MyMedR

Displaying publications 61 - 80 of 114 in total

Abstract:

Sort:

Adsorption and self-assembly in methyl ester sulfonate surfactants, their eutectic mixtures and the role of electrolyte

Xu H, Li P, Ma K, Welbourn RJL, Doutch J, Penfold J, et al.

J Colloid Interface Sci, 2018 Apr 15;516:456-465.
PMID: 29408135 DOI: 10.1016/j.jcis.2018.01.086

The α-methyl ester sulfonate, MES, anionic surfactants are a potentially important class of sustainable surfactants for a wide range of applications. The eutectic-like Kraft point minimum in the C16 and C18-MES mixtures is an important feature of that potential. Understanding their individual adsorption properties and the surface mixing of the eutectic mixtures are key to their wider exploitation. Neutron reflectivity has been used to investigate the adsorption at the air-water interface of the C16 and C18-MES surfactants and the eutectic mixture of C16 and C18-MES, in aqueous solution and in electrolyte. The micelle mixing of the eutectic mixture is investigated using small angle neutron scattering. The adsorption isotherms for C14 to C18-MES are found to scale with their critical micelle concentration value. The surface and micelle compositions of the C16 and C18-MES eutectic mixture differ from the eutectic composition; with compositions in the limit of high concentrations richer in C16-MES. The mixing properties are described by the pseudo phase approximation with a repulsive interaction between the two surfactants. The impact of the multivalent ions Al3+ on the adsorption at the air-water interface results in a transition from monolayer to multilayer adsorption.
Rational design of aromatic surfactants for graphene/natural rubber latex nanocomposites with enhanced electrical conductivity

Mohamed A, Ardyani T, Abu Bakar S, Sagisaka M, Umetsu Y, Hamon JJ, et al.

J Colloid Interface Sci, 2018 Apr 15;516:34-47.
PMID: 29360058 DOI: 10.1016/j.jcis.2018.01.041

HYPOTHESIS: Graphene nanoplatelets (GNPs) can be dispersed in natural rubber matrices using surfactants. The stability and properties of these composites can be optimized by the choice of surfactants employed as stabilizers. Surfactants can be designed and synthesized to have enhanced compatibility with GNPs as compared to commercially available common surfactants. Including aromatic groups in the hydrophobic chain termini improves graphene compatibility of surfactants, which is expected to increase with the number of aromatic moieties per surfactant molecule. Hence, it is of interest to study the relationship between molecular structure, dispersion stability and electrical conductivity enhancement for single-, double-, and triple-chain anionic graphene-compatible surfactants.
EXPERIMENTS: Graphene-philic surfactants, bearing two and three chains phenylated at their chain termini, were synthesized and characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy. These were used to formulate and stabilize dispersion of GNPs in natural rubber latex matrices, and the properties of systems comprising the new phenyl-surfactants were compared with commercially available surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS). Raman spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM) were used to study structural properties of the materials. Electrical conductivity measurements and Zeta potential measurements were used to assess the relationships between surfactant architecture and nanocomposite properties. Small-angle neutron scattering (SANS) was used to study self-assembly structure of surfactants.
FINDINGS: Of these different surfactants, the tri-chain aromatic surfactant TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate) was shown to be highly graphene-compatible (nanocomposite electrical conductivity = 2.22 × 10-5 S cm-1), demonstrating enhanced electrical conductivity over nine orders of magnitude higher than neat natural rubber-latex matrix (1.51 × 10-14 S cm-1). Varying the number of aromatic moieties in the surfactants appears to cause significant differences to the final properties of the nanocomposites.
Janus graphene oxide nanosheet: A promising additive for enhancement of polymeric membranes performance prepared via phase inversion

Akbari M, Shariaty-Niassar M, Matsuura T, Ismail AF

J Colloid Interface Sci, 2018 Oct 01;527:10-24.
PMID: 29775817 DOI: 10.1016/j.jcis.2018.05.012

