Synthesis of cobalt doped silica thin film for low temperature optical gas sensor

A modified sol–gel method was used to prepare cobalt doped silica thin film with a cobalt content of 10, 20 and 30 mol% (10Co, 20Co and 30Co). The prepared films were annealed at different temperatures in the range 400–1,000 °C, and their structural evolution examined. The mixed valence cobalt oxide, Co₃O₄, crystallizes only in the sample with the higher cobalt content, while cobalt silicate is the only crystalline phase detected in the sample 10Co and 20Co. Both the cobalt content and the temperature of heat treatment resulted to affect the nature of cobalt species dispersed in the silica matrix. The 30Co was selected for further investigations by FTIR spectroscopy to follow the structural evolution of 30Co film as function of the temperature and UV–Vis to get information on the cobalt valence state. The optical gas-sensing properties of 30Co films, containing Co₃O₄ as the major cobalt phase, were studied through the measuring of the film transmittance in dry air and in presence of dry air containing variable concentrations of polluting gases, CO and NO₂. The 30Co samples resulted to be highly sensitive to CO at room temperature. An explanation for the CO sensing characteristics, at low temperature, was proposed by referring to the physisorption-related mechanics of CO.     

The solid-liquid phase diagrams of binary mixtures of even saturated fatty alcohols

This study is part of a work developed in the author's research group on the solid-liquid equilibrium of fatty substances. The phase diagrams of the following fatty alcohol systems were determined by differential scanning calorimetry (DSC): 1-octanol + 1-dodecanol, 1-octanol + 1-tetradecanol, 1-decanol + 1-tetradecanol, 1-decanol + 1-hexadecanol and 1-dodecanol + 1-octadecanol. The liquidus lines of three of these systems were previously reported in the literature but the other two systems were never published. Moreover other transitions, in addition to the eutectic temperature, were also detected in all the systems. A region of solid solution at the extreme left of the phase diagrams was observed for all the binary mixtures. Polarized light microscopy was used to complement the characterization of the systems for a full grasp of the phase diagrams. The solid-liquid equilibrium was modeled using the Margules 2-suffix, Margules 3-suffix, NRTL and UNIFAC Dortmund equations.     

Transformations of biomass-derived platform molecules: from high added-value chemicals to fuels via aqueous-phase processing

Global warming issues and the medium-term depletion of fossil fuel reserves are stimulating researchers around the world to find alternative sources of energy and organic carbon. Biomass is considered by experts the only sustainable source of energy and organic carbon for our industrial society, and it has the potential to displace petroleum in the production of chemicals and liquid transportation fuels. However, the transition from a petroleum-based economy to one based on biomass requires new strategies since the petrochemical technologies, well-developed over the last century, are not valid to process the biomass-derived compounds. Unlike petroleum feedstocks, biomass derived platform molecules possess a high oxygen content that gives them low volatility, high solubility in water, high reactivity and low thermal stability, properties that favour the processing of these resources by catalytic aqueous-phase technologies at moderate temperatures. This tutorial review is aimed at providing a general overview of processes, technologies and challenges that lie ahead for a range of different aqueous-phase transformations of some of the key biomass-derived platform molecules into liquid fuels for the transportation sector and related high added value chemicals.     

Synthesis, structural characterization, photophysical properties and theoretical analysis of gold(I) thiolate-phosphine complexes

A series of luminescent dinuclear neutral complexes of stoichiometry [(AuSPh)(2)(PPh(2)-(C(6)H(4))(n)-PPh(2))] (n = 1, 2, 3) as well as their tetranuclear cationic derivatives [(Au(2)SPh)(2)(PPh(2)-(C(6)H(4))(n)-PPh(2))(2)](PF(6))(2) are reported. Their crystal structures have been elucidated by X-ray studies. These studies indicate that, for the dinuclear species, only when n = 1 the molecules exhibit intermolecular aurophilic interactions. None of the tetranuclear species crystallizes in their molecular form, due to the formation of aggregates through Au···Au interactions. The origin of the luminescence has been analyzed by computational studies indicating that the presence or absence of aurophilic interactions does not affect the luminescent behavior and that intraligand charge transfer processes which involve the thiolate and the diphosphine are responsible for the emissions. The result is in contrast with the thiolate-gold charge transfer processes which dominate the photophysics of gold-thiolate compounds and reveals the influence of the phenylene spacers in the emissive behavior of these compounds.     

Fast determination of the functional peptide soymetide in different soybean derived foods by capillary-high performance liquid chromatography

The determination of bioactive peptides derived from food sources is gaining special attention in last years, due to their ability to promote health and their potential to reduce the risk of chronic diseases. In this work, a new analytical methodology has been developed enabling for the first time the determination of soymetide, a new immunostimulating peptide derived from soybean, in different soybean derived foodstuffs. Capillary-HPLC was employed for peptide separation after accelerated tryptic digestion of soybean proteins. Two different capillary-HPLC columns were tested and chromatographic separation was optimized in each case. The use of a 300 μm fused-core technology C18 column enabled a suitable separation of soymetide from the other peptides in less than 18 min. Different analytical characteristics of the method were evaluated: selectivity, linearity, accuracy, precision, limit of detection and quantitation, and stability. The developed method was applied to the determination of soymetide content in different soybean dairy-like products for human consumption (powdered milks and infant formulas).     

