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Low density, high stability and strong dielectric loss capacity endow carbon-based nanocomposites with superb microwave dissipation performances. Different from grapheme or carbon nanotubes, the graphitization degrees of carbon-based composites derived from the organic precursor pyrolysis can be accurately regulated by controlling the carbonization temperature. As such, their electromagnetic properties can be easily tuned. In this work, we report the preparation of TiO2/Co/Carbon nanofibers (CNFs) through a combined approach of electrospun and carbonization at different temperatures. The nanofibers with an average diameter of 300 nm were coated by a dense layer of TiO2 and embedded by Co/CoO nanoparticles. The performance evaluation indicated the composite obtained at 700 °C exhibits remarkably strong absorption of −63.2 dB at 9.8 GHz and wide effective absorption bandwidth of 6.4 GHz with a pretty low filling rate of 15 wt%. Further analysis on the electromagnetic behaviors shows that the composite possesses regulable impedance matching characteristic and absorption performances, implying the huge application potential under various demand conditions.

Broadband absorbers derived from metal–organic frameworks are highly desirable in the electromagnetic (EM) wave absorption field. Herein, a strategy for cobalt-decorated porous ZrO2/C hybrid octahe...

In this work, we report the synthesis of porous flower-like Co/MnO composite microspheres assembled by plentiful lamellae for microwave absorption applications. Electron microscopy observations indicated that, in the composites, Co nanoparticles with the size of 20–30 nm are uniformly distributed in the MnO matrix. We investigated the electromagnetic (EM) wave absorption properties of the Co/MnO composites with different Co proportions. When the molar ratio between Co and MnO is 2:1, the best electromagnetic wave absorption performance is achieved. Notably, the optimal reflection loss value reaches −64.2 dB at 10.9 GHz corresponding to the thickness of 2.3 mm, and the effective absorption bandwidth (RL < −10 dB) is up to 6.0 GHz with the thickness of 2.1 mm. The prominent absorption performance of the as-prepared Co/MnO composites mainly arises from the superior impedance matching behavior and strong attenuation capacity as a consequence of the synergistic effect between Co and MnO nanoparticles as well a...

Significance Three-dimensional refinement is a critical component of cryo-EM single-particle reconstruction. In this paper, we report the development of a computational method, OPUS-SSRI, and its application to seven real cryo-EM datasets. Our data clearly demonstrated that OPUS-SSRI can improve the final resolutions and structural details in cryo-EM single-particle analysis., In this paper, we present a refinement method for cryo-electron microscopy (cryo-EM) single-particle reconstruction, termed as OPUS-SSRI (Sparseness and Smoothness Regularized Imaging). In OPUS-SSRI, spatially varying sparseness and smoothness priors are incorporated to improve the regularity of electron density map, and a type of real space penalty function is designed. Moreover, we define the back-projection step as a local kernel regression and propose a first-order method to solve the resulting optimization problem. On the seven cryo-EM datasets that we tested, the average improvement in resolution by OPUS-SSRI over that from RELION 3.0, the commonly used image-processing software for single-particle cryo-EM, was 0.64 Å, with the largest improvement being 1.25 Å. We expect OPUS-SSRI to be an invaluable tool to the broad field of cryo-EM single-particle analysis. The implementation of OPUS-SSRI can be found at https://github.com/alncat/cryoem.

In this paper, we report the facile synthesis of CoNi/C nanocomposites derived from bimetallic metal organic frameworks for electromagnetic wave absorption applications. The effects of carbonation temperature on the phase structure, morphology and microwave absorption properties of the derived nanocomposites were thoroughly studied. Micro-structure characterization results indicated that the obtained CoNi/C composites are composed of numerous fine particles with the size of 20 nm, and in the composites, Ni, Co, and C elements are uniformly distributed. Electromagnetic wave absorption property evaluation showed that CoNi/C obtained at 650 °C outperformed those samples prepared at 500, 800 or 950 °C. The minimum reflection loss (RL) of −74.7 dB could be achieved with a thickness of 1.8 mm at 15.6 GHz. The effective absorption bandwidth (RL ≤ −10 dB) ranged from 2.9 GHz to 18 GHz. This study shows that these porous Co–Ni/C nanocomposites derived from MOFs are attractive candidates as electromagnetic (EM) wave absorbers due to the combined advantages of excellent impedance matching and strong interfacial loss between metallic NPs and porous carbon composites.

