The design of new molecules for photochemical studies typically requires knowledge of spectral features of pertinent chromophores beginning with the absorption spectrum (λabs ) and accompanying molar absorption coefficient (e, m-1 cm-1 ) and often extending to the fluorescence spectrum (λem ) and fluorescence quantum yield (Φf ), where the fluorescence properties may be of direct relevance or useful as proxies to gain insight into the nature of the first excited singlet state. PhotochemCAD databases, developed over a period of 30 years, are described here. The previous databases for 150 compounds have been expanded to encompass 339 compounds for which absorption spectra (including e values), fluorescence spectra (including Φf values) and references to the primary literature have been included where available (552 spectra altogether). The compounds exhibit spectra in the ultraviolet, visible and/or near-infrared spectral regions. The compound classes and number of members include acridines (21), aromatic hydrocarbons (41), arylmethane dyes (11), azo dyes (18), biomolecules (18), chlorins/bacteriochlorins (16), coumarins (14), cyanine dyes (19), dipyrrins (7), heterocycles (26), miscellaneous dyes (13), oligophenylenes (13), oligopyrroles (6), perylenes (5), phthalocyanines (11), polycyclic aromatic hydrocarbons (16), polyenes/polyynes (10), porphyrins (34), quinones (24) and xanthenes (15). A database of 31 solar spectra also is included.

Database of Absorption and Fluorescence Spectra of >300 Common Compounds for use in PhotochemCAD.

Studies on structure and electronic properties of amorphous nitrogenated carbon films prepared in dual electron cyclotron resonance–radio frequency plasma from a mixture of methane and nitrogen are presently reported. These films are characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS), electrical conductivity measurement, and optical absorption spectroscopy. Symmetry breaking of aromatic rings are at a very small amount of nitrogen incorporation is understood from FTIR spectra. The relative contribution of C=N and C–N bonds is found to change with the variation of the nitrogen content in the samples, which shows a similar trend with the shift of the G peak to a higher wave number and the increase of the ID/IG ratio. From decomposition of XPS C 1s and N 1s peaks a three-phase model of CN bonds is proposed. UPS valence band spectra obtained by using a Helium II source, are decomposed into p-...

Spectroscopic determination of the structure of amorphous nitrogenated carbon films

Suppressing self-discharge of supercapacitors via electrorheological effect of liquid crystals

Dielectric study of the molecular mobility and the isothermal crystallization kinetics of an amorphous pharmaceutical drug substance

Polarised Raman spectroscopy is a vibrational spectroscopic technique that is used widely for the chemical and physical analyses of materials since it is both non-destructive and suitable for remote analysis. In particularly over the last 40 years, the technique has been developed and applied for the study of molecular orientation distributions in polymers. Compared to other analytical techniques, polarised Raman spectroscopy has the following advantages, (1) quantitative and precise measurement of molecular orientation distributions, and (2) study of these distributions in both the crystalline and amorphous phases. Knowledge obtained from the technique is of both academic and industrial interest to study relationships between microstructure and macroscopic physical properties in polymers. In this paper, polarised Raman spectroscopy is reviewed with regard to the study of molecular orientation distributions in polymeric materials. The basis of polarised Raman scattering is first described, and this is followed by the procedure for obtaining spectra. It is shown how Raman scattering intensities for different polarised scattering geometries can be interpreted to give parameters and functions representing quantitative measures of the degree of molecular orientation. Factors affecting the evaluation of these parameters are also summarised. Finally, the usefulness of the technique is demonstrated by practical applications including a study of molecular orientation distributions in poly(ethylene terephthalate) (PET) fibres.

Review Polarised Raman spectroscopy for the study of molecular orientation distributions in polymers

The complex dielectric permittivity of right-handed isooctyloxycyanobiphenyl (IOOCB) has been studied in the frequency range 10-1−105 Hz and over a wide temperature range. On cooling the isotropic liquid a supercooled liquid is formed that becomes a glass below 220 K. On heating the glass, the material crystallized at about 250 K and remelted at 285 K. The dielectric α-relaxation in the isotropic liquid was found to conform with the Vogel−Fulcher Tamman equation for its average relaxation time and the Kohlrausch−Williams−Watts function for its spectral line shape. The isothermal crystallization of the supercooled liquid to form a crystalline solid was monitored by dielectric relaxation spectroscopy, and the Avrami exponent was found to be 1.51 at a crystallization temperature of 263 K.

W. Jeremy Jones

Papers

Molecular Dynamics and Crystallization Behavior of Chiral Isooctyloxycyanobiphenyl as Studied by Dielectric Relaxation Spectroscopy

Determination of the thickness and optical constants of thin films from transmission spectra

On the determination of order parameters for homogeneous and twisted nematic liquid crystals from Raman spectroscopy

Rotational reorientation dynamics of nile blue A and oxazine 720 in protic solvents

Intermolecular photoinduced proton transfer in nile blue and oxazine 720