Formation of gold-capped silicon nanocolumns on silicon substrate

Gold-capped silicon nanocolumns regularly distributed over silicon substrate were obtained. The columns length was roughly 100?nm; their deviation from perpendicular axis was less than 2°. The diameter of the columns was of the order of 10?nm or below of that. The proposed procedure of nanostructuring included the following main steps: deposition of aluminum thin layer (100?C500?nm) by magnetron sputtering on (100) oriented Si wafers; formation of porous self-ordered alumina structures by electrochemical anodizing of the Al film in oxalic acid; electroless inversion of Au in alumina pores; and reactive ion etching. The obtained Si?CAu structures are of importance as the platforms for biosensing applications, while the gold-free structures are of interest in photovoltaics.     

Tower-like structure of ZnO nanocolumns

The tower-like structure of ZnO nanocolumns grows normal to alumina substrates via pyrolysis and oxidation of ZnS, and is formed by stacking of ZnO nanocrystals layer upon layer.     

Vertical growth of cadmium sulfide crystals on a silicon substrate

Russian Journal of Physical Chemistry A - The results of the technological and microscopy studies of the mechanisms of the vertical growth of cadmium sulfide crystals during vacuum synthesis from...     

Formation of nanocomposite platinum catalysts on porous silicon

Platinum nanoparticles supported on porous silicon were synthesized by radiation-chemical reduction in solutions of reverse micelles. The Pt nanoparticles obtained are electrondeficient. The degree of porosity, conductivity type, pore geometry of the silicon matrix, and precursor parameters affect the size, shape, and charge state of the platinum catalysts.     

Methodology for miniaturized CE and insulation on a silicon substrate

We have developed a synchronously switched cyclic capillary electrophoresis (CE) separator that is fabricated on a silicon substrate and glass. Au electrodes were also integrated on the chip that could be wire bonded to the printed circuit board (PCB). The advantage of using a cyclic separator is that it has the high resolution and the ability to separate each sample to the designated reservoir from mixed samples. This approach makes it possible to reduce the supplied voltage and the total chip size. Another goal of this work was to introduce the methodology of electroosmotic flow (EOF) on the silicon substrate and to separate DNA samples using a modified double-T injector.     

Protein adsorption and cell adhesion on RGD-functionalized silicon substrate surfaces

A method was developed to modify silicon surfaces with good protein resistance and specific cell attachment. A silicon surface was initially deposited using a block copolymer of N-vinylpyrrolidone (NVP) and 2-hydroxyethyl methacrylate (HEMA) (PVP-b-PHEMA) film through surface-initiated atom transfer radical polymerization and then further immobilized using a short arginine-glycine-aspartate (RGD) peptide. Our results demonstrate that the RGD-modified surfaces (Si-RGD) can suppress non-specific adsorption of proteins and induce the adhesion of L929 cells. The Si-RGD surface exhibited higher cell proliferation rates than the unmodified silicon surface. This research established a simple method for the fabrication of dual-functional silicon surface that combines antifouling and cell attachment promotion.     

Formation of silver nanoparticles and nanocraters on silicon wafers

Silver nanocraters and monodisperse nanoparticles were formed on silicon wafers by spin-coating of an aqueous AgNO3/PVA solution and calcination of the resulting Ag+/PVA composite film. The monodisperse Ag nanoparicles were formed from small Ag+/PVA aggregates and were uniformly and stably distributed on the substrate surface. They were located as close as 2.8 nm apart (edge to edge) without coalescence. This nanoparticle stability was apparently derived from their interaction with the oxidized wafer surface. On the other hand, Ag metallic nanocraters with and without nanodots at their centers were produced from large Ag+/PVA aggregates. The explosive decomposition of AgNO3 and PVA by calcination could explain their formation. When Ag+ ions were reduced to Ag nanoparticles prior to calcination, larger Ag nanoparticles were produced probably due to aggregation of closely situated nanoparticles. Those nanoparticles that were located far enough stayed intact. Perspectives are discussed in terms of potential applications.     

Elimination of aggregates of ferredoxin from its self-assembled monolayer on silicon substrate

The self-assembled ferredoxin monolayer onto the (100) surface of the silicon substrate was prepared and the nonspecifically adsorbed aggregates of ferredoxin on the substrate were successfully eliminated by using a zwitterionic surfactant, 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS). The AFM image of the self-assembled ferredoxin monolayer on the silicon substrate treated with CHAPS clearly shows that the size of ferredoxin clusters is about 20–30 nm, which is on the order of an aggregate of about five ferredoxin molecules, whereas the size of ferredoxin aggregates on the substrate without CHAPS treatment was measured to be about 100–200 nm. Those results offer a useful method for the elimination of the nonspecific adsorption of proteins onto inorganic substrates, which has been a long-term problem in the fabrication of biomolecular electronic devices by the self-assembly technique.     

