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Perovskite oxides (ABO₃) have been widely recognized as a class of promising noble-metal–free electrocatalysts due to their unique compositional flexibility and structural stability. Surprisingly, investigation into their size-dependent electrocatalytic properties, in particular barium titanate (BaTiO₃), has been comparatively few and limited in scope. Herein, we report the scrutiny of size- and dopant-dependent oxygen reduction reaction (ORR) activities of an array of judiciously designed pristine BaTiO₃and doped BaTiO₃(i.e., La- and Co-doped) nanoparticles (NPs). Specifically, a robust nanoreactor strategy, based on amphiphilic star-like diblock copolymers, is employed to synthesize a set of hydrophobic polymer-ligated uniform BaTiO₃NPs of different sizes (≤20 nm) and controlled compositions. Quite intriguingly, the ORR activities are found to progressively decrease with the increasing size of BaTiO₃NPs. Notably, La- and Co-doped BaTiO₃NPs display markedly improved ORR performance over the pristine counterpart. This can be attributed to the reduced limiting barrier imposed by the formation of -OOH species during ORR due to enhanced adsorption energy of intermediates and the possibly increased conductivity as a result of change in the electronic states as revealed by our density functional theory–based first-principles calculations. Going beyond BaTiO₃NPs, a variety of other ABO₃NPs with tunable sizes and compositions may be readily accessible by exploiting our amphiphilic star-like diblock copolymer nanoreactor strategy. They could in turn provide a unique platform for both fundamental and practical studies on a suite of physical properties (dielectric, piezoelectric, electrostrictive, catalytic, etc.) contingent upon their dimensions and compositions.

Despite recent progress in producing perovskite nanowires (NWs) for optoelectronics, it remains challenging to solution‐print an array of NWs with precisely controlled position and orientation. Herein, we report a robust capillary‐assisted solution printing (CASP) strategy to rapidly access aligned and highly crystalline perovskite NW arrays. The key to the CASP approach lies in the integration of capillary‐directed assembly through periodic nanochannels and solution printing through the programmably moving substrate to rapidly guide the deposition of perovskite NWs. The growth kinetics of perovskite NWs was closely examined by in situ optical microscopy. Intriguingly, the as‐printed perovskite NWs array exhibit excellent optical and optoelectronic properties and can be conveniently implemented for the scalable fabrication of photodetectors.

Despite recent progress in producing perovskite nanowires (NWs) for optoelectronics, it remains challenging to solution‐print an array of NWs with precisely controlled position and orientation. Herein, we report a robust capillary‐assisted solution printing (CASP) strategy to rapidly access aligned and highly crystalline perovskite NW arrays. The key to the CASP approach lies in the integration of capillary‐directed assembly through periodic nanochannels and solution printing through the programmably moving substrate to rapidly guide the deposition of perovskite NWs. The growth kinetics of perovskite NWs was closely examined by in situ optical microscopy. Intriguingly, the as‐printed perovskite NWs array exhibit excellent optical and optoelectronic properties and can be conveniently implemented for the scalable fabrication of photodetectors.

Thermoresponsive nanoparticles (NPs) represent an important hybrid material comprising functional NPs with temperature‐sensitive polymer ligands. Strikingly, significant discrepancies in optical and catalytic properties of thermoresponsive noble‐metal NPs have been reported, and have yet to be unraveled. Reported herein is the crafting of Au NPs, intimately and permanently ligated by thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM), in situ using a starlike block copolymer nanoreactor as model system to resolve the paradox noted above. As temperature rises, plasmonic absorption of PNIPAM‐capped Au NPs red‐shifts with increased intensity in the absence of free linear PNIPAM, whereas a greater red‐shift with decreased intensity occurs in the presence of deliberately introduced linear PNIPAM. Remarkably, the absence or addition of free linear PNIPAM also accounts for non‐monotonic or switchable on/off catalytic performance, respectively, of PNIPAM‐capped Au NPs.