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1.
Anatase TiO2 thin films with high optical modulation, better reversibility, fast switching time, and enhanced coloration efficiency were prepared by nebulized spray pyrolysis technique. X-ray diffraction study confirmed the formation of anatase phase TiO2 in the present work. This inference was substantiated from the Raman active modes of A1g, 2 B1g, and 3 Eg corresponding to O–Ti–O bond in TiO2. The PL emission peak observed at 400 nm is corresponds to the indirect transition (X1b?→?Γ3) from the conduction band to the valence band. The average reflectance of TiO2 thin films was varied from 31 to 20%. The electrochemical study revealed the excellent performance of TiO2 films with high optical modulation (ΔT?=?61%), fast switching kinetics (t b ?=?1.6 s, t c ?=?2.4 s), good coloration efficiency (100 cm2 C?1), and better reversibility (86%). The efficient electrochromic behavior of films may be due to the smooth microstructure nature, which provides an easy pathway for the diffusion and charge transfer process of Li+ ions in TiO2 film matrix. The fast transfer of Li+ ion was realized from the electrochemical impedance spectroscopic measurement.  相似文献   

2.
Calculations are made using the equations Δr G = Δr H ? TΔr S and Δr X = Δr H ? Δr Q where Δr X represents the free energy change when the exchange of absorbed thermal energy with the environment is represented by Δr Q. The symbol Q has traditionally represented absorbed heat. However, here it is used specifically to represent the enthalpy listed in tabulations of thermodynamic properties as (H T  ? H 0) at T = 298.15 K, the reason being that for a given substance TS equals 2.0 Q for solid substances, with the difference being greater for liquids, and especially gases. Since Δr H can be measured, and is tangibly the same no matter what thermodynamics are used to describe a reaction equation, a change in the absorbed heat of a biochemical growth process system as represented by either Δr Q or TΔr S would be expected to result in a different calculated value for the free energy change. Calculations of changes in thermodynamic properties are made which accompany anabolism; the formation of anabolic, organic by-products; catabolism; metabolism; and their respective non-conservative reactions; for the growth of Saccharomyces cerevisiae using four growth process systems. The result is that there is only about a 1% difference in the average quantity of free energy conserved during growth using either Eq. 1 or 2. This is because although values of TΔr S and Δr Q can be markedly different when compared to one another, these differences are small when compared to the value for Δr G or Δr X.  相似文献   

3.
Green fabricated nanoparticles often need to be encapsulated and stabilized, to ensure uniform dispersion in the aquatic environment and relevant larvicidal activity over time. However, recent research showed that nanoencapsulation processes led to a reduction of nanoparticle larvicidal efficacy. We used an extract of Argemone mexicana to reduce TiO2 nanoparticles, which were then capped with PSS/PAH (poly(styrene sulfonate)/poly(allylamine hydrochloride)). The toxic and repellent potential of the nanoparticles were compared to elucidate their potential effects against the Zika virus vector Aedes aegypti. Nanoparticles were characterized by biophysical methods including UV–Vis, EDX and FTIR spectroscopy, SEM, TEM, XRD and DLS analyses. In larvicidal and pupicidal experiments, TiO2 nanoparticles achieved LC90 values from 41.648 (larva I), to 71.74 ppm (pupa). Nanoencapsulated TiO2 achieved LC90 values from 39.16 (I), to 69.12 ppm (pupa). In adulticidal experiments, LC90 of TiO2 nanoparticles on Ae. aegypti was 10.31 ppm, while LC90 of nanoencapsulated TiO2 was 9.54 ppm. At 10 ppm, the repellency towards Ae. aegypti was 80.43% for TiO2 nanoparticles, and 88.04% for nanoencapsulated TiO2. This research firstly highlighted the promising potential of PSS/PAH encapsulation, leading to the production of highly effective titania nanostructures, if compared to titania nanoparticles synthesized with eco-friendly routes without further stabilization.  相似文献   

4.
Green synthesis of TiO2 nanoparticles (NPs) from Prunus × yedoensis leaf extract (PYLE), and their application for removal of phosphate and their antibacterial activity, were studied for the first time. NPs were obtained using a green chemistry approach from 0.1 M TiO2 and PYLE at ratio of 1:1 (v/w). Initial confirmation of production of TiO2 NPs was provided by a color change from white to light yellow, then calcination was performed at 500 °C for 1 h. The TiO2 NPs were characterized using various analytical techniques such as ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The results indicated that the optimal amount of TiO2 NPs for removal of phosphate was 10 mg/l (10 ppm) with duration of 25 min. Furthermore, the antibacterial activity of TiO2 NPs was also investigated using two different bacteria (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) in aqueous medium. The results revealed highly efficient sunlight-driven photocatalytic and antibacterial activity of TiO2 NPs.  相似文献   

