Dr. Swathi Suran Profile

Dr. Swathi Suran

at Indian Institute of Science

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Publications (2)

Proceedings Article | 20 February 2018 Presentation + Paper

Direct optical imaging of nanoscale internal organization of polymer films

Swathi Suran, Manoj Varma

Proceedings Volume 10506, 105060J (2018) https://doi.org/10.1117/12.2289615

KEYWORDS: Germanium, Etching, Polymers, Diffusion, Optical imaging, Mathematical modeling, Polymer thin films, Ions, Atomic force microscopy, Hydrogen

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Owing to its sensitivity and precise control at the nanoscale, polyelectrolytes have been immensely used to modify surfaces. Polyelectrolyte multilayers are generally water made and are easy to fabricate on any surface by the layer-by-layer (LbL) self-assembly process due to electrostatic interactions. Polyelectrolyte multilayers or PEMs can be assembled to form ultrathin membranes which can have potential applications in water filtration and desalination [1-3]. Hydration in PEMs is a consequence of both the bulk and surface phenomenon [4-7]. Bulk behavior of polymer membranes are well understood. Several techniques including reflectivity and contact angle measurements were used to measure the hydration in the bulk of polymer membranes [4, 8]. On the other hand their internal organization at the molecular level which can have a profound contribution in the transport mechanism, are not understood well. Previously, we engineered a technique, which we refer to as Bright-field Nanoscopy, which allows nanoscale optical imaging using local heterogeneities in a water-soluble germanium (Ge) thin film (~ 25 nm thick) deposited on gold [8]. We use this technique to study the water transport in PEMs. It is understood that the surface charge and outer layers of the PEMs play a significant role in water transport through polymers [9-11]. This well-known ‘odd-even’ effect arising on having different surface termination of the PEMs was optically observed with a spatial resolution unlike any other reported previously [12]. In this communication, we report that on increasing the etchant’s concentration, one can control the lateral etching of the Ge film. This allowed the visualization of the nanoscale internal organization in the PEMs. Knowledge of the internal structure would allow one to engineer polymer membranes specific to applications such as drug delivering capsules, ion transport membranes and barriers etc. We also demonstrate a mathematical model involving a surface permeability term which captures the experimentally observed odd-even effect.

Proceedings Article | 22 April 2016 Presentation + Paper

Seeing the unseen with localized optical contrast

Swathi Suran, Krishna Bharadwaj, Srinivasan Raghavan, Manoj Varma

Proceedings Volume 9721, 97210U (2016) https://doi.org/10.1117/12.2212028

KEYWORDS: Visualization, Graphene, Thin films, Image processing, Nanostructures, Optical microscopes, Molecules, Chemical vapor deposition, Metals, Super resolution microscopy, Germanium, Etching, Gold, Raman spectroscopy

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