Greatly increased electrical conductivity of PBTTT-C14 thin film via controllable single precursor vapor phase infiltration.

Doping is an important strategy for effectively regulating the charge carrier concentration of semiconducting materials. In this study, the electronic properties of organic-inorganic hybrid semiconducting polymers, synthesized viain situcontrolled vapor phase infiltration (VPI) of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C14) with the metal precursors molybdenum pentachloride (MoCl5) and titanium tetrachloride (TiCl4), were altered and characterized. The conductivities of the infiltration-doped PBTTT-C14 thin films were enhanced by up to 9 and 4 orders of magnitude, respectively. The significantly improved electrical properties may result from interactions between metal atoms in the metal precursors and sulfur of the thiophene rings, thus forming new chemical bonds. Importantly, VPI doping has little influence on the structure of the PBTTT-C14 thin films. Even if various dopant molecules infiltrate the polymer matrix, the interlayer spacing of the films will inevitably expand, but it has negligible effects on the overall morphology and structure of the film. Also, Lewis acid-doped PBTTT-C14 thin films exhibited excellent environmental stability. Therefore, the VPI-based doping process has great potential for use in processing high-quality conductive polymer films.

Omniphobic Etched Aluminum Surfaces with Anti-Icing Ability.

In this work, omniphobic surfaces are developed by combining chemical etching and surface modification of aluminum. In the first step, hierarchical micro/nanostructuring is carried out by chemical etching. Thereafter, a perfluoropolyether is grafted onto the corrugated aluminum substrate, decreasing its surface free energy and turning the system omniphobic. The morphology and chemical composition of the developed surfaces are characterized. We observed a low affinity toward liquids, regardless of their chemical nature and surface tension. The surface shows superhydrophobic properties with a water contact angle of 160° and simultaneously strong oleophobic properties with a hexadecane contact angle of 141°. Furthermore, these omniphobic surfaces significantly delay the freezing time of water droplets to 5100 s, which is about 20-fold of the freezing time on pristine aluminum (260 s), and they even inhibit ice growth by repelling the incoming droplets prior to ice nucleation.

'Sandwich'-like hybrid ZnO thin films produced by a combination of atomic layer deposition and wet-chemistry using a mercapto silane as single organic precursor.

This study describes a straightforward preparation of hybrid organic-inorganic thin films containing a stable 'sandwich'-like structure of two atomic layer deposited (ALD) ZnO layers separated by a thin organosilane phase, which is built from a single organic component (3-mercaptopropyl)trimethoxysilane (MPTMS). Grafting of MPTMS on the first ALD ZnO layer was performed in solution and driven by the strong affinity of the terminal thiol functionality (-SH) towards ZnO. We demonstrate that under different reaction conditions, either MPTMS monolayers are prepared or a 5 nm thick cross-linked polymeric network is formed due to the self-condensation of silane, which covers the ALD ZnO surface. This film served as a soft template for the nucleation of an ALD ZnO top layer by creation of S-Zn and Si-O-Zn bonds at the upper interface, as confirmed by XPS measurements. An increase in surface roughness, as compared to the initial ZnO film, is observed after removal of the organic layer from the hybrid structure by calcination, which is accompanied by an improvement in UVA photocatalytic activity towards the degradation of methyl orange dye. Thus, MPTMS can be used as a sacrificial agent in combination with low temperature ALD processes for building rougher and photocatalytically efficient ZnO coatings.

Comparison of two endogenous delivery agents in cancer therapy: Exosomes and ferritin.

Exosomes and ferritin: Two biomacromolecules from our human bodies both draw increasing interest for advanced drug delivery due to their endogenous origin and their morphology, the cage-like structures. They possess perfect naturally designed structures for loading and shielding of cargo. Their intrinsic biological functions enable a natural delivery of the load and specific targeting. More and more evidences point towards the evolution of a new era of drug delivery strategies with exosomes and ferritin, even for potential personalized therapy. This review focuses on the advantages as well as limits of exosomes and ferritin as endogenous carriers for cancer therapy. We compare their structure-specific cargo loading and their intrinsic cancer-related biological functions. Remaining challenges and promising perspectives for future development to use these two endogenous agents are discussed.

Multilayer Fresnel zone plates for high energy radiation resolve 21 nm features at 1.2 keV.

