silicon and aniline

The modification of a surface at the molecular level with precise control of the building blocks generates an integrated molecular system. This field has progressed rapidly in recent years through the use of self-assembled monolayer (SAM) interfaces. Recent developments on surface-initiated chemical reactions, functionalization, and graft polymerization on SAM interfaces are emphasized in the present review. A number of surface modifications by grafting are reviewed. The grafting of polyaniline on a glass surface, previously modified with a silane self-assembled monolayer (SAM), is examined in detail for both planar and 3-D systems, such as fibers, nanoparticles, and even polymer patterned surfaces. We also discuss the graft polymerization of water-soluble polymers on the surface of silicon nanoparticles, which generate stable aqueous colloidal solutions and have numerous applications. Finally, we compare and review some surface-modification techniques on the surfaces of polymers, such as two-solvent entrapment, polymer blending, and chemical grafting, which improve their biocompatibility.

Topics: Aniline Compounds; Biocompatible Materials; Nanostructures; Polymers; Silicon

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS), a parallel technique to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), utilizes inorganic particles or porous surfaces to aid in the desorption/ionization of low-molecular-weight (MW) analytes. As a matrix-free and "soft" LDI approach, SALDI offers the benefit of reduced background noise in the low MW range, allowing for easier detection of biologically significant small MW species. Despite the inherent advantages of SALDI-MS, it has not reached comparable sensitivity levels to MALDI-MS. In relation to mass spectrometry imaging (MSI), intense efforts have been made in order to improve sensitivity and versatility of SALDI-MSI. We describe herein a detailed protocol that utilizes a hybrid LDI method, matrix-enhanced SALDI-MS (ME-SALDI MS), to detect and image low MW species in an imaging mode.

Topics: Analytic Sample Preparation Methods; Aniline Compounds; Molecular Imaging; Molecular Weight; Pyridines; Silicon; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Gold nanopillars, functionalized with an organic self-assembled monolayer, can be used to measure the electrical conductance properties of immobilized proteins without aggregation. Measurements of the conductance of nanopillars with cytochrome P450 2C9 (CYP2C9) proteins using conducting probe atomic force microscopy demonstrate that a correlation exists between the energy barrier height between hopping sites and CYP2C9 metabolic activity. Measurements performed as a function of tip force indicate that, when subjected to a large force, the protein is more stable in the presence of a substrate. This agrees with the hypothesis that substrate entry into the active site helps to stabilize the enzyme. The relative distance between hopping sites also increases with increasing force, possibly because protein functional groups responsible for electron transport (ETp) depend on the structure of the protein. The inhibitor sulfaphenazole, in addition to the previously studied aniline, increased the barrier height for electron transfer and thereby makes CYP2C9 reduction more difficult and inhibits metabolism. This suggests that P450 Type II binders may decrease the ease of ETp processes in the enzyme, in addition to occupying the active site.

Topics: Aniline Compounds; Catalytic Domain; Cytochrome P-450 CYP2C9; Cytochrome P-450 Enzyme System; Dapsone; Electric Conductivity; Electron Transport; Electrons; Flurbiprofen; Gold; Humans; Immobilized Proteins; Metal Nanoparticles; Microscopy, Electron, Scanning; Protein Binding; Protein Conformation; Protein Engineering; Silicon; Sulfaphenazole

Mechanical abrasion is an extremely simple, rapid, and low-cost method for deposition of carbon-based materials onto a substrate. However, the method is limited in throughput, precision, and surface compatibility for drawing conductive pathways. Selective patterning of surfaces using laser-etching can facilitate substantial improvements to address these current limitations for the abrasive deposition of carbon-based materials. This study demonstrates the successful on-demand fabrication of fully-drawn chemical sensors on a wide variety of substrates (e.g., weighing paper, polymethyl methacrylate, silicon, and adhesive tape) using single-walled carbon nanotubes (SWCNTs) as sensing materials and graphite as electrodes. Mechanical mixing of SWCNTs with solid or liquid selectors yields sensors that can detect and discriminate parts-per-million (ppm) quantities of various nitrogen-containing vapors (pyridine, aniline, triethylamine).

