Preparation of manganese-53

The nuclide⁵³Mn was produced by the following three nuclear reactions,⁵²Cr(d, n)⁵³Mn,⁵¹V(³He n)⁵³Mn and⁵⁰Cr(α, n), (α, p)⁵³Mn. Enriched⁵²Cr and⁵⁰Cr metal targets were prepared on copper plate holder by electrodeposition. The commercially available natural vanadium foil was used for the⁵¹V(³He, n)⁵³Mn reaction. Each target was bombarded in a cyclotron. Manganese was extracted and purified without using carrier from the bombarded targets by anion and cation exchanges and solvent extraction. The isotopic ratio⁵³Mn/⁵⁵Mn was measured by mass spectrometry and the amount of⁵⁵Mn was determined by neutron activation analysis. The activity of⁵³Mn obtained was 7 dpm by 750 millicoulombs in³He bombardment (E³He=20 MeV). The activity due to by-product⁵⁴Mn was about several thousands times higher than that of⁵³Mn in³He and deuteron bombardments, which were produced through⁵¹V(³He, γ)⁵⁴Mn and⁵³Cr(d, n)⁵⁴Mn. In alpha bombardment (E_α=15 MeV), the activity of⁵³Mn produced was 8 dpm by 95 millicoulombs. The activity ratio, dpm⁵⁴Mn/dpm⁵³Mn, was about 3, and this ratio was the best one among the results so far obtained.     

Selective reductive dimerization of homocubane series oximes

The mixture of di- and monoethylene ketals obtained by the reaction of 1,9-dibromopentacyc lo[5.4.0.0^2,6.0^3,10.0^5,9]-undeca-8,11-dione followed by hydrolysis and ring contraction by Faworsky method was converted into a mixture of ethylene ketals of 7-bromopentacyclo[5.3.0.0^2,5.0^3,9.0^4,8]decan-6-one-4- and 5-bromopentacyclo[5.3.0.0^2,5.0^3,9.0^4,8]decan-6-one-8-carboxylic acid where the carboxy group was replaced by bromine along the procedure of Hunsdiecker-Borodine-Cristol. 6-Ethylene ketal of the pentacyclo[5.3.0.0^2,5.0^3,9.0^4,8] decan-6-one obtained by the debromination of ethylene ketals of 4,7- and 5,8-dibromopentacyclo[5.3.0.0^2,5.0^3,9.0^4,8] decan-6-one was hydrolyzed to ketone whose oxime was selectively reduced on a platinum catalyst into the di-6-pentacyclo[5.3.0.0^2,5.0^3,9.0^4,8]decylamine. The reaction of reductive dimerization was also characteristic of pentacyclo[4.3.0.0^2,5.0^3,8.0^4,7]-nonan-9-one and pentacyclo[6.3.0.0^2,6.0^3,10.0^5,9]undecan-4-one oximes, whereas the composition of the reduction products of pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecan-8-one oxime depended on the amount of the catalyst.     

Cation binding by 2<Superscript>1</Superscript>,3<Superscript>1</Superscript>-diphenyl-l <Superscript>2</Superscript>,4<Superscript>2</Superscript>-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2 (2,3),3(3,2)-diindolizinacyclopentadecaphane and its acyclic analog

The binding of cations Li⁺, Na⁺, K⁺, Cs⁺, Ag⁺, Zn²⁺, Ni²⁺, Co²⁺, NH₄ ⁺ (group I), H⁺, Mg²⁺, Al³⁺, Ga³⁺ (group II), and Ca²⁺, Pb²⁺ (group III) by 2¹,3¹-diphenyl-l ²,4²-dioxo- 7,10,13-trioxa-l,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane (1), which contains two indolizine and two quinoxaline fragments and 3,6,9-trioxaundecanes spacer, and by its acyclic analog (2) was studied using cyclic voltammetry in MeCN/0.1 M Bu₄NBF₄. It was concluded that the ions of group I are not bound by these compounds, the ions of group II exhibit the reversible redox-switched binding by the carbamoyl groups of the quinoxaline fragments, whereas the ions of group III are bound not only by the initial compounds and radical cations 1 and 2, but also by dication 1. This binding of the Ca²⁺ and Pb²⁺ ions stabilizes dication 1.     

