Abstract A robust synthesis approach to Al/SnO2 based formaldehyde gas sensing xerogels using epoxide assisted sol-gel chemistry is reported. The route utilizes simple tin and aluminum salt precursors in alcohol/water mixture, thus eliminating the need for organometallic precursors. Propylene oxide acts as a proton scavenger and drives metal hydroxide formation and subsequent polycondensation reactions. Al/SnO2 xerogels (with Al doping 1–4 mol%) were aged for 24 h to strengthen the gel network, followed by sintering and screen printed thick films formation. Prior to gas sensing investigations, the physico-chemical properties of the material were analysed using TG-DTA, XRD, FE-SEM, TEM, SAED, EDAX, UV–Visible and FTIR spectroscopic techniques. The developed material showcase tetragonal rutile structure of SnO2 with porous morphology required for effective gas diffusion. Al/SnO2 with 3 mol% doping level exhibited excellent gas sensing ability (Ra/Rg = 15 @ 300 °C operating temperature) towards barely 100 ppm formaldehyde concentration. Not only sensor response was got improved (from Ra/Rg value 5 to 15), but also the operating temperature got reduced from 325 °C to 300 °C). An effect of formaldehyde concentration, the sensor response got increased rapidly up to 100 ppm concentration, thereafter the increase in response was observed almost stagnant. By keeping the measurement parameters as is, the sensor performance was checked six times after the initial measurement with the interval of 10 days, which showed ~89% of its initial sensitivity. The developed material showcase the potentiality of being formaldehyde gas sensor.

中文翻译：

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通过环氧化物辅助凝胶化开发 Al/SnO2 干凝胶的简便方法：甲醛气体传感器的高度通用途径

摘要报道了一种使用环氧化物辅助溶胶-凝胶化学合成基于 Al/SnO2 的甲醛气敏干凝胶的稳健合成方法。该路线在醇/水混合物中使用简单的锡和铝盐前体，因此不需要有机金属前体。环氧丙烷充当质子清除剂并推动金属氢氧化物的形成和随后的缩聚反应。Al/SnO2 干凝胶（Al 掺杂 1-4 mol%）老化 24 小时以加强凝胶网络，然后烧结和丝网印刷厚膜形成。在进行气敏研究之前，使用 TG-DTA、XRD、FE-SEM、TEM、SAED、EDAX、UV-Visible 和 FTIR 光谱技术分析了材料的物理化学性质。开发的材料展示了 SnO2 的四方金红石结构，具有有效气体扩散所需的多孔形态。具有 3 mol% 掺杂水平的 Al/SnO2 表现出出色的气体传感能力（Ra/Rg = 15 @ 300 °C 工作温度），甲醛浓度仅为 100 ppm。不仅传感器响应得到改善（从 Ra/Rg 值 5 到 15），而且工作温度也从 325°C 降低到 300°C）。在甲醛浓度的影响下，传感器响应迅速增加到 100 ppm 浓度，此后观察到响应的增加几乎停滞。通过保持测量参数不变，在初始测量后以 10 天的间隔检查传感器性能 6 次，显示出其初始灵敏度的 89%。