The bandgap in graphene‐based materials can be tuned from 0 eV to that of benzene by changing size and/or surface chemistry, making it a rising carbon‐based fluorescent material. Here, the surface chemistry of small size graphene (graphene quantum dots, GQDs) is tuned programmably through modification or reduction and green luminescent GQDs are changed to blue luminescent GQDs. Several tools are employed to characterize the composition and morphology of resultants. More importantly, using this system, the luminescence mechanism (the competition between both the defect state emission and intrinsic state emission) is explored in detail. Experiments demonstrate that the chemical structure changes during modification or reduction suppresses non‐radiative recombination of localized electron‐hole pairs and/or enhances the integrity of surface π electron network. Therefore the intrinsic state emission plays a leading role, as opposed to defect state emission in GQDs. The results of time‐resolved measurements are consistent with the suggested PL mechanism. Up‐conversion PL of GQDs is successfully applied in near‐IR excitation for bioimaging.

Swimming microrobots that are energized by external magnetic fields exhibit a variety of intriguing collective behaviors, ranging from dynamic self-organization to coherent motion; however, achieving multiple, desired collective modes within one colloidal system to emulate high environmental adaptability and enhanced tasking capabilities of natural swarms is challenging. Here, we present a strategy that uses alternating magnetic fields to program hematite colloidal particles into liquid, chain, vortex, and ribbon-like microrobotic swarms and enables fast and reversible transformations between them. The chain is characterized by passing through confined narrow channels, and the herring school–like ribbon procession is capable of large-area synchronized manipulation, whereas the colony-like vortex can aggregate at a high density toward coordinated handling of heavy loads. Using the developed discrete particle simulation methods, we investigated generation mechanisms of these four swarms, as well as the “tank-treading” motion of the chain and vortex merging. In addition, the swarms can be programmed to steer in any direction with excellent maneuverability, and the vortex’s chirality can be rapidly switched with high pattern stability. This reconfigurable microrobot swarm can provide versatile collective modes to address environmental variations or multitasking requirements; it has potential to investigate fundamentals in living systems and to serve as a functional bio-microrobot system for biomedicine.

An in situ catalytic etching strategy is developed to fabricate holey reduced graphene oxide along with simultaneous coupling with a small-sized Mo N-Mo C heterojunction (Mo N-Mo C/HGr). The method includes the first immobilization of H PMo O (PMo ) clusters on graphite oxide (GO), followed by calcination in air and NH to form Mo N-Mo C/HGr. PMo not only acts as the Mo heterojunction source, but also provides the Mo species that can in situ catalyze the decomposition of adjacent reduced GO to form HGr, while the released gas (CO) and introduced NH simultaneously react with the Mo species to form an Mo N-Mo C heterojunction on HGr. The hybrid exhibits superior activity towards the hydrogen evolution reaction with low onset potentials of 11 mV (0.5 m H SO ) and 18 mV (1 m KOH) as well as remarkable stability. The activity in alkaline media is also superior to Pt/C at large current densities (>88 mA cm ). The good activity of Mo N-Mo C/HGr is ascribed to its small size, the heterojunction of Mo N-Mo C, and the good charge/mass-transfer ability of HGr, as supported by a series of experiments and theoretical calculations.