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Electrochemical and photoelectrochemical water oxidation of solvothermally synthesized Zr-doped α-Fe2O3 nanostructures
摘要： To investigate the oxygen evolution reaction of overall water-splitting process, Zr-doped α-Fe2O3 nanostructures were synthesized by employing one-pot solvothermal route. This work reported the electrochemical and photoelectrochemical (PEC) properties of synthesized photoanodes depending on solvothermal treatment time (i.e., 12, 16, and 20 h) maintained during synthesis. The treatment time influenced the morphology of Zr-doped α-Fe2O3 nanostructures, which directly exert an effect on the electrochemical and PEC performance of the synthesized photoanodes. The high conductivity and lowest Tafel slope value (83 mV/decade) were attained from electrochemical studies for the nanoflake morphology. The highest photocurrent of about 0.52 mA/cm2 at 1.5 V Vs RHE was obtained for Zr-doped α-Fe2O3 nanoflakes and 16.17% intrinsic photon conversion efficiency was achieved for the same sample with high photostability for 2 h under continuous irradiation of light. We reported the treatment time-dependent morphology effect on both electrochemical and PEC water oxidation of Zr-doped hematite nanoflakes in this work.
关键词： IPCE,Zr-doped hematite,Nanostructures,Water oxidation
更新于2025-09-04 15:30:14
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Fabrication of Heterogeneous Photocatalysts for Insight role of Carbon Nanofibre in Hierarchical WO3/ MoSe2 composite for Enhanced Photocatalytic Hydrogen Generation
摘要： Mimicking the natural photosynthesis system, artificial photocatalysis facilitates effective utilization of solar energy for environmental sustainability and hydrogen energy production. In this work, the robust and efficient carbon fiber has been successfully incorporated into the interface between WO3 nanodots and MoSe2 needles using the facile hydrothermal and solvothermal method. The suitable interfacial contact of heterogeneous photocatalysts plays a significant role in the separation/transfer of interfacial photogenerated electron-hole pairs and hetero-junction. It seems an efficient approach for enhanced photocatalytic performance since the greater area of contact could improve the interfacial rate of charge transfer. The phase structure of prepared WO3 nanodots changed from the monoclinic to hexagonal phase by the addition of co-catalyst. The experimental results exhibited that carbon fiber played a tri-functional role to boost up the photocatalytic activity over MoSe2 nanostructures. It’s not only act as operative co-catalyst but could also serve as the conductive electron bridges, rather than general cocatalyst, to accumulate electrons and encourage the hydrogen generation kinetics over the WO3 photocatalysts. More interestingly, the WO3-1% MoSe2-1.5% carbon fiber and WO3-1%MoSe2 nanocomposites demonstrated the excellent rates of hydrogen evolution 438.7 and 356.2 mmol/g.h, which were 7.6 and 6.17 times higher when compared to that of pure MoSe2, respectively. Under the visible light excitation, the atomically junction encourages fast electron transfer from nanofibers to MoSe2 to suppress the rapid recombination kinetics within WO3 nanodots and extend the lifetime of WO3 charge carrier’s, thereby releasing more photogenerated electrons with higher reducing power for hydrogen evolution. The current work can contribute with new perspectives and mechanistic insight for the design and development of heterogeneous photocatalysts WO3 based nanostructures using the combination of MoSe2 and trifunctional carbon nanofibers for environment and energy harvesting applications.
关键词： Sustainable Environment,Hydrogen Evolution,Carbon nanofibers,Photocatalysis,Nanostructures
更新于2025-09-04 15:30:14
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Shaped Fe2O3 nanoparticles – synthesis and enhanced photocatalytic degradation towards RhB
摘要： Iron oxide nanoparticles of different shape were synthesized via an ion-mediated hydrothermal route. The addition of Zn2+ and Al3+ to the reaction system is no doubt the reason for the formation of hematite with cubic and disc structures, respectively. The growth mechanism of iron oxides is proposed. The morphology of the obtained nanostructures was analyzed by SEM and HR-TEM. The phase identification was performed by XRD and FTIR spectroscopy. Nanopowders were characterized by optical and zeta potential PZ measurements. The overall density of hydroxyl groups depends on the crystal structure and crystal faces. Placing oxides in the Rhodamine B RhB solution reduces the potential value PZ. The observed changes are the most pronounced for discs (ΔPZ=16.2 mV) and the least pronounced for cubes (ΔPZ=5.5 mV). A significant degree of adsorption of the dye on the surface of the discs, which confirms the presence of a significant number of hydroxyl groups responsible for surface activity. The photocatalytic activity of the obtained nanostructures investigated by photodecomposing RhB can be improved by applying H2O2 as an electron trap. Cyclic photodegradation experiments show that iron oxides with variously exposed planes can be used multiple times without losing their photocatalytic properties. Discs exhibited the most desirable photocatalytic behavior. Based on the performed addition of hydrogen peroxide, it seems that the shape of the particles affects the diffusion of H2O2 at the surface.
