Silicon Ions Research Articles

Human osteoblasts grow transitional Si/N apatite in quickly osteointegrated Si3N4 cervical insert.

This research studies osseointegration processes comparing results from explanted PEEK and Si3N4 spinal spacers. Data show that the formation of hydroxyapatite on silicon nitride bio-ceramic surfaces happens with a peculiar mechanism inside the human body. Silicon and nitrogen were incorporated inside the bony tissue structure allowing the developing of off-stoichiometric bony apatite and stimulating progenitor cell differentiation/osteoblastic activity. Silicon and nitrogen ions released from the Si3N4 surface were detected through combined histologic analyses, Raman microspectroscopy, Fourier-transform-infrared, and X-ray photoelectron spectroscopies.

The stability of titania‐silica interface

AbstractSilica is very often the catalyst support of choice for transition metal oxides such as titania, and specially anatase. Titania is an excellent absorber and photocatalyst for many organic molecules degradation. In order to understand the chemical nature of the interaction between titania and silica, we have performed a theoretical study using density functional theory aiming to elucidate the role on the stability of the interface of the specific type of interactions, H‐bonding, covalent bonding of the pristine surfaces, and covalent bonding after silicon and titanium ions interdiffusion. The calculations were carried out for hydrogen and oxygen terminated surface, comparing the bonding types and the forces acting along the interface. The interface dynamics was studied for interfaces under applied stress in order to elucidate their stability and failure limits. The shearing forces and the mechanisms of interface failure were determined. Interfaces with interdiffused Si and Ti ions were studied to improve the interface stabilization. The results demonstrate that high‐temperature treatment leading to formation of SiOTi bonds at the interface is responsible for the formation of strong and flexible binding interaction between both oxides. At high strains, the SiOTi interface failure is observed due to lattice mismatch between the SiO2 and TiO2. The failure is a result of forces acting orthogonal to the interface shearing. In case of hydrogen terminated surface, the interface binding is a result of hydrogen bond network. Such interface is fragile at moderate shearing forces along the applied strain. The hydrogen bond network decreases the elastic properties and flexibility of the interface. The SiO2/TiO2 interface is further stabilized by Si/Ti ion interdiffusion. The ionic interdiffusion process also increases the interface flexibility. Thus, in order to obtain more stable anatase photocatalyst supported on silica, the synthetic routes should favor silicon and titanium ions interdiffusion along the interface.

Bulk, surface structures and properties of sodium borosilicate and boroaluminosilicate nuclear waste glasses from molecular dynamics simulations

The bulk and surface structures, as well as physical properties such as ionic diffusion and mechanical moduli, of sodium borosilicate and boroaluminosilicate model nuclear waste glasses with composition similar to the international simplified glass (ISG) have been studied using molecular dynamics simulations with the recently developed partial charge composition dependent potentials. Short and medium range structures of these glasses were analyzed and it was found that, for glass former cations, silicon ion is all four-fold coordinated by oxygen, aluminum is also mainly four-fold coordinated, while boron exists in a mixture of 3- and 4-fold coordination, with the fraction of 4-fold coordinated B (N4 value) close to but slightly higher than the experimental and theoretical values. The medium range structure features such as network former cation oxygen polyhedral connectivity, sodium distribution around the network formers, and network ring size distribution were characterized. The surface structure was generated from the simulated bulk glass structures and showed sodium enrichment on the glass surface. Addition of alumina to borosilicate glasses increased B N4 value and overall glass network connectivity that led to improved mechanical properties. Ion diffusion properties, mechanical properties as well as surface characteristics for the simplified ISG have also been investigated with simulations and compared with available experimental data. This detailed atomic structure information provides insight of the physical properties of these glasses and a step further in understanding the chemical durability and dissolution behaviors.

Electrochemical Nucleation and Growth of Metals in Molten Salts

Investigation of electrochemical nucleation and growth mechanism is of great significance for controlling morphology of elctrodeposited metals on substrate. However, information concerning nucleation and growth mechanism in molten salts has not been sufficient, although it is necessary to understand growth processes of electrodeposition of metals in molten salt for realizing practical process. In particular, investigation of electrodeposited metals at early stage is expected to give us new information about morphogenetic process during electrolysis in molten salts. From the background, molten chloride salts containing silicon ions was used for studying electrochemical nucleation and growth mechanism of metallic silicon by using electrochemical techniques combined with micro-spectroscopic techniques. After conducing electrolysis for one second, hemispherical nucleated Si was observed by SEM, and process of agglomeration was also observed as time proceeded. The effect of time evolution on growth process has been also studied by conduction potentiostatic electrolysis. The growth mechanisum from the experiments will be presented at the symposium.

