The main thrust of our research is to understand the solid-liquid and solid-solid interfaces involving modified surfaces and new materials.

Organic thin films - self assembled monolayers, (SAMs) and Langmuir-Blodgett films, (LB films): Our objective is to prepare stable, compact and well oriented 2-dimensional and 3-dimensional thin films and characterize them for applications such as electrocatalysis, sensing and tribology. The substrates presently used are gold, platinum,silver and stainless steel. Three-dimensional monolayers are assembled on to colloids of Au and Ag and their alloys. Specific systems include, quinone - s spacer - ferrocene molecules, phthalocyanines, silanes and alkane thiols.

Orientation dependent electrocatalysis – Cobalt phthalocyanine molecules assembled on gold and silver assume different orientations and electrocatalyze oxygen reduction reaction to different products. Quinone – methylene spacer – ferrocene assembly is constructed on gold and studied for sensing and electrocatalysis. Rectification is a possibility that is being looked at. Thermal electron transfer involving the SAMs is also addressed. Determination of thermodynamic parameters (DG, DH and DS) associated with the adsorption / desorption of thiol monolayers on gold using electrochemistry and quartz crystal microbalance has been carried out. Study of thermal stability of thiol and silane monolayers on various substrates including steel reveals different transitions such as trans – gauche, rotation and desorption, associated with these assemblies.

Exfoliated inorganic materials: We have been exploring the possibility of modifying exfoliated graphite particles with redox active compounds. Exfoliated or expanded graphite (EG) is a low dense graphitic carbon with a high temperature resistance. The density of the expanded material is very low, of the order of 0.004 g/cm3. These graphite particles can be recompressed or re-stacked without any binder. Simultaneous determination of dopamine, ascorbic acid and uric acid has been achieved on an unmodified EG electrode surface. Covalent functionalization of EG with a variety of redox mediators such as quinones, hydroquinone and dyes have led to bulk-modified electrodes for NADH (reduced form of nicotinamide adenine dinucleotide) and ethanol sensing.

Nanostructures - sol-gel stabilization of nano(bi)metallic and alloy particles: Nanobimetallic particles of Pt-Pd, Ag-Pt, Au-Pd and Au-Ag are prepared and stabilized in sol-gel based silicates, both in the liquid and solid phases. Au-Ag alloy clusters are assembled on to solid substrates such as ITO, gold, glass and further used for electrochemistry and surface enhanced Raman scattering (SERS) studies.

Solid polymer electrolytes based on magnesium and zinc ion conducting matrices: We have been using a sol-gel process to prepare solid polymer electrolytes by forming an organic-inorganic composite based on silicate-polyethylene glycol (PEG)-magnesium salt. Other magnesium based gel electrolytes comprising PAN and PMMA are also being studied. Solid electrolytes based on Zn²⁺ are also explored in the context of Zn-MnO₂ batteries. PEG – silicate composites containing magnesium salts with various anions such as triflate, nitrate and chloride areprepared and characterized using vibrational spectroscopy and electrochemistry.

Supercapacitors: In recent years, capacitive systems for reversible electrical energy-storage and delivery have been developed for a number of applications. We have been exploring the use of solid electrolytes based on silicate - polyethylene glycol - ionic salt composites, polyacrylonitrile (PAN)- ionic salt based gel electrolytes as possible alternatives for supercapacitor applications. As for the electrodes, the use of high-density graphite and exfoliated graphite is being studied.

Representative Publications

N S Venkata Narayanan, B V Ashok Raj and S.Sampath , Magnesium Ion Conducting, Room Temperature Molten Electrolytes,
Electrochem. Comm.,In Press (2009).

N S Venkata Narayanan, B V Ashok Raj and S.Sampath , Physicochemical, Electrochemical and Spectroscopic Characterization of Zinc-Based, Room Temperature Molten Electrolytes and Their Application in Rechargeable Batteries ,
J. Electochem. Soc.,, In Press (2009).

G K Ramesha and S.Sampath , Electrochemical reduction of oriented graphene oxide films: An in-situ Raman spectroelectrochemical study,
J. Phys. Chem.C (Lett), 113(19), 7985, 2009.

N A Choudhury, A K Shukla and S.Sampath , Hydrogel Membrane Electrolyte for electrochemical capacitors ,
J. Chem. Sci.,, In Press (2009).

N S Venkatanarayanan and S.Sampath,Amide-Based Room Temperature Molten Salt as Solvent cum Stabilizer for Metallic Nanochains ,
J. Cluster Science., 20, 375, 2009.