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An Efficient Room Temperature Ethanol Sensor Device Based on p-n Homojunction of TiO <sub/>2</sub> Nanostructures
摘要： In this paper, an efficient room temperature ethanol sensor device based on p-n homojunction of p-TiO2 nanoparticles (NPs) and n-TiO2 nanotubes (NTs) is reported. p-TiO2 NPs were prepared by low-temperature sol–gel method and coated on n-TiO2 NTs (NPs) grown by electrochemical anodization. Field emission scanning electron microscopy and X-ray diffraction authenticated the formation of stable homojunction between p-type anatase TiO2 NPs and n-type anatase TiO2 NTs. Current–voltage characteristics of the device, in the lower voltage range (0–1.26 V) for 30 °C, followed nonlinear characteristics (Schottky). With increase in voltages (>1.26 V) and temperature (40 °C–100 °C) such nonlinear behavior moves toward more linear ones. The gas sensing performance of the homojunction device was studied at room temperature with alcohols as the test species. The device offered the maximum response magnitude of ～57% (toward ethanol) at 100 ppm with appreciably fast response time and recovery time of ～30 and ～16 s, respectively. Dramatic increase in the effective depletion region area distributed throughout the nanotubular voids and the associated localized electric filed originated from the electrostatic charge separation therein (which helps in easy dissociation of target species) is possibly responsible for such efficient room temperature sensing performance.
关键词： room temperature,Ethanol sensing,fabrication and characterization,p-TiO2 nanoparticles (NPs)/n-TiO2 nanotubes (NTs),homojunction
更新于2025-09-19 17:15:36
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Conformal Filling of TiO <sub/>2</sub> Nanotubes with Dense M <sub/>x</sub> S <sub/>y</sub> Films for 3D Heterojunctions: The Anion Effect
摘要： It is appealing to fill up TiO2 nanotube arrays with other semiconductors to form three-dimensional heterojunctions of interdigitated feature. This benefits from the large interfacial area for rapid charge separation and the ordered vertical channels for oriented charge transport. However, it remains a great challenge to fill the nanotubes with dense films and more importantly in a conformal manner. In this study, the TiO2 nanotubes are conformally filled with ZnS by successive ionic layer adsorption and reaction. The ZnS exists in the form of either discrete nanoparticles or dense films when using nitrate or acetate precursor solutions, respectively. This is attributed to the hydrolysis process of the acetates in aqueous solutions, which releases extra hydroxyl ions beneficial to film formation. The CuS/TiO2 heterojunctions, resulted from ZnS dense films, show better rectifying behaviors in view of the interdigitated structure. Such a conformal filling process with dense films can also be used to form other MxSy/TiO2 bulk heterojunctions toward applications in optoelectronics, photovoltaics, photocatalysis, and so on.
关键词： conformal coating,heterojunction,TiO2 nanotubes,Anodization,rectifying behavior
更新于2025-09-19 17:15:36
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Enhanced visible-light-photoconversion efficiency of TiO2 nanotubes decorated by pulsed laser deposited CoNi nanoparticles
摘要： The pulsed laser deposition (PLD) technique has been used to decorate TiO2 nanotubes (NTs) with cobalt-nickel (CoNi) nanoparticles (NPs). The TiO2 NTs were produced beforehand through the controlled anodic oxidation of titanium substrates. The effect of the nature of the PLD background gas (Vacuum, O2 and He) on the microstructure, composition and chemical bondings of the CoNi-NPs deposited onto the TiO2-NTs has been investigated. We found that the PLD CoNi-NPs have a core/shell (oxide/metal) structure when deposited under vacuum, while they are fully oxidized when deposited under O2. On the other hand, by varying the CoNi-NPs loading of the TiO2-NTs (through the increase of the number of laser ablation pulses (NLP)), we have systematically studied their photocatalytic effect by means of cyclic-voltammetry (CV) measurements under both AM1.5 simulated solar light and filtered visible light. We show that depositing CoNi-NPs on the substrate under vacuum and He increases the photo-electrochemical conversion effectiveness (PCE) by 600% (at NLP = 10,000) in the visible light domain, while their overall PCE degrades with NLP under solar illumination. In contrast, the fully oxidized CoNi-NPs (deposited under O2) are found to be the most effective catalyst under sunlight with an overall increase of more than 50% of the PCE at the optimum loading around NLP ~1000. Such catalytic enhancement is believed to result from both an enhanced light absorption by CoO (of which bandgap is of ~2.4 eV) and the formation of a heterojunction between NiO/CoO nanoparticles and TiO2 nanotubes.
