a sulfonamide fragment but also conformational equilibrium among these types of intramolecular interactions are essential for the manifestation of high efficiency in suppressing HIV-infection in cell culture.Introduction. Many derivatives of aminophenols (AP) are known to be effective antioxidants that are capable of changing the course of free-radical processes [1]. These compounds also have traditional applications as stabilizers of industrial organic materials and as food preservatives [2,3]. They exhibit high efficiency for prevention and treatment of pathologies due to disorders in the human antioxidant system [4] and as antiviral agents against herpes simplex and flu A virus [5][6][7][8][9]. AP derivatives that suppress HIV-infection in cell culture were recently synthesized [10].The pharmacological properties of AP are related to their effect on the course of free-radical processes in biological systems. Steady-state radiolysis and IR spectroscopic methods found that the antioxidant properties of AP are enhanced when the hydroxyls in the molecules are free and diminished upon forming various types of intramolecular hydrogen-bonds (IHB) [11]. As a rule, reactions involving active oxygen species occur nonselectively. Their occurrence in biological systems can damage both the cells themselves and viruses incorporated into them if highly active antioxidants are used.The question of which AP derivatives that are added to biological systems can change the course of free-radical reactions so that an effective and stable antiviral effect is obtained remains open. Therefore, it is important in principle to study properties of individual molecules such as the ability to form IHB because the type of IHB found in the AP is frequently related to their antiradical and antiviral activity [12,13].Herein IR-Fourier spectroscopy is used to study intramolecular interactions (IMI) in CCl 4 solutions of five structurally similar AP derivatives, 4,6-di-tert-butyl-2-(phenylamino)phenol (AP I), N-(3,5-di-tert-butyl-2-hydroxyphenyl)acetamide (AP II), N-(2-hydroxy-3,5-di-tert-butylphenyl)-4-methylbenzenesulfonamide (AP III), N-(2-methoxy-3,5-di-tert-butylphenyl)-4-methylbenzenesulfonamide (AP IV), and N-(2-hydroxy-3,5-di-tert-butylphenyl) methanesulfo-namide (AP V):

Mathematical relations defining distortions from true values of photoluminescence intensities that arise during measurements due to absorption at the luminescence frequencies are derived for various experimental designs. The adequacy of the derived relations is confirmed by special experiments. The relations allow one to define correctly the contours, widths, and maximum frequencies of luminescence bands of absorbing media and to deduce absorption coefficients of substances from luminescence measurements.Introduction. Luminescent methods are commonly used to solve scientific and practical problems [1,2]. A mathematical relation describing the law of formation of a photoluminescence (PL) spectrum of each of the components in a substance that have overlapping absorbance bands was obtained without limitations on the optical density [3]. The resulting relation makes it possible to determine absorption coefficients of components (including those without luminescence), absorption contours, and ratios of PL quantum yields. Use of these capabilities requires measurements of actual PL intensities, which may be made in relative units. However, they should not be distorted by any associated factors, for example, absorption in the PL frequency range.PL and absorption bands of different components and a single component may overlap under actual conditions of scientific research and analytical measurements although the total optical density of absorption is not negligible compared with unity. Under such conditions the measured PL intensity does not correspond to the true intensity. Therefore, absorption may produce errors in the determination of contours, central frequencies of PL bands, and calculations that use the intensities. This problem has been discussed relative to various experimental designs in all monographs on luminescent methods for studying a substance (e.g., [1, 2, 4]). Certain qualitative empirical recommendations are given in those references. It is also concluded that methods for accurate determination of corrections that would allow distortions of PL intensities caused by absorption to be taken into account do not exist [2,4]. A fundamental solution of the situation proposes performing investigations at low optical densities of absorption, which in many instances is impossible. For example, optical densities of absorption were several units for investigations of color centers in dielectrics even for sample thicknesses of the order of 1 mm [5].Herein mathematical relations allowing distortions of PL intensities arising from absorption effects to be taken into account are derived. Various experimental designs that were classified [2, 4] as illumination at a right angle, illumination in line, and frontal illumination are examined. The adequacy of the resulting relations is demonstrated by measurements of Rhodamine 6G luminescence, the fluorescence and absorption spectra of which overlap considerably. The relations are used in studies of radiation color centers in lithium fluoride crystals to determine the conto...

Approximately 102‐fold enhancement of Raman scattering by ultramarine microcrystals is reported by means of interaction with silver nanoparticles in films and powders. Theoretical modeling predicts the maximal 1010‐fold enhancement in close vicinity of a silver spherical nanoparticle (0.24 nm) with rapid decay of enhancement factor to 1 in the range of approximately 50 nm. Experimental enhancement factor is treated as overall effect within the small portion of every microcrystal in the close vicinity of silver nanoparticle(s). The results are considered as an important extension of traditional surface enhanced molecular Raman spectroscopy towards bigger inorganic probes. Copyright © 2012 John Wiley & Sons, Ltd.

Semiconductor self-assembled Ge-on-Si quantum dot structures coated with Au film were successfully employed as surface-enhanced Raman scattering (SERS) substrates to characterize ultramarine blue inorganic art pigment. To assign the bands and to reveal the enhancement mechanisms, the quantum-chemical calculations of vibration spectra of linear and cyclic model compound of SiO 4 and AlO 4 tetrahedra were carried out. The overtones are observed in the SERS spectra and the unharmonicity constants were estimated. The development of a series of new bands in SERS spectra of ultramarine are discussed in terms of electro-optical unharmonicity.