Synthesis Of Nitrogen-doped Carbon Quantum Dots From Cornstalk For Detection Of Candida Albicans

Carbon quantum dots?CQDs?are emerging carbon nanomaterials with a monodisperse shape and a nearly spherical shape below 10 nm.Compared with metal quantum dots,CQDs are less harmful to the environment,low preparation cost,low toxicity,easy to functionalize,and have good biocompatibility.Therefore,more and more researchers apply them to cell markers,bio-imaging,drug delivery,fluorescent probes,organic pollutant degradation,photohydrolysis of water for hydrogen production,photocatalyst and other fields.In this paper,CQDs were synthesized by hydrothermal method using agricultural waste biomass cornstalk as carbon source.The structure,morphology and properties of CQDs were investigated in detail,and the prepared carbon quantum dots were modified for detection of Candida albicans.The CQDs were successfully synthesized by hydrothermal method using cornstalk as carbon source.The effects of hydrothermal time,hydrothermal temperature and raw material ratio on the fluorescence intensity of CQDs during the preparation of CQDs were investigated and determined optimal preparation conditions.Subsequently,the surface of the CQDs was passivated by PEG with different polymerization degrees to reduce the number of surface traps,thereby improving the fluorescence intensity and stability of the CQDs.At the same time,the same hydrothermal method was used with ethylenediamine as the nitrogen source.Nitrogen-doped carbon quantum dots?N-CQDs?were prepared,and the influencing factors of the fluorescence intensity of CQDs and N-CQDs were investigated to determine the optimal conditions.Finally,the structural information and optical properties of CQDs and N-CQDs were studied by a series of instruments.N-CQDs were combined with water-soluble amphotericin B for the first time to form a composite probe?N-CQDs@AmpB?.The specificity of water-soluble amphotericin B and the fluorescence of N-CQDs were used to quantitatively detect C.albicans.In this experiment,the composite conditions,influencing factors and specificity of the composite probes were explored,and a series of characterizations of the N-CQDs@AmpB were carried out.The optical properties were studied and it was proved that N-CQDs and water-soluble amphotericin B were connected by bonding together instead of physical adsorption.The N-CQDs@AmpB had a good effect on the detection of C.albicans.The experimental results showed that the fluorescence intensity of the N-CQDs@AmpB had a linear relationship with the concentration of C.albicans.The detection limit of the method was 1124 cfu·mL^-1.Considering the economic cost factor of the method,the experiment of the combination of alcohol-soluble amphotericin B and N-CQDs to detect the concentration of C.albicans was carried out.The experimental results showed that the method also exhibited a similar rule,which was calculated by fitting.The detection limit of this method was also obtained to be 2485 cfu·mL^-1.This subject invented a rapid method for the detection of fungi,providing a new method for the detection of C.albicans in food.The subject provides a new way for the resource utilization of agricultural waste cornstalk,especially the CQDs derived from corn stalks have the advantages of abundant material sources,simple preparation methods,low cost and easy modification.N-CQDs are prepared by nitrogen doping for detection of C.albicans.In the field of food testing,this research provides a rapid and accurate method for the detection of C.albicans.This method overcomes the drawbacks of conventional methods for detecting fungi.