Tecani g2 f20

CDs were prepared by directly pyrolyzing citric acid (Figure 1). Briefly, 1 gr of anhydrous citric acid was heated at specific temperatures for defined incubation times. The liquid changed from colorless to dark brown, implying the formation of CDs. Then, all samples were neutralized using a 0.5 M NaOH solution to a pH of 7.0. Samples were assigned to four groups based on the temperature and incubation time, i.e., 220-20, 200-30, 180- 40, and 160-50, where the first number in each pair shows temperature in degrees Celsius and the second number shows incubation time in minutes. Dynamic light scattering (DLS) was used to measure CDs particle size. Zeta potential of the CDs was determined using ZEN 3600 (Malvern Instruments Co., USA) for different formation samples. The identification of functional groups was done using a Bruker, Tensor27, FT-IR. To confirm morphological characteristics of the particles, scanning transmission electron microscopy (Tecani™ G² F20, FEI Company) was used at 200 kV.Figure 1

Synthetic production of CDs. Carbon dots with high yield were directly synthesized by pyrolizing citric acid in different time and temperature range. The CDs possess bright blue luminescence.

Figure 1

The conspicuous pictures of transmission electron microscopy (TEM) were captured utilizing an FEI Tecani G2 F20 operating at an acceleration voltage of 200 kV. A Shimadzu UV-2600 spectrometer was used to record the CDs’ UV-Vis spectra. Measurements of fluorescence were conducted using a Shimadzu RF-6000 fluorescence spectrophotometer. Via the KBr pellet method, the Fourier transform infrared (FT-IR) spectrum was acquired under transmission mode using a Thermal Scientific Nicolet iS5 spectrometer. X-ray photoelectron spectroscopy (XPS) was obtained using an Al K excitation K-Alpha spectrometer with a single X-ray source. Binding energy calibration was performed based on C 1s at 284.7 eV. A 290 nm (<1 ns) and a 485 nm (200 ps) nano-LED light source was used to excite the samples. The CIE chromaticity coordinates were measured using a KONICA MINOLTA CS-150 colorimeter. Absolute quantum yield (QY) measurements were performed using a FLS1000 spectrometer (Techcomp, Livingston, Edinburgh, UK) equipped with a calibrated integrating sphere. As the QY was determined by the ratio between photons emitted and absorbed by CDs, it was desirable to place the ethanol solution of CDs in a cuvette to measure their QY, while using solvent ethanol as a blank sample for the reference measurement.