TGA–FTIR study of a lead zirconate titanate gel made from a triol-based sol–gel system

A Pb(Zr,Ti)O₃ precursor gel made from a sol prepared using 1,1,1,-tris(hydroxymethyl)ethane, lead acetate and zirconium and titanium propoxides, stabilised with acetylacetone, was analysed using TGA–FTIR analysis. Decomposition under nitrogen (N₂) gave rise to evolved gas absorbance peaks at 215 °C, 279 °C, 300 °C and 386 °C, but organic vapours continued to be evolved, along with CO₂ and CO until 950 °C. The final TGA step in N₂ is thought to relate to decomposition of an intermediate carbonate phase and the final elimination of residues of triol or acetylacetonate species which form part of the polymeric gel structure. By contrast, heating in air promoted oxidative pyrolysis of the final organic groups at ≤450 °C. In air, an intermediate carbonate phase was decomposed by heating at 550 °C, allowing Pb(Zr,Ti)O₃ to be produced some 400 °C below the equivalent N₂ decomposition temperature.     

Enhanced tungstate electrochromism via formation of transparent conductive networks

Indium tin oxide (ITO) nanopowder was added to a polymer film containing WO₃ · H₂O particles to enhance electron conductivity and complimentary Li ion kinetics in an electrochromic device. Film conductivity increased dramatically with ITO content, suggesting the formation of conductive ITO networks in the film. The improved electron conductivity leads to a substantial increase of the effective Li⁺ ion diffusion coefficient in the composite film, from 10⁻¹¹ to 10⁻⁹ cm²/s. Electrochromic contrast studies revealed that the presence of the ITO networks leads to enhanced blue/green color contrast.     

Effects of carbon dioxide in breath gas on proton transfer reaction-mass spectrometry (PTR-MS) measurements

PTR-MS is becoming a common method for the analysis of volatile organic compounds (VOCs) in human breath. Breath gas contains substantial and, particularly for bag samples, highly variable concentrations of water vapour (up to 6.3%) and carbon dioxide (up to 6.5%). The goal of this study was to investigate the effects of carbon dioxide on PTR-MS measurements; such effects can be expected in view of the already well known effects of water vapour. Carbon dioxide caused an increase of the pressure in the PTR-MS drift tube (1% increase for 5% CO₂), and this effect was used to assess the CO₂ concentration of breath gas samples along the way with the analysis of VOCs. Carbon dioxide enhanced the concentration ratio of protonated water clusters (H₃O⁺H₂O) to protonated water (H₃O⁺) in the drift tube. Using the observed increase, being 60% for 5% CO₂, it is estimated that the mobility of water cluster ions in pure CO₂ is almost 65% lower than in air. Carbon dioxide had a significant effect on the mass spectra of the main breath gas components methanol, ethanol, 1-propanol, 2-propanol, acetone, and isoprene. Carbon dioxide caused a small increase (<10% for 5% CO₂) of the normalised main signals for the non-fragmenting molecules methanol and acetone. The increase can be much higher for the fragmenting VOCs (ethanol, propanol, and isoprene) and was, for 5% CO₂, up to 60% for ethanol. This effect of CO₂ on fragment patterns is mainly a consequence of the increased abundance of protonated water clusters, which undergo softer reactions with VOCs than the hydronium ions. Breath gas samples stored in Teflon bags lost 80% of CO₂ during 3 days, the decrease of VOC signals, however, is mainly attributed to decreasing VOC concentrations and to the loss of humidity from the bags.     

Fabrication and superhydrophobicity of fluorinated titanium dioxide nanocoatings

This study demonstrates the fabrication of a stable superhydrophobic surface with low contact angle hysteresis (CAH) using an arrangement of nanoscale TiO₂ spheres. The control of precursor quantity is selected as the key factor in determining surface roughness that significantly intensifies water contact angle (CA) of TiO₂ films. After surface fluorination treatment, the anatase-type crystalline surfaces exhibit good water repellency (CA 166.1°), low CAH (6°), and superhydrophobic stability (>60 min). Enhanced water repellency is attributed to the fact that the higher density of TiO₂ spheres results in more tortuous three-phase contact line, leading to the self-cleaning effect. Such a unique textured surface imparts many promising potentials for engineering and the development of optics devices with robust superhydrophobic materials.     

