ZnO precipitation experiments were carried out in a Trizma (tris(hydroxymethyl)aminomethane)-buffered aqueous solution at 37 °C and in the presence of three ZnO-binding 12-mer peptide pairs, which have nearly the same isoelectric point (pI). With this new approach, the influence of peptide sequences on ZnO mineralization under moderate conditions was investigated. Previous work was focused on electrostatic interactions between inorganic-binding peptides and inorganic surfaces. The precipitates were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, the peptide binding to crystallographic planes of ZnO crystals was modeled by molecular dynamics (MD) simulation in explicit water. The binding free energies of all ZnO-binding peptides were calculated. The combined experimental and modeled results demonstrated a direct correlation between the binding strength of the peptide and the morphology of the ZnO particle, due to differences in their specific binding strength towards polar ZnO (001) and nonpolar (100) surfaces. As a consequence, the ZnO-binding peptides inhibited the growth of ZnO crystals by selective adsorption on the polar or nonpolar ZnO surfaces. This was demonstrated by comparison with a precipitation experiment under peptide-free conditions.

Aluminum-doped ZnO (AZO) thin films were produced via template-directed deposition at 60 °C. By adding organic molecules to the deposition solution, it is possible to control the crystallite growth, and nanocrystallinity is achieved. An organic template, 3-aminopropyltriethoxysilane (APTES), is used to direct the attachment of the crystallites on the substrate. The optical properties and the incorporation of the aluminum from solution into the ZnO films were measured using photoluminescence (PL) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The morphology of the film was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The latter revealed a preferred orientation of the crystallites in the samples where more than 15 mol% Al was added to the stock solution.For values higher than 30 mol% Al in solution, no ZnO was found at all.

SummaryIn this study we investigated the influence of an organic polystyrene brush on the deposition of ZnO thin films under moderate conditions. On a non-modified SiOx surface, island growth is observed, whereas the polymer brush induces homogeneous film growth. A chemical modification of the polystyrene brushes during the mineralization process occurs, which enables stronger interaction between the then polar template and polar ZnO crystallites in solution. This may lead to oriented attachment of the crystallites so that the observed (002) texture arises. Characterization of the templates and the resulting ZnO films were performed with ζ-potential and contact angle measurements as well as scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). Infrared spectroscopy (IR) measurements were used to investigate the polystyrene brushes before and after modification.

Biomaterials are used as model systems for the deposition of functional inorganic materials under mild reaction conditions where organic templates direct the deposition process. In this study, this principle was adapted for the formation of piezoelectric ZnO thin films. The influence of two different organic templates (namely, a carboxylate-terminated self-assembled monolayer and a sulfonate-terminated polyelectrolyte multilayer) on the deposition and therefore on the piezoelectric performance was investigated. While the low negative charge of the COOH-SAM is not able to support oriented attachment of the particles, the strongly negatively charged sulfonated polyelectrolyte leads to texturing of the ZnO film. This texture enables a piezoelectric performance of the material which was measured by piezoresponse force microscopy. This study shows that it is possible to tune the piezoelectric properties of ZnO by applying templates with different functionalities.

SummaryWe present a promising first example towards controlling the properties of a self-assembling mineral film by means of the functionality and polarity of a substrate template. In the presented case, a zinc oxide film is deposited by chemical bath deposition on a nearly topography-free template structure composed of a pattern of two self-assembled monolayers with different chemical functionality. We demonstrate the template-modulated morphological properties of the growing film, as the surface functionality dictates the granularity of the growing film. This, in turn, is a key property influencing other film properties such as conductivity, piezoelectric activity and the mechanical properties. A very pronounced contrast is observed between areas with an underlying fluorinated, low energy template surface, showing a much more (almost two orders of magnitude) coarse-grained film with a typical agglomerate size of around 75 nm. In contrast, amino-functionalized surface areas induce the growth of a very smooth, fine-grained surface with a roughness of around 1 nm. The observed influence of the template on the resulting clear contrast in morphology of the growing film could be explained by a contrast in surface adhesion energies and surface diffusion rates of the nanoparticles, which nucleate in solution and subsequently deposit on the functionalized substrate.

We present a promising first example towards controlling the properties of a self-assembling mineral film by means of the functionality and polarity of a substrate template. In the presented case, a zinc oxide film is deposited by chemical bath deposition on a nearly topography-free template structure composed of a pattern of two self-assembled monolayers with different chemical functionality. We demonstrate the template-modulated morphological properties of the growing film, as the surface functionality dictates the granularity of the growing film. This, in turn, is a key property influencing other film properties such as conductivity, piezoelectric activity and the mechanical properties. A very pronounced contrast is observed between areas with an underlying fluorinated, low energy template surface, showing a much more (almost two orders of magnitude) coarse-grained film with a typical agglomerate size of around 75 nm. In contrast, amino-functionalized surface areas induce the growth of a very smooth, fine-grained surface with a roughness of around 1 nm. The observed influence of the template on the resulting clear contrast in morphology of the growing film could be explained by a contrast in surface adhesion energies and surface diffusion rates of the nanoparticles, which nucleate in solution and subsequently deposit on the functionalized substrate.1763

No abstract