Enhanced optical sensing of anions with amide-functionalized gold nanoparticles

A gold nanoparticle surface-modified with amide ligands shows enhanced optical sensing of anions: the detection limit is increased by about three orders of magnitude higher than that originally expected from the anion binding ability of neutral amide ligands.     

Stereocontrolled synthesis of 8,11-dideoxytetrodotoxin,unnatural analogue of puffer fish toxin

[structure: see text] 8,11-Dideoxytetrodotoxin, an unnatural tetrodotoxin analogue, was synthesized in a highly stereoselective manner from a common intermediate in our synthetic studies on tetrodotoxin. The synthesis features neighboring group participation of trichloroacetamide for stereoselective hydroxylation, protection of ortho ester, and guanidine installation with Boc-protected isothiourea.     

Self-oscillation of polymer chains with rhythmical soluble-insoluble changes

Self-oscillation of polymer chains in an aqueous solution has been achieved. The ruthenium catalyst for the Belousov-Zhabotinsky reaction was polymerized by using N-isopropylacrylamide and dissolved into the solution containing the BZ substrates. Periodical soluble-insoluble changes of the polymer chain were spontaneously induced by the BZ reaction. The conformational oscillations of the polymer were measured as the optical transmittance changes of the solution. This is the first report that rhythmical and reversible soluble-insoluble changes of polymer chains are realized under constant and homogeneous conditions. The transducing system from chemical energy of the BZ reaction to optical information has been constructed.     

Concentration of nonylphenol and its polyethoxylated derivatives by polymer-mediated extraction

Polymer-mediated extraction based on thermoresponsive precipitation of poly(N-isopropylacrylamide) [PNIPAAm] was applied to the concentration of amphiphilic compounds, nonylphenyl polyethoxylates (NPnEOs), in water. Among these nonionic surfactants, NPnEOs possessing the number, n, of ethoxy unit less than 5 were quantitatively recovered in polymer precipitates when a 0.100-g portion of PNIPAAm was used for a 10 ml sample solution. Torelance limit (30 ppm) against a typical industrial anionic surfactant, sodium dodecylsulfate, strongly suggests the potential to use the present method for practical purposes. After preconcentration, trace nonylphenol and mono-ethoxylated nonylphenol (ppb-level) in a river water sample were successfully determined by high-performance liquid chromatography with ultra-violet photometric detection.     

A cyclic oligophenylene containing two 1,8-naphthalene units bridged by two face-to-face biphenyl linkages exhibiting unusual strain and pi-pi interaction

1,8-[1,8-Naphthalenediylbis(4',4-biphenyldiyl)]naphthalene, a very stable strained cyclophane, has been synthesized in moderate yield using the copper-catalyzed coupling of 1, 8-bis(4-(tributylstannyl)phenyl)naphthalene. The X-ray analysis of the titled compound discloses bent p,p'-biphenylylene chains with splayed naphthalene rings, and the p,p'-biphenylylene chains located face-to-face indicate a fairly strong pi-pi interaction.