On the Remarkable Role of the Nitrogen Ligand in the Gas‐Phase Redox Reaction of the N2O/CO Couple Catalyzed by [NbN]+

The thermal gas‐phase catalytic reduction of N₂O by CO, mediated by the transition‐metal nitride cluster ion [NbN]⁺, has been explored by using FT‐ICR mass spectrometry and complemented by high‐level quantum chemical calculations. In contrast to the [Nb]⁺/[NbO]⁺ and [NbO]⁺/[Nb(O)₂]⁺ systems, in which the oxidation of [Nb]⁺ and [NbO]⁺ with N₂O is facile, but in which neither [NbO]⁺ nor [Nb(O)₂]⁺ react with CO at room temperature, the [NbN]⁺/[ONbN]⁺ system at ambient temperature mediates the catalytic oxidation of CO. The origins of the distinctly different reactivities upon nitrogen ligation are addressed by quantum chemical calculations.     

Purification of 89Sr source obtained from 89Y(n,p) 89Sr by ion-exchange chromatography using tri-sodium tri-meta phosphate (SMP) as eluant

⁸⁹Sr was produced via ⁸⁹Y(n, p) ⁸⁹Sr using yttria as target in Fast Breeder Test Reactor (FBTR), Kalpakkam, India. A radiochemical procedure has been developed for the separation of bulk yttrium using TBP by solvent extraction followed by purification of ⁸⁹Sr source by ion exchange chromatography using the cation exchange resin Dowex 50WX8 (100–200 mesh) and nitric acid of variable molarity as eluant. The present study establishes the purification of ⁸⁹Sr source from the other radionuclidic impurities like ⁸⁸Y, ⁶⁵Zn, ⁵⁴Mn, ⁶⁰Co, ⁸⁶Rb, ¹⁹²Ir, ¹⁰³Ru, ¹¹³Sn, ¹³⁹Ce, ¹⁶⁰Tb, ¹⁵⁴Eu etc. produced during the irradiation of yttria by using the complexing agent tri-sodium tri-meta phosphate (SMP) in nitric acid medium instead of nitric acid alone as an eluant. The purification was achieved by using 0.1 M SMP as complexing agent which was optimized based on the distribution ratio data and final elution of Sr fraction was obtained in nitric acid medium. This resulted into a faster purification of ⁸⁹Sr source in a smaller volume of eluant. Purity of Sr source from the cross contamination of the complexing agent SMP was also ensured.     

Energy-transfer processes in decaying helium-cadmium plasmas

Light absorption and emission spectroscopy were used in studies of the time dependences of the CdII spectral emission and He^m(2³S) number density in the stationary afterglow of helium-cadmium mixtures. Transitions from 12 CdII energy levels were monitored in the afterglow. The five CdII states below 20 eV are produced, either directly or via cascading, by the Penning ionization of Cd by He^m(2³S). The remaining CdII states studied are produced by the chargeexchange excitation of Cd by He⁺. No evidence was found for the production of CdII energy levels by charge transfer between Cd and He ₂ ⁺ or by Penning ionization of Cd by He ₂ ^m (2³ _u ⁺ ). A value of (5.4±0.3)×10^–10 cm³ sec^–1 was measured for the reaction rate coefficient for the Penning ionization of Cd by He^m(2³S), and a value of (2.1±0.2)×10^–10 cm³ sec^–1 was measured for the reaction rate coefficient for charge exchange between He⁺ and Cd at a gas temperature of 200°C.     

