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Chemistry Group
Research Activities

The Chemistry Group is primarily engaged in basic research in thrust areas of radiation and photochemistry, superconductivity, metal hydrides, catalysis, solid state reactions and chemical synthesis and studies of organometallics, bioactive catalysts, chirons, peptides and bioactive compounds. Applied research is being actively pursued in thermodynamic studies particularly with reactor applications, diamond film deposition, dry combustion plasma, pheromones for pest control applications, radio pharmaceuticals, solvents for fuel reprocessing, etc. Basic and applied research is being carried out in analytical chemistry to develop newer and improved analytical methodologies.

Facilities have been set up for investigation of the dynamics of ultrafast chemical reactions in the femto second regime, and for generation and study of atomic clusters. The necessary capability for ultra trace analysis of high purity materials exists in the Group.

The Chemistry Group has an active reactor-oriented programme on decontamination studies, activity transport studies, studies related to biofouling etc.

Collaboration, consultancy and analytical services are being offered by the Chemistry Group to various units of BARC and DAE, government and private sector organisations, academic institutions and advisory bodies/organisations.

The Chemistry Group gives extensive help to Training and Management Division, BARC in teaching and practicals on several advanced topics.

1. Radiation and Photochemistry & Laser Induced Chemistry

The major facilities for studying these include pulse radiolysis equipment based on 7 Mev electron linear accelerator, laser flash photolysis equipments in nano, pico and femtosecond time domains. Using recently developed ultrafast pump-probe spectrometer based on CPM dye laser (see under Facilities), work on vibronic relaxation in laser dyes is in progress. Studies on electron transfer processes with dissociative electron transfer, inter and intramolecular H-bonding effects and their influence on photoprocesses in hydroxy substituted benzophenones have been carried out. Photophysical processes in substituted fullerenes (e.g. halo, hydroxy) is another area of intense activity. Gas phase dynamics studies on O (3P) with nitromethane and reactions of NO2 with free radicals like CF2Br and Br. are in progress.

Pulse radiolysis studies in nano and microsecond time domains are being carried out on biologically important systems like antioxidants (derivatives of curcumin, vanillin), substituted quinones, bilrubin and lysozyme in microemulsions, peroxy radical reactions with proteins. Investigations on nanoparticles of Tl, Cu, Co, Ag, Pd generated by radiolysis and their properties are being pursued. Studies on radical cation generation in organic halo and sulphur compounds and on 2 centre - 3 electron bonds are in progress.

Work has been carried out on the oxidative photodegradation of model pollutants such as aromatic amines in aqueous solutions and carbon dioxide formed was estimated by gas chromatography. In this context, pulse radiolysis technique was employed to study one-electron oxidation of 2, 3, 4-amino phenols and 1-napthyl amine 4-sulphonic acid in order to understand the mechanism of photodegradation of these compounds in aqueous solutions. Radiation chemistry of ammonia and hydrazine in aerated aqueous solutions was studied in the context of their use as `oxygen scavengers' in the primary coolant circuits of VVERs. The radiolysis products were identified and the mechanism of oxygen removal was elucidated. A new colorimetric method for estimation of hydrazine in presence of ammonia was standardised.

A lot of applied work on radiation polymerization and hydrogels is being carried out.

2. Solid State Reactions & Thermodynamic Studies

Solid state reactions in a number of systems are being investigated to understand the basic mechanism and to evolve alternative routes to the synthesis of useful materials. They include preparation of chromium ferrite using an alternative oxalic acid route, synthesis and magnetic properties of parent and substituted scandium manganates, preparation of KMgF3 and KCuF3, phase transition and bulk thermal expansion studies on La1-xMxCrO3[M = Sr, Nd; x = 0.10 to 0.30], synthesis of VO, synthesis and characterisation of Sr++ doped Mn2O3, mixed fluorides etc. Other areas pursued include preparation and characterisation of ß-Li3MF6 (M = Ga and Mn), M7Er6F32 (M = Ba, Sr).

