Novel Synthesis of Pt₆Si₅ Nanowires and Pt₆Si₅–Si Nanowire Heterojunctions by Using Polycrystalline Pt Nanowires as Templates

Abstract

poly(oxyethylene) methacrylate (HPOEM), M n~5 26 g/mol, corresponding to m~10) and poly(ethylene glycol) methyl ether methacrylate, (referred to herein as poly(oxyethylene) methacrylate (POEM), M n~4 75 g/mol, corresponding to n~8.5). The comb polymer was carboxylated by succinic anhydride, as described elsewhere [24]. The comb polymer was characterized by 1 H NMR in CDCl 3 ; 4.12 ppm (±OCH 3 ), 3.6±3.65 ppm (CH 2 ±CH 2 ±O±), 0.5±2 ppm (CH 2 ±C±(CH 3 )±) and 3.39 ppm (±OH). The composition of the terpolymer was 61 wt.-% MMA, 21 wt.-% HPOEM, and 18 wt.-% POEM using the peaks at 4.12 ppm and 3.39 ppm for quantification. The molecular weight of the comb polymer was~21 000 Da with a polydispersity of~1.7, as measured by a gel permeation chromatography±laser light scattering system (a Shimadzu LC-10 AD VP pump, Waters 410 differential refractometer, miniDawn laser light scatterer, and two Polymer Labs Plgel columns connected in series). The comb polymer solution (4 mg mL ±1 in THF) was pre-filtered through a 0.2 lm filter and eluted at 35 C. The value of dn/dc = 0.086 was based on the assumption of 100 % recovery of the injected mass, and calculated using the software provided with the miniDawn system.Micropatterning of Comb Polymer: PMMA, PET, and PS were purchased from GoodFellow Corp., and were washed with ethanol prior to use. For the substrates coated with FN, the substrates were incubated with 20 lg mL ±1 FN solution in PBS for 1 h. The comb polymer was micropatterned using an oxidized poly(dimethyl siloxane) (PDMS) stamp presenting micrometer-sized negative features. The stamp was inked with a 1 % (w/v) solution of the comb polymer in a 50:50 (v/v) H 2 O/ethanol mixture and brought into conformal contact with either unmodified surfaces or FN-preadsorbed surfaces, resulting in the transfer of the comb polymer to the regions of the surface that were in contact with the stamp (Scheme 1). We used this procedure to create periodic 20 or 40 lm wide stripes, and negatives of squares and circles on the surface that were separated by 20 or 40 lm. For FN adsorption, the surface (native polymer, gold, or surfaces that were micropatterned with comb polymer) were incubated with a 20 lg mL ±1 FN solution in PBS for 1 h at room temperature, and then rinsed with PBS.Atomic Force Microscopy: Contact mode AFM imaging was performed on a MultiMode SPM (Digital Instruments) in air, using a standard silicon nitride tip (Nanoprobe SPM, Digital Instruments) with a spring constant of 0.12 N m ±1 at a scan rate of 3.05 Hz.Time-of-Flight Secondary Ion Mass Spectrometry: TOF-SIMS spectra and images were collected on a TOF-SIMS IV instrument (ION-TOF, Münster, Germany). A 25 keV monoisotopic 69 Ga + primary ion beam generated by a Ga + gun was used. ªBunched modeº was used to achieve highest mass resolution (m/Dm % 10 000) for collection of mass spectra. The typical target current of the primary Ga + beam in the bunched mode for TOF-SIMS was 1 pA, with a pre-bunched pulse width of 20 ns. The raster area of the Ga + ion gun was 384 384 lm 2...

Arrays of Heterojunctions of Ag Nanowires and Amorphous Carbon Nanotubes

“…After this, the a-CNTs were synthesized by using the decomposition of ethylene (15 sccm) in Ar (75 sccm) at 750 C for 1.5 h in a quartz tube. The process is similar to those described in [5,6].…”

“…[1][2][3][4] In our experiments, we have synthesized arrays of 1D heterojunctions of Ag nanowires (AgNWs) and amorphous carbon nanotubes (a-CNTs), using an approach developed in our group. [5,6] In the 1D heterojunctions, the a-CNTs are contacted ohmically by the AgNWs. This is based on general characteristics of the electronic structure of amorphous semiconductors, which cause contacts between metals and most amorphous semiconductors to be ohmic.…”

Polymeric spheres on substrates from a spin-coating process

“…Some important nanomaterials including C 60 [1][2][3][4][5], carbon nanotubes [6][7][8], nanowires [9][10][11][12], and nanoparticles [13][14][15][16] have been widely reported in the literature. However, reports on the preparation of polymeric nanomaterials are relatively in minority.…”

Size dependence in one-dimensional nano-materials and one-dimensional heterojunctions

“…For example, in our group, size effects on the crystal structures of Ag nanowires [3] and on the mechanical property of ZnO nanowire [4], respectively, have been revealed and modeled. Arrays of four types of one-dimensional (1D) metal/semiconductor heterojunctions, which are either functional or interconnecting elements in electronic devices, have been synthesized and characterized [7][8][9][10][11]. Arrays of four types of one-dimensional (1D) metal/semiconductor heterojunctions, which are either functional or interconnecting elements in electronic devices, have been synthesized and characterized [7][8][9][10][11].…”