Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents

The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.     

A solid-phase extraction procedure for the clean-up of thiram from aqueous solutions containing high concentrations of humic substances

A simple solid-phase extraction (SPE) procedure with an octadecyl bonded phase silica (C₁₈) was developed for clean-up of the fungicide thiram from aqueous solutions containing high concentrations of humic substances, for future studies of thiram adsorption onto solid humic substances or soils. Suspensions of humic acids and soil, in aqueous 0.01 M CaCl₂ solution, were prepared and used as samples. These extracts were spiked with thiram and immediately applied to a C₁₈-SPE cartridge. Thiram was eluted with chloroform and its concentration measured by spectrophotometry at 283 nm. Non-spiked aqueous extracts (blanks) and a control sample of thiram in 0.01 M CaCl₂ aqueous solution were also prepared and submitted to the same SPE procedure. The results show that humic substances are extensively retained by the C₁₈ cartridge but are not eluted with CHCl₃. Recoveries of 100-104% were obtained for thiram in the presence of humic substances. The SPE procedure described in this work is an efficient clean-up step to remove the interference of humic substances absorbance and to be coupled to any spectrophotometric or HPLC-UV method, usually used for thiram analysis in food extracts.     

Anion Binding by Fluorescent Ureido-Hexahomotrioxacalix[3]arene Receptors: An NMR,Absorption and Emission Spectroscopic Study

Fluorescent receptors (4a–4c) based on (thio)ureido-functionalized hexahomotrioxacalix[3]arenes were synthesised and obtained in the partial cone conformation in solution. Naphthyl or pyrenyl fluorogenic units were introduced at the lower rim of the calixarene skeleton via a butyl spacer. The binding of biologically and environmentally relevant anions was studied with NMR, UV–vis absorption, and fluorescence titrations. Fluorescence of the pyrenyl receptor 4c displays both monomer and excimer fluorescence. The thermodynamics of complexation was determined in acetonitrile and was entropy-driven. Computational studies were also performed to bring further insight into the binding process. The data showed that association constants increase with the anion basicity, and AcO⁻, BzO⁻ and F⁻ were the best bound anions for all receptors. Pyrenylurea 4c is a slightly better receptor than naphthylurea 4a, and both are more efficient than naphthyl thiourea 4b. In addition, ureas 4a and 4c were also tested as ditopic receptors in the recognition of alkylammonium salts.     

Adsorptive Capacity,Inhibitory Activity and Processing Techniques for a Copper-MOF Based on the 3,4-Dihydroxybenzoate Ligand

Due to the fast, emerging development of antibiotic-resistant bacteria, the need for novel, efficient routes to battle these pathogens is crucial; in this scenario, metal-organic frameworks (MOFs) are promising materials for combating them effectively. Herein, a novel Cu-MOF—namely 1—that displays the formula [Cu₃L₂(DMF)₂]_n (DMF = N,N-dimethylformamide) is described, synthesized by the combination of copper(II) and 3,4-dihydroxybenzoic acid (H₃L)—both having well-known antibacterial properties. The resulting three-dimensional structure motivated us to study the antibacterial activity, adsorptive capacity and processability of the MOF in the form of pellets and membranes as a proof-of-concept to evaluate its future application in devices.     

Electrochemical and associated techniques for the study of the inclusion complexes of thymol and β-cyclodextrin and its interaction with DNA

Journal of Solid State Electrochemistry - Thymol, a potent agent for microbial, fungal, and bacterial disease, has low aqueous solubility and it is genotoxic, i.e., is capable of damaging...     

Complete assignment of 1H and 13C NMR spectra of some alpha-arylthio and alpha-arylsulfonyl substituted N-methoxy-N-methyl propionamides

The complete assignments of the 1H and 13C NMR spectra of the some alpha-arylthio and alpha-arylsulfonyl substituted N-methoxy-N-methyl propionamides, bearing methoxy, methyl, chloro, and nitro as substituents at the phenyl ring are reported.     

PVC formulation study for the manufacturing of a skin smart structure based in optical fiber elements

The development of smart solutions based on optical fiber technology for any kind of structure such as buildings, aircrafts, or even for human body kinematics, is becoming more and more common. The ability to provide coverings for different structures that can enable monitoring functions beside the esthetic purpose of the covering is an important add‐value characteristic. Nevertheless, an open issue is to find an effective solution for the fabrication and application procedure, preferably that scales at a production level. This article explores the insertion of optical fibers into polymeric PVC foils based on the spread‐coating fabrication process. The success of this integration approach allows the use of photonic technology in different fields with minor application issues. The material choice for the substrate is a crucial step when choosing integrated solution. Three PVC paste formulations were explored in order to guarantee the optimal integration of optical fiber. A high‐viscosity and not monolithic paste formulation emerged as the best choice. This formulation provided the best adhesion, reducing in great scale the surface undulation and paste displacement that the optical fiber tends to do and, its 362% stretch capability is sufficient for special applications, as strain sensitive one. Copyright © 2010 John Wiley & Sons, Ltd.     

A high-nuclearity 3d/4f metal oxime cluster: an unusual Ni(8)Dy(8) "core-shell" complex from the use of 2-pyridinealdoxime

The initial employment of 2-pyridinealdoxime in 3d/4f chemistry has led to a Ni(II)(8)Dy(III)(8) cluster with an unprecedented metal topology; the compound has an unusual structure, is the highest-nuclearity metal oxime cluster to date, and exhibits slow magnetization relaxation.     

Exact travelling wave solutions of the generalized Bretherton equation

We search for exact travelling wave solutions of the generalized Bretherton equation for integer, greater than one, values of the exponent m of the nonlinear term by two methods: the truncated Painlevé expansion method and an algebraic method. We find periodic solutions for m=2 and m=5, to add to those already known for m=3; in all three cases these solutions exist for finite intervals of the wave velocity. We also find a “kink” shaped solitary wave for m=5 and a family of elementary unbounded solutions for arbitrary m.