Photoluminescence and Photodetecting Properties of the Hydrothermally Synthesized Nitrogen-Doped Carbon Quantum Dots

Abstract

Carbon quantum dots (CQDs) have attracted more and more attention as the representative of a new generation of photoluminescence (PL) and photodetecting materials due to their unique optoelectrical properties. However, the formation mechanism of the CQDs as well as the origin of the PL from the CQDs are still open questions to be issued. Here, we report our recent progress on the synthesis of the nitrogen-doped carbon quantum dots (N-CQDs) with a high photoluminescence quantum yield (PLQY) of 97.4% by adjusting the hydrothermal synthesis parameters with citric acid (CA) and ethylenediamine (EDA) as the precursors. The detailed structure and properties indicate that N-CQDs are synthesized by dehydration, condensation, and carbonization, and the PL is attributed to the synergistic effect of the carbogenic core and the surface/molecule state. With the above progress, an all-carbon-based ultraviolet (UV) photodetector is fabricated based on the N-CQDs/graphene hybrid composites, which exhibits a significant negative photoconductivity phenomenon. A maximal negative responsivity up to 2.5 × 104 AW–1 in the UV region has been observed, which was attributed to the two competing mechanisms. One is the oxygen adsorption and photodesorption induced negative photoresponse, while the other is the surface defects in N-CQDs related positive photoconducting. Our work reveals the mechanisms driving force behind the positive and the negative photoconductance phenomenon of photodetectors based on CQDs, which not only contributes to further understanding of the fluorescent and photoresponse mechanisms of CQDs, but also promotes the application potential of CQDs in the field of photodetection and nano-optoelectronic sensors.

Recent advances of biomass carbon dots on syntheses, characterization, luminescence mechanism, and sensing applications

“…[ 151 ] Similarly, Wu et al. [ 152 ] synthesized N‐CQDs were more likely to be attributed to surface defects. One of luminescence mechanisms of the adjustable‐size carbon dots synthesized using coal [ 153 ] as carbon source was caused by surface defects.…”

Fluorescent “on–off–on” sensor based on N,S co-doped carbon dots from seaweed (Sargassum carpophyllum) for specific detection of Cr(vi) and ascorbic acid

“…The peaks (Fig. 2b) at 282.0, 40 In the high-resolution spectrum of N1s, the two peaks at 397.0, 401.2 eV (Fig. 2c) are attributed to the C-N-C, N-H groups, respectively.…”

Flexible and transparent memristive synapse based on polyvinylpyrrolidone/N-doped carbon quantum dot nanocomposites for neuromorphic computing

“…As a novel zero-dimensional carbon nanomaterial, nitrogendoped carbon quantum dots (NCQDs) possess unique properties, such as small sizes, excellent biocompatibility, excellent aqueous solubility, and low toxicity, and they are considered to be promising materials for a number of biological and optoelectronic applications. [27][28][29][30] Doping CQDs with electron-rich N atoms is considered to be a valid strategy to modulate their intrinsic properties and improve their uorescent properties and quantum yield. 31,32 More importantly, the polar groups and defects on the surface of NCQDs can regulate generation and recombination of electron-hole pairs, [33][34][35] suggesting the potential feasibility of doping polymers with NCQDs to achieve closely biorealistic articial synapses based on the trappingassisted hopping effect.…”