X-ray microscopy is a successful technique with applications in several key fields. Fresnel zone plates (FZPs) have been the optical elements driving its success, especially in the soft X-ray range. However, focusing of hard X-rays via FZPs remains a challenge. It is demonstrated here, that two multilayer type FZPs, delivered from the same multilayer deposit, focus both hard and soft X-rays with high fidelity. The results prove that these lenses can achieve at least 21 nm half-pitch resolution at 1.2 keV demonstrated by direct imaging, and sub-30 nm FWHM (full-pitch) resolution at 7.9 keV, deduced from autocorrelation analysis. Reported FZPs had more than 10% diffraction efficiency near 1.5 keV.

Novel three-dimensional nanoporous alumina as a template for hierarchical TiO2 nanotube arrays.

Hierarchical micro-/nano-structures made easy. By using extremely rough, chemically etched microstructured aluminium foils, anodization in phosphoric acid under very harsh conditions, e.g., 10 wt% phosphoric acid and room temperature, can be repeatedly accomplished without suffering from breakdown. As a result, an alumina membrane with a three-dimensionally distributed nanopore structure is formed, which can be used as a general template to fabricate hierarchical micro-/nano-structures.

Efficient focusing of 8 keV X-rays with multilayer Fresnel zone plates fabricated by atomic layer deposition and focused ion beam milling.

Fresnel zone plates (FZPs) recently showed significant improvement by focusing soft X-rays down to ~10 nm. In contrast to soft X-rays, generally a very high aspect ratio FZP is needed for efficient focusing of hard X-rays. Therefore, FZPs had limited success in the hard X-ray range owing to difficulties of manufacturing high-aspect-ratio zone plates using conventional techniques. Here, employing a method of fabrication based on atomic layer deposition (ALD) and focused ion beam (FIB) milling, FZPs with very high aspect ratios were prepared. Such multilayer FZPs with outermost zone widths of 10 and 35 nm and aspect ratios of up to 243 were tested for their focusing properties at 8 keV and shown to focus hard X-rays efficiently. This success was enabled by the outstanding layer quality thanks to ALD. Via the use of FIB for slicing the multilayer structures, desired aspect ratios could be obtained by precisely controlling the thickness. Experimental diffraction efficiencies of multilayer FZPs fabricated via this combination reached up to 15.58% at 8 keV. In addition, scanning transmission X-ray microscopy experiments at 1.5 keV were carried out using one of the multilayer FZPs and resolved a 60 nm feature size. Finally, the prospective of different material combinations with various outermost zone widths at 8 and 17 keV is discussed in the light of the coupled wave theory and the thin-grating approximation. Al2O3/Ir is outlined as a promising future material candidate for extremely high resolution with a theoretical efficiency of more than 20% for as small an outermost zone width as 10 nm at 17 keV.

Nanoscale patterning of organosilane molecular thin films from the gas phase and its applications: fabrication of multifunctional surfaces and large area molecular templates for site-selective material deposition.

A simple methodology to fabricate micrometer- and nanometer-scale patterned surfaces with multiple chemical functionalities is presented. Patterns with lateral dimensions down to 110 nm were made. The fabrication process involves multistep gas-phase patterning of amine, thiol, alkyl, and fluorinated alkyl-functional organosilane molecules using PDMS molds as shadow masks. Also, a combination process of channel diffused plasma etching of organosilane molecular thin films in combination with masked gas-phase deposition to fabricate multilength scale, multifunctional surfaces is demonstrated.

Unexpected oxidation behavior of Cu nanoparticles embedded in porous alumina films produced by molecular layer deposition.

This work reports an unexpected oxidation behavior of Cu nanoparticles embedded in porous Al(2)O(3) confinements that are produced by annealing alucone (an organic-inorganic hybrid material) deposited by molecular layer deposition. An oxidation of such encapsulated Cu nanoparticles by annealing in air produces Cu oxide nanoparticles attached to the outer surface of the hollow Al(2)O(3) nanostructures, which is in strong contrast to bare or compact, nonporous Al(2)O(3)-coated Cu nanoparticles, which result in hollow oxide nanospheres or do not undergo oxidation, respectively. The conversion from encapsulated Cu to supported oxide nanoparticles is explained by a concerted pore-assisted diffusion and oxidation mechanism. The micropores in the films, having diameters of several angstroms, permit a selective out-diffusion of Cu atoms and prevent the inward diffusion of oxygen. The subsequent oxidation occurs at the pore entrances, which work as multiple nucleation sites for the formation of oxide nanoparticles with a small size and good dispersion.

