title: Molecules, Macromolecules, and Supramolecules Incorporating Gold Nanoparticles and their Applications in Catalysis, and Photobiology
Creators: name: Liang, Chen
Publisher: name: University of Bayreuth
Year: 2022
Subjects: subject: Gold Nanoparticles Catalysis
subject: 540

description: Gold nanoparticles have been widely studied in the fields of nanoscience and nanotechnology in the past few decades, the AuNP have one of the most popular functionalized building platforms. In my work, the AuNP conjugate with small molecules, supramolecular and macromolecular, and proteins were prepared and their applications in catalysis and photobiology were studied thoroughly. For the first part of my work, the size-dependent catalytic activity of Ct@AuNP and PVP@AuNP with an average size in the range of 10 to 58 nm were studied by keeping the total surface area of the AuNP in the catalytic reaction the same. The results indicated that the apparent catalytic reaction rate constant presents an increasing tendency with an increase of the average size of the AuNP, for either Ct@AuNP or PVP@AuNP. To exploit the reason behind it, the results revealed that the large NP might contain more defects than the smaller NP, and this might be the crucial factor resulting in their higher catalytic activity in the 4-nitrophenol reduction. The reagent can attach or detach more easily, or it can leach more gold clusters or gold atoms during the catalytic reaction. The influence of ligand density and the diffusion of the reactant to the active site of the AuNP are excluded. For the second part of this work, composite nonwovens containing supramolecular BTA nanofibers and short PAN fibers were developed. Such composite nonwovens can be fabricated by the facile electrospinning technique and self-assembly combined with a sheet forming wet-laid process via two different routes. These composite nonwovens presented good mechanical properties via route B (wet-laid processing by using mixture of the BTA solution and dispersion of short PAN fibers), because the homogenously distributed BTA nanofibers and short PAN fibers within, an interpenetrating mesoscale network and the entanglement of the BTA nanofibers with the short PAN fibers all contributed to achieve good mechanical property. The formation of the AuNP within the composite nonwovens can be achieved by in situ reduction. The results revealed that the AuNP distributed on the BTA nanofibers homogenously and the obviously aggregation of the AuNP cannot be observed. The catalytic activity of the AuNP-decorated composite nonwoven was studied in the batch system. The results indicated that catalysts of this type yield comparable apparent catalytic reaction rate constants in comparison with those in the literature. These fabricated AuNP-decorated composite nonwovens can be used continuously for five cycles without any obvious deactivation of the AuNP. In addition, no significant amount of leaching can be observed during the catalytic reaction. Based on the groundwork mentioned above, a versatile BTA-sponge with 3D porous architecture was readily fabricated by combining a wet-laid process and the freezing dry method. It can serve as an effective AuNP carrier and exhibits excellent performance at the separation of the AuNP under gravitational force due to their porous structure and the high affinity of the functional terpyridine group to the AuNP. The efficiency of the separation of the AuNP can be 99 % reach by using BTA-sponges I–III. Subsequently, the catalytic activity of the AuNP-incorporated BTA-sponge was studied in this work in both the batch and the continuous flow system. The immobilization of the AuNP within the BTA-sponge can be achieved by an formation method in situ. Regarding the study of the catalytic performance of the AuNP-incorporated BTA-sponge in the batch system, the apparent catalytic reaction rate constant per mg was comparable with those in the literature. It presents high reusability without obviously leaching of gold during the catalytic reaction. Regarding the comparison with the batch system, the 4-nitrophenol reduction was carried out in the continuously flow model. The results indicated that the catalytic performance of the AuNP-incorporated BTA-sponge can be significantly improved compared to the batch system, since the excellent accessibility of the reagent to the active site of the AuNP and the improved mass transportation in the catalytic reaction can be dramatically developed. In the last part of this thesis work incorporated in this thesis, photobiologically directed assembly of the AuNP was realized by conjugating LOV receptors with AuNP in the presence of a NTA ligand as the linker. A novel composite system was developed here by incorporating the AuNP, the linker and LOV receptors. This created a pathway to control the light-stimulated self-assembly of the AuNP. After thorough characterization, it could be deduced that the AuNP conjugated with a proteinaceous building block can remain stable in the dark, whereas the assembly of the AuNP into a large aggregate is initiated when exposed to blue light. Hence, the assembly of the AuNP can be stimulated by light with spatial resolution due to their conjugation to the genetically encodable LOV proteins.