Caihui Feng

Photodegradation of rhodamine B under visible light by bimetal codoped TiO2 nanocrystals

In the search for efficient photocatalysts working under visible light, we have investigated the effect of metal ions (Bi/Co, Fe/Co) codoping on the photocatalytic activity of TiO(2) prepared by stearic acid gel method. UV-vis spectra revealed that doped Co enhanced the absorbency of TiO(2) under visible light, and Bi/Co codoped TiO(2) showed higher absorbance than Fe/Co codoped TiO(2). The photoreaction based on the prepared samples for photodegradation of 20mg/l rhodamine B solution was examined. The results showed that Fe(0.1%)/Co(0.4%) codoped TiO(2) had the highest photoactivity among all as-prepared samples under visible light, though less absorbency of visible light, indicating that the photoactivity not only benefits from absorbency but also relates to the cooperative effect of the two dopants.

Schottky Diode Ultraviolet Detector Based on

In this letter, a Schottky diode ultraviolet (UV) detector based on TiO2 nanowire (NW) array with Ag electrode is fabricated. The TiO2 NW array was prepared via a low-temperature hydrothermal method and characterized by means of X-ray diffraction, scanning electron microscope, and XPS. The Schottky barrier character of Ag/TiO2 contact was researched in detail. At -5-V bias, the dark current of the detector was less than 35 nA. Under the irradiation of 350-nm UV light, a high responsivity of 3.1 A/W was achieved due to the internal gain. The Schottky diode detector with simple fabrication process, low cost, and superior performance would provide a new way in fabricating UV imaging arrays.

\hbox{TiO}_{2}

α-MoO3/α-Fe2O3 nanostructure composites were fabricated via a facile and low-cost hydrothermal strategy. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the samples. The results revealed that the α-Fe2O3 nanorods grew on the surface of α-MoO3 nanobelts. The result shows the length and the width of α-MoO3 nanobelts to be about 6 μm and 200 nm. The average length of an α-Fe2O3 nanorod was 10 nm. The sensing properties towards various kinds of gases were tested and the heater-type gas sensors based on α-MoO3 nanobelts and α-MoO3/α-Fe2O3 nanostructure composites showed excellent performance towards xylene. It was found that such heterostructure composites exhibited enhanced xylene sensing properties compared with α-MoO3 nanobelts. For example, at a xylene concentration of 5 ppm, the response of the α-MoO3/α-Fe2O3 composites was 4.79, which was about 3 times higher than that of α-MoO3 nanostructures at 206 °C.

Nanowire Array

In this article, the heterostructure of ZnO particles on single-crystal CdS nanowires (ZnO@CdS) has been successfully synthesized via a facile two-step solvothermal process. The appealing application of the ZnO@CdS heterostructure as visible-light photodetector (PD) is presented. Photocurrent illuminated with light (shorter than 510 nm) to dark-current ratio of structurally-optimized ZnO@CdS nanomaterials based photon detector was enhanced significantly compared to the value of the pristine CdS nanowires based one. The corresponding mechanism for the phenomenon was discussed. Additionally, measurements of time resolved responses were conducted. The ZnO@CdS heterostructure based device kept a fast rise (5 ms) and decay (10 ms) speed to irradiation. This work demonstrates a promising application of ZnO@CdS heterostructure based visible-light detectors with high photocurrent/dark-current ratio, ultrafast time response and very good stability.

Xylene gas sensor based on α-MoO3/α-Fe2O3 heterostructure with high response and low operating temperature

In this work, novel bowl-like TiO2 submicron scale particles were prepared via a simple electrospray technique combined with high-temperature calcination. The morphologies of the particles are easily controlled by changing the TBT content (16 wt%, 23 wt%, 30 wt%, 37 wt%) in the precursor solutions. To improve the xylene sensing properties of the TiO2, appropriate Ni amounts (0, 2, 4, and 6 mol% doping) were doped into the bowl-like particles. Among them, the 2 mol% Ni doped TiO2 bowl-like particles show the lowest optimum working temperature and highest response while demonstrating a fast response (9 s) and recovery speed (1.2 s) to 100 ppm xylene gas.

