Influence of temperature on the colloidal stability of the F-DPPC and DPPC liposomes induced by lanthanum ions

The influence of La(3+) on the colloidal stability of liposomes made up by two zwitterionic phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine (F-DPPC), in aqueous media has been investigated by dynamic light scattering and electrophoretic mobility. The critical aggregation concentration (c.a.c.) of La(3+) for F-DPPC and DPPC liposomes were experimentally obtained, and the results were compared with theoretical predictions using the Derjaguin-Landau-Verwey-Overbeek theory. In order to evaluate the influence of the state of the bilayer on the stability of liposomes, all experiments were performed at temperatures below and above the chain-melting phase-transition temperature of lipids (transition temperature of lipids). Changes in the size of both types of liposomes and high values of polydispersity in the presence of La(3+) showed that these ions induce aggregation of liposomes at 25 °C and at 60 °C. At 25 °C, when the bilayer of F-DPPC liposomes is interdigited, DPPC liposomes are more resistant to aggregation than the liposomes formed with F-DPPC. However, this difference disappears at 60 °C, when both bilayers have the same conformation. The experimental results also indicate that the c.a.c. is higher at 60 °C than at 25 °C for both types of liposomes. In fact, it has been observed by dynamic light scattering measurements that aggregation of liposomes at 25 °C can be prevented by increasing the solution temperature for La(3+) concentrations near to the c.a.c. Moreover, the behavior of these liposomes in the presence of the ion was studied at temperatures above and below the transition temperature of the phospholipids.     

Tailoring the carbon nanostructures grown on the surface of Ni-Al bimetallic nanoparticles in the gas phase

A gas-phase, one-step method for producing various aerosol carbon nanostructures is described. The carbon nanostructures can be selectively tailored with either straight, coiled, or sea urchin-like structures by controlling the size of Ni-Al bimetallic nanoparticles and the reaction temperature. The carbon nanostructures were grown using both conventional spray pyrolysis and thermal chemical vapor deposition. Bimetallic nanoparticles with catalytic Ni (guest) and non-catalytic Al (host) matrix were reacted with acetylene and hydrogen gases. At the processing temperature range of 650-800 °C, high concentration straight carbon nanotubes (S-CNTs) with a small amount of coiled carbon nanotubes (C-CNTs) can be grown on the surface of seeded bimetallic nanoparticle size <100 nm, resulting from consumption of the melting Al matrix sites; sea urchin-like carbon nanotubes (SU-CNTs) of small diameter (～10±4 nm) can be grown on the bimetallic nanoparticle size >100 nm, resulting from the significant size reduction of the available Ni sites due to thermal expansion of molten Al matrix sites without consumption of Al matrix. However, at the processing temperature range of 500-650 °C, C-CNTs can be grown on the bimetallic nanoparticle size <100 nm due to the presence of Al matrix in the bimetallic nanoparticles; SU-CNTs of large diameter (～60±13 nm) can also be grown on the bimetallic nanoparticle size >100 nm due to the isolation of Ni sites in the Al matrix.     

Ternary cobalt-iron phosphide nanocrystals with controlled compositions, properties, and morphologies from nanorods and nanorice to split nanostructures

Structural phase-controlled formation of binary Co(2)P and CoP nanocrystals is achieved by reacting cobalt(II) oleate with trioctylphosphine. In the absence of oleylamine, Co(2)P nanowires are formed at both 290 and 320 °C. In the presence of oleylamine, Co(2)P nanorods are formed at 290 °C, and CoP nanorods are formed at 320 °C. With the simultaneous reaction of iron(III) oleate and cobalt(II) oleate with trioctylphosphine in the presence of oleylamine, ternary Co(2)P-type cobalt-iron phosphide nanostructures are produced at both 290 and 320 °C, corresponding to rice-shaped Co(1.5)Fe(0.5)P nanorods and split Co(1.7)Fe(0.3)P nanostructures, respectively. The controlled incorporation of iron into cobalt phosphide can alter the magnetic properties from paramagnetic binary Co(2)P to ferromagnetic Co(2)P-type ternary cobalt-iron phosphide nanostructures. Meanwhile, the time-dependent morphological evolution from small nanodots/nanorods, through seeded growth to unique split nanostructures is demonstrated in one-pot reaction at 320 °C.     

