No abstract

Graphene oxide (GO) is attracting an ever-growing interest in different fields and applications. Not much is known about the possible impact of GO sheet lateral dimensions on their effects in vitro, especially on human primary cells. In an attempt to address this issue, we present a study to evaluate, how highly soluble 2-dimensional GO constituted of large or small flakes affects human monocyte derived macrophages (hMDM). For this purpose, the lateral size of GO was tuned using sonication and three samples were obtained. The non sonicated one presented large flakes (~1.32 μm) while sonication for 2 and 26 hours generated small (~0.27 μm) and very small (~0.13 μm) sheets of GO, respectively. Cell studies were then conducted to evaluate the cytotoxicity, the oxidative stress induction, the activation potential and the pro-inflammatory effects of these different types of GO at increasing concentrations. In comparison, the same experiments were run on murine intraperitoneal macrophages (mIPM). The interaction between GO and cells was further examined by TEM and Raman spectroscopy. Our data revealed that the GO sheet size had a significant impact on different cellular parameters (i.e. cellular viability, ROS generation, and cellular activation). Indeed, the more the lateral dimensions of GO were reduced, the higher were the cellular internalization and the effects on cellular functionality. Our data also revealed a particular interaction of GO flakes with the cellular membrane. In fact, a GO mask due to the parallel arrangement of the graphene sheets on the cellular surface was observed. Considering the mask effect, we have hypothesized that this particular contact between GO sheets and the cell membrane could either promote their internalization or isolate cells from their environment, thus possibly accounting for the following impact on cellular parameters.

No abstract

No abstract

Graphene and its related materials have attracted much interest in sensing applications because of their optimized ratio between active surface and bulk volume. In particular, several forms of oxidized graphene have been studied to optimize the sensing efficiency, sometimes moving away from practical solutions to boost performance. In this paper, we propose a practical, high-sensitivity, and easy to fabricate gas sensor based on high quality graphene oxide (GO), and we give the rationale to the high performance of the device. The device is fabricated by drop-casting water-dispersed single-layer GO flakes on standard 30 μm spaced interdigitated Pt electrodes. The exceptional size of the GO flakes (27 μm mean size and ∼500 μm maximum size) allows single GO flake to bridge adjacent electrodes. A typical p-type response is observed by testing the device in both reducing and oxidizing environments. The specific response to NO 2 is studied by varying the operating temperature and the gas concentration. Sensing activity is demonstrated to be mainly mediated by the oxygen functional groups. A 20 ppb detection limit is measured. Besides illustrating a simple and efficient approach to gas sensing, this work is an example of the versatility of graphene oxide, accomplishing tasks that are complementary to graphene.