Thermal and Optical Activation Mechanisms of Nanospring-Based Chemiresistors

Abstract

Chemiresistors (conductometric sensor) were fabricated on the basis of novel nanomaterials—silica nanosprings ALD coated with ZnO. The effects of high temperature and UV illumination on the electronic and gas sensing properties of chemiresistors are reported. For the thermally activated chemiresistors, a discrimination mechanism was developed and an integrated sensor-array for simultaneous real-time resistance scans was built. The integrated sensor response was tested using linear discriminant analysis (LDA). The distinguished electronic signatures of various chemical vapors were obtained at ppm level. It was found that the recovery rate at high temperature drastically increases upon UV illumination. The feasibility study of the activation method by UV illumination at room temperature was conducted.

A Method for Integrating ZnO Coated Nanosprings into a Low Cost Redox-Based Chemical Sensor and Catalytic Tool for Determining Gas Phase Reaction Kinetics

“…On the other hand, these devices are necessary for acquiring a fundamental understanding of corresponding physical and chemical processes triggered by surface-molecule interactions (chemisorption), as well as for interpreting the electrical transport properties of gas sensitive materials. The use of metal oxide nanocrystalline thin films, as well as other more complex nano-morphologies, as the gas sensitive layers in chemiresistors is well documented [1][2][3][4][5][6][7][8][9][10][11]. These studies demonstrated that if the dimensions of the nanostructures are comparable to the characteristic length scales of surface interactions, the sensor will be more responsive to changes in surface stoichiometry.…”

“…The effects of chemisorption on the electrical transport properties of metal oxides is well documented [1][2][3][4][5][6][7][8][9][10][11][19][20][21][22]. In the case of ZnO 1- , where the surface is oxygen deficient, the surface readily oxidized in ambient air to obtain the ideal surface stoichiometry of ZnO.…”

“…In chemiresistors the catalytic oxidation of analyte at the metal oxide surface depletes the surface of oxygen, which leads to a change in the surface depletion layer. If the depletion layer is comparable to the dimensions of the nanostructured metal oxide, small changes in the depth of the surface depletion layer can produce large swings in the resistivity of the chemiresistor [1][2][3][4][5][6][7][8][9][10][11].…”

Vapor Trace Recognition Using a Single Nonspecific Chemiresistor

“…The contact potential can be viewed as a tunneling barrier to electrons, which in our case is modulated by the oxidation of the analyte. It is well known that the surface area and the surface defects are crucial for a high sensitivity given that the ionization happens primarily on the edges and corners of the nanocrystals [4–6]. This explains the superior sensitivity of the ALD fabricated polycrystalline oxide films.…”

Gas sensor array based on surface acoustic wave devices for rapid multi-detection

“…A SAW device with high sensitivity, fast response and low cost can be used in kinds of applications [1,2] such as indoor air measurement, food product quality control, environmental monitoring [3,4], military applications, and national security. Comparing with other microsensors such as potentiometric charge sensitive devices, thermally based detectors, and chemiresistors [5,6], an electronic nose device has higher sensitivity, smaller size and cheaper cost. The advantage of high sensitivity results from the fact that surface acoustic waves are mostly confined to the piezoelectric substrate surface within one or two wavelengths and thus are very sensitive to changes of sensitive film properties such as the surface electrical conductivity, elastic moduli, mass, and permittivity when exposed to target gases.…”