Functional Metal Oxide Surfaces: Photocatalytic, Self-Cleaning and Micro-/Nanostructuring Applications

Photocatalysis is the most applicable approach to decompose various organic pollutants due to its high efficiency, low-cost, and eco-friendly nature. Heterogeneous photocatalysis has become a hot topic in the field of green chemistry. Titanium (IV) oxide (TiO2) photocatalyst has been widely investigated in comparison to other metal oxide semiconductors due to its high activity, low cost, and high chemical and physical stability. On the other hand, TiO2 is also preferable materials in some specific applications such as self-cleaning (indoor and outdoor applications). This dissertation covers the development of TiO2 based functional metal oxide surfaces for photocatalytic and self-cleaning applications as well as micro-/nanostructuring of gold (Au) and silver (Ag). This thesis is composed of 14 Chapters: Following Introduction (Chapter 1) and Theoretical Background (Chapter 2), Method and Characterization processes are described in Chapter 3. The Results and Discussion, which are originally based on peer-reviewed nine publications, are presented in corresponding nine chapters (Chapters 4, 5, 6, 7, 8, 9, 10, 11, and 12). Afterward, Summary & Conclusion and Outlook are presented in Chapter 13 and Chapter 14, respectively.Photokatalyse is die effektivste Art der Zersetzung von unterschiedlichsten organischen Verunreinigungen aufgrund der hohen Effizienz, ihrer niedrigen Kosten und ihres umweltschonenden Verhaltens. Heterogene Photokatalyse ist ein hoch aktuelles Thema im Kontext der nachhaltigen grünen Chemie. Titan (IV) oxid (TiO2) Photokatalysatoren wurden, im Vergleich zu anderen Metalloxiden, besonders weitgehend untersucht, aufgrund ihrer hohen Aktivität, niedrigen Kosten und hoher chemischer und physikalischer Stabilität. Ebenfalls ist TiO2 auch bevorzugtes Material für einige spezielle Anwendungen wie z.B. selbstreinigende Oberflächen (im Indoor- bzw. Outdoorbereich). Diese Dissertaton behandelt die Herstellung von funktionalen Metalloxidoberflächen für photokatalytische und selbstreinigende Anwendungen sowie der Mikro- und Nanostrukturierung von Gold (Au) und Silber (Ag). Diese Thesis besteht aus 14 Kapiteln: Nach einer Einleitung (Kapitel 1) und der Behandlung der theoretischen Grundlagen (Chapter 2) werden Methoden und Charakterisierungsprozesse erklärt (Kapitel 3). Daraufhin werden die Ergebnisse auf Grundlage von 9 wissenschaftlich begutachteten (Engl.: Peer-reviewed) Publikationen diskutiert und jeweils in den damit assozierten Kapiteln aufgezeigt (Kapitel 4-12). Im Anschluss werden die Ergebnisse zusammengefasst, es wird ein Fazit dieser Arbeit gezogen und es werden Zukunftsperspektiven aufgezeigt (Kapitel 13 und 14)

Nanoscale Synergetic Effects on Ag-TiO2 Hybrid Substrate for Photoinduced Enhanced Raman Spectroscopy (PIERS) with Ultra-Sensitivity and Reusability

Here, a 4N-in-1 hybrid substrate concept (nanocolumnar structures, nanocrack network, nanoscale mixed oxide phases, and nanometallic structures) for ultra-sensitive and reliable photo-induced-enhanced Raman spectroscopy (PIERS), is proposed. The use of the 4N-in-1 hybrid substrate leads to an ≈50-fold enhancement over the normal surface-enhanced Raman spectroscopy, which is recorded as the highest PIERS enhancement to date. In addition to an improved Raman signal, the 4N-in-1 hybrid substrate provides a high detection sensitivity which may be attributed to the activation possibility at extremely low UV irradiation dosage and prolonged relaxation time (long measurement time). Moreover, the 4N-in-1 hybrid substrate exhibits a superior photocatalytic degradation performance of analytes, allowing its reuse at least 18 times without any loss of PIERS activity. The use of the 4N-in-1 concept can be adapted to biomedicine, forensic, and security fields easily

