A sensitive plasmonic copper(II) sensor based on gold nanoparticles deposited on ITO glass substrate

• The Au NPs onto ITO solid substrate was fabricated by self-assembly method and calcination.
• The ITO/Au NPs/Cys probe can be used to plasmonic detection of Cu2+ ions.
• The introduction of BSA can greatly improve the sensitivity of detection.
• The plasmonic sensor was of high sensitivity and wide linear range.

Gold nanoparticles (Au NPs) based plasmonic probe was developed for sensitive and selective detection of Cu2+ ion. The Au NPs were self-assembled on transparent indium tin oxide (ITO) film coated glass substrate using poly dimethyl diallyl ammonium chloride (PDDA) as a linker and then calcined at 400 °C to obtain pure Au NPs on ITO surface (ITO/Au NPs). The probe was fabricated by functionalizing l-cysteine (Cys) on to gold surface (ITO/Au NPs/Cys). The strong chelation of Cu2+ with Cys formed a stable Cys-Cu complex, and resulted in the red-shift of localized surface plasmon resonance (LSPR) peak of the Au NPs. The introduction of bovine serum albumin (BSA) as the second complexant could form complex of Cys-Cu-BAS and further markedly enhanced the red-shift of the LSPR peak. This plasmonic probe provided a highly sensitive and selective detection towards Cu2+ ions, with a wide linear detection range (10−11–10−5 M) over 6 orders of magnitude. The simple and cost-effective probe was successfully applied to the determination of Cu2+ in real samples.