Omar Abdel Moneim Abou El Seoud (original) (raw)
Papers by Omar Abdel Moneim Abou El Seoud
Macromolecular Chemistry and Physics, Sep 28, 2017
Carbohydrate Polymers, May 1, 2019
The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution... more The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution and derivatization depends on the structures of both components. We investigated the ILs 1-(1butyl)-3-methylimidazolium acetate (C4MeImAc) and 1-(2-methoxyethyl)-3-methylimidazolium acetate (C3OMeImAc) and their solutions in dimethyl sulfoxide, DMSO, to assess the effect of presence of an ether linkage in the IL side-chain. Surprisingly, C4MeImAc-DMSO was more efficient than C3OMeImAc-DMSO for the dissolution and acylation of cellulose. We investigated both solvents using rheology, NMR spectroscopy, and solvatochromism. Mixtures of C3OMeImAc-DMSO are more viscous, less basic, and form weaker hydrogen bonds with cellobiose than C4MeImAc-DMSO. We attribute the lower efficiency of C3OMeImAc to "deactivation" of the ether oxygen and C2-H of the imidazolium ring due to intramolecular hydrogen bonding. Using the corresponding ILs with C2-CH3 instead of C2-H, namely, 1-butyl-2,3dimethylimidazolium acetate (C4Me2ImAc) and 1-(2-methoxyethyl)-2,3-dimethylimidazolium acetate (C3OMe2ImAc) increased the concentration of dissolved cellulose; without noticeable effect on biopolymer reactivity.
Energy & Fuels, 2018
We extended the oil compatibility model to the dissolution of asphaltenes (Asps) in maltenes from... more We extended the oil compatibility model to the dissolution of asphaltenes (Asps) in maltenes from ten crude oils (COs). As scales for the power of solvents of interest, vide infra, we used solvatochromic parameters, calculated from the Uv-Vis spectra of solvatochromic compounds (probes), Hildebrand/Hansen solubility parameters, and the colloidal instability index of COs. As the colors of maltenes or asphaltene-free crude oils CO (Asp-free) were too dark to permit recording the absorption spectra of the probes, we formulated models for these fractions, (MCO (Asp-free)). They were composed of low molar mass hydrocarbons, namely cis and trans decalines, isooctane, 1-methylnaphthalene and-as model for resins-benzothiazole/n-octyl-1-naphthoate. We based formulations of these MCO (Asp-free) on SARA analysis of the COs, and elemental analysis of the corresponding resins. We validated MCO (Asp-free) as models for the corresponding CO (Aspfree) by showing that the correlation between Hildebrand solubility parameter (δ t) of (COs) and δ t for MCO (Asp-free) is linear with a slope close to unity. Regarding Asp dissolution, we show that the correlations between log (dissolved Asp, mass%) and each of the following solvent descriptors is linear: empirical polarity of MCOs (Asp-free) ; (δ t) of COs; colloidal instability index of COs. Furthermore, the multiple correlation between log (dissolved Asp, mass-%) and other solvatochromic parameters showed that solvent dipolarity and
Journal of the Brazilian Chemical Society
Dyeing of cellulose with reactive dyes (RDs) is an important commercial process because the fiber... more Dyeing of cellulose with reactive dyes (RDs) is an important commercial process because the fibers/fabrics have vivid colors with excellent fastness, since the RD is covalently bonded to cellulose. The subject of the present study is dying of cotton-polyethylene terephthalate (PET) blends using a flow system where the RD absorbance is contentiously monitored by UV-Vis spectroscopy. This allows the collection of extensive data points (≥ 300) to calculate the rate constants, hence the corresponding activation parameters. At a fixed pH = 11.2, a pseudo second-order rate law fits the absorbance vs. time data satisfactorily. At a constant temperature, the order of the dyeing rate constant (k2) is higher for the blend containing 88.9% cotton. The dyeing activation energy, on the other hand, is higher for the blend containing 50% cotton. These results were attributed to the adverse effects of (hydrophobic) PET on the diffusion of RD into the blend. We calculated an equation that shows the ...
