Creatinine-Modified Gold Nanoparticles for Highly Sensitive Colorimetric Sensing of Nitroguanidine Explosive

We report a simple, facile, selective, and highly sensitive colorimetric sensor for nitroguanidine explosive. The colorimetric sensor utilizes the aggregation of creatinine-modified gold nanoparticles (AuNPs), which was caused by nitroguanidine via hydrogen bond interaction between nitroguanidine and creatinine, leading to a color change from red to blue to colorless dependent on the concentration of nitroguanidine. Under optimum sensing concentrations, the absorbance changes of AuNPs at 519 nm were linear with the concentration of nitroguanidine in the range of 15-55 mu M with a correlation coefficient of 0.997. The limit of detection of the colorimetric sensor was 1 mu M based on the signal-to-noise of three, which has improved by as much as five orders of magnitude as compared with the traditional volumetric method and up to three orders of magnitude as compared with fluorescence approach as well. Moreover, as low as 15 mu M of nitroguanidine can be visually detected by the naked eye without instrumentation. The colorimetric sensor also displayed remarkable selectivity to nitroguanidine against other explosives and common inorganic salts. It was robust and can be employed for reliable sensing of spiked nitroguanidine in real water samples with good recovery and accuracy.