Solvent Effects on Fluorescence Properties of Carbon Dots: Implications for Multicolor Imaging

Abstract

Carbon dots (CDs) are synthesized by the solvothermal method with four kinds of solvents including water, dimethylformamide (DMF), ethanol, and acetic acid (AA). The aqueous solutions of the above CDs emit multiple colors of blue (470 nm), green (500 nm), yellow (539 nm), and orange (595 nm). The structures, sizes, and chemical composition of the CDs are characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The optical properties of multicolored CDs are analyzed by UV−vis absorption and photoluminescence (PL) spectra. It has been revealed that DMF is the key solvent to synthesized CDs for the red shift of fluorescence emission, which could be enhanced by adding an AA solvent. The structures of functional groups such as the contents of graphitic N in carbon cores and oxygencontaining functional groups on the surface of CDs are affected by these four solvents. According to the oxidation and selective reduction of NaBH 4 , the implication for multicolor imaging has been discussed based on the COOH, C−O−C, and CO functional groups.

Fluorescent Polymer Carbon Dots for the Sensitive–Selective Sensing of Fe3+Metal Ions and Cellular Imaging

“…To explore the effect of the Stokes shift on the fluorescence behavior of FPCDs, we obtained the excitation spectra with different maximum emission wavelengths and overlapped the excitation and emission spectra (Figure S3). Next, the Stokes shift was calculated for all cases; a red shift of the fluorescence of FPCDs was observed with an increase in the Stokes shift from ∼67 to ∼159 nm . As a result of the presence of various functional groups with different energy levels, FPCDs show an excitation-dependent emission phenomenon, which is very common in carbon-based materials .…”

“…Next, the Stokes shift was calculated for all cases; a red shift of the fluorescence of FPCDs was observed with an increase in the Stokes shift from ∼67 to ∼159 nm. 58 As a result of the presence of various functional groups with different energy levels, FPCDs show an excitation-dependent emission phenomenon, which is very common in carbon-based materials. 59 The fluorescence stability of FPCDs was explored under continuous irradiation for 2 h at 360 nm wavelength, showing their excellent photostability (Figure S4).…”

N-Dopant Site Formulation for White-Light-Emitting Carbon Dots with Tunable Chromaticity

“…Water and glycol, which are normally used as solvents, may affect organic groups on CD surfaces, leading to blue emissions. Excitation wavelength-dependent m-CDs consist of sp 2 hybridized core structures coated with an amorphous shell or nearly sp 3 hybridized structures (amorphous nature). ,, In our present study, C-CDs were successfully prepared from the reaction between CA and FA. FT-IR and XPS experiments confirm that the FA solvent reacts with the CA and accelerates cleavage of the N–H bond (in FA) and formation of the C–N–C bond.…”

“…Excitation wavelengthdependent m-CDs consist of sp 2 hybridized core structures coated with an amorphous shell or nearly sp 3 hybridized structures (amorphous nature). 45,68,69 In our present study, C- 5a, and S6) images reveal that C-CD structure is nearly amorphous with tiny crystal lattice features. On the other hand, deconvoluted HRXPS spectra (Figure 2f) reveal formation of various types of N center (pyridinic, amide, pyrrolic, and graphitic).…”

Ultrasonic-Assisted Synthesis of N-Doped, Multicolor Carbon Dots toward Fluorescent Inks, Fluorescence Sensors, and Logic Gate Operations

“…The adopted avenues to obtain M-CDs are nothing more than adjusting raw materials, reaction conditions (temperatures, reaction times, reaction solvents), and/or separation methods, etc. [ 22 , 23 , 24 , 25 , 26 , 27 ] C. Dong et al prepared color-tunable CDs by a one-pot hydrothermal method, and the optimized emission of CDs progressively shifted from green to red with the adjustment of the precursor solution from alkali to acid [ 22 ]. S. K. Sahu and coworkers synthesized the multicolor emissive CDs by solvent-controlled and solvent-responded approaches [ 24 ].…”