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We here report on the formation of well-ordered 2D gold nanostructures at the air/water interface. Spreading a mixture of alkanethiol-capped gold nanoparticles (AuNPs) and an amphiphilic poly(p-phenylene) on a water surface and compressing the mixture to a surface pressure of 40 mN/m lead to the formation of a network of well-ordered gold nanostructures. The structures are transferred horizontally (Langmuir-Schafer) onto a solid substrate and investigated with TEM, AFM, and X-ray reflectivity, showing a pattern that is repeating over several micrometers. AFM and X-ray reflectivity data at different surface pressures reveal that the polymer is lifting the AuNPs 1.5-2 nm in the vertical direction, away from the polymer layer, when the pressure is increased from 20 to 40 mN/m.

We here report on the formation of well-ordered 2D gold nanostructures at the air/water interface. Spreading a mixture of alkanethiol-capped gold nanoparticles (AuNPs) and an amphiphilic poly(p-phenylene) on a water surface and compressing the mixture to a surface pressure of 40 mN/m lead to the formation of a network of well-ordered gold nanostructures. The structures are transferred horizontally (Langmuir-Schafer) onto a solid substrate and investigated with TEM, AFM, and X-ray reflectivity, showing a pattern that is repeating over several micrometers. AFM and X-ray reflectivity data at different surface pressures reveal that the polymer is lifting the AuNPs 1.5-2 nm in the vertical direction, away from the polymer layer, when the pressure is increased from 20 to 40 mN/m.

In recent years, the application of fluorescent conjugated polymers for sensing chemical and biological analytes has received much attention from many researchers. A promising development in this direction was the fabrication of conducting polymer-based sensors for the detection of metal ions, small organic molecules and biomolecules. Herein, we have designed, synthesized and studied a series of copolymers containing alternate phenylene and 2,5- or 2,6-substituted pyridine rings. The basic N-atom of the pyridine ring and the adjacent –OH group from the phenyl ring provide binding sites for metal ions. Another series of water-soluble conjugated polymers with propoxy sulfonate side chains are investigated for biosensor applications. Significant quenching of the polymer fluorescence upon addition of viologen derivatives was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers can be useful in the application of metal and biological sensors., Singapore-MIT Alliance (SMA)

In recent years, application of fluorescent conjugated polymers to sense chemical and biological analytes has received much attention owing to its technological significance. Water soluble conjugated polymers are interesting towards the developing sensors for biomolecules. In this present contribution, we describe the syntheses and characterization of a series of water soluble conjugated polymers with sulfonic acid groups in the side chain. Such anionic conjugated polymers are designed to interact with biomolecules such as cytochrome-C. All polymers are water soluble and showed strong blue emission. Significant quenching of the fluorescence from our functionalized PPP was observed upon addition of viologen derivatives or cytochrome -C., Singapore-MIT Alliance (SMA)

Design and synthesis of novel supramolecular architectures is an interesting area of research in the last two decades. Intermolecular interactions assisted self-assembly of molecular and macromolecular building blocks play an important role in obtaining the desired shape and function of the supramolecular architectures. A combination of the classical covalent synthesis with the self-assembly assisted formation of well-defined architectures (noncovalent synthesis) allows us to develop novel multifunctional materials. Our approach in this area is focused on the design of novel molecular and biomolecular building blocks and the optimization of structure-property relationship of the materials using self-assembly approach. This presentation will focus on our recent efforts on the design and synthesis of polymers and oligopeptides for investigation of the self-assembly and fine-tuning the structure-property relationship. Also, some highlights will be given on our initial investigation on how hard minerals are synthesized by natural molecules through the self-assembly processes., Singapore-MIT Alliance (SMA)

Natural bone is a composite of collagen based hydrogel and inorganic dahilite crystals. The unusual combination of a hard inorganic material and an underlying elastic hydrogel network endows native bone with unique mechanical properties, such as low stiffness, resistance to tensile and compressive forces and high fracture toughness. Throughout the cavities of the bone, there are bone cells and myriads of soluble and extracellular matrix components that are constantly involved in the bone formation and remodeling process. Among the extra cellular component the acidic matrix proteins that are attached to the collagen scaffold play important templating and inhibitory roles during the mineralization process. It would be interesting to generate such functional scaffolds that mimic a template driven mineralization and which can assist cell adhesion, proliferation, migration and differentiation. Towards this direction, we have chosen one synthetic (Nylon 66 membrane) and one natural (eggshell membrane) scaffold and carried out a template driven mineralization of CaCO₃ as model systems. The surface modifications were carried out by the pre-adsorption of acidic polymers before the deposition of the CaCO₃. The deposition of the crystalline calcium carbonate on these modified templates were archived from a supersaturated solution of Ca(HCO₃)₂., Singapore-MIT Alliance (SMA)

