Influence of precursor chemistry on CVD grown TiO2 coatings: differential cell growth and biocompatibility

Nanocrystalline titanium oxide (TiO2) coatings with different phases and surface topographies were deposited using chemical vapor deposition (CVD) of different homo- and heteroleptic titanium precursors of general formula [XTi(OiPr)3] (X = Cl (1), -NEt2 (2), -N(SiMe3)2 (3), -C5H5 (4), -OiPr (5) and -OtBu (6)) to elucidate the influence of molecular configuration on resulting material properties. The interdependence of precursor chemistry and materials features of the CVD deposits was verified by performing film growth under similar conditions using different precursor molecules (1-6). Studies on composition (XPS), structure (SEM, XRD) and bio-functional properties (cell tests) revealed that the decomposition process is markedly influenced by the auxiliary ligands, which led to incorporation of heteroelements (Si, Cl, N) in the films. Cell tests performed to evaluate the biocompatibility of the coatings towards the growth of bone cells showed a pronounced correlation between cell adhesion and surface morphology as well as the chemical composition. Growth of osteoblast cells was strongly enhanced on films obtained using [Ti(OiPr)4] and [CpTi(OiPr)3], whereas TiO2 coatings produced by [ClTi(OiPr)3] significantly inhibited the cell growth and their proliferation due to Cl contamination. Also, the nanomorphological features of the films were found to stimulate the cell adhesion and growth

Homo- and heteroleptic transition- and lanthanide metal precursors and their application in material science

Zur Entwicklung und Herstellung neuartiger funktioneller und technologisch relevanter Beschichtungssysteme besitzt die molekülbasierte chemische Gasphasenabscheidung (MBCVD) vielfältiges Potential. Dabei nimmt die thermische Zersetzung des Precursormoleküls zur Filmbildung eine Schlüsselposition ein. Um nun die Auswirkungen des molekularen Designs von metallorganischen Precursorverbindungen durch Ligandenmodifikation auf die resultierenden Materialeigenschaften zu untersuchen, wurden im Rahmen dieser Dissertation mittels CVD unter Verwendung verschiedener homo- und heteroleptischer Precursorsysteme dünne Filme abgeschieden. Die an den resultierenden Beschichtungen durchgeführten Untersuchungen bzgl. Morphologie, chemischer Zusammensetzung und Phasenevolution geben Aufschluss über die Korrelation von Precursormolekül, Prozessparametern und Materialeigenschaften, wodurch die Kontrolle der Schichtkonstitution allein durch gezieltes Precursordesign ermöglicht wird. In diesem Zusammenhang wurden nanokristalline Zirkoniumcarbonitrid (Zr-C-N) und Zirkoniumoxid (ZrO2) Schichten aus Zr(NEt2)4, einem Zr(NEt2)4/Et2NH Gemisch, bzw. Zr(OtBu)4 auf Stahl- und Siliziumsubstraten erzeugt und bezüglich der mechanischen Eigenschaften bei variierten Prozessbedingungen untersucht. Neuartige heteroleptische Übergangsmetallprecursoren Zr(OtBu)2{N(SiMe3)2}2, Hf(OtBu)2{N(SiMe3)2}2, [Ti(OtBu)2N(SiMe3)2ClLiN(SiMe3)2]2 und Zr(OtBu)2(NiPr2)2 konnten durch Einkristallröntgenstrukturanalyse vollständig charakterisiert und im thermischen CVD-Verfahren eingesetzt werden. Außerdem ermöglichte die Verwendung homoleptischer (Ti(OtBu)4 und Ti(OiPr)4) sowie heteroleptischer Titanverbindungen der allgemeinen Form XTi(OiPr)3, (X = Cl, Me, NMe2, NEt2, NiPr2, C5H5, OtBu und N(SiMe3)2) die Untersuchung des Einflusses der Ligandensphäre auf die Erzeugung von TiO2-Filmen. Im Falle der ZrO2- Zr-C-N- sowie TiO2- Filme erfolgte eine Evaluation von Zell-Oberflächen-Wechselwirkungen. Darüber hinaus wurden metallorganische Moleküle der Lanthanoide, [Nd(OiPr){N(SiMe3)2}2]2, [Ce(OiPr){N(SiMe3)2}2]2, [Eu(Mal)3]2, ErN(SiMe3)2(Mal)2, [Nd{OCH(CF3)2}3(H2O)2]2 und Er3O(OSiMe3)7(HOSiMe3)(THF)2 synthetisiert und strukturell aufgeklärt. Diese Synthesen erfolgten ebenfalls unter dem Aspekt der Generierung einer heteroleptischen Ligandensphäre.Thin film deposition by molecule-based chemical vapor growth techniques shows great potential for the development and synthesis of new functional coating systems of technological interest. In a CVD-process the thermolysis reaction of a precursor molecule has the major impact on the film formation. The influence of molecular precursor design by ligand modification on resulting material properties, such as morphology, chemical composition and crystallinity was elaborated. In addition studies on the impact of molecular constitution and process parameter on the resulting film quality were performed using various homo- and heteroleptic precursor systems. The results demonstrated the control of resulting material- and film properties by specific precursor design. In this context nanocrystalline zirconium carbonitride (Zr-C-N)- and zirconium oxide (ZrO2)-films were deposited by MBCVD of Zr(NEt2)4, a mixture of Zr(NEt2)4/Et2NH and Zr(OtBu)4 on iron and Si(100), respectively, while the evolution of the mechanical properties was analyzed upon parameter variations. Moreover new heteroleptic transition metal precursors Zr(OtBu)2{N(SiMe3)2}2, Hf(OtBu)2{N(SiMe3)2}2, Zr(OtBu)2(NiPr2)2 and [Ti(OtBu)2N(SiMe3)2ClLiN(SiMe3)2]2 were structurally characterized and used in a thermal CVD process. Various homo- (Ti(OtBu)4 and Ti(OiPr)4) and heteroleptic titanium precursors of the general formula XTi(OiPr)3 (X = Cl, Me, NMe2, NEt2, NiPr2, C5H5, OtBu and N(SiMe3)2) were synthesized and the impact on the precursor-dependent coating properties was investigated in detail. Morphology, chemical composition and phase evolution of the CVD deposits were explored, while ZrO2, Zr-C-N as well as TiO2 showed interesting cell-surface-interactions. Besides transistion metal complexes metal organic lanthanide compounds [Nd(OiPr){N(SiMe3)2}2]2, [Ce(OiPr){N(SiMe3)2}2]2, [Eu(Mal)3]2, ErN(SiMe3)2(Mal)2, [Nd{OCH(CF3)2}3(H2O)2]2, and Er3O(OSiMe3)7(HOSiMe3)(THF)2 were synthesized and structurally characterized, while we focused on formation of heteroleptic molecules showing low tendency to oligomerisation