Thermodynamic studies center around reactor applications and include investigation of CaO-TeO2 system , thermodynamic properties of UTeO5 and UTe3O9, characterisation and thermal stability of uranium tellurites and tellurates [UTe3O5, UTeO4 UTe3O9 and UTe3O8], vapour pressure of uranium-iron alloys, determination of standard Gibbs energy of formation of Th2Mo2O8, standard enthalpies of formation of BaTe2O5 and BaTeO3 and phase diagram of the pseudo binary BaO-TeO2 system. Differential thermal analysis study of phase transitions in BaCO3 and SrCO3 and several other compounds recommended as standards in thermal analysis is also carried out.

3. Diamond Film Deposition

The laboratory set up of the HFCVD equipment set up in the previous years has been scaled up to coat larger samples. Diamond films have been successfully coated on 5 cm diameter samples of zircaloy, molybdenum, silicon (on the 100 crystallographic plane) etc. P-30 tool inserts have also been coated which are being tested in the Central Workshop.

4. Dry Combustion Plasma

Investigations have shown that dry combustion plasma and its precursor fuels offer such technological and economical advantages that electricity generation by magnetohydrodynamic process, presently globally discounted, can be reconsidered as highly possible. High thermal to electrical conversion, use of conventional saturated ion core magnet instead of cryogenic magnet in the channel, easy availability and low cost of fuels are the main advantages envisaged.

5. Chemical Synthesis

Several organometallic compounds of palladium, gallium, indium, arsenic and antimony which would be potential candidates for the preparation of advanced materials like catalysts/ semiconductors have been synthesised and characterised. A series of bi- and tri- nuclear palladium and platinum organochalcogenides were prepared which showed interesting pyrolytic decomposition resulting in the formation of respective selenides and sulpho-selenides.

6. Superconductivity

 A synthesis protocol was developed for making Bi-2223 tapes by powder in tube method starting from lead doped Bi-2122 and infinite layer compound Ca0.85Sr0.15CuO2. In order to identify phase responsibe for superconductivity in the multiphase sample of nominal composition (Nd4/6Th1/6)2[Nd1/3(Ba0.67Sr0.33)2/3]2 Cu3O9, a number of compounds with T* - and 223-type structures not containing Ce were prepared. Their properties are being studied.

7. Studies on Metal Hydrides

Effect on the H2 absorption on the structural, magnetic and superconducting characteristics of Zr, rare earth annd uranium based intermetallics is being investigated.

8. Catalysis studies

Using hydrogen TPD method the metal surface area of a polycrystalline ruthenium catalyst and a 2% Ru/TiO2 catalyst was evaluated. Enthalpy changes involved during adsorption/interaction of He, H2 and O2 over Au/Fe2O3 catalysts were evaluated at adsorption temperature of 300 K. Irrespective of the nature of pretreatment an almost similar fraction of CO2- (55%) was found to adsorb/interact over both the catalysts during exposure to successive CO2 pulses. The methods based on D2O/OH group isotopic exchange and NH temperature programmed description were used to evaluate the concentration of the hydroxyl groups in ZSM-5 and HZSM-5 zeolites as a function of heat pretreatment in the temperature range 573-1173 K. A deuterated ZSM-5 catalyst was prepared by ion exchange method using 10 % solution of ND4NP3.

Simulated gas adsorption/ desorption experiment on dehydrated molecular sieve-5 A and Fe-doped and Fe free alumina were carried out to evaluate the H2/D2 exchange phenomenon noticed in gas chromatographic analysis with D2 carrier gas using these column packings.

 9. Analytical Chemistry

Research on various aspects of analytical chemistry is pursued. These include: a systematic study on the permeation of various metal ions like silver and zinc through Nafion ionomer membrane as well as the transport of halides through modified membranes; thermal analysis study of ammonium uranyl carbonate coprecipitated with gadolinium carbonate; X ray diffraction of copper tellurium intermetallic compound; fabrication of biosensors; cyclic voltammetric behaviour of Pd on biotin; investigation on the effect of magnetic field on the manifestation of anomalous phenomena during electrolytic charging of deuterium into palladium and nuclear transmutation reactions in the cold by means of Patterson Power Cell.

