Nitrogen coordinated metal single atoms in carbon have aroused extensive interest recently and have been growing as the active research frontier in a wide range of key renewable energy reactions and devices. However, single-atom catalysts with isolated metallic active components cannot satisfy the demand of electrocatalysis with the requirement in selectivity. Herein, we develop a step-by-step self-assembly strategy to allocate nickel (Ni) and iron (Fe) single atoms respectively on the inner and outer walls of graphene hollow nanospheres (GHSs), for the first time realizing the separate-sided different single-atom functionalization of hollow graphene. The Ni or Fe single atom is demonstrated to be coordinated with four N atoms via the formation of a Ni-N 4 or Fe-N 4 planar experimental observations. As a proof-of-concept demonstration for realistic application, the Ni-N 4 /GHSs/Fe-N 4 endows the rechargeable Zn-air battery with excellent energy efficiency and cycling stability as an air-cathode, outperforming the performance of benchmark Pt/C+RuO 2 air-cathode. The current work paves a new avenue for precise control of single-atom sites on carbon surface for the high-performance and selective electrocatalysts.

close-packed structures with lower surface energy and anisotropy, leading to great challenges in stabilizing and synthesizing 2D noble metal nanomaterials. To this end, a variety of synthetic strategies, such as hard-template-directed synthesis, capping-agent-assisted synthesis, and secondary assembly methods, have been developed for the synthesis of 2D noble metal-based nanostructures. [2] As one of the alternatives, self-assembly from 0D or 1D primary building blocks has been identified as a sophisticated and reliable approach for the generation of 2D noble metal nanostructures. [3] Ultrathin noble metal nanowires with high surface-tovolume ratios and atom utilization efficiency hold promising applications in widespread fields, including catalysis, optics devices, and biomedicine, etc. [4] Rational engineering of 1D nanowires into 2D nanosheets may bring about many novel structural characteristics, including high porosity, large area per unit volume, good flexibility, and an interconnected open pore structure. [5] Therefore, succinct-operated and controllable synthesis of ultrathin free-standing 2D nanosheets with 1D primary building blocks would be of great significance for fundamental scientific interest and technological applications, yet still remains greatly challenging.Herein, for the first time, we present a novel and facile one-pot, simultaneous stepwise self-assembly approach for the synthesis of freestanding porous Pd nanosheets (≈2.5 µm in lateral size and 10 nm in thickness) with the assistance of a functional polymer, poly(diallyldimethylammonium chloride) (PDDA; Figure S1, Supporting Information). Essentially, the obtained porous Pd nanosheets are flexibly knitted by numerous interweaved ultrathin nanowires. Different from the previously reported 2D noble metal nanosheets with smooth surface, [6,7] the obtained Pd nanosheets with large porosity and rough surface are achieved by particle spontaneous attachment and subsequent self-assembly in the one-pot synthesis process. To the best of our knowledge, this is the first report that the construction of 2D sheet-like Pd porous nanostructures through such a simple and efficient approach so far, and the elaborate adoption of eco-friendly PDDA as a structuredirecting agent also plays a crucial role in the formation of the Freestanding ultrathin 2D noble metal nanosheets have drawn enormous attention due to their potential applications in various fields. However, the synthesis of 2D noble metal nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of 2D structures. Here, a facile one-pot synthesis of ultrathin freestanding porous Pd nanosheets (≈2.5 µm in lateral size and 10 nm in thickness) flexibly knitted by interweaved ultrathin nanowires with the assistance of poly(diallyldimethylammonium chloride) is presented. Nanoparticles attachment and subsequent self-assembly in the synthetic process are responsible for the formation of such intriguing nanostructures. Moreover, finely controlling the p...

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The rational design of economical and high‐performance nanocatalysts to substitute Pt for the oxygen reduction reaction (ORR) is extremely desirable for the advancement of sustainable energy‐conversion devices. Isolated single atom (ISA) catalysts have sparked tremendous interests in electrocatalysis due to their maximized atom utilization efficiency. Nevertheless, the fabrication of ISA catalysts remains a grand challenge. Here, a template‐assisted approach is demonstrated to synthesize isolated Fe single atomic sites anchoring on graphene hollow nanospheres (denoted as Fe ISAs/GHSs) by using Fe phthalocyanine (FePc) as Fe precursor. The rigid planar macrocycle structure of FePc molecules and the steric‐hindrance effect of graphene nanospheres are responsible for the dispersion of Fe–Nx species at an atomic level. The combination of atomically dispersed Fe active sites and highly steady hollow substrate affords the Fe ISAs/GHSs outstanding ORR performance with enhanced activity, long‐term stability, and better tolerance to methanol, SO2, and NOx in alkaline medium, outperforming the state‐of‐the‐art commercial Pt/C catalyst. This work highlights the great promises of cost‐effective Fe‐based ISA catalysts in electrocatalysis and provides a versatile strategy for the synthesis of other single metal atom catalysts with superior performance for diverse applications.

While TR4 nuclear receptor plays key roles to promote prostate cancer progression, its roles to alter the progression of clear cell renal cell carcinoma (ccRCC), remains unclear. Here, we demonstrate that TR4 can promote the ccRCC cell vasculogenic mimicry (VM) formation and its associated metastasis via modulating the miR490-3p/vimentin (VIM) signals. Mechanism dissection revealed that TR4 might increase the oncogene VIM expression via decreasing the miR-490-3p expression through direct binding to the TR4-response-elements (TR4REs) on the promoter region of miR-490-3p, which might then directly target the 3' UTR of VIM-mRNA to increase its protein expression. Preclinical studies using the in vivo mouse model with xenografted RCC Caki-1 cells into the sub-renal capsule of nude mice also found that TR4 could promote the ccRCC VM and its associated metastasis via modulating the miR490-3p/VIM signals. Together, results from preclinical studies using multiple RCC cell lines and the in vivo mouse model all conclude that TR4 may play a key role to promote ccRCC VM formation and metastasis and targeting the newly identified TR4/miR-490-3p/VIM signals with small molecules may help us to develop a new therapeutic approach to better suppress the ccRCC metastasis.