不同浓度和温度时无机盐和尿素对抗抑郁剂药物丙咪嗪盐酸盐的胶束化行为的影响

In the present study we report the micellization behavior of imipramine hydrochloride(IMP)in absence and presence of different concentrations of inorganic salts(LiCl,NaF,NaCl,NaBr,and KCl)and ureas(urea and thiourea)over the temperature range from 288.15 to 303.15 K.The critical micellization concentrations(cmc)of drug and drug+additive systems were determined by conductometric technique. With increasing temperature the cmc first increases then decreases.Maximum cmc values were obtained at 293.15 K with or without additives.In presence of inorganic salts the cmc value decreases which is explained on the basis of nature and ion size of the added ion.Urea and thiourea also decrease the cmc at low concentrations(0.2 mmo·lL -1 urea and 0.1 mmo·lL -1 thiourea),but,at higher concentrations,increase in cmc is observed.The related thermodynamic parameters are also evaluated and discussed.     

Interaction and solubilization of some phenolic antioxidants in Pluronic® micelles

The solubilization of four phenolic antioxidants, namely p-hydroxybenzoic acid (PHBAA), syringic acid, sinapic acid, and quercetin in micelles of an ethylene oxide (EO)–propylene oxide (PO) triblock copolymer Pluronic^® P104 (EO₂₇–PO₆₁–EO₂₇, PPO mol wt = 3540, % PEO = 40) was examined at different temperatures, pHs, and in the presence of sodium chloride. The nano-size core–shell micelles of P104 characterized by dynamic light scattering had hydrodynamic diameter of about 18–20 nm with low polydispersity. Antioxidants induced micellization and micellar growth were observed. The critical micellar concentration (CMC), critical micellar temperature (CMT), cloud point (CP) of P104 decreased due to solubilization and interactions of antioxidants. The solubilization was favored at higher temperature, pH and in the presence of salt and follows the order PHBA > syringic acid > sinapic acid > quercetin which corresponds to the trend in their aqueous solubility. The location of antioxidant in micelles observed from NOESY spectra. Structure and hydrophobicity of antioxidants were found to be governing factors for their interaction and location in the micelles.     

Synthesis and surface activity of a novel heterodouble chained N-acyltaurate amphiphile

A novel double chained amphiphile,N-(α-4-hexylphenoxy)-lauroyltaurate(abbreviated as 10 6B-T),has been synthesized. The structures of main intermediate products and the title product were characterized by ~1H NMR.The new amphiphile shows high surface activity.The critical micelle concentration(cmc),which is 1.1×10~(-5)mol/L,is much lower than that of conventional double chained surfactants,such as sodium bis(2-ethylhexyl)sulfosuccinate(AOT).     

Monolayers of an amphiphilic para-carboxy-calix[4]arene act as templates for the crystallization of acetaminophen

The title compound, 5,11,17,23-tetra-carboxy-25,26,27,28-tetradodecyloxy-calix[4]arene, 1, has been studied at the air–water interface, self-assembled as Langmuir monolayers, for its ability to interact with an active pharmaceutical ingredient (API), acetaminophen (APAP), and to initiate its crystallization. The Π/A isotherm study shows that there is a clear interaction between 1 and APAP causing an expansion of the monolayer. In addition to the known phase transition occurring at a surface tension of 38 mN m^?1, an additional kink is observed in the compression isotherm for concentrations of APAP above 40 mM suggesting that this API is causing an additional phase transition of the monolayer. Interface-initiated crystallization studies show that the presence of a monolayer spread on a supersaturated solution of APAP (26 g L^?1) triggers this API crystal growth from the interface. The transfer of 1-based monolayers on glass surfaces has been carried out using the Langmuir–Blodgett technique. The so-produced monolayers have been shown to template the crystallization of APAP. LB films of 1 have characterized using imaging and spectroscopic ellipsometry. The results suggest that each monolayer has an average thickness of 18 Å, which is consistent with the molecular structure of 1 self-organized parallel to the interface with the alkyl chains pointing out parallel to the axis of the macrocycle and without interdigitation of the alkyl chains. The presence of APAP in the subphase during the LB transfer causes a limited but relevant increase in the layer thickness. The study of the capabilities of the LB films to initiate crystallization of APAP is also demonstrated showing the influence of the monolayer packing on the quantity of formed crystals.     

