Abstract
UV–visible absorption spectra and probe image before and after Cys interaction.
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•Cit Au NPs was synthesized by chemical reduction method.•Selective detection towards cysteine was observed with LOD of 0.012 nM.•Temperature and salinity did not influence Cys detection.•XPS spectra of cit-Au-Cys-Cr(III) complex was used to elucidate mechanism.•Practical applicability of Cit-Au NPs probe was tested with milk, urine, blood serum and environmental samples.
A selective and sensitive detection of L-cysteine (Cys) is an important tool for various biological studies. Here, Au nanoparticles (NPs) were prepared by chemical reduction technique. The probe was developed to detect and quantify Cys in the presence of Cr3+ ions which acts as a cross linker. The citrate capped Au NPs probe was analyzed by UV–visible spectrophotometry, TEM, EDAX, FTIR, DLS, XPS and zetasize. The zeta potential and effective size of Au NPs were −41.22 mV and 12 nm, respectively. The Cys interaction with Au NPs showed drastic colour variation from red to purple and colourless with rapid response time of 1 min. The limit of detection (LOD) of Au NPs probe was as low as 0.012 nM. The TEM image of Au NPs after Cys interaction verified the aggregation that resulted in colour change. The XPS core level scans of Au 4f showed 0.3 eV red shift when Cyswas interacted. The Au NPs sensor is highly selective for Cys with excellent reproducibility. Acidic pH slightly favored Cys detection. Further, the probe was applied to estimate Cys quantity from milk, urine, blood and environmental augmented samples in the presence of other amino acids . The study suggests that the proposed Au NPs could detect Cys with high accuracy from various biological samples.