UV-activated luminescence/colourimetric O-2 indicator

An oxygen indicator is described, comprising nanoparticles of titania dispersed in hydroxyethyl cellulose (HEC) polymer film containing a sacrificial electron donor, glycerol, and the redox indicator, indigo-tetrasulfonate (ITS). The indicator is blue-coloured in the absence of UV light, however upon exposure to UV light it not only loses its colour but also luminesces, unless and until it is exposed to oxygen, whereupon its original colour is restored. The initial photobleaching spectral ( absorbance and luminescence) response characteristics in air and in vacuum are described and discussed in terms of a simple reaction scheme involving UV activation of the titania photocatalyst particles, which are used to reduce the redox dye, ITS, to its leuco form, whilst simultaneously oxidising the glycerol to glyceraldehye. The response characteristics of the activated, that is, UV photobleached, form of the indicator to oxygen are also reported and the possible uses of such an indicator to measure ambient O-2 levels are discussed. Copyright (C) 2008 Andrew Mills et al.

Luminescence temperature sensing using poly(vinyl alcohol)-encapsulated Ru(bpy)(3)(2+) films

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.

Luminescence of leuco-thiazine dyes

Details of the novel luminescence of the leuco forms of the thiazine dyes, methylene blue and thionine, are reported, including their emission maxima, quantum yields and lifetimes of the luminescence. Other work shows that this luminescence is independent of reducing agent type and solution pH and is a common feature of most thiazine dyes.

Chemical influences on the luminescence of ruthenium diimine complexes and its response to oxygen

Different luminescent, hydrophillic ruthenium diimine cationic complexes are rendered soluble in the hydrophobic medium of a plasticised polymer through ion-pair coupling with a hydrophobic anion, such as tetraphenyl berate. Based on this approach, a number of different oxygen sensitive films, i.e., luminescent, thin plastic films which respond to oxygen-the latter quenches the luminescence were prepared, using the polymer, cellulose acetate, plasticised with tributylphosphate. Of the resultant thin oxygen sensitive films tested, the one containing the luminescent ion-pair ruthenium (II) tris(4,7-diphenyl-1,IO-phenanthroline) ditetraphenyl berate, [Ru(dpp)(3)(2+)(Ph4B-)(2)], was found to be the most sensitive, and its response characteristics were subsequently studied as a function of plasticiser content, temperature and stability in use, and with age. The major response characteristics, i.e., film sensitivity towards oxygen and response and recovery times, depend very strongly upon the overall level of plasticiser present in film; the film is more sensitive and faster in response and recovery the greater the level of plasticiser employed. Thus, the response of the film towards oxygen can be tuned by varying the level of plasticiser in the film. Film sensitivity towards oxygen is largely independent on temperature, whereas its response and recovery times decrease with increasing temperature (E-a = -10.3+/-0.4 kJ mol(-1)). The sensitivity of a typical luminescent film is very stable when used continuously over a 24-h period, decreases by ca. 20% with age when stored at ambient temperature over a period of 29 days, but very little over the same period of time when stored in the freezer section of a fridge. (C) 1997 Elsevier Science S.A.

AND Logic Gates Based on Small Molecules with Chemical Inputs and Luminescence Output

AND logic gate behaviour can be recognized in chemical-responsive luminescence phenomena concerning small molecules. Though initial developments concerned separate and distinguishable chemical species as inputs, consideration of other types of input sets allows substantial expansion of the sub-field. Dissection of these molecular devices into modules, where possible, enables analysis of their logic behaviour according to supramolecular photochemical mechanisms.

Tunable Enhancement of High Harmonic Emission from Laser Solid Interactions

Coherent wake emission is a unique source of extreme ultraviolet radiation and has been recently shown to provide the basis for intense attosecond light. Here we present a novel scheme, supported by particle-in-cell simulations, demonstrating that enhancement and spectral control of the coherent wake emission signal can be achieved by modifying the interaction plasma density ramp. Significant tunable enhancement of harmonic emission is verified experimentally, with factors of > 50 in relative signal increase achieved in a narrow band of harmonics at the cutoff frequency.

Tunable 3D Plasmonic Swiss Rolls

Novel 3D plasmonic rolls are fabricated through strain-induced self-rolling of metallic nanopore sheets attached to elastomeric thin films, with optical properties tunable by varying the size and thickness of nanopores, and dynamically by light irradiation.

