Metal-halide-perovskites revolutionized the field of thin-film semiconductor technology, due to their favorable optoelectronic properties and facile solution processing. Further improvements of perovskite thin-film devices require structural coherence on the atomic scale. Such perfection is achieved by epitaxial growth, a method that is based on the use of high-end deposition chambers. Here epitaxial growth is enabled via a ≈1000 times cheaper device, a single nozzle inkjet printer. By printing, single-crystal micro-and nanostructure arrays and crystalline coherent thin films are obtained on selected substrates. The hetero-epitaxial structures of methylammonium PbBr 3 grown on lattice matching substrates exhibit similar luminescence as bulk single crystals, but the crystals phase transitions are shifted to lower temperatures, indicating a structural stabilization due to interfacial lattice anchoring by the substrates. Thus, the inkjet-printing of metal-halide perovskites provides improved material characteristics in a highly economical way, as a future cheap competitor to the high-end semiconductor growth technologies.
Snowman-shaped Au-FeO nanoheterodimers were synthesized by thermal decomposition of iron oleate on presynthesized Au nanoparticles. Subsequently performed ligand exchange with nitrosyl tetrafluoroborate provided water solubility and enabled X-ray-induced NO release. These Au-FeO nanoheterodimers combine high- Z material with catalytically active FeO surfaces and, moreover, plasmonic properties with superparamagnetic performance. We could establish synergetic interactions between X-radiation and both the Au and FeO surfaces, which resulted in the simultaneous production of the nitric oxide radical at the FeO surface and the superoxide radical at the Au surface. The surface-confined reaction between these radicals generated peroxynitrite. This highly reactive species may cause nitration of mitochondrial proteins and lipid peroxidation and induce DNA strand breaks. Therefore, high concentrations of peroxynitrite are expected to give rise to severe cellular energetic derangements and thereupon entail rapid cell death. As providing a common platform for X-ray-induced formation of the highly reactive radical nitric oxide, superoxide, and peroxynitrite, nitrosyl tetrafluoroborate functionalized Au-FeO nanosnowmen were shown to exhibit excellent performance as X-ray-enhancing agents in radiation therapy.
Dielectric mirrors based on bilayers of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) and poly(vinyl alcohol) (PVA)–zirconium dioxide (ZrO2) nanocomposites are fabricated for vapor sensing. When exposed to specific solvent vapor, the layers of dielectric mirrors can gradually swell and cause a red-shift of the reflection band. Because PVA solely responds to water and SEBS is sensitive to several different types of organic solvents, the mirrors can respond to a large variety of solvents. The dual-functional hydrophilic ZrO2 nanoparticles are introduced to not only enlarge the refractive index contrast but also increase the permeability. Time-resolved measurements show that mirrors with nanoparticles have a significantly faster response than those without nanoparticles. Moreover, the dependence on relative humidity is studied for representative solvents, and several types of solvents are selected to show the dependence on the solvent–polymer interaction parameters at typical relative humidity, which allows one to predict the responsivity and selectivity of the sensors.
Bifunctional Au–Fe3O4 nanoheterodimers were synthesized by thermally decomposing Fe(III)oleate on gold nanoparticles followed by functionalizing with tiron, 2,3-dihydroxybenzoic acid, or caffeic acid. These catechol derivatives are antioxidative and thus are predicted to function as superoxide scavengers. In particular, caffeic acid lost its antioxidant capacity, although it was covalently linked through its carboxyl moiety to the Fe3O4 surface. Tiron was shown to bind via its catechol group to the Au–Fe3O4 nanoheterodimers, and 2,3-dihydroxybenzoic was just physisorbed between the oleic acid surface structures. Caffeic-acid stabilized Au–Fe3O4 nanoheterodimers turned out to act as X-ray protector in healthy cells but as X-ray enhancing agents in cancer cells. Furthermore, these functionalized Au–Fe3O4 nanoheterodimers were found to inhibit the migratory capacity of the cancer cells.
Au−Fe 3 O 4 nanoheterodimers were obtained by thermally decomposing iron oleate on presynthesized gold nanoparticles. Water solubility as well as surface charges were achieved by encapsulating the initially hydrophobic Au−Fe 3 O 4 nanoheterodimers in a self-assembled bilayer shell formed either by 1octadecylpyridinium, providing positive surface charges, or by 4-dodecylbenzenesulfonate, yielding a negatively charged surface. The surface charge and surface architecture were shown to control both the cellular entry and the intracellular trafficking of the Au−Fe 3 O 4 nanoheterodimers. The positively charged (1octylpyridinium-terminated) Au−Fe 3 O 4 nanoheterodimers were internalized by both breast cancer cells (MCF-7) and epithelial cells (MCF-10 A), wherein they were electrostatically bound at the negatively charged membranes of the cell organelles and, in particular, adsorbed onto the mitochondrial membrane. The treatment of MCF-7 and MCF-10 cells with a fractional X-radiation dose of 1 Gy resulted into a large increase of superoxide production, which arose from the Au− Fe 3 O 4 nanoheterodimer-induced mitochondrial depolarization. In contrast, the negatively charged (4-dodecylbenzenesulfonateterminated) Au−Fe 3 O 4 nanoheterodimers preferentially invaded the cancerous MCF-7 cells by direct permeation. X-ray treatment of MCF-7 cells, loaded with anionic Au−Fe 3 O 4 nanoheterodimers, yielded the increase of both hydroxyl radical and cytoplasmic superoxide formation. The X-radiation-induced activation of the Fe 3 O 4 surfaces, consisting of Fe 2+ and Fe 3+ cations, triggered the catalysis of the hydroxyl radical production, whereas superoxide formation presumably occurred through X-rayinduced photoelectron emission near the Au surface. Since hydroxyl radicals are highly cytotoxic and the negatively charged Au−Fe 3 O 4 NHDs spare the healthy MCF-10A cells, these Au−Fe 3 O 4 nanoheterodimers exhibit a higher potential for radiation therapy than the positively charged Au−Fe 3 O 4 nanoheterodimers. Encouraging results from the clonogenic cell survival assay and DMF calculations corroborate the excellent performance of the anionic Au−Fe 3 O 4 nanoheterodimers as an X-ray dosage enhancer.
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