Photoelectron Production Research Articles

Sunlight-Driven Direct/Mediated Electron Transfer for Cr(VI) Reductive Sequestration on Dissolved Black Carbon-Ferrihydrite Coprecipitates.

Surface runoff horizontally distributed chromium (Cr) pollution into various surface environments. Sunlight is a vital factor for the Cr cycle in the surface environment, which may be affected by photoactive substances such as ferrihydrite (Fh) and dissolved black carbon (DBC). Herein, sunlight-driven transformation dynamics of Cr species on DBC-Fh coprecipitates were studied. Under sunlight, the removal of aqueous Cr(VI) by DBC-Fh coprecipitates occurred through sunlight-driven reductive sequestration including adsorption, followed by surface reduction (pathway 1) and aqueous reduction, followed by precipitation (pathway 2). Additionally, coprecipitates with a higher DBC content exhibited a more effective reduction of both adsorbed (kapp,S_red) and aqueous Cr(VI) (kapp,A_red). Photoelectrons facilitated Cr(VI) reduction through direct electron transfer; notably, electron donating DBC promoted the production of photoelectrons by consuming photogenerated holes. Photogenerated Fe(II) species (mineral-phase and aqueous Fe(II)) mediated electron transfer for Cr(VI) reduction, which was reinforced via a ligand-to-metal charge transfer (LMCT) process between DBC-organic ligands and mineral Fe(III). Furthermore, ·O2- also mediated Cr(VI) reduction, although this impact was limited. Overall, this study demonstrates that photoelectrons and photogenerated electron mediators play a crucial role in Cr(VI) reductive sequestration on DBC-Fh coprecipitates, providing new insights into the geochemical cycle of Cr pollution in sunlight-influenced surface environments.

Natural AIEgens as Ultraviolet Sunscreens and Photosynergists for Solar Fuel Production.

Bio-nano hybrids (BNH), combining semiconductors and microorganisms, have shown great promise for effective solar-to-fuel energy conversion. However, the high-energy ultraviolet (UV) photons in the solar spectrum can cause severe photocorrosion of semiconductors and irreversible photodamage to microorganisms within BNH. Here, we developed an encapsulation strategy using natural luminogens with aggregation-induced emission characteristics (AIEgens) to construct a protective layer for BNH, effectively shielding them against high-energy UV photons. We incorporated natural berberine (BBR) into the BNH composed of Methanosarcina barkeri and polymeric carbon nitrides (CNx). The self-assembled BNH-BBR system displayed a 2.75-fold higher CH4 yield than BNH under simulated solar irradiation. Mechanism analysis revealed that BBR acted as a UV sunscreen for BNH by converting high-energy short wavelengths into low-energy long wavelengths, thereby reducing the accumulation of reactive oxygen species and alleviating the photocorrosion of CNx. Furthermore, BBR functioned as a photosynergist for BNH by regulating photoelectron production and utilization, enhancing the intracellular energy formation in M. barkeri for growth and metabolism. This work provides important insights into the effective and scalable conversion of CO2 into valuable biofuels with BNH under light illumination containing high-energy photons.

Parameterization of Secondary Ionization Rates and Photoelectron Heating Rates of Venus and Mars

AbstractAs a fundamental physical process in the ionosphere, photoionization and the associated photoelectrons play vital roles in determining the ionospheric electron density and temperature for Earth and other planets with atmospheres such as Mars and Venus. The production and transport of ionospheric photoelectrons have been widely examined on Earth, but relatively less studied for other terrestrial planets, such as Mars and Venus. In this study, a two‐stream photoelectron transport model for Mars and Venus is constructed, in which the photoelectron fluxes, photoelectron heating rates, primary and secondary ionization rates are calculated. The simulated photoelectron fluxes agree with Mars Atmosphere and Volatile Evolution (MAVEN) observations at various altitudes, with the input of solar spectrum irradiance, electron density and temperature, neutral density and temperature observed by MAVEN. Moreover, by parametrically fitting the simulation results for various solar zenith angles and solar activities, we obtain empirical parameterized formulas for ionization and heating efficiencies which can potentially be adapted to planetary ionospheric models for the community.

