Nano

Lithium ion batteries (LIBs) are one of the most promising secondary batteries due to their advantages including long cycle life, high energy density, limited self-discharge, high operating voltage and environmental friendliness. The development of electrode materials is crucial for the further application of LIBs. There are many effective ways to enhance the performance of positive electrode materials of LIBs such as surface coating, ion doping, preparation of composite materials and nanosized materials and so forth. Among them, surface coating is considered to be a promising way to improve the electrochemical performance of LIBs. Surface coating can normally form a physical barrier or a doped surface layer to play favorable roles for the electrode materials, such as hindering side reactions between positive electrode materials and the electrolyte. In this paper, different kinds of surface coating layers will be discussed according to previous research, including carbon materials, metal oxides, metal fluorides, metal phosphates, nonmetal oxides, electrode materials coating layer, hybrid coating layer, polymer and so forth. In addition, the mechanism of these coating materials will be summarized, and the future development will be discussed in this paper.

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, Fe/TiO₂ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the Fe/TiO₂/Al₂O₃ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the Fe/TiO₂ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the Fe/TiO₂/Al₂O₃ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below $-$10dB (90% absorption) over 10.2–14.8GHz, with a thickness of 3.0mm and the minimum value of $-$39.4dB at 11.7GHz.

Flexible strain sensors, as the core member of the family of smart electronic devices, along with reasonable sensing range and sensitivity plus low cost, have rose a huge consumer market and also immense interests in fundamental studies and technological applications, especially in the field of biomimetic robots movement detection and human health condition monitoring. In this paper, we propose a new flexible strain sensor based on thick CVD graphene film and its low-cost fabrication strategy by using the commercial adhesive tape as flexible substrate. The tensile tests in a strain range of $\sim$30% were implemented, and a gage factor of 30 was achieved under high strain condition. The optical microscopic observation with different strains showed the evolution of cracks in graphene film. Together with commonly used platelet overlap theory and percolation network theory for sensor resistance modeling, we established an overlap destructive resistance model to analyze the sensing mechanism of our devices, which fitted the experimental data very well. The finding of difference of fitting parameters in small and large strain ranges revealed the multiple stage feature of graphene crack evolution. The resistance fallback phenomenon due to the viscoelasticity of flexible substrate was analyzed. Our flexible strain sensor with low cost and simple fabrication process exhibits great potential for commercial applications.

Bi metal deposited on Bi₂MoO₆ composite photocatalysts have been successfully synthesized via a simple reduction method at room temperature with using NaBH₄ as the reducing agent. The photocatalytic activity of the composite was evaluated by degradation of rhodamine B (RhB) and bisphenol A (BPA) solution under visible light. The rate constant of Bi/Bi₂MoO₆ composite to RhB is 10.8 times that of Bi₂MoO₆, and the degradation rate constant of BPA is 6.9 times of that of Bi₂MoO₆. Nitrogen absorption–desorption isotherm proved that the increase of specific surface area is one of the reasons for the improvement of photocatalytic degradation activity of Bi/Bi₂MoO₆ composites. The higher charge transfer efficiency of Bi/Bi₂MoO₆ is found through the characterization of the photocurrent and impedance, which are attributed to the surface plasmon resonance (SPR) effect produced by the introduction of the metal Bi monomer in the composite. Free radical capture experiments proved that cavitation is the main active species. Based on the above conclusions, a possible mechanism of photocatalytic degradation is proposed.

Glutathione (GSH), the protective agent and reducing agent, has been widely used to prepare gold nanoclusters (GSH-Au NCs) with stable fluorescence properties and negative charge of the surface. Meanwhile, polyethyleneimine (PEI) was used as the modification agent to synthesize magnetic ferroferric oxide nanoparticles (Fe₃O₄) with fantastic dispersibility and positive charge of the surface. Based on the electrostatic adsorption force, magnetic nano-Fe₃O₄@GSH-Au NCs core–shell microspheres composed of magnetic Fe₃O₄ nanoparticles modified by PEI as the core and GSH-Au NCs as the shell were assembled. The prepared Fe₃O₄@GSH-Au NCs microspheres harbored a uniform size (88.6nm), high magnetization (29.2emu/g) and excellent fluorescence. Due to the coordination bond action between Au atom and sulfhydryl (–SH), amino (–NH₂), carboxyl (–COOH) in sweat, Fe₃O₄@GSH-Au NCs could combine with latent fingerprints. In addition, Fe₃O₄@GSH-Au NCs with good fluorescence and magnetism could detect fingerprints on various objects. Significantly, the powders were not easy to suspend in the air, which avoided the damage to the health of forensic experts and the fingerprints by only powder contacting. Above all, Fe₃O₄@GSH-Au NCs was successfully applied to the latent fingerprint visualization, which has great potential in forensic science.