Single molecule imaging of oxygenation of cobalt octaethylporphyrin at the solution/solid interface: thermodynamics from microscopy

For the first time, the pressure and temperature dependence of a chemical reaction at the solid/solution interface is studied by scanning tunneling microscopy (STM), and thermodynamic data are derived. In particular, the STM is used to study the reversible binding of O(2) with cobalt(II) octaethylporphyrin (CoOEP) supported on highly oriented pyrolytic graphite (HOPG) at the phenyloctane/CoOEP/HOPG interface. The adsorption is shown to follow the Langmuir isotherm with P(1/2)(298K) = 3200 Torr. Over the temperature range of 10-40 °C, it was found that ΔH(P) = -68 ± 10 kJ/mol and ΔS(P) = -297 ± 30 J/(mol K). The enthalpy and entropy changes are slightly larger than expected based on solution-phase reactions, and possible origins of these differences are discussed. The big surprise here is the presence of any O(2) binding at room temperature, since CoOEP is not expected to bind O(2) in fluid solution. The stability of the bound oxygen is attributed to charge donation from the graphite substrate to the cobalt, thereby stabilizing the polarized Co-O(2) bonding. We report the surface unit cell for CoOEP on HOPG in phenyloctane at 25 °C to be A = (1.46 ± 0.1)n nm, B = (1.36 ± 0.1)m nm, and α = 54 ± 3°, where n and m are unknown nonzero non-negative integers.     

Effect of reduction treatment on copper modified activated carbons on NO(x) adsorption at room temperature

Activated carbon was impregnated with copper salt and then exposed to reductive environment using hydrazine hydrate or heat treatment under nitrogen at 925 °C. On the obtained samples, adsorption of NO(2) was carried out at dynamic conditions at ambient temperature. The adsorbents before and after exposure to nitrogen dioxide were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N(2)-sorption at -196 °C, and potentiometric titration. Copper loading improved the adsorption capacity of NO(2) as well as the retention of NO formed in the process of NO(2) reduction on the carbon surface. That improvement is linked to the presence of copper metal and its high dispersion on the surface. Even though both reduction methods lead to the reduction of copper, different reactions with the carbon surface take place. Heat treatment results in a significant percentage of metallic copper and a reduction of oxygen functional groups of the carbon matrix, whereas hydrazine, besides reduction of copper, leads to an incorporation of nitrogen. The results suggest that NO(2) mainly is converted to copper nitrates although the possibility to its reduction to N(2) is not ruled out. A high capacity on hydrazine treated samples is linked to the high dispersion of metallic copper on the surface of this carbon.     

Temperature responsive carbon nanotubes/poly(N-isopropylacrylamide)-modified electrodes for electrochemical selective determination of dopamine, uric acid, and ascorbic acid

Poly(N-isopropylacrylamide)(PNIPAAm) with a lower critical solution temperature of about 32?°C was used as matrix to prepare temperature responsive carbon nanotubes (CNT) and functionalized CNT (fCNT) composites to modify glassy carbon electrode (GCE) as working electrode for electrochemical selective detection of dopamine, uric acid, and ascorbic acid. The GCE modification temperature (25 and 37?°C, denoted as 25f and 37f), working temperature (25 and 37?°C, denoted as 25aq and 37aq), and the type of CNT (CNT and fCNT) were found to significantly affect the electrocatalytic activity of the composites toward redox reactions of Fe(CN) ₆ ^3?/4? as a probe and the selective detection ability for the three analytes. The fCNT/PNIPAAm composite with the 25f–37aq temperature combination exhibited strong electrocatalytic activity and highly selective detection ability for the three analytes. In contrast, the same composite with the other three combinations (25f–25aq, 37f–25aq, and 37f–37aq) and the CNT/PNIPAAm composite with all four combinations exhibited insignificant electrocatalytic activity and no selective detection ability.     

