Spin-coated silicon nanoparticle/graphene electrode as a binder-free anode for high-performance lithium-ion batteries

Si has been considered as a promising anode material but its practical application has been severely hindered due to poor cyclability caused by the large volume change during charge/discharge. A new and effective protocol has been developed to construct Si nanoparticle/graphene electrodes with a favorable structure to alleviate this problem. Starting from a stable suspension of Si nanoparticles and graphene oxide in ethanol, spin-coating can be used as a facile method to cast a spin-coated Si nanoparticle/graphene (SC-Si/G) film, in which graphene can act as both an efficient electronic conductor and effective binder with no need for other binders such as polyvinylidenefluoride (PVDF) or polytetrafluoroethylene (PTFE). The prepared SC-Si/G electrode can achieve a high-performance as an anode for lithium-ion batteries benefiting from the following advantages: i) the graphene enhances the electronic conductivity of Si nanoparticles and the void spaces between Si nanoparticles facilitate the lithium ion diffusion, ii) the flexible graphene and the void spaces can effectively cushion the volume expansion of Si nanoparticles. As a result, the binder-free electrode shows a high capacity of 1611 mA·h·g^?1 at 1 A·g^?1 after 200 cycles, a superior rate capability of 648 mA·h·g^?1 at 10 A·g^?1, and an excellent cycle life of 200 cycles with 74% capacity retention.      

Design of hierarchical buffer structure for silicon/carbon composite as a high-performance Li-ion batteries anode

Silicon-based materials are used as anode material for lithium-ion batteries, due to ultra-high theoretical specific capacity. However, large volume changes, continuous formation of unstable solid electrolyte interface film and low conductivity greatly restricted its large-scale development and application. In this case, a composite with hierarchical buffer structure coated Si nanoparticles (Si@RF@MP) was designed and manufactured by the surfactant template and emulsification method in this study. The resorcinol–formaldehyde resin acts as the structural buffer and the conductive layer to accommodate the volume change of silicon and provide fast channels for electron transfer and lithium-ion diffusion. The unique turbostratic structure of mesophase pitch can effectively improve the integral conductivity and the structural stability of the electrode. As a result, the Si@RF@MP composite exhibited an excellent reversible discharge capacity of 389 mA h g^?1 after 200 cycles at 200 mA g^?1, and retained a discharge capacity of 345 mA h g^?1 after 300 cycles at a high current density of 1000 mA g^?1. In addition, the Si@RF@MP composite delivered reversible capacities of about 546 mA h g^?1, 495 mA h g^?1, and 437 mA h g^?1 in current densities of 500 mA g^?1, 1000 mA g^?1, and 2000 mA g^?1, respectively, indicating good rate performance. Hence, this strategy provides a new method and idea for the further development of silicon/carbon composites and a strategy to achieve high value and green utilization of pitch.

     

Silica xerogel as a continuous column support for high-performance liquid chromatography

A preliminary study of the chromatographic performance and permeability of a continuous silica xerogel column under reversed-phase HPLC conditions was performed. A porous chromatographic support was synthesized inside a 0.32 mm i.d. × 13 cm fused silica tube from potassium silicate solution and derivatized with dimethyloctadecylchlorosilane. The plate height at 0.01 cm/s (0.5 μL/min), near the apparent optimum linear velocity, was about 65 μm. The column efficiencies in terms of numbers of plates per meter were 5000 and 13?000 for ethyl benzoate (k = 0.8) and naphthalene (k = 2.0), respectively, at 0.5 μL/min. The major parameter affecting column efficiency was the heterogeneous morphology of the xerogel, modifications to which are expected to improve chromatographic performance. The column provided efficiencies comparable to those reported for continuous polymeric columns but less than that previously reported for a continuous silica column. Gradient elution mode was demonstrated with a mixture of polycyclic aromatic hydrocarbons. The column was highly permeable, exhibiting a linear dependence of pressure to flow rate and a back pressure of only 632 psi at 10 μL/min when a 95% aqueous mobile phase was used.     

Facile fabrication of a nanoporous Si/Cu composite and its application as a high-performance anode in lithium-ion batteries

Nanoporous (NP) Si/Cu composites are fabricated by means of alloy refining followed by facile electroless dealloying in mild conditions. NP-Si/Cu composites with a three-dimensional porous network nanoarchitecture with different Cu contents are obtained by changing the feeding ratio of alloy precursors. Owing to the rich porosity and integration of conductive Cu into a nanoporous Si backbone, the NP-Si₈₅Cu₁₅ composite exhibits modified conductivity and reduced volumetric expansion/fracture during repeated charging-discharging processes in lithium-ion batteries (LIBs), thus exhibiting much higher cycling reversibility than NP-Si₉₂Cu₈ and pure NP-Si. With the advantages of unique performance and easy preparation, NP-Si/Cu composite has potential for application as an advanced anode material for LIBs.

