Unusual conductance of polyyne-based molecular wires

We report a full self-consistent ab initio calculation of the current-voltage curve and the conductance of thiolate capped polyynes in contact with gold electrodes. We find the conductance of polyynes an order of magnitude larger compared with other conjugated oligomers. The reason lies in the position of the Fermi level deep in the HOMO related resonance. With the conductance weakly dependent on the applied bias and almost independent of the length of the molecular chain, polyynes appear as nearly perfect molecular wires.Comment: 4 pages, 5 figures, 3 table

Characterization of summer savory (Satureja hortensis L.) honey by physico-chemical parameters and chromatographic/spectroscopic techniques (GC-FID/MS, HPLC-DAD, UV/VIS and FTIR-ATR

Satureja hortensis L. unifloral honey was characterized by pollen analysis, electrical conductivity, pH and extensively by chromatographic and spectroscopic techniques. UV / VIS spectro-scopy measurements revealed total phenol content of 682.1 mg GAE / kg by Folin-Ciocalteu assay, antiox-idant capacity by DPPH assay of 1.7 mmol TEAC / kg and by FRAP assay of 4.3 mmol Fe2+ / kg as well as CIE L*a*b*Cab*h°ab chromaticity coordinates. GC-MS after headspace solid-phase microextraction (HS-SPME) revealed hotrienol (22.8 %) along with other linalool derivatives, benzaldehyde (6.1 %), phenylacetaldehyde (4.9 %) and few norisoprenoids (safranal (7.6 %) as the major). Ultrasonic solvent ex-traction (USE) followed by GC-MS allowed identification of methyl syringate (54.7 %) as predominant compound along with other benzene derivatives. HPLC-DAD analysis determined tyrosine (382.0 mg kg−1), phenylalanine (140.4 mg kg−1) and methyl syringate (39.32 mg kg−1). Methyl syringate and hotrienol can be considered non-specific chemical markers of S. hortensis honey. FTIR-ATR spectral characteristics of S. hortensis honey in fingerprinting region were not significantly different from other honey types, but the integrated intensity of the region was smaller than in other unifloral honeys

Time-resolved resonance Raman study of S1 cis-stilbene and its deuterated isotopomers

We present the picosecond time-resolved resonance Raman (ps-TR3) spectra of the first excited singlet state (S1) of cis-stilbene (d0), fully deuterated cis-stilbene (d12) and α,α′-d2-cis-stilbene (d2) measured in hexane at pump and probe wavelengths 267 and 630 nm, respectively. The main observation is that in the lower wavenumber region the spectra are dominated by a second-order overtone progression originating from a 229 cm -1 fundamental band for the S1d0 cis-stilbene. The observed low-wavenumber modes of the excited cis-stilbene are substantially more resonantly enhanced than the modes around 1600 cm -1. Copyright © 2003 John Wiley & Sons, Ltd.link_to_subscribed_fulltex