Molecular fine structure and transition dipole moment of NO2 using an external cavity quantum cascade laser

Rotational vibrational fine structure and transition dipole moment of NO₂ is measured using Doppler free saturation spectroscopy with an external grating cavity quantum cascade laser (QCL). The QCL wavelength is calibrated using a 310 cm long internally coupled Fabry–Perot interferometer. We obtain a frequency splitting of 139.68 ± 0.06 MHz (0.0047 cm⁻¹) between the spin doublets (17) of 000 → 001 transition of NO₂. The resolution of the QCL based saturation spectrometer is limited by the QCL linewidth of 3.99 MHz ( 0.00013 cm⁻¹) deduced from the half width of the Lamb dips. The Lamb dip spectroscopy is utilized to obtain a vibrational dipole moment of 0.37 Debye for the (17) transitions.     

Isoconversional kinetics of degradation of polyvinylpyrrolidone used as a matrix for ammonium nitrate stabilization

Thermogravimetric analyzer (TGA) has been applied to measure the kinetics of the thermal degradation of virgin polyvinylpyrrolidone (PVP) and a phase stabilized PVP–ammonium nitrate (AN) material. The PVP–AN samples have been prepared by using 20 wt.% of AN and PVP of three different molecular weights. Virgin PVP undergoes a major mass loss in the region 380–550 °C leaving a small amount of nonvolatile residue. The application of an advanced isoconversional method to the respective degradation process demonstrates that its effective activation energy increases from 70 kJ mol⁻¹ to a plateau value at 250–300 kJ mol⁻¹, which is independent of the molecular weight. The PVP–AN materials lose spontaneously 20% of their mass on heating above the glass transition temperature of the PVP matrix (160–180 °C). After the escape of AN, the remaining PVP matrix degrades in the same temperature region as virgin PVP, however, the effective activation energy of this degradation is 150–200 kJ mol⁻¹.     

Dual electrochemical microsensor for simultaneous measurements of nitric oxide and oxygen: Fabrication and characterization

A planar-type amperometric dual microsensor was developed for the simultaneous measurement of the nitric oxide (NO) and oxygen (O₂) concentrations. The sensor (overall diameter = 500 μm) consisted of a dual working electrode (WE) containing two platinized platinum microdisks (25 μm diameter, WE1, WE2, distance between two disks > 330 μm) and a Ag/AgCl wire reference electrode covered with an expanded poly(tetrafluoroethylene) gas-permeable membrane. The differentiation and concurrent measurements of NO and O₂ were obtained successfully using two sensing WEs with different applied potentials (+0.75 V for WE1 and −0.4 V for WE2). Cross-talk between WE1 and WE2 was eliminated with an optimized internal solution composition. Linear dynamic range, selectivity, sensitivity, detection limit (<5 nM for NO; <500 nM for O₂), and stability (>50 h) were evaluated.     

Monoclinic iron hydroxy sulphate: A new route to electrode materials

The monoclinic form of FeOHSO₄ was prepared by dehydration of FeSO₄·7H₂O. We show that reversible insertion of up to 1Li/f.u. is possible in this compound at an average voltage of 3.2 V. The insertion/deinsertion is a biphasic process. The high voltage plateau, a reversible capacity of 110 mAh/g after 20 cycles and good cycling behavior make this compound an attractive positive electrode material for rechargeable Li-ion batteries, suggesting also that transition metal sulphates need to be explored.     