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One-step scalable preparation of N-doped nanoporous carbon as a high-performance electrocatalyst for the oxygen reduction reaction

N-doped porous carbon materials have been prepared by a simple one-step pyrolysis of ethylenediaminetetraacetic acid (EDTA) and melamine in the presence of KOH and Co(NO₃)₂·6H₂O. The combination of the high specific area (1485 m²·g^?1), high nitrogen content (10.8%) and suitable graphitic degree results in catalysts exhibiting high activity (with onset and half-wave potentials of 0.88 and 0.79 V vs the reversible hydrogen electrode (RHE), respectively) and four-electron selectivity for the oxygen reduction reaction (ORR) in alkaline medium—comparable to a commercial Pt/C catalyst, but far exceeding Pt/C in stability and durability. Owing to their superb ORR performance, low cost and facile preparation, the catalysts have great potential applications in fuel cells, metal-air batteries, and ORR-related electrochemical industries.      

Application of nanoporous silicon for a metal-semiconductor-metal visible light photodetector

In this paper we present a study on the application of nanoporous silicon to an optoelectronic device called a nanoporous silicon metal-semiconductor-metal (MSM) visible light photodetector. This device was fabricated on a nanoporous silicon layer which was formed by electrochemical etching of a silicon wafer in a hydrofluoric acid solution under various anodization conditions such as the resistivity of the silicon wafer, current density, concentration of the hydrofluoric acid solution and anodization time. The structure of this device has two square Al/nanoporous silicon Schottky-barrier junctions on the silicon substrate and the electrode spacing is 500 microm. The experiment will study photoresponse and the response time of a nanoporous silicon MSM photodetector which was fabricated on the various porosity of a nanoporous silicon layer. It is found that when devices are fabricated on a higher porosity nanoporous silicon layer, the photoresponse of the device will expand toward the short-wavelength and the bandwidth of the spectrum response will cover visible light. In addition, it is found that the response time of the device decreases.     

金/硅纳米孔柱阵列的场发射

利用浸溃技术在硅纳米孔柱阵列(silicon nanoporous pillar array(简称Si-NPA))上制备了复合纳米薄膜Au/Si-NPA.测试了其场发射性能.测试结果显示,Au/Si-NPA的开启电场为约2V/μm;在7.59V/μm的外加电场下,其发射电流密度为67μA/cm2;在外加电压2000V时,其电流浮动率为21%.导致Au/Si-NPA优良的发射性能是由于其独特的表面形貌和结构所致.     

Patterned resonance plasmonic microarrays for high-performance SPR imaging

We report a novel optical platform based on SPR generation and confinement inside a defined three-dimensional microwell geometry that leads to background resonance-free SPR images. The array shows an exceptionally high signal-to-noise ratio (S/N > 80) for imaging analysis and subnanometric thickness resolution. An angular sensitivity of 1°/0.01 RIU has been achieved and the signal to background ratio (S/B) improves to 20, 1 order of magnitude higher than that of the best literature results. The design proves effective for probing-supported lipid membrane arrays in real time with a thickness resolution of 0.24 nm and allows for imaging analysis of microfluidic circuits where resonant spots are separated by only one pixel (～7 μm). The high image quality and unique chip geometry open up new avenues for array screening and biomicrofluidics using SPRi detection.     

Rohacell foam as a silicon support structure material for the PHENIX multiplicity vertex detector

Rohacell [1], a low-density rigid foam, has been investigated as a support structure material for silicon strip detectors in the Multiplicity Vertex Detector (MVD) in the PHENIX experiment. Although Rohacell is susceptible to changes in humidity, tests have shown that it is an acceptable material for the MVD silicon support structure. The advantage of using Rohacell is that it offers a mechanically robust structure in which secondary interactions are minimized.     

