Ultrasensitive detection of l-cysteine using gold–5-amino-2-mercapto-1,3,4-thiadiazole core–shell nanoparticles film modified electrode

We are reporting the selective, sensitive and stable determination of l-cysteine (CY) at physiological pH (pH = 7.2) using a gold–aminomercaptothiadiazole core–shell nanoparticles (p-GAMCS NPs) film modified GC electrode. The p-GAMCS NPs film was fabricated on GC electrode by potentiodynamic method using 5-amino-2-mercapto-1,3,4-thiadiazole stabilized gold nanoparticles (AMT-AuNPs). The fabricated p-GAMCS NPs film was characterized by cyclic voltammetry and atomic force microscopy (AFM) techniques. The AFM image of the p-GAMCS NPs film showed that it contains a homogeneously distributed AuNPs with a spherical shape of ∼10 nm. The p-GAMCS NPs film modified GC electrode was exploited for the determination of CY. The bare GC electrode failed to show any response for CY (pH = 7.2) whereas p-GAMCS NPs film on GC electrode showed a well-defined oxidation peak for CY at 0.51 V. Further, p-GAMCS NPs film modified electrode successfully resolved the voltammetric signals of ascorbic acid (AA) and CY with a peak separation of 500 mV. This is the first report for the large voltammetric peak separation between CY and AA to the best of our knowledge. The amperometric current was increased linearly from 10 nM to 140 nM CY with a detection limit of 3 pM (S/N = 3). The present modified electrode showed better recoveries for spiked CY into the human blood serum and urine samples.