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Experimental and theoretical calculations confirm, for the first time, the existence of two different kinds of electronic structures of a surface complex formed by a particular molecule bonded to charged metal electrodes, clusters, or nanoparticles. Surface-enhanced Raman scattering (SERS) of cyanine adsorbed on a silver electrode shows three regions, which are selected by the electrode potential and characterized by the differentiated response of the vibrational wavenumbers of the ?(CN) stretching band to the electrode potential. The combination between the experimental SERS and DFT calculations has allowed for relating the three regions to chemisorbed (C-hybrid) and physisorbed (P-hybrid) surface complexes, where cyanide is bonded through the carbon on top of a single silver atom of the surface and to bidentate species, respectively. The electrode potential selects one or another type of electronic structure of the surface complex, which are of different natures and with a differentiated response to the applied potential. The electric potential tunes smoothly the wavenumbers, bond energies, and injected charges of the P-hybrid at more negative potentials than that of the zero charge of the electrode, but the very strong C-hybrid prevents significant changes of these properties at positive excesses of charge. The existence of the dual electronic structure of metal-molecule interfaces might require reinterpreting experiments that are usually discussed by resorting to, for instance, the reorientation of the adsorbate, the formation of complexes with different stoichiometries, the existence of nonequivalent local sites on the surface, or to instrumental artifacts.

[EN] The characteristics and electromechanical properties of conductive polymers together to their biocompatibility have boosted their application as a suitable tool in regenerative medicine and tissue engineering. However, conducting polymers as drug release materials are far from being ideal. A possibility to overcome this drawback is to combine conducting polymers with on-command delivery particles with inherent high-loading capacity. In this scenario, we report here the preparation of conduction polymers containing gated mesoporous silica nanoparticles (MSN) loaded with a cargo that is delivered on command by electro-chemical stimuli increasing the potential use of conducting polymers as controlled delivery systems. MSNs are loaded with Rhodamine B (Rh B), anchored to the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)], functionalized with a bipyridinium derivative and pores are capped with heparin (P3) by electrostatic interactions. P3 releases the entrapped cargo after the application of ¿640 mV voltage versus the saturated calomel electrode (SCE). Pore opening in the nanoparticles and dye delivery is ascribed to both (i) the reduction of the grafted bipyridinium derivative and (ii) the polarization of the conducting polymer electrode to negative potentials that induce detachment of positively charged heparin from the surface of the nanoparticles. Biocompatibility and cargo release studies were carried out in HeLa cells cultures., Alba Garcia-Fernandez, Beatriz Lozano-Torres contributed equally to this work. A. Garcia-Fernandez and B. Lozano-Torres are grateful to the "Ministerio de Economia y Competitividad" of the Spanish Government for her PhD fellowships. J. F. Blandez thanks the "Universitat Politecnica de Valencia" for his postdoctoral fellowship (PAID-10-17). The authors thank to the Spanish Government (Projects RTI2018-100910-B-C41 and RTI2018-101599-B-C22 (MCUI/AEI/FEDER, EU)) and the Generalitat Valencia (Project PROMETEO2018-024) for support.

This work studies the photochemical and thermal decompositions of azidoacetonitrile (N3 CH2 CN) from both the experimental and theoretical points of view. The data of the photochemical experiments are taken from the literature, while the thermal decomposition have been carried out by us. In addition, we have performed ab initio calculations of the multiconfigurational type [complete active space self-consistent field (CASSCF) and the multistate multireference perturbation theory (MS-CASPT2)]. It is found that the first step of both type of decompositions is N2 elimination and formation of closed shell singlet nitrene. Afterwards, the nitrene tends to rapidly rearrange into formimidoyl cyanide (HNCHCN). As both reactions progress, the imine isomerizes into formimidoyl isocyanide (HNCHNC). The photoisomerization of the imine takes places thorough a conical intersection, while the same reaction on the ground electronic state occurs via a conventional transition state. The last step of the global reaction is decomposition of the imines into HCN and CNH. In photochemical conditions, the conjunction of the imines and its dissociation products (HCN and CNH) yields adenine.

The photodissociation channels of nitrosobenzene (PhNO) induced by a 255 nm photolytic wavelength have been studied using the complete active space self-consistent method and the multistate second-order multiconfigurational perturbation theory. It is found that there exists a triplet route for photodissociation of the molecule. The reaction mechanism consists of a complex cascade of nonadiabatic electronic transitions involving triple and double conical intersections as well as intersystem crossing. Several of the relevant states (S2, S4, and S5 states) correspond to double excitations. It is worth noting that the last step of the photodissociation implies an internal conversion process. The experimentally observed velocity pattern of the NO fragment is a signature of such a conical intersection.

The reaction mechanisms for the carbon-based acid catalytic conversion of 2-butanol into dehydration and dehydrogenation products (alkene derivatives and ketone) have been theoretically studied by assuming that the acid site is a dihydrogen phosphate group bonded to one of the carbon atoms of the central ring of anthracene. The structural model of the active site of the surface of the catalyst reproduces properly the experimental results. Kinetic and thermodynamic magnitudes have been obtained by using standard expressions of Eyring’s transition-state theory and statistical thermodynamics. Interpretation of the calculations (molecular charges, geometries, and energies) demonstrates that the dehydration reaction process is an E2 mechanism (one-step reaction) with strong character of E1 mechanism (two-step reaction). The study of the mechanism has been carried out by applying density functional theory with the metaexchange–correlation functional M06-2X. The reactants and products connected by the respective...

Aryl azides photochemistry is strongly dependent on the substituent relative position, as has been studied by time resolved resonant Raman (TR3) spectroscopy for 4-methoxyphenyl azide and its isomer 3-methoxyphenyl azide. When irradiated at 266 nm, the former results in 4,4’-dimethoxyazobenzene whereas the latter forms 1,2-didehydroazepine. It is proposed that the key step of the reactions is the formation of a nitrene derivative. Recently, it has been proposed by us that nitrenes might have a relevant role in the Surface-Enhanced Raman Scattering (SERS) of p-aminothiophenol, however, the molecular mechanism is not well known in neither of these cases. Therefore, we studied the photodecomposition of 4-methoxyphenyl azide using multiconfigurational self-consistent field methods (MC-SCF) with the CAS-SCF and MS-CASPT2 approximations and calculated the resonant Raman spectra of the relevant species using a multi-state version of Albrecht’s vibronic theory. The results propose that the reaction follows a two steps sequence after irradiation at 266 nm: an intersystem crossing 21A’/23A’’ which decays through a 21A’/21A’’ conical intersection producing molecular nitrogen and triplet 4-methoxyphenyl nitrene in its ground state. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Metal acetate complexes are highly interesting in designing and synthesizing metal–organic frameworks, which have potential applications in gas storage, molecular sieves, ion exchange, and catalysis. Cadmium is well recognized as an industrial pollutant and a food contaminant that severely affects human health. For these reasons, the detection and analysis of Cd are of great interest. A major challenge in studying cadmium compounds' structure is that Cd2+ can have a wide range of coordination numbers and diverse geometries. (MA)LDI is extremely useful for detecting Cd(OAc)2·2H2O and investigating Cd's complex and flexible nature. We applied LDI to detect and characterize the Cd-related clusters and MALDI approach to investigate the Cd(OAc)2x2H2O reactivity and detectability with the five different organic matrices. The results revealed that in the solid-state Cd(OAc)2x2H2O tend to form coordination polymers, and in the presence of coordinating ligands (matrix molecules) form smaller complexes. In addition, the correlation between Cd-related LOD and matrix features was observed and discussed, indicating that the LODs of this analyte strongly depend on the optical absorption of the matrix-analyte adduct.

