Light absorption properties of mesoporous barium hexaferrite, BaFe12O19

Light absorption properties are one of the most important characteristics of semiconductor materials, since it is related to particle size, electric resistance, powder density, and dielectric constant. Barium hexaferrite (BaFe12O19) particles were synthesized by ceramic and chemical co-precipitation method. Light absorption properties were studied in relation to the particle size, morphology, and surface porosity. The band gap was calculated by the Kubelka-Munk method from the obtained experimental absorption spectrum. Band gap energies of 1.82 and 1.86 eV were estimated for the particles synthesized by the ceramic method and for the co-precipitation method respectively. The results show that both synthesized BaFe12O19 samples can be effectively excited with visible light irradiation. In addition to this, due to its other good characteristics such as its magnetic properties, high resistance to corrosion, and chemical stability, make the barium hexaferrite an excellent material for diverse technological applications

Hybrid Porous Silicon- Rhodamine B Derivative Nanostructures as Chemical Sensor for Hg(II) Detection.

Sensing of heavy metals in aqueous solutions has been performed by developing porous silicon (PSi) hybrid materials. The Rhodamine organosilane derivative (Rh-UTES) was used as metal receptor through formation of luminescence chelates within the porous silicon microcavities (PSiMc). The attachment of organic derivative into PSiMc was confirmed by FTIR, specular reflectance and scanning electron microscopy (SEM). The +2 complexing ability of Rh-UTES receptor to Hg investigated by fluorescent spectroscopy and microscopy. We found that the fluorescent intensity of the PSiMc hybrid device is metal concentration dependent. Similar behavior was observed in liquid and solid phase. Metal-Ligand affinity was study by electrochemical techniques

Neutron spectra and H*(10) around an 18 MV LINAC by ANNs

Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An Artificial Neural Network (ANN) were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm The mean squared error (mse) set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this Artificial Intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiatio

A turn-on fluorescent solid-sensor for Hg(II) detection

A rhodamine organosilane derivative (Rh-UTES) has been obtained by one-pot synthesis. The chemical structure of Rh-UTES was confirmed by nuclear magnetic resonance (NMR) and infrared (FTIR) techniques. To obtain an inorganic-organic hybrid sensor, Rh-UTES was covalently immobilized on a porous silicon microcavity (PSiMc) via triethoxysilane groups. The attachment of the organic derivative into PSiMc was confirmed by FTIR, specular reflectance, and scanning electron microscopy (SEM). The optical performance of Rh-UTES receptor for Hg2+ detection was investigated by fluorescent spectroscopy and microscopy. Upon the addition of increasing amounts of Hg2+ ions, a remarkable enhancement in emission intensity was produced in both systems. In the solid phase, an increase of integrated fluorescent emission of 0.12- and 0.15-fold after Hg2+ receptor coordination was observed. The light harvesting capability of PSiMc devices allowed obtaining an enhanced fluorescent emission after Rh-UTES immobilization (277-fold). The fluorescence microscopy of hybrid PSiMc sensor provided an optical qualitative test for Hg2+ detection.A rhodamine organosilane derivative (Rh-UTES) has been obtained by one-pot synthesis. The chemical structure of Rh-UTES was confirmed by nuclear magnetic resonance (NMR) and infrared (FTIR) techniques. To obtain an inorganic-organic hybrid sensor, Rh-UTES was covalently immobilized on a porous silicon microcavity (PSiMc) via triethoxysilane groups. The attachment of the organic derivative into PSiMc was confirmed by FTIR, specular reflectance, and scanning electron microscopy (SEM). The optical performance of Rh-UTES receptor for Hg2+ detection was investigated by fluorescent spectroscopy and microscopy. Upon the addition of increasing amounts of Hg2+ ions, a remarkable enhancement in emission intensity was produced in both systems. In the solid phase, an increase of integrated fluorescent emission of 0.12- and 0.15-fold after Hg2+ receptor coordination was observed. The light harvesting capability of PSiMc devices allowed obtaining an enhanced fluorescent emission after Rh-UTES immobilization (277-fold). The fluorescence microscopy of hybrid PSiMc sensor provided an optical qualitative test for Hg2+ detection

Synthesis and characterization of extremely small gold nanoshells, and comparison of their photothermal conversion capacity with gold nanorods

The current methods for preparing gold nanoshells (AuNSs) produce shells with a diameter of approximately 40 nm or larger, with a relatively large polydispersity. However, AuNSs with smaller diameters and more monodispersity are better suited for biomedical applications. In this work, we present a modified method for the preparation of AuNSs, based on the use of sacrificial silver nanoparticles (AgNPs). We customized the Lee–Meisel method to prepare small and monodisperse AgNPs that were used as sacrificial nanoparticles to prepare extremely small monodispersed AuNSs with an average diameter from 17 to 25 ± 4 nm. We found that these AuNSs are faceted, and that the oxidized silver likely dissolves out of the nanoparticles through some of the facets on the AuNSs. This leads to a silver oxide plug on the surface of the AuNSs, which has not been reported before. The smaller AuNSs, prepared under the best conditions, absorb in the near infrared region (NIR) that is appropriate for applications, such as photothermal therapy or medical imaging. The AuNSs showed absorption peaks in the NIR similar to those of gold nanorods (AuNRs) but with better photothermal capacity. In addition, because of their negative charge, these AuNSs are more biocompatible than the positively charged AuNRs. The synthesis of small, monodisperse, stable and biocompatible nanoparticles, like the ones presented in this work, is of prime importance in biomedical applications.The current methods for preparing gold nanoshells (AuNSs) produce shells with a diameter of approximately 40 nm or larger, with a relatively large polydispersity. However, AuNSs with smaller diameters and more monodispersity are better suited for biomedical applications. In this work, we present a modified method for the preparation of AuNSs, based on the use of sacrificial silver nanoparticles (AgNPs). We customized the Lee–Meisel method to prepare small and monodisperse AgNPs that were used as sacrificial nanoparticles to prepare extremely small monodispersed AuNSs with an average diameter from 17 to 25 ± 4 nm. We found that these AuNSs are faceted, and that the oxidized silver likely dissolves out of the nanoparticles through some of the facets on the AuNSs. This leads to a silver oxide plug on the surface of the AuNSs, which has not been reported before. The smaller AuNSs, prepared under the best conditions, absorb in the near infrared region (NIR) that is appropriate for applications, such as photothermal therapy or medical imaging. The AuNSs showed absorption peaks in the NIR similar to those of gold nanorods (AuNRs) but with better photothermal capacity. In addition, because of their negative charge, these AuNSs are more biocompatible than the positively charged AuNRs. The synthesis of small, monodisperse, stable and biocompatible nanoparticles, like the ones presented in this work, is of prime importance in biomedical applications