Although polymeric membranes find important role in water and waste water treatment in recent years, their fouling is still an important problem. Application of hydrophilic nanoparticles (NPs) is one of the proposed methods for reducing fouling of membranes but their dispersion and stability in hydrophobic polymer matrix is challenging. In this study Janus functionalization of the NPs was introduced as a promising technique toward achieving this goal. Polysulfone (PSf) membranes containing various concentrations of graphene oxide (GO) nanosheets and Janus graphene oxide (Janus GO) nanosheets (as additives) were fabricated via phase inversion. The synthesized nanosheets were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy and dynamic light scattering (DLS). The prepared membranes also were then characterized by scanning electron microscopy (SEM), contact angle (CA), water uptake, porosity, mean pore size and casting solution viscosity. The membrane performance was also tested by determining pure water flux (PWF), bovine serum albumin (BSA) separation, flux reduction by fouling and flux recovery. CA reduced from 85° to 68° and PWF increased from 23.15 L/m2 h to 230.61 L/m2 h for PSF and Janus GO nanosheets containing membrane, respectively. Also investigation of antifouling performance of membranes revealed that membrane with the 1 wt.% of Janus GO nanosheets had higher water flux recovery ratio (FRR) and lower irreversible fouling (Rir) of 84% and 16%, respectively. These improvements were attributed to the better dispersion and stability of Janus GO nanosheets in the prepared mixed matrix membranes.
Self-assembled three-dimensional reduced graphene oxide-based hydrogel for highly efficient and facile removal of pharmaceutical compounds from aqueous solution

Umbreen N, Sohni S, Ahmad I, Khattak NU, Gul K

J Colloid Interface Sci, 2018 Oct 01;527:356-367.
PMID: 29843021 DOI: 10.1016/j.jcis.2018.05.010

Herein, self-assembled three-dimensional reduced graphene oxide (RGO)-based hydrogels were synthesized and characterized in detail. A thorough investigation on the uptake of three widely used pharmaceutical drugs, viz. Naproxen (NPX), Ibuprofen (IBP) and Diclofenac (DFC) was carried out from aqueous solutions. To ensure the sustainability of developed hydrogel assembly, practically important parameters such as desorption, recyclability and applicability to real samples were also evaluated. Using the developed 3D hydrogels as adsorptive platforms, excellent decontamination for the above mentioned persistent pharmaceutical drugs was achieved in acidic pH with a removal efficiency in the range of 70-80%. These hydrogels showed fast adsorption kinetics and experimental findings were fitted to different kinetic models, such as pseudo-first order, pseudo-second order, intra-particle and the Elovich models in an attempt to better understand the adsorption kinetics. Furthermore, equilibrium adsorption data was fitted to the Langmuir and Freundlich models, where relatively higher R2 values obtained in case of former one suggested that monolayer adsorption played an important part in drug uptake. Thermodynamic aspects were also studied and negative ΔG0 values obtained indicated the spontaneous nature of adsorption process. The study was also extended to check practical utility of as-prepared hydrogels by spiking real aqueous samples with drug solution, where high % recoveries obtained for NPX, IBP and DFC were of particular importance with regard to prospective application in wastewater treatment systems. We advocate RGO-based hydrogels as environmentally benign, readily recoverable/recyclable material with excellent adsorption capacity for application in wastewater purification.
Membrane-lytic actions of sulphonated methyl ester surfactants and implications to bactericidal effect and cytotoxicity

Pan F, Li Z, Gong H, Petkov JT, Lu JR

J Colloid Interface Sci, 2018 Dec 01;531:18-27.
PMID: 30015167 DOI: 10.1016/j.jcis.2018.07.031

Surfactants are multifunctional molecules widely used in personal care and healthcare formulations to cleanse, help disperse active ingredients (e.g., forming emulsions) and stabilise products. With increasing demands on improving biosafety, there is now mounting pressure to understand how different surfactants elicit toxicities at molecular and cellular levels. This work reports the membrane-lytic behaviour of a group of sulphonated methyl ester (SME) surfactants together with representative conventional surfactants. All surfactants displayed the clear rise of lysis of the model lipid bilayer membranes around their CMCs, but the two ionic surfactants SDS and C12TAB even caused measurable lysis below their CMCs, with membrane-lytic actions increasing with monomer concentration. Furthermore, whilst ionic and nonionic surfactants could achieve full membrane lysis once above their CMCs, this ability was weak from the SME surfactants and decreased with increasing the acyl chain length. In contrast to the conventional anionic surfactants such as SDS and SLES, the protein solubilizing capability of the SME surfactants was also low. On the other hand, MTT assays against 3T3 fibroblast cells and human chondrocyte cells revealed high toxicity from SDS and C12TAB against the other surfactants studied, but the difference between SME and the rest of conventional surfactants was small. Similar behaviour was also observed in their bactericidal effect against E. coli and S. aureus. The trend is broadly consistent with their membrane-lytic behaviour, indicating little selectivity in their cytotoxicity and bactericidal action. These results thus reveal different toxicities implicated from different surfactant head groups. Increase in acyl chain length as observed from SME surfactants could help improve surfactant biocompatibility.
Hybrid membrane filtration-advanced oxidation processes for removal of pharmaceutical residue

