Fluorescent carbon dots in PEC-GS/BG hybrids and their application for bioimaging

Abstract

Carbon dots (CDs), renowned for their distinctive photoluminescence properties, have emerged as a prominent material in the field of luminescence. They are extensively utilized in bioimaging, drug delivery, theranostics, and other applications. In this study, CDs were successfully prepared and isolated from PEC-GS/BG hybrids. Their chemical composition, surface functional groups, and crystal structure were comprehensively characterized. The results demonstrated that the CDs are mainly composed of carbon and oxygen. They exhibit a near-spherical morphology with an average diameter of about 7.4 nm. Then, the fluorescent properties of the CDs were thoroughly assessed. Photoluminescence (PL) measurements revealed that the CDs display intense blue fluorescence upon exposure to ultraviolet (UV) light. This emission is excitation-dependent and shows resilience to variations in pH, high ionic strength, and photobleaching. The quantum yield (QY) was determined to be around 4.5%. Additionally, the synthesized CDs exhibited excellent biocompatibility and cell-labeling capability. These findings indicate that the synthesized CDs hold significant potential for practical applications in various fields.

Keywords: bioactive glass; bioimaging; carbon dots; citric acid; photoluminescence.

FIGURE 1

(A) Fourier transform infrared (FTIR) spectrum, (B) X-ray photoelectron spectroscopy (XPS) survey scan and (C) energy dispersive X-ray spectroscopy (EDS) of CDs.

FIGURE 2

(A) Typical TEM image and (B) corresponding particle size distribution of as prepared CDs.

FIGURE 3

(A) UV-vis absorption spectrum of CDs. Inset: photographs of the CD aqueous solutions under visible light (left) and UV light (right), respectively; (B) Excitation dependent photoluminescence behavior of CDs.

FIGURE 4

(A) Effect of pH on the photoluminescence intensity of CDs; (B) Fluorescence intensity of CDs in NaCl aqueous solution (pH = 7) against the ionic strength; (C) Dependence of the fluorescence intensity of CDs on excitation time under 488 nm irradiation in ultrapure water; (D) Effect of storage time on the photoluminescence intensity of CDs.

FIGURE 5

(A) Cell viability of MC3T3-E1 cells after 24-h incubation with various concentrations of CDs; (B) Fluorescence images of MC3T3-E1 cells incubated with CDs for 2 h under 488 nm filter irradiation. Scale bar:50 μm.