Liquid-Crystalline Photonic Sandwich: Electroresponsive Colloids of Clay Nanosheets Loading Photofunctional Dyes.

Colloidal clay nanosheets obtained by the delamination of layered crystals of smectite-type clay minerals in water form liquid crystals because of their shape anisotropy. Loading of organic dyes onto the liquid crystalline clay nanosheets will enable novel photonic materials, where photofunctions of the loaded dye are controlled by the liquid crystallinity of the clay nanosheets. However, adsorption of organic dyes onto the nanosheets renders the nanosheet surfaces hydrophobic, and consequently, colloidal stability of the nanosheets is lost.

Effect of Dispersants on Photochromic Behavior of Tungsten Oxide Nanoparticles in Methylcellulose.

Tungsten oxide-based photochromic films that change reversibly in air between colorless-transparent in the dark and dark blue under UV irradiation were prepared by using methylcellulose as a film matrix and various dispersants. Alpha-hydroxyl acid such as glycolic acid (GA) or glyceric acid (GlyA) is the best dispersant because it can make the film transparent by adding a small quantity much less than that of 3-hydroxypropionic acid or ethylene glycol. Fourier-transform infrared spectra and Raman spectra indicate that a strong interaction exists between WO and GA or GlyA.

Tunable High-Pressure Field Operating on a Cationic Biphenyl Derivative Intercalated in Clay Minerals.

We propose a methodology for applying a pseudo uniaxial pressure to an organic molecule under ordinary temperature and pressure, namely by intercalation into smectites. The pseudo pressure on a biphenyl derivative (BP) was estimated from the averaged dihedral angle around the central bond of BP. In a high hydrostatic pressure field, biphenyl takes a planar conformation.

A biphenyl type two-photon fluorescence probe for monitoring the mitochondrial membrane potential.

Here we describe the design and synthesis of a bifunctional two-photon fluorescence probe, N,N'-‍dimethyl-4,4'-(biphenyl-2,1-ethenediyl)dipyridinium hexafluorophosphate (BP6). HeLa, Hek293, and Paramecium caudatum cells were stained with BP6. BP6 accumulated on the mitochondria of all three cell types when the mitochondrial membrane potential was high.

The size control of nano-cluster formed on an inorganic nanosheet/cationic organic molecule hybrid Langmuir-Blodgett film.

Organic molecules adsorbed on an inorganic nanosheet often form a nanometer-sized cluster. In this study, we propose novel strategy for controlling the cluster size. We fabricated hybrid Langmuir-Blodgett (LB) films consisting of N-n-octadecyl-4-[2-(4-dimethylaminophenyl)ethenyl]-pyridinium bromide and a clay mineral, sodium montmorillonite, with varying subphase temperature.

Fluorescence imaging of mitochondria in living cells using a novel fluorene derivative with a large two-photon absorption cross-section.

We have examined optical properties of a fluorene derivative with two positively charged substituents, 1,1'- diethyl-4,4'-(9,9-diethyl-2,7-fluorenediyl-2,1-ethanediyl)dipyridinium perchlorate (1), in water. The photoluminescence quantum yield of 1 was relatively high (35%) for use as a fluorescent probe in water. We also examined two-photon absorption (TPA) properties of 1 in methanol.

Enhanced photodegradation of organic dyes adsorbed on a clay.

The interaction of three photoactive organic dyes, Rhodamine B, Rhodamine 6G and a stilbazolium derivative 4'-dimethylamino-N-methyl-4-stilbazolium with synthetic sodium-saponite has been examined by UV-visible absorption spectroscopy. In all cases, bathochromic shifts and the reduction of peak absorbance for the dyes were observed in the absorption spectra at a low dye concentration (25% adsorption of the cation exchange capacity (CEC) of the clay), although the shape and the width of their absorption bands were similar to those in aqueous solution. This absorption behavior indicates that the organic dye molecules adsorbed onto the surface of the negatively charged clay particles and the adsorbed molecules were well dispersed.

Two-photon absorption properties of azulenyl compounds having a conjugated ketone backbone.

Two-photon absorption (TPA) properties of newly synthesized conjugated ketone derivatives that include nonalternant azulenyl moieties in the pi-conjugation system, alpha,alpha'-bis(1-azulenylidene)cyclopentanone (1Az), alpha,alpha'-bis(2-azulenylidene)cyclopentanone (2Az), and alpha,alpha'-bis(6-azulenylidene)cyclopentanone (6Az) are reported. TPA spectra of these azulenyl compounds were measured using the open-aperture Z-scan method with a femtosecond laser. The TPA cross section at the peak position (sigma(2)peak) of 1Az was found to be the largest among the three azulenyl compounds, which is almost 7 times larger than that of the alpha,alpha'-bis(1-naphthylidene)cyclopentanone (1Nph), an alternant isomer of 1Az with the same number of pi-electrons.

The interaction of 2-phenylbenzimidazole compounds with DNA: the influence of terminal substituents.

We have studied the influence of terminal substituents, amidinium group and N-methylpiperazine ring, of 2-phenylbenzimidazole compounds (1-6; Figure 1) on their DNA-binding modes. Experimental results reveal that 1-3 are accepted in intercalation pockets owing to structural flexibility of the N-methylpiperazine ring, while 4-6 bind to the groove of DNA because of steric hindrance between the amidinium group and the DNA phosphate-sugar backbone.

Solution structure of the DNA complexes with an alkyl-linked bis(benzimidazole) compound, 1,4-bis[5-(4-methyl-1-piperazinyl)-2-benzimidazolyl]butane.

Solution structures of the 1:1 complexes of an alkyl-linked bis(benzimidazole) compound (4; Figure 1(a)) with the self-complementary DNA duplexes, d(CGCGAATTCGCG)2 and d(CGCAAATTTGCG)2, have been studied by 1H NMR spectroscopy and molecular mechanics calculations. The intermolecular NOE data and the energy-minimized geometries of the 1:1 complexes indicate that 4 binds in the minor groove of the 5'-GAATTCG and 5'-CAAATTT regions of the DNA duplexes.