Rosman N, Salleh WNW, Mohamed MA, Jaafar J, Ismail AF, Harun Z

J Colloid Interface Sci, 2018 Dec 15;532:236-260.
PMID: 30092507 DOI: 10.1016/j.jcis.2018.07.118

Reports of pharmaceuticals exist in surface water and drinking water around the world, indicate they are ineffectively remove from water and wastewater using conventional treatment technologies. The potential of adverse effect of these pharmaceuticals on public health and aquatic life, also their continuos accumulation have raised the development of water treatment technologies. Hybrid treatment processes like membrane filtration and advance oxidation processes (AOPs) are likely to give rise to efficient simultaneous degradation and separation mechanisms. Conventional membrane filtration techniques can remove the majority of contaminants, but the smallest, undegraded, and stabilized pharmaceutical wastes persist in the treated water. After some 20 years, researchers have recognized the important role of AOPs in the treatment of pharmaceutical wastewater because these technologies are capable of oxidizing recalcitrant, toxic, and non-biodigradable compounds into numerous by-products and finally, inert end-products via the intermediacy of hydroxyl and other radicals. Evidently, membranes are subjected to the fouling phenomenon by the contaminants in wastewater, hence resulting in a reduction of clean water flux and increase in energy demand. In such situations, these membrane hybrid AOPs exert a complementary effect in the elimination of membrane fouling, thus enhancing the performance of the membrane. Therefore, in this review, we describe the basic aspects of the removal and transformation of certain pharmaceuticals via membranes and AOPs. In addition, information and evidences on membrane hybrid AOPs in the field of pharmaceutical wastewater treatment is also presented.
The role of competitive counterion adsorption on the electrolyte induced surface ordering in methyl ester sulfonate surfactants at the air-water interface

Xu H, Li P, Ma K, Welbourn RJL, Penfold J, Thomas RK, et al.

J Colloid Interface Sci, 2019 Jan 01;533:154-160.
PMID: 30153592 DOI: 10.1016/j.jcis.2018.08.061

The strong binding of Al3+ trivalent counterions to the anionic surfactants sodium polyethylene glycol monoalkyl ether sulfate and α-methyl ester sulfonate results in surface multilayer formation at the air-water interface. In contrast the divalent and monovalent counterions Ca2+ and Na+ result only in monolayer adsorption. Competitive counterion adsorption has been extensively studied in the context of surfactant precipitation and re-dissolution, but remains an important feature in understanding this surface ordering and how it can be manipulated. The α-methyl ester sulfonate surfactants are a promising class of anionic surfactants which have much potential for improved performance in many applications, greater tolerance to extreme solvent conditions such as water hardness, biocompatibility and sustainable production. Hence in this study we have used neutron reflectivity to extend previous studies on the surface ordering of the α-methyl ester sulfonate surfactant, sodium tetradecanoic 2-sulfo 1-methyl ester, in the presence of electrolyte to investigate the role of binary mixtures of electrolytes, AlCl3/CaCl2, and AlCl3/MgCl2. In the mixed electrolytes the evolution of the surface structure, from monolayer to multilayer with increasing AlCl3 concentration, is observed. It is broadly similar to that reported for the addition of only AlCl3. However with increasing CaCl2 concentration the structural evolution is shifted progressively to higher AlCl3 concentrations. Similar observations occur for the AlCl3/MgCl2 mixtures. However the presence of the MgCl2 results in an additional phenomenon; the partial co-adsorption of a more compact lamellar structure which exists until the highest AlCl3 concentrations. The results demonstrate the importance of the competitive adsorption of different counterions in driving and controlling the formation of surface multilayer structures with anionic surfactants. Furthermore it offers a facile route to the manipulation of these surface structures.
Fulltext Properties of the micelles of sulfonated methyl esters determined from the stepwise thinning of foam films and by rheological measurements

Basheva ES, Danov KD, Radulova GM, Kralchevsky PA, Xu H, Ung YW, et al.