Transitions between P21, , and P6322 modifications of SrAl2O4 by in situ high-temperature X-ray and neutron diffraction

The results of in situ high-temperature X-ray and neutron powder diffraction experiments reconcile inconsistencies in previous reports on the symmetry of high-temperature phases of SrAl₂O₄. The material undergoes two reversible phase transitions and at 680 and 860 °C, respectively, and the latter one is experimentally observed and characterized for the first time. The higher symmetry above the transition is gained by disordering off-center split site of oxygen atoms around trigonal axis rather than by unbending Al–O–Al angle to the ideal value 180°. The analysis of the literature suggests that it is a common feature of the P6₃22 phases of stuffed tridymites.     

Photodegradation of poly(neopentyl isophthalate) part I: Laboratory and outdoor conditions

In this paper the mechanisms of photodegradation of poly(neopentyl isophthalate) (PNI) in laboratory (Suntest XXL+, λ > 300 nm) and outdoor conditions are compared. Changes in the chemical composition were studied with ATR-FTIR, SEC and MALDI-ToF MS. Furthermore, the results were compared with data presented in our previous paper on PNI coatings that were aged in the UVACUBE (λ > 254 nm). Two main aspects of photodegradation of PNI are addressed in the present paper: the influence of different wavelengths and the comparison of laboratory and outdoor exposure regarding the mechanism of degradation. Under short (λ > 254 nm) and long (λ > 300 nm) wavelength irradiation similar products of degradation are formed. However, the presence of short wavelength radiation dramatically accelerates the overall rate of photodegradation of PNI. UV light absorption calculations confirm this experimentally found acceleration. Exposure of PNI in laboratory and outdoor conditions, both with wavelengths λ > 300 nm resulted in similar degradation products in the initial stage of ageing.     

Copper(II) coordination compounds with ferulic acid

The first two molecular structures of the ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid, C₁₀H₁₀O₄) coordination compounds are presented, namely, [Cu₂(C₁₀H₉O₄)₄(CH₃CN)₂] 1 and [Cu₂(C₁₀H₉O₄)₄(C₆H₆N₂O)₂]·4CH₃CN (C₆H₆N₂O = nicotinamide) 2. Both compounds were synthesised from the starting mixture of Cu₂O and CuCl upon copper oxidation in the acetonitrile solution. The single-crystal X-ray diffraction analysis of 1 and 2 reveals the binuclear structure of the ‘paddle–wheel’ type for both complexes. 1 and 2 are unstable outside mother liquid due to loosely bound acetonitrile molecules. The final products of decomposition are [Cu₂(C₁₀H₉O₄)₄] 1a and [Cu₂(C₁₀H₉O₄)₄(C₆H₆N₂O)₂] 2a, which were characterized by several physico-chemical methods. The triplet X-band EPR spectra of 1a and 2a, showing signals B_Z1  15 mT, B₂  460 mT and B_Z2  580 mT, are in agreement with the expected data for the binuclear tetracarboxylate units, found in the structures of the parent complexes 1 and 2. Together with the room temperature magnetic susceptibility data, μ_eff/B.M. 1.40 (1a), 1.48 (2a), the EPR spectra analysis confirm the antiferromagnetic interaction in 1a and 2a. This is suggesting preservation and stability of the paddle–wheel structures in 1a and 2a.     

Molecular structure and conformation of diethylmethylamine determined by gas electron diffraction and vibrational spectroscopy combined with theoretical calculations

We have investigated the molecular structure and conformation of diethylmethylamine, C(4)H₃C(2)H₂N(1)[CH₃]C(3)H₂C(5)H₃, by gas electron diffraction and vibrational spectroscopy with the aid of theoretical calculations. Diffraction data are consistent with a conformational mixture of 35(14)% tt + 27(14)% g⁺t + 20(17)% g⁻t + 18(23)% g⁺g⁺ where the numbers in parentheses denote three times the standard errors (3σ). Normal-coordinate analysis based on B3LYP/6-311+G^** calculations supports the existence of the four conformers. The dihedral angle ₁(C4C2N1C3) (= −₂(C5C3N1C2)) of the tt conformer was 170(4)° whereas the ₁ and ₂ values of the other conformers were fixed at the B3LYP/6-311++G(2df,p) values: 72.4° and −163.3° for the g⁺t, −66.0° and −158.2° for the g⁻t, and 60.3° and 63.5° for the g⁺g⁺. Average values of the structural parameters (r_g/Å and _α/°) with 3σ are: r(N–C) = 1.462(2), r(C–C) = 1.523(3), r(C–H) = 1.113(2), CNC = 111.6(5), NCC = 114.5(5), NCH/CCH_Me = 110.6(5).     

