Browsing by Author "Barsbay, Murat"
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Item Open Access Effect of brush length of stabilizing grafted matrix on size and catalytic activity of metal nanoparticles(Elsevier, 2020-06-01) Barsbay, Murat; Özgür, T. Ç.; Sütekin, S. D.; Güven, O.The rationale of this work is to investigate the effect of chain length of stabilizing polymer brushes attached to silica surface on the formation and catalytic activity of metallic palladium nanoparticles (Pd NPs). Poly(vinyl pyrrolidone) (PVP) brushes forming a very thin shell were grafted on silica microparticles (PVP@SiO2) via RAFT mediated graft polymerization, thus controlling the molecular weights and structures of PVP grafts. Pd nanoparticles were formed in PVP stabilizing matrix by gamma-induced reduction of polymer-bound Pd(II) ions to yield Pd(0) decorated core-shell particles (PVP-PdNP@SiO2). SEC and TGA results indicated the formation of PVP brushes with different molecular weights on silica substrate. DLS and TEM measurements revealed that particle growth was sterically blocked by the increase in PVP brush length, thereby forming a greater number of small Pd nanoparticles rather than larger ones. PVP-PdNP@SiO2 samples with different PVP chain lengths and Pd sizes were evaluated for their catalytic activity and reusability in the reduction of 4-nitrophenol to 4-aminophenol. Although the nanoparticles formed in the presence of longer grafted chains are smaller, their leakage into the solution has been found to be more effectively prevented by these long grafts. Thus, PVP-PdNP@SiO2 samples with longer PVP grafts showed more stable catalytic activity in repeated reaction cycles. These findings are particularly important for heterogeneous catalysis systems in that they show the effect of the size of surface-bound polymeric stabilizers on metal NP formation and catalytic activity.Item Open Access A smartphone-based colorimetric PET sensor platform with molecular recognition via thermally initiated RAFT-mediated graft copolymerization(Elsevier, 2019) Kuşçuoğlu, C.; Güner, Hasan; Söylemez, M.; Güven, O.; Barsbay, MuratIn this work, we report a low-cost and easy-to-use molecularly-imprinted colorimetric sensor platform that can sense target analyte with high sensitivity and good selectivity. The platform has been examined for colorimetric detection and quantitation of a model textile dye, basic red 9 (BR9), by employing methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA) and cumyl dithiobenzoate (CDB) as functional monomer, crosslinker and RAFT agent, respectively. Benzophenone (BP), a photoinitiator, was covalently immobilized on the surface of poly(ethylene terephthalate) (PET) and then thermally activated by homolytic cleavage to form radicals on the surface that initiate RAFT-mediated grafting of a thin recognition layer. The molecularly imprinted polymer (MIP) layer of about 100 nm showed excellent removal of 76.7% target dye in 10 min and high selectivity compared to other similar dyes with an imprinting factor of 10.31 in the competitive environment. The resulting MIP grafted PET substrate was efficiently used as recognition unit in a smartphone-based colorimetric detection method using a color adaptation algorithm for point-of-care applications. Based on the obtained performance, it is promising to use the method for the detection and quantification of various analytes with chromophores.