Quantitative 3D Determination of Radiosensitization by Bismuth-Based Nanoparticles.

The nanoparticle-induced dose enhancement effect has been shown to improve the therapeutic efficacy of ionizing radiation in external beam radiotherapy. Whereas previous studies have focused on gold nanoparticles (AuNPs), no quantitative studies have been conducted to investigate the potential superiority of other high atomic number (Z) nanomaterials such as bismuth-based nanoparticles. The aims of this study were to experimentally validate and quantify the dose enhancement properties of commercially available bismuth-based nanoparticles (bismuth oxide (Bi2O3-NPs) and bismuth sulfide (Bi2S3-NPs)), and investigate their potential superiority over AuNPs in terms of radiation dose enhancement. Phantom cuvettes doped with and without nanoparticles where employed for measuring radiation dose enhancement produced from the interaction of radiation with metal nanoparticles. Novel 3D phantoms were employed to investigate the 3D spatial distribution of ionising radiation dose deposition. The phantoms were irradiated with kilovoltage and megavoltage X-ray beams and optical absorption changes were measured using a spectrophotometer and optical CT scanner. The radiation dose enhancement factors (DEFs) obtained for 50 nm diameter Bi2O3-NPs and AuNPs were 1.90 and 1.77, respectively, for 100 kV energy and a nanoparticle concentration of 0.5 mM. In addition, the DEFs of 5 nm diameter Bi2S3-NPs and AuNPs were determined to be 1.38 and 1.51, respectively, for 150 kV energy and a nanoparticle concentration of 0.25 mM. The results demonstrate that both bismuth-based nanoparticles can enhance the effects of radiation. For 6 MV energy the DEFs for all the investigated nanoparticles were lower (< 15%) than with kilovoltage energy.

Enhanced photocatalytic degradation of norfloxacin in aqueous Bi2WO6 dispersions containing nonionic surfactant under visible light irradiation.

Photocatalytic degradation is an alternative method to remove pharmaceutical compounds in water, however it is hard to achieve efficient rate because of the poor solubility of pharmaceutical compounds in water. This study investigated the photodegradation of norfloxacin in a nonionic surfactant Triton-X100 (TX100)/Bi2WO6 dispersion under visible light irradiation (400-750nm). It was found that the degradation of poorly soluble NOF can be strongly enhanced with the addition of TX100. TX100 was adsorbed strongly on Bi2WO6 surface and accelerated NOF photodegradation at the critical micelle concentration (CMC=0.25mM). Higher TX100 concentration (>0.25mM) lowered the degradation rate. In the presence of TX100, the degradation rate reached the maximum value when the pH value was 8.06. FTIR analyses demonstrated that the adsorbed NOF on the catalyst was completely degraded after 2h irradiation. According to the intermediates identified by HPLC/MS/MS, three possible degradation pathways were proposed to include addition of hydroxyl radical to quinolone ring, elimination of piperazynilic ring in fluoroquinolone molecules, and replacement of F atoms on the aromatic ring by hydroxyl radicals.

Bandgap Tunability in Sb-Alloyed BiVO4 Quaternary Oxides as Visible Light Absorbers for Solar Fuel Applications.

The challenge of fine compositional tuning and microstructure control in complex oxides is overcome by developing a general two-step synthetic approach. Antimony-alloyed bismuth vanadate, which is identified as a novel light absorber for solar fuel applications, is prepared in a wide compositional range. The bandgap of this quaternary oxide linearly decreases with the Sb content, in agreement with first-principles calculations.

Synthesis of BiVO4@C Core-Shell Structure on Reduced Graphene Oxide with Enhanced Visible-Light Photocatalytic Activity.

Herein, a facile strategy for the controllable synthesis of BiVO4@C core-shell nanoparticles on reduced graphene oxide (RGO) is reported. The BiVO4 particle size can be controlled in the process by adjusting the volume ratio of glycerol in the sol-gel solution. The glycerol layers adsorbed on BiVO4 (BiVO4@glycerol) made it possible to form hydrogen bonds between BiVO4@glycerol and graphene oxide with the assistance of ultrasound. After thermal treatment, glycerol adsorbed on the BiVO4 particles formed amorphous carbon shells to link the particles and RGO. As a result, the obtained RGO-BiVO4@C nanocomposite showed a five times higher rate in O2 evolution from water under visible-light irradiation. Also, it demonstrated a six times higher photocatalytic performance enhancement than that of pure BiVO4 in the degradation of Rhodamine B. The enhanced performance is attributed to the carbon shells that restrict the growth of BiVO4 , the reduced graphene oxide that improves the electronic conductivity of the composite, and importantly, the bonds formed between the carbon shells and RGO that reduce the recombination loss of photogenerated charges effectively. The strategy is simple, effective, and can be extended to other ternary oxides with controlled size and high performance.

