An ultra-sensitive non-enzymatic hydrogen peroxide sensor based on SiO2-APTES supported Au nanoparticles modified glassy carbon electrode

A novel electrochemical sensor based on (3-aminopropyl)triethoxysilane (APTES) functionalized SiO₂ supported Au nanoparticles and Nafion (Nf) as the protective membrane was fabricated for the electrochemical determination of H₂O₂ in contact lens-cleaning solution. The modification steps of glassy carbon working electrode (GCE) were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The amperometric results showed that Nf/[email protected]₂-APTES/GCE sensor can be used to determine H₂O₂ in contact lens solutions with the linear ranges of 14–180 μM and 0.18–7.15 mM, excellent sensitivities of 2514.6 and 894.2 μA mM cm^?2, and a low limit of detection (LOD) of 4.25 μM depending upon signal-to-noise ratio of 3. Nf/[email protected]₂-APTES/GCE exhibited excellent repeatability with relative standard deviation (RDS) of 2.66% and acceptable reproducibility with RSD of 3.35%. The sensor displayed reasonable selectivity in the presence of uric acid, dopamine, ascorbic acid, glucose, mannose, glycine, fructose, histidine, and arginine with RSD less than 2.5%. The fabricated Nf/[email protected]₂-APTES/GCE sensor has been successfully applied to detect H₂O₂ in contact lens cleaning solutions.     

Rational design of carbon shell-encapsulated cobalt nanospheres to enhance microwave absorption performance

Co@C core–shell nanospheres highly dispersed on carbon supports were rationally designed to improve the microwave absorbing property of the composite material, and fabricated by one pot thermal decomposition and simple annealing process. The Co nanospheres were completely encapsulated with thin carbon shells, which can effectively prevent the oxidation of the Co surface. Additionally, the particle size of Co nanospheres were properly controlled to optimize the electromagnetic property of the composite material. As a result, the lightweight Co@C/C composites with the particle size of 20 nm exhibited much enhanced microwave absorption properties. The improved microwave absorption performance is attributed mainly to the enhanced isotropic ratio and impedance matching of magnetic composites via tuning the Co particle size. Therefore, the welldesigned core-shell Co@C composite structure will provide a new insight for the development of high performance microwave absorbers.     

Synthesis of the 3D porous carbon-manganese oxide (3D-C@MnO) nanocomposite and its supercapacitor behavior study

A 3D porous carbon-manganese oxide ([email protected]) nanocomposite is successfully synthesized via a thermal plasma deposition method. The chemical bonds and compositions, phase structures, surface morphologies, etc. of as-obtained [email protected] nanocomposite were characterized by the various equipment, such as X-ray diffractometer, X-ray photoelectron spectroscopy, and electron microscopes. The electrochemical performances of the [email protected] nanocomposite electrode showed a specific capacitance of 780 F g^?1 at a current density of 2 A g^?1 and a capacitance retention rate of 99% after 5000 charge-discharge cycles at a high current density of 10 A g^?1. These excellent capacitive performances may be attributed to the encapsulation of MnO nanoparticles by porous carbon sheets in the [email protected] MnO nanocomposite structure. It is believed that the carbon-encapsulated MnO nanoparticles can be protected from a volume deformation during the charge adsorption/desorption cycle and can be electrically improved by the encapsulated carbon sheets, resulting in better overall capacitive performance. In addition, this study also demonstrates the practical applicability by assembling a supercapacitor using the as-obtained [email protected] nanocomposite to glow a light emitting diode.     