关键词： TiO2 nanotubes,Pulsed laser deposition,Cobalt/nickel nanoparticles,Photo-electrochemistry,Water-splitting
更新于2025-09-19 17:13:59
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Study of TiO2 nanotubes decorated with PbS nanoparticles elaborated by pulsed laser deposition: microstructural, optoelectronic and photoelectrochemical properties
摘要： Titanium dioxide nanotube arrays (TiO2 NTAs) have been synthesized using the electrochemical anodization procedure. Lead sulfide nanoparticles (PbS NPs) were deposited on TiO2 NTAs (PbS NPs/TiO2 NTAs) using the pulsed laser deposition (PLD) method. The prepared samples (PbS NPs/TiO2 NTAs) were characterized using scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis spectroscopy and photoluminescence. The size of the PbS NPs was controlled by varying the number of laser pulses (NLP) during the PLD process. TEM observations show that the PbS NPs are in the range of 10–20 nm, consistent with the results obtained from XRD. HRTEM and diffuse reflectivity show that, at NLP ≥ 2500, the growth of the PbS NPs occurs on a previously formed PbS layer. Transmission and absorption spectra show that the PbS-NPs have an indirect optical bandgap which is particle size independent. This optical bandgap corresponds to excitonic transitions, which are greatly affected by oxygen defects, off-stoichiometry and other surface state defects, particularly for smaller NPs (NLP < 2500). The absorption spectra of the TiO2 NTAs show that the PbS NPs extend the absorption range of the TiO2-NTAs from the ultraviolet to the visible region, indicating that the PbS NPs/TiO2 NTAs heterojunction facilitates the separation of the photogenerated charge carriers. Photoelectrochemical analyses show that a maximum photocurrent current density of ~1.05 mA/cm2 and a photoelectrochemical conversion efficiency of 2.5% are reached for NLP = 2500 under an illumination of 100 mW/cm2 in the UV–Vis range.
关键词： TiO2 nanotubes,Photoelectrochemical properties,PbS nanoparticles,PLD
更新于2025-09-16 10:30:52
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The In-Depth Studies of Pulsed UV Laser-Modified TiO2 Nanotubes: The Influence of Geometry, Crystallinity, and Processing Parameters
摘要： The laser processing of the titania nanotubes has been investigated in terms of morphology, structure, and optical properties of the obtained material. The length of the nanotubes and crystallinity, as well as the atmosphere of the laser treatment, were taken into account. The degree of changes of the initial geometry of nanotubes were checked by means of scanning electron microscopy, which visualizes both the surface and the cross-section. The phase conversion from the amorphous to anatase has been achieved for laser-treated amorphous material, whereas modification of calcined one led to distortion within the crystal structure. This result is confirmed both by Raman and grazing incident XRD measurements. The latter studies provided an in-depth analysis of the crystalline arrangement and allowed also for determining the propagation of laser modification. The narrowing of the optical bandgap for laser-treated samples has been observed. Laser treatment of TiO2 nanotubes can lead to the preparation of the material of desired structural and optical parameters. The usage of the motorized table during processing enables induction of changes in the precisely selected area of the sample within a very short time.
关键词： laser treatment,TiO2 nanotubes,phase transformation,surface modification
更新于2025-09-16 10:30:52
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A nanoreactor based on SrTiO3 coupled TiO2 nanotubes confined Au nanoparticles for photocatalytic hydrogen evolution
摘要： A TiO2 nanotube-based nanoreactor was designed and fabricated by facile two steps synthesis: firstly, hydrothermal synthesized SrTiO3 was deposited on TiO2 nanotubes (TiO2NTs). Secondly, the Au nanoparticles (NPs) were encapsulated inside the TiO2NTs followed by vacuum-assisted impregnation. The as-synthesized composites were characterized using Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectra (PL) and Ultravioletevisible absorption spectroscopy (UVevis). The photocatalytic performance was evaluated by the hydrogen evolution reaction. The results revealed that the SrTiO3 modified TiO2NTs confined Au NPs (STO-TiO2NTs@Au) achieved an enhanced hydrogen evolution rate at 7200 mmol h?1 g?1, which was 2.2 times higher than that of bald TiO2NTs@Au at 3300 mmol h?1 g?1. The improved photocatalytic activity could be attributed to the synergistic effect of the electron-donating of SrTiO3 and TiO2NTs confinement. The as-designed nanoreactor structure provides an example of efficient carriers’ separation photocatalyst.
关键词： Au nanoparticles,Confinement,SrTiO3,TiO2 nanotubes,Photocatalytic hydrogen evolution
更新于2025-09-12 10:27:22
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Highly ordered combined structure of anodic TiO2 nanotubes and TiO2 nanoparticles prepared by a novel route for dye-sensitized solar cells
摘要： Combined structure of anodic TiO2 nanotubes and TiO2 nanoparticles (TiNTs-TiNPs) has been synthesized by a facile combination of hydrothermal and chemical vapor deposition methods. Ordered TiO2 nanotubes with smooth walls were fabricated by two step anodization method in ethylene glycol containing NH4F at 50V. This nanotubular array after annealing at 450 oC was subjected to the hydrothermally produced gaseous environment in an autoclave with diluted TiCl4 solution at its bottom. Vapors of TiCl4 were allowed to react chemically with water vapors for predefined time durations at 180 oC that resulted in the deposition of TiO2 nanoparticles on tubes’ surface and side walls. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that for one hour reaction duration, nanoparticles were evenly coated on the walls of nanotubes, whereas, longer durations tend to deteriorate the tubular structure. Consequently, the ordered TiNTs-TiNPs array produced after one hour coating has shown better performance for dye-sensitized solar cell DSSC) in back illumination mode with 130 % increase in efficiency as compared to the device based on bare TiO2 nanotubes. The same photoanode has higher reflective properties with higher scattering ability. The solar cell based on this photoanode exhibits higher external quantum efficiency and effective charge transport properties. This study shows that porous ordered 1D structures based on TiO2 are of crucial importance for the high performance of DSSCs.
