Three-Dimensional Photonic Crystals Based on Porous Anodic Aluminum Oxide.

Photonic crystals (PCs) consisting of a periodic arrangement of holes in dielectric media have found success in light manipulation and sensing. Among them, three-dimensional (3D) PCs are in high demand due to their unique properties originating from multiple photonic band gaps (PBGs) and even full ones. Here, 3D PCs based on porous anodic aluminum oxide (AAO) were fabricated for the first time. Our approach involves prepatterning of the aluminum surface by a focused ion beam to form a hexagonal array of pore nuclei. Subsequent anodization in 1 M H3PO3 using a sine wave profile of voltage provides AAO with a defect-free in-plane porous structure and out-of-plane porosity modulation. The ability to tune the position, width, and depth of the PBGs is demonstrated. The combination of the flexibility of the proposed approach with the unique properties of AAO extends the range of practical applications of 3D PCs far beyond the current achievements.

Two-Photon Luminescence and Second-Harmonic Generation in Organic Nonlinear Surface Comprised of Self-Assembled Frustum Shaped Organic Microlasers.

An ultrathin nonlinear optical (NLO) organic surface composed of numerous self-assembled frustum-shaped whispering-gallery-mode resonators displays both two-photon luminescence and second-harmonic-generation signals. A super-second-order increase of the NLO intensity with respect to pump power confirms the microlasing action and practical usefulness of the NLO organic surfaces.

New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 1. Assessment of van der Waals interactions.

Solvent effects on OH stretching vibrations in several complexes with hydrogen bonding have been investigated by FTIR spectroscopy. To assess the influence of van der Waals (vdW) interactions on frequency shifts, a new parameter of solvent, square root deltacavhS, is proposed. This parameter has been derived from equations describing enthalpy of non-specific solvation. Linear correlation was established between the OH frequency shift (with respect to the gas phase) and parameter square root deltacavhS for a series of complexes of aliphatic alcohols with standard proton acceptors. Linear correlations with square root deltacavhS were also observed for a series of "free" O-H and also C=O, P=O, S=O and C-Br stretching vibrations. A new method is proposed for estimating the gas-phase stretching frequency from IR spectra of solutions. In addition, frequencies of "free" X-H groups in neat bases were deduced from the experimental data.

New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 2. Assessment of cooperativity effects.

Solvent effects on O-H stretching vibration frequency of methanol in hydrogen bond complexes with different bases, CH3OH...B, have been investigated by FTIR spectroscopy. Using chloroform as a solvent results in strengthening of CH3OH...B hydrogen bonding due to cooperativity between CH3OH...B and Cl3CH...CH3OH bonds. A method is proposed for quantifying the hydrogen bond cooperativity effect. The determined cooperativity factors take into account all specific interactions of the solute in proton-donor solvents. In addition, a method of estimation of cooperativity factors Ab and AOX in system (CH3OH)2...B is proposed. It is demonstrated that in such systems, the cooperativity factor of the OH...B bond decreases and that of the OH...O bond increases with increasing the acceptor strength of the base B. The obtained results are in a good agreement with the data obtained previously from matrix-isolation FTIR spectroscopy.