Consequences of the One‐Electron Reduction and Photoexcitation of Unsymmetric Bis‐imidazolium Salts

Coupling of uronium salts with in situ generated N‐heterocyclic carbenes provides straightforward access to symmetrical [ 4 ]²⁺ and unsymmetrical bis‐imidazolium salts [ 6 ]²⁺ and [ 9 ]²⁺. As indicated by cyclic and square‐wave voltammetry, [ 6 ]²⁺ and [ 9 ]²⁺ can be (irreversibly) reduced by one electron. The initially formed radicals [ 6 ]^.+ and [ 9 ]^.+ undergo further reactions, which were probed by EPR spectroscopy and density functional calculations. The final products of the two‐electron reduction are the two carbenes. Upon irradiation with UV light both [ 6 ]²⁺ and [ 9 ]²⁺ emit at room temperature in solution but with dramatically different characteristics. The different fluorescence behavior is analyzed by emission spectroscopy and interpreted by using time‐dependent density functional calculations as largely due to different excited‐state dynamics of [ 6 ]²⁺ and [ 9 ]²⁺. The geometries of both radicals [ 6 ]^.+ and [ 9 ]^.+ and excited states {[ 6 ]²⁺} * and {[ 9 ]²⁺}* are substantially different from those of the parent ground‐state molecules.     

Radiochemical determination of the yields of transuranium nuclides produced from natural uranium irradiated in a reactor

Transuranium nuclides were produced by irradiating a pellet of natural uranium sulfide in the Japan Material Testing Reactor (JMTR). After irradiation, a successive separation of uranium, plutonium, americium and curium was carried out. The fractional concentrations of the nuclides²³⁸Pu,²³⁹Pu,²⁴⁰Pu,²⁴¹Am,²⁴³Am,²⁴²Cm and²⁴⁴Cm were determined by α-ray spectrometry, and those of²⁴¹Pu and^242mAm were estimated from the build-up of α-emitting daughters,²⁴¹Am and²⁴²Cm, respectively. As the yield of²⁴²Pu was too slight to be detected by α-counting, the neutron activation analysis of the plutonium fraction based on the²⁴²Pu(n, γ)²⁴³Pu reaction was carried out by γ-ray spectrometry, and it was shown that a few pg of²⁴²Pu could be determined. A burn-up of²³⁵U was also estimated by neutron activation analysis. The experimental results are compared with the calculated ones.     

The Tunable Luminescence of Ruthenium(II) Complexes Containing Different Tetrazolate Ligands

Three luminescent mononuclear Ru^II compounds, [Ru^II(bpy)₂( L¹ )](BF₄) ( 1 ), [Ru^II(bpy)₂( L² )](BF₄) ( 2 ), and the neutral compound [Ru^II(bpy)₂( L³ )] ( 3 ), were obtained, by treatment of [Ru^II(bpy)₂Cl₂] with the tetrazolate (tz)-containing ligands L¹ – L³ . All the compounds were well characterized by IR, UV/Vis, and ¹H NMR and their redox properties were also investigated by cyclic voltammogram. The crystal structure of 3 was determined by X-ray crystallography and it clearly shows that the Ru^II ion is octahedrally coordinated by two bpy ligands and a deprotonated L³ ligand. After introduction of these tz ligands, 1 – 3 are more sensitive towards the change of micro-environment of solvents as compared with that of [Ru^II(bpy)₃]²⁺. This effect is most obvious in 3 , since it contains a 2^– ligand L³ . The slight modification of diimine ligand make these complexes have potential applications as sensors.     

Cu(II) Hexacyanoferrate(III) Modified Carbon Paste Electrode; Application for Electrocatalytic Detection of Nitrite