An efficient and solvent-free one-pot synthesis of dihydropyrimidinones under microwave irradiation

An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives using formic acid as catalyst, from aldehydes,β-ketoester and urea(thiourea) without solvent under the irradiation of microwave is described. Compared with the classical Biginelli reaction, this new method has the advantage of good yields (77-94% for aromatic aldehydes) and short reaction time (3-8 min).     

Amperometric glucose sensor based on glucose oxidase immobilized on gelatin-multiwalled carbon nanotube modified glassy carbon electrode

We investigated the direct electrochemistry of glucose oxidase (GOx) at gelatin-multiwalled carbon nanotube (GCNT) modified glassy carbon electrode (GCE). GOx was covalently immobilized onto GCNT modified GCE through the well known glutaraldehyde (GAD) chemistry. The immobilized GOx showed a pair of well-defined reversible redox peaks with a formal potential (E⁰′) of ? 0.40 V and a peak to peak separation (ΔE_p) of 47 mV. The surface coverage concentration (Г) of GOx in GCNT/GOx/GAD composite film modified GCE was 3.88 × 10^? 9 mol cm^? 2 which indicates the high enzyme loading. The electron transfer rate constant (k_s) of GOx immobilized onto GCNT was 1.08 s^? 1 which validates a rapid electron transfer processes. The composite film shows linear response towards 6.30 to 20.09 mM glucose. We observed a good sensitivity of 2.47 μA mM^?1 cm^? 2 for glucose at the composite film. The fabricated biosensor displayed two weeks stability. Moreover, it shows no response to 0.5 mM of ascorbic acid (AA), uric acid (UA), acetaminophen (AP), pyruvate (PA) and lactate (LA) which shows its potential application in the determination of glucose from human serum samples. The composite film exhibits excellent recovery for glucose in human serum at physiological pH with good practical applicability.     

Multi-technique approach on the effect of surfactant concentrations on the thermal unfolding of rabbit serum albumin: Formation and solubilization of the protein aggregates

Effect of cationic surfactant, cetyltrimethylammonium bromide (CTAB) addition on the thermal denaturation of rabbit serum albumin (RSA) has been studied by employing small-angle neutron scattering (SANS), circular dichroism (CD), intrinsic fluorescence and ultra violet (UV) spectroscopy. The studies were performed at three different temperatures viz., 30, 50 and 70 °C and at two different concentrations of CTAB: the low concentration of CTAB used was 1 mM and the higher concentration was 80 mM (for SANS) and 20 mM (for CD, fluorescence and UV). A collective effect of high temperature and low concentration of CTAB led to the protein aggregation followed by solubilization of these aggregates at higher concentration of surfactant. At 1 mM CTAB and 30 °C, the protein–surfactant complex has a prolate ellipsoidal shape with semi-major axis of 88.9 Å and semi-minor axis of 19.6 Å which are slightly greater than the values of the native RSA. At 50 °C, the size of the semi-major axis increases while at 70 °C an increase in the size of both axes was found. The thermal outcome at higher concentration of CTAB (80 mM) was rather different. Higher concentration of CTAB unfolds the protein by the formation of micelle-like aggregates along the polypeptide chains of the protein and the complex was stabilized at higher temperatures, which was not found with lower concentration of CTAB. The CD results were found to be consistent with the SANS results, i.e., decrease in α-helicity of RSA was more when less amount of surfactant was present as compared to the system with higher surfactant concentration. In a similar fashion, results of relative fluorescence intensity (RFI) reveal that increase in temperature causes decrease in λ_max of native RSA as well as RSA + 1 mM CTAB, whereas the λ_max remains unchanged for RSA + 20 mM CTAB systems. That means the structure remains compact in presence of 20 mM CTAB while the structure becomes loose when low or zero amount of surfactant was present. The UV results indicate that the protein aggregation takes place in presence of low amount of CTAB and these aggregates become soluble at high concentration of CTAB.     