Facile Fabrication of Gold Nanorods@Polystyrenesulfonate Yolk-Shell Nanoparticles for Spaser Applications.

We present a method for producing gold nanorods surrounded by a hollow polymeric shell of polystyrenesulfonate and show that the cavities of such particles can be filled with various organic dyes. The approach consists of covering gold nanorods with silica, followed by its slow hydrolysis in an aqueous medium in the presence of the polymer thin layer permeable for dye molecules. The proposed method enables the yolk-shell nanoparticles to be obtained and loaded with organic dyes without a need to use thermal treatment and/or chemical etching, which makes it suitable for use in the creation of spasers.

Entropy-Driven Self-Healing of Metal Oxides Assisted by Polymer-Inorganic Hybrid Materials.

Enabling self-healing of materials is crucially important for saving resources and energy in numerous emerging applications. While strategies for the self-healing of polymers are advanced, mechanisms for semiconducting inorganic materials are scarce due to the lack of suitable healing agents. Here a concept for the self-healing of metal oxides is developed. This concept consists of metal oxide nanoparticle growth inside the bulk of halogenated polymers and their subsequent entropy-driven migration to externally induced defect sites, leading to recovery of the defect. Herein, it is demonstrated that the pool of self-healing materials is expanded to include semiconductors, thereby increasing the reliability and sustainability of functional materials through the use of metal oxides. It is revealed that electrical properties of tin-doped indium oxide can be partially restored upon healing. Such properties are of immediate interest for the further development of transparent flexible electrodes.

Metal infiltration into biomaterials by ALD and CVD: a comparative study.

Atomic layer deposition (ALD) is a subset of chemical vapor deposition (CVD) and both use very similar chemistry. Recently, it has been reported that ALD has the potential to realize a new design paradigm of bioinorganic materials through metal infiltration, which in nature has been employed as a hardening strategy for many tissues in diverse biological organisms. Herein, using a spider dragline silk and a collagen membrane as targets, we have performed a comparative study to elucidate the difference of the metal infiltration effect by ALD and CVD. From the comparison of mechanical properties, concentration of the infiltrated metal, and structural changes induced by the infiltrated metal, it has been proven that the metal can effectively infiltrate biomaterials by ALD and the infiltrated metal leads to highly improved mechanical properties accompanied by substantial changes in the protein structures, whereas CVD is less effective.

Reducing stress on cells with apoferritin-encapsulated platinum nanoparticles.

The great potential for medical applications of inorganic nanoparticles in living organisms is severely restricted by the concern that nanoparticles can harmfully interact with biological systems, such as lipid membranes or cell proteins. To enable an uptake of such nanoparticles by cells without harming their membranes, platinum nanoparticles were synthesized within cavities of hollow protein nanospheres (apoferritin). In vitro, the protein-platinum nanoparticles show good catalytic efficiency and long-term stability. Subsequently the particles were tested after ferritin-receptor-mediated incorporation in human intestinal Caco-2 cells. Upon externally induced stress, for example, with hydrogen peroxide, the oxygen species in the cells decreased and the viability of the cells increased.

Lasing Spaser in Photonic Crystals.

Plasmonic nanolasers (spasers) are of intense interest, attributable to their ability to generate a high-intensity coherent radiation. We infiltrated a three-dimensional silica-based photonic crystal (PhC) film with spasers, composed of spherical gold cores, surrounded by silica shells with dye molecules. In spasers, the gold nanospheres supported the surface plasmons and the dye molecules transferred incoming optical energy to the surface plasmons. Our experiments show that such a structure, consisting of a PhC, which acts as an external distributed feedback resonator, and spasers, can serve as a coherent source of electromagnetic radiation. Spasers were locked in phase by the common radiation causing a phenomenon called the lasing spaser: the emission of spatially and temporarily coherent light normal to the surface of the PhC film. The far-field radiation patterns appeared in the shape of the Star-of-David, which is due to the dispersion along the Brillouin zone boundary. The infiltration of the spasers into the PhC led to drastic narrowing of the emission peak and an 80-fold decrease in the spaser generation threshold with respect to the same spasers in a suspension at room temperature.