J Colloid Interface Sci, 2019 Mar 07;538:660-670.
PMID: 30572230 DOI: 10.1016/j.jcis.2018.12.034

HYPOTHESES: The micellar solutions of sulfonated methyl esters (SME) are expected to form stratifying foam films that exhibit stepwise thinning. From the height of the steps, which are engendered by micellar layers confined in the films, we could determine the micelle aggregation number, surface electric potential, and ionization degree. Moreover, addition of the zwitterionic surfactant cocamidopropyl betaine (CAPB) is expected to transform the small spherical micelles of SME into giant wormlike aggregates.
EXPERIMENTS: Stratifying films from SME solutions are formed and the heights of the steps are recorded. The viscosity of mixed SME + CAPB solutions is measured at various concentrations and weight ratios of the two surfactants.
FINDINGS: By theoretical analysis of the foam film data, we established that at 30-100 mM SME spherical micelles are formed and their aggregation number was determined. The addition of calcium ions, as in hard water, does not produce significant effect. However, SME and CAPB exhibit a strong synergism with respect to micelle growth as indicated by the high solution's viscosity. For this reason, the SME + CAPB mixtures represent a promising system for formulations in personal-care and house-hold detergency, having in mind also other useful properties of SME, such as high hard water tolerance, biodegradability and skin compatibility.
Mesoporous silica from batik sludge impregnated with aluminum hydroxide for the removal of bisphenol A and ibuprofen

Choong CE, Ibrahim S, Basirun WJ

J Colloid Interface Sci, 2019 Apr 01;541:12-17.
PMID: 30682589 DOI: 10.1016/j.jcis.2019.01.071

The present study reports the removal of Bisphenol A (BPA) and Ibuprofen (IBP) using adsorbents prepared from batik sludge. The calcite sludge-aluminum hydroxide (CAl) adsorbent was prepared by calcination and followed by aluminum hydroxide impregnation. The batik sludge and prepared adsorbents were characterized by FESEM, TGA, XRD, FTIR and BET techniques. The maximum adsorption capacity, adsorption time, different initial solution pH, ionic strength and regeneration study of the adsorbents were also investigated. Furthermore, the sorption behavior of the pollutants were studied by the Langmuir and Freundlich isotherms. The deposition of Al(OH)3 enhanced the BPA and IBP adsorption capacity on the CAl surface. The maximum removal capacity of BPA and Ibuprofen were 83.53 mg g-1 and 34.96 mg g-1 for the CAl adsorbent. In addition, the kinetic data for BPA and IBP were fitted to the pseudo first order, pseudo second order, Elovich, parabolic diffusion and power function equations to understand the sorption behavior. The adsorption behavior of BPA and IBP was mainly chemisorption. This study shows that CAl is a promising adsorbent for the removal of BPA and IBP.
Distinguishing characteristics and usability of graphene oxide based on different sources of graphite feedstock

Mahmoudi E, Ang WL, Ng CY, Ng LY, Mohammad AW, Benamor A

J Colloid Interface Sci, 2019 Apr 15;542:429-440.
PMID: 30771638 DOI: 10.1016/j.jcis.2019.02.023

Graphene oxide (GO) has gained popularity in scientific research and industry due to its superior properties, which can be controlled by the synthesis method and graphite feedstock. Despite the availability of different graphite sources, most of the reported studies used natural graphite flake (NGF) as a source of oxidation for GO synthesis. The effect of various alternative graphite feedstocks on the GO properties has not been investigated systematically. This study investigated the influence of graphite feedstock (natural and synthetic) on the characteristics and properties of GO via modified Hummer's method. Natural graphite flake (NGF), natural graphite powder (NGP), and synthetic graphite powder (SGP) were used as graphite feedstock in the study. Energy-dispersive X-ray analysis revealed that the GO produced using NGP (NGP-GO) has higher oxygen to carbon ratio in comparison to GO made from NGF (NGF-GO) and GO made from SGP (SGP-GO) (35.4, 32.7, and 32.2%, respectively), indicating higher oxidation degree for NGP-GO. Zeta potential analysis for NGP-GO, NGF-GO and SGP-GO were -47.8, -42.6 and -39.4 mV, respectively. Morphological analysis revealed that the structures of GO varied according to graphite feedstock, in which (NGP-GO) and (NGF-GO) were highly exfoliated (single-layered structure) while (SGP-GO) showed a multi-layered structure. Further testing was conducted by decorating silver (Ag) nanoparticles on the GO. The results showed that Ag could be uniformly decorated (no agglomeration) on the surface of GO-NGP, due to the presence of more functional groups. Subsequently, the antimicrobial property of Ag-NGP was the highest with an inhibition diameter of 14.7 ± 1.2 mm (30% higher than the other samples). In conclusion, the properties of GO can be tuned by selecting the suitable graphite feedstock and this might pave the way to new developments in the GO-based applications.
Impact of molecular structure, headgroup and alkyl chain geometry, on the adsorption of the anionic ester sulfonate surfactants at the air-solution interface, in the presence and absence of electrolyte

Wang Z, Li P, Ma K, Chen Y, Campana M, Penfold J, et al.

