Detection Of Small Molecules Based On Carbon Nanomaterials And Metal Nanomaterials

Carbon nanomaterials and metal nanomaterials are the most broadly explored nanomaterials because of their exceptional properties,for example,enzymes catalytic activity similar to natural enzymes,re-markable optical properties.Base on the recombination of split aptamer chip and utilizing single-walledcarbon nanotubes(SWCNTs)as quencher,a new label-free fluorometric for adenosine triphosphate(ATP)detection was constructed.In this thesis,we synthesized silver nanoparticle(AgNP)–single-walled carbon nanotube(SWCNT)nanocomposites through a microwave-assisted method and the catalytic properties of the nanocomposites were studied in detail.Based on the oxidase-like and pe-roxidase-like activity,we developed new methods for the determination of ascorbic acid(AA)and L-cysteine(L-Cys).And a ratiometric fluores-cent probe for determination of doxorubicin(DOX)was established based on copper nanoclusters(CuNCs)and carbon dots(CDs).The major contents are as follows:1.A novel Label-Free Fluorometric Assay based on the recombina-tion of split aptamer chip was developed for the detection of ATP.In this strategy,the split aptamer was selected as a specific capture probe for the split two fragments aptamers could specifically form a ternary assembly in the presence of ligand and the two separate oligonucleotides lack sec-ondary structures,thus not yielding false-positive or nonspecific signals,while the Thiazole orange(TO),an almost non-fluorescence dye in buffer solution,was used as signal probe,and the SWCNTs was applied to re-duce the background signals.In the p H 8.0 Tris-HCl buffer solution,the ATP concentration in the range of 9.0×10^-91.0×10^-7 mol/L has a good linear relationship with the fluorescence quenching degree?F/F₀ at the emission wavelength of 550 nm.The correlation coefficient r=0.9964and the limit of detection(LOD)is 2.67×10^-9 mol/L.2.AgNP/SWCNT nanocomposites were successfully synthesized through a microwave-assisted methodand and were found to possess oxi-dase-like xidase-like activity.AgNP/SWCNT nanocomposites can di-rectly catalyze the oxidation of 3,3?,5,5?-Tetramethylbenzidine(TMB)to oxidized TMB(ox TMB)in absence of H₂O₂,with distinct appearance of blue color of the solution(?_max 652 nm).AA specifically inhibits the oxi-dation of TMB,decreasing the absorbance value of the system,thus,we have described a novel colorimetric strategy for sensing of ascorbic acid(AA).The concentration of AA in the range of 0.4⁵.0?mol/L showed a good linear relationship with?A at 652 nm,the correlation coefficient r=0.9969,the detection limit was 130 nmol/L.3.In this paper,DNA-templated Agnanoclusters(DNA-AgNCs)synthesized using hairpin DNA can bind to the SWCNTs surface by?–?stacking,causing the fluorescence quenching.The oxidase activity of AgNP/SWCNT nanocomposites as an artificial enzyme was applied to catalyze the oxidation of L-cys with the generation of hydrogen peroxide.Coupling with the peroxidase-like activity of AgNP/SWCNT nanocom-posite,hydrogen peroxide can generate·OH radicals,which attacks and cleaves the DNA resulting in a turn-on of fluorescence.The concentration of L-cys in the range of 0.8¹0 nmol/L showed a good linear relationship with the value of?F_{535 nm.}The correlation coefficient r=0.9971 and the detection limit was 0.22 nmol/L.4.In this work,under mild conditions,through the electrostatic at-traction between positively charged CDts and negatively charged CuNCs,a novel F(?)rster resonance energy transfer(FRET)ratiometric fluorescent probe was established for sensing of DOX.The as-prepared probe shows dual emission peaks at 485 nm and 560 nm with efficient FRET under a single excitation wavelength of 430 nm.The concentration of DOX in the range of 0.01¹00?mol/L showed a good linear relationship with the value of F₅₆₀/F₄₈₅.The correlation coefficient r=0.9927 and the detection limit was 3.7 nmol/L.