We recorded fluorescence excitation and emission spectra of uro- and coproporphyrin under different experimental conditions, to see how these conditions influence quantifications based on measurement of fluorescence intensity. We found that, for bands alpha and beta of the emission spectra and the main peak of the excitation spectra, fluorescence depends on pH and is minimal near pH 5 and near ...

The use of ultrabright light-emitting diodes as a potential substitute for conventional excitation light sources in fluorescence microscopy is demonstrated. We integrated ultrabright light-emitting diodes in the filter block of a conventional fluorescence microscope together with a collimating Fresnel lens, a holographic diffuser and emission filters. This setup enabled convenient changes betwe...

A new emitter-detector-cuvette assembly for the standard PAM fluorometer is described which leads to substantial improvement of signal/noise ratio and increased flexibility with respect to the choice of excitation and emission wavelengths. These features are particularly useful for work with very dilute suspensions of unicellular algae and isolated chloroplasts. Instead of fiber optics perspex ...

A possibility of the two-photon excitation of an isomeric state in a nucleus of thorium-229 has been discussed. The fluorescence intensity of the excitation is demonstrated to be identical for the irradiation of nuclei with either monochromatic light or polychromatic radiation consisting of a sequence of short light pulses of the same intensity. The two-photon excitation of Th3+ ion in an elect...

The complex nature of natural organic matter (NOM), and the impact of this matter on drinking water quality have necessitated the characterization studies of NOM. A fluorescence technique for the characterization of NOM in Malaysian river water is reported. Water samples from several river sampling sites were collected and concentrated using a low-pressure reverse osmosis (LPROM). Solid phase e...

1.1 Fluorescence phenomenon The absorption and subsequent emission of light by organic and inorganic specimens is typically the result of physical phenomena known as luminescence, which occurs at electronically excited states. Luminescence is formally divided into two categories: fluorescence and phosphorescence, depending on the nature of the excited state. Fluorescence occurs when a photon ex...

Vertically aligned carbon nanotube films with diameters smaller than 5 nm, high densities up to 10/cm, and lengths of ~ 5–8 Am were deposited by microwave plasma-assisted chemical vapor deposition. Experiments show that, by continuous reduction in the thickness of the iron film (i.e., ~0.3–0.5 nm), small diameter carbon nanotubes can be achieved with diameters that ranged from 1–5 nm, and the f...

An analytical method is described for the simultaneous quantitation of polycyclic aromatic hydrocarbons pAHs] and alkylderivatives [alkyl-PAHs] in "real world" samples using microbore reversed-phase high performance liquid chromatography in conjunction with two programmable fluorescence detectors. Sensitivity and selectivity were enhanced by analyzing PAHs under their optimum fluorescence wavel...

Highly resolved emission and one-photon fluorescence excitation spectra for 1,4-diphenyl-1,3-butadiene seeded in a supersonic expansion of helium have been measured. The spectra show a long-lived (52.8 nsec for excitation at the 0-0) state at 29,652.5 cm(-1), approximately 1,150 cm(-1) below the well-characterized (1)B(u) state, which is assigned as (1)A(g)-i.e., we have directly observed a pol...