title: Synthesis of a novel nitrogen-doped carbon dot by microwave-assisted carbonization method and its applications as selective probes for optical pH (acidity) sensing in aqueous/nonaqueous media, determination of nitrate/nitrite, and optical recognition of NOXgas.
abstract: A novel nitrogen-doped carbon dot (N-CD) was synthesized via carbonization of citric acid in the presence of triethylenetetramine as a nitrogen source. The average size of the N-doped CDs and also the quantum yield of the synthesized N-doped CDs were both estimated to be 9 ± 2 nm and 39.5%, respectively. The applications of the synthesized carbon nanostructure as a high quantum yield fluorescence probe were initially adopted in the fabrication of a novel optical pH (acidity) sensor in both aqueous and nonaqueous environments. Two optimum dynamic intervals were obtained with the ranges of1.5-5.0 and 7.0-10.0. for the fabricated pH sensor with a standard deviation of 0.09 pH (n = 4). The quantity of HClO4inside acetic acid was determined as the degree of acidity with a linear range between 1.0 and 4.0%. Determination of nitrate (NO3-) and nitrite (NO2-) based on the fluorescence quenching of N-CDs was also evaluated in detail. The linear ranges for NO2-and NO3-species were estimated to be from 1 × 10-7to 7.5 × 10-5and from 2.5 × 10-6to 7.5 × 10-4mol L-1, respectively with RSD of 3.69% (n = 5) for NO2-and 3.54% (n = 5) for NO3-. The LODs (X+3Sb) for both NO2-and NO3-were estimated to be 2.5 × 10-8and 7.5 × 10-7mol L-1, respectively. The synthesized N-CDs were also applicable for NOXrecognition in the gaseous form at part per thousand (ppt) levels with linear ranges of 3.77-36.51 and 27.67-43.77 ppt, LOD (X+3Sb) of 1.41 ppt (n = 4) and RSD of 4.37% (n = 5). The reliability of these methods was also evaluated via the analyses of different forms of gaseous, water and rumen samples.
authors.affiliation: Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran. Electronic address: doroodmand@shirazu.ac.ir.
authors.forename: Mohammad Mahdi
authors.initials: MM
authors.lastname: Doroodmand
authors.affiliation: Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Askari
mesh_terms: D000818:Animals; D002244:Carbon; D008872:Microwaves; D009566:Nitrates / Q000032:analysis*; D009573:Nitrites / Q000032:analysis*; D009584:Nitrogen; D045663:Quantum Dots; D015203:Reproducibility of Results; D012417:Rumen / Q000737:chemistry
chemical_list: D009566:Nitrates; D009573:Nitrites; D002244:Carbon; D009584:Nitrogen
keywords: Acidity; Fluorescence probe; Nitrogen-doped carbon dots; Quantum yield; Quenching process