Colorimetric screening of nitramine explosives by molecularly imprinted photonic crystal array

Colorimetric, selective and sensitive screening of explosives is important not only to military action but also to public security. Normal explosives detection is mainly targeted for nitroaromatic compounds, however, ntiramine explosive is used more widely due to its outstanding performance. Herein, molecularly imprinted photonic crystal (MIPC) sensors were made to detect typical nitramine explosives: 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), cyclotetramethylenete-tranitramine (HMX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20). And 2,4,6-trinitrotoluene (TNT) templated MIPC was also made to discriminate not only nitramines but also nitrobenzene explosives. With explosives concentration increase, the diffraction peak and structure color of MIPC sensors both red shifted within 5 min. By adding alkaline solution, the MIPC sensors were softened, and the mass transfer and the sensitivity were improved. The MIPC sensors could respond to lower than 0.05 mM explosives with the limit of detection of 0.01 mM. A MIPC sensor array with the above MIPCs was constructed to achieve a semi-quantitative detection, and Pattern Recognition with a 48 x 4 multivariate data matrix was using to discriminate different explosive molecules. According to principal component analysis, the response of RDX, HMX, CL-20 and TNT scattered in separate areas, and the sensor array could discriminate with a LOD of 1 mM.