A multi-ion beam microanalysis approach for the characterization of plasma polymerized allylamine films

EPJ Applied Physics 56. 2 (2011): 24021 with kind permission of The European Physical Journal (EPJ)A full characterization of plasma polymerized biofunctional films requires the use of multi-analytical approaches to determine the chemical composition, topography and potential interaction mechanisms of such films with biomolecules and cells. In this work we aim at underlining the versatility of ion-based techniques to contribute to the chemical characterization of plasma polymerized surfaces. The simultaneous use of energy recoil detection (ERD) and Rutherford backscattering (RBS) spectroscopies with incident He ions is an example of this versatility. Performing sequential measurements and the use of correlating computing tools for ERD-RBS interpretation allows providing in-depth concentration profiles of light elements, including namely hydrogen. More accurate analysis of light elements in polymer films can be increased by looking for particular ions with resonant backscattering responses (i.e., non-Rutherford Scattering). In particular, proton beams of 1.765 MeV are used to increase the detection of C and N, and particular incidence and detector angles to diminish the Si substrate contribution. These analytical tools have been applied to allylamine films and multi-layers crosslinked in a capacitive plasma onto both Si and porous Si substratesWe acknowledge MICINN funding provided by Grant No. MAT2008-06858-C02-01 and grant from Fundación Domingo Martíne

Visible light assisted organosilane assembly on mesoporous silicon films and particles

Porous silicon (PSi) is a versatile matrix with tailorable surface reactivity, which allows the processing of a range of multifunctional films and particles. The biomedical applications of PSi often require a surface capping with organic functionalities. This work shows that visible light can be used to catalyze the assembly of organosilanes on the PSi, as demonstrated with two organosilanes: aminopropyl-triethoxy-silane and perfluorodecyl-triethoxy-silane. We studied the process related to PSi films (PSiFs), which were characterized by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF-SIMS) and field emission scanning electron microscopy (FESEM) before and after a plasma patterning process. The analyses confirmed the surface oxidation and the anchorage of the organosilane backbone. We further highlighted the surface analytical potential of 13 C, 19 F and 29 Si solid-state NMR (SS-NMR) as compared to Fourier transformed infrared spectroscopy (FTIR) in the characterization of functionalized PSi particles (PSiPs). The reduced invasiveness of the organosilanization regarding the PSiPs morphology was confirmed using transmission electron microscopy (TEM) and FESEM. Relevantly, the results obtained on PSiPs complemented those obtained on PSiFs. SS-NMR suggests a number of siloxane bonds between the organosilane and the PSiPs, which does not reach levels of maximum heterogeneous condensation, while ToF-SIMS suggested a certain degree of organosilane polymerization. Additionally, differences among the carbons in the organic (non-hydrolyzable) functionalizing groups are identified, especially in the case of the perfluorodecyl group. The spectroscopic characterization was used to propose a mechanism for the visible light activation of the organosilane assembly, which is based on the initial photoactivated oxidation of the PSi matrixWe acknowledge MSC funding provided by the European Commission through FP7 grant THINFACE (ITN GA 607232) and by Ministerio de Economía y Competitividad through grant NANOPROST (RTC-2016-4776-1

Fabrication of zinc oxide and nanostructured porous silicon composite micropatterns on silicon

The luminescent properties of zinc oxide (ZnO) and nanostructured porous silicon (PSi) make these materials very appealing for photoemission applications. The current study reports on the fabrication of a composite of ZnO and nanostructured porous silicon micropatterns (ZnO + PSi micropatterns) onto heavily-doped silicon surfaces. The proposed composite micropattern is devoted to the future development of light-emitting diodes. The fabrication of the ZnO + PSi micropatterns was carried out in a two–step process. (1) A regular hexagonal micropattern of a photoresist/ZnO stack was fabricated by UV lithography on crystalline silicon substrates. (2) Before being lifted off the photoresist, nanostructured PSi micropatterns were fabricated by electrochemically etching the exposed areas of the silicon substrate. Subsequently, wet etching of the photoresist was carried out for the final development of the composite ZnO and PSi micropatterns. Further, thin films of ZnO and nanostructured PSi layers were characterized. In particular, their photoluminescent properties were analyzed, as well as their morphology and composition. The experimental PL results show that the ZnO layers have emission broadbands centered at (2.63 eV, blue), while the PSi layers show a band centered at (1.71 eV, red). Further, the emission peaks from the PSi layers can be tuned by changing their fabrication conditions. It was observed that the properties of the ZnO thin films are not influenced by either the surface morphology of PSi or by its PL emissions. Therefore, the PL properties of the composite ZnO + PSi micropatterns are equivalent to those featuring the addition of PSi layers and ZnO thin films. Accordingly, broadband optical emissions are expected to arise from a combination between the ZnO layer (blue band) and PSi (red band). Furthermore, the electrical losses associated with the PSi areas can be greatly reduced since ZnO is in contact with the Si surface. As a result, the proposed composite micropatterns might be attractive for many solid-state lighting applications, such as light-emitting diodesThis research was partially funded by Universidad Autónoma de Madrid, FPI-UAM grant (2019) and by the Egyptian Ministry of Higher Education, Missions Section under Egyptian Joint Supervision Grant, call 015/01