To improve the high charge carrier recombination rate and low visible light absorption of {001} facets exposed TiO₂ [TiO₂(001)] nanosheets, few-layered MoS₂ nanoparticles were loaded on the surfaces of TiO₂(001) nanosheets by a simple photodeposition method. The photocatalytic activities towards Rhodamine B (RhB) were investigated. The results showed that the MoS₂–TiO₂(001) nanocomposites exhibited much enhanced photocatalytic activities compared with the pure TiO₂(001) nanosheets. At an optimal Mo/Ti molar ratio of 25%, the MoS₂–TiO₂(001) nanocomposites displayed the highest photocatalytic activity, which took only 30min to degrade 50mL of RhB (50mg/L). The active species in the degradation reaction were determined to be h${}^{+}$ and ${}^{•}$OH according to the free radical trapping experiments. The reduced charge carrier recombination rate, enhanced visible light utilization and increased surface areas contributed to the enhanced photocatalytic performances of the 25% MoS₂–TiO₂(001) nanocomposites.

A novel strontium titanate/binary metal sulfide (SrTiO₃/SnCoS₄) heterostructure was synthesized by a simple two-step hydrothermal method. The visible-light-driven photocatalytic performance of SrTiO₃/SnCoS₄ composites was evaluated in the degradation of methyl orange (MO) under visible light irradiation. The photocatalytic performance of SrTiO₃/SnCoS₄-5% is much higher than that of pure SrTiO₃, SnCoS₄, SrTiO₃/SnS₂ and SrTiO₃/CoS₂. The SrTiO₃/SnCoS₄ composite material with 5wt.% of SnCoS₄ showed the highest photocatalytic efficiency for MO degradation, and the degradation rate could reach 95% after 140min irradiation time. The enhanced photocatalytic activity was ascribed to not only the improvement of visible light absorption efficiency, but also the construction of a heterostructure which make it possible to effectively separate photoexcited electrons and holes in the two-phase interface.

In this paper, an electrochemical sensor for epinephrine (EP), a neurotransmitter was developed by anchoring molecularly imprinted polymeric matrix (MIP) on the surface of gold-coated quartz crystal electrode of electrochemical quartz crystal microbalance (EQCM) using starch nanoparticles (Starch NP) — reduced graphene oxide (RGO) nanocomposite as polymeric format for the first time. Use of EP in therapeutic treatment requires proper dose and route of administration. Proper follow-up of neurological disorders and timely diagnosis of them has been found to depend on EP level. The MIP sensor was developed by electrodeposition of starch NP-RGO composite on EQCM electrode in presence of template EP. As the imprinted sites are located on the surface, high specific surface area enables good accessibility and high binding affinity to template molecule. Differential pulse voltammetry (DPV) and piezoelectrogravimmetry were used for monitoring binding/release, rebinding of template to imprinted cavities. MIP-coated EQCM electrode were characterized by contact angle measurements, AFM images, piezoelectric responses including viscoelasticity of imprinted films, and other voltammetric measurements including direct (DPV) and indirect (using a redox probe) measurements. Selectivity was assessed by imprinting factor (IF) as high as 3.26 (DPV) and 3.88 (EQCM). Sensor was rigorously checked for selectivity in presence of other structurally close analogues, real matrix (blood plasma), reproducibility, repeatability, etc. Under optimized conditions, the EQCM-MIP sensor showed linear dynamic ranges (1–10$\mu$M). The limit of detection 40 ppb (DPV) and 290 ppb (EQCM) was achieved without any cross reactivity and matrix effect indicating high sensitivity and selectivity for EP. Hence, an eco-friendly MIP-sensor with high sensitivity and good selectivity was fabricated which could be applied in “real” matrices in a facile manner.

