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For example, a graphene sensor has been used to detect various gas molecules such as NO 2 . [7] For important healthcare applications, medical devices built with sensors have been used to measure various vital signals such as blood pressure, body temperature, blood glucose, etc. [8] For example, pressure sensors can be used to test the pulse [9] while chemical sensors allowed the measurement of lactate concentration in blood and analysis of sweat composition for the real time physiologic monitoring. [10] Among the various types of sensors mentioned above, stress sensors play an important role in the sensor family. With the rapid development in the Internet of Thing (IoT) and the big data technology [11] in recent years, the use of artificial intelligence (AI) becomes increasingly significant, [12] accelerating the progress in robotics and automation. Because of this, stress sensors are more and more significant for the development of robotic science and AI technology, including artificial skin. [13] In addition, stress sensors can also be applied in photonics, for example microbend optical stress sensor is a typical application. With the advantages presented by microbend optical stress sensors, such as their flexibility, sensitivity, low-cost, and reliability, [14] they can be used in extreme environments, [15] which greatly extends the applied range of the stress sensors. Despite recent advancement of the microbend optical sensors, almost no review to account for the achievements and promote the future development in this area of research is found in the literature. In this review, the theoretical principles and the assembly of typical optical stress sensors are presented. Three physical mechanisms of the bend-loss-based optical stress sensors are introduced. As one type of the bend-loss-based optical stress sensor, the progress of microbend optical sensors for applications in various areas is discussed. The optical stress sensors have already shown potential in a broader spectrum of applications, from healthcare to robotic science. We anticipate that optical stress sensors, in particular microbend optical sensors, will continue to attract attention of researchers globally. This review provides a comprehensive information pack for the community to advance the future development in optical stress sensor. Optical Stress SensorsStress sensors are designed to sense changes in pressure. Traditional stress sensors detect the stress via the Optical stress sensors have been considered to be amongst the most important categories in the development of stress sensors. Recently, the advancement of microbend optical sensors has been playing a pivotal role in the stress sensor development. In this review, the principles and the architectures of the optical stress sensors are reviewed, and the physical mechanisms of the bend-loss-based optical stress sensors are presented. The latest development and applications of microbend optical sensors in key areas are discussed. The authors aim to provide some guidance in the optical sen...

Vanadium–oxygen species are very harmful to the environment and human health, and also some vanadium–oxygen species have good biological and biomedical effects to human beings. Thus, the study of vanadium–oxygen species is very significant. The types of V–O species are very complex. So far, however, the various structures of V–O species cannot be identified clearly. In this work, the surface‐enhanced Raman spectroscopy (SERS) was used to study vanadium–oxygen species in aqueous solution directly. The SERS spectra with high enhancement factor (EF) and detail information were obtained by the enhancement substrates such as gold nanoparticles (AuNPs), Ag mirror, the Au‐deposited Pt electrodes, and rough Au electrodes. The structures of vanadium‐oxygen species in solutions with different concentration and pH had been well‐characterized firstly by the combination of SERS experiments with density functional theory (DFT) calculations. This work will promote the basic study of the V–O species, and it is also a promotion for the SERS and analytical chemistry.

NO x is the main pollutant in the air, which causes many harmful effects on society. The V 2 O 5 /TiO 2 catalysts are very important to reduce the NO x from the heat engine plants and vehicle exhausts. However, various reasons will affect the performance of the catalysts. In this paper, the polymerization state of surface VO x of supported V 2 O 5 /TiO 2 catalysts was controlled by changing the pH value of the impregnation precursor solutions, and the redox and acidity properties of the catalysts can be adjusted consequently. The Raman spectroscopy, 51 V magicangle spinning nuclear magnetic resonance (MAS NMR), H 2temperature-programmed reduction (H 2-TPR), NH 3-temperature-programmed desorption (NH 3-TPD), NH 3-temperature-programmed oxidation (TPO) and 15 NH 3-NO-O 2-temperature-programmed surface reaction (TPSR) were mainly used for the characterization and properties tests of the samples. Although all catalysts in this work had similar surface morphology and the same vanadium loading, the catalyst oxidability decreased while acidity increased with the increasing of VO x polymerization, which causes the NO conversion increases with the increasing of VO x polymerization below 300°C in selective catalytic reduction (SCR) de-NO x reaction. This work will promote the advance in catalysis and anti-pollution fields for human and nature.