Multiphase Biomineralization: Enigmatic Invasive Siliceous Diatoms Produce Crystalline Calcite

Diatoms are considered unicellular eukaryotic organisms exclusively depositing biogenic silica. Heretofore there has been no report of calcification by these algae. Here it is shown that calcium carbonate within the stalks of Didymosphenia geminata, a nuisance species that has prolifically colonized streams and rivers globally, is biogenic in origin and occurs as a network of calcite nanofibers. The nanofibrous framework in the mineralized polysaccharide matrix imparts mechanical support to the stalks, providing stability in variable flow conditions. The results demonstrate that D. geminata possesses cellular and periplasmic carbonic‐anhydrases that contribute to carbon fixation and biomineralization, respectively. The activity of external carbonic‐anhydrase was more than 50% of the total activity, which points to its role in anchoring this bioeroding diatom on hard surfaces. The first evidence of multiphase biomineralization by diatoms that deposit both biogenic silica and crystalline biogenic calcite which are imparting distinct functional advantage to the organism is provided.     

Thermodynamic Aspects of Molluscan Shell Ultrastructural Morphogenesis

Over the years, molluscan shells have become an exemplar model system to study the process of mineral formation by living organisms, the process of biomineralization. Typically, the shells consist of a number of mineralized ultrastructural motifs, each exhibiting a specific mineral‐organic composite architecture. These are made of calcium carbonate building blocks having a well‐defined three‐dimensional morphology that is significantly different from the shape of inorganically formed counterparts. Shell ultrastructures are known to form via a biologically controlled extracellular mineralization pathway in which the organism has no direct control over mineral formation. The cellular tissue, responsible for shell biomineralization, forms an organic framework and sets‐up the physical conditions necessary for the deposition of a specific morphology, whereas the growth of the mineral part of the shell proceeds spontaneously via the process of self‐assembly. In this feature article, the ability to employ thermodynamic models from classical materials science to describe the process of self‐assembly and structural evolution of a variety of shell architectures is reviewed. Having the potential to offer an analytical framework to express ultrastructure formation in time and in space, these models not only provide a deeper insight into shell biomineralization, but also suggest tools for novel composite materials design.     

Unlocking the Latent Antimicrobial Potential of Biomimetically Synthesized Inorganic Materials

Inspired by biomineralization, biomimetic approaches utilize biomolecules and synthetic analogs to produce materials of controlled chemistry, morphology, and function under relatively benign conditions. A common characteristic of biological and biomimetic mineral‐forming processes is the generation of mineral/biomolecule nanocomposites. In this work, it is demonstrated that a facile chemical reaction may be utilized to halogenate the nitrogen‐containing moieties of the organics entrapped within bio‐inorganic composites to yield halamine compounds. This process provides rapid and potent bactericidal activity to biomimetically and biologically produced materials that otherwise lack such functionality. Additionally, bio‐inorganic composites containing the chlorinated peptide protamine are effective in rapidly neutralizing Bacillus spores (≥99.97% reduction in colony forming units within 10 min). The straightforward nature of the described process, and the efficacy of halamine compounds in neutralizing biological and chemical agents, provide new applicability to biogenic and biomimetic materials.     

Biocatalytic Nanoscale Coatings Through Biomimetic Layer‐by‐Layer Mineralization

Recent insight into the molecular mechanisms of biological mineral formation (biomineralization) has enabled biomimetic approaches for the synthesis of functional organic‐inorganic hybrid materials under mild reaction conditions. Here we describe a novel method for enzyme immobilization in thin (nanoscale) conformal mineral coatings using biomimetic layer‐by‐layer (LbL) mineralization. The method utilizes a multifunctional molecule comprised of a naturally‐occurring peptide, protamine (PA), covalently bound to the redox enzyme Glucose oxidase (GOx). PA mimics the mineralizing properties of biomolecules involved in silica biomineralization in diatoms, and its covalent attachment to GOx does not interfere with the catalytic activity. Highly efficient and stable incorporation of this modified enzyme (GOx‐PA) into nanoscale layers (～5–7 nm thickness) of Ti‐O and Si‐O is accomplished during protamine‐enabled LbL mineralization on silica spheres. Depending on the layer location of the enzyme and the type of mineral (silica or titania) within which the enzyme is incorporated, the resulting multilayer biocatalytic hybrid materials exhibit between 20–100% of the activity of the free enzyme in solution. Analyses of kinetic properties (V_max, K_M) of the immobilized enzyme, coupled with characterization of physical properties of the mineral‐bearing layers (thickness, porosity, pore size distribution), indicates that the catalytic activities of the synthesized hybrid nanoscale coatings are largely determined by substrate diffusion rather than enzyme functionality. The GOx‐PA immobilized in these nanoscale layers is substantially stabilized against heat‐induced denaturation and largely protected from proteolytic attack. The method for enzyme immobilization described here enables, for the first time, the high yield immobilization and stabilization of enzymes within continuous, conformal, and nanoscale coatings through biomimetic LbL mineralization. This approach will likely be applicable to a wide variety of surfaces and functional biomolecules. The ability to synthesize thin (nanoscale) conformal enzyme‐loaded layers is of interest for numerous applications, including enzyme‐based biofuel cells and biosensors.     

