Simple synthesis of photoluminescent carbon dots from a marine polysaccharide found in shark cartilage

BACKGROUND: For more than a decade, water-soluble, eco-friendly, biocompatible, and low-toxicity fluorescent nanomaterials have received considerable attention for their numerous in vivo and in vitro applications in biomedical imaging, disease diagnostics, and environmental monitoring. Owing to their tunable photoluminescence properties, carbon-based luminescent nanomaterials have shown great potential in bioimaging, photocatalysis, and biosensing among other applications. RESULTS: Marine environments provide excellent resources for the fabrication of these nanomaterials, because many marine organisms contain interesting trigger organic compounds that can be used as precursors. Herein, we synthesize multi-color emissive carbon dots (CDs) with an intrinsic photoluminescence quantum yield of 20.46%. These nanostructures were achieved through the one-step hydrothermal treatment of marine polysaccharide chondroitin sulfate, obtained from shark cartilage, in aqueous solution. CONCLUSIONS: We successfully demonstrate the low toxicity of our marine resource-derived CDs in zebrafish, and provide an initial assessment of their possible use as a bioimaging agent. Notably, the newly synthesized CDs localize in the intestines of zebrafish larvae, thereby indicating their biocompatibility and potential use as in vivo dyes.

Determination of Glucose Based on Carbon Quantum Dots as Peroxidase Mimetic Enzyme / 分析化学

Water soluble carbon quantum dots ( CQDs) were prepared by using soot as carbon source. The obtained CQDs showed an excellent intrinsic peroxidase-like activity, which could catalyze the oxidization of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2and thus resulted in color change. Glucose could react with dissolved oxygen to produce H2O2in the presence of glucose oxidase ( GOx) . A colorimetric method using CQDs as peroxidase mimetic enzyme was developed for glucose determination. When TMB was acted as a substrate, the effect of a series of conditions, such as temperature and pH on the catalytic activity of the obtained CQDs, was systematically studied. Under optimal conditions, e. g. pH 3. 5 and temperature 35℃, 0. 5 mmol/L TMB and 1 μg/mL CQDs, the absorbance at 652 nm showed linear response with glucose concentrations ranging from 0. 025 mmol/L to 0. 40 mmol/L, with detection limit of 5. 10 μmol/L (3σ/k). The proposed method exhibited excellent selectivity and the common substances did not interfere with detection of glucose. This method was successfully applied to detect glucose in real samples with recoveries of 95. 0%-105. 1% .

Detection of Arginine by AuNPs / CQDs Nanoprobes Based on Fluorescence Resonance Energy Transfer Effect / 分析化学

A novel method for rapid detection of arginine based on fluorescence resonance energy transfer effect (FRET) between carbon quantum dots ( CQDs) and gold nanoparticles ( AuNPs) was developed. Firstly, the CQDs with excellent fluorescence properties were synthesized by one-step microwave assisted method. The AuNPs/ CQDs composites were characterized and their quenching mechanism was analyzed. Then the amount of AuNPs/ CQDs, the pH value and the reaction time were optimal. Under the optimum conditions, the fluorescence system was used to detect the content of arginine, showing a good linear relationship ( R2 = 0. 993 ) between fluorescence intensity and concentration of arginine in the range of 0. 1-10. 0 μmol/ L, and the detection limit was 5. 8 nmol/ L. Finally, the content of arginine in grape juice was determined by this method with recoveries of 105. 4％ -110. 8％ , which indicated that the proposed FRET system had the potential for practical detection of arginine in fruit juice.

