Colorimetric detection of Cr~(3+) using tripolyphosphate modified gold nanoparticles in aqueous solutions

摘要

A sensitive and selective colorimetric assay method for the detection of Cr~(3+) has been developed using tripolyphosphate functionalized gold nanoparticles (P3O_(10)~(5-)-AuNPs). Infrared (IR) spectra and energy dispersive X-ray spectroscopy (EDS) confirmed that tripolyphosphates capped on the surfaces of gold nanoparticles (AuNPs). Gold nanoparticles were prepared by reducing HAuCl4 with sodium borohydride (NaBH4) in the presence of sodium tripolyphosphate (Na5P3O_(10)). Upon exposure to Cr~(3+), the color of the gold nanoparticle solution changed from red to violet, which was in response to the surface plasmon absorption of dispersed and aggregated nanoparticles. The P3O_(10)~(5-)-AuNPs were bound by Cr~(3+) and showed excellent selectivity compared to other ions (Hg~(2+), Fe~(3+), Cr~(6+), Mn~(2+), Cd~(2+), Ni~(2+), Pb~(2+), Ba~(2+), Co~(2+), Cu~(2+), Ca~(2+), Mg~(2+), Zn~(2+), Al~(3+), Na~+, Cl~-, SO_4~(2-), PO_4~(3-), CO_3~(2-), NO_3~-, and all of the above interfering ions with the exception of Cr~(3+)) and had a detection limit of 10~(-7) M by the naked eye in this way. Most importantly, the P3O_(10)~(5-)-AuNPs can be stored at room temperature over half a year. In addition, the P3O_(10)~(5-)-AuNPs were also used to detect Cr~(3+) in real environmental water samples, with low interference.