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We have studied optical properties of single-layer and multi-fold nanoporous gold leaf (NPGL) metamaterials and observed highly unusual transmission spectra composed of two well-resolved peaks. We explain this phenomenon in terms of a surface plasmon absorption band positioned on the top of a broader transmission band, the latter being characteristic of both homogeneous “solid” and inhomogeneous “diluted” Au films. The transmission spectra of NPGL metamaterials were shown to be controlled by external dielectric environments, e.g. water and applied voltage in an electrochemical cell. This paves the road to numerous functionalities of the studied tunable and active metamaterials, including control of spontaneous emission, energy transfer and many others.

The ability to control the growth of materials with nanosized precision as well as a complex hollow morphology provides rationale for the study of systems comprising both characteristics. This study explores the design of TiO hollow nanotube shells deposited by atomic layer deposition (ALD) on vertically aligned SnO nanorods grown using the vapor-liquid-solid technique. The sacrificial template approach in combination with highly conformal coating advantages of ALD resulted in a highly reproducible method to create a large surface area covered by TiO-protected SnO nanorods, which are about 60-100 nm in diameter and approximately 1 μm in length. ZnO was used as a sacrificial layer to create a 30 nm gap between SnO nanorods and 10 nm of TiO shells. Chemical etching of the sacrificial layer was used to create the desired hollow nanocomposite. A coin half-cell battery has been assembled using the TiO-protected SnO nanorods as an anode electrode and lithium foil as a counter electrode and tested for lithium storage during 70 cycles of charge/discharge in a range of 0.5-2.5 V. The TiO hollow shell functioned as a good and robust enhancer for both absolute capacity and current rate capabilities of vertically aligned SnO nanorods; an improvement in cyclic stability was also observed. This advanced self-standing hollow configuration provides several unique advantages for energy storage device applications including enhanced lithiation for superior energy storage performance.

We have studied the dependence of concentration quenching of luminescence (donor–acceptor energy transfer) on the thickness d of dye-doped polymeric films (HITC:PMMA) and found its strong inhibition at small values of d. This phenomenon is tentatively explained by a limited number of acceptors, which donors’ excitation can reach in thin samples, if the film’s thickness is comparable to the diffusion length of the energy transfer. The latter mechanism, along with effective reduction of the dye concentration, is responsible for an inhibition of the concentration quenching of dye molecules impregnating porous alumina membranes. The elongation of emission kinetics in thick (≥3 μm) HITC:PMMA films is cautiously attributed to the samples’ crystallinity.

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