Well-dispersed copper and molybdenum co-doped g-C3N4 as an excellent persulfate activator for highly efficient removal of bisphenol a in wastewater

Degradation of endocrine disrupting compounds by optimizing advanced oxidation processes is highly feasible, but remains a daunting challenge. In this work, a novel copper and molybdenum co-doped g-C3N4 (Cu/Mo@CN) were successfully synthesized via a simple dip-calcination approach, of which highly dispersed Cu and Mo atom sites were doped in the ring of g-C3N4. The Cu/Mo@CN catalysts were characterized by XRD, SEM, TEM, XPS, UV–vis DRS analyses, etc. The optimized system of Cu1/Mo3@CN catalyst in the visible light-persulfate oxidation (Vis + PS + Cu1/Mo3@CN system) had high photocatalytic activity to remove 97.2 % of bisphenol A (BPA, 5 mg/L) within 60 min. Compared to pure g-C3N4, Cu/Mo@CN has better visible-light (Vis) response function and narrower band gap (2.58 eV), which are easier to get excited by Vis illuminate. The results showed that reactive oxygen species of SO4• −, •OH and •O2− could be stably produced to contribute to the BPA degradation in Vis + PS + Cu/Mo@CN systems. Meanwhile, the Cu and Mo elements co-doped in g-C3N4 can also effectively activate PS to promote the production of reactive oxygen substances. In addition, the continuous production of photoelectrons enhanced the cycling of Cu2+/Mo6+ and Cu+/Mo4+, which could be further improved the removal efficiency of Vis + PS + Cu/Mo@CN towards BPA. The degradation mechanism of BPA were proposed according to the identification of intermediate products and DFT calculation. Overall, this study provides a viable pathway for BPA abatement in actual wastewater treatment applications.

In-situ production and activation of H2O2 over hydroxyapatite modified CuFeO2 for self-sufficient heterogeneous photo-Fenton degradation of doxycycline hydrochloride

The self-sufficient heterogeneous photo-Fenton (SH-PF) system was constructed for doxycycline hydrochloride (DOH) degradation with hydroxyapatite (Hap) modified CuFeO2 (Hap/CuFeO2) composites through H2O2 in-situ production. The modification of Hap could improve the specific surface area, visible-light response, light conversion efficiency, photoelectron lifetime and oxygen vacancies (OVs) of CuFeO2, which was conducive to H2O2 production and DOH degradation in SH-PF system. Notably, Hap/CuFeO2 fabricated with 0.5 g Hap (Hap/CuFeO2-0.5) displayed more superior performance for DOH degradation compared to other synthesized catalysts. The Hap/CuFeO2-0.5 load and initial solution pH for DOH degradation in SH-PF system were optimized, and the Hap/CuFeO2-0.5 had good reusability and stability. The •OH was the main active species for DOH degradation, and the facilitation effect of •O2– and photoelectrons on DOH degradation was associated with the H2O2 production in the present work. In addition, the capture of photogenerated holes suppressed the recombination of photogenerated carriers, elevating the production of photoelectrons and thereby enhancing H2O2 production and DOH degradation. The degradation pathways for DOH were proposed and the comprehensive toxicities of DOH were relieved after degradation in SH-PF system.

Biophotoelectrochemical process co-driven by dead microalgae and live bacteria.