关键词： crystal,iron hydroxides,Fe2O3,nanostructures
更新于2025-09-04 15:30:14
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Al-doped Ag2S nanostructures: ultrasonic synthesis and physical properties
摘要： Un- and aluminum (Al)-doped silver sulfide (Ag2S) nanostructures were grown by the sonochemical method. The samples were studied by employing various identification methods including X-ray diffraction (XRD), field emission electron microscopy (FESEM), photoluminescence (PL), Raman and UV-Visible. The results showed that adding Al dopant shifts the diffraction peaks to higher angles and reduces their intensity. Furthermore, the size of the nanocrystal was reduced compared to the undoped sample. It was found that the strain in the doped samples is greater than the un-doped sample by the use of Hall-Williamson (W-H) method. FESEM images demonstrate the composition of spherical forms of nanostructures, which is converted to a quadrilateral shape by adding dopant. PL analysis illustrated the presence of emission bands in the visible region that was resulted by the emission of the near band edge (NBE), as well as the percentage of the density and type of defects. Moreover, Al reduced the optical energy band gap of the nanostructures. Finally, the influence of the parameters affecting the crystalline and the optical properties of the material over the growth process was investigated using Raman analysis.
关键词： Al-doped Ag2S nanostructures,Structural features,Sonochemical,Optical properties
更新于2025-09-04 15:30:14
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Controllable coating polypyrrole on silicon carbide nanowires as a core-shell nanostructure: a facile method to enhance attenuation characteristics against electromagnetic radiation
摘要： Continuous polypyrrole (PPy) shells were coated on silicon carbide (SiC) nanowires to form core-shell nanostructures and the thicknesses of the shells were efficiently tuned through controlling the rate of polymerization. Compared with the composites loaded with pure SiC nanowires, the values of ε′ and ε′′ for the composites loaded with PPy@SiC nanowires were strengthened remarkably along with the increased thickness of the shells. The electromagnetic absorption (EA) bandwidth lower than ?10 and ?20 dB can be monitored in the area of 3.67-18.00 and 4.13-18.00 GHz, when 5 wt% of PPy@SiC nanowires were loaded in the composite. Meanwhile, the effective EA bandwidth can reach 6.88 GHz and the strongest reflection loss is ?58.6 dB.
关键词： dielectric properties,polypyrrole,silicon carbide nanowires,core-shell nanostructures,electromagnetic absorption
更新于2025-09-04 15:30:14
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Photoluminescence from GaAs nanostructures
摘要： The confinement properties of semiconductor nanostructures have promising potential in technological application. The main objective of this study is to describe the dependence of Photoluminescence (PL) intensity on different parameters like temperature, excitation wavelength, time and photon energy of GaAs quantum dots (QDs). The model equations are numerically analyzed and simulated with matlab and FORTRAN codes. The experimental fitted values and physical properties of materials are used as data source for our simulation. The result shows that at low temperature the peak is quite sharp, as temperature increases the PL intensity decreases and get quenched at particular thermal energy.
关键词： quantum confinement,Photoluminescence (PL) intensity,GaAs quantum dots,nanostructures,thermal quenching energy
更新于2025-09-04 15:30:14
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Enhanced Temperature-Tunable Narrow-Band Photoluminescence from Resonant Perovskite Nanograting
摘要： Tunable light-emitting nanostructures are prospective for reconfigurable compact optoelectronic devices. In this regard, halide perovskites are one of the most efficient class of materials, because of their outstanding electronic and optical properties as well as low cost of fabrication and nanostructuring. Here, we study the temperature-tunable reconfiguration of photonic modes in periodically nanostructured perovskite (MAPbI3) film probed by enhanced photoluminescence. We achieved the quality factors of resonances around 500 at wavelengths 750–760 nm. The experimental results are in well agreement with theoretical simulations. Our study reveals the origin of the emission enhancement from such kind of perovskite nanostructures and paves the way to highly directional, efficient, and tunable narrowband emission from optoelectronic devices.
关键词： Optoelectronic devices,Photoluminescence,Tunable light-emitting nanostructures,Halide perovskites,Nanogratings
更新于2025-09-04 15:30:14
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Effect of Chloride and pH on the Electrochemical Surface Oxidation Enhanced Raman Scattering
摘要： In the present work, electrochemical surface oxidation enhanced Raman scattering (EC-SOERS) was studied using time resolved Raman spectroelectrochemistry. This multiresponse technique allows us to obtain dynamic information about the processes taking place during the electrochemical oxidation of a silver substrate. EC-SOERS is particularly found in specific electrolytic conditions, namely, HClO4 0.1 M + KCl 5·10-3 M, and has a clear dependence on chloride concentration and pH, being the optimum values between 5·10-3 M and 1·10-2 M for chloride and pH = 1. In light of the results of this study, the appearance of the phenomenon is related to the modification of the electrode surface, yielding Ag/AgCl cubes as plasmonic structures, and the stability of such structures at low pH values. The results presented in this work could shed more light into the intricate EC-SOERS phenomenon which can be summarized as the increase of the Raman signal for a Raman probe molecule exclusively during the electrochemical oxidation of silver electrodes.