Journal of Molecular Liquids, 2021
Polymers, 2021
The impetus for the expanding interest in ionic liquids (ILs) is their favorable properties and i... more The impetus for the expanding interest in ionic liquids (ILs) is their favorable properties and important applications. Ionic liquid-based surfactants (ILBSs) carry long-chain hydrophobic tails. Two or more molecules of ILBSs can be joined by covalent bonds leading, e.g., to gemini compounds (GILBSs). This review article focuses on aspects of the chemistry and applications of ILBSs and GILBSs, especially in the last ten years. Data on their adsorption at the interface and micelle formation are relevant for the applications of these surfactants. Therefore, we collected data for 152 ILBSs and 11 biamphiphilic compounds. The head ions of ILBSs are usually heterocyclic (imidazolium, pyridinium, pyrrolidinium, etc.). Most of these head-ions are also present in the reported 53 GILBSs. Where possible, we correlate the adsorption/micellar properties of the surfactants with their molecular structures, in particular, the number of carbon atoms present in the hydrocarbon “tail”. The use of ILB...
New Journal of Chemistry, 2020
The quantification of interactions of solvatochromic probes with ionic liquids/DMSO serves as an ... more The quantification of interactions of solvatochromic probes with ionic liquids/DMSO serves as an expedient approach for predicting the solvent efficiency in dissolving carbohydrates
Molecules, 2020
We studied the dissolution of microcrystalline cellulose (MCC) in binary mixtures of dimethyl sul... more We studied the dissolution of microcrystalline cellulose (MCC) in binary mixtures of dimethyl sulfoxide (DMSO) and the ionic liquids: allylbenzyldimethylammonium acetate; 1-(2-methoxyethyl)-3-methylimidazolium acetate; 1,8-diazabicyclo [5.4.0]undec-7-ene-8-ium acetate; tetramethylguanidinium acetate. Using chemometrics, we determined the dependence of the mass fraction (in %) of dissolved cellulose (MCC-m%) on the temperature, T = 40, 60, and 80 °C, and the mole fraction of DMSO, χDMSO = 0.4, 0.6, and 0.8. We derived equations that quantified the dependence of MCC-m% on T and χDMSO. Cellulose dissolution increased as a function of increasing both variables; the contribution of χDMSO was larger than that of T in some cases. Solvent empirical polarity was qualitatively employed to rationalize the cellulose dissolution efficiency of the solvent. Using the solvatochromic probe 2,6-dichloro-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (WB), we calculated the empirical polarity ET(WB) of c...
Memórias do Instituto Oswaldo Cruz, 2020
Malaria and tuberculosis are no longer considered to be neglected diseases by the World Health Or... more Malaria and tuberculosis are no longer considered to be neglected diseases by the World Health Organization. However, both are huge challenges and public health problems in the world, which affect poor people, today referred to as neglected populations. In addition, malaria and tuberculosis present the same difficulties regarding the treatment, such as toxicity and the microbial resistance. The increase of Plasmodium resistance to the available drugs along with the insurgence of multidrug-and particularly tuberculosis drug-resistant strains are enough to justify efforts towards the development of novel medicines for both diseases. This literature review provides an overview of the state of the art of antimalarial and antituberculosis chemotherapies, emphasising novel drugs introduced in the pharmaceutical market and the advances in research of new candidates for these diseases, and including some aspects of their mechanism/sites of action.
Catalysts, 2018
The use of titanium dioxide, TiO2 as a photocatalyst in water decontamination has witnessed conti... more The use of titanium dioxide, TiO2 as a photocatalyst in water decontamination has witnessed continuous interest due to its efficiency, stability, low toxicity and cost-effectiveness. TiO2 use is limited by its large band gap energy leading to light absorbance in the UV region of the spectrum, and by the relatively fast rate of recombination of photogenerated electrons and positive holes. Both limitations can be mitigated by using carbon-TiO2 nanocomposites, such as those based on graphene (G) and graphene oxide (GO). Relative to bare TiO2, these nanocomposites have improved photocatalytic activity and stability under the UV–visible light, constituting a promising way forward for improved TiO2 photocatalytic performance. This review focuses on the recent developments in the chemistry of TiO2/G and TiO2/GO nanocomposites. It addresses the mechanistic fundamentals, briefly, of TiO2 and TiO2/G and TiO2/GO photocatalysts, the various synthesis strategies for preparing TiO2/G and TiO2/GO ...