Annealing temperature dependent catalytic water oxidation activity of iron oxyhydroxide thin films

Nanostructured iron oxyhydroxide(Fe OOH) thin films have been synthesized using an electrodeposition method on a nickel foam(NF) substrate and effect of air annealing temperature on the catalytic performance is studied. The as-deposited and annealed thin films were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS), field emission scanning electron microscopy(FE-SEM) and linear sweep voltammetry(LSV) to determine their structural, morphological, compositional and electrochemical properties, respectively. The as-deposited nanostructured amorphous Fe OOH thin film is converted into a polycrystalline Fe_2O_3 with hematite crystal structure at a high temperature. The Fe OOH thin film acts as an efficient electrocatalyst for the oxygen evolution reaction(OER) in an alkaline 1 M KOH electrolyte. The film annealed at 200 °C shows high catalytic activity with an onset overpotential of 240 m V with a smaller Tafel slope of 48 m V/dec. Additionally, it needs an overpotential of 290 mV to the drive the current density of 10 m A/cm~2 and shows good stability in the 1 M KOH electrolyte solution.     

Impedance spectroscopy and conductometric biosensing for probing catalase reaction with cyanide as ligand and inhibitor

In this work, a new biosensor was prepared through immobilization of bovine liver catalase in a photoreticulated poly (vinyl alcohol) membrane at the surface of a conductometric transducer. This biosensor was used to study the kinetics of catalase–H₂0₂ reaction and its inhibition by cyanide. Immobilized catalase exhibited a Michaelis–Menten behaviour at low H₂0₂ concentrations (< 100 mM) with apparent constant K_M^app = 84 ± 3 mM and maximal initial velocity V_M^app = 13.4 μS min^? 1. Inhibition by cyanide was found to be non-competitive and inhibition binding constant K_i was 13.9 ± 0.3 μM. The decrease of the biosensor response by increasing cyanide concentration was linear up to 50 μM, with a cyanide detection limit of 6 μM. In parallel, electrochemical characteristics of the catalase/PVA biomembrane and its interaction with cyanide were studied by cyclic voltammetry and impedance spectroscopy. Addition of the biomembrane onto the gold electrodes induced a significant increase of the interfacial polarization resistance R_P. On the contrary, cyanide binding resulted in a decrease of Rp proportional to KCN concentration in the 4 to 50 μM range. Inhibition coefficient I₅₀ calculated by this powerful label-free and substrate-free technique (24.3 μM) was in good agreement with that determined from the substrate-dependent conductometric biosensor (24.9 μM).     

The impact of uni-univalent electrolytes on (water + acetic acid + toluene) equilibria: Representation with electrolyte-NRTL model

The presence of salts can significantly alter the (liquid + liquid) equilibrium and extraction process. In this work, a study was conducted on the (liquid + liquid) equilibria of (water + acetic acid + toluene + sodium chloride or potassium chloride) at temperatures (288.2, 298.2 and 313.2) K. This chemical system, irrespective of salt, is frequently used in (liquid + liquid) extraction investigations. The selected salt concentrations in initial aqueous solutions were (0.9 and 1.7) mol · L⁻¹. The results show that salting-out effect of the salts was significant, so that an enhancement in the acetic acid distribution coefficient was achieved within (15.6 to 66.8)% with NaCl and within (2.5 to 37.6)% with KCl. Meantime, high separation factors were found at low temperatures and low solute concentrations. The electrolyte-NRTL model was satisfactorily used to correlate the phase equilibria. In this regard for each salt, the temperature dependent binary interaction parameters between components were calculated. The predicted tie-line mole fractions give root-mean square deviation (RMSD) values of only 0.0038 and 0.0045 for the systems containing NaCl and KCl, respectively.     