Applied research is pursued to develop newer and improved analytical methodologies. These include determination of traces of uranium in zircaloy, assay of trace metals in calcium, estimation of Mg and Zn in semen samples, determination of nitrogen and trace metals in hydrogel, analysis of trace impurities in diverse materials like calcium sulphate TLD powder, lithium pentaborate, environmental sample solutions etc. A Electroanalytical procedure for determination of palladium in recombiner catalysts was developed. Methods were standardised for characterisation of several trace impurities in high purity arsenic using DCPAES, GFAAS and electroanalytical techniques. NAA methods were developed for the analysis of platinum group metals in rock samples and copper plant tailings. Work was pursued on the potentiality of charged particle activation analysis (CPAA) for the determination of rare earth elements in geological samples and determination of light elements in high purity materials. Thin layer activation analysis (TLA) was applied for surface wear studies in zircaloy-2.

10. Biocatalysts

To cater to the demand for compounds with varied molecular structure, design of new synthetic strategies is an important activity. Use of biocatalysts (enzymes) is likely to contribute significantly in future. Efforts were directed to design novel asymmetric synthesis of high value, low volume bioactive compounds such as agrochemicals and pharmaceuticals. The specificity of the enzymes could be altered by solvent enginnering thereby increasing their utility.

11. Chirons

Due to importance of optically pure compounds in chemical industries, several asymmetric methodologies (chirotechnology) were developed. Using readily available carbohydrates as starting materials, highly functionalised chirons were prepared; these would be useful for synthesis of drug intermediates and other bioactive compounds. A highly convergent protocol which allows enantiocontrol of three stereogenic centres has been developed and used in enantiomeric synthesis of antifungal compound.

2-alkenyl-4-chromanones are attractive substrates for intramolecular arene-alkene photoadditions. Using suitably designed substrates highly strained (energy rich) multicyclic systems, with hitherto unknown carbon framework with defined stereochemistry could be synthesised. A low valent titanium mediated protocol for low temperature carbonyl coupling (McMurray Reaction) which is the backbone of nuclear medicine has been developed.

12. Peptides

Peptides containing non-natural amino acids have been synthesised. Some of these show strong chiral recognition as evidenced by NMR studies. These studies will be useful in the design of peptides of therapeutic value. Molecular interactions of fullerenes (C60) with different classes of compounds were studied using 1H an 13C NMR spectroscopy. The solubility trends of fullerenes could be rationalised on the basis of charge transfer complexes and resulted in the discovery of new solvents.

13. Pest Control

Integrated pest management programmes based on the use of insect pheromones provide an eco-friendly alternative to toxic pesticides. Additional amount of the pheromone which is useful for control of the weevil menace of the sweet potato crop has been synthesised and field trials have been continued in collaboration with Central Tuber Crop Research Institute. Repeated trials revealed excellent efficacy of the synthetic pheromone both in the control of the pest as well as improvement of the quality of the crop. Pink bollworm (Pectinophora gossypiella) and American bollworm (Helicoverpa armigera) are the two major pests of cotton. Pheromones of these pests were made available by synthesis and trials for their control were continued for the third successive year. Prediction of the population build-up of pests could be made by careful monitioring the extent of infestation. Studies on mating disruption have also been carried out against pink bollworm. A pheromone mimic was evaluated for mating disruption of pink bollworm.

14. Radiopharmaceuticals

Improvement in the methods for the preparation of known radiopharmaceuticals and design of new ones are some important goals of the IAEA Coordinated Research Programme. Expertise gained from the basic work on bioorganometallics was utilised towards the development of new generation of organic ligands which are likely to find use in the radiopharmaceuticals as well as in chelation therapy and biochemistry. The reaction is based on single electron transfer induced reductive dimerisation of imines. More than fifteen ligands with rigid, multidentate and macrocyclic frameworks have been synthesised. These allow modulation of physical characteristics (e.g. hydrophobicity) and altering the chelate ring size to the desired stability by using appropriate substrates.

