Department of Analytical Chemistry, Faculty of Chemistry, University College of Science, University of Tehran, P.O. Box 14155-6455, Tehran, Iran.
Department of Applied Chemistry, Faculty of Science, University of Mohaghegh Ardabili, Daneshgah Street, P.B179, 56199-11367 Ardabil, Iran.
Anal Chim Acta. 2015 Oct 15;897:87-95. doi: 10.1016/j.aca.2015.09.031. Epub 2015 Sep 21.
As a result of this study, a new and simple method was proposed for the fabrication of an ultra sensitive, robust and reversible ammonia gas sensor. The sensing mechanism was based upon the change in electrical resistance of a graphene aerogel as a result of sensor exposing to ammonia. Three-dimensional graphene hydrogel was first synthesized via hydrothermal method in the absence or presence of various amounts of thiourea. The obtained material was heated to obtain aerogel and then it was used as ammonia gas sensor. The materials obtained were characterized using different techniques such as Fourier transform infra red spectroscopy (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thiourea-treated graphene aerogel was more porous (389 m(2) g(-1)) and thermally unstable and exhibited higher sensitivity, shorter response time and better selectivity toward ammonia gas, compared to the aerogel produced in the absence of thiourea. Thiourea amount, involved in the hydrogel synthesis step, was found to be highly effective factor in the sensing properties of finally obtained aerogel. The sensor response time to ammonia was short (100 s) and completely reversible (recovery time of about 500 s) in ambient temperature. The sensor response to ammonia was linear between 0.02 and 85 ppm and its detection limit was found to be 10 ppb (3S/N).
这项研究提出了一种新的、简单的方法来制造超灵敏、坚固和可逆的氨气传感器。其传感机制基于石墨烯气凝胶的电阻变化，这种变化是由于传感器暴露在氨气中引起的。首先通过水热法在没有或存在不同量硫脲的情况下合成了三维石墨烯水凝胶。所得材料被加热以获得气凝胶，然后将其用作氨气传感器。使用不同的技术对获得的材料进行了表征，例如傅里叶变换红外光谱（FT-IR）、热重分析（TGA）、X 射线衍射（XRD）和扫描电子显微镜（SEM）。与在没有硫脲的情况下制备的气凝胶相比，硫脲处理的石墨烯气凝胶具有更高的多孔性（389 m2 g-1）和热不稳定性，并且对氨气具有更高的灵敏度、更短的响应时间和更好的选择性。参与水凝胶合成步骤的硫脲量被发现是最终获得的气凝胶传感性能的一个非常有效的因素。该传感器在环境温度下对氨气的响应时间很短（100 s），完全可逆（恢复时间约为 500 s）。传感器对氨气的响应在 0.02 和 85 ppm 之间呈线性，检测限为 10 ppb（3S/N）。
