/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

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).

/pdf/lanthanide-luminescence-for-functional-materials-and-bio-1w9cppwf8r.pdf

Lanthanide luminescence for functional materials and bio-sciences

Surface-enhanced Raman spectroscopy.

Thiolated heme derivatives were synthesized and their self-assembly behaviors on gold surfaces together with that of native heme were studied. The kinetics of this adsorption and the thickness of the formed monolayer were investigated by surface plasmon resonance spectroscopy. Native heme shows a different adsorption behavior compared to that of the synthesized derivatives. Though the heme derivatives were found to form monolayers, native heme formed only irregular aggregates on gold surfaces. IR spectroscopy was used to reveal the molecular structure of the adsorbates in the vicinity of the peptide linkage in the heme molecules on the gold surfaces. UV spectroscopy was employed to determine the tilt angle of the porphyrin rings relative to the gold surface normal. Cyclic voltammograms and potential-modulated UV-vis reflectance spectra of heme derivatives were observed in order to estimate the adsorbed amount and the redox behaviors of heme derivatives on gold surfaces.

Self-assembled monolayers of heme derivatives on a gold surface

: Second order molecular susceptibilities B of Poly (y benzyl L-glutamate)(PBLG) and poly(y -p-nitrobenzyl Lglutamate) (PNBLG) were determined by means of dc-induced second harmonic generation (dc-SHG) technique in solutions at a wavelength of 1064nm as 1.5x10-29 esu and -4.9xlO-29 esu, respectively. Among PBLG, PNBLG and nitrobenzene, it was found that only PNBLG has negative value of B. It follows that the effect of nitrophenyl groups in side chains is dominant for B whereas the contribution of carbonyl groups in main chain is dominant for the permanent dipole moment u in PNBLG.

Molecular Design of Synthetic Polypeptides for Nonlinear Optics

Influence of substrate surface on Langmuir-Blodgett multilayers

Second-harmonic generation together with linear dichroism has been studied on monolayer assemblies of 4-octadecylamino- and 4-docosylamino-4′-nitro-tolan. These amphiphiles form condensed monolayers at the air–water interface. Using the conventional Langmuir–Blodgett and the horizontal lifting methods, we obtained the alternating Y-type and the nonalternating X-type multilayers, respectively, and the considerably anisotropic second-harmonic generation of both types was observed, depending on the dipping direction of solid substrates or the monolayer compression.

Linear and nonlinear optical behaviors of Langmuir–Blodgett multilayers of push–pull tolan derivatives

Large third‐order optical nonlinearity was found with the soluble conjugated polymers (substituted polyacetylenes) synthesized by the ring‐forming metathesis polymerization of 4,4‐disubstituted‐1,6‐heptadiynes. These polymers were of quite high molecular weight (∼105) and were highly soluble in common organic solvents. The linear optical property and the third‐order optical nonlinearity of these polymers were investigated in terms of the chemical structure of the 4,4‐disubstituents using the polymer films of around 100‐nm thickness fabricated by the spin coating of tetrahydrofuran solutions. The π‐π* transition of the conjugated π‐electron main chain was characterized as the strong absorption peak at around 540 nm of the electronic spectra, where the optical density of the transition was found to be largely dependent on the molar volume of the substituents. The near‐resonant values of the third‐order nonlinear optical coefficient, χ(3)(−3ω;ω,ω,ω) were found to be 2.6 to 6.5×10−11 esu, which also were cont...

Hiroyuki Sasabe

Papers

Self-assembled monolayers of heme derivatives on a gold surface

Molecular Design of Synthetic Polypeptides for Nonlinear Optics

Influence of substrate surface on Langmuir-Blodgett multilayers

Linear and nonlinear optical behaviors of Langmuir–Blodgett multilayers of push–pull tolan derivatives

Third‐order optical nonlinearity of conjugated poly(4,4‐disubstituted‐1,6‐heptadiyne)s