Influence Of Different Solvents Research Articles

Influence of Different Solvents on the Morphology of the Hybrid Layer Using Two-Step Etch-and-Rinse Adhesives

To evaluate if different etch-and-rinse adhesive solvents influenced the hybrid layer's morphology. Four one-bottle etch-and-rinse adhesive systems containing different solvents—Group A: Scotchbond 1XT™– 3 M ESPE, Group B: XP – Bond™ – Dentsply, Group C: Prime&Bond NT® – Dentply, and Group D: One Coat Bond® - Coltène Whaledent—were applied onto 32 dentin discs which were thermocycled, prepared, and examined using field-emission scanning electron microscopy. Micrographs were scanned and the data were processed using Statistical Package for Social Sciences. The mean value and standard deviation were calculated and the Anova Multivariant Test was used. The hybrid layer thickness average found was 3.23 µm (±0.53) in Group A, 3.13 µm (±0.73) in Group B, 2.53 µm (±0.50) in Group C, and 1.84 µm (±0.27) in Group D. Prime&Bond NT® presented a more inconsistent hybrid layer. The solvent seems to play a significant role in hybrid layer structure and thickness.

Influence of different solvents in extraction of phenolic compounds from vegetable residues and their evaluation as natural sources of antioxidants.

Dried residues from four different vegetables, viz. pea pod (pp), cauliflower waste (CW), potato peel (PP) and tomato peel (TP) were extracted using four solvents i.e., hexane, chloroform, ethyl acetate and methanol. Among the four solvents, methanolic extracts showed the highest total phenolic content (TPC) for all the four vegetable residues. Methanolic extracts were evaluated for antioxidant activities using diphenylpicryl-hydrazyl (DPPH) and reducing power assay. Tomato peel extract showed highest phenolic content of 21.0mg GAE/g-dw and 80.8% DPPH free radical scavenging ability, whereas potato peel extract had a low phenolic content, and it also showed the least antioxidant activity among the residues examined in this study. Total phenolic content and DPPH free radical scavenging activity in pea pods and cauliflower waste were 13.6mg GAE/g-dw and 72% and 9.2mg GAE/g-dw and 70.7%, respectively. The coefficient of determination (r(2)) for correlation between TPC and reducing power, DPPH and TPC, DPPH and reducing power for all extracts was 0.85, 0.91and 0.87, respectively, suggesting an important role of phenolics in imparting antioxidant ability. Extracts from vegetables residues therefore represent a significant source of phenolic antioxidants for use as nutraceuticals or biopreservatives.

Isothermal Calorimetric Titrations on Charge-Assisted Halogen Bonds: Role of Entropy, Counterions, Solvent, and Temperature

We have conducted isothermal calorimetric titrations to investigate the halogen-bond strength of cationic bidentate halogen-bond donors toward halides, using bis(iodoimidazolium) compounds as probes. These data are intended to aid the rational design of halogen-bond donors as well as the development of halogen-bond-based applications in solution. In all cases examined, the entropic contribution to the overall free energy of binding was found to be very important. The binding affinities showed little dependency on the weakly coordinating counteranions of the halogen-bond donors but became slightly stronger with higher temperatures. We also found a marked influence of different solvents on the interaction strength. The highest binding constant detected in this study was 3.3 × 10(6) M(-1).

Characterizations of chitosan‐based highly porous hydrogel—The effects of the solvent

AbstractIn this study, the influences of different solvents on highly porous chitosan (CS)‐based hydrogel have been investigated by monitoring the characterizations of the hydrogel. The results determined from rheological analysis and scanning electron microscope showed that all the CS dissolved in different solvents used in this study, when neutralized by α,β‐glycerophosphate solution, could transform into a highly porous three‐dimensional hydrogel at a certain temperature, and the aperture size and shape of the pores were related to solvent variety and solvent strength. The cytocompatibility and in vivo injection experiments demonstrated that the hydrogel prepared with acetic acid, hydrochloric acid, or lactic acid as the solution of CS had low toxicity and high histocompatibility. This study suggested that the gelation temperatures, pH values, turbidity, complex viscosities, and porous structures of the hydrogels for certain experimental applications could be tailored by adjusting the solvent variety and solvent strength of the CS solution. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Improved activity and stability of lipase immobilized in cage-like large pore mesoporous organosilicas

