In 2020-2021, we carried out in designing a sample holder and low-T insert for the existing cryostat in the lab. It involved to make a working low-T insert with sample holder (designed using VARICAD software) for the measurements down to 4K, starting from drawing and designing the setup. During this one year, following steps were carried out : (1) Setting up the whole gas measurements setup starting from scratch (i.e. buying leak detector, pressure gauge, connectors etc.); (2) For leak check, it required checking of various crucial steps such as (i) whether wafer is intact after the sample loading with proper screws and indium wire, (ii) various sealing is properly tight or not at room temperature as well as liquid nitrogen temperature (cold leak for the Pb-soldered junctions with the insert); (3) After two times failure of making leak-proof sample holder, third sample holder was made (designed) successfully to get the leak proof as well as contamination free of the insert. At present this setup is working very well in the lab.
In 2021-2022, we carried out research on GDY nanoporous membrane. The following research works were carried out : (1) we investigated the room temperature (T) permeance of helium (He) and hydrogen isotopes (D2 and HD) using helium leak detector; (2) We moved to measure permeability of larger and heavier inert gas molecules like Ne, Ar, Kr and Xe using residual gas analyser (RGA); (3) Then, we revisited to measure the gas permeation for lighter gas molecules at room temperature and it turned out that the sample has larger pore size (straight-though holes); (4) we carried out low T measurements (down to 10-30K) with He and hydrogen isotopes and the results are in agreement with the larger pore sizes of the GDY membranes.
--Overview of the results
Our work reveals fast and selective gas permeation through graphdiyne-based nanoporous membranes, and mechanisms of molecular transport in such “quansi-2D” membranes. Adsorption plays a completely different role as compared to 2D membranes of e.g. graphene. Molecules adsorbed on graphene can easily move in-plane, which enhances permeation by many orders of magnitude. In contrast, no evidence of surface motion along the internal surface of the relatively long channels in graphdiyne membranes is observed. Moreover, the inner-pore adsorption gives rise to a counterintuitive effect of interacting flows of supposedly non-interacting, inert gases. No noticeable gas transport through the intrinsic mesh within graphdiyne’s crystal structure has been evidenced, due to their small effective diameter of < 4 Å which yields high energy barriers and/or the non-aligned intrinsic meshes from adjacent atomic layers in ABC stacked multi-layer graphdiyne that blocks gas flows.
--Exploitation and dissemination
The dissemination of the published results was carried out in a seminar (NGI building) to the graphene community of researchers at The University of Manchester who are working on 2D-materials (around 60-70 attendees each seminar) on 6th May, 2022. Outside UK, Achintya has presented his research works in India: (1) on 25th June, 2022 at Physics Department, IIT- Hyderabad, (2) on 14th July, 2022 at Physics Department, IIT-Guwahati. In terms of outreach activities outside UK, Achintya has participated as a motivational speaker in awareness of science and career in science. For that, Achintya went to Bishnujyoti Academy (higher secondary & undergraduate students) on 19th July 2022 (It has been posted by Achintya on social media).
In addition to the above dissemination, Achintya spent one week (23rd June-28th June, 2022) at Bose Institute, Kolkata, India where he described his research results to the Prof. A. Singha’s group. The outcome of the discussions ended up in future collaborations. Achintya also spent two days (8th and 11th July, 2022) in two colleges (Midnapore College and Ghatal Rabindra Satabarsiki Mahavidyalaya) placed in the rural areas to meet professors (Dr. T. Pal & Dr. A. Thander) and principals (Dr. G. C. Bera & Dr. M. K. Das) to discuss how the scientific activities were carried out in Manchester, UK. On 1st July, 2022, Achintya spent one day with Headmaster (Dr. D. Kamilya) and other teachers of the school (G.S.K.B.A.S.) to discuss the outreach and scientific activities.
Regarding transfer of knowledge, Achintya has been working with four PhD students and two postdocs over the last 2 years. He has trained them to measure gas permeation at room and low temperatures.
This work has been published in Nature Communications.
On a note : This project was carried out during Covid-19 outbreak.
