Plasma Oxidation Kinetics of Gold Nanoparticles and Their Encapsulation in Graphene Shells by Chemical Vapor Deposition Growth
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- 作者：Junchi Wu ; Wenwu Shi ; Nitin Chopra
- 刊名：The Journal of Physical Chemistry C
- 出版年：2012
- 出版时间：June 14, 2012
- 年：2012
- 卷：116
- 期：23
- 页码：12861-12874
- 全文大小：834K
- 年卷期：v.116,no.23(June 14, 2012)
- ISSN：1932-7455
文摘
High-throughput chemical vapor deposition (CVD) growth of carbon or graphene shells encapsulating gold nanoparticles (AuNPs) is a challenge due to limited solubility of carbon in AuNPs. Such a growth is only possible by utilizing surface-oxidized AuNPs. There is a lack of fundamental understanding regarding the role of morphology and surface oxidation of AuNPs in the formation of graphene shells. Here, we studied a simple wet-chemical synthesis of AuNPs with hexadecyltrimethylammonium bromide as a surfactant and the effect of postsynthesis quenching on size, shape, and defect density of AuNPs. In the next step, plasma oxidation kinetics of AuNPs to form surface gold oxide (AuOx) was studied. The surface gold oxide shell thickness was found to be independent of stoichiometry of AuOx and followed the Cabrera鈥揗ott model for oxidation kinetics. The surface-oxidized AuNPs were further utilized as catalysts for the growth of graphene shell encapsulated AuNPs (GNPs) in a xylene CVD process. The unstable surface gold oxide played a major role in the CVD process by accepting electrons from the incoming carbon feed, resulting in graphene shells around AuNPs. On the other hand, surface oxidized AuNPs with lattice defects, in a similar xylene CVD process, resulted in amorphous carbon and distorted graphene shells encapsulating AuNPs. Overall, this study reveals the mechanisms and critical factors relevant to the growth of GNPs. Such an approach for hybridizing graphene shells with AuNPs is promising for nanoelectronics and sensing.