Lipase from Thermomyces lanuginosus has been immobilized in different mesoporous organosilicas (PMOs) containing ethane and benzene groups with large cage-like pores. The immobilization of lipase as well as the application of these catalysts in hydrolysis and transesterification reactions is studied in detail. The results show that the structural properties of the support employed have a significant influence on the adsorption capacity. In general, materials with high specific surface areas and pore volumes show high adsorption capacity. However, in the case of monolayer adsorption, the hydrophobicity of the surface has a significant impact on the adsorption efficiency due to strong hydrophobic interactions. Furthermore, the transesterification of vinyl propionate with 1-butanol catalyzed by immobilized lipase was studied. The influence of lipase loading, the effect of water content in the reaction mixture and the influence of different solvents were investigated. The results show that lipase immobilized in the most hydrophobic material (LPbenzene) exhibits excellent catalytic performance, which is attributed to the enhanced interfacial activity of lipase due to the interaction between lipase and the hydrophobic surface of the material. In order to further disclose the influence of the hydrophobic surface on the lipase activity, ATR-FTIR spectroscopy was used to study the secondary structure of lipase immobilized on different supports. The results confirm that a structural transition of entrapped lipase to the open-lid conformation takes place on LPbenzene, which shows that the observed increase in enzymatic activity is triggered by interfacial activation of lipase.

Synthesis, structural characterization, solvatochromism, and ion-binding studies of a ditopic receptor based on 2-(4-[2,2′: 6′,2′′]terpyridin-4′-yl-phenyl)-1H-phenanthro[9,10-d] imidazole (tpy-HImzphen) unit

A terpyridyl-imidazole based ditopic receptor 2-(4-[2,2′:6′,2′′]terpyridin-4′-yl-phenyl)-1H-phenanthro[9,10-d]imidazole (tpy-HImzphen) has been synthesized and characterized using standard analytical and spectroscopic techniques and also by single crystal X-ray crystallography. The receptor shows multi-channel sensing ability towards F− and Fe2+ ions. Both the anion and cation binding properties of the receptor were thoroughly investigated in dimethylformamide–acetonitrile (1 : 9) solution using absorption, emission, and 1H NMR spectral studies. In the presence of excess of F− ions, deprotonation of the imidazole N–H fragment occurs, an event which is signalled by the development of bright yellow color visible with the naked eye. Anion-induced lifetime enhancing makes the receptor a suitable lifetime-based sensor for F− ions. The absorption and emission titration of the receptor with Fe2+ ion indicates that single conversion of free tpy-HImzphen (colorless) to Fe2+ complex (deep violet color) of 2 tpy-HImzphen : 1 Fe2+ stoichiometry. The influence of different solvents on the absorption and emission spectral behavior and on the lifetime of the receptor and its Zn(II) complex have also been investigated in detail.

P–n junction organic photovoltaics fabricated by all solution processing

We have prepared p–n junction organic photovoltaic cells using an all solution processing method with poly(3-hexylthiophene) (P3HT) as the donor and phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor. Interdigitated donor/acceptor interface morphology was observed in the device processed with the lowest boiling point solvent for PCBM used in this study. The influences of different solvents on donor/acceptor morphology and respective device performance were investigated simultaneously. The best device obtained had characteristically rough interface morphology with a peak to valley value ∼15nm. The device displayed a power conversion efficiency of 1.78%, an open circuit voltage (Voc) 0.44V, a short circuit current density (Jsc) 9.4mA/cm2 and a fill factor 43%.

Heteronuclear NOE Spectroscopy of Ionic Liquids

(19)F,(1)H HOESY experiments with three ionic liquids ([bmim]BF(4), [bmim]PF(6) and [emim]BF(4)) were run in two different solvents and neat. The results give preferred probabilities of presence and enable us to systematically study interactions between the cations and the anions in the ionic liquid phase by NMR spectroscopy. The influence of different solvents and of the presence or absence of air (i.e. oxygen) is discussed. This enabled us to substantially speed up the NMR experiments and to develop a more precise method for the investigation of liquid-phase structures in ionic liquids.

