Detection of NO2- with a colorimetric sensor based on etching Au NBPs

Nitrite (NO 2 - ) in water and food is a potential threat to the environment, human health, and other living organisms. Therefore, the detection of NO 2 - is highly essential. Herein, a simple and fast colorimetric method for NO 2 - detection is realized based on the etching of non-modified gold nanobipyramids (Au NBPs), which results in the blue-shift of longitude local surface plasmon resonance (LSPR) peak and obvious color changes. The NO 2 - was detected through this method with a linear response ranging from 2.0 to 20 μM, a limit of detection (LOD) of 0.17 μM and a naked eye LOD of 6.0 μM under the optimal conditions. The LOD is sufficiently for the detection of NO 2 - in food in real life applications. During the detection, the morphology of Au NBPs generally changes from the bipyramid shape to the rice shape, and then to the final spheroid shape with increasing NO 2 - concentration. The feasibility of this method was verified in real samples with good recovery. Compared with other methods, this colorimetric sensor has advantages such as its low cost, excellent sensitivity and selectivity, and the most importantly, it can be applied to visually detect NO 2 - .