IR study on hydrogen bonding in epoxy resin–silica nanocomposites

The chemical and physical interactions between ingredients in composites play an important role in the improvement of service properties. The nucleophilic addition between polymer and isophoron diisocyanate molecules was monitored by FT-IR technique. The intensity loss of isocyanate absorption band in conjunction with the intensity growth of carboxyl absorption band indicates the progress of reaction. FT-IR spectroscopy was also adopted to examine the intermolecular hydrogen bonding of epoxy resin with silica as well as intramolecular one within polymer matrix. The vibration frequency of carboxyl group （-C=O） and hydroxyl group （-OH） shifts from 1736 to 1728 cm^-1and 3420 to 3414 cm^-1, respectively, indicating the occurrence of hydrogen bonding between -C=O and -OH. The vibration frequency of Si-OH moves from 3435 to 3414 cm^-1, suggesting the involvement of silica. Whereas the vibration frequency of pending -OH in polymer chain moves from 3435 to 3420 cm^-1 or 3414 cm^-1, proposing that this kind of interaction can also happen within polymer matrix.     

Low temperature hydrothermal synthesis and electrochemical performances of LiFePO4 microspheres as a cathode material for lithium-ion batteries

Mesoporous LiFePO4 microspheres were simply synthesized by a low temperature(130℃),template-free hydrothermal route using low cost LiOH,Fe(NO3)3 and NH4H2PO4 as starting raw materials.These microspheres are composed of densely aggregated LiFePO4 nanoparticles and filled with interconnected mesochannels,which demonstrates not only a high tap density(≥1.4 g cm-3),a high capacity of 150 mAh g-1(～90% of its theoretical capacity) at 0.5 C rate,but also a ≥ 80% utilization of its theoretical capacity at a high rate of 1 C.In addition,the hydrothermal synthesis developed in this work is simple and cost-effective,it may provide a new route for production of the LiFePO4 material in battery applications.     

Thermal shock resistance and crack growth behavior of Aurivillius phase Bi_4Ti_3O_(12)-based ferroelectric ceramics

A type of W/Cr co-doped Bi_4Ti_3O_(12)(ab. BTWC) ceramics were synthesized utilizing the traditional solid-state reaction process, and its thermal shock resistance(TSR) as well as the crack growth behavior was systematically investigated by water quenching technology. It can be found by the succeeded fractographic analysis that many edge thermal cracks began to appear in the samples subjected to thermal shock with ΔT=400°C. According to an integrated TSR model, the critical thermal-shock temperature difference ΔTCwas calculated to be 356°C. Moreover, it can be noticed that the indenter induced crack growth behaviors under thermal shock loads presented three stages, i.e. no growth, large growth, and moderate growth, along with ΔT increasing from 0°C to 700°C. Finally, the asymmetry of P-E hysteresis loops was observed and understood by the orientated polarization of defect dipoles after the sample was thermally shocked, while the water-quenching process above the Curie temperature of the ceramics could lead to a random orientation of the defect dipoles. This research can not only evaluate the service conditions of Bi_4Ti_3O_(12) high-temperature piezoceramics, but also understand the failure mechanism of bismuth layer structured ferroelectric ceramics in the case of thermal shock.     

Preparation and electrochemical properties of carbon-coated LiFePO4 hollow nanofibers

Carbon-coated LiFePO₄ hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO₄ hollow nanofibers have good long-term cycling performance and good rate capability: at a current density of 0.2C (1.0C = 170 mA·g-1) in the voltage range of 2.5–4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mAh·g-1 with a first charge–discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mAh·g-1, even at 2C.     

CoPt-Co hybrid supported on amino modified SiO_2 nanospheres as a high performance catalyst for hydrogen generation from ammonia borane

CoPt-Co hybrids were successfully supported on amino modified SiO_2 nanospheres by a chemical reduction method at a temperature of 278 K.The solid carrier i.e.amino modified SiO_2,provides numerous anchoring sites for the metal nanoparticles(NPs)to improve the dispersion while reducing the size of metal NPs.The supported NPs displayed a narrow particle size distribution on the SiO_2 surface with an average diameter of 12 nm.The XRD results alongside with the binary alloy phase diagram suggest that the resulted NPs are bimetallic,composed of CoPt and amorphous Co.Among the prepared materials,the solid with the specific composition of SiO_2@Pt_(0.1)Co_(0.9)was proved to be effective catalyst for ammonia borane(AB)hydrolysis in aqueous solution.The turnover frequency(TOF)value of the supported nanocatalyst was 25.59mol_(H_2)min~(-1)·mol_M~(-1),almost twice as that of unsupported Pt_(0.1)Co_(0.9)NPs while the activation energy was 37.05 kJ mol~(-1).Furthermore,the SiO_2@Pt_(0.1)Co_(0.9)composite manifested high catalytic activity even after five cycles of reuse.     