Copper hexacyanoferrate (CuHCF) film‐modified carbon paste electrode (CPE) has been prepared from various electrolytic aqueous solutions using consecutive cyclic voltammetry. The cyclic voltammograms showed the direct deposition of CuHCF films from the mixing of Cu²⁺ and Fe(CN)₆^3? ions and each time with one of the six cations: H⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, and Al³⁺. The CuHCF film showed a single redox couple that exhibited a cation effect (Na⁺, K⁺, Mg²⁺, and NH₄⁺) and anion effect (Cl^?, NO₃^?, SO₄^2?, ClO₄^?, and BrO₃^?) in the cyclic voltammograms. Voltammetric studies have indicated that in presence of nitrite, the cathodic peak current of CuHCF increases, followed by a decrease in the corresponding anodic current. This indicated that nitrite was reduced by the redox mediator immobilized on the electrode surface via an electrocatalytic mechanism. The process of reduction and its kinetics were investigated by using cyclic voltammetry, differential pulse voltammetry, chronoamperometry and chronocoulometry techniques. The electrocatalytic ability about 800 mV can be seen. The rate constant of the catalytic reduction of nitrite was found to be 7.9×10⁵ cm³ mol^?1 s^?1. Linearity range obtained was 5×10^?5?8.4×10^?3 by cyclic voltammetry and 8×10^?6?1.3×10^?3 and 4×10^?3?2×10^?2 by differential pulse voltammetry.     

Evolution of Ate-Organoiron(II) Species towards Lower Oxidation States: Role of the Steric and Electronic Factors

Ate-iron(II) species such as [Ar₃Fe^II]⁻ (Ar=aryl) are key intermediates in Fe-catalyzed couplings between aryl nucleophiles and organic electrophiles. They can be active species in the catalytic cycle, or lead to Fe⁰ and Fe^I oxidation states, which can themselves be catalytically active or lead to unwished organic byproducts. Analysis of the reactivity of the intermediates obtained by step-by-step displacement of the mesityl groups in high-spin [Mes₃Fe^II]⁻ by less hindered phenyl ligands was performed, and uncovered the crucial role of both steric and electronic parameters in the formation of the Fe⁰ and Fe^I oxidation states. The formation of quaternized [Ar₄Fe^IIMgBr(THF)]⁻ intermediates allows the bielectronic reductive elimination energy required for the formation of Fe⁰ to be reduced. Similarly, the small steric pressure of the aryl groups in [Ar₃Fe^II]⁻ enables the formation of aryl-bridged [{Fe^II(Ar)₂}₂(μ-Ar)₂]²⁻ species, which afford the Fe^I oxidation state by bimetallic reductive elimination. These results are supported by ¹H NMR, EPR, and ⁵⁷Fe Mössbauer spectroscopies, as well as by DFT calculations.     

Precise trace rare earth analysis by radiochemical neutron activation

A rare earth group separation scheme followed by normal Ge(Li), low energy photon detector (LEPD), and Ge(Li)−NaI(Tl) coincidence-noncoincidence spectrometry significantly enhances the detection sensitivity of individual rare earth elements (REE) at or below the ppb level. Based on the selected γ-ray energies, normal Ge(Li) counting is favored for¹⁴⁰La,¹⁷⁰Tb and¹⁶⁹Yb; LEPD is favored for low γ-ray energies of¹⁴⁷Nd,¹⁵³Sm,¹⁶⁶Ho and¹⁶⁹Yb; and noncoincidence counting is favored for¹⁴¹Ce,¹⁴³Ce,¹⁴²Pr,¹⁵³Sm,¹⁷¹Er and¹⁷⁵Yb. The detection of radionuclides^152mEu,¹⁵⁹Gd and¹⁷⁷Lu is equally sensitive by normal Ge(Li) and noncoincidence counting;¹⁵²Eu is equally sensitive by LEPD and normal Ge(Li); and¹⁵³Gd and¹⁷⁰Tm is equally favored by all the counting modes. Overall, noncoincidence counting is favored for most of the REE. Precise measurements of the REE were made in geological and biological standards. Prepared for the U.S. Department of Energy under Contract DE-AC06-76RLO 1830.     

