Multiple amplifications of NIR-I ECL signals of Au6PtAg 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 Au6PtAg nanoclusters (GSH/LA/Au6PtAg 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 Au2.5 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 (λemit = 910 nm) was enhanced. More importantly, the utilization of GSH/LA/Au6PtAg NCs μg-1 is enhanced by 3000 times after embedding into SiO2 microspheres (D, 318 nm). Because noradrenalin has substantial inhibition effects to NIR-I ECL of GSH/LA/Au6PtAg/SiO2, 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.