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The chemiresistive sensors have enabled the sensing of diverse organoamines, but the low-temperature detection of highly carcinogenic and combustible dibutylamine (DBA) has not been achieved to date. Herein, based on the concept of waste reuse and sustainable development, the discarded willow catkins were served as biotemplates and soaked into zinc or iron nitrates and their mixed solution. The above precursors were calcined at 500 °C in the air to controllably synthesize two homo-tubes and two ZnFe 2 O 4 /ZnO hetero-tubes, all of which are assembled by uniform nanoparticles. Among, the 1.25 at% ZnFe 2 O 4 /ZnO hetero-tubes possess uniform mesoporous distribution, high content of adsorbed oxygen species, and catalytic sites of high-valent Fe4+ Lewis acid, thus realizing the first metal oxide-based sensor with excellent trace DBA sensing at low temperature. The 1.25 at% ZnFe 2 O 4 /ZnO sensor exhibits high response of 79–100 ppm DBA at low 133 °C, which is 1.4, 1.8 and 2.3 times higher than those of 3.2 at% ZnFe 2 O 4 /ZnO, ZnO and ZnFe 2 O 4 tubes, respectively. Furthermore, it also behaves rapid response kinetics (11 s∼10 ppm), good humidity resistance, reliable long-term stability (60 days), and the ability to actually detect prometryn herbicide. In addition, its response mechanism for the enhanced DBA sensing was investigated. [Display omitted] • 1.25 at% ZnFe 2 O 4 /ZnO hetero-tube was simply and controllably prepared using waste catkins as biotemplate. • The sensor exhibited high sensitivity and rapid response-recovery to trace DBA at low 133 °C for the first time. • The good performance is mainly attributed to the synergism of more adsorbed oxygen species and Fe4+ Lewis acid sites. • The simple and sustainable biotemplate method provides a new inspiration for preparing other tubular metal oxides. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-crystal WO 3 sheet-like structure was simply prepared by calcining waste WCl 6. • The sensor firstly achieved low temperature-dependent dual-sensing to DMA and NO 2. • The good property stems from synergy of unique microstructure and W6+ Lewis acid. • Usage of spoiled reagent provides an idea for synthesizing other porous nanosheets. Herein, nanoparticle-supported WO 3 sheets were simply prepared by direct pyrolysis of spoiled WCl 6 powder. The influence of calcination temperature on their composition and morphology transformation was explored through the characterizations of powder X-ray diffractometer, X-ray photoelectron spectrometer, scanning and transmission electron microscope. Amongst, the W-600 sheet-like structure obtained by calcination at 873 K is cross-linked by homogeneous nanoparticles, and has meso/macro-pore distribution, single-crystal nature and relatively small band gap. These favorable factors promote rapid gas diffusion, increase the electron migration rate, as well as expose more active sites for surface chemical reaction. Especially, under the synergism of surface unsaturated W6+ Lewis acid, the fabricated W-600 sensor achieves dual-sensing to dimethylamine (DMA) and NO 2 for the first time. It exhibits a good response (S = 35.3) to 100 ppm DMA at 298 K, and also presents a high response (S = 125) to 1 ppm NO 2 at 323 K. The actual detection limit can be as low as 1 ppm (DMA) and 10 ppb (NO 2). Meanwhile, this sensor still has reversible response-recovery characteristics, satisfactory stability and moisture resistance. Furthermore, the dual-functional sensing mechanism was also explored in detail. [ABSTRACT FROM AUTHOR]

The development of low-temperature metal oxide-based sensors with high sensing response towards harmful ppb-level gases remains challenging. Based on the idea of biological structure imitation, we choose wooden hydrangea petals as biotemplate and carbon source to controllably replicate graphitic carbon-doped SnO 2 material (GC/SnO 2 -6) by simply calcining the salt solution-soaked precursor at 600 °C. Its morphology is tube bundle wrapped by corrugated sheets that formed by cross-linkage of nanoparticles. The internal surface of tube wall is decorated with nanoaggregates. The fabricated GC/SnO 2 -6 sensor exhibits response value of 256.3 towards 1 ppm NO at 50 ℃, which is 9.9 times higher than that (S = 26.0) of pure SnO 2 -7 material obtained by calcining at 700 ℃ in air. Meanwhile, this sensor also has short recovery time (42 s), low actual detection limit (50 ppb), satisfactory moisture resistance and long-term stability. Such excellent comprehensive gas-sensing performance is attributed to the homogeneous mesopore and large specific surface area of its biomorphic structure, as well as the synergism of graphitic carbon doping and abundant oxygen vacancies. In addition, the enhanced sensing mechanism is also explored in detail. [Display omitted] • Graphitic carbon-doped SnO 2 nanosheets-wrapped tubes were simply and controllably prepared by wood hydrangea petal template. • GC/SnO 2 -6 sensor realizes the high sensing and rapid detection to ppb-level NO at near room temperature for the first time. • The good sensing performance stems from the synergism of unique microstructure, graphitic carbon doping and oxygen vacancies. • The green and repeatable bio-template method provides a new vision for preparing graphitic carbon-doped metal oxides. [ABSTRACT FROM AUTHOR]