15. Solvent for Fuel Reprocessing

Solvent extraction is used in nuclear fuel reprocessing. Work on CMPO (n-octyl-phenyldiisobutylcarbomoylmethyl phosphine oxide) has been supported by synthesising the ligand in sufficient quantities. Studies on radiolytic degradation of TRUEX solvent were continued using GC and GC-MS (in collaboration with RCD). Interpretation of the mass spectra shows that CMPO undergoes fragmentation at different sites giving various products. An understanding of the nature of the radiolytic products will be useful for their removal so that CMPO can be repeatedly recycled. Use of alkyl malonamides as extractants for actinides offers advantages owing to their ready incineratibility. Several malonamides have been synthesised.

16. Bio Active Compounds

Studies towards isolation and characterisation of the immunomodulatory principle from Gulvel were continued. Composition of the monosachharides of the active principle was determined by GC-MS. The linkages between the monosachharides have been partly established. Chemotherapeutic potential of two alkaloids, pergularine annd tylophorinidine were evaluated. Both compounds showed significant inhibition against thymidylate synthase activity of leukaemia leukocytes. Ecdysoids and precocenoids (the insect growth regulators) have been isolated from plant sources. Some of the growth regulators have been found to be toxic to marine fouling organisms. Some synthetic analogs of garlic constituents were found to inhibit HMG CoA reductase activity and were evaluated for hypolipidemic activity. Significant reduction in triglyceride and cholesterol levels were observed in cholesterol induced hypercholesterolemic rats. In addition, the synthetic compound showed antioxidant properties. It exhibited significant in vitro inhibition of CCl4 or Fe2+ induced lipid peroxidation.

FACILITIES

1. Femto second Laser Spectrometer

An important equipment to investigate the dynamics of ultrafast chemical reactions, the Femto second Laser Spectrometer for measurement of transient optical absorptions of extremely short lived chemical species in the time scale of 10-15 second (femto second, fs) has been set up in the Group. The desired chemical species are generated by the interaction of 100 fs pulses of a colliding pulse mode locked (CPM) dye laser pumped by Argon ion laser. This output is then amplified in a 5 stage dye amplifier pumped by seeded Nd-YAG laser to give amplified pulses of 300 µJ energy at 30Hz rep rate. The spectrometer is based on pump-probe configuration, the white light probe continuum pulses being generated by focussing part of the amplified output of CPM laser on a jet of ethylene glycol. The range of the spectrometer is 0-6600 fs and is achieved by using an ultrafine optical delay with a resolution of 1 fs.

2. Laser Vapourisation Cluster Equipment

The equipment for generation of atomic clusters of metals and for study of their reactions has been set up in the laboratory. The clusters are generated by laser pulses and are characterised by a captive time of flight mass spectrometer. Trial experiments with aluminium are being carried out to evaluate the performance of the unit.

The ultra trace analytical facilities at HRD Complex, BARC have been refurbished to cater to the needs for the analysis of high purity materials. A sophisticated AAS unit with provision for flame and electrothermal atomisation and vapour and hydride generation measurements has been procured and installed.

REACTOR ORIENTED ACTIVITIES

1. Decontamination of BWR surfaces

Studies on decontamination of BWR surfaces is under way. A comparative assessment of LOMI and EAC formulations has been completed. A feasibility report for carrying out chemical decontamination of the clean-up system of TAPS Unit # 2 is being prepared and the details regarding ion exchanger column size, quantity of chemicals needed and operational procedure are being worked out.

2. Decontamination of PHWRs

Water and Steam Chemistry Laboratory, Kalpakkam in collaboration with MAPS has successfully decontaminated the PHT systems of MAPS-1 and MAPS-2. The technology for this was developed in-house and employs a decontaminant formulation to remove the oxide deposits from the PHT system surfaces.

Recently a repeat decontamination of MAPS-1 PHT system was carried out in November 1997 using the same methodology. 160 Ci of Co and 40 Ci of fission produts were removed. Decontamination factors ranging from 2 to 15 were achieved on the system surfaces thereby bringing down the radiation fields significantly and resulting in considerable man-rem savings for carrying out maintenance jobs.

