School of Chemistry - Research Publications
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ItemNo Preview AvailableIncorporating whey protein aggregates produced with heat and ultrasound treatment into rennet gels and model non-fat cheese systems(Elsevier, 2020-12-01)Native whey proteins (WP) are expulsed from cheese coagulation during syneresis. Although incorporating denatured WP aggregates into cheese gels has been previously proposed to improve the overall cheese yield, the effects of WP aggregate properties on gelation kinetics and protein retention are not yet fully understood. In this study, heat and power ultrasound were used to produce denatured whey protein aggregates with a wide range of sizes. The effects of size and hydrophobicity differences in WP aggregates produced by heat and heat coupled with ultrasound were investigated in relation to the kinetics of rennet gelation and protein retention in model non-fat cheddar cheeses. Rheological measurements showed that sufficiently large, denatured WP aggregates could avoid impairment of rennet gelation caused by native WP, irrespective of changes in the soluble calcium concentration or the surface hydrophobicity of the aggregates. WP aggregates formed by the combined heat and ultrasound treatment were more hydrophobic than the larger heat-treated aggregates and were better retained in the cheese. However, inclusion of sufficiently large aggregates in cheese milk conferred an openness to the cheese microstructure and showed promise in improving the otherwise rigid non-fat cheese.
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ItemShape-Dependent Interactions of Palladium Nanocrystals with Hydrogen(WILEY-V C H VERLAG GMBH, 2016-05-11)Elucidation of the nature of hydrogen interactions with palladium nanoparticles is expected to play an important role in the development of new catalysts and hydrogen-storage nanomaterials. A facile scaled-up synthesis of uniformly sized single-crystalline palladium nanoparticles with various shapes, including regular nanocubes, nanocubes with protruded edges, rhombic dodecahedra, and branched nanoparticles, all stabilized with a mesoporous silica shell is developed. Interaction of hydrogen with these nanoparticles is studied by using temperature-programmed desorption technique and by performing density functional theory modeling. It is found that due to favorable arrangement of Pd atoms on their surface, rhombic dodecahedral palladium nanoparticles enclosed by {110} planes release a larger volume of hydrogen and have a lower desorption energy than palladium nanocubes and branched nanoparticles. These results underline the important role of {110} surfaces in palladium nanoparticles in their interaction with hydrogen. This work provides insight into the mechanism of catalysis of hydrogenation/dehydrogenation reactions by palladium nanoparticles with different shapes.
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ItemSono‐RAFT Polymerization in Aqueous Medium(Wiley, 2017-09-25)The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition–fragmentation chain transfer (RAFT) agent. This allows for a highly “green” method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.
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ItemSono-RAFT Polymerization in Aqueous Medium(WILEY-V C H VERLAG GMBH, 2017-09-25)The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition-fragmentation chain transfer (RAFT) agent. This allows for a highly "green" method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.
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ItemUltrasound and Sonochemistry for Radical Polymerization: Sound Synthesis(WILEY-V C H VERLAG GMBH, 2019-04-11)The use of ultrasound as an external stimulus for promoting polymerization reactions has received increasing attention in recent years. In this Review article, the fundamental processes that can lead to either the homolytic cleavage of polymer chains, or the sonolysis of solvent (or other) small molecules, under the application of ultrasound are described. These reactions promote the production of reactive radicals, which can be utilized in chain-growth radical polymerizations under the right conditions. A full historical overview of the development of ultrasound-assisted radical polymerization is provided, with special attention given to the recently described systems that are "controlled" by methods of reversible (radical) deactivation. Perspectives are shared on what challenges still remain in polymer sonochemistry, as well as new areas that are yet to be explored.