Recently, we reported the extraction, purification and amino acid sequence of ansocalcin, the major goose eggshell matrix protein. In vitro studies showed that ansocalcin induces spherical calcite crystal aggregates. We designed two peptides using the unique features of the sequence of ansocalcin and the role of these peptides in CaCO₃ crystallization was investigated. The peptides showed similar activities as compared to ansocalcin, but at a higher concentration. The full characterization of the peptides and a rational for the observed morphology for the calcite crystals are discussed in detail., Singapore-MIT Alliance (SMA)

Design and synthesis of novel supramolecular architectures is an interesting area of research in the last two decades. Intermolecular interactions assisted self-assembly of molecular and macromolecular building blocks play an important role in obtaining the desired shape and function of the supramolecular architectures. A combination of the classical covalent synthesis with the self-assembly assisted formation of well-defined architectures (noncovalent synthesis) allows us to develop novel multifunctional materials. Our approach in this area is focused on the design of novel molecular and biomolecular building blocks and the optimization of structure-property relationship of the materials using self-assembly approach. This presentation will focus on our recent efforts on the design and synthesis of polymers and oligopeptides for investigation of the self-assembly and fine-tuning the structure-property relationship. Also, some highlights will be given on our initial investigation on how hard minerals are synthesized by natural molecules through the self-assembly processes., Singapore-MIT Alliance (SMA)

Model peptides were designed, synthesized and conducted a detailed structure-property study to unravel the molecular mechanism of goose eggshell calcification. The peptides were designed based on the primary structural features of the eggshell matrix proteins ansocalcin and OC-17. In vitro CaCO₃ crystal growth experiments in presence of these peptides showed calcite crystal aggregation as observed in the case of the parent protein ansocalcin. The structure of these peptides in solution was established using intrinsic tryptophan fluorescence studies and quasi-elastic light scattering experiments. The structural features are correlated with observed results of the in vitro crystallization studies., Singapore-MIT Alliance (SMA)

Recently, we reported the extraction, purification and amino acid sequence of ansocalcin, the major goose eggshell matrix protein. In vitro studies showed that ansocalcin induces spherical calcite crystal aggregates. We designed two peptides using the unique features of the sequence of ansocalcin and the role of these peptides in CaCO₃ crystallization was investigated. The peptides showed similar activities as compared to ansocalcin, but at a higher concentration. The full characterization of the peptides and a rational for the observed morphology for the calcite crystals are discussed in detail., Singapore-MIT Alliance (SMA)

Complexes of 5-ociadecyloxyisophthalic acid with piperazine, 1,4,7-triazacyclononane and 1,4,7,10-hexaazacyclooctadecane were selectively deuterated in various positions, and investigated with variable-temperature solid-state 2H n. m. r. spectroscopy. Al! systems form stable, enantiotropic liquic-crystailine phases at high temperature, and the dynamics in these phases can be described by a single motional model. This model involves fast rotation around the director coupled with a rapid phenyl flip. Macroscopically oriented liquid-crystalline phases with the director parallel to the magnetic field are found on cooling in a magnetic field of 7 T for the piperazine complexes, but only partial macroscopic order was achieved for the complexes with 1,4,7,10-hexaazacyclooctadecane and 1,4,7-triazacyclononane under these conditions, and also for the former in a magnetic field of ; 1 T. In contrast to the pure acid C18ISA, the stability of the phases is determined by the hydrogen/ionic bonds between the acid and the bases, and not by the alkyl-alkyl interactions.

Complexes of 5-ociadecyloxyisophthalic acid with piperazine, 1,4,7-triazacyclononane and 1,4,7,10-hexaazacyclooctadecane were selectively deuterated in various positions, and investigated with variable-temperature solid-state 2H n. m. r. spectroscopy. Al! systems form stable, enantiotropic liquic-crystailine phases at high temperature, and the dynamics in these phases can be described by a single motional model. This model involves fast rotation around the director coupled with a rapid phenyl flip. Macroscopically oriented liquid-crystalline phases with the director parallel to the magnetic field are found on cooling in a magnetic field of 7 T for the piperazine complexes, but only partial macroscopic order was achieved for the complexes with 1,4,7,10-hexaazacyclooctadecane and 1,4,7-triazacyclononane under these conditions, and also for the former in a magnetic field of ; 1 T. In contrast to the pure acid C18ISA, the stability of the phases is determined by the hydrogen/ionic bonds between the acid and the bases, and not by the alkyl-alkyl interactions.