Nanostructure changes in protic ionic liquids (PILs) through adding solutes and mixing PILs

The effect of adding primary n-alcohols with aliphatic chains and hexane on the nanostructure of a series of 14 protic ionic liquids (PILs) was explored using small and wide angle X-ray scattering (SAXS and WAXS). PILs were investigated with primary, secondary and tertiary ammonium cations containing different alkyl chain lengths, with and without hydroxyl substitution of the alkyl chain. Formate or nitrate anions were paired with these cations. The PILs which had no identified intermediate range order between 5-16 ? had very low solubilities of the solutes. The other PILs, which had non-polar domains present, were mostly miscible with the primary alcohols of ethanol, propanol and butanol. When the alkyl chain length of the alcohols was similar to the PILs then the alcohols co-partitioned with the alkylammonium cation components of the PILs and caused either an increase or decrease in the size of the non-polar domains, depending on whether the alcohol chain length was longer or shorter than that of the cation in the PIL respectively. For ethylammonium nitrate (EAN) with propanol or butanol and propylammonium nitrate (PAN) with butanol, the difference between the alcohol chain length and the alkyl chain length was too great to lead to a modified nanostructure, and instead large aggregates were present. The solubility of hexane in the alkylammonium nitrate PILs had a very strong correlation to the alkyl chain length. The addition of hexane had very little effect on the non-polar domain sizes, which was attributed to it not being orientated in alignment with the alkylammonium cations in the non-polar domains. Lastly, seven binary PIL-PIL solution series were investigated using SAXS and WAXS to show how the nanostructure of these systems can be fine tuned to control the size and structure of the non-polar domains.     

PLUXter: rapid discovery of metal-organic framework structures using PCA and HCA of high throughput synchrotron powder diffraction data

This paper reports on a systematic method--called PLUXter--developed for screening and data mining of large numbers of potential metal-organic framework compounds that have been synthesized then subsequently analyzed with high throughput synchrotron radiation X-ray powder diffraction. The first part of the method utilizes principal components analysis (PCA), which allows materials to be ranked in order of crystallinity so that undesirable amorphous materials may be identified and eliminated. The second part allows structural grouping within and between samples to be observed using hierarchical cluster analysis (HCA). Classification using a single linkage distance produced unsatisfactory clusters however the dendrogram's structural relationships were used to establish and guide the boundaries of groups. The resultant grouping identities allowed further structure-property studies to be undertaken on representative structures from the clusters, significantly reducing time and the use of resources.     

Flow injection on-line minicolumn preconcentration and determination of trace copper ions using an alumina/titanium oxide grafted silica matrix and FAAS

We describe the analytical performance of a hybrid material composed of SiO₂, Al₂O₃ and TiO₂. It was prepared by a sol–gel process and can act as an adsorbent in the continuous-flow enrichment of copper. A minicolumn was packed with the material, copper ions are adsorbed at pH 9.13, then eluted with 1.0?mol?L^?1 nitric acid, and determined by FAAS. The material was characterized by infrared spectroscopy, scanning electron and energy dispersive spectroscopy, energy dispersive X-ray fluorescence analysis, powder X-ray diffraction, and specific surface area analysis. No significant interference was observed for most ions in up to copper/interferent ratios of 1:100 and of 1:500 in case of Ca(II), Ba(II), and Mg(II). The breakthrough capacity is 1.4?mg?g^?1 under dynamic conditions. The limits of detection and of quantification are 0.50 and 1.4?μg?L^?1, respectively, and the calibration plot is linear in the range from 5.0 to 245.0?μg?L^?1 (r?=?0.999). The relative standard deviation is 3.20 (for n?=?7 and at a Cu(II) concentration of 10?μg?L^?1). The method was applied to the determination of trace copper ions in water, vegetable and alcohol fuel samples.

Real time quantitative amplification detection on a microarray: towards high multiplex quantitative PCR

Quantitative real-time polymerase chain reaction (qrtPCR) is widely used as a research and diagnostic tool. Notwithstanding its many powerful features, the method is limited in the degree of multiplexing to about 6 due to spectral overlap of the available fluorophores. A new method is presented that allows quantitative amplification detection at higher multiplexing by the integration of amplification in solution and monitoring via hybridization to a microarray in real-time. This method does not require any manipulation of the PCR product and runs in a single closed chamber. Employing labeled primers, one of the main challenges is to measure surface signals against a high fluorescence background from solution. A compact, confocal scanner is employed, based on miniaturized optics from DVD technology and combined with a flat thermocycler for simultaneous scanning and heating. The feasibility of this method is demonstrated in singleplex with an analytical sensitivity comparable to routine qrtPCR.     