Structural characterization and in vivo evaluation of retinyl palmitate in non-ionic lamellar liquid crystalline system

Carrier systems for lipophilic drugs, such as the liquid crystalline systems (LCS) have been extensively studied to improve effect and selectivity. Retinyl palmitate (RP) is widely used in pharmaceutical and cosmetics products to improve the skin elasticity. The aim of this study was the development, characterization and the in vivo effectiveness of RP in non-ionic LCS structures. LCS containing polyether functional siloxane as oil phase, silicon glycol copolymer as surfactant and water in the ratio 30:10:60, with and without RP were studied. The results of the polarized light microscopy, small-angle X-ray scattering and rheology analysis indicated the presence of typical LCS structures with lamellar arrangement. Regardless of the presence of RP, the rheological studies showed the pseudo plastic behavior of the systems. However, highest hysteresis area was verified when comparing the system in the presence and in the absence of RP. Stability study SAXS monitored, carried out up to 30 days in various storage temperature conditions (25±2 °C, 37±2 °C and 5±2 °C) demonstrated the great structural stability of the LCS systems. The in vivo effectiveness analysis suggests that the RP-loaded LCS provided a significant reduction of the orbicular wrinkles in human volunteers (P=0.048).     

Thermodynamic and kinetic behaviour of [Pt(2-methylthiomethylpyridine)(OH2)2]2+

The diaqua complex [Pt(2-methylthiomethylpyridine)(OH(2))(2)](2+), Pt(mtp), was synthesized and investigated thermodynamically as well as kinetically. Spectrophotometric acid-base titrations were performed to determine the pK(a) values of the two coordinated water ligands. A low pK(a1) value of 3.15 was observed for the water molecule trans to the pyridine donor, whereas a pK(a2) value of 6.84 was found for the water molecule trans to the labilising sulphur donor. The substitution of coordinated water by a series of sterically hindered S-containing nucleophiles, viz. thiourea (tu), N,N'-dimethylthiourea (dmtu) and N,N,N',N'-tetramethylthiourea (tmtu), was studied under pseudo first-order conditions as a function of nucleophile concentration, pH (2, 4.75, 7.4), temperature and pressure, using stopped-flow techniques and UV-vis spectroscopy. In general the first substitution reaction takes place trans to the sulphur donor. At pH 2 the nucleophiles react in the order tu (634 ± 10) > dmtu (507 ± 5) ? tmtu (165 ± 3 M(-1) s(-1) at 25 °C), which is caused by steric hindrance. The second observed reaction involves two steps, viz. the displacement of the second water ligand and dechelation of the pyridine ring with the third-order rate constants 73.3 ± 0.8 (tu), 22.1 ± 0.1 (dmtu) and 6.8 ± 0.2 M(-2) s(-1) (tmtu) at 25 °C. At pH 4.75 the reactions are in general slower due to the presence of aqua-hydroxo species. The same order in reactivity was found, viz. tu (106 ± 1) > dmtu (72 ± 1) ? tmtu (14.1 ± 0.5 M(-1) s(-1) at 25 °C). No evidence for ring-dechelation could be observed under these conditions. At pH 7.4 the inert dihydroxo species is predominantly present in solution and consequently no substitution reaction was observed. Quantum chemical calculations were performed to support the interpretation and discussion of the experimental results.     