5.
The isolated polystyrene chains spin-labeled with peroxide radical at the free end (IPSOO) in which the chain roots were covalently bonded to the surface of microcrystalline cellulose (MCC) powder were produced by mechanochemical polymerization of styrene initiated by MCC mechanoradicals. The IPSOO was used as motional probes at the ends of isolated polystyrene chains tethered on the surface of MCC powder. Two modes for the molecular motion of IPSOO were observed. One was a tumbling motion of IPSOO on the MCC surface, defined as a train state, and another was a free rotational motion of IPSOO protruding out from the MCC surface, defined as a tail state. The temperature of tumbling motion (T tum ) of IPSOO at the train state was at 90 K with anisotropic correlation times. T tum (90 K) is extremely low compared to the glass transition temperature (T g b ; 373 K) of polystyrene in the bulk. At temperatures above 219 K, the IPSOO was protruded out from the MCC surface, and freely rotated at the tail state. The train–tail transition temperature (T traintail ) was estimated to be 222 K. T tum (90 K) and T traintail (222 K) are due to the extremely low chain segmental density of IPSOO on the MCC surface under vacuum. The interaction between IPSOO and the MCC surface is a minor contributing factor in the mobility of IPSOO on the surface under vacuum. It was found that peroxy radicals are useful probes to characterize the chain mobility reflecting their environmental conditions.  相似文献   

6.
Structure and dynamics of a free aquaporin (AQP1) are studied by a coarse-grained Monte Carlo simulation as a function of temperature using a phenomenological potential with the input of a knowledge-based residue–residue interaction. Response of the radius of gyration (R g) of the protein to the temperature (T) is found to be nonlinear: Decay of R g at T ≤ T c is followed by a continuous increase at T ≥ T c before reaching its saturation. In thermo-responsive regime, the protein exhibits segmental globularization with the persistence of three regions along its sequence involving residues 1M–25V and 250V–269K toward the beginning and end segments with a narrow intermediate region around 155A–163D. A detail analysis of the structure factor S(q) shows a global random coil conformation at high temperatures with an effective dimension D e ~ 1.74 and a globular structure (D e ~ 3) at low temperatures. In thermo-responsive regime, the variation of S(q) with the wave vector q reveals a systematic redistribution of self-organizing residues (in globular and fibrous sections) that depends on the length scale and the temperature.  相似文献   

7.
Orthovanadate ErVO4 has been prepared by solid-phase synthesis from a stoichiometric mixture of high pure V2O5 and chemically pure Er2O3 by multistage calcination in air in the temperature range 873–1273 K. The effect of temperature (380–1000 K) on the heat capacity of orthovanadate ErVO4 was studied by hightemperature calorimetry. Thermodynamic properties of erbium orthovanadate (enthalpy change H°(T)–H°(380 K), entropy change S°(T)–S°(380 K), and reduced Gibbs energy Φ°(T)) have been calculated from the experimental Cp = f(T) data. It has been shown that the specific heat varies in a row of oxides and orthovanadates of Gd-Lu naturally depending on the radius of the R3+ ion within the third and fourth tetrads.  相似文献   

8.
In this work, we have prepared Al-doped TiO2 nanoparticles via a hydrothermal method and used it for making photoanode in dye-sensitized solar cell (DSSC). Material characterizations were done using XRD, AFM, SEM, TEM and EDAX. XPS results reveal that Al is introduced successfully into the structure of TiO2 creating new impurity energy levels in the forbidden gap. This resulted in tuning of the conduction band of TiO2 and reduced charge recombination which led to better current conversion efficiency of DSSC. Greater dye loading and enhanced surface area was obtained for Al-doped TiO2 compared to un-doped TiO2. I-V analysis, EIS and Bode plots are employed to evaluate photovoltaic performance. The short-circuit current density (J sc) and efficiency (η) of cell employing Al-doped TiO2 photoanode were extensively enhanced compared to the cell using un-doped TiO2. The optical band gap (E g) for Al-doped and un-doped TiO2 was obtained as 2.8 and 3.2 eV, respectively. J sc and η were 13.39 mAcm?2 and 4.27%, respectively, under illumination of 100 mWcm?2 light intensity when thin films of 1% Al-doped TiO2 was employed as photoanode in DSSC using N719 as the sensitizer dye. With the use of un-doped TiO2 as photoanode under similar conditions, J sc 5.12 mAcm?2 and η 1.06% only could be obtained. The maximum IPCE% obtained with Al-doped TiO2 and un-doped TiO2 was 67 and 38% respectively at the characteristic wavelength of dye (λ max = 540 nm). The EIS analyses revealed resistive and capacitive elements that provided an insight into various interfacial processes in terms of the charge transport. It was observed that Al-doping reduced the interfacial resistance leading to better charge transport which has improved both photocurrent density and conversion efficiency. Higher electron mobility and fast diffusion resulting in greater charge collection efficiency was obtained for Al-doped TiO2 compared to the un-doped TiO2. Using the Mott–Schottky plot, the donor density was calculated for un-doped and Al-doped TiO2. The work demonstrated that the Al-doped TiO2 is potential photoanode material for low-cost and high-efficiency DSSC.  相似文献   