Influence of second coordination sphere hydroxyl groups on the reactivity of copper(I) complexes

We report the enhanced reactivity of hydroxyl substituted CuN(3)(+) derivatives, where N(3) = tris(picolinyl)methane (tripic) and related derivatives, upon deprotonation of the O-H functionality. The work capitalizes on new methodology for incorporating hydroxyl groups into the second coordination sphere of copper centers. The key synthetic methodology relies on Pd-catalyzed coupling reactions of dilithiated 6-methyl-2-pyridone with bromopyridyl derivatives. These building blocks allow the preparation of tridentate N(3) ligands with OH and OMe substituents flanking the fourth coordination site of a tetrahedral complex. Coupling of these tridendate ligands gives the corresponding hydroxy- and methoxy-functionalized bistripodal ligands. [Cu[bis(2-methylpyrid-6-yl)(2-hydroxypyrid-6-yl)methane](NCMe)](+) ([Cu(2H)(NCMe)](+)) oxidizes readily in air to afford the mixed valence Cu(1.5) dimer ([Cu(2)(2)(2)](+)). Formation of [Cu(2)(2)(2)](+) is accelerated in the presence of base and can be reversed with a combination of decamethylferrocene and acid. The reactivity of [Cu(2H)(NCMe)](+) with dioxygen requires deprotonation of the hydroxyl substituent: neither [Cu(tripic)(NCMe)](+) nor the methoxy-derivatives displayed comparable reactivity. A related mixed valence dimer formed upon oxidation of the dicopper(I) complex of a tetrahydroxy bis(tridentate) ligand, [Cu(2)(6H(4))(NCMe)(2)](2+). The dicopper(I) complex of the analogous tetramethoxy N(6)-ligand, [Cu(2)(5)(NCMe)(2)](2+), instead reversibly binds O(2). Deprotonation of [Cu(2H)(CO)](+) and [Cu(2H)(NCMe)](+) afforded the neutral derivatives Cu(2)(CO) and Cu(2)(2)(2), respectively. The dicopper(I) derivative Cu(2)(2)(2) can be reoxidized, reprotonated, and carbonylated. The silver(I) complex, [Ag(2H)(NCMe)]BF(4), forms an analogous neutral dimer (Ag(2)(2)(2)) upon deprotonation of the hydroxyl group. The structures of ligand 2H, [Cu(2)(5)(NCMe)(2)](+), [Cu(2)(2)(2)](+), [Cu(2)(6H(2))](+), [Ag(2H)(NCMe)]BF(4), and Ag(2)(2)(2) were confirmed by single crystal X-ray diffraction.     

Statistical anisotropy from vector curvaton in D-brane inflation

We investigate the possibility of embedding the vector curvaton paradigm in D-brane models of inflation in type IIB string theory in a simple toy model. The vector curvaton is identified with the U(1)$U(1)$ gauge field that lives on the world volume of a D3-brane, which may be stationary or undergoing general motion in the internal space. The dilaton is considered as a spectator field which modulates the evolution of the vector field. In this set-up, the vector curvaton is able to generate measurable statistical anisotropy in the spectrum and bispectrum of the curvature perturbation assuming that the dilaton evolves as e^−?∝a²$e^{-?}\propto a^2$ where a(t)$a(t)$ is the scale factor. Our work constitutes a first step towards exploring how such distinctive features may arise from the presence of several light fields that naturally appear in string theory models of cosmology.     

Radiation-induced cathodoluminescent signatures in calcite

At ambient temperatures, a permanent change due to neutron irradiation has been identified in the luminescent properties of the common mineral calcite. Calcite is one of many ubiquitous minerals that are known to exhibit luminescence under electron bombardment, a process known as cathodoluminescence (CL). The UV–Visible spectra of individual calcite grains were measured with CL spectroscopy before and after neutron irradiation. Exposure to neutrons causes additional crystal lattice defects (beyond those naturally-occurring) that leave a permanent, readily-measurable CL signature in the 515 nm region of the spectrum. Dose response results following irradiation have been measured and a spectroscopic signature is described that increases proportionately to neutron dose. The CL measurements are complicated by a dependence on the orientation relative to direction of excitation. When taken into account, the total dose to the crystal can be estimated, and possibly even the direction of the neutron source can be determined. This signature could potentially be developed into a nuclear forensics tool to help identify locations where special nuclear materials have been stored.     

Ultrasound promoted Staudinger-Aza-Wittig tandem reaction on a monoazido-O-peracetylated-β-cyclodextrin: effect of ultrasound power

A preliminary study on an ultrasound promoted Staudinger-Aza-Wittig tandem reaction (S.A.W.) is reported. It was demonstrated that reaction is strongly favored under ultrasound (US) irradiation in terms of either reaction time or yield.