ACS Omega, 2018
Surfactant-mediated coacervates are termed as the new age microreactors for their ability to spon... more Surfactant-mediated coacervates are termed as the new age microreactors for their ability to spontaneously sequester the molecules with varied polarities and functionalities. Efforts to emulate this applicability of coacervates through synthetic control of surfactant structures are finding success; however, there is little understanding of how to translate these changes into tailor-made properties. Herein, we designed 3-methyl-1-(octyloxycarbonylmethyl)imidazolium bromide (C 8 EMeImBr), an ester-functionalized ionic liquidbased surfactant, which shows better surface active properties than the nonfunctionalized and conventional cationic surfactant and forms complex coacervates over the broad range of concentration with sodium salicylate (NaSal). Monoand divalent cations as well as ionic strength, viscosity, and time-dependent stability of the coacervates had also been addressed in order to study whether these coacervates could work as microreactors to encapsulate various molecules. The anionic charged complex coacervates with sponge morphology and honey comb-like interior show good efficiency to sequester cationic dyes from water because of electrostatic and hydrophobic interactions and good encapsulation efficiency for curcumin owing to their high surface area. Results suggest that ionic liquid-based coacervates studied here could be exploited as a novel low-cost, effective, and environmentally benign alternative to sequester dyes from the contaminated water and their recovery.
ACS omega, Jan 30, 2018
An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium an... more An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium and forms ionogels at 8.80% (w/v) concentration at physiological pH. The ionogel exhibited a remarkable change in its appearance with temperature from fibrillar opaque to transparent because of the dynamic changes within its supramolecular structure. This gel-to-gel phase transition occurs below the melting point of the solid ionic liquid. The ionogels were investigated using turbidity, differential scanning calorimetry, scanning electron microscopy (SEM), field emission SEM (FE-SEM), inverted microscopy, transmission electron microscopy imaging, Fourier transform infrared spectroscopy, and rheological measurements. The fibrillar opaque ionogel and transparent ionogel were studied for their ability to absorb dyes (methyl orange and crystal violet) and to encapsulate drugs (diclofenac sodium and imatinib mesylate).
Molecules (Basel, Switzerland), Jan 25, 2018
There is a sustained interest in developing solvents for physically dissolving cellulose, i.e., w... more There is a sustained interest in developing solvents for physically dissolving cellulose, i.e., without covalent bond formation. The use of ionic liquids, ILs, has generated much interest because of their structural versatility that results in efficiency as cellulose solvents. Despite some limitations, imidazole-based ILs have received most of the scientific community's attention. The objective of the present review is to show the advantages of using quaternary ammonium electrolytes, QAEs, including salts of super bases, as solvents for cellulose dissolution, shaping, and derivatization, and as a result, increase the interest in further investigation of these important solvents. QAEs share with ILs structural versatility; many are liquids at room temperature or are soluble in water and molecular solvents (MSs), in particular dimethyl sulfoxide. In this review we first give a historical background on the use of QAEs in cellulose chemistry, and then discuss the common, relatively ...
RSC Advances, 2017
Solubilization of the drug diclofenac sodium (DS) in micellar aggregates of ionic liquid-based su... more Solubilization of the drug diclofenac sodium (DS) in micellar aggregates of ionic liquid-based surfactants and cetyltrimethylammonium bromide at 25 °C induces changes to worm-like micelles and vesicles, with potential use in drug delivery.
Energy & Fuels, 2016
The oil compatibility model is important for assessing the stability of crudes. The compatibility... more The oil compatibility model is important for assessing the stability of crudes. The compatibility between maltenes and the corresponding asphaltenes, Asphs, can be assessed from the solubility parameters (Hildebrand and Hansen) of both components of the crude. Solvatochromism is the effect of the medium on the UV/vis spectra of substances (solvatochromic probes) that are sensitive to the properties of the medium, namely, its empirical (or overall) polarity, Lewis acidity and basicity, dipolarity, and polarizability. Therefore, the solubility and solvatochromic parameters of solvents should be related. We synthesized a novel solvatochromic probe (E-2,6-di-tert-butyl-4-(2-(1-hexylquinolin-1-ium-4-yl)vinyl)phenolate, HxQMBu2) whose properties are convenient to study in nonpolar and polar solvents. The empirical solvent polarities measured with HxQMBu2 in 38 solvents correlated linearly with the corresponding Hildebrand solubility parameters. Likewise, the solvent Lewis acidity/basicity, dipolarity, and polar...
