[en] One important potential application of ionic liquids (IL) is as a medium for processing of spent nuclear fuel. It is therefore imperative to study the radiation chemistry of ILs, not only to determine their radiolytic products and degradation pathways, but also to describe how the radiolysis may affect or interfere in the separation processes. An understanding of Radiation Chemistry of ILs would also facilitate general chemical reactivity in this medium, which will aid in the development of energy production, chemical industry and environmental applications. We were interested in understanding how the specific physical properties of ionic liquids influence the dynamical processes that determine the stability and lifetimes of reactive intermediates and thereby affect the courses of chemical reactions and product distributions in this medium. In the pulse radiolysis experiments on Imidazolium based ILs (1-Ethyl-3-methylimidazolium) (Ethyl sulphate) or (Emim) (EtSO4) under oxidizing or reducing conditions, we observed a transient peak at 320 nm. This absorption may be due to the formation of a radical as electron reacts with the imidazolium cation of the ionic liquid. We have not observed hydrated electrons because the electron reacts with imidazolium cation very fast. Pulse radiolysis experiments have also been performed on FAP (Fluoro Alkyl Phosphates) ILs having imidazolium as cation e.g. (1-Ethyl-3-methylimidazolium) (tris(pentafluoroethyl) trifluorophosphate) or FAP-1 and (1-(2-HydroxyEthyl-3-methylimidazolium) (tris(pentafluoroethyl) trifluorophosphate) or FAP-2. FAP-ionic liquids show an excellent hydrolytic stability, low viscosity and high electrochemical and thermal stability that makes them attractive for use in electrochemical devices and as a new media for application in modern technologies and chemical synthesis. The time-resolved transient spectra of FAP ILs were recorded and characterized under different experimental conditions. The formation and decay constants of the transient species were determined as well as their variation at different radiation doses. These ILs seem to be more radiation resistant than other ILs probably because of their less hygroscopic nature. (author)

[en] Radiation chemistry of porphyrin derivatives has been given much attention in recent years. Although till date photo dynamic therapy (PDT) with Hematoporphyrin (HP) has already proved its effectiveness in the treatment of cancer, the molecular mechanisms by which this therapy-destroys tumour cells as well as its optimal physical parameters are still not fully understood. Thus it becomes necessary to understand the interaction of different free radicals with HP. Pulse radiolysis studies have been performed to understand the interaction of different free radicals with HP. The product formation along with bleaching and presence of a number of transients makes it difficult to pin point the mode and site of free radical attack. The radiation-induced formation of various transients (HP-OH, HO^-, HP⁺) in aqueous solution was investigated at various pHs by pulse radiolysis technique by means of N₃, O^- and CCl₃O₂ radicals with and without triethyl-amine, under different dose conditions. The observed intermediates are characterized by their kinetic and spectroscopic data. The absorption spectrum of each transient could be differentiated from each other by their absorption maxima, extinction coefficients and kinetics. A clear indication of product formation has also been observed by employing continuous electron pulse and the solution shows a green coloration. It is conceivable that under certain conditions, similar transients may be produced when HP is used as a sensitizer in radiation chemotherapy of cancer patients. Our study may throw some light into the breakdown mechanism of haemoglobin to BV in addition to the understanding of free radical interaction of HP. (author)

[en] Impending applications of room temperature ionic liquids (RTILs) in the areas involving high radiation fields (nuclear fuel cycle and space) requires microscopic understanding of the radiation induced perturbations in their molecular structure. Here in, the photophysical properties of the post-irradiated imidazolium ILs revealed significant changes in their molecular structure and bonding interactions, however their physicochemical properties do not change significantly, even at high absorbed doses. (author)

[en] Black shale is the unconventional resource of uranium. Recovery of uranium from black shale has been carried out by the following steps: i) size reduction, ii) leaching of uranium in the aqueous medium, iii) fluoride ion removal, iv) solvent extraction of uranium from the aqueous leach solution, v) scrubbing of the loaded solvent after extraction to remove impurities as much as possible and vi) stripping of uranium from the loaded organic into the aqueous phase. Leaching of black shale has been carried out in hydrochloric acid. Free acidity of the leach solution has been determined by potentiometric titration method. Removal of fluoride ions has been done using sodium chloride. Solvent extraction has been carried out by both tributyl phosphate and alamine-336 as extractants. Scrubbing has been tried with oxalic acid and sulphuric acid. Stripping with sodium carbonate solution has been carried out. Overall recovery of uranium is 95%. (author)

[en] The geological resources of coal in India are more than 308 billion tonnes upto a depth of 1200 m, out of which proved reserve has been reported at around 130 billion tonnes. There is an increasing requirement to increase the energy extraction efficiency from coal as the developmental prospects of India increase. Underground coal gasification (UCG) is a potential mechanism which may be utilized for extraction of deep-seated coal reserves. Some previous studies suggest that lignites from Gujarat and Rajasthan, along with tertiary coals from northeastern India can be useful from the point of view of UCG. We discuss some geological literature available for these areas. Coming to the rock mechanics perspectives, during UCG the rock temperature is considerable high. At this temperature, most empirical models of rock mechanics may not be applied. In this situation, the challenges for numerical modelling of UCG sites increases manifold. We discuss some of the important modelling geomechanical issues related to UCG in India. (paper)