Cu-FeOx@AC活化PMS体系除藻效能与机制

为探究富营养化水体中藻类的新型治理技术，通过水热法和高温煅烧法，使颗粒活性炭（AC）表层上负载铜铁双金属氧化物Cu-FeO_x，制得可回收的Cu-FeO_x@AC复合催化剂。以XRD、SEM、FTIR和XPS对Cu-FeO_x@AC的表征为基础，研究Cu-FeO_x占AC的负载比、过一硫酸盐（PMS）使用量、初始pH及不同反应体系对除藻的影响，探究Cu-FeO_x@AC活化过一硫酸盐体系的除藻效能。Cu-FeO_x@AC活化过一硫酸盐体系反应机理，通过自由基淬灭实验、XPS表征进行探究。结果可知，初始pH为6，初始藻细胞密度为1.4×10⁹个/L，使用催化剂0.5 g/L，PMS 0.2 g/L时，反应90 min，该体系对藻的降解率有97.25%。在该体系中，藻细胞能被吸附在Cu-FeO_x@AC复合催化剂表面，在铜、铁不同价态离子的转换及AC的协同作用下，产生空穴、·O2-、·OH、SO4-·，单线态氧等多种氧化基团而被去除。     

Synthesis, Characterization and Properties of LiFePO4/C Cathode Material

Lithium iron phosphate coated with carbon (LiFePO₄/C) was synthesized by improved solid-state reaction using comparatively lower temperature and fewer sintering time. The carbon came from citric acid, which acted as a new carbon source. It was characterized by thermogravimetry and differential thermal analysis (TG/DTA), X ray diffractometer (XRD), Element Analysis (EA) and Scanning electron microscope (SEM). We also studied the electrochemical properties of the material. The first discharge capacity of the LiFePO₄/C is 121 mAh·g⁻¹ at 10 mA·g⁻¹, at room temperature. When the current density increased to 100 mA·g⁻¹, the first discharge capacity decreased to 110 mAh·g⁻¹ and retained 95% of the initial capacity after 100 cycles. The LiFePO₄/C obtained shows a good electrochemical capacity and cycle ability at a large current density. Foundation item: Supported by the National Natural Science Foundation of China (20071026) Biography: ZHOU Xin-wen (1980-), male, Master, research direction: inorganic material chemistry.     

高腐蚀条件下用铝合金材料腐蚀机理

铝合金具有低密度、低熔点、高比强度及优良的耐腐蚀性能等特点，被广泛用于航空航天、建筑、船舶等领域。在服役过程中，铝合金的表层氧化膜易受到环境中活性阴离子的破坏而发生腐蚀，对其性能造成严重的损害，故研究铝合金在高腐蚀性环境的腐蚀行为对工程选材具有非常重要的指导意义。选择6061铝合金、2195铝锂合金和7075铝合金为研究对象，对其在特定腐蚀介质中的腐蚀过程和力学性能进行分析，研究了铝合金在特定腐蚀介质中腐蚀形貌与力学性能的变化规律。结果表明：腐蚀初期，在高Cl^-、NO₂^3-、SO₂^4-离子浓度的腐蚀环境中，3种铝合金的氧化膜受到阴离子破坏后发生点腐蚀，使基体暴露在腐蚀环境中，进而发生电化学腐蚀，6061铝合金和2195铝锂合金腐蚀方式是由点腐蚀向面腐蚀转变，7075铝合金腐蚀方式为晶间腐蚀；经过腐蚀后6061铝合金能保持稳定的强度和塑性，7075铝合金和2195铝锂合金的强度和塑性都明显降低。     

