Room temperature VOC gas detection using a gated lateral BJT with an assembled solvatochromic dye

A novel volatile organic compound (VOC) gas sensor utilizing a gated lateral bipolar junction transistor (BJT) with an assembled solvatochromic dye is proposed. Because of its threshold voltage, the proposed gas sensor device can be used under room temperature conditions, unlike common semiconductor-based gas sensors. For this study, a metal-oxide-semiconductor field-effect transistor (MOSFET)-gated lateral, hybrid mode-operated BJT that could be driven using base current control with a gate bias supply was zero. A solvatochromic 4-amino-N-methylphthalimide (4-ANMP) dye, which had its molecules immobilized on the floating gate of the gated lateral BJT using a self-assembled monolayer (SAM) method based on the amino-group holding within its molecular structure, was also used. The charge-transfer (CT) property of this dye could respond to changes in polarities of gases and solutions in the surrounding environment. In this study, three types of VOC gases, namely, benzene, hexane, and acetic acid gas, were detected. It was shown that, by using the proposed sensor, the acetic acid gas and the benzene gas could be detected at room temperature at sensitivities of approximately 0.046 and 0.052 μA/decade for benzene and acetic acid gas, respectively. And the non-polar hexane gas could not be detected.