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Efficient UV photodetectors based on Ni-doped ZnS nanoparticles prepared by facial chemical reduction method
摘要： Ni-doped ZnS nanoparticles are synthesized by simple hydrothermal process for the utilization in UV photodetectors. Surface morphology of the prepared samples is investigated through high resolution transmission electron microscopy (HRTEM), which reveals that the prepared nanoparticles are smaller than 20 nm. The well visualized selected area electron diffraction rings suggests the nanocrystalline nature of the prepared nanoparticles with (hkl) planes (111), (220) and (311). The structural analysis is done by x-ray diffraction (XRD) studies; which reveal the decrease in crystallite size with increase in Ni-doping concentration. The device performance of the photodetectors is tested under UV-A light (wavelength ?365 nm) and found that the ability of the prepared devices increases with increase in Ni-doping concentration. This can be attributed to the enhanced surface to volume ratio and increase in charge carrier concentration. The adsorption-desorption of oxygen molecules on the nanoparticles’ surface is considered to be the mechanism for UV photodetection.
关键词： Hydrothermal process,UV-Photodetectors,ZnS nanoparticles
更新于2025-09-16 10:30:52
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Rapid and green synthesis of fluorescent carbon dots from starch for white light-emitting diodes
摘要： A simple and green synthesis of fluorescent carbon dots (CDs) was achieved by a microwave-assisted hydrothermal method using potato starch as the carbon source. CDs with a maximum quantum yield of 2.46% were prepared by hydrothermal treatment of a 1 mg/mL starch solution at 220 oC for 30 min. Nitrogen doped CDs (N-CDs) were obtained under the same conditions using starch and ethylenediamine as the carbon and nitrogen sources, respectively, and their quantum yield was twice that of the undoped CDs. Both the CDs and N-CDs exhibit excellent water solubility and good thermal stability, emit blue fluorescence under UV light, but the fluorescent intensity of the latter is obviously higher than that of the former. Two white light-emitting diodes using the CD/starch composite and N-CDs as the phosphors emit yellowish white light and white light, respectively with xy coordinates of (0.38, 0.45) and (0.33, 0.35) in the Chromaticity Diagram of the Commission Internationale de L'Eclairage, suggesting that they have great potential application in optoelectronic devices.
关键词： Fluorescent carbon dots,Nitrogen doping,Light-emitting diodes,Microwave-assisted hydrothermal,Starch
更新于2025-09-16 10:30:52
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Orange photoluminescent N-doped graphene quantum dots as an effective co-sensitizer for dye-sensitized solar cells
摘要： In this research, nanocoral (NC) film of TiO2 was decorated with nitrogen-doped graphene quantum dots (NGQDs, average size of ～ 9 nm) and photovoltaic properties were investigated for dye-sensitized solar cell application. TiO2 NCs and NGQDs synthesized separately using the hydrothermal method and TiO2 NCs were decorated with NGQD solution by spin coating. FESEM images prove that TiO2 NCs are composed from nanorods, with an average diameter of about 60 nm. Optical characterization shows that the NGQDs are highly orange-luminescent (emission at 590 nm) and absorb UV and visible light photons. Using NGQDs together with N719 dye as co-sensitizers led to an improvement in efficiency of DSSC, as investigated by photoelectrical measurements. The experimental analysis reveals that this improvement arises from enhancement of charge separation and collection due to the cascaded energy levels because of presence of NGQDs. By addition of NGQDs into TiO2 NC photoanode, we were able to increase the short-circuit current density and efficiency by 40% (from 12.61 to 17.65 mA/cm2) and 31% (from 5.72 to 7.49%), respectively.
关键词： Nitrogen,Hydrothermal,Graphene quantum dots,Dye-sensitized solar cell
更新于2025-09-16 10:30:52
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Preparation and Photocatalytic Activity of Ag-Modified SnO2@TiO2 Core- Shell Composites
摘要： Photocatalytic degradation is an important method to mediate organic pollution in the environment. This article reports Ag-modified SnO2@TiO2 core-shell composite photocatalysts prepared via a hydrothermal method. The composite materials were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetry, X-ray photoelectron spectrometry, and UV-vis diffuse reflectance spectroscopy. The Ag modification and core structure in the composite enhanced the photocatalytic activity and stability of TiO2 for Rhodamine B degradation under visible light irradiation. The composite modified in 0.15 M AgNO3 showed an optimal level of photocatalytic activity, as it degraded 99.14% of Rhodamine B in 60 min while pure TiO2 only degraded 45.7% during the same time.
