A catalytic activity model based on the structural defects of catalysts II. Alumina catalyst characterisation by radioluminescence method

The characterisation by radiothermoluminescence /RTL/ method of alumina TA 600 catalyst used for 1-butene isomerisation in cis- and trans-2-butene is described. The glow curve, the RTL parameters and the catalyst-reactant radiative coupling evidenced by RTL method are presented. Using the correlation between catalytic activity and RTL data a catalytic activity model is suggested. On the basis of such a model the importance of the structural defects of the catalyst and/or support for the catalytic activity is explained.     

Radiothermoluminescence of surface layers of n-tetracosane crystals

A radiothermoluminescence (RTL) curve of surface layers of n-tetracosane crystals has been obtained, which appear to be similar but not identical to the RTL of the evacuated sample or the sample with CCl₄. Since CCl₄ does not penetrate the crystal, the difference between the RTL curves of the evacuated sample and the one with CCl₄ represents the RTL of crystal surface layers. The RTL curve of tetracosane with the scavenger is that of RTL of intracrystalline areas of the alkane. The difference in shape between the surface and bulk RTL curves is manifested well in the ratio of the RTL curves for the surface and the evacuated sample.     

Correlations between radiothermoluminescence and the catalytic properties of some active aluminas. A catalysis model

The present paper reports correlations between data obtained by the radiothermoluminescence (RTL) method and the catalytic activity of active aluminas. The correlations between the intensity of RTL signals, glow peak temperatures and activation energy obtained by RTL and the data referring to the history, catalytic activity and activation energy of the catalyzed reaction, require the use of RTL as a supplementary method in the characterization of catalysts. The results underline the role of structural defects in the catalyst (or support) on the catalysis as illustrated by the present model.     

Optical dating of the hydroponic farm at Korea

Red thermoluminescence (RTL) using a SAR (single-aliquot regenerative-dose) method has been applied to artificial ceramic samples to determine retrospective doses, and to estimate the naturally accumulated doses for natural quartz grains. In the RTL measurement of quartz grains, several preheating effects on equivalent doses around 200 °C were examined for extracted quartz grains from tephra (Medeshima, Miyagi). Preheating at 200 °C for 10 seconds gave better reproducibility and response than those for preheating at 80 °C for 5 minutes. The RTL/SAR method was used to quartz grain samples extracted from pottery pieces with preheating at 200 °C for 10 seconds.     

RTL Investigation on the Radiochemical Oxidation of Polyolefins

High energy radiation causes deep modification of exposed polymers. In the irradiated polymers, the main macroscopic process is the formation of free radicals. The “cooled” electron distribution at the temperature of liquid nitrogen will develop the existence of various electron gaps with certain depths by smooth heating up to room temperature. In this paper, low density polyethylene, high density polyethylene and polypropylene were subjected to the action of gamma rays for causing structural modifications. The glow curves of quantum emission were recorded by slow heating from 106 to 286 K. The characteristic shoulders were obtained, which were ascribed to various electron traps consisting of unsaturation or carbonyl groups. For depicting the influence of molecular structures, the influence of CH₃ number/100 carbon atoms on the intensity of radiothermoluminescence (RTL) signal was studied on three types of LDPEs. A sharp decrease of maximum RTL intensity at advanced branching was pointed out. A mechanism of RTL emission is based on the present measurements.     

Red-thermoluminescence dating using quartz grains extracted from a roof-tile of an old Japanese temple

Red-thermoluminescence (RTL) dating was applied to quartz grains from a flat roof-tile of “Shin-Yakushiji” temple, Nara, built in Japan, probably 1258 years ago. Based on overlapping patterns with other roof-tiles, one flat roof-tile was separated into several zones. The equivalent doses were accurately evaluated to be 4.4–5.1 Gy for each zone. The evaluation of annual doses has been done under the consideration of overlapped numbers of roof-tiles and soil layers under the roof-tiles. Evaluated RTL ages were in good agreement with the construction date of the temple. The present evaluated age was the youngest one within several ages we previously have been deduced from the RTL dating.     

Radiothermoluminescence of <Emphasis Type="Italic">n</Emphasis>-eicosane mixtures with <Emphasis Type="Italic">n</Emphasis>-tetracosane: Effect of mixture composition

Radiothermoluminescence (RTL) curves of mixtures of C20 and C24 n-alkanes have been deconvoluted into the curves of crystalline and disordered regions, and their change depending on the mixture composition has been analyzed. The shape of the total RTL curve of the mixture regardless of the its composition is fundamentally different from that shape of the sum of the curves of the individual components taken in the relevant ratios. The difference becomes noticeable at as low a C20 amount in the mixture as 2% and is manifested in the disappearance of the intense RTL peaks of the individual components and appearance of new intense peaks in temperature intervals other than those of the RTL peaks of the components. It has been shown that these changes correlate with changes of the crystalline structure of the mixture: a new crystalline structure other than the structure of any of the individual components emerges and the mixture becomes amorphous. High selectivity of charge trapping in disordered regions of the mixture has been revealed: the contribution of RTL of the disordered regions to the total curve is many times higher than their volume fraction in the mixture. This selectivity might be due to an increase in concentration of defects in the unordered regions of the mixture in comparison with their concentration in the pure alkanes. These defects are traps for electrons that are accessible to acceptors introduced into the mixture.     