J Colloid Interface Sci, 2019 May 15;544:293-302.
PMID: 30861434 DOI: 10.1016/j.jcis.2019.03.011

The transition from monolayer to multilayer adsorption at the air-water interface in the presence of multivalent counterions has been demonstrated for a limited range of anionic surfactants which exhibit increased tolerance to precipitation in the presence of multivalent counterions. Understanding the role of molecular structure in determining the transition to surface ordering is an important aspect of the phenomenon. The focus of the paper is on the alkyl ester sulfonate, AES, surfactants; a promising group of anionic surfactants, with the potential for improved performance and biocompatibility. Neutron reflectivity measurements were made in aqueous solution and in the presence of NaCl, CaCl2, MgCl2 and AlCl3, for a range of alkyl ester sulfonate surfactants, in which the headgroup and alkyl chain geometries were manipulated. In the regions of monolayer adsorption changing the AES headgroup and alkyl chain geometries results in an increased saturation adsorption and in a more gradual decrease in the adsorption at low concentrations, consistent with a greater adsorption efficiency. Changing the AES headgroup and alkyl chain geometries also results in changes in the transition from monolayer adsorption to more ordered surface structures with the addition of AlCl3 and mixed multivalent electrolytes. A more limited surface layering is observed for the ethyl ester sulfonate, EES, with a C14 alkyl chain. Replacing the C14 alkyl chain with a C18 isostearic chain results in only monolayer adsorption. The results demonstrate the role and importance of the surfactant molecular structure in determining the nature of the surface adsorption in the presence of different electrolytes, and in the tendency to form extended surface multilayer structures.
Surfactants with aromatic headgroups for optimizing properties of graphene/natural rubber latex composites (NRL): Surfactants with aromatic amine polar heads

Ardyani T, Mohamed A, Bakar SA, Sagisaka M, Umetsu Y, Mamat MH, et al.

J Colloid Interface Sci, 2019 Jun 01;545:184-194.
PMID: 30878784 DOI: 10.1016/j.jcis.2019.03.012

HYPOTHESIS: The compatibility of surfactants and graphene surfaces can be improved by increasing the number of aromatic groups in the surfactants. Including aniline in the structure may improve the compatibility between surfactant and graphene further still. Surfactants can be modified by incorporating aromatic groups in the hydrophobic chains or hydrophilic headgroups. Therefore, it is of interest to investigate the effects of employing anilinium based surfactants to disperse graphene nanoplatelets (GNPs) in natural rubber latex (NRL) for the fabrication of electrically conductive nanocomposites.
EXPERIMENTS: New graphene-philic surfactants carrying aromatic moieties in the hydrophilic headgroups and hydrophobic tails were synthesized by swapping the traditional sodium counterion with anilinium. 1H NMR spectroscopy was used to characterize the surfactants. These custom-made surfactants were used to assist the dispersion of GNPs in natural rubber latex matrices for the preparation of conductive nanocomposites. The properties of nanocomposites with the new anilinium surfactants were compared with commercial sodium surfactant sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and the previously synthesized aromatic tri-chain sodium surfactant TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate). Structural properties of the nanocomposites were studied using Raman spectroscopy, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). Electrical conductivity measurements and Zeta potential measurements were used to assess the relationships between total number of aromatic groups in the surfactant molecular structure and nanocomposite properties. The self-assembly structure of surfactants in aqueous systems and GNP dispersions was assessed using small-angle neutron scattering (SANS).
FINDINGS: Among these different surfactants, the anilinium version of TC3Ph3 namely TC3Ph3-AN (anilinium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate) was shown to be highly efficient for dispersing GNPs in the NRL matrices, increasing electrical conductivity eleven orders of magnitude higher than the neat rubber latex. Comparisons between the sodium and anilinium surfactants show significant differences in the final properties of the nanocomposites. In general, the strategy of increasing the number of surfactant-borne aromatic groups by incorporating anilinium ions in surfactant headgroups appears to be effective.
Why does vacuum drive to the loading of halloysite nanotubes? The key role of water confinement