Visible-light photodetector with enhanced performance based on a ZnO@CdS heterostructure

The chemical and optical properties of 1D single-crystalline cadmium sulfide (CdS) nanowires (NWs) synthesized by a solvothermal method were discussed systematically. The CdS NW was characterized using different analytical techniques. In our work, CdS was employed as the active nanomaterial to detect ethanol gas for the first time and showed good gas sensing performance. Especially, the fast response (0.4 s) and recovery speed (0.2 s) to 100 ppm ethanol were much faster than the reported values. The visible-light detector based on CdS NWs demonstrated ultrafast decay speed (3.77 ms), which was the fastest in the reported photodetectors (PDs) based on randomly oriented CdS NW networks. This research indicates that the CdS NW is an excellent nanomaterial for high performance gas sensors and PDs.

Xylene gas sensor based on Ni doped TiO2 bowl-like submicron particles with enhanced sensing performance

A hydrothermal treatment strategy was used to synthesize α-MoO3 nanobelts. X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the phase and the morphology of the samples, respectively. The results show the length and the width of the α-MoO3 nanobelts were about 6 μm and 200 nm, respectively. The sensing properties towards various types of gases were tested and heater-type sensors coated with α-MoO3 nanobelts showed excellent performance towards xylene. The sensors achieved a response of 3 to 100 ppm xylene at an operating temperature of 206 °C. The response and recovery time were 7 s and 87 s, respectively.

Excellent gas sensing and optical properties of single-crystalline cadmium sulfide nanowires

High-responsivity metal-semiconductor-metal TiO(2) UV photodetectors with Ni and Au electrodes were fabricated identically. Their Schottky barrier heights and photocurrent gain mechanism were studied. The effective barrier height Φ and ideality factor n were evaluated according to the thermionic emission theory. The result that Φ(Ni) was lower than Φ(Au) may be attributed to the electron transfer from Ni to the TiO(2) substrate, which would lead to a dipole layer and, accordingly, decrease the barrier height. In addition, the I-V characteristics of the Ni/TiO(2)/Ni and Au/TiO(2)/Au photodetectors were observed. A significant internal gain was obtained, and the mechanism of the internal gain was studied by the phototransistor model in detail.

Xylene sensor based on α-MoO3 nanobelts with fast response and low operating temperature

SrTiO3 nanospheres were synthesized by a hydrothermal method and characterized by X-ray diffraction and scanning electron microscopy. Then, the material was coated on an Al2O3 ceramic substrate to fabricate humidity sensors using Ag–Pd interdigitated electrodes. The sensor shows high humidity sensitivity and fast response and recovery. The impedance changes by four orders of magnitude over a relative humidity (RH) range from 11% to 95%. At the frequency of 100 Hz, response and recovery times are both 2 s, and the maximum hysteresis is <1% RH. In addition, the complex impedance at different RH was investigated to understand the sensing mechanism. The results indicate potential applications of SrTiO3 for fabricating high-performance humidity sensors.

Schottky barrier characteristics and internal gain mechanism of TiO2 UV detectors.

Abstract The nanocrystalline LaCo x Fe 1– x O 3 with different concentrations of Co was prepared by polyethylene glycol (PEG) sol-gel method and characterized by differential thermal analysis and thermal gravimetric analysis (DTA-TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). It was found that the crystal structure of perovskite-type could be obtained at 600 °C, and the concentration of Co had significant effects on the solid-state reaction and the average particle size of the obtained nanocrystals. Furthermore, the humidity-sensitive properties of nanocrystalline LaCo x Fe 1– x O 3 were investigated, and it was found that LaCo 0.3 Fe 0.7 O 3 exhibited higher sensitivity to humidity compared with other samples. The addition of Na 2 CO 3 improved the humidity-sensitive properties of this sample, and made its response to humidity good in the whole humidity range of 11%–95% relative humidity (RH).