Captured by the low-cost and high theoretical specific capacity, Na-S systems have garnered much attention. However, their intermediate products (dissolved polysulfide) are always out of control. ...Considering the excellent space confinements and conductivity, they have been regarded as promising candidates. Herein, the hollow spheres with suitable thickness shell (~20 nm) are designed as hosting materials, accompanied by in-depth complexing. Benefitting from the abundant micro-pores (mainly about conical-type and slits-type pores < 1.0 nm), the active S4 molecules are successfully filled in the pores through vacuum tube sealing technology, effectively avoiding the process from solid S8 to liquid Na2S6. As cathode for Na-S systems, their capacity could remain at 920 mAh g−1 at 0.1 C after 100 cycles. Even at 10.0 C, the capacity still remained at about 310 mAh g−1 after 7000 cycles. Supported by the detailed kinetic behaviors, the improvement of ions diffusion behaviors is noted, bringing about the effective thorough redox reactions. Moreover, the enhanced surface-controlling behaviors further induces the evolution of rate properties. Therefore, their stable phase changing is further confirmed through in situ resistances. Thus, the work is anticipated to offer significant design for hosting carbon materials and complexing manners.
Nickel‐rich layered transition metal oxides are considered as promising cathode candidates to construct next‐generation lithium‐ion batteries to satisfy the demands of electrical vehicles, because of ...the high energy density, low cost, and environment friendliness. However, some problems related to rate capability, structure stability, and safety still hamper their commercial application. In this Review, beginning with the relationships between the physicochemical properties and electrochemical performance, the underlying mechanisms of the capacity/voltage fade and the unstable structure of Ni‐rich cathodes are deeply analyzed. Furthermore, the recent research progress of Ni‐rich oxide cathode materials through element doping, surface modification, and structure tuning are summarized. Finally, this review concludes by discussing new insights to expand the field of Ni‐rich oxides and promote practical applications.
Nickel for better batteries: This Review systematically summarizes Ni‐rich layered materials as cathodes for lithium‐ion batteries through six aspects: synthesis, mechanism, element doping, surface coating, compositional partitioning, and electrolyte adjustment with the aim to boost the development and achieve expectations.
Biological applications of silver nanoparticles (AgNPs) depend on the covalently attached or adsorbed proteins. A series of biological effects of AgNPs within cells are determined by the size, shape, ...aspect ratio, surface charge, and modifiers. Herein, the morphology dependent interaction between AgNPs and protein was investigated. AgNPs with three different morphologies, such as silver nanospheres, silver nanorods, and silver nanotriangles, were employed to investigate the morphological effect on the interaction with a model protein: bovine serum albumin (BSA). The adsorptive interactions between BSA and the AgNPs were probed by UV-Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), Fourier transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), and circular dichroism (CD) techniques. The results revealed that the particle size, shape, and dispersion of the three types of AgNPs markedly influence the interaction with BSA. Silver nanospheres and nanorods were capsulated by protein coronas, which led to slightly enlarged outer size. The silver nanotriangles evolved gradually into nanodisks in the presence of BSA. Fluorescence spectroscopy confirmed the static quenching the fluorescence emission of BSA by the three AgNPs. The FTIR and CD results suggested that the AgNPs with different morphologies had different effects on the secondary structure of BSA. The silver nanospheres and silver nanorods induced more pronounced structural changes than silver nanotriangles. These results suggest that the formation of a protein corona and the aggregation behaviors of AgNPs are markedly determined by their inherent morphologies.
A nanoparticle, under biological milieu, is inclined to be combined with various biomolecules, particularly protein, generating an interfacial corona which provides a new biological identity. Herein, ...the binding interaction between silver nanoparticles (AgNPs) and human serum albumin (HSA) was studied with transmission electron microscopy (TEM), circular dichroism (CD), and multiple spectroscopic techniques. Due to the ground state complex formed mainly through hydrophobic interactions, the fluorescence titration method proved that intrinsic fluorescence for HSA was probably statically quenched by AgNPs. The complete thermodynamic parameters were derived, indicating that the interaction between HSA and AgNPs is an entropy-driven process. Additionally, synchronous fluorescence and CD spectrum results suggested the conformational variation it has upon binding to AgNPs and the α-helix content has HSA visibly decreased. The kinetic experiments proved the double hysteresis effect has in HSA’s binding to the AgNPs surface. Moreover, the binding has between HSA and AgNPs follows the pseudo-second-order kinetic characteristic and fits the Freundlich model for multilayer adsorption. These results facilitate the comprehension about NPs’ underlying biological effects under a physiological environment and promote the secure applications of NPs biologically and medically.
In this work, a novel approach for selective and sensitive detection of ascorbic acid (AA) was proposed combined molecularly imprinted polymers and electrochemical sensor. The molecularly imprinted ...sensor was prepared by cyclic voltammetry on pencil graphite electrode with pyrrole (Py) and o-phenylenediamine (o-PD) as functional monomers and AA as template molecule. The sensor was evaluated through scanning electron microscope (SEM) and square wave voltammetry (SWV). The factors affecting electrochemical response of sensor were investigated and optimized. Under the optimum conditions, the imprinted sensor exhibited good selectivity and stability. The linear range of the sensor was 1×10−6 to 1×10−3mol/L, meanwhile, the detection limit was 2.63×10−7mol/L (S/N=3). This molecularly imprinted sensor has been successfully used in AA determination in real tablet samples with good recovery.