In situ study of electrochemical activation and surface segregation of the SOFC electrode material La0.75Sr0.25Cr0.5Mn0.5O(3±δ)

Mixed-conducting perovskite-type electrodes which are used as cathodes in solid oxide fuel cells (SOFCs) exhibit pronounced performance improvement after cathodic polarization. The current in situ study addresses the mechanism of this activation process which is still unknown. We chose the new perovskite-type material La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±δ) which is a potential candidate for use in symmetrical solid oxide fuel cells (SFCs). We prepared La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±δ) thin film model electrodes on YSZ (111) single crystals by pulsed laser deposition (PLD). Impedance spectroscopy (EIS) measurements show that the kinetics of these electrodes can be drastically improved by applying a cathodic potential. To understand the origin of the enhanced electrocatalytic activity the surfaces of operating LSCrM electrodes were studied in situ (at low pressure) with spatially resolving X-ray photoelectron spectroscopy (μ-ESCA, SPEM) and quasi static secondary ion mass spectrometry (ToF-SIMS) after applying different electrical potentials in the SIMS chamber. We observed that the electrode surfaces which were annealed at 600 °C are enriched significantly in strontium. Subsequent cathodic polarization decreases the strontium surface concentration while anodic polarization increases the strontium accumulation at the electrode surface. We propose a mechanism based on the reversible incorporation of a passivating SrO surface phase into the LSCrM lattice to explain the observed activation/deactivation process.     

Changes in morphology and activity of transglutaminase following cross-linking and immobilization on a polypropylene microporous membrane

Transglutaminase (TGase) was cross-linked with glutaraldehyde, and cross-linked crystalline transglutaminase was immobilized on a polypropylene microporous membrane by UV-induced grafting. Immobilized enzyme activity were calculated to be 0.128 U/cm2 polypropylene microporous membrane. The microstructure and enzyme characteristics of free, cross-linked and immobilized transglutaminase were compared. The optimum temperature of free transglutaminase was determined to be approximately 40 °C, while cross-linking and immobilization resulted in an increase to approximately 45 °C and 50 °C. At 60 °C, immobilized, cross-linked and free transglutaminase retained 91.7 ± 1.20%, 63.2 ± 1.05% and 37.9 ± 0.98% maximum activity, respectively. The optimum pH was unaffected by the state of transglutaminase. However, the thermal and pH stabilities of cross-linked and immobilized transglutaminase were shown to increase.     

Selective etching of graphene edges by hydrogen plasma

We devised a controlled hydrogen plasma reaction at 300 °C to etch graphene and graphene nanoribbons (GNRs) selectively at the edges over the basal plane. Atomic force microscope imaging showed that the etching rates for single-layer and few-layer (≥2 layers) graphene are 0.27 ± 0.05 nm/min and 0.10 ± 0.03 nm/min, respectively. Meanwhile, Raman spectroscopic mapping revealed no D band in the planes of single-layer or few-layer graphene after the plasma reaction, suggesting selective etching at the graphene edges without introducing defects in the basal plane. We found that hydrogen plasma at lower temperature (room temperature) or a higher temperature (500 °C) could hydrogenate the basal plane or introduce defects in the basal plane. Using the hydrogen plasma reaction at the intermediate temperature (300 °C), we obtained narrow, presumably hydrogen terminated GNRs (sub-5 nm) by etching of wide GNRs derived from unzipping of multiwalled carbon nanotubes. Such GNRs exhibited semiconducting characteristics with high on/off ratios (～1000) in GNR field effect transistor devices at room temperature.     

