Non-equilibrium configurations of swelling polymer brush layers induced by spreading drops of weakly volatile oil

Polymer brush layers are responsive materials that swell in contact with good solvents and their vapors. We deposit drops of an almost completely wetting volatile oil onto an oleophilic polymer brush layer and follow the response of the system upon simultaneous exposure to both liquid and vapor. Interferometric imaging shows that a halo of partly swollen polymer brush layer forms ahead of the moving contact line. The swelling dynamics of this halo is controlled by a subtle balance of direct imbibition from the drop into the brush layer and vapor phase transport and can lead to very long-lived transient swelling profiles as well as non-equilibrium configurations involving thickness gradients in a stationary state. A gradient dynamics model based on a free energy functional with three coupled fields is developed and numerically solved. It describes experimental observations and reveals how local evaporation and condensation conspire to stabilize the inhomogeneous non-equilibrium stationary swelling profiles. A quantitative comparison of experiments and calculations provides access to the solvent diffusion coefficient within the brush layer. Overall, the results highlight the - presumably generally applicable - crucial role of vapor phase transport in dynamic wetting phenomena involving volatile liquids on swelling functional surfaces

Poly(2-Hydroxyethyl Methacrylate) Hydrogel-Based Microneedles for Metformin Release

The release of metformin, a drug used in the treatment of cancer and diabetes, from poly(2-hydroxyethyl methacrylate), pHEMA, hydrogel-based microneedle patches is demonstrated in vitro. Tuning the composition of the pHEMA hydrogels enables preparation of robust microneedle patches with mechanical properties such that they would penetrate skin (insertion force of a single microneedle to be ≈40 N). Swelling experiments conducted at 20, 35, and 60 °C show temperature-dependent degrees of swelling and diffusion kinetics. Drug release from the pHEMA hydrogel-based microneedles is fitted to various models (e.g., zero order, first order, second order). Such pHEMA microneedles have potential application for transdermal delivery of metformin for the treatment of aging, cancer, diabetes, etc

Polymer hydrogel-based microneedles for metformin release

Drug delivery devices ensure the effective delivery of a broad range of therapeutics to millions of patients worldwide on a daily basis.1 Microneedles are a class of drug delivery device that provide pain free transdermal delivery with improved patient compliance.2-4 The release of metformin, a drug used in the treatment of cancer and diabetes, from polymer hydrogel-based microneedle patches was demonstrated in vitro. Tuning the composition of the polymer hydrogels enabled preparation of robust microneedle patches with mechanical properties such that they would penetrate skin (insertion force of a single microneedle to be ca. 40 N). Swelling experiments conducted at 20°C, 35°C and 60°C show temperature dependent degrees of swelling and kinetics (Fickian diffusion). Drug release from the hydrogel-based microneedles was fitted to various models (e.g., zero order, first order, second order, Korsmeyer-Peppas, Peppas-Sahlins), observing the best fit for the zero-order model. Such microneedles have potential application for transdermal delivery of metformin for the treatment of cancer and diabetes