In the present work, we demonstrate that the formation of triplet and singlet phenylnitrene, when arises from the photodissociation of phenyl azide, fulfills El-Sayed's rules or the electronic angular momentum conservation law. It is shown that the singlet-triplet inversion of phenylnitrene via the vibronic coupling mechanism is not an effective process. In contrast, it is found that there exist two independent dissociation channels that yield alternatively singlet and triplet phenylnitrene. Therefore, a proposed mechanism that violates the angular momentum low is avoided. The clue of the photoreaction lies in the conjunction (energetic and spatial) of two crossing points in a very narrow region of the multidimensional space: (i) an intersystem crossing (ISC1) and (ii) a conical intersection (CI1). The geometrical separation between these two crossing geometries is only 0.016 A measured in Cartesian coordinates, and the respective energy difference is 2 kcal/mol. This work has been performed by application of the complete active space self-consistent field and multiconfigurational second-order perturbation method.

A Surface-Enhanced Raman Scattering (SERS) spectrum of 4-cyanopyridine (4CNPy) was recorded on silver plasmonic nanoparticles and analyzed by using Density Functional Theory (DFT) calculations. Two simple molecular models of the metal&ndash, 4CNPy surface complex with a single silver cation or with a neutral dimer (Ag+&ndash, 4CNPy, Ag2&ndash, 4CNPy), linked through the two possible interacting sites of 4CNPy (aromatic nitrogen, N, and nitrile group, CN), were considered. The calculated vibrational wavenumbers and intensities of the adsorbate and the isolated species are compared with the experimental Raman and SERS results. The analysis of the DFT predictions and the experimental data indicates that 4CNPy adsorbs preferentially on neutral/charged active sites of the silver nanoparticles through the nitrogen atom of the aromatic ring with a perpendicular orientation.

Vibrational wavenumbers of pyridine adsorbed on a silver electrode have been correlated to the calculated ones from different theoretical approaches based on DFT methods. The vibrational tuning caused by the electrode potential has been simulated by means of pyridine-silver clusters with different densities of charge or, alternatively, under applied external electric fields. Both methodologies predict correctly a qualitative red-shift of the vibrational wavenumbers at negative potentials. As a result, harmonic frequency calculations performed at the B3LYP/LanL2DZ level of theory by using a linear [Ag n Py] q complex model with different densities of charge (q eff = q/n) have exhibited the best agreement with the experimental observations although the tuning amplitudes are overestimated. Electric fields calculations are unable to account for subtle details observed in the spectra related to the differentiated chemical nature of the metal-molecule bond at positive or negative potentials with respect to the potential of zero charge of the electrode.

9 pags. 6 figs., In this work, the adsorption of a type of cruciform system integrated by an anthracene central part and two side chains with a pyridine-vinyl structure (DPAC) was studied on plasmonic nanoparticles of silver and gold. The adsorption was investigated by surface-enhanced Raman scattering, which reveals very valuable information about both the interaction mechanism and the molecular orientation. The highest Raman enhancement was measured on Ag nanostars due to the combination of gaps and tips in these nanostructures. The changes observed in the surface-enhanced Raman scattering spectra indicate that the adsorption of DPAC on the metal is bifunctional in the case of Ag and Au nanoparticles. Considering that the Raman signals enhancement is several orders of magnitude higher in gaps in relation to regions out of these areas, it is estimated that the enhancement ability of DPAC in Ag nanostars is so high that it allows the detection of a concentration close to pM., This work was supported by MINECO under FIS2014‐52212‐R and CTQ2015‐65816‐R projects. P. Leyton acknowledges to the project FONDECYT 1140810 as wellas the FONDEQUIP EQM130170 project from CONICYT.E. Imbarack acknowledges the financial supports fromBeca Doctorado Nacional N°21140360 CONICYT.

Photochemistry of 3- and 4-methoxyphenyl azide at 266 nm has been studied by means of the complete active space self-consistent field (CASSCF) and multi-configurational second-order perturbation (MS-CASPT2) methods. Minima and interstate crossing points have been optimized using the CASSCF method. The calculations predict that the key step of the photolysis of both azides is a non-radiative process. However, an important difference is found when we compare the reactivity of both isomers of azide, deactivation of 3-methoxyphenyl azide (1) can occur via two reaction channels (internal conversion or intersystem crossing), which lead to formation of the dimer of 2H-azepine derivative (2a) and 3,3'-dimethoxyazobenzene (2b). In contrast, deactivation of 4-methoxyphenyl azide (3) takes place via a singlet to triplet intersystem crossing, which leads to formation of 4,4'-dimethoxyazobenzene (4). After initial deactivation, both isomers follow a cascade of surface crossings until they reach the final nitrenes, respectively. The reference active space for the two azides is 14 electrons in 13 orbitals and comprises the six π-type orbitals of the aromatic ring plus four σ-(N-N2) and five π-type orbitals of the -N3 moiety.

9 pags., 6 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 3.0, The electron donor-acceptor properties of 9,10-bis((E)-2-(pyridin-4-yl)vinyl) anthracene (BP4VA) are studied by means of surface-enhanced Raman scattering (SERS) spectroscopy and vibronic theory of resonance Raman spectroscopy. The SERS spectra recorded in an electrochemical cell with a silver working electrode have been interpreted on the basis of resonance Raman vibronic theory assisted by DFT calculations. It is demonstrated that the adsorbate-metal interaction occurs through the nitrogen atom of the pyridyl moiety. Concerning the electron donor-acceptor properties of the adsorbate, it is shown that the charge transfer excited states of BP4VA are not optically active, in contrast, an internal transition to an excited state of BP4VA, which is localized in the anthracene framework, is strongly allowed. The charge transfer states will be populated by an ultrafast non-radiative process, that is, internal conversion. Thus, irradiation of BP4VA interacting with an appropriate surface creates an effective charge separation., This research has been supported by the Spanish Ministerio de Economıa y Competitividad (Projects: FIS2017-84318-R and CTQ2015-65816-R). EI and PL acknowledges the financial supports from the projects FONDECYT 1140810 and Beca Doctorado Nacional No. 21140360 from CONICYT. The authors thank Rafael Larrosa and Dar´ıo Guerrero for the technical support in running the calculations and the SCBI (Supercomputer and Bioinformatics) center of the University of Malaga for computer resources.