Determination of the second critical micelle concentration of benzyldimethyltridecylazanium chloride in aqueous solution by acoustic and conductometric measurements

Density, speed of sound, and conductivity of benzyldimethyltridecylazanium chloride as a cationic surfactant in aqueous solutions have been measured as a function of concentration at atmospheric pressure and at five temperatures (293.15, 298.15, 303.15, 308.15, and 313.15) K. Isentropic compressibility values have also been calculated from the experimental density and speed of sound results. The critical micelle concentration (cmc) values of investigated cationic surfactant were evaluated by using conductivity measurements. The speed of sound, isentropic compressibility and also the conductivity values of the solutions have been employed to determine the second critical micelle concentrations (2nd cmc). The temperature dependence of the speed of sound and isentropic compressibility is shown to be sensitive to the aggregation process. The 2nd cmc values of the surfactant obtained at different temperatures by conductivity, speeds of sound and isentropic compressibility data are in agreement with each other.     

Preparation of novel magnetic hollow mesoporous silica microspheres and their efficient adsorption

Ordered mesoporous aluminas with high surface areas (up to 783 m²/g), large pore volumes (up to 0.82 cm³/g) and the presence of complementary micropores (up to 0.17 cm³/g) are synthesized with Pluronic® F127 or P123 triblock copolymers in a one-pot synthesis of metal alkoxide, template and cosolvent molecules such as 1,3,5-trimethylbenzene or 1,3,5-triisopropylbenzene in an acidic ethanol solution at 15 °C. Materials are characterized by nitrogen adsorption analysis, small-angle X-ray diffraction and transmission electron microscopy.     

Bubble points of the systems isopropanol–water,isopropanol–water–sodium acetate and isopropanol–water–sodium oleate at high pressure

Supercritical water oxidation (SCWO) is a powerful technology for destroying organic wastes with high removal efficiencies. Corrosion and salt deposition are the main challenges for the industrial development of the SCWO process. In SCWO heteroatoms are oxidized until high oxidation states: oxides, acids or salts. If there are enough cations, the heteroatoms precipitate as salts and eventually can be recovered. Cations can be introduced in the system by adding organic salts to the feed. The organic part of the salt is oxidized to CO₂ and water, and the cations remain free to join the free anions and precipitate as inorganic salts. The thermodynamic study of this system it is very interesting for future modeling of the SCWO process.Bubble points of the systems isopropanol (IPA)–water, IPA–water–sodium acetate and IPA–water–sodium oleate were determined in the temperature range (396 and 460 K), pressures higher than 0.35 MPa, with IPA concentrations lower than 5 mol% and salt concentrations of 5 and 8.2 mol% for sodium acetate, and 0.11 and 0.25 mol% for sodium oleate. Bubble points were determined using a Cailletet apparatus that operates with the synthetic method.As expected, the vapor pressure of the system increases as IPA concentration is increased, and in general decreases when salt concentration increases. The measured vapor pressures of mixtures of water and IPA were consistent with literature data.The experimental data were correlated using the Anderko–Pitzer EoS, which was specially developed for water–salt systems at high temperatures and pressures. Densities and vapor pressures of IPA and the experimental data presented in this work were used for obtaining the parameters of the EoS in the range of pressure and temperature of the data. In the range of temperature and concentration considered, the average deviations between experimental and calculated vapor pressures were %ΔP = 1.18% for the system IPA–water, %ΔP = 4.03% for the system IPA–water–NaAc and %ΔP = 2.77% for the system IPA–water–NaOl.     

