Wang Zhongying, Lv Xiaoshu, Chen Yantao, Liu Dan, Xu Xinhua, Palmore G Tayhas R, Hurt Robert H
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
Nanoscale. 2015 Jun 14;7(22):10267-78. doi: 10.1039/c5nr00963d. Epub 2015 May 20.
Nanoreactors are material structures that provide engineered internal cavities that create unique confined nanoscale environments for chemical reactions. Crumpled graphene nanoparticles or "nanosacks" may serve as nanoreactors when filled with reactive or catalytic particles and engineered for a specific chemical function. This article explores the behavior of crumpled graphene nanoreactors containing nanoscale ZnO, Ag, Ni, Cu, Fe, or TiO2 particles, either alone or in combination, in a series of case studies designed to reveal their fundamental behaviors. The first case study shows that ZnO nanoparticles undergo rapid dissolution inside the nanoreactor cavity accompanied by diffusive release of soluble products to surrounding aqueous media through the irregular folded shell. This behavior demonstrates the open nature of the sack structure, which facilitates rapid small-molecule exchange between inside and outside that is a requirement for nanoreactor function. In a case study on copper and silver nanoparticles, encapsulation in graphene nanoreactors is shown in some cases to enhance their oxidation rate in aqueous media, which is attributed to electron transfer from the metal core to graphene that bypasses surface oxides and allows reduction of molecular oxygen on the high-area graphene shell. Nanoreactors also allow particle-particle electron transfer interactions that are mediated by the connecting conductive graphene, which give rise to novel behaviors such as galvanic protection of Ag nanoparticles in Ag/Ni-filled nanoreactors, and the photochemical control of Ag-ion release in Ag/TiO2-filled nanoreactors. It is also shown that internal graphene structures within the sacks provide pockets that reduce particle mobility and inhibit particle sintering during thermal treatment. Finally, these novel behaviors are used to suggest and demonstrate several potential applications for graphene nanoreactors in catalysts, controlled release, and environmental remediation.
纳米反应器是一种材料结构，它提供了经过设计的内部腔体，为化学反应创造了独特的受限纳米级环境。当填充有反应性或催化性颗粒并针对特定化学功能进行设计时，皱巴巴的石墨烯纳米颗粒或“纳米袋”可以用作纳米反应器。本文通过一系列案例研究，探讨了单独或组合含有纳米级ZnO、Ag、Ni、Cu、Fe或TiO2颗粒的皱巴巴的石墨烯纳米反应器的行为，旨在揭示其基本行为。第一个案例研究表明，ZnO纳米颗粒在纳米反应器腔内迅速溶解，同时可溶性产物通过不规则折叠的外壳扩散释放到周围的水性介质中。这种行为证明了袋状结构的开放性，这有助于内部和外部之间快速进行小分子交换，这是纳米反应器功能的一个要求。在一项关于铜和银纳米颗粒的案例研究中，结果表明，在某些情况下，将它们封装在石墨烯纳米反应器中可提高其在水性介质中的氧化速率，这归因于电子从金属核转移到石墨烯，绕过了表面氧化物，并允许在高面积的石墨烯壳上还原分子氧。纳米反应器还允许由连接的导电石墨烯介导的颗粒-颗粒电子转移相互作用，这会产生新的行为，例如Ag/Ni填充的纳米反应器中Ag纳米颗粒的电偶保护，以及Ag/TiO2填充的纳米反应器中Ag离子释放的光化学控制。研究还表明，袋内的内部石墨烯结构提供了一些口袋，可降低颗粒迁移率并抑制热处理过程中的颗粒烧结。最后，利用这些新行为提出并展示了石墨烯纳米反应器在催化剂、控释和环境修复方面的几种潜在应用。
