Gram-Scale Synthesis of Graphene Quantum Dots from Single Carbon Atoms Growth via Energetic Material Deflagration

Graphene quantum dots (GQDs) with quantum confinement and size effect are proposed to be applicable in photovoltaic, nanodevices, and so on, due to extraordinary electronic and optical properties. Here we report a facile approach to synthesize gram-scale GQDs from active carbon atoms, which are obtained via the deflagration reaction of polytetrafluoroethylene (PTFE) and Si, growing from high- to low-temperature zones when traveling through the deflagration flame in a short time with releasing gas as the carrier medium. The prepared GQDs were aggregated into carbon nanospheres; thus, Hummer’s method was utilized to exfoliate the GQD aggregations into individual GQDs. We show that the length of GQDs is ∼10 nm and the exfoliated GQDs solution presents an obvious fluorescence effect with a strong emission peak at 570 at 460 nm excitation. And these GQDs are demonstrated to be excellent probes for cellular imaging. Furthermore, we propose a growth mechanism based on computer simulation, which is well verified by experimental reproduction. Our study opens up a promising route for high-yield and high-quality GQDs, as well as other various quantum dots

Hydrogenated Oxygen-Deficient Blue Anatase as Anode for High-Performance Lithium Batteries

Blue oxygen-deficient nanoparticles of anatase TiO₂ (H-TiO₂) are synthesized using a modified hydrogenation process. Scanning electron microscope and transmission electron microscope images clearly demonstrate the evident change of the TiO₂ morphology, from 60 nm rectangular nanosheets to much smaller round or oval nanoparticles of ∼17 nm, after this hydrogenation treatment. Importantly, electron paramagnetic resonance and positronium annihilation lifetime spectroscopy confirm that plentiful oxygen vacancies accompanied by Ti³⁺ are created in the hydrogenated samples with a controllable concentration by altering hydrogenation temperature. Experiments and theory calculations demonstrate that the well-balanced Li⁺/e^– transportation from a synergetic effect between Ti³⁺/oxygen vacancy and reduced size promises the optimal H-TiO₂ sample a high specific capacity, as well as greatly enhanced cycling stability and rate performance in comparison with the other TiO₂