In diesem Beitrag wird ein im Chemieunterricht umsetzbarer Versuch zur Herstellung verschiedenfarbig fluoreszierender Zinkoxid‐Nanopartikeldispersionen vorgestellt. Es wird gezeigt, dass sich sowohl das Phänomen der Fluoreszenz als auch die verschiedenen Fluoreszenzfarben mit Hilfe chemischer Basiskonzepte deuten lassen. Neben der grundsätzlichen Erkenntnis, dass sich Nanomaterialien in ihren Eigenschaften von denen ihrer makroskopisch großen Analoga unterscheiden, kann mit Hilfe des vorgestellten Versuchs anschaulich erarbeitet werden, dass sich innerhalb eines Größenbereichs auf der Nanomaterskala Stoffeigenschaften in Abhängigkeit von der Teilchengröße steuern lassen, was heute in diversen technischen Anwendungen genutzt wird. Darüber hinaus werden im Beitrag auch Versuche zur Verwendung von Zinkoxid‐Nanopartikeln als „low cost“ UV‐Lichtdetektor, zum Nachweis der photokatalytischen Aktivität sowie zur Wirkung auf pflanzliche Zellen präsentiert.

The optical and photoelectrochemical properties of ordered mesoporous a-LiFe 5 O 8 thin films have been investigated. These solÀgel thin films exhibit a complex band structure, indicating a band gap of 2.45 eV, with additional absorption in the visible region up to l = 600 nm. MottÀSchottky plots reveal their applicability as photoanodes for water splitting (as they are ntype semiconductors) and photoelectrochemical tests show good performance for water oxidation.Spinel ferrites have gained tremendous interest in the last decade as low-cost and earth-abundant electrodes for magnetic, charge storage, and photoelectrochemical applications. Regarding photoelectrochemical water splitting, spinel ferrites are particularly investigated as alternative photoanode materials to a-Fe 2 O 3 , looking for better charge diffusion properties. [1] Spinel ferrites of composition MFe 2 O 4 (M=Cu, Co, Mg, Ni, Zn) have been intensively investigated concerning their applicability in water oxidation, and many different preparation techniques have been presented, recently especially for highly considered ZnFe 2 O 4 , including CVD, [2] ALD, [3] and solutionprocessing routes. [4] When not employed as single-phase electrodes, spinel ferrites are also often used in the form of composites as a kind of sensitizer for better charge separation, e. g. in combinations like ZnFe 2 O 4 /a-Fe 2 O 3 [5] or NiFe 2 O 4 /TiO 2 . [6] Recently, it has been shown that the photoelectrochemical properties of ZnFe 2 O 4 can be tailored by mesostructural engineering. [7] To this end, large-pore mesoporous ZnFe 2 O 4 thin films, prepared using an evaporation-induced self-assembly (EISA) process along with different polymer structure-directing agents, were applied.The EISA process was introduced in the late 1990s, [8] and many important thin-film materials with ordered mesoporous structures have been reported since then, including ferrites with garnet [9] and spinel [10] structures. For example, an interesting room-temperature magnetic spinel ferrite, namely LiFe 5 O 8 , with large mesopores and nanocrystalline walls was reported, showing promise for use in micromagnetic actuation. [11] LiFe 5 O 8 exhibits promising photocatalytic properties, but in the application as pure photoelectrode for water oxidation, the material showed hardly any performance with addition of reduced graphene oxide, below 1 mA/cm 2 . [12] Here, we present investigations into the optical and photoelectrochemical properties of mesoporous LiFe 5 O 8 thin-film photoanodes. Both SEM and TEM reveal highly porous and phase-pure material with nanocrystalline walls. MottÀSchottky analysis indicates n-type behavior and flat-band potential of the photoelectrodes below the hydrogen production potential, making mesoporous LiFe 5 O 8 photoanodes interesting for oxygen generation. Photoelectrochemical studies show good performance under visible light irradiation; no photocurrent transients were observed, thereby demonstrating low surface recombination losses when using a hole scavenger. IPCE measurem...

Mesoporous CsTaWO6 for photocatalytic hydrogen production has been prepared via hard-templating with a surface area of up to 115 m2 g−1.