Lisuzzo L, Cavallaro G, Pasbakhsh P, Milioto S, Lazzara G

J Colloid Interface Sci, 2019 Jul 01;547:361-369.
PMID: 30974251 DOI: 10.1016/j.jcis.2019.04.012

The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the desorption isotherms allowed us to determine the water adsorption properties of the investigated nanoclays. The pore sizes of the nanotubes' lumen was determined by combining the vapor pressure of the confined water with the nanoparticles wettability, which was studied through contact angle measurements. The thermodynamic description of the water confinement inside the lumen was correlated to the influence of the vacuum pumping in the experimental loading of halloysite. Metoprolol tartrate, salicylic acid and malonic acid were selected as anionic guest molecules for the experimental filling of the positively charged halloysite lumen. According to the filling mechanism induced by the water confinement, the vacuum operation and the reduced pressure enhanced the loading of halloysite nanotubes for all the investigated bioactive compounds. This work represents a further and crucial step for the development of halloysite based nanocarriers being that the filling mechanism of the nanotube's cavity from aqueous dispersions was described according to the water confinement process.
Synthesis and characterization of choline-fatty-acid-based ionic liquids: A new biocompatible surfactant

Ali MK, Moshikur RM, Wakabayashi R, Tahara Y, Moniruzzaman M, Kamiya N, et al.

J Colloid Interface Sci, 2019 Sep 01;551:72-80.
PMID: 31075635 DOI: 10.1016/j.jcis.2019.04.095

Ionic liquid (IL) surfactants have attracted great interest as promising substitutes for conventional surfactants owing to their exceptional and favorable physico-chemical properties. However, most IL surfactants are not eco-friendly and form unstable micelles, even when using a high concentration of the surfactant. In this study, we prepared a series of halogen-free and biocompatible choline-fatty-acid-based ILs with different chain lengths and degrees of saturation, and we then investigated their micellar properties in aqueous solutions. Characterization of the synthesized surface-active ILs (SAILs) was performed by 1H and 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and elemental analysis. The surface-active properties of the SAILs were investigated by tensiometry, conductometry, and dynamic light scattering measurements. The critical micelle concentration of the SAILs was found to be 2-4 times lower than those of conventional surfactants. The thermodynamic properties of micellization (ΔG0m, ΔH0m, and ΔS0m) indicate that the micellization process of the SAILs is spontaneous, stable, and entropy-driven at room temperature. The cytotoxicity of the SAILs was evaluated using mammalian cell line NIH 3T3. Importantly, [Cho][Ole] shows lower toxicity than the analogous ILs with conventional surfactants. These results clearly suggest that these environmentally friendly SAILs can be used as a potential alternative to conventional ILs for various purposes, including biological applications.
The structure of alkyl ester sulfonate surfactant micelles: The impact of different valence electrolytes and surfactant structure on micelle growth

Wang Z, Li P, Ma K, Chen Y, Penfold J, Thomas RK, et al.

J Colloid Interface Sci, 2019 Sep 05;557:124-134.
PMID: 31518834 DOI: 10.1016/j.jcis.2019.09.016

The ester sulfonate anionic surfactants are a potentially valuable class of sustainable surfactants. The micellar growth, associated rheological changes, and the onset of precipitation are important consequences of the addition of electrolyte and especially multi-valent electrolytes in anionic surfactants. Small angle neutron scattering, SANS, has been used to investigate the self-assembly and the impact of different valence electrolytes on the self-assembly of a range of ester sulfonate surfactants with subtly different molecular structures. The results show that in the absence of electrolyte small globular micelles form, and in the presence of NaCl, and AlCl3 relatively modest micellar growth occurs before the onset of precipitation. The micellar growth is more pronounced for the longer unbranched and branched alkyl chain lengths. Whereas changing the headgroup geometry from methyl ester to ethyl ester has in general a less profound impact. The study highlights the importance of relative counterion binding strengths and shows how the surfactant structure affects the counterion binding and hence the micelle structure. The results have important consequences for the response of such surfactants to different operational environments.
Reduced graphene/nanostructured cobalt oxide nanocomposite for enhanced electrochemical performance of supercapacitor applications

Sagadevan S, Marlinda AR, Johan MR, Umar A, Fouad H, Alothman OY, et al.

