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SnO2 has been extensively used in the detection of various gases. As a gas sensing material, SnO2 has excellent physical-chemical properties, high reliability, and short adsorption-desorption time. The application of the traditional SnO2 gas sensor is limited due to its higher work-temperature, low gas response, and poor selectivity. Nanomaterials can significantly impact gas-sensitive properties due to the quantum size, surface, and small size effects of nanomaterials. By applying nanotechnology to the preparation of SnO2, the SnO2 nanomaterial-based sensors could show better performance, which greatly expands the application of SnO2 gas sensors. In this review, the preparation method of the SnO2 nanostructure, the types of gas detected, and the improvements of SnO2 gas-sensing performances via elemental modification are introduced as well as the future development of SnO2 is discussed.

Hazardous gases have been strongly associated with being a detriment to human life within the environment. The development of a reliable gas sensor with high response and selectivity is of great significance for detecting different hazardous gases. TiO2 nanomaterials are promising candidates with great potential and excellent performance in gas sensor applications, such as hydrogen, acetone, ammonia, and ethanol detection. This review begins with a detailed discussion of the different dimensional morphologies of TiO2, which affect the gas sensing performance of TiO2 sensors. The diverse morphologies of TiO2 can easily be tuned by regulating the manufacturing conditions. Meanwhile, they exhibit unique characteristics for detecting gases, including large specific surface area, superior electron transport rates, extraordinary permeability, and active reaction sites, which offer new opportunities to improve the gas sensing properties. In addition, a variety of efforts have been made to functional TiO2 nanomaterials to further enhance sensing properties, including TiO2-based composites and light-assisted gas sensors. The enhanced gas sensing mechanisms of multi-component composite nanomaterials based on TiO2 include loaded noble metals, doped elements, constructed heterojunctions, and compounded with other functional materials. Finally, several studies have been summarized to demonstrate the comparative sensing properties of TiO2-based gas sensors.

Formaldehyde (HCHO) is a colorless and irritating volatile organic compound, which has been proven to be one of the raw materials that cause pathological building syndrome, as well as a major source of indoor environmental pollution. Long-term exposure of human body to formaldehyde will cause certain health risks, so it is of great practical significance to develop a fast and effective formaldehyde detection sensor. Tin dioxide (SnO2), an n-type semiconductor metal oxide with a specific bandgap (3.62 eV, at 300 K), has been widely used as efficient sensors material for hazardous gases detecting. Different ratios of Sm-doped SnO2 nanoparticles had been successfully prepared by a simple solvothermal route and used as sensing materials in this work. The sample structure, micromorphology, and ingredient were characterized by XRD, SEM, TEM, XPS, and other methods of formaldehyde gas-sensing characteristics were studied. The results shown the optimum compound ratio of Sm-doped SnO2 nanoparticles was 5.0 mol%, the optimal operating temperature was 160 °C, and the sensor shown high gas response, reliable stability and selectivity to formaldehyde. The sensor shown the outstanding gas-sensing performances to formaldehyde ascribed the average grain size of the Sm-doped SnO2 nanoparticles and the positive role of Sm. Besides, the possible gas-sensing mechanism of the prepared sensor to formaldehyde was analyzed in detail.

Due to the poor conductivity of Fe based, Cu based and Co based electrode materials commonly used in the electrochemical detection of glucose, and the uneven stirring and poor conductivity of the traditional preparation method based on glassy carbon electrode. In order to solve the above problems, in this work, CdIn2O4with high electrical conductivity was directly grown on three-dimensional (3D) Ni foam to prepare electrode materials for non-enzymatic glucose sensors. CdIn2O4nanoparticles is prepared from cadmium acetate and indium nitrate hydrate in benzyl alcohol by non-aqueous sol-gel method. The electrocatalytic oxidation performances of CdIn2O4electrode material for non-enzymatic glucose are studied. The results show that the proposed CdIn2O4electrode material has good electrochemical properties and sensing performance for glucose detection. The electrochemical response of CdIn2O4electrode material to glucose is recorded that calibration plot for glucose concentrations ranging from 1.0μM to 1.0 mM (R2 = 0.99), a limit detection of 0.08μM, an excellent sensitivity of 3.2925 mA.mM-1.cm-2, a rapid response time of 1.58 s, a good selectivity and a good long-term stability. These demonstrate the significant potential of CdIn2O4electrode material based on 3D Ni foam as non-enzymatic glucose sensors, which makes it possible to use it as a practical glucose detector. This work could introduce a new concept of nanoparticles modified electrode material grown directly on 3D Ni foam, thus a simple and reliable electrochemical glucose sensor platform is realized. This study was completed in 2019 in the school of materials and energy, Yunnan University.