Self-doping of SnO2−x nanocrystals accompanying abundant oxygen vacancies results in significant enhancement in the gas sensing performance.

Defect engineering has been the most promising strategy to modulate the surface microstructure and electronic structure of the metal oxides, which will govern the efficiency of a given oxide for the applications in heterogeneous catalysis, energy storage and conversion fields, and gas sensing. This review summarizes recent research advances on understanding the role of oxygen vacancies of the metal oxides in gas sensing. First, different strategies for oxygen vacancy productions are summarized and compared. Then, the proper characterization techniques for oxygen vacancy are introduced. Importantly, the structure-activity relationships between vacancy engineering and gas sensing ability are further illustrated coupling the experimental results and theoretical studies. Finally, the key challenges and prospects regarding defect engineering in gas sensing are highlighted. Wenjie Ding (left) obtained his bachelor degree from Beijing Forestry University in 2018. Currently, he is pursuing his master degree under the supervision of Associate Professor Jiajia Liu in Beijing Instituted of Technology, China. His current research interests mainly focus on the synthesis of nanomaterials for the application of gas sensing. Dr. Jiajia Liu (middle) received her PhD degree in 2010 from Department of Chemical & Biomolecular Engineering of National University of Singapore, Singapore. Currently, she is Associate Professor in School of Materials and Engineering, Beijing Institute of Technology, China. Her current research interest is the development of metal oxide nanostructures and their applications in sensor, catalysis, and optoelectronics. Jiatao Zhang (right) was born in 1975. He earned his PhD from the Department of Chemistry, Tsinghua University, in 2006. Currently, he is Xu Teli Professor in the School of Materials and Engineering, BIT. He was awarded the Excellent Young Scientist foundation of NSFC in 2013. He also serves as the director of Beijing Key Laboratory of Construction-Tailorable Advanced Functional Materials and Green Applications. His current research interest is inorganic chemistry of semiconductor-based hybrid nanostructures with novel optical, electronic properties for the applications in energy conversion and storage, catalysis, optoelectronics and biology.

As a gram-positive foodborne pathogen, Listeria monocytogenes (LM) can cause many serious diseases to the human health coupled with high mortality rates, thus constructing effective method to detect LM is of great significance. Herein, a novel sandwich-type electrochemical immunosensor was proposed for LM by introducing 3,4,9,10-perylene tetracarboxylic acid/graphene ribbons (PTCA/GNR) nanohybrids as sensing platform and ferrocene/gold nanoparticles (Fc/Au NPs) as signal amplifier. The high conductivity and large surface area of GNR can increase the immobilizing amount of primary antibody (PAb) and enhance the electron transport rate, while Au NPs can carry secondary antibodies (SAb) and Fc derivative (Fc-SH) to form SAb-Au NPs-Fc signal amplifier. Through using Fc molecules as signal probe, its peak current can appear and increase varied from the LM concentrations, hence a highly sensitive sandwich-type immunosensor was constructed: the linear range is wide from 10 to 2×10 4 CFU mL -1 and the limit of detection is low to 6 CFU mL -1 . Furthermore, the specificity of the immunosensor was also studied and a satisfactory result was obtained.

In order to reveal the influence of the metals of soil-water interface in a manganese mine (Xiangtan, China), on local water environment, there are six kinds of metals (Mn, Ni, Cu, Zn, Cd, and Pb) characterized by measuring their concentration, correlation, source, and special distribution using principal component analysis, single factor, and Nemero comprehensive pollution index. The results showed that the corresponding average concentration was 0.3358, 0.045, 0.0105, 0.0148, 0.0067, and 0.0389 mg/L. The logarithmic concentration of Mn, Zn, and Pb was normal distribution. The correlation coefficients (between Mn and Pb, Mn and Zn, Mn and Ni, Cu and Zn, Cu and Pb, and Zn and Cd) were found to range from 0.5 to 0.6, and those between Cu and Ni and Cu and Cd were below 0.3. It was found that Zn and Mn pollution were caused primarily by ore mining, mineral waste transportation, tailing slag, and smelting plants, while Cu and Ni mainly originate from the mining industry activities and the traffic transportation in the mining area. In addition, the Cd was considered to be produced primarily from the agricultural or anthropogenic activities. The pollution indexes indicated that metal pollution degree was different in soil-water interface streams as listed in increasing order of pollution level as Zn > Ni > Cu > Pb > Mn > Cd. For all of the pollution of the soil-water interface streams, there was moderate metal pollution but along the eastern mine area the pollution seemed to get more serious. There was only a small amount of soil-water interface streams not contaminated by the metals.