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 HO 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.