Brominated Graphene as Mimetic Peroxidase for Sulfide Ion Recognition

Brominated graphene (GBR) with ∼3% bromine content has shown novel peroxidase mimetic activity toward 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O_2. Optimum activity has been observed at pH 4.48 and after a minimum ∼30 min of equilibration time. Among the different analytes studied using the sensor combining TMB, H₂O₂, and GBR in phosphate buffer of pH 4.48, the S^2- ion has effectively shown a short duration of sensing (∼2 min) within the detection range of 0.04-1 mM. A calibration curve for S^2- ion estimation has been constructed with the experimental linearity in 0.04-0.4 mM range and having the limit of detection (LOD) value of 25.3 μM. A standard addition experiment has validated the method. A paper strip sensor has been fabricated for successful detection of S^2- ion.