Temperature responsive flocculation and solid-liquid separations with charged random copolymers of poly(N-isopropyl acrylamide)

Temperature-responsive random copolymers based on poly(N-isopropyl acrylamide) (PNIPAM) with 15 mol% of either acrylic acid or dimethylaminoethyl acrylate quaternary chloride were prepared. The effect of the charge and its sign were investigated in the solid-liquid separation of silica and alumina mineral suspensions. The results were compared to PNIPAM homopolymer of similar molecular weight. PNIPAM copolymers of the same charge as the particles (co-ionic PNIPAM) act as dispersants at both 25°C and 50°C. Flocculation occurs when counter-ionic PNIPAM facilitates selective aggregation and rapid sedimentation of minerals at both 25°C and 50°C. Adsorption and desorption studies showed that, unlike non-ionic PNIPAM, little desorption of the counter-ionic copolymers from the oxides occurred after cooling a suspension from 50°C to below the lower critical solution temperature. Thus, incorporation of counter-ionic charge into the temperature sensitive polymer PNIPAM was found to reduce the sediment bed consolidation upon cooling when compared to PNIPAM homopolymers. The lack of secondary consolidation upon cooling is attributed to attractive inter-particle forces, such as conventional polyelectrolyte flocculation mechanisms (bridging, charge neutralization or charge patch) which persist at both 25°C and 50°C when counter-ionic PNIPAM is used. On the other hand, it was possible to obtain rapid sedimentation with the counter-ionic PNIAPMs even when they were added to the suspension already at 50°C, a process which has not been possible with neutral PNIPAM homopolymers.     

In situ coarsening study of inverse micelle-prepared Pt nanoparticles supported on γ-Al2O3: pretreatment and environmental effects

The thermal stability of inverse micelle prepared Pt nanoparticles (NPs) supported on nanocrystalline γ-Al(2)O(3) was monitored in situ under different chemical environments (H(2), O(2), H(2)O) via extended X-ray absorption fine-structure spectroscopy (EXAFS) and ex situ via scanning transmission electron microscopy (STEM). Drastic differences in the stability of identically synthesized NP samples were observed upon exposure to two different pre-treatments. In particular, exposure to O(2) at 400 °C before high temperature annealing in H(2) (800 °C) was found to result in the stabilization of the inverse micelle prepared Pt NPs, reaching a maximum overall size after moderate coarsening of ～1 nm. Interestingly, when an analogous sample was pre-treated in H(2) at ～400 °C, a final size of ～5 nm was reached at 800 °C. The beneficial role of oxygen in the stabilization of small Pt NPs was also observed in situ during annealing treatments in O(2) at 450 °C for several hours. In particular, while NPs of 0.5 ± 0.1 nm initial average size did not display any significant sintering (0.6 ± 0.2 nm final size), an analogous thermal treatment in hydrogen leads to NP coarsening (1.2 ± 0.3 nm). The same sample pre-dosed and annealed in an atmosphere containing water only displayed moderate sintering (0.8 ± 0.3 nm). Our data suggest that PtO(x) species, possibly modifying the NP/support interface, play a role in the stabilization of small Pt NPs. Our study reveals the enhanced thermal stability of inverse micelle prepared Pt NPs and the importance of the sample pre-treatment and annealing environment in the minimization of undesired sintering processes affecting the catalytic performance of nanosized particles.     

Pressure-induced disordered substitution alloy in Sb2Te3

A new type of disordered substitution alloy of Sb and Te at above 15.1 GPa was discovered by performing in situ high-pressure angle-dispersive X-ray diffraction experiments on antimony telluride (Sb(2)Te(3)), a topological insulator and thermoelectric material, at room temperature. In this disordered substitution alloy, Sb(2)Te(3) crystallizes into a monoclinic structure with the space group C2/m, which is different from the corresponding high-pressure phase of the similar isostructural compound Bi(2)Te(3). Above 19.8 GPa, Sb(2)Te(3) adopts a body-centered-cubic structure with the disordered atomic array in the crystal lattice. The in situ high-pressure experiments down to about 13 K show that Sb(2)Te(3) undergoes the same phase-transition sequence with increasing pressure at low temperature, with almost the same phase-transition pressures.     