Magnetic field effect on chemical compositions of spherical Fe/Co fine particles synthesized from a gaseous mixture of iron pentacarbonyl and cobalt tricarbonyl nitrosyl

Under UV light irradiation on a gaseous mixture of Fe(CO)₅ and Co(CO)₃NO, both the crystalline deposits with sizes of 5 and 18 μm and the spherical particles with a mean diameter of 0.3 μm were produced. From FT-IR spectra and SEM–EDS analysis, it was suggested that the chemical structure of the crystalline deposits was the one of Fe₂(CO)₉ being modified by involving Fe(CO)Co bond. By decreasing a partial pressure of Fe(CO)₅ to 0.5 Torr in the gaseous mixture, only the spherical aerosol particles could be produced. Chemical composition of the particles was rich in Co species. From the disappearance of bridging CO band in the FT-IR spectra of the particles and the appearance of CO bands coordinated to a metal atom, Fe atom in Fe(CO)₄ was suggested to be coordinated by the O atom in bridging CO bond in Co(CO)Co structure and/or in α-diketone structure which was formed from two CO groups in dicobalt species. Chemical compositions of the crystalline deposits and the spherical particles were influenced differently by the application of a magnetic field. Atomic ratio of Fe to Co atom decreased in the crystalline deposits whereas it increased in the spherical particles with increasing magnetic field up to 5 T. Linearly aggregated particles (i.e., particle wires) as long as 30 μm were produced on the front side of a glass plate placed at the bottom of the irradiation cell.     

An efficient biosurfactant-producing bacterium Pseudomonas aeruginosa MR01, isolated from oil excavation areas in south of Iran

A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in southern Iran. It was affiliated with Pseudomonas. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, MR01, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. Compositional analysis revealed that the extracted biosurfactant was composed of high percentages lipid (65%, w/w) and carbohydrate (30%, w/w) in addition to a minor fraction of protein (4%, w/w). The best production of 2.1 g/l was obtained when the cells were grown on minimal salt medium containing 1.2% (w/v) glucose and 0.1% (w/v) ammonium sulfate supplemented with 0.1% (w/v) isoleucine at 37 °C and 180 rpm after 2 days. The optimum biosurfactant production pH value was found to be 8.0. The MR01 could reduce surface tension to 28 mN/m and emulsified hexadecane up to E24  70. The results obtained from time course study indicated that the surface tension reduction and emulsification potential was increased in the same way to cell growth. However, maximum biosurfactant production occurred and established in the stationary growth phase (after 84 h). Fourier Transform Infrared spectrum of extracted biosurfactant indicates the presence of carboxyl, amine, hydroxyl and methoxyl functional groups. Thermogram of biosurfactant demonstrated three sharp endothermic peaks placing between 200 and 280 °C. The core holder flooding experiments demonstrated that the oil recovery efficiencies varied from 23.7% to 27.1% of residual oil.     

