Exploring the hidden depth by confocal Raman experiments with variable objective aperture and magnification.

The article analyzes experimentally and theoretically the influence of microscope parameters on the pinhole-assisted Raman depth profiles in uniform and composite refractive media. The main objective is the reliable mapping of deep sample regions. The easiest to interpret results are found with low magnification, low aperture, and small pinholes.

Pigmentation of White, Brown, and Green Chicken Eggshells Analyzed by Reflectance, Transmittance, and Fluorescence Spectroscopy.

We report on the reflectance, transmittance and fluorescence spectra (=200-1200 nm) of four types of chicken eggshells (white, brown, light green, dark green) measured in situ without pretreatment and after ablation of 20-100 μm of the outer shell regions. The color pigment protoporphyrin IX (PPIX) is embedded in the protein phase of all four shell types as highly fluorescent monomers, in the white and light green shells additionally as non-fluorescent dimers, and in the brown and dark green shells mainly as non-fluorescent poly-aggregates. The green shell colors are formed from an approximately equimolar mixture of PPIX and biliverdin.

Comparative Raman study of transparent and turbid materials: models and experiments in the remote sensing mode.

The influence of turbidity on the Raman signal strengths of condensed matter is theoretically analyzed and measured with laboratory - scale equipment for remote sensing. The results show the quantitative dependence of back- and forward-scattered signals on the thickness and elastic-scattering properties of matter. In the extreme situation of thin, highly turbid layers, the measured Raman signal strengths exceed their transparent analogs by more than a factor of ten.

Penetration of light into multiple scattering media: model calculations and reflectance experiments. Part II: The radial transfer.

In continuation of our contribution to "The Axial Transfer" (Appl. Spectr. 2012.

Quantitative Raman spectroscopy in turbid matter: reflection or transmission mode?

Raman intensities from reflection (X(R)) and transmission (X(T)) setups are compared by calculations based on random walk and analytical approaches with respect to sample thickness, absorption, and scattering. Experiments incorporating strongly scattering organic polymer layers and powder tablets of pharmaceutical ingredients validate the theoretical findings. For nonabsorbing layers, the Raman reflection and transmission intensities rise steadily with the layer thickness, starting for very thin layers with the ratio X(T)/X(R) = 1 and approaching for thick layers, a lower limit of X(T)/X(R) = 0.

Penetration of light into multiple scattering media: model calculations and reflectance experiments. Part I: the axial transfer.

The article presents two general equations of radiation penetration into layers of diffuse reflectors. One of the equations describes the depth origins of reflection, the other the depth profiles of absorption. The equations are evaluated within the theory of radiative transfer applying various degrees of analytical approximations and Monte Carlo simulations.

Dark-field scattering microscopy for spectral characterization of polystyrene aggregates.

Light scattering measurements of particle aggregates contain complex information which is difficult to decrypt. Dark-field scattering microscopy in the visible range is used to characterize multi-arranged polystyrene beads. First, measured light scattering spectra of single spheres are compared with the Mie theory.

Using scattering and absorption spectra as MCR-hard model constraints for diffuse reflectance measurements of tablets.

One of the most often used tools in process analytical technology (PAT) is NIR spectroscopy as a non-destructive fast and reliable method to identify and quantify active pharmaceutical ingredients (API) in tablets. Very little work has been devoted to analyse the effects of scatter on quantitative analysis of the chemical composition. A novel approach to compensate scatter in reflectance spectroscopy which is more science based will be presented here.

Design of pi-conjugated organic materials for one-dimensional energy transport in nanochannels.

Various end-substituted distyrylbenzenes have been synthesized to serve as guest molecules in inclusion compounds to promote efficient energy transport along one-dimensional channels. Their optical and photophysical properties have been characterized at both experimental and theoretical levels. All molecules display a large transition dipole moment between the ground state and lowest excited state and hence a short radiative lifetime (on the order of 1-2 ns).

Spatially Resolved Immobilization of Peptides by Electrochemical Polymerization after Photolytic Cleavage of a Protecting Group.

Microstructuring of surfaces: Electrochemical polymerization after removal of a photolabile protecting group (nitrobenzyl group) represents a new method for spatially resolved immobilization of ligands or receptors. Thus, the electropolymerization of 3-hydroxyphenylacetyl peptides such as 1 on electrodes can be controlled by light.

Investigating the Selectivity of Triacontyl Interphases.

What causes the shape selectivity of C phases? This question can be answered by combining NMR and fluorescence spectroscopies with HPLC separations at various temperatures. The selectivities depend on the ratio of trans to gauche conformations of the alkyl chains, whose dynamic behavior was characterized with a two-dimensional solid-state NMR spectrum (shown on the right).