Nanocomposites consisting of a metal core, a silica-spacer shell with controlled thickness, and a dye-labelled shell were synthesized and separation distance dependent fluorescence enhancement of fluorescein isothiocyanate by silver nanoparticles was studied; the results indicated an optimum enhancement of 4.8 times with a spacer shell thickness of 21 nm.

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We report the preparation of ordered polyaniline (PANI) nanorod arrays in an aqueous medium. The oriented PANI nanorods (80-400 nm in diameter and 8-15 mum in length) were synthesized in the presence of hydrophilic Allura Red AC (ARAC) as the structure-directing agent and ammonium persulfate as an oxidant in HCl solution. The morphologies of the oriented PANI nanoparticle nanorods were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy images, and the effect of reaction conditions on the morphology of PANI nanostructures was also studied. On the basis of the result obtained from small-angle X-ray scattering, we propose that rodlike micelle arrays of ARAC-aniline are responsible for directing the formation of oriented PANI nanoparticle nanorods. SEM images and the data analysis of static and dynamic light scattering give supportive evidence to the formation of the PANI nanoparticle nanorods by an elongation process. The chemical and electronic structures of the PANI nanorods were also studied by Fourier transform IR and UV-vis spectrometries, respectively.

Although biochemical sensing using liquid crystals (LC) has been demonstrated, relatively little attention has been paid towards the fabrication of in situ-formed LC sensing devices. Herein, we demonstrate a highly reproducible method to create uniform LC thin film on treated substrates, as needed, for LC sensing. We use shear forces generated by the laminar flow of aqueous liquid within a microfluidic channel to create LC thin films stabilized within microfabricated structures. The orientational response of the LC thin films to targeted analytes in aqueous phases was transduced and amplified by the optical birefringence of the LC thin films. The biochemical sensing capability of our sensing devices was demonstrated through experiments employing two chemical systems: dodecyl trimethylammonium bromide (DTAB) dissolved in an aqueous solution, and the hydrolysis of phospholipids by the enzyme phospholipase A2 (PLA2).

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