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An urchin-like SnO2/NaNbO3 nanocomposite with stable humidity-sensing properties at room temperature
摘要： An urchin-like nano-composite of SnO2/NaNbO3 was fabricated by the hydrothermal method and the influence of the Sn/Nb ratio in the samples on their humidity-sensing properties was investigated. The phases and morphologies of these composites and their elemental distributions were analyzed by X-ray diffraction scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The sensor based on the optimum Sn/Nb ratio of 1:0.4 exhibited remarkable humidity-sensing properties, including a good response (S = 4823.8) that was 8.72 times higher than that of the pure SnO2 sensor (S = 553.01). The composites showed rapid response and recovery times (3/9 s), as well as good stability, linearity, and excellent selectivity. The fabrication and humidity-sensing mechanisms were systematically analyzed using analog computations and Nyquist diagrams, respectively. Compared with pure NaNbO3 and SnO2 sensors, our easily prepared SnO2/NaNbO3 sensor demonstrates good sensing properties and holds great promise for use in humidity-sensing applications.
关键词： Humidity,SnO2,Urchin-like structure,NaNbO3,Hydrothermal method
更新于2025-09-19 17:15:36
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Optical fiber coated Zinc Oxide (ZnO) nanorods decorated with Palladium (Pd) for hydrogen sensing
摘要： A novel hydrogen (H2) sensor was developed using acid-etched optical fiber coated with zinc oxide (ZnO) nanorods. The sensing performance was done by comparing the acid-etched fiber coated with ZnO nanorods with and without decorated Palladium (Pd). The conventional optical single-mode fiber (SMF) with a diameter of 125 μm has been modified as a transducing platform by etching it to 11 μm diameter using hydrofluoric acid (HF) to enhance the evanescent field of the light propagates in the fiber core. The etched fiber was coated with ZnO nanorods via hydrothermal process by using seeding and growth solution method. The sensing layer was characterized through Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to verify the properties of ZnO. Catalyst Palladium (Pd) was sputtered onto the ZnO nanorods to improve H2 detection. The developed sensor operating temperature was found to be 150 °C that produces 6.36 dBm increase in response towards the 1% concentration of H2 in synthetic air. It was then tested with different concentration of H2. The sensor decorated with Pd has better performance in sensing compared to non-decorated Pd based on the output power versus time. The sensor best response and recovery times is 6 and 5 min respectively, for acid-etched optical fiber coated with ZnO nanorods decorated with Pd for 0.75% of H2 concentrations at 150 °C. The results indicate the optical fiber sensor might improve the performance towards H2 as oppose to the conventional electrical sensor.
关键词： Zinc oxide nanorods,Etching optical fiber,Hydrothermal method,Light-intensity response,Hydrogen sensor,Fiber optic sensor
更新于2025-09-19 17:13:59
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Facile and highly effective synthesis of nitrogen-doped graphene quantum dots as a fluorescent sensing probe for Cu2+ detection
摘要： Nitrogen-doped graphene quantum dots (N-GQDs) with high blue fluorescence efficiency were synthesized by the hydrothermal method from p-Phenylenediamine and p-Coumaric acid. The N-GQDs possess several superiorities, most significantly in excellent solubility and superior photostability. Besides, the as-prepared N-GQDs exhibit a uniform size distribution with a diameter of about 3.8±0.5 nm. After dispersing the N-GQDs in water, the formed aqueous solution still presents a stable and homogeneous phase even after 2 months at room temperature. The N-GQD dispersion was further utilized as sensing probes for the selective detection of copper ions (Cu2+), which is realized by the photoluminescence (PL) quenching of N-GQDs after adding Cu2+. The detection limit for Cu2+ was found to be 57 nM L-1, with superior selectivity in the presence of other commonly interfering metal ions. The presented results in this study provide a facile and high-efficiency method for synthesizing N-GQDs, with ultra-high detectivity and selectivity for Cu2+ detection, offering numerous opportunities for the development of biosensing, bioimaging, environment monitoring, and others.
关键词： Nitrogen-doped graphene quantum dots,Hydrothermal method,Photoluminescence quenching,Cu2+ detection
更新于2025-09-19 17:13:59
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Hydrothermally-Grown TiO2 Thin Film-Based Metal–Semiconductor–Metal UV Photodetector
摘要： A metal–semiconductor–metal (MSM) ultraviolet photodetector has been fabricated by using hydrothermally-grown TiO2 thin films. Ag paint was used as a contact electrode which showed the good ohmic contact between the metal–semiconductor junctions. The effect of deposition time on the structural, morphological and photodetector properties have been studied. The prepared TiO2 thin films are polycrystalline and show a rutile crystal structure with the preferred orientation along the (110) plane. The MSM UV photodetector was illuminated under a UV lamp with an intensity of 1.8 lW/cm2 and at 5-V bias. The photocurrent of the device increased linearly with the applied voltage. The maximum photocurrent of 3.96 lA was obtained for the film deposited at 5 h and maximum spectral photoresponsivity was 13.29 A/W. The device showed a fast optical switching behavior. The high responsivity and fast photoresponse shows that fabricated TiO2 detectors are good candidates for ultraviolet photodetectors.