Anaerobic reduction processes in natural waters can be promoted by dead microalgae that have been attributed to nutrient substances provided by the decomposition of dead microalgae for other microorganisms. However, previous reports have not considered that dead microalgae may also serve as photosensitizers to drive microbial reduction processes. Here we demonstrate a photoelectric synergistic linkage between dead microalgae and bacteria capable of extracellular electron transfer (EET). Illumination of dead Raphidocelis subcapitata resulted in two-fold increase in the rate of anaerobic bioreduction by pure Geobacter sulfurreducens, suggesting that photoelectrons generated from the illuminated dead microalgae were transferred to the EET-capable microorganisms. Similar phenomena were observed in NO3- reduction driven by irradiated dead Chlorella vulgaris and living Shewanella oneidensis, and Cr(VI) reduction driven by irradiated dead Raphidocelis subcapitata and living Bacillus subtilis. Enhancement of bioreduction was also seen when the killed microalgae were illuminated in mixed-culture lake water, suggesting that EET-capable bacteria were naturally present and this phenomenon is common in post-bloom systems. The intracellular ferredoxin-NADP+-reductase is inactivated in the dead microalgae, allowing the production and extracellular transfer of photoelectrons. The use of mutant strains confirmed that the electron transport pathway requires multiheme cytochromes. Taken together, these results suggest a heretofore overlooked biophotoelectrochemical process jointly mediated by illumination of dead microalgae and live EET-capable bacteria in natural ecosystems, which may add an important component in the energetics of bioreduction phenomena particularly in microalgae-enriched environments.

X-ray sensitive selenium-containing Ru complexes sensitize nasopharyngeal carcinoma cells for radio/chemotherapy.

Radiotherapy has been extensively applied to cancer therapy in clinical trials. However, radiation resistance and dose limitation generally hamper the efficacy of radiotherapy. There is an urgent need for radiosensitizers with high efficiency and safety to enhance the anti-tumor effect of radiotherapy. In this paper, a selenium-containing (Se) ruthenium (Ru) complex (RuSe) was designed as a radiosensitizer to synergistically augment the killing effect of radiotherapy on nasopharyngeal carcinoma cells. In this system, the heavy atomic effect of Ru enhances the photoelectron production triggered by X-rays, thus inducing a burst of reactive oxygen species (ROS). In addition, Se atoms with a strong polarization property were introduced into the ligand of the metal complex to enhance the tumor chemo/radiotherapy effect. Consequently, RuC with a weak atomic polarization effect, as a comparison for RuSe, was also rationally explored to elucidate the role of Se atoms on chemo/radiotherapy sensitization. Indeed, compared with RuC, RuSe at a sub-toxic dose was able to potentiate the lethality of radiotherapy after preconditioning with cancer cells, by inducing ROS over-production, decreasing the mitochondrial membrane potential, and arresting the cell cycle at the sub-G1 phase. Furthermore, upon radiation, RuSe was superior to RuC, by inducing apoptotic cell death by activating caspase-3, -8, and -9. In summary, this study not only demonstrates an effective and safe strategy for the application of RuSe complexes to the cancer-targeted chemo/radiotherapy of human cancers, but also sheds light on the potential mechanisms of such Se-containing drugs as efficient radiotherapy sensitizers.

Preparation of a CeO2 ball-core structure and its application in quantum dot sensitized solar cells.

A pomegranate-like nanosphere structure of CeO2 was prepared by a simple one-step hydrothermal method, and the novel CeO2 structure was printed on a TiO2 film to form a scattering layer, which constituted the composite structure of a photoanode in a thin film optoelectronic device. Then ZnCuInSe quantum dots, a ZnS passivation layer and a CuS counter electrode were prepared, and these parts were assembled into quantum dot-sensitized solar cells. By changing the thickness of the scattering layer film in the photoanode, the quantum dots were adsorbed on TiO2 more effectively. By using the special ball-core structure, light was scattered so that the photoanode used the light many times, which effectively increased the efficiency of photoelectron production. After electrochemical testing of the device, it was found that the photoconversion efficiencies of the TiO2 transparent layer and the CeO2 scattering layer composite photoanode were greater than that of a single TiO2 photoanode without a scattering layer. The results showed that when the thickness of the scattered layer was 10 ± 1 μm, the highest photoelectric conversion efficiency (PCE) was obtained, which was 20% higher than that seen with TiO2 alone.