Colloid & Polymer Science, 1997
1H NMR chemical shifts of solutions of the following cationic surfactants in D 2 0 were determine... more 1H NMR chemical shifts of solutions of the following cationic surfactants in D 2 0 were determined as a function of their concentrations: cetyltrimethylammonium chloride, CTAC1, a 1 : 1 molar mixture of CTACI and toluene, cetylpyridinium chloride, CPyCl, cetyldimethylphenylammonium chloride, CDPhAC1, cetyldimethylbenzylammonium chloride, CDBzAC1, cetyldimethyl-2phenylethylammonium chloride, CDPhEtAC1, and cetyldimethyl-3phenylpropylammonium chloride, CDPhPrAC1. Plots of observed chemical shifts versus [surfactant] are sigmoidal, and were fitted to a model based on the mass-action law. Satisfactory fitting was obtained for the discrete protons of all surfactants. From these fits, we calculated the equilibrium constant for micelle formation, K, the critical micelle concentration, CMC and the chemical shifts of the monomer, 6mo n and the micelle 6mic. 1H NMRbased CMC values are in excellent agreement with those which we perpendicular to the interface in CDPhAC1 and is more or less parallel to it in CDBzAC1, CDPhEtACI, and CDPhPrAC1.
Polymers, 2021
We studied the dependence of dissolution of silk fibroin (SF) in mixtures of DMSO with ionic liqu... more We studied the dependence of dissolution of silk fibroin (SF) in mixtures of DMSO with ionic liquids (ILs) on the temperature (T = 40 to 80 °C) and DMSO mole fraction (χDMSO = 0.5 to 0.9). The ILs included BuMeImAcO, C3OMeImAcO, AlBzMe2NAcO, and Bu4NAcO; see the names and structures below. We used design of experiments (DOE) to determine the dependence of mass fraction of dissolved SF (SF-m%) on T and χDMSO. We successfully employed a second-order polynomial to fit the biopolymer dissolution data. The resulting regression coefficients showed that the dissolution of SF in BuMeImAcO-DMSO and C3OMeImAcO-DMSO is more sensitive to variation of T than of χDMSO; the inverse is observed for the quaternary ammonium ILs. Using BuMeImAcO, AlBzMe2NAcO, and molecular dynamics simulations, we attribute the difference in IL efficiency to stronger SF-IL hydrogen bonding with the former IL, which is coupled with the difference in the molecular volumes and the rigidity of the phenyl ring of the latte...
Macromolecular Chemistry and Physics, Nov 17, 2015
Acetylation of microcrystalline cellulose (MCC) by ethanoic anhydride (Ac2O) in mixtures of the i... more Acetylation of microcrystalline cellulose (MCC) by ethanoic anhydride (Ac2O) in mixtures of the ionic liquid (IL) 1‐allyl‐3‐methylimidazolium chloride and the (structurally related) molecular solvents (MSs), dimethylsulfoxide (DMSO) and sulfolane (Sulfn), is studied. Values of the reaction third‐order rate constants, k3, are calculated from conductivity data; they are linearly dependent on c(IL), due to (cellulose‐solvent) complex formation, as corroborated by Fourier Transform Infrared (FTIR) spectroscopy. The observed order of reactivity (IL/DMSO > IL/Sulfn) is explained by examining differences in the following properties of the MCC‐IL/MS solutions: macroscopic (viscosity); microscopic (empirical polarity and basicity), and from the results of molecular dynamics simulations. The latter indicate faster reactant diffusion in IL/DMSO and more interaction between the biopolymer hydroxyl groups and the ions of the IL. image
Collection of Czechoslovak Chemical Communications, 1973
Journal of the Chemical Society, Perkin Transactions 2, 1976
The spontaneous hydration of acetaldehyde by water and D2O localized in micellar Triton X-100 in ... more The spontaneous hydration of acetaldehyde by water and D2O localized in micellar Triton X-100 in carbon tetrachloride is 1.5 × 104 and 5.4 × 104 times faster than that in bulk water and D2O, respectively. In the presence of the surfactant, the rates of specific acid-catalysed hydration are between 2.4–1.2 and 3.6–2 times faster than those of perchloric acid-catalysed reactions in bulk water and D2O, respectively. The rates of the specific acid-catalysed hydration decrease as a function of Increasing the concentration of the micelle solubilized water or D2O.
