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1.
K. P. Singh Harshit Agarwal Vivek Kumar Shukla Isht Vibhu Manisha Gupta J. P. Shuka 《Journal of solution chemistry》2010,39(11):1749-1762
Measurements of the ultrasonic velocity (u), density (ρ) and refractive index (n) for binary mixtures of polyethylene glycol 250 dimethyl ether with 1-propanol and 1-butanol have been made at three temperatures
(T=293, 303 and 31 K) over the entire composition range in order to investigate the nature of intermolecular interactions between
the components of these liquid mixtures. Various excess thermodynamic properties such as the excess ultrasonic velocity (Δu), deviation in isentropic compressibility (Δk
S
), excess intermolecular free length (LfE)(L_{\mathrm{f}}^{\mathrm{E}}), excess acoustic impedance (Z
E), excess pseudo-Grüneisen parameter (Γ
E), and molar refraction deviation (ΔR
m) were calculated using experimental values of the ultrasonic velocity, density and refractive index and were then represented
with the Redlich-Kister polynomial equation. The observed excess deviation parameter values were explained on the basis of
the strength of intermolecular interactions between the components of the mixtures. Estimations of the refractive index and
ultrasonic velocity have also been made using various empirical relations and are discussed in terms of the average percentage
deviations (APD). 相似文献
2.
Jaka Horvat Marija Bešter-Rogač Cveto Klofutar Darja Rudan-Tasic 《Journal of solution chemistry》2008,37(9):1329-1342
The viscosities of aqueous solutions of lithium, sodium, potassium, rubidium and caesium cyclohexylsulfamates were measured
at 293.15, 298.15, 303.15, 313.15 and 323.15 K. The relative viscosity data were analyzed and interpreted in terms of the
Kaminsky equation, η
r=1+Ac
1/2+Bc+Dc
2. The viscosity A-coefficient was calculated from the Falkenhagen-Dole theory. The viscosity B-coefficients are positive and relatively large. Their temperature coefficient ∂
B/∂
T is negative or near zero for lithium and sodium salts whereas for potassium, rubidium and caesium salts it is positive. The
viscosity D-coefficient is positive. This was explained by the size of the ions, structural solute–solute interactions, hydrodynamic
effect, and by higher terms of the long-range Debye-Hückel type of forces. From the viscosity B-coefficients the thermodynamic functions of activation of viscous flow were calculated. The limiting partial molar Gibbs
energy of activation of viscous flow of the solute was divided into contributions due to solvent molecules and the solute
in the transition state. The activation energy of the solvent molecules was calculated using the limiting Gibbs energy of
activation for the conductance of the solute ions. The activation energy of the solvent molecules was then discussed in terms
of the nature of the alkali-metal ions and their influence on the structure of water. The limiting activation entropy and
enthalpy of the solute for activation of viscous flow were interpreted by ion-solvent bond formation or breaking in the transition
state of the solvent. The hydration numbers of the investigated electrolytes were calculated from the specific viscosity of
the solutions. 相似文献
3.
In this work, we examined the role of a non-ionic surfactant, Tween 20, on enzymatic hydrolysis of lignocelluloses. Delignified
lignocelluloses (pine wood chip) were used as model substrates. Effects of Tween 20 on adsorption/desorption onto/from lignocelluloses
with and without hydrolysis were evaluated respectively. Tween 20 lowered the non-biospecific adsorption of β-glucosidase and enhanced the bio-specific adsorption of cellulase. Tween 20 did not affect the liquid phase reaction (cellobiose
hydrolysis). However, for the solid surface reaction (cellulose hydrolysis), cellulose conversion for 72 hrs was increased
9–21% and 1–8.5% for samples with high lignin contents (PI) and low lignin contents (PIII) by injection of Tween 20 (0.024–0.24 mM),
respectively. Moreover, Tween 20 increased the cellulose conversion rate substantially. It is suggested that the increase
of cellulase amount adsorbed due to the increase of effective cellulose surface by Tween 20 contribute to the enhancement
of cellulose conversion. 相似文献
4.
Complexes of copper(II) with a number of polyphosphate and polymetaphosphate anions have been studied in aqueous solutions
by potentiometric, spectroscopic and theoretical methods. Stability constants of the complexes have been determined as well
as their coordination modes. Results of the equilibrium studies provided evidence for the formation of ML, MHL and ML(OH)
x
type complexes with the ligands studied. The length of the polyphosphate chain was found to affect the oxygen atom charge
that is reflected in the stability constants of the ML type complexes. Moreover, the stability of the complex is also influenced
by the spatial arrangement of the phosphate groups in phosphates and metaphosphates. The spectral parameters observed for
certain complexes have permitted us to deduce the inner coordination sphere of the studied complexes. 相似文献
5.