The direct synthesis of metal-organic frameworks (MOFs) with acidic and basic active sites is challenging due to the introduction of functional groups by post-functionalization method often jeopardize the framework integrity. Herein, we report the direct synthesis of acid-base bi-functional MOFs with tuning acid-base strength. Employing modulated hydrothermal (MHT) approach, microporous MOFs named UiO-66-NH₂ was prepared. Through the ring-opening reaction of 1,3-propanesultone with amino group, UiO-66-NH₂-SO₃H-type catalysts can be obtained. The synthesized catalysts were well characterized and their catalytic performances were evaluated in one-pot glucose to 5-HMF conversion. Results revealed the acid-base bi-functional catalyst possessed high activity and excellent stability. This work provides a general and economically viable approach for the large-scale synthesis of acid-base bi-functional MOFs for their potential use in catalysis field.

The hexagonal boron nitride nanosheets (BN) were firstly treated by silane coupling agents 3-aminopropyltriethoxysilane (KH550) and 3-glycidoxypropyl-trimethoxysilane (KH560) to introduce some amino and epoxy (EP) groups on the BN surface. These modified BN nanosheets were incorporated into an EP matrix to prepare BN@KH560/EP composites with excellent thermal conductivity and electrical insulation properties. Results showed that the thermal conductivity of BN@KH560/EP composite with 20vol% BN dosage was found to be 0.442W/(m$\cdot$K), which was 81% higher than that of pure EP resin. Both BN/EP composites treated by KH550 and KH560 showed rather good electrical insulation properties, although the dielectric constant of BN@KH550/EP composites were slightly higher than BN@KH560/EP composites. Moreover, BN@KH560/EP composites also showed better thermal and mechanical properties than that of BN@KH550/EP composites.

Increasing active sites and enhancing electric conductivity are critical factors to improve sensing performance toward phenol. Herein, Ni nanoparticle was successfully anchored on acidified multi-walled carbon nanotube (a-MWCNT) surface by electroless plating technique to avoid Ni nanoparticle agglomeration and guarantee high conductivity. The crystal structure, phase composition and surface morphology were characterized by XRD, SEM and TEM measurement. The as-prepared Ni/a-MWCNT nanohybrid was immobilized onto glassy carbon electrode (GCE) surface for constructing phenol sensor. The phenol sensing performance indicated that Ni/a-MWCNT/GCE exhibited an amazing detection performance with rapid response time of 4s, a relatively wide detection range from 0.01mM to 0.48mM, a detection limit of 7.07$\mu$M and high sensitivity of 566.2$\mu$AmM${}^{-1}$cm${}^{-2}$. The superior selectivity, reproducibility, stability and applicability in real sample of Ni/a-MWCNT/GCE endowed it with potential application in discharged wastewater.

A one-step high-temperature solvothermal approach to the synthesis of monolayer or bilayer MoS₂ anchored onto reduced graphene oxide (RGO) sheet (denoted as MoS₂/RGO) is described. It was found that single-layered or double-layered MoS₂ were synthesized directly without an extra exfoliation step and well dispersed on the surface of crumpled RGO sheets with random orientation. The prepared MoS₂/RGO composites delivered a high reversible capacity of 900mAhg${}^{-1}$ after 200 cycles at a current density of 200mAg${}^{-1}$ as well as good rate capability as anode active material for lithium ion batteries. This one-step high-temperature hydrothermal strategy provides a simple, cost-effective and eco-friendly way to the fabrication of exfoliated MoS₂ layers deposited onto RGO sheets.

Three-dimensional (3D) mixed phases NiSe nanoparticles growing on the nickel foam were synthesized via a simple one-step hydrothermal method. A series of experiments were carried out to control the morphology by adjusting the amount of selenium in the synthetic reaction. Meanwhile, the as-prepared novel column-acicular structure NiSe exist three advantages including ideal electrical conductivity, high specific capacity and high cycling stability. It delivered a high capacitance of 10.8Fcm${}^{-2}$ at a current density$-$ of 5mAcm${}^{-2}$. An electrochemical capacitor device operating at 1.6V was then constructed using NiSe/NF and activated carbon (AC) as positive and negative electrodes. Moreover, the device showed high energy density of 31Whkg${}^{-1}$ at a power density of 0.81kWkg${}^{-1}$, as well as good cycling stability (77% retention after 1500 cycles).