title: Natural carbon-based dots from humic substances.
abstract: For the first time, abundant natural carbon-based dots were found and studied in humic substances (HS). Four soluble HS including three humic acids (HA) from different sources and one fulvic acids (FA) were synthetically studied. Investigation results indicate that all the four HS contain large quantities of Carbon-based dots. Carbon-based dots are mainly small-sized graphene oxide nano-sheets or oxygen-containing functional group-modified graphene nano-sheets with heights less than 1 nm and lateral sizes less than 100 nm. Carbon-based nanomaterials not only contain abundant sp2-clusters but also a large quantity of surface states, exhibiting unique optical and electric properties, such as excitation-dependent fluorescence, surface states-originated electrochemiluminescence, and strong electron paramagnetic resonance. Optical and electric properties of these natural carbon-based dots have no obvious relationship to their morphologies, but affected greatly by their surface states. Carbon-based dots in the three HS have relative high densities of surface states whereas the FA has the lowest density of surface states, resulting in their different fluorescence properties. The finding of carbon-based dots in HS provides us new insight into HS, and the unique optical properties of these natural carbon-based dots may give HS potential applications in areas such as bio-imaging, bio-medicine, sensing and optoelectronics.
authors.affiliation: College of Chemistry, Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Fuzhou University, Fujian 350108, China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Dong
authors.affiliation: College of Chemistry, Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Fuzhou University, Fujian 350108, China.
authors.forename: Lisi
authors.initials: L
authors.lastname: Wan
authors.affiliation: College of Chemistry, Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Fuzhou University, Fujian 350108, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Cai
authors.affiliation: College of Chemistry, Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Fuzhou University, Fujian 350108, China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Fang
authors.affiliation: College of Chemistry, Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Fuzhou University, Fujian 350108, China.
authors.forename: Yuwu
authors.initials: Y
authors.lastname: Chi
authors.affiliation: College of Chemistry, Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, and Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Fuzhou University, Fujian 350108, China.
authors.forename: Guonan
authors.initials: G
authors.lastname: Chen