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Author: search.filters.author.Mdluli, Phumlani SelbyHas files: No

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    Experimental and theoretical study of molecular interactions between 2-vinyl pyridine and acidic pharmaceuticals used as multi-template molecules in molecularly imprinted polymer
    (Elsevier, 2016) Madikizela, Lawrence Mzukisi; Mdluli, Phumlani Selby; Chimuka, Luke
    Molecular interactions between functional monomer and template molecules are regarded as the driving force for the success of a molecularly imprinted polymer. In this study, a multi-template molecularly imprinted poly-mer (MIP) for ibuprofen, naproxen and diclofenac was synthesized in an oil bath set at 70 °C for 24 hours. 2-vinyl pyridine, ethylene glycol dimethacrylate, toluene and 1,1’-azobis-(cyclohexanecarbonitrile) were used as func-tional monomer, cross-linker, porogen and radical initiator, respectively. A non-imprinted polymer (NIP) was synthesized using a similar approach with the omission of templates. Monomer-template interactions were ex-amined using Molecular Dynamics and Fourier Transform Infrared Spectroscopy (FTIR). Both molecular dynam-ics and FT-IR results indicated the formation of the hydrogen bond between the templates and 2-vinyl pyridine. Molecular dynamics further revealed the identity of the hydrogen atoms in the templates involved in interactions with nitrogen atom on the functional monomer in the presence of toluene molecules. Surface area obtained for the MIP using Brunauer, Emmett and Teller method was 282 m2/g, whereas 232 m2/g was obtained for the NIP. This indicated that MIP has more binding sites compared to the NIP. Furthermore, batch adsorption and se-lectivity experiments were carried out in the presence of gemfibrozil as the competitor. When such experiments were carried out in toluene, the adsorption capacities (mg/g) obtained for naproxen, ibuprofen, diclofenac and gemfibrozil were 14.4, 11.0, 14.0 and 7.5, respectively. These results show that the MIP was more selective to the compounds that were used as template molecules.
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    A size-controlled synthesis and characterization of mixed monolayer protected silver-S-(CH2)11-NHCO-coumarin nanoparticles and their Raman activities
    (Materials Research Society, 2015-06-28) Mlambo, Mbuso; Mdluli, Phumlani Selby; Moloto, Nosipho; Shumbula, Poslet; Skepu, Amanda; Tshikhudo, Robert
    The study reports the functionalization of the size-controlled synthesized silver nanoparticles (AgNPs) with coumarin derivative. The size and the morphology of the as-synthesized AgNPs were obtained in the presence of glycerol and sodium citrate which acted as the reducing agent which led to nucleation of silver ions thus yielding different sizes of AgNPs. The obtained AgNPs were functionalized with different stoichiometric ratios of [HS-(CH2)11-NHCO-coumarin: HS-PEG-(CH2)11COOH] to form mixed monolayer protected silver clusters and their Raman activities were evaluated to determine the effect of particle size on the enhancement factor (EF). The functionalization and the stability of AgNPs were confirmed using a combination of techniques, namely UV–Visible spectroscopy, transmission electron microscopy, Zetasizer, and Raman spectroscopy. The obtained Raman spectra were used to calculate the EF of the HS-(CH2)11-NHCO-coumarin adsorbed on AgNPs, which was observed to increase with an increase in size of AgNPs from 16 to 30 nm. Increasing the particle size to 43 nm lowered the EF by 10-fold and hence an optimal size of ;30 nm was achieved for the coumarin derivative adsorbate.