Optically stimulated luminescence (OSL) and thermoluminescence (TL) measurements on red TL (RTL) quartz samples using a new automated OSL/TL measuring system

A new automated OSL/TL measuring system, equipped with a small X-ray irradiator applicable to a single-aliquot method, has been developed. To ensure cross check between OSL and RTL, the naturally accumulated doses evaluated with OSL and RTL measurements were compared. The results nearly agreed with each other, although the ages estimated from the experimental data were different from the real ages of Shin-Yakushiji temple because of the uncertainty of the annual dose. Nevertheless, it was concluded that the application of this system to the dating could be performed owing to uses of the luminescence measurements.     

Changes in the radiothermoluminescence curve of crystalline regions of polyethylene during storage of its irradiated samples in liquid nitrogen

It has been shown that radiothennoluminescence (RTL) ofthe crystalline regions ofpolyethylene (PE) irradiated in liquid nitrogen is due to the recombination of charges trapped by defects inside the crystallites. The presence of shallow charge traps (less than 0.15 eV) leads to the appearance of one of the main features of the RTL of PE crystalline regions, which consists in reduction in the RTL intensity over the entire temperature range of 100–300 K during the storage of irradiated samples in liquid nitrogen.     

The relationship between phase transition and luminescence in simple hydrocarbons

A satisfactory correlation between the temperature of radiothermoluminescence (RTL) peaks and phase transition points has been found in simple hydrocarbons. RTL peaks due to a glass transition phenomenon are observed clearly in ethane, propane and other compounds. These compounds were deposited rapidly onto a cooled cooper surface from the vapour (the vapour condensation method). A method for studying phase transitions in several substances by means of RTL is proposed.     

Radiothermoluminescence of tetiamethylene sulfoxide

Radiothermoluminescence (RTL) and ESR spectra of tetramethylene sulfoxide (TMSO) irradiated by X-ray and⁶⁰Co γ-ray radiation have been studied at 77 K. The temperatures of RTL maxima were correlated with the changes in color of specimens and the shape of the ESR spectral lines. The temperatures at which maxima or inflections are observed (depending on the kind of irradiation, dose, and introduced additives) were determined: 90, 115, 125, 133, 145, and 155 K. A signal of the TMSO radical cation was observed in the ESR spectrum (a singfet with g = 2.008±0.001 and δH = 12 Oc); it completely disappeared after the cessation of luminescence at the maximum at 133 K. An analogous result is achieved by illumination of the specimen with maximum effect in the yellow-green region of the spectrum. Activation of RTL by the UO₂ ²⁺ and Tb³⁺ ions was studied. Their thermal deactivation was correlated with molecular mobility manifested in RTL.     

Mechanism of radiothermoluminescence of crystalline tetracosane

Radiothermoluminescence (RTL) of tetracosane irradiated in liquid nitrogen with γ-rays is due to trapped charges. At doses below 2 kGy, all processes leading to RTL are localized in tetracosane intracrystalline areas in traps with a depth of 0.1–2.0 eV that were present in tetracosane before irradiation. With increasing the dose, radiation-induced traps with a depth of 3 eV or higher appear in addition. At the same time, part of the charges reach the surface and become available for interaction with an electron acceptor. The presence of shallow traps (less than 0.15 eV) leads to a decrease in the RTL intensity over the entire temperature range from 100 to 300 K during storage of irradiated samples in liquid nitrogen.     

Four-way kinetic-excitation-emission fluorescence data processed by multi-way algorithms. Determination of carbaryl and 1-naphthol in water samples in the presence of fluorescent interferents

Four-way data were obtained by recording the kinetic evolution of excitation-emission fluorescence matrices for samples containing the analytes carbaryl and 1-naphthol, two widely employed pesticides, in the concentration ranges 0-363 μg L⁻¹ and 0-512 μg L⁻¹, respectively. The reaction followed was the alkaline hydrolysis of carbaryl to produce 1-naphthol, a fact which introduced strong linear dependencies and multi-linearity losses in the analyzed system. Data processing was performed with unfolded partial least-squares combined with residual trilinearization (U-PLS/RTL) and also with a suitably initialized and restricted parallel factor model (PARAFAC), combined with calibration based on multi-linear regression. U-PLS/RTL is shown to be significantly simpler in its implementation and to provide similar figures of merit. The applied chemometric strategy is able to successfully determine the analytes in water samples containing uncalibrated interferences, such as other commonly employed agrochemicals and also a naturally occurring background signal.     

