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The impact of electrolyte on the adsorption of the anionic surfactant methyl ester sulfonate at the air-solution interface: Surface multilayer formation

Xu H, Thomas RK, Penfold J, Li PX, Ma K, Welbourne RJL, et al.

J Colloid Interface Sci, 2018 Feb 15;512:231-238.
PMID: 29073464 DOI: 10.1016/j.jcis.2017.10.064

The methyl ester sulfonates represent a promising group of anionic surfactants which have the potential for improved performance and biocompatibility in a range of applications. Their solution properties, in particular their tolerance to hard water, suggests that surface ordering may occur in the presence of multi-valent counterion. Understanding their adsorption properties in a range of different circumstances is key to the exploitation of their potential. Neutron reflectivity and surface tension have been used to characterise the adsorption at the air-aqueous solution interface of the anionic surfactant sodium tetradecanoic 2-sulfo 1-methyl ester, C14MES, in the absence of electrolyte and in the presence of mono, di, and tri-valent counterions, Na+, Ca2+, and Al3+. In particular the emphasis has been on exploring the tendency to form layered structures at the interface. In the absence of electrolyte and in the presence of NaCl and CaCl2 and AlCl3 at low concentrations monolayer adsorption is observed, and the addition of electrolyte results in enhanced adsorption. In the presence of NaCl and CaCl2 only monolayer adsorption is observed. However at higher AlCl3 concentrations surface multilayer formation is observed, in which the number of bilayers at the surface depends upon the surfactant and AlCl3 concentrations.
Enhanced solubility of methyl ester sulfonates below their Krafft points in mixed micellar solutions

Yavrukova VI, Danov KD, Slavova TG, Stanimirova RD, Wei Ung Y, Tong Kim Suan A, et al.

J Colloid Interface Sci, 2024 Jan 22;660:896-906.
PMID: 38280282 DOI: 10.1016/j.jcis.2024.01.127

HYPOTHESIS: Methyl ester sulfonates (MES) show limited water solubility at lower temperatures (Krafft point). One way to increase their solubility below their Krafft points is to incorporate them in anionic surfactant micelles. The electrostatic interactions between the ionic surfactant molecules and charged micelles play an important role for the degree of MES solubility.
EXPERIMENTS: The solubility and electrolytic conductivity for binary and ternary surfactant mixtures of MES with anionic sodium alpha olefin sulfonate (AOS) and sodium lauryl ether sulfate with two ethylene oxide groups (SLES-2EO) at 5 °C during long-term storage were measured. Phase diagrams were established; a general phase separation theoretical model for their explanation was developed and checked experimentally.
FINDINGS: The binary and ternary phase diagrams for studied surfactant mixtures include phase domains: mixed micelles; micelles + crystallites; crystallites, and molecular solution. The proposed general phase separation model for ionic surfactant mixtures is convenient for construction of such complex phase diagrams and provides information on the concentrations of all components of the complex solution and on the micellar electrostatic potential. The obtained maximal MES mole fraction of transparent micellar solutions could be of interest to increase the range of applicability of MES-surfactants.
Prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method

Chan ES, Lee BB, Ravindra P, Poncelet D

J Colloid Interface Sci, 2009 Oct 1;338(1):63-72.
PMID: 19604515 DOI: 10.1016/j.jcis.2009.05.027

The aim of this work was to develop prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method. The relationship between the process variables on the shape and size of the alginate drops before and after gelation was established with the aid of image analysis. The results show that a critical Ohnersorge number (Oh)>0.24 was required to form spherical beads. The shape transition of ca-alginate beads could be typically distinguished into three phases along the collecting distance and it was affected by the combined influence of the solution properties, the collecting distance and the drop size. Mathematical equations and a master shape diagram were developed to reveal a clear operating region and the overall process limits within which spherical ca-alginate beads could be formed. In terms of bead size, the overall size correction factor (K) which accounted for the liquid loss factor (k(LF)) and the shrinkage factor (k(SF)), varied between 0.73 and 0.85 under the experimental conditions. The size prediction model correlated well with the experimental data. The approach and the outcome could be used as a model to develop prediction tools for similar bead production systems.
Low cost, robust, environmentally friendly, wood supported 3D-hierarchical Cu3SnS4 for efficient solar powered steam generation

Ali N, Abbas S, Cao Y, Fazal H, Zhu J, Lai CW, et al.