Vertical nanowires enhanced X-ray radiation damage of cells

Cell behavior is affected by nanostructured surface, but it remains unknown how ionizing radiation affects cells on nanostructured surface. This paper reports an experimental investigation of X-ray radiation induced damage of cells placed on an array of vertically aligned silicon nanowires. X-ray photoelectrons and secondary electrons produced from nanowire array are measured and compared to those from flat silicon substrate. The cell functions including morphology, viability, adhesion and proliferation have been examined and found to be drastically affected when cells are exposed to X-ray radiation, compared to those sitting on flat substrate and those only exposed to X-ray. The enhanced cell damage on nanowires upon X-ray exposure is attributed to nanowire enhanced production of photoelectrons including Auger electrons and secondary electrons, which have high escaping probability from sharp tips of nanowires. The escaped photoelectrons ionize water molecules and generate hydroxyl free radicals that can damage DNAs of cells. An inference of this work is that the contrast in scanning electron microscopy is useful in assessing the effects of nanomaterials for enhanced X-ray radiation therapy.

Influence of nano-sized horizontal inhomogeneities on surface profiling by means of XPS

Quantitative analysis of thin films surface is performed by means of X-ray electron spectroscopy (XPS) according to a calculation model assuming surface layers of the target to be homogeneous and parallel. However, almost every surface of an ultra-thin film is rough. A study of such surface using the plane-parallel layer model will lead to incorrect results. This work proposes to use the model of inhomogeneous stochastic nano-structured surface layer for ultra-thin film profiling. Surface stochastic nano-structured inhomogeneities are described by the normal Gauss distribution function. To determine these inhomogeneities, three parameters are specified: dispersion (spread of thicknesses by the layer), mean and maximal thickness of the surface layer. For the first time, the type of X-ray photoelectron spectrum of an inhomogeneous stochastic nano-structured surface is found that is determined by functions of photoelectron production and transmission through that surface layer. The designed model is based on the following assumptions: photoelectrons are produced in substance and travel straight-forward (Straight Line Approximation) along the surface, photoelectron flux density decreases in the layer according to the Bouguer–Lambert law, photoelectrons of different energies lose energy differently, photoelectron energy losses in bulk and on surface differ. Modeling of X-ray photoelectron spectra of an oxidized metal film is performed using different models: homogeneous plane-parallel layers, an island nano-structured surface layer and an inhomogeneous stochastic nano-structured surface layer. Ranges of applicability of plane-parallel layer models and simple periodical nano-structured island surface layer for inhomogeneous stochastic nano-structured surface profiling are determined. The model of homogeneous plane-parallel layers shows satisfactory profiling results by some values of parameters of an inhomogeneous stochastic surface layer. It is shown that the model of a simple periodically nano-structured island layer leads to inadequate results by profiling of an inhomogeneous stochastic surface. The investigation shows that for more accurate profiling of an inhomogeneous ultra-thin film, it is necessary to consider inhomogeneity of a real surface, otherwise the calculated results would not match the true profile.

Core-shell nanosheets@MIL-101(Fe) heterostructures with enhanced photocatalytic activity promoted by peroxymonosulfate

BackgroundMetal organic frameworks (MOFs) heterojunctions, especially MOF-on-MOF structures, have provided a great opportunity to extend their applications in various fields. But it is still a great challenge to develop MOF-based heterogeneous architectures for high-efficient photocatalysts. MethodThe core-shell NS@MIL-101(Fe) architectures were synthesized through a solvothermal method in one pot. The moderately active precursor was selected as the precursor which could promote the generation of hybrid MOFs with different microstructures. Significant findingsNS@MIL-101(Fe) heterojunctions exhibit hierarchical structures composed of the octahedron MIL-101(Fe) cores covered with the ultrathin sheet-like shells. The architectures are beneficial to the production of stable photoelectrons and holes, their easy transfer and separation, which further promote the generation of various reactive oxygen species, such as •OH and SO4•−. The surface-bound metal active sites are also favorable to the formation of various radicals. The unique hybrid MOFs exhibit enhanced degradation efficiency towards Orange II through the visible-light-assisted activation of the PMS process. This facile route for the synthesis of multi-component MOFs provides a new strategy for the design of MOF-based photocatalysts.

