Palladium nanoparticles (Pd-NPs) have been approved as an effective catalyst for hydrogen peroxide decomposition which is released during specific enzymatic reactions. However, the general ...operational principles and electrochemical performance of Pd-NPs-based nanobiosensors have been poorly exploited. Here, the electrochemical behavior of oxidase-associated peroxide oxidation co-catalysis of the modelled microanalytical system based on screen-printed electrodes modified by electroplated Pd-NPs as an electrocatalyst, glucose oxidase (GOx) or alcohol oxidase (AOx) as a bioreceptor and the ionomer Nafion as a polymeric binding agent was studied in detail. The impact of palladium surface oxides and adsorbed oxygen on the activity and product selectivity in an oxidase type of nanobiosensor was ascertained. To avoid PdO and oxygen electroreduction affecting the entire amperometric response of Pd-NPs-based nanobiosensors, a special two-step polarization procedure was proposed. Under the established electrochemical conditions, Pd-NPs-based nanobiosensors with encapsulated oxidases showed a wide dynamic range towards selective bioanalyte detection, excellent basic line stability, accuracy and resistance to the presence of interfering electrochemical species. This work can serve as a guideline for the search and validation of operational principles of novel biosensors based on nanoparticles.
The role of palladium surface oxides and adsorbed oxygen in the analytical performance of Pd-NPs-based nanobiosensors is ascertained.
PdRh/C catalyst and electrodeposited Pd, Rh and PdRh particles on glassy carbon electrode were studied in methanol and ethanol oxidation reactions in comparison with Pt-containing catalysts. Some ...features of this process have been described: (1) the appearance of oxidation peak in acidic and neutral media is possible only when polarization on CV is prolonged to hydrogen adsorption region where the surface OH-group formation occurred and surface oxides are reduced; (2) the CV-responses of model systems (electrodeposited Pd, Rh, PdRh) corresponding to alcohol oxidation increase and deform even during relaxation period when polarization is switched off; (3) experiments with addition of corresponding aldehydes (formaldehyde, acetaldehyde) to alcohol solution with stabilized CV responses showed that only increase in currents but not deformation of CV occurred. The addition of acid residue did not change the response noticeably. The formation of the same electroactive species, gem-diolate, for both alcohol and aldehyde electrooxidation mechanisms was supposed.
Several features probably formed by contour bottom currents were recognized on the Rio Grande Rise by high-resolution seismic survey in the transatlantic profiles of the #32 and #52 cruises of R/V
...Akademik Ioffe
carried out by the Shirshov Institute of Oceanology, Russian Academy of Sciences. The deposits of mixed turbidite–contourite sedimentary systems near the base of its southern and northern slopes seem to be formed as a result of the interaction of downslope gravity flows and the along-slope deep-water Lower Circumpolar Water + Weddell Sea Deep Water current. Sediment waves and disputable small plaster contourite drifts are probably formed by circulation of the Antarctic Intermediate Water in the Cruzeiro-do-Sultrough at the top of the rise.
A spontaneous Raman signal at the frequency of the triply degenerate optical phonon of diamond is observed in the photoluminescence spectrum under the pre-filamentation excitation of natural diamond ...by ultrashort laser pulses with a wavelength of 515 nm, fixed intensity, and a duration varied in the range of 0.3–12 ps. The inhomogeneous blue broadening of the line (0.6–1.3 ps), almost symmetric splitting of the line into three components (2.3–6.3 ps), and very strong homogeneous broadening of the entire line are observed at pulse durations of 6.3–12 ps. Transformations of the lineshape of the optical phonon, which are observed for the first time, are attributed to the subpicosecond dynamics of the electron–hole plasma and the (sub)picosecond dynamics of local mechanical stresses induced by the plasma and nonequilibrium phonons.
The first stage of the petawatt excimer laser project started at the P.N. Lebedev Physical Institute, implements a development of multiterawatt hybrid GARPUN-MTW laser facility for generation of ...ultra-high intensity subpicosecond ultraviolet (UV) laser pulses. Under this project, a multi-stage e-beam-pumped 100-J, 100-ns GARPUN KrF laser was upgraded with a femtosecond Ti:Sapphire front-end, to produce combined subpicosecond/nanosecond laser pulses with variable time delay. Attractive possibility to amplify simultaneously short and long pulses in the same large-scale KrF amplifiers is analyzed with regard to the fast-ignition, inertial confinement fusion problem. Detailed description of hybrid laser system is presented with synchronized KrF and Ti:Sapphire master oscillators. Based on gain and absorption measurements at GARPUN amplifier and numerical simulations with a quasi-stationary code, we are predicting that 1.6 J can be obtained in a short pulse at hybrid GARPUN-MTW Ti:Sapphire/KrF laser facility, combined with several tens of joules in nanosecond pulse. Amplified spontaneous emission, which is responsible for the pre-pulse formation on a target, was also investigated: its acceptable level can be provided by properly choosing staged gain or loading the amplifiers by quasi-steady laser radiation. Fluorescence and transient absorption spectra of Ar/Kr/F2 mixtures conventionally used in KrF amplifiers were recorded to find out the possibility for femtosecond pulse amplification at the broadband Kr2F (42Γ → 1,2 2Γ) transition, which benefits in 100 times higher saturation energy density than for KrF (B → X) transition.
Morphology of the Rio Grande Rise and the acoustic structure of different types of deposits in its uppermost sedimentary cover were discussed based on high-resolution seismoacoustic profiling of ...cruises #32 (2010) and #52 (2016) of R/V
Akademik Ioffe
. Slopes of the Rio Grande Rise are composed mainly of landslide deposits and gravitites, but contourite sedimentation is possible on its southern slope. Contourite sedimentary waves and, probably, small drifts are identified in the Cruzeiro do Sul Trough at the top of the Rio Grande Rise. Mixed gravitite–contourite sedimentary systems seem to be located at the foot of northern and southern slopes. The downslope density flows and the Antarctic Bottom Water (AABW) contourite current are responsible for the formation of these features.
► Mn3+ ions form the anti-site defects in A-site of ABO3 perovskite cell for x>0.1 sample. ► Griffiths-like singularity is originated by strain accommodation field. ► Strain accommodation is caused ...by the vacancies in A- and B-sites of the perovskite cell.
Self-doped La1−xMnO3+δ manganites (x=0.0, 0.05, 0.1, and 0.15) have been studied by X-ray diffraction, X-ray absorption near K-edge spectroscopy and magnetization measurements. The x=0.0 composition is the orthorhombic Pnma phase with a small amount of the rhombohedral R3¯c one, the compounds with x=0.05, 0.1 and 0.15 exhibit the R3¯c space group. The Curie temperature, TC, increases with x increase substantially. The TC of the x=0.1 and x=0.15 samples are almost the same, but magnetization of the x=0.15 composition is much higher than that of the x=0.1 sample. The results for the x=0.15 sample are in agreement with the suggestion that a part of manganese ions, being in a trivalent state, occupies a vacant A-site of the perovskite ABO3 cell. Magnetic behavior of the samples above TC exhibits Griffiths-like features. The observed Griffiths singularity is suggested to be due to strain accommodation caused by the vacancies in the A- and B-positions of the ABO3 perovskite cell.
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