Biofunctionalization on alkylated silicon substrate surfaces via "click" chemistry

Biofunctionalization of silicon substrates is important to the development of silicon-based biosensors and devices. Compared to conventional organosiloxane films on silicon oxide intermediate layers, organic monolayers directly bound to the nonoxidized silicon substrates via Si-C bonds enhance the sensitivity of detection and the stability against hydrolytic cleavage. Such monolayers presenting a high density of terminal alkynyl groups for bioconjugation via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC, a "click" reaction) were reported. However, yields of the CuAAC reactions on these monolayer platforms were low. Also, the nonspecific adsorption of proteins on the resultant surfaces remained a major obstacle for many potential biological applications. Herein, we report a new type of "clickable" monolayers grown by selective, photoactivated surface hydrosilylation of α,ω-alkenynes, where the alkynyl terminal is protected with a trimethylgermanyl (TMG) group, on hydrogen-terminated silicon substrates. The TMG groups on the film are readily removed in aqueous solutions in the presence of Cu(I). Significantly, the degermanylation and the subsequent CuAAC reaction with various azides could be combined into a single step in good yields. Thus, oligo(ethylene glycol) (OEG) with an azido tag was attached to the TMG-alkyne surfaces, leading to OEG-terminated surfaces that reduced the nonspecific adsorption of protein (fibrinogen) by >98%. The CuAAC reaction could be performed in microarray format to generate arrays of mannose and biotin with varied densities on the protein-resistant OEG background. We also demonstrated that the monolayer platform could be functionalized with mannose for highly specific capturing of living targets (Escherichia coli expressing fimbriae) onto the silicon substrates.     

七氟丁酸酐有序超薄膜的制备与结构

在涂敷有聚合物PEI涂层的单晶硅表面上制备了HFBA单层分子膜,接触解测量及XPS结果表明,PFBA在PEI表面产生了化学吸附发生了化学键合(酰胺键),形成了低表面能的HFBA单分子层膜,这一吸附反应的动力学行为可能表现为Langmuir单分子层化学吸附。     

Formation of organic monolayers on silicon via gas-phase photochemical reactions

A new method for the formation of molecular monolayers on silicon surfaces utilizing gas-phase photochemical reactions is reported. Hydrogen-terminated Si(111) surfaces were exposed to various gas-phase molecules (hexene, benzaldehyde, and allylamine) and irradiated with ultraviolet light from a mercury lamp. The surfaces were studied with in situ Fourier transform infrared spectroscopy, high-resolution electron energy loss spectroscopy, and scanning tunneling microscopy. The generation of gas-phase radicals was found to be the initiator for organic monolayer formation via the abstraction of hydrogen from the H/Si(111) surface. Monolayer growth can occur through either a radical chain reaction mechanism or through direct radical attachment to the silicon dangling bonds.     

Formation of threadlike nanostructures of silicon and silicon carbide by chemical vapor deposition

Synthesis of threadlike nanostructures of silicon and silicon carbide by chemical vapor deposition (CVD) using dichlorosilane pyrolysis in the presence of CCl4 and CF2Cl2 in nitrogen has been carried out. Nitrogen molecules react on active surface areas of the substrate originating during etching with a gaseous mixture of 7.5% SiH2Cl2–7.5% CCl4–85% N2.     

Selective deposition of polystyrene nanoparticles in a nanoetchpit array on a silicon substrate

Nanometer-sized polystyrene particles were selectively deposited by interfacial tension in nanometer-sized etchpit arrays made on a silicon substrate.     

Autoassembly of nanofibrous zeolite crystals via silicon carbide substrate self-transformation

ZSM-5 zeolite nanofibers with a size of 90 nm and lengths up to several micrometers were prepared via in-situ silicon carbide support self-transformation. The morphology and aggregation degree of these zeolite nanofibers could be modified by adjusting the pH conditions, the nature of the mineralizer (OH- or F-), or the synthesis duration. The novelty consists of the preparation of zeolite nanowires without the use of any organogelating agent, along with controlled macroscopic shapes (extrudates, foam monolith) for direct use as a structured reactor. Finally, these materials are catalytically active in the conversion of methanol to gasoline range hydrocarbons (MTG process) and hence exhibit the typical solid acidity of zeolitic materials.     