Organik katmanların AU(111) üzerinde yapısal ve elektronik özellikleri

Thesis (Doctoral)--Izmir Institute of Technology, Materials Science and Engineering, Izmir, 2018Includes bibliographical references (leaves: 65-78)Text in English; Abstract: Turkish and EnglishSelf-assembled monolayers (SAMs) have attracted attention due to their chemical and structural properties providing numerous new applications such as molecular electronics and electrochemistry. SAMs were optimized by experimental techniques including Scanning Tunneling Microscope (STM), Scanning Tunnelling Spectroscopy (STS), X-Ray Photoelectron Spectroscopy (XPS), Polarization-Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS). The first part of this dissertation deals with the dynamic behaviour of decanethiol SAMs. The dynamic behaviour alkanethiols SAM is unique for its configuration giving indirect evidence for the structural ordering within the formation. Structural stability of decanethiol (decanesulfonates) SAMs were investigated by space- and time- resolved STM. Decanesulfonate phase shows less dynamic behaviour and is structurally more stable compared to the decanethiol phases. The second part of this dissertation describes the binding properties of alkyne molecules adsorbed on gold. Alkyne oxidation occurs at ambient conditions but it is found that unlike thiols, ordered alkyne SAM structure has still chemical bonding between carbon and gold. Alkyne SAMs are good candidates for the ambient molecular electronics application. The last part of this dissertation presents the study of a monolayer of a Ru(II) complex which is prepared on gold substrate. With the help of STM and XPS methods, the ordered structure and binding properties of the CS28 molecules were characterized by providing a deeper insight into the carboxyl and sulfur groups binding affinity to gold substrate. CV and EIS methods were used to compare the adsorption properties and charge transfer process with the bare gold substrate and SAMs.Kendiliğinden düzenlenen tek katmanlı yapılar (SAM), moleküler elektronik ve elektrokimya gibi alanlarda çok sayıda yeni uygulamaya olanak sağlayan kimyasal ve yapısal özelliklerinden dolayı dikkat çekmektedir. Kendiliğinden düzenlenen tek katmanlı yapı, taramalı tünelleme mikroskobu, taramalı tünelleme spektroskopisi, X-Işını fotoelektron spektroskopisi, polarizasyon-modülasyon kızılötesi yansıma emilim spektroskopisi, döngüsel voltammetri, elektrokimyasal empedans spektroskopisi gibi çeşitli deneysel tekniklerle optimize edilmiştir. Bu tezin ilk bölümü dekantiyolun kendiliğinden düzenlenen tek katmanlı yapısının dinamik davranışı ile ilgilidir. Tek katmanlı alkantiyol yapıların dinamik davranışı, konfigürasyonu nedeniyle önemlidir çünkü oluşum içerisindeki yapı düzeni hakkında dolaylı kanıt sağlar. Dekantiyol ve hava ile okside olmuş dekantiyolün (dekansülfonat) yapısal kararlılığı uzay- ve zaman- çözünürlüklü taramalı tünelleme mikroskopisi tarafından incelenmiştir. Dekansülfonat fazı, dekantiyol fazlarına kıyasla daha az dinamik davranış gösterir ve yapısal olarak daha kararlıdır. Bu tezin ikinci kısmı, altın üzerine adsorbe edilmiş alkin moleküllerinin bağlanma özelliklerini açıklamaktadır. Alkin oksidasyonu normal şartlarda oluşur, ancak kendiliğinden düzenlenen tek katmanlı yapının tiyollerden farklı olarak, karbon ve altın arasında hala kimyasal bağa sahip olduğu anlaşılmıştır. Alkin tabanlı kendiliğinden düzenlenen tek katmanlar, moleküler elektronik uygulamaları için iyi bir adaydır. Tezin son kısmı, altın alt katman üzerinde çözelti yöntemiyle hazırlanan bir Ru (II) kompleksi tek tabakasının incelenmesini açıklamaktadır. Taramalı tünelleme mikroskopu ve X-Işını fotoelektron spektroskopisi yöntemleri ile CS28 molekülünün yapı düzeni ve bağlanma özellikleri, karboksil ve sülfür yapıların, altın alt katman üzerinde bağlanma eğilimleri derinlemesine incelenerek ortaya koyulmuştur. Çevrimsel voltametri ve empedans spektroskopisi yöntemleri, altın üzerinde kendiliğinden düzenlenenen tek katmanlı yapının ve boş altın alt tabakanın adsorpsiyon özelliği ve yük aktarım olaylarını kıyaslamak amacıyla kullanılmıştır

Sodium laurly sulphate/su/hexanol liyotropik sıvı kristalik sistemin fiziksel özelliklerinin incelenmesi

