This is a copy of the slides presented at the meeting but not formally written up for the volume.

We have explored the properties of triplet excited states in a series of platinum acetylide oligomers of the type [trans-Pt(PBu3)2(-CC-Ar)2], where Ar is a highly conjugated two-photon absorbing organic chromophore. Incorporation of two-photon absorbers into a pi-conjugated system produces short-lived excited states (fs/ps) with high efficiency. Platinum acetylide units introduce strong spin-orbit coupling into the pi-conjugated system to give rise to high yields of long-lived triplet excited states (ns/us) having large triplet-triplet absorption cross sections. Thus, a platinum acetylide having two-photon absorbers will, in principle, feature a strong non-linear absorption in broad time domain. The presentation will focus on (1) the synthesis and photophysical characterization under one- and two-photon excitation, (2) the effect of two-photon absorbing chromophores on nonlinear absorption properties of platinum acetylides and (3) the evidence for reverse saturable absorption.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Single-molecule manipulation and detection of biomolecules has significantly advanced our understanding of the molecular movement, dynamics, and biological function of proteins. Fluorescence microscopy currently serves as one of the primary noninvasive techniques for the sensitive detection of molecules in solution and on surfaces. However, the performance and sensitivity of this laser-induced fluorescence technique is strongly influenced by the fluorescent labels attached to DNA, proteins or cells. Organic dyes have most commonly been used as fluorescent biolabels; however, they quickly photobleach, limiting the time scale over which molecular events can be followed. Quantum dots show great promise for fluorescence measurements due to their improved photophysical properties, such as size-tunable narrow emissions, large Stokes shifts and minimal photobleaching. However, problems still exist for the use of quantum dots as biolabels, including: photoblinking, toxic synthetic approaches, surface passivation issues and relatively large physical sizes that are comparable to proteins. Here, we report the synthesis of a new class of fluorescent labels, gold nanoclusters, which consist of several gold atoms (<1 nm in size) with strong fluorescence emission. These small fluorescent gold nanoclusters are synthesized at physiological temperature using poly(amidoamine) dendrimer as a template. Small blue emissive gold nanoclusters were produced without the use of a reductant and without concurrent nanoparticle formation. Gold nanoclusters with green and red emissions were synthesized using a mild reductant, also without nanoparticle formation. The studies of pH-dependent stability suggest that these fluorescent nanoclusters are very stable in a pH range of 6 - 8. These new approaches produce gold nanoclusters with a much higher yield and eliminate the toxicity of the previously reported process, resulting in a biologically compliant approach. This work is the first known report of fluorescent gold nanoclusters via a green-chemistry approach and without the formation of gold nanoparticles. This work is funded by Los Alamos Laboratory Directed research and Development program.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Electrochromic and electrofluorescent cell was fabricated by the combination of electrochromic (EC) viologen and a fluorescent anthracene polymer. All-solid-state dual electrochromic windows which have color transition from yellow to dark blue were assembled by employing benzyl viologen, photo polymerizable electrolyte and polyanthracene (PAN). EC contrast and response of ECDs adopting the viologen and PAN could be optimized by changing the content of PAN. In the optimized condition, EC-EF device showed optical contrast and fluorescence switching with response time less than 5 sec.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Presented is the initial photophysical investigation of a series of transition metals complexed with an organic, two photon absorbing chromophore. This system is capable of a dual-mode nonlinear response. Upon two photon excitation, rapid intersystem crossing generates a long-lived and strongly absorbing triplet excited state capable of further nonlinear absorption via a reverse saturable absorption pathway.

