Periodic Reporting for period 1 - QCNGas (Quantum Conductance of Neutral Gas Molecules)
Reporting period: 2020-08-01 to 2022-07-31
In the era of nanofluidics with rapid advancements in fabricating nanoscale devices, understanding and exploiting molecular flow transport properties under nanoscale confinements become extremely essential. The trade-off feature (known as Robeson limit) between gas permeability and selectivity are being explored extensively for nanoporous membranes. With respect to that, 2D-membranes are of interests compared to their three-dimensional counterpart in exploration of novel materials which could perform beyond Robeson limit or provide better trade-off boundary.
Therefore, graphdiyne (GDY) nanoporous membranes (90 nm thickness) with intrinsic pores have been studied to show that the unexpected fast permeation combined with selective gas transport through graphdiyne provide a better permeability-selectivity trade-off compare to that of state-of-art membranes, beyond the existing bounds. Our study provides a feedback on the extensive theoretical simulations of molecule sieving through graphdiyne with intrinsic lattice pores in angstrom scale. Despite being nearly a hundred of nanometers thick, the membranes allow fast, Knudsen-type permeation of light gases such as helium and hydrogen whereas heavy noble gases like xenon exhibit strongly suppressed flow.
From the fundamental point of view, it is intriguing to explore quantum-limited conductance (similar to mesoscopic physics for electrons) of neutral gas molecules through such tight nanopores in the mesoscopic regime at low temperature down to 10-30K.
Therefore, graphdiyne (GDY) nanoporous membranes (90 nm thickness) with intrinsic pores have been studied to show that the unexpected fast permeation combined with selective gas transport through graphdiyne provide a better permeability-selectivity trade-off compare to that of state-of-art membranes, beyond the existing bounds. Our study provides a feedback on the extensive theoretical simulations of molecule sieving through graphdiyne with intrinsic lattice pores in angstrom scale. Despite being nearly a hundred of nanometers thick, the membranes allow fast, Knudsen-type permeation of light gases such as helium and hydrogen whereas heavy noble gases like xenon exhibit strongly suppressed flow.
From the fundamental point of view, it is intriguing to explore quantum-limited conductance (similar to mesoscopic physics for electrons) of neutral gas molecules through such tight nanopores in the mesoscopic regime at low temperature down to 10-30K.
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.
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.
An establishment of a new domain of research area related to “Cryogenic gas transport facility”, an essential step towards the understanding of quantum aspects of molecular gas transport, was carried out during this project. With this cryogenic facility and the current state-of-the-art technologies for the device fabrication, it is possible now to explore the quantum-limited neutral gas flow conductance of lighter gas molecules in the mesoscopic regime utilizing the associated de Broglie wavelengths (similar to quantum signatures of conductance for electrons).
On a relatively flat surface such as for graphene or other 2D materials, the adsorption gives rise to enhanced permeation because of surface assisted diffusion. Whereas for GDY having curved pores instead of flat surface, our observation towards the transport mechanisms via adsorption is quite contrary to that. Our unexpected findings of adsorption of heavier gas molecules on the nanopore walls which reduces the permeation instead of enhancing is very crucial to understand the transport mechanisms playing at nanoscale.
Graphene-derivatives still hold potential applications in terms of gas filtrations and fundamental studies as long as their mechanical stability is assured, especially when monolayers are considered.
On a relatively flat surface such as for graphene or other 2D materials, the adsorption gives rise to enhanced permeation because of surface assisted diffusion. Whereas for GDY having curved pores instead of flat surface, our observation towards the transport mechanisms via adsorption is quite contrary to that. Our unexpected findings of adsorption of heavier gas molecules on the nanopore walls which reduces the permeation instead of enhancing is very crucial to understand the transport mechanisms playing at nanoscale.
Graphene-derivatives still hold potential applications in terms of gas filtrations and fundamental studies as long as their mechanical stability is assured, especially when monolayers are considered.