Polarised infrared reflectance spectra have been obtained for oriented single crystals of the polar organic nonlinear optical material 2-(α-methylbenzylamino)-5-nitropyridine (MBANP). The strong charge transfer electronic absorption was measured in several solvents and as a thin solid film. DFT calculations of vibrational frequencies and eigenvectors were used to assign relevant vibrational features and to derive useful information about the molecular structure. The intensities of the bands associated with the donor and acceptor groups are increased by electron phonon coupling with the strong charge transfer transition. This results in unusually strong NO2 and N–H stretching vibrations. The spectra are consistent with a large rotation of the optical indicatrix with increasing wavelength due to the bent shape and strong electron-phonon coupling in the molecule.

Observations of second harmonic generation and ferroelectric behaviour in in vitro biological structures are reported. The scales of the Indian freshwater fish (Catla catla, Cytrinidae) have been found to have nonlinear optical properties, exhibiting frequency doubling (second harmonic generation, SHG). In contrast to this behaviour it has not proved possible to obtain SHG signals from the scales of British freshwater fish (Roach, Rutilus rutilus L). Experiments were also conducted on scales treated with various organic solvents and on dry collagen. Optical transmission and infra-red spectra have also been measured and the latter indicate that the scales obtained from both species have nearly the same composition and are collagen rich. The dry collagen itself gives rise to an SHG signal which is about eight times as intense as that from the Indian fish scales. The fish scales and collagen are found to be ferroelectric at room temperature.

Robust thin-film oxygen sensors were fabricated by encapsulating a lipophilic, polynuclear gold(I) complex, bis{m-(bis(diphenylphosphino)octadecylamine-P,P′)}dichlorodigold(I), in oxygen permeable polystyrene and ormosil matrices. Strong phosphorescence, which was quenched by gaseous and dissolved oxygen, was observed from both matrices. The polystyrene encapsulated dye exhibited downward-turning Stern–Volmer plots which were well fitted by a two-site model. The ormosil trapped complex showed linear Stern–Volmer plots for dissolved oxygen quenching but was downward turning for gaseous oxygen. No leaching was observed when the ormosil based sensors were immersed in flowing water over an 8h period. Both films exhibited fully reversible response and recovery to changing oxygen concentration with rapid response times.

Orientated single-crystal infrared, Raman and terahertz measurements have been carried out for the molecular charge transfer material 2-(α-methylbenzylamino)-5-nitropyridine. This information, together with experimental frequency doubling data and theoretical calculations of the electro-optic coefficient, was used to deduce the optical phonon contribution to the linear electro-optic coefficient. The optical phonon spectra are dominated by three intense bands attributed to vibrations of the ring, NO2 substituent and N–H bond. The most intense scattering arose from the αbb component of the polarisability tensor. This implied that the most significant contribution to the transition polarisability arises from the electronic transition near 435nm, polarised along the b-axis of the crystal. The strongest bands in the infrared spectra are also associated with the same three bands. This implies that efficient electron-phonon coupling (or electronic delocalization) in the conjugated system. DFT calculations of optical phonon frequencies and eigenvectors were used to help assign relevant vibrational features and to derive useful information about the molecular structure. The information obtained from this study is important for assessing the suitability of this material for generating terahertz frequencies by optical rectification.

Single-crystal Raman and polycrystalline thin-film infrared measurements have been obtained for the polar organic nonlinear optical material 2-(alpha-methylbenzylamino)-5-nitropyridine(MBANP). For comparison, thin-film polycrystalline infrared measurements were also made on 2-(alpha-methylbenzylamino)-3,5-dinitropyridine (MBADNP). The long wavelength electronic absorption was measured in several solvents and as a thin solid film. The Raman spectra are dominated by three intense bands attributed to vibrations of the ring, the NO(2) substituent, and the N-H bond. The most intense scattering and absorption arose from the alpha(bb) component of the polarisability tensor. This implies that the most significant contribution to the transition polarisability arises from the electronic transition near 383 nm, polarised along the b-axis of the crystal. The strongest bands in the infrared spectra are also associated with the same three bands, consistent with the predictions of the effective conjugation coordinate (ECC) theory, implying efficient electron-phonon coupling (or electronic delocalisation) in the conjugated system. DFT calculations of vibrational wavenumbers and eigenvectors were used to assign relevant vibrational features and to derive useful information about the molecular structure. This single-crystal material is also a strong candidate for an efficient laser Raman converter with a large wavenumber shift of 3404 cm(-1) and a high damage threshold. Copyright (C) 2010 John Wiley & Sons, Ltd.

