Abstract The tailoring of active sites is closely related to the substrate. Dual‐atom catalysts (DACs) have been achieved on doped carbon, oxides, and 2D materials, but are rarely reported on metals, due to the challenges of sintering and alloying using metal as the host. Herein, an innovative approach to anchor isolated single atoms as dual‐atomic‐site alloy (DASA) through two‐step pyrolysis of porous structure is proposed. Firstly, the role of Zn and Co in generating pores during the pyrolysis of zeolite imidazolate framework (ZIFs) is revealed, and a hierarchical porous structure with self‐supported Co particles is achieved by the first‐step pyrolysis. Diffusion‐controlled reduction of precursors containing target metals is then allowed through hierarchical structures by second‐step pyrolysis, so to address the challenge of sintering and alloying at pyrolysis of high temperatures. The approach is demonstrated by synthesizing Ir 1 Ni 1 @Co/N‐C DASA, with outstanding bifunctional oxygen reduction/evolution reaction (ORR/OER) performance in both acidic and alkaline media, which is rarely reported. The density functional theory (DFT) calculations represent that adsorption‐free energies of intermediates OH and O are regulated to nearly 0 eV by Ir 1 and Ni 1 on Co. This work demonstrates a new path of constructing DASA using the designed porous structure, inspiring catalysts design in a related field.
Organic–inorganic hybrid perovskite materials have had remarkable success in photovoltaics due to their superior optoelectronic properties and compositional abundance. Most advances focus on the improvement of the heterojunction, in which nonperovskite materials are employed at the pertaining interfaces. Herein we demonstrate the modification of perovskite absorber by incorporation of CsPbBr3 nanocrystals, which is congeneric to the absorber in terms of crystal structure and stoichiometry. It led to significant enhancement in photovoltaic performance in the corresponding devices, which was mainly attributed to the improved carrier dynamics over the resultant heterojunction. Therefore, a different strategy is suggested for further improvement of the perovskite heterojunction by using congeneric materials.
There remain significant challenges in developing fast-charging materials for lithium-ion batteries (LIBs) due to sluggish ion diffusion kinetics and unfavorable electrolyte mass transportation in battery electrodes. In this work, a mesoporous single-crystalline lithium titanate (MSC-LTO) microrod that can realize exceptional fast charge/discharge performance and excellent long-term stability in LIBs is reported. The MSC-LTO microrods are featured with a single-crystalline structure and interconnected pores inside the entire single-crystalline body. These features not only shorten the lithium-ion diffusion distance but also allow for the penetration of electrolytes into the single-crystalline interior during battery cycling. Hence, the MSC-LTO microrods exhibit unprecedentedly high rate capability, achieving a specific discharge capacity of ≈174 mAh g-1 at 10 C, which is very close to its theoretical capacity, and ≈169 mAh g-1 at 50 C. More importantly, the porous single-crystalline microrods greatly mitigate the structure degradation during a long-term cycling test, offering ≈92% of the initial capacity after 10 000 cycles at 20 C. This work presents a novel strategy to engineer porous single-crystalline materials and paves a new venue for developing fast-charging materials for LIBs.
Carbon nanotubes (CNTs) have been proposed as one of the most promising nanomaterials to be used in biomedicine for their applications in drug/gene delivery as well as biomedical imaging. The present study developed radio-labeled iron oxide decorated multi-walled CNTs (MWNT) as dual magnetic resonance (MR) and single photon emission computed tomography (SPECT) imaging agents. Hybrids containing different amounts of iron oxide were synthesized by in situ generation. Physicochemical characterisations revealed the presence of superparamagnetic iron oxide nanoparticles (SPION) granted the magnetic properties of the hybrids. Further comprehensive examinations including high resolution transmission electron microscopy (HRTEM), fast Fourier transform simulations (FFT), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) assured the conformation of prepared SPION as γ-Fe2O3. High r2 relaxivities were obtained in both phantom and in vivo MRI compared to the clinically approved SPION Endorem®. The hybrids were successfully radio-labeled with technetium-99m through a functionalized bisphosphonate and enabled SPECT/CT imaging and γ-scintigraphy to quantitatively analyze the biodistribution in mice. No abnormality was found by histological examination and the presence of SPION and MWNT were identified by Perls stain and Neutral Red stain, respectively. TEM images of liver and spleen tissues showed the co-localization of SPION and MWNT within the same intracellular vesicles, indicating the in vivo stability of the hybrids after intravenous injection. The results demonstrated the capability of the present SPION-MWNT hybrids as dual MRI and SPECT contrast agents for in vivo use.
Abstract Moiré fringe, originated from the beating of two sets of lattices, is a commonly observed phenomenon in physics, optics, and materials science. Recently, a new method of creating moiré fringe via scanning transmission electron microscopy (STEM) has been developed to image materials’ structures at a large field of view. Moreover, this method shows great advantages in studying atomic structures of beam sensitive materials by significantly reduced electron dose. Here, the development of the STEM moiré fringe (STEM‐MF) method is reviewed. The authors first introduce the theory of STEM‐MF and then discuss the advances of this technique in combination with geometric phase analysis, annular bright field imaging, energy dispersive X‐ray spectroscopy, and electron energy loss spectroscopy. Applications of STEM‐MF on strain, defects, 2D materials, and beam‐sensitive materials are further summarized. Finally, the authors′ perspectives on the future directions of STEM‐MF are presented.
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