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Determine the Complete Configuration of Single-Walled Carbon Nanotubes by One Photograph of Transmission Electron Microscopy
No full textDeveloping a convenient method to determine the complete structure of single-walled carbon nanotubes (SWNTs) is important to achieve the fully controlled growth of this nanomaterial. However, approaches that can identify handedness at the atomic level with simple equipment, operation, and data analysis are still lacking. Here, the SWNTs/graphene (Gr) vertical heterostructures are artificially constructed with aligned interfaces to realize the lattice interpretation of SWNT upper and lower walls separately by only one transmission electron microscopy image, thus transforming the 3D handedness information to projected 2D space. Gr displays prominent out-of-plane deformation at the interface, promoting the energetic advantage for the aligned interface construction. The interfacial alignment between the SWNT and Gr shows no obvious dependence on either the helical angle or diameter of SWNTs. The half-wrapping of SWNTs by deformed Gr also triggers diversified alterations in electronic structures based on theoretical calculations. 27 specimens with SWNTs prepared by two disparate methods are examined, implying equal handedness distribution in the randomly aligned SWNTs grown on quartz and potential handedness enrichment in horizontal SWNT arrays grown on a-sapphire. This work provides a simple strategy for chiral discrimination and lays a characterization foundation for handedness-selective growth of nanomaterials
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No full textHalide-chalcogenide hetero-structure for efficient and stable perovskite solar cells
No full textOrganic-inorganic halide perovskite solar cells (PSCs) have experienced rapid growth in power conversion ef-ficiencies (PCEs), however, their commercialization is limited by their inherent poor long-term stability. Mixed halide and chalcogenide is a good pathway to fabricate highly efficient and stable solar cells. Here, we con-structed halide-chalcogenide hetero-structure in PSCs by incorporating Bi2S3 quantum dots (QDs) into 2,2 ',7,7 '- tetrakis-(N,N-di-4-methoxyphenylamino)-9,9 '-spirobifluorene (spiro-OMeTAD). The construction of halide-chalcogenide hetero-structure optimizes the energy level matching between spiro-OMeTAD and perovskite, in-hibits the decomposition of alpha-phase FAPbI3 and the formation of delta-phase FAPbI3, increases the hole mobility of spiro-OMeTAD, reduces the defect density, and passivates the defect states. The solar cells with halide-chalcogenide hetero-structure prepared by 0.5 mg/mL Bi2S3 QDs exhibited the highest PCE of 23.31% at stan-dard air mass 1.5 global with enhanced humidity stability. This work provides a perspective on the introduction of halide-chalcogenide hetero-structure to enhance the stability of PSCs
Bioprinting of pre-vascularized constructs for enhanced in vivo neo-vascularization
No full textPre-vascularization has been receiving significant attention for developing implantable engineered 3D tissues. While various pre-vascularization techniques have been developed to improve graft vascularization, the effect of pre-vascularized patterns on in vivo neo-vessel formation has not been studied. In this study, we developed a functional pre-vascularized construct that significantly promotes graft vascularization and conducted in vivo evaluations of the micro-vascular patterns (??VP) in various printed designs. ??VP formation, composed of high-density capillaries, was induced by the co-printing of endothelial cells (EC) and adipose-derived stem cells (ADSC). We implanted the printed constructs with various ??VP designs into a murine femoral arteriovenous bundle model and evaluated graft vascularization via 3D visualization and immune-histological analysis of the neo-vessels. The ??VP-distal group (??VP located away from the host vessel) showed approximately 2-fold improved neo-vascularization compared to the ??VP-proximal group (??VP located near the host vessel). Additionally, we confirmed that the ??VP-distal group can generate the angiogenic factor gradient spatial environment for graft vascularization via computational simulations. Based on these results, the ADSC mono pattern (AMP), which secretes four times higher angiogenic factors than ??VP, was added to the ??VP + AMP group design. The ??VP + AMP group showed approximately 1.5- and 1.9-fold higher total sprouted neo-vessel volume than the ??VP only and AMP only groups, respectively. In immunohistochemical staining analysis, the ??VP + AMP group showed 2-fold improved density and diameter of the matured neo-vessels. To summarize, these findings demonstrate graft vascularization accelerated due to design optimization of our pre-vascularized constructs. We believe that the developed pre-vascularization printing technique will facilitate new possibilities for the upscaling of implantable engineered tissues/organs
Porous zeolitic imidazolate frameworks assembled with highly-flattened tetrahedral copper(ii) centres and 2-nitroimidazolates
No full textCu(ii)-based zeolitic imidazolates (Cu-ZIFs), Cu-ZIF-gis and -rho, formulated as Cu(nIm)(2) (nIm = 2-nitroimidazolate) have highly-flattened tetrahedral coordination geometry. Cu-ZIF-gis has 2.4 & ANGS; cylindrical pores that can adsorb H-2 gas, and Cu-ZIF-rho has 19.8 & ANGS; cages with a BET surface area of 1320 m(2) g(-1)
A High Conversion Ratio DC-DC Boost Converter with Continuous Output Current Using Dual-Current Flows
No full textRecently, the demand for small, low-cost electronics has increased the use of cost-effective tiny inductors in power-management ICs (PMICs). However, the conduction loss caused by the parasitic DC resistance (RDCR) of a small inductor leads to low efficiency, which reduces the battery usage time and may also cause thermal problems in mobile devices. In particular, these issues become critical when a conventional boost converter (CBC) is used to achieve high-output voltage due to the large inductor current. In addition, as the output voltage increases, a number of issues become more serious, such as large output voltage ripple, conversion-ratio limit, and overlap loss. To solve these issues, this paper proposed a high-voltage boost converter with dual-current flows (HVDF). The proposed HVDF can achieve a higher efficiency than a CBC by reducing the total conduction loss in heavy load current conditions with a small inductor. Moreover, because in the HVDF, the current delivered to the output becomes continuous, unlike in the CBC with its discontinuous output delivery current, the output voltage ripple can be significantly reduced. Also, the conversion gain of the HVDF is less sensitive to RDCR than that of the CBC. To further increase the conversion gain, a time-interleaved charge pump can be connected in series with the HVDF (HVDFCP) to achieve higher output voltage beyond the limit of the conversion gain in the HVDF while maintaining the advantages of a low inductor current and small output voltage ripple. Simulations using PSIM were performed along with a detailed numerical analysis of the conduction losses in the proposed structures. The simulation results were discussed and compared with those of the conventional structures