A paper-based colorimetric sensor using Au/Ag nanocages for sensitive detection of hydrazine in water samples by smartphone

Abstract

In this work, Au/Ag nanocages have been used as an effective platform for sensitive colorimetric detection of hydrazine. By adding hydrazine together with silver ions to the hollow Au/Ag nanocages, they undergo a morphological transformation to closed nanoboxes. This leads to a noticeable blue shift in the localized surface plasmon resonance (LSPR) peak position and a distinct color change from blue to purple in the solution. The extent of shift in the LSPR peak of the Au/Ag nanocages exhibited a direct correlation with the concentration of hydrazine within the range of 0.1 to 10.0 µM. The limit of detection (LOD) achieved was 0.03 µM, with a relative standard deviation (RSD) of 1.7% at a concentration of 0.5 µM. Furthermore, we developed a paper-based sensor with smartphone readout for hydrazine detection within the range of 0.5 to 10.0 µM, with an LOD of 0.3 µM and an RSD of 3.3% at a concentration of 2.0 µM. The effectiveness of the sensor was successfully demonstrated in the analysis of hydrazine in environmental samples. This is the first time that Au/Ag nanocages are used for simple paper-based assay. With its high sensitivity, low cost, and rapid analysis time, this method offers a promising solution for the quantitative measurement of hydrazine in environmental samples by portable paper-based test strips.