关键词： Hydrothermal method,Core-shell composites,Photocatalytic activity
更新于2025-09-16 10:30:52
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Hierarchical flower-like TiO2 microspheres with improved dye-sensitized solar cell performance
摘要： Hierarchical flower-like TiO2 microspheres (FMS) and TiO2 nanorice (NR) were obtained, respectively, by controlling the dosage of Ti precursor via a simple hydrothermal process. Flower-like TiO2 microspheres consist of nanopetals grown from the center radially, the nanopetals are about several nm in average thickness, and each nanopetal has a thinned tip with an average size of 15 nm. The unique hierarchical TiO2 microspheres with large surface area (118.6 m2 g?1) suggested its potential application in dye-sensitized solar cells (DSSCs). The power conversion efficiency of FMS-based DSSCs (9.58%) is much higher than that of NR-based DSSCs (7.13%), which could be ascribed to its excellent light-scattering and dye absorption ability, shorter electron transport pathway and longer electron recombination time derived from the thin thickness and large specific surface area of nanopetals.
关键词： Dye absorption,Hierarchical flower-like TiO2 microspheres,Hydrothermal process,Light-scattering,Dye-sensitized solar cells
更新于2025-09-12 10:27:22
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Deposition of orientation-controlled thick (K,Na)NbO<sub>3</sub> films on metal substrates by repeated hydrothermal deposition technique
摘要： (K,Na)NbO3 thick films were grown at 240°C on Ni-based metal substrates by repeated hydrothermal method. The metal substrates were covered with two types of buffer layers; SrRuO3/LaNiO3 and SrRuO3. Film thickness monotonically increased with increasing number of deposition cycles. The 27 μm-thick film was obtained on the metal substrate with SrRuO3/LaNiO3 by four cycles. The obtained films tended to show {100}c orientation and their degree of orientation increased with increasing number of deposition cycles. Films deposited on SrRuO3/LaNiO3-covered metal substrates showed more highly {100}c orientation compared with those on SrRuO3-covered metal substrates. Remnant polarization and coercive field measured at 5 kHz were 12 μC/cm2 and 70 kV/cm, while their effective values of piezoelectric coefficient (d33) was 35–40 pm/V for both films. These properties remained unchanged irrespective of a number of deposition cycles despite the orientation change of films. These results show that repeated hydrothermal deposition technique is one of the effective ways to prepare thick (K,Na)NbO3 films on metal substrates.
关键词： Metal substrate,Lead-free (K,Na)NbO3 film,Orientation control,Ferroelectric and piezoelectric properties,Hydrothermal,synthesize
更新于2025-09-12 10:27:22
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Dye sensitized solar cells based on titanium dioxide nanoparticles synthesized by flame spray pyrolysis and hydrothermal sol-gel methods: a comparative study on photovoltaic performances
摘要： Synthesis methods, shape and size of the nanocrystalline titanium dioxide (TiO2) are very crucial parameters for the power conversion efficiency of dye sensitized solar cells. In this article, nanoparticles of TiO2 powders have been synthesized via flame spray pyrolysis and hydrothermal sol-gel methods. These powders have been characterized by X-ray diffraction and scanning electron microscopy. In particular, the photovoltaic performances of the dye sensitized solar cells based on TiO2 synthesized by flame spray pyrolysis and hydrothermal sol-gel method have been compared. A commercial dye, N719 and a platinum doped counter electrode have been used for fabricating cells. Furthermore, a standard dye sensitized solar cell device has been fabricated by using a commercial Titania electrode in order to use as a reference cell. As a result, power conversion efficiencies of solar cells (under standard conditions, AM 1.5 G, 100 mW cm?2) have been calculated as 2.44, 3.94, and 7.67 % with TiO2 synthesized via flame spray pyrolysis method, hydrothermal sol-gel method and reference Titania electrode, respectively.
