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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

The development of white organic light-emitting diodes (OLEDs) holds great promise for the production of highly efficient large-area light sources. High internal quantum efficiencies for the conversion of electrical energy to light have been realized. Nevertheless, the overall device power efficiencies are still considerably below the 60-70 lumens per watt of fluorescent tubes, which is the current benchmark for novel light sources. Although some reports about highly power-efficient white OLEDs exist, details about structure and the measurement conditions of these structures have not been fully disclosed: the highest power efficiency reported in the scientific literature is 44 lm W(-1) (ref. 7). Here we report an improved OLED structure which reaches fluorescent tube efficiency. By combining a carefully chosen emitter layer with high-refractive-index substrates, and using a periodic outcoupling structure, we achieve a device power efficiency of 90 lm W(-1) at 1,000 candelas per square metre. This efficiency has the potential to be raised to 124 lm W(-1) if the light outcoupling can be further improved. Besides approaching internal quantum efficiency values of one, we have also focused on reducing energetic and ohmic losses that occur during electron-photon conversion. We anticipate that our results will be a starting point for further research, leading to white OLEDs having efficiencies beyond 100 lm W(-1). This could make white-light OLEDs, with their soft area light and high colour-rendering qualities, the light sources of choice for the future.

White organic light-emitting diodes with fluorescent tube efficiency

The ability to control the size, shape, and material of a surface has reinvigorated the field of surface-enhanced Raman spectroscopy (SERS). Because excitation of the localized surface plasmon resonance of a nanostructured surface or nanoparticle lies at the heart of SERS, the ability to reliably control the surface characteristics has taken SERS from an interesting surface phenomenon to a rapidly developing analytical tool. This article first explains many fundamental features of SERS and then describes the use of nanosphere lithography for the fabrication of highly reproducible and robust SERS substrates. In particular, we review metal film over nanosphere surfaces as excellent candidates for several experiments that were once impossible with more primitive SERS substrates (e.g., metal island films). The article also describes progress in applying SERS to the detection of chemical warfare agents and several biological molecules.

Surface-Enhanced Raman Spectroscopy

Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

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Lanthanide luminescence for functional materials and bio-sciences

Surface-enhanced Raman spectroscopy.

The linear and the nonlinear optical properties of soluble phthalocyanines in the condensed states were investigated by the absorption and the electroabsorption spectra. By a Kramers-Kronig analysis of the electroabsorption spectra, the wavelength of the maximum refractive index changes is located at around 980 nm for the casted polymer film doped with binuclear phthalocyanine.

Molecular Interaction of Phthalocyanine Studied by Electroabsorption in Near IR

Dewetting-induced crystallization from hot trichlorobenzene solutions led to the formation of aligned pentacene microfibers or plates, depending on preparation conditions. Fibers with a length of several hundred micrometer and a width of less than one micrometer can be prepared. Bottom-contact field effect transistors with fibers that were oriented perpendicular to the source and drain electrodes showed carrier mobilities as high as 0.04 cm2/Vs. In comparison, plate-like pentacene gave corrected mobilities of up to 0.2 cm2/Vs. [DOI: 10.1380/ejssnt.2009.568]

Preparation of Pentacene Organic Field Effect Transistors by a Wet Process and their Carrier Mobilities

Preparation of polythiophene copolymer for third order nonlinear optics

On the basis of highly reproducible scanning tunneling microscopy (STM) images of the tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) surface with atomic resolution, a new interpretation for such STM images from the viewpoint of the relative phase difference of the molecular orbital in each organic molecule is presented. The interpretation is based on the interference effect on tunneling because of the short tip-sample distance.

Interpretation for STM Imaging of One-Dimensional Organic Conductors

Cytoscreening of normal and cancer cells was performed using an infrared Raman spectroscopy together with data analysis software. The samples used were WFB (normal cell), W31 (cancer cell) and W14 (attenuated virulence cancer cell). Differential Raman spectra of cell samples were analyzed by using principal component analysis and discriminant analysis. Comparing the characteristic results, the increase of protein amide I, the significant decrease of lipid and the decrease of nucleic acid were observed. The accuracy of cell discrimination was around 93% for WFB, W31 and W14.

Hiroyuki Sasabe

Papers

Molecular Interaction of Phthalocyanine Studied by Electroabsorption in Near IR

Preparation of Pentacene Organic Field Effect Transistors by a Wet Process and their Carrier Mobilities

Preparation of polythiophene copolymer for third order nonlinear optics

Interpretation for STM Imaging of One-Dimensional Organic Conductors

Vibrational Spectroscopy Using Infrared Raman Microscope for Cytoscreening