Macromolecular Chemistry and Physics, Sep 28, 2017
Carbohydrate Polymers, May 1, 2019
The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution... more The efficiency of mixtures of ionic liquids (ILs) and molecular solvents in cellulose dissolution and derivatization depends on the structures of both components. We investigated the ILs 1-(1butyl)-3-methylimidazolium acetate (C4MeImAc) and 1-(2-methoxyethyl)-3-methylimidazolium acetate (C3OMeImAc) and their solutions in dimethyl sulfoxide, DMSO, to assess the effect of presence of an ether linkage in the IL side-chain. Surprisingly, C4MeImAc-DMSO was more efficient than C3OMeImAc-DMSO for the dissolution and acylation of cellulose. We investigated both solvents using rheology, NMR spectroscopy, and solvatochromism. Mixtures of C3OMeImAc-DMSO are more viscous, less basic, and form weaker hydrogen bonds with cellobiose than C4MeImAc-DMSO. We attribute the lower efficiency of C3OMeImAc to "deactivation" of the ether oxygen and C2-H of the imidazolium ring due to intramolecular hydrogen bonding. Using the corresponding ILs with C2-CH3 instead of C2-H, namely, 1-butyl-2,3dimethylimidazolium acetate (C4Me2ImAc) and 1-(2-methoxyethyl)-2,3-dimethylimidazolium acetate (C3OMe2ImAc) increased the concentration of dissolved cellulose; without noticeable effect on biopolymer reactivity.
Energy & Fuels, 2018
We extended the oil compatibility model to the dissolution of asphaltenes (Asps) in maltenes from... more We extended the oil compatibility model to the dissolution of asphaltenes (Asps) in maltenes from ten crude oils (COs). As scales for the power of solvents of interest, vide infra, we used solvatochromic parameters, calculated from the Uv-Vis spectra of solvatochromic compounds (probes), Hildebrand/Hansen solubility parameters, and the colloidal instability index of COs. As the colors of maltenes or asphaltene-free crude oils CO (Asp-free) were too dark to permit recording the absorption spectra of the probes, we formulated models for these fractions, (MCO (Asp-free)). They were composed of low molar mass hydrocarbons, namely cis and trans decalines, isooctane, 1-methylnaphthalene and-as model for resins-benzothiazole/n-octyl-1-naphthoate. We based formulations of these MCO (Asp-free) on SARA analysis of the COs, and elemental analysis of the corresponding resins. We validated MCO (Asp-free) as models for the corresponding CO (Aspfree) by showing that the correlation between Hildebrand solubility parameter (δ t) of (COs) and δ t for MCO (Asp-free) is linear with a slope close to unity. Regarding Asp dissolution, we show that the correlations between log (dissolved Asp, mass%) and each of the following solvent descriptors is linear: empirical polarity of MCOs (Asp-free) ; (δ t) of COs; colloidal instability index of COs. Furthermore, the multiple correlation between log (dissolved Asp, mass-%) and other solvatochromic parameters showed that solvent dipolarity and
Journal of the Brazilian Chemical Society
Dyeing of cellulose with reactive dyes (RDs) is an important commercial process because the fiber... more Dyeing of cellulose with reactive dyes (RDs) is an important commercial process because the fibers/fabrics have vivid colors with excellent fastness, since the RD is covalently bonded to cellulose. The subject of the present study is dying of cotton-polyethylene terephthalate (PET) blends using a flow system where the RD absorbance is contentiously monitored by UV-Vis spectroscopy. This allows the collection of extensive data points (≥ 300) to calculate the rate constants, hence the corresponding activation parameters. At a fixed pH = 11.2, a pseudo second-order rate law fits the absorbance vs. time data satisfactorily. At a constant temperature, the order of the dyeing rate constant (k2) is higher for the blend containing 88.9% cotton. The dyeing activation energy, on the other hand, is higher for the blend containing 50% cotton. These results were attributed to the adverse effects of (hydrophobic) PET on the diffusion of RD into the blend. We calculated an equation that shows the ...
