Rhodamine B derivative-modified up-conversion nanoparticle probes based on fluorescence resonance energy transfer (FRET) for the solid-based detection of copper ions.

Herein, a novel solid-based up-conversion fluorescence resonance energy transfer (FRET) sensor was developed using rhodamine B hydrazide, which provided a selective fluorescence response and suitable affinity towards Cu 2+ ions over other biologically relevant metal ions because the Cu 2+ ion could promote the hydrolysis of α-amino acid esters of rhodamine B hydrazide and yield the Cu·α-amino acid chelate. This solid-based detection system is more convenient for the detection of Cu 2+ based on color change and emission spectra instead of the complicated and tedious measurements than other up-conversion sensors and up-conversion luminescent nanoparticles used as an excitation source; moreover, the proposed system shows high selectivity, minimum photo-damage to living organisms, and high chemical stability.