J Colloid Interface Sci, 2022 Feb 07;615:707-715.
PMID: 35168019 DOI: 10.1016/j.jcis.2022.02.012

Solar steam generation has great potential in alleviating freshwater crises, particularly in regions with accessible seawater and abundant insolation. Inexpensive, efficient, and eco-friendly photothermal materials are desired to fabricate sunlight-driven evaporation devices. Here, we have designed an economical strategy to fabricate a high-performance wood-based solar steam generation device. In current study, 3D-hierarchical Cu3SnS4 has been loaded on wood substrates of variable sizes via an in-situ solvothermal method. Considering the water transportation capacity and thermal insulation property of wood, an enhanced light absorption was achieved by a uniform coating of Cu3SnS4 on the inside and outside of the 3D porous structure of the wood. Thanks for the synergistic effect of Cu3SnS4 and wood substrate, the obtained composite endorsed high-performance solar steam generation with a steam generation efficiency of 90% and an evaporation rate as high as 1.35 kg m-2h-1 under one sun.
Facile sonochemical synthesis of nanostructured NiO with different particle sizes and its electrochemical properties for supercapacitor application

Duraisamy N, Numan A, Fatin SO, Ramesh K, Ramesh S

J Colloid Interface Sci, 2016 Jun 01;471:136-144.
PMID: 26995554 DOI: 10.1016/j.jcis.2016.03.013

In this work, we demonstrate the influence of nickel oxides with divergent particle sizes as the working electrodes for supercapacitor application. The nanostructured nickel oxide (NiO) is synthesized via facile sonochemical method, followed by calcination process. The crystallinity and surface purity of prepared samples are clearly examined by X-ray diffraction and Raman analysis. NiO crystallinity is significantly increased with increasing calcination temperatures. The surface analysis confirmed that the calcination at 250°C exhibited nanoclutser like NiO with average particle size of ∼6nm. While increasing the calcination temperature beyond 250°C, hexagonal shaped NiO is observed with enhanced particle sizes. The electrochemical performance confirmed the good redox behavior of NiO electrodes. Moreover, NiO with average particle size of ∼6nm exhibited high specific capacitance of 449F/g at a scan rate of 5mV/s compared to other samples with particle sizes of ∼21nm (323F/g) and ∼41nm (63F/g). This is due to the good ion transfer mechanism and effective electrochemical utilization of the working electrode.
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.
Influence of multi-walled carbon nanotubes on textural and adsorption characteristics of in situ synthesized mesostructured silica

Karim AH, Jalil AA, Triwahyono S, Kamarudin NH, Ripin A

J Colloid Interface Sci, 2014 May 1;421:93-102.
PMID: 24594037 DOI: 10.1016/j.jcis.2014.01.039

Carbon nanotubes-mesostructured silica nanoparticles (CNT-MSN) composites were prepared by a simple one step method with various loading of CNT. Their surface properties were characterized by XRD, N2 physisorption, TEM and FTIR, while the adsorption performance of the CNT-MSN composites were evaluated on the adsorption of methylene blue (MB) while varying the pH, adsorbent dosage, initial MB concentration, and temperature. The CNTs were found to improve the physicochemical properties of the MSN and led to an enhanced adsorptivity for MB. N2 physisorption measurements revealed the development of a bimodal pore structure that increased the pore size, pore volume and surface area. Accordingly, 0.05 g L(-1) CNT-MSN was able to adsorb 524 mg g(-1) (qm) of 60 mg L(-1) MB at pH 8 and 303 K. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, with the Langmuir model affording the best fit to the adsorption data. The adsorption kinetics were best described by the pseudo-first order model. These results indicate the potential of CNT-MSN composites as effective new adsorbents for dye adsorption.
Synthesis of CTAB intercalated graphene and its application for the adsorption of AR265 and AO7 dyes from water

Yusuf M, Khan MA, Otero M, Abdullah EC, Hosomi M, Terada A, et al.

