Synthesis of nanostructured materials

Almost monodisperse, crystalline metal nanopaticles can be synthesized in situ by co-sputtering a magnetic and a non-magnetic metals onto a Si substrate at an elevated temperature. Also, metal silicide microparticles were demonstrated to be formed from a metal thin film on a Si substrate through post-annealing in a vacuum. Furthermore, magnetic nanoparticles such as ZnFe2O4 and Fe3O4 nanoparticles were synthesized using wet chemical methods.

J. S. Noh, “Aluminum Silicide Microparticles Transformed from Aluminum Thin Films by Hypoeutectic Interdiffusion”, Nanoscale Research Letters 9, 312 (2014).

D. Thakur, S. Govindaraju, K. S. Yun, and J. S. Noh, “The Synergistic Effect of Zinc Ferrite Nanoparticles Uniformly Deposited on Silver Nanowires for the Biofilm Inhibition of Candida albicans”, Nanomaterials 9, 1431 (2019).

Various nanostructures such as nanorods, nanocones, nanoflowers, and nanoplatelets can be synthesized by wet-chemical methods. Their morphologies and dimensions can be finely tuned via the fine adjustment of synthesis conditions. Furthermore, the growth direction of the nanostructures can be aligned simply by the introduction of a seed layer.

S. T. Nguyen, J. S. Noh, and I. H. Lee, “Low-Temperature Solution Syntheses of Hexagonal ZnO Nanorods and Morphology-Controlled Nanostructures”, Chemical Physcis Letters 646, 185 (2016).

Dimension-controlled metal nanowires can be synthesized by solution methods. They are widely explored for flexible transparent electrodes and further able to play as a conductive component of functional composites for diverse applications.

H. S. Lee, Y. W. Kim, J. E. Kim, S. W. Yoon, T. Y. Kim, J. S. Noh, and K. S. Suh, “Synthesis of Dimension-Controlled Silver Nanowires for Highly Conductive and Transparent Nanowire Films”, Acta Materialia 83, 84 (2015).

Thermoelectric and metal nanowires can be grown by a compressive-stress-driven method, termed “on-film formation of nanowires (OFF-ON)”. When a source material with a large thermal expansion coefficient deposited on a substrate undergoes high-temperature annealing, a compressive stress is stored in the film due to the difference in thermal expansions of the film and the substrate. Nanowires are spontaneously grown to relieve the stress and they are highly single-crystalline.

S. Lee, J. Ham, K. Jeon, J. S. Noh, and W. Lee, “Direct Observation of the Semimetal-to-Semiconductor Transition of Individual Single-Crystal Bismuth Nanowires Grown by On-Film Formation of Nanowires”, Nanotechnology 21, 405701 (2010).

Nanogaps or nanocracks can be introduced into a metal film on an elastomeric substrate by a simple stretching technique. Since the nanogaps on an elastomer easily respond to any type of external force or medium, they can be applied to a wide variety of applications such as a hydrogen sensor, toxic gas sensor, bio sensor, strain sensor, and chemical filter.

J. Lee, W. Shim, E. Lee, J. S. Noh, and W. Lee, “Highly Mobile Palladium Thin Films on an Elastomeric Substrate: Nanogap-Based Hydrogen Gas Sensors”, AngewandteChemie-International Edition 50, 5301 (2011). (Cover article)

Layered structures such as graphene, g-C3N4, and MXenes can be prepared by various methods. For example, g-C3N4, which is a semiconducting polymer with a band gap of 2.7 eV, can be synthesized by thermal pyrolysis. MXenes that are usually prepared from MAX phase materials by a selective etching method attract increasing interest from both aspects of fundamental science and applications.

Q. T. H. Ta, G. Namgung, and J. S. Noh, “Facile Synthesis of Porous Metal-doped ZnO/g-C3N4 Composites for Highly Efficient Photocatalysts”, Journal of Photochemistry & Photobiology A: Chemistry 368, 110 (2019).

N. M. Tran, Q. T. H. Ta, A. Sreedhar, and J. S. Noh, “Ti3C2Tx MXene Playing as A Strong Methylene Blue Adsorbent in Wastewater”, Applied Surface Science 537, 148006 (2021).

Technology fusion of different disciplines that are all based on nanotechnology becomes more important. An example is a combination of Ag nanowires and ZnO nanobush for improved photocatalysis. As another example, there is a fusion of thermoelectricity and magnetism, pursuing enhanced thermoelectric performance that is assisted by controlled magnetism. Furthermore, mesoporous g-C3N4 nanosheets can be hybridized with Pd and Fe3O4 nanoparticles for improved antibacterial activity.

Q. T. H. Ta, E. Cho, A. Sreedhar, and J. S. Noh, “Mixed-dimensional, Three-level Hierarchical Nanostructures of Silver and Zinc Oxide for Fast Photocatalytic Degradation of Multiple Dyes”, Journal of Catalysis 371, 1 (2019).

J. S. Noh, M. K. Lee, J. Ham, and W. Lee, “Co Nanoparticle Hybridization with Single-Crystalline Bi Nanowires”, Nanoscale Research Letters 6, 598 (2011).

D. Thakur, Q. T. H. Ta, and J. S. Noh, “Photon-Induced Superior Antibacterial Activity of Palladium-Decorated, Magnetically Separable Fe3O4/Pd/mpg-C3N4Nanocomposites”, Molecules 24, 3888 (2019).