Structural behaviour of mixed cationic surfactant micelles: a small-angle neutron scattering study

Self-assembly in mixtures of two single-chain cationic surfactants, with different tail lengths (CTAB and DTAB) as well as of a single-chain (DTAB) and a double-chain (DDAB) cationic surfactant, with identical tail lengths, have been investigated with small-angle neutron scattering (SANS) and rationalised in terms of bending elasticity properties. The growth behaviour of micelles with respect to surfactant composition appears completely different in the two surfactant mixtures. DTAB form small oblate spheroidal micelles in presence of [NaBr] = 0.1 M that transform into prolate spheroidal mixed CTAB/DTAB micelles upon adding moderate amounts of CTAB, so as to give a mole fraction y = 0.20 in solution. Most unexpectedly, upon further addition of CTAB the mixed CTAB/DTAB micelles grow with an almost equal rate in both length and width directions to form tablets. In contrast to this behaviour, mixed DDAB/DTAB micelles grow virtually exclusively in the length direction, in presence of [NaBr] = 0.1 M, to form elongated ellipsoidal (tablet-shaped) and subsequently long wormlike micelles as the fraction of DDAB in the micelles increases. Mixed DDAB/DTAB micelles grow to become as long as 2000 Å before an abrupt transition to large bilayer structures occurs. This means that the micelles are much longer at the micelle-to-bilayer transition as compared to the same mixture in absence of added salt. It is found that the point of transition from micelles to bilayers is significantly shifted towards higher fractions of aggregated DTAB as an appreciable amount of salt is added to DDAB/DTAB mixtures, indicating a considerable reduction of the spontaneous curvature with an increasing [NaBr]. By means of deducing the various bending elasticity constants from our experimental results, according to a novel approach by ours, we are able to conclude that the different growth behaviours appear as a consequence of a considerably lower bending rigidity, as well as higher saddle-splay constant, for DDAB/DTAB surfactant mixtures in presence of [NaBr] = 0.1 M, as compared to mixtures of CTAB/DTAB in [NaBr] = 0.1 M and DDAB/DTAB in absence of added salt.     

Effect of Deposition Temperature on Structural and Optical Properties of Chemically Sprayed ZnS Thin Films

Zinc sulfide (ZnS) thin films have been successfully deposited via spray pyrolysis using an aqueous solution of thiourea and zinc acetate onto glass substrate. The effect of varying substrate temperature (150, 200,250 and 300 °C) on structure and optical properties is presented. The films have been characterized by X- ray diffraction (XRD), UV-Vis-NIR spectrometry, photoluminescence (PL) spectroscopy and field emission scanning electron microscopy (FESEM). All the deposited ZnS films exhibit a cubic structure, while crystallinity and morphology are found to depend on spray temperature. PL analysis indicates the presence of violet and green emissions arising from Zn and S vacancies. The value of bandgap of ZnS films is found to decrease slightly with increasing substrate temperature; varying in the range 3.52–3.25 eV, most probably associated with the formation of Zn(S,O) solid solution.     

Selective binding of bile salts by β-cyclodextrin derivatives with appended quinolyl arms

Two β-cyclodextrin derivatives bearing appended quinolyl and isoquinolyl arms,i.e.mono-(6-quinolyl- 6-deoxy)-β-cyclodextrin(1) and mono-(6-isoquinolyl-6-deoxy)-β-cyclodextrin(2) were synthesized in satisfactory yields and fully characterized.Their original conformations and binding behaviors toward four bile salt guests,that is,sodium cholate(CA),sodium deoxycholate(DCA),sodium glycocholate (GCA),and sodium taurocholate(TCA),were investigated by means of fluorescence,circular dichroism and 2D NMR spectroscopy.The study of solution structures revealed that both quinolyl and isoquinolyl arms were located outside the cyclodextrin cavity.The results obtained from the fluorescence titrations showed that the binding abilities of hosts 1 and 2 with selected bile salts varied in an order of DCA > CA > GCA.The selective binding of hosts toward bile salt guests was discussed from the viewpoints of induced-fit and multiple binding.     