Surface-enhanced Raman scattering of thiobenzoic acid and thiobenzamide have been recorded on three different silver colloids in order to find the chemical species responsible for the spectra and to detect differences in the adsorption with respect to their oxygen counterparts, benzoic acid and benzamide, respectively. Very significant and unexpected shifts of opposite sign between the Raman and SERS wavenumbers have been detected. By comparing the experimental and DFT calculated wavenumbers, it can be concluded that the acid is bonded to the metal as thiobenzoate through the sulfur atom with unidentate coordination. SERS spectra of thiobenzamide can be explained by assuming that it is adsorbed as azanion, like in the case of benzamide, linking to the metal through the sulfur and nitrogen atoms of the ionized thiocarboxamide group. In order to support these conclusions, B3LYP/LanL2DZ force field calculations for different complexes of silver cations with the thiobenzoate anion, the neutral thiobenzamide as well as its azanion have been carried out. Additionally, the 8a;?ring mode is the most enhanced band in the SERS of both adsorbates pointing to the participation of a metal-to-molecule resonant charge transfer mechanism.

This study demonstrates the feasibility of using a voltammetric electronic tongue to monitor effluent dissolved orthophosphate concentration in a struvite precipitation reactor. The electrochemical response of the electronic tongue to the presence of orthophosphate in samples collected from the effluent of the precipitation reactor is used to predict orthophosphate concentration via a statistical model based on Partial Least Squares (PLS) Regression. PLS predictions were suitable for this monitoring application in which precipitation efficiencies higher than 80% (i.e., effluent dissolved orthophosphate concentrations lower than 40 mg P-PO43- L-1) could be considered as indicator of good process performance. The electronic tongue consisted of a set of metallic (noble and non-noble) electrodes housed inside a stainless steel cylinder which was used as the body of the electronic tongue system. Fouling problems were prevented via a simple mechanical polishing of the electrodes. The measurement of each sample with the electronic tongue was done in less than 3 s. Conductivity of the samples only affected the electronic tongue marginally, being the main electrochemical response due to the orthophosphate concentration in the samples. Copper, silver, iridium and rhodium were the electrodes that exhibited noticeable response correlated with the dissolved orthophosphate concentration variations, while gold, platinum and especially cobalt and nickel were the less useful electrodes for this application. (C) 2016 Elsevier B.V. All rights reserved., Financial support from the Spanish Government (Project MAT2015-64139-C4-1), the Generalitat Valencia (Project PROME-TEOII/2014/047) is gratefully acknowledged. This research work was also possible thanks to FCC Aqualia participation in IN-NPRONTA 2011 IISIS IPT-20111023 project (partially funded by The Centre for Industrial Technological Development (CDTI) and supported by the Spanish Ministry of Economy and Competitiveness).

DFT calculations predict that plasmon-like excitations in small metal clusters are able to selectively modify the relative intensities of specific SERS bands of adsorbed molecules. These electronic resonances provide new kinds of SERS selection rules which can explain the huge enhancement of mode 9a of pyridine in the spectra recorded at negative electrode potentials.

[EN] We report herein the design a hybrid material for the recognition of Ochratoxin A (OTA) by using an aptamer gated-material able to release electroactive species, which can be measured using differential pulse voltammetry. Mesoporous silica nanoparticles loaded with Methylene Blue and capped with an OTA aptamer were prepared and characterised. A highly selective and sensitive response due to the displacement of the capping aptamer in the presence of OTA and subsequent MB release was found in aqueous media. Finally, the possible use of the gated material for the detection of OTA in a real matrix was also explored., This work was supported by the Spanish Government [project MAT2015-64139-C4-1-R]; the Generalitat Valenciana [project PROMETEOII/2014/047].

[EN] The use of a voltammetric electronic tongue for the quantitative analysis of quality parameters in spring water is proposed here. The electronic voltammetric tongue consisted of a set of four noble electrodes (iridium, rhodium, platinum, and gold) housed inside a stainless steel cylinder. These noble metals have a high durability and are not demanding for maintenance, features required for the development of future automated equipment. A pulse voltammetry study was conducted in 83 spring water samples to determine concentrations of nitrate (range: 6.9-115 mg/L), sulfate (32-472 mg/L), fluoride (0.08-0.26 mg/L), chloride (17-190 mg/L), and sodium (11-94 mg/L) as well as pH (7.3-7.8). These parameters were also determined by routine analytical methods in spring water samples. A partial least squares (PLS) analysis was run to obtain a model to predict these parameter. Orthogonal signal correction (OSC) was applied in the preprocessing step. Calibration (67%) and validation (33%) sets were selected randomly. The electronic tongue showed good predictive power to determine the concentrations of nitrate, sulfate, chloride, and sodium as well as pH and displayed a lower R-2 and slope in the validation set for fluoride. Nitrate and fluoride concentrations were estimated with errors lower than 15%, whereas chloride, sulfate, and sodium concentrations as well as pH were estimated with errors below 10%., The authors gratefully acknowledge the Ministerio de Economia y Competitividad and FEDER, providing funds amounting to (sic)664.525,75 for the project "Desarrollo de sistemas basados en lenguas electronicas para el control y monitorizacion del ciclo integral del agua" INNPACTO. IPT-2012-0069-310000. Moreover, the authors gratefully acknowledge the Ministerio de Economia y Competitividad and FEDER (projects MAT2015-64139-C4-1-R (MINECO/FEDER), MAT2015-64139-C4-3-R (MINECO/FEDER)), the Generalitat Valenciana (project PROMETEOII/2014/047), and CIBER-BBN (NANOPROBE project) for their financial support.

