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The α-MoO 3 -based materials have been intensively investigated as chemiresistive-type gas sensors due to their excellent sensing performances for gas sensing applications. However, there still remains formidable challenges for developing a simple and scalable approach to synthesize α-MoO 3 with controllable structures. Herein, we demonstrated a glucose-assisted combustion synthesis strategy for the synthesis of α-MoO 3 materials with controllable structures. They were obtained by heat treatment of the gels containing ammonium heptamolybdate tetrahydrate and glucose. Owing to the coordination interactions between glucose and heptamolybdate, α-MoO 3 -2 sample obtained by adding 1.8 g of glucose featured the highest oxygen vacancy concentration with an O/Mo atomic ratio of 2.61. The gas sensing measurements indicated that α-MoO 3 -2 had excellent sensing performances for detecting ethanol. Such ethanol sensor displayed the lowest detection concentration of 5 ppm ethanol, high response of 3.86 toward 20 ppm ethanol, and wide detection range of 5–100 ppm. This study sheds light on preparation of metal oxides with controllable structures on a scalable way for various applications. • A glucose-assisted combustion synthesis method have been developed to preparation of MoO3 samples. • The MoO3 sample thus obtained possesses high oxygen vacancy concentration and surface chemical-adsorbed oxygen species. • The MoO3 sample exhibits excellent sensing performances for ethanol sensing. [ABSTRACT FROM AUTHOR]

The α-Fe 2 O 3 /SnO 2 -RGO-15 possessed a competitive sensing performance with a high response of 7.4 towards 1 ppm NO 2 at room temperature. [Display omitted] As promising sensing materials, reduced graphene oxide (RGO)-based nanomaterials have drawn considerable attention in the fields of gas monitoring owing to their low operating temperature. However, constructing RGO-based room-temperature gas sensors possessing ppb-level limit of detection with high sensitivity remains challenging. In this work, a series of highly sensitive NO 2 sensors were fabricated using α-Fe 2 O 3 and SnO 2 co-decorated RGO hybrids (designated as α-Fe 2 O 3 /SnO 2 -RGO) as sensing materials. They were rationally synthesized by a one-pot hydrothermal method. Compared to SnO 2 modified RGO hybrids (SnO 2 -RGO with bandgap of 3.88 eV), the bandgap energy of α-Fe 2 O 3 /SnO 2 -RGO hybrids (3.53 eV) was reduced by adding α-Fe 2 O 3; the narrower bandgap facilitated the sensing materials to release more electrons and form more oxygen ions at room temperature. Besides, the high carrier migration of RGO, which served as continuous phase, identical structure with ultrasmall particle size of α-Fe 2 O 3 and SnO 2 (about 3–6 nm), and abundant chemisorbed oxygen species on the surface (20.8%) of the sensing materials, as well as their suitable bandgap (3.53 eV) in the sensing materials, significantly improved NO 2 response at room temperature. Among the sensors fabricated, α-Fe 2 O 3 /SnO 2 -RGO-15-based NO 2 sensor had the highest response of 7.4 with a short response time of 59 s towards 1 ppm NO 2 ; it could even reach a response of 2.6 towards 100 ppb NO 2. Notably, α-Fe 2 O 3 /SnO 2 -RGO-15 sample has excellent capability to recognize NO 2 , where the response value (7.4) towards 1 ppm NO 2 is about 7 times higher than that of 100 ppm ammonia and common volatile organic compounds (formaldehyde, toluene, ethanol and acetone). Such NO 2 sensor has superior repeatability with negligible response deviation towards 1 ppm NO 2 for four reversible cycles. This makes it to have a great potential application in the field of NO 2 detection. [ABSTRACT FROM AUTHOR]

[Display omitted] The metal oxides-based chemiresitive gas sensors have attracted enormous interest because of their exellent sensing perforamcnes, which have emerged as very promising candidates for gas monitoring. However, from the view of organophosphorus compounds detection, a unique combination of low detection limit and fast respons/recovery rate remains challenging. Herein, the synersgitic effects of oxygen vacancy engineering and surface gold decoration enabling excellent sensing performances for detection of dimethyl methyl phosphonate (DMMP, a typical organophosphorus) is reported. To demonstrate the proof of concept, Au nanoparticles (NPs) decorated oxygen vacancy-enriched SnO 2 hybrids (designated as Au-O-SnO 2) were designed as sensing materials, where the O-SnO 2 samples were fabricated by introduction of oxygen vacancies onto commercial SnO 2 through organometallic chemistry-assisted approach using (CH 3) 2 SnCl 2 as precursor, followed by deposition of Au NPs by an in-situ reduction routine. After optimizing Au NPs content in hybrids (1 wt%, 3 wt%, 5 wt% and 7 wt%), O-SnO 2 decorated with 5 wt% Au NPs (designated as Au-O-SnO 2 -5) exhibits excellent DMMP sensing performances, such as, an enhanced recoverable response of 1.67 to 680 ppb DMMP, low detection limit of 4.8 ppb, short response time of 26 s and recovery time of 32 s, as well as good selectivity, which are much better than that of commercial SnO 2 (C-SnO 2) and O-SnO 2 , and Au NPs decorated C-SnO 2. Based on the detailed investigation, the enhanced DMMP sensing performances of Au-O-SnO 2 hybrids can be mainly ascribed to the synergistic effect of increasing surface active sites induced by oxygen vacancies, the chemical and electronic sensitization of Au NPs. As a result, Au-O-SnO 2 -5 hybrids display relatively low activation energy of 24.11 kJ/mol for DMMP oxidization, which is lower than that of O-SnO 2 (35.54 kJ/mol). Our results provide a feasible method for boosting sensing performances for DMMP detection, paving new way for fabrication of metal oxides-based gas sensors for rapid detection of trace organic compounds with complexed structures. [ABSTRACT FROM AUTHOR]