Preventing bacterial growth on implanted device with an interfacial metallic film and penetrating X-rays.

Device-related infections have been a big problem for a long time. This paper describes a new method to inhibit bacterial growth on implanted device with tissue-penetrating X-ray radiation, where a thin metallic film deposited on the device is used as a radio-sensitizing film for bacterial inhibition. At a given dose of X-ray, the bacterial viability decreases as the thickness of metal film (bismuth) increases. The bacterial viability decreases with X-ray dose increases. At X-ray dose of 2.5 Gy, 98% of bacteria on 10 nm thick bismuth film are killed; while it is only 25% of bacteria are killed on the bare petri dish. The same dose of X-ray kills 8% fibroblast cells that are within a short distance from bismuth film (4 mm). These results suggest that penetrating X-rays can kill bacteria on bismuth thin film deposited on surface of implant device efficiently.

Production of (211)At by a vertical beam irradiation method.

We produced (211)At by irradiating the semi-sealed encapsulated Bi target with an external vertical beam. At 28.5MeV, the yield of (211)At was 22MBq/µAh (600µCi/µAh). (211)At was recovered by dry distillation, and 80% of the produced (211)At was successfully obtained in dry Na(211)At form within 2h from the end of bombardment (EOB). The radionuclidic purity of (211)At was >99% at 5h from EOB.

A superior photocatalytic performance of a novel Bi2SiO5 flower-like microsphere via a phase junction.

A phase junction over a Bi(2)SiO(5) photocatalyst with the orthorhombic Bi(2)SiO(5) and the tetragonal Bi(2)SiO(5) structure was successfully synthesized via an ion exchange method using BiOBr solid microspheres as the sacrificial template. In the meantime, the as-prepared Bi(2)SiO(5) phase junction possesses a novel morphology of a flower-like microsphere with nanoparticles evenly embedded in its nano-petals. It was found that the Bi(2)SiO(5) phase junction not only showed a highly enhanced photocatalytic activity and excellent durability under UV or simulated solar irradiation, but also showed a remarkable visible-light activity for photo-degradation of phenol. Experimental results reveal that the tetragonal Bi(2)SiO(5) phase in this phase junction possesses a narrower band gap, thus leading to its extended light absorption. The efficient charge separation via a phase junction would make a great contribution to its highly enhanced photocatalytic activity under UV or simulated solar irradiation. The high efficiency in the degradation of organic pollutants makes the as-prepared photocatalyst a promising candidate for photocatalytic environmental purification.

A computational study on the photoelectric properties of various Bi2O3 polymorphs as visible-light driven photocatalysts.

This paper presents first-principle studies on the photoelectric properties of various Bi2O3 polymorphs. The intrinsic reason of different photocatalytic activities was revealed by electronic structures and optical features. Results showed that for α, ß, and γ-Bi2O3, the top of valence bands were mainly constructed by Bi6s and O2p orbitals, and the bottom of conduction bands were dominantly composed by Bi6p orbital. However, two intermediate bands were found at the Fermi level for γ-Bi2O3, which leads to a two-step transition from the top of valence band to the bottom of conduction band and facilitates electron transition under irradiation. Absent forbidden gap was found in δ-Bi2O3, resulting in a semimetallic character due to its intrinsic oxygen vacancy and high ionic conductivity. Moreover, the optical properties of α, ß, and γ-Bi2O3 were investigated by absorption spectrum, dielectric constant function, and energy loss spectroscopy. We concluded that the photocatalytic activities followed in the order of γ-Bi2O3 > ß-Bi2O3 > α-Bi2O3, in accord with the experimental report. Calculation results illustrated the experimental observations and provided a useful guidance in exploring promising visible-light semiconductor photocatalysts.

