Influence of gas adsorption on the surface photovoltage of Au nanorods embedded polymer coated ZnO nanorods under visible light irradiation

Abstract

The synergism between the photosensitivity and gas sensitivity enabled the development of low powered highly selective gas sensors. In particular, organic/inorganic hybrid materials contribute to the coupling effect of light activated surface photovoltage modifications. In this report, the effect of visible light and volatile organic compounds (VOCs) on the hybrid sensing layer involving organic/inorganic/noble metal through scanning kelvin probe was disseminated. The sensor was fabricated by spin coating the layer-by-layer assembled poly (allylamine hydrochloride) (PAH) and dextran sulfate (DS) on hydrothermally grown ZnO nanorods followed by the incorporation of gold nanorods on ITO substrates. Structural and optical characterizations revealed the assembly of Au nanorods on the polymer coated ZnO nanorods and maximum absorbance in the visible light region, respectively. The optical nature of the hybrid sensor facilitated significant changes in contact potential difference (CPD) when irradiated with light. Changes in CPD values were measured with respect to alcohol, alkane and amine under illumination. A non-selective interaction was observed, yet the enhanced visible light response to triethylamine (TEA) corresponds to the formation of coordination bonds between the hybrid sensor and adsorbed species. The potential shift of ∼31 mV, ∼67 mV and ∼164 mV were observed for TEA by ZnO, ZnO/Poly and ZnO/Poly/Au, respectively. The simultaneous charge transfer/separation ability, surface plasmon resonance and inhibition of recombination of photogenerted carriers by Au promoted the interaction. Evidence of selective interaction can be elucidated through the selection of different VOCs under specific type of gas for CPD measurements.