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ItemUltrasound-Assisted Synthesis of Cross-Linked Poly(ethylene glycol) Nanostructures with Hydrophobic Core and Hydrophilic Shell(WILEY-V C H VERLAG GMBH, 2018-12-01)Abstract One‐pot synthesis of polymeric nanostructures, by using ultrasound without adding initiators and surfactants, is a straightforward approach that has attracted significant attention in polymer science. In this study, the ultrasonic polymerization technique is employed to synthesize poly(ethylene glycol) based nanoparticles with a hydrophobic core and a hydrophilic shell. Interfacial polymerization is performed using an oil‐in‐water emulsion containing oligo (ethylene glycol) methyl ether methacrylate as a water‐soluble monomer, and ethylene glycol dimethacrylate acting as an oily‐cross‐linker phase. Both the radicals and physical effects generated by acoustic cavitation are crucial to conduct this surfactant and initiator‐free process and obtain uniform nanoparticles endowed with a hydrophobic core and hydrophilic shell. It is shown that the nanoparticle's core can be loaded with hydrophobic compounds. This technique can be applied to different monomers containing various functional moieties such as amines and carboxyl groups to obtain multifunctional nanoparticles.
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ItemElectrochemical investigation of the interaction between lysozyme-shelled microbubbles and vitamin C(SPRINGER HEIDELBERG, 2013-06-01)We report loading of vitamin C (ascorbic acid) on to lysozyme-shelled microbubbles. The interaction between lysozyme-shelled microbubbles and vitamin C was studied by use of cyclic and differential pulse voltammetry, zeta potential measurements, and scanning electron microscopy. The effect of microbubbles on electrochemical measurement of ascorbic acid was evaluated. The linear range for ascorbic acid obtained for differential pulse measurement in the presence of 1 mg mL(-1) microbubbles was 1-50 μmol L(-1) (y = 0.067x + 0.130, r(2) = 0.995), with a detection limit of 0.5 μmol L(-1). The experimental conditions, i.e., pH and ionic strength, were optimized to improve the interaction between ascorbic acid and lysozyme-shelled microbubbles. The results were satisfactory when the interaction was performed for 1 h in aqueous solution at pH 6. The amount of vitamin C loaded on the microbubbles (90% of the analyte added, RSD(inter-expt.) = 3%, n = 6) and the stability of microbubbles-ascorbic acid complex (until 72 h at 25 °C) were also evaluated by use of differential pulse voltammetry and zeta potential measurements.
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ItemNovel molecularly imprinted polymeric microspheres for preconcentration and preservation of polycyclic aromatic hydrocarbons from environmental samples(SPRINGER HEIDELBERG, 2014-09-01)Molecularly imprinted polymer (MIP) microspheres with diameters in the range 60-500 μm were synthesized in a continuous segmented flow microfluidic reactor and used as packing material for microtraps for the selective separation of benzo[a]pyrene (BAP) from environmental aqueous samples. The synthesis involved the pumping of monodisperse droplets of acetonitrile containing methacrylic acid as the functional monomer, BAP as a template, and ethylene glycol dimethacrylate as the cross-linking monomer into the microchannels of the microfluidic reactor. The microspheres showed high adsorption capacity and selectivity for BAP in aqueous solutions; both are important for the environmental monitoring and analysis of BAP. The adsorption capacity for BAP of the smallest MIP microspheres (size range 60-80 μm), prepared as part of this study, was 75 mg g(-1) in aqueous solutions; furthermore, this adsorption capacity was close to 300 % higher than that of commercially used activated carbon. Microtraps packed with MIP retained BAP intact for at least 30 days, whereas microtraps packed with activated carbon for BAP showed 40 % reduction in BAP concentration for the same period. This study has demonstrated that MIP microtraps have significant potential for the selective enrichment and preservation of targeted polycyclic aromatic hydrocarbons from complex environmental samples.
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ItemTheory of Sonochemistry(SPRINGER INT PUBL AG, 2016-08-01)Sonochemistry refers to ultrasound-initiated chemical processes in liquids. The interaction between bubbles and sound energy in liquids results in acoustic cavitation. This review presents the fundamental aspects of acoustic cavitation and theoretical aspects behind sonochemistry such as dynamics of bubble oscillation, the rectified diffusion process that is responsible for the growth of cavitation bubbles, near adiabatic collapse of cavitation bubbles resulting in extreme reaction conditions and several chemical species generated within collapsing bubbles that are responsible for various redox reactions. Specifically, a detailed discussion on single bubble sonochemistry is provided.
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