A shift in the wavelength of maximum fluorescence emission toward higher wavelengths, caused by a shift in the excitation wavelength toward the red edge of the absorption band, is termed the Red Edge Excitation Shift (REES). This effect is mostly observed with polar fluorophores in motionally restricted media such as very viscous solutions or condensed phases. In this paper, we report the red e...

Molecular sensors based on intramolecular Förster resonance energy transfer (FRET) have become versatile tools to monitor regulatory molecules in living tissue. However, their use is often compromised by low signal strength and excessive noise. We analyzed signal/noise (SNR) aspects of spectral FRET analysis methods, with the following conclusions: The most commonly used method (measurement of ...

Many naturally occurring substances are intrinsically fluorescent (autofluorescent) when excited with UV or visible wavelengths. Autofluorescence emission typically spans the visible spectrum with a lifetime (?) measured in nanoseconds. Time-resolved fluorescence techniques exploit the large difference in ? that exists between typical autofluorophores and for example, lanthanide chelates (typic...

We present photoluminescence properties of Tb(3+) doped borosilicate glasses modified by Cu(+). Around 5-time enhanced emission at 541 nm due to the superposed emission of Tb(3+) and Cu(+) is observed under the deep UV excitation. Excitation spectra demonstrate a greatly increased absorption of Tb(3+) ions in the deep UV region towards the Cu(+) excitation band, while the shortened Cu(+) emissi...

In glow discharge optical emission spectrometry, two-dimensional emission images for iron atomic lines were measured by using an imaging spectrograph equipped with a CCD detector, when a radio-frequency (r.f.) power source was employed for excitation. Emission images at the Fe I 371.99-nm and the Fe I 375.82-nm lines, having different excitation energies, were analyzed by the two-line method to...

OBJECTIVE The objective of this study was to compare the effects of chemopreventive agents on natural fluorescence emission of ovarian cells in a cell culture and in a primate model as a feasibility trial to monitor drug activity. METHODS Fluorescence emission spectra were collected from normal (NOE) and immortalized ovarian surface epithelial cells at 290, 360, and 450 nm excitation. Redox p...

A thorough analysis of the photophysical properties involved in electronic transitions in excitation-emission spectra of xylene isomers has been carried out using the time-dependent density functional theory (PBEPBE/6-31 + G(d,p)) method. For the first time a structural and spectroscopic investigation to distinguish isomers of xylene, a widespread priority pollutant, was conducted experimentall...

We have used pulse time-of-flight techniques to examine the phonon emission from an optically excited GaAs/AlAs superlattice structure. For laser excitation wavelengths shorter than 767 nm ~the energy of E1HH1 transition!, we detect a significant longitudinal acoustic phonon component directed in a narrow beam normal to the structure. Under identical excitation conditions, generation of coheren...

Shockley-Read-Hall recombination kinetics has been applied to explain the luminescence mechanism of erbium luminescence in silicon. Erbium atoms in silicon have been considered as recombination centers with specific values of capture and emission coefficients. Electron-hole recombination through these levels has been considered to be the origin of erbium excitation. Equating the capture and emi...

In this paper, we report a detailed computational and experimental investigation of the structural, electronic and dynamic properties of undoped and Er-doped Y2O2S phosphors by using computational crystal field (CF) calculations and electronic density of states by density functional theory (DFT), combined with optical measurements including excitation spectra, emission spectra from X-ray, ultra...