Selective Laser Melting of 316L Austenitic Stainless Steel: Detailed Process Understanding Using Multiphysics Simulation and Experimentation

The parameter sets used during the selective laser melting (SLM) process directly affect the final product through the resulting melt-pool temperature. Achieving the optimum set of parameters is usually done experimentally, which is a costly and time-consuming process. Additionally, controlling the deviation of the melt-pool temperature from the specified value during the process ensures that the final product has a homogeneous microstructure. This study proposes a multiphysics numerical model that explores the factors affecting the production of parts in the SLM process and the mathematical relationships between them, using stainless steel 316L powder. The effect of laser power and laser spot diameter on the temperature of the melt-pool at different scanning velocities were studied. Thus, mathematical expressions were obtained to relate process parameters to melt-pool temperature. The resulting mathematical relationships are the basic elements to design a controller to instantly control the melt-pool temperature during the process. In the study, test samples were produced using simulated parameters to validate the simulation approach. Samples produced using simulated parameter sets resulting in temperatures of 2000 (K) and above had acceptable microstructures. Evaporation defects caused by extreme temperatures, unmelted powder defects due to insufficient temperature, and homogenous microstructures for suitable parameter sets predicted by the simulations were obtained in the experimental results, and the model was validated

PTFEP-Al2O3 hybrid nanowires reducing thrombosis and biofouling

Thrombosis and bacterial infection are major problems in cardiovascular implants. Here we demonstrated that a superhydrophobic surface composed of poly(bis(2,2,2-trifluoroethoxy)phosphazene) (PTFEP)-Al2O3 hybrid nanowires (NWs) is effective to reduce both platelet adhesion/activation and bacterial adherence/colonization. The proposed approach allows surface modification of cardiovascular implants which have 3D complex geometries. © 2019 The Royal Society of Chemistry

Initiated Chemical Vapor Deposition (iCVD) Functionalized Polylactic Acid-Marine Algae Composite Patch for Bone Tissue Engineering

The current study aimed to describe the fabrication of a composite patch by incorporating marine algae powders (MAPs) into poly-lactic acid (PLA) for bone tissue engineering. The prepared composite patch was functionalized with the co-polymer, poly (2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) (p(HEMA-co-EGDMA)) via initiated chemical vapor deposition (iCVD) to improve its wettability and overall biocompatibility. The iCVD functionalized MAP-PLA composite patch showed superior cell interaction of human osteoblasts. Following the surface functionalization by p(HEMA-co-EGDMA) via the iCVD technique, a highly hydrophilic patch was achieved without tailoring any morphological and structural properties. Moreover, the iCVD modified composite patch exhibited ideal cell adhesion for human osteoblasts, thus making the proposed patch suitable for potential biomedical applications including bone tissue engineering, especially in the fields of dentistry and orthopedy

Marine Algae Incorporated Polylactide Acid Patch: Novel Candidate for Targeting Osteosarcoma Cells without Impairing the Osteoblastic Proliferation

Biodegradable collagen-based materials have been preferred as scaffolds and grafts for diverse clinical applications in density and orthopedy. Besides the advantages of using such bio-originated materials, the use of collagen matrices increases the risk of infection transmission through the cells or the tissues of the graft/scaffold. In addition, such collagen-based solutions are not counted as economically feasible approaches due to their high production cost. In recent years, incorporation of marine algae in synthetic polymers has been considered as an alternative method for preparation grafts/scaffolds since they represent abundant and cheap source of potential biopolymers. Current work aims to propose a novel composite patch prepared by blending Sargassum vulgare powders (SVP) to polylactide (PLA) as an alternative to the porcine-derived membranes. SVP-PLA composite patches were produced by using a modified solvent casting method. Following detailed material characterization to assess the cytocompatibility, human osteoblasts (HOBs) and osteosarcoma cells (SaOS-2) were seeded on neat PLA and SVP-PLA patches. MTT and BrdU assays indicated a greater cytocompatibility and higher proliferation for HOBs cultured on SVP-PLA composite than for those cultured on neat PLA. SaOS-2 cells cultured on SVP-PLA exhibited a significant decrease in cell proliferation. The composite patch described herein exhibits an antiproliferative effect against SaOS-2 cells without impairing HOBs' adhesion and proliferation

