Displaying publications 21 - 40 of 114 in total

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  1. Effects of aminoacids on the autooxidation of 3,5-di-tert-butylcatechol in the presence of surface-active copper(II) complexes
    Lim YY, Liew LP
    J Colloid Interface Sci, 2002 Nov 15;255(2):425-7.
    PMID: 12505092
    The rate of autooxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) in the presence of micelles formed from mixing equal concentrations of [Cu(C(12)-tmed)Br(2)] (where C(12)-tmed is N,N,N'-trimethyl-N'-dodecylethylenediamine) and several amino acids has been investigated. It was found that the rate in air-saturated solution is very much dependent on pH, which affects the availability of copper(II) coordination site for the catechol and the degree of micellization. At a given pH, the rates in [Cu(C(12)-tmed)Br(2)] micellar media are greatly enhanced in the presence sodium halide.
  2. Effects of nonionic micelles on the rate of alkaline hydrolysis of N-(2'-methoxyphenyl)phthalimide (1): kinetic and rheometric evidence for a transition from spherical to rodlike micelles under the typical reaction conditions
    Sim YL, Yusof NS, Ariffin A, Niyaz Khan M
    J Colloid Interface Sci, 2011 Aug 1;360(1):182-8.
    PMID: 21549387 DOI: 10.1016/j.jcis.2011.04.021
    Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of N-(2'-methoxyphenyl)phthalimide (1) decrease nonlinearly with increasing total concentration of nonionic surfactant C(m)E(n) (i.e. [C(m)E(n)](T) where m and n represent the respective number of methyl/methylene units in the tail and polyoxyethylene units in the headgroup of a surfactant molecule and m/n=16/20, 12/23 and 18/20) at constant 2% v/v CH(3)CN and 1.0 mM NaOH. The k(obs)vs. [C(m)E(n)](T) data follow the pseudophase micellar (PM) model at ≤ 50 mM C(16)E(20), ≤ 1.4 mM C(12)E(23) and ≤ 2.0 mM C(18)E(20) where rate of hydrolysis of 1 in micellar pseudophase could not be detected. The values of k(obs) fail to follow the PM model at > ∼50 mM C(16)E(20), > ∼1.4 mM C(12)E(23) and > ∼2.0 mM C(18)E(20) which has been attributed to a micellar structural transition from spherical to rodlike which in turn increases C(m)E(n) micellar binding constant (K(S)) of 1 with increasing values of [C(m)E(n)](T). Rheological measurements show the presence of spherical micelles at ≤ 50 mM C(16)E(20), ≤ 1.4 mM C(12)E(23) and ≤ 3.0 mM C(18)E(20). The presence of rodlike micelles is evident from rheological measurements at > ∼50 mM C(16)E(20), > ∼1.4 mM C(12)E(23) and > ∼3.0 mM C(18)E(20).
  3. Effects of the crown ether cavity on the performance of anion exchange membranes
    Chen JH, Choo YSL, Wang XH, Liu YJ, Yue XB, Gao XL, et al.
    J Colloid Interface Sci, 2023 Apr 06;643:62-72.
    PMID: 37044014 DOI: 10.1016/j.jcis.2023.04.011
    Anion exchange membrane fuel cells (AEMFCs) have emerged as a promising alternative to proton exchange membrane fuel cells (PEMFCs) due to their adaptability to low-cost stack components and non-noble-metals catalysts. However, the poor alkaline resistance and low OH- conductivity of anion exchange membranes (AEMs) have impeded the large-scale implementation of AEMFCs. Herein, the preparation of a new type of AEMs with crown ether macrocycles in their main chains via a one-pot superacid catalyzed reaction was reported. The study aimed to examine the influence of crown ether cavity size on the phase separation structure, ionic conductivity and alkali resistance of anion exchange membranes. Attributed to the self-assembly of crown ethers, the poly (crown ether) (PCE) AEMs with dibenzo-18-crown-6-ether (QAPCE-18-6) exhibit an obvious phase separated structure and a maximum OH- conductivity of 122.5 mS cm-1 at 80 °C (ionic exchange capacity is 1.51 meq g-1). QAPCE-18-6 shows a good alkali resistance with the OH- conductivity retention of 94.5% albeit being treated in a harsh alkali condition. Moreover, the hydrogen/oxygen single cell equipped with QAPCE-18-6 can achieve a peak power density (PPD) of 574 mW cm-2 at a current density of 1.39 A cm-2.
