Martin Steinhart

Nanostructured Fibers via Electrospinning

[23] M. DeLong, Optoelectronic Materials Laboratory/Physics Department,University of Utah, Salt Lake City, USA.[24] S. Setayesh, D. Marsitzky, K. Mullen, Macromolecules 2000, 33, 2016.[25] D. Sainova, T. Miteva, H. G. Nothofer, U. Scherf, I. Glowacki, J. Ulanski,H. Fujikawa, D. Neher, Appl. Phys. Lett. 2000, 76, 1810.[26] T. Pauck, H. Bassler, J. Grimme, U. Scherf, K. Mullen, Chem. Phys. 1996,210, 219.

Nanoshell tubes of ferroelectric lead zirconate titanate and barium titanate

Wafer-scale fabrication of ferroelectric oxide nanoshell tubes as well as ordered nanotube arrays have been accomplished using a simple and convenient fabrication method that allows full tailoring of tube dimensions as well as array pattern and size. Using different silicon and alumina templates, barium titanate and lead zirconate titanate tubes with diameters ranging from 50 nm up to several micrometers meter and lengths of more 100 μm have been fabricated. Ferroelectric switching of submicrometer tubes has been shown using piezoresponse scanning probe microscopy.

Self-ordered anodic aluminum oxide formed by H2SO4 hard anodization.

The self-ordering of nanoporous anodic aluminum oxide (AAO) in the course of the hard anodization (HA) of aluminum in sulfuric acid (H2SO4) solutions at anodization voltages ranging from 27 to 80 V was investigated. Direct H2SO4-HA yielded AAOs with hexagonal pore arrays having interpore distances D(int) ranging from 72 to 145 nm. However, the AAOs were mechanically unstable and cracks formed along the cell boundaries. Therefore, we modified the anodization procedure previously employed for oxalic acid HA (H2C2O4-HA) to suppress the development of cracks and to fabricate mechanically robust AAO films with D(int) values ranging from 78 to 114 nm. Image analyses based on scanning electron micrographs revealed that at a given anodization voltage the self-ordering of nanopores as well as D(int) depend on the current density (i.e., the electric field strength at the bottoms of the pores). Moreover, periodic oscillations of the pore diameter formed at anodization voltages in the range from 27 to 32 V, which are reminiscent of structures originating from the spontaneous growth of periodic fluctuations, such as topologies resulting from Rayleigh instabilities.

From heterogeneous to homogeneous nucleation of isotactic poly(propylene) confined to nanoporous alumina.

The crystallization of highly isotactic polypropylene confined in self-ordered nanoporous alumina is studied by differential scanning calorimetry. A transformation from a predominantly heterogeneous to predominantly homogeneous nucleation takes place if the pore diameter is smaller than 65 nm. Crystallization is suppressed with decreasing pore size, and the absence of nucleation below 20 nm pores indicates the critical nucleus size. The results reported here might enhance the understanding of nanocomposites containing semicrystalline polymers and reveal design criteria for polymeric nanofibers with tailored mechanical and optical properties.

Nanostructured gold films for SERS by block copolymer-templated galvanic displacement reactions.

Up to now, little effort has been made to exploit large-area high-throughput patterning by block copolymer (BCP) lithography to generate nanostructured substrates with periods well below 100 nm for surface-enhanced Raman scattering (SERS). We show that simple BCP-templated galvanic displacement reactions yield dense arrays of mushroom-shaped gold nanopillars with a period of 50 nm. The nanoporous BCP films used as templates were obtained by swelling-induced reconstruction of reverse micelle monolayers deposited on silicon wafers. Coupling of adjacent mushroom caps almost impinging on each other combined with their strong local curvature results in a high spatial density of hot spots in the narrow gaps between them. Thus, substrates characterized by high SERS efficiencies are obtained.