Enhanced broadband excited upconversion luminescence in Ho-doped glasses by codoping with bismuth.

We report enhanced green and red upconversion (UC) luminescence in Ho3+-doped oxyfluoride germanate glass by introducing bismuth near-infrared active centers as sensitizers. The UC excitation bands at 750 and 970 nm show a full width at half-maximum of 20 and 45 nm, respectively. Energy transfer from sensitizers, the excited-state absorption, and phonon-coupled absorption of Ho3+ jointly contribute to the enhanced UC luminescence. Our approach provides an efficient methodology to broaden the excitation bandwidth of UC luminescent materials, which may have the potential for promising application in solar cells.

Influence of ultrasonic activation of 4 root canal sealers on the filling quality.

INTRODUCTION: The purpose of this study was to evaluate the effects of ultrasonic activation on the filling quality (intratubular sealer penetration, interfacial adaptation, and presence of voids) of 4 epoxy resin-based sealers. METHODS: Eighty-four extracted human canines were divided into 4 groups (n = 20) according to the sealer used to obturate the root canals instrumented with F5 ProTaper instruments (50/05) (Dentsply Maillefer, Ballaigues, Switzerland). The canals were filled by the lateral compaction technique. Previously, the sealers were labeled with rhodamine B dye to allow analysis under a confocal microscope. At the time of obturation, the specimens were divided again into 2 groups (n = 10) according to the ultrasonic activation of the sealers: ultrasonically activated and nonultrasonically activated groups. All samples were sectioned at 2, 4, and 6 mm from the apex. The percentages of voids, gaps, and dentinal sealer penetration segments of the canal were analyzed. RESULTS: Regarding the sealer penetration segments, there was a significant increase for the AH Plus (Dentsply Maillefer), Acroseal (Specialités Septodont, Saint Maur-des-Fossés, France), and Sealer 26 (Dentsply Maillefer) at the 4-mm level and the AH Plus and Sealer 26 at the 6-mm level with ultrasonic activation (P < .05). Concerning the gaps, the ultrasonic activation promoted a smaller presence for all sealers at the 4- and 6-mm levels (P < .05). No statistical significant differences were found for the percentages of voids (P < .05). CONCLUSIONS: The use of ultrasonic activation of an epoxy resin-based sealer promoted greater dentinal sealer penetration and less presence of gaps.

Efficient adsorption and photocatalytic degradation of Rhodamine B under visible light irradiation over BiOBr/montmorillonite composites.

BiOBr/Na-montmorillonite composites (BiOBr-Mt) were prepared under laboratory ambient conditions by using the surfactant cetyltrimethylammonium bromide (CTAB) as the Br source and template, and the as-synthesized samples were characterized by XRD, FT-IR, FESEM, TEM equipped with EDS, BET and UV-vis DRS techniques. Interestingly, the particle size of BiOBr can be controlled by CTAB modified Na-montmorillonite. The photocatalytic activity of the as-prepared was further evaluated by decomposition of Rhodamine B (RhB) under visible light irradiation; the obtained results revealed that the BiOBr-Mt sample had strong photoabsorption in the visible light region. It has higher photocatalytic activity than pure BiOBr alone. There exists an efficient adsorption for RhB onto BiOBr-Mt contrast to that onto the pure BiOBr. The adsorption processes can be well described by pseudo-second-order kinetic model; meanwhile, the adsorption behaviors can be described by both Freundlich and Langmuir equations but the former was better. Additionally, the relevant adsorption and degradation mechanisms were explored and the possible mechanisms were presented. The photocatalytic activity has high effect both in acidic and basic conditions on the degradation reaction but in acidic condition is more favorable. After three recycles, BiOBr-Mt did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst was essentially stable.

Highly visible-light-responsive photocatalytic AgCl/BiOCl hetero-nanostructures synthesized by a chemical coprecipitation method.

AgCl/BiOCl heteronanostructures were synthesized by a room-temperature chemical coprecipitation method. The as-obtained products were characterized by energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse spectra, which show the structures, morphologies, and optical properties. The results revealed that the absorption edge of AgCl/BiOCl shifted towards visible light regions. Meanwhile, the AgCl/BiOCl heteronanostructures showed better photocatalytic properties than the pure BiOCl to degrade rhodamine B and the 5% AgCl/BiOCl showed the best photocatalytic ability, which completely decomposed the target molecules in 17 minites with the visible-light illumination. The formation of heteronanostructures might improve the separation of photogenerated electrons and holes derived from the coupling effect of BiOCl and AgCl heteroarchitectures, which was regarded as the main reason for the high photocatalytic activity.