Origin and release date assessment of environmental plutonium by isotopic composition

The origin and release date of environmental plutonium have been assessed by the measurement of plutonium and americium isotopic composition. The applicability and sensitivity of different plutonium isotope ratios, ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu measured by inductively coupled plasma sector field mass spectrometry and ²³⁸Pu/²³⁹Pu analysed by alpha spectrometry, have been evaluated for origin determination in several types of environmental samples. With use of mixing models the contribution of different sources (e.g. global fallout or Chernobyl) can be calculated. By the measurement of the ²⁴¹Am/²⁴¹Pu isotope ratio, the release date (i.e. formation of ²⁴¹Pu by irradiation) can be estimated in environmental samples, which is an important parameter to distinguish recent plutonium release from previous (e.g. Chernobyl) emissions.     

Preparation of 616X,6Y-Tris-O-(tert-butyldimethyl-silyl)-β-cyclodextrins,and Isolation and Regiochemical Determination of Five Positional Isomers

Abstract

Five positional isomers of 6¹,6^X,6^Y-tris-O-(tert-butyldimethylsilyl)-cyclomaltoheptaose (β-cyclodextrin, βCD) were prepared by reaction of β CD with tert-butyldimethylsilyl chloride in pyridine, and were isolated by HPLC and characterized by ¹³C NMR spectroscopy. The regiochemical determination of those positional isomers was carried out by the extended Körner's method, that is, by comparison with compounds obtained by additional monosilylation of 6¹, 6^X-bis-O-(tert-butyldimethylsilyl)-βCDs, and by conversion to the known compounds, 6¹,6^X,6^Y-tri-O-(toluene-sulfonyl)-βCDs.     

Chemical study on the separation and purification of promethium-147

A chemical process for the separation of¹⁴⁷Nd/¹⁴⁷Pm from fission products of synthetic radioactive waste solution has been developed. The process includes: (1) denitration, (2) removal of high concentration of uranium by 30% TBP/kerosene extraction, (3) removal of⁹⁵Nb,¹⁰³Ru,¹³⁷Cs and part of⁹⁰Sr by 50% TBP/dodecane extraction, (4) separation of¹⁴⁷Nd/¹⁴⁷Pm from part of⁹⁰Sr and⁹⁵Zr by oxalic acid precipitation, and (5) removal of¹⁴⁴Ce by mixture of 0.4M D2EHPA and 0.2M TBP extraction. Experimental results indicate that the recovery of¹⁴⁷Nd/¹⁴⁷Pm in the final separated solution is about 90%. The purification of¹⁴⁷Nd and¹⁴⁷Pm from some other rare earth elements, viz.¹⁵³Sm,¹⁵⁴Eu and¹⁴⁴Ce was further investigated by using a Dowex 50W×8 ion-exchanger. Parameters of flow rate, eluent concentration and pH were examined. The results show that the recovery and radionuclide purity of¹⁴⁷Nd plus¹⁴⁷Pm under the present separation conditions are 77.8% and 98.6% for diethylenetriaminepentaacetic acid (DTPA) and 87.3% and 99.5% for nitrilotriacetic acid (NTA), respectively.     

Emissive Synthetic Cofactors: Enzymatic Interconversions of tzA Analogues of ATP,NAD+, NADH,NADP+, and NADPH

A series of enzymatic transformations, which generate visibly emissive isofunctional cofactors based on an isothiazolo[4,3‐d]pyrimidine analogue of adenosine ( ^tz A ), was developed. Nicotinamide adenylyl transferase condenses nicotinamide mononucleotide and ^tz ATP to yield N^tzAD⁺ , which can be enzymatically phosphorylated by NAD⁺ kinase and ATP or ^tz ATP to the corresponding N^tzADP⁺ . The latter can be engaged in NADP‐specific coupled enzymatic transformations involving conversion to N^tzADPH by glucose‐6‐phosphate dehydrogenase and reoxidation to N^tzADP⁺ by glutathione reductase. The N^tzADP⁺ / N^tzADPH cycle can be monitored in real time by fluorescence spectroscopy.     

