Polyvinyl alcohol–ionic liquid composition for promoting the direct electron transfer and electrocatalysis of hemoglobin

The direct electron transfer and electrocatalysis of hemoglobin (Hb) entrapped in polyvinyl alcohol (PVA)–room temperature ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM]PF₆) composition has been investigated by using cyclic voltammetry and chronocoulometry. It is found that the composition can promote the direct electron transfer of Hb and the heterogeneous electron transfer rate constant (k_s) of immobilized Hb is enhanced to 19.9 s⁻¹. The immobilized Hb also shows high electro-catalytic activity towards the redox of oxygen, hydrogen peroxide and nitrite. The Michaelis constants (K_m) decrease to 1.2 × 10⁻⁴ M (for hydrogen peroxide) and 9.4 × 10⁻³ M (for nitrite). The surface concentration of electroactive Hb is estimated and it is ca. 1.4 × 10⁻¹⁰ mol cm⁻², meaning that several layers of immobilized Hb take part in the electrochemical reaction. When gold nanoparticles (GNP) is introduced into the composition, the resulting PVA–GNP–[OMIM]PF₆ composition presents better performance. The electrochemical characteristic of immobilized Hb is improved further. Thus PVA–GNP–[OMIM]PF₆ composition is more suitable for the immobilization of Hb. Therefore, it is a good strategy to prepare novel composition for protein immobilization by using several materials with different function.     

Attachment and ionization in a self-consistent treatment of the electron kinetics of a collision-dominated rf plasma

This paper deals with the self-consistent determination of the rf field amplitude for sustaining the steady-state collision-dominated weakley ionized plasmas in the bulk of the rf discharge and of the time-resolved behavior of the isotropic part of the distribution function as well as of relevant macroscopic quantities in plasmas whose particle loss is dominantly determined by electron attachment. The strict timeresolved treatment is based on the nonstationary Boltzmann equation of the electrons and its numerical solution including, apart from electron number conservative collision processes, the electron attachment and ionization. The investigations are related to an rf plasma in a model gas and in SF₆ and are performed for reduced rf field frequencies around 10 MHz Torr^–1 which are of particular interest from the point of application of rf discharges for plasma processing. The numerical results show that a large field amplitude of around 160 V cm^–1 Torr^–1 is necessary to maintain the discharge and that the isotropic distribution, the relevant collision frequencies for attachment and ionization, and the electron density undergo a large modulation during a period of the rf field.     

Pulse radiolysis study of ion-species effects on the solvated electron in alkylammonium ionic liquids

The spectra and kinetic behavior of solvated electrons (e_sol⁻) in alkyl ammonium ionic liquids (ILs), i.e. N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEMMA-TFSI), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate (DEMMA-BF₄), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13-TFSI), and N-methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P14-TFSI) were investigated by the pulse radiolysis method. The e_sol⁻ in each of the ammonium ILs has an absorption peak at 1100 nm, with molar absorption coefficients of 1.5–2.3×10⁴ dm³ mol⁻¹ cm⁻¹. The e_sol⁻ decayed by first order with a rate constant of 1.4–6.4×10⁶ s⁻¹. The reaction rate constant of the solvated electron with pyrene (Py) was 1.5–3.5×10⁸ dm³ mol⁻¹ s⁻¹ in the various ILs. These values were about one order of magnitude higher than the diffusion-controlled limits calculated from measured viscosities. The radiolytic yields (G-value) of the e_sol⁻ were 0.8–1.7×10⁻⁷ mol J⁻¹. The formation rate constant of e_sol⁻ in DEMMA-TFSI was 3.9×10¹⁰ s⁻¹. The dry electron (e_dry⁻) in DEMMA-TFSI reacts with Py with a rate constant of 7.9×10¹¹ dm³ mol⁻¹ s⁻¹, three orders of magnitude higher than that of the e_sol⁻ reactions. The G-value of the e_sol⁻ in the picosecond time region is 1.2×10⁻⁷ mol J⁻¹. The capture of e_dry⁻ by scavengers was found to be very fast in ILs.     