  4. Electrochemical investigation on the corrosion inhibition of mild steel by Quinazoline Schiff base compounds in hydrochloric acid solution
    Khan G, Basirun WJ, Kazi SN, Ahmed P, Magaji L, Ahmed SM, et al.
    J Colloid Interface Sci, 2017 Sep 15;502:134-145.
    PMID: 28478220 DOI: 10.1016/j.jcis.2017.04.061
    The inhibitory effect of two Schiff bases 3-(5-methoxy-2-hydroxybenzylideneamino)-2-(-5-methoxy-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (MMDQ), and 3-(5-nitro-2-hydroxybenzylideneamino)-2(5-nitro-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (NNDQ) on the corrosion of mild steel in 1M hydrochloric acid were studied using mass loss, potentiodynamic polarization technique and electrochemical impedance spectroscopy measurements at ambient temperature. The investigation results indicate that the Schiff Bases compounds with an average efficiency of 92% at 1.0mM of additive concentration have fairly effective inhibiting properties for mild steel in hydrochloric acid, and acts as mixed type inhibitor character. The inhibition efficiencies measured by all measurements show that the inhibition efficiencies increase with increase in inhibitor concentration. This reveals that the inhibitive mechanism of inhibitors were primarily due to adsorption on mild steel surface, and follow Langmuir adsorption isotherm. The temperature effect on the inhibition process in 1MHCl with the addition of investigated Schiff bases was studied at a temperature range of 30-60°C, and the activation parameters (Ea, ΔH and ΔS) were calculated to elaborate the corrosion mechanism. The differences in efficiency for two investigated inhibitors are associated with their chemical structures.
  5. Electrokinetic Behavior of Palm Oil Emulsions in Dilute Electrolyte Solutions
    Ho CC, Ahmad K
    J Colloid Interface Sci, 1999 Aug 1;216(1):25-33.
    PMID: 10395758
    The effect of metal cations, both nonhydrolyzable and hydrolyzable, on the zeta potential of palm olein emulsions stabilized by the nonionic emulsifier, polyoxyethylene nonyl phenyl ether, was investigated as a function of pH and cation concentrations, respectively. The oil drops were found to be negatively charged in the presence of simple mono- and divalent cations. Charge reversal of the oil drops was observed when hydrolyzable cations (Zn2+, Cu2+, Fe3+, and Al3+) were used and the behavior is strongly dependent on the type of cation, its concentration, and the pH of the dispersion. The results are discussed in terms of current theories of electrophoresis and adsorption-precipitation at interfaces. The chemical free energies of adsorption of the cations were calculated. Copyright 1999 Academic Press.
  6. 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.
  7. Electrospun nylon 6,6 membrane as a reusable nano-adsorbent for bisphenol A removal: Adsorption performance and mechanism
    Jasni MJF, Arulkumar M, Sathishkumar P, Mohd Yusoff AR, Buang NA, Gu FL
    J Colloid Interface Sci, 2017 Dec 15;508:591-602.
    PMID: 28869916 DOI: 10.1016/j.jcis.2017.08.075
    Bisphenol A (BPA) is highly considered as an emerging contaminants (ECs) due to their endocrine disrupting and reproductive toxicant nature. It has been detected in drinking water sources in many countries. This study deals with the adsorptive removal of BPA using nylon 6,6 nanofibrous membrane (NNM) fabricated by electrospinning technique. Langmuir and Freundlich isotherm models (R2=0.99) were obeyed for BPA adsorption, which indicates the monolayer adsorption of BPA and also surface heterogeneity of NNM. The adsorption kinetics of BPA was followed pseudo second order rate (R2=0.89-0.99), which suggests the occurrence of rapid adsorption rate through interaction of surface functional groups present in NNM. The maximum adsorption of BPA (91.3mgg-1) was attained at 30°C. The hydroxyl groups of BPA form hydrogen bonding with carbonyl groups of NNM during the adsorptive removal process. Reusability study confirmed a much better stability of NNM in the recyclic application. Finally, this study suggests that NNM might be an outstanding nano-adsorbent for the emerging contaminants removal, including BPA from drinking water sources.