Miniaturized electrospraying as a technique for the production of microarrays of reproducible micrometer-sized protein spots

Electrospraying in a stable cone-jet mode at <400 microm above a substrate is shown to be a powerful technique to produce arrays of identical micrometer-sized spots consisting of biologically active substances. Aqueous solutions with a surface tension of 0.04 N m(-1) and conductivities ranging from 0.04 to 2.2 S m(-1) were sprayed at ultralow flow rates ranging from 100 to 300 pL s(-1). The charged jet that emanates from the cone tip breaks up into a spray of charged droplets that are deposited in the form of a uniform spot of 130-350 microm in diameter by spraying during 0.5-3 s at 220-400 microm above a substrate, respectively. After a spot was deposited, spraying was stopped instantaneously by increasing the distance between the capillary tip and the substrate by an additional 100 microm using a computer-controlled x-y-z table. This was immediately followed by a rapid shift of the substrate 400 microm sideways and 100 microm upward, thus causing spraying to resume instantaneously because of the increased electric field strength, which resulted in the deposition of the next spot. It is shown here that spraying of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6P-DH), and pyruvate kinase (PK) on a liquid layer resulted in the complete preservation of their activities despite the high solution conductivity of 3.3 S m(-1) and high currents ranging from 300 to 500 nA. LDH and PK activities were fully preserved after spraying onto dry aluminum by adding 0.05 M buffer and 0.5 and 1 wt % of trehalose, respectively, to the spray solutions. Electrospraying allows for accurate dispensing of liquid volumes as small as 50 pL. Enzymatic activities of LDH and PK are fully preserved after spraying.     

Conductive rigid skeleton supported silicon as high-performance li-ion battery anodes

A cost-effective and scalable method is developed to prepare a core-shell structured Si/B(4)C composite with graphite coating with high efficiency, exceptional rate performance, and long-term stability. In this material, conductive B(4)C with a high Mohs hardness serves not only as micro/nano-millers in the ball-milling process to break down micron-sized Si but also as the conductive rigid skeleton to support the in situ formed sub-10 nm Si particles to alleviate the volume expansion during charge/discharge. The Si/B(4)C composite is coated with a few graphitic layers to further improve the conductivity and stability of the composite. The Si/B(4)C/graphite (SBG) composite anode shows excellent cyclability with a specific capacity of ～822 mAh·g(-1) (based on the weight of the entire electrode, including binder and conductive carbon) and ～94% capacity retention over 100 cycles at 0.3 C rate. This new structure has the potential to provide adequate storage capacity and stability for practical applications and a good opportunity for large-scale manufacturing using commercially available materials and technologies.     

Dealloying-derived nanoporous deficient titanium oxide as high-performance bifunctional sulfur host-catalysis material in lithium-sulfur battery

In this work,we report a facile dealloying strategy to tailor the surface state of nanoporous TiO2 towards high-efficiency sulfur host material for lithium-sulfur(Li-S)batteries.When used as a sulfur cathode material,the oxygen-deficient TiO2-x exhibits enhanced lithium polysulfides(LiPS)adsorption and con-version kinetics that effectively tackle the shuttle effect in lithium-sulfur batteries.The excellent ability of the oxygen vacancy sites on TiO2-x surface to trap LiPS is proved by experimental observations and density functional theory(DFT)calculations.Meanwhile,it also promotes conversion kinetics of lithium polysul-fides,as verified by the asymmetric cell experiment.Accordingly,compared with the S/TiO2 cathode,the oxygen-deficient S/TiO2-x electrode exhibits preeminent rate and cycling performance in lithium-sulfur batteries:it delivers an ultra-low capacity decay of0.039％per cycle after 1000 cycles at 1 C.Tunning the surface state of metal oxides by dealloying method offers a new facile strategy to design efficient sulfur cathode materials for lithium-sulfur batteries.     

Bioconjugated fluorescent zeolite L nanocrystals as labels in protein microarrays

Zeolite L nanocrystals, as inorganic host material containing hydrophobic fluorophore N,N'-bis(2,6-dimethylphenyl)perylene-3,4,9,10-tetracarboxylic diimide in the unidirectional channels, are developed as new labels for biosensor systems. The external surface of the particles is modified with carboxylic acid groups for conjugation to primary amines of biomolecules such as antibodies. Anti-digoxigenin (anti-DIG) is selected to be immobilized on zeolite L via N-hydroxysulfosuccinimide ester linker. Together with DIG, it serves as a good universal binding pair for diverse analyte detection owing to the high binding affinity and low background noise. The conjugates are characterized by the dynamic light scattering technique for their hydrodynamic diameters and by enzyme-linked immunosorbent assay for antigen-antibody binding behavior. The characterizations prove that anti-DIG antibodies are successfully immobilized on zeolite L with their binding activities maintained. The microarray fluorescent sandwich immunoassay based on such nanocrystalline labels shows high sensitivity in a thyroid-stimulating hormone assay with the lower detection limit down to the femtomolar range. These new fluorescent labels possess great potential for in vitro diagnostics applications.     