J Colloid Interface Sci, 2017 05 01;493:51-61.
PMID: 28088121 DOI: 10.1016/j.jcis.2017.01.015

Environmental applications of graphene (GN) are limited by the occurrence of aggregation. Herein, graphene oxide (GO) was synthesized, reduced to GN by ascorbic acid, and intercalated with cetyltrimethylammonium bromide (CTAB). GN-CTAB was characterized by Boehm's titration, N2 adsorption/desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, Fluorescence spectrophotometry, X-ray diffraction and Scanning electron microscopy. Then, GN-CTAB was used for the adsorptive removal of acid red 265 (AR265) and acid orange 7 (AO7) dyes from water both under batch and column operation. Under batch operation, the effect of pH, adsorbent dosage, initial dye concentration, contact time and temperature on dyes adsorption were assessed. Adsorption isotherms, kinetics, and thermodynamics were analyzed systematically. Regarding the fixed bed operation, the effect of both the bed height and flow rate were studied and experimental results fitted to the Thomas and BDST models. Then, the bed loss capacity along five adsorption-regeneration cycles was determined in order to further approach the practical application of GN-CTAB for wastewater treatment, namely for the removal of dyes.
α-Sulfo alkyl ester surfactants: Impact of changing the alkyl chain length on the adsorption, mixing properties and response to electrolytes of the tetradecanoate

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

J Colloid Interface Sci, 2021 Mar 15;586:876-890.
PMID: 33309145 DOI: 10.1016/j.jcis.2020.10.122

HYPOTHESIS: The α-sulfo alkyl ester, AES, surfactants are a class of anionic surfactants which have potential for improved sustainable performance in a range of applications, and an important feature is their enhanced tolerance to precipitation in the presence of multivalent counterions. It is proposed that their adsorption properties can be adjusted substantially by changing the length of the shorter alkyl chain, that of the alkanol group in the ester.
EXPERIMENTS: Surface tension and neutron reflectivity have been used to investigate the variation in the adsorption properties with the shorter alkyl chain length (methyl, ethyl and propyl), the impact of NaCl on the adsorption, the tendency to form surface multilayer structures in the presence of AlCl3, and the effects of mixing the methyl ester sulfonate with the ethyl and propyl ester sulfonates on the adsorption.
FINDINGS: The variations in the critical micelle concentration, CMC, the adsorption isotherms, the saturation adsorption values, and the impact of NaCl illustrate the subtle influence of varying the shorter alkyl chain length of the surfactant. The non-ideal mixing of pairs of AES surfactants with different alkanol group lengths of the ester show that the extent of the non-ideality changes as the difference in the alkanol length increases. The surface multilayer formation observed in the presence of AlCl3 varies in a complex manner with the length of the short chain and for mixtures of surfactants with different chains lengths.
Electrophoretic deposition of collagen/chitosan films with copper-doped phosphate glasses for orthopaedic implants

Deen I, Selopal GS, Wang ZM, Rosei F

J Colloid Interface Sci, 2022 Feb;607(Pt 1):869-880.
PMID: 34536940 DOI: 10.1016/j.jcis.2021.08.199

Coatings with bioactive properties play a key role in the success of orthopaedic implants. Recent studies focused on composite coatings incorporating biocompatible elements that can increase the nucleation of hydroxyapatite (HA), the mineral component of bone, and have promising bioactive and biodegradable properties. Here we report a method of fabricating composite collagen, chitosan and copper-doped phosphate glass (PG) coatings for biomedical applications using electrophoretic deposition (EPD). The use of collagen and chitosan (CTS) allows for the co-deposition of PG particles at standard ambient temperature and pressure (1 kPa, 25 °C), and the addition of collagen led to the steric stabilization of PG in solution. The coating composition was varied by altering the collagen/CTS concentrations in the solutions, as well as depositing PG with 0, 5 and 10 mol% CuO dopant. A monolayer of collagen/CTS containing PG was obtained on stainless steel cathodes, showing that deposition of PG in conjunction with a polymer is feasible. The mass of the monolayer varied depending on the polymer (collagen, CTS and collagen/CTS) and combination of polymer + PG (collagen-PG, CTS-PG and collagen/CTS-PG), while the presence of copper led to agglomerates during deposition at higher concentrations. The deposition yield was studied at different time points and showed a profile typical of constant voltage deposition. Increasing the concentration of collagen in the PG solution allows for a higher deposition yield, while pure collagen solutions resulted in hydrogen gas evolution at the cathode. The ability to deposit polymer-PG coatings that can mimic native bone tissue allows for the potential to fabricate orthopaedic implants with tailored biological properties with lower risk of rejection from the host and exhibit increased bioactivity.
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.
Photocatalytic decolourisation of Reactive Red 4 dye by an immobilised TiO2/chitosan layer by layer system