关键词： Sol gel,Flame spray pyrolysis,Dye sensitized solar cells,Hydrothermal method
更新于2025-09-12 10:27:22
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Three-dimensional ZnO/ZnxCd1?xS/CdS nanostructures modified by microwave hydrothermal reaction-deposited CdSe quantum dots for chemical solar cells
摘要： Effective interfaces composed of smart materials could play a critical role in the rapid transfer and separation of charges to achieve the high power-conversion efficiency of solar cells. In this work, we report an efficient chemical solar cell that uses a ZnO/ZnxCd1?xS/CdS structure, modified with CdSe deposited with a microwave hydrothermal technique, for rapid transport of charges using a frame construction to allow for reuse. The morphology, nanostructure, and reaction mechanisms of CdS nanorods and the ZnxCd1?xS layer were systematically investigated. The results indicated that light absorption expands from 550 nm of CdS to 700 nm because of the absorption of nearly all the visible light by deposited CdSe quantum dots. The effects of the compositional structure on cell performance are investigated to reveal the enhancement mechanism, which is mainly attributed to the suitable nano-branch structure, high light absorbability, low charge transfer resistance, and low recombination rate. This work demonstrates a potential universal method of designing an interface with a multi-component composite for efficient charge transport and separation, not only in chemical solar cells but with extensions to photocatalysis and water splitting uses as well.
关键词： Chemical solar cell,Composite structures,ZnO/ZnxCd1?xS/CdS,CdSe quantum dots,Microwave hydrothermal
更新于2025-09-12 10:27:22
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Hydrothermal processed heterogeneous MoS2 assisted charge transport in dye sensitized solar cells
摘要： Photovoltaic performance in dye sensitized solar cells (DSSCs) was improved by incorporating hydrothermal processed molybdenum disulfide (MoS2) into the bulk of titanium dioxide (TiO2) nanoparticle film. MoS2 exhibits a heterogeneous morphology comprising randomly distributed clustered nanoparticles and one dimensional nano-needles. The heterogeneous MoS2 was examined by X-ray photoelectron spectroscopy to study Mo 3d and S 2p peaks. Transmission electron microscopic studies on the heterogeneous MoS2 assert the presence of multilayers which further confirmed by UV–visible optical absorption spectroscopy showed absence of band-edge excitonic peaks at 612 nm and 674 nm. DSSCs show 17% enhancement in performance for 0.09 wt% of heterogeneous MoS2 incorporated TiO2 nanoparticle film compared to reference DSSC fabricated using only TiO2. Further changes in performance was examined by varying the concentration of MoS2 in TiO2 and observed that there is an optimum value to facilitate photo-generated charge transport kinetics in TiO2. The heterogeneous nature of MoS2 effectively acquired photo-electrons from TiO2 due to the presence of conduction band edge few meV below than that of in TiO2 and helps improving the performance.
关键词： TiO2,MoS2,Charge transport,Hydrothermal processing,Dye sensitized solar cells
更新于2025-09-12 10:27:22
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MoC/MnO composite materials as high efficient and stable counter electrode catalysts for dye-sensitized solar cells
摘要： MoC/MnO composite materials have been easily synthesized via a two-step hydrothermal and one-step carbonization method and used as counter electrode catalysts in DSSCs for the first time. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). And their electrocatalytic properties were also thoroughly studied by electrochemical impedance spectroscopy (EIS), Tafel polarization and so on. It is found that the electrocatalytic properties of the MoC/MnO CEs can be greatly enhanced. After optimizing the molar ratio of MoO3 precursor and KMnO4, the as-obtained MoC/MnO-0.25 CE has superior electrocatalytic ability, low charge transfer resistance and high incident photon-to-current conversion efficiency (IPCE). And the power conversion efficiency of the DSSC based on the MoC/MnO-0.25 CE is up to 8.00%, better than that of the DSSC used standard Pt CE (7.36%) in the same test environment, meanwhile the MoC/MnO-0.25 CE also has good electrochemical stability in the iodine-based electrolyte, which shows a promising candidate to replace Pt for DSSCs.
关键词： MoC/MnO composite materials,carbonization method,hydrothermal method,counter electrode catalysts,dye-sensitized solar cells
更新于2025-09-12 10:27:22