Topics: Aluminum Oxide; Aniline Compounds; Carbon; Electrodes; Ethylamines; Glass; Paper; Polymethyl Methacrylate; Pyridines; Silicon; Surface Properties

Heterolytic splitting of the Si-H bond mediated by a Ru-S bond forms a sulfur-stabilized silicon cation that is sufficiently electrophilic to abstract fluoride from CF(3) groups attached to selected anilines. The ability of the Ru-H complex, generated in the cooperative activation step, to intramolecularly transfer its hydride to the intermediate carbenium ion (stabilized in the form of a cationic thioether complex) is markedly dependent on the electronic nature of its phosphine ligand. An electron-deficient phosphine thwarts the reduction step but, based on the Ru-S catalyst, half of an equivalent of an added alkoxide not only facilitates but also accelerates the catalysis. The intriguing effect is rationalized by the formation of a hydride-bridged Ru-S dimer that was detected by (1)H NMR spectroscopy. A refined catalytic cycle is proposed.

Topics: Aniline Compounds; Catalysis; Cations; Dimerization; Molecular Structure; Organometallic Compounds; Ruthenium; Silicon; Sulfur

Surface functionalization of semiconductors has been the backbone of the newest developments in microelectronics, energy conversion, sensing device design, and many other fields of science and technology. Over a decade ago, the notion of viewing the surface itself as a chemical reagent in surface reactions was introduced, and adding a variety of new functionalities to the semiconductor surface has become a target of research for many groups. The electronic effects on the substrate have been considered as an important consequence of chemical modification. In this work, we shift the focus to the electronic properties of the functional groups attached to the surface and their role on subsequent reactivity. We investigate surface functionalization of clean Si(100)-2 × 1 and Ge(100)-2 × 1 surfaces with amines as a way to modify their reactivity and to fine tune this reactivity by considering the basicity of the attached functionality. The reactivity of silicon and germanium surfaces modified with ethylamine (CH(3)CH(2)NH(2)) and aniline (C(6)H(5)NH(2)) is predicted using density functional theory calculations of proton attachment to the nitrogen of the adsorbed amine to differ with respect to a nucleophilic attack of the surface species. These predictions are then tested using a model metalorganic reagent, tetrakis(dimethylamido)titanium (((CH(3))(2)N)(4)Ti, TDMAT), which undergoes a transamination reaction with sufficiently nucleophilic amines, and the reactivity tests confirm trends consistent with predicted basicities. The identity of the underlying semiconductor surface has a profound effect on the outcome of this reaction, and results comparing silicon and germanium are discussed.

Topics: Amines; Aniline Compounds; Chemistry, Physical; Electronics; Ethylamines; Germanium; Organometallic Compounds; Semiconductors; Silicon; Spectrophotometry, Infrared; Surface Properties

Topics: Amines; Aniline Compounds; Benzene Derivatives; Electrons; Silicon; Stereoisomerism

We present a scanning tunneling microscopy and first-principles calculations study of the adsorption structures of aniline on a Si(5 5 12)-2x1 surface. Dissociation from the aniline molecules of one or two H atom(s) bonded to N is favored, and then adsorption onto adatom, tetramer, and dimer rows of Si(5 5 12)-2x1 occurs in several distinct configurations. On the adatom row, aniline binds to an adatom in a tilted configuration, which is formed via a sigma bond between the adatom and N, with one dissociated H atom adsorbed on a nearby adatom. No further hydrogen dissociation occurs. On the tetramer and dimer rows, the structures with two dissociated hydrogens and upright configurations are the most stable. Aniline does not adsorb onto the honeycomb chains; this adsorption configuration has a low adsorption energy. In all the adsorption configurations of aniline on this surface, the molecule's aromaticity is preserved. Thus Si-N bonding of aromatic amine molecules provides a strategy for the homogeneous aromatic functionalization of high index Si surfaces.

Topics: Adsorption; Aniline Compounds; Computer Simulation; Microscopy, Scanning Tunneling; Models, Chemical; Models, Molecular; Silicon; Surface Properties

Au and Ag nanoshells are investigated as substrates for surface-enhanced Raman scattering (SERS). We find that SERS enhancements on nanoshell films are dramatically different from those observed on colloidal aggregates, specifically that the Raman enhancement follows the plasmon resonance of the individual nanoparticles. Comparative finite difference time domain calculations of fields at the surface of smooth and roughened nanoshells reveal that surface roughness contributes only slightly to the total enhancement. SERS enhancements as large as 2.5 x 10(10) on Ag nanoshell films for the nonresonant molecule p-mercaptoaniline are measured.

Topics: Aniline Compounds; Gold; Microscopy, Electron, Scanning; Models, Theoretical; Nanotechnology; Normal Distribution; Polyvinyls; Scattering, Radiation; Silicon; Silver; Spectrophotometry; Spectrophotometry, Infrared; Spectrum Analysis; Spectrum Analysis, Raman; Surface Properties; Time Factors; Ultraviolet Rays