Solid Aromatic Hydrocarbons Research Articles

Relaxation of the Energy of Optically Excited States in the Carbon Quantum Dots

Recently, in connection with the achievement of new technological opportunities for fabrication nanostructured carbon-containing objects, namely, carbon quantum dots (CQDs) and clusters, studies of their various physical properties have been intensively carried out. Investigation of the photoluminescence (PL) properties of these objects have revealed a number of unique features: a wide structureless band of the radiation in the ultraviolet and visible regions of the spectrum, the fluorescent kinetics of the luminescence decay, and the independence of the longwavelength edge of the band on the excitation quantum energy. Similar features of PL are observed early in the different nanostructured carbon-containing materials. A common structural feature of the different nanostructured carbon-containing materials, such as CQD, liquid and solid aromatic hydrocarbons, amorphous hydrogenated carbon films, natural biopolymer – collagen is the existence of carbon sextets-aromatic rings connected by Van der Waals forces. This representation of the structure made it possible in the present work to develop a dimer-excimer model of radiative processes in the CQD. The studies are related to the prospects of application due to the unique combination of a number of key properties including tunable photoluminescence, important for the development of tunable lasers, biomedical applications where photostability, biocompatibility, molecular dimensions are essential to allow chemical connection with any biomolecule without compromising its functions. Further development of the theory of PL mechanisms in the CQD can help to identify other important features of the studied objects that will be of fundamental and practical importance.

Prediction of the solubility of aromatic hydrocarbons in supercritical CO 2 with EoS GE models

Prediction of the solubility of liquid and solid aromatic hydrocarbons in supercritical CO 2 with the recently proposed LCVM model and the MHV2 model is presented. Satisfactory results are obtained in the case of LCVM, considering in particular the uncertainty of experimental measurements at such low mole fraction values and the pure component properties involved. Correlation of existing data is also considered in order to determine the limits of our expectations for the prediction results, including cases where the required solid vapor pressures are not available.

Positron states between positronium and “free positron” states in condensed matter

Positronium (Ps), the bound state of an electron and a positron, is formed in many insulating solids and liquids. Recently, several cases of a transition from a Ps state to a non-Ps state have been observed. This has been found for liquid CS2 if the temperature is decreased from about −40 °C to the melting point, −110.8 °C. In some solid aromatic hydrocarbons, such as naphthalene, biphenyl and p-terphenyl, similar transitions occur upon decreasing the temperature. These transitions are unique in physics since Ps is the only bound state of two light particles in normal low-energy physics. Measurements of the positron lifetime, angular correlation of the annihilation radiation, Ps chemical reactions, and Zeeman effect of Ps give information on the transitions.

A Modified Vapor Saturation Method for Preparing Aqueous Solutions of Solid Aromatic Hydrocarbons

Abstract An excess quantity of a solid hydrocarbon is dispersed in water, and then air is bubbled through the aqueous phase to produce the solute vapor. The vapor is introduced into a separate water phase and circulated in a closed system. Aqueous solutions saturated with some solid aromatic hydrocarbons can be prepared in a relatively short time without any need to remove solute microcrystals. It can be confirmed whether the solubility obeys Henry’s law. The present method provides us with rough enthalpy of sublimation of a solute if its solubility follows Henry’s law. Biphenyl, naphthalene, phenanthrene, and anthracene were examined as solutes.

Reinterpretation of charge-transfer bands observed in the electroabsorption spectra of solid aromatic hydrocarbons

The second-derivative bands observed in the electroabsorption spectra of solid aromatic hydrocarbons are reinterpreted. The usual interpretation in terms of charge-transfer transitions can only hold in the presence of a perturbation that induces permanent dipole moments in charge transfer states. The possibility that imperfections induce such moments is investigated. Alternatively, the moments could possibly be induced by phonons.

The Vapor Saturation Method for Preparing Aqueous Solutions of Solid Aromatic Hydrocarbons

Abstract A new method to prepare aqueous solutions saturated with solid aromatic hydrocarbons by making use of solute vapor is presented. Air is bubbled through an organic solvent in which an excess quantity of a solid hydrocarbon to be studied has been added, and the resulting vapor is introduced into water and circulated in a closed system. An aqueous solution saturated with a solid solute can thus be prepared in a short time without any need to remove solute microcrystals. Of benzene, cyclohexane, and 1-octanol used as organic solvents, 1-octanol is most promising for this purpose. Solubilities in water at 25.0 °C of nine aromatic hydrocarbons have been measured: Naphthalene, biphenyl, anthracene, phenanthrene, fluoranthene, (o-, m-, p-)terphenyl, and triphenylene. This method can be used for these solutes except phenanthrene.

Temperature effects in positronium formation: Solid aromatic hydrocarbons

The temperature dependence of the probability of positronium formation was investigated in a series of solid aromatic hydrocarbons. The results are dis

The Ultraviolet Photoelectron Spectroscopy of Aliphatic Hydrocarbons and Tetramethylsilane in the Solid State

Abstract He I, Ne I, and Ar I ultraviolet photoelectron spectra were measured for solid hexane, 3-methylpentane, 2,2-dimethylbutane, neopentane, tetramethylsilane, cyclohexane, and 1-hexene deposited on a substrate at the temperature of liquid nitrogen. The spectra of all the compounds except hexane showed valence-band features. The threshold ionization potential was 7.6–8.9 eV, with a lowering of the threshold from the gas to the solid phase (polarization energy PS) of 1.2–1.8 eV. These PS values are in reasonable agreement with theoretical model calculations. To clarify the effect of intra- and intermolecular factors on PS, the observed PS values were compared with those of liquid-phase and solid-aromatic hydrocarbons. For compounds in which the bottom of the conduction band lies above the vacuum level, the polarization energy data showed that electrons with energies between these states are also emitted, possibly without any excitation of electrons to the conduction band in the bulk of the solid.

Temperature dependence of solubilities in water and heats of fusion of solid aromatic hydrocarbons

Temperature dependence of solubilities in water and heats of fusion of solid aromatic hydrocarbons

Heats of combustion of biphenyl, bibenzyl, naphthalene, anthracene and phenanthrene

The heats of combustion at 25°C of the following solid aromatic hydrocarbons were measured in a static-bomb calorimeter: ΔH°c(biphenyl, c)=–1494.22±0.33 kcal mole–1, ΔH°c(bibenzyl, c)=–1807.24±0.26 kcal mole–1, ΔH°c(naphthalene, c)=–1232.35±0.22 kcal mole–1, ΔH°c(anthracene, c)=–1689.17±0.41 kcal mole–1, ΔH°c(phenanthrene, c)=–1686.06±0.30 kcal mole–1. These results were used to derive the heats of formation of each of the hydrocarbons. The dissociation energies of the central (C—C) bonds in biphenyl and bibenzyl were calculated to be 97.5±4.5 and 56.6±4.0 kcal mole–1, respectively.