Time-resolved spectroscopy at the picosecond laser-triggered electron accelerator ELYSE

ELYSE is a fast kinetics center created for pulse radiolysis with picosecond time-resolution. The facility is a 4–9 MeV electron accelerator using a subpicosecond laser pulse to produce an electron pulse from a Cs₂Te semiconductor photocathode and RF gun technology for the electron acceleration. The pulse duration is around 5 ps at low charge (<2 nC) and high energy (9 MeV), and is under routine conditions 10 ps at higher charge (5 nC) and >8 MeV. The dark current at the target is less than 1% of the pulse photocurrent.Time-resolved absorbance measurements in cells placed in front of the electron beam are achieved using pulsed laser diodes, or a xenon flash lamp as light sources, and photodiodes connected to a 3 GHz transient digitizer or a streak camera (250–800 nm range and 3.7 ps time resolution) as detection instruments. In addition, the synchronization between the laser beam and the electron beam is exploited to measure the absorbance by a pump-probe set-up, the pump being the electron pulse produced by the laser pulse, and the probe being part of the laser beam (120 fs–3 ps) delayed by a variable optical line.     

Breaking the barrier to fast electron transfer

A study of the electron transfer for a non-glycosylated redox variant of GOx is reported, immobilised onto an electrode via a polyhistidine tag. The non-glycosylated variant allows the enzyme to be brought closer to the electrode, and within charge transfer distances predicted by Marcus' theory. The enzyme-electrode-hybrid shows direct very fast reversible electrochemical electron transfer, with a rate constant of ~ 350 s^− 1 under anaerobic conditions. This is 2 orders of magnitude faster than the enzyme-free flavin adenine dinucleotide (FAD). These results are discussed in the context of the conformation of FAD in the active site of GOx. Further data, presented in the presence of oxygen, show a reduced electron transfer rate (~ 160 s^− 1) that may be associated with the oxygen interaction with the histidines in the active site. These residues are implicated in the proton transfer mechanism and thus suggest that the presence of oxygen may have a profound effect in attenuating the direct electron transfer rate and thus moderating ‘short-circuit’ incidental electron transfer between proteins.     

Development of compact coherent EUV source based on laser Compton scattering

High-power extreme ultra-violet (EUV) sources are required for next generation semiconductor lithography. We start to develop a compact EUV source in the spectral range 13–14 nm, which is based on a laser Compton scattering between a 7 MeV micro-bucnhed electron beam and a high-intensity CO₂ laser pulse. The electron beam extracted from a DC photocathode gun is micro-bunched using a laser modulation techinque with the Compton wavelength at a harmonic of the seeding laser before the main laser Compton scattering for EUV generation. A considerating scheme for the compact EUV source based on the laser Compton scattering with micro-bunched electron beam and the analytical study of micro-bunch generation are described in this paper.     

Characterization of THz radiation generated by ultra-short bunch from energy chirping cell attached RF electron gun

The coherent radiation spectrum extends into the far-infrared/THz region when the electron bunch is shorter than 1 ps (0.3 mm). Such ultra-short electron bunches can be produced using a variety of bunching schemes in electron accelerators. We have designed a photocathode RF electron gun, named ECC RF gun, specifically for ultra-short bunch generation. ECC stands for energy chirping cell. This paper describes the brief principle of the ECC RF gun, CTR (coherent transition radiation) observation using Schottky barrier diodes (SBD) and spectrum measurement using interferometry with SBDs. We have successfully confirmed the generation of 0.05–0.3 THz high peak power pulsed CTR.     

Ultra-low intensity electron beams of a linear accelerator for irradiation

Ultra-low intensity electron pulsed beams for irradiation have been developed by the use of the electron linear accelerator at Radiation Research Center of Osaka Prefecture University. The energy and the pulse width of the beams are about 4–12 MeV and 0.5–4 μs, respectively. The minimum beam charge has been estimated to be about several aC/pulse. These electrons are basically mono energetic, controllable, collimated and synchronized with the master oscillator of the accelerator, which are favorable features for various uses compared with β-ray sources. Especially, the system is suitable for evaluation of response of radiation detectors. In this study, the response of the TLD for high energetic electron irradiation was also evaluated by the use of these electrons.     

