ISBN 9783843908030

978-3-8439-0803-0, Reihe Nanotechnologie

Lisong Xiao
Green Nanochemistry: Synthesis and Surface Functionalization of Tin and Iron Oxide Nanoparticles for Gas Sensing, Imaging (MRI) and Cellular Uptake Applications

167 Seiten, Dissertation Universität Köln (2012), Softcover, A5

Zusammenfassung / Abstract

This thesis is based on the new development of Green Nanochemistry to synthesize, functionalize and explore the potential applications of engineered metal oxide nanoparticles (EMONs). The preparation of EMONs with desired sizes, coatings and properties was precisely controlled by Nanochemistry approaches; at the same time the concepts of Green Chemistry were applied in the whole process to reduce raw materials, energy, hazard, risk, cost and waste. By applying the principle of Green Nanochemistry, SnO2 quantum dots (QDs) and Fe3O4 nanoparticles (NPs) with different coatings have been successfully prepared. Their potential applications have also been studied.

SnO2 QDs with a narrow size distribution (4.3 ±0.7 nm) were achieved by directly decomposition of SnIV(OtBu)4 precursor in an ionic liquid ([BMIM]BF4) under microwave irradiation. The microwave-assisted method especially combined with ionic liquid exhibited high efficiency, which led to the formation of highly crystalline SnO2 QDs within a minute. Due to the surface adsorption of the ionic liquid, the prepared SnO2 QDs could be redispersed in water, and sequentially the suspension was used as an ink for ink-jet printing applications. A gas sensor was fabricated by ink-jet printing of SnO2 QDs ink over an electrode on a silicon clip. The printed sensor showed a fast response and a high selectivity toward ethanol compared to other gases such as CH4, NH3 and CO. These results implied that the water-based transparent SnO2 QDs suspension has a promising application potential for directly writing gas sensors and other semiconductor devices. Fe3O4 nanoparticles were also prepared under microwave irradiation by decomposition of [FeIII(OtBu)3]2 precursor in tetraethylene glycol (TEG).

Ultra-small superparamagnetic Fe3O4 nanoparticles (SPIONs) were synthesized using natural products of vitamin C (VC), green tea solution (GT), green tea extracts of epigallocatechin gallate (EGCG) and epicatechin (EC), respectively. In the syntheses, these natural products acted as reducing agent and their oxidized products further played a role as surfactant; therefore, the synthesis and the functionalization of SPIONs were integrated in a one-pot reaction. Due to the strong capping effect and hydrophilic properties of these natural oxidized products, the prepared SPIONs showed excellent water redispersibility and colloidal stability, which are pre-request for further biological applications. The use of these natural antioxidants in the syntheses also favored the formation of safer SPIONs for biomedicine applications.