Effect of small amount of poly(ethylene naphthalate) on isothermal crystallization and spherulitic morphology of poly(trimethylene terephthalate)

The effect of a small amount of poly(ethylene naphthalate) (PEN) in its blends with poly(trimethylene terephthalate) (PTT) on isothermal melt-crystallization kinetics and spherulitic morphology of the blends was thoroughly investigated. The maximum PEN content in the blends was 9 wt%. Due to the single composition-dependent glass transition temperature (T_g) that was observed for each blend, these blends appeared to be miscible in the amorphous state. After isothermal crystallization from the melt state, the neat PTT and its blends with PEN exhibited either double or triple melting endotherms. The triple endothermic peaks were observed in both the neat PTT and the blends when being crystallized at crystallization temperatures (T_c) of less than or equal to 195 °C. The equilibrium melting temperature () for the neat PTT was determined based on the linear Hoffman–Weeks extrapolative method to be 248 °C. Such values for the blends were found to decrease with the addition and increasing amount of PEN. Both the neat PTT and the blends were isothermally crystallized over the T_c range of 190–205 °C. At a given T_c, the 97PTT/3PEN blend exhibited a half-time of crystallization (t_0.5) value that was lower, while it exhibited reciprocal half-time (), Avrami rate constant (K_A), and spherulitic growth rate (G) values that were greater, than those of the neat PTT. With further increase in the PEN content, the t_0.5 value increased, while the , K_A, and G values decreased. Analysis of the G values based on the Lauritzen–Hoffman's (LH) secondary nucleation theory showed that the neat PTT and the 91PTT/9PEN blend exhibited a regime II→III transition at 194 °C (467.2 K), while no regime transition was observed for the other two blends. The lateral and the fold surface free energies (σ and σ_e) and the work of chain folding (q) for the neat PTT and the blends were 19.4, 30.2–46.3 erg cm⁻², and 2.4–3.6 kcal mol⁻¹, respectively. Lastly, the effect of both the T_c and the PEN content on morphology and texture of the PTT spherulites was also investigated and the results showed that the texture of the spherulites became coarser with increasing T_c and PEN content.     

高热稳定性纳米Au/TiO2催化剂的制备与表征

 采用三嵌段共聚物聚乙醚-聚丙醚-聚乙醚EO20PO70EO20 (P123)为有机模板剂合成了介孔TiO2载体,用沉积-沉淀法制得Au/TiO2催化剂. 运用N2 吸附-脱附、 X射线衍射、 X射线光电子能谱和高分辨电镜技术对催化剂的结构与形貌进行了表征. 采用P123模板剂合成的TiO2具有较均匀的介孔结构,孔径集中在6.1 nm附近,负载金后,其介孔结构保持良好,但孔径下降至5.4 nm. 400 ℃焙烧后,介孔TiO2负载的Au催化剂中Au主要以金属态存在. 负载在三种TiO2载体(介孔TiO2、溶胶-凝胶法合成的TiO2和工业TiO2)上的Au晶粒大小和分散度差异较大,其中介孔TiO2载体更有利于金的分散,以该载体制备的催化剂400 ℃焙烧后金的晶粒尺寸在1～5 nm范围内,催化剂显示了很好的CO氧化活性和抗热稳定性,即使在420 ℃焙烧,其室温下CO的转化率也在90%以上. 而溶胶-凝胶法制备的TiO2和工业TiO2负载的纳米金催化剂中,金晶粒尺寸约为10 nm,催化剂的CO氧化活性和抗热稳定性较差.     

Negatively charged micelles directed synthesis of snow-ball flower like superparamagnetic Ni nanoparticles and investigation of their properties

Snow-ball flower like Ni nanoparticles have been synthesized using negatively charged micelles. Negatively charged micelles incorporate the Ni⁺² onto its head group by electrostatic attraction and again a surfactant layer is arranged on positively charged Ni and thus in a repetitive way layer-by-layer a snow-ball flower like structure is formed. After reduction of Ni⁺² to Ni atom by sodium borohydride and hydrated hydrazine the Ni clusters (3 nm) are formed and confined in micelles in snow-ball flower like pattern. The sizes of these nanoflowers are of 30 nm order. The particles are superparamagnetic in nature with blocking temperature about 117 K.     

