Mikrowellen‐unterstützte Synthese von kolloidalen anorganischen Nanokristallen

Abstract

Kolloidale anorganische Nanokristalle bestechen durch chemische Eigenschaften, die im Synthesestadium flexibel über Größe, Form und passend zugeschnittene Zusammensetzungen einstellbar sind, und eine Einsetzbarkeit in einem weiten Bereich technischer Anwendungen, angefangen mit der Optoelektronik, über die Energieumwandlung/ ‐erzeugung und Katalyse bis hin zur Biomedizin. Der Einsatz von Mikrowellenbestrahlung als nicht klassische Energiequelle hat bei der Nanokristallsynthese (die im Allgemeinen eine komplexe und zeitaufwändige Verarbeitung von molekularen Vorstufen in Gegenwart von Lösungsmitteln, Liganden und/oder Tensiden bei erhöhten Temperaturen umfasst) an Popularität gewonnen. Ebenso wie bei der mittlerweile weit verbreiteten Anwendung in der organischen Chemie ist die Effizienz des schnellen Aufheizens mit Mikrowellen bei Verringerung der Gesamtprozesssdauer einer der Hauptvorteile dieser Technik. Dieser Aufsatz beschreibt Mikrowellen‐unterstützte Vorgehensweisen, die zur Synthese von kolloidalen anorganischen Nanokristallen entwickelt wurden, und untersucht kritisch die jeweilige Rolle, die der Mikrowellenstrahlung bei der Bildung dieser Nanomaterialien zugeschrieben wird.

Semiconductor and Metallic Core–Shell Nanostructures: Synthesis and Applications in Solar Cells and Catalysis

“…The main benefit of using microwave radiation is that it offers rapid and uniform heating of the entire reaction solution, and thus leads to an improvement in reaction reproducibility and product uniformity as well as a shortening of reaction time in comparison with the conventional synthesis routes using oil-bath heating. [67] This method has recently been demonstrated to facilitate the formation of core-shell QDs. For example, water-dispersed CdTe/CdS core-shell QDs with enhanced PL QY as high as 75 % were synthesized by He et al by microwave heating.…”

Colloidal Magnetic Heterostructured Nanocrystals with Asymmetric Topologies: Seeded-Growth Synthetic Routes and Formation Mechanisms

“…Importantly, the dynamic binding of organic stabilizers can significantly affect the relative stability of the surface facets enclosing the growing NCs, thereby driving their shaping into non-spherical habits (e.g., cubes, polyhedrons, rods, wires, and polypods). In particular, anisotropic lattice development and branching-out, most frequently observed for materials forming in reduced-symmetry crystal phases and/or featuring polytypism during their evolution, may be promoted within kinetically dominated growth regimes and/or under conditions facilitating growth symmetry breaking (e.g., in the presence of soft surfactant or polymer lamellar templates, of foreign particle catalysts, or when crystal-oriented attachment pathways are allowed, or growth is conducted in external electric or magnetic fields or under microwave irradiation) Jun et al, 2006;Talapin et al, 2010;Zhang et al, 2010;Baghbanzadeh et al, 2011;Bouet et al, 2013;Hu and Wang, 2013;Li et al, 2013;Yang et al, 2013;Hu et al, 2014;Wang et al, 2014;Lhuillier et al, 2015).…”

“…For several material associations, careful investigation of the conditions underlying selection of MHNCs in non-equivalent topologies has suggested that the site-dependent accessibility and chemical reactivity of anisotropically shaped seeds may be governed by dynamic facet-preferential adhesion of surfactants or ligands (Figures 8A-C), a mechanism that has frequently been invoked to explain anisotropic growth of NCs (Burda et al, 2005;Cozzoli et al, 2006;Jun et al, 2006;Baghbanzadeh et al, 2011). Examples of elaborate MHNCs, which demonstrate the involvement of these pathways, are reported in Figures 8D-L. A clear influence of the growth environment on the ultimate location of the secondary material domains was drawn in the synthesis of magnetic-plasmonic Au-Co-Au nanodumbbells ( Figure 8D) accomplished by reacting Co nanorods with a AuCl(tetrahydrothiophene) complex precursor in the presence of LA and HAD (Wetz et al, 2007).…”

“…In the realm of nanomaterials, colloidal inorganic nanocrystals (NCs), solution free-standing crystalline nanoparticles entirely synthesized and processable in liquid media, have now raised to the rank of model systems for assessing the foundations of the physical-chemical laws of nanoscale matter owing to the precision and flexibility with which their crystal habit, shape, dimensions, and surface moieties can be tailored in the preparation stage (Burda et al, 2005;Cozzoli et al, 2006;Cozzoli, 2008;Baghbanzadeh et al, 2011). In addition, NCs are robust and versatile enough to be exploited as key active elements in artificial mesoscopic materials, innovative processes, and devices of great fundamental and practical significance for optoelectronics (Talapin et al, 2010;Vanmaekelbergh, 2011), catalysis (Chng et al, 2013;Vaneski et al, 2014;Xu et al, 2016), energy conversion (Carey et al, 2015;Xu et al, 2016) and storage (Frey et al, 2009;Niederberger and Pinna, 2009;Lee and Cho, 2011;Oszajca et al, 2014), sensing (Freeman and Willner, 2012;Palui et al, 2015), environmental remediation (Tong et al, 2012;Wilker et al, 2012;Rawalekar and Mokari, 2013), and biomedicine (Parak et al, 2003;Michalet et al, 2005;Palui et al, 2015).…”

“…Colloidal approaches, which enable governing the thermodynamics and kinetics of nucleation, growth, and crystallization of solids in liquid media Kwon and Hyeon, 2008;Erdemir et al, 2009;Wang et al, 2015), have demonstrated to be powerful synthetic routes to precisely phase-engineered NCs for a huge materials library across diverse size-morphological regimes Jun et al, 2006;Park et al, 2007;Cozzoli, 2008;Baghbanzadeh et al, 2011;Kim et al, 2013;Yang et al, 2013;Lhuillier et al, 2015). Recently, to meet the raising demand for intelligent nanosystems capable to exhibit enhanced, diversified, or even completely unprecedented properties and capabilities for multitask applications, synthetic nanochemistry research has opened up new horizons in the design, creation, and mastering of increasingly complex NC-based assemblies and architectures.…”