Nawi MA, Sabar S, Sheilatina

J Colloid Interface Sci, 2012 Apr 15;372(1):80-7.
PMID: 22321991 DOI: 10.1016/j.jcis.2012.01.024

The synergistic photocatalysis-adsorption processes by the immobilized TiO(2)/chitosan layer by layer system on a glass support (TiO(2)/CS/glass) were investigated for the decolourisation of Reactive Red 4 (RR4) dye solution. Effects of different reaction parameters such as TiO(2) loading, initial pH of the solution, visible light, dissolved oxygen and radical quenchers were studied. The decolourisation rate of RR4 by TiO(2)/CS/glass was more than 32 times faster than a single layer of TiO(2) but was highly dependent on the TiO(2) loading and the initial pH of the solution. A thin layer of TiO(2) and acidic conditions favoured the adsorption of RR4 at the TiO(2)/CS interface. The h(+)/OH() species that diffused from the TiO(2) layer into the TiO(2)/CS interface oxidised the chemisorbed RR4 anions at the interface, and the generated electrons were then transferred to the conduction band of TiO(2). Excess electrons in the conduction band of TiO(2) increased the number of superoxide ions produced and thus improved the photocatalytic decolourisation of RR4. Therefore, apart from the synergistic photocatalysis-adsorption processes, a charge transfer process was also found to be responsible for maintaining the efficiency, sustainability and reusability of the TiO(2)/CS/glass layer by layer system.
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.
Insights into complex nanopillar-bacteria interactions: Roles of nanotopography and bacterial surface proteins

Ishak MI, Jenkins J, Kulkarni S, Keller TF, Briscoe WH, Nobbs AH, et al.

J Colloid Interface Sci, 2021 Dec 15;604:91-103.
PMID: 34265695 DOI: 10.1016/j.jcis.2021.06.173

Nanopillared surfaces have emerged as a promising strategy to combat bacterial infections on medical devices. However, the mechanisms that underpin nanopillar-induced rupture of the bacterial cell membrane remain speculative. In this study, we have tested three medically relevant poly(ethylene terephthalate) (PET) nanopillared-surfaces with well-defined nanotopographies against both Gram-negative and Gram-positive bacteria. Focused ion beam scanning electron microscopy (FIB-SEM) and contact mechanics analysis were utilised to understand the nanobiophysical response of the bacterial cell envelope to a single nanopillar. Given their importance to bacterial adhesion, the contribution of bacterial surface proteins to nanotopography-mediated cell envelope damage was also investigated. We found that, whilst cell envelope deformation was affected by the nanopillar tip diameter, the nanopillar density affected bacterial metabolic activities. Moreover, three different types of bacterial cell envelope deformation were observed upon contact of bacteria with the nanopillared surfaces. These were attributed to bacterial responses to cell wall stresses resulting from the high intrinsic pressure caused by the engagement of nanopillars by bacterial surface proteins. Such influences of bacterial surface proteins on the antibacterial action of nanopillars have not been previously reported. Our findings will be valuable to the improved design and fabrication of effective antibacterial surfaces.
Superior photoelectrocatalytic performance of ternary structural BiVO4/GQD/g-C3N4 heterojunction

