Bansal Prerna, Doshi Sejal, Panwar Ajay S, Bahadur Dhirendra
Department of Metallurgical Engineering and Materials Science, IIT Bombay , Mumbai 400076, India.
ACS Appl Mater Interfaces. 2015 Sep 23;7(37):20576-84. doi: 10.1021/acsami.5b04390. Epub 2015 Sep 14.
Reduced graphene oxide (RGO) has been prepared by a simple, cost-effective, and green route. In this work, graphene oxide (GO) has been reduced using Gram-negative facultative anaerobe S. dysenteriae, having exogenic properties of electron transfer via electron shuttling. Apparently, different concentrations of GO were successfully reduced with almost complete mass recovery. An effective role of lipopolysaccharide has been observed while comparing RGO reduced by S. dysenteriae and S. aureus. It was observed that the absence of lipopolysaccharide in Gram-positive S. aureus leads to a disrupted cell wall and that S.aureus could not survive in the presence of GO, leading to poor and inefficient reduction of GO, as shown in our results. However, S. dysenteriae having an outer lipopolysaccharide layer on its cell membrane reduced GO efficiently and the reduction process was extracellular for it. RGO prepared in our work has been characterized by X-ray diffraction, ζ potential, X-ray photoelectron spectroscopy, and Raman spectroscopy techniques, and the results were found to be in good agreement with those of chemically reduced GO. As agglomeration of RGO is the major issue to overcome while chemically reducing GO, we observed that RGO prepared by a bacterial route in our work has ζ potential value of -26.62 mV, good enough to avoid restacking of RGO. The role of exoelectrogens in electron transfer in the extracellular space has been depicted. Toxin released extracellularly during the process paves the way for reduction of GO due to its affinity towards oxygen.
还原氧化石墨烯（RGO）已通过一种简单、经济高效且绿色的途径制备出来。在这项工作中，利用具有通过电子穿梭进行外源电子转移特性的革兰氏阴性兼性厌氧菌痢疾志贺氏菌对氧化石墨烯（GO）进行了还原。显然，不同浓度的GO均成功被还原，且质量几乎完全回收。在比较痢疾志贺氏菌和金黄色葡萄球菌还原的RGO时，观察到脂多糖发挥了有效作用。结果表明，革兰氏阳性菌金黄色葡萄球菌中脂多糖的缺失导致细胞壁破坏，且金黄色葡萄球菌在GO存在的情况下无法存活，从而导致GO的还原效果不佳且效率低下。然而，在其细胞膜上具有外脂多糖层的痢疾志贺氏菌能够高效还原GO，并且其还原过程是在细胞外进行的。我们工作中制备的RGO已通过X射线衍射、ζ电位、X射线光电子能谱和拉曼光谱技术进行了表征，结果发现与化学还原的GO的表征结果高度一致。由于在化学还原GO时，RGO的团聚是需要克服的主要问题，我们观察到在我们的工作中通过细菌途径制备的RGO的ζ电位值为 -26.62 mV，足以避免RGO的重新堆叠。已描述了外生电微生物在细胞外空间电子转移中的作用。在此过程中细胞外释放的毒素因其对氧气的亲和力为GO的还原铺平了道路。
