Graphene quantum dots (GQDs) which are nanofragments of graphene with an average size between 2 and 50 nm have attracted much attention due to their outstanding properties such as high conductivity, high surface area, and good solubility in various solvents. GQDs combine the quantum confinement and edges effects and the properties of graphene. Therefore, GQDs offers a broad range of applications in various fields (medicine, energy conversion, and energy storage devices). This review will present the recent research based on the introduction of GQDs in batteries, supercapacitors, and micro‐supercapacitors as electrodes materials or mixed with an active material as an auxiliary agent. Tables, discussed on selected examples, summarize the electrochemical performances and finally, challenges and perspectives are recalled for the subsequent optimization strategy of electrode materials. This review is expected to appeal a broad interest on functional GQDs materials and promote the further development of high‐performance energy storage device.

Here, we demonstrate for the first time a strategy to self-assemble ZnO nanoparticles (NP) on a large area by a facile one-step process. First, rough and random ZnO nanocrystals (NC), were produced by free-stabilizing aqueous synthesis. Therefore, a post thermal treatment at various temperatures ranging from 80 to 800 °C was necessary to obtain size-tunable and photoluminescent crystalline NP. The fabricated NP had both efficient UV photoluminescence and photocatalytic activity by photo-degradation of Methylene Blue (MB) dye. The annealed NP showed an absorption blue shift in the UV region with decreasing size. This shift was attributed to high quantum confinement effect since ZnO NP diameter reached values lower than the Bohr radius of ZnO (~2.7 nm). The photocatalytic activity displayed dependency on the particle’s size, number, and crystallinity. Subsequently, the NP were self-assembled inside poly(methyl methacrylate) (PMMA) nanoholes. Subsequently, large area substrate of homogenous properties ZnO NP was obtained. Moreover, the synthesis facility, photoemission and photocatalytic properties of ZnO NP could be a new insight into the realization of high performance and low cost UV laser devices.

The Bi2Te3 and its derivative compounds are very interesting materials in the field of thermoelectric refrigeration at room temperature. An electrochemical deposition that is an alternative process of the standard synthesis is developed in our laboratory. The study of the reduction of TeIV+ and BiIII+ and their mixtures, in aqueous solvent, evidences the direct formation of near stoichiometric Bi2Te3 compounds. The electrodeposition is performed according to the reaction: 2BiO++3HTeO+ 2+13H++18e−→Bi2Te3↓+8H2OThe synthesis is realized in an acid electrolyte (HNO31M), allowing the stability of TeIV+ and BiIII+ salts. The Bi/Te ratio in the electroformatted films is varying with the solution composition and the applied current density. The X‐ray controls of all the compounds obtained by this method show only one product, with a good crystallinity. The patterns are consistent with the space group R‐3m of Bi2Te3. However, it should be noted orientation effects. The films exhibit qualitative thermoelectric properties of as n‐type semiconductor.

The emergence of bio-based carbonaceous materials for various applications has attracted significant attention during the last few years. Here, we report a rapid, efficient, and reproducible microwave-assisted synthesis of graphene quantum dots (GQDs) with identical features irrespective of the nature of biomass waste investigated. The synthesized GQDs were fully characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and dynamic light scattering. The nanoparticles displayed narrow sizes of 1–2 nm and high solubility in polar solvents such as water and ethanol. The protocol described herein is advantageous in comparison to dealing with the synthesis of GQDs from biomass waste previously reported since our protocol is faster owing to the use of microwave heating and the avoidance of dialysis for the purification step. Furthermore, in solution, the water-soluble particles showed excitation-dependent photoluminescence ranging from blue to orange emission wavelengths. Interestingly, thin films displayed white-light emission under 325 nm UV-light excitation, while aggregation-induced quenching was usually observed, opening the way for their potential use as a phosphor in white-light-emitting diodes.