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•Selectively determination of ascorbic acid using molecularly imprinted polymers as recognition element.•Direct electrochemical determination of ascorbic acid using MIPs film modified electrode.•Copolymerization of o-phenylenediamine and pyrrole as functional monomers.
The detection of Pb2+ with DNA-based biosensor is usually susceptible to severe interference from Hg2+ because of the T–Hg2+–T interaction between Hg2+ and T residues. In this study, we developed a ...rapid, sensitive, selective and label-free sensor for the detection of Pb2+ in the presence of Hg2+ based on the Pb2+-induced G-quadruplex formation with cationic water-soluble conjugated polymer (PMNT) as a “polymeric stain” to transduce optical signal. We selected a specific sequence oligonucleotide, TBAA (5′-GGAAGGTGTGGAAGG-3′), which can form a G-quadruplex structure upon the addition of Pb2+. This strategy provided a promising alternative to Pb2+ determination in the presence of Hg2+ instead of the universal masking agents of Hg2+ (such as CN−, SCN−). Based on this observation, a simple “mix-and-detect” optical sensor for the detection of Pb2+ was proposed due to the distinguishable optical properties of PMNT–ssDNA and PMNT–(G-quadruplex) complexes. By this method, we could identify micromolar Pb2+ concentrations within 5min even with the naked eye. Furthermore, the detection limit was improved to the nanomolar range by the fluorometric method. We also successfully utilized this biosensor for the determination of Pb2+ in tap water samples.
► A rapid, sensitive, selective and label-free optical Pb2+ sensor was developed. ► This sensor shows high selectivity for the detection of Pb2+ in the presence of other metal ions. ► The limit of detection is as low as 6nM. ► The whole detection process only takes 5min. ► This sensor was successfully employed to determine Pb2+ in tap water samples.
Silver is one of the most important heavy metals with a broad range of applications; however, it can have significant negative impacts on both the ambient environment and organisms. For this work, an ...interesting fluorescence polarization sensor based on SH-DNA functionalized gold nanoparticles (AuNPs) was proposed for the detection of Ag+ in aqueous solutions. Moreover, this sensing strategy is quite simple, sensitive, selective, and cost-effective. Ag+ ions can interact specifically with a cytosine–cytosine (C–C) mismatch in DNA duplexes to form stable metal-mediated cytosine–Ag+–cytosine (C–Ag+–C) base pairs. The creation of these C–Ag+–C complexes results in evident changes in the molecular volume and fluorescence polarization signal. The stable hybridization between the two probes occurs with the formation of the C–Ag+–C complex in the presence of Ag+ ions, which leads to obvious fluorescence quenching in contrast to the system without AuNP. This assay may be employed to identify nanomolar levels of Ag+ within 6 min at room temperature. Furthermore, the sensor was successfully adopted to detect Ag+ ions in environmental water samples, which may facilitate the potential development of a range of environmental monitoring applications.
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The Ni-rich cathodes are considered as the next generation candidate cathode material of lithium-ion batteries due to the high-energy–density and environmentally friendly. Unfortunately, the cathodes ...are up against severe structure instability at the repeated charge/discharge process, resulting in the attenuation of voltage and capacity. Herein, we proposed a novel strategy with uniform Al and Ti cations co-doping of LiNi
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cathode. The modification strategy not only stabilizes the vulnerable layered structure but also mitigate voltage/capacity attenuation at different cutoff voltages. As a result, the modified cathode with trace content of Al and Ti cations co-doping can broaden the lithium ions diffusion channels, mitigate the structural collapse, and unfavorable phase transformation to some extent. Specifically, the modified sample exhibits remarkable enhanced electrochemical performance in discharge capacity and voltage retention of 76.75%, 98.78% at 1 C after 200 cycles. Even though at elevated voltage, the modified sample shows improved cycle life with a capacity retention of 70.93% after 200 cycles.
A rapid, sensitive and selective fluorescence sensor for detection of Pb(2+) was developed based on a Pb(2+)-induced G-quadruplex and graphene oxide. By using a specific G-rich DNA sequence, this ...strategy provided a promising alternative to Pb(2+) determination in the presence of Hg(2+) escaping from the use of a masking agent of Hg(2+).
High-voltage photovoltaic (PV) techniques have their own advantages in PV plants for reducing the construction cost and improving the operational efficiency. However, the high input PV voltage ...increases the mismatch losses of PV arrays, which is also a key factor that influences the energy yield of PV plants. This paper proposes a three-input central capacitor (TICC) dc/dc converter for a high-voltage PV system, where four low-rating cascaded buck-boost converters connect to the series-connected three low-voltage PV arrays and two capacitors and realize the maximum power point tracking independently. Meanwhile, there is a neutral point in the proposed converter, enabling it to be connected with the rear-end three-level inverter directly. It can also help balance the three-level dc-link voltage by properly regulating the transferred energy among three input sources. Compared with other transformer-less dc-dc converters, the proposed converter is able to reduce the semiconductor voltage/current stress and therefore achieve the high efficiency. Simulation and experimental results verified the performance of the proposed TICC converter.