Photonic Lab-on-a-Chip analytical systems for nuclear applications: optical performance and UV–Vis–IR material characterization after chemical exposure and gamma irradiation

Journal of Radioanalytical and Nuclear Chemistry - The use of microfluidics technology and the miniaturization of analytical techniques is of high interest for the chemical and nuclear industries....     

Panchromatic Light Harvesting and Stabilizing Charge-Separated States in Corrole–Phthalocyanine Conjugates through Coordinating a Subphthalocyanine

Owing to the electron-donating and -accepting nature of corroles (Corr) and phthalocyanines (Pc), respectively, we designed and developed two novel covalently linked Corr-Pc conjugates. The synthetic route allows the preparation of the target conjugates in satisfying yields. Comprehensive steady-state absorption, fluorescence, and electrochemical assays enabled insights into energy and electron-transfer processes upon photoexcitation. Coordinating a pyridine-appended subphthalocyanine (SubPc) to the Pc of the conjugate sets up the ways and means to realize the first example of an array composed by three different porphyrinoids, which drives a cascade of energy and charge-transfer processes. Importantly, the SubPc assists in stabilizing the charge-separated state, that is, one-electron oxidized Corr and the one electron-reduced Pc, upon photoexcitation by means of a reductive charge transfer to the SubPc. To the best of our knowledge, this is the first case of an intramolecular oxidation of a Corr within electron-donor–acceptor conjugates by means of just photoexcitation. Moreover, the combination of Corr, Pc, and SubPc guarantees panchromatic absorption across the visible range of the solar spectrum, with the SubPc covering the „green gap“ that usually affects porphyrinoids.     

Simple,fast, and low-contamination microwave-assisted digestion procedures for the determination of chemical elements in biological and environmental matrices by sector field ICP-MS

A simple and convenient method for the digestion of animal tissues, lichens, and plants for 33 metals measured by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) was described. Microwave-assisted acid digestions were performed at atmospheric pressure by means of a multi-samples rotor designed for processing a large number of samples at once in screw-capped disposable polystyrene liners. The digested samples were filled up to final volume directly in the polystyrene liners ready for elemental quantification. Seven certified reference materials, namely BCR 184 (bovine muscle), BCR 186 (pig kidney), DORM-2 (dogfish muscle), BCR 422 (cod muscle), BCR 62 (olive leaves), BCR 100 (beech leaves), and BCR 482 (lichen) were analysed to verify the accuracy of the method. The linearity range, limit of quantification, precision, and recovery by addition of non-certified elements were also assessed. All elements, with the exception of Hg in BCR 184 and As in BCR 186, were above the quantification limit and blank concentrations, and good agreement existed between found and target values in bovine muscle, pig kidney, and cod muscle. Significant deviations were observed for Al, Co, Cr, Mn, and Ni in dogfish muscle and for Ca, Cr, Fe, and Hg in lichens and plants. The proposed digestion procedure offers a low contamination risk, simplicity, speed, low cost, and applicability in routine analysis, and the SF-ICP-MS method allowed metals from a fraction of ng?g^?1 to hundreds of µg?g^?1 to be quantified in one analytical run.     

Infinitely many solutions for a fourth-order elastic beam equation

Existence results of infinitely many solutions for a fourth-order nonlinear boundary value problem are established. No symmetric condition on the nonlinear term is assumed. The main tool is an infinitely many critical points theorem.     

Basic sites on periodic mesoporous organosilicas investigated by XPS and in situ FTIR of adsorbed pyrrole

Oxygen sites in ethane-bridged and phenylene-bridged PMOs prepared using neutral templates in acidic conditions are characterized by means of XPS and FTIR spectroscopy of adsorbed pyrrole. Their electron donor ability is observed to be stronger than that of oxygens in pure amorphous silica of MCM-41 type and comparable to that reported for oxygen atoms in some alkali metal exchange zeolites. For pyrrole adsorbed on PMOs double interactions most probably occur, involving both silanols and electron donor sites at the surface. In the case of phenylene-bridged PMO preferential electron donor sites for interaction with pyrrole N-H group are aromatic rings rather than oxygens, as previously observed for adsorbed iodine.     