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Complex structures, such as living organisms or highly structured materials, share in common the fact that their inherent complexity may be accounted for by the tangled organization of a vast number of simple units. The complex behaviour arises not necessarily due to the atomic structure of the system, but to the orderly assembly of all, or part, of its constituents. Self-assembly of synthetic soft-matter components (polymers, liquid crystals, surfactants, colloids and organic/inorganic hybrids) results in regular hierarchically-organized structures. Here, we report on a photoluminescent highly-organized bilayer alkylene/siloxane hybrid self-assembled by intermolecular hydrogen bonding between amide groups, van der Waals interactions between the alkylene chains and an entropic term related to the organic-inorganic phase separation [1]. These factors are decisive for the emergence of a thermally-actuated photoluminescence memory effect induced by a reversible order-disorder phase transition of the alkylene chains involving ~30 lamellae (~150 nm). The reversibility of this phase transition is attained through a heating/cooling cycle (20-120 C) from which a hysteretic behaviour of the emission energy emerges. The initial emission energy value is recovered after ~300 h, following a logarithmic time dependence, due to the slow kinetics of the restoration of the hydrogen-bonded amide-amide network. The photoluminescence is thus responsive to the annihilation/formation of the amide-amide array displaying nanoscopic sensitivity, contrarily to the customary case for which the local environment around the emitter probe determines the emission features. Moreover, the emission energy logarithmic time dependence reflects hierarchically constrained dynamics deprived of any characteristic microscopic time, meaning that the emission is governed by interactions at larger length scales.[1]LD Carlos, V de Zea Bermudez, VS Amaral, SC Nunes, NJO Silva, RA Sá Ferreira, J Rocha, CV Santilli, D Ostrovskii, Adv. Mater., accepted

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Recently, the telecommunication market experiences an explosion in the subscribers of emergent high-debit services which require bandwidth that exceeds the one provided by actual copper based access networks [1]. To cope with these demands and keep competitive, great efforts have been done to develop access networks based on optical technology, such as passive all-optical networks due to their intrinsic low cost [2]. Sol-gel processing is suitable for the development of organic-inorganic hybrid (OIH) materials for the production of functional integrated optic (IO) devices in a cost effective way. Urea cross-linked OIH show acceptable transparency, mechanical flexibility and thermal stability [3-6]. The control over the refractive index is achieved by zirconium (IV) n-propoxide (ZPO) doping stabilized with methacrylic acid (MA) [3-5]. The combination in a single material of urea cross-linked OIH and ZPO allowed the preparation of UV written low losses planar waveguides [3] and low rugosity diffraction grating [4,5]. It has been demonstrated that MA acts not only as ZPO stabilizer but impacts directly on the photopolimerization properties as it contains a photopolymerizable group making the OIH easily UV patterned without photoinitiator [5]. Moreover, it also impacts on the OHIs local structure as it forms a complex with ZPO, that originate ordered clusters dispersed within the OIH host [4,5]. Besides the potential of this OIH as IO components, the hybrid hosts are room-temperature efficient white light emitters lacking metal activator ions, presenting quantum yields as higher as 20 % [6]. In this work, a series of OIH, so called di-ureasils, formed of a siliceous skeleton to which oligopolyether chains of different lengths are covalently grafted by means of urea bridges and modified by ZPO and MA will be prepared and characterized by X-ray and small angle X-ray diffractions, Raman, infrared, atomic force and photoluminescence spectroscopies. The use of the proposed OIH in the development of IO functionalities such as optical filters will be evaluated based on waveguide numerical simulation methods (beam propagation method). Waveguides will be written and characterized using the OIH aforementioned. The recording of a Bragg grating in the waveguides allow the implementation of a wavelength discrimination device with applications on optical filtering. The relevant properties of the devices, such as spectral rejection and insertion losses will be characterized. [1] S-J Park et al. Journal of Lightwave Tech. 22, 2004. [2] D.J. Shin et al., Journal of Lightwave Tech. 23, 2005. [3] C. Molina et al., J. Mater. Chem. 15, 3937, 2005. [4] R.A. Sá Ferreira et al., Proceedings of the International Conference on Telecomunications, 2006. [5] P.S. André et al. Proceedings ICTON, 1, We.C1.6, 223, 2006. [6] a) L.D. Carlos et al., Adv. Func. Mater. 11, 111, 2001; b) J. Chem. Phys. B. 108, 14924, 2004. Siemens SA and FCT (POCTI/CTM/59075/2004) is gratefully acknowledged.