Graphene is the most broadly discussed and studied two‐dimensional material because of its preeminent physical, mechanical, optical, and thermal properties. Until now, metal‐catalyzed chemical vapor ...deposition (CVD) has been widely employed for the scalable production of high‐quality graphene. However, in order to incorporate the graphene into electronic devices, a transfer process from metal substrates to targeted substrates is inevitable. This process usually results in contamination, wrinkling, and breakage of graphene samples ‐ undesirable in graphene‐based technology and not compatible with industrial production. Therefore, direct graphene growth on desired semiconductor and dielectric substrates is considered as an effective alternative. Over the past years, there have been intensive investigations to realize direct graphene growth using CVD methods without the catalytic role of metals. Owing to the low catalytic activity of non‐metal substrates for carbon precursor decomposition and graphene growth, several strategies have been designed to facilitate and engineer graphene fabrication on semiconductors and insulators. Here, those developed strategies for direct CVD graphene growth on semiconductors and dielectrics for transfer‐free fabrication of electronic devices are reviewed. By employing these methods, various graphene‐related structures can be directly prepared on desired substrates and exhibit excellent performance, providing versatile routes for varied graphene‐based materials fabrication.
Recently proposed strategies for direct graphene growth on semiconductors and dielectrics via chemical vapor deposition for transfer‐free device fabrication are reviewed. The growth mechanisms in the absence of a metal catalyst are discussed and direct transfer‐free applications with pristine properties are presented. This facile and versatile graphene preparation technology provides a feasible route to promote practical graphene industrialization.
Lithium batteries are currently the most popular and promising energy storage system, but the current lithium battery technology can no longer meet people's demand for high energy density devices. ...Increasing the charge cutoff voltage of a lithium battery can greatly increase its energy density. However, as the voltage increases, a series of unfavorable factors emerges in the system, causing the rapid failure of lithium batteries. To overcome these problems and extend the life of high‐voltage lithium batteries, electrolyte modification strategies have been widely adopted. Under this content, this review first introduces the degradation mechanism of lithium batteries under high cutoff voltage, and then presents an overview of the recent progress in the modification of high‐voltage lithium batteries using electrolyte modification strategies. Finally, the future direction of high‐voltage lithium battery electrolytes is also proposed.
High‐voltage lithium batteries have some challenges, e.g., electrolyte decomposition, parasitic oxidation reaction, transition metal dissolution and surface cracks and phase changes in regards with cathodes. In this review, we will overview the recent progress in the modification of high‐voltage lithium batteries using electrolyte modification strategies, and propose future research directions.
The ability to pick up a single carbon nanotube (CNT) from a bundle of CNTs is of great importance for nanodevice fabrication. In this study, we propose a nanorobotic manipulation system allowing ...automated pick-up of CNTs based on visual feedback. We used histogram thresholding for automatic binarization, and it clearly distinguished CNTs from the substrate and other impurities under various image brightnesses and contrasts. Furthermore, the CNT tip was successfully extracted by making use of the geometrical characteristics of the CNT. We designed a segment detection method to separate the CNT and atomic force microscope cantilever during overlapping. The contact detection between them was identified by evaluating the linearity of the fitted CNT curve. We also further analyzed the specific properties of point contact and linear contact, significantly improving the success rate of pick-up. Finally, the experimental results show that our method is highly promising for realistic fabrication of nanodevices.
CdS nanoparticles have been synthesized and stabilized on unique bacterial cellulose (BC) nanofibers in situ. The obtained nanocomposite material have been characterized by scanning electron ...microscopy (SEM), X-ray diffraction (XRD), fourier transformed infrared (FTIR), thermogravimetric analysis (TGA), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. The results indicated that CdS nanoparticles of about 30
nm diameter deposited on BC nanofibres are well-dispersed in the BC nanofibre-network and the uniform spherical CdS nanoparticles are comprised of nano-sized CdS crystal. Moreover, the crystallite sizes of CdS crystals are about 8
nm. The nanocomposites would have potential application as photocatalyst, novel luminescence and photoelectron transfer devices.
► Zinc oxide nanoparticles were successfully synthesized using BC as a template. ► The synthesized method is very simple and green. ► BC/ZnO shows good mechanical properties and high photocatalytic ...activity.
Zinc oxide nanoparticles have been successfully synthesized through a facile polyol method using bacterial cellulose (BC) as a template. BC membrane was used as a host matrix to introduce quantitatively Zn2+ ions and then as nanoreactors to fabricate ZnO nanoparticles by hydrolysis of zinc acetate in a polyol medium. The influence of the concentration of zinc acetate and hydrolytic time on the morphologies and size of ZnO nanoparticles were investigated. The results indicated that the uniform spherical ZnO nanoparticles were incorporated into BC fibers. The resulting nanocomposites show good mechanical properties and high photocatalytic activity in the degradation of methyl orange.
We synthesize the porous sulfur-doped porous hard carbon by templated method, which exhibits a long cycling life with ∼191 mAh/g after 300 cycles at 1 A/g, and an excellent rate capability with ∼100 ...mAh/g at 5 A/g for potassium storage.
