An ultrasensitive and selective “off-on” rhodamine-based colorimetric and fluorescent chemodosimeter for the detection of Cu2+

Abstract

A novel “off-on” colorimetric and fluorescent chemodosimeter, N-(2,4-dinitrophenyl) rhodamine B-hydrazide (DNPRH), has been designed and synthesized via integrating 2,4-dinitrophenylhydrazine with rhodamine B acid chloride, which can selectively detect the presence of Cu2+ with about 500-fold enhancement in fluorescence emission intensity at 578nm over various environmentally relevant metal cations such as K+, Na+, Ag+, Mg2+, Ca2+, Al3+, Pb2+, Zn2+, Cd2+, Hg2+, Ni2+, Cr3+, Fe2+ and Fe3+ in pH 7.0 media. The significant change in color of DNPRH solution from colorless to pink induced by the addition of Cu2+ makes the “naked-eye” recognition of copper ion possible. In addition, the ultrasensitive detection limit for Cu2+ on the UV–vis and fluorescence measurement is down to 2.6×10−8molL−1 and 1.2×10−9molL−1, respectively.