Amplified electrochemical DNA-sensing of nanostructured metal oxide films deposited on disposable graphite electrodes functionalized by chemical vapor deposition

WOS: 000264089600025Metal oxide nanostructures offer interesting possibilities to design functional surfaces for biosensing applications, for instance, through higher surface area leading to enhanced immobilization of biomolecules, which increases the detection limit. Herein, an amplified electrochemical sensing method has been presented for the detection of DNA based on the readout resulting from chemical oxidation of guanine on nanoscaled metal oxides (TiO(2), SnO(2) and Fe(3)O(4)) obtained by chemical vapor deposition (CVD) onto pencil graphite electrode (PGE) as electrochemical transducer. The proposed strategy is suitable to produce cost-effective disposable sensor elements enabling quantitative detection of nanomolar concentrations of DNA. When preparing these metal oxide surfaces by CVD onto PGEs, the various experimental conditions; such as, the effect of different concentrations of 20 mer-bases DNA oligonucleotide (ODN20), and the surface pretreatment steps were Studied to obtain better surface properties for DNA immobilization. The detection limit estimated for signal-to-noise ratios >3 corresponds to 21.3, 519 and 45.8 nmole/ml ODN20 concentrations for PGEs modified with TiO(2), SnO(2) and Fe(3)O(4) films, respectively. The electrochemical detection of DNA onto metal oxide@PGEs is discussed together with the application potential. (c) 2008 Elsevier B.V. All rights reserved.German Science FoundationGerman Research Foundation (DFG); Turkish Academy of Sciences (TUBA)Turkish Academy of SciencesS.M. and A.E. acknowledge the German Science Foundation for a grant under the international short visit scheme. A.E. would also like to express her gratitude to the Turkish Academy of Sciences (TUBA) as an associate member for their support