Optical Characterization of Quinoline Yellow Fluorochemosensors for Analyzing Its Photonics Applications With Synthesized Nano Particles

Quinoline Yellow (QY) with the scientific name [sodium 2-(2, 3-dihydro-1,3-dioxo-1H-inden-2-yl) quinoline-6,8-disulfonate] (SQDS) is investigated for its sensing properties as fluorochemosensors and its NLO applications. Pure SQDS is doped with copper ferrite and cerium oxide nanoparticles and studied for changes in spectral results. Change in absorption spectrum is observed depending on the polarity of solvents. Intensity of fluorescence also varies with different type of solvents. Optical characterization for SQDS is carried out via various spectroscopic techniques including UV-VIS spectroscopy, FTIR spectroscopy, Scanning Electron Microscopy and Photo Luminescence (PL) spectroscopy. Optical parameters like extinction coefficient, refractive index and bandgap energy are determined from absorption spectrum for both solution and film samples. XRD characterization is also performed for QY and for nanoparticle doped QY. For investigating Non-Linear optical (NLO) application of QY, films are prepared and optical imaging is performed via Atomic Force Microscopy (AFM). Characterization results are analysed and predicted for application in non-linear optics.

In vitro Assessment of Solar Filters for Erythropoietic Protoporphyria in the Action Spectrum of Protoporphyrin IX

Introduction: Subjects with erythropoietic protoporphyria rely on broad-spectrum sunscreens with high sun protection factor, which is not informative on efficacy in the absorption spectrum of protoporphyrin IX, spanning visible radiation and peaking around 408 nm. Photoactivation of protoporphyrin IX is responsible for painful skin photosensitivity in erythropoietic protoporphyria.The authors assessed the protective efficacy of six sunscreens in vitro in the absorption spectrum of protoporphyrin IX.Method: Transmittance measurements were performed in the 300–850 nm wavelengths on samples of six photoprotective products applied to polymethyl methacrylate plates. Porphyrin protection factor was calculated in the 300–700 nm region to provide a measurement for the efficacy of each product based on the action spectrum of protoporphyrin IX.Results: Product A showed the highest porphyrin protection factor among tested products with a median value of 4.22. Product A is a sunscreen containing organic filters, titanium dioxide and synthetic iron oxides, pigmentary grade active ingredients that absorb visible radiation. Other products showed inefficient protection in the visible, with transmittance between 75 and 95% at 500 nm. The low porphyrin protection factor of inorganic filter product B was attributed to particle micronization, as declared by the manufacturer.Conclusion: Adding porphyrin protection factor to sunscreen labeling could help patients with erythropoietic protoporphyria and other photosensitivity disorders identify products tailored on their specific needs. The development of sunscreens providing protection from visible radiation and excellent cosmetical tolerability could improve the lifestyle of patients with erythropoietic protoporphyria.

Synthesis, characterization, and femtosecond third-order optical nonlinearity of Au@Ag core–shell nanoparticles

In this work, the Au@Ag bimetallic core–shell nanostructures were synthesized by a seed-mediated growth. The crystal structure, morphology, elemental composition, atomic concentration, and absorption spectrum of the as-synthesized nanoparticles were characterized by means of X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible linear absorption spectrum, respectively. The femtosecond third-order optical nonlinearities of nanoparticle dispersions were investigated by carrying out the femtosecond-pulsed [Formula: see text]-scan measurements at 800[Formula: see text]nm. The experimental results indicate that Au@Ag core–shell nanoparticles exhibit the positive refractive nonlinearity and negative absorptive nonlinearity. The third-order nonlinear refraction indexes of Au and Au@Ag nanoparticles are measured to be [Formula: see text] and [Formula: see text][Formula: see text]cm2/GW, respectively. The results show that the bimetallic nanoparticle has potential possibility in nonlinear photonic applications.

Study on non-local effects in dimers of circular and elliptical cross-sections

The nonlocal effects of dimers consisted of two cylinders are studied, whose cross section is elliptical. Importantly, the results with dimers whose cross section is circular are compared. For comparison, the curvature of the ellipse is set the same with the circle, and four different geometries are considered. The electric field enhancement at the gap center and the absorption spectrum of the dimers are calculated. For the second geometry, either the electric field enhancement at the gap center or the absorption spectrum is approximately calculated using the first geometry, the frequencies corresponding to the peaks are totally different. Similarly, for the fourth geometry, either the electric field enhancement at the gap center or the absorption spectrum is approximately calculated using the third geometry, the disciplines of the peak values change as radius of curvature increases are totally different.

Vibronic absorption spectra and excited states of acridine red dye in aqueous solution: TD-DFT/DFT study

The vibronic absorption spectra of acridine red (AR) xanthene dye in an aqueous solution using 40 hybrid functionals, the 6-31++G(d,p) basis set, and the IEFPCM solvent model were calculated. It turned out that the O3LYP functional provided the best agreement with the experiment in the positions of the main maximum and the short-wavelength subband (shoulder). The calculations showed that this shoulder is vibronic. At the same time, the shoulder intensity in the calculated spectrum turned out to be lower than in the experimental one. Apparently, insignificant dimerization, which occurs even at low concentrations of the dye in solution, contributes to the shoulder of the experimental absorption spectrum. Various parameters of the AR cation in the ground and excited states (IR spectra, atomic charges, dipole moments, and transition moment) were calculated. Maps of the distribution of electron density and electrostatic potential have been built. The influence of the strong hydrogen bonds of the dye with three water molecules on the absorption spectrum was analyzed. It has been shown that these bonds are strengthened upon AR excitation. The strengthening of two hydrogen bonds with water upon excitation leads to a lowering of the potential energy surface of the excited state, which causes a decrease in the excitation energy (i.e., an increase in the wavelength of the absorbed photon) as compared to a purely implicit specification of the water environment. Therefore, explicit assignment of waters strongly bound to the dye leads to spectrum redshift.