Supramolecular Organization of Polymeric Materials in Nanoporous Hard Templates

A broad range of polymeric materials can be formed into nanotubes by means of nanoporous hardtemplates containing arrays of aligned, cylindrical nanopores. Functional hybrid membranes consisting ofthe nanoporous matrix and the nanotubes as well as released arrays of aligned nanotubes are thus accessible.The mechanical, chemical, optical, and electronic properties of the nanotubes as well as their specificsurface are largely determined by the supramolecular organization of the material they consist of, and onlythe rational design of their internal morphology will pave the pay for their use as functional device components.Herein, recent efforts to tailor the mesoscopic structure of nanotubes by controlling the way precursorsand target materials are deposited into the nanopores are reviewed. Moreover, specific attention is directedto structure formation processes such as crystallization, phase separation and mesophase formation underthe influence of the two-dimensional confinement imposed by the pore geometry and the interfacial interactionswith the pore walls. Nanoporous hard templates are particularly suitable for the rational generation ofmesocopic fine structures in nanofibers because equilibrium and non-equilibrium states as well as unprecedentedconfinement-induced morphologies with new and exciting properties can be realized.

Nanoporous Metal Membranes with Bicontinuous Morphology from Recyclable Block‐Copolymer Templates

[*] Prof. Y. Wang, Prof. W. Xing, F. Li, L. Tong, Z. Chen, X. Liao, X. Liao State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology Nanjing 210009, Jiangsu (P. R. China) E-mail: yongwang@njut.edu.cn; xingwh@njut.edu.cn Fax: 0086-25-8317-2292 Dr. C. He College of Chemistry, Beijing Normal University Beijing, 100875 (P. R. China)

Stabilization of the amorphous state of pharmaceuticals in nanopores

Confinement in nanoporous host systems with strongly interacting pore walls is shown to be a powerful approach to increase the lifetime of amorphous drugs based on changes in thermodynamics and crystallization kinetics in nano-sized systems.

Functional quantum-dot/dendrimer nanotubes for sensitive detection of DNA hybridization.

The functionalization of nanotubes (NTs) is an effective strategy towards design of new hybrid materials combining customized properties and anisotropy. Such materials have attracted considerable interest for applications such as biocatalysts, biosensors, and as platforms for bioseparation. For example, quantum dots (QDs) exhibiting narrow emission bandwidth, photochemical stability, and high quantum yield have been incorporated into the walls of NTs. However, the strategies for producing QD-modified NTs reported up to now suffer from low efficiency of chemical functionalization and a lack of control over the spatial assembly of the QDs. Layer-by-layer (LBL) deposition, which involves the successive deposition of oppositely charged polyelectrolytes, allows generation of functional multilayer systems with high precision, even onto complex substrates such as nanoparticles and nanoporous matrices. Nanoparticles bearing charged ligands can easily be incorporated into multilayer systems, and the rational assembly of different-sized QDs in LBL structures can yield so-called ‘‘nanorainbows’’ that emit white light. By controlling the distance between the layers of different-sized QDs funnel-like bandgap profiles can be realized, which can show rapid and efficient fluorescence resonance energy transfer (FRET) along the bandgap gradient. A configuration that would be particularly advantageous for sensing consists of functionalized nanotubes aligned within

Nondestructive Replication of Self-Ordered Nanoporous Alumina Membranes via Cross-Linked Polyacrylate Nanofiber Arrays

Ordered nanofiber arrays are a promising material platform for artificial adhesive structures, tissue engineering, wound dressing, sensor arrays, and self-cleaning surfaces. Their production via self-ordered porous alumina hard templates serving as shape-defining molds is well-established. However, their release requires the destruction of the hard templates, the fabrication of which is costly and time-consuming, by wet-chemical etching steps with acids or bases. We report the nondestructive mechanical extraction of arrays of cross-linked polyacrylate nanofibers from thus recyclable self-ordered nanoporous alumina hard templates. Silica replicas of the latter were synthesized using the extricated nanofiber arrays as secondary molds that could be mechanically detached from the molded material. The approach reported here, which can be combined with microstructuring, may pave the way for the high-throughput production of both functional nanofiber arrays and ordered nanoporous membranes consisting of a broad range of material systems.