Preparation Of Carbon Dot Nanomaterials And Applications In The Detection Of Food Additives

In recent years,food safety issues have attracted widespread attention from people around the world.Especially,abuse of food additives has seriously affected people's health.Therefore,it is necessary to establish simple,rapid,economical and applicable methods for the assays of food additives.Compared to organic dyes,semiconductor and metal quantum dots,carbon dots(CD)as new fluorescent carbon nanomaterials,exhibit more excellent capabilities.Therefore,CD can be used in bioimaging,biomedicine delivery,biosensing,nanomedicine,and chemical sensors.In the study,the carbon dots were prepared by the hydrothermal method.Moreover,the selectivity and antiinterference ability of sensors were improved based on doping or combining different materials for the detections of food additives.The contents were as follows:(1)Boron doped carbon dots(B-CD)were synthesized by a one-step hydrothermal method using phenylboronic acid as the starting material,and its average size is about 3.3 nm.The excitation/emission wavelength of 247/323 nm and a quantum yield of 12% were obtained for the B-CD.The B-CD is shown to be viable fluorescent probe for sorbate(PS)and vitamin B12(VB12).The fluorescence(FL)of the B-CD is quenched in the presence of PS or VB12 mainly coming from inner filter effect(IFE),but F?rster resonance energy transfer(FRET)from the B-CD(as a donor)to PS/VB12(as an acceptor)cannot be excluded.The probe enables PS to be detected by fluorometry with a linear response in the 0.20-24 ?mol/L concentration range and a 6.1 nmol/L detection limit(at 3?/slope).For VB12,the data are 0.20-30 ?mol/L and 8.0 nmol/L.(2)Nitrogen doped carbon dots(N-CD)were synthesized by a hydrothermal method using sodium citrate and polyethyleneimine as raw materials.They have an average size of about 1.2 nm,with excitation/emission wavelength of 356/446 nm and a quantum yield of 62%.Based on the IFE,N-CD combines with Mn O2 to form N-CD-Mn O2,and it is used as a fluorescent probe for detecting tert-butyl hydroquinone(TBHQ).The fluorescence of N-CD-Mn O2 can be restored by TBHQ,which is mainly due to the redox reaction between TBHQ and Mn O2,and the result indicates that IFE of N-CD-Mn O2 is weakened,so the fluorescence of N-CD restores.The probe enables TBHQ to be detected by fluorometry with a linear response in the concentration range of 0.07-66.67 ?mol/L and a 10.1 nmol/L detection limit.(3)Nitrogen and sulfur co-doped carbon dots(N,S-CD)were prepared by hydrothermal method using thiamine nitrate and sodium molybdate as raw materials.They have an average size of about 1.4 nm,with excitation/emission wavelength of 370/443 nm and aquantum yield of 14%(Taking Rhodamine B as a reference).The N,S-CD combines with Ag NCs to form a ratio probe(N,S-CD-Ag NCs).Ag-S bonds can be formed between 2-Methyl-3-furanthiol(MFT)and N,S-CD-Ag NCs,which will cause the decomposition of Ag NCs.Besides,MFT does not react with N,S-CD.Therefore,the FL intensity of N,SCD-Ag NCs remains unchanged at 443 nm,and decreases at 670 nm.The probe enables MFT to be detected by fluorometry with a linear response in the 0.07-18.67 ?mol/L concentration range and a 3.6 nmol/L detection limit.