Homogeneous liquid-liquid extraction combined with gas chromatography-electron capture detector for the determination of three pesticide residues in soils

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid–liquid extraction (HLLE) and gas chromatography with electron capture detector (GC–ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to carbon tetrachloride, using HLLE. Under the optimum conditions, linearity was obtained in the range of 0.05–40 μg kg⁻¹ for malathion, 0.04–10 μg kg⁻¹ for lambda-cyhalothrin and 0.05–50 μg kg⁻¹ for cypermethrin, respectively. Coefficients of correlation (r²) ranged from 0.9993 to 0.9998. The repeatability was carried out by spiking soil samples at concentration levels of 2.5 μg kg⁻¹ for lambda-cyhalothrin, and 10 μg kg⁻¹ for malathion and cypermethrin, respectively. The relative standard deviations (RSDs) varied between 2.3 and 9.6% (n = 3). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, varied between 0.01 and 0.04 μg kg⁻¹. The relative recoveries of three pesticides from soil A1, A2 and A3 at spiking levels of 2.5, 5 and 10 μg kg⁻¹ were in the range of 82.20–91.60%, 88.90–110.5% and 77.10–98.50%, respectively. In conclusion, the proposed method can be successfully applied for the determination of target pesticide residues in real soil samples.     

Transient absorption measurement system using pulsed energetic ion

This article reports a highly sensitive transient absorbance measurement system using pulsed energetic ions. The ions were pulsed by a beam chopper, which was synchronized with the cyclotron, and accelerated to the desired energy around 18 MeV/u. H, He, C and Ne ions can be used for the transient absorption measurement. The optical system can measure an absorbance smaller than 1.0×10⁻⁴ in the wavelength range of 400–740 nm.     

Ultramicrohardness tester for use in a scanning electron microscope

Summary A novel microhardness-tester has been designed for loads between 10^–2 N and 5 x 10^–5 N. The apparatus can be operated in a scanning electron microscope without installation of additional adjusting shafts. The force is generated electromagnetically, transduced to the indenter (diamond cone or pyramid) by bending a double leaf spring, and measured by means of strain gauges fixed to the springs. The indentation cycle is fully programmable and is controlled by the strain gauge signal. The equipment can be tilted with respect to the electron beam thus making possible the observation of the tip during indentation.With 2 figures     

Production of123I on linear electron accelerator using highly-enriched124Xe

Highly enriched xenon¹²⁴Xe /99.85%/ has been used for the experimental production of iodine¹²³I by the /,n/ reaction. As the radiation source served a 30–45 MeV electron beam produced by a linear accelerator and converted by a tungsten converter to -radiation. The yield and radionuclidic purity of¹²³I have been estimated, the content of isotopic impurities /¹²⁴I and¹²⁵I/ being for 30 MeV irradiations lower than 4×10^–3%/.     

Palladized aluminum electrode covered by Prussian blue film as an effective transducer for electrocatalytic oxidation and hydrodynamic amperometry of N-acetyl-cysteine and glutathione

