traversing from pure to 10% Ce-doped CaRuO3 films. Overall, a nearly Fermi liquid behavior, effective carrier switching and unusual features in THz conductivity, were all novel features realized for the first time in physically and/or chemically modified CaRuO3. These new phases highlight the novel subtleties and versatility of the systems lying near the quantum critical point.
关键词： epitaxial strain,terahertz,allovalent doping,Hall carrier switching
更新于2025-09-23 15:23:52
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Improved charge separation of NiS nanoparticles modified defect-engineered black TiO2 hollow nanotubes for boosting solar-driven photocatalytic H2 evolution
摘要： NiS nanoparticles (NPs) modified black TiO2 hollow nanotubes (NBTNs) are successfully synthesized via surface hydrogenation and facile solvothermal method. The unique structure with intensified surface and interface characteristic endow NBTNs with more catalytic sites, and increase charge carrier separation efficiency with a extended charge lifetime, overwhelmingly promoting its photocatalytic performance. The resultant NBTNs possess a relatively high surface area and pore size of ~89 m2 g-1 and ~9.8 nm, respectively. The resultants NBTNs exhibit an excellent solar-driven photocatalytic hydrogen rate (3.17 mmol h-1 g-1), which almost as high as that of Pt as cocatalyst, in which the apparent quantum (AQE) yield of 5.4 % (420 nm) is recorded for the NBTNs sample. Moreover, the turnover number (TON) can be up to 116000 within 48 h. And the turnover frequency (TOF) is 2400 for NiS. This novel strategy could provide a better understanding of cocatalyst photocatalytic mechanism, and a scheme simultaneously regulating the morphology and structure of photocatalyst for promoting H2 generation.
关键词： Mesoporous TiO2 nanotube,Oxygen vacancy defect,NiS cocatalyst,Photocatalysis,Ti3+ self-doping
更新于2025-09-23 15:23:52