Polyoxometalates (POMs), as a kind of electron acceptors, comes into sight in gas sensing field. Here, we in situ construct a group of polyoxomethoate/semiconductor one-dimensional tandem heterojunction materials using convenient one-step coaxial electrospinning method. A polyoxometalates electron acceptor layer was intercalated into In2O3@SnO2 nanofibers (NFs), forming In2O3@PW12@SnO2 coaxial core-middle-shell NFs. Gas sensing performances of the one-dimensional In2O3@PW12@SnO2 tandem heterojunctions were investigated for the first time. The fabricated NFs exhibited excellent detection performances for ethanol gas. The optimal sensitivity response to 100 ppm ethanol can reach 22.6, which is about 4 times that of POMs-free samples. Other gas sensing parameters were also comprehensively studied. The significant enhancement can be attributed to the addition of appropriate amount of PW12 electron acceptor which accelerate electrons transfer and reduce the recombination of electron-hole pairs. This work provides a novel strategy for developing high performance gas sensors by constructing tandem heterojunctions as well as introducing POMs electron acceptor, and offers new insight into the development of POMs-based gas sensors.

Early detection of meningococcus is critical to controlling its spread and saving lives in time. In this paper, a surface acoustic wave (SAW) device based on Electrode Width Control (EWC) IDT/PMMA/54°Y-X LiNbO3 is proposed to the detection of meningococcus by Love wave. The advantage of EWC IDT lies not only in overcoming the shortcomings of bidirectional and focused IDTs, but in improving the utilization of acoustic waves and the sensitivity of the sensor. The optimal waveguide layer thickness is determined to be λ/12 by comparing the S21 parameters with different waveguide layers thicknesses. On this basis, the Love wave sensor shows a sensitivity of 330 Hz (ng µL− 1)−1 and a detection limit of 50 pg µL− 1.

Acoustophoresis separation technique has attracted great attention due to its superior properties, such as biocompatibility, non-contact, label-free and high-efficiency. In this paper, separation of particles based on motion modes via tilt angle standing surface acoustic wave (TaSSAW) driven by a unidirectional transducer is developed theoretically. It is verified that the designed electrode width controlled unidirectional transducers are effective to improve the intensity of the acoustic field and the acoustic radiation force of the particles in the channel. The results show that when the density and compressibility of the particles are close to those of the fluid and the particle shape is close to spherical, the influences of fluid viscosity and particle shape on the acoustic radiation force are negligible. It is found that in the TaSSAW system the motion modes of the particles are divided into locked mode and drift mode, and they depend on the fluid velocity, acoustic field intensity and tilt angle. polystyrene (PS) particles with radii of 4 and 5 µm are separated based on the differences of motion modes. For further smaller size difference (4.5 and 5 µm) particles, the separation is also realized successfully by making particles move in the same drift mode.

Herein, we provide a new strategy to construct TiO2 @POMs@ alpha-Fe2O3 one-dimensional tandem heterojunctions materials utilizing one-step coaxial electrospinning. Three series of TiO2 @POMs@ alpha-Fe2O3 core-middle-shell nanoribbons with different Keggin-type POMs are synthesized. The tandem heterogeneous interfaces between the three layers are continuously distributed in a one-dimensional line along the nanoribbons. Gas sensing performances of the nanoribbons are investigated. The gas sensors show significantly improved sensitivity and selectivity to acetone compared with both composite nanoribbons and POMs-free nanoribbons. The enhancement can be due to the addition of POMs electron acceptors, the construction of tandem heterojunctions and the onedimensional nano-structure, which can together accelerate electrons transfer and reduce their recombination. Besides, the effects of different kinds and contents of POMs on gas sensing performance are studied. The results show that the response value of the optimal sensor to 100 ppm acetone can reach 14.81, which is 2.9 times of that of TiO2 @ alpha-Fe2O3 double-layered nanoribbons. This work provides a novel strategy for developing high performance gas sensors by constructing tandem heterojunctions as well as introducing POMs electron acceptor, and offers new insight into the development of POMs-based gas sensors.

Gas sensing performances of homogenous semiconductors materials are limited by their high carriers recombination rate. Polyoxometalates (POMs), as a kind of electron acceptors, comes into sight in gas sensing field. In this study, three series of SnO2 @POMs@WO3 layered core-middle-shell nanofibers with tandem heterojunctions are first prepared utilizing one-step coaxial electrospinning. The tandem heterojunctions are continuously distributed in a one-dimensional line along the nanofibers. For the first time the gas sensing performances of one-dimensional tandem heterojunctions are investigated. Furthermore, the effects of different contents and types of POMs on gas sensing performance are studied. The response of POMs-modified nanofibers can be significantly improved compared to SnO2 @WO3 nanofibers. The optimized response to 100 ppm ethanol can reach 8.8. The enhancement can be attributed to that the addition of POMs electron acceptor, the construction of POMs/semiconductor tandem heterojunctions and the one-dimensional nano-structure can together promote the separation of carriers, which could remarkably improve gas sensing performances. These results provide a new strategy for developing high-performance gas sensors by synthesizing one-dimensional tandem heterojunctions as well as introducing POMs.

Gas sensing materials with one-dimensional (1D) structure can provide a pathway for carriers migration. In this work, Cu2ZnSnS4/polyoxometalate (CZTS/PW12) nanofibers were synthesized by electrospinning. This is the first study on the sensing performance of 1D CZTS in the field of gas sensors. Moreover, PW12 can work as electron acceptor and improve the sensing properties. CZTS/3%PW12 has the highest response value (2.1) compared with the gas-sensing performance of all CZTS-based sensors studied previously. The 1D nanofiber structure allows carriers move in an orderly manner. Moreover, the PW12 electron acceptor can reduce electron-hole recombination. This work broadens the ideas for improving the performance of CZTS-based sensors.

In this work, a Cu2ZnSnS4(CZTS)-based gas sensor incorporated by polyoxometalate(POMs) electron acceptor were synthesized by hydrothermal method. For the first time we investigated on the application of CZTS in NO2 sensor and the influence of POMs incorporating on gas sensing performances of CZTS sensor. As a result, the gas sensing response could be remarkably improved to 6.12 times by incorporating POMs compared with pure CZTS. This is mainly attributed to introducing POMs into CZTS could reduce electron-hole recombination and facilitate electrons transfer. The research results exhibit the highest gas sensing response of CZTS-based gas sensor up to now. This research reveals a new idea for developing high-performance gas sensors based on CZTS by introducing POMs.