A Tunable Encryption Scheme and Analysis of Fast Selective Encryption for CAVLC and CABAC in H.264/AVC

Recently, two fast selective encryption methods for context-adaptive variable length coding and context-adaptive binary arithmetic coding in H.264/AVC were proposed by Shahid et al. In this paper, it was demonstrated that these two methods are not as efficient as only encrypting the sign bits of nonzero coefficients. Experimental results showed that without encrypting the sign bits of nonzero coefficients, these two methods can not provide a perceptual scrambling effect. If a much stronger scrambling effect is required, intra prediction modes, and the sign bits of motion vectors can be encrypted together with the sign bits of nonzero coefficients. For practical applications, the required encryption scheme should be customized according to a user's specified requirement on the perceptual scrambling effect and the computational cost. Thus, a tunable encryption scheme combining these three methods is proposed for H.264/AVC. To simplify its implementation and reduce the computational cost, a simple control mechanism is proposed to adjust the control factors. Experimental results show that this scheme can provide different scrambling levels by adjusting three control factors with no or very little impact on the compression performance. The proposed scheme can run in real-time and its computational cost is minimal. The security of the proposed scheme is also discussed. It is secure against the replacement attack when all three control factors are set to one.

The controlled fabrication and geometry tunable optics of gold nanotube arrays

Arrays of vertically aligned gold nanotubes are fabricated over several square centimetres which display a geometry tunable plasmonic extinction peak at visible wavelengths and at normal incidence. The fabrication method gives control over nanotube dimensions with inner core diameters of 15–30 nm, wall thicknesses of 5–15 nm and nanotube lengths of up to 300 nm. It is possible to tune the position of the extinction peak through the wavelength range 600–900 nm by varying the inner core diameter and wall thickness. The experimental data are in agreement with numerical modelling of the optical properties which further reveal highly localized and enhanced electric fields around the nanotubes. The tunable nature of the optical response exhibited by such structures could be important for various label-free sensing applications based on both refractive index sensing and surface-enhanced Raman scattering.

Nanocomposite-Coated Open-Cell Foams with Tunable Mechanical and Multifunctional Properties

No abstract available

Tunable thermomorphism and applications of ionic liquid analogues of Girard's reagents

A series of ionic liquids based on Girard's reagents was synthesised. Their tunable thermomorphic behaviour with water was demonstrated, and slight modifications in the cationic structure led to drastic changes in their water miscibility. Their phase behaviour, involving monophasic–biphasic transitions, drove a number of practical applications, including scavenging water-soluble dyes and the extraction of metals from water.

Tunable gold nanoparticles shape and size in reductive and structuring media containing protic ionic liquids

Herein, a facile method was developed for preparing high concentration of monodispersed gold nanoparticles (NPs) at room temperature from gold(III) chloride by using different media based on N,N-dimethylformamide or water solutions containing a protic ionic liquid (PIL), namely, the octylammonium formate or the bis(2-ethyl-hexyl)ammonium formate, based on which both PILs were used as redox-active structuring media. The formation of gold NPs in these systems was then characterized using UV-visible spectroscopy, transmission electron microscopy, and dynamic light scattering. From these investigations, it appears that the structure and aggregation pathway of PILs in selected solvents affect strongly the formation, growth, the shape, and the size of gold NPs. In fact, by using this approach, the shape-/ size-controlled gold NPs (branched and spherical) can be generated under mild condition. This approach suggests also a wealth of potential for these designer nanomaterials within the biomedical, materials, and catalysis communities by using designer and safer media based on PILs.

Novel titania sol-gel derived film for luminescence-based oxygen sensing.

A novel method for the preparation of titania sol–gel derived oxygen sensors based on the ruthenium(II) dye, [Ru(bpy)3]2+, is described. A titania sol–gel paste film was cast onto microscope slides, and the dye ion-paired to the deprotonated, hydroxylated groups on the film's surface from an aqueous solution of the dye at pH 11. The resulting sensor film is extremely oxygen sensitive, with a PO2 (S = 1/2) value (i.e. the partial pressure of oxygen required in order to reduce the original, oxygen free, luminescence intensity by 50%) of 0.011 atm. The sensor undergoes 95% response to oxygen in 4 s, and shows 95% recovery of its luminescence in argon within 7 s.