Biodegradation Of Carbon Dots By Two Typical Oxidoreductases In The Presence Of Phenolic Contaminants

Carbon dots(CDs),as a new class of carbon nanomaterials,have attracted much attention in recent years due to their excellent optical properties,high fluorescence emission,and good biocompatibility.These excellent characteristics enable CDs to be widely developed and applied in biological imaging,medicine,medical chemical sensing,biological imaging,and other fields,and become a research hotspot in chemical materials science and biological science at home and abroad.Because of the broad application prospect of CDs,CDs may inevitably leak and pollute the environment,leading to potential environmental risks and human health risks.Therefore,it is very necessary to find a fast,economical and effective method to degrade carbon quantum dots in the natural environment.Typical oxidoreductases have high efficiency and specificity for enzymatic reactions of pollutants in the environment,reasonable degradation reaction time and less energy consumption,and can obtain higher benefits.At the same time,many enzymatic processes are considered as the environmentally friendly treatment methods,which can effectively reduce the toxicity of pollutants.Therefore,it is necessary and of great significance to explore the-enzymatic degradation method of carbon quantum dots.There are also highly polluting phenol molecules in the water environment,and related research on the degradation of phenolic substances by biological enzymes are increasing.However,it is not common to explore the double degradation of carbon nanomaterials and phenols by typical oxidoreductases.Through the interaction of the two substrates,it is possible to explore and use reasonable enzyme treatment methods to achieve more efficient degradation results,which is of great practical significance for safe production and environmental and ecological applications.In this thesis,two typical oxidoreductases,Laccase and HRP,were used,carbon dots(CDs),bisphenol A(BPA)paracetaminophenol(ACE),trichlorophenol(TCP),and trimethylphenol(TMP)were used as substrates to explore the degradation and transformation of CDs and phenol by related enzymes,as well as the interaction and environmental significance of CDs and phenol enzymatic degradation process.The main contents are as follows:(1)Nitrogen-doped carbon dots were prepared by hydrothermal method using citric acid and urea as material,and the degradation and transformation process of CDs in two typical oxidoreductases and the changes in their physical and chemical properties were studied.Studies have shown that CDs degrade in both of the two typical oxidoreductases.Environmental factors also have varying degrees of influence on the degradation and transformation of CDs,p H acidic conditions have a greater impact on the degradation of CDs by laccase,and humic acid has a strong inhibition on the degradation of CDs.(2)The degradation and transformation of CDs and phenol mixtures in typical oxidoreductases and their interaction were investigated.Studies have shown that taking BPA as an example,can promote the degradation of CDs,which may be related to the phenoxy attack on CDs and the formation of carbon center free radicals caused by BPA through EPR free radical detection,and CDs has an inhibitory effect on the degradation of BPA in lassase.The degradation of CDs and other three phenols in HRP promoted each other,which was speculated to be related to the change of heme active site proximity of HRP and the protective mechanism of free radicals in CDs on HRP.(3)The chemical classification and molecular composition of CDs products before and after the reaction were explored by ESI-FT-ICR MS technology and the allocation algorithm of TRFu and FTMSDeu to the mass spectrometry molecular formula.After degradation,the proportion of aromatic structure products increased,which may be related to the more stable chemical properties of the aromatic structure,and the proportion of unsaturated hydrocarbons in a small amount decreased,which is inferred to be related to the instability of double and triple bonds contained in unsaturated hydrocarbons and easy to fracture.