MRI-guided neutron capture therapy by use of a dual gadolinium/boron agent targeted at tumour cells through upregulated low-density lipoprotein transporters

The upregulation of low-density lipoprotein (LDL) transporters in tumour cells has been exploited to deliver a sufficient amount of gadolinium/boron/ligand (Gd/B/L) probes for neutron capture therapy, a binary chemio-radiotherapy for cancer treatment. The Gd/B/L probe consists of a carborane unit (ten B atoms) bearing an aliphatic chain on one side (to bind LDL particles), and a Gd(III)/1,4,7,10-tetraazacyclododecane monoamide complex on the other (for detection by magnetic resonance imaging (MRI)). Up to 190 Gd/B/L probes were loaded per LDL particle. The uptake from tumour cells was initially assessed on cell cultures of human hepatoma (HepG2), murine melanoma (B16), and human glioblastoma (U87). The MRI assessment of the amount of Gd/B/L taken up by tumour cells was validated by inductively coupled plasma-mass-spectrometric measurements of the Gd and B content. Measurements were undertaken in vivo on mice bearing tumours in which B16 tumour cells were inoculated at the base of the neck. From the acquisition of magnetic resonance images, it was established that after 4-6 hours from the administration of the Gd/B/L-LDL particles (0.1 and 1 mmol kg(-1) of Gd and (10)B, respectively) the amount of boron taken up in the tumour region is above the threshold required for successful NCT treatment. After neutron irradiation, tumour growth was followed for 20 days by MRI. The group of treated mice showed markedly lower tumour growth with respect to the control group.     

On the interaction of bovine serum albumin with ionic surfactants: temperature induced EPR changes of a maleimide nitroxide reflect local protein dynamics and probe solvent accessibility

The interaction of bovine serum albumin (BSA) with the ionic surfactants sodium dodecylsulfate (SDS, anionic), cetyltrimethylammonium chloride (CTAC, cationic) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS, zwitterionic) was studied by electron paramagnetic resonance (EPR) spectroscopy of spin label covalently bound to the single free thiol group of the protein. EPR spectra simulation allows to monitor the protein dynamics at the labeling site and to estimate the changes in standard Gibbs free energy, enthalpy and entropy for transferring the nitroxide side chain from the more motionally restricted to the less restricted component. Whereas SDS and CTAC showed similar increases in the dynamics of the protein backbone for all measured concentrations, HPS presented a smaller effect at concentrations above 1.5mM. At 10mM of surfactants and 0.15 mM BSA, the standard Gibbs free energy change was consistent with protein backbone conformations more expanded and exposed to the solvent as compared to the native protein, but with a less pronounced effect for HPS. In the presence of the surfactants, the enthalpy change, related to the energy required to dissociate the nitroxide side chain from the protein, was greater, suggesting a lower water activity. The nitroxide side chain also detected a higher viscosity environment in the vicinity of the paramagnetic probe induced by the addition of the surfactants. The results suggest that the surfactant-BSA interaction, at higher surfactant concentration, is affected by the affinities of the surfactant to its own micelles and micelle-like aggregates. Complementary DLS data suggests that the temperature induced changes monitored by the nitroxide probe reflects local changes in the vicinity of the single thiol group of Cys-34 BSA residue.     

Lanthanide(III)/pyrimidine-4,6-dicarboxylate/oxalate extended frameworks: a detailed study based on the lanthanide contraction and temperature effects

Detailed structural, magnetic, and luminescence studies of six different crystalline phases obtained in the lanthanide/pyrimidine-4,6-dicarboxylate/oxalate system have been afforded: {[Ln(μ-pmdc)(μ-ox)(0.5)(H(2)O)(2)]·3H(2)O}(n) (1-Ln), {[Ln(μ-pmdc)(μ-ox)(0.5)(H(2)O)(3)]·2H(2)O}(n) (2-Ln), {[Ln(μ(3)-pmdc)(μ-ox)(0.5)(H(2)O)(2)]·~2.33H(2)O}(n) (3-Ln), {[Ln(2)(μ(3)-pmdc)(μ(4)-pmdc)(μ-ox)(H(2)O)(3)]·5H(2)O}(n) (4-Ln), {[Ln(μ(3)-pmdc)(μ-ox)(0.5)(H(2)O)(2)]·H(2)O}(n) (5-Ln), and [Ln(pmdc)(1.5)(H(2)O)(2.5)] (6-Ln). The slow generation of the oxalate (ox) anion, obtained from the in situ partial hydrothermal decomposition of the pyrimidine-4,6-dicarboxylate (pmdc) ligand, allows us to obtain good shaped single crystals, while direct addition of potassium oxalate provides the same compounds but as polycrystalline samples. The crystal structures of all compounds are based on the double chelation established by the pmdc and ox ligands to provide distorted 2D honeycomb layers that, in some cases, are fused together, leading to 3D systems, by replacing some of the coordinated water molecules that complete the coordination sphere of the lanthanide by uncoordinated carboxylate oxygen atoms of the pmdc. The presence of channels occupied by crystallization water molecules is also a common feature with the exception of compounds 5-Ln. It is worth noting that compounds 3-Ln present a commensurate crystal structure related to the partial occupancy of the crystallization water molecules placed within the channels. Topological analyses have been carried out, showing a previously nonregistered topology for compounds 4-Ln, named as jcr1. The crystal structures are strongly dependent on the lanthanide ion size and the temperature employed during the hydrothermal synthesis. The lanthanide contraction favors crystal structures involving sterically less hindranced coordination environments for the final members of the lanthanide series. Additionally, reinforcement of the entropic effects at high temperatures directs the crystallization process toward less hydrated crystal structures. The magnetic data of these compounds indicate that the exchange coupling between the lanthanide atoms is almost negligible, so the magnetic behavior is dominated by the spin-orbit coupling and the ligand field perturbation. The luminescence properties that exhibit the compounds containing Nd(III), Eu(III), and Tb(III) have been also characterized.     

