Experimental Investigation of Self-Assembled Opal Structures by Atomic Force Microscopy, Spectroscopic Ellipsometry and Reflectometry doi: https://doi.org/10.13052/jsame2245-4551.124
Natalia Alekseeva1, Grigory Cema1, Aleksey Lukin1, Svetlana
Pan’kova1, Sergei Romanov2, Vladimir Solovyev1,
Victor Veisman1 and Mikhail Yanikov1
1Department of Physics, Faculty of Physics and Mathematics, Pskov State
University, Lenin Square 2, 180000 Pskov, Russia
2Institute of Optics, Information and Photonics, University of Erlangen-Nürnberg,
Haber Str. 9a, 91058 Erlangen, Germany; Ioffe Physical Technical Institute,
Polytechnicheskaya Street, 26,194021 St. Petersburg, Russia,
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Abstract: Self-assembled opal crystals (bulk silica opals and PMMA thin opal films)
have been studied by atomic force microscopy (AFM) and optical spectroscopy.
Reflectance and transmittance spectra (R(λ) and T(λ), respectively)
as well as spectra of ellipsometric parameters Ψ(λ) and Δ(λ)demonstrate
pronounced changes with changing the angle of light incidence. Diameters of
spheres obtained from AFM-images correspond to those obtained from Bragg
fit to the diffraction resonance dispersions. The band of light losses detected by
ellipsometry at the spectral range of avoided band crossing of opal eigenmodes
was assigned to the energy exchange between these modes.
Keywords: opal, photonic crystal, Bragg diffraction, photonic bandgap
structure, reflectance and transmittance spectra, ellipsometry, atomic force
microscopy.
Abstract: Diphenylalanine dipeptide is well known to form complex self-assembled
structures, including peptide nanowires, with morphologies depending on Nand
C-terminal modifications. Here we report that significant morphological
variations of self-assembled structures are attainable through pH variation of
unmodified diphenylalanine in trifluoroethanol. The obtained self-assembled
diphenylalanine nanostructures are found to vary drastically with pH, incubation
time, and diphenylalanine concentration in solution. The observed
structures ranged from structured films at neutral and alkaline conditions
to vertically aligned nanowires and sponge-like structures at acidic conditions.
In comparison to the commonly described procedure of diphenylaniline
nanowire growth through aniline vapor treatment, our results suggest that
strictly anhydrous conditions are not necessarily required.
Keywords: Diphenylalanine, peptide self-assembly, peptide nanowires, peptide
nanotubes
Integrating DNA with Functional Nanomaterials doi: https://doi.org/10.13052/jsame2245-4551.122
Shalom J. Wind,1 Erika Penzo,1 Matteo Palma,1 Risheng Wang,1 Teresa Fazio,1 Danny
Porath,2 Dvir Rotem,2 Gideon Livshits,2 Avigail Stern2
1Department of Applied Physics and Applied Mathematics
Columbia University, New York, NY, USA
1Department of Chemistry
Hebrew University of Jerusalem, Jerusalem, Israel
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Abstract: DNA may be the most versatile molecule discovered to date. Beyond its well-known
central role in genetics, DNA has the potential to be a remarkably useful technological
material. It has been demonstrated as a scaffold for the assembly of organic and inorganic
nanomaterials [1]; a vehicle for drug delivery [2]; a medium for computation [3]; and a
possible wire for transporting electrical signals [4]. A key factor in exploiting DNA in these
ways is the ability to integrate DNA with other materials. In this paper, we review two
approaches to forming DNA complexes with functional nanomaterials: (1) linking DNA with
single-wall carbon nanotubes (SWCNTs), which can then be used as nanoscale electrical
contacts for probing electron transport in DNA; and (2) directed nanoassembly of Au
nanoparticles using DNA/PNA (peptide nucleic acid) hybrid scaffolds.
Keywords: DNA-SWCNT
Abstract: The phenomena that results on supramolecular aggregations of bimetallic [Pt2 L4 ] and
[AuL2 ] are reviewed. Supramolecular [AuL2]n (n=2,3) were observed in some cases in
solution as a result of Au(I)···Au(I) aurophilic interactions, which also direct the assembly
of oligomeric structures in crystal phase. Analogously, Pt(II)···Pt(II) attraction accounts
for the assembly of [Pt2 L4 ]n supramolecules which can result on 1D semiconductive
arrangements in crystal phase and direct the formation of 1D nanofibres on surfaces.
Finally, oxidation of [Pt2L4] to [Pt2L4]n produces highly conductive polymers that can
reversibly assemble/disassemble into [Pt2L4] and [Pt2L4]. Such outstanding ability results
on an unprecedented processability that enables MMX polymers for technological
applications as molecular wires.
Keywords: Metal-metal interactions, Supramolecular assemblies, MMX Chains,
Molecular wires.