3. Chemical Cleaning of Steam Generators

Fouling of nuclear steam generators by the oxides and scale forming impurities transported from the feed water systems is not uncommon. To prevent the occurence of steam generator tube failures by the aggressive ions which may get concentrated in the sludge pile, it is desirable to periodically remove the fouling sludge deposits. Detailed investigations have been carried out to evaluate EDTA based chemical cleaning formulations for their efficacy in dissolving the copper and iron containing sludge and their compatibility with the Monel-400 steam generator tubes. Electrochemical evaluation has shown that the formulations do not cause any localised attack on the SG tube materials. Based on these studies it is shown that a two stage chemical cleaning process using EDTA as the complexant can be used to chemically clean the MAPS steam generators.

4. SIM Loop Commissioning

A modular simulated test facility (SIM LOOP) has been constructed out of stainless steel for testing of decontamination formulations at pilot plant scale. SIM loop can also be used to carry out component decontaminnation, corrosion studies, ion exchange behaviour related to decontamination etc. This loop has recently been commissioned.

5. Studies Related to Biofouling

In the area of biofouling, investigations are carried out on evaluation of water quality, rearing of barnacle larvae for laboratory biofouling studies, microbiological studies in fresh water and sea water, biofilm development and its dependence on plant nutrients, chlorination and biofouling studies at MAPS etc. As a part of these studies a Biofouling Test Loop is being set up at MAPS site and is nearing completion.

6. Activity Transport Studies

A computer code is being developed to calculate the build-up of mass and activity on PHWR primary transport system surfaces. As a firt step, a simplified model of a single metal pipe closed loop with three different diameter has been chosen. This loop also has a sink for corrosion products. It utilises variable parameters such as deposition coefficient, release coefficient and purification factor. The model at present calculates the build-up of iron on surface and in the coolant as a function of time.

R & D studies for understanding the corrosion and ion exchange behaviour in dilute decontaminant formulation are being pursued. Besides dissolution of corrosion product oxides such as mixed ferrites and iron oxides in other prospective decontaminant formulations such as pyridine di carboxylic acid (PDCA), picolinic acid and nitrilo triacetic acid was investigated for understanding mechanism of oxide dissolution in these media.

COLLABORATION, SERVICES AND CONSULTANCY

Analysis of samples emanating from various Divisions of BARC, units of DAE and Government and private sector organisations constitutes the analytical service support. The number of samples analysed every year averages 2500 involving more than 7500 determinations. The samples analysed include materials of nuclear importance, organic and inorganic compounds, rocks and minerals, biological and environmental specimens, transformer oils, and diverse materials like molecular sieves, glass powder, PTFE etc. Besides, a number of solution samples are also analysed. Analytical techniques like UV/VIS spectrophotometry, AAS, GFAAS, DCPAES, CHN and elemental analyser, gas and ion chromatography, XRF, nuclear analytical techniques like INAA, RNAA and charged particle activation analysis are employed to provide the best service support to users. Specialised services like determination of particle size, surface area and thermoanalytical properties are provided. To cater to the increasing demand for fast and accurate analyses, it is proposed to modernise the analytical laboratory by aquiring state of the art equipments. Analytical services (XRD, HTXRD, TG, DTA) are provided to other Divisions/DAE units.

In collaboration with Central Forensic Science Laboratory, the Division has contributed to the solution of several forensic cases. Irradiation facilities are being offered to Geological Surey of India for the analysis of rock samples. Cooperation is extended to various academic institutions for training in sophisticated analytical methods. Consultancy is rendered to various Advisory Bodies/ organisations viz. COSWAC, DST, BIS etc.

Consultancy services to Nuclear Power stations/ reactors/ Heavy Water Plants are being provided.

The Group gives extensive help to Training and Management Services Division by giving lectures, tutorials, practicals on several topics such as Thermodynamics, Radiation & Photochemistry, Reactor Chemistry, Chemical Dynamics and Rate Processes, Material Science, Analytical Chemistry, Molecular Structure and Spectroscopy etc. to Chemistry Trainees of BARC Training School.