Sol-gel TiO2 nanoparticles prompt photocatalytic cement for pollution degradation

TiO2 nanoparticles (TiO2NPs) prepared by the sol–gel method have been incorporated to cement paste with the aim of creating a photocatalytic system capable of compensating, through degradation of hazardous molecules, the envi- ronmental impact associated to the production of the clinker. Doping was carried out at different mass ratios with TiO2NPs precursor solutions within a fresh ce- ment paste, which was then characterized using scanning electron microscopy (SEM). The photocatalytic performance was evaluated by the degradation of Methylene Blue (MB) using a 125W UV lamp as irradiating source. Main cement properties such as hydration degree and C-S-H content are affected by TiO2NPs doping level. Cement containing TiO2NPs exhibited an increasing photocatalytic activity for increasing doping, while the pure cement paste control could hardly degrade MB. The kinetics of the system where also studied and their second order behavior related to microstructural aspects of the system

Luminescence and fine structure correlation in ZnO permeated porous silicon nanocomposites

Nanocomposites formed by porous silicon (PS) and zinc oxide (ZnO) have potential for applications in optoelectronic devices. However, understanding the distribution of both materials in the nanocomposite, and especially the fine structure of the synthesized ZnO crystals, is key for future device fabrication. This study focuses on the advanced characterization of a range of PS-ZnO nanocomposites by using photon- and ion-based techniques, such as X-ray absorption spectroscopy (XAS) and elastic backscattering spectroscopy (EBS), respectively. PS substrates formed by the electrochemical etching of p+-type Si are used as host material for the sol-gel nucleation of ZnO nanoparticles. Different properties are induced by annealing in air at temperatures ranging from 200°C to 800°C. Results show that wurtzite ZnO nanoparticles form only at temperatures above 200°C, coexisting with Si quantum dots (QDs) inside a PS matrix. Increasing the annealing temperature leads to structural and distribution changes that affect the electronic and local structure of the samples changing their luminescence. Temperatures around 800°C activate the formation of a new zinc silicate phase and transform PS into an amorphous silicon oxide (SiOx, x ≈ 2) matrix with a noticeably reduced presence of Si QDs. Thus, these changes affect dramatically the emission from these nanocomposites and their potential applicationsFunding through grant MAT2013-46572-C2-1-R from Ministerio de Economía y Competitivida

Synaptic and fast switching memristance in porous silicon-based structures

Memristors are two terminal electronic components whose conductance depends on the amount of charge that has flown across them over time. This dependence can be gradual, such as in synaptic memristors, or abrupt, as in resistive switching memristors. Either of these memory effects are very promising for the development of a whole new generation of electronic devices. For the successful implementation of practical memristors, however, the development of low cost industry compatible memristive materials is required. Here the memristive properties of differently processed porous silicon structures are presented, which are suitable for different applications. Electrical characterization and SPICE simulations show that laser-carbonized porous silicon shows a strong synaptic memristive behavior influenced by defect diffusion, while wet-oxidized porous silicon has strong resistance switching properties, with switching ratios over 8000. Results show that practical memristors of either type can be achieved with porous silicon whose memristive properties can be adjusted by the proper material processing. Thus, porous silicon may play an important role for the successful realization of practical memristorics with cost-effective materials and processesThis work is part of ATTRACT that has received funding from the European Union’s Horizon 2020 Research and Innovation Programm

Nanostructured porous silicon photonic crystal for applications in the infrared

In the last decades great interest has been devoted to photonic crystals aiming at the creation of novel devices which can control light propagation. In the present work, two-dimensional (2D) and three-dimensional (3D) devices based on nanostructured porous silicon have been fabricated. 2D devices consist of a square mesh of 2 μm wide porous silicon veins, leaving 5x5 μm square air holes. 3D structures share the same design although multilayer porous silicon veins are used instead, providing an additional degree of modulation. These devices are fabricated from porous silicon single layers (for 2D structures) or multilayers (for 3D structures), opening air holes in them by means of 1KeV argon ion bombardment through the appropriate copper grids. For 2D structures, a complete photonic band gap for TE polarization is found in the thermal infrared range. For 3D structures, there are no complete band gaps, although several new partial gaps do exist in different high-symmetry directions. The simulation results suggest that these structures are very promising candidates for the development of low-cost photonic devices for their use in the thermal infrared rangeThe authors also gratefully acknowledge funding from Comunidad de Madrid (Spain) under project “Microseres” and Ministerio de Economía y Competitividad (Spain) under Research Project MAT2011-28345-C02-0