9.
The expansion of an oxygen low-pressure microwave plasma was investigated in order to determine the optimal plasma parameters for the growth of functional oxide semiconductors. Langmuir probe measurements show that the electron density (n e ) increases with the injected power up to a saturation value of 3.0 × 109 cm?3 determined at 10 mTorr while electron temperature (T e ) remains constant at a value of 1.5 eV. When pressure is varied, n e shows a maximum value at a range from 12 to 20 mTorr while T e decreases monotonously with increasing pressure. In addition, both n e and T e decrease with the axial distance from the plasma source. These effects were discussed through the loss mechanisms in the remote plasma. For a pressure of 13 mTorr and at a substrate temperature of 500 °C, plasma enhanced oxidation of pure metallic Ti thin films lead to the formation of a pure TiO2 anatase phase compared to a mixed phase of TiO2 and TiO in the absence of plasma activation. For Mn thin films, the exposure to oxygen remote plasma led to the formation of MnO2 as opposed to obtaining Mn3O4 when oxidation is performed in the oxygen gas ambient. Remote plasma processing was thus found to provide selective pathways to control oxidation states, stoichiometry and phase composition of technologically attractive oxide thin films.  相似文献   

10.
Densities for aqueous solutions of magnesium tetraborate MgB4O7(aq) at the molalities of (0.00556–0.03341) mol·kg?1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K from 283.15 to 363.15 K and 0.1 MPa. Apparent molar volumes were obtained based on the experimental density data, and the 3D diagrams of the apparent molar volume (V ? ) of MgB4O7(aq) against temperature (T) and molality (m) were plotted. On the basis of the Vogel–Tamman–Fulcher equation, the coefficients of the correlation equation for densities of MgB4O7(aq) against temperature and molality were parameterized. According to the Pitzer ion-interaction model of the apparent molar volume, the temperature correlation equations of Pitzer single-salt parameters F(i,p,T)?=?a0?+?a1?×?T?+?a2?×?T 2?+?a3/T?+?a4?×?ln(T)?+?a5?×?T 3 (where T is temperature in Kelvin, a i are model parameters) for MgB4O7 were obtained for the first time.  相似文献   

11.
The temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph3Sb(OC(O)Ph)2 is studied in the range of 6–480 K by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry. The melting of the compound is observed in this temperature range, and its standard thermodynamic characteristics are identified and analyzed. Ph3Sb(OC(O)Ph)2 is obtained in a metastable amorphous state in a calorimeter. The standard thermodynamic functions of Ph3Sb(OC(O)Ph)2 in the crystalline and liquid states are calculated from the obtained experimental data: Cp°(T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) for the region from T → 0 to 480 K. The standard entropy of formation of the compound in the crystalline state at T = 298.15 K is determined. Multifractal processing of the low-temperature (T < 50 K) heat capacity of the compound is performed. It is concluded that the structure of the compound has a planar chain topology.  相似文献   

