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Carbon dots, which are less than 10 nm in diameter, have been widely investigated because of their unique luminescence properties and potential for use in bioimaging. In the present work, natural carbon dots (L-CDs) were obtained by molecular aggregation, using ethanol-extracted cellulolytic enzyme lignin. The whole process for the preparation of L-CDs was green and simple to operate and did not use toxic chemical reagents or harsh conditions. The newly prepared L-CDs emitted multicolor photoluminescence following one- and two-photon excitation. The L-CDs also showed good cellular biocompatibility, which is crucial for biological applications. One- and two-photon cell-imaging studies demonstrated the potential of L-CDs for bioimaging. [ABSTRACT FROM AUTHOR]

A robustreusable fluoride sensor comprised of a receptor in charge of thechemical recognition and a fluorophore responsible for signal recognitionhas been designed. Highly fluorescent carbon quantum dot (CD) andmagnetically separable nickel ethylenediaminetetraaceticacid (EDTA) complex bound-silica coated magnetite nanoparticle (Fe3O4@SiO2–EDTA–Ni) havebeen used as fluorophore and fluoride ion receptor, respectively.The assay is based on the exchange reaction between the CD and F–, which persuades the binding of fluoride to magneticreceptor. This method is highly sensitive, fast, and selective forfluoride ion in aqueous solution. The linear response range of fluoride(R2= 0.992) was found to be 1–20μM with a minimum detection limit of 0.06 μM. Excellentmagnetic property and superparamagnetic nature of the receptor areadvantageous for the removal and well quantification of fluoride ion.The practical utility of the method is well tested with tap water.Because of high sensitivity, reusability, effectivity, and biocompatibility,it exhibits great promise as a fluorescent probe for intracellulardetection of fluoride. [ABSTRACT FROM AUTHOR]

In this study, we describe a solutionprocedure for the preparationand surface modification of photostable colloidal silicon quantumdots (SiQDs) for imaging of cancer cells. Photoluminescent SiQDs weresynthesized by reduction of halogenated silane precursors using amicroemulsion process. It was shown that 1,8-nonadiyne molecules couldbe grafted onto the surface of hydrogen-terminated SiQDs via ultraviolet(UV)-promoted hydrosilylation, demonstrated by Fourier transform infraredspectroscopy (FTIR) measurements. In addition, various azide moleculeswere coupled onto nonadiyne-functionalized particles, rendering particlesdispersible in selected polar and nonpolar solvents. The photoluminescenceof functionalized SiQDs was stable against photobleaching and didnot vary appreciably within biologically applicable pH and temperatureranges. To demonstrate compatibility with biological systems, water-solubleSiQDs were used for fluorescent imaging of HeLa cells. In addition,the SiQDs were shown to be non-cytotoxic at concentrations up to 240μg/mL. The results presented herein provide good evidence forthe versatility of functionalized SiQDs for fluorescent bioimagingapplication. [ABSTRACT FROM AUTHOR]