Template-free hydrothermal synthesis different morphologies of visible-light-driven BiVO4 photocatalysts.

Monoclinic BiVO4 nano- and microstructures with a diversity of well-defined morphologies, such as nanoplates, dendrite leaves-like structures, sub-microrods, and microflowers were synthesized via a template-free hydrothermal process with bismuth nitrate and ammonium metavanadate as metal source. The crystal structures, morphologies and optical properties of the as-prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectra (UV-vis). Results showed that the pH value of the solution and the volume of ethylenediamine have great effect on the formation of these unique structures. The photocatalytic activity of these as-prepared samples had been tested by degradation of methylene blue under visible light, indicating that showed good photocatalytic performance.

Study on detecting spatial distribution of neutrons and gamma rays using a multi-imaging plate system.

In order to measure the spatial distributions of neutrons and gamma rays separately using the imaging plate, the requirement for the converter to enhance specific component was investigated with the PHITS code. Consequently, enhancing fast neutrons using recoil protons from epoxy resin was not effective due to high sensitivity of the imaging plate to gamma rays. However, the converter of epoxy resin doped with (10)B was found to have potential for thermal and epithermal neutrons, and graphite for gamma rays.

Controlled synthesis of uniform BiVO4 microcolumns and advanced visible-light-driven photocatalytic activity for the degradation of metronidazole-contained wastewater.

Well-defined, uniform bismuth vanadate (BiVO4) microcolumns were synthesized through a refined hydrothermal route. During the fabrication process, a detailed orthogonal design on the synthetic conditions was performed, aiming to optimize the experimental parameters to produce BiVO4 materials (BiVO4 (Opt.)) with the most prominent visible-light-driven photocatalytic efficiency, where the catalytic activities of the synthesized materials were evaluated via the decolorization of methylene blue under visible light irradiation. The BiVO4 (Opt.) were then targetedly produced according to the determined optimal conditions and well characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet and visible diffuse-reflectance spectroscopy and photoluminescence spectroscopy. Compared with the commercial P25-TiO2 photocatalysts, the as-synthesized BiVO4 (Opt.) displayed superior visible-light-driven photocatalytic activities for the degradation of metronidazole-contained wastewater with the presence of H2O2. The degradation efficiency of metronidazole reached up to 70 % within 180 min, leading to a brief speculation on the possibly major steps of the visible-light-driven photocatalytic process. The current study provides a distinctive route to design novel shaped BiVO4 architectures with advanced photocatalytic capacities for the treatment of organic pollutants in the aqueous environment.

Laser-induced oxidation kinetics of bismuth surface microdroplets on GaAsBi studied in situ by Raman microprobe analysis.

We report the cw-laser-induced oxidation of molecular-beam-epitaxy grown GaAsBi bismuth surface microdroplets investigated in situ by micro-Raman spectroscopy under ambient conditions as a function of irradiation power and time. Our results reveal the surface droplets are high-purity crystalline bismuth and the resultant Bi2O3 transformation to be ß-phase and stable at room temperature. A detailed Raman study of Bi microdroplet oxidation kinetics yields insights into the laser-induced oxidation process and offers useful real-time diagnostics. The temporal evolution of new ß-Bi2O3 Raman modes is shown to be well described by Johnson-Mehl-Avrami-Kolmogorov kinetic transformation theory and while this study limits itself to the laser-induced oxidation of GaAsBi bismuth surface droplets, the results will find application within the wider context of bismuth laser-induced oxidation and direct Raman laser processing.

Graphene sheets grafted three-dimensional BiOBr0.2I0.8 microspheres with excellent photocatalytic activity under visible light.

