Multi-component, Self-assembled, Functional Soft Materials

Supramolecular chemistry is an emerging tool for devising materials that can perform specified functions. The self-assembly of facially amphiphilic bile acid molecules has been extensively utilized for the development of functional soft materials. Supramolecular hydrogels derived from the bile acid backbone act as useful templates for the intercalation of multiple components. Based on this, synthesis of gel-nanoparticle hybrid materials, photoluminescent coating materials, development of a new enzyme assay technique, etc. were achieved in the author's laboratory. The present account highlights some of these achievements

Remarkable isomer-selective gelation of aromatic solvents by a polymorph of a urea-linked bile acid-amino acid conjugate

We report an unusual, isomer-selective gelation of aromatic solvents by a polymorph of a urea-linked bile acid-amino acid conjugate. The gelator showed selectivity towards gelation of 1,2-disubstituted aromatic solvents

Hydrogelation of bile acid-peptide conjugates and in situ synthesis of silver and gold nanoparticles in the hydrogel matrix

Fabricating supramolecular hydrogels with embedded metal nanostructures is important for the design of novel hybrid nanocomposite materials for diverse applications such as biosensing and chemosensing platforms, catalytic and antibacterial functional materials etc. Supramolecular self-assembly of bile acid-dipeptide conjugates has led to the formation of new supramolecular hydrogels. Gelation of these molecules depends strongly on the hydrophobic character of the bile acids. The possibility of in situ fabrication of Ag and Au NPs in these supramolecular hydrogels by incorporating Ag+ and Au3+ salts was investigated via photoreduction. Chemical reductions of Ag+ and Au3+ salts in the hydrogels were performed without adding any external stabilizing agents. In this report we have shown that the color, size and shape of silver nanoparticles formed by photoreduction depend on the amino acid residue of the side chain

Appearance of Different Conductance States in Monomolecular Films of Ferrocene-Decorated Triptycene-Based Tripods

Ferrocene (Fc) is a widely used building block of molecular rectifiers in the context of molecular electronics. Here, we studied the molecular organization and charge transport properties of the Fc-substituted, triptycene-based tripodes (Fc-Trip), assembled on Au(111) in the self-assembled monolayer-like fashion. The most intriguing property of this system is the occurrence of two distinctly different conductance states, high and low (HCS and LCS, respectively), which can be accessed dynamically by either asymmetric or symmetric bias sweeping in molecular junctions featuring bottom Au (substrate) and top EGaIn electrodes. For the asymmetric sweeping mode, the difference between these states results in an effective rectification ratio (RR) of ∼400–600 at such a small bias as 0.1–0.2 V, which is in contrast to other Fc-based molecular rectifiers showing high RR at a bias of 1.0 V and higher. Following a literature model, the observed behavior was explained by bias-induced, nonreversible oxidation of the Fc groups in combination with conformational changes in the molecular film. The above results show that redox groups in ME systems, including metallocenes in particular, can exhibit a complex behavior that can only be observed by the variation of the sweeping mode and monitoring of individual sweeps