Retention Time Locking in the Determination of Narcotic Drugs by Chromatography and Chromatography–Mass Spectrometry

The use of retention time locking (RTL) in the development of unified procedures for the detection and quantitative determination of drugs in biological fluids was considered. With consideration for the use of RTL, a chromatographic procedure with flame-ionization and mass-selective detection was developed for the detection and quantitative determination of opiates and their synthetic analogs; phenylalkylamine derivatives; cocaine; ketamine; and other narcotic drugs, their derivatives, and metabolites in urine. The analytical ranges for chromatography–mass spectrometry were 0.05–1000 and 0.005–1000 g/mL under the conditions of total ion current (TIC) scanning and selected ion monitoring (SIM), respectively. With flame-ionization detection (GC–FID), the analytical range was 0.5–1000 g/mL.     

Distinctive features of radiothermoluminescence curves of alkanes

Radiothermoluminescence (RTL) curves of alkanes have a special character: each curve is specific to a particular alkane and thus can be used for identifying it. The RTL curve of a mechanical mixture of two alkanes quantitatively coincides with the sum of the curves for the individual components of the mixture. The additivity property is lost for the mixtures prepared from a melt or chloroform solution. The loss is due to the change of the crystalline state of the mixture. An X-ray study shows that the X-ray diffractogram of such a mixture does not coincide with the sum of diffractograms of the individual components (even the crystal lattice type changes).     

Ion recombination in PMMA doped with pyrene as observed by wavelength selected radiothermoluminescence

Radioluminescence from electron-irradiated poly(methyl methacrylate), PMMA, pure and doped with pyrene (Py) was investigated in the temperature range of 77-295 K. The spectra of emission were recorded, and temperature dependences of radioluminescence intensities at chosen wavelengths were examined using a novel wavelength-selected radiothermoluminescence (WS RTL) technique. The correlation between the WS RTL peaks and matrix relaxation temperatures were found. The experimental results were explained in terms of solute radical ion recombination leading to the Py monomer and excimer fluorescence. The luminescence results were correlated with the decay of Py ions as observed by spectrophotometric absorption method.     

Effect of the structure of frozen solutions of H2SO4 on radiothermoluminescence

A pronounced effect of structural heterogeneity (cracks) of glass-like solutions of 4.9M H₂SO₄ on their radiothermoluminescence (RTL) was found. In perfect glasses one RTL peak was observed at 115 K. Additional luminescence peaks appeared at 165, 195, and 240 K in glasses having cracks. The effect observed was explained by elevated thermal stability of the SO₄ ^– radical stabilized on the surface of sulfuric acid crystal hydrates: H₂SO₄ · 4H₂O and H₂SO₄· 6.5H₂O.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1566–1568, June, 1996.     

Evaluation of unfolded-partial least-squares coupled to residual trilinearization for four-way calibration of folic acid and methotrexate in human serum samples

The combination of unfolded-partial least-squares (U-PLS) with a recently proposed separate procedure, known as residual trilinearization (RTL), has been successfully employed for four-way data calibration. The chemometric method employs the evolution of excitation-emission matrices (EEMs) with time, for the resolution of folic acid-methotrexate mixtures, in human serum samples. The fluorogenic products monitored correspond to the oxidation of the studied analytes with potassium permanganate, in slightly acidic medium. The reaction is developed in 7 min and followed using a fast-scanning spectrofluorimeter, capable of recording each complete EEM in 12 s. This allows the acquisition of 10 successive EEMs, at different reaction times, during the development of the oxidation reaction, given rise to the four-way data set employed. The procedure, which had been previously reported for urine determination, is extended to serum analysis in this work. The combination of U-PLS/RTL is providing enhanced predictive results in comparison with standard methods as PARAFAC and N-PLS, in the presence of human serum, where significant unexpected components and or inner filter effects may occur.     

Radioluminescence of ice containing MgCl2 and CaCl2

The efficiency of electron trapping and reactions in ice containing MgCl₂ or CaCl₂ (0.5–5 mol dm^-3) and γ-irradiated at 77 K was investigated by isothermal—(ITL) and radiothermo— (RTL)—luminescence.Both ITL and RTL emissions are influenced by solute concentration in a similar way, revealing a maximum at ca 3.5 mol dm^-3 MgCl₂ and at ca 2.5 mol dm^-3 CaCl₂.The RTL emission exhibits two broad peaks. The low temperature peak RTL_I is only slightly dependent on matrix composition, whereas the position of the high temperature peak RTL_II shifts with glass transition point of the matrix.The influence of scavengers NaNO₃ and CH₃OH on radioluminescence (RL) was also investigated and found to be dependent on the nature of the cation.It is suggested that the RL emission is due to radiative recombination of e^-_t (e^-_ir, e^-_vis) with H atoms, metal cations and Cl^-₂ ion radicals.