关键词： MSM UV photodetector,Titanium dioxide,photoresponsivity,hydrothermal method
更新于2025-09-19 17:13:59
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Modulation doping of absorbent cotton derived carbon dots for quantum dot-sensitized solar cells
摘要： In order to improve the power conversion efficiency (PCE) of quantum dot-sensitized solar cells (QDSC), a series of absorbent cotton derived carbon quantum dots (CQDs) with different dopants (namely carbamide, thiourea, and 1,3-diaminopropane) have been successfully synthesized by a one-pot hydrothermal method. The average particle sizes of the three doped CQDs are 1.7 nm, 5.6 nm, and 1.4 nm respectively, smaller than that of the undoped ones (24.2 nm). The morphological and structural characteristics of the four CQDs have been studied in detail. In addition, the three doped CQDs exhibit better optical properties compared with the undoped ones in the UV-vis and PL spectra. Then CQD-based QDSC are experimentally fabricated, showing that the short current density (Jsc) and open circuit voltage (Voc) of the QDSC are distinctly improved owing to the dopants. Especially the QDSC with the 1,3-diaminopropane doped CQD achieves the highest PCE (0.527%), 299% larger than that without dopant (0.176%). In order to highlight a reasonable mechanism, the UV-vis diffuse reflectance spectrum of CQD sensitized TiO2 and the calculated energy band structures of various CQDs are investigated. It’s found from the above analysis that the addition of carbamide, thiourea, and 1,3-diaminopropane is beneficial to obtain CQDs of smaller size, and with a smaller band gap and more nitrogenous or sulphureous functional groups, which enhance the light absorption performance and photo-excitation properties. The above factors are helpful to improve the Jsc of QDSC. Nitrogen, acting as a donor to the CQDs, will assist the sensitized photoanode with a higher Fermi level, resulting in a larger Voc of the QSDC. Finally this study builds the relation among the microstructure of the CQDs, three characteristics of the CQDs (namely the spectra, energy band structure and functional groups) and the photoelectric properties of the QDSC, which will provide guidance for the modulation doping of CQDs to improve the PCE of QDSC.
关键词： dopants,carbon quantum dots,hydrothermal method,power conversion efficiency,quantum dot-sensitized solar cells
更新于2025-09-16 10:30:52
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Ni3S2@MWCNTs films for effective counter electrodes of dye-sensitized solar cells
摘要： Composite films nickel sulfide (Ni3S2) nanoparticles were grown on multiwall carbon nanotubes (MWCNTs) and in situ coated onto conducting glass substrates by the hydrothermal process at 170 °C. These Ni3S2@MWCNTs films were applied for counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). In this work, nanostructure, crystalline structure, electrochemical activities and electron-charge transfer resistance of CEs were studied. In addition, the effective surface areas of CEs were analyzed and discussed as well. The power conversion efficiency (PCE) enhancement of up to 7.48%, compared with that of Ni3S2-DSSC, was demonstrated for a Ni3S2@MWCNTs DSSC.
关键词： Counter electrode,Ni3S2,Dye-sensitized solar cell,Hydrothermal method,Multiwall carbon nanotubes
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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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
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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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ZnO nanorods array as light absorption antenna for high-gain UV photodetectors
摘要： Hydrothermal method provides the advantages of simple, low-temperature growth conditions, low cost and large surface areas for the samples. Also, exciton dissociation can be enhanced by surface plasmon resonance (SPR) due to the plasmonic absorption enhancement of incident light. In this paper, high-gain ultraviolet (UV) photodetectors based on vertically aligned ZnO nanorods (ZnO-NRs) array as light absorption antenna were presented, in which ZnO-NRs array was prepared by hydrothermal method. Our experimental data showed that the device performance of the UV photodetector Au/ZnO(ZnO-NRs:Au-NPs)/Au can be further enhanced after the gaps of ZnO-NRs array were filled with Au nanoparticles (Au-NPs). The photo-to-dark current ratio and the specific detectivity of the UV photodetector Au/ZnO(ZnO-NRs:Au-NPs)/Au reached to 1×105 and 1.84×1013 Jones at 2 V under 100 μW/cm2 365 nm illumination, respectively. The physical mechanism for the enhanced performance of the UV photodetectors is discussed.
关键词： Surface plasmon resonance (SPR),ZnO nanorods (ZnO-NRs) array,Ultraviolet (UV) photodetectors,Hydrothermal method,Schottky contact
更新于2025-09-12 10:27:22