Recent Advances in Structure Design and Application of Metal Halide Perovskite-Based Gas Sensor.

Metal halide perovskites (MHPs) are emerging gas-sensing materials and have attracted considerable attention in gas sensors due to their unique bandgap structure and tunable optoelectronic properties. The past decade has witnessed significant developments in the gas-sensing field; however, their intrinsic structural instability and ambiguous gas-sensing mechanisms hamper their practical applications. Herein, we summarize the recent advances in MHP-based gas sensors. The physicochemical properties of MHPs are discussed at first. The structure design, including dimension design and engineering design, is overviewed as well as their fabrication methods, and we put forward our insights into the gas-sensing mechanism of MHPs. It is believed that enhanced understanding of gas-sensing mechanisms of MHPs are helpful for their application as gas-sensing materials, and structure design can enhance their stability, sensing sensitivity, and selectivity to target gases as gas sensors. Subsequently, the latest developments in MHP-based gas sensors are summarized according to their different application scenarios. Finally, we conclude with the current status and challenges in this field and propose future perspectives.

High Response and Selectivity of the SnO2 Nanobox Gas Sensor for Ethyl Methyl Carbonate Leakage Detection in a Lithium-Ion battery.

It is well-known that metal-oxide semiconductors (MOS) have significant gas sensing activity and are widely used in harmful gas monitoring in various environments. With the rapid development of new energy vehicles, the monitoring of the gas composition and concentration in LIB has become an effective way to avoid safety problems. However, the study of typical electrolyte solvent detection, such as EMC and DMC detection by the MOS sensor, is still in its infancy. Here, the SnO2 nanoboxes are synthesized by coordination dissolution using cubic Cu2O as the template, and its sensor shows high sensitivity (0.27 to 10 ppb EMC), excellent response (32.46 to 20 ppm EMC), and superior selectivity. Additionally, the sensor possesses fast and clear response to lithium-ion battery (LIB) leakage simulation tests, suggesting that it should be a promising candidate for LIB safety monitors. These sensing performances are attributed to large specific surface area, small grain size, and high size/thickness ratio of nanoboxes. More importantly, DFT calculations confirm the adsorption of EMC on the surface of the SnO2 nanoboxes, and the EMC decomposition processes catalyzed by SnO2 are deduced by in situ FTIR and GC-MS.

Ce-Ag Active Bimetallic Pairs in Two-Dimensional SnS2 for Enhancing NO2 Sensing.

Developing gas sensors capable of efficiently detecting harmful gases is urgent to protect the human environment. Here, an active Ce-Ag bimetallic pair was innovatively introduced into SnS2, which successfully exhibited excellent NO2 gas sensing performance. 0.8% Ce-SnS2-Ag showed a gas sensing response of 5.18 to 1 ppm of NO2 at a low temperature of 80 °C, with a lower limit of detection as low as 100 ppb. DFT calculations revealed that Ce atoms are substituted into the main lattice of SnS2, which opens up the interlayer spacing and serves as an anchor point to fix the Ag atoms in the interlayer. The Ce-Ag bimetallic pairs successfully modulate the electronic structure of SnS2, which promotes the adsorption and charge transfer between NO2 and Ce-SnS2-Ag and thus achieves such an outstanding gas sensing performance. This work opens an avenue for the rational functional modification of SnS2 with an optimized electronic structure and enhanced gas sensing.

Carboxymethyl chitosan assembled piezoelectric biosensor for rapid and label-free quantification of immunoglobulin Y.

Immunoglobulin Y (IgY) proves advantageous to IgG in prophylaxis and diagnosis. Quantification of IgY is therefore becoming a topic of interest. Here, we demonstrate a piezoelectric biosensor with carboxymethyl chitosan (CMCS) as the immobilization matrix. Gelation and hydrophilic nature of CMCS are favored to form a crosslinked matrix for antibody immobilization, and a comparison was made between carboxymethyl cellulose (CMC) and CMCS to investigate the benefits of such substitution. Calibration from 500 ng/mL to 200 µg/mL was established in buffer with the detection limit (LOD) down to 270 ng/mL, confirming its feasibility. As-prepared biosensor effectively prevents non-specific binding of bovine serum albumin (BSA) and lysozyme. Each real-time assay took 15 min including sensor regeneration, which can be further reduced to 4 min for signal readout only, ready for both repeated measurements after regeneration and disposable devices. Thus, as-prepared biosensor offers a rapid, label-free and cost-effective approach for IgY quantification.

Highly sensitive formaldehyde sensors based on CuO/ZnO composite nanofibrous mats using porous cellulose acetate fibers as templates.

An innovative formaldehyde sensor based on CuO/ZnO composite nanofibrous mats (C-NFMs) coated quartz crystal microbalance (QCM), which is capable of stable determination of formaldehyde gas at ambient temperatures sensitively and selectively, has been successfully fabricated. Triaxial and highly porous C-NFMs with high surface area (126.53 m2 g-1) were synthesized by electrospinning a sol-gel cellulose acetate (CA)/CuAc2/ZnAc2 complex solution and following by calcination process. Benefiting from the unique heterojunction structure, immense pore interconnectivity and large surface area of C-NFMs, the as-developed QCM sensors exhibited an extremely low limit of detection (LOD) down to 26 ppb and a limit of quantification value equals to 87 ppb. Besides, the C-NFMs coated QCM sensors also demonstrated short response times (80s), the long-term stability during 3 weeks as well as good selectivity to formaldehyde over diverse volatile organic compounds. The sorption equilibrium in the adsorption process of QCM coated sensors was well met with the Freundlich model, which certified the heterogeneous adsorption between formaldehyde gas and C-NFMs.

H-bonding effect of oxyanions enhanced photocatalytic degradation of sulfonamides by g-C3N4 in aqueous solution.

In this study, the effect of oxyanions on the photodegradation of sulfonamides by graphitic carbon nitride (g-C3N4) was investigated. The results showed that the presence of disilicate (DS) could substantially improve the photodegradation of sulfamethazine (SMZ) in g-C3N4 aqueous suspension. The primary mechanism for the enhancing effect of DS was hydrogen bonding (H-bonding) interaction. The hydroxyl groups (OH) and bridging oxygen (SiOSi) of DS can form H-bonds with the amine groups of g-C3N4 particles and sulfonamides, therefore soluble DS can act as a bridge to enhance the transfer and adsorption of SMZ onto the surface of g-C3N4 particles. The presence of DS did not change the mechanism of photodegradation, but there was an optimal concentration for DS to achieve the strongest enhancing effect. H-bonding effect was also found for other oxyanions derived from weak acids, such as silicate, dihydrogen phosphate and borate ions, because the partial ionization of these oxyanions allowed the existence of hydroxyl groups to form H-bonds. The present study not only deepens our understanding of the interface process of the photodegradation of sulfonamides in g-C3N4 aqueous suspension, but also provides a potential method to enhance the photocatalytic degradation of antibiotics in wastewater streams.