Linghui Zhu

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

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.

Gas Sensors Based on Metal Sulfide Zn1–xCdxS Nanowires with Excellent Performance

Metal sulfide Zn1-xCdxS nanowires (NWs) covering the entire compositional range prepared by one step solvothermal method were used to fabricate gas sensors. This is the first time for ternary metal sulfide nanostructures to be used in the field of gas sensing. Surprisingly, the sensors based on Zn1-xCdxS nanowires were found to exhibit enhanced response to ethanol compared to those of binary CdS and ZnS NWs. Especially for the sensor based on the Zn1-xCdxS (x = 0.4) NWs, a large sensor response (s = 12.8) and a quick rise time (2 s) and recovery time (1 s) were observed at 206 °C toward 20 ppm ethanol, showing preferred selectivity. A dynamic equilibrium mechanism of oxygen molecules absorption process and carrier intensity change in the NWs was used to explain the higher response of Zn1-xCdxS. The reason for the much quicker response and recovery speed of the Zn1-xCdxS NWs than those of the binary ZnS NWs was also discussed. These results demonstrated that the growth of metal sulfide Zn1-xCdxS nanostructures can be utilized to develop gas sensors with high performance.

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

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.

Special nanostructure control of ethanol sensing characteristics based on Au@In2O3 sensor with good selectivity and rapid response

A unique Au@In2O3 core–shell nanostructure was firstly prepared through a simple sol–gel method, the structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The results showed that unique architectures were core–shell nanostructure assembled from an Au core and an In2O3 shell. The gas sensing properties of the as-prepared pure In2O3 and Au@In2O3 core–shell samples were tested toward various gases. The sensor based on a Au@In2O3 core–shell nanostructure showed excellent selectivity toward ethanol at the operating temperature of 160 °C, giving a response of about 36.14 to 100 ppm, which was about 1.5 times higher than that of the sensor based on pure In2O3. The τres and the τrec values of the Au@In2O3 sensor to 100 ppm ethanol were 4 s and 2 s respectively, while those of the pure In2O3 sensor were relatively long. The enhancement might be attributed to the unique core–shell structure and existence of a Schottky junction between Au/In2O3.

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

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

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.

The preparation of Cr2O3@WO3 hierarchical nanostructures and their application in the detection of volatile organic compounds (VOCs)

Cr2O3@WO3 and WO3 hierarchical nanostructures are prepared using a two-step water bath method, which just needs mild conditions and takes little time. The response to xylene of the Cr2O3@WO3-based sensor is much higher (about 4 times) than that of a WO3-based sensor, and both of the response and recovery processes are quick. As for the selectivity, the Cr2O3@WO3-based sensor shows a better response to xylene, while the WO3-based sensor shows a better response to ethanol. The reason for the response and selectivity change is considered to be that a heterostructure is formed between Cr2O3 (a P-type semiconductor) and WO3 (an N-type semiconductor). Moreover, Cr2O3 is reported to show catalytic oxidation of methyl groups.

Synthesis and highly enhanced acetylene sensing properties of Au nanoparticle-decorated hexagonal ZnO nanorings

Hexagonal ZnO nanorings were synthesized using a one-step hydrothermal method and Au nanoparticles were decorated on the surface of the ZnO nanorings through a facile deposition process. The as-prepared ZnO nanorings showed a well-defined hexagonal shape with a width of 0.75–1.4 μm, a thickness of 0.17–0.33 μm and a hollow size of 0.2–1 μm. For the Au nanoparticle-decorated hexagonal ZnO nanorings (Au–ZnO nanorings), Au nanoparticles with a size of 3–10 nm were distributed discretely on the surface of the ZnO nanorings. The acetylene sensing performance was tested for the ZnO nanorings and Au–ZnO nanorings. The results indicated that the Au–ZnO nanorings showed a higher response (28 to 100 ppm acetylene), lower operating temperature (255 °C), faster response/recovery speed (less than 9 s and 5 s, respectively), and lower minimum detectable acetylene concentration (about 1 ppm). In addition, the mechanism for the enhanced acetylene-sensing performance of the Au–ZnO nanorings was discussed.

Three dimensions sphere formaldehyde nanosensor applications: preparation and sensing properties

Zn@SnO2 microspheres with hierarchical structure were prepared through a simple solvothermal method; the structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) showing the materials with extraordinary 3D nanoarchitectures. The gas sensing properties of the as-prepared pure SnO2 and Zn-doped SnO2 were tested toward various gases. The results showed that the SnO2 sensor with 6.67 wt% Zn-doping displayed an excellent selectivity toward formaldehyde at the operating temperature 160 °C, which was considerably lower than most formaldehyde sensors in heater type among previous reports, in addition to giving a response of about 15.2 to 100 ppm, which is about 2.1 times higher than that of sensors based on pure SnO2. The τres and the τrec values of the 6.67 wt% Zn-doped SnO2 sensor to 100 ppm formaldehyde were 2 s and 2 s respectively, demonstrating extraordinary gas sensing properties, whereas those of the pure SnO2 sensor were relatively long. The enhancement might be attributed to the unique morphology and increased oxygen vacancy due to the Zn doping.

Preparation and NO2 Sensing Properties of the Ni-Doped In2O3 Nanofibers

In this letter, pure and 10% (mol) Ni-doped In2O3 nanofibers were prepared by an electrospinning method and characterized by differential thermal analyse (DTA), thermal gravimetric analyse (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) etc. The fibers after calcining at 600°C for 4 h belong to cubic structure. SEM images exhibited that the nanofibers had an average diameter of about 100 nm and are several tens of microns long. The NO2 sensing properties based on these fibers at 95°C were also investigated. In the low concentration range (5–150 ppm), the Ni-doped sensor exhibited excellent linear dependence. Moreover, good selectivity was also observed in our investigations.