writer：Yi Lin, Shaohua Xu, Jiao Yang, Youju Huang,* Zhitao Chen, Bin Qiu, Zhenyu Lin, Guonan Chen, and Longhua Guo*
keywords：colorimetric sensor; Au Nanobipyramid@Ag Nanorods
source：期刊
specific source：Sensors and Actuators B: Chemical
Issue time：2018年

Common colorimetric immunoassays only show monochromatic intensity variations, and the absorbance intensity is utilized for the quantitative detection of the analytes. Recently we have shown that gold nanorods and Au Nanobipyramids are good multicolor chromogenic substrates for immunoassays, and the LSPR peak shifts are used for the quantitative

detection of the analytes. Herein, we demonstrate for the first time that Au Nanobipyramid@Ag Nanorods (Au NBP@Ag) is an ideal multicolor chromogenic substrate for immunoassays which combines the advantages of the above mentioned approaches: both the absorbance intensity and the LSPR peak shifts are utilized for quantitative detection of the analytes, and the vivid color variations is used for semi-quantitative detection of the analytes as well. Our investigation reveals that unlike the single metallic nanoparticles such

as gold nanorods and gold nanobipyramids which show one-way LSPR peak shifts during the etching process, Au NBP@Ag Nanorods shows an interesting multi-way peak shifts: the LSPR peak would initially blue shift, and then red shift, and finally blue shift again during the etching process. As a result, a series of vivid colors can be observed during the etching process. This phenomenon is incorporated to the conventional immunoassays for the ultrasensitive colorimetric detection of squamous cell carcinoma antigen (SCCA) in human serum. The results indicate that the correlation linear range for the detection of SCCA was 2.5 ~ 105 ng/mL, with a limit of detection (LOD) of 2.5 ng/mL for naked eye inspection, and a LOD of 0.85 ng/mL when detected with a spectrometer. Although only the detection of SCCA is demonstrated in this work, this method is easy to expand to the detection of other biomarkers since our method is based on conventional immunoassay strategy.