  8. Enhanced dispersion of multiwall carbon nanotubes in natural rubber latex nanocomposites by surfactants bearing phenyl groups
    Mohamed A, Anas AK, Bakar SA, Ardyani T, Zin WM, Ibrahim S, et al.
    J Colloid Interface Sci, 2015 Oct 1;455:179-87.
    PMID: 26070188 DOI: 10.1016/j.jcis.2015.05.054
    Here is presented a systematic study of the dispersibility of multiwall carbon nanotubes (MWCNTs) in natural rubber latex (NR-latex) assisted by a series of single-, double-, and triple-sulfosuccinate anionic surfactants containing phenyl ring moieties. Optical polarising microscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy have been performed to obtain the dispersion-level profiles of the MWCNTs in the nanocomposites. Interestingly, a triple-chain, phenyl-containing surfactant, namely sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sulfonate (TCPh), has a greater capacity the stabilisation of MWCNTs than a commercially available single-chain sodium dodecylbenzenesulfonate (SDBS) surfactant. TCPh provides significant enhancements in the electrical conductivity of nanocomposites, up to ∼10(-2) S cm(-1), as measured by a four-point probe instrument. These results have allowed compilation of a road map for the design of surfactant architectures capable of providing the homogeneous dispersion of MWCNTs required for the next generation of polymer-carbon-nanotube materials, specifically those used in aerospace technology.
  9. 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.

  10. Enhancement of the photocatalytic activity of TiO(2) by doping it with calcium ions
    Akpan UG, Hameed BH
    J Colloid Interface Sci, 2011 May 1;357(1):168-78.
    PMID: 21345441 DOI: 10.1016/j.jcis.2011.01.014
    Titanium dioxide (TiO(2)) with an enhanced photocatalytic activity was developed by doping it with calcium ions through a sol-gel method. The developed photocatalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, N(2) physisorption, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction. Their surface morphologies were studied using surface scanning electron microscopy (SEM). The XPS analyses confirmed the presence of Ti, O, Ca, and C in the Ca-doped TiO(2) sample. The activities of the catalysts were evaluated by photocatalytic degradation of an azo dye, acid red 1 (AR1), using UV light irradiation. The results of the investigations revealed that the samples calcined at 300 °C for 3.6h in a cyclic (2 cycles) mode had the best performance. Lower percentage dopant, 0.3-1.0 wt.%, enhanced the photocatalytic activity of TiO(2), with the best at 0.5 wt.% Ca-TiO(2). The performance of 0.5 wt.% Ca-TiO(2) in the degradation of AR1 was far superior to that of a commercial anatase TiO(2) Sigma product CAS No. 1317-70-0. The effect of pH on the degradation of AR1 was studied, and the pH of the dye solution exerted a great influence on the degradation of the dye.
  11. Evaluation of the effect of precursor ratios on the electrochemical performances of binder-free NiMn-phosphate electrodes for supercapattery
    Gerard O, Ramesh S, Ramesh K, Numan A, Norhaffis Mustafa M, Khalid M, et al.
    J Colloid Interface Sci, 2024 Apr 16;667:585-596.
    PMID: 38657542 DOI: 10.1016/j.jcis.2024.04.101
    Binary metal phosphate electrodes have been widely studied for energy storage applications due to the synergistic effects of two different transition elements that able to provide better conductivity and stability. Herein, the battery-type binder-free nickel-manganese phosphate (NiMn-phosphate) electrodes were fabricated with different Ni:Mn precursor ratios via microwave-assisted hydrothermal technique for 5 min at 90 °C. Overall, NiMn3P electrode (Ni:Mn = 1:3) showed an outstanding electrochemical performance, displaying the highest specific (areal) capacity at 3 A/g of 1262.4 C/g (0.44 C/cm2), and the smallest charge transfer resistance of 108.8 Ω. The enhanced performance of NiMn3P electrode can be ascribed to the fully grown amorphous nature and small-sized flake and flower structures of NiMn3P electrode material on the nickel foam (NF) surface. This configuration offered a higher number of active sites and a larger exposed area, facilitating efficient electrochemical reactions with the electrolyte. Consequently, the NiMn3P//AC electrode combination was chosen to further investigate its performance in supercapattery. The NiMn3P//AC supercapattery exhibited remarkable energy density of 105.4 Wh/kg and excellent cyclic stability with 84.7% retention after 3000 cycles. These findings underscored the superior electrochemical performance of the battery-type binder-free NiMn3P electrode, and highlight its potential for enhancing the overall performance of supercapattery.
