SUPRAMOLECULAR ASSEMBLY OF NANOSTRUCTURED MATERIALS FOR FABRICATION OF FUNCTIONAL INTERFACESByAnkush Ashok GokhaleIn recent years, there has been increased focus towards miniaturization to build sustainable devices by harnessing the power of synergistic nanoarchitectures. Drawing upon the strength of the intermolecular forces, supramolecular assembly techniques have enabled the inclusion of a host of inhomogeneous nanomaterials to give form and structure to macroscopic objects. Supramolecular techniques are well suited to customize and improvise the assembly of nanomaterials to allow full translation of their nanoscale properties to macroscopic structures. In our work, we have primarily focused on developing novel supramolecular multifunctional architectures for fabrication of nanostructured interfaces. Firstly, we designed a unique recyclable two-tier carbonaceous biocatalyst consisting of a polyelectrolyte modified iron-oxide doped graphene support and a biocatalytic component in the form of cellulase, an enzyme capable of hydrolyzing lignocelluloses to reducing sugars. A combination of strong and weak polyelectrolytes enabled long-term stabilization of hydrophobic graphene platelets in aqueous medium and provided an effective means to control the biocatalytic activity of the immobilized cellulase as a function of pH and temperature. We also show how the effect of the dissociation of weak polyelectrolytes can overcome the geometric disadvantage imposed by flat 2D supports. A combination of polyelectrolyte swelling, improved colloidal stability and enhanced enzyme mobility contributed to preservation of the biocatalytic activity.Secondly, we also designed a novel supramolecular conductive interface consisting of multilayered thin films of functionalized graphene platelets in conjunction with anionic polyelectrolytes. The interplay of hydrogen bonding and electrostatic forces was studied and its effect on film thickness and morphology was evaluated. Films developed in this work show impressive gas shielding capabilities comparable to commercial grade silicon oxide coatings and almost a five orders of magnitude reduction in sheet resistance. Lastly, a bioelectronic interface to detect and quantify the presence of anionic nitrate species was assembled from a surfactant stabilized supramolecular matrix. Nitrate based fertilizers pose major health hazards when they combine with sources of drinking water. In this work, we developed a novel 1D nanoarray of polyethylenedioxythiophene based nitrate biosensor capable of detecting and quantifying minute concentrations of nitrate species. Low detection limit (0.1 ppm), high signal to noise ratio and improved affinity towards nitrate species as compared to other interfering ions are significant features of this sensor.
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