Investigation of radioactive lead,uranium, and thorium in environmental waters by extraction chromatography resins

A time-saving and sensitive method for monitoring low concentration (activities) of ²¹⁰Pb, ²³²Th, and ²³⁰Th and ²³⁸U, ²³⁴U, and ²³⁵U in water samples has been developed. Through the combination of co-precipitation and extraction chromatography by 3M RAD disks and UTEVA (Eichrom) columns effective radiochemical separation of the analytes was carried out. Thorium and uranium activities were determined by alpha spectrometry and lead activity by LSC, respectively. The minimal detectable activities obtained were 0.6?Bq?m^?3 for uranium, 0.29?Bq?m^?3 for thorium, and 2.5?Bq?m^?3 for ²¹⁰Pb. More than 150 different waters were analysed for uranium content and only 30 for lead and thorium. The investigations are still in progress.     

Temperature programmed desorption of F-doped SnO<Subscript>2</Subscript> films deposited by inverted pyrosol technique

Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.2·10^–4 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H⁺), 2(H₂ ⁺), 12(C⁺), 14(N⁺), 15(CH₃ ⁺), 16(O⁺), 17(OH⁺ or NH₃ ⁺), 18(H₂O⁺ or NH₄ ⁺), 19(F⁺), 20(HF⁺), 28(CO⁺ or N₂ ⁺), 32(O₂ ⁺), 37(NH₄F⁺), 44(CO₂ ⁺), 120(Sn⁺), 136(SnO⁺) and 152(SnO₂ ⁺). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400°C.     

All Alkoxide Sol–Gel Route to CoO-TiO2 Nano-Powders

The molecular alkoxide, ErNb₂(OPrⁱ)₁₃ was prepared by metathesis with 2KNb(OPrⁱ)₆, KOPrⁱ and ErCl₃, and structurally determined by single-crystal X-ray diffraction techniques. Each molecule contains a central Er³⁺-ion coordinated by six OPrⁱ groups of which one is terminal. On each side is an Nb⁵⁺-ion coordinated by six OPrⁱ groups placed, one via a double alkoxo-bridge and the other via a triple alkoxo-bridge. It is isostructural with LaNb₂(OPrⁱ)₁₃, in spite of the large difference in ionic radius between Er³⁺ and La³⁺ (16%). The compound was characterized by its IR- and UV-vis-NIR-spectroscopic fine structures, and found to be structurally intact in hexane:isopropanol solution.     

Sequential separation and determination of plutonium, americium-241 and strontium-90 in soils and sediments

A sensitive and reliable metbod for the sequential separation and determination of plutonium,²⁴¹Am and⁹⁰Sr in soil samples was developed. Plutonium was separated by a Microthene-TNOA column. Then⁹⁰Y (for⁹⁰Sr determination) was separated from americium by a HDEHP column after elimination of large amounts of interfering stable or radioactive nuclides (iron,²¹⁰Bi and²¹⁰Po etc.) by an oxalate precipitation and a Microthene-TNOA column. Finally americium was purified by another HDEHP column and a PMBP-TOPO extraction. A special attention was paid to the decontamination of Pu and Am from²¹⁰Po and of⁹⁰Y from²¹⁰Bi; the relevant decontamination factors resulted greater than 10⁵, 10⁶ and 10⁴ respectively. The detection limits were 1.2 mBq/kg for Pu and 1.7 mBq/kg for²⁴¹Am and 0.32 Bq/kg for⁹⁰Sr. The procedure was checked by analyzing three certified samples supplied by IAEA. Some Italian soil samples were also analyzed giving average yields of 84.9±7.2% for Pu, 57.8±3.2%for Am and 96.7±1.6% for Y; the^239+240Pu,²³⁸Pu,²⁴¹Am and⁹⁰Sr contents (Bq/kg) ranged from 0.347 to 1.53, from 0.013 to 0.048, from 0.126 to 0.556 and from 2.89 to 11.6 respectively and the average ratios were 0.037±0.017 for²³⁸Pu/^239+240Pu, 0.357±0.040 for²⁴¹Am/^239+240Pu and 7.0±1.2 for⁹⁰Sr/^239+240Pu.