In this work, hollow ZnO/Co hybrid nanotubes are prepared by electrospinning followed by calcination and hydrogen reduction process for electromagnetic wave absorption. The texture and electromagnetic wave absorption performance of ZnO/Co hybrid nanotubes with different Co contents are thoroughly investigated. Among the studied hybrid nanotubes, ZnO/Co hybrid nanotubes with the same molar concentrations exhibit superb electromagnetic wave absorbing property. The maximum reflection loss reaches −68.4 dB at 11.4 GHz with a matching thickness of 3.0 mm and the maximum effective absorption (reflection loss ≤ −10 dB) bandwidth is up to 5.9 GHz (9.5–15.4 GHz) with a matching thickness of 2.6 mm. The superior property could be attributed to the favored impedance matching performance and various loss pathways including natural resonance, interfacial polarizations, dipole polarization, and conductive loss. The unique three-dimensional network structure formed by nanotubes further contributes to the loss performanc...

Directed co-assembly of binary nanoparticles (NPs) into one-dimensional copolymer-like chains is fascinating but challenging in the realm of material science. While many strategies have been developed to induce the polymerization of NPs, it remains a grand challenge to produce colloidal copolymers with widely tailored compositions and precisely controlled architectures. Herein we report a robust colloidal polymerization strategy, which enables the growth of sophisticated NP chains with elaborately designed structures. By quantifying NP assembly statistics and kinetics, we establish that the linear assembly of colloidal NPs, with the assistance of PbSO4 clusters, follows a step-growth polymerization mechanism, and on the basis of this, we design and fabricate NP chains structurally analogous to random, block, and alternating copolymers, respectively. Our studies offer mechanistic insights into cluster-mediated colloidal polymerization, paving the way toward the rational synthesis of colloidal copolymers with quantitatively predicted architectures and functionalities.

Broadband absorbers derived from metal-organic frameworks are highly desirable in the electromagnetic (EM) wave absorption field. Herein, a strategy for cobalt-decorated porous ZrO

Discretely sized semiconductor clusters have attracted considerable attention due to their intriguing optical properties and self-assembly behaviors. While lead halide perovskite nanostructures have been recently intensively explored, few studies have addressed perovskite clusters and their self-assembled superstructures. Here, we report the room-temperature synthesis of sub-2 nm CsPbBr3 clusters and present strong evidence that these ultrasmall perovskite species, obtained under a wide range of reaction conditions, possess a specific size, with optical properties and self-assembly characteristics resembling those of well-known II–VI semiconductor magic-sized clusters. Unlike conventional CsPbBr3 nanocrystals, the as-synthesized CsPbBr3 nanoclusters spontaneously self-assemble into a hexagonally packed columnar mesophase in solution, which can be further converted to single-crystalline CsPbBr3 quantum nanoribbons with bright deep-blue emission at room temperature. Such a conversion of CsPbBr3 nanoclusters to nanoribbons is found to be driven by a ligand-destabilization-induced crystallization and mesophase transition process. Our study will facilitate the investigation of perovskite nanoclusters and offer new possibilities in the low-temperature synthesis of anisotropic perovskite nanostructures.

Fe3O4 has a broad application prospect in electrode materials of supercapacitors due to its high theoretical specific capacitance, low cost, and environmental friendliness. However, its easy agglomeration property and low charge/discharge cycle stability limit its further application. In order to overcome these issues, the preparation conditions for Fe3O4 nanoparticles with high specific capacitance were optimized. Then the Fe3O4 was used as the feedstock to prepare the Fe3O4/graphene nanocomposites using solvothermal method for the in-situ reduction of graphene oxide and the combination of Fe3O4 nanoparticles with graphene. The Fe3O4 nanoparticles, graphene oxides and Fe3O4/graphene nanocomposites were characterized by X-ray diffraction (XRD), N2 adsorption, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The capacitance and stability of these samples were obtained from charge/discharge curves and cyclic voltammograms. The results show that during preparation process, Fe3+ ions could combine with the O-containing functional groups on the surface of graphene oxide to form Fe3O4 nanoparticles, and the graphene oxide could be in-situ reduced to form graphene simultaneously. This could effectively prevent aggregation of Fe3O4 and stacking of graphene as electrode materials. Moreover, the optimal conditions for preparing Fe3O4/graphene nanocomposites (BF24G60) are 60% of graphene theoretical percentage in Fe3O4/graphene nanocomposites, 205 °C of preparation temperature, and 24 h of reaction time. For the BF24G60 sample, it has excellent cycle stability (93% after 500 cycles) and specific capacitance (300 F/g at 0.4 A/g), which is higher than that of the single graphene (77 F/g) and Fe3O4 nanoparticles (222 F/g).

