Carbon quantum dots (C-Dots) have drawn extensive attention in recent years due to their stable physicochemical and photochemical properties. However, the development of nitrogen-doped carbon quantum dots (N-doped C-Dots) is still on its early stage. In this paper, a facile and high-output solid-phase synthesis approach was proposed for the fabrication of N-doped, highly fluorescent carbon quantum dots. The obtained N-doped C-Dots exhibited a strong blue emission with an absolute quantum yield (QY) of up to 31%, owing to fluorescence enhancement effect of introduced N atoms into carbon dots. The strong coordination of oxygen-rich groups on N-doped C-Dots to Fe(3+) caused fluorescence quenching via nonradiative electron-transfer, leading to the quantitative detection of Fe(3+). The probe exhibited a wide linear response concentration range (0.01-500 μM) to Fe(3+) with a detection limit of 2.5 nM. Significantly, the N-doped C-Dots possess negligible cytotoxicity, excellent biocompatibility, and high photostability. All these features are favorable for label-free monitoring of Fe(3+) in complex biological samples. It was then successfully applied for the fluorescence imaging of intracellular Fe(3+). As an efficient chemosensor, the N-doped C-Dots hold great promise to broaden applications in biological systems.

Single‐phase perovskite oxides that contain nonprecious metals have long been pursued as candidates for catalyzing the oxygen evolution reaction, but their catalytic activity cannot meet the requirements for practical electrochemical energy conversion technologies. Here a cation deficiency‐promoted phase separation strategy to design perovskite‐based composites with significantly enhanced water oxidation kinetics compared to single‐phase counterparts is reported. These composites, self‐assembled from perovskite precursors, comprise strongly interacting perovskite and related phases, whose structure, composition, and concentration can be accurately controlled by tailoring the stoichiometry of the precursors. The composite catalyst with optimized phase composition and concentration outperforms known perovskite oxide systems and state‐of‐the‐art catalysts by 1–3 orders of magnitude. It is further demonstrated that the strong interfacial interaction of the composite catalysts plays a key role in promoting oxygen ionic transport to boost the lattice‐oxygen participated water oxidation. These results suggest a simple and viable approach to developing high‐performance, perovskite‐based composite catalysts for electrochemical energy conversion.

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Interfacial engineering is a simple and effective strategy that can improve the photovoltaic performance in organic-inorganic perovskite solar cells (PSCs). Herein, a dopamine (DA) self-assembled monolayer (SAM) was introduced on the top of the SnO electron transporting layer (ETL) to modify the SnO/perovskite interface. The processing temperature of the present devices is around 150 °C, and the power conversion efficiency of the PSCs was significantly improved to 16.65% compared to that of the device without modification (14.05%). Such enhancement in efficiency is mainly attributed to the improved quality of perovskite films by improving the affinity of the SnO ETL, thus leading to better carrier transport and low charge recombination at the SnO/perovskite interface. Moreover, the modified device by the DA SAM exhibited enhanced stability compared to the device without modification. Our results suggest that the introduction of the DA SAM on the ETL/perovskite interface is a promising method for highly efficient and stable PSCs.