An Efficient Synthesis and Photoelectric Properties of Green Carbon Quantum Dots with High Fluorescent Quantum Yield

Abstract

To greatly improve the production quality and efficiency of carbon quantum dots (CQDs), and provide a new approach for the large-scale production of high-quality CQDs, green carbon quantum dots (g-CQDs) with high product yield (PY) and high fluorescent quantum yield (QY) were synthesized by an efficient one-step solvothermal method with 2,7-dihydroxynaphthalene as the carbon source and ethylenediamine as the nitrogen dopant in this study. The PY and QY of g-CQDs were optimised by adjusting reaction parameters such as an amount of added ethylenediamine, reaction temperature, and reaction duration. The results showed that the maximum PY and QY values of g-CQDs were achieved, which were 70.90% and 62.98%, respectively when the amount of added ethylenediamine, reaction temperature, and reaction duration were 4 mL, 180 °C, and 12 h, respectively. With the optimised QY value of g-CQDs, white light emitting diodes (white LEDs) were prepared by combining g-CQDs and blue chip. The colour rendering index of white LEDs reached 87, and the correlated colour temperature was 2520 K, which belongs to the warm white light area and is suitable for indoor lighting. These results indicate that g-CQDs have potential and wide application prospects in the field of white LEDs.

Triphenylphosphonium‐Derived Bright Green Fluorescent Carbon Dots for Mitochondrial Targeting and Rapid Selective Detection of Tetracycline

“…Defect sites were formed because of the presence of sp 3 carbon atoms and heteroatoms such as oxygen, phosphorous, and nitrogen, which further lead to strong fluorescence character. It is reported that the defect sites induce the fluorescence nature [21,24] . The strong fluorescence of the synthesized C‐dots has been explained in the following by considering the above mentioned aspects.…”

“…The QY was measured as 43.5% and 24.5% for 24 h and 32 h respectively. Long‐time continuous heating can result in further carbonization reaction, gradual growth in the carbon core, weakening of the surface state, and strengthening of the new carbon core state [21] . The combined effect of these four factors could result in the decline of fluorescence QY.…”

“…The bright green fluorescence nature of the C‐dots is considered for the presence of sp 2 graphitic carbon core and defect sites in the C‐dots matrix [21,29] . The conjugated sp 2 carbon core can strongly tune the band gap and UV‐vis absorbance properties, and thereby enhance C‐dots’ visible fluorescence [18b] .…”

“…The optimum temperature and heating duration were chosen at 140 °C and 12 h to synthesize high‐quality green fluorescence C‐dots. Less time heating duration will cause fewer carbon core formations, thus, lowering the QY value, whereas, prolonged carbonization after 12 h may lead to gradual growth of the carbon core, weakening the surface state and strengthening the new carbon core state which were responsible for a decline in QY [21,30] . Thus, a significant amount of precipitate was observed over the longer time heating period.…”

You Don’t Learn That in School: An Updated Practical Guide to Carbon Quantum Dots

“…However, employing CQDs capped with EDA generates a low turn-on voltage of 4.90 V, and regardless of the luminance of 70 cd/m 2 , CQDs can be used as hole transport materials. In 2020, Zheng et al [ 169 ] fabricated CQDs through a one-step solvothermal method using 2,7-dihydroxynaphthalene and ethylenediamine as the carbon and nitrogen sources, respectively. The CQDs displayed an excellent QY value of 62.98%.…”