Design Of Carbon Quantum Dots On The Surface Of States And Their Impact On Performance

Carbon quantum dots attract people because of the unique optical and electrical properties, high stability and environment friendly. The size of semiconductor quantum dots plays an vital role on it properties, unlike traditional semiconductor quantum dots, for carbon quantum dots, its performance decided by not only the different size, but also the surface composition and functional groups. Therefore, in this article, we design the surface composition and functional groups of carbon quantum dots through chemical reaction,studied the composition, group especially the elements of nitrogen, sulfur and oxygen on the influence of the quantum dots and their dependencies. Based on carbon quantum dots were modified, studied the nitrogen and sulfur elements on the influence of the properties of the carbon quantum dots, and assess the photocatalytic activities of the oxygen-containing groups on the surface of the carbon quantum dots. Specific research innovation work is as follows:Firstly, Sulfur- and nitrogen- co-doped carbon quantum dots(SN-CQDs) were synthesized by one-step hydrothermal method using p-aminobenzenesulfonicacid as carbon source. Experimental results indicate that the obtained SN-CQDs have a uniform size and are modified by amine and sulphonic acid groups at their surface. Unlike previous reports, the SN-CQDs show the excitation-wavelength-independent photoluminescence behavior and their fluorescence can be quenched by Fe~3+ ions. The obtained SN-CQDs have the ability of high selectivity, high sensitivity and good anti-jamming capability to ferric iron ions. Accordingly,SN-CQDs can be used for the detection of Fe~3+ ions in the environment and organism.Secondly, Using p-aminobenzenesulfonicacid and 4-aminothiophenol to react with citric acid carbon quantum dots respectively through the hydrothermal method, thus, the sulfonic group and thiol group will graft to the surface of citric acid carbon quantum dots.Experimental results indicate that by changing the surface state of the carbon quantum dots,the photoluminescence properties could be controled. The emission peak of the citric acid carbon quantum dots modified by Sulfonic group from 453 nm to 491 nm, while the emission peak of the citric acid carbon quantum dots modified by thiol from 453 nm to 530 nm.Thirdly, Fluorescent carbon quantum dots with oxygen-containing functional groups were prepared by a hydrothermal method. Three kinds of typical oxygen functional groups, i.e.hydroxyl, carbonyl, and carboxylic acid groups, were selectively deactivated to independently assess their photocatalytic activities on the surface of CDs. The presented results indicate that the carbonyl group on CDs is their photocatalytic active sites. Hereby, the high photocatalytic activities of CDs could be produced by enhancing carbonyl group concentration on their surface.