Precise control over doping of photocatalysts is required to modulate their photocatalytic activity in visible light‐driven reactions. Here, a single precursor‐employing bottom‐up approach is developed to produce different heteroatom‐doped graphene quantum dots (GQDs) with unique photocatalytic activities. The solvothermal reaction of a norepinephrine precursor with redox active and condensable moieties effectively produces both nitrogen/sulfur codoped GQDs (NS‐GQDs) and nitrogen‐doped GQDs (N‐GQDs) by simply varying solvents (from dimethyl sulfoxide to water) under microwave irradiation. As‐prepared NS‐GQDs and N‐GQDs show similar lateral sizes (3–4 nm) and heights (1–2 nm), but they include different dopant types and doping constitution and content, which lead to changes in photocatalytic activity in aerobic oxidative coupling reactions of various amines. NS‐GQDs exhibit much higher photocatalytic activity in reactions under visible light than N‐GQDs and oxygen‐doped GQDs (O‐GQDs). The mechanism responsible for the outstanding photocatalytic activity of NS‐GQDs in visible light‐driven oxidative coupling reactions of amines is also fully investigated.

There is an increasing demand for control over the dimensions and functions of transition metal dichalcogenides (TMDs) in aqueous solution toward biological and medical applications. Herein, an approach for the exfoliation and functionalization of TMDs in water via modulation of the hydrophobic interaction between poly(ε-caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) and the basal planes of TMDs is reported. Decreasing the hydrophobic PCL length of PCL-b-PEG from 5000 g mol (PCL ) to 460 g mol (PCL ) significantly increases the exfoliation efficiency of TMD nanosheets because the polymer-TMD hydrophobic interaction becomes dominant over the polymer-polymer interaction. The TMD nanosheets exfoliated by PCL -b-PEG (460-WS , 460-WSe , 460-MoS , and 460-MoSe ) show excellent and prolonged scavenging activity for reactive oxygen species (ROS), but each type of TMD displays a different scavenging tendency against hydroxyl, superoxide, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals. A mechanistic study based on electron paramagnetic resonance spectroscopy and density functional theory simulations suggests that radical-mediated oxidation of TMDs and hydrogen transfer from the oxidized TMDs to radicals are crucial steps for ROS scavenging by TMD nanosheets. As-prepared 460-TMDs are able to effectively scavenge ROS in HaCaT human keratinocytes, and also exhibit excellent biocompatibility.