Discretely sized semiconductor clusters have attracted considerable attention due to their intriguing optical properties and self-assembly behaviors. While lead halide perovskite nanostructures have been recently intensively explored, few studies have addressed perovskite clusters and their self-assembled superstructures. Here, we report the room-temperature synthesis of sub-2 nm CsPbBr

Investigating the correlation between the electronic structure of indium oxide materials with oxygen vacancy defects and their sensing property to nitrogen dioxide is important for future development of high-efficient sensing materials. For the first time, the defective structure of porous In2O3 nanospheres was introduced in a two-zone tube furnace using metallic Al as reducing agent. Texture characterizations show that In2O3 and In2O3-x are porous nanospheres assembled by small particles with the size of ca. 10–20 nm. The surface oxygen vacancy defects and electronic structure of samples were characterized by X-ray power diffraction, X-ray photoelectron spectroscopy, electron paramagnetic resonance, photoluminescence, ultraviolet-visible spectrophotometer and Hall analysis, and the sensing performance of samples to NO2 gas was evaluated. The results display that the porous In2O3-x nanospheres prepared at the reducing temperature of 300 °C (Vo-In2O3-300) exhibits improved response of 130 to 3 ppm NO2 at 80 °C, which is almost 2.5-folds as high as the response (55) of the porous In2O3 nanospheres. The sensing mechanism study carried out using DFT indicates that oxygen vacancies on the surface of In2O3 as donor level optimize the electron structure and electrical properties of materials, such as supplying more free-electrons in the conduction band, narrowing the band gap and improving the mobility of electrons, which result in the low energy barrier for the adsorption of NO2 molecules on the surface and in turn enhance the gas-sensing performance of In2O3. Therefore, this work can provide some instructive thoughts for constructing In2O3-based sensing materials for high-efficient nitrogen dioxide detection.

Carbon materials are widely used for electromagnetic wave absorption. However, to find out a more rational approach to improve the electromagnetic (EM) wave absorption performance is still worthy of attention. In this work, the carbon nanofibers (CNFs) decorated by titanium oxide and metallic cobalt (TiO2/Co/CNFs) were synthesized by electrospinning and carbonizing process, and the microtopography, structure, composition and magnetic properties of which were characterized in detail. The TiO2/Co/CNFs nanocomposites acquired optimal electromagnetism parameters and exhibited superb electromagnetic wave absorption property. The results showed that the minimum reflection loss (RL) values of TiO2/Co/CNFs samples with different filling ratios are less than −50 dB with the matching thickness less than 3.5 mm. The maximum effective absorption bandwidths (RL ≤ −10 dB) exceed 5.2 GHz. Besides, the strong absorption frequency range can be regulated by adjusting filling ratios to broaden the application. This work provides a unique approach to design carbon nanofibers loaded with oxides or metals, and the TiO2/Co/CNFs nanocomposites could be an ideal candidate as light-weight and high-efficiency electromagnetic wave absorption materials and the tunable absorption property portend the potential application in various environmental conditions.

The conversion of CO2 to valuable substances (methane, methanol, formic acid, etc.) by photocatalytic reduction has important significance for both the sustainable energy supply and clean environment technologies. This review systematically summarized recent progress in this field and pointed out the current challenges of photocatalytic CO2 reduction while using metal-organic frameworks (MOFs)-based materials. Firstly, we described the unique advantages of MOFs based materials for photocatalytic reduction of CO2 and its capacity to solve the existing problems. Subsequently, the latest research progress in photocatalytic CO2 reduction has been documented in detail. The catalytic reaction process, conversion efficiency, as well as the product selectivity of photocatalytic CO2 reduction while using MOFs based materials are thoroughly discussed. Specifically, in this review paper, we provide the catalytic mechanism of CO2 reduction with the aid of electronic structure investigations. Finally, the future development trend and prospect of photocatalytic CO2 reduction are anticipated.

All-inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) nanocrystals (NCs) are emerging as an important class of semiconductor materials with superior photophysical properties and wide potential applications in optoelectronic devices. So far, only a few studies have been conducted to control the shape and geometry of CsPbX3 NCs. Here we report a general approach to directly synthesize two-dimensional (2D) CsPbX3 perovskite and mixed perovskite nanosheets with uniform and ultrathin thicknesses down to a few monolayers. The key to the high-yield synthesis of perovskite nanosheets is the development of a new Cs-oleate precursor. The as-synthesized CsPbX3 nanosheets exhibit bright photoluminescence with broad wavelength tunability by composition modulation. The excellent optoelectronic properties of CsPbX3 nanosheets combined with their unique 2D geometry and large lateral dimensions make them ideal building blocks for building functional devices. To demonstrate their potential applications in optoelectronics, photodetectors based on CsPbBr3 nanosheets are fabricated, which exhibit high on/off ratios with a fast response time.

Self-assembly of nanocrystal (NC) building blocks into mesoscopic superstructures with well-defined symmetry and geometry is essential for creating new materials with rationally designed properties. Despite the tremendous progress in colloidal assembly, it remains a fundamental challenge to assemble isotropic spherical NCs into one-dimensional (1D) ordered superstructures. Here, we report a new and general methodology that utilizes molecular clusters to induce the anisotropic assembly of NCs in solution, yielding polymer-like, single-NC-wide linear chains comprising as many as ∼1000 close-packed NCs. This cluster-assisted assembly process is applicable to various metallic, semiconductor, and magnetic NCs of different sizes and shapes. Mechanistic investigation reveals that the solvent-induced association of clusters plays a key role in driving the anisotropic assembly of NCs. Our work opens a solution-based route for linearly assembling NCs and represents an important step toward the bottom-up construction of 1D ordered NC superstructures.