12.
Thermal analysis on organically modified Ca2+-montmorillonite (OMON) and its source materials—octadecylamine (ODA) and Ca2+-montmorillonite (Ca2+-Mon)—was studied using thermally stimulated current (TSC) technique. The appearance of ρ MON peak with the T max = 75 °C shows the ability of the developed TSC system to demonstrate the relaxation effects of dehydration in Ca2+-Mon. It appeared within the temperature range of DSC endothermic peak (30–100 °C) where the T mMON = 58 °C. Segmental motions of ODA chains and structural disruptions in the modifier agent compound produced TSC α ODA, ρ ODA and ρ 1ODA peaks that are comparable to thermal transition and endothermic peaks in DSC profile (T gODA, T m1ODA and T m2ODA). The effect of localized motion in ODA chains as revealed by the TSC βOMON peak (T max = ?23 °C), however, is absent in the DSC profile of OMON. It shows TSC technique has high sensitivity in detecting various relaxation behaviors at molecular level. More evidences are demonstrated by the ρ OMON (T max = 86 °C) and ρ 1OMON (T max = 105 °C) peak originated from the ODA chains structures. These peaks also confirm the intercalation of the modifier cations inside the Ca2+-Mon gallery.  相似文献   

13.
Temperature dependences of the heat capacity of new zincate-manganites of LaM2IIZnMnO6 (MII = Mg, Ca, Sr, Ba) composition are studied via experimental calorimetry in the interval of 298.15–673 K. It is found that all compounds have λ-shape effects on the curve of dependence Cp° ~ ?(T) with respect to phase transitions of the second kind. Equations for the temperature dependence of the heat capacity are derived with allowance for phase transition temperatures, and thermodynamic functions H°(T) ? H°(298.15), S°(T) and Φxx(T) are calculated on the basis of experimental data on Cp°(T) and the calculated S°(298.15) value.  相似文献   

14.
Densities ρ and viscosities η were measured for the binary mixtures of ethylenediamine (EDA) and ethylene glycol (EG) in the temperature range 288.15–323.15 K for ρ and at 273.15–323.15 K for η, both of which are broader temperature ranges than those reported previously. The value of ρ monotonously decreases against the mole fraction of EDA, x EDA, and increasing temperature. The concentration dependence of η exhibits a maximum in the intermediate concentration range at all temperatures measured. The glass transition temperature, T g, for samples with x EDA < 0.7 was measured using differential scanning calorimetry. The measured T g values show a peak in the intermediate concentration range, which is a behavior similar to that of η; however, the peak concentrations for η and T g did not precisely align because of a deviation in the maximum hydrogen-bond density. The partial molar volumes for EDA and EG and the thermal expansivities, α, were obtained from ρ. Results in the present study are discussed in terms of the extensively increasing hydrogen-bond density for polyamine–polyhydric alcohol systems.  相似文献   

15.
With the Gibbs free energy method, we determine the molar fraction in a plasma at and out of thermal equilibrium consisting of air and aluminum for several percentages in the temperature range of 500–6000 K. We take three temperatures into account (T rot  = T h ; T vib ; T ex  = T e ). We indicate the formulae and the numerical method used to perform the calculation taking three condensed phases AlN, Al, Al2O3 into account. We show that the air percentage plays a major role to create these phases. We clarify the role plays on the vaporization temperatures and on the sublimation temperature by the non-thermal equilibrium of the plasma. This kind of plasma is found in arc roots, near a wall, in plasmas with a high value of electrical field,… The influence of the pressures until 30 × 105 Pa. is shown on molar fraction of the chemical species, on the vaporization temperatures and on the sublimation temperature. The vaporization temperatures are given versus the thermal non equilibrium versus various mixtures (air, aluminum) and versus the pressures (105 Pa–30 × 105 Pa).  相似文献   

16.
Linear isotherm regularity works very well for fluids at high densities, and it has been shown that it is compatible with the EOSs based on statistical–mechanical theory. On the other hand, at low densities, the first few terms of virial EOS have the most contribution to express the deviations from ideal behavior. For finding similarities between dense and dilute states, experimental pvT data of 14 fluids (He, Ne, Ar, Kr, H2, O2, N2, CO, NH3, CH3OH, CH4, C2H4, C2H6 and C3H8) are examined. Comparing the thermal dependencies of the attraction and repulsion terms (A and B) of the LIR with the second and third virial coefficients (B 2 and B 3) in liquid and supercritical regions (0.7 < T r < 3.0) shows a remarkable similarity. Square-well potential is applied to examination and comparison of theoretical results with experimental results. It is shown that in liquid and supercritical regions, (1) the short-range potential governs among particles in dense fluids, and the long-range interactions become important in the less dense fluid, (2) similar to Boyle temperature, T B, in dilute state, there is a temperature as TB (in dense fluids) that the attractive forces and the repulsive forces acting on the dense-fluid particles balance out; thus, probably there is a maximum σ (molecular diameter) at nearly 2T c (TB), and (3) in the liquid and supercritical regions (0.7 < T r < 3.0), in the first-order approximation, there are no significant interactions higher than triple interactions in dense-fluid particles.  相似文献   

