Toward the nanospring-based artificial olfactory system for trace-detection of flammable and explosive vapors

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

“…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.…”

“…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.…”

“…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].…”

Semiconducting Metal Oxides Nanocomposites for Enhanced Detection of Explosive Vapors

“…Moreover, response and recovery times of the sensors heated at 400 • C were very fast: 2 and 3 s, respectively, for nickel-doped ZnO sensor in the presence of 4.9 ppt of RDX. These results are due to the higher number of oxygen vacancies in the doped samples after the thermal treatment at 400 • C, with respect to the powders heated at 200 • C or 600 • C. Silica nanosprings 80 μm thick were produced in about 15 min on gold-coated silica substrates in presence of a silica precursor [43]. Then, the springs were coated with ZnO nanoparticles by an atomic layer deposition (ALD) from a solution of zinc diethyl and deionized water at 175 °C under 1 Torr of Ar.…”

“…Finally, the ZnO-coated nanosprings were immersed in a solution of Pd acetylacetonate dissolved in ethanol (having a concentration of 1.95 × 10 −2 M), dried, and heat-treated at 500 °C for 15 min under a hydrogen and nitrogen flow to reduce the palladium precursor in metallic palladium having an average size of 2.4 ± 1.3 nm (Figure 7). Silica nanosprings 80 µm thick were produced in about 15 min on gold-coated silica substrates in presence of a silica precursor [43]. Then, the springs were coated with ZnO nanoparticles by an atomic layer deposition (ALD) from a solution of zinc diethyl and deionized water at 175 • C under 1 Torr of Ar.…”