Tanmay Bera

Polyelectrolyte-coated liquid crystal droplets for detecting charged macromolecules

Chemically engineered liquid crystal droplets with stimuli responsive director configurations are attractive for sensing applications. Here, we find that the adsorption of positively charged poly(amido amine) (PAMAM) dendrimers on negatively charged poly(styrenesulfonate sodium) (PSS)-coated liquid crystal droplets can trigger a bipolar-to-radial configuration transition of the liquid crystal in the droplets, which can be easily detected with a polarizing optical microscope. The sensitivity of the PSS-coated liquid crystal droplets for detecting PAMAM dendrimers depends on the size and number of liquid crystal droplets as well as the dendrimer generation.

Longitudinal zipping/unzipping of self-assembled organic tubes.

Stimuli-responsive organic tubes are an attractive supramolecular assembly which has potential applications as a controlled release vehicle. We synthesize a smart organic tube by the coassembly of lithocholic acid (LCA) and taurolithocholic acid (TLCA) in aqueous solution. The coassembled LCA/TLCA tubes can be longitudinally unzipped into flat sheets by capillary force after being dehydrated on substrates. Consequently, the encapsulated guest molecules are released from the unzipping tubes. After the release of guest molecules, the flat sheets can be zipped back into hollow tubes upon hydration with aqueous solution. The zipping/unzipping LCA/TLCA tubes provide a new type of delivery vehicles, which may have potential for surface decontaminations.

Transcription of pH-sensitive supramolecular assemblies into silica: from straight, coiled, and helical tubes to single and double fan-like bundles

The transcription of self-assembled organic structures by the sol–gel process is a powerful method in the synthesis of inorganic materials with controlled sizes, shapes, and porosities. Lithocholic acid (LCA) shows pH-sensitive supramolecular assemblies in aqueous solution, which can be used as tunable templates in the synthesis of silica replicas. Micro- and submicro-scale silica structures from straight, coiled, and helical tubes to single and double fan-like bundles are formed by the sol–gel transcription of pH-sensitive LCA assemblies with tetraethoxysilane (TEOS) in the presence of ammonia catalyst.

Tailoring the surface of liquid crystal droplets with chitosan/surfactant complexes for the selective detection of bile acids in biological fluids

We report an approach for tailoring the surface of 4-n-pentyl-4′-cyanobiphenyl (5CB) droplets by the adsorption of chitosan (CHI) at the 5CB/aqueous interface, followed by the penetration of sodium tetradecyl sulfate (SC14S). The CHI/SC14S complex-coated 5CB droplets can be used as optical probes for the detection of cholic acid (CA) in phosphate-buffered saline and urine without dilution. We find that the CHI coating can significantly reduce the detection limit of 5CB droplets for CA. By controlling the number of CHI/SC14S complex-coated 5CB droplets, the detection limit for CA can be changed from ∼75 μM to ∼0.5 μM, which covers the concentration range of CA in individual urine with and without intestinal diseases.

Self-assembled palladium–organic composite nanofibers and their applications as a recyclable catalyst

We report the formation of palladium nanoparticle (PdNP)–lithocholic acid (LCA) composite nanofibers by the self-assembly of Pd2+-coordinated LCA molecules and an ex situ reduction. The ex situ reduction by sodium borohydride or ascorbic acid produces the composite nanofibers with PdNPs grown on the surface of LCA nanofibers. The catalytic activity of the PdNP–LCA composite nanofibers in the decolourization of 4-phenyl azo benzoic acid is investigated. We find that the composite nanofibers can be recycled without significantly losing their catalytic activities.