Facile synthesis of water-soluble and pH-stable silicon quantum dots and their application in enzyme-free hydrogen peroxide sensing

A sensor for non-enzymatic hydrogen peroxide (H₂O₂) detection was developed based on silicon quantum dots (SiQDs). The fluorescent SiQDs were synthesized using a one-pot hydrothermal method. The SiQDs were made water-soluble and pH-stable by covering their surfaces with amino and hydroxyl groups. Additionally, the prepared SiQDs had a large Stokes shift (131 nm), excellent photostability (442 min), and hypotoxicity (<i>e.g.</i>, 99% cell viability was retained after a 24 h-treatment at 8.0 mg mL^-1 of SiQDs). The dynamic quenching effect induced by H₂O₂ effectively suppresses the blue fluorescence of SiQDs. Under the optimum conditions, the SiQD-based H₂O₂ sensor exhibited a wide linear range (10-1000 μM), high sensitivity and selectivity, and good anti-interference ability. The detection limit and relative standard deviation were 1.7 μM and 4.5% (<i>c</i> = 20 μM, <i>n</i> = 7), respectively. Accordingly, a simple, enzyme-free, and highly efficient method was established for detecting H₂O₂ in aqueous solutions. Moreover, this eco-friendly fluorescent sensor successfully determined the H₂O₂ concentration in human serum samples with 92.0-102.4% recoveries.