共查询到20条相似文献,搜索用时 31 毫秒
1.
Ren A. Rozendal Emilie Leone Jürg Keller Korneel Rabaey 《Electrochemistry communications》2009,11(9):1752-1755
Hydrogen peroxide (H2O2) is an important industrial chemical, but its current production methods are highly energy-intensive. This study presents a novel process for the production of H2O2 based on the bioelectrochemical oxidation of wastewater organics at an anode coupled to the cathodic reduction of oxygen to H2O2. At an applied voltage of 0.5 V, this system was capable of producing 1.9 ± 0.2 kg H2O2/m3/day from acetate at an overall efficiency of 83.1 ± 4.8%. As most of the required energy was derived from the acetate, the system had a low energy requirement of 0.93 kWh/kg H2O2. 相似文献
2.
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. 相似文献
3.
Silver platinum binary alloys with compositions between about Ag2Pt98 and Ag95Pt5 at < 400 °C have largely not been observed in bulk due to the large immiscibility between these two metals. We present in this paper that Ag–Pt alloy nanostructures can be made in a broad composition range. The formation of Ag–Pt nanostructures is studied by powder X-ray diffraction (PXRD) and energy-dispersive X-ray (EDX). Our results indicate that lattice parameter changes almost linearly with composition in these Ag–Pt nanomaterials. In another word, lattice parameter and composition relationship follows the Vegard's law, which is a strong indication for the formation of metal alloys. Our transmission electron microscopy (TEM) study shows that the silver-rich Ag–Pt alloy nanostructures have spherical shape, while the platinum-rich ones possess wire-like morphology. The stability and crystal phase are investigated by annealing the alloy nanostructures directly or on carbon supports. 相似文献
4.
Chien-Te Hsieh Meng-Hsuan Lai Yu-Shun Cheng 《Journal of colloid and interface science》2009,340(2):237-242
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. 相似文献
5.
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. 相似文献
6.
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. 相似文献
7.
高热稳定性纳米Au/TiO2催化剂的制备与表征 总被引:3,自引:0,他引:3
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. 相似文献
8.
Tayebe Bagheri Lotfabad Mitra Shourian Reza Roostaazad Abdolhossein Rouholamini Najafabadi Mohammad Reza Adelzadeh Kambiz Akbari Noghabi 《Colloids and surfaces. B, Biointerfaces》2009,69(2):183-193
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. 相似文献
9.
Marta Sevilla Teresa Valds-Solís Pedro Tartaj Antonio B. Fuertes 《Journal of colloid and interface science》2009,340(2):230-236
A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO2–C–Fe3O4/γ–Fe2O3 samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g−1 for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field. 相似文献
10.
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 (Tg) 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 (Tc) 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 Tc range of 190–205 °C. At a given Tc, the 97PTT/3PEN blend exhibited a half-time of crystallization (t0.5) value that was lower, while it exhibited reciprocal half-time (), Avrami rate constant (KA), and spherulitic growth rate (G) values that were greater, than those of the neat PTT. With further increase in the PEN content, the t0.5 value increased, while the , KA, 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 σe) 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 Tc 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 Tc and PEN content. 相似文献
11.
Przemyslaw Malanowski Saskia Huijser Rolf A.T.M. van Benthem Leendert G.J. van der Ven Jozua Laven Gijsbertus de With 《Polymer Degradation and Stability》2009,94(11):2086-2094
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. 相似文献
12.
Daniel A. Caminos Edgardo N. Durantini 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):274-281
The interaction of amphiphilic cationic porphyrins, containing different patterns of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, with guanosine 5′-monophosphate (GMP) and calf thymus DNA have been studied by optical methods in phosphate buffer solution. The properties of these synthetic porphyrins were compared with those of representative standard of anionic 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS44−) and cationic 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TMAP4+). Stable complexes with GMP were found for cationic porphyrins, except for monocationic AB3+. The binding constant (KGMP 104 M−1) follows the order: A3B3+ ABAB2+ > A44+ TMAP4+. Also, interaction with DNA was observed for all evaluated cationic porphyrins. For these related cationic porphyrins, the binding constant (KDNA 105 M−1) increases with the number of cationic charges. On the other hand, the photodynamic activity of porphyrins was analyzed in solution of GMP and DNA. Monocationic AB3+ is a less effective sensitizer to oxidize GMP in comparison with the other cationic porphyrins, in agreement with the lack of detected interaction with this nucleotide. The electrophoretic analysis of DNA indicates that photocleavage takes place when the samples are exposed to photoexcited tricationic and tetracationic porphyrins. In the presence of sodium azide the DNA decomposition was diminished. Also, reduction in the DNA photocleavage was observed under anoxic condition, indicating that oxygen is essential for DNA photocleavage sensitized by these cationic porphyrins. In addition, an increase in DNA degradation was not observed in deuteriated water. Therefore, an important contribution of type I photoreaction processes could be occurring in the DNA photodamage sensitized by these cationic porphyrins. These results provide a better understanding of the characteristics needed for sensitizers to produce efficient DNA photocleavage. 相似文献
13.