17.
With urea as nitrogen source, N-doped TiO2 powders were synthesized and fabricated for low-temperature dye-sensitized solar cells (DSSCs) by the method of doctor-blade, and the highest temperature of the whole process was 120 °C. SEM, TEM, XRD, DRS, and XPS were used to analyze the microstructure of the N-doped TiO2 powders. EIS, Bode plot, UV–Vis and IV were employed to measure the photovoltaic performance of the DSSCs. The maximum photoelectric conversion efficiency (η) was 5.18 % when the amount of the doped nitrogen was 4 %, and, when compared with the η of 4.22 % for pure TiO2, the short circuit current was increased by 22.2 % and the efficiency was increased by 22.7 %. It has been shown that the doped nitrogen could effectively suppress TiO2 crystal phase transition from anatase to rutile, and decrease the size of particles. Therefore, the increased photoelectric conversion efficiency of the N-doped TiO2-based DSSC was ascribed to the more suitable crystal phase, sizes and inner structure.  相似文献   

18.
Molecular properties are computed as responses to perturbations (energy derivatives) in coupled-cluster (CC)/many-body perturbation theory (MBPT) models. Here, the CC/MBPT energy derivative with respect to a general two-electron (2-e) perturbation is assembled from gradient theory for 2-e property evaluation, including the electron repulsion energy. The correlation energy (?E) is shown to be the sum of response kinetic (?T), electron–nuclear attraction (?V), and electron repulsion (?V ee ) energies. Thus, evaluation of total V ee for energy component analysis is simple: For total energy (E), total 1-e responses T and V, and nuclear–nuclear repulsion energy (V NN ), V ee  = E ? V NN  ? T ? V is the true 2-e response value. Component energy analysis is illustrated in an assessment of steric repulsion in ethane’s rotational barrier. Earlier SCF-based results (Bader et al. in J Am Chem Soc 112:6530, 1990) are corroborated: The higher-energy eclipsed geometry is favored versus staggered in the two repulsion energies (V NN and V ee ), while decisively disfavored in electron–nuclear attraction energy (V). Our best quality calculations (CCSD/cc-pVQZ) attain practical Virial Theorem compliance (i.e., agreement among the kinetic energy, potential energy, and total energy representations) in assigning 2.70 ± 0.06 to the barrier height; ?195.80 kcal/mol is assigned to the drop in “steric” repulsion upon going to the eclipsed geometry. Steric repulsion is not responsible for any fraction of the ~3 kcal/mol barrier.  相似文献   

19.
In treating the experimental data on the heat capacity of solids, the essence of any model application is in the searching for the scaling factors (k i or 1/Θi) which transform a set of independent functions C P,i(T) for every substance into a function C P(T·k i) universal for the particular set of substances. DSC heat capacities of I–III–VI2 compounds at elevated temperatures exceed the upper limit of 12R (3R per mole of atoms) and make impossible application of any model. Nevertheless, the temperature scaling of heat capacity can be solved as a pure mathematical problem without any physical model (theory). The benefits of the model-free scaling are illustrated with the case of four isostructural chalcogenides (LiInS2, LiInSe2, LiGaS2, and LiGaSe2) measured recently with DSC in a temperature range from 180 to 460 K. The upper limit of C P(T·k i) functions was expanded up to 635 K. Low-temperature heat capacity of LiInSe2 published in 1995 made it possible to derive the thermodynamic functions (enthalpy and entropy) for LiInS2 (0–590 K), LiGaS2 (0–640 K), and LiGaSe2 (0–490 K) and expand those data for LiInSe2 from 300 to 460 K.  相似文献   

20.
The heat capacity and the temperatures and enthalpies of physical transformations of the alternating terpolymer of carbon monoxide, ethylene, and 1-butene (the content of butene units is 10.7 mol.%) were studied by adiabatic and differential scanning calorimetry in the temperature range from 6 to 520 K. The energy of terpolymer combustion was measured at 298.15 K on an calorimeter with an isothermal shell and static bomb. The standard thermodynamic functions C°p(T), H°(T)–H°(0), S°(T)–S°(0), and G°(T)–H°(0) for the range from Т → 0 to 400 K, the standard enthalpy of combustion, and the thermodynamic parameters of formation of the partially crystalline CO—ethylene—1-butene terpolymer at 298.15 K, as well as the thermodynamic characteristics of its synthesis in the range from T → 0 to 400 K were calculated.  相似文献   

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