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.

The proton exchange membrane fuel cells (PEMFCs) have been considered as promising future energy conversion devices, and have attracted immense scientific attention due to their high efficiency and environmental friendliness. Nevertheless, the practical application of PEMFCs has been seriously restricted by high cost, low earth abundance and the poor poisoning tolerance of the precious Pt-based oxygen reduction reaction (ORR) catalysts. Noble-metal-free transition metal/nitrogen-doped carbon (M–N_xC) catalysts have been proven as one of the most promising substitutes for precious metal catalysts, due to their low costs and high catalytic performance. In this review, we summarize the development of M–N_xC catalysts, including the previous non-pyrolyzed and pyrolyzed transition metal macrocyclic compounds, and recent developed M–N_xC catalysts, among which the Fe–N_xC and Co–N_xC catalysts have gained our special attention. The possible catalytic active sites of M–N_xC catalysts towards the ORR are also analyzed here. This review aims to provide some guidelines towards the design and structural regulation of non-precious M–N_xC catalysts via identifying real active sites, and thus, enhancing their ORR electrocatalytic performance.

It is indispensable to synthesize deep-blue light emitting materials with high luminous efficiency for realizing full-colour organic light emitting diode (OLED) displays. The hybridized local and charge-transfer (HLCT) state is a special excited state that hybridizes the local state and the charge transfer state to ensure a high fluorescence quantum yield (η_pl). Herein, a blue fluorescent material of TPA-DFCP was designed and synthesized, with a twisted D–π–A configuration, in which triphenylamine (TPA), benzonitrile (CP) and 9,9-dioctylfluorene serve as the D, A, and π-conjugation unit, respectively. It also exhibits good solubility and can be dissolved in several organic solvents with different polarities. The non-doped device, with TPA-DFCP as the emitter, shows excellent electroluminescent (EL) efficiency with a maximum EQE of 7.74%. Furthermore, the doped device of TPA-DFCP exhibits excellent deep-blue emission with the EL emission peak at 436 nm and the CIE coordinates at (0.153, 0.077), which are very close to the NTSC standard blue CIE (x, y) coordinates of (0.140, 0.080). Meanwhile, the doped device also exhibited excellent EL performance, with a maximum external quantum efficiency (EQE) and radiative exciton utilization (η_r) of 8.30% and 57.67%, respectively.

A novel white-light hyperbranched conjugated polymer utilizing polyfluorene as the branches and Ir(piq)₃ as the cores has been investigated.

The crystal growth behavior of dendrite-like Cu₂O crystals during galvanostatic electrodeposition was investigated. The deposited Cu₂O particles are single-phase cuprites and their morphologies change from octahedral in a static electrolyte to dendrites in a stirred electrolyte. The morphology evolution is attributed to the enhancement of the transfer of Cu²⁺ and the break in the Cu²⁺ depletion zone around the nuclei, which promotes the deposition of Cu²⁺ ions along the directions to form a face-centered cubic (FCC) Cu lattice under a cathodic potential. Meanwhile, O atoms diffuse into the Cu lattice to form a cuprite Cu₂O lattice with a corresponding lattice expansion. Consequently, the morphology of the Cu₂O crystals develops into dendrites and the growth direction of the dendritic branches are all along the directions. Furthermore, the conduction type of Cu₂O was also changed from p-type to n-type when the morphology of the Cu₂O crystals varied from octahedral to dendrites. The mechanism of the morphology evolution in the present reaction system is helpful for controlling the morphology of the Cu₂O crystals.

The role of the nucleation layer thickness on the GaN crystal quality grown by metal organic chemical vapor deposition is explored.