God made the bulk; surfaces were made by the devil
- Wolfgang Pauli
A material’s chemical properties are often different at its surface compared to its bulk. This phenomenon lies in the heart of nanotechnology and soft-matter in general due to the relatively high specific surface areas of their components. Soft-matter structure at the nanoscale can vary depending on the non-covalent electromagnetic interactions between the components. Conversely, the nanoscale structure affects its properties. These structure-function relationships are a hallmark of soft-matter systems. Understanding the rules of these structure-function relationships is necessary in diverse fields, from biology to physical and materials chemistry. As a postdoc in the Heavy Elements and Separation Science group, I am studying the role of interfacial phenomena in the chemical separation of rare earths, with a soft-matter perspective.
Rare-earth elements (REE) are identified as critical materials due to their importance in several industrial sectors (notably as permanent magnets in electric vehicles and wind turbines) and supply-chain risks. The main technological barrier in rare-earth economy is the chemical separation of individual REE from each other. Liquid-liquid extraction (solvent extraction) has been the dominant industrial process for the separation of rare earths but its mechanisms are not clearly understood. The extracting liquid phase (typically referred to as the organic phase), after extraction, is a complex fluid containing non-polar organic solvents, amphiphilic “extractants”, and the extracted species such as metal ion, co-ions, and water. The interactions between these components and their structural organization determine the selectivity and partition (“distribution ratio”) of the extraction process. In other words, there is a structure-function relationship. I use synchrotron X-ray scattering techniques to investigate the correlation between the structure of the complex fluids and interfaces involved in extraction and the extraction performance.
- Ph.D in Chemical Engineering, Iowa State University
- B.Tech and M.Tech in Chemical Engineering, Indian Institute of Technology, Kharagpur
- Nayak, S. et. al., “Origins of Clustering of Metalate-Extractant Complexes in Liquid-Liquid Extraction”,
- Nayak, S. et al., “Ion-Specific Clustering of Metal-Amphiphile Complexes in Rare Earth Separations”, Nanoscale, 2020,12, 20202-20210 (selected for 2020 Nanoscale HOT Article Collection)
- Nayak, S. et al., “Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces”, J. Phys. Chem. Lett., 2020, 11, 11, 4436–4442 (Presentation here)
- Nayak, S. et al., “Interpolymer Complexation as a Strategy for Nanoparticle Assembly and Crystallization”, J. Phys. Chem. C, 2019, 123, 836–840.