Journal of Molecular Liquids, 2021
Polymers, 2021
The impetus for the expanding interest in ionic liquids (ILs) is their favorable properties and i... more The impetus for the expanding interest in ionic liquids (ILs) is their favorable properties and important applications. Ionic liquid-based surfactants (ILBSs) carry long-chain hydrophobic tails. Two or more molecules of ILBSs can be joined by covalent bonds leading, e.g., to gemini compounds (GILBSs). This review article focuses on aspects of the chemistry and applications of ILBSs and GILBSs, especially in the last ten years. Data on their adsorption at the interface and micelle formation are relevant for the applications of these surfactants. Therefore, we collected data for 152 ILBSs and 11 biamphiphilic compounds. The head ions of ILBSs are usually heterocyclic (imidazolium, pyridinium, pyrrolidinium, etc.). Most of these head-ions are also present in the reported 53 GILBSs. Where possible, we correlate the adsorption/micellar properties of the surfactants with their molecular structures, in particular, the number of carbon atoms present in the hydrocarbon “tail”. The use of ILB...
New Journal of Chemistry, 2020
The quantification of interactions of solvatochromic probes with ionic liquids/DMSO serves as an ... more The quantification of interactions of solvatochromic probes with ionic liquids/DMSO serves as an expedient approach for predicting the solvent efficiency in dissolving carbohydrates
Molecules, 2020
We studied the dissolution of microcrystalline cellulose (MCC) in binary mixtures of dimethyl sul... more We studied the dissolution of microcrystalline cellulose (MCC) in binary mixtures of dimethyl sulfoxide (DMSO) and the ionic liquids: allylbenzyldimethylammonium acetate; 1-(2-methoxyethyl)-3-methylimidazolium acetate; 1,8-diazabicyclo [5.4.0]undec-7-ene-8-ium acetate; tetramethylguanidinium acetate. Using chemometrics, we determined the dependence of the mass fraction (in %) of dissolved cellulose (MCC-m%) on the temperature, T = 40, 60, and 80 °C, and the mole fraction of DMSO, χDMSO = 0.4, 0.6, and 0.8. We derived equations that quantified the dependence of MCC-m% on T and χDMSO. Cellulose dissolution increased as a function of increasing both variables; the contribution of χDMSO was larger than that of T in some cases. Solvent empirical polarity was qualitatively employed to rationalize the cellulose dissolution efficiency of the solvent. Using the solvatochromic probe 2,6-dichloro-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (WB), we calculated the empirical polarity ET(WB) of c...
Memórias do Instituto Oswaldo Cruz, 2020
Malaria and tuberculosis are no longer considered to be neglected diseases by the World Health Or... more Malaria and tuberculosis are no longer considered to be neglected diseases by the World Health Organization. However, both are huge challenges and public health problems in the world, which affect poor people, today referred to as neglected populations. In addition, malaria and tuberculosis present the same difficulties regarding the treatment, such as toxicity and the microbial resistance. The increase of Plasmodium resistance to the available drugs along with the insurgence of multidrug-and particularly tuberculosis drug-resistant strains are enough to justify efforts towards the development of novel medicines for both diseases. This literature review provides an overview of the state of the art of antimalarial and antituberculosis chemotherapies, emphasising novel drugs introduced in the pharmaceutical market and the advances in research of new candidates for these diseases, and including some aspects of their mechanism/sites of action.
Catalysts, 2018
The use of titanium dioxide, TiO2 as a photocatalyst in water decontamination has witnessed conti... more The use of titanium dioxide, TiO2 as a photocatalyst in water decontamination has witnessed continuous interest due to its efficiency, stability, low toxicity and cost-effectiveness. TiO2 use is limited by its large band gap energy leading to light absorbance in the UV region of the spectrum, and by the relatively fast rate of recombination of photogenerated electrons and positive holes. Both limitations can be mitigated by using carbon-TiO2 nanocomposites, such as those based on graphene (G) and graphene oxide (GO). Relative to bare TiO2, these nanocomposites have improved photocatalytic activity and stability under the UV–visible light, constituting a promising way forward for improved TiO2 photocatalytic performance. This review focuses on the recent developments in the chemistry of TiO2/G and TiO2/GO nanocomposites. It addresses the mechanistic fundamentals, briefly, of TiO2 and TiO2/G and TiO2/GO photocatalysts, the various synthesis strategies for preparing TiO2/G and TiO2/GO ...
