title: A general quantitative pH sensor developed with dicyandiamide N-doped high quantum yield graphene quantum dots.
abstract: A general quantitative pH sensor for environmental and intracellular applications was developed by the facile hydrothermal preparation of dicyandiamide (DCD) N-doped high quantum yield (QY) graphene quantum dots (GQDs) using citric acid (CA) as the carbon source. The obtained N-doped GQDs have excellent photoluminesence (PL) properties with a relatively high QY of 36.5%, suggesting that N-doped chemistry could promote the QY of carbon nanomaterials. The possible mechanism for the formation of the GQDs involves the CA self-assembling into a nanosheet structure through intermolecular H-bonding at the initial stage of the reaction, and then the pure graphene core with many function groups formed through the dehydration between the carboxyl and hydroxyl of the intermolecules under hydrothermal conditions. These N-doped GQDs have low toxicity, and are photostable and pH-sensitive between 1.81 to 8.96, giving a general pH sensor with a wide range of applications from real water to intracellular contents.
authors.affiliation: Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China. chengzhi@swu.edu.cn.
authors.forename: Zhu Lian
authors.initials: ZL
authors.lastname: Wu
authors.forename: Ming Xuan
authors.initials: MX
authors.lastname: Gao
authors.forename: Ting Ting
authors.initials: TT
authors.lastname: Wang
authors.forename: Xiao Yan
authors.initials: XY
authors.lastname: Wan
authors.forename: Lin Ling
authors.initials: LL
authors.lastname: Zheng
authors.forename: Cheng Zhi
authors.initials: CZ
authors.lastname: Huang
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019343:Citric Acid / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D006146:Guanidines / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018613:Microscopy, Confocal; D045663:Quantum Dots / Q000737:chemistry* / Q000633:toxicity; D014867:Water / Q000737:chemistry
chemical_list: D006146:Guanidines; D014867:Water; D019343:Citric Acid; D006108:Graphite; C004711:dicyandiamido