关键词： Silver,Raman enhancement,nanostructures,spectroelectrochemistry
更新于2025-09-04 15:30:14
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Hydrothermal Approach to Spinel-Type 2D Metal Oxide Nanosheets
摘要： The peculiar physical and chemical properties of 2D nanostructures have aroused global research interest in developing new members, synthetic technology, and exploring their potential applications in functional nanodevices. However, it is extremely challenging to directly obtain the 2D nanosheets for these extrinsic layered structures using conventional routines. In this work, we demonstrate the facile and general synthesis of 2D spinel-type metal oxides nanosheets through a simple hydrothermal reaction. Using this method, cubic γ-Ga2O3, ZnGa2O4 and MnGa2O4 nanosheets with triangular/hexagonal configuration and ultrathin thickness have been synthesized, and all these nanosheets show preferential growth along (111) plane with the minimum formation energy. Microstructural and composition analyses using HRTEM, EDS, XPS, and so on reveal that the as-synthesized 2D nanosheets are well-crystallized in cubic fcc-phase and show high purity in composition, and the formation process of MGa2O4 nanosheets can be regarded as the competition of M2+ and Ga3+ in tetrahedral site. Spatially resolved cathodoluminescence measurement of individual 2D nanosheet shows that the γ-Ga2O3, ZnGa2O4, and MnGa2O4 nanosheets exhibit distinct luminescence behavior, and ZnGa2O4 nanosheets show the strongest emission in visible region. It is expected that the facile synthesis of spinel-type metal oxides of γ-Ga2O3, ZnGa2O4, and MnGa2O4 nanosheets will further promote the exploration of a variety of semiconductor nanostructures that could not be achieved using conventional technology suitable for layered structures and will also open up some opportunities for the integration of advanced functional nanodevices such as photodetectors, phosphors on the basis of them.
关键词： spinel-type metal oxides,functional nanodevices,2D nanostructures,luminescence behavior,hydrothermal reaction
更新于2025-09-04 15:30:14
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Metamorphic InAs(Sb)/InGaAs/InAlAs nanoheterostructures grown on GaAs for efficient mid-IR emitters
摘要： High-efficiency semiconductor lasers and light-emitting diodes operating in the 3–5 μm mid-infrared (mid-IR) spectral range are currently of great demand for a wide variety of applications, in particular, gas sensing, noninvasive medical tests, IR spectroscopy etc. III-V compounds with a lattice constant of about 6.1 ? are traditionally used for this spectral range. The attractive idea to fabricate such emitters on GaAs substrates by using In(Ga,Al)As compounds is restricted by either the minimum operating wavelength of ～8 μm in case of pseudomorphic AlGaAs-based quantum cascade lasers or requires utilization of thick metamorphic InxAl1-xAs buffer layers (MBLs) playing a key role in reducing the density of threading dislocations (TDs) in an active region, which otherwise result in a strong decay of the quantum efficiency of such mid-IR emitters. In this review we present the results of careful investigations of employing the convex-graded InxAl1-xAs MBLs for fabrication by molecular beam epitaxy on GaAs (001) substrates of In(Ga,Al)As heterostructures with a combined type-II/type-I InSb/InAs/InGaAs quantum well (QW) for efficient mid-IR emitters (3–3.6 μm). The issues of strain relaxation, elastic stress balance, efficiency of radiative and non-radiative recombination at T = 10–300 K are discussed in relation to molecular beam epitaxy (MBE) growth conditions and designs of the structures. A wide complex of techniques including in-situ reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning and transmission electron microscopies, X-ray diffractometry, reciprocal space mapping, selective area electron diffraction, as well as photoluminescence (PL) and Fourier-transformed infrared spectroscopy was used to study in detail structural and optical properties of the metamorphic QW structures. Optimization of the growth conditions (the substrate temperature, the As4/III ratio) and elastic strain profiles governed by variation of an inverse step in the In content profile between the MBL and the InAlAs virtual substrate results in decrease in the TD density (down to 3 × 107 cm?2), increase of the thickness of the low-TD-density near-surface MBL region to 250–300 nm, the extremely low surface roughness with the RMS value of 1.6–2.4 nm, measured by AFM, as well as rather high 3.5 μm-PL intensity at temperatures up to 300 K in such structures. The obtained results indicate that the metamorphic InSb/In(Ga,Al)As QW heterostructures of proper design, grown under the optimum MBE conditions, are very promising for fabricating the efficient mid-IR emitters on a GaAs platform.
关键词： Buffer layer,Non-radiative recombination,Mid-infrared emitters,Photoluminescence,Metamorphic heterostructures,InSb,InAs,Structural properties,Molecular beam epitaxy,Nanostructures,In(Ga,Al)As ternary alloys,Threading dislocations,Quantum well
更新于2025-09-04 15:30:14