Insight into the Excitation‐Dependent Fluorescence of Carbon Dots

Abstract

High quantum yield, photoluminescence tunability, and sensitivity to the environment are a few distinct trademarks that make carbon nanodots (CDs) interesting for fundamental research, with potential to replace the prevalent inorganic semiconductor quantum dots. Currently, application and fundamental understanding of CDs are constrained because it is difficult to make a quantitative comparison among different types of CDs simply because their photoluminescence properties are directly linked to their size distribution, the surface functionalization, the carbon core structures (graphitic or amorphous) and the number of defects. Herein, we report a facile one-step synthesis of mono-dispersed and highly fluorescent nanometre size CDs from a 'family' of glucose-based sugars. These CDs are stable in aqueous solutions with photoluminescence in the visible range. Our results show several common features in the family of CDs synthesized in that the fluorescence, in the visible region, is due to a weak absorption in the 300-400 nm from a heterogeneous population of fluorophores. Fluorescence quenching experiments suggest the existence of not only surface-exposed fluorophores but more importantly solvent inaccessible fluorophores present within the core of CDs. Interestingly, time-resolved fluorescence anisotropy experiments directly suggest that a fast exchange of excitation energy occurs that results in a homo-FRET based depolarization within 150 ps of excitation.[a] Dr.

N-Doped Carbon Dots Synthesized from Ethylene Glycol and β-Alanine for Detection of Cr(VI) and 4-Nitrophenol via Photoluminescence Quenching

“…This is typically due to the presence of different emissive sites of N-CDs and attributable to functional groups in the structure of carbon dots. 31 The relative PLQY values of N-CDs(I) and N-CDs(II) were estimated to be 7.4 and 14.3%, respectively. The higher PLQY of N-CDs(II) is attributable to more nitrogen doping 32 and due to a more rigid and crystalline structure.…”

“…Furthermore, both N-CDs­(I) and N-CDs­(II) exhibited an excitation wavelength-dependent PL property (Figure S2, Supporting Information). This is typically due to the presence of different emissive sites of N-CDs and attributable to functional groups in the structure of carbon dots …”

Nitrogen-Doped Carbon Nanodots Produced by Femtosecond Laser Synthesis for Effective Fluorophores

“…Similar anisotropy decay kinetics, which was anomalously fast compared with carbon nanodot size, was observed in a number of studies and was attributed to either rotation of small subunits of nanodots or resonance energy transfer between fluorophores. 10 , 39 , 40 To verify that depolarization results from rotation rather than from other physical effects, we carried out the measurement of p-CND anisotropy kinetics in an ethanol–glycerin mixture with a viscosity more than 15 times higher than the viscosity of ethanol (21 mPa·s). As demonstrated in Figure 5 a, increased viscosity resulted in much longer emission anisotropy decay than that in ethanol, thus confirming that depolarization is mostly caused by rotational motion.…”

From cow manure to bioactive carbon dots: a light-up probe for bioimaging investigations, glucose detection and potential immunotherapy agent for melanoma skin cancer

“…These uorophores can be responsible for the typical excitation-dependent emission spectra. 39 Interest in boronic-acid-functionalized C-dots has soared in recent years concomitant to the huge evolution of glycobiology and its implications in treatments and diagnostics of severe pathologies. Production of boronic-containing C-dots is cheap, fast and can be rapidly performed in a unique step via hydrothermal or microwave synthesis.…”