Melamine modified carbon felts anode with enhanced electrogenesis capacity toward microbial fuel cells

Surface electropositivity and low internal resistance are important factors to improve the anode performance in microbial fuel cells(MFCs). Nitrogen doping is an effective way for the modification of traditional carbon materials. In this work, heat treatment and melamine were used to modify carbon felts to enhance electrogenesis capacity of MFCs. The modified carbon felts were characterized using X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), atomic force microscopy(AFM)and malvern zeta potentiometer. Results show that the maximum power densities under heat treatment increase from 276.1 to 423.4 m W/m~2(700 °C) and 461.5 m W/m~2(1200 °C) and further increase to472.5 m W/m~2(700 °C) and 515.4 m W/m~2(1200 °C) with the co-carbonization modification of melamine.The heat treatment reduces the material resistivity, improves the zeta potential which is beneficial to microbial adsorption and electron transfer. The addition of melamine leads to the higher content of surface pyridinic and quaternary nitrogen and higher zeta potential. It is related to higher MFCs performance. Generally, the melamine modification at high temperature increases the feasibility of carbon felt as MFCs' s anode materials.     

Highly enantioselective Michael additions of α-cyanoacetate with chalcones catalyzed by bifunctional cinchona-derived thiourea organocatalyst

The conjugate addition of ethyl α-cyanoacetate with chalcones has been developed. In the presence of cinchona alkaloid-derived thiourea organocatalyst 1i (10 mol %), ethyl α-cyanoacetate could react with various chalcones to afford Michael adducts with high yields (80–92%) and enantioselectivities (83–95% ee).     

Reaction of nitrous oxide with methane to synthesis gas: A thermodynamic and catalytic study

The aim of the present study is to explore the coherence of thermodynamic equilibrium predictions with the actual catalytic reaction of CH4 with N_2O,particularly at higher CH4 conversions.For this purpose,key process variables,such as temperature(300℃-550℃) and a molar feed ratio(N_2O/CH4 = 1,3,and 5),were altered to establish the conditions for maximized H_2 yield.The experimental study was conducted over the Co-ZSM-5 catalyst in a fixed bed tubular reactor and then compared with the thermodynamic equilibrium compositions,where the equilibrium composition was calculated via total Gibbs free energy minimization method.The results suggest that molar feed ratio plays an important role in the overall reaction products distribution.Generally for N_2O conversions,and irrespective of N_2O/CH_4 feed ratio,the thermodynamic predictions coincide with experimental data obtained at approximately 475℃-550℃,indicating that the reactions are kinetically limited at lower range of temperatures.For example,theoretical calculations show that the H2 yield is zero in presence of excess N2O(N_2O/CH_4 = 5).However over a Co-ZSM-5 catalyst,and with a same molar feed ratio(N_2O/CH_4) of 5,the H_2 yield is initially 10%at 425℃,while above450℃ it drops to zero.Furthermore,H_2 yield steadily increases with temperature and with the level of CH4 conversion for reactions limited by N_2O concentration in a reactant feed.The maximum attainable(from thermodynamic calculations and at a feed ratio of N_2O/CH4=3) H_2 yield at 550℃ is 38%,whereas at same temperature and over Co-ZSM-5,the experimentally observed yield is about 19%.Carbon deposition on Co-ZSM-5 at lower temperatures and CH4 conversion(less than 50%) was also observed.At higher temperatures and levels of CH_4 conversion(above 90%),the deposited carbon is suggested to react with N_2O to form CO_2.     

Emitting stability of poly（9,9-dialkylfluorene-co-N-butylcarbazole） by solid-state oxidative coupling polymerization

Dihexylfluorene and N-butylcarbazole were copolymerized by solid-state oxidative coupling polymerization in the presence of anhydrous FeCl_3 at room temperature.The solid-state films of the copolymers emitted blue light after heating at 150℃in air for 24 h,no red-shifted emission was observed by fluorescence spectroscopy.