锂离子电池正极材料LiFePO4/C的制备与表征

采用溶胶-凝胶法合成了LiFePO₄/C复合材料,利用元素分析、X射线衍射（XRD）、扫描电镜（SEM）等方法对其进行了表征,将其组装成模拟电池测试了其电化学性能.结果表明：LiFePO₄/C具有单一的橄榄石型晶体结构,碳粒子平均颗粒大小在1μm左右.LiFePO₄/C复合材料在3.4 V处具有很好的充放电电压平台,与LiFePO₄相比,具有更高的放电比容量和更好的循环性能,在60 ℃时的首次放电容量达到133 mAh/g,经20次循环后的容量保持率为93.8%.     

Facile synthesis of nanostructured LiFePO4/C cathode material for lithium-ion batteries

Nanostructured LiFePO4/C cathode material was prepared by FePO4·2H2O/C precursor by in situ restriction reaction.The synthesized LiFePO4/C cathode material presents a narrow distribution of nano-sized particles and exhibits an excellent electrochemical property with various rates.The facile synthesis route for the preparation of nano-sized LiFePO4 material has the particular advantage of simple synthesis process and low synthesis cost.     

Electrochemical performance of MCMB/(AC+LiFePO4) lithium-ion capacitors

Lithium-ion capacitors(LICs) were fabricated using mesocarbon microbeads(MCMB) as a negative electrode and a mixture of activated carbon(AC) and LiFePO4 as a positive electrode(abbreviated as LAC).The phase structure and morphology of LAC samples were characterized by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM).The electrochemical performance of the LICs was studied using cyclic voltammetry,charge-discharge rate measurements,and cycle performance testing.A LIC with 30 wt% LiFePO4 was found to have the best electrochemical performance with a specific energy density of 69.02 W h kg-1 remaining at 4 C rate after 100 cycles.Compared with an AC-only positive electrode system,the ratio of practical capacity to theoretical calculated capacity of the LICs was enhanced from 42.22% to 56.59%.It was proved that adding LiFePO4 to AC electrodes not only increased the capacity of the positive electrode,but also improved the electrochemical performances of the whole LICs via Li+ pre-doping.     

厄尔尼诺-南方涛动影响下月尺度水文模型参数可移植性

以浙江省3个流域作为研究对象，采用两参数月水量平衡模型（XM模型）和四参数月水量平衡模型（ABCD模型），结合极大似然不确定性估计方法（GLUE）对水文模拟的不确定性区间进行估计，在此基础上，研究不同模型在ENSO（厄尔尼诺-南方涛动）和不同流域地理情况下的参数移植能力。结果表明，厄尔尼诺时期的参数移植至拉尼娜时期，模型模拟效果要略好于拉尼娜时期的参数移植至厄尔尼诺时期；参数少的模型（XM模型）参数移植合格率要优于参数多的模型（ABCD模型）；相邻流域间的参数移植效果要明显优于距离较远的流域；ABCD模型具有更好的空间可参数移植能力。     

Enhanced low-temperature performance of slight Mn-substituted LiFePO<Subscript>4</Subscript>/C cathode for lithium ion batteries

Low temperature performance of LiFePO₄/C cathode was remarkably improved by slight Mn-substitution. Electrochemical measurements showed that about 95% of the discharge capacity of LiFe_0.98Mn_0.02PO₄/C cathode at 20°C was obtained at 0°C, compared to 85% of that of LiFePO₄/C cathode. The LiFe_0.98Mn_0.02PO₄/C sample also presented enhanced rate performance at −20°C with the discharge capacities of 124.4 mA h/g (0.1C), 99.8 mA h/g (1C), 80.7mAh/g (2C) and 70 mA h/g (5C), respectively, while pristine LiFePO₄/C only delivered capacities of 120.5 mA h/g (0.1C), 90.7 mA h/g (1C), 70.4 mA h/g (2C) and 52.2 mA h/g (5C). Cyclic voltammetry measurements demonstrated an obvious improvement of the lithium insertion-extraction process of the LiFePO₄/C cathode by slight Mn-substitution. The results of FSEM observation and electrical conductivity measurement indicated that slight Mn-substitution minimized the particle size of LiFe_0.98Mn_0.02PO₄/C and also obviously improved the electrical conductivity of the compound, thus obviously enhances the interface reaction process on the cathode.     

