Size-dependent penetration of carbon dots inside the ferritin nanocages: evidence for the quantum confinement effect in carbon dots

Abstract

The origin of the excitation wavelength (λex)-dependent photoluminescence (PL) of carbon dots (CDs) is poorly understood and still remains obscured. This phenomenon is often explained on the basis of surface trap/defect states, while the effect of quantum confinement is highly neglected in the literature. Here, we have shown that the λex-dependent PL of CDs is mainly due to the inhomogeneous size distribution. We have demonstrated the λex-dependent PL quenching of CDs inside the ferritin nanocages through selective optical excitation of differently sized CDs. It has been observed that Fe(3+) ions of ferritin effectively quench the PL of CDs due to static electron transfer, which is driven by favorable electrostatic interactions. However, control experiment with aqueous Fe(3+) ions in bulk medium revealed λex-independent PL quenching of CDs. The λex-dependent PL quenching of CDs by Fe(3+) ions of ferritin has been rationalized on the basis of a different extent of accessibility of Fe(3+) ions by differently sized CDs through the funnel-shaped ferritin channels. PL microscopy of individual CDs has been performed to get further information about their inherent PL properties at single dot resolution. Our results have shown that these hydrophilic CDs can be used as potential iron sensors in biological macromolecules.

Light emitting diodes based on carbon dots derived from food, beverage, and combustion wastes

“…Utility of exhaust carbon fumes for CDs production also provides a new method of carbon capture. 14 Very limited research has been performed to examine the inhomogeneous distribution of CDs and the associated quantum confinement effect. 10 These CDs can be synthesized using methods such as chemical ablation, 8 electrochemical carbonization, 8 laser ablation, 8 microwave 11 irradiation, 8 or solvothermal treatment.…”

Temperature‐Dependent Dual Emission from Sucrose‐Derived Carbon Nanodots: A Ratiometric Fluorescent Thermometer

“…[1][2][3] Recently,t here has been plenty of literature reporting the fluorescencef rom CNDs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] However,t he fluorescence properties reported by differentg roups vary greatly, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] for instance, some of them are excitation-dependentw hile others are excitation-independent. [4,5] This diversity may be ascribed to different preparation methods and reactants, which lead to different surfaces, sizes and structures.…”

“…[4,5] This diversity may be ascribed to different preparation methods and reactants, which lead to different surfaces, sizes and structures. Regardless of the fabrication strategies used for the fluorescent CNDs,t hey are widely appliedf or bioimaging and biosensing, [7][8][9][10][11][12][13] such as in fluorescent sensors for temperature, pH andm etal-ion concentration. [10][11][12][13] Generally speaking, fluorescent sensors work based on the principle that variations in circumstances cause changes in fluorescentc haracteristics such as wavelength,l ifetime and intensity.I no ther words, the fluorescent variationsr eflect the changes in temperature, pH and metal-ion concentration, etc.…”

Incorporation of Graphene Quantum Dots, Iron, and Doxorubicin in/on Ferritin Nanocages for Bimodal Imaging and Drug Delivery

“…The close proximity results in efficient Förster resonance energy transfer between GQDs sheets prior to energy emissions and quench of their fluorescence . Additionally, π–π interaction between aromatic rings of GQDs and amino acids as well as electrostatic interactions between GQDs and Fe 3+ ions in the cores may further enhance electron transfer leading to the quench of fluorescence . However, (GQDs/Fe)AA exhibited a considerable increase in the fluorescence intensity by decreasing the pH of the solution from 7.4 to 5 and 2.…”

“…Studies showed that DOX molecules can form complexes with iron ions that exist in the channels of nanocages, which may significantly contribute to their high loading onto ferritin nanocage . Previous reports suggest that particles <2 nm can easily penetrate through the channels due to highly dynamic and flexible feature of channels . Considering 1.5 nm as maximum possible molecular size of DOX, it is not impossible that a fraction of the 35% DOX is loaded inside the ferritin shell.…”