Yonit Sembira-Nahum Alexander Apelblat Emanuel Manzurola 《Journal of solution chemistry》2008,37(3):391-401
Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes,
V
2,φ
(m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂
C
p
/∂
p)
T,m
. They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate
are present. 相似文献
6.
Xiao-Hui Wang Hong-Shang Peng Wei Yang Zhao-Di Ren Yuan-An Liu 《Mikrochimica acta》2016,183(10):2723-2731
We report on a novel kind of mitochondria-targeted theranostic nanoparticles (NPs). The NPs are doped with the oxygen-sensitive probe Pt(II)-porphyrins (PtTFPP) which exerts a dual role in acting as a diagnostic tool that can sense oxygen via quenching of luminescence, but also acts as an agent in photodynamic therapy (PDT) of cancer. In addition, it allows therapeutic efficacy to be assessed in-situ. Upon appropriate high-energy photoirradiation, the NPs generate singlet oxygen by energy transfer from triplet PtTFPP to ground state oxygen, and cell death is induced via PDT. Under low-energy light irradiation, in contrast, the NPs can be utilized to detect oxygen consumption rate via time-resolved luminescence measurements in order to study the efficacy of PDT. This is the first report where a single nanoagent is used to stimulate PDT and also to assess the efficacy of PDT. In our perception, the method provides a promising platform for testing anti-cancer drugs. 相似文献
7.
Heats of solution, Δsol
H
m
, of L-cysteine, L-serine and L-asparagine amino acids have been measured at different concentrations of aqueous ethanol,
propanol and 2-propanol at 298.15 K using solvation calorimetry. These data are compared with the results reported earlier
for L-alanine in ethanol. The enthalpic coefficients, h
xy
, of the solute-organic cosolvent pair interaction in water have been obtained from the McMillan-Mayer approach and the data
have been interpreted in terms of various interactions and changes in solvent structure. 相似文献
8.
Rabindra N. Roy Lakshmi N. Roy Michael S. Fuge Chandra N. Roy Curtis A. Himes Paul A. Bryant Kyle T. Robinson Daniel A. Kaufmann II Colby H. Grove Toshi Gosh Adonis Bwashi 《Journal of solution chemistry》2009,38(4):471-483
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over
the temperature range 5 to 55 °C including 37 °C. This paper reports the pa
H values of four chloride ion free buffer solutions and eight buffer solutions with I=0.16 mol⋅kg−1, matching closely that of the physiological sample. Conventional pa
H values for all twelve buffer solutions from 5 to 55 °C are reported. The residual liquid-junction potential correction for
two widely used temperatures, 25 and 37 °C, has been made. The flowing-junction calomel cell method has been utilized to measure
E
j
, the liquid-junction potential. The operational pH values for four buffer solutions at 25 and 37 °C are calculated using
the physiological phosphate buffer standard based on the NBS/NIST convention. These solutions are recommended as pH standards
in the pH range of 6.8 to 7.2 for physiological fluids. 相似文献
9.
David Reinhoudt 《Supramolecular chemistry》2016,28(5-6):342-350
AbstractDuring the Calix2015 conference that took place in Giardini Naxos in July of this year, the first C. David Gutsche Award for Calixarene Chemistry was awarded to one of the founders of the field, Professor Rocco Ungaro of the University of Parma. In this paper, Rocco Ungaro’s seminal contributions to the field are described. His collaborations with many other groups, his role in the European supramolecular chemistry community and his most important scientific results are briefly summarised. 相似文献
10.
Júlia Ričanyová Renata Gadzała-Kopciuch Katarina Reiffova Yaroslav Bazel Bogusław Buszewski 《Adsorption》2010,16(4-5):473-483
The use of a novel procedure of solid-phase extraction with molecularly imprinted polymers (MISPE) has been described. A MISPE procedure relying on tailor-made, artificial-mimic materials capable of selectively rebinding target analytes (steroids) based on a combination of recognition mechanisms, such as size, shape and functionality, was custom designed for progesterone and testosterone. The combination of MISPE with LC/DAD is a simple and an efficient method for the determination and quality control of progesterone and testosterone in human urine samples. 相似文献
11.
Lakshmi N. Roy Rabindra N. Roy Sean R. LeNoue Cole E. Denton Michael S. Fuge Craig D. Dunseth Chandra N. Roy Shawn M. Hayden Joshua T. Wollen Kripa Sreepada 《Journal of solution chemistry》2009,38(4):459-469
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already
been reported over the temperature range 5 to 55 °C including 37 °C. This paper reports the pH values of four NaCl-free buffer
solutions and four buffer composition containing NaCl salt at I=0.16 mol⋅kg−1. Conventional pa
H values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions
recommended as pH standards, at 25 and 37 °C after correcting the liquid junction potentials with the flowing junction cell. 相似文献
12.
