The successful synthesis of noble-metal nanocrystals with controlled shapes offers many opportunities to not only maneuver their physicochemical properties but also optimize their figures of merit in a wide variety of applications. In particular, heterogeneous catalysis and surface science have benefited enormously from the availability of this new class of nanomaterials as the atomic structure presented on the surface of a nanocrystal is ultimately determined by its geometric shape. The immediate advantages may include significant enhancement in catalytic activity and/or selectivity and substantial reduction in materials cost while providing a well-defined model system for mechanistic study. With a focus on the monometallic system, this review article provides a comprehensive account of recent progress in the development of noble-metal nanocrystals with controlled shapes, in addition to their remarkable performance in a large number of catalytic and electrocatalytic reactions. We hope that this review article offers the impetus and roadmap for the development of next-generation catalysts vital to a broad range of industrial applications.

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Copper nanostructures are promising catalysts for the electrochemical reduction of CO 2 because of their unique ability to produce alarge proportion of multi-carbon products. Despite great progress,t he selectivity and stability of such catalysts still need to be substantially improved. Here,w e demonstrate that controlling the surface oxidation of Cu nanowires (CuNWs) can greatly improve their C 2+ selectivity and stability.S pecifically,w ea chieve af aradaic efficiency as high as 57.7 and 52.0 %f or ethylene when the CuNWs are oxidized by the O 2 from air and aqueous H 2 O 2 ,r espectively, and both of them showh ydrogen selectivity below1 2%.T he high yields of C 2+ products can be mainly attributed to the increase in surface roughness and the generation of defects and cavities during the electrochemical reduction of the oxide layer. Our results also indicate that the formation of arelatively thick, smooth oxide sheath can improve the catalytic stability by mitigating the fragmentation issue.

Despite extensive efforts devoted to the synthesis of Pt−Co bimetallic nanocrystals for fuel cell and related applications, it remains a challenge to simultaneously control atomic arrangements in the bulk and on the surface. Here we report a synthesis of Pt−Co@Pt octahedral nanocrystals that feature an intermetallic, face-centered tetragonal Pt−Co core and an ultrathin Pt shell, together with the dominance of {111} facets on the surface. When evaluated as a catalyst toward the oxygen reduction reaction (ORR), the nanocrystals delivered a mass activity of 2.82 A mg −1 and a specific activity of 9.16 mA cm −2 , which were enhanced by 13.4 and 29.5 times, respectively, relative to the values of a commercial Pt/C catalyst. More significantly, the mass activity of the nanocrystals only dropped 21% after undergoing 30 000 cycles of accelerated durability test, promising an outstanding catalyst with optimal performance for ORR and related reactions.

Integrated theranostic agents can provide comprehensive and efficient tools for simultaneous cancer diagnosis and therapy; however, limitations on efficiency and safety offer great room for improvement. Artesunate (AS), as an iron-dependent drug, has been investigated in cancer therapy, depending on free-radical generation for its action, which may reduce side effects commonly associated with conventional chemotherapy agents with low selectivity to target tumors. However, rapid clearance of its free form and limited availability of Fe ion in tumor sites become the main bottlenecks in cancer therapy. Herein, core−shell Mn 3 [Co(CN) 6 ] 2 @MIL-100(Fe) metal-organic frameworks (CS-MOFs) nanocube was designed using a layer-by-layer method, which holds great potential for synchronous co-delivery of AS and ferric ions for cancer therapy. Moreover, the heterogeneous hybrid CS-MOFs show single-and two-photon fluorescence, together with T 2 and enhanced T 1 magnetic resonance imaging ability. pH-responsive degradation of CS-MOFs enables on-demand Fe(III) and AS release in the tumor microenvironment. The intracellular ferric ions will further be reduced to ferrous ion that catalyze AS to generate carbon-centered free radicals and reactive oxygen species (ROS). The potential of this alternative antitumor modality under multimodality imaging is demonstrated both in vitro and in vivo. In addition, compared with free AS alone, the nanodrug system CS-MOFs@AS shows significantly enhanced tumor delivery specificity and negligible long-term toxicity. In vivo therapy results indicate that the antitumor efficacy of CS-MOFs@AS was 5.79 times greater than that of free AS, making it a promising Fe 2+ -mediated drugs delivery system.

Metal-organic-frameworks (MOFs) possess high porosity, large surface area, and tunable functionality are promising candidates for synchronous diagnosis and therapy in cancer treatment. Although large number of MOFs has been discovered, conventional MOF-based nanoplatforms are mainly limited to the sole MOF source with sole functionality. In this study, surfactant modified Prussian blue (PB) core coated by compact ZIF-8 shell (core-shell dual-MOFs, CSD-MOFs) has been reported through a versatile stepwise approach. With Prussian blue as core, CSD-MOFs are able to serve as both magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI) agents. We show that CSD-MOFs crystals loading the anticancer drug doxorubicin (DOX) are efficient pH and near-infrared (NIR) dual-stimuli responsive drug delivery vehicles. After the degradation of ZIF-8, simultaneous NIR irradiation to the inner PB MOFs continuously generate heat that kill cancer cells. Their efficacy on HeLa cancer cell lines is higher compared with the respective single treatment modality, achieving synergistic chemo-thermal therapy efficacy. In vivo results indicate that the anti-tumor efficacy of CSD-MOFs@DOX+NIR was 7.16 and 5.07 times enhanced compared to single chemo-therapy and single thermal-therapy respectively. Our strategy opens new possibilities to construct multifunctional theranostic systems through integration of two different MOFs.

Palladium is one of the few metals capable of forming hydrides, with the catalytic properties being dependent on the elemental composition and spatial distribution of H atoms in the lattice. Herein, we report a facile method for the complete transformation of Pd nanocubes into a stable phase made of PdH0.706 by treating them with aqueous hydrazine at a concentration as low as 9.2 mM. Using formic acid oxidation (FAO) as a model reaction, we systematically investigated the structure–catalytic property relationship of the resultant nanocubes with different degrees of hydride formation. The current density at 0.4 V was enhanced by four times when the nanocubes were completely converted from Pd to PdH0.706. On the basis of a set of slab models with PdH(100) overlayers on Pd(100), we conducted density functional theory calculations to demonstrate that the degree of hybrid formation could influence both the activity and selectivity toward FAO by modulating the relative stability of formate (HCOO) and carboxyl (COOH) intermediates. This work provides a viable strategy for augmenting the performance of Pd-based catalysts toward various reactions without altering the loading of this scarce metal.