Neutron spectra and H*(10) of photoneutrons inside the vault room of an 18 MV LINAC

Neutron spectra and the ambient dose equivalent were estimated inside the radiotherapy hall with an 18 MV linac. Estimations were carried out using Monte Carlo methods where a realist hall was modeled including a phantom made of equivalent tissue. The source term for photoneutrons was calculated using the Tosi et al. function that account for evaporation and knock-on neutrons. The spectra were estimated using two different energy distributions. Detectors were located in several sites inside the hall including the maze and outside the hall door, all detectors were located at the plane were the isocenter is located. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays.El espectro de neutrones y el equivalente de dosis ambiental fueron estimados dentro de una sala de radioterapia con un Linac de 18 MV. Las estimaciones se llevaron a cabo utilizando m´etodos Monte Carlo donde una sala realista fue modelada incluyendo un fantoma de tejido equivalente. El t´ermino fuente para neutrones fue calculado usando la funci´on de Tosi et al, la cual contabiliza los neutrones de evaporaci´on y reacci´on directa. El espectro fue estimado usando dos diferentes distribuciones de energ´ıa. Los detectores fueron colocados en el plano donde se encuentra el isocentro. Dentro de la sala de tratamiento, como la distancia respecto al isocentro aumenta, la cantidad de neutrones y H*(10) se reduce, los neutrones dentro de la regi´on de alta energ´ıa son desplazados a una regi´on de menor energ´ıa de alrededor de 0.1 MeV. Sin embargo, los neutrones epit´ermicos y t´ermicos permanecen constantes debido al efecto de room-return. En el laberinto el espectro es dominado peor neutrones t´ermicos y epit´ermicos los cuales contribuyen a la producci´on de activaci´on y a la producci´on de rayos gamma prontos

DLP fabrication of TiO2 nanoparticle thin films

3D printing technology has become a valuable and successful tool for many areas, including materials sciences.Nanoparticle thin film fabrication commonly requires expensive, highly specialized equipment not available in basic sciences laboratories. A simple, inexpensive, and straightforward methodology for the deposition of thin films composed of semiconductor TiO2 nanoparticles using a DLP (Digital Light Processing) 3D printer is pre-sented in this work. X-ray diffraction (XRD), Raman, Ultraviolet-visible (UV-Vis), and Photoluminescence (PL) spectroscopies were used to study the film's structural and optical properties. By analyzing Scanning Electron Microscopy (SEM) micrographs, particle size distribution and film thickness were studied. Single-layer TiO2 (an-atase) thin films with thickness around 114.3 ± 39.5 nm were successfully deposited through DLP 3D printing. The deposited films can be used in sensors, energy harvesting, catalysis, hydrogen production, and other UV light applications

Neutron absorbed dose in a pacemaker CMOS

The neutron spectrum and the absorbed dose in a Complementary Metal Oxide Semiconductor, has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes an oncology patient that must be treated in a linear accelerator. Pacemaker has integrated circuits as CMOS that are sensitive to intense and pulsed radiation fields. Above 7 MV therapeutic beam is contaminated with photoneutrons that could damage the CMOS. Here, the neutron spectrum and the absorbed dose in a CMOS cell was calculated, also the spectra were calculated in two point-like detectors in the room. Neutron spectrum in the CMOS cell shows a small peak between 0.1 to 1 MeV and a larger peak in the thermal region, joined by epithermal neutrons, same features were observed in the point-like detectors. The absorbed dose in the CMOS was 1:522 £ 10¡17 Gy per neutron emitted by the source.El espectro y la dosis absorbida, debida a neutrones, por un Semiconductor de O´ xido Meta´lico Complementario ha sido estimada utilizando m´etodos Monte Carlo. Eventualmente, una persona con marcapasos se convierte en un paciente oncol´ogico que debe ser tratado en un acelerador lineal. El marcapasos contiene circuitos integrados como los CMOS que son sensibles a los campos de radiaci ´on intensos y pulsados. El haz terap´eutico de un LINAC operando a voltajes mayores a 7 MV est´a contaminado con fotoneutrones que pueden da˜nar el CMOS. En este trabajo se estim´o el espectro de neutrones y la dosis absorbida por un CMOS; adem´as, se calcularon los espectros de neutrones en dos detectores puntuales ubicados dentro de la sala. El espectro de neutrones en el CMOS tiene un pico entre 0.1 y 1 MeV y otro en la regi´on de los t´ermicos, conectados mediante neutrones epit´ermicos. Estas mismas caracter´ısticas se observan en los otros detectores. La dosis absorbida por el CMOS es 1:522 £ 10¡17 Gy por cada neutr´on emitido por el t´ermino fuente