Bu tezde sodium laurly sulphate/su/hexanol üçlü sıvı kristalik sisteminin geniş konsantrasyon aralığında gösterdiği faz halleri incelenmiştir. Sabit sıcaklıkta polarize mikroskopi yöntemi kullanılarak mezofazların morfolojik özellikleri incelenmiş ve bu sisteme ait faz diyagramı oluşturulmuştur. Sistemin izotropik miseller L , nematik-kalamatik Nc, hegzagonal E ve lamelar D mezofazlarına ait tekstürler sergilediği gözlenmiştir. Bu mezofazlara ait örneklerin kırılma indisi sıcaklığa bağlı olarak ölçülmüş ve sıcaklıkla kırılma indisinin azaldığı görülmüştür

Organik katmanların AU(111) üzerinde yapısal ve elektronik özellikleri

Thesis (Doctoral)--Izmir Institute of Technology, Materials Science and Engineering, Izmir, 2018Includes bibliographical references (leaves: 65-78)Text in English; Abstract: Turkish and EnglishSelf-assembled monolayers (SAMs) have attracted attention due to their chemical and structural properties providing numerous new applications such as molecular electronics and electrochemistry. SAMs were optimized by experimental techniques including Scanning Tunneling Microscope (STM), Scanning Tunnelling Spectroscopy (STS), X-Ray Photoelectron Spectroscopy (XPS), Polarization-Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS). The first part of this dissertation deals with the dynamic behaviour of decanethiol SAMs. The dynamic behaviour alkanethiols SAM is unique for its configuration giving indirect evidence for the structural ordering within the formation. Structural stability of decanethiol (decanesulfonates) SAMs were investigated by space- and time- resolved STM. Decanesulfonate phase shows less dynamic behaviour and is structurally more stable compared to the decanethiol phases. The second part of this dissertation describes the binding properties of alkyne molecules adsorbed on gold. Alkyne oxidation occurs at ambient conditions but it is found that unlike thiols, ordered alkyne SAM structure has still chemical bonding between carbon and gold. Alkyne SAMs are good candidates for the ambient molecular electronics application. The last part of this dissertation presents the study of a monolayer of a Ru(II) complex which is prepared on gold substrate. With the help of STM and XPS methods, the ordered structure and binding properties of the CS28 molecules were characterized by providing a deeper insight into the carboxyl and sulfur groups binding affinity to gold substrate. CV and EIS methods were used to compare the adsorption properties and charge transfer process with the bare gold substrate and SAMs.Kendiliğinden düzenlenen tek katmanlı yapılar (SAM), moleküler elektronik ve elektrokimya gibi alanlarda çok sayıda yeni uygulamaya olanak sağlayan kimyasal ve yapısal özelliklerinden dolayı dikkat çekmektedir. Kendiliğinden düzenlenen tek katmanlı yapı, taramalı tünelleme mikroskobu, taramalı tünelleme spektroskopisi, X-Işını fotoelektron spektroskopisi, polarizasyon-modülasyon kızılötesi yansıma emilim spektroskopisi, döngüsel voltammetri, elektrokimyasal empedans spektroskopisi gibi çeşitli deneysel tekniklerle optimize edilmiştir. Bu tezin ilk bölümü dekantiyolun kendiliğinden düzenlenen tek katmanlı yapısının dinamik davranışı ile ilgilidir. Tek katmanlı alkantiyol yapıların dinamik davranışı, konfigürasyonu nedeniyle önemlidir çünkü oluşum içerisindeki yapı düzeni hakkında dolaylı kanıt sağlar. Dekantiyol ve hava ile okside olmuş dekantiyolün (dekansülfonat) yapısal kararlılığı uzay- ve zaman- çözünürlüklü taramalı tünelleme mikroskopisi tarafından incelenmiştir. Dekansülfonat fazı, dekantiyol fazlarına kıyasla daha az dinamik davranış gösterir ve yapısal olarak daha kararlıdır. Bu tezin ikinci kısmı, altın üzerine adsorbe edilmiş alkin moleküllerinin bağlanma özelliklerini açıklamaktadır. Alkin oksidasyonu normal şartlarda oluşur, ancak kendiliğinden düzenlenen tek katmanlı yapının tiyollerden farklı olarak, karbon ve altın arasında hala kimyasal bağa sahip olduğu anlaşılmıştır. Alkin tabanlı kendiliğinden düzenlenen tek katmanlar, moleküler elektronik uygulamaları için iyi bir adaydır. Tezin son kısmı, altın alt katman üzerinde çözelti yöntemiyle hazırlanan bir Ru (II) kompleksi tek tabakasının incelenmesini açıklamaktadır. Taramalı tünelleme mikroskopu ve X-Işını fotoelektron spektroskopisi yöntemleri ile CS28 molekülünün yapı düzeni ve bağlanma özellikleri, karboksil ve sülfür yapıların, altın alt katman üzerinde bağlanma eğilimleri derinlemesine incelenerek ortaya koyulmuştur. Çevrimsel voltametri ve empedans spektroskopisi yöntemleri, altın üzerinde kendiliğinden düzenlenenen tek katmanlı yapının ve boş altın alt tabakanın adsorpsiyon özelliği ve yük aktarım olaylarını kıyaslamak amacıyla kullanılmıştır

