Measuring the lamellarity of giant lipid vesicles with differential interference contrast microscopy

Giant unilamellar vesicles are a widely utilized model membrane system, providing free-standing bilayers unaffected by support-induced artifacts. To measure the lamellarity of such vesicles, fluorescence microscopy is one commonly utilized technique, but it has the inherent disadvantages of requiring lipid staining, thereby affecting the intrinsic physical and chemical properties of the vesicles, and it requires a calibration by statistical analysis of a vesicle ensemble. Herein we present what we believe to be a novel label-free optical method to determine the lamellarity of giant vesicles based on quantitative differential interference contrast (qDIC) microscopy. The method is validated by comparison with fluorescence microscopy on a statistically significant number of vesicles, showing correlated quantization of the lamellarity. Importantly, qDIC requires neither sample-dependent calibration nor sample staining, and thus can measure the lamellarity of any giant vesicle without additional preparation or interference with subsequent investigations. Furthermore, qDIC requires only a microscope equipped with differential interference contrast and a digital camera

Cascaded Optical Field Enhancement in Composite Plasmonic Nanostructures

Copyright © 2010 The American Physical SocietyWe present composite plasmonic nanostructures designed to achieve cascaded enhancement of electromagnetic fields at optical frequencies. Our structures were made with the help of electron-beam lithography and comprise a set of metallic nanodisks placed one above another. The optical properties of reproducible arrays of these structures were studied by using scanning confocal Raman spectroscopy. We show that our composite nanostructures robustly demonstrate dramatic enhancement of the Raman signals when compared to those measured from constituent elements

Polarization anomaly in near-field magnetooptical microscopy

The near-field magnetooptical microscopy of thin ferromagnetic films deals with the spatial distribution of intensity and polarization of light in a focused spot. The authors performed imaging of such distributions using a W tip as an apertureless probe. At distance

Light-induced ESR studies in conjugated polymer-fullerene composites

In this contribution we discuss photo-induced electron transfer in conjugated polymer/fullerene composites and compare this with light induced effects in pure components. Two overlapping LESR lines are observed, from positive polarons on the polymer chains and negative charges on the fullerene moieties. Microwave power saturation studies show different relaxation times for these two spins, giving clear evidence for independent spins. The unusually high relaxation rate of the fullerene monoanionic spins is of intrinsic origin and discussed in terms of a splitting of the T1u level by a Jahn-Teller type distortion as proposed in the literature. We observed two distinct contributions to LESR signals, a prompt and a persistent one. Excitation light intensity dependence of the prompt contributions into P+ and C60- ESR signals is of bimolecular type (I0.5) and implies the mutual annihilation within (P+...C60-) pair. The persistent contribution is found to be excitation intensity independent and proposed to originate from deep traps due to disorder.

Studies Of Photoinduced Charge Transfer In Conjugated Polymer-fullerene Composites By Light-induced ESR

In this work we present comparative studies of the photoinduced electron transfer (PIT) in a number of conjugated polymer/fullerene composites and in pure components by using light-induced electron spin resonance. PIT from the polymer onto fullerene in the composites results in the appearance of two LESR lines: i) g=2.0025, attributed to the positive polaron on the polymer chain and ii) g=1.9995 originating from the fullerene anion-radical. These signals have different spin-lattice relaxation times with different temperature dependencies, the low field line possessing the longer relaxation time. The amount of light induced charges is proportional to the square root of the excitation light intensity, which indicates bimolecular recombination of polarons. Both lines have reversible light-induced ESR components and persistent light-induced contribution attributed to trapped polarons