Simultaneous Identification of Spectral Properties and Sizes of Multiple Particles in Solution with Subnanometer Resolution

We report an unsurpassed solution characterization technique based on analytical ultracentrifugation, which demonstrates exceptional potential for resolving particle sizes in solution with sub‐nm resolution. We achieve this improvement in resolution by simultaneously measuring UV/Vis spectra while hydrodynamically separating individual components in the mixture. By equipping an analytical ultracentrifuge with a novel multi‐wavelength detector, we are adding a new spectral discovery dimension to traditional hydrodynamic characterization, and amplify the information obtained by orders of magnitude. We demonstrate the power of this technique by characterizing unpurified CdTe nanoparticle samples, avoiding tedious and often impossible purification and fractionation of nanoparticles into apparently monodisperse fractions. With this approach, we have for the first time identified the pure spectral properties and band‐gap positions of discrete species present in the CdTe mixture.     

Reactions of Azolium cations. II [1]. Regioselective N2 alkylation of 5-aryltetrazoles with isopropyl alcohol in sulfuric acid media: Effect of electronic properties of aryl substituents on the reaction rate

Kinetics of regioselective N2 alkylation of a series of 5-(R-phenyl)tetrazoles with isopropyl alcohol has been studied in 88.2, 94.3, and 98.3% (w/w) sulfuric acid at 25°. The true rate constants were evaluated, logarithms of which were found to correlate with σ° constants of phenyl substituents as log k = ?0.488 σ° ? 0.417. Small value of Hammett constant ρ is evidence of a considerable isolation of the reaction center from the influence of the substituent at position C5 of the heteroring. This conclusion is confirmed by results of MNDO quantum chemical calculations of a series of 5-substituted tetrazolium cations. A correlation between logarithms of the true rate constants and the calculated net effective charges on atoms N2(N3) for 5-(R-phenyl)tetrazolium cations has been revealed. © 1995 John Wiley & Sons, Inc.     

Sulfonated Petroleum Polymeric Resins as Plasticizers for Cement Mortars

Sulfonation of petroleum polymeric resins based on the C₉ fraction with various suilfonatic agents was studied, and procedure was developed for preparing sulfonated resins. The possibility of using sulfo resins as effective plasticizers for concrete was examined.     

Exhaustive N-tert-butylation of tetrazoles in thet-BuOH-HBF4 system

Tetrazole and its N-monosubstituted and C,N-disubstituted derivatives in a 48% HBF₄ medium react with tertbutyl alcohol, forming the corresponding tetrazolium salts. In this case, tert-burylation of 2-monosubstituted and 2,5-disubstituted tetrazoles occurs at the N₍₄₎ atom, as in the case of other allcylating agents; the 1-substituted isomers, in contrast, are quaternized preferentially at the less basic atom N₍₃₎, while the 1,5-disubstituted isomers are quaternized exclusively at the N₍₃₎ atom.Scientific-Research Institute of Physicochemical Problems, Belorussian State University, Minsk 220080. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 915–921, July, 1995. Original article submitted December 30, 1994; revised, June 13, 1995.     

Copolymerization of styrene and 1-hexene with a TiCl<Subscript>4</Subscript>-Al(C<Subscript>6</Subscript>H<Subscript>13</Subscript>)<Subscript>3</Subscript> · Mg(C<Subscript>6</Subscript>H<Subscript>13</Subscript>)<Subscript>2</Subscript> catalytic system

The copolymerization of styrene and 1-hexene with the TiCl₄-Al(C₆H₁₃)₃ · Mg(C₆H₁₃)₂ catalytic system has been investigated. The microstructure of polymer chains, molecular-mass characteristics, and thermophysical properties of the resulting copolymers have been studied. These copolymers contain 15 to 65 mol % styrene and mostly consist of isotactic polystyrene and poly(1-hexene) blocks.     

Synthesis and properties of phenylenebis-1H-tetrazoles

Heterocyclization of m- and p-phenylenediamines with orthoformic ester and sodium azide has given phenylenebis-1H-tetrazoles. Under these conditions, o-phenylenediamine gives benzimidazole. o-, m-, and p-Phenylenebis-1H-tetrazoles were also obtained from the nitroanilines via the intermediate nitro- and aminophenyltetrazoles. The reactions of the bistetrazoles examined were basic hydrolysis, aminomethylation, and complex formation with copper salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1528–1532, November, 1990.