ACS Omega, 2018
Surfactant-mediated coacervates are termed as the new age microreactors for their ability to spon... more Surfactant-mediated coacervates are termed as the new age microreactors for their ability to spontaneously sequester the molecules with varied polarities and functionalities. Efforts to emulate this applicability of coacervates through synthetic control of surfactant structures are finding success; however, there is little understanding of how to translate these changes into tailor-made properties. Herein, we designed 3-methyl-1-(octyloxycarbonylmethyl)imidazolium bromide (C 8 EMeImBr), an ester-functionalized ionic liquidbased surfactant, which shows better surface active properties than the nonfunctionalized and conventional cationic surfactant and forms complex coacervates over the broad range of concentration with sodium salicylate (NaSal). Monoand divalent cations as well as ionic strength, viscosity, and time-dependent stability of the coacervates had also been addressed in order to study whether these coacervates could work as microreactors to encapsulate various molecules. The anionic charged complex coacervates with sponge morphology and honey comb-like interior show good efficiency to sequester cationic dyes from water because of electrostatic and hydrophobic interactions and good encapsulation efficiency for curcumin owing to their high surface area. Results suggest that ionic liquid-based coacervates studied here could be exploited as a novel low-cost, effective, and environmentally benign alternative to sequester dyes from the contaminated water and their recovery.
ACS omega, Jan 30, 2018
An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium an... more An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium and forms ionogels at 8.80% (w/v) concentration at physiological pH. The ionogel exhibited a remarkable change in its appearance with temperature from fibrillar opaque to transparent because of the dynamic changes within its supramolecular structure. This gel-to-gel phase transition occurs below the melting point of the solid ionic liquid. The ionogels were investigated using turbidity, differential scanning calorimetry, scanning electron microscopy (SEM), field emission SEM (FE-SEM), inverted microscopy, transmission electron microscopy imaging, Fourier transform infrared spectroscopy, and rheological measurements. The fibrillar opaque ionogel and transparent ionogel were studied for their ability to absorb dyes (methyl orange and crystal violet) and to encapsulate drugs (diclofenac sodium and imatinib mesylate).
Molecules (Basel, Switzerland), Jan 25, 2018
There is a sustained interest in developing solvents for physically dissolving cellulose, i.e., w... more There is a sustained interest in developing solvents for physically dissolving cellulose, i.e., without covalent bond formation. The use of ionic liquids, ILs, has generated much interest because of their structural versatility that results in efficiency as cellulose solvents. Despite some limitations, imidazole-based ILs have received most of the scientific community's attention. The objective of the present review is to show the advantages of using quaternary ammonium electrolytes, QAEs, including salts of super bases, as solvents for cellulose dissolution, shaping, and derivatization, and as a result, increase the interest in further investigation of these important solvents. QAEs share with ILs structural versatility; many are liquids at room temperature or are soluble in water and molecular solvents (MSs), in particular dimethyl sulfoxide. In this review we first give a historical background on the use of QAEs in cellulose chemistry, and then discuss the common, relatively ...
RSC Advances, 2017
Solubilization of the drug diclofenac sodium (DS) in micellar aggregates of ionic liquid-based su... more Solubilization of the drug diclofenac sodium (DS) in micellar aggregates of ionic liquid-based surfactants and cetyltrimethylammonium bromide at 25 °C induces changes to worm-like micelles and vesicles, with potential use in drug delivery.
Energy & Fuels, 2016
The oil compatibility model is important for assessing the stability of crudes. The compatibility... more The oil compatibility model is important for assessing the stability of crudes. The compatibility between maltenes and the corresponding asphaltenes, Asphs, can be assessed from the solubility parameters (Hildebrand and Hansen) of both components of the crude. Solvatochromism is the effect of the medium on the UV/vis spectra of substances (solvatochromic probes) that are sensitive to the properties of the medium, namely, its empirical (or overall) polarity, Lewis acidity and basicity, dipolarity, and polarizability. Therefore, the solubility and solvatochromic parameters of solvents should be related. We synthesized a novel solvatochromic probe (E-2,6-di-tert-butyl-4-(2-(1-hexylquinolin-1-ium-4-yl)vinyl)phenolate, HxQMBu2) whose properties are convenient to study in nonpolar and polar solvents. The empirical solvent polarities measured with HxQMBu2 in 38 solvents correlated linearly with the corresponding Hildebrand solubility parameters. Likewise, the solvent Lewis acidity/basicity, dipolarity, and polar...