Determination of the temperature dependence of the dynamic nuclear polarisation enhancement of water protons at 3.4 Tesla

It is shown that the temperature dependence of the DNP enhancement of the NMR signal from water protons at 3.4 T using TEMPOL as a polarising agent can be obtained provided that the nuclear relaxation, T(1I), is sufficiently fast and the resolution sufficient to measure the (1)H NMR shift. For high radical concentrations (～100 mM) the leakage factor is approximately 1 and, provided sufficient microwave power is available, the saturation factor is also approximately 1. In this situation the DNP enhancement is solely a product of the ratio of the electron and nuclear gyromagnetic ratios and the coupling factor enabling the latter to be directly determined. Although the use of high microwave power levels needed to ensure saturation causes rapid heating of the sample, this does not prevent maximum DNP enhancements, ε(0), being obtained since T(1I) is very much less than the characteristic heating time at these concentrations. It is necessary, however, to know the temperature variation of T(1I) to allow accurate modelling of the behaviour. The DNP enhancement is found to vary linearly with temperature with ε(0)(T) = -2 ± 2 - (1.35 ± 0.02)T for 6 °C ≤ T ≤ 100 °C. The value determined for the coupling factor, 0.055 ± 0.003 at 25 °C, agrees very well with the molecular dynamics simulations of Sezer et al. (Phys. Chem. Chem. Phys., 2009, 11, 6626) who calculated 0.0534, however the experimental values increase much more rapidly with increasing temperature than predicted by these simulations. Large DNP enhancements (|ε(0)| > 100) are reported at high temperatures but it is also shown that significant enhancements (e.g.～40) can be achieved whilst maintaining the sample temperature at 40 °C by adjusting the microwave power and irradiation time. In addition, short polarisation times enable rapid data acquisition which permits further enhancement of the signal, such that useful liquid state DNP-NMR experiments could be carried out on very small samples.     

A large volume, portable, real-time PCR reactor

A point-of-care, diagnostic system incorporating a portable thermal cycler and a compact fluorescent detector for real-time, polymerase chain reaction (PCR) on disposable, plastic microfluidic reactors with relatively large reaction volume (ranging from 10 μL to 100 μL) is described. To maintain temperature uniformity and a relatively fast temperature ramping rate, the system utilizes double-sided heater that features a master, thermoelectric element and a thermal waveguide connected to a second thermoelectric element. The waveguide has an aperture for optical coupling between a miniature, fluorescent reader and the PCR reaction chamber. The temperature control is accomplished with a modified, feedforward, variable structural proportional-integral-derivative controller. The temperature of the liquid in the reaction chamber tracks the set-point temperature with an accuracy of ± 0.1 °C. The transition times from one temperature to another are minimized with controllable overshoots (< 2 °C) and undershoots (< 5 °C). The disposable, single-use PCR chip can be quickly inserted into a thermal cycler/reader unit for point-of-care diagnostics applications. The large reaction chamber allows convenient pre-storing of dried, paraffin-encapsulated PCR reagents (polymerase, primers, dNTPs, dyes, and buffers) in the PCR chamber. The reagents are reconstituted "just in time" by heating during the PCR process. The system was tested with viral and bacterial nucleic acid targets.     

Thermal effectiveness of different IR radiators employed in rheumatoid hand therapy as assessed by thermovisual examination

We conducted a thermovisual comparison of mean hand surface temperature changes upon local heating with two different IR sources. Sixty-six patients with rheumatoid arthritis (47 women and 19 men; average age, 56.1 ± 8.6 years) were subjected to topical heat therapy for one hand with either the standard IR radiator (SIR) or the water filter IRA (wIRA). The surface temperature of the dorsal side of both hands was measured, and thermal images were taken before and up to 2 h after treatment. At 1 min after treatment, SIR application increased the surface skin temperature of the heated hand from 31.5 ± 1.9 to 35.0 ± 1.9 °C (P<0.05), while wIRA increased it from 32.1 ± 1.6 to 34.2 ± 1.1 °C (P<0.05). Constant decline in temperature was observed immediately after treatment, with the temperatures reaching baseline in about 30 and 120 min after wIRA and SIR treatment, respectively. Similar temperature changes were observed in the heated hands for wIRA and SIR, except at 1 min after treatment. Changes in the untreated hands indicated contralateral reaction. The temperature of the warmed hand showed a correlation to the body mass index.     

