Stable and uniform SERS signals from self-assembled two-dimensional interfacial arrays of optically coupled Ag nanoparticles.

Densely packed interfacial nanoparticle films form spontaneously when aqueous Ag colloid is shaken with CH2Cl2 in the presence of a "promoter" such as 10(-4) mol dm(-3) tetrabutylammonium nitrate (TBA(+)NO3(-)), which induces rapid self-assembly of the nanoparticles at the liquid/liquid interface without adsorbing onto their surfaces. The particles within these reflective, metal-like liquid films (MeLLFs) are optically coupled and give strong SERS enhancement, similar to that obtained for the same colloid aggregated with optimized concentration of metal salt. However, unlike aggregated colloids their structure means they do not sediment out of solution so they give SERS spectra that are stable for >20 h) and have good uniformity (relative standard deviation in absolute intensity over 1 mm(2) array of 25 points was 1.

Drag enhancement of aqueous electrolyte solutions in turbulent pipe flow.

Detailed experimental results are presented for both laminar and turbulent flow of aqueous solutions in pipes of different diameters. Nonelectrolytes, such as sugar solutions followed the normal Moody pressure loss curves. Drag enhancement was demonstrated for turbulent flow of aqueous electrolyte solutions but not for laminar flow.

Mechanism of 2,2'6,6'-tetramethylpiperidin-N-oxyl-mediated oxidation of alcohols in ionic liquids.

The mechanism of 2,2'6,6'-tetramethylpiperidin- N-oxyl (TEMPO)-mediated oxidation of alcohols to aldehydes and ketones in ionic liquids has been investigated using cyclic voltammetry and rotating disk electrode voltammetry. It is shown that the presence of bases (B) and their conjugate acids (BH (+)), as well as their p K as, strongly influences the rate of reaction. Data indicated that the first step in the oxidation is the formation of the alcoholate species via acid-base equlibrium with B.

Behavior of electrogenerated bases in room-temperature ionic liquids.

The reductive electrochemistry of substituted benzophenones in the aprotic room-temperature ionic liquid (RTIL) 1-butyl-1-methylpyrrolidinium bistriflimide occurs via two consecutive one-electron processes leading to the radical anion and dianion, respectively. The radical anion exhibited electrochemical reversibility at all time-scales whereas the dianion exhibited reversibility at potential sweep rates of >or=10 V s(-1), collectively indicating the absence of strong ion-paring with the RTIL cation. In contrast, reduction in 1-butyl-3-methylimidazolium bistriflimide is complicated by proton-transfer from the [Bmim] cation.

Anion detection driven by a surprising internal hydrogen-bonding association in a dinuclear rhenium(I) complex.

A neutral dinuclear rhenium(I) bipyridinetricarbonyl bromide complex has been investigated with a range of anions, giving a remarkable binding affinity for dihydrogenphosphate. These studies highlight that anion sensing can be achieved with structurally simple species provided that the compound adopts an unconventional conformation, through, for example, intramolecular hydrogen bonding in solution.

New stepwise approach to inert heterometallic triple-stranded helicates.

The new tripodal fac-functionalized building block, fac-ruthenium(II) tris-(5-hydroxymethyl-2,2'-bipyridine), has been synthesized as a single geometric isomer and used as starting point in the isolation of a kinetically inert heterometallic helicate by the stepwise inclusion of additional 2,2'-bipyridine chelating groups followed by a second metal ion. This stepwise synthetic methodology gives access to a new range of chiral nanoscale structures inaccessible by traditional self-assembly procedures.

Electrogenerated radical anions in room-temperature ionic liquids.

The sequential two-electron reduction of benzaldehyde to the radical anion and dianion species in 1-butyl-3-methylimidazolium triflimide and 1-butyl-1-methylpyrrolidinium triflimide is reported. In 1-butyl-1-methylpyrrolidinium triflimide, the heterogeneous electrochemistry and follow-up chemical reactivity are essentially equivalent to that in conventional molecular-solvent-based electrolytes where no interaction with the media is observed. In 1-butyl-3-methylimmidazolium triflimide, reduction occurs via the same two heterogeneous processes; however, the apparent heterogeneous rate constants are smaller by ca.