Self-supporting,eutectic-like,nanoporous biphase bismuth-tin film for high-performance magnesium storage

Magnesium ion batteries are emerging as promising alternatives to lithium ion batteries because of their advantages including high energy density, dendrite-free features and low cost. Nevertheless, one of the major challenges for magnesium ion batteries is the kinetically sluggish magnesium insertion/extraction and diffusion in electrode materials. Aiming at this issue, biphase eutectic-like bismuth-tin film is designed herein to construct a self-supporting anode with interdigitated phase distribution and hierarchically porous structure, and further fabricated by a facile one-step magnetron cosputtering route. As benchmarked with single-phase bismuth or tin film, the biphase bismuth-tin film delivers high specific capacity (538 mAh/g at 50 mA/g), excellent rate performance (417 mAh/g at 1,000 mA/g) and good cycling stability (233 mAh/g at the 200th cycle). The superior magnesium storage performance of the sputtered bismuth-tin film could be attributed to the synergetic effect of the interdigitated bismuth/tin phase distribution, hierarchically porous structure and biphase buffering matrices, which could increase ionic transport channels, shorten diffusion lengths and reduce total volume changes.

     

Characterization of functionalized nanoporous supports for protein confinement

Here we characterize a highly efficient approach for protein confinement and enzyme immobilization in NH(2)-?or HOOC-?functionalized mesoporous silica (FMS) with pore sizes as large as tens of nanometres. We observed a dramatic increase of enzyme loading in both enzyme activity and protein amount when using appropriate FMS in comparison with unfunctionalized mesoporous silica and normal porous silica. With different protein loading density in NH(2)-FMS, the negatively charged glucose oxidase (GOX) displayed an immobilization efficiency (I(e), the ratio of the specific activity of the immobilized enzyme to the specific activity of the free enzyme in stock solution) in a range from 30% to 160%, while the same charged glucose isomerase (GI) showed an I(e) of 100% to 120%, and the positively charged organophosphorus hydrolase (OPH) exhibited I(e) of more than 200% in HOOC-FMS. The enzyme-FMS composite was stained with the charged gold nanoparticles and imaged by transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy showed no major secondary structural change for the enzymes entrapped in FMS. Thanks to the large, rigid, open pore structure of FMS, the reaction rate and K(m) of the entrapped enzymes in FMS were comparable to those of the free enzymes in solution. In principle, the general approach described here should be applicable to many enzymes, proteins, and protein complexes since both pore sizes and functional groups of FMS are controllable.     

DNA binding to fluorescent ruthenium species released from calcium phosphate/nanoporous silicon structures

This work centers on an analysis of calf thymus DNA binding to emissive Ru complexes which diffuse from biocompatible calcium phosphate/nanoporous silicon films. These nanostructures were characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis, and infrared vibrational spectroscopy. In terms of polynucleotide binding, three different systems were analyzed: (1) an aqueous solution of Ru(phen)(3)2+ (a control); (2) surface-adsorbed Ru(phen)(3)2+ onto undoped calcium phosphate/porous Si/Si in aqueous solution; (3) as-prepared and annealed Ru(phen)3(2+)-doped calcium phosphate/porous Si structures in water. For films with fluorescent Ru originally embedded throughout the film, biphasic diffusion character is found; such behavior is attributed to DNA binding to both surface-bound Ru(phen)(3)2+ and species which originate from deeper regions of the film.     

Patterning multiplex protein microarrays in a single microfluidic channel

The development of versatile biofunctional surfaces is a fundamental prerequisite in designing Lab on a Chip (LOC) devices for applications in biosensing interfaces and microbioreactors. The current paper presents a rapid combinatorial approach to create multiplex protein patterns in a single microfluidic channel. This approach consists of coupling microcontact printing with microfluidic patterning, where microcontact printing is employed for silanization using (3-Aminopropyl) triethoxysilane (APTES), followed by microfluidic patterning of multiple antibodies. As a result, the biomolecules of choice could be covalently attached to the microchannel surface, thus creating a durable and highly resistant functional interface. Moreover, the experimental procedure was designed to create a microfluidic platform that maintains functionality at high flow rates. The functionalized surfaces were characterized using X-ray photoelectron spectroscopy (XPS) and monitored with fluorescence microscopy at each step of functionalization. To illustrate the possibility of patterning multiple biomolecules along the cross section of a single microfluidic channel, microarrays of five different primary antibodies were patterned onto a single channel and their functionality was evaluated accordingly through a multiplex immunoassay using secondary antibodies specific to each patterned primary antibody. The resulting patterns remained stable at shear stresses of up to 50 dyn/cm(2). The overall findings suggest that the developed multiplex functional interface on a single channel can successfully lead to highly resistant multiplex functional surfaces for high throughput biological assays.