An electronic nose system (E-nose) with metal oxide semiconductor sensors (MOS) has been designed to discriminate and quantify different chemical warfare agents (CWA) mimics. The E-nose consists of an array of commercial MOS for different gases, two sensors for temperature sensing, a sample handling system, a data acquisition system and a laptop with the data acquisition system control. With this device, discrimination studies have been carried out to detect specific CWA simulants (diethyl chlorophosphonate (DCP), diethyl cyanophosphate (DCNP), diisipropyl fluoride (DFP)), their derivatives (diethyl 1-phenylethyl phosphonate (OP-1), diethyl (2- cyanoethyl)phosphonate (OP-2), dimethyl methyl phosphonate (OP-3) and diethyl (2-oxopropyl)phosphonate (OP-4)) and some potential interfering substances (sulfuric acid, ammonia, ethanol and acetone). Principal components analyses (PCA) show that it is possible to discriminate the studied organophosphorous CWA mimics (DCP, DCNP and DFP) from the other studied derivatives and potential interfering agents. In addition, DCNP quantification studies have been done by using partial least squares (PLS) and a mathematical model has been obtained to predict DCNP concentrations in air. In this model, the coefficient of determination (R2) is 0.9567, the root mean square error of prediction (RMSEP) is 30 and the limit of detection (LOD) is 5 ppm so the model is considered valid. These results suggest that this E-nose system is capable to discriminate and quantify CWA mimics and it would be a feasible system to be used in a real scenario., Financial support from the Spanish Government (MAT2009-14564-C04-02 and MAT2009-14564-C04-01), the Grant BES-2010-034031 from the FPI-MINECO Subprogram and the Spanish Government and European FEDER funds (MAT2012-38429-C04-04) are gratefully acknowledged.

A humid electronic nose device based on pulse voltammetry has been applied to detect nerve agentsimulants in gas phase. The humid electronic nose consists in a polypropylene piece which containsan array of eight metallic electrodes (i.e., Ir, Rh, Pt, Au Ag, Co, Cu and Ni) divided into two sets of fourworking electrodes housed inside a homemade steel cylinder, and a salt bridge connection to a referenceelectrode. The electrochemical system is fitted to a nylon membrane damped with a background solutionof sodium tetraborate 0.01 M by a second polypropylene piece. The PCA analysis demonstrated that thesystem is able to discern principal organophosphorous nerve agent mimics (DCP, DCNP and DFP) fromorganophosphorous derivatives and some other potential interferents. Besides, the PLS quantificationanalysis showed sound accuracy in the concentration prediction for DCNP in air, good linearity and alimit of detection (LOD) of some a few ppm., Financial support from the Spanish Government (project MAT2012-38429-004) and the Generalitat Valenciana (project PROMETEO/2009/016) is gratefully acknowledged. L.P. is grateful to the Universitat Politecnica de Valencia for her grant.

Concerns about the bioaccumulation and toxicity of gold nanoparticles inside humans have recently risen. HT-29 and HepG2 cell lines and Wistar rats were exposed to 10, 30 or 60 nm gold nanoparticles to determine their tissue distribution, subcellular location and deleterious effects. Cell viability, ROS production and DNA damage were evaluated in vitro. Lipid peroxidation and protein carbonylation were determined in liver. ICP-MS measurements showed the presence of gold in intestine, kidney, liver, spleen, feces and urine. Subcellular locations of gold nanoparticles were observed in colon cells and liver samples by transmission electron microscopy. Inflammatory markers in liver and biochemical parameters in plasma were measured to assess the inflammatory status and presence of tissue damage. The size of the nanoparticles determined differences in the biodistribution and the excretion route. The smallest nanoparticles showed more deleterious effects, confirmed by their location inside the cell nucleus and the higher DNA damage.

An electronic tongue has been developed to monitor the presence of ammonium nitrate in water. It is based on pulse voltammetry and consists of an array of eight working electrodes (Au, Pt, Rh, Ir, Cu, Co, Ag and Ni) encapsulated in a stainless steel cylinder. In a first step the electrochemical response of the different electrodes was studied in the presence of ammonium nitrate in water in order to further design the wave form used in the voltammetric tongue. The response of the electronic tongue was then tested in the presence of a set of 15 common inorganic salts, i.e., NH4NO3, MgSO4, NH4Cl, NaCl, Na2CO3, (NH4)2SO4, MgCl2, Na3PO4, K2SO4, K2CO3, CaCl2, NaH2PO4, KCl, NaNO3, K2HPO4. A PCA plot showed a fairly good discrimination between ammonium nitrate and the remaining salts studied. In addition Fuzzy Art map analyses determined that the best classification was obtained using the Pt, Cu and Ni electrodes. Moreover, PLS regression allowed the creation of a model to correlate the voltammetric response of the electrodes with concentrations of ammonium nitrate in the presence of potential interferents such as ammonium chloride and sodium nitrate.

[EN] Mesoporous silica microparticles capped with TTF moieties and containing a ruthenium dye in the pores were used for the turn-on optical detection of the nitroaromatic explosives Tetryl and TNT via a selective pore uncapping and release of the entrapped dye., Financial support from the Spanish Government (project MAT2012-38429-C04-01) and the Generalitat Valencia (project PROMETEO/2009/016) is gratefully acknowledged. Y.S. is grateful to the Spanish Ministry of Science and Innovation for her grant. J.O.J. gratefully acknowledge financial support provided by the Villum Foundation and the Danish Natural Science Research Council (#11-106744).

A new electronic tongue to monitor the presence of glyphosate (a non-selective systemic herbicide) has been developed. It is based on pulse voltammetry and consists in an array of three working electrodes (Pt, Co and Cu) encapsulated on a methacrylate cylinder. The electrochemical response of the sensing array was characteristic of the presence of glyphosate in buffered water (phosphate buffer 0.1 mol·dm-3, pH 6.7). Rotating disc electrode (RDE) studies were carried out with Pt, Co and Cu electrodes in water at room temperature and at pH 6.7 using 0.1 mol·dm-3 of phosphate as a buffer. In the presence of glyphosate, the corrosion current of the Cu and Co electrodes increased significantly, probably due to the formation of Cu2+ or Co2+ complexes. The pulse array waveform for the voltammetric tongue was designed by taking into account some of the redox processes observed in the electrochemical studies. The PCA statistical analysis required four dimensions to explain 95% of variance. Moreover, a two-dimensional representation of the two principal components differentiated the water mixtures containing glyphosate. Furthermore, the PLS statistical analyses allowed the creation of a model to correlate the electrochemical response of the electrodes with glyphosate concentrations, even in the presence of potential interferents such as humic acids and Ca2+. The system offers a PLS prediction model for glyphosate detection with values of 098, -2.3 ¿ 10-5 and 0.94 for the slope, the intercept and the regression coefficient, respectively, which is in agreement with the good fit between the predicted and measured concentrations. The results suggest the feasibility of this system to help develop electronic tongues for glyphosate detection. © 2012 by the authors; licensee MDPI, Basel, Switzerland., Financial support from the Spanish Government (Project MAT2009-14564-C04-01 and PCI-Mediterraneo A/024590/09/A/ 03044/10), the Generalitat Valenciana (Project PROMETEO/2009/016), the UPV (project PAID-05-10) and its Centre de Cooperacio al Desenvolupament (Programa ADSIDEO-COOPERACIO 2010) is gratefully acknowledged.

