Abstract
In the present study, we successfully synthesized N-doped carbon quantum dots (N-CQDs) using a top-down approach, i.e., hydroxyl radical opening of fullerene with hydrogen peroxide, in basic ambient using ammonia for two different reaction times. The ensuing characterization via dynamic light scattering, SEM, and IR spectroscopy revealed a size control that was dependent on the reaction time, as well as a more pronounced -NH2 functionalization. The N-CQDs were probed for metal ion detection in aqueous solutions and during bioimaging and displayed a Cr3+ and Cu2+ selectivity shift at a higher degree of -NH2 functionalization, as well as HEK-293 cell nuclei marking.
Highlights
We present a simplified and low-cost top-down synthesis for obtaining N-doped Carbon quantum dots (CQDs), with a size control that depends on the initial material and can be further refined through the reaction time
A layer of N-doped carbon quantum dots (N-CQDs) was deposited on a clean Al foil using dropcasting and the deposits were dried in air before measurements were taken
Presence of functional groups on the surface of the quantum dots was assessed using the average size of the quantum dots was estimated using dynamic light scattering (DLS) and scanning electron microscope (SEM) imaging
Summary
The subsequent interaction of ions or molecules can modify the localized surface states, causing a photoluminescence quenching or enhancement effect. As a consequence, these materials are promising candidates for replacing the metal-based quantum dots in various applications, such as bioimaging [11,12,13], biosensing [14,15], drug delivery [16,17], adjuvant selection in vaccines [18], and photocatalysis [19]. The working mechanism in sensing and imaging applications is related to the presence of functional groups, which can coordinate the metals being detected, affecting the optical properties. The coordinating role is often played by oxygenated functional groups, such hydroxyls and carboxylates, that are attached to CQDs, but additional N-doping is sought for shifting selectivity parameters or spectral features [20]
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