Search

The continuous nonpolar phase can change the morphology of lecithin reverse micelles dramatically. In alkane solvents, increasing the hydration leads to gelation as isolated water droplets transform into an entangled tube network. In contrast, increasing the hydration for lecithin in benzene maintains isolated, largely spherical traditional reverse micelles. Solvation dynamics experiments have been carried out in the two different micellar environments. These measurements show that solvation dynamics are considerably more restricted in the tubular micelles than in the spherical droplets. This is interpreted as evidence for water pool formation and disorder at the interface in the spherical micelles and supports the hypothesis of substantial water incorporation into the tubular micelles. To perform solvation dynamics experiments in the benzene/lecithin/water reverse micelles, we have synthesized a new headgroup-labeled probe molecule. This synthesis, coupling the standard solvation dynamics probe, coumarin...

The mobility of water in water/Aerosol OT (AOT)/isooctane reverse micelles has been investigated via polar solvation dynamics measurements using ultrafast, time-resolved fluorescence-upconversion spectroscopy. For the smallest reverse micelles studied, w0 = 1.1, no solvation dynamics are observed on the time scale of the instrument, suggesting that the water is essentially frozen. As w0 increases, the mobility of water increases, and the time-correlation functions exhibit multiexponential decays. A subpicosecond component is observed on a time scale similar to that of diffusive bulk-water motion.1 The other components decay on time scales of a few picoseconds to hundreds of picoseconds. The amplitude of the solvent response increases as w0 increases, which is attributed to increased mobility of the water inside the reverse micelles. Because the micellar interior is highly ionic, the solvation dynamics of coumarin 343 in a 1 M Na+ (Na2SO4) solution were also investigated to compare the dynamics of water in...

Nanoscale sensors can be created when an expected energetic pathway is created and then that pathway is either initiated or disrupted by a specific binding event. Constructing the sensor on the nanoscale could lead to greater sensitivity and lower limits of detection. To this end, quantum dots (QDs) can be considered prime candidates for the active components. Relative to organic chromophores, QDs have tunable spectral properties, show less susceptibility to photobleaching, have similar brightness, and have been shown to display electro-optical properties. In this review, we discuss recent articles that incorporate QDs into directed energy flow systems, some with the goal of building new and more powerful sensors and others that could lead to more powerful sensors.

A technique for micrometer-scale patterning of multiple functional biological molecules on surfaces is demonstrated. The technique is referred to as single-feature inking and stamping (SFINKS). It combines elements of dip-pen nanolithography and microcontact printing. "Inked" atomic force microscopy probes are used to ink individual features of an elastomer stamp. From a single stamp, we printed three different probe ssDNA with10 mum resolution and showed that they specifically hybridize the complementary DNA labeled with different fluorophores. As a further demonstration of SFINKS' versatility, we patterned a silane onto a silicon wafer consisting of four subpatterns separated by100 mum and composed of 2 mum lines. We discuss why patterns such as these are impractical with available techniques. Furthermore, we comment on the prospects for multiple stamping after a single inking.