J Colloid Interface Sci, 2020 Jan 15;558:68-77.
PMID: 31585223 DOI: 10.1016/j.jcis.2019.09.081

We demonstrate the preparation of nanostructures cobalt oxide/reduced graphene oxide (Co3O4/rGO) nanocomposites by a simple one-step cost-effective hydrothermal technique for possible electrode materials in supercapacitor application. The X-ray diffraction patterns were employed to confirm the nanocomposite crystal system of Co3O4/rGO by demonstrating the existence of normal cubic spinel structure of Co3O4 in the matrix of Co3O4/rGO nanocomposite. FTIR and FT-Raman studies manifested the structural behaviour and quality of prepared Co3O4/rGO nanocomposite. The optical properties of the nanocomposite Co3O4/rGO have been investigated by UV absorption spectra. The SEM/TEM images showed that the Co3O4 nanoparticles in the Co3O4/rGO nanocomposites were covered over the surface of the rGO sheets. The electrical properties were analyzed in terms of real and imaginary permittivity, dielectric loss and AC conductivity. The electrocatalytic activities of synthesized Co3O4/rGO nanocomposites were determined by cyclic voltammetry and charge-discharge cycle to evaluate the supercapacitive performance. The specific capacitance of 754 Fg-1 was recorded for Co3O4/rGO nanocomposite based electrode in three electrode cell system. The electrode material exhibited an acceptable capability and excellent long-term cyclic stability by maintaining 96% after 1000 continuous cycles. These results showed that the prepared sample could be an ideal candidate for high-energy application as electrode materials. The synthesized Co3O4/rGO nanocomposite is a versatile material and can be used in various application such as fuel cells, electrochemical sensors, gas sensors, solar cells, and photocatalysis.
Facile fabrication of thin metal oxide films on porous carbon for high density charge storage

Vijayan BL, Misnon II, Anil Kumar GM, Miyajima K, Reddy MV, Zaghib K, et al.

J Colloid Interface Sci, 2020 Mar 07;562:567-577.
PMID: 31780115 DOI: 10.1016/j.jcis.2019.11.077

In an effort to minimize the usage of non-renewable materials and to enhance the functionality of the renewable materials, we have developed thin metal oxide coated porous carbon derived from a highly abundant non-edible bio resource, i.e., palm kernel shell, using a one-step activation-coating procedure and demonstrated their superiority as a supercapacitive energy storage electrode. In a typical experiment, an optimized composition contained ~10 wt% of Mn2O3 on activated carbon (AC); a supercapacitor electrode fabricated using this electrode showed higher rate capability and more than twice specific capacitance than pure carbon electrode and could be cycled over 5000 cycles without any appreciable capacity loss in 1 M Na2SO4 electrolyte. A symmetric supercapacitor prototype developed using the optimum electrode showed nearly four times higher energy density than the pure carbon owing to the enhancements in voltage window and capacitance. A lithium ion capacitor fabricated in half-cell configuration using 1 M LiPF6 electrolyte showed larger voltage window, superior capacitance and rate capability in the ~10 wt% Mn2O3 @AC than the pure analogue. These results demonstrate that the current protocol allows fabrication of superior charge storing electrodes using renewable materials functionalized by minimum quantity of earthborn materials.
Self-assembled reduced graphene oxide nanoflakes assisted by post-sonication boosted electrical performance in gold interdigitated microelectrodes

Taniselass S, Arshad MKM, Gopinath SCB, Ramli MM

J Colloid Interface Sci, 2020 Oct 01;577:345-354.
PMID: 32485416 DOI: 10.1016/j.jcis.2020.05.070

Reduced graphene oxide (rGO) is widely utilised to develop various types of biosensors; however, producing self-assembled rGO nanoflake networks through single-droplet drop-casting remains inconsistent. In the present work, we systematically used three different methods to prepare rGO suspensions in order to produce large scale self-assembled rGO nanoflake networks through single-droplet drop-casting. The rGO suspensions were prepared using only deionised water with no added any chemicals/organic solvents, which we considered to be a low-cost method. Subsequently, the most effective preparation method was used to deposit rGO nanoflakes onto commercial gold interdigitated microelectrodes (Au-IDE) to examine their electrical performance. Assessment of the yields, developed methods, surface morphologies, spectroscopy and structural analyses of the as-prepared rGO nanoflakes were conducted. The results revealed that method-3 (involving sonication, centrifugation and post-sonication) produced large self-assembled rGO nanoflake networks with strong adhesion to glass substrates. Furthermore, the as-prepared rGO/Au-IDE modified sensors showed excellent electron mobility where the electrical conductivity was enhanced approximately ~ 1000 fold compared to the bare devices. The present work provided new insights for depositing large self-assembled interconnected rGO nanoflake networks through single-droplet drop-casting which will be beneficial for biosensor development and other downstream applications.
Coordination polymer-derived cobalt-embedded and N/S-doped carbon nanosheet with a hexagonal core-shell nanostructure as an efficient catalyst for activation of oxone in water