Nanoscale Electrochemistry Via Lithium Focused Ion Beam

The increasing demand for smaller, lighter, cheaper, and more stable power sources for portable electronics, vehicles and aircrafts spurs intensive research of the lithium ion batteries. Rational battery engineering, including design of smart electrode materials, is impossible without in-depth understanding of the chemical and physical processes in galvanic cells at the microscopic, nanoscopic, and eventually, molecular levels. Reaction mechanisms, cathode expansion, formation of cracks and SEI layer, electrolyte decomposition etc., are being extensively studied with a variety of ex and in situ microscopic, spectroscopic and electrochemical techniques. However, a significant drawback of the existing methodologies is their inability to deliver Li+ ions and control their concentration at the nanoscale level. In addition, the classic electrochemical techniques imply existence of liquid-solid interfaces and inevitable formation of SEI layer. This is a significant impediment for studying lithium diffusion and associated morphological changes in cathode materials. We report progress in developing Li+ focused ion beams (FIB) as a novel probe for exploring nanoscale electrochemistry in battery-relevant materials. This work focuses on implantation of lithium ions in crystalline silicon to benchmark this technique and builds on recent, qualitative studies of FIB implantation in Sn microspheres [Takeuchi et al. JES 163 (6), A1010-A1012]. FIB implantation opens the possibility of precise spatial control of nanoscale lithium concentration though variation of the beam positioning and current. Experiments are performed in vacuo without the presence of electrolytes or associated solid-electrolyte interface. The Li+ ion beam operates with energies ranging from 0.5 to 5 keV, currents up to 15 pA, and minimum spot size of 27 nm using a magneto-optical trap ion source (MOTIS). WRM acknowledges support from the National Research Council Research Associateship Program. ES and JG acknowledge support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology, Award 70NANB14H209, through the University of Maryland.

Effects of Glow-Discharge Parameters on Silicon Coating Thickness Deposited on 316 Stainless Steel Samples

Silicon as a light element can be used as the tokamak first wall coating in order to protect the plasma from impurities which come from the wall. In this paper, we deposit an amorphous-silicon layer by the use of the glow discharge technique on the wall surface of the test chamber made from SS316. To do so, we employ silane as a source of silicon ions. The siliconization process is conducted at two time durations of 90 and 150 min. SEM image of the coated surface shows that the structure of the coated layer deposited by the 150-min is more compact in comparison with that of 90-min. Effect of current density on coating properties is evaluated by placing four samples at different locations on the wall surface which shows that the optimal values of current density are in the range of 14–20 μA/cm2 and the higher range of current density can damage the coating. The results confirm that by increasing the time of siliconization the coating thickness is increased successfully from 100 to 250 nm without appearance of any damage in coating.

Genomic instability induced in distant progeny of bystander cells depends on the connexins expressed in the irradiated cells

Purpose: To examine the time window during which intercellular signaling though gap junctions mediates non-targeted (bystander) effects induced by moderate doses of ionizing radiation; and to investigate the impact of gap junction communication on genomic instability in distant progeny of bystander cells.Materials and methods: A layered cell culture system was developed to investigate the propagation of harmful effects from irradiated normal or tumor cells that express specific connexins to contiguous bystander normal human fibroblasts. Irradiated cells were exposed to moderate mean absorbed doses from 3.7 MeV α particle, 1000 MeV/u iron ions, 600 MeV/u silicon ions, or 137Cs γ rays. Following 5 h of co-culture, pure populations of bystander cells, unexposed to secondary radiation, were isolated and DNA damage and oxidative stress was assessed in them and in their distant progeny (20–25 population doublings).Results: Increased frequency of micronucleus formation and enhanced oxidative changes were observed in bystander cells co-cultured with confluent cells exposed to either sparsely ionizing (137Cs γ rays) or densely ionizing (α particles, energetic iron or silicon ions) radiations. The irradiated cells propagated signals leading to biological changes in bystander cells within 1 h of irradiation, and the effect required cellular coupling by gap junctions. Notably, the distant progeny of isolated bystander cells also exhibited increased levels of spontaneous micronuclei. This effect was dependent on the type of junctional channels that coupled the irradiated donor cells with the bystander cells. Previous work showed that gap junctions composed of connexin26 (Cx26) or connexin43 (Cx43) mediate toxic bystander effects within 5 h of co-culture, whereas gap junctions composed of connexin32 (Cx32) mediate protective effects. In contrast, the long-term progeny of bystander cells expressing Cx26 or Cx43 did not display elevated DNA damage, whereas those coupled by Cx32 had enhanced DNA damage.Conclusions: In response to moderate doses from either sparsely or densely ionizing radiations, toxic and protective effects are rapidly communicated to bystander cells through gap junctions. We infer that bystander cells damaged by the initial co-culture (expressing Cx26 or Cx43) die or undergo proliferative arrest, but that the bystander cells that were initially protected (expressing Cx32) express DNA damage upon sequential passaging. Together, the results inform the roles that intercellular communication play under stress conditions, and aid assessment of the health risks of exposure to ionizing radiation. Identification of the communicated molecules may enhance the efficacy of radiotherapy and help attenuate its debilitating side-effects.