Samsudin MFR, Ullah H, Tahir AA, Li X, Ng YH, Sufian S

J Colloid Interface Sci, 2021 Mar 15;586:785-796.
PMID: 33198982 DOI: 10.1016/j.jcis.2020.11.003

Herein, we performed an encyclopedic analysis on the photoelectrocatalytic hydrogen production of BiVO4/g-C3N4 decorated with reduced graphene oxide (RGO) or graphene quantum dots (GQDs). The differences between RGO and GQDs as an electron mediator was revealed for the first time in the perspective of theoretical DFT analysis and experimental validation. It was found that the incorporation of GQDs as an electron mediator promotes better photoelectrocatalytic hydrogen performance in comparison to the RGO. The addition of GQD can significantly improve the activity by 25.2 and 75.7% in comparison to the BiVO4/RGO/g-C3N4 and binary composite samples, respectively. Correspondingly, the BiVO4/GQD/g-C3N4 attained the highest photocurrent density of 19.2 mA/cm2 with an ABPE of 0.57% without the presence of any sacrificial reagents. This enhancement is stemming from the low photocharge carrier transfer resistance which was further verified via DFT study. The DFT analysis revealed that the BiVO4/GQD/g-C3N4 sample shared their electronic cloud density through orbital hybridization while the BiVO4/RGO/g-C3N4 sample show less mutual sharing. Additionally, the charge redistribution of the GQDs-composite at the heterostructure interface articulates a more stable and stronger heterojunction than the RGO-composite. Notably, this study provides new insights on the effect of different carbonaceous materials (RGO and GQDs) which are often used as an electron mediator to enhance photocatalytic activity.
Corrigendum to "Superior photoelectrocatalytic performance of ternary structural BiVO4/GQD/g-C3N4 heterojunction" [J. Col. Interf. Sci. 586 (2021) 785-796]

Fakhrul Ridhwan Samsudin M, Ullah H, Tahir AA, Li X, Hau Ng Y, Sufian S

J Colloid Interface Sci, 2021 Nov 15;602:900.
PMID: 34088501 DOI: 10.1016/j.jcis.2021.04.096
In-situ growth of TiO2 imbedded Ti3C2TA nanosheets to construct PCN/Ti3C2TA MXenes 2D/3D heterojunction for efficient solar driven photocatalytic CO2 reduction towards CO and CH4 production

Tahir M, Tahir B

J Colloid Interface Sci, 2021 Jun;591:20-37.
PMID: 33588310 DOI: 10.1016/j.jcis.2021.01.099

Constructing efficient structured materials for artificial photosynthesis of CO2 is a promising strategy to produce renewable fuels in addition of mitigating greenhouse effect. In this work, 2D porous g-C3N4 (PCN) coupled exfoliated 3D Ti3C2TA MXene (TiC) nanosheets with TiO2 NPs in-situ growth was constructed in a single step through HF treatment approach. The different exfoliated TiC structures were successfully synthesized for adjusting HF etching time (24 h, 48 h and 96 h). With growing etchant time from 24 to 96 h, the amount of TiO2 produced was increased, but it has adverse effects on CO and CH4 production rate. The maximum production rates for CO and CH4 of 317.4 and 78.55 µmol g-1 h-1 were attained when the 10TiC-48/PCN was employed than using TiC-24/PCN, TiC-96/PCN and PCN composite samples, respectively. The performance of 10TiC-48/PCN composite for CO and CH4 evolution were 9.9 and 6.7 folds higher than using pristine PCN sample, respectively. The possible mechanism is assigned to porous structure with intimate contact enabling efficient charge carrier separation with the role of TiO2 NPs to work as a bridge to transport electrons towards MXene surface. Among the reducing agents, water was favorable for CO evolution, whereas, methanol-water system promoted CH4 production. All these findings confirm that heterojunction formation facilitates charges separation and can be further used in solar energy relating application.
Acoustically-controlled Leidenfrost droplets

Ng BT, Hung YM, Tan MK

J Colloid Interface Sci, 2016 Mar 1;465:26-32.
PMID: 26641561 DOI: 10.1016/j.jcis.2015.11.047

