Conductometric sensor for ammonia and ethanol using gold nanoparticle-doped mesoporous TiO2
- 437 Downloads
We describe uniform and high-temperature-stable mesoporous TiO2 beads functionalized with gold nanoparticles (AuNPs-TiO2) for use in conductometric sensing of gases and organic vapors. The size of the interconnected main mesopores of the TiO2 beads ranges from 8 to 15 nm, and the AuNPs have diameters between 8 and 10 nm. The mesoporous TiO2 beads are formed during calcination while the structure-directing template agent is removed. Monodispersed AuNPs are formed by reduction in-situ and are placed inside the mesoporous TiO2 framework. This prevents aggregation of the AuNPs even at 500 °C. The materials were characterized by UV–vis spectroscopy, scanning and transmission electron microscopy, nitrogen adsorption-desorption, and X-ray diffraction. Comb-type gold electrodes were then fabricated on an alumina substrate and are shown to display excellent properties in terms of sensing ammonia, ethanol, methanol or acetone. The sensitivity (defined as the ratio of resistivities under vapor and air) of a typical AuNPs(0.5 %)-TiO2 gas sensor for ethanol reached up to 5.65 at above 600 ppm at 75 °C. Response time and recovery times (t90 ≤ 20 s) are faster than (or comparable to) other metal-doped TiO2 sensors, and working temperatures are much lower. An interesting observation was made in that the changes in the conductivity of the sensor change with temperature. The sensor prepared with AuNPs(0.5 %)-TiO2 is of the p-type (in its response to ammonia gas) at 45 °C, but becomes n-type at 20 °C. Obviously, rather slight changes in temperature lead to a complete change in the direction of the conductometric signal change. This may provide a new aspect in terms of selective and highly sensitive detection of ammonia at ambient and slightly elevated temperatures.
KeywordsGold nanoparticles Mesoporous TiO2 Titanium dioxide Gas sensor Ammonia sensor Ethanol sensor
The project was supported by the National Natural Science Foundation of China (No. 21471120), the Natural Science Foundation of Hubei Province (2014CFB782).
- 7.Zeng W, Liu TM, Herzog A, Liu DJ (2010) Formaldehyde gas sensing property and mechanism of TiO2–Ag nanocomposite. J Phys B 45:4235–4239Google Scholar
- 12.Wang GY, Zhang WX, Cui YC, Jiang DZ, Wu TH (2001) Effect of H2O on catalytic performance of MOx and Au/MOx catalysts for CO oxidation. Chin J Catal 22:408–410Google Scholar
- 26.Sze SM, Ng KK (1981) Physics of semiconductor devices. John Wiley and sons, New York, pp 160–180Google Scholar
- 32.Boccuzzi F, Chiorino A, Tsubota S, Haruta M (1996) FTIR study of carbon monoxide oxidation and scrambling at room temperature over gold supported on ZnO and TiO2. 2. J Phys Chem 100:3635–3631Google Scholar