Quantifying the impact of homogeneous metal contamination usingtest structure metrology and device modeling

Deposition of metallic impurities from HF process solutions has been investigated experimentally and explained theoretically in a qualitative manner. The depositions are shown to be electrochemical in nature in that an oxidation reduction reaction results in metal ions in solution depositing on the wafer as elements with an oxidation state of 0. The theory is only qualitative in that it can only predict which metals will deposit, not how much. Experimentally, simple transmission equations can be determined which relate metallic contamination levels on Si wafer surfaces (atoms/cm²) to metal concentration in the solution (ppb). Simple test structures have been fabricated with known amounts of iron and copper contamination in the pregate oxide clean of a 1.25 μm CMOS process. Device measurements indicate device degradation in the case of copper, confirming deposition studies that copper deposits from HF solutions. Iron contaminated wafers show no contamination related device effects, in support of theoretical predictions and deposition studies indicating iron does not deposit from HF solutions. The importance and potential usefulness of test structures as homogeneous contamination monitors is illustrated through device modeling of the contamination effects observed in the test structures that can then be used to estimate the effects of such contamination on ULSI circuit performance     

In Situ Construction of High-Density Solid Electrolyte Interphase from MOFs for Advanced Zn Metal Anodes

Aqueous zinc anode has been re-evaluated due to the superiority in tackling safety and cost concerns. However, the limited lifespan originating from Zn dendritic and side reactions largely hamper commercial development. Currently, the coating prepared by simple slurry mixing is leaky and ineffectively isolate sulfate and water. Herein, inspired by the DFT calculations and the easy hydrolysis characteristic of MIL-125 (Ti), an in-situ grown high-dense TiO_2-x solid electrolyte interphase (HDSEI) with rich oxygen vacancies is successfully constructed in an aqueous electrolyte, in which the oxygen vacancies not only strengthen the hydrogen binding force thereby inhibiting the hydrogen precipitation by-reaction, but also reduce the migration energy barrier of zinc ions and enhance the mechanical properties. Profiting from the HDSEI, symmetric Zn cells survive up to remarkable 4200 h at 1 mA cm⁻², nearly 42-times than that of bare Zn anodes. In situ optical microscopy clearly reveals that the in situ grown HDSEI homogenizes the zinc deposition process, while bare zinc without HDSEI shows significant dendrites, confirming the protective nature of HDSEI. Furthermore, full Zn ion capacitors can deliver excellent electrochemical performance, providing a feasible in situ approach to construct HDSEI to implement dendrite-free metal anodes.     

Electrical and microstructural characterisation of an ultrathinsilicon interlayer used in a silicon dioxide/germanium-based MISstructure

Ultrathin (1.0 nm) Si layers have been deposited on Ge(100) surfaces using remote plasma-enhanced chemical vapour deposition (RPECVD) at 350°C followed by in situ RPECVD deposition of an SiO ₂ insulating layer. Micro-structural data from transmission electron microscopy along with elemental analysis from X-ray photoelectron spectroscopy and ion scattering spectroscopy indicate that the Si layer is present and may be pseudomorphic in nature. The formation of a Si/Ge heterojunction prior to oxide deposition minimises the formation of Ge oxides and thus controls the chemical nature of the Ge surface. Indeed, dramatic improvements in the electrical interfacial characteristics were observed in the SiO₂/Si/Ge over the SiO ₂/Ge MIS structure     

Combined Optical and MR Bioimaging Using Rare Earth Ion Doped NaYF4 Nanocrystals

Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF₄) nanocrystals (20–30 nm size) co‐doped with the rare earth ions Gd³⁺ and Er³⁺/Yb³⁺/Eu³⁺ are synthesized and dispersed in water. An efficient up‐ and downconverted photoluminescence from the rare‐earth ions (Er³⁺ and Yb³⁺ or Eu³⁺) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two‐photon induced process and allowing two‐photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two‐photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti‐claudin‐4 and anti‐mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd³⁺ co‐doped within the nanophosphors imparts strong T1 (Spin‐lattice relaxation time) and T2 (spin‐spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging.     