Hybridized Nanomaterials for Enhancing Photocatalytic Activity in Solar Fuel Production

Meeting the increasing demand for energy and clean water, access to these resources has become an essential requirement of modern human life. Nanohybrid material engineering is significant for the development of functional materials which can be used as photocatalyst. By optimizing the size, shape, and surface properties of such nanostructures, the photocatalytic process in terms of ensuring sustainable resource supply can be improved. The hybrid nanomaterials aim to obtain a high visible light absorption and low charge recombination resulting in a superior efficiency of photocatalytic reactions. The application areas which benefit from such nanohybrid materials are the filtration and degradation of organic pollutants and the photochemical hydrogen production for solar water splitting. This chapter describes in detail the nanohybrid materials including metal oxides, carbon-based materials, metal sulfides, metal–organic frameworks, and transition metal phosphides as well as bandgap tuning based on these structures, which affect the efficiency of photocatalysis

Anticorrosion coating for magnesium alloys: Electrospun superhydrophobic polystyrene/SiO2 composite fibers

Superhydrophobic nanocomposite coatings for magnesium surfaces with remarkable corrosion resistance were fabricated by electrospinning in the presence of fluorosilane-functionalized silica (SiO2) nanoparticles. The effects of surface-modified silica (mod-SiO2) nanoparticles on the superhydrophobicity and corrosion resistance of polystyrene (PS)/mod-SiO2 fiber coatings were evaluated. The incorporation of the SiO2 nanoparticles endows PS fibers with rough surfaces exhibiting a water contact angle (WCA) of 165◦. The surface wettability, corrosion resistance, and their relation to the inorganic content in the PS fibers and the contact angle of the composite coatings were explored. Analysis of the corrosion results confirmed that the PS/mod-SiO2 coating protected the Mg surface from corrosion. In addition, PS fibers containing mod-SiO2 nanoparticles showed improved hydrophobicity, and excellent corrosion resistance was achieved with PS fibers containing 4 wt% SiO2 nanoparticles

Smartphone-based colorimetric detection systems for glucose monitoring in the diagnosis and management of diabetes

Diabetes is a group of metabolic conditions resulting in high blood sugar levels over prolonged periods that affects hundreds of millions of patients worldwide. Measuring glucose concentration enables patient-specific insulin therapy, and is essential to reduce the severity of the disease, potential complications, and related mortalities. Recent advances and developments in smartphone-based colorimetric glucose detection systems are discussed in this review. The importance of glucose monitoring, data collection, transfer, and analysis, via non-invasive/invasive methods are highlighted. The review also presents the various approaches using 3D-printed materials, screen-printed electrodes, polymer templates, designs allowing multiple glucose analysis, bioanalytes, and/or nanostructures for glucose detection. The positive effects of advances in improving the performance of smartphone-based platforms are introduced, as are future directions and trends in the application of emerging technologies in smartphone-based diagnostics