Radioprotective effect of ultra-small carbon quantum dots in mice in vivo / 国际生物医学工程杂志

Objective To study the radioprotective effects of ultra-small carbon quantum dots (CQDs) in mice in vivo,and to reveal the protective mechanism,as well as to study the body immune response to CQDs and the toxicity in vivo.Methods Mice were injected with different concentrations of CQDs solution.Mice models of systemic radiation injury were constructed by high dose gamma rays radiation.The 30-days survival rate,bone marrow DNA,femoral bone marrow nucleated cells (BMNC),tissue superoxide dismutase (SOD) and malondialdehyde (MDA) were measured to evaluate the radioprotective effects of CQDs,and to investigate the possible protective mechanism.The toxicity of CQDs in vivo was studied by measuring the changes of body weight,liver index and spleen index before and after injections of CQDs in mice.Results CQDs showed obvious radioprotective effects on mice in vivo.Compared with the control group,the 30-days survival rate of irradiated mice treated with CQDs increased from 0％ to 40％.CQDs could effectively reduce the hematopoietic system damages caused by radiation,and increase the level of bone marrow DNA,femur BMNC,liver and lung SOD,as well as reduce the production of MDA in liver and lung.The results of immunological reaction tests showed that CQDs had less toxicity in vivo and did not trigger the body immune response.Conclusions CQDs has tremendous application prospects in the field of radiation protection.This study can provide new ideas for the application of new nano-materials in medical field.

Detection of Ferric Iron Based on Fluorescence Quenching Effect of N-doped Carbon Quantum Dots / 分析化学

The photoluminescence properties of carbon quantum dots depend on their size and the properties of surface functional groups. The N-doped carbon dots ( using small molecular ethylenediamine ) with high quantum yield and excellent dispersibility were synthesized by one-step hydrothermal method with biomass tar that was generated in the reductive smelting process as a precursor. Rapid and accurate Fe3+ detection based on the selective fluorescence quenching effect of N-doped carbon quantum dots was achieved. The results showed that the as-synthesized N-doped carbon quantum dots were regular spherical, uniform in size with an average particle size of 2. 64 nm with a quantum yield of 26. 1%, and the crystal lattice spacing was 0. 25 nm, corresponding to the ( 100 ) facet of graphitic carbon structure. The functional groups on the surface of N-doped carbon quantum dots could interact with Fe3+ to form complex compound by coordination, leading to the fluorescence quenching effect. Fluorescence emission ratios kept a linear relationship with the concentrations of Fe3+ in the range of 0. 23-600 μmol/L with the detection limit of 230 nmol/L.

Detection of Ferric Iron Based on Fluorescence Quenching Effect of N-doped Carbon Quantum Dots / 分析化学

The photoluminescence properties of carbon quantum dots depend on their size and the properties of surface functional groups. The N-doped carbon dots ( using small molecular ethylenediamine ) with high quantum yield and excellent dispersibility were synthesized by one-step hydrothermal method with biomass tar that was generated in the reductive smelting process as a precursor. Rapid and accurate Fe3+ detection based on the selective fluorescence quenching effect of N-doped carbon quantum dots was achieved. The results showed that the as-synthesized N-doped carbon quantum dots were regular spherical, uniform in size with an average particle size of 2. 64 nm with a quantum yield of 26. 1%, and the crystal lattice spacing was 0. 25 nm, corresponding to the ( 100 ) facet of graphitic carbon structure. The functional groups on the surface of N-doped carbon quantum dots could interact with Fe3+ to form complex compound by coordination, leading to the fluorescence quenching effect. Fluorescence emission ratios kept a linear relationship with the concentrations of Fe3+ in the range of 0. 23-600 μmol/L with the detection limit of 230 nmol/L.

Green Synthesis of Fluorescent Carbon Quantum Dots for Detection of Hg2+ / 分析化学

Fluorescent carbon quantum dots ( CQDs) were synthesized by one-step hydrothermal treatment of apple juice. Experiments showed that Hg2+could quench the fluorescence of the CQDs with specificity. Based on this phenomenon, a selective and sensitive sensor was constructed for Hg2+ detection. In a NaH2 PO4-Na2HPO4 buffer solution (pH 7. 0), their fluorescence intensity showed good linear relationship with the concentrations of Hg2+ from 5 to 100 nmol/L and 1 to 50 μmol/L, respectively, with the detection limit of 2. 3 nmol/L (S/N=3). Its practical application was further demonstrated by the detection of Hg2+ in real water samples.