Dynamic pressure evolution during the LHC operation

For the accelerator community and the vacuum scientists, the understanding of the beam interactions with a vacuum chamber is fundamental to provide solutions to mitigate pressure rises induced by electron, photon, and ion molecular desorption. Moreover, beam instabilities induced by ion and electron clouds must be investigated in order to find solutions to reduce them. This study presents in situ measurements of pressure evolutions and electrical currents performed during the LHC RUN II (2018). The proton beam circulating in the LHC vacuum chamber ionizes the residual gas producing electrons as well as positive ions. These charged particles are accelerated away from the beam and reach the vacuum chamber wall, inducing, among other phenomena, stimulated desorption and secondary electron emission. Moreover, protons emit synchrotron radiations that also induce photodesorption and photoelectron production. Experimental measurements of the electrical signals recorded on copper electrodes were compared to calculations considering both the secondary electron yield of copper and the electron energy distribution. All measurements performed with the Vacuum Pilot Sector in the LHC ring show the importance of taking into account a large variety of phenomena in order to understand the pressure evolution in the LHC. Results show that the multipacting threshold, corresponding to an increase in the electron cloud density, strongly depends on the number of protons per bunch. Finally, the ion current was measured with a biased electrode lower than $\ensuremath{-}500\text{ }\text{ }\mathrm{V}$. It was much higher than expected, pointing its origin not only from simple beam-gas ionization but also from the ionization of the residual gas by the electron cloud.

Visible-light-driven CQDs/TiO2 photocatalytic simultaneous removal of Cr(VI) and organics: Cooperative reaction, kinetics and mechanism

CQDs/TiO2 was synthesized with a coprecipitation method and characterized by XRD, SEM, TEM/HRTEM, BET, XPS, UV–Vis DRS and I-t curve technologies. UV–Vis DRS displayed that absorption spectrum of CQDs/TiO2 enlarged to visible light zone, suggesting that CQDs/TiO2 can be irradiated by visible light. I-t curve showed that photocurrent of CQDs/TiO2 was higher than that of bare TiO2, revealing that the doping of CQDs accelerated the transfer of photoelectrons and restrained the recombination of photoinduced carriers. Simultaneous removal of Cr(VI) and organics with CQDs/TiO2 photocatalytic reaction was investigated and factors were optimized, and almost all Cr(VI) and organics were removed under the optimum conditions. Experimental results displayed that there was a distinct cooperation removal effect between Cr(VI) and organics in CQDs/TiO2 photocatalytic reaction. XPS analysis proved that Cr(VI) was reduced to Cr(III) in situ on CQDs/TiO2 surface. There were e−, h+,·OH and ·O2− active species which were detected with DMPO in ESR test during CQDs/TiO2 photocatalytic reaction, and scavenger experiment proved that e− and h+ were the substantial reactants for Cr(VI) and organics, respectively. The pathway of photocatalytic simultaneous removal of Cr(VI) and organics underwent four steps: adsorption of Cr(VI) and organics on CQDs/TiO2 surface; production of photo electrons and holes in visible light; reduction of Cr(VI) and oxidation of organics; desorption of Cr(III) and intermediates. Photocatalytic reaction kinetics of Cr(VI) and organics were both confirmed to pseudo first-order reaction. Life span and small scale real application tests both demonstrated that CQDs/TiO2 had a potential application to wastewater containing Cr(VI) and organics.

Self-replicating Biophotoelectrochemistry System for Sustainable CO Methanation.

Efficient conversion of CO-rich gas to methane (CH4) provides an effective energy solution by taking advantage of existing natural gas infrastructures. However, traditional chemical and biological conversions face different challenges. Herein, an innovative biophotoelectrochemistry (BPEC) system using Methanosarcina barkeri-CdS as a biohybrid catalyst was successfully employed for CO methanation. Compared with CO2-fed BPEC, BPEC-CO significantly extended the CH4 producing time by 1.7-fold and exhibited a higher CH4 yield by 9.5-fold under light irradiation. This superior conversion of CO resulted from the fact that CO could serve as an effective quencher of reactive species along with the photoelectron production. In addition, CO was used as a carbon source either directly or indirectly via the produced CO2 for M. barkeri. Such a process improved the redox activities of membrane-bound proteins for BPEC methanogenesis. These results were consistent with the transcriptomic analyses, in which the genes for the putative CO oxidation and CO2 reduction pathways in M. barkeri were highly expressed, while the gene expression for reactive oxygen species detoxification remained relatively stable under light irradiation. This study has provided the first proof-of-concept evidence for sustainable CO methanation under a mild condition in the self-replicating BPEC system.