关键词： TiO2 nanotubes,anodization,ordering,TiO2 nanoparticles,hydrothermal
更新于2025-09-11 14:15:04
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Influence of PbS Quantum Dots-Doped TiO2 Nanotubes in TiO2 Film as an Electron Transport Layer for Enhanced Perovskite Solar Cell Performance
摘要： Lead sulfide quantum dots-doped titanium dioxide nanotubes (PbS QDs-doped TNTs) were successfully prepared by the hydrothermal and impregnation methods. A thin layer of titanium dioxide (TiO2) comprising of PbS QDs-doped TNTs was applied as an electron transport layer (ETL) in order to improve the planar perovskite solar cell efficiency. The role of incorporating a high surface area of one-dimensional nanotube structure of TiO2 in the conventional TiO2 layer provided a special unidirectional charge transport and a high charge collection. Moreover, doping PbS QDs onto the surface of TNTs modified the electronic and optical properties of the ETL by downshifting the conduction band of TiO2 from ?4.22 to ?4.58 eV, therefore promoting the driving force of an electron injection to the transparent conductive electrode. By varying the concentration of PbS QDs-doped TNTs dispersed in 2-butanol from 0.1 to 0.9 mg/mL, a concentration of 0.3 mg/mL PbS QDs-doped TNTs was the optimum concentration to be mixed with TiO2 solution for the ETL deposition. The best perovskite solar cell performance with the optimum loading of PbS QDs-doped TNTs provided 14.95% power conversion efficiency, which was increased from 12.82% obtained from the cell with pristine TiO2 film as ETL.
关键词： PbS quantum dots (PbS QDs),perovskite solar cells (PSCs),TiO2 nanotubes (TNTs),Electron transport layer (ETL)
更新于2025-09-11 14:15:04
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Impact of TiO2 Nanotubes’ Morphology on the Photocatalytic Degradation of Simazine Pollutant
摘要： There are various approaches to enhancing the catalytic properties of TiO2, including modifying its morphology by altering the surface reactivity and surface area of the catalyst. In this study, the primary aim is to enhance the photocatalytic activity by changing the TiO2 nanotubes’ architecture. The highly ordered infrastructure is favorable for a better charge carrier transfer. It is well known that anodization affects TiO2 nanotubes’ structure by increasing the anodization duration which in turn in?uence the photocatalytic activity. The characterizations were conducted by FE-SEM (?end emission scanning electron microscopy), XRD (X-ray diffraction), RAMAN (Raman spectroscopy), EDX (Energy dispersive X-ray spectroscopy), UV-Vis (Ultraviolet visible spectroscopy) and LCMS/MS/MS (liquid chromatography mass spectroscopy). We found that the morphological structure is affected by the anodization duration according to FE-SEM. The photocatalytic degradation shows a photodegradation rate of k = 0.0104 min?1. It is also found that a mineralization of Simazine by our prepared TiO2 nanotubes leads to the formation of cyanuric acid. We propose three Simazine photodegradation pathways with several intermediates identi?ed.
关键词： Simazine,TiO2 nanotubes,anodization,photodegradation mechanism,photocatalytic,photocatalyst
更新于2025-09-10 09:29:36
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Solid Acids Accelerate the Photocatalytic Hydrogen Peroxide Synthesis over a Hybrid Catalyst of Titania Nanotube with Carbon Dot
摘要： Photocatalytic synthesis of hydrogen peroxide (H2O2) from water and oxygen is an alternative route for clean energy storage and chemical synthesis, but still having problems with insufficient H2O2 productivity and solar-to-chemical energy conversion efficiency. Herein, we reported a hybrid catalyst of proton-form titania nanotube with carbon dot (HTNT-CD) that is highly efficient for the production of H2O2 under visible-light irradiation (λ>420 nm, H2O2 productivity at 3.42 mmol gcat-1·h-1), outperforming the titania catalysts containing noble metals and the carbon nitride catalysts reported previously. Multiple studies demonstrate that the protons on the HTNT-CD are crucial for the production of H2O2 by efficiently accelerating the half reaction of molecular oxygen reduction to form H2O2, and effectively hindering H2O2 decomposition under the irradiation conditions. This HTNT-CD catalyst gives solar-to-H2O2 apparent energy conversion efficiency at 5.2%, which is even 4.9 times of that (1.06%) over the catalyst derived from commercial P25 and CDs. More importantly, the HTNT-CD is stable, giving high H2O2 productivity in the continuous recycle tests.
关键词： photocatalyst,carbon dots,TiO2 nanotubes,H2O2 synthesis
更新于2025-09-10 09:29:36