A series of graphene sheets grafted three-dimensional BiOBr0.2I0.8 microspheres with different graphene contents have been synthesized by a simple one-step solvothermal method. The BiOBr0.2I0.8 microspheres were composed of numerous nanoplates with a thickness of about 10nm and dispersed uniformly on the surface of graphene. The assembled BiOBr0.2I0.8/graphene composites exhibited excellent photocatalytic activity in the degradation of rhodamine B (RhB) and phenol under visible light irradiation (λ>420 nm). The optimal graphene content was found to be 10.0 wt.%, and the corresponding photocatalytic activity in degradation of RhB and phenol was 3.19 and 3.27 times that of pure BiOBr0.2I0.8, respectively. The enhanced photocatalytic activity could be attributed to more effective charge transportations and separations, larger specific surface areas and the increased light absorption. A possible photocatalytic mechanism of the BiOBr0.2I0.8/graphene composites was also proposed.

Caracterização de uma blindagem de chumbo protetora de mamas para redução de dose em exames de Tomografia Computadorizada

Diversos estudos foram publicados quanto ao uso de blindagens de bismuto para proteção de mamas em exames de Tomografia Computadorizada (CT), e, até a redação desse artigo, encontrou-se apenas uma publicação sobre blindagens de bário. O objetivo deste estudo foi caracterizar, pela primeira vez, uma blindagem de chumbo protetora de mamas. Materiais e Métodos: Foram avaliadas a redução percentual da dose e a influência desta blindagem em parâmetros quantitativos da imagem. Medidas de dose foram feitas em um equipamento de CT com auxílio de fantomas específicos e detectores de radiação. Um software de processamento auxiliou na análise qualitativa, que consistiu em avaliar a variação no número médio de CT e do ruído nas imagens. Resultados: Uma redução de dose na entrada em até 30% e do CTDIvol em até 17% foi encontrada. Como previsto na literatura, a presença do algodão como objeto espaçador reduziu significativamente os artefatos presentes na imagem. Em todas as medidas realizadas, foi constatado aumento do número médio de CT e do ruído das imagens na presença da manta. Conclusões: Como esperado, os dados encontrados para a blindagem com chumbo foram da mesma ordem daqueles encontrados na literatura para blindagem com bismuto .

Evidence of superoxide radical contribution to demineralization of sulfamethoxazole by visible-light-driven Bi2O3/Bi2O2CO3/Sr6Bi2O9 photocatalyst.

Photocatalytic degradation of sulfamethoxazole (SMX) was investigated using Bi2O3/Bi2O2CO3/Sr6Bi2O9 (BSO) photocatalyst under visible light (>420 nm) irradiation. The photochemical degradation of SMX followed pseudo-first-order kinetics. The reaction kinetics was determined as a function of initial SMX concentrations (5-20 mg L(-1)), initial pH (3-11) and BSO concentrations (6-600 mg L(-1)). Approximately, 90% of SMX (10 mg L(-1)) degradation and 36% of TOC reduction were achieved at pH 7.0 after 120 min irradiation. The main mineralization products, including NH4(+), NO3(-), SO4(2-) and CO2, as well as intermediates 3-amino-5-methylisoxazole (AMI), p-benzoquinone (BZQ), and sulfanilic acid (SNA) were detected in aqueous solution. The formation of O2(*-) radical was evidenced by using electron spin resonance and a chemiluminescent probe, luminal. A possible degradation mechanism involving excitation of BSO, followed by charge injection into the BSO conduction band and formation of reactive superoxide radical (O2(*-)) was proposed for the mineralization of SMX. During the reaction, the O2(*-) radical attacks the sulfone moiety and causes the cleavage of the SN bond, which leads to the formation of two sub-structure analogs, AMI and SNA.

Effective visible light-active boron and europium co-doped BiVO4 synthesized by sol-gel method for photodegradion of methyl orange.

Eu-B co-doped BiVO4 visible-light-driven photocatalysts have been synthesized using the sol-gel method. The resulting materials were characterized by a series of joint techniques, including XPS, XRD, SEM, BET, and UV-vis DRS analyses. Compared with BiVO4 and B-BiVO4 photocatalysts, the Eu-B-BiVO4 photocatalysts exhibited much higher photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The optimal Eu doping content is 0.8 mol%. It was revealed that boron and europium were doped into the lattice of BiVO4 and this led to more surface oxygen vacancies, high specific surface areas, small crystallite size, a narrower band gap and intense light absorbance in the visible region. The doped Eu(III) cations can help in the separation of photogenerated electrons. The synergistic effects of boron and europium in doped BiVO4 were the main reason for improving visible light photocatalytic activity.