Nanozymatic detection of thiocyanate through accelerating the growth of ultra-small gold nanoparticles/graphene quantum dots hybrids.

Thiocyanate (SCN-) concentration monitoring in food is important to ensure the health and safety of the consumers.A colorimetric detection of thiocyanate (SCN-) based on the nanozymatic activity of gold nanoparticle-graphene quantum dots (GQDs-Au NPs) hybrids in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 has been proposed. Here, a new synthesis method of GQDs directly from graphite was introduced. Transmission electron microscopy (TEM) images revealed that the size of the GQDs was 3-5 nm, and the emission peak appeared at 450 nm. As-synthesized GQDs was utilized to produce GQDs-Au NPs hybrids without additional chemicals. However, the presence of SCN- inhibits the growth of Au NPs, the resulting Au NPs are smaller in size. Moreover, SCN- group is well-known for hydroxyl radical (OH) scavenging activity that could oxidize TMB. Both effects boosted the nanozymatic activity of GQDs-Au NPs to detect SCN- under optimized conditions with a limit of detection (LOD) of 3 nM. Present study also validates the methodology to detect SCN- in raw milk.