Enhancing thermal conductivity of epoxy with a binary filler system of h-BN platelets and Al2O3 nanoparticles

Epoxy resin is a common adhesive bonding material used to join dissimilar materials, especially in the electronics and aerospace industries. However, its low thermal conductivity and high coefficient of thermal expansion limit the direct use of epoxy in practical applications. In order to improve thermo-mechanical properties, we have prepared a series of epoxy composites using a binary system of hexagonal-boron nitride (h-BN) and aluminum oxide (Al2O3) fillers and analyzed the effect of the ratio of these fillers on the thermal conductivity of composites. While h-BN platelets form the main thermal conductive network, Al2O3 nanoparticles bridge the separated h-BN platelets to build more thermal conductive pathways. We proposed the improving of thermal conductivity as well as the mechanical properties of the epoxy matrix by incorporating h-BN and Al2O3 fillers at an optimum ratio

SYNTHESIS, CHARACTERIZATION AND IMPROVEMENT OF alpha-Co(OH)(2) FOR SUPERCAPACITOR APPLICATIONS

In the present study, alpha-Co(OH)(2) was prepared by a potentiostatic deposition process at -1.0V (vs. Ag/AgCl) onto a nickel electrode by using a aqueous solution of 0.1 M Co(NO3)(2). The structure and surface morphology of the obtained the alpha - Co(OH)(2) were studied by using X-ray diffraction analysis and scanning electron microscopy. XRD data and the scanning electron microscopy images showed that the as-deposited films have an interlaced nanosheet-like surface morphology and possess a regular nanostructure with hexagonal arrays of pores of nanometer dimension and extended periodicit

Influence of Succinic Acid and Polyethylene Glycol (PEG) Additives on Electrochemical Performance of Lithium-ion Batteries

In this study, we report results of succinic acid and polyethylene glycol (PEG) additives at different rates in mass (the rates of %0-%200.) The structure and electrochemical properties of the LiFePO4/C were characterized by XRD, SEM, and galvanostatic charge-discharge measurements. Among the materials studied, the sample (A) which contains %100 succinic acid and %200PEG (w/w), exhibits a 150mAhg(-1) discharge capacity and it is corresponding to 88% of the theoretical capacity. The improved electrochemical properties were attributed to the reduced particle size and enhanced electrical contacts by carbon

Ultra-fast degradation of methylene blue by Au/ZnO-CeO2 nano-hybrid catalyst

Au/ZnO-CeO2 hybrid structure was prepared by in-situ synthesis of 15-20 nm CeO2 particles in aqueous environment, in which ZnO particles ( 400-500 nm) were dispersed, using surfactant assisted precipitation method. Au was loaded on prepared structures through the reduction of AuCl3 by ascorbic acid. TEM analysis and Raman spectroscopy showed that synthesized hybrid structure is composed of both hexagonal ZnO and cubic CeO2 phases. While methylene blue test solution was degraded totally within 8 min in the presence of Au/ZnO-CeO2 hybrid catalysis, use of Au/ZnO and Au/CeO2 led to a significantly low degradation rate (about 22% and 11%, respectively). As proven by XPS analysis the incorporation of ZnO to CeO2 seem to trigger the formation of Ce+3/Ce+4 dynamic equilibria and this enhances the catalytic efficiency enormously. (C) 2017 Elsevier B.V. All rights reserved