Preparation and Characterization of Strong Polar Macro Porous Resin

The macro porous adsorption resin produced in this experiment mainly uses dipole dichloride etc. as the material, a certain proportion of mixed solution composed of pyridine and 1, 4-dioxane as the composite oxidant. Then adding a certain proportion of mixed solution composed of cyclopean and paraffin in the homogeneous solution of cellulose as the photogenic agent. As a result, these materials will polymerize, and generate the resin. Among these materials, the cellulose is polymeric monomer, dipole dichloride is cross linker, and they crosslink and polymerize each other, forming the porous skeletal structure of the macro porous adsorption resin, which is a kind of cross linked polymer consisting of ion exchange group. For the synthetic macro porous resin, using Fourier infrared spectrometer for pressed characterization, and scanning electron microscope (SEM) for resin pore-forming characterization, the result shows that the new macro porous resin has been synthesized. This paper taking ruin as adsorb ate explores the adsorption property of the synthetic macro porous resin to glycoside material, including property of equilibrium adsorption, static adsorption and adsorption. Meanwhile the influence of different solvents on the resin adsorption property is testified. After a general comparison, we have found that the resin has the strongest adsorption property in ethanol solvent, while for adsorption, the best effect is reached when using water as the elegant. What's more, the adsorption data shows that the adsorption of ruin on the very resin conforms to the Freundlich isothermal adsorption equation.

Synthesis of N,N,N-trimethyl chitosan homopolymer and highly substituted N-alkyl-N,N-dimethyl chitosan derivatives with the aid of di-tert-butyldimethylsilyl chitosan

A highly chemoselective strategy for the synthesis of N,N,N-trimethyl chitosan (TMC) homopolymer and highly substituted N-alkyl-N,N-dimethyl chitosan derivatives was achieved using di-tert-butyldimethylsilyl-3,6-O-chitosan (di-TBDMS chitosan) as a precursor. The influence of different solvents, reagents and other reaction conditions on the reduction, trimethylation and quaternization of these di-TBDMS chitosan derivatives was studied. Products were characterized by NMR after each step. Di-TBDMS chitosan was reacted with methyl iodide in NMP, giving a 100% substituted TMC with the trimethyl group appearing at 3.35ppm in 1H NMR spectrum. N-Propyl-, N-butyl- and N-hexyl-N,N-dimethyl chitosan derivatives were synthesized by stepwise reductive alkylation of di-TBDMS chitosan, followed by quaternization with dimethyl sulfate in dichloromethane, giving 65–72% substituted N-alkyl-N,N-dimethyl chitosan derivatives under optimized conditions. Analysis of these water-soluble chitosan derivatives by FT-IR, 1H NMR, 13C NMR, 1H–1H COSY and 1H–13C HSQC NMR enabled detailed structural characterization. All peaks could be assigned to N-modification, showing the selectivity of the di-TBDMS protection.

Influence of different solvents on the structural, optical and morphological properties of CdS nanoparticles

CdS is one of the most important II–VI semiconductors, with applications in solar cells, optoelectronics and electronic devices. CdS nanoparticles were synthesized via microwave-assisted solvothermal technique. Structural and morphological characterization revealed the presence of crystalline structures presenting single phase with different morphologies such as “nanoflowers” and nanoplates depending on the solvent used. Optical characterization was made by diffuse reflectance and photoluminescence spectroscopy, revealing the influence of the different solvents on the optical properties due to structural defects generated during synthesis. It is proposed that these defects are related to sulfur vacancies, with higher concentration of defects for the sample synthesized in ethylene glycol in comparison with the one synthesized in ethylene diamine.

Influence of a reaction medium on the oxidation of aromatic nitrogen-containing compounds by peroxyacids

The influence of different solvents on the oxidation reaction rate of pyridine (Py), quinoline (QN), acridine (AN), α-oxyquinoline (OQN) and α-picolinic acid (APA) by peroxydecanoic acid (PDA) was studied. It was found that the oxidation rate grows in the series Py < QN < AN, and the rate of the oxidation reaction of compounds containing a substituent in the α position from a reactive center is significantly lower than for unsubstituted analogues. The effective energies of activation of the oxidation reaction were found. It was shown that in the first stage, the reaction mechanism includes the rapid formation of an intermediate complex nitrogen-containing compound, peroxyacid, which forms products upon decomposing in the second stage. A kinetic equation that describes the studied process is offered. The constants of equilibrium of the intermediate complex formation (K eq) and its decomposition constant (k 2) in acetone and benzene were calculated. It was shown that the nature of the solvent influences the numerical values of both K p and k 2. It was established that introduction of acetic acid (which is able to form compounds with Py) into the reaction medium slows the rate of the oxidation process drastically. Correlation equations linking the polarity, polarizability, electrophilicity, and basicity of solvents with the constant of the PDA oxidation reaction rate for Py were found. It was concluded that the basicity and polarity of the solvent have a decisive influence on the oxidation reaction rate, while the polarizability and electrophilicity of the reaction medium do not influence the oxidation reaction rate.

What is Solvatochromism?

