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Abstract Development of semiconductor sensing materials with fast response requires low reaction barrier between gas species and materials surface, hence contributing to real-time gas monitoring. Herein, mullite SmMn 2 O 5 nanofibers (SNFs), nanotube-in-tubes (NT@NTs), and porous nanotubes (PNTs) have been achieved, via optimized electrospinning technique and annealing procedure. The formation mechanism for present shapes of SmMn 2 O 5 nanostructures was discussed. With respect to the sensing properties to acetone, three sensors prototypes employed with SmMn 2 O 5 NT@NTs, SNFs and PNTs were built and in detail studied by taking SmMn 2 O 5 SNFs sensor as an example. Delightfully, the sensor exhibited the response and recovery time as short as 3 s and 8 s at 300 °C, respectively. The intrinsic high catalytic activity of SmMn 2 O 5 lowers the sensing reaction barrier, which might contribute to the reaction kinetics thereby the fast sensing behavior. This work provides synthetic strategies towards one-dimensional (1D) mullite families and the novel material for acetone gas detection would facilitate further development of gas sensing. Graphical abstract fx1 Highlights • Mullite SmMn 2 O 5 solid nanofibers (SNFs), nanotube@tubes and porous nanotubes are firstly synthesized via electrospinning. • The unique shapes of 1D mullite SmMn 2 O 5 are tuned by optimized annealing. • The mullite sensors exhibit fast response and recovery to acetone (3 s and 8 s), for the real-time monitoring. [ABSTRACT FROM AUTHOR]

ZnO@Al 2 O 3 NCBs sensors show excellent response to 3-hydroxy-2-butanone biomarkers for indirectly monitoring Listeria monocytogenes. • ZnO@Al 2 O 3 nanocables are synthesized combined electrodeposition and etching. • The pores are made by optimized etching inside the cable-shell of Al 2 O 3. • ZnO@Al 2 O 3 nanocables are able to detect 3-hydroxy-2-butanone biomarkers. We report zinc oxide (core) coated with alumina (shell) single-shelled nanocables (ZnO@Al 2 O 3 NCBs) for detection of 3-hydroxy-2-butanone (3H-2B) biomarker, which was prepared via aluminum-anodic-oxide (AAO) template confined electrodeposition, chemical etching and leaving thin AAO-channel wall with broken surface. In the core/shell nanostructure, the outer Al 2 O 3 layer protects ZnO from interference gases, while the pores allow the target gas to react with the oxygen specie on the surface of ZnO. For as-built ZnO@Al 2 O 3 NCBs sensors, the detection limit is as low as 1 ppm, and the response value to 50 ppm 3H-2B is 37.2 at 300 °C. Moreover, the ZnO@Al 2 O 3 NCBs show excellent selectivity and cyclic stability. Our ZnO@Al 2 O 3 NCBs sensors in future monitoring Listeria monocytogenes. [ABSTRACT FROM AUTHOR]

Acetoin (also known as 3-hydroxy-2-butanone) is a metabolic biomarker gas of Listeria monocytogenes (food pathogenic bacteria). Sensitive and selective detection of acetoin biomarker can lead to indirect online monitoring of Listeria monocytogenes, which has attracted much attention in gas sensing field recent years. At present, different from the mature researches towards other VOCs biomarkers, the researches on acetoin gas sensors are newly emerged and still in the infancy. The structure of sensing materials needs to be optimized and the intrinsic sensing mechanism still needs to be further clarified. In order to promote the development of acetoin gas sensors, in this mini-review we present recent advances of acetoin gas sensors based on semiconductor metal oxides (SMOs) for the first time, expound the sensing mechanism, and put forward the research shortcomings and future prospects. [ABSTRACT FROM AUTHOR]