  12. Experimental investigation on the use of highly charged nanoparticles to improve the stability of weakly charged colloidal system
    Zubir MN, Badarudin A, Kazi SN, Misran M, Amiri A, Sadri R, et al.
    J Colloid Interface Sci, 2015 Sep 15;454:245-55.
    PMID: 26048724 DOI: 10.1016/j.jcis.2015.05.019
    The present work highlighted on the implementation of a unique concept for stabilizing colloids at their incipiently low charge potential. A highly charged nanoparticle was introduced within a coagulated prone colloidal system, serving as stabilizer to resist otherwise rapid flocculation and sedimentation process. A low size asymmetry of nanoparticle/colloid serves as the new topic of investigation in addition to the well-established large size ratio nanoparticle/microparticle study. Highly charged Al2O3 nanoparticles were used within the present research context to stabilize TiO2 and Fe3O4 based colloids via the formation of composite structures. It was believed, based on the experimental evidence, that Al2O3 nanoparticle interact with the weakly charged TiO2 and Fe3O4 colloids within the binary system via absorption and/or haloing modes to increase the overall charge potential of the respective colloids, thus preventing further surface contact via van der Waal's attraction. Series of experimental results strongly suggest the presence of weakly charged colloids in the studied bimodal system where, in the absence of highly charged nanoparticle, experience rapid instability. Absorbance measurement indicated that the colloidal stability drops in accordance to the highly charged nanoparticle sedimentation rate, suggesting the dominant influence of nanoparticles to attain a well-dispersed binary system. Further, it was found that the level of colloidal stability was enhanced with increasing nanoparticle fraction within the mixture. Rheological observation revealed that each hybrid complexes demonstrated behavior reminiscence to water with negligible increase in viscosity which serves as highly favorable condition particularly in thermal transport applications.
  13. Fabrication of green dye-sensitized solar cell based on ZnO nanoparticles as a photoanode and graphene quantum dots as a photo-sensitizer
    Zamiri G, Bagheri S
    J Colloid Interface Sci, 2018 Feb 01;511:318-324.
    PMID: 29031151 DOI: 10.1016/j.jcis.2017.10.026
    Zero-dimensional graphene quantum dots (GQDs) consist of single- or few-layer graphene with a size less than 20 nm and stand for a new type of QDs with unique properties combining the graphene nature and size-resulted quantum effects. GQDs possess unique optical and electronic properties, and in particular possess a band-gap less than 2.0 eV because of quantum confinement and edge effects. In this study, we investigated the performance of DSSCs using different thicknesses of ZnO nanoparticles as a photo-anode and GQDs as a green photosensitizer. The current voltage (I-V) test results indicate that the performance of DSSCs is improved by increasing the thickness of the photo-anode and the thickness of 40 μm shows the highest efficiency for DSSC device based on ZnO nanoparticles photo-anodes. The DSSC using ZnO nanoparticles as a photo-anode with thickness of 40 μm shows almost same efficiency when we replaced N-719 with GQDs which is confirmed that using GQDs as an alternative to ruthenium based dyes is a new approach for DSSCs.
  14. Facile asymmetric modification of graphene nanosheets using κ-carrageenan as a green template
    Tiong ACY, Tan IS, Foo HCY, Lam MK, Mahmud HB, Lee KT
    J Colloid Interface Sci, 2022 Feb;607(Pt 2):1131-1141.
