Nanosized pores are omnipresent in nature and central to many biological processes. Their importance to the functioning of cells is difficult to overestimate. Thus is their promise for applications: selective sieving of gas molecules, DNA sequencing, nano-nozzle assisted patterning, just to mention a few.
In the Strano Research Group, we pursue interdisciplinary approaches both to deepen our understanding of nanopores as well as to harness their potential. We not only push the experimental frontier [3, 4, 5, 6, 8, 9, 10] but also seek to extend and refine the required theoretical framework [1, 2, 7]. Our recent efforts concentrate in particular on two classes of solid-state nanopores: i) carbon nanotubes (1D) [3, 5, 8, 9, 10] and ii) defects in layered materials such as graphene and hexagonal boron nitride (2D) [1, 4, 6, 7].
In the 1D field, we mainly study individual, millimeter-long carbon nanotubes synthesized on a substrate. Their supreme quality and direct accessibility makes them an ideal testbed for nano-confined fluid phase transitions and transport. Certain vibrational modes of these tubes are known to be susceptible to fluid-phase filling, a change in which can easily be detected by Raman spectroscopy. This allowed us to probe the extreme diameter-dependence of the freezing point of water confined within, which we found to even exceed +100 °C in some tubes [8]. We also investigate on the transport of different ionic species through carbon nanotubes, most prominently evidenced via stochastic pore-blocking behavior [5, 10]. Note however, that also the nanotube’s exterior can provide a transport channel which proved cation-selective in our experiment [3].
In the 2D field, we pursue efforts in engineering defects in single atomic sheets in reliable and scalable fashion. We reported first systematic experimental studies on the temperature-dependent gas permeance through nanoporous single layer graphene membranes [4, 6]. Some of these membranes even showed selectivities in excess of the Knudsen effusion limit [4]. On the theoretical side, we also work on improving our analytical understanding of the gas permeation process [7]. More recently, we addressed the isomer cataloguing problem, putting forward a tool to predict the most likely configurations for nanopores in 2D materials [1].
References:
[1] A. G. Rajan, Silmore, K. S. , Swett, J. , Robertson, A. W. , Warner, J. H. , Blankschtein, D. , and Strano, M. S. , “Addressing the isomer cataloguing problem for nanopores in two-dimensional materials”, Nature Materials, p. 1, 2019.
[2] L. W. Drahushuk, Rajan, A. G. , and Strano, M. S. , “Fundamental scaling laws for the direct-write chemical vapor deposition of nanoscale features: modeling mass transport around a translating nanonozzle”, Nanoscale, 2019.
[3] Y. – T. Kim, Joo, S. H. , Min, H. , Lee, J. , Moon, S. M. , Byeon, M. , Hong, T. E. , Strano, M. S. , Han, J. – H. , Kwak, S. K. , and Lee, C. Y. , “The Exterior of Single-Walled Carbon Nanotubes as a Millimeter-Long Cation-Preferring Nanochannel”, Chemistry of Materials, vol. 30, pp. 5184-5193, 2018.
[4] Z. Yuan, Benck, J. D. , Eatmon, Y. , Blankschtein, D. , and Strano, M. S. , “Stable, Temperature-Dependent Gas Mixture Permeation and Separation through Suspended Nanoporous Single-Layer Graphene Membranes”, Nano Letters, vol. 18, pp. 5057-5069, 2018.
[5] M. D. Ellison, Menges, S. , Nebel, L. , D’Arcangelo, G. , Kramer, A. , Drahushuk, L. , Benck, J. , Shimizu, S. , and Strano, M. S. , “Electrokinetic transport of methanol and lithium ions through a 2.25-nm-Diameter carbon nanotube nanopore”, Journal of Physical Chemistry C, vol. 121, pp. 2005-2013, 2017.
[6] K. V. Agrawal, Benck, J. D. , Yuan, Z. , Misra, R. P. , A. Rajan, G. , Eatmon, Y. , Kale, S. , Chu, X. S. , Li, D. O. , Gong, C. , Warner, J. , Wang, Q. H. , Blankschtein, D. , and Strano, M. S. , “Fabrication, Pressure Testing, and Nanopore Formation of Single-Layer Graphene Membranes”, Journal of Physical Chemistry C, vol. 121, pp. 14312-14321, 2017.
[7] Z. Yuan, A. Rajan, G. , Misra, R. P. , Drahushuk, L. W. , Agrawal, K. V. , Strano, M. S. , and Blankschtein, D. , “Mechanism and Prediction of Gas Permeation through Sub-Nanometer Graphene Pores: Comparison of Theory and Simulation”, ACS Nano, vol. 11, pp. 7974-7987, 2017.
[8] K. V. Agrawal, Shimizu, S. , Drahushuk, L. W. , Kilcoyne, D. , and Strano, M. S. , “Observation of extreme phase transition temperatures of water confined inside isolated carbon nanotubes”, Nature Nanotechnology, vol. 12, no. 3, pp. 267 – 273, 2017.
[9] R. N. Gontijo, Sáfar, G. A. M. , Righi, A. , Jain, R. M. , Strano, M. S. , and Fantini, C. , “Quantifying (n,m) species in single-wall carbon nanotubes dispersions by combining Raman and optical absorption spectroscopies”, Carbon, vol. 115, pp. 681 – 687, 2017.
[10] M. D. Ellison, Bricker, L. , Nebel, L. , Miller, J. , Menges, S. , D’Arcangelo, G. , Kramer, A. , Drahushuk, L. , Benck, J. , Shimizu, S. , and Strano, M. S. , Transport of Amino Acid Cations through a 2.25-nm-Diameter Carbon Nanotube Nanopore: Electrokinetic Motion and Trapping/Desorption, vol. 121. 2017, pp. 27709-27720.