Gas Sensitive Performance Research Articles

Preparation of In<sub>2</sub>O<sub>3</sub>/MWCNTs Nanocomposites and their Gas-Sensing Property to Ethanol

In2O3/multi-walled carbon nanotube (MWCNT) nanocomposites containing different MWCNT contents were synthesized via direct growth of In2O3 nanoparticles on the functionalized MWCNTs. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results exhibited that In2O3 nanoparticles with a diameter of approximate 10 nm were densely decorated on the surface of the MWCNTs. The gas sensitive performance of the nanocomposites to ethanol was also investigated. It was found that In2O3/MWCNTs sensor showed much higher response than that of the pure In2O3 sensor. Moreover, the sensing mechanism was discussed.

Facile synthesis of CaO–SnO2 nanocrystalline composite rods by electrospinning method with enhanced gas sensitive performance at room temperature

CaO–SnO2 nanocrystalline composites with rod-like structures had been fabricated through an efficient and facile electrospinning approach, followed by appropriate thermal treatment in ambient conditions. The morphology of CaO–SnO2 composite nanorods consisted of fine grain sized SnO2 nanoparticles. The 2 at% CaO–SnO2 L-NRs (loose nanorod structure) do not array closely in the center of the nanorods, showed a unique nanocrystalline structure and exhibit excellent sensing properties with high response and good selectivity at room temperature, by using NOx as a probe molecule. Moreover, 2 at% CaO–SnO2 L-NRs revealed a favourable linear relationship in the whole NOx detection region. The high response of 2 at% CaO–SnO2 L-NRs may be attributed to one-dimensional loose nanostructures for every SnO2 nanoparticle which overlapping and being connected with four or more adjacent grains through necks can adsorb a NOx molecule. The necks stabilized at the ideal size which enhances electron ‘‘injection’’ in the depleted inter-crystal boundaries and the large number of sensing activity sites (chemisorbed oxygen: O−, O2−, O2−). Furthermore, the joining of nanocrystals by annealing can improve the conduction of electrons. The 2 at% CaO–SnO2 L-NRs showed excellent sensitivity characteristics to NOx even at the level less than 10 ppb. The excellent gas sensing properties can be a reference for the preparation of other semiconductors for sensor applications.

Nanoheterostructures on TiO2 nanobelts achieved by acid hydrothermal method with enhanced photocatalytic and gas sensitive performance

Nanoheterostructures of TiO2 nanoparticles/TiO2 nanobelts and Ag/TiO2 nanoparticles/TiO2 nanobelts are prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The experimental parameters, including acid corrosion time and calcination temperature, are investigated in detail. Compared with TiO2 nanobelts, the single nanoheterostructure TiO2 nanoparticles/TiO2 nanobelts have a better photocatalytic activity. The double nanoheterostructure Ag/TiO2 nanoparticles/TiO2 nanobelts can further dramatically enhance photocatalytic properties of TiO2 nanobelts. The mechanisms for formation of the heterostructure and the enhanced photocatalytic effect of the heterostructure are discussed. The liquid continuous-flow photocatalysis based on TiO2 nanobelt nanopaper with different heterostructures is carried out, which has an efficient photocatalytic ability. At the same time, the obtained TiO2 nanobelt heterostructures have a good gas sensitive performance for ethanol.

Synthesis, electrochemical, and gas sensitivity performance of polyaniline/MoO3 hybrid materials

Hybrid material of polyaniline with molybdenum trioxide (MoO3) xerogel obtained by ion exchange of (NH4)6Mo7O24·4H2O was synthesized via polymerization of the monomer by ammonium peroxydisulfate/HCl oxidant system. The properties of MoO3 and hybrid material were investigated through thermogravimetry, X-ray diffraction, scanning electron microscopy, charge–discharge test, cyclic voltammetry, electrochemical impedance spectroscopy, and gas sensing experiments. Results show that hybrid material exhibits higher capacity, more excellent cycling reversibility, and better sensitivity to ethanol gas than MoO3 xerogel.