Poly(1-methylpyrrol-2-yl)squaraine (PMPS) particles have been characterised using SEM. The PMPS particles were used as templates to prepare bare silica and iron-silica hollow spheres, which were characterised using TEM and SEM. The PMPS particles and the hollow spheres are not uniformly sized and are agglomerated. The hollow spheres with larger diameters ([900 nm) contain an internal 'Russian doll' structure. The iron-silica hollow spheres are fused to one another, and the hollow spheres have a heterogeneous wall thickness. The silica and ironsilica hollow spheres both aggregate by size. There are two different size populations (for the diameter) of the bare silica and iron-silica hollow spheres. The smaller silica spheres have thinner walls compared to the larger silica hollow spheres. The larger silica hollow spheres and the iron-silica hollow spheres have similar wall thicknesses. The iron compound in the iron-silica hollow spheres has an oxidation state of 3? and is crystalline.
A concentrated citrate-stabilised Au nanoparticle (NP) colloid has been prepared using a modified Frens procedure, and characterised using transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. The average diameter determined from TEM images of concentrated Au NPs (16.57 AE 0.65 nm) is similar to the diameter reported by Frens (16 nm). The surface plasmon band of the concentrated Au NPs UV-Vis spectrum has a max at 522 nm. Bare silica ('Si') and iron-'Si' hollow microsphere surfaces have been functionalised with amino groups using the surfactant 3-aminopropyltrimethoxysilane (APTMS). The Au NPs have been assembled onto the APTMS-treated hollow spheres by dispersing a colloid of Au NPs into a suspension of hollow spheres at pH 4.5 (2 h). The volume ratio of Au NPs: hollow spheres was adjusted until maximum deposition could be achieved in a single step. TEM micrographs of ultrathin (80-100 nm) ultramicrotome sections through the Au NP-coated hollow spheres reveal that a single layer of Au NPs is mainly distributed on (1) the external side of the shell wall for 'Si' and (2) both sides of the shell wall for iron-'Si'. UV-Vis absorption spectra of the Au NP-coated hollow spheres show that the surface plasmon band shifts (524-613 nm) and broadens as the density of Au NPs is increased on the shell surface.
Novel self-assembled monolayers of 3,4-disubstituted thiophenes (3,4-dioctylthiophene and 3,4-diheptyloxythiophene) were prepared and characterized by contact angle measurements, ellipsometry and X-ray photoelectron spectroscopy. In addition, Au nanoparticles passivated with the 3,4-disubstituted thiophenes (3,4-dioctylthiophene and 3,4-diheptyloxythiophene) and monosubstituted thiophene (3-octylthiophene) were synthesized and characterized by UV/visible spectroscopy, transmission electron microscopy and dynamic light scattering. The Au nanoparticles had diameters in the range 5-7 nm. The Au nanoparticles stabilized with the thiophene derivatives were, as expected, less stable than the Au nanoparticles passivated with decanethiol and didecylsulfide. Surprisingly, the particles passivated with the monosubstituted 3-octylthiophene were more stable than the 3,4-dioctyl and 3,4-diheptyloxythiophene passivated particles. Such lower stability Au nanoparticles may find uses as negative tone resists in the formation of nanowires by e-beam lithography, via the more readily cleavable Au-S bond
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