Leydi Erika Sarmiento Mildred Rodríguez Lorenzo Echevarria Vito Lubes 《Journal of solution chemistry》2010,39(10):1484-1491
The complex species formed between vanadium(III) and 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), and 8-hydroxyquinoline
(8hq) were studied in aqueous solution by means of electromotive forces measurements, emf(H), at 25 °C with 3.0 mol⋅dm−3 KCl as the ionic medium. The potentiometric data were analyzed using the least-squares computational program LETAGROP, taking
into account the hydrolytic vanadium(III) species formed in solution. Analysis of the vanadium(III)–phen system data shows
the formation of [VHL]4+, [V(OH)L]2+, [V2OL2]4+ and [V2OL4]4+ complexes. In the vanadium(III)–bipy system the [VHL]4+, [V(OH)L]2+, [V2OL2]4+ and [V2OL4]4+ complexes were observed, and in the vanadium(III)–8hq system the complexes [V(OH)L]+, [V(OH)2L], [VL2]+ and [VL3] were detected. 相似文献
13.
Fluorescence emission spectroscopy have been used to investigate the effects of electrolytes on the excited state intramolecular
charge transfer (ICT) reaction in 4-(1-azetidinyl)benzonitrile (P4C) in very dilute to concentrated electrolyte solutions
of ethyl acetate (EA), acetonitrile (AN) and ethanol (EtOH). In the limit of very low electrolyte concentrations, the reaction
rate (=1/τ
rxn, τ
rxn being the reaction time) is found to decrease with increasing electrolyte concentration, the extent of decrease being the maximum in EA and the minimum in AN. At moderate
to higher electrolyte concentrations, however, the rate increases upon further addition of electrolyte. The observed non-monotonic
electrolyte concentration dependence of rate is believed to occur due to a novel interplay between friction and solvation
experienced by the photo-excited reactant in solution. Moreover, the long time decay constant and amplitude of the bi-exponential
decay of the time resolved fluorescence emission intensity also show a significant electrolyte concentration dependence which
corroborates the relevant steady-state results.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
14.
Zhongyong Zha Dingna Wang Wei Hong Li Liu Sai Zhou Xiaojie Feng Bing Qin Jianmei Wang Yi Yang Liang Du Dong Zhang Zhendong Fang Chuanqin Xia 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):257-262
This study aimed at influence of europium speciation on its accumulation in Brassica napus (CK) and over-expressing BnTR1 lines (OE), and the kinetics of Eu uptake were investigated. These results indicated that the uptake in the roots of OE was higher than that of CK at high concentrations of europium and even the enrichment in the roots of OE was as high as 20,000 mg/kg at 328.9 μΜ Eu, this suggested that OE might have better resistance to uranium than CK. The time kinetics in plants showed that there had the similar trend between CK and OE. The formation of Eu3+at pH 5 in deionized water was beneficial to plants enrichment Eu and carbonate could reduce the adsorption of Eu in two group and phosphate almost completely impress the adsorption of Eu in two group, but citric acid could enhance europium root-to-shoot translocation in two group. These results would help understanding the mechanism of Eu uptake in Brassica napus (CK) and over-expressing BnTR1 lines (OE), therefore properly developing efficient europium/americium phytoremediation. 相似文献
15.
Sulfoxides are reduced by a combination of sodium borohydride, a catalytic amount of cobalt(II) chloride hexahydrate, and chromatographic neutral alumina preloaded with a small amount of water (moist alumina) in hexane to produce the corresponding sulfides in good to excellent yields under mild conditions. An interesting structural influence of sulfoxides on their reactivity is observed.
16.
A. F. Fucaloro K. Dewey G. Fan K. Imuta D. Jensen M. Muranaka 《Journal of solution chemistry》2008,37(9):1289-1304
The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine,
at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil
and thymine are less than in pure water. 相似文献
17.