Uncertainty evaluation in the analysis of biological samples by sector field inductively coupled plasma mass spectrometry. Part B: measurements of As, Co, Cr, Mn, Mo, Ni, Sn and V in human serum

This protocol was developed to estimate the uncertainty of measurements in the sector field inductively coupled plasma mass spectrometry analysis of As, Co, Cr, Mn, Mo, Ni, Sn and V in human serum by utilizing in-house validation data. The approach is outlined in the Eurachem/Citac Guide and other relevant publications. The results generated were the followings: (i) coefficients of regression >0.9995 over two orders of magnitude of metal concentration; (ii) method quantification limits between 0.05 μg/L (Cr, Mn) and 0.49 μg/L (As); (iii) mean trueness checked against a certified reference material between 95.4% (As) and 107.7% (Ni); (iv) repeatability better than 10.2% over the range 0.1-2.0 μg/L; (v) reproducibility better than 12.0% over the range 0.1-2.0 μg/L; and (vi) expanded uncertainty budget comprised between 14.7% (Mn) and 27.9% (Cr) over the range 0.1-2.0 μg/L.     

Order conditions for General Linear Nyström methods

The purpose of this paper is to analyze the algebraic theory of order for the family of general linear Nyström (GLN) methods introduced in D’Ambrosio et al. (Numer. Algorithm 61(2), 331–349, 2012) with the aim to provide a general framework for the representation and analysis of numerical methods solving initial value problems based on second order ordinary differential equations (ODEs). Our investigation is carried out by suitably extending the theory of B-series for second order ODEs to the case of GLN methods, which leads to a general set of order conditions. This allows to recover the order conditions of numerical methods already known in the literature, but also to assess a general approach to study the order conditions of new methods, simply regarding them as GLN methods: the obtained results are indeed applied to both known and new methods for second order ODEs.     

Numerical integration of Hamiltonian problems by G-symplectic methods

It is the purpose of this paper to consider the employ of General Linear Methods (GLMs) as geometric numerical solvers for the treatment of Hamiltonian problems. Indeed, even if the numerical flow generated by a GLM cannot be symplectic, we exploit here a concept of near conservation for such methods which, properly combined with other desirable features (such as symmetry and boundedness of parasitic components), allows to achieve an accurate conservation of the Hamiltonian. In this paper we focus our attention on the connection between order of convergence and Hamiltonian deviation by multivalue methods. Moreover, we derive a semi-implicit GLM which results competitive to symplectic Runge-Kutta methods, which are notoriously implicit.     

The Influence of Alkali Metal Ions on the Stability and Reactivity of Chromium(III) Superoxide Moieties Spanned by Siloxide Ligands

In recent years, it has become clear that the presence of redox-inactive Lewis acidic metal ions can decisively influence the reactivity of metal–dioxygen moieties that are formed in the course of O₂ activation, in molecular complexes, and metalloenzymes. Superoxide species are often formed as the primary intermediates but they are mostly too unstable for a thorough investigation. We report here a series of chromium(III) superoxide complexes [L₂Cr]M₂O₂(THF)_y (L=⁻OSiPh₂OSiPh₂O⁻, M⁺=Li⁺, Na⁺, K⁺ and y=4, 5), which could be accessed, studied spectroscopically and partly crystallized at low temperatures. They only differ in the two incorporated Lewis acidic alkali metal counterions (M⁺) and it could thus be shown that the nature of M⁺ determines considerably its interaction with the superoxide ligand. This interaction, in turn, has a significant influence on the stability and reactivity of these complexes towards substrates with OH groups. Furthermore, we show that stability and reactivity are also highly solvent dependent (THF versus nitriles), as donor solvents coordinate to the alkali metal ions and thus also influence their interaction with the superoxide moiety. Altogether, these results provide a comprehensive and detailed picture concerning the correlation between spectroscopic properties, structure, and behavior of such superoxides, that may be exemplary for other systems.