Identification of Nanoparticles with a Colorimetric Sensor Array

A simple colorimetric sensor array technique was developed for the detection of various different nanoparticles (NPs) in aqueous solutions. The sensor array consists of five different cross-reactive chemoresponsive dyes, whose visible absorbances change in response to their interactions with NPs. Although no single dye is specific for any one NP, the pattern of color changes for all dyes provides a unique molecular fingerprint for each type of NP studied. Based on the responses of various dyes, a semiquantitative determination of concentration of each type of NP could also be accomplished with excellent sensitivity (<100 ng/mL). A variety of chemically distinct NPs were unambiguously identified using a standard chemometric approaches, including gold nanospheres (2 through 40 nm diameter), gold nanorods (2.4 and 3.5 aspect ratios), and multifunctional carbon nanospheres without errors in 112 trials. This colorimetric approach may pave the way for a fast, reliable, and inexpensive method to detect nanopollution and to characterize the physiochemical properties of NPs.