真空紫外光学薄膜及薄膜材料

概述了真空紫外(VUV)波段光学薄膜及薄膜材料的研究进展,金属Al膜因到短至80nm还能提供较高的反射率而得到普遍关注,在高真空和30 nm/s左右沉积速率下沉积了保护层的金属Al膜在157 nm处反射率可达90%.介质氧化物薄膜机械应力小,环境稳定性比氟化物薄膜好,在190 nm以上波段应用较广泛,但在180 nm以下波段吸收大大增加而应由氟化物薄膜取代.氟化物薄膜带宽大、吸收系数小,沉积了致密SiO2保护层的氟化物高反膜,在中心波长180 nm处可得到接近99%的反射率,而且膜系的稳定性和抗激光损伤也大大提高.氟化物减反膜在157 nm处可得到0.1%以下的反射率;到目前为止氟化物薄膜最好的沉积工艺是电阻热蒸发.     

碳酸镍沉淀过程的研究以及介孔氧化镍的制备

Nickel carbonate and nickel oxide are important inorganic fine chemicals, widely used in chemical, metallurgical, electronic and energy sources industries. The research was beginning with studying the effects of anions on precipitation process of nickel carbonate. Activity coefficient shows the effect size of the microcosmic effects between ions and solvent. Meissner's semi empirical model was applied to calculate the average activity coefficients of nickel carbonate in different electrolyte solutions at different conditions. And the conditional solubility of nickel carbonate was also calculated. The calculated results show that activity coefficients of NiCO3 in sodium sulphate solutions are less than that in sodium chloride solutions, and the solubilities in sodium sulphate solutions are larger. To improve the confidence of the calculations, Bromley's and Pitzer's models were also applied to calculate activity coefficients. The calculation results of Bromley's and Pitzer's models are very close to Meissner's results. And then experiments were carried out to measure the surface tensions, and contact angles of solutions on NiCO3 surface. According to the experiment results, the solid-liquid interface tension between NiCO3 and sodium sulphate solution is larger than that between NiCO3 and sodium chloride solution. And the tiny crystal NiCO3 has larger solubility in sodium sulphate solutions, which indicates that crystallization of NiCO3 in sodium sulphate solution is more difficult than in sodium chloride solution. The influence of SO 42- and Cl- on precipitation and crystallization process of NiCO3 was also studied based on crystal dynamics. The supersaturations at different initial concentration of reaction system were compared. Diffusion coefficients of ions were described by Glasstone's model. The diffusion coefficients of Ni2+ and CO 32- in chloride solutions are larger than those in sulphate solutions. In sulphate solutions, the diffusion coefficients and supersaturation are both less, therefore nucleation and growth rates are more slowly. Furthermore, the experiments of crystallization dynamics show that the reaction of nickel carbonate precipitation is a first order reaction while the reaction rate constant is about 0.02 min-1. Based on the theoretical analysis above, technology process of nickel carbonate precipitation was studied subsequently. The effects of nickel salt, feeding mode, controlling pH, reaction temperature and aging condition on purity, particle size, appearance of product and recovery ratio of nickel were investigated. Then using industrial nickel electrolyte solution and sodium carbonate as the raw materials, nickel carbonate product with nickel content of about 51%,average particle size of 17 μm was prepared at optimal conditions, and the recovery ratio of nickel is around 99.5%. Nickel carbonate with high purity was obtained via an innovative impurity removal process, called wash-dry-rewash-redry process. The sodium and chlorine qualitative contents of the nickel carbonate purified by the innovative method are both less than 0.01% and the sulphate content is no more than 0.1%. The mechanism of sodium and chlorine adsorption onto nickel carbonate's surface was discussed, using Stern's model of electric double layer. Moreover computational simulation technology was applied to investigate on how anions affect the crystallization of NiCO3 at atom scale. The lattice structure was relaxed before establishing crystal surfaces. The computational unit cell parameters are very close to the experimental data. Five main surfaces were studied, i.e. the (104), (100), (110), (001) and (101) surfaces. SO 42- substitutes the CO 32- on the outmost layer. Cl- adsorbs onto the surfaces and has relative weaker interaction with the surfaces. Compared with only hydrated surfaces, the growth rates of defected hydrated surfaces significantly decrease, especially for SO 24- defected ones. The (104) surface is the most stable surface and is mainly expressed in the equilibrium morphology of the resulting crystal. Finally, based on the study of nickel carbonate synthesis, nickel oxide with mesoporous structure was prepared by adding template into the nickel source and calcination. The effects of types of surfactant, dosage of surfactant, calcination temperature and calcination time on pore structure and specific surface area of nickel oxide were investigated. The results show that the surface area of the nickel oxide prepared by sodium dodecyl sulphate (SDS, anion surfactant) is much larger than those of which prepared by CTAB and octadecylamine. It is suggested that the inorganic species, basic nickel carbonate, is interacted with the template, SDS, by electrostatic attraction force. The precursor hardly has any surfactant residue after calcination. Nickel oxide with high specific surface area (>200 m2· g-1) is synthesized by adding low amount of template at the mole ratio of SDS:Ni less than 0.1:1.0. The nickel oxide has H3 type hysteresis and the pore size distribution mainly ranges from 2 nm to 10 nm. And it has good thermal stability.     