[en] CdSe quantum dots (QDs) were synthesized by a rapid and one step templated approach inside the water pool of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) based water-in-oil microemulsions (MEs) via electron beam (EB) irradiation technique with high dose rate, which favours high nucleation rate. The interplay of different experimental parameters such as precursor concentration, absorbed dose and ${\mathcal{W}}_0$ values (aqueous phase to surfactant molar ratio) of MEs were found to have interesting consequences on the morphology, photoluminescence (PL), surface composition and carrier recombination dynamics of as-grown QDs. For instance, highly stable ultrasmall (∼1.7 nm) bluish-white light emitting QDs were obtained with quantum efficiency (η) of ∼9%. Furthermore, QDs were found to exhibit tunable broadband light emission extending from 450 to 750 nm (maximum FWHM ∼180 nm). This could be realized from the CIE (Commission Internationale d’Eclairage) chromaticity co-ordinates, which varied across the blue region to the orange region thereby, conferring their potential application in white light emitting diodes. Additionally, the average PL lifetime $(⟨\mathrm{\tau <!--\; ??\; -->}⟩)$ values could be varied from 18 ns to as high as 74 ns, which reflect the role of surface states in terms of their density and distribution. Another interesting revelation was the self-assembling of the initially formed QDs into nanorods with high aspect ratios ranging from 7 to 20, in correspondence with the ${\mathcal{W}}_0$ values. Besides, the fundamental roles of the chemical nature of water pool and the interfacial fluidity of AOT MEs in influencing the photophysical properties of QDs were investigated by carrying out a similar study in CTAB (cetyltrimethylammonium bromide; cationic surfactant) based MEs. Surprisingly, very profound and contrasting results were observed wherein $⟨\mathrm{\tau <!--\; ??\; -->}⟩$ and η of the QDs in case of CTAB MEs were found to be at least three times lower as compared to that in AOT MEs. (paper)

[en] This paper examines the applicability of femtosecond laser induced breakdown spectroscopy for the compositional analysis of vitrified waste product (VWP) used for immobilization of high level radioactive liquid waste (HLW). Analysis of the emission spectra allowed the identification, not only of the major components but also most of the fission products within the HLW. (author)

[en] Optical absorption and fluorescence (FL) spectra of 2-, 6-, 7-, 8-hydroxyquinolines (2-,6-,7- and 8-HQs) have been measured at room temperature in the wide range of solvents of different polarities, dielectric constant and refractive index. The ground state dipole moment ( µ _g) and excited state dipole moment ( µ _e) of 2-, 6-, 7- and 8-HQs were obtained using solvatochromic shift (SS) methods and microscopic solvent polarity parameters (MSPP). Change in the dipole moment (Δ µ ) between the ground and photo-excited states was estimated from SS and MSPP methods. DFT and TDDFT based theoretical calculations were performed for the ground and excited states dipole moments, and for vertical transitions. A significant enhancement in the excited state dipole moment was observed following photo-excitation. The large value of Δ µ clearly indicates to the charge-separation in the photo-excited states, which in turn depends on the position of the hydroxyl group in the ring. (paper)

[en] Femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) gives access to ultrafast molecular dynamics. However, femtosecond laser pulses are spectrally broad and therefore coherently excite several molecular modes. While the temporal resolution is high, usually no mode-selective excitation is possible. This paper demonstrates the feasibility of selectively exciting specific molecular vibrations in solution phase with shaped fs laser excitation using a feedback-controlled optimization technique guided by an evolutionary algorithm. This approach is also used to obtain molecule-specific CARS spectra from a mixture of different substances. The optimized phase structures of the fs pulses are characterized to get insight into the control process. Possible applications of the spectrum control are discussed.

[en] Coal gasification processes are crucial to decarbonisation in the power sector. While underground coal gasification (UCG) and integrated gasification combined cycle (IGCC) are different in terms of the site of gasification, they have considerable similarities in terms of the types of gasifiers used. Of course, UCG offers some additional advantages such as reduction of the fugitive methane emissions accompanying the coal mining process. Nevertheless, simulation of IGCC plants involving surface coal gasification is likely to give reasonable indication of the 3E (efficiency, economics and emissions) prospects of the gasification pathway towards electricity. This paper will aim at Estimating 3E impacts (efficiency, environment, economics) of gasification processes using simulation carried out in the Integrated Environmental Control Model (IECM) software framework. Key plant level controls which will be studied in this paper will be based on Indian financial regulations and operating costs which are specific to the country. Also, impacts of CO₂ capture and storage (CCS) in these plants will be studied. The various parameters that can be studied are plant load factor, impact of coal quality and price, type of CO2 capture process, capital costs etc. It is hoped that relevant insights into electricity generation from gasification may be obtained with this paper. (paper)