A family of ferrocene-functionalised receptors of different topologies have been used as receptors for anions. The compounds have been designed to contain both amine nitrogen and ether oxygen atoms and comprises from monoaza to pentaaza derivatives both open-chain (L1, L2, L3) or cyclic (L4, L5) and having from one to five ferrocenyl groups. Solution studies directed to determine the protonation constants of L1, L2 and L3 have been carried out in water (0.1 mol dm3 KNO3, 25 °C) and those of L4 and L5 in 1,4-dioxane-water (70:30 v/v, 0.1 mol dm -3 KNO 3, 25 °C). The protonation behaviour of the receptors can be explained taking into account electrostatic considerations. Speciation studies in the presence of phosphate have been carried out in water for L', L2 and L3 and in dioxane-water for L4 and L5. Speciation studies have also been performed in the presence of ATP with L1, L2 and L3 in water. Selectivity of a mixture of receptors against a certain anion is discussed in terms of ternary diagrams. The shift of the redox potential of the ferrocenyl groups as a function of the pH has been studied. The difference between the oxidation potentials at basic and acidic pH has been determined experimentally and is compared with that theoretically predicted using an electrostatic model previously reported. The electrochemical shift in the presence of ATP and phosphate has been measured in water for L1, L2 and L3 and in the presence of phosphate and sulfate in 1,4-dioxane-water for L4 and L5 as a function of the pH. The electrochemical response found against those anions is quite poor with maximum cathodic shifts off. 30tO mV. The electrochemical response induced by HSO4 and H2PO4- has also been studied in acetonitrile solutions where a large cathodic shift for H 2PO 4- up to ca. 200 mV was found. © The Royal Society of Chemistry 2000.

Potentiometric and electrochemical studies have been carried out with a family of ferrocene redox-functionalised polyamines (L1–L5) and have been directed towards the discrimination, using electrochemical techniques, between the two oxoanions phosphate and sulfate and the electrochemical sensing of ATP. Potentiometric titrations were carried out in THF–water (70∶30 v/v, 0.1 mol dm–3 tetrabutylammonium perchlorate, 25 °C) for L1, L2, L3, L5 and in water (0.1 mol dm–3 potassium nitrate, 25 °C) for L4. Potentiometric data indicate that all receptors studied form stable complexes with sulfate, phosphate and ATP. Distribution for the ternary diagram system sulfate–phosphate–L2 shows pH dependent selectivity patterns; [L2HjSO4]j – 2 species exist at greater than 90% in the pH range 3–4, whereas the corresponding phosphate complexes are the main species in the neutral and basic pH range. The electrochemical studies are in agreement with the speciation results. Sulfate produces in all cyclic receptors maximum cathodic shifts of the redox potential of the ferrocenyl groups around pH 3–4, whereas maximum cathodic shifts for phosphate were found between pH 7 and 8. This behaviour is not observed for the open-chain tetraamine L5. Selective quantitative electrochemical recognition of sulfate and phosphate in the presence of competing anions in aqueous solution has been achieved using the redox-active polyaza ferrocene macrocyclic L2, L3 and L4 receptors. Additionally ATP is able to cathodically shift the oxidation potential of the ferrocenyl groups of L2 and L3 receptors by up to 100 mV. The electrochemical response of L3 against ADP and AMP is also reported.

The analysis of photoinduced charge transfer (CT) processes in a particular SERS spectrum is not a trivial task since each system must be studied separately and no universal selection rules can be proposed for this kind of enhancement mechanism. Despite this, we found out in previous studies that the SERS-CT spectra of benzene-like molecules are mainly characterized by the strong enhancement of the totally symmetric 8a ring-stretching vibration and we have used this as a propensity rule to recognize the presence of resonant CT processes in the SERS of these adsorbates. However, it is necessary to cautiously consider the relevant symmetry of the system under study before applying this simplified rule. When the molecule shows a low symmetry (or the relevant symmetry is reduced by the adsorption on the metal as it was demonstrated in the case of pyrimidine), the selective intensification of the 8a mode can be disguised by the redistribution of the CT enhancement with another close vibration in wavenumber, na...

[EN] The synthesis of capped mesoporous silica nanoparticles (MSN) conjugated with an antibody (AB) as a gatekeeper has been carried out in order to obtain a delivery system able to release an entrapped cargo (dye) in the presence of a target molecule (antigen) to which the conjugated antibody binds selectively. In particular, MSN loaded with rhodamine B and functionalized on the external surface with a suitable derivative of N-(t-butyl)- 3-oxo-(5a,17b)-4-aza-androst-1-ene-17-carboxamide (finasteride) have been prepared (S1). The addition of polyclonal antibodies against finasteride induced capping of the pores due to the interaction with the anchored hapten-like finasteride derivative to give a MSN¿hapten¿AB nanoparticle S1-AB. It was found that the addition of capped material S1-AB to water solutions containing finasteride resulted in displacement of the antibody, pore uncapping and entrapped-dye release. The response of the gated material is highly selective, and only finasteride, among other steroids, was able to induce a significant uncapping process. Compared with finasteride, the finasteride metabolite was able to release 17% of the dye, whereas the exogen steroids testosterone, metenolone and 16-b-hydroxystanozolol only induced very little release of rhodamine B (lower than 10%) from aqueous suspensions containing sensing solid S1-AB. A detection limit as low as 20 ppb was found for the fluorimetric detection of finasteride. In order to evaluate a possible application of the material for label-free detection of finasteride, the capped material was isolated and stored to give final sensing solid S1-AB-i. It was found to display a similar behavior towards finasteride as to that shown by freshly prepared S1-AB; even after a period of two months, no significant loss of selectivity or sensitivity was noted. Moreover, to study the application for the detection of finasteride in biological samples, this ¿aged¿ material, S1-AB-i, was tested using commercially available blank urine as matrix. Samples containing 70 and 90% blank urine were spiked with a defined amount of finasteride, and the concentration was determined using capped S1-AB-i. Recovery ranges from 94% to 118% were reached., Financial support from the Spanish Government (project MAT2009-14564-C04-01) and the Generalitat Valenciana (Spain) (projects PROMETEO/2009/016 and PROMETEO/2010/008) is gratefully acknowledged. E. C. thanks the Minesterio de Ciencia e Innovacion (MICINN, Spain) for her fellowship.

