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Jillian M Buriak

Publications and source records attributed to Jillian M Buriak.

11 recordsLinked to original sources
PubMed2006

Trapping silicon surface-based radicals.

The spontaneous one-electron reduction of diazonium salts on hydride-terminated porous silicon (pSi) and flat silicon produces surface radicals that can be trapped chemically. These silicon radicals react with reagents such as alkyl/arylselenoethers, alkenes, alkynes, and alkylbromide groups to generate covalently bound functionalities in a manner analogous to the chemistry of molecular-based silicon radical species, prepared via different methods. When pSi is exposed to an acetonitrile solution of any of the three diazonium salts examined in this study, aryl groups from the diazonium precursor become covalently bound and significant oxidation is noted; if, however, a reactive trapping agent is added, such as an alkyl/arylselenoether or a carbon-carbon unsaturated bond, no aryl group attachment is observed and oxidation is circumvented due to the efficiency of the trapping chemistry. The reactions proceed rapidly, in less than 3 h to maximum coverage, at room temperature. The diazonium salt-initiated radical reaction with alpha,omega-alkenes and alkynes tolerates various functional groups including aryl, diene, diyne, carboxylic acid, and hydroxyl, reacting exclusively via the carbon-carbon unsaturated bond; alpha,omega-bromoalkenes are not, however, compatible with this chemistry. A silicon-based molecule, tris(trimethylsilyl)silane, in the presence of a diazonium salt initiator and a primary alkyne does not lead to the hydrosilylation product but to tris(trimethylsilyl)silylbromide and the hydrogenated arene, derived from the diazonium. The difference in reactivity between the molecule and the surface is due to the fact that the silicon surface is a source of electrons to reduce the diazonium salts to aryl radicals, whereas a heterolytic pathway is followed in the molecular silane case.

Journal Article↗
PubMed2006

Nanoscale patterning of two metals on silicon surfaces using an ABC triblock copolymer template.

Patterning technologically important semiconductor interfaces with nanoscale metal films is important for applications such as metallic interconnects and sensing applications. Self-assembling block copolymer templates are utilized to pattern an aqueous metal reduction reaction, galvanic displacement, on silicon surfaces. Utilization of a triblock copolymer monolayer film, polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO), with two blocks capable of selective transport of different metal complexes to the surface (PEO and P2VP), allows for chemical discrimination and nanoscale patterning. Different regions of the self-assembled structure discriminate between metal complexes at the silicon surface, at which time they undergo the spontaneous reaction at the interface. Gold deposition from gold(III) compounds such as HAuCl4(aq) in the presence of hydrofluoric acid mirrors the parent block copolymer core structure, whereas silver deposition from Ag(I) salts such as AgNO3(aq) does the opposite, localizing exclusively under the corona. By carrying out gold deposition first and silver second, sub-100-nm gold features surrounded by silver films can be produced. The chemical selectivity was extended to other metals, including copper, palladium, and platinum. The interfaces were characterized by a variety of methods, including scanning electron microscopy, scanning Auger microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.

Journal Article↗
PubMed2006

Dehydrogenative silane coupling on silicon surfaces via early transition metal catalysis.

Derivatization of silicon surfaces is an area of intense interest due to the centrality of silicon in the microelectronics industry and because of potential promise for a myriad of other applications. In this paper, we investigate the feasibility of Si-Si bond formation directly on the surface to contrast with the more widely studied Si-C and Si-O bond forming reactions. Functionalization of hydride-terminated silicon surfaces with silanes is carried out via early transition metal mediated dehydrogenative silane coupling reactions. Zirconocene and titanocene catalyst systems were evaluated for heterocoupling of a molecular silane, RSiH3, with a surface Si-H group on Si(s). The zirconocene catalysts proved to be much more reactive than the titanium system, and so the former was examined exclusively. The silanes, aromatic or aliphatic, are bonded to the silicon surface through direct Si-Si bonds, although the level of incorporation of the trihydroarylsilanes was substantially higher than that of the aliphatic silanes. The reaction proceeds on nanocrystalline hydride-terminated porous silicon surfaces, as well as flat Si(100)-H(x) and Si(111)-H interfaces. The reactions were studied by a variety of techniques, including FTIR, SIMS, and XPS.

