Biomedical subjects

Martin Moskovits

Publications and source records attributed to Martin Moskovits.

4 recordsLinked to original sources

PubMed2006

Hot spots in silver nanowire bundles for surface-enhanced Raman spectroscopy.

We report a simple strategy for placing analyte molecules in hot spots between closely spaced nanowires leading to intense SERS enhancement. The results are highly reproducible from experiment to experiment likely because of the regularity of the SERS substrate, which consists of highly ordered and regular silver nanowires fabricated in porous aluminum oxide. Because the silver nanowires are sealed in the pores of PAO, this system is potentially immune to contamination until it is ready for use, at which point the alumina matrix is etched, thereby allowing the silver nanowires to collapse into bundles and form hot spots in the region of close contact between the nanowires, trapping the analyte in those junctions.

Journal Article↗

PubMed2005

Adsorbate-induced silver nanoparticle aggregation kinetics.

Metal sols are often stabilized in solution by the presence of a charged double layer surrounding each colloidal nanoparticle that produces a coulomb barrier to aggregation. The nanoparticles can be induced to aggregate by replacing the charged surface species by uncharged adsorbate. We present a simple analysis that produces an expression for the initial rate constant describing the aggregation process, which is shown to depend nontrivially on the adsorbate concentration. The expression is tested experimentally by following and analyzing the time rate of decrease of the surface plasmon resonance absorption of isolated Ag nanoparticles in aqueous solution. The experimental result accords well with theory, producing a rough estimate of the (adsorbate-concentration dependent) barrier to aggregation that in the absence of added adsorbate is approximately equal to 0.08 eV.

Letter↗

PubMed2005

Encoding morphology in oxide nanostructures during their growth.

Programmable control over the overall structure of SnO(2) nanowires grown by vapor-solid synthesis is shown to be possible by pulse modulating the flow rate of the carrier gas in which oxygen (one of the reactants) is entrained. The control is shown to depend on the local oscillation of the supersaturation condition for the SnO vapor (another reactant) in the vicinity of the growing nanostructure. The latter triggers dramatic, reproducible oscillations in the lateral dimensions of the nanostructure and in the direction of its growth. The method provides a means for producing predictable morphological and compositional variations in 1D nanostructures, thereby potentially resulting in a high yield of custom-designed nanostructures.

Journal Article↗

PubMed2004

Composite mesostructures by nano-confinement.

In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration and confinement-induced entropy loss can play dominant roles in determining molecular organization. Here we present a systematic study of the confined assembly of silica-surfactant composite mesostructures within cylindrical nanochannels of varying diameters. Using exactly the same precursors and reaction conditions that form the two-dimensional hexagonal SBA-15 mesostructured thin film, unprecedented silica mesostructures with chiral mesopores such as single- and double-helical geometries spontaneously form inside individual alumina nanochannels. On tightening the degree of confinement, a transition is observed in the mesopore morphology from a coiled cylindrical to a spherical cage-like geometry. Self-consistent field calculations carried out to account for the observed mesostructures accord well with experiment. The mesostructures produced by confined syntheses are useful as templates for fabricating highly ordered mesostructured nanowires and nanowire arrays.

Microscopy, Electron↗