Oil-Dispersible Green-Emitting Carbon Dots: New Insights on a Facile and Efficient Synthesis

Abstract

Carbon dots (CDs) have been progressively attracting interest as novel environmentally friendly and cost-effective luminescent nanoparticles, for implementation in light-emitting devices, solar cells, photocatalytic devices and biosensors. Here, starting from a cost-effective bottom-up synthetic approach, based on a suitable amphiphilic molecule as carbon precursor, namely cetylpyridinium chloride (CPC), green-emitting CDs have been prepared at room temperature, upon treatment of CPC with concentrated NaOH solutions. The investigated method allows the obtaining, in one-pot, of both water-dispersible (W-CDs) and oil-dispersible green-emitting CDs (O-CDs). The study provides original insights into the chemical reactions involved in the process of the carbonization of CPC, proposing a reliable mechanism for the formation of the O-CDs in an aqueous system. The ability to discriminate the contribution of different species, including molecular fluorophores, allows one to properly single out the O-CDs emission. In addition, a mild heating of the reaction mixture, at 70 °C, has demonstrated the ability to dramatically decrease the very long reaction time (i.e. from tens of hours to days) at room temperature, allowing us to synthesize O-CDs in a few tens of minutes while preserving their morphological and optical properties.

Luminescent PLGA Nanoparticles for Delivery of Darunavir to the Brain and Inhibition of Matrix Metalloproteinase-9, a Relevant Therapeutic Target of HIV-Associated Neurological Disorders

“…Such a variation in the PL QY is typically observed in the case of luminescent NPs, such as colloidal inorganic QDs and C-Dots, when postsynthesis processing procedures are required to make the “as-synthesized” nanostructures, originally dispersed in organic solvent, dispersible in aqueous medium. 47 , 48 Indeed, changes in surface chemistry and/or dispersing medium and, in general, in the NP surrounding environment can induce even a drastic modification of the optical properties of the fluorescent probe, ultimately leading to the detrimental deterioration of their emission features. 49 The slight reduction in QY observed in the case of DRV/C-Dot/PLGA nanosystems can be here ascribed mainly to the processing procedure and to changes in the medium composition due to the presence of PLGA and DRV residuals.…”

Development of Highly Luminescent Water-Insoluble Carbon Dots by Using Calix[4]pyrrole as the Carbon Precursor and Their Potential Application in Organic Solar Cells

“…The absorption spectrum of CP-DOTs had typical absorption bands observed for conventional carbon dots in the literature, − ,, with an extra band around 460 nm, which was attributed to the crystal band edge absorption (Figure a). The emission spectrum of CP-DOTs exhibited an excellent gaussian-shaped peak around 470 nm at excitation wavelength (λ exc ) 400 nm (Figure a).…”

“…When the photophysical properties of the carbon dots synthesized using only toluene (T-DOTs) were compared with those of CP-DOTs, significant differences were observed ( Figure 3 b). T-DOTs had the typical absorption peaks of carbon dots, but did not have the crystal band edge absorption peak that the CP-DOTs had 18 − 20 , 22 , 36 ( Figure 3 a,b). This clear difference was considered as a strong evidence for the formation of a smooth nanocrystalline structure for CP-DOTs.…”

“…This clear difference was considered as a strong evidence for the formation of a smooth nanocrystalline structure for CP-DOTs. 18 − 20 , 22 , 36 At λ exc = 400 nm, the emission peak of T-DOTs was around 455 nm with a slightly distorted gaussian distribution. The full width at half-maximum (FWHM) was comparable for the emission peaks of both carbon dots: 95 nm for CP-DOTs and 105 nm for T-DOTs ( Figure 3 a,b).…”

“…Also, amphiphilic CDs were synthesized by using several organic solvents (like toluene, dimethylformamide, acetonitrile, etc. ), which act as the carbon precursor and solvent together, through hydrothermal synthesis methods. , However, the highest fluorescence quantum yield, an important indicator to determine the quality of carbon dots, obtained in these studies was around 35%, − which was not comparable to the quantum yields of metal-based quantum dots. , Different single or multiple carbon precursor systems, such as citric acid + phenylenediamine, cetylpyridinium chloride, cetylpyridinium bromide, and octadecylamine + glucose, were used to synthesize amphiphilic or hydrophobic CDs with high fluorescence quantum yield, − but the highest obtained quantum yield was around 47%, which can be still considered low compared to the quantum yield of their metal-based alternatives. , …”