The mediated oxidation of N-acetyl cysteine (NAC) and glutathione (GL) at the palladized aluminum electrode modified by Prussian blue film (PB/Pd–Al) is described. The catalytic activity of PB/Pd–Al was explored in terms of Fe^III[Fe^III(CN)₆]/Fe^III[Fe^II(CN)₆]¹⁻ system by taking advantage of the metallic palladium layer inserted between PB film and Al, as an electron-transfer bridge. The best mediated oxidation of NAC and GL on the PB/Pd–Al electrode was achieved in 0.5 M KNO₃ + 0.2 M potassium acetate of pH 2. The mechanism and kinetics of the catalytic oxidation reactions of the both compounds were monitored by cyclic voltammetry and chronoamperometry. The charge transfer-rate limiting step as well as overall oxidation reaction of NAC or GL is found to be a one-electron abstraction. The values of transfer coefficients α, catalytic rate constant k and diffusion coefficient D are 0.5, 3.2 × 10² M⁻¹ s⁻¹ and 2.45 × 10⁻⁵ cm² s⁻¹ for NAC and 0.5, 2.1 × 10² M⁻¹ s⁻¹ and 3.7 × 10⁻⁵ cm² s⁻¹ for GL, respectively. The modifying layers on the Pd–Al substrate have reproducible behavior and a high level of stability in the electrolyte solutions. The modified electrode is exploited for hydrodynamic amperometry of NAC and GL. The amperometric calibration graph is linear in concentration ranges 2 × 10⁻⁶–40 × 10⁻⁶ for NAC and 5 × 10⁻⁷–18 × 10⁻⁶ M for GL and the detection limits are 5.4 × 10⁻⁷ and 4.6 × 10⁻⁷ M, respectively.     

A positron annihilation lifetime measurement system with an intense positron microbeam

An intense positron microbeam was formed using an electron linear accelerator. The beam is pulsed to apply positron lifetime spectroscopy to very small samples and to obtain positron lifetime images by scanning it. Positron lifetimes are measured with time resolution of <300 ps and with lateral spatial resolution of 30–100 μm. A counting rate of the γ-ray to measure positron lifetime is about 10³ s⁻¹ which is 10 times higher than that achieved by the radioisotope based microbeam.     

An extraction system for low-energy hydrogen ions formed by electron impact

A system has been developed for extracting near-zero kinetic energy H⁻ and D⁻ ions formed by dissociative electron attachment. It is the essential part of a new set-up for vibrational spectroscopy of hydrogen molecules. A magnetic field is used to collimate the probing electron beam. Ions produced by electron collision with the target molecules are collected by the combined action of this field and an electrostatic field penetrating into the interaction region. Highly effective extraction is achieved by taking into account the correct out-of plane displacement of ion trajectories which is usually neglected in similar arrangements. The extraction conditions are mass dependent so that by proper tuning, mass selection of detected ions is achieved. The new system is also used for detecting positive ions created by electron collisions with hydrogen atoms and molecules.     

Large optical Kerr effect in bulk GeSe2–In2Se3–CsI chalcohalide glasses

Third-order nonlinear optical properties of GeSe₂–In₂Se₃–CsI chalcogenide bulk glasses are studied by Standard pico-second (ps) time-resolved optical Kerr effect (OKE) technique. The obtained χ⁽³⁾ and n₂ at 1064 nm of the glass 72.25GeSe₂–23.75In₂Se₃–5CsI are as large as 10.07 × 10⁻¹² esu and 6.5 × 10⁻¹⁸ m²/W, respectively, more than twice that of As₂S₃ glass. The relationship between glass compositions and the third-order nonlinear optical responses was analyzed by Raman spectra in terms of structural evolution. It is suggested that the tetrahedral units ([GeSe₄] and [InSe₄]) play an important role in the ultrafast third-order nonlinear optical responses of these chalcohalide glasses.     

Nitric oxide and singlet oxygen photo-generation by light irradiation in the phototherapeutic window of a nitrosyl ruthenium conjugated with a phthalocyanine rare earth complex