Biocompatible Cubic Boron Nitride: A Noncytotoxic Ultrahard Material

Cubic boron nitride (c-BN) has an ultrahardness and a large bandgap energy like diamond. In the last 30 years, most of the attention has been directed towards the mechanical and electronic applications of c-BN, while its biological potential has been overlooked. The authors report in vitro biocompatibility of high-quality c-BN films prepared by plasma-enhanced chemical vapor deposition using the chemistry of fluorine. c-BN films become superhydrophilic when chemical-treated in hydrogen and nitrogen plasmas with or without the impact of low-energy ions due to a marked increase in polar part of the surface free energy by removal of the fluorine atoms terminating c-BN surfaces. Satisfactory proliferation and differentiation of osteoblastic cells comparable with a control sample and a superhydrophilic nanocrystalline diamond film, and the formation of mineral deposits by biomineralization are confirmed on the superhydrophilic c-BN films with negative values of zeta potential. The results demonstrate a high potential of c-BN as a noncytotoxic ultrahard coating material for biological and biomedical applications.     

Fabrication and Characterization of Superhydrophobic Surfaces with Dynamic Stability

Superhydrophobic surfaces of dynamic stability are crucial for applications in water‐repellent materials. In this work, a hierarchical structure composed of a dendritic microporous surface with nanostructured porosity is demonstrated that shows robust superhydrophobicity with dynamic stability. The hierarchical structures are obtained on both copper foils and wires by a dynamic gas‐bubble template‐assisted electrochemical deposition method. The substrates can then be modified with alkyl thiols to obtain the surface superhydrophobicity. A new kind of testing, mechanical monitor‐assisted continuous water surface strokes, is developed to reveal the dynamic stability of the as‐prepared superhydrophobic copper wires. The as‐prepared superhydrophobic copper wires can exert a high propulsive force, and particularly, show little adhesive force in the process of continuous strokes on the water surface, exhibiting robust superhydrophobicity with dynamic stability. The approach allows a strategy for the fabrication of superhydrophobic surfaces with dynamic stability, and suggests a new method to evaluate the dynamic stability of superhydrophobic surfaces.     

Biological Assemblies Provide Novel Templates for the Synthesis of Biocomposites and Facilitate Cell Adhesion

Mechanical mismatch and the lack of interactions between implants and the natural tissue environment are major drawbacks in bone tissue engineering. Biomaterials mimicking the self‐assembly process and the composition of the bone matrix should provide new routes for fabricating biomaterials possessing novel osteoconductive and osteoinductive properties for bone repair. In the present study, bioinspired strategies are employed to design de novo self‐assembled chimeric protein hydrogels comprising leucine zipper motifs flanking a dentin matrix protein 1 domain, which is characterized as a mineralization nucleator. Results show that this chimeric protein could function as a hydroxyapatite nucleator in pseudo‐physiological buffer with the formation of highly oriented apatites similar to biogenic bone mineral. It could also function as an inductive substrate for osteoblast adhesion, promote cell surface integrin presentation and clustering, and modulate the formation of focal contacts. Such biomimetic “bottom‐up” construction with dual osteoconductive and osteoinductive properties should open new avenues for bone tissue engineering.     