Solvatochromism is commonly used in many fields of chemical and biological research to study bulk and local polarity in macrosystems (membranes, etc.), or even the conformation and binding of proteins. Despite its wide use, solvatochromism still remains a largely unknown phenomenon due to the extremely complex coupling of many different interactions and dynamical processes which characterize it. In this study we analyze the influence of different solvents on the photophysical properties of selected charge-transfer probes (4-AP, PRODAN, and FR0). The purpose is to achieve a microscopic understanding of the intermolecular effects which govern the absorption and fluorescence properties of solvated molecular probes, such as solvent-induced structural modifications, polarization effects, solubility, solute-solvent hydrogen-bonding interactions, and solute aggregation. To this aim we have exploited a time dependent density functional theory (TDDFT) approach coupled to complementary solvation approaches (continuum, discrete and mixed discrete and continuum). Such an integration has allowed us to clearly disentangle the complex interplay between specific and nonspecific interactions of the solvent with the probes and show that strong H-bonding effects not only can lead to large solvatochromic shifts but also can affect the nature of the emitting species with resulting reduction of the quantum yield.

Manipulation of Molecular and Supramolecular Structure in Cobalt(II) Complexes with Tetrachloroterephthalate through the Influence of Different Solvents

AbstractThe reactions of cobalt acetates with tetrachloroterephthalic acid (H2BDC‐Cl4) in different solvents gave two polymeric and one mononuclear CoII complexes. X‐ray single‐crystal structural determination revealed that the ligand BDC‐Cl4 displays a reliable bridging tecton to construct diverse supramolecular architectures through coordinative bonds or secondary hydrogen‐bonding interactions. The complexes [Co(BDC‐Cl4)(DMF)2(EtOH)2]n (1) and {[Co(BDC‐Cl4)(DMF)2(MeOH)2]·2DMF}n (2) demonstrate a one‐dimensional (1D) coordination motif with infinite CoII‐tetrachloroterephthalate chains, which are tuned by different binding solvent systems of DMF/ethanol (EtOH) and DMF/methanol (MeOH). [Co(DMF)2(H2O)4]·(BDC‐Cl4) (3) represents a two‐dimensional (2D) metallosupramolecular network by hydrogen‐bonded bridging between the aqua ligand of the mononuclear complex with the uncoordinated BDC‐Cl4 solvates. The spectroscopic, thermal, and fluorescent properties of 1–3 were also investigated.

Ligand-assisted preparation of highly active and stable nanometric Pd confined catalysts for deep catalytic oxidation of toluene

In this study, mesoporous SBA-15 supported Pd catalysts were synthesized through impregnation and grafting approaches. Moreover, the influences of different solvents (ethanol, H 2O, tetrahydrofuran, dimethyl sulphoxide and N, N-dimethylformamide) on the dispersion of supported Pd nanoparticles were also systematically investigated. The prepared materials were comprehensively explored by various techniques, including XRD, EDS, ICP-OES, H 2 chemisorption, N 2 adsorption/desorption, TG-DSC, FT-IR, TEM and STEM. It is found that the traditional impregnation method has some disadvantages in obtaining highly dispersed Pd active phase. Whereas, the grafting method could highly disperse Pd nanoparticles within the mesoporous channels of support material, and the grafting procedure should be promising in designing highly dispersed Pd particles on the silica-based mesoporous materials. The catalyst prepared via the grafting procedure possesses much higher activity and selectivity than that prepared by impregnation method for deep catalytic oxidation of toluene.

Evaluation of synthetic methods for microporous metal–organic frameworks exemplified by the competitive formation of [Cu 2(btc) 3(H 2O) 3] and [Cu 2(btc)(OH)(H 2O)

Six different synthetic methods (solvothermal, microwave-assisted, atmospheric pressure and reflux, ultrasonic and mechanochemical conditions) for the metal–organic framework [Cu 3(btc) 2(H 2O) 3] (btc = benzene-1,3,5-tricarboxylate) were compared. The advantages and disadvantages of the various synthetic methods were discussed including the influence of different solvents and reaction conditions on product formation, microporosity and crystallisation. Therefore, pressure and temperature for the solvothermal synthesis (autoclave and microwave) were monitored during the reaction. The characterization of the samples was performed by X-ray powder diffraction, scanning electron microscopy, infrared-spectroscopy, thermogravimetric analysis and specific surface determination using the BET method. The experimental results show that microwave-assisted solvothermal synthesis is the best method to produce crystalline [Cu 3(btc) 2(H 2O) 3] in a short time associated with high purity, high specific pore volume (0.79 cm 3/g) and quantitative yield. Noteworthy, the solvent-assisted mechanochemical approach gave a comparable specific pore volume of 0.74 cm 3/g. Furthermore, synthesis conditions were explored which enable to control the product formation of either [Cu 3(btc) 2(H 2O) 3] or [Cu 2(btc)(OH)(H 2O)]. Finally, it is shown that water stability of [Cu 3(btc) 2(H 2O) 3] at higher temperatures is low, if the adsorbed and coordinated water is not removed rapidly upon heating.