The photochemical, photophysical and photobiological studies of a mixture containing cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] (H₂-dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and Na₄[Tb(TsPc)(acac)] (TsPc = tetrasulfonated phthalocyanines; acac = acetylacetone), a system capable of improving photodynamic therapy (PDT), were accomplished. cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] was obtained from cis-[Ru(H₂-dcbpy)₂Cl₂]·2H₂O, whereas Na₄[Tb(TsPc)(acac)] was obtained by reacting phthalocyanine with terbium acetylacetonate. The UV–Vis spectrum of cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] displays a band in the region of 305 nm (λ_max in 0.1 mol L⁻¹ HCl)(π–π*) and a shoulder at 323 nm (MLCT), while the UV–Vis spectrum of Na₄[Tb(TsPc)(acac)] presents the typical phthalocyanine bands at 342 nm (Soret λ_max in H₂O) and 642, 682 (Q bands). The cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] FTIR spectrum displays a band at 1932 cm⁻¹ (Ru–NO⁺). The cyclic voltammogram of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] complex in aqueous solution presented peaks at E = 0.10 V (NO^+/0) and E = −0.50 V (NO^0/−) versus Ag/AgCl. The NO concentration and ¹O₂ quantum yield for light irradiation in the λ > 550 nm region were measured as [NO] = 1.21 ± 0.14 μmol L⁻¹ and ø_OS = 0.41, respectively. The amount of released NO seems to be dependent on oxygen concentration, once the NO concentration measured in aerated condition was 1.51 ± 0.11 μmol L⁻¹ The photochemical pathway of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)]/Na₄[Tb(TsPc)(acac)] mixture could be attributed to a photoinduced electron transfer process. The cytotoxic assays of cis-[Ru(H-dcbpy^-)₂(Cl)(NO)] and of the mixture carried out with B16F10 cells show a decrease in cell viability to 80% in the dark and to 20% under light irradiation. Our results document that the simultaneous production of NO and ¹O₂ could improve PDT and be useful in cancer treatment.     

Femtosecond diffraction with chirped electron pulses

Here, we report on the possible achievement, in ultrafast electron diffraction and imaging, of temporal resolution of tens of femtoseconds through the use of chirped electron packets in combination with energy filtering. Space–charge forces in multi-electron packets accelerate leading electrons and retard trailing ones, thus inducing correlations of momentum and time. By resolving the diffraction images with an energy analyzer, well-defined temporal slices of the long electron packet can be selected. Numerical simulations show that conventional electron sources are sufficient to reach the 30-fs domain of resolution without electron packet compression. They also reveal the influence of packet shape, electron density and photoemission bandwidth on the achievable time resolution.     

Characterization of a 10.3-μm pulsed DFB quantum cascade laser

We have measured the output parameters of a 10.3-μm pulsed distributed-feedback (DFB) quantum cascade (QC) laser manufactured by Alpes Lasers and intended for high-sensitivity detection of ammonia and ethylene. The laser beam was collimated with an AR-coated aspheric ZnSe lens with focal length of 11.6 mm and clear aperture of 16.5 mm. Near- and far-field distributions of the laser emission were recorded with an infrared imaging camera. The fast-and slow-axis laser beam divergences were measured to be 1.2 and 1.4 mrad (FWHM), respectively. The divergence was found to be increasing with injection current. An air-spaced Fabry–Perot interferometer with free spectral range of 0.05 cm⁻¹ was used to measure the frequency tuning rates of the laser. The laser was tuned by either heat sink temperature, injection current or pulse repetition rate with rates of −8 × 10⁻² cm⁻¹ K⁻¹, −7 × 10⁻² cm⁻¹ A⁻¹ and −9 × 10⁻⁴ cm⁻¹ kHz⁻¹, respectively. The laser frequency decreased linearly with a rate of 10⁻² cm⁻¹ ns⁻¹ (300 MHz ns⁻¹) for laser pulses varied from 10 to 50 ns, and the frequency chirp rate was found to decrease for longer laser pulses.     

1-Chloronaphthalene decomposition in different gas mixtures under electron beam irradiation

The decomposition by electron beam (EB) irradiation of 1-chloronaphthalene in different gas matrices (air, N₂) was studied. Over 80% 1-chloronaphthalene was decomposed in air at 58 kGy dose when the initial concentration of 1-chloronaphthalene was 12–30 mg/Nm³. Over 50% 1-chloronaphthalene was decomposed in nitrogen when the initial concentration of 1-chloronaphthalene was 15–42 mg/Nm³.