Jian Ding,Shuqun Chen,Ning Han,Yi Shi,Peng Hu,Hongyi Li,Jinshu Wang
Gas response control through structural and defect engineering in metal oxides are critical approaches to realize high performance sensors. Herein, we present the fabrication of ZnO thin films containing nanosized structures and high concentration of zinc interstitials for NO 2 and ethanol monitoring. The target materials were fabricated by aerosol assisted chemical vapour deposition (AACVD) method on ceramic and glass substrates, and were characterized by complementary analytical techniques. The obtained ZnO nanoparticulate and nanopyramidal thin films yielded an outstanding response of ~41 to 1 ppm NO 2 and ~236 towards 100 ppm ethanol, respectively. The reasons accounting for such an enhancement were revealed by the surface-depletion model in ZnO and the chemisorption energies of oxygen molecules on Zn i -enriched crystal facets.
Chao Wang,Ming Yang,Lihong Liu,Yingming Xu,Xianfa Zhang,Xiaoli Cheng,Shan Gao,Yuan Gao,Lihua Huo
In order to enhance the gas response of polypyrrole to NO 2 , the polypyrrole/Fe 2 O 3 nanocomposites are synthesized by one-step hydrothermal route. The presence of ferric oxide in composites is demonstrated by XPS, HRTEM and TG analyses. The polypyrrole/Fe 2 O 3 sensor exhibits high selectivity and response to NO 2 at 50 °C. Compared with other polypyrrole/metal oxide materials, the polypyrrole/Fe 2 O 3 materials are easy to be synthesized, and the gas sensor has a higher response of 220.7%, lower detection limit of 0.1 ppm and good linear relationship when the NO 2 concentrations range from 0.1 ppm to 10 ppm. The gas response is greatly improved in comparison with the pure polypyrrole and Fe 2 O 3 . The reason for the improved response is also discussed.
Novel nanocomposites consisting of polystyrene-block-polybutadienyl polyhexamethylene dicarbamate-block-polystyrene (PS-b-HTPB5-b-PS) and multiwalled carbon nanotubes (MWCNTs) were designed and prepared via noncovalent interactions. Scanning electron microscopy and transmission electron microscopy observations showed that segregated networks of MWCNTs were formed due to the cladding of PS-b-HTPB5-b-PS, presenting a parallel-arranged topology of the MWCNTs in a continuous PS-b-HTPB5-b-PS phase, which improved the dispersibility of the MWCNTs. The nanocomposites were fabricated into vapor sensing elements to detect CH2Cl2 vapor in the environment, exhibiting excellent responsive sensitivity, reproducibility and a low limit of detection (LOD) of 1 ppm when exposed to CH2Cl2 vapor. The chain extension of HTPB overcame the fragility and improved the tenacity of the thin films, and the responsivity was optimized by adjusting the content of the MWCNTs and the length of the PS chains. The newly developed conductive composites can be applied as a promising vapor sensor to accurately monitor CH2Cl2 vapor in the environment.
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