The effect of mixing Chlorophyll-Antocyanin as a natural source dye on the efficiency of dye-sensitized solar cell (DSSC)

Sunlight is a natural alternative energy as a renewable energy source. Dye-Sensitized Solar Cell (DSSC) is third generation solar cell as a substitute for conventional solar cells made from silicon because it is easy to manufacture. One important part of DSSC is dye because it has an important role in light absorption, photoelectron production, and electron transfer processes to increase the efficiency of electrical energy conversion. Modification of dye as an active material for DSSC as an effort to improve the performance of optical properties and photoconductivity of the dye. Mixing chlorophyll dye with anthocyanin dye aims to widen the area of the visible light absorption band. Chlorophyll dye obtained from green spinach extract and anthocyanin dye obtained from red rose extract. Absorbance test using UV-Vis Spectrophotometer obtained a widening of the light absorption range at 400-700 nm. The conductivity test using Keithley I-V meter 2602A to determine the dye’s ability to conduct electric current, the best conductivity was obtained in the 1:2 chlorophyll-anthocyanin mixture is 4.83 x10−2 Ω−1 m−1. The I-V DSSC test using Keithley I-V meter 2602A obtained the best electrical energy conversion efficiency in the 1:2 chlorophyll-anthocyanin dye mixture is 5.8 x10−2 %.

Cation-exchange synthesis of PbSe/ZnSe hetero-nanobelts with enhanced near-infrared photoelectronic performance

To develop excellent photoelectronic and photovoltaic devices, a semiconductor with high photoelectron production efficiency and broad band absorption is urgently required. In this article, novel II-type PbSe/ZnSe hetero-nanobelts with enhanced near-infrared absorption have been synthesized via a facile strategy of a partial cation-exchange reaction and thermal treatment. Derived from ZnSe·0.5N2H4 nanobelts as templates, the belt-like morphology was preserved. Due to the mismatch of the crystal type and parameters between PbSe and ZnSe, the formed PbSe in the form of nanoparticles were separated out and decorated on the nanobelts. Furthermore, the composition ratio of Pb/Zn can be tuned through manipulating the adding amount of Pb2+ cations, the reaction temperature and time. The ultraviolet−visible−infrared diffuse spectra measurements suggest that the as-prepared PbSe/ZnSe hetero-nanobelts exhibited a broad band absorption from 300 to 1000 nm. In addition, they demonstrated excellent photoresponsivity in the same wavelength region and displayed a peak at approximately 840 nm. Finally, the enhanced photoelectronic sensing mechanism was discussed.

Role of MnO2 in controlling iron and arsenic mobilization from illuminated flooded arsenic-enriched soils

This study examined the role of intermittent illumination/dark conditions coupled with MnO2-ammendments to regulate the mobility of As and Fe in flooded arsenic-enriched soils. Addition of MnO2 particles with intermittent illumination led to a pronounced increase in the reductive-dissolution of Fe(III) and As(V) from flooded soils compared to a corresponding dark treatments. A higher MnO2 dosage (0.10 vs 0.02 g) demonstrated a greater effect. Over a 49-day incubation, maximum Fe concentrations mobilized from the flooded soils amended with 0.10 and 0.02 g MnO2 particles were 2.39 and 1.85-fold higher than for non-amended soils under dark conditions. The corresponding maximum amounts of mobilized As were at least 92 % and 65 % higher than for non-amended soils under dark conditions, respectively. Scavenging of excited holes by soil humic/fulvic compounds increased mineral photoelectron production and boosted Fe(III)/As(V) reduction in MnO2-amended, illuminated soils. Additionally, MnO2 amendments shifted soil microbial community structure by enriching metal-reducing bacteria (e.g., Anaeromyxobacter, Bacillus and Geobacter) and increasing c-type cytochrome production. This microbial diversity response to MnO2 amendment facilitated direct contact extracellular electron transfer processes, which further enhanced Fe/As reduction. Subsequently, the mobility of released Fe(II) and As(III) was partially attenuated by adsorption, oxidation, complexation and/or coprecipitation on active sites generated on MnO2 surfaces during MnO2 dissolution. These results illustrated the impact of a semiconducting MnO2 mineral in regulating the biogeochemical cycles of As/Fe in soil and demonstrated the potential for MnO2-based bioremediation strategies for arsenic-polluted soils.