Embedded benzocyclobutene in silicon: An integrated fabrication process for electrical and thermal isolation in MEMS

This paper reports a novel fabrication process to develop planarized isolated islands of benzocyclobutene (BCB) polymer embedded in a silicon substrate. Embedded BCB in silicon (EBiS) can be used as an alternative to silicon dioxide in fabrication of electrostatic micromotors, microgenerators, and other microelectromechanical devices. EBiS takes advantage of the low dielectric constant and thermal conductivity of BCB polymers to develop electrical and thermal isolation integrated in silicon. The process involves conventional microfabrication techniques such as photolithography, deep reactive ion etching, and chemical mechanical planarization (CMP). We have characterized CMP of BCB polymers in detail since CMP is a key step in EBiS process. Atomic force microscopy (AFM) and elipsometry of blanket BCB films before and after CMP show that higher polishing down force pressure and speed lead to higher removal rate at the expense of higher surface roughness, non-uniformity, and scratch density. This is expected since BCB is a softer material compared to inorganic films such as silicon dioxide. We have observed that as the cure temperature of BCB increases beyond 200 °C, the CMP removal rate decreases drastically. The results from optical microscopy, scanning electron microscopy, and optical profilometry show excellent planarized surfaces on the EBiS islands. An average step height reduction of more than 95% was achieved after two BCB deposition and three CMP steps.     

Oxidative Inorganic Multilayers for Polypyrrole Film Generation

A controlled nanoscale fabrication of conducting polymer films sets severe requirements for the preparation method and substrate. A new and versatile approach for producing thin polypyrrole films on a variety of surfaces is presented. Purely inorganic thin films are first prepared from poly(metaphosphate) and tetravalent metal ions using a sequential layer‐by‐layer technique. Redox‐active cerium(IV) polyphosphate multilayer and redox‐inactive zirconium(IV) and hafnium(IV) polyphosphate multilayers are prepared. Cerium‐based polyphosphate films grow exponentially with the number of layers but multilayers containing zirconium or hafnium exhibit a linear buildup process. All the studied systems produce relatively smooth films with initial bilayer thickness less than 2 nm. The cerium(IV) containing film is redox‐active, which is shown by its capability to form a polypyrrole layer on its surface by oxidation of pyrrole monomers in the adjacent aqueous solution. This is a general method to produce thin oxidative films of arbitrary size and form on a wide variety of surfaces.     

Integrated monitoring of ULK dielectrics out-gassing and measurement of pore sealing efficiency by residual gas analysis technique

Residual gas analysis is a well-known technique used in the semi-conductor industry. This paper presents the RGA as an effective method to monitor wafer out-gassing during the degas process prior to barrier/copper seed deposition. The technique is easy to use, repeatable and very sensitive to the hydrophobic or hydrophilic nature of the surfaces. Moreover, it has been demonstrated that RGA is the technique of choice to evaluate the pore sealing efficiency of ultra low-k dielectric in high volume manufacturing environment.     

Excimer-laser ablation and etching

The characteristics of excimer lasers and the nature of ablation and etching processes are described. The two kinds of laser ablation mechanisms, thermal and electronic, are discussed. Thermal processes all rely on an intense laser pulse to heat a surface very rapidly. Electronic mechanisms do not rely on heating. Two of these quantum-type processes have been discussed widely. In the first, laser photons directly excite and break the bonds of the solid, causing ejection of material. In the second, photoexcitation creates electron-hole pairs, the potential energy of which can be coupled directly into kinetic energy of the atoms via a radiationless process. The energized atoms are able to overcome the surface binding energy, and again material is ejected. Pulsed laser etching has many of the same physical-interaction mechanisms as laser ablation but requires an active chemical medium to be in contact with the solid because laser-induced chemical reactions serve as the driving force for material removal. Issues that must be addressed prior to the successful implementation of an excimer-laser fabrication tool are discussed. The use of patterned beams for direct patterning of surfaces is considered. Microelectronic applications suitable for excimer-laser ablation and etching are examined     

电化学STM及对固液界面的研究

电化学扫描探针显微术是将电化学研究系统和扫描探针显微技术（Scanning Probe Microscopy:SPM)相结合而产生的一门新的研究技术。该技术的最大特点是可以在溶液环境下工作,以原子分辨率,实时,原位,三维空间观察,控制化学反应及过程,又可以对材料进行原子级加工等,本文将以SPM技术的重要分支－电化学扫描隧道显微技术（ECSTM：electrochemical scanning tunneling microscopy)为主,简要介绍其工作原理,对固液界面的研究及发展趋势。