Palaniappan Arumugam

Self-assembly and cross-linking of FePt nanoparticles at planar and colloidal liquid-liquid interfaces

Terpyridine thiol functionalized FePt and Au NPs were self-assembled and cross-linked at the liquid-liquid interfaces using Fe(II) metal ion. Complexation of terpyridine with Fe(II) metal ion leads to NP network and affords stable membranes and colloidal shells at the liquid-liquid interfaces.

Synthesis of gold nanoparticles: an ecofriendly approach using Hansenula anomala.

This work describes a bioassisted approach for the preparation of metal nanoparticles using yeast species Hansenula anomala. Gold nanoparticles were prepared using gold salt as the precursor, amine-terminated polyamidoamine dendrimer as the stabilizer, and the extracellular material from H. anomala as the bioreductant. It could also be demonstrated that, using our approach, small molecules such as cysteine can act as stabilizers as well. This synthetic approach offers a greener alternative route to the preparation of gold sols that are devoid of cellular and toxic chemical components. The ability of as-synthesized gold sol to function as biological ink for producing patterns for the analysis of fingerprints and to act as an antimicrobial reagent is evaluated. The generality of this toxin-free synthetic approach to other metals was assessed using palladium and silver.

Structural control of the monolayer stability of water-soluble gold nanoparticles

The thermodynamic and kinetic stability of three structurally related monolayer-protected gold clusters have been systematically investigated, revealing that the nanoparticles display significantly different stability against thermo- and cyanide-induced decomposition and external thiol agents.

DNA-mediated assembly of iron platinum (FePt) nanoparticles

Nanocomposite materials consisting of FePt nanoparticles and DNA were constructed via DNA-mediated “bricks and mortar” self-assembly. Electrostatic interaction between the cationic nanoparticles and the DNA through surface recognition led to the formation of extended composite aggregates. These DNA-assembled aggregates feature increased interparticle spacing arising from the DNA “mortar”. The enhanced structure and increased spacing in the bio-nanocomposite assembly was found to alter the magnetic properties of the assemblies, as demonstrated by a 54 K change in blocking temperature (TB).

Nitric oxide releasing photoresponsive nanohybrids as excellent therapeutic agent for cervical cancer cell lines.

Gold nanoparticles (GNPs) that can release nitric oxide (NO) on visible-light irradiation were prepared using 2-mercapto-5-nitro benzimidazole (MNBI) as stabilizer. These nanoparticles meet overall prerequisites for biomedical applications like small sizes, water solubility, and stability. It was found that even a very low dosage of MNBI-stabilized GNPs exhibit appreciable tumor cell mortality against cervical cancer cell lines, demonstrating the role of NO in killing cancer cells.

Fabrication and Functionalization of Supramolecular Microgel Arrays Through Complementary Hydrogen-Bonding Interactions

Molecular self-assembly can be described as the thermodynamically controlled association of molecules into structurally well-defined, stable aggregates through noncovalent interactions, including van der Waals interactions, p–p stacking, electrostatics, metal coordination, and hydrogen bonding. These supramolecular interactions that define the self-assembly process are responsible for the highly ordered, diverse systems found in nature, and also provide inspiration for the creation of new self-assembled supramolecular materials. Supramolecular gels represent a particularly interesting family of self-assembled structures and are 3D networks formed by small molecules, oligomers, or polymers through noncovalent interaction linkages. These systems feature reversibility, the ability to self-heal, and selectivity compared with traditional polymer gels, and have applications in areas including biodelivery, controlled membranes, and tissue engineering. Specific interactions, such as multiple hydrogen bonding motifs and metal coordination, have been widely employed in the construction of supramolecular polymeric materials. For example, we have shown that random copolymers of polystyrene functionalized with complementary diamidopyridine (PS-DAP) and thymine (PS-Thy) moieties (Figure 1A and 1B) form supramolecular assemblies including vesicular complexes in non-competitive solvents. A key feature of these vesicular structures is that they are metastable, forming gels over the course of hours. These gels provide a potentially useful system for integrating material properties of gels with ‘lock and key’ capabilities offered by molecular recognition. Here, we demonstrate selective deposition of PS-DAP/PSThy gels onto pre-patterned silicon substrates. These microgel arrays can be crosslinked and selectively and reversibly

From ribbons to nanodot arrays: nanopattern design through reductive annealing

A new approach to the generation of nanoparticle arrays in periodic as well as non-periodic fashions has been discovered based on reduction of oxidized nanoscroll/nanoribbon precursors in the transmission electron microscope (carbothermal reduction) or by hydrogen annealing. Arrays consisting of nickel arsenide nanoparticles of size 3-4 nm have been generated.