Surface functionalized GdVO4:Eu3+ nanocrystals as turn-off luminescent probe for selective sensing of Cu2+ ions: role of pH

Abstract Poly(ethylene glycol) bis(carboxymethyl) ether (PEG-diacid) functionalized GdVO4:Eu3+ (5 at%) nanocrystals have been synthesized by polyol method. X-ray diffraction and transmission electron microscopy were used for the structural and morphology characterization of GdVO4:Eu3+ samples. Fourier transform infrared spectroscopy confirms the functionalization of nanocrystal surface by PEG-diacid. The resonance energy transfer from the vanadate (VO43−) to Eu3+ results in enhanced red emission. The GdVO4:Eu3+ as luminescent probe can selectively detect the presence of Cu2+ ions out of various metal ions investigated. Upon addition of Cu2+ ions, photoluminescence intensity of Eu3+ reduces instantaneously more than 90%, which is related to energy transfer from Eu3+ to Cu2+ ions. This shows the fast response during sensing. Surface functionalized particles shows a significant sensitivity as compared to the non-functionalized particles. These probes show more favourable in the alkaline aqueous medium for sensing. The possibility of reabsorption is ruled out. The limit of detection is about 9 nM of Cu2+ with the first response time and this method will be useful in selective sensing of Cu2+ ions in aqueous medium.