A DFT study on the mechanism of the gas phase reaction of ground-state Y (4d5s,D) with 2-butyne

The reaction of ground-state Y with 2-butyne has been investigated in detail using B3LYP method. Four pathways for elimination of H₂ were identified. Two isomers, Y(HCCC)CH₃ and Y(H₂CCCCH₂) were assigned to the observed product, YC₄H₄. The calculated PESs suggest that the concerted H₂-elimination leading to Y(H₂CCCCH₂) + H₂ product is the most favorable pathway. For the elimination of CH₃, combining the results of this work with our previous study on Y + propyne reaction, a general mechanism for the reactions of Y with 2-alkynes bearing RCCCH₃ structure was established: Y + RCCCH₃ → π-complex → TS(H-migration) → HY(CH₂CC)R → TS (CC insertion) → (CH₂)HYCCR → TS(H-migration) → H₃CYCCR → CH₃ + YC₂R. Such mechanism was found to be always energetically more favorable than the direct sp–sp³ CC bond insertion mechanism. Further, such mechanism can also be applied to the elimination of CH₄ and it can be described as: Y + CH₃CCCH₃ → π-complex → TS (H-migration) → HY(H₂CCC)CH₃ → TS(CC insertion) → (H₂CCC)HYCH₃ → TS(H-migration) → CH₄ + YC₃H₂.     

Atmospheric chemistry of CF3CFCH2: Products and mechanisms of Cl atom and OH radical initiated oxidation

The products of Cl atom and OH radical initiated oxidation of CF₃CFCH₂ were studied in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The reactions of Cl atoms and OH radicals with CF₃CFCH₂ proceed via electrophilic addition to the double bond. The reaction with chlorine atoms proceeds 56 ± 5% via addition to the central carbon. The chlorine atom initiated oxidation of CF₃CFCH₂ gives CF₃C(O)F in a molar yield which is indistinguishable from 100% and independent of [O₂], and HC(O)Cl in a molar yield which increased from 30% to 59% as [O₂] was increased from 3 to 700 Torr. The OH radical initiated oxidation of CF₃CFCH₂ gives CF₃C(O)F as major product in a yield of 91 ± 6%. The results are discussed with respect to the atmospheric chemistry and environmental impact of CF₃CFCH₂.     

H NMR Dynamic study of thermal Z/E isomerization of 5-substituted 2-alkylidene-4-oxothiazolidine derivatives: Barriers to rotation about CC bond

The rotational barriers between the configurational isomers of two structurally related push–pull 4-oxothiazolidines, differing in the number of exocyclic CC bonds, have been determined by dynamic ¹H NMR spectroscopy. The equilibrium mixture of (5-ethoxycarbonylmethyl-4-oxothiazolidin-2-ylidene)-1-phenylethanone (1a) in CDCl₃ at room temperature to 333 K consists of the E- and Z-isomers which are separated by an energy barrier ΔG^# 98.5 kJ/mol (at 298 K). The variable-temperature ¹H NMR data for the isomerization of ethyl (5-ethoxycarbonylmethylidene-4-oxothiazolidin-2-ylidene)ethanoate (2b) in DMSO-d₆, possessing the two exocyclic CC bonds at the C(2)- and C(5)-positions, indicate that the rotational barrier ΔG^# separating the (2E,5Z)-2b and (2Z,5Z)-2b isomers is 100.2 kJ/mol (at 298 K). In a polar solvent-dependent equilibrium the major (2Z,5Z)-form (>90%) is stabilized by the intermolecular resonance-assisted hydrogen bonding and strong 1,5-type S · · · O interactions within the SCCCO entity. The ¹³C NMR Δδ_C(2)C(2′) values, ranging from 58 to 69 ppm in 1a–d and 49-58 ppm in 2a–d, correlate with the degree of the push-pull character of the exocyclic C(2)C(2′) bond, which increases with the electron withdrawing ability of the substituents at the vinylic C(2′) position in the following order: COPh COEt > CONHPh > CONHCH₂CH₂Ph. The decrease of the Δδ_C(2)C(2′) values in 2a–d has been discussed for the first time in terms of an estimation of the electron donor capacity of the S fragment on the polarization of the CC bonds.