Fluorescent silver nanoclusters in condensed DNA.

We study the formation and fluorescent properties of silver nanoclusters encapsulated in condensed DNA nanoparticles. Fluorescent globular DNA nanoparticles are formed using a dsDNA-cluster complex and polyallylamine as condensing agents. The fluorescence emission spectrum of single DNA nanoparticles is obtained using tip-enhanced fluorescence microscopy. Fluorescent clusters in condensed DNA nanoparticles appear to be more protected against destructive damage in solution compared to clusters synthesized on a linear polymer chain. The fluorescent clusters on both dsDNA and ssDNA exhibit the same emission bands (at 590 and 680 nm) and the same formation efficiency, which suggests the same binding sites. By using density functional theory, we show that the clusters may bind to the Watson-Crick guanine-cytosine base pairs and to single DNA bases with about the same affinity.

Self-assembled photonic structure: a Ga optical antenna on GaP nanowires.

Semiconductor nanowires are the perfect platform for nanophotonic applications owing to their resonant, waveguiding optical properties and technological capabilities providing control over their crystalline and chemical compositions. The vapor-liquid-solid growth mechanism allows the formation of hybrid metal-dielectric nanostructures promoting sub-wavelength light manipulation. In this work, we explore both experimentally and numerically the plasmonic effects promoted by a gallium (Ga) nanoparticle optical antenna decorating the facet of gallium phosphide (GaP) nanowires. Raman, photoluminescence and near-field mapping techniques are used to study the effects. We demonstrate several phenomena including field enhancement, antenna effect and increase in internal reflection. We show that the observed effects have to be considered when nanowires with a plasmonic particle are used in nanophotonic circuits and discuss the ways for utilization of these effects for efficient coupling of light into nanowire waveguide and field tailoring. The results open up promising pathways for the development of both passive and active nanophotonic elements, light harvesting and sensorics.

Soft x-ray reflectometry, hard x-ray photoelectron spectroscopy and transmission electron microscopy investigations of the internal structure of TiO2(Ti)/SiO2/Si stacks.

We developed a mathematical analysis method of reflectometry data and used it to characterize the internal structure of TiO2/SiO2/Si and Ti/SiO2/Si stacks. Atomic concentration profiles of all the chemical elements composing the samples were reconstructed from the analysis of the reflectivity curves measured versus the incidence angle at different soft x-ray reflection (SXR) photon energies. The results were confirmed by the conventional techniques of hard x-ray photoelectron spectroscopy (HXPES) and high-resolution transmission electron microscopy (HRTEM). The depth variation of the chemical composition, thicknesses and densities of individual layers extracted from SXR and HXPES measurements are in close agreement and correlate well with the HRTEM images.

Laser printing of optically resonant hollow crystalline carbon nanostructures from 1D and 2D metal-organic frameworks.

Using a hybrid approach involving a slow diffusion method to synthesize 1D and 2D MOFs followed by their treatment with femtosecond infrared laser radiation, we generated 100-600 nm well-defined hollow spheres and hemispheres of graphite. This ultra-fast technique extends the library of shapes of crystalline MOF derivatives appropriate for all-dielectric nanophotonics.

Correction: Laser printing of optically resonant hollow crystalline carbon nanostructures from 1D and 2D metal-organic frameworks.

Correction for 'Laser printing of optically resonant hollow crystalline carbon nanostructures from 1D and 2D metal-organic frameworks' by Leila R. Mingabudinova et al., Nanoscale, 2019, 11, 10155-10159.

Dopant-stimulated growth of GaN nanotube-like nanostructures on Si(111) by molecular beam epitaxy.

In this paper we study growth of quasi-one-dimensional GaN nanowires (NWs) and nanotube (NT)-like nanostructures on Si(111) substrates covered with a thin AlN layer grown by means of plasma-assisted molecular beam epitaxy. In the first part of our study we investigate the influence of the growth parameters on the geometrical properties of the GaN NW arrays. First, we find that the annealing procedure carried out prior to deposition of the AlN buffer affects the elongation rate and the surface density of the wires. It has been experimentally demonstrated that the NW elongation rate and the surface density drastically depend on the substrate growth temperature, where 800 °C corresponds to the maximum elongation rate of the NWs. In the second part of the study, we introduce a new dopant-stimulated method for GaN nanotube-like nanostructure synthesis using a high-intensity Si flux. Transmission electron microscopy was used to investigate the morphological features of the GaN nanostructures. The synthesized structures have a hexagonal cross-section and possess high crystal quality. We propose a theoretical model of the novel nanostructure formation which includes the role of the dopant Si. Some of the Si-doped samples were studied with the photoluminescence (PL) technique. The analysis of the PL spectra shows that the highest value of donor concentration in the nanostructures exceeds 5∙1019 cm-3.