To most, the word “nano” brings the thought of science fiction – generally from a negative perspective, the nano-bots swarming the protagonist of your favorite show. However, in the realm of materials development, nano is thought as the future. Simply put, making a material tiny at the nanometer, nm, scale can vastly change its properties – making them more useful in many applications. For perspective, a human hair are ≈ 100,000 nm in diameter. Said otherwise, 1 millimeter comprises 1,000,000 nm.
We recently discovered how to mass produce easily and cheaply the world’s thinnest spaghetti; one whose cross-section is less than 1 nm squared [1,2]. Our spaghetti is so thin that if we took one gram and placed all the one-dimensional (1D) snippets end-to-end they would span 700 million kilometers, a truly staggering number!
The astute, or informed, reader may shrug and note that many plastics/polymers are also comprised of organic strands with cross-sections comparable to ours. And while that is true, polymers are for the most part up of organic molecules like C and H. What sets ours apart is that it is not organically based like actual spaghetti, but is comprised of Ti and O atoms, neither of which as organic. It is the oxide of titanium or TiO2 and water. It follows that ours is thinnest inorganic polymer ever produced. This polymeric behavior allows our material to assemble into hydrogels without binders [3] and micro-assemblies that mirror cellulose networks [4], below:
Polymers are quite inert and when they end up in the environment many can be dangerous. TiO2 on the other hand, is not only biocompatible, but we have shown that our material can readily degrade dangerous dyes with a little help from sunlight [5, 6]. We also just showed that our material can effectively kill bacteria by simple piercing their outer membranes. Previous TiO2-based antibacterial materials only worked under illumination. Our material is lethal even in the dark, which, needless to add, is much more practical.
Where our material differs from polymers is in its function. For example, our material can produce hydrogen from water by simply shining light on a water that has been spiked with some alcohol [7]. The system is even more effective when you supply some electricity. When splitting water, into H2 and O2 the slow electrode is the oxygen side. Currently, the only materials that are usable on the oxygen side are precious metals like iridium – which we come close to in performance, at a fraction of the cost.
In general, making nanomaterials at scale is non-trivial, complicated and expensive. It is thus important to note that our material can be synthesized, at the kilogram scale, in any laboratory. All that is needed is a plastic container that is vented since gases are released.
References
[1] Badr, H. O.; El-Melegy, T.; Carey, M.; Natu, V.; Hassig, M. Q.; Johnson, C.; Qian, Q.; Li, C. Y.; Kushnir, K.; Colin-Ulloa, E.; et al. Bottom-up, scalable synthesis of anatase nanofilament-based two-dimensional titanium carbo-oxide flakes. Materials Today 2022, 54, 8-17. DOI: 10.1016/j.mattod.2021.10.033.
[2] Badr, H. O.; Lagunas, F.; Autrey, D. E.; Cope, J.; Kono, T.; Torita, T.; Klie, R. F.; Hu, Y.-J.; Barsoum, M. W. On the structure of one-dimensional TiO2 lepidocrocite. Matter 2022. DOI: 10.1016/j.matt.2022.10.015.
[3] Mieles, M.; Walter, A. D.; Wu, S.; Zheng, Y.; Schwenk, G. R.; Barsoum, M. W.; Ji, H.-F. Hydronium-Crosslinked Inorganic Hydrogel Comprised of 1D Lepidocrocite Titanate Nanofilaments. Advanced Materials 2024, 2409897. DOI: 10.1002/adma.202409897.
[4] Schwenk, G. R.; Walter, A. D.; Barsoum, M. W. Solvent-Driven Self-Assembly of One-Dimensional Lepidocrocite Titanium-Oxide-Based Nanofilaments. Nano Lett. 2024, 24 (25), 7584-7592. DOI: 10.1021/acs.nanolett.4c00921.
[5] Walter, A. D.; Schwenk, G. R.; Cope, J.; Sudhakar, K.; Hassig, M. Q.; Ferrer, L.; Mininni, A.; Lindsay, A. J.; Barsoum, M. W. Adsorption and self-sensitized, visible-light photodegradation of rhodamine 6G and crystal violet by one-dimensional lepidocrocite titanium oxide. Matter 2023, 6 (11), 4086-4105. DOI: 10.1016/j.matt.2023.09.008.
[6] Walter, A. D.; Benamor, H.; Ferrer, L. M.; Reji, T.; Curran, T.; Schwenk, G. R.; Hadji, M.; Creighton, M. A.; Barsoum, M. W. Self-sensitized photodegradation and adsorption of aqueous malachite green dye using one-dimensional titanium oxide nanofilaments. iScience 2024, 27 (9), 110647. DOI: 10.1016/j.isci.2024.110647.
[7] Badr, H. O.; Natu, V.; Neațu, Ș.; Neațu, F.; Kuncser, A.; Rostas, A. M.; Racey, M.; Barsoum, M. W.; Florea, M. Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures. Matter 2023, 6 (9), 2853-2869. DOI: 10.1016/j.matt.2023.05.026.
PhD Candidate in the Department of Materials Science and Engineering at Drexel University. His expertise lies in the surface characterization and modification of nanomaterial oxides, in particular titanium oxides.
Distinguished Professor in the Department of Materials Science and Engineering at Drexel University. He is an internationally recognized leader in the area of the MAX phases and their derivatives MXenes. Recently he also discovered the thinnest inorganic titania material ever. With over 550 refereed publications and a Google h-index is 149, his work has been cited >128,000 times to date.