Full wetting of plasmonic nanopores through two-component droplets.

Benefiting from the prospect of extreme light localization, plasmonic metallic nanostructures are bringing advantages in many applications. However, for use in liquids, the hydrophobic nature of the metallic surface inhibits full wetting, which is related to contact line pinning in the nanostructures. In this work, we use a two-component droplet to overcome this problem.

Matrix isolation FT-IR and theoretical DFT/B3LYP spectrum of 1-naphthol.

The FT-IR spectrum of 1-Naphthol isolated in an argon matrix is performed and compared to the infrared spectra calculated at the DFT (B3LYP)/6-31+G(d) level for cis-1-Naphthol and trans-1-Naphthol rotamers in order to clarify the existence of both rotamers in the standard temperature. Comparison of the computed and the experimental matrix spectra reveals the presence in 1-Naphthol argon matrices in the standard temperature of both cis and trans rotameric forms of 1-Naphthol, the last predominating. The relative stability of the trans-1-Naphthol rotamer has also been supported by a fit comparison between the difference of predicted total energy (ETC) of both rotamers of 0.

Experimental and theoretical observation of different intramolecular H-bonds in lysine conformations.

Due to the importance of the structure of amino acids for the folding and functionality of proteins, the conformational behavior of lysine has been investigated. Experimental matrix-isolation FT-IR spectra have been recorded. These spectra were interpreted using an extended theoretical DFT and MP2 study.

Simulating the interaction between amino acids and DNA: a combined matrix-isolation FT-IR and theoretical study of the 1-methyluracil·glycine H-bond complexes using a dual sublimation furnace.

The H-bond complex formation between 1-methyluracil and glycine has been investigated by theoretical calculations and the most stable complex configurations have been identified by FT-IR spectroscopy in Ar matrices. The importance of this H-bonding system is huge since all DNA biological functions are dependent on the interactions with proteins. The theoretical optimizations have revealed six different closed H-bond complexes between 1-methyluracil and glycine.

Theoretical study of the regioselectivity of the interaction of 3-methyl-4-pyrimidone and 1-methyl-2-pyrimidone with Lewis acids.

A density functional theory (DFT) study is performed to determine the stability of the complexes formed between either the N or O site of 3-methyl-4-pyrimidone and 1-methyl-2-pyrimidone molecules and different ligands. The studied ligands are boron and alkali Lewis acids, namely, B(CH(3))(3), HB(CH(3))(2), H(2)B(CH(3)), BH(3), H(2)BF, HBF(2), BF(3), Li(+), Na(+), and K(+). The acids are divided into two groups according to their hardness.

The conformational behavior and H-bond structure of asparagine: a theoretical and experimental matrix-isolation FT-IR study.

Due to the high importance of the structural properties of peptides, the conformational behavior of one of their elementary building blocks, asparagine, has been investigated in this work. Matrix-isolation FT-IR spectroscopy is a suitable technique to investigate the intrinsic properties of small molecules. Asparagine has been subjected to matrix-isolation FT-IR spectroscopy supported with DFT and MP2 calculations.

Potential energy surface and matrix isolation FT-IR study of isoleucine.

The conformational landscape of isoleucine was investigated by a theoretical DFT and MP2 study. This investigation has revealed new important conformations in comparison to a previous study. Five conformations have been predicted with an abundance larger than 5% at both levels of theory.

Excitation wavelength dependent surface enhanced Raman scattering of 4-aminothiophenol on gold nanorings.

Detailed understanding of the underlying mechanisms of surface enhanced Raman scattering (SERS) remains challenging for different experimental conditions. We report on an excitation wavelength dependent SERS of 4-aminothiophenol molecules on gold nanorings. SERS and normal Raman spectra, combined with well-characterized surface morphology, optical spectroscopy and electromagnetic (EM) field simulations of gold nanoring substrates indicate that the EM enhancement occurs at all three excitation wavelengths (532, 633 and 785 nm) employed but at short wavelengths (532 and 633 nm) charge transfer (CT) results in additional strong enhancements of particular Raman transitions.

Comparison of the conformational behavior of amino acids and N-acetylated amino acids: a theoretical and matrix-isolation FT-IR study of N-acetylglycine.

Within the structure determination task for peptides, which is of large interest due to the relation between structure and functionality, infrared spectra can provide detailed information on the conformational behavior. The conformational landscape ofN-acetylgycine has been studied by a combined theoretical and matrix-isolation FT-IR study. The acetylation simulates an amino acid a peptide bond.

Enhanced optical trapping and arrangement of nano-objects in a plasmonic nanocavity.

Gentle manipulation of micrometer-sized dielectric objects with optical forces has found many applications in both life and physical sciences. To further extend optical trapping toward the true nanometer scale, we present an original approach combining self-induced back action (SIBA) trapping with the latest advances in nanoscale plasmon engineering. The designed resonant trap, formed by a rectangular plasmonic nanopore, is successfully tested on 22 nm polystyrene beads, showing both single- and double-bead trapping events.

Estimation of the rotamerization constants of different conformations of N-acetylalanine: a theoretical and matrix-isolation FT-IR study.

The conformational landscape of N-acetylalanine has been investigated by a theoretical and matrix-isolation FT-IR study. Optimizations of N-acetylalanine structures has been conducted at successive higher levels of theory HF/3-21G, DFT(B3LYP)/6-31++G** and MP2/6-31++G**. This resulted in three stable conformations.

The influence of the peptide bond on the conformation of amino acids: a theoretical and FT-IR matrix-isolation study of N-acetylproline.

A combined experimental matrix-isolation FT-IR and theoretical study has been performed to investigate the conformational behavior of N-acetylproline. The conformational landscape of N-acetylproline was explored using successively higher computational methods, i.e.