Colloid & Polymer Science, 1997
1H NMR chemical shifts of solutions of the following cationic surfactants in D 2 0 were determine... more 1H NMR chemical shifts of solutions of the following cationic surfactants in D 2 0 were determined as a function of their concentrations: cetyltrimethylammonium chloride, CTAC1, a 1 : 1 molar mixture of CTACI and toluene, cetylpyridinium chloride, CPyCl, cetyldimethylphenylammonium chloride, CDPhAC1, cetyldimethylbenzylammonium chloride, CDBzAC1, cetyldimethyl-2phenylethylammonium chloride, CDPhEtAC1, and cetyldimethyl-3phenylpropylammonium chloride, CDPhPrAC1. Plots of observed chemical shifts versus [surfactant] are sigmoidal, and were fitted to a model based on the mass-action law. Satisfactory fitting was obtained for the discrete protons of all surfactants. From these fits, we calculated the equilibrium constant for micelle formation, K, the critical micelle concentration, CMC and the chemical shifts of the monomer, 6mo n and the micelle 6mic. 1H NMRbased CMC values are in excellent agreement with those which we perpendicular to the interface in CDPhAC1 and is more or less parallel to it in CDBzAC1, CDPhEtACI, and CDPhPrAC1.
Polymers, 2021
We studied the dependence of dissolution of silk fibroin (SF) in mixtures of DMSO with ionic liqu... more We studied the dependence of dissolution of silk fibroin (SF) in mixtures of DMSO with ionic liquids (ILs) on the temperature (T = 40 to 80 °C) and DMSO mole fraction (χDMSO = 0.5 to 0.9). The ILs included BuMeImAcO, C3OMeImAcO, AlBzMe2NAcO, and Bu4NAcO; see the names and structures below. We used design of experiments (DOE) to determine the dependence of mass fraction of dissolved SF (SF-m%) on T and χDMSO. We successfully employed a second-order polynomial to fit the biopolymer dissolution data. The resulting regression coefficients showed that the dissolution of SF in BuMeImAcO-DMSO and C3OMeImAcO-DMSO is more sensitive to variation of T than of χDMSO; the inverse is observed for the quaternary ammonium ILs. Using BuMeImAcO, AlBzMe2NAcO, and molecular dynamics simulations, we attribute the difference in IL efficiency to stronger SF-IL hydrogen bonding with the former IL, which is coupled with the difference in the molecular volumes and the rigidity of the phenyl ring of the latte...
Macromolecular Chemistry and Physics, Nov 17, 2015
Acetylation of microcrystalline cellulose (MCC) by ethanoic anhydride (Ac2O) in mixtures of the i... more Acetylation of microcrystalline cellulose (MCC) by ethanoic anhydride (Ac2O) in mixtures of the ionic liquid (IL) 1‐allyl‐3‐methylimidazolium chloride and the (structurally related) molecular solvents (MSs), dimethylsulfoxide (DMSO) and sulfolane (Sulfn), is studied. Values of the reaction third‐order rate constants, k3, are calculated from conductivity data; they are linearly dependent on c(IL), due to (cellulose‐solvent) complex formation, as corroborated by Fourier Transform Infrared (FTIR) spectroscopy. The observed order of reactivity (IL/DMSO > IL/Sulfn) is explained by examining differences in the following properties of the MCC‐IL/MS solutions: macroscopic (viscosity); microscopic (empirical polarity and basicity), and from the results of molecular dynamics simulations. The latter indicate faster reactant diffusion in IL/DMSO and more interaction between the biopolymer hydroxyl groups and the ions of the IL. image
Collection of Czechoslovak Chemical Communications, 1973
Journal of the Chemical Society, Perkin Transactions 2, 1976
The spontaneous hydration of acetaldehyde by water and D2O localized in micellar Triton X-100 in ... more The spontaneous hydration of acetaldehyde by water and D2O localized in micellar Triton X-100 in carbon tetrachloride is 1.5 × 104 and 5.4 × 104 times faster than that in bulk water and D2O, respectively. In the presence of the surfactant, the rates of specific acid-catalysed hydration are between 2.4–1.2 and 3.6–2 times faster than those of perchloric acid-catalysed reactions in bulk water and D2O, respectively. The rates of the specific acid-catalysed hydration decrease as a function of Increasing the concentration of the micelle solubilized water or D2O.