The Carbon Dots / Au Nanocomposites With Peroxidase-like Activity And Detection Of Small Biomolecules

Small biomolecules play a very important role in the human body.For example,glucose is an indispensable substance in life activities.It can directly participate in metabolic processes in the human body,mainly providing energy.The small biological molecules present in the human body are ascorbic acid,dopamine and the like.Since the introduction of glucose biosensors,enzyme biosensors have been widely used in clinical medicine,environmental monitoring and food processing because of their high sensitivity and selectivity.Carbon dots?CDs?have attracted considerable attention as mimetic enzymes due to their low toxicity and biocompatibility.The surface of the carbon dots is rich in functional groups and can be combined with gold nanoparticles?Au NPs?to form new gold nanoparticles/carbon quantum dot nanocomposites?GCDs?.Compared with the individual carbon dots,the composite has better properties in photoelectric,thermal,magnetism,etc.,and can be applied to actual production and life in many fields.For example,surface-enhanced Raman spectroscopy,biosensor and oncology treatment have achieved remarkable results,especially in the field of catalysis.Gold nanoparticles/carbon quantum dots nanocomposites can be used as peroxidase-like enzymes to monitor glucose and ascorbic acid by enzyme biosensor,which provides a new way for the detection of small biological molecules.Based on the above,how to improve the catalytic activity of gold/carbon nanocomposites and establish a biosensor for colorimetric detection of glucose and ascorbic acid,the following research contents are proposed:?1?Gold induces the polymerization of carbon dots and forms a chain-like gold/carbon nanocomposite through cross-linking reaction.With the addition of Au NPs,fluorescence quenches and electron transfer occurs.The GCDs with optimum carbon film thickness were selected as peroxidase-like enzymes for TMB oxidation in the presence of H2O2.Raman spectroscopy and absorption spectroscopy are used to realize multi-mode monitoring,and the color change from colorless to blue can be found.On this basis,the colorimetric detection of glucose was carried out.?2?Futher study the effect of the addition of Cu²⁺on the properties of GCDs.It is found through experiments that the addition of Cu²⁺not only enhances the photothermal and SERS effects of GCDs,but also enhances the peroxidase activity of GCDs.The amino group on the surface of the composite carbon film can capture Cu²⁺to form a new substance,amine copper,which causes fluorescence quenching and promotes the progress of electron,thereby improving the catalytic performance.Ascorbic acid?AA?was continuously added to the obtained blue oxidized mixed solution,and the solution was changed from blue to colorless.Based on this,the detection of AA in orange juice is achieved.