碳包埋固相法制备LiFePO4及其电化学性能研究

用石墨粉包埋取代保护性气氛,一步固相法制备LiFePO4.采用XRD,FTIR,SEM和恒电流充放电等方法对材料结构、形貌和电化学性能进行了表征.利用循环伏安法研究了Li+在LiFePO4中的嵌/脱过程.结果表明,这种改进的固相法可以合成亚微米级纯相橄榄石结构LiFePO4,所得材料具有良好的倍率性能和循环稳定性,在0.1C和1C倍率首次放电比容量分别为148.3和131.9mAh.g-1,1C和5C倍率下循环50次容量保持率分别为96%和90%.由循环伏安法计算得到阳极峰和阴极峰处Li+的表观扩散系数分别为1.64×10-13和1.94×10-13cm2.s-1.     

Synthesis of LiFePO4 in situ vapor-grown carbon fiber （VGCF） composite cathode material via microwave pyrolysis chemical vapor deposition

One of the most important factors that limits the use of LiFePO 4 as cathode material for lithium ion batteries is its low electronic conductivity.In order to solve this problem,LiFePO 4 in situ vapor-grown carbon fiber (VGCF) composite cathode material has been prepared in a single step through microwave pyrolysis chemical vapor deposition.The phase,microstructure,and electrochemical performance of the composites were investigated.Compared with the cathodes without in situ VGCF,the initial discharge capacity of the composite electrode increases from 109 to 144 mA h g-1 at a 0.5-C rate,and the total electric resistance decreases from 538 to 66.The possible reasons for these effects are proposed.     

Earth-abundant photovoltaic semiconductor NaSbS_2 in the rocksalt-derived structure:A first-principles study

NaSbS_2 was recently proposed as a novel photovoltaic semiconductor with earth-abundant component elements,but its fundamental material properties have not been well studied.The systematical first-principles calculations for its electronic,optical and defect properties were carried out in the present study,and the results show that:i)NaSbS_2 in the rocksalt-derived structure has a quasi-direct band gap and thus may have long minority carrier lifetime;ii) its absorption coefficients are as high as 10~4～10~5 cm~(-1) for the visible light and almost isotropic despite that the structure is distorted relative to the high-symmetry rocksalt structure;iii) the effective masses of the electron and hole carriers are anisotropic with much larger values along the z direction than in the x-y plane,and hence the orientational control of thin films should be important for enhancing the photovoltaic performance;iv) the valence and conduction band edges of NaSbS_2 are close to those of CuGaSe_2) so the n-CdS/pCuGaSe_2 device structure can be inherited to form the n-CdS/p-NaSbS_2 solar cells;v) the acceptor defects (Na_(Sb)antisites and Na vacancies) have very high concentration,making the synthesized NaSbS_2 always be p-type;vi)the S-rich condition can suppress the formation of deep-level donor defects (S vacancies and Sb_(Na) antisites) and therefore should be adopted for fabricating high-efficiency NaSbS_2 solar cells.     

The voltammetric behavior of concanavalin a at bare silver electrode and analytical application

The voltammetric behavior of concanavalin A at the bare silver electrode is described. Cyclic voltammograms show a pair of well-defined redox peaks for concanavalin A in the medium of phosphate buffer(pH=7.0) with electrochemical reaction rate constant ofK ₂=0.053 s^?1 and electron transfer number ofn=2. Moreover, both the oxidation currents and the reduction currents have linear relationship with concanavalin A concentrations in the range of 1.0×10^?6～2.0×10^?5 mol/L, which can be used as an analytical method for determining concanavalin A concentration.