ALD coating of centrifugally spun polymeric fibers and postannealing: case study for nanotubular TiO2 photocatalyst.

This work describes the synthesis of highly photocatalytically active TiO2 tubes (TiTBs) by combining centrifugal spinning and atomic layer deposition (ALD). Poly(vinyl pyrrolidone) (PVP) fibers were first produced by centrifugal spinning and subsequently coated with TiO2 with various film thicknesses in a fluidized bed ALD reactor. After annealing of the TiO2 ALD coated PVP fibers, TiO2 tubes (TiTBs) with excellent textural properties and diameters in the range from approx. 170 to 430 nm were obtained. The morphology and structure of all TiTBs were investigated by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller analysis (BET). Liquid phase photocatalysis was conducted to determine the photocatalytic activity of the TiTBs. The photocatalytic activity of the TiTBs obtained after 50 TiO2 ALD cycles (degradation rate 0.123 min-1) was twice that of the reference TiO2 P25. The underlying reasons for the remarkable photocatalytic performance were textural properties of the resulting tubes along with suitable crystallinity, embedded within the 1D tubular morphology. The herein presented proof-of-concept approach paves a way for the processing of various polymeric fibers into various tubular nanostructures.

Amorphous AlN films grown by ALD from trimethylaluminum and monomethylhydrazine.

The great interest in aluminium nitride thin films has been attributed to their excellent dielectric, thermal and mechanical properties. Here we present the results of amorphous AlN films obtained by atomic layer deposition. We used trimethylaluminum and monomethylhydrazine as the precursors at a deposition temperature of 375-475 °C. The structural and mechanical properties and chemical composition of the synthesized films were investigated in detail by X-ray diffraction, X-ray photoelectron spectroscopy, electron and probe microscopy and nanoindentation. The obtained films were compact and continuous, exhibiting amorphous nature with homogeneous in-depth composition, at an oxygen content of as low as 4 at%. The mechanical properties were comparable to those of AlN films produced by other techniques.

Radical-triggered cross-linking for molecular layer deposition of SiAlCOH hybrid thin films.

Here, we report on a simultaneous growth and radical-initiated cross-linking of a hybrid thin film in a layer-by-layer manner via molecular layer deposition (MLD). The cross-linked film exhibited a self-limiting MLD growth behavior and improved properties like 12% higher film density and enhanced stability compared to the non-cross-linked film.

Flexible replication technique for high-aspect-ratio nanostructures.

A flexible, nondestructive, and cost-effective replication technique for nanostructures is presented. The advantages of the process are: 1) it allows for tailoring structural parameters of the replica (e.g., line width) nearly independent of the structural geometry of the master; 2) it allows for replication of high-aspect-ratio structures also in polymer materials from solution (especially noncurable polymers) such as polystyrene and polymethylmethacrylate; 3) it includes an easy separation process, thus preserving the master for repeated use. Linear grating replicas with line widths ranging from 88 to 300 nm are obtained using a single nanostructured master. Nanofibers and complex nanopatterned replicas are achievable. The presented technique and its flexibility show that atomic layer deposition is a unique tool for the preparation of high-efficiency polarizer diffractive optics, photonics, electronics, and catalysts.

SCIP: a new simultaneous vapor phase coating and infiltration process for tougher and UV-resistant polymer fibers.

The physical properties of polymers can be significantly altered by blending them with inorganic components. This can be done during the polymerization process, but also by post-processing of already shaped materials, for example through coating by atomic layer deposition (ALD) or hybridizing through vapor phase infiltration (VPI), both of which are beneficial in their own way. Here, a new processing strategy is presented, which allows distinct control of the coating and infiltration. The process is a hybrid VPI and ALD process, allowing separate control of infiltrated and coated components. This new simultaneous vapor phase coating and infiltration process (SCIP) enhances the degrees of freedom for optimizing the properties of polymers, as shown on the example of Kevlar 29 fibers. The SCIP treated fibers show an increase of 17% of their modulus of toughness (MOT) in comparison to native Kevlar, through the nanoscale coating with alumina. At the same time their intrinsic sensitivity to 24 hours UV-irradiation was completely suppressed through another infiltrated material, zinc oxide, which absorbs the UV irradiation in the subsurface area of the fibers.