Temperature determination of resonantly excited plasmonic branched gold nanoparticles by X-ray absorption spectroscopy.

The fields of bioscience and nanomedicine demand precise thermometry for nanoparticle heat characterization down to the nanoscale regime. Since current methods often use indirect and less accurate techniques to determine the nanoparticle temperature, there is a pressing need for a direct and reliable element-specific method. In-situ extended X-ray absorption fine structure (EXAFS) spectroscopy is used to determine the thermo-optical properties of plasmonic branched gold nanoparticles upon resonant laser illumination.

Specific cell targeting with nanobody conjugated branched gold nanoparticles for photothermal therapy.

Branched gold nanoparticles are potential photothermal therapy agents because of their large absorption cross section in the near-infrared window. Upon laser irradiation they produce enough heat to destroy tumor cells. In this work, branched gold nanoparticles are biofunctionalized with nanobodies, the smallest fully functional antigen-binding fragments evolved from the variable domain, the VHH, of a camel heavy chain-only antibody.

A simple double-bead sandwich assay for protein detection in serum using UV-vis spectroscopy.

In this study a double-bead sandwich assay, employing magnetic nanoparticles and gold nanoparticles is proposed. The magnetic nanoparticles allow specific capturing of the analyte in biological samples, while the optical properties of the gold nanoparticles provide the signal transduction. We demonstrated that a major improvement in the assay sensitivity was obtained by selecting an optimal gold nanoparticle size (60 nm).

Poly(acrylic acid)-stabilized colloidal gold nanoparticles: synthesis and properties.

Combining the intriguing optical properties of gold nanoparticles with the inherent physical and dynamic properties of polymers can give rise to interesting hybrid nanomaterials. In this study, we report the synthesis of poly(acrylic acid) (PAA)-capped gold nanoparticles. The polyelectrolyte-wrapped gold nanoparticles were fully characterized and studied via a combination of techniques, i.

Strong location dependent surface enhanced Raman scattering on individual gold semishell and nanobowl particles.

We demonstrate strong spatial localization of SERS on single symmetry-reduced gold semishell and nanobowl particles. A ∼30 nm carbon nanoparticle acts as a Raman reporter and is placed on different locations on a single semishell or nanobowl by e-beam induced deposition method, and remarkably different SERS intensities are observed.

Plasmonic modes of metallic semishells in a polymer film.

The symmetry-broken geometry and variation of metal composition of semishells induce new plasmonic properties. A system of separated metallic semishells embedded in a poly(dimethylsiloxane) polymer film provides an ideal platform to investigate the localized surface plasmon resonance modes of semishells. We demonstrate experimentally that silver, gold, copper, and aluminum semishells can offer distinct plasmonic responses due to the wide range of their material parameters.

Symmetry breaking induced optical properties of gold open shell nanostructures.

We use the finite difference time domain method to predict how optical plasmon properties are modified if the symmetrical geometry of gold shell nanostructures is broken. The simulations include three kinds of gold open shell nanostructures of nanobowls, open nanocages, and open eggshells. For all structures, the optical extinction spectra commonly display a distinct red shift when the full shell geometry is broken and a hyperbola-like dipolar plasmonic shift when the fractional height continuously decreases.

Observation of plasmonic dipolar anti-bonding mode in silver nanoring structures.

We report on a clear experimental observation of the plasmonic dipolar anti-bonding resonance in silver nanorings. The data can be explained effectively by the plasmon hybridization model, which is confirmed by the numerical calculations of the electromagnetic field and surface charge distribution profiles. The experimental demonstration of the plasmon hybridization model indicates its usefulness as a valuable tool to understand, design and predict optical properties of metallic nanostructures.

Focusing plasmons in nanoslits for surface-enhanced Raman scattering.

The focusing of plasmons to obtain a strong and localized electromagnetic-field enhancement for surface-enhanced Raman scattering (SERS) is increasing the interest in using plasmonic devices as molecular sensors. In this Full Paper, we report the successful fabrication and demonstration of a solid-state plasmonic nanoslit-cavity device equipped with nanoantennas on a freestanding thin silicon membrane as a substrate for SERS. Numerical calculations predict a strong and spatially localized enhancement of the optical field in the nanoslit (6 nm in width) upon irradiation.

Dynamic light scattering as a powerful tool for gold nanoparticle bioconjugation and biomolecular binding studies.

Dynamic light scattering (DLS) is an analytical tool used routinely for measuring the hydrodynamic size of nanoparticles and colloids in a liquid environment. Gold nanoparticles (GNPs) are extraordinary light scatterers at or near their surface plasmon resonance wavelength. In this study, we demonstrate that DLS can be used as a very convenient and powerful tool for gold nanoparticle bioconjugation and biomolecular binding studies.

Fiber optic SPR biosensing of DNA hybridization and DNA-protein interactions.

In this paper we present a fiber optic surface plasmon resonance (SPR) sensor as a reusable, cost-effective and label free biosensor for measuring DNA hybridization and DNA-protein interactions. This is the first paper that combines the concept of a fiber-based SPR system with DNA aptamer bioreceptors. The fibers were sputtered with a 50nm gold layer which was then covered with a protein repulsive self-assembled monolayer of mixed polyethylene glycol (PEG).

Shrinking solid-state nanopores using electron-beam-induced deposition.

Solid-state nanopores of only a few nanometres in size show a great potential for applications such as molecule detection and DNA sequencing. In most cases, the fabrication of such a nanopore requires the high energy beam of a transmission electron microscope (TEM) or focused ion beam (FIB) tool to drill or reshape a small hole in a freestanding membrane. Here, we present a novel method to reduce the size of existing nanopores using electron-beam-induced deposition (EBID) of carbon in a conventional scanning electron microscope (SEM).