Sponsored Projects:

Devising strategies for the synthesis of various nanostructures:

1. One of the primary aspects of a strategy for nanomaterials synthesis is to provide control over the size and distribution. The presence of ligands or capping agents during the nanoparticle synthesis leads to capped nanoparticles with tunable size.In order to control the growth of nanoparticles, we used solid citric acid, which acts as both a matrix and reducing agent. The gold nanoclusters possessed a size of 0.8 nm to 1.4 nm. These nanoclusters can be stored as they are stable in the citric acid solid matrix. Under specific reaction conditions in water, these catalysts complete 50% of the p-nitrophenol reduction before they aggregate to form bigger-sized nanoparticles. Thus, these Au nanoclusters exhibit a very high turn-over frequency.Due to the surface energy, the metals tend to ball up on the surface of metal-oxide systems, thus, preventing uniform coating or shell layer. We have devised a solid-state approach for the preparation of metal-oxide@metal core-shell nanostructures.
2. Due to the surface energy, the metals tend to ball up on the surface of metal-oxide systems, thus, preventing uniform coating or shell layer. We have devised a solid-state approach for the preparation of metal-oxide@metal core-shell nanostructures. We mixed surfactant-based precursor with the pre-formed metal-oxide core material and ground further. After the grinding process, thermal decomposition of the precursor leads to metal-oxide(core) – metal(shell) nanostructures. The efficiency of the coating depends on the inherent surface energy of the metals. E.g., it is not easy to form a continuous metal layer in the case of Pd. The core-shell nanostructures were tested for their catalytic H₂ generation efficacy from ammonia borane.
3.  The issues with using metal-oxide nanoparticles as a source of micronutrients for plants are aggregation, segregation, and lack of leaching. As a result, the nutrient uptake by plants is not appreciable. We circumvent this by synthesizing chelate-based iron citrate and zinc citrate nanoparticles which are water-soluble and can mitigate the problems posed by metal-oxide nanoparticles. The Fe and Zn citrate nanoparticles were prepared by solid-state grinding of ferric nitrate and citric acid. These novel chelate-based metal ion precursor nanoparticles were absorbed by plants more than the commercial sources.

Understanding structure-property correlation in nanomaterials:

1.  Using the wet-chemical method, we prepared Fe₃O₄ nanoparticles coated with oleic acid and oleylamine. The particle size and size distribution were studied by small-angle x-ray scattering techniques. Fe₃O₄ nanoparticles were also characterized by Faraday rotation measurements. The presence of spacer ligands (oleic acid) reduces the aggregation and thus the magnetic dipolar interaction between nanoparticles. As a result, the Faraday rotation data fits the single-scattering model rather than the chain model.  
2.  Fe₃O₄@Pd core-shell nanoparticles possess multiple functions. Pd acts as a catalyst center, and Fe₃O₄ provides magnetic recoverability functions. These nanostructures were tested for catalytic H₂ generation efficacy from ammonia borane. The characterization data of the used catalysts (from successive catalysis reaction cycles) indicates the formation of Fe(0) as an intermediate. The Fe(0) that is located beneath the Pd enhances the rate of H₂ generation.