We present a facile electrochemical method for synthesizing uniform sized graphene quantum dots (GQDs) with a strong yellow emission at 14% quantum yield. This approach has enabled a large-scale production of aqueous GQD solution without the need for polymeric or surfactant stabilizers. The structure and emission mechanism of the GQDs have been studied by combining extensive characterization techniques, rigorous control experiments and theoretical calculations. We further demonstrate the distinctive advantages of such GQDs for direct and efficient stem cell labeling, opening up great opportunities for their bio-medical applications.

Facile synthesis of water-soluble, highly fluorescent graphene quantum dots as a robust biological label for stem cells

Despite the various synthesis methods to obtain carbon dots (CDs), the bottom-up methods are still the most widely administrated route to afford large-scale and low-cost synthesis. However, as CDs are developed with increasing reports involved in producing many CDs, the structure and property features have changed enormously compared with the first generation of CDs, raising classification concerns. To this end, a new classification of CDs, named carbonized polymer dots (CPDs), is summarized according to the analysis of structure and property features. Here, CPDs are revealed as an emerging class of CDs with distinctive polymer/carbon hybrid structures and properties. Furthermore, deep insights into the effects of synthesis on the structure/property features of CDs are provided. Herein, the synthesis methods of CDs are also summarized in detail, and the effects of synthesis conditions of the bottom-up methods in terms of the structures and properties of CPDs are discussed and analyzed comprehensively. Insights into formation process and nucleation mechanism of CPDs are also offered. Finally, a perspective of the future development of CDs is proposed with critical insights into facilitating their potential in various application fields.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201901316

Evolution and Synthesis of Carbon Dots: From Carbon Dots to Carbonized Polymer Dots

Carbon quantum dots (CQDs) have emerged as promising materials for optoelectronic applications on account of carbon’s intrinsic merits of high stability, low cost, and environment-friendliness. However, the CQDs usually give broad emission with full width at half maximum exceeding 80 nm, which fundamentally limit their display applications. Here we demonstrate multicolored narrow bandwidth emission (full width at half maximum of 30 nm) from triangular CQDs with a quantum yield up to 54–72%. Detailed structural and optical characterizations together with theoretical calculations reveal that the molecular purity and crystalline perfection of the triangular CQDs are key to the high color-purity. Moreover, multicolored light-emitting diodes based on these CQDs display good stability, high color-purity, and high-performance with maximum luminance of 1882–4762 cd m−2 and current efficiency of 1.22–5.11 cd A−1. This work will set the stage for developing next-generation high-performance CQDs-based light-emitting diodes.

/pdf/engineering-triangular-carbon-quantum-dots-with-3xv4tpjege.pdf

Engineering triangular carbon quantum dots with unprecedented narrow bandwidth emission for multicolored LEDs

Red emissive carbon quantum dots (R-CQDs) with quantum yield of 53% is successfully prepared. An ultraviolet (UV)-pumped CQD phosphors-based warm white light-emitting diode (WLED) is realized for the first time and achieves a color rendering index of 97. This work provides a new avenue for the exploration of low cost, environment-friendly, and high-performance CQD phosphors-based warm WLEDs.

53% Efficient Red Emissive Carbon Quantum Dots for High Color Rendering and Stable Warm White-Light-Emitting Diodes

Shining carbon dots: Synthesis and biomedical and optoelectronic applications

Effects of polymerization potential on the properties of electrosynthesized PEDOT films

In recent years, graphene quantum dots (GQDs) have attracted tremendous attention for their potential for biological, optoelectronic and energy-related applications, owing to their excellent biocompatibility, low cytotoxicity, stable photoluminescence (PL) and resistance to photobleaching. Among these applications, GQD-based biosensors are rapidly developed due to their particular PL, electrochemiluminescence (ECL) and electrochemical properties, which are highly sensitive to minute perturbations. In this review, recent exciting progress in GQD-based biosensors, such as PL sensors, ECL sensors and electrochemical sensors is highlighted. First, the synthesis and the fundamental properties of GQDs are briefly introduced. Then, emerged applications of PL, ECL and electrochemical biosensors are mainly addressed. Finally, their future potential developments are discussed and speculated.

Graphene quantum dots as smart probes for biosensing

Directed Assembly of Hierarchical CdS Nanotube Arrays from CdS Nanoparticles: Enhanced Solid State Electro‐chemiluminescence in H2O2 Solution

The negative impact of rare-earth elements (REEs) on the environment, limited supply and high cost prompt the need for REE-free phosphor-converted white light-emitting diodes (LEDs). Here, we report the gram-scale synthesis of red/green/blue solid-state bandgap fluorescent carbon quantum rings (R/G/B-SBF-CQRs) with high quantum yields up to 30-46 %. This was achieved using cyano-group-bearing p-phenyldiacetonitrile as precursor and forming carbon quantum rings of different diameters through the linkage of curved carbon quantum ribbons of different lengths. The results show the role of cyano groups in inducing the curvature of the carbon quantum ribbons for CQR formation and emission of stable solid-state bandgap fluorescence. R/G/B-SBF-CQRs-phosphor-based LEDs emitted warm white light with low CCT (3576 K), high CRI (96.6), and high luminous efficiency (48.7 lm W-1 ), comparable to REE-phosphor-based LEDs.

Gram-Scale Synthesis of Highly Efficient Rare-Earth-Element-Free Red/Green/Blue Solid-State Bandgap Fluorescent Carbon Quantum Rings for White Light-Emitting Diodes

Zifei Wang

Papers

53% Efficient Red Emissive Carbon Quantum Dots for High Color Rendering and Stable Warm White-Light-Emitting Diodes

Effects of polymerization potential on the properties of electrosynthesized PEDOT films

Graphene quantum dots as smart probes for biosensing

Directed Assembly of Hierarchical CdS Nanotube Arrays from CdS Nanoparticles: Enhanced Solid State Electro‐chemiluminescence in H2O2 Solution

Gram-Scale Synthesis of Highly Efficient Rare-Earth-Element-Free Red/Green/Blue Solid-State Bandgap Fluorescent Carbon Quantum Rings for White Light-Emitting Diodes