Unprecedented luminescent heteropolynuclear aggregates with gold thiolates as building blocks

The reaction of [AuCl(P-N)], in which P-N represents a heterofunctional phosphine ligand, with pentafluorothiophenol, HSC(6)F(5), gives the thiolate gold derivatives [Au(SC(6)F(5))(P-N)] (P-N = PPh(2)py (1), PPh(2)CH(2)CH(2)py (2), or PPhpy(2) (3)). Complex [Au(SC(6)F(5))(PPh(2)py)] (1) reacts with [Au(OTf)(PPh(2)py)] in a 1:1 or 1:2 molar ratio to afford the di- or trinuclear species [Au(2)(μ-SC(6)F(5))(PPh(2)py)(2)]OTf (4) and [Au(3)(μ(3)-SC(6)F(5))(PPh(2)py)(3)](OTf)(2) (5), with the thiolate acting as a doubly or triply bridging ligand. The reactivity of the mononuclear compounds [Au(SC(6)F(5))(P-N)] toward silver or copper salts in different ratios has been investigated. Thus, the treatment of [Au(SC(6)F(5))(P-N)] with Ag(OTf) or [Cu(NCMe)(4)]PF(6) in a 1:1 molar ratio gives complexes of stoichiometry [AuAg(OTf)(μ-SC(6)F(5))(P-N)] (P-N = PPh(2)py (6), PPh(2)CH(2)CH(2)py (7), or PPhpy(2) (8)) or [AuCu(μ-SC(6)F(5))(P-N)(NCMe)]PF(6) (P-N = PPh(2)py (9), PPh(2)CH(2)CH(2)py (10), or PPhpy(2) (11)). These complexes crystallize as dimers and display different coordination modes of the silver or copper center, depending on the present functionalized phosphine ligand. The treatment of [Au(SC(6)F(5))(PPh(2)py)] with silver and copper compounds in other molar ratios has been carried out. In a 2:1 ratio, the complexes [Au(2)M(μ-SC(6)F(5))(2)(μ-PPh(2)py)(2)]X (M = Ag, X = OTf (12); M = Cu, X = PF(6) (13)) are obtained. The same reaction in a 4:3 molar ratio affords the species [Au(4)M(2)(μ-SC(6)F(5))(3)(μ-PPh(2)py)(4)]X(3) (M = Ag, X = OTf (14); M = Cu, X = PF(6) (15)). The crystal structures of some of these complexes reveal different interactions among the metallic d(10) centers. The complexes display dual emission. The band at higher energy has been attributed to intraligand (IL) transitions, and the one at lower energy has been assigned to a ligand to metal (LM) charge transfer process. The latter emission is modulated by the heterometal (silver or copper).     

Molecularly imprinted polymer grafted to porous polyethylene frits: a new selective solid-phase extraction format

In this paper, a novel format for selective solid-phase extraction based on a molecularly imprinted polymer (MIP) is described. A small amount of MIP has been synthesized within the pores of commercial polyethylene (PE) frits and attached to its surface using benzophenone (BP), a photo-initiator capable to start the polymerisation from the surface of the support material. Key properties affecting the obtainment of a proper polymeric layer, such as polymerisation time and kind of cross-linker were optimised. The developed imprinted material has been applied as a selective sorbent for cleaning extracts of thiabendazole (TBZ), as model compound, from citrus samples. The use of different solvents for loading the analyte in the imprinted frits was investigated, as well as the binding capacity of the imprinted polymer. Imprinted frits showed good selectivity when loads were performed using toluene and a linear relationship was obtained for the target analyte up to 1000 ng of loaded analyte. Prepared composite material was applied to the SPE of TBZ in real samples extracts, showing an impressive clean-up ability. Calibrations showed good linearity in the concentration range of 0.05-5.00 μg g(-1), referred to the original solid sample, and the regression coefficients obtained were greater than 0.996. The calculated detection limit was 0.016 μg g(-1), low enough to satisfactory analysis of TBZ in real samples. RSDs at different spiking levels ranged below 15% in all the cases and imprinted frits were reusable without loss in their performance.