硅基底金纳米粒子微阵列电极的制备及其电化学性质的研究— 多孔硅电致发光 生物传感器研究的前期探索

用Frens法制备了不同粒径的金纳米粒子,并用透射电镜、紫外可见分光光度法进行了表征。用自组装技术得到了金膜电极表面的金纳米粒子二维阵列电极,用扫描电镜、电化学等方法对该微阵列电极进行了表征。结果表明,当金电极表面被自组装膜完全覆盖后,电化学反应不再发生,而将金纳米粒子组装到膜上以膈,才得到电化学信号。我们认为,金纳米粒子在这里对电荷的跨膜转移有很强的促进作用。对于该过程的研究,用助于理解电荷的转移机制,对进一步理解电荷隧穿过程有一定的指导意义。     

Effect of negative substrate bias on HWCVD deposited nanocrystalline silicon (nc-Si) films

The influence of the negative substrate bias on the interfacial and microstructural characteristics of nanocrystalline silicon (nc-Si) thin films was deposited by hot wire chemical vapor deposition (HWCVD). Structural characterization of nc-Si films was performed by small angle X-ray diffraction (SAXRD), Raman spectroscopy, X-ray reflectivity (XRR) and field emission scanning electron microscopy (FESEM). Crystalline fraction and crystallite size increases from 61.31 to 74.13% and 13.3 to 21.6 nm, respectively, with an increasing negative bias from 0 to ?200 V. Furthermore, the deposition rate of nc-Si films increases from 25 to 68 nm/min by increase of negative substrate bias from 0 to ?200 V.     

Epitaxial chemical deposition of ZnO nanocolumns from NaOH solutions

A new method of depositing expitaxial ZnO nanocolumns on sputter-coated ZnO substrates is described that utilizes supersaturated zincate species in sodium hydroxide solutions and requires no complexing agents. Uniform arrays of columns are grown reproducibly over entire substrates in 10-50 min. Columns are 50-2000 nm long and 50-100 nm wide. Strict substrate cleaning and/or preparation was not necessary with this method, in contrast to many other techniques, probably because the high pH generates a reproducible surface. The interfacial properties of the substrate are critical to lowering the activation energy for columnar growth; therefore films grow only on substrates precoated with ZnO, not on bare glass or ITO- or SnO2-coated glass. Factors affecting the column growth are elucidated, and experimental observations are correlated with crystal growth theory.     

Characterization of sol-gel processing of calcium phosphate thin films on silicon substrate by FTIR spectroscopy

Calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, CHAp) films were obtained on silicon substrates by a sol-gel method using a spin-coating technique. In the sol-gel process, ethylendiamintetraacetic acid and 1,2-ethandiol, triethanolamine and polyvinyl alcohol were used as complexing agents and gel network forming agents, respectively. The samples were annealed at 1000 °C for 5 h in air after each spinning procedure. Spin-coating and annealing procedures were repeated 5, 8 and 10 times. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDX) and Fourier Transform infrared spectroscopy (FTIR). FTIR-spectroscopy allowed us to predict the formation of oxyhydroxyapatite Ca₁₀(PO₄)₆(OH)_2-2xO_x on the Si substrate. Moreover, according to the FTIR results, the side phase β-Ca₃(PO₄)₂ has been formed instead of α-Ca₃(PO₄)₂. In addition, the anhydrous dicalcium, phosphate phase CaHPO₄ was also detected spectroscopically.     

Electroformation of giant phospholipid vesicles on a silicon substrate: advantages of controllable surface properties

We introduce the use of silicon (Si) as a substrate for the electroformation of giant phospholipid vesicles. By taking advantage of the tunability of silicon surface properties, we varied the organization of the phospholipid film on the electrode and studied the consequences on vesicle formation. In particular, we investigated the effects of Si surface chemistry and microtopology on the organization of the phospholipid film and the properties of the final vesicles. We established correlations between chemical homogeneity, film defects, and resulting vesicle size distribution. By considering phospholipid films that are artificially fragmented by electrode microstructures, we showed that the characteristic size of vesicles decreases with a decrease in microstructure dimensions. We finally proposed a way to control the vesicle size distribution by using a micropatterned silicon dioxide layer on a Si substrate.     

Formation and thermal decomposition of silicon oxynitride compounds II

In studies on the reactions of silicon oxynitride, Si₂N₂O, with lithium oxide and of lithium metasilicate with lithium nitride, the formation of a previously unknown compound with stoichiometry Li₅SiNO₃ has been observed.

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Zusammenfassung Eine bisher unbekannte Verbindung der Zusammensetzung Li₅SiNO₃ wurde bei Reaktionen von Siliciumoxynitrid (Si₂N₂O) mit Lithiumoxid und von Lithiummetasilikat mit Lithiumnitrid erhalten.

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(Si₂N₂O) , Li₅SiNO₃.