Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 15Citation - Scopus: 14Electroactive Nanogel Formation by Reactive Layer-By Assembly of Polyester and Branched Polyethylenimine Via Aza-Michael Addition(American Chemical Society, 2021) Yıldırımkaraman, Öykü; Özenler, Sezer; Günay, Ufuk Saim; Durmaz, Hakan; Yıldız, Ümit HakanWe here demonstrate the utilization of reactive layer-by-layer (rLBL) assembly to form a nanogel coating made of branched polyethylenimine (BPEI) and alkyne containing polyester (PE) on a gold surface. The rLBL is generated by the rapid aza-Michael addition reaction of the alkyne group of PE and the -NH2 groups of BPEI by yielding a homogeneous gel coating on the gold substrate. The thickness profile of the nanogel revealed that a 400 nm thick coating is formed by six multilayers of rLBL, and it exhibits 50 nm roughness over 8 mu m distance. The LBL characteristics were determined via depth profiling analysis by X-ray photoelectron spectroscopy, and it has been shown that a 70-100 nm periodic increase in gel thickness is a consequence of consecutive cycles of rLBL. A detailed XPS analysis was performed to determine the yield of the rLBL reaction: the average yield was deduced as 86.4% by the ratio of the binding energies at 286.26 eV, (C CN-C bond) and 283.33 eV, (C C triple bond). The electrochemical characterization of the nanogels ascertains that up to the six-multilayered rLBL of BPEI-PE is electroactive, and the nanogel permeability had led to drive mass and charge transfer effectively. These results promise that nanogel formation by rLBL films may be a straightforward modification of electrodes approach, and it exhibits potential for the application of soft biointerfaces.Article Citation - WoS: 83Precipitation of Monodisperse Zno Nanocrystals Via Acid-Catalyzed Esterification of Zinc Acetate(Royal Society of Chemistry, 2006) Demir, Mustafa Muammer; Muñozz-Espí, Rafael; Lieberwirth, Ingo; Wegner, GerhardA wet-chemical method to produce zinc oxide nanocrystals of monodisperse size distribution (diameter range of 20-80 nm) is presented. The synthesis starts from zinc acetate dihydrate which is converted to ZnO in the presence of 1-pentanol in m-xylene at 130 °C. We report for the first time catalysis of this reaction by p-toluene sulfonic acid monohydrate (p-TSA), which allows a shorter reaction time and improves both the reproducibility of the particle size distribution and the crystallinity of the particles. The reaction can be scaled up to give multigram quantities of product per batch. Particles were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and photoluminesence (PL) spectroscopy. Room temperature PL spectra of ZnO prepared without catalyst exhibit a strong and sharp UV emission band at ca. 385 nm and a weak and very broad green-yellow visible emission centered at ca. 550-560 nm. However, for nanoparticles precipitated in the presence of p-TSA, the UV emission is enhanced by a factor of 4, which can be correlated with the improvement of crystal perfection. A particle formation mechanism is discussed.