Suppressing the Leidenfrost effect can significantly improve heat transfer from a heated substrate to a droplet above it. In this work, we demonstrate that by generating high frequency acoustic wave in the droplet, at sufficient vibration displacement amplitudes, the Leidenfrost effect can be suppressed due to the acoustic radiation pressure exerted on the liquid-vapor interface; strong capillary waves are observed at the liquid-vapor interface and subsequently leads to contact between the liquid and the heated substrate. Using this technique, with 10(5)Hz vibration frequency and 10(-6)m displacement amplitude of the acoustic transducer, a maximum of 45% reduction of the initial temperature (T0∼200-300°C) of the heated substrate can be achieved with a single droplet of volume 10(-5)l.
Tailoring the CO2-selectivity of interfacial polymerized thin film nanocomposite membrane via the barrier effect of functionalized boron nitride

Wong KC, Goh PS, Suzaimi ND, Ng ZC, Ismail AF, Jiang X, et al.

J Colloid Interface Sci, 2021 Dec;603:810-821.
PMID: 34237599 DOI: 10.1016/j.jcis.2021.06.156

Membrane-based separation is an appealing solution to mitigate CO2 emission sustainably due to its energy efficiency and environmental friendliness. Attributed to its excellent separation endowed by nanomaterial incorporation, nanocomposite membrane is rigorously developed. This study explored the feasibility of boron nitride (BN) embedment and changes to formation mechanism of ultrathin selective layer of thin film nanocomposite (TFN) are investigated. The effects of amine-functionalization on nanosheet-polymer interaction and CO2 separation performance are also identified. Participation of nanosheets during interfacial polymerization reduced the crosslinking of selective layer, hence, improved TFN permeance while the formation of contorted diffusion paths by the nanosheets favors transport of small gases. Amine-functionalization enhanced the nanosheet-polymer interaction and elevated the membrane affinity towards CO2 which led to enhanced CO2 selectivity. The best TFN prepared in this study exhibited 37% and 20% increment in permeability and selectivity, respectively with respect to neat thin film composite (TFC). It is found that the CO2 separation performance of BN incorporated TFN is on par with many non-porous nanosheet-incorporated TFNs reported in literatures. The transport and barrier effects of BN and functionalized BN are discussed in detail to provide further insights into the development of commercially attractive CO2 selective TFN membranes.
Kaolin-Carbon Adsorbents for Carotene Removal of Red Palm Oil

Hussein MZ, Kuang D, Zainal Z, Teck TK

J Colloid Interface Sci, 2001 Mar 1;235(1):93-100.
PMID: 11237447

Kaolin-carbon adsorbents were prepared with and without sulfuric acid pretreatment followed by activation-carbonization at 500 degrees C. The total surface area of the resulting kaolin-carbon adsorbents was found to be decreased with the increase in kaolin loading. Sulfuric acid pretreatment of the precursor prior to the carbonization-activation processes resulted in the enhancement of total surface area but reduced the micropore surface area of the resulting adsorbents. At the same time, this improved carotene adsorption capacity from red palm oil. However, recovery of carotene from the carotene-adsorbed adsorbent is only improved when the acid pretreatment of the precursor was done at a high loading percentage of activated carbon. Similarly, the peroxide value (PV) increased. A maximum removal of carotene from red palm oil was obtained at 20% kaolin loading for both adsorbents prepared with and without sulfuric acid pretreatment with about 45 and 65% carotene removal, respectively, from a 30-ppm solution. This indicates that pretreatment with sulfuric acid, prior to the activation-carbonization process, increased the carotene uptake by the resulting adsorbent. However, a further increase in the kaolin loading resulted in the decrease of carotene removal. About 3-4% of carotene adsorbed can be recovered from both types of adsorbents under optimum condition, in which the percentage recovered decreased with the increase in kaolin loading. On the other hand, the PV increased with kaolin loading at around 54-64 mEq/kg for both types of adsorbents. It was also found that carotene uptake by the adsorbents is high if the adsorbent contains a high percentage of activated carbon. Similarly, carotene recovery is high and less oxidation can be observed, as indicated by the lower PV value. Copyright 2001 Academic Press.

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