Development and cultivation of undergraduate party members concern the general situation of socialist construction with Chinese characteristics, and great party construction project. Through the analysis of the advantages and disadvantages of college student party members development in our country, putting forward the corresponding improvement, in order to enhance the effectiveness of development and cultivate the university student party members. Development and Cultivation Status of Chinese Undergraduate Party Members Advantages Development and Cultivation Mode of Chinese Undergraduate Party Members Active Implementation of Ideological and Political Education for Party Members. In the new period of reform and opening up, Chinese Communist Party proposed a series of new views and new measures to enhance ideological and political education. These lay theoretical foundation for quality assurance of undergraduate party members and for development of undergraduate party members. Meanwhile, they make development of undergraduate party members thrive. Ideological education work is beneficial for undergraduate party members to establish communist lofty ideals inwardly and offers powerful spiritual strength for quality assurance mechanism of undergraduate party members. In 1990, the Central Committee of the Communist Party of China issued Notice on Enhancing Party Building in Institutions of Higher Education. Since then, annual nationwide university party building conference has been held as scheduled to discuss current situation and prospect of university student party building, in the hope of keeping improving the quality of undergraduate party members. Effective Construction of Party Member Quality Assurance Mechanism. Quality assurance mechanism construction for undergraduate party members has achieved significant progress. “It is necessary to carry out ideological and political education for undergraduates, well develop undergraduate party members and gather excellent undergraduates in party member team”. This is the guiding ideology of development of undergraduate party members. The quality of undergraduate party members decides the success or failure of socialist construction. In order to guarantee the quality of undergraduate party members, Chinese Communist Party continuously formulates measures and issues documents. Chinese Communist Party hopes to guarantee the quality of undergraduate party members through system construction. As undergraduate party building work goes deep, the researches on quality assurance mechanism of undergraduate party members increase gradually. Aiming at the International Conference on Humanities and Social Science (HSS 2016) © 2016. The authors Published by Atlantis Press 779 problems existing in development of undergraduate party members, university party building workers keep on studying and exploring quality assurance mechanism and have obtained preliminary achievements. Shortcomings of Development and Cultivation Mode of Chinese Undergraduate Party Members Working Procedure Lacks Norms. During development of undergraduate party members, some party workers often fail to work according to rules and regulations in order to save time, fail to arrange trainers for activists of party membership application and fail to cultivate and fill in training investigation registration sheet one year in advance as required. Instead, they let the activists of party membership application self-develop, self-cultivate and self-grow. Only when they consider the activists of party membership application basically comply with the conditions of a probationary party member will they hurry to supplement relevant teaching materials, and arrange training time. In short, they cannot carefully execute relevant policy regulations. Since working system and working procedure lack norms, many potential applicants are lost in this process, or probationary party members who scrape in party member team fail to reach the due effect, because they are not well trained. Some student party members fail to fully cultivate party spirit. In recent years, the vast majority of undergraduate party members can consciously maintain the image of the party, stick to and publicize path and policy of the party, actively boycott impacts of various bad phenomena and consciousness and show brisk vitality and vigor. However, some student party members fail to fully cultivate party spirit, pay no attention to maintaining the image of the party, relax and even give up political study after joining the party, and weaken party member awareness and the concept of party spirit. Meanwhile, their goal pursuit weakens, and they lose their enterprise and sense of responsibility. Suggestions on Improving Development and Cultivation of Chinese Undergraduate Party members Cultivation of undergraduate party members is based on certain political goal and aims to reach the purpose of party spirit culture and political accomplishment under effective system guarantee through selection, recommendation, party school training, brand training. In such way, they can own the awareness of serving the people wholeheartedly and firm communistic belief. Thus, scientific guarantee mechanism should be established to ensure cultivation quality of student party members. To Perfect Party Member Selection Mechanism and Grasp the Quality of “entry” Selection and recommendation are the preconditions of cultivation quality of student party members, and also the key to “selecting good seeds”. Party workers must control the “entry” for party member development, and adhere to comprehensive quality in political accomplishment, organizational discipline, learning ability and mass base as assessment criterion. In terms of development procedure, the procedure of each link should be controlled strictly, including recommendation, cultivation and education of activists of party membership application; political review and publicity of development objects; acceptance, education, investigation, publicity and regularization of probationary party members. The principle of “developing the party member whenever he (she) becomes mature” should be adhered to. In the aspect of development