Electroluminescence of carbon ‘quantum’ dots – From materials to devices

Facilely synthesized carbon dots and configurated light-emitting diodes with efficient electroluminescence

High-quality carbon dots are facilely synthesized and serve as emitters of light-emitting diodes with efficient electroluminescence.

Structural Engineering toward High Monochromaticity of Carbon Dots-Based Light-Emitting Diodes

Monochromaticity for light-emitting diodes (LEDs) is an important parameter. However, carbon dots-based light-emitting diodes (CDs-LEDs) usually suffer from broad emission, which limits the development of this material. In this work, high-quality carbon dots (CDs) with a quantum yield of 16.2% were synthesized. When they were mixed with poly(N-vinyl carbazole) (PVK) to form a homogeneous film, the solid-state fluorescence of CDs was realized. After fabrication and systematic optimization of the device, the full width at half-maximum (fwhm) of EL spectra could be narrowed to 64 nm in comparison with the fwhm of 77 nm for PL, demonstrating that structural engineering is an effective approach for improving the color purity of CDs-LEDs. Meanwhile, the performance of the devices is improving. The obtained CDs-LEDs display high monochromaticity with a maximum luminance of 681 cd/m². This work provides a new way to optimize the monochromaticity and performance of CDs-LEDs.

Recent advances in carbon quantum dot (CQD)-based two dimensional materials for photocatalytic applications

This review presents up-to-date research findings and critical insights on trending topics of pristine CQDs and CQDs-based 2D nanomaterial composites.

Excited states and excitonic interactions in prototypic polycyclic aromatic hydrocarbon dimers as models for graphitic interactions in carbon dots

The HOMO–LUMO transition in a stacked circum-1-coronene dimer as a model for excimer interactions in carbon dots.

Zero-Dimensional Carbon Allotropes-Carbon Nanoparticles Versus Fullerenes in Functionalization by Electronic Polymers for Different Optical and Redox Properties

Fullerene cages are known as being able to participate in radical initiated copolymerization reactions with vinyl monomers for polymer-functionalized fullerenes. In this work, poly(N-vinylcarbazole) (PVK) was selected as a representative of electronic polymers in the functionalization of fullerene C₆₀ by the same copolymerization reaction to yield the PVK-C₆₀. Similarly found was that small carbon nanoparticles could also participate in the same copolymerization reaction for the nanoparticles to be surface-functionalized and -passivated by the attached PVK polymers, which are structurally adhering to the general definition on carbon dots (CDots), thus PVK-CDots. In the comparison between PVK-CDots and PVK-C₆₀, the former was found to be more absorptive and therefore more effective in photon harvesting across the visible spectral region and also brightly fluorescent, orders of magnitude more so than the latter. Similar to the PVK-C₆₀ and C₆₀ cages in general, the PVK-CDots exhibited significant photoinduced electron accepting characteristics and, at the same time, also extraordinary electron donating abilities that are not available to fullerenes. Because fullerene-based composites with electronic polymers including PVK have found significant applications in optoelectronic devices and systems, the prospect of CDots represented by the PVK-CDots for similar purposes is discussed.

Modified Facile Synthesis for Quantitatively Fluorescent Carbon Dots

A simple yet consequential modification was made to the popular carbonization processing of citric acid - polyethylenimine precursor mixtures to produce carbon dots (CDots). The modification was primarily on pushing the carbonization processing a little harder at a higher temperature, such as the hydrothermal processing condition of around 330 °C for 6 hours. The CDots thus produced are comparable in spectroscopic and other properties to those obtained in other more controlled syntheses including the deliberate chemical functionalization of preprocessed and selected small carbon nanoparticles, demonstrating the consistency in CDots and reaffirming their general definition as carbon nanoparticles with surface passivation by organic or other species. Equally significant is the finding that the modified processing of citric acid - polyethylenimine precursor mixtures could yield CDots of record-setting fluorescence performance, approaching the upper limit of being quantitatively fluorescent. Thus, the reported work serves as a demonstration on not only the need in selecting the right processing conditions and its associated opportunities in one-pot syntheses of CDots, but also the feasibility in pursuing the preparation of quantitatively fluorescent CDots, which represents an important milestone in the development and understanding of these fluorescent carbon nanomaterials.

Synthesis of short-chain passivated carbon quantum dots as the light emitting layer towards electroluminescence

S-CQDs were chosen as a light emitting layer by virtue of their structure characteristics, optical properties and film-forming ability to obtain CQD-LEDs.

Preparation of Gold-Carbon Dots and Ratiometric Fluorescence Cellular Imaging

In this study, we synthesized novel gold-carbon dots (GCDs) with unique properties by microwave-assisted method. The characterization of high-resolution transmission electron microscope (HRTEM), XRD, high-angle annular dark field scanning transmission electron microscope (HAADF-STEM), and energy dispersive spectrometer demonstrates that GCDs are composed of carbon and Au. Tiny Au clusters are dispersed in a 2 nm-size carbon skeleton, which integrates the properties of typical CDs and gold nanoclusters (AuNCs), displaying fascinating peroxidase-like activity and single excitation/dual emission. Dual emission of the GCDs exhibits different fluorescent response to the target species and enables the GCDs to be exploited for sensing and bioimaging. The highly photostable and biocompatible GCDs were applied to dual fluorescent imaging for breast cancer cells and normal rat osteoblast cells under a single excitation. Moreover, ratiometric fluorescence imaging was used to monitor Fe(3+) level in normal rat osteoblast cells.