Multiple amplifications of NIR-I ECL signals of AuPtAg nanoclusters and applications in fast detections of noradrenaline.

NIR-I electrochemiluminescence (ECL) is emerging as highly sensitive detection strategy due to its low background at the ambient conditions. Nonetheless, the applications of current NIR-I ECL nanoprobes are limited to the harsh synthetic/testing condition, high toxicity, low signal, and poor biocompatibility. In this study, glutathione/lipoic acid-protected trimetallic AuPtAg nanoclusters (GSH/LA/AuPtAg NCs) are demonstrated as an efficient nanoprobe with strong ECL signals around 850 nm in the presences of triethylamine. Critically, the alloying of Ag  into the bimetallic Au Pt NCs altered the electronic structures of Pt(II), valences of Au(0), and the zata potentials of NCs, promoting the ECL intensities at 850 nm by 1.0 time. Additionally, the partly ligand-exchange of GSH by LA further increased the ECL intensities at 850 nm by 2.2 times through accelerating electron transfer processes. Meanwhile, the NIR-I fluorescence (λ = 910 nm) was enhanced. More importantly, the utilization of GSH/LA/AuPtAg NCs μg is enhanced by 3000 times after embedding into SiO microspheres (D, 318 nm). Because noradrenalin has substantial inhibition effects to NIR-I ECL of GSH/LA/AuPtAg/SiO, 1.0 nM-0.1 mM noradrenalin was detected with the low limit of detection as 0.04 nM (S/N = 3) selectively. Biomolecules, glucose, ascorbic acid, or uric acid didn't interrupt the detection of noradrenalin. The sensitivity of this ECL method to detect noradrenalin is much higher than those in previous reports, enabling the early diagnosis of neurogenic diseases.