Xie Weiwei

Bio: Xie Weiwei is an academic researcher from Tianjin University. The author has contributed to research in topics: Nanowire & Nanorod. The author has an hindex of 5, co-authored 7 publications receiving 87 citations.

Thermal-oxidative growth of aligned W18O49 nanowire arrays for high performance gas sensor

Abstract: Gas sensors based on aligned arrays of W 18 O 49 nanowires were formed directly via a novel route of in situ thermal oxidation of sputtered W film on the substrate attached patterned Pt electrodes. The well-developed nanowires have diameter of 10–20 nm and show roughly aligned morphology. It is found that the duration of oxygen exposure during thermal annealing plays a crucial role to harvest a pure phase of W 18 O 49 nanowire with desired length. The roughly aligned W 18 O 49 nanowires show favourable microstructure for gas adsorption and rapid gas diffusion. The NO 2 -sensing properties of aligned W 18 O 49 nanowires sensor were evaluated at 50 °C up to 200 °C over NO 2 concentration ranging from 250 ppb to 2.5 ppm. The results indicate that the W 18 O 49 nanowire arrays sensor exhibits good NO 2 -sensing performances at its optimal operating temperature of 150 °C, especially perfect stability and fast response–recovery characteristics. The reliable interface performance and fast gas adsorption–desorption properties of the directly assembled vertically aligned nanowire array attribute to the superior stability and quick response/recovery. The growth mechanism of aligned W 18 O 49 nanowires is proposed based on the direct SEM observations on the intermediate products, and meanwhile the sensing mechanism of the corresponding sensor is analyzed.

Preparation method of gas sensor element based on quasi-directed tungsten oxide nanowires

Abstract: The invention discloses a preparation method of a gas sensor based on quasi-directed tungsten oxide nanowires. An interdigital electrode and a deposited metal tungsten thin layer are plated on the substrate of the sensor in sequence, and futher the quasi-directed tungsten oxide nanowire with good appearance is obtained through annealing treatment in an assisted manner after recrystallization in a tubular vacuum oven. The nanowires are self-assembled to form a sensitive film layer with crossed quasi-directed tungsten oxide nanowires through upward recrystallization growth on the metal tungsten thin layer on the surface of the electrode. The sensor for the quasi-directed tungsten oxide nanowires based on the method disclosed by the invention has higher sensitivity for NO2 and good selectivity and stability. Good gas-sensitive property attributes to the special structural property of the sensitive film layer of the gas sensor element of the quasi-directed tungsten oxide nanowires, and great application potential is shown in the field of monitoring of poisonous NO2.

Preparation method of tungsten trioxide one-dimensional structure nanowire and multi-stage nano structure

Abstract: The invention discloses a preparation method of a tungsten trioxide one-dimensional structure nanowire and a multi-stage nano structure. A WO3 nano material of a multi-stage structure from a shape-controlled one-dimensional structure nanowire is prepared by using a hydrothermal method. By controlling two main parameters, namely, hydrothermal reaction time and hydrothermal reaction temperature, the tungsten trioxide one-dimensional structure nanowire and the multi-stage nano structure are directly synthesized on the surface of an aluminum oxide substrate. The preparation method has the advantages of simple equipment, convenience in operation, easily controlled process parameters, low cost and the like, and a great application and research space is provided for reducing the working temperature of a gas sensor and improving the sensitivity and the response speed of the gas sensor.

How shell thickness can affect the gas sensing properties of nanostructured materials: Survey of literature

Abstract: High-performance gas sensors are needed to improve safety in daily life. Even though the gas sensing performance of new nanostructured metal oxides has improved significantly, some aspects of these novel nanomaterials have not been fully explored. Core-shell (C-S) and hollow shell nanostructures are two types of advanced materials for gas sensing applications. Their popularity is mainly due to the synergetic effects of the core and shell in C-S nanostructures, the high surface areas of both C-S and hollow nanostructures, and the possibility of tuning the shell thickness within the range of the Debye length for such nanostructures. In addition to the type of sensing material, morphology, sensing temperature, and porosity, shell thickness is one of the most important design parameters. Unfortunately, less attention has been paid to the effect of shell thickness on the gas sensing properties. Herein, we demonstrate that the thickness has an undeniable role in the gas sensing response of the resulting material. In this review, we present the first overview of this aspect of sensing materials. By referring to related works, we show how shell thickness can affect the sensing properties of both C-S and hollow nanostructures. Researchers in this field will be able to fabricate more sensitive gas sensors for real applications by better understanding the effect of shell thickness on the gas sensing properties of C-S and hollow nanostructured materials.

Highly sensitive H2S gas sensors based on Pd-doped CuO nanoflowers with low operating temperature

Abstract: A facile method was used to prepare Pd-doped CuO nanoflowers with various doping concentrations. The samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma atomic emission spectrometer (ICP-AES), and Brunauer – Emmett – Teller (BET) specific surface area analysis. The responses (Rg/Ra or Ra/Rg, where Rg is the resistance in gas, and Ra is the resistance in air) of such sensors exposed to 50 ppm CH4, NO2, C2H5OH, H2S, NH3, and H2 were measured for comparison. For 1.25 wt% Pd-doped CuO nanoflowers, the response (Rg/Ra) to 50 ppm H2S was 123.4 at 80 °C, which was significantly higher than that of pure CuO (Rg/Ra = 15.7). Furthermore, excellent stability and repeatability of the gas sensor were also demonstrated. The observed results clearly revealed that it is an important and facile approach to detect the H2S at low operating temperature for practical applications.

Chemiresistive Hydrogen Sensors: Fundamentals, Recent Advances, and Challenges.

Abstract: Hydrogen (H2) is one of the next-generation energy sources because it is abundant in nature and has a high combustion efficiency that produces environmentally benign products (H2O). However, H2/air mixtures are explosive at H2 concentrations above 4%, thus any leakage of H2 must be rapidly and reliably detected at much lower concentrations to ensure safety. Among the various types of H2 sensors, chemiresistive sensors are one of the most promising sensing systems due to their simplicity and low cost. This review highlights the advances in H2 chemiresistors, including metal-, semiconducting metal oxide-, carbon-based materials, and other materials. The underlying sensing mechanisms for different types of materials are discussed, and the correlation of sensing performances with nanostructures, surface chemistry, and electronic properties is presented. In addition, the discussion of each material emphasizes key advances and strategies to develop superior H2 sensors. Furthermore, recent key advances in other types of H2 sensors are briefly discussed. Finally, the review concludes with a brief outlook, perspective, and future directions.