Catalysis↗
PubMed2005

Block copolymer-templated chemistry on Si, Ge, InP, and GaAs surfaces.

Patterning of semiconductor surfaces is an area of intense interest, not only for technological applications, such as molecular electronics, sensing, cellular recognition, and others, but also for fundamental understanding of surface reactivity, general control over surface properties, and development of new surface reactivity. In this communication, we describe the use of self-assembling block copolymers to direct semiconductor surface chemistry in a spatially defined manner, on the nanoscale. The proof-of-principle class of reactions evaluated here is galvanic displacement, in which a metal ion, M+, is reduced to M0 by the semiconductor, including Si, Ge, InP, and GaAs. The block copolymer chosen has a polypyridine block which binds to the metal ions and brings them into close proximity with the surface, at which point they undergo reaction; the pattern of resulting surface chemistry, therefore, mirrors the nanoscale structure of the parent block copolymer. This chemistry has the added advantage of forming metal nanostructures that result in an alloy or intermetallic at the interface, leading to strongly bound metal nanoparticles that may have interesting electronic properties. This approach has been shown to be very general, functioning on a variety of semiconductor substrates for both silver and gold deposition, and is being extended to organic and inorganic reactions on a variety of conducting, semiconducting, and insulating substrates.

Arsenicals↗
PubMed2005

Silver nano-inukshuks on germanium.

The integration of metallic nanostructures with semiconductors is important for a variety of technological applications. Through an efficient galvanic displacement reaction on germanium, complex silver nanostructures form spontaneously in aqueous conditions at room temperature. The structures, termed nano-inukshuks, are based on stacks of hexagonal metallic structures that grow, initially, parallel to the surface normal of the germanium. TEM, SEM, XPS, XRD, and EDS indicate that the structures are crystalline silver and, based on open cell potential studies, that their nucleation takes place in the first 100 s, followed by growth of the silver structures, most likely through Volmer-Weber growth.

Crystallization↗
PubMed2004

Optical sensing of amine vapors with a series of tin compounds.

Certain common Sn(2+) salts exhibit bright luminescence of various optical wavelengths upon excitation with 254 nm UV irradiation at room temperature. Light emission can be selectively quenched by exposure to low concentrations of amines, and can in some cases be regenerated with either a nitrogen purge or exposure to acid vapors, rendering the compounds useful for application in optical sensing arrays.

Journal Article↗
PubMed2003

Nanopatterning of alkynes on hydrogen-terminated silicon surfaces by scanning probe-induced cathodic electrografting.

The electrochemical cathodic electrografting reaction, previously demonstrated on bulk silicon surfaces, can be patterned on the nanoscale utilizing conducting probe atomic force microscopy (CP-AFM). Alkyne electrografting is a particularly useful chemical technique since it leads to direct covalent attachment of conjugated alkynes to silicon. In addition, application of a forward bias during the reaction renders the surface less sensitive to oxidation and the resulting monolayers are very stable in air and basic aqueous solution. Alkyne monolayer lines can be drawn down to 40 nm resolution using a Pt-coated AFM tip, and the heights of the monolayers scale with the molecular length of the alkyne. The tip is biased (+) and the surface is biased (-) to drive the cathodic electrografting reaction under ambient conditions. The resistance of the monolayers to fluoride, as well as friction force microscopy, indicate that the alkynes are covalently bonded to the surface, not oxide-based, and hydrophobic. The reaction does not work with alkenes, and therefore hydrosilylation is not the primary mode of reaction. Wider lines (300 nm) can be produced using broadened Pt-coated AFM tips. This reaction could be important for the interfacing of conjugated molecules directly to silicon in a spatially controlled fashion.

Journal Article↗