K.S. Rutkowski S.M. Melikova P. Rodziewicz W.A. Herrebout B.J. van der Veken A. Koll 《Journal of Molecular Structure》2008,880(1-3):64
Solvent effect on the νc frequency of CH stretching vibration of the blue shifted F3CH…FCD3 complex has been studied in liquefied N2, CO, Ar, Kr and Xe. In the case of Xe, the spectroscopic measurements have also been extended to the solid state. It was found that the νc position of the complex in the solutions studied lowers with respect to the value in the gas phase. In liquid Xe, characterized by the largest permittivity, this effect reaches its maximum value of −14.5 cm−1. The νc frequency begins to grow again just below the freezing point of Xe, where a noticeable (15%) increase of the density of Xe occurs. The experimental results obtained for the liquid phase have been analyzed in the framework of the Onsager-like reaction field model and Polarizable Continuum Model (PCM) implemented into a standard Gaussian 98 Program. 相似文献
14.
A DFT computational study is performed on different Cp2TiIV(L,L′-BID) complexes with L,L′-BID = dioxolene, dithiolene or diselenolene. A fragment analysis of the titanocene-ligand bonding in the DFT optimized geometries showed that out of plane folding for maximum Ti ← L π donation increases Cp2TiIV(O,O′-BID) (35°) < Cp2TiIV(S,S′-BID) (43–49°) < Cp2TiIV(Se,Se′-BID) (48–53°). 相似文献
15.
K. Benthami S. Ait Lyazidi M. Haddad M. Choukrad B. Bennetau S. Shinkaruk 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):385-390
Genistein isoflavone is shown to exist in two different conformations which are the 90° completely twisted geometry and the 50° less twisted one. Specific interactions with the solvent cage as well as self-association processes seem shifting the isoflavone from the perpendicular conformation towards the less twisted one. The theoretical simulation, using analytical atom–atom pair potential, predicts a self-dimer in a slipped non-sandwich, face to river, perpendicular structure. From the UV–visible photophysics investigations it is revealed that monomeric species cannot exist alone even at very low solute concentration (10−6 M), the self-association process occurs already in this concentration range. 相似文献
16.
Hiroshi Morita Anzu Kasai Jan ubrt Zdenk Bastl 《Journal of photochemistry and photobiology. A, Chemistry》2009,206(2-3):205-212
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. 相似文献
17.
Robert Kun Sndor Tarjn Albert Oszk Torben Seemann Volker Zllmer Matthias Busse Imre Dkny 《Journal of solid state chemistry》2009,182(11):3076-3084
Nitrogen-doped TiO2 catalysts were prepared by a precipitation method. The samples were calcined at 400 °C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N2-adsorption was used for structural characterization and UV-diffuse reflectance (UV-DR) was applied to investigate the optical properties of the as-prepared samples. It was found that microporous N-doped catalysts have solely anatase crystalline structure. Acidic treatment of the calcined samples was performed using sulfuric acid agitation. The crystalline structure remained unchanged due to surface treatment, while the porosity and the surface areas were decreased dramatically. Optical characterization of the doped catalysts showed that they could be excited by visible light photons in the 400–500 nm wavelength range (λg,1=390 nm, λg,2=510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO2 powders. Finally the catalysts were tested in the photocatalytic degradation of phenol in aqueous suspensions. Two different light sources were used; one of them was a UV-rich high pressure Hg-lamp, while the other was a tubular visible light source. We found that using visible light illumination N-doped, acid treated TiO2 samples were more catalytically active than non-doped TiO2 catalysts. 相似文献
18.
Excitation spectra of Na fluorescence in mixtures with CF4 display a new band shifted by the energy of one-vibrational quantum of the IR active ν3-mode of CF4 (1281 cm−1) from Na 3d states. This band is attributed to a Na(3s)CF4(ν3 = 0) → Na(3d)CF4(ν3 = 1) transition and its intensity is explained by coupling with Na(4p)CF4(v3 = 0) resonance state which lies 180 cm−1 below in energy. An analogous satellite of the Na 6p state combined with the same vibration and lying close to the Na 7p state is reported and discussed. 相似文献
19.
X-ray diffraction study of supercooled water has been performed using an imaging-plate X-ray detector down to −15 °C. The peak at 10.8 Å, which grows with decreasing temperature, in the radial distribution function {D(r) − 4πr2ρ0} indicates the existence of clathrate-like structures in supercooled water. It is suggested that anomalous properties of water, which become more pronounced at low temperatures, are closely linked to the development of clathrate-like structures in water at low temperatures. 相似文献
20.
M. Anji Reddy V. Pralong V. Caignaert U.V. Varadaraju B. Raveau 《Electrochemistry communications》2009,11(9):1807-1810
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. 相似文献