Preparation Of Near-infrared Carbon Dots And Their Biolocial Applications

As the latest emerging fluorescent carbon nanomaterials,carbon nanodots have many promising characteristics such as tunable luminescence,high photostability and chemical stability,which have been widely used in sensor,photocatalysis,lasing and optoelectronic devices.Carbon nanodots also exhibit biocompatibility,low cytotoxicity and good cell membrane permeability,which attracts people to develop their applications in the biological field.At first,carbon nanodots were used in cell imaging,bio-in vivo imaging.Now with the continuous development of researchment,people have focused on the application in cancer treatment.As a new type of tumor treatment method,photothermal therapy(PTT)has the advantages of small wound section,short treatment time and obvious therapeutic effect,which has great potential applications.However,the choice of materials for photosensitizers hinders the development of photothermal therapy.Common nanoparticles such as molecular polymers,semiconductor quantum dots and heavy metal nanoparticles are not ideal materials for photosensitizers because of their properties.In this paper,two kinds of carbon nanodots with excellent near-infrared absorption and photothermal conversion efficiency were prepared by hydrothermal method using citric acid and urea as precursor materials.Morphological characterization and property analysis of the two carbon dots were carried out and applied to biological experiments.(1)Carbon nanodots were synthesised by hydrothermal method using citric acid and urea as precursor materials.The carbon nanodot powder was placed into a humid environment to self-assemble into super-carbon nanodots(Supra-CND)with large particle size.Supra-CND exhibits good visible-NIR absorption in the 470-1000 nm spectral range with up to 50% photothermal conversion efficiency.This made it a potential application for photosensitizers.(2)The carbon nanodots with great near-infrared absorption(NIR-CND)between550nm and 700 nm were prepared by using citric acid and urea as raw materials and dimethyl sulfoxide as solvent via hydrothermal method.NIR-CND exhibited NIR fluorescence emission with excitation of 655 nm laser as well showing high photothermal conversion efficiency(? = 59.2%).The photothermal cycle test showed NIR-CND had excellent light stability and thermal stability,which has a board application in biological field.(3)The above two materials were applied to biological experiments.Cellular experiments have shown that the two carbon nanodots have low biotoxicity and high cell phototoxicity.Bioimaging experiments showed that NIR-CND can be applied in bioluminescence imaging,and Supra-CND can be used for photoacoustic imaging.Finally,the Supra-CND were applied to the photothermal treatment of mice.After the experiment,the malignant tumors in the mice were inhibited or disappeared,which proved that the Supra-CND can be used as photosensitizers for photothermal therapy.