Microwave plasma and rapid thermal processing of indium-tin oxide thin films for enhancing their performance as transparent electrodes

Rehab Ramadan, Kamal Abdel-Hady, Miguel Manso-Silván, Vicente Torres-Costa, and Raúl J. J. Martín-Palma "Microwave plasma and rapid thermal processing of indium-tin oxide thin films for enhancing their performance as transparent electrodes," Journal of Photonics for Energy 9(3), 034001 (27 August 2019). https://doi.org/10.1117/1.JPE.9.034001Indium-tin oxide (ITO) is widely used as a transparent electrode for optoelectronic devices given its large transparency and high conductivity. However, the particular properties of this material greatly depend on the overall fabrication process. We report on the effect of four different postfabrication processes on ITO thin films grown by electron beam evaporation. More specifically, the effect on the overall properties of the evaporated ITO thin films of microwave plasma annealing, rapid thermal processing, and the two processes combined were analyzed. In particular, the morphological, chemical, optical, and electrical properties of the annealed ITO thin films were studied. The experimental results show that the ITO thin films can be turned from opaque to transparent, and their conductivity can be improved by one order of magnitude depending on the particular postfabrication proces

ANÁLISE COMPARATIVA DO PERFIL DE IDOSAS PRATICANTES E NÃO PRATICANTES DE ATIVIDADE FÍSICA EM TERESINA-PIAUÍ

INTRODUÇÃO: O envelhecimento populacional e aumento da expectativa de vida evidenciam necessidade de ações preventivas que visem a manutenção da capacidade funcional e melhora da qualidade de vida. OBJETIVO: Comparar o perfil de características de saúde e qualidade de vida de idosas ativas e sedentárias. METODOLOGIA:Estudo observacional, transversal e descritivo realizado com amostra de 60 idosas, sendo 30 praticantes de atividade física e 30 não praticantes, no bairro São Pedro em Teresina-PI. Utilizou-se entrevista e avaliação clínica domiciliar aplicando-se questionário de comorbidades associadas, de Qualidade de vida ”“ Whoqol-bref, avaliação da capacidade funcional RESULTADOS: As cormobidades encontradas com maior freqüência em ativas e sedentárias, respectivamente, foram: Hipertensão Arterial Sistêmica (38,00% e 37,00%), Diabetes (10,00% e 2,00%) e Osteoporose (15,00% e 12,00%). Nos resultados sobre teste de força, as praticantes tiveram médias de repetições maiores em membros inferiores (22,9/12,97) e superiores ( 15/9,07). As ativas apresentaram melhor nível de equilíbrio e coordenação no teste Time UpandGo Test (9,74s e 19,4s). As ativas demonstraram ainda pontuação maior em todos os domínios do WHOQOL-BREF. CONCLUSÃO: As idosas praticantes de atividade física apresentaram melhores níveis de desempenho funcional e qualidade de vida em relação às sedentárias. DESCRITORES: Perfil de saúde, idoso, terapia por exercício

Near ambient pressure X-ray photoelectron spectroscopy monitoring of the surface immobilization cascade on a porous silicon-gold nanoparticle FET biosensor

Porous silicon (PSi) offers extremely attractive optical, electronic and biofunctional properties for the development of biosensors. In the present work, we have studied the step by step sandwich biofunctionalization cascade of a PSi platform by near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and, in parallel, we have developed a three electrode PSi device sensitive to changes in surface conductance. Prior to the NAP-XPS characterization, the organosilanization with glycidyloxy-propyl-trimethoxy-silane, the bioconjugation, and the gold nanoparticle (AuNP) sensitization layer were monitored by spectroscopic ellipsometry. The NAP-XPS analysis revealed outstanding results: a) the NAP-XPS chamber allows detecting the pristine PSi with negligible adventitious carbon contamination, b) the single oxygen bonded carbon component of the Glycidyl group dominates the C1s core level after organosilanization, c) the good progress of the biofunctionalization/recognition is confirmed by the increase of the silica to silicon component ratio in the Si2p core level and, d) the N1s core level describes identical features from the presence of aminoacid sequences in the capture/detection steps. A FET sensing of a prostate specific antigen (PSA) marker was performed through conjugation with AuNPs. For a given concentration of PSA (and AuNPs) the conductance increased with the increase of the gate voltage. For a given gate voltage, the conductance was observed to increase for increasing concentration of PSA. This allowed proposing a calibration line for the biosensor, which is valid from a clinically relevant range of 0.1 ng/mLWe acknowledge MSC funding provided by the European Commission through FP7 grant THINFACE (ITN GA 607232) and from Ministerio de Economía y Competitividad, Spain, through grant SPECTRASENSE (RTC-2017-6311-1