This paper proposes a reasonable methodology for the design of pulse arrays applied in classification and quantification techniques based on the use of pulse voltammetric electronic tongues. As model problem we designed a procedure to predict levels of ferrocene, TCNQ and Ru(bipy)(3)(2+) using a voltammetric electronic tongue employing a set of noble electrodes; i.e. Au, Pt, Ir and Rh. Ferrocene, TCNQ and Ru(bipy)(3)(2+) have been selected as model compounds because these are molecules with well-defined redox processes. The electrodes were housed inside a stainless steel cylinder which was used as the body of the electronic tongue system. A SCE was used as reference electrode. An electrochemical study of the response of ferrocene TCNQ and Ru(bipy)(3)(2+) was carried out as a first step with the aim of characterise the redox processes in these compounds. Different samples containing ferrocene,TCNQ and Ru(bipy)(3)(2+) were prepared following an experimental design in which a system of three compounds/three levels was established. Multivariate analysis based on Partial Least Square (PLS) techniques was applied for data management and prediction models building. Several set of pulses were tested and a general procedure to their design for their use in voltammetric electronic tongues is discussed and proposed. (C) 2011 Elsevier B.V. All rights reserved., We thank the Spanish Government (projects MAT2009-14564-C04-01), Generalitat Valenciana (project PROMETEO/2009/016) for support. PCI-Mediterraneo A/024590/09/A/03044/10) and the UPV (project PAID-05-10) are gratefully acknowledged.

A method for predicting levels of sodium chloride, sodium nitrite and potassium nitrate in minced meat by using a combination of two different electrochemical methods; namely an electronic tongue (ET) based on pulse voltammetry and electrochemical impedance spectroscopy measurements is proposed here. The measurements with the voltammetric ET were carried out on both saline solutions (brines) and minced meat, whereas the impedimetric sensor was used only in minced meat. The addition of the salts was performed following an experimental design in which a system of three compounds/three levels was established. Multivariate analysis including Cross validation and Partial Least Square (PLS) techniques were applied for data management and prediction models building. A very good prediction of the concentration of chloride was achieved, whereas the prediction for the concentration of nitrate and nitrite can be considered as moderate.

The molecular mechanism of the reaction of nitroglycerin with a cysteil-cysteine derivative has been studied by quantum mechanical methods; in particular, density functional theory with the accurate meta exchange-correlation functional M06-2X was used. The first reaction step is nitration of a deprotonated cysteine of the dipeptide. Afterward, six reaction steps are followed to yield the final products of the process: 1,2-glyceryl dinitrate (GDN), nitric oxide (NO), peroxynitrite anion (−OONO), and superoxide anion (O2 −) plus an intramolecular disulfide bond in the dipeptide. Two nitroglycerin molecules are decomposed for each disulfide bond formation in the dipeptide. A reducing agent is necessary to complete the global reaction. The action of the reductant triggers S-peroxynitrite formation, which, in turn, can decompose into −OONO or NO plus O2 −.

A method for predicting levels of chloride, nitrite and nitrate in minced meat by using an electronic tongue based on pulse voltammetry is proposed here. The electronic tongue consists of a set of noble (Au, Pt, Rh, Ir, Ag) and non-noble (Ni, Co, Cu) electrodes that were housed inside a stainless steel cylinder used at the same time as both the body of the electronic tongue system and the counter/reference electrode. An electrochemical study of the response of the anions Cl − , NO 3 − and NO 2 − using the different noble and non-noble electrodes was carried out in water in order to design a set of pulses for the electronic tongue. The determination of the concentration of chloride, nitrate and nitrite with the voltammetric tongue was carried out on both saline solutions (brines) and minced meat. The addition of the salts was performed following an experimental design in which a system of three compounds/three levels was established. Multivariate analysis including cross validation and partial least square (PLS) techniques were applied for data management and prediction models building. A very good prediction of the concentration of the anions chloride, nitrate and nitrite was achieved in brines. In minced meat, PLS models showed reduction in the prediction capabilities caused by a matrix effect, nevertheless the system still shows good accuracy and precision in the determination of concentration levels of these anions.

We report the preparation of a MCM-41 mesoporous material that contains the dye [Ru(bipy) 3 ]Cl 2 (bipy= bipyridine) inside the mesopores and functionalised with suitable binding groups at the entrance of the pores. Solids S1―S3 were obtained by the reaction of the mesoporous material with N-methyl-N'-propyltrimethoxysilylimidazolium chloride, N-phenyl-N'-[3-(trimethoxysilyl)propyl]thiourea, or N-phenyl-N'-[3-(trimethoxysilyl)propy1]urea, respectively. A study of the dye delivery of these systems in buffered water (pH 7.0, 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (HEPES), 10 ―3 mol dm ―3 ) in the presence of a family of carboxylate ions was carried out. In the interaction of the anions with the surface of the solids, the response depends on the characteristics of the binding groups (i.e., imidazolium, urea and thiourea) at the pore outlets and their specific interaction with the corresponding anion. The interaction of long-chain carboxylate ions with the binding sites at the surface of the solids resulted in a remarkable inhibition of the delivery of the dye. This inhibition was observed clearly for the dodecanoate anion, whereas the octanoate, decanoate, cholate, deoxycholate, glycodeoxycholate and taurocholate anions induced a certain pore blockage that varied according to the solid studied. The interaction of smaller anions, such as acetate, butanoate, hexanoate and octanoate, with the solids had no effect on the dye release process. The possible use of the gating system for the chromo-fluorogenic detection of anionic surfactants through selective dye delivery inhibition was also explored. Molecular dynamic simulations that use force-field methods have been made to theoretically study the capping carboxylate mechanism. The calculations are in agreement with the experimental results, thus allowing a representation of the dye delivery inhibition in the presence of long-chain carboxylate ions.

Chemical warfare (CW) agents are toxic chemicals that have been used in several terrorist attacks in recent years. Among CW species, nerve agents are probably the most dangerous; their high toxicity and facile synthesis underscores the need to detect these lethal compounds with quick, reliable procedures. Analytical methods based on enzymatic assays and physical measurements have generally been used to detect these hazards. However, these protocols usually have limitations such as low selectivity, poor portability, and a certain level of complexity. In recent years, several chromogenic and fluorogenic sensors, and reagents for the detection of nerve agents have been described. For instance, approaches that involve perborate-mediated oxidation of organophosphorus agents, fluorescent probes based on polyethylene terephthalate (PET), assays that use oximate-containing derivatives, molecularly imprinted polymers, nanoparticles, carbon nanotubes, porous silicon, displacement-like procedures, and cyclization reactions in push–pull chromophores have been reported. Most of these protocols rely on changes in fluorescence properties, whereas few examples deal with color modulations. Colorimetric detection is particularly appealing because it uses low-cost, widely available instrumentation and allows assays to be detected with the naked eye. However, the development of selective, sensitive chromogenic probes for the detection of deadly chemical species is still rare. Given our interest in the design of novel hybrid organic– inorganic materials as probes, we focused on the preparation of a new optical test for the detection of nerve agent mimics based on nerve agent control of mass transport to the surface of functionalized silica nanoparticles. The chromogenic approach (Scheme 1) involves the use of silica nanoparticles that are functionalized with two different subunits— thiol groups (SH) and aliphatic alcohols (OH). The role of the