Comparison of Bi2S3 and Ta2O5 as alternative materials to gold in nanoparticles used as agents to increase the dose in radiotherapy

Radiotherapy is an essential component in the treatment of all types of cancer. Radiotherapy uses ionizing radiation to destroy tumor tissue while reducing the damage to normal tissue as much as possible. In this work we study the effects of the spherical Bi2S3 and Ta2O5 nanoparticles (NPs) used as a radio-sensitization agent to increase local doses around the nanoparticle in a water medium. For low energy X-rays the dominant interaction is the photoelectric effect, which involves the absorption of a photon and the subsequent production of photoelectrons, characteristic X-rays and Auger electrons. Using a GEANT4 based simulation was determined the kinetic energy spectra of secondary electrons produced by the interaction of X-ray beam and Au, Bi2S3 and Ta2O5 NPs, after that was calculated the interaction processes, energy deposited, absorbed dose and the effective range distributions for the secondary electrons generated by the interaction of 100 million incident photons in the nanoparticles. The size of the nanoparticles was 20 nm and the energy distribution of the photons corresponds to the spectrum of a tube of x-rays with Tungsten anode and a peak voltage applied of 40 kV. This study demonstrates that Bi2S3 and Ta2O5 NPs are a viable alternative to Au NPs as a dose enhancing agent in radiotherapy.

Photoelectron balance in the dayside Martian upper atmosphere

Photoelectrons are produced by solar Extreme Ultraviolet radiation and contribute significantly to the local ionization and heat balances in planetary upper atmospheres. When the effect of transport is negligible, the photoelectron energy distribution is controlled by a balance between local production and loss, a condition usually referred to as local energy degradation. In this study, we examine such a condition for photoelectrons near Mars, with the aid of a multi-instrument Mars Atmosphere and Volatile Evolution data set gathered over the inbound portions of a representative dayside MAVEN orbit. Various photoelectron production and loss processes considered here include primary and secondary ionization, inelastic collisions with atmospheric neutrals associated with both excitation and ionization, as well as Coulomb collisions with ionospheric thermal electrons. Our calculations indicate that photoelectron production occurs mainly via primary ionization and degradation from higher energy states during inelastic collisions; photoelectron loss appears to occur almost exclusively via degradation towards lower energy states via inelastic collisions above 10 eV, but the effect of Coulomb collisions becomes important at lower energies. Over the energy range of 30–55 eV (chosen to reduce the influence of the uncertainty in spacecraft charging), we find that the condition of local energy degradation is very well satisfied for dayside photoelectrons from 160 to 250 km. No evidence of photoelectron transport is present over this energy range.

Investigation of the Strongly Correlated Two-Hole State of Copper in Resonant Photoemission States of Chalcogenide Materials for Photovoltaics

The processes of direct and two-stage production of photoelectrons and the participation of internal states in the spectra of electrons from valence bands with resonant photoemission in copper chalcogenides Cu(In,Ga)Se2 have been studied experimentally. Final two-hole states in photoemission have been obtained at the threshold excitation of the Cu 2p level. The strong interaction of holes leads to the multiplet splitting of these states. The value of the Hubbard repulsion of holes on the copper atom has been found to be 7 eV.