An azaindole–hydrazine imine moiety as sensitive dual cation chemosensor depending on surface plasmon resonance and emission properties

Abstract

A novel azaindole-based colorimetric and fluorescent sensor with an attached hydrazine group (L) was synthesized and characterized by FT-IR, NMR, and CHNS analyses. L exhibited high colorimetric selectivity and sensitivity toward Ag+ ions over other common cation solutions (Ag+, Na+, K+, Ba2+, Cd2+, Co2+, Cu2+,Cr3+, Fe2+, Mg2+, Mn2+, Ni2+, Sr2+, Zn2+, and Al3+) in ethanol:HEPES buffer (1:9, v/v) solution. Upon addition of Ag+ ions, the maximum absorption band of L displayed a red shift from 332 to 400nm. The efficient electron transfer ability of the molecular receptor L lead to the easy formation of silver nanoparticles (AgNPs) that manifested naked eye detection through color change of solution from colorless to yellow. The AgNPs thus obtained using organic compound L as stabilizer were characterized by light scattering, zeta potential and transmission electron microscopy (TEM). Meanwhile, the results of fluorescence titration experiments illustrated that the sensor functions as “turn-off” receptor upon selective binding with Fe2+. Comparative studies revealed that quenched emission originated from selective chelation of Fe2+ ions with the lone pair of the azaindole receptor's nitrogen atom and causes enhanced PET process Both B.-H. plot and emission spectra analysis reveals a 1:2 stoichiometric relationship between L and the added Fe2+ ions. The designed probe L permitted accurate detection of respectiveAg+ and Fe2+ down to 2.8nM and 2.17×10−7M with rapid response times. Finally, by using Ag+ and Fe2+ ions as chemical inputs and the absorbance and emission response as outputs, logic circuits are constructed at the nanoscale level.