    PMID: 34571300 DOI: 10.1016/j.jcis.2021.09.042
    The synthesis of Janus nanosheets using κ-carrageenan (κ-Ca) as a green template endows a greener and more straightforward method compared to traditional approaches of using wax template. We hypothesize that the hydrogen bonding interaction between κ-Ca and graphene oxide (GO) allows partial masking of GO's single facet, paving the way for the asymmetric modification of the exposed surface. GO is first encapsulated within the porous hydrogel matrix formed by κ-Ca to isolate one of the facets. The exposed surface was then selectively hydrophobized to produce an amphiphilic asymmetrically modified graphene oxide (AMGO). The properties of AMGO synthesized under different κ-Ca/GO ratios were studied. The κ-Ca/GO interactions and the properties of GO and AMGO were investigated and characterized. AMGO was successfully produced with a yield of 90.37 % under optimized synthesis conditions. The separation of κ-Ca and AMGO was conducted without organic solvents, and the κ-Ca could be subsequently recovered. Furthermore, the porous hydrogel matrix formed by κ-Ca and GO exhibited excellent shape-retaining properties with high thermal tolerance of up to 50 °C. Given these benefits, this newly developed method endows sustainability and open the possibility of formulating more flexible material synthesis protocols.
  15. 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.
  16. Facile one pot preparation of magnetic chitosan-palygorskite nanocomposite for efficient removal of lead from water
    Rusmin R, Sarkar B, Mukhopadhyay R, Tsuzuki T, Liu Y, Naidu R
    J Colloid Interface Sci, 2021 Sep 22;608(Pt 1):575-587.
    PMID: 34628317 DOI: 10.1016/j.jcis.2021.09.109
    Development of polymeric magnetic adsorbents is a promising approach to obtain efficient treatment of contaminated water. However, the synthesis of magnetic composites involving multiple components frequently involves tedious preparation steps. In the present study, a magnetic chitosan-palygorskite (MCP) nanocomposite was prepared through a straight-forward one pot synthesis approach to evaluate its lead (Pb2+) removal capacity from aqueous solution. The nano-architectural and physicochemical properties of the newly-developed MCP composite were described via micro- and nano-morphological analyses, and crystallinity, surface porosity and magnetic susceptibility measurements. The MCP nanocomposite was capable to remove up to 58.5 mg Pb2+ g-1 of MCP from water with a good agreement of experimental data to the Langmuir isotherm model (R2 = 0.98). The Pb2+ adsorption process on MCP was a multistep diffusion-controlled phenomenon evidenced by the well-fitting of kinetic adsorption data to the intra-particle diffusion model (R2 = 0.96). Thermodynamic analysis suggested that the adsorption process at low Pb2+ concentration was controlled by chemisorption, whereas that at high Pb2+ concentration was dominated by physical adsorption. X-ray photoelectron and Fourier transform infrared spectroscopy results suggested that the Pb adsorption on MCP was governed by surface complexation and chemical reduction mechanisms. During regeneration, the MCP retained 82% Pb2+ adsorption capacity following four adsorption-desorption cycles with ease to recover the adsorbent using its strong magnetic property. These findings highlight the enhanced structural properties of the easily-prepared nanocomposite which holds outstanding potential to be used as an inexpensive and green adsorbent for remediating Pb2+ contaminated water.
  17. 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.
  18. Film-pore-concentration-dependent surface diffusion model for the adsorption of dye onto palm kernel shell activated carbon
    Choong TS, Wong TN, Chuah TG, Idris A
    J Colloid Interface Sci, 2006 Sep 15;301(2):436-40.
    PMID: 16814316
    The rate of dye adsorption from aqueous effluents onto palm kernel shell (PKS) activated carbon has been studied experimentally using the batch adsorption method. The adsorption rates of methylene blue on PKS for systems of different initial dye concentrations are modeled using a film-pore-concentration dependent surface diffusion (FPCDSD) model. The FPCDSD model is sufficiently general and can be reduced easily to describe other simplified models. Using the FPCDSD model, only a single set of mass transfer parameters is required to describe the methylene blue/PKS system for different initial concentrations. A different set of mass transfer parameters are needed to obtain the best fitting if the pore diffusion is not included in the model.
  19. 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.
  20. Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact
    Gorji MS, Razak KA, Cheong KY
    J Colloid Interface Sci, 2013 Oct 15;408:220-8.
    PMID: 23932085 DOI: 10.1016/j.jcis.2013.07.026
    Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.
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