The ruthenium(II) diimine complexes, such as ruthenium(II) tris( bipyridyl), Ru(bpy)(3)(2+), possess highly luminescent excited states that are not only readily quenched by oxygen but also by an increase in temperature. The former effect can be rendered insignificant by encapsulating the complex in an oxygen impermeable polymer, although encapsulation often leads also to a loss of temperature sensitivity. The luminescence properties of Ru(bpy)(3)(2+) encapsulated in PVA were studied as a function of oxygen concentration and temperature and found to be independent of the former, but still very sensitive towards the latter. The results were fitted to an established Arrhenius-type equation, based on thermal quenching of the emitting state by a slightly higher (Delta E = 3100 cm(-1)) (3)d-d state that deactivates very rapidly (10(-13) s) via a non-radiative process.

A series of side chain liquid crystalline polymers based on a polystyrene backbone has been synthesized and characterized for non-linear optical applications. Key Words: liquid crystal polymersnon-linearopticalpolystyrene

A robust optical composite thin film dissolved oxygen sensor was fabricated by ionically trapping the dye ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) dichloride in a blended fluoropolymer matrix consisting of Nafion® and Aflas®. Strong phosphorescence, which was strongly quenched by dissolved oxygen (DO), was observed when the sensor was immersed in water. The sensor was robust, optically transparent, with good mechanical properties. Fast response, of a few seconds, coupled with sensitivity of about 0.1 mg L−1 (DO) over the range 0–30 mg L−1 and resistance to leaching, were also exhibited by this system. The Stern–Volmer (SV) plot exhibited slight downward turning at all oxygen concentrations. A linear plot was obtained when the SV equation was modified to account for the varying sensitivity of dye molecules in the matrix to the quencher. Good long term stability was observed.

. SUMMARY Laser trabeculotomies produced by directing a pulsed neodymium/YAG laser beam at specimens of human anterior chamber angle obtained post mortem or after enucleation were studied by light microscopy and by scanning and transmission electron microscopy to assess the dimensions of the openings created in the trabecular meshwork, their penetrance to the canal of Schlemm, and the extent or absence of laser induced cellular damage in immediately adjacent tissue. A pulse duration of 40-50 ns at energy levels of around 30 mJ was used and the laser cavity carefully tuned to give a Gaussian spatial mode pattern. Openings in the trabecular meshwork typically of 100 FIm in diameter and penetrating through to the canal of Schlemm could be regularly created with only minimal damage to adjacent tissue as judged by transmission electron microscopy. The information so gained may be useful in determining the parameters required for successful laser trabeculotomy as a treatment for primary open-angle glaucoma. A Q-switched neodymium/YAG laser system has been developed with the intention of performing internal laser trabeculotomies as a treatment for primary open-angle glaucoma.' The ultimate aim of such a treatment would be to create dimensionally

A robust thin film dissolved oxygen sensor was fabricated by encapsulating platinum octaethylporphyrin (PtOEP) in an oxygen permeable elastic fluorinated co-polymer matrix. Phosphorescence, which was partially quenched by dissolved oxygen, was observed when the sensor was immersed in water. Aggregation of the dye was observed at elevated temperatures. Dye aggregate phosphorescence was not or only partially quenched by dissolved oxygen. The downward-turning Stern–Volmer plot was well fitted by a Langmuir adsorption isotherm. Good sensitivity, rapid response and photostability were observed for this detector.