Tuan DD, Oh WD, Ghanbari F, Lisak G, Tong S, Andrew Lin KY

J Colloid Interface Sci, 2020 Nov 01;579:109-118.
PMID: 32574728 DOI: 10.1016/j.jcis.2020.05.033

As sulfate-radical (SR)-based advanced oxidation processes are increasingly implemented, Oxone has been frequently-used for generation of SR. While Co3O4 nanoparticle (NP) has been widely-accepted as a promising catalyst for activating Oxone, Co3O4 NPs tend to aggregate in water, losing their reactivity. Thus, many attempts have immobilized Co3O4 NPs on supports, especially carbonaceous substrates, because combination of Co NPs with carbon substrates offers synergistic effects for boosting catalytic activities. Moreover, carbon substrates doped with hetero-atoms (N and S) further increase electron transfer and reactivity. Therefore, it is even promising to immobilize Co NPs onto N/S-doped carbon (NSC) to form Co-embedded NSC (denoted as CoNSC) for enhancing Oxone activation. In this study, a convenient and facile technique is proposed to prepare such a CoNSC via a simple carbonization treatment of a coordination polymer of Co and trithiocyanuric acid (TTCA). The resulting CoNSC exhibits the sheet-like hexagonal morphology with the core-shell configuration, and Co NPs are well-embedded into the N/S-doped carbonaceous matrix, making it an advantageous heterogeneous catalyst for Oxone activation. As Azorubine S (ARS) decolorization is employed as a model reaction of Oxone activation, CoNSC exhibits a higher catalytic activity than pristine Co3O4 and NSC for Oxone activation to decolorize ARS. In comparison to the other reported catalysts, CoNSC also possesses a much lower Ea for ARS decolorization. CoNSC can be also reusable and stable for Oxone activation over multiple cycles without loss of catalytic activity. These features validate that CoNSC is a promising and useful Co-based catalyst for Oxone activation.
Friction at nanopillared polymer surfaces beyond Amontons' laws: Stick-slip amplitude coefficient (SSAC) and multiparametric nanotribological properties

Ishak MI, Dobryden I, Martin Claesson P, Briscoe WH, Su B

J Colloid Interface Sci, 2021 Feb 01;583:414-424.
PMID: 33011410 DOI: 10.1016/j.jcis.2020.09.038

Frictional and nanomechanical properties of nanostructured polymer surfaces are important to their technological and biomedical applications. In this work, poly(ethylene terephthalate) (PET) surfaces with a periodic distribution of well-defined nanopillars were fabricated through an anodization/embossing process. The apparent surface energy of the nanopillared surfaces was evaluated using the Fowkes acid-base approach, and the surface morphology was characterized using scanning electron microscope (SEM) and atomic force microscope (AFM). The normal and lateral forces between a silica microparticle and these surfaces were quantified using colloidal probe atomic force microscopy (CP-AFM). The friction-load relationship followed Amonton's first law, and the friction coefficient appeared to scale linearly with the nanopillar height. Furthermore, all the nanopillared surfaces showed pronounced frictional instabilities compared to the smooth sliding friction loop on the flat control. Performing the stick-slip amplitude coefficient (SSAC) analysis, we found a correlation between the frictional instabilities and the nanopillars density, pull-off force and work of adhesion. We have summarised the dependence of the nanotribological properties on such nanopillared surfaces on five relevant parameters, i.e. pull-off force fp, Amontons' friction coefficient μ, RMS roughness Rq, stick-slip amplitude friction coefficient SSAC, and work of adhesion between the substrate and water Wadh in a radar chart. Whilst demonstrating the complexity of the frictional behaviour of nanopillared polymer surfaces, our results show that analyses of multiparametric nanotribological properties of nanostructured surfaces should go beyond classic Amontons' laws, with the SSAC more representative of the frictional properties compared to the friction coefficient.

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links