title: Chemical regulation of carbon quantum dots from synthesis to photocatalytic activity.
abstract: Carbon quantum dots (CQDs) were synthesized by heating various carbon sources in HNO3 solution at reflux, and the effects of HNO3 concentration on the size of the CQDs were investigated. Furthermore, the oxygen-containing surface groups of as-prepared CQDs were selectively reduced by NaBH4 , leading to new surface states. The experimental results show that the sizes of CQDs can be tuned by HNO3 concentration and then influence their photoluminescent behaviors; the photoluminescent properties are related to both the size and surface state of the CQDs, but the photocatalytic activities are determined by surface states alone. The different oxygen-containing groups on the surface of the CQDs can induce different degrees of the band bending upward, which determine the separation and combination of the electron-hole pairs. The high upward band bending, which is induced by C=O and COOH groups, facilitates separation of the electron-hole pairs and then enhances high photocatalytic activity. In contrast, the low upward band bending induced by C-OH groups hardly prevents the electron-hole pairs from surface recombination and then exhibits strong photoluminescence. Therefore, both the photocatalytic activities and optical properties of CQDs can be tuned by their surface states.
authors: Key Laboratory of Instrumentation Science, and Dynamic Measurement, Ministry of Education, Science and Technology on Electronic Test and Measurement Laboratory, Taiyuan 030051, China. hsliang@yeah.net
authors: Shengliang
authors: S
authors: Hu
authors: Ruixue
authors: R
authors: Tian
authors: Lingling
authors: L
authors: Wu
authors: Qing
authors: Q
authors: Zhao
authors: Jinlong
authors: J
authors: Yang
authors: Jun
authors: J
authors: Liu
authors: Shirui
authors: S
authors: Cao
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D049449:Luminescence; D017942:Nitric Acid / Q000737:chemistry; D010316:Particle Size; D055668:Photochemical Processes; D045663:Quantum Dots; D013499:Surface Properties
chemical_list: D017942:Nitric Acid; D002244:Carbon