Application of an enzymatic cascade reaction for the synthesis of the emeraldine salt form of polyaniline

The synthesis of the emeraldine salt form of polyaniline (PANI-ES) from aniline with Aspergillus sp. glucose oxidase (GOD), d-glucose, dissolved O2, and horseradish peroxidase isoenzyme C (HRPC) in the presence of large unilamellar vesicles of AOT (sodium bis-(2-ethylhexyl)sulfosuccinate) as templates at pH = 4.3 and T ~ 25 °C was investigated in a systematic way. In this cascade reaction mixture, the oxidation of aniline is catalyzed by HRPC with H2O2 that is formed in situ as byproduct of the GOD-catalyzed oxidation of d-glucose with O2. Under the elaborated experimental conditions which we considered ideal, the formation of PANI-ES products is evident, as judged by UV/Vis/NIR and EPR measurements. Comparison was made with a reference reaction, which was run under similar conditions with added H2O2 instead of GOD and d-glucose. Although the reference reaction was found to be superior, with the cascade reaction, PANI-ES products can still be obtained with high aniline conversion (> 90%) within 24 h as stable dark green PANI-ES/AOT vesicle dispersion. Our results show that the in situ formation of H2O2 does not prevent the inactivation of HRPC known to occur in the reference reaction. Moreover, the GOD used in the cascade reaction is inactivated as well by polymerization intermediates.

Measurement of the 234U(n,f) cross section in the energy range between 14.8 and 17.8 MeV using Micromegas detectors

The 234U(n,f) reaction cross section was measured for three neutron energies 14.8, 16.5 and 17.8 MeV, relative to the238U(n,f) reference reaction. The in-beam measurements were carried out by using a set-up based on Micromegas detectors, while the quasi-monoenergetic neutron beams were produced by means of the 3H(d,n)4He reaction at the 5.5MV Tandem T11/25 Accelerator Laboratory of the National Center for Scientific Research "Demokritos" in Athens (Greece). Additionaly, α-spectroscopy measurements were performed in order to determine the active mass of the samples and the corresponding impurities. In order to estimate the fission-fragment detection efficiency, Monte Carlo simulations were carried out using the GEF and FLUKA codes. Furthermore, simulations were also performed by coupling the NeuSDesc and MCNP5 codes for the determination of the neutron energy distribution in all the irradiated samples and the results were used in order to correct for the contribution of low energy parasitic neutrons in the fission yield. The final cross section data are presented, along with the methodology adopted for the treatment of the parasitic neutrons.

New measurement of the 241Am(n,2n)240Am cross section

Cross section for 241Am(n,2n)240Am reaction has been measured at the VdG Tandem accelerator of NCSR “Demokritos", at neutron beam energy 10.4 MeV, using the activation technique. The high purity and high radioactivity (5GBq) Am target has been constructed at IRMM, Belgium and consisted of 40 mg Am in the form of AmO2 pressed into pellet with Al2O3 and encapsulated into Al container. The absolute flux of the beam was obtained with respect to the 27Al(n,α)24Na reference reaction. The induced gamma-ray activity of 240Am and 24Na was measured with high resolution HPGe detectors.

Measurement of the 241Am(n,2n)240Am cross section at 17.5 MeV

The 241Am(n,2n)240Am reaction cross section has been measured at neutron beam energy 17.5 MeV, relative to the 27Al(n,α)24Na, 197Au(n,2n)196Au and 93Nb(n,2n)92mNb reference reaction cross sections, using the activation technique. The irradiation was carried out at the Van der Graaff 5.5 MV Tandem accelerator laboratory of NCSR “Demokritos” with monoenergetic neutron beam provided by means of the 3H(d,n)4He reaction, implementing a new Ti-tritiated target. The high purity Am target has been constructed at IRMM, Geel, Belgium and consisted of 40 mg 241Am in the form of AmO2 pressed into pellet with Al2O3 and encapsulated into Al container. Due to this high radioactivity (5 GBq), the Am target was enclosed in a Pb container for safety reasons. After the end of the irradiation, the activity induced by the neutron beam at the target and reference foils, was measured off-line by two 100%, a 50% and a 16% relative efficiency, HPGe detectors.

Activation cross section of the (n,2n) reaction on Hf isotopes

Cross sections of the 174Hf(n,2n)173Hf and 176Hf(n,2n)175Hf reactions have been experimentally determined relative to the 27Al(n,α)24Na reference reaction at incident neutron energies of 15.3 and 17.1 MeV by means of the activation technique. The irradiations were carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beams provided via the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. In the determination of the 176Hf(n,2n)175Hf reaction cross section the contamination of the 174Hf(n,γ)175Hf and 177Hf(n,3n)175Hf reactions has been taken into account. Moreover, the neutron beam energy has been studied by means of Monte Carlo simulation codes and the neutron flux has been determined via the 27Al(n,α)24Na reference reaction.

Activation cross section for the (n,2n) reaction on 197Au

The cross section of the reaction channels 197Au(n,2n)196Aug+m1 and 197Au(n,2n)196Aum2 has been experimentally determined at 15.3 MeV, relative to the 27Al(n,α)24Na reference reaction, using the activation technique. The irradiation was carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beam provided by means of the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. The induced γ- ray activity was measured with a high resolution HPGe detector.

Neutron Beam Characterization at the Athens Tandem Accelerator NCSR “Demokritos”

A new Ti-tritiated target of 373 GBq activity has been installed at the 5.5MV tandem T11/25 Accelerator of NCSR "Demokritos", to produce neutrons in the energy range ~15-21 MeV by means of the 3H(d,n)4He reaction. The flux variation of the neutron beam is monitored with a BF3 detector, while the absolute flux is obtained with respect to reference reactions, such as the 27Al(n,a) reference reaction. In absence of time-of-flight capabilities, the energy spectrum of the neutron beam has been investigated by means of Monte Carlo simulations as well as by the Multiple Foil Activation Analysis technique, using reactions with different energy thresholds. The experimental results have been compared with the simulated ones in order to validate the simulations