Studies On Eco-friendly Preparation,Characterization And Bio-sensing Application Of Novel Carbon Dots

As a rising star in the carbon nanomaterial family,carbon dots(CDs)have shown high stability,good biocompatibility,low toxicity,and excellent optical properties.The fascinating nature endows CDs with a more fascinating applied research.Three fluorescent CDs were prepared in this paper.Since the three CDs have their own characteristics,CDs are used for various aspects,such as colorimetric detection,fluorescence detection,biological system detection,and p H detection.1.We present a green and facile strategy for fabrication of concentrationdependent multicolor fluorescent CDs by using coffee,salvia,and urea as the starting material via a one-step hydrothermal method.The obtained CDs emit three different colors of fluorescence(i.e.orange,yellow,and blue)with their concentration reduction.Moreover,yellow fluorescent CDs(Y-CDs)are utilized as a platform for colorimetric and fluorescent dual-mode detections of Fe3+ and L-ascorbic acid(L-AA)with high selectivity and sensitivity.The fluorescence of Y-CDs can be effectively quenched by Fe3+ based on static quenching and subsequently recovered upon the addition of L-AA due to the competitive complexation of L-AA with Fe3+.Therefore,the as-prepared YCDs could serve as a highly efficient fluorescent probe for “ON-OFF-ON” sequential determination of Fe3+ and L-AA.It is more attractive that Fe3+ and L-AA can also be visualized by this nanosensor via evident color changes under daylight.Furthermore,the designed nanosensor can be extended to detect intracellular Fe3+ and L-AA with outstanding biocompatibility and cellular imaging capability,which holds great promise in biomedical applications.2.We have developed a simple one-step method for preparing highfluorescence CDs by hydrothermally treating Ganoderma lucidum without further surface passivation or modification.The prepared CDs emitted strong blue light under 360 nm light irradiation and showed maximum emission at 448 nm.CDs show an ultra-small particle size(2.43 nm),and the fluorescence of CDs can be effectively quenched by Fe3+.Based on these remarkable characteristics,CDs can be effectively used as a fluorescent probe for Fe3+ ions in an aqueous solution with excellent sensitivity and repeatability.Furthermore,according to co-fluorescence imaging of human hepatocellular carcinoma(Hep G2)cells and E.coli,CDs can penetrate into cells and enter the cytoplasm and nucleus,demonstrating their potential for multiple applications.3.We have proposed a yellow fluorescent CDs by microwave method using safflower as a raw material without further surface passivation or modification.The CDs show yellow under sunlight and emit bright yellow fluorescence under 470 nm excitation.Through testing,the CDs are not responsive to ions or amino acids,but responsive to p H,exhibiting a highly selective detection of p H.Applying this property,we use CDs in cell imaging.The fluorescence intensity of cells labeled with CDs changes with the change of p H around the cells,which indicates that the CDs can be used to label cells and visualize p H changes of cells.