A novel two-step protocol for the colorimetric detection of ionic surfactants was developed using simple silica supports functionalised with suitable binding groups. Solid S1 was synthesised by reaction of silica with N-methyl-N′-propyltrimethoxysilylimidazolium chloride to obtain a final solid containing imidazolium coordinating moieties. In the first step, solid S1 in contact with anionic surfactant solutions provides the superficial self-assembly organization of the surfactants on the cationic functionalised surface. This layer would be remarkably hydrophobic with the long alkyl chains most likely pointing toward the bulk solution, which in the second step is able to extract a suitable dye (Methylene Blue) from water. The detection principle depends on the fact that the self-assembly process of the anionic surfactant is selective as a consequence of unique strong hydrophobic interactions between surfactant molecules in the monolayer formed. The final behaviour signalling the presence of anionic surfactants would be depletion of the dye solution and coloration of the solid, both visible to the naked eye. A similar protocol was used for the detection of cationic surfactants. In this case solid S2 was prepared containing sulfonate groups. S2 was obtained by reaction of silica with 3-mercaptopropyltriethoxysilane (MPTS) following the oxidation of the mercapto group to sulfonate by adding H2O2. In this case the interaction of cationic surfactants with the S2 surface results in the self-assembly of the cationic surfactants on the anionic surface. In the second step, the addition of a suitable anionic dye (i.e. Patent Blue) then leads to the signalling of the presence of cationic surfactants. S1 and S2 solids were characterised using standard solid-state techniques. A study of the response of these solids was carried out on different concentrations of anionic, cationic and neutral surfactants and in the presence of compulsory water-present anions and cations. The partial decolouration of the dye solution or the corresponding colouration of the solid was related to the concentration of the surfactants in the aqueous solution. The method comprises a novel organic-solvent-free approach for the colorimetric detection of anionic or cationic surfactants. A model was also developed able to interpret the colorimetric behaviour of the solids based on (i) surfactant adsorption on the charged surface and (ii) further extraction of the corresponding dye.

This paper describes the design of new controlled delivery systems consisting of a mesoporous support functionalized on the pore outlets with a certain hapten able to interact with an antibody that acts as a nanoscopic cap. The opening protocol and delivery of the entrapped guest is related by a displacement reaction involving the presence in the solution of the antigen to which the antibody is selective. As a proof-of-the-concept, the solid MCM-41 was selected as support and was loaded with the dye [Ru(bipy)(3)]Cl(2). Then a suitable derivative of the hapten 4-(4-aminobenzenesulfonylamino)benzoic acid was anchored on the outer surface of the mesoporous support (solid S1). Finally the pores were capped with a polyclonal antibody for sulfathiazole (solid S1-AB). Delivery of the dye in the presence of a family of sulfonamides was studied in phosphate-buffered saline (PBS; pH 7.5). A selective uncapping of the pores and dye delivery was observed for sulfathiazole. This delivery behavior was compared with that shown by other solids that were prepared as models to assess the effect of the hapten and its interaction with antibody in the dye delivery control in the presence of the antigen.

A new hybrid system for surfactant removal from water has been developed using mesoporous material (MCM-41) functionalised with suitable binding groups. Solid S1, S2 and S3 were prepared by reaction of the mesoporous material with N-methyl-N′-(propyltrimethoxysilyl)imidazolium chloride, (3-aminopropyl)trimethoxysilane or 4-[(triethoxysilylpropylthio)methyl]pyridine, respectively. The functionalised materials were characterised following standard solid-state techniques. The final prepared solids consist of a siliceous MCM-41-type mesoporous support with the surface decorated by imidazolium, amine and pyridine binding groups suitable for anion coordination. Equilibrium adsorption studies of linear alkylbenzenesulfonate (LAS) using S1, S2 and S3 in water have been carried out. The obtained adsorption data were correlated with a Langmuir isotherm model that gives an acceptable description of the experimental data. The maximum surfactant uptake/binding site (mol mol–1) and the surfactant adsorption capacity (mmol g–1) for materials S1, S2 and S3 were calculated. S1 shows a positive-charged functionalised surface that is independent of the pH of the solution, whereas S2 and S3 are functionalised with neutral groups that need to be protonated in order to display electrostatic binding interactions with the anionic surfactants. Therefore, whereas the adsorption capacity of S1 is pH-independent, S2 and S3 display larger LAS adsorption at acidic pH. The adsorption ability at a certain pH follows the order S1 >> S3 > S2. A remarkable maximum surfactant adsorption of 1.5 mmol per gram of material was observed for S1 at neutral pH. S2 and S3 behave as poorer adsorbents and show maximum surfactant adsorption of 0.197 and 0.335 mmol per gram of material, respectively, at pH 2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

To help understand the mechanism of chemical peeling of boron nitride nanotubes, single-walled model systems have been studied using Density Functional Theory. Dimethyl sulfoxide acts as a water tr...

2,4,6-Triphenylthiopyrylium functionalized with an aza-oxa-thia macrocycle is able to selectively recognize Hg2+ cation by a color change and Cu2+ cation by a remarkable significant emission enhancement.

Based on the cross-sensitivity shown by certain metal electrodes for some anions in a liquid media, an array of five potentiometric electrodes (Au, Ag, Pt, Cu and Zn) has been used as an electronic tongue device for the recognition and prediction of common anions chloride, sulfate and bicarbonate in mineral waters. The recognition testing studies included measurements of potential (emf) on solutions of pure salts, mixtures of salt and some mineral waters. Predictions were performed by using partial least square. A good discrimination between different water samples by PCA analysis was found as well as an adequate prediction of the concentration of chloride and sulfate.

This paper focuses on the removal of nitro substituted polycyclic aromatic hydrocarbon compounds (NPAHs) from water using low cost synthesized zirconium phosphate mesoporous materials. These materials are lamellar type incorporating n-alkyl-(n = 12 and n = 16) trimethylamonium bromide molecules with different concentrations. For comparison of their performance as adsorbents and in the recovery of NPAH, their results were compared with commercial ENVI-18 extraction tubes and three dimensional type material incorporating hexadecyl-trimethyl ammonium bromide. The adsorption yield for the new materials were almost 100% and the recovery factors with dichloromethane as eluent was nearly 100%. Best results were obtained by preparing lamellar zirconium and titanium phosphates in the presence of n-dodecyl-trimethylammonium. This material has several environmental advantages because zirconium salts are non-toxic and their synthesis costs is relatively small.

