Local force titration of wood surfaces by chemical force microscopy

Cellulose - Chemical force microcopy, a variation of atomic force microscopy, opened the door to visualize chemical nano-properties of various materials in their natural state. The key function of...     

Mapping Dicorynia guianensis Amsh. wood constituents by submicron resolution cluster‐TOF‐SIMS imaging

The preparation of tropical wood surface sections for time‐of‐flight secondary ion mass spectrometry imaging is described, and the use of delayed extraction of secondary ions and its interest for the analysis of vegetal surface are shown. The method has been applied to the study by time‐of‐flight secondary ion mass spectrometry imaging with a resolution of less than one micron of a tropical wood species, Dicorynia guianensis, which is one of the most exploited wood in French Guiana for its durable heartwood. The heartwood of this species exhibits an economical importance, but its production is not controlled in forestry. Results show an increase of tryptamine from the transition zone and a concomitant decrease of inorganic ions and starch fragment ions. These experiments lead to a better understanding of the heartwood formation and the origin of the natural durability of D. guianensis. Copyright © 2016 John Wiley & Sons, Ltd.     

Zwitterionic Cellulose Carbamate with Regioselective Substitution Pattern: A Coating Material Possessing Antimicrobial Activity

A polyzwitterion is synthesized by regioselective functionalization of cellulose possessing a uniform charge distribution. The positively charged ammonium group is present at position 6, while the negative charge of carboxylate is located at positions 2 and 3 of the repeating unit. The molecular structure of the biopolymer derivative is proved by NMR spectroscopy. This cellulose‐based zwitterion is applied to several support materials by spin‐coating and characterized by means of atomic force microscope, contact angle measurements, ellipsometry, and X‐ray photoelectron spectroscopy. The coatings possess antimicrobial activity depending on the support materials (glass, titanium, tissue culture poly(styrene)) as revealed by confocal laser scanning microscopy and live/dead staining.

     

Racemic 2‐isopropyl‐3‐(2‐nitrobenzyl)‐1,3‐thiazolidin‐4‐one crystallizes in the space group P212121 with Z′ = 2: two different interpenetrating three‐dimensional frameworks formed by C—H...O hydrogen bonds

rac‐2‐Isopropyl‐3‐(2‐nitrobenzyl)‐1,3‐thiadiazolin‐4‐one, C₁₃H₁₆N₂O₃S, is a rare example of a racemate crystallizing in the space group P2₁2₁2₁, with one molecule each of S and R configurations, whose conformations are almost mirror images, within the asymmetric unit. The molecules of S configuration are linked by two C—H...O hydrogen bonds into a three‐dimensional framework, and the molecules of R configuration are linked by two further C—H...O hydrogen bonds into a different type of three‐dimensional framework; the two frameworks are linked by a fifth C—H...O hydrogen bond.     

Modeling of Thin-Layer Chromatographic Separation of Androstane Isomers

JPC – Journal of Planar Chromatography – Modern TLC - Modeling of thin-layer chromatographic separation of androstane isomers to find the optimum mobile phase is described in this...     

Functionalization of zeolitic cavities: grafting NH2 groups in framework T sites of B-SSZ-13--a way to obtain basic solids catalysts?

Insertion of B atoms into an Al-free zeolitic framework with CHA topology results in the formation of B-SSZ-13 zeotype with Si/B = 11. B K-edge NEXAFS testifies that B forms [B(OSi)4] units in a Td-like geometry (sp3-hybridized B atoms). According to B K-edge NEXAFS and IR, template burning results in the formation of [B(OSi)3] units in a D3h-like geometry (sp2-hybridized B atoms) with a break of a B-O-Si bond and the formation of a Si-OH group. The activated material contains B(III) Lewis acid centers able to specifically coordinate bases like NH3. Such [B(OSi)3] units are reactive toward ammonia, resulting in the formation of B-NH2 surface functionality inside the pores of B-SSZ-13 already under mild conditions, i.e., 35 mbar of NH3 at 373 K for 30 min and without crystallinity degradation. A minor fraction of Si-NH2 cannot be excluded owing to the presence of two IR doublets at 3500 and 3430 cm-1 and at 1600 and 1550 cm-1. Ab initio B3LYP/6-31+G(d,p) calculations on a cluster model, supported by a single-point MP2 on B3LYP/6-31+G(D,P) optimized structures, found the break by NH3 of a B-O-Si bond of the [B(OSi)3] unit with formation of [SiOH] and [H2N-B(OSi)2] species to be energetically favored. Comparison between experimental and computed frequency shifts shows them to be in semiquantitative agreement. The high stability of the B-NH2 surface functionality is probed by N K-edge NEXAFS spectra collected under UHV conditions. These findings can open a new route in the preparation of shape selective solid basic catalysts.     

Convenient synthesis of highly functionalized pyrazolines via mild, photoactivated 1,3-dipolar cycloaddition

A mild, photoactivated 1,3-dipolar cycloaddition procedure was successfully developed for the synthesis of polysubstituted pyrazolines. This procedure involved the in situ generation of the reactive nitrile imine dipoles using a hand-held UV lamp at 302 nm, followed by spontaneous cycloaddition with a broad range of 1,3-dipolarophiles with excellent solvent compatibility, functional group tolerance, regioselectivity, and yield.     

SIT parameters for 1:2 electrolytes and correlation with Pitzer coefficients

The empirical parameters of a two-parameter SIT equation were determined for some 1:2 electrolytes: chlorides, bromides, iodides, nitrates, perchlorates of alkali earth metals and sulfates of alkali metals. A wide range of ionic strengths (0 < I < or = 18 mol kg(-1)) and t = 25 degrees C was considered. Canonical correlation analysis showed quite significant correlations between SIT and Pitzer interaction coefficients for different classes of 1:2 type electrolytes.     

Covalent palladium-zinc bonds and their reactivity

Photolysis of ((F)PNP)Pd-Et in the presence of Et(2)Zn leads to the formation of ((F)PNP)Pd-Zn-Pd(PNP(F)), the first example of a compound with a covalent Pd-Zn bond.