Strontium-doped calcium silicate bioceramic with enhanced in vitro osteogenic properties

Gehlenite (GLN, Ca2SiAl2O7) is a bioceramic that has been recently shown to possess excellent mechanical strength and in vitro osteogenic properties for bone regeneration. Substitutional incorporation of strontium in place of calcium is an effective way to further enhance biological properties of calcium-based bioceramics and glasses. However, such strategy has the potential to affect other important physicochemical parameters such as strength and degradation due to differences in the ionic radius of strontium and calcium. This study is the first to investigate the effect of a range of concentrations of strontium substitution of calcium at 1, 2, 5, 10 mol% (S1-GLN, S2-GLN, S5-GLN and S10-GLN) on the physicochemical and biological properties of GLN. We showed that up to 2 mol% strontium ion substitution retains the monophasic GLN structure when sintered at 1450 °C, whereas higher concentrations resulted in presence of calcium silicate impurities. Increased strontium incorporation resulted in changes in grain morphology and reduced densification when the ceramics were sintered at 1450 °C. Porous GLN, S1-GLN and S2-GLN scaffolds (∼80% porosity) showed compressive strengths of 2.05 ± 0.46 MPa, 1.76 ± 0.79 MPa and 1.57 ± 0.52 MPa respectively. S1-GLN and S2-GLN immersed in simulated body fluid showed increased strontium ion release but reduced calcium and silicon ion release compared to GLN without affecting overall weight loss and pH over a 21 d period. The bioactivity of the S2-GLN ceramics was significantly improved as reflected in the significant upregulation of HOB proliferation and differentiation compared to GLN. Overall, these results suggest that increased incorporation of strontium presents a trade-off between bioactivity and mechanical strength for GLN bioceramics. This is an important consideration in the development of strontium-doped bioceramics.

Radiation damage and defects in NPN bipolar junction transistors irradiated by silicon ions with various energies

The characteristic of incident particle is an important factor to evaluate the correlation of radiation damage. It is useful to investigate the influence of incident particle with various energies on radiation effects of BJTs. Radiation effects in bipolar junction transistors are examined under the irradiation with 10, 24 and 40MeV Si ions in this paper. Based on the electrical performance degradation, it is shown that the change in the reciprocal of current gain is dominated by the ionizing damage during the heavy ion irradiations at low fluence, leading to a non-linear behavior. While at a higher fluence, displacement damage is the domain effect to show a linear curve. Deep level transient spectroscopy (DLTS) is used to analyze the characteristic of the deep level defects induced by irradiations. DLTS results show that for the BJTs under various Si ions irradiations, the types of deep level defects induced by Si ions are similar, while the concentration of the defects is different at the same displacement dose.

Mesoporous SiO2 produced by mineralization of yeast cells as an efficient electrocatalyst for oxygen reduction reaction

Mes oporous SiO2 (yeast-SiO2/C) was successfully prepared by mineralization of yeast cell template under different pH values. Analysis of the nitrogen adsorption-desorption isotherms indicated that the pore size distribution of the mesoporous yeast-SiO2 samples significantly varies depending on the pH value used f or biomineralization. Average pore diameters for the samples synthesized at pH 5.0, 7.0, and 11.0 were found to be 7.9, 17