Supercritical Antisolvent Micronization of Cyclotrimethylenetrinitramin: Influence of the Organic Solvent

A supercritical antisolvent (SAS) process was used to prepare micronized cyclotrimethylenetrinitramin (RDX). This study examined the influence of different solvents at a fixed temperature (50 °C) and pressure (13.7 or 15 MPa) on the morphology, particle size (PS), and particle size distribution (PSD) using a semicontinuous SAS process. Dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetone (AC), acetonitrile (ACN), n-methyl 2-pyrrolidone (NMP), and cyclohexanone (CHN) were used as solvents. The recrystallized RDX particles were characterized by scanning electron microscopy (SEM), particle size analyzer (PSA), Fourier transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). Depending on the solvent used, the recrystallized RDX particles showed a variety of morphologies, particle sizes, and particle size distributions (PSD). The mean particle size of the recrystallized RDX ranged from 2.6 to 17.7 μm. The enthalpy change (ΔH = 583.4, 847.7, 967.1, 823.9, 1131, and 1620 J/g) ...

Media effects on the optical properties of proton donor group containing azobenzene derivatives

A series of hydroxy and carboxy group containing azobenzene compounds were synthesized and investigated by UV–vis and fluorescence spectroscopy. It could be shown that the ambient medium exerted a strong influence on the absorption behavior and the trans– cis isomerization behavior of the azo compounds. Especially in the case of hydroxy group functionalized azobenzenes, deprotonation with NaOH or a polymeric base changed the spectral behavior of the compounds remarkably. A strong bathochromic shift of the dyes’ longest wavelength absorption band was observed. Furthermore, the influence of different solvents and different polymeric matrices on the trans–cis isomerization behavior of the azobenzenes was investigated. The results are discussed in terms of utilization of the azo dyes as probe molecules for interactions in polymer blends.

70]FULLERENE-BASED EFFICIENT BULK HETEROJUNCTION SOLAR CELLS

A bulk heterojunction photovoltaic cell in which an isomeric mixture of fullerene derivatives,PC[70]BM is used as an electron acceptor in combination with poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene)(MEH-PPV) as an electron donor has been reported.PC[70]BM is the higher fullerene analogue of PC[60]BM,and displays improved light absorption in the visible region.It is found out when this material is used instead of PC[60]BM in a photovoltaic cell with MEH-PPV as donor,a value of 6.07 mA/cm2 current density for the PC[70]BM∶MEH-PPV devices means an increase of over 40% with respect to an optimized PC[60]BM∶MEH-PPV cell.The open-circuit voltage Voc of 0.85 V and a fill factor(FF) of 0.53 for the PC[70]BM∶MDMO-PPV devices resulted in an overall power-conversion efficiency of 3.42%,measured under AM1.5G,solar simulater(80 mW/cm2).The influence of different solvents used for spin-casting of active layer on device performance was studied.The results showed that 1,2-dichlorobenzene was a best solvent for PC[70]BM/MEH-PPV system.The mechanism of the solvent influence on the device performance was analyzed by light and dark I-V curve,AFM,and reasonable explanations were given.Morphology studies on the blend films indicated that excellent miscibility between polymer and PC[60]BM favored exciton separation.Because the exciton diffusion length in organic materials is typically small,the intimate mixture favors exciton separation and therefore higher photocurrent.

Solvent-reagent effect in chemical detection of energetic materials type contaminants

Present study extended the list of solvent and reagents appropriate to use for the colorimetric detection and semi quantitative analysis of various energetic compounds. The new reagents used in this study include DMSO as solvent/reagent, and tetramethylammonium hydroxide and tetrabutylammonium hydroxide for the generation of a basic medium. The advantages of these reagents vs. older procedures are discussed in this paper. Also, a standardized procedure for the analysis of several classes of energetic compounds has been developed, allowing an excellent practical application of the recommended method. The influence of different solvents on the changes in the UV/VIS spectra were evaluated and an attempt to interpret the resulting absorption UV spectra based on quantum-chemical calculations has been done.