| Carbon quantum dots(CDs) is formed of SP2 bonded carbon or amorphous carbon, steady glow, with a spherical structure of nanoparticles, have attracted increasing attention in recent years because of their interesting properties, such as water solubility, biocompatibility, good photostability and low cytotoxicity. These make CDs good alternative to QDs for sensing metal ions small molecule and other bio-species in food, environment and biological samples. CDs fluorescent nanosensor for mental ions with wide linear range, high sensitivity and less interference of fluorescence spectrum, moreover, spectrophotofiuorometer ’s prices is inexpensive, require small amounts of sample without pre-treatment of complicated process. Although CDs fluorescence nanosensor has many advantages, but it still has some problems in practical application: these CDs have low quantum yield and poor metalloform-selective.For these problem this subject main for has following research:(1) A simple and effective strategy for designing a fluorescent probe for metal ions is described in this work. Organosilane modified carbon dots(CDs) was prepared using N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane(AEAPMS) as the main raw material and they were doped into silica nanoparticles by silylation reaction. The ethylenediamine groups on the surface of CDs can serve as the Cu2+ recognition sites.Upon binding to Cu2+, the fluorescence of CDs was quenched, and the quenching exhibited good selectivity to Cu2+ over other metal ions. The parameters affecting the performance of the probe, such as pH, reaction temperature and time were investigated and optimized. The detection limit of this method was 1.08 ng·mL-1 with a linear range from 20 to 400 ng·mL-1. The analytical result for the certified reference tea sample(GBW07605) was in a good agreement with the certified value. And it also was applied successfully to determine Cu2+ in different tea samples with satisfactory results.(2) Anhydrous citric acid and n-(β-aminoethyl-γ-Aminopropyl) methyl-methoxy-silane as the carbon source, CDs was prepared by thermal cracking. Afterwards, silica nanoparticles as interconnect medium, links CDs to RhB which is another organic fluorescent dye, to be synthesis of CDs coated dual-emission silica nanoparticles. This dual-emission nanoparticles combining tow different fluorophores, which are CDs and RhB, CDs’ s fluorophore as reference and RhB’s fluorophore as a signal report unit., use of ratiometric fluorescence method for quantitative analysis.A new catalytic fluorimetric method for determination of Cr(Ⅵ) is proposed. In sulfuric acid media(0.2 M), the oxidation of CDs coated dual-emission silica nanoparticles by potassium bromate(KBrO3) is catalyzed by Cr(Ⅵ). Resulting in the ratiometric fluorescence quenching of the dual-emission silica nanoparticles.Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 1.3 ng·mL-1 with a linear range from 20 to 500 ng·mL-1. Use of delta rule, it has been applied successfully to determine Cr in the water sample with satisfactory results.(3) A simple and effective strategy for designing ratiometric fluorescent nanosensor has been described in this work. A carbon dots(CDs) based dual-emission nanosensor for Bisphenol A(BPA) was prepared by coating CDs on the surface of dye doped silica nanoparticles. In hydrochloric acid media(0.2 M), the fluorescence of dual-emission silica nanoparticles was quenched by potassium bromate(KBrO3) oxidating effect, and BPA had an inhibition effect on KBrO3 oxidating nanosensor, resulting in the ratiometric fluorescence response of the dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80 ng·mL-1 with a linear range from 10 to 500 ng·mL-1. It has been applied successfully to determine BPA in the leaching solution of different plastic products with satisfactory results. |
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