Defect-Mediated Reduction in Barrier for Helium Tunneling through Functionalized Graphene Nanopores

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• 作者：Murugan Lalitha ; Senthilkumar Lakshmipathi ; Suresh K. Bhatia
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：September 10, 2015
• 年：2015
• 卷：119
• 期：36
• 页码：20940-20948
• 全文大小：592K
• ISSN：1932-7455

文摘

We investigate the separation of helium isotopes by quantum tunneling through graphene nanopores, recently proposed as an alternative to conventional methods for ³He production. We propose here a novel defective nanopore created by removing two pentagon rings of a Stone鈥揟hrower鈥揥ales (STW) defect, which significantly decreases the helium tunneling barrier by 50鈥?5%. The barrier height is fine-tuned by adjusting the effective pore size, which is achieved by pore rim passivation using an appropriate functionalizing atom. This fine-tuning leads to positive deviation in the tunneling probability of ³He compared to that of ⁴He in the low-energy region, and thereby to high selectivity and transmission of the former isotope. It is found that fluorine-passivated nanopores restrict helium atom penetration because of their highly reduced pore size. Defective nanopores in nitrogen- and oxygen-passivated structures exhibit relatively high transmission values of 10^鈥? for the oxygen variant and improved selectivity value of 669 for the nitrogen variant. It is demonstrated that defective nanopores passivated on both sides with oxygen are the most attractive for ³He/⁴He separation on the basis of their much higher flux values while still providing good selectivity.