A robust thin film dissolved oxygen sensor was fabricated by trapping erythrosin B in a flexible fluoropolymer matrix. Strong phosphorescence, which was partially quenched by dissolved oxygen, was observed when the sensor was immersed in water. Residual phosphorescence, which was not quenched by dissolved oxygen, was attributed to the presence of aggregated dye species. The sensor was optically transparent, resistant to contamination, with good mechanical properties. Fast response, coupled with good sensitivity and resistance to leaching, were also exhibited by this system. The Stern–Volmer (SV) plot exhibited marked downward turning at higher oxygen concentrations. A linear plot was obtained when the SV equation was modified to account for the varying sensitivity of dye molecules in the matrix to the quencher.

A thin film dissolved oxygen optical sensor was fabricated by encapsulating the phosphorescent dye erythrosin B in a sol–gel/fluoropolymer composite matrix. Strong phosphorescence, which was efficiently quenched by dissolved oxygen, was observed. The sensor was stable, optically transparent, resistant to contamination, with good mechanical properties. Fast response, coupled with good sensitivity and resistance to leaching, were also exhibited by this system. The Stern–Volmer (SV) plot was linear at low dissolved oxygen concentrations, but exhibited marked upward turning at higher concentrations due to combined dynamic and static quenching processes.

A thin film dissolved oxygen sensor was fabricated by trapping erythrosin B in a sol–gel matrix. No phosphorescence was observed when the sensor was immersed in water. Very weak phosphorescence was observed when erythrosin B was dissolved in aqueous ethanol and acetone solutions. However, fluorescence at 590nm, which was efficiently quenched by dissolved oxygen, was observed from the doped sol–gel sensor in water. A singlet oxygen feedback mechanism was proposed. Good sensitivity and stability were observed for this detector.

Organic molecular crystals that are extremely efficient at terahertz-pulse generation are in- vestigated. Terahertz pulses produced by optical rectification at 800 nm in (−)2-(α-methylbenzyl-amino)-5-nitropyridine have an order of magnitude higher power than those generated in the commonly used inorganic crystal ZnTe. The organic molecular crystals were also found to generate terahertz pulses when excited on resonance at 400 nm. This may pave the way for studying ultrafast charge-transport dynamics in three dimensions.

The organic crystal (S)-3-methyl-5-nitro-N-(1 -phenylethyl)-2-pyridinamine has been previously identified by the powder technique as a promising nonlinear optical material. Large single crystals (3 x 3 x 2 cm(3)) of this material have been grown by temperature lowering of a seeded supersaturated solution in acetone, Refined refractive indices were obtained from the predicted angles of incidence of the phase-matched second harmonic signals. Second-order nonlinear optical coefficients, d(ij), as measured by the Maker fringe technique, are 11, 9, and 7 pm V-1 for d(14), d(25), and d(36). respectively. The results are compared with calculations based on the oriented gas model.

An assessment of the acousto-optic figure of merit, M, was performed for the highly-polar non-centrosymmetric crystal, (-) 2--(methylbenzylamino)-5-nitropyridine. Its estimated value is as large as 1.3 × 10-13 s3 kg-1 at an ultrasound frequency of 15.4 MHz with light of wavelength 632.8 nm. This value is about four times as large as that of the widely used inorganic crystal, PbMoO4.

In addition to possessing strong optical nonlinearity, the (−)-2-( α -methylbenzylamino)-5-nitropyridine (MBANP) crystal has been shown to have unusual linear optical properties. Two methyl derivatives of MBANP have now been synthesized and grown as large single crystals; their refractive indices have been measured as a function of frequency and second-harmonic generation, including the determination of the phase matching loci has been investigated. Data is also available on the racemic form of crystalline MBANP. The properties of this family of crystals have been reviewed and an attempt is made to relate the experimental responses of the crystals to their molecular structure and the calculated properties of the molecules.