Responsive microgrooves for the formation of harvestable tissue constructs

Given its biocompatibility, elasticity, and gas permeability, poly(dimethylsiloxane) (PDMS) is widely used to fabricate microgrooves and microfluidic devices for three-dimensional (3D) cell culture studies. However, conformal coating of complex PDMS devices prepared by standard microfabrication techniques with desired chemical functionality is challenging. This study describes the conformal coating of PDMS microgrooves with poly(N-isopropylacrylamide) (PNIPAAm) by using initiated chemical vapor deposition (iCVD). These microgrooves guided the formation of tissue constructs from NIH-3T3 fibroblasts that could be retrieved by the temperature-dependent swelling property and hydrophilicity change of the PNIPAAm. The thickness of swollen PNIPAAm films at 24 °C was approximately 3 times greater than at 37 °C. Furthermore, PNIPAAm-coated microgroove surfaces exhibit increased hydrophilicity at 24 °C (contact angle θ = 30° ± 2) compared to 37 °C (θ = 50° ± 1). Thus PNIPAAm film on the microgrooves exhibits responsive swelling with higher hydrophilicity at room temperature, which could be used to retrieve tissue constructs. The resulting tissue constructs were the same size as the grooves and could be used as modules in tissue fabrication. Given its ability to form and retrieve cell aggregates and its integration with standard microfabrication, PNIPAAm-coated PDMS templates may become useful for 3D cell culture applications in tissue engineering and drug discovery.     

Sonochemical synthesis and properties of nanoparticles of FeSbO4

A sonochemical method was employed to prepare reactive nanoparticles of FeSbO(4) at 300 °C, which is the lowest calcination temperature reported so far for preparing FeSbO(4). A systematic evolution of the FeSbO(4) phase formation as a function of temperature was monitored by in situ synchrotron X-ray measurements. The 300 and 450 °C calcined powders exhibited specific surface areas of 116 and 75 m(2)/g, respectively. The X-ray photoelectron spectra analysis confirmed the presence of mainly Fe(3+) and Sb(5+) in the calcined powder. The response of the fabricated sensors (using both 300 and 450 °C calcined powders) toward 1000 ppm and 1, 2, 4, and 8% hydrogen, respectively, has been monitored at various operating temperatures. The sensors fabricated using 300 °C calcined powder exhibited a response of 76% toward 4% H(2) gas at an operating temperature of 300 °C, while those fabricated using 450 °C calcined powder exhibited a higher response of 91% with a quick recovery toward 4% H(2) gas at 300 °C. The results confirmed that a higher calcination temperature was preferred to achieve better sensitivity and selectivity toward hydrogen in comparison to other reducing gases such as butane and methane. The experimental results confirmed that the sonochemical process can be easily used to prepare FeSbO(4) nanoparticles for various catalytic applications as demonstrated. Here, we project FeSbO(4) as a new class of material exhibiting high sensitivity toward a wide range of hydrogen gas. Such sensors that could detect high concentrations of hydrogen may find application in nuclear reactors where there will be a leakage of hydrogen.     

Mild reaction conditions for the terminal deuteration of alkynes

Routinely employed syntheses of terminally deuterated alkynes often utilize strong bases (i.e., LDA, n-BuLi, or Grignard reagents) or low (i.e., -78 °C) or elevated (i.e., 56 °C) reaction temperatures; furthermore many of these procedures afford average yields and in some cases less than optimum deuterium incorporation. Herein we report the application of alternative extremely mild reaction conditions that readily afford quantitative yields of terminally deuterated alkynes in a matter of minutes with exceptional isotope incorporation at ambient temperature.