Free-standing Au-Ag nanoparticles on carbon cloth: A non-enzymatic flexible electrochemical sensor for the biomarker of oxidative stress

Hydrogen peroxide (HP) is considered as cytotoxic and its levels in human may be controlled by catabolism and excretion. It plays an important role in renal function regulations and as an antibiotic in urine and the urinary HP level under certain conditions will be a precious biomarker of oxidative stress. Hence, this study aimed to develop a sensitive electrochemical flexible sensor to determine HP in human urine using Au-AgNPs fabricated carbon cloth. Initially, Au-AgNPs were fabricated by electroless deposition which involves immersion of electrode in AgNO₃-ascorbic acid bath for an hour followed by its immersion in HAuCl₄. The deposited AgNPs served as a sacrificial system for Ag-AuNPs growth by galvanic displacement. SEM images exhibited the 30 and 55 nm sized AgNPs and Au-AgNPs, respectively at optimized conditions and their zero valent nature was confirmed by XPS. Further, composition dependent HP reduction was realized at the Au-AgNPs electrode. Amperometric HP determination was achieved in 500 nM-2 mM range with 59 nM (S/N = 3) limit of detection. The present sensor shows superior sensitivity of 3523.14 μA mM⁻¹ cm⁻² than the reported sensors. Ultimately, the flexible electrochemical sensor fabricated on carbon cloth detects HP in freshly voided human urine and blood serum samples.