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Hard carbon is promising anode for potassium-ion batteries (PIBs), however, the poor rate capability hinders its development as potential anode. To address this question, we design a sulfur-doped porous hard carbon (S-HC) for PIBs through the combination of structural design and composition adjustment. The as-designed S-HC exhibits a long cycling life with ∼191 mA h/g after 300 cycles at 1 A/g, and an excellent rate capability with ∼100 mA h/g at 5 A/g, which was attributed to its structural characteristics and compositions. The S-HC demonstrates to be promising anode in the future.
Abstract
With the ability to focus and rotate the acoustic field in a given region while keeping the outside region unchanged, the acoustic concentrator and rotator has been developed for the ...versatile manipulations of acoustic wave. In this letter, we report the design of acoustic concentrator and rotator facilitated by linear coordinate transformation. Compared with the previous ones that have inhomogeneous parameter distributions, the designed devices are composed of several parts with homogeneous parameters, which can be achieved with the help of few homogeneous layered structures. Simulations are also performed to verify the functions of the designed device. The proposed acoustic concentrators and rotators would be useful in numerous applications such as acoustic sensing and communication.
The morphology of bacterial cellulose (BC) is quite different in the static and agitated culture. In this study, the snow-like cellulose assemblies are synthesized in the agitated culture and the ...fibrous and rice-like cellulose assemblies are produced in the presence of multi-walled carbon nanotubes (MWNTs) in agitated culture. The microstructure of BC synthesized in agitated culture are investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD). The analysis results reveal that the crystallinity index, crystallite size and cellulose I
α content for cellulose synthesized in agitated culture are lower than those for cellulose synthesized in static culture. The agitating stress influences the aggregation and crystallization of sub-elementary fibrils, further changes the intramolecular and intermolecular hydrogen bond patterns. The stress makes greater effect on BC synthesized in the absence of MWNTs than in the presence of MWNTs.
Carboxymethylated-bacterial cellulose (CM-BC) was synthesized by
Acetobacter xylinum by adding water-soluble carboxymethylated cellulose (CMC) in the culture medium. The CM-BC was examined for the ...removal of copper and lead ions from aqueous solution compared with BC. The effects of performance parameters such as pH, adsorbent dose, contact time on copper and lead ion adsorption were analyzed. Both BC and CM-BC show good adsorption performance at optimized pH 4.5. Compared with BC, CM-BC performs better adsorption, with the value of 9.67
mg (copper)/g, 22.56
mg (lead)/g for BC and 12.63
mg (copper)/g, 60.42
mg (lead)/g for CM-BC, respectively. The adsorption rate closely follows pseudo-second-order rate model and the adsorption isotherm data well follows the Langmuir model.
Engineered three-dimensional (3D) microtissues that recapitulate in vivo tissue morphology and microvessel lumens have shown significant potential in drug screening and regenerative medicine. ...Although microfluidic-based techniques have been developed for bottom-up assembly of 3D tissue models, the spatial organization of heterogeneous micromodules into tissue-specific 3D constructs with embedded microvessels remains challenging. Inspired by a hydrodynamic-based classic game which stacks rings in water through the flow, a facile strategy is proposed for effective assembly of heterogeneous hierarchical micromodules with a central hole, into permeable hollow 3D tissue-like constructs through hydrodynamic interaction in a versatile microfluidic chip. The micromodules are fabricated by in situ multi-step photo-crosslinking of cell-laden hydrogels with different mechanical properties to give the high fidelity. With the hydrodynamic interaction derived from the discontinuous circulating flow, the micromodules are spatially organized layer-by-layer to form a 3D construct with a microvessel-like lumen. As an example, a ten-layered liver lobule-like construct containing inner radial-like poly(ethylene glycol) diacrylate (PEGDA) structure with hepatocytes and outer hexagonal gelatin methacrylate (GelMA) structure with endothelial cells are assembled in 2 min. During 10 days of co-culture, cells maintain high viability and proliferated along with the composite lobule-like morphology. The 3D construct owns a central lumen, which allows perfusion culture to promote albumin secretion. We anticipate that this microassembly strategy can be used to fabricate vascularized 3D tissues with various physiological morphologies as alternatives for biomedical research applications.
Microfluidic-based assembly is an attractive approach for the fabrication of 3D tissue models using cell-laden hydrogel microstructures with single mechanical stability. However, native tissues are complex 3D structures with indispensable vessels and multiple mechanical properties, which is still challenging to recreate. This study proposed a novel strategy to fabricate tissue-like 3D constructs with embedded lumen through hydrodynamic interaction using multicellular micromodules with hierarchical mechanical properties. The resultant hollow 3D constructs allow perfusion co-culture to enhance cell activity. This strategy relies on a simple and facile microfluidic chip to fabricate various 3D tissue-like constructs with hierarchical mechanical properties and permeable lumen, which can potentially be used as in vitro perfusion models for biomedical research.
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