Raphael da C. Cruz Rosana J. Martins Márcio J. E. de M. Cardoso Oswaldo E. Barcia 《Journal of solution chemistry》2009,38(8):957-981
Density measurements were made for binary aqueous solutions of polyethylene glycol at seven temperatures: 283.15, 288.15,
293.15, 298.15, 303.15, 308.15, and 313.15 K. Polyethylene glycol samples with nominal average molar masses of 3000 g⋅mol−1 (PEG 3000), 6000 g⋅mol−1 (PEG 6000), 10000 g⋅mol−1 (PEG 10000) and 20000 g⋅mol−1 (PEG 20000) were used. These results were used to determine the specific volumes of solutions with solute-to-solvent mass
ratios (mass of the solute/mass of the solvent) in the range 0.0546 to 1.4932 for PEG 3000, from 0.0553 to 1.4986 for PEG
6000, from 0.0552 to 1.2241 for PEG 10000, and from 0.0530 to 1.2264 for PEG 20000. The differences between the specific volume
of a solution and the specific volume of the pure solvent, at a given temperature, were represented by a virial-type equation
in terms of solute concentration. The first-order coefficient of the expansion is the partial specific volume of the solute
at infinite dilution. The higher-order coefficients are related to the contribution of pairs, triplets, and higher-order solute
aggregates, according to the Constant-Pressure Solution Theory. The functional dependence of the virial coefficients upon
temperature is discussed in terms of solute-solute and solute-solvent interactions. The effect of the PEG molar mass on the
partial specific volume of solute at infinite dilution, as well as the contributions of pairs of solute molecules to the solution
volume, are also investigated. The apparent specific volume, apparent specific expansibility, apparent specific expansibility
at infinite dilution and virial coefficients of the apparent specific expansibility are also presented. 相似文献
18.
Gas adsorption process in activated carbon over a wide temperature range above the critical point. Part 1: modified Dubinin-Astakhov model 总被引:1,自引:1,他引:0
Simulations of the thermal effects during adsorption cycles are valuable tools for the design of efficient adsorption-based
systems such as gas storage, gas separation and adsorption-based heat pumps. An analytical representation of the measured
adsorption data over the wide operating pressure and temperature swing of the system is necessary for the calculation of complete
mass and energy conservation equations. In Part 1, the Dubinin-Astakhov (D-A) model is adapted to model hydrogen, nitrogen,
and methane adsorption isotherms on activated carbon at high pressures and supercritical temperatures assuming a constant
microporous adsorption volume. The five parameter D-A type adsorption model is shown to fit the experimental data for hydrogen
(30 to 293 K, up to 6 MPa), nitrogen (93 to 298 K, up to 6 MPa), and for methane (243 to 333 K, up to 9 MPa). The quality
of the fit of the multiple experimental adsorption isotherms is excellent over the large temperature and pressure ranges involved.
The model’s parameters could be determined as well from only the 77 K and 298 K hydrogen isotherms without much reducing the
quality of the fit. 相似文献
19.
Nikos G. Tsierkezos 《Journal of solution chemistry》2008,37(10):1437-1448
The cyclic voltametric technique utilizing a platinum working electrode was applied for the investigation of the electrochemical
oxidation of bis(benzene)chromium(0), (C6H6)2Cr to bis(benzene)chromium(I), (C6H6)2Cr+ in diethyl ketone (DEK), N,N-dimethylformamide (DMF), and DEK/DMF binary mixtures containing n-tetrabutylammonium hexafluorophosphate (TBAPF6) as the supporting electrolyte at T=298.15 K. The half-wave potentials (E
1/2) of the (C6H6)2Cr+/0 redox couple in DEK, DMF and DEK/DMF binary mixtures, were determined. The variation of E
1/2 with the solvent composition was found to be almost linear. The E
1/2 results were analyzed in terms of the electron-donating power of the solvent medium. The diffusion coefficients, D, were calculated using the Randles-Sevcik equation. The kinetics of the electrode reaction were investigated through the
determination of the heterogeneous electron-transfer rate constants, k
s, according to the electrochemical rate equation proposed by Nicholson. Furthermore, the activation Gibbs energies for the
electron-transfer process (ΔG
≠) were also calculated. The results indicate that the redox couple (C6H6)2Cr+/0 exhibits an electrochemically reversible and diffusion-controlled process in all the investigated solvent media. 相似文献
20.
The apparent molar volumes, V
φ
, of two series of homologous aliphatic carboxylic acids, H(CH2)
n
COOH [n=0–5] and (CH2)
n
(COOH)2 [n=0–5], were determined in dilute aqueous solutions by density measurements at T=298.15 K. Densities were measured using a vibrating-tube densimeter (DMA 5000, Anton Paar, Austria) at T=298.15 K. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.0050≤m/(mol⋅kg−1)≤0.3000. Values of the apparent molar volumes of undissociated acids Vf(u)0V_{\phi (u)}^{0} were also calculated. The variation of Vf(u)0V_{\phi (u)}^{0} was determined as a function of the aliphatic chain length of the studied carboxylic acids. 相似文献