Bifunctionalised hybrid silica nanoparticles have been synthesised and characterised, and their optical emission properties in the presence of certain anions in acetonitrile solutions have been studied. The alkoxysilane derivatives N-butyl-N′-[3-(trimethoxysilyl)propyl]thiourea (1), N-phenyl-N′-[3-(trimethoxysilyl)propyl]thiourea (2) and 3-[(anthracen-10-yl)methylthio]propyltriethoxysilane (3) were prepared and used to functionalise uncoated LUDOX silica nanoparticles with a mean diameter of 18 ± 2 nm. The functionalisation of the nanoparticle surfaces was carried out by two different approaches. The first approach relies on the consecutive grafting of the two subunits. In this protocol, the nanoparticles were first functionalised with anthracene derivative 3 (solid NA), and then treated with the corresponding binding sites 1 or 2 to result in the NA-Pt3 and NA-Bt3 solids. The second approach deals with the simultaneous grafting of 1 or 2 and the signalling subunit 3 in different ratios. This method was used for the preparation of the NA1Pt1, NA1Bt1, NA1Pt3 and NA1Bt3 nanoparticles. The bifunctionalised silica nanoparticles were characterised by using standard techniques. Acetonitrile suspensions of NA nanoparticles (5 mg in 20 mL) showed anthracene bands centred at ca. 350, 370 and 390 nm. Upon excitation at 365 nm, a typical emission band with fine structure in the 390–450 nm range was observed. Similar absorption and emission spectra were found for the bifunctionalised nanoparticles. The work is completed with a prospective study of the fluorescence of the prepared nanoparticles in the presence of organic (acetate, benzoate) and inorganic (F–, Cl–, Br–, CN–, HSO4– and H2PO4–) anions. The apparent binding constants (adsorption constants) for the interaction of NA-Pt3 with anions in acetonitrile were determined by performing a Langmuir-type analysis of fluorescence titration data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption. This hybrid solid is the chemodosimeter for Hg(2+) detection. Hg(2+) reacts with the APC fragment in U1 with release of the squaraine dye into the solution, which turns deep blue and fluoresces strongly. Naked-eye Hg(2+) detection is thus accomplished in an easy-to-use procedure. In contrast, U1 remains silent in the presence of other thiophilic transition metal ions, alkali and alkaline earth metal ions, or anions ubiquitously present in water such as chloride, carbonate, sulfate, and phosphate. Material U1 acts not only as chemodosimeter that signals the presence of Hg(2+) down to parts-per-billion concentrations, but at the same time is also an excellent adsorbent for the removal of mercury cations from aqueous solutions. The amount of adsorbed mercury ranges from 0.7 to 1.7 mmol g(-1), depending on the degree of functionalisation. In addition, hybrid material U1 can be regenerated for both sensing and removal purposes. As far as we know, U1 is the first example of a promising new class of polyfunctional hybrid supports that can be used as both remediation and alarm systems by selective signalling and removal of target species of environmental importance. Model compounds based on silica gel (G1), fumed silica (F1), and micrometre-sized MCM-41 scaffolds (M1) were also prepared and studied for comparative purposes.

The photochemical behavior of the protonated simplest nitrosamine [NH2NO-H](+) has been addressed by means of the CASPT2//CASSCF methodology in conjunction with the ANO-L basis sets. The relative stability of the different tautomers, namely, (1) NH2NOH(+), (2) NH3NO(+), and (3) NH2NHO(+), has been considered, and the corresponding tautomerization transition states have been characterized. With respect to the most chemically relevant species, it has been found that NH2NOH(+) corresponds to a bound structure, while NH3NO(+) corresponds to an adduct between NH3 and NO(+) at both CASSCF and CASPT2 levels of theory. Vertical transition calculations and linear interpolations on the homolytic dissociation of NH3NO(+) in combination with previous results on neutral nitrosamine [J. Chem. Phys. 2006, 125, 164311] and neutral N,N-dimethylnitrosamine [J. Org. Chem. 2007, 72, 4741] indicate that, in acidic diluted solutions, the protonation of nitrosamine takes place on the excited surface. The N-N dissociation channels have been studied both in ground and first excited singlet state. An S1/S0 conical intersection is found to be responsible for the photostability of NH2NOH(+). On the contrary, NH3NO(+) is photochemically unstable as its first excited state is purely dissociative. The latter species is characterized by a twofold reactivity: the formation of nitrosyl cation (NO(+)) in the ground state and the photorelease of physiologically relevant nitric oxide radical (NO) in its first excited state.

Molecular planarity of penta-p-phenylene (P5P) and several substituted derivatives with four side chains of various lengths, including deca(ethylene glycol) groups, is discussed by considering the changes in the intensity ratio between the Raman bands recorded at 1280 and 1220 cm(-1). The intensity ratio between both bands I(1280)/I(1220) shows a small increase with the size of the substituent, indicating a high rigidity for all these compounds, even those with long oligo(ethylene glycol) side chains. This result is important given that these phenylene derivatives are versatile building blocks for the construction of nanometric tripod-shaped adsorbates for biological applications since the side chains should prevent the nonspecific interaction with proteins.

A tripodal receptor functionalized with a stilbazolium dye derivative has been designed, synthesized and has been used for the colorimetric discrimination between certain ω-amino acids in mixed DMSO–water 90:10 v/v solutions.

Potential energy surfaces, minimum energy reaction paths, minima, transition states, reaction barriers, and conical intersections for the most important atmospheric reactions of methyl nitrate (CH(3)ONO(2)) and methylperoxy nitrite (C(3)HOONO) on the electronic ground state have been studied (i) with the second-order multiconfigurational perturbation theory (CASPT2) by computation of numerical energy gradients for stationary points and (ii) with the density functional theory (DFT). The proposed mechanism explains the conversion of unreactive alkyl peroxy radicals into alkoxy radicals: CH(3)O(2) + NO=CH(3)OONO=CH(3)O + NO(2) left arrow over right arrow CH(3)ONO(2). Additionally, several discrepancies found in the comparison of the results obtained from the two employed approaches are analyzed. CASPT2 predicts that all dissociation reactions into radicals occur without an extra exit energy barrier. In contrast, DFT finds transition states for the dissociations of cis- and trans-methylperoxy nitrite into CH(3)O + NO(2). Furthermore, multiconfigurational methods [CASPT2 and complete active space SCF (CAS-SCF)] predict the isomerization of CH3ONO2 to CH3OONO to occur in a two-step mechanism: (i) CH(3)ONO(2) --CH(3)O + NO(2); and (ii) CH(3)O + NO(2) --CH(3)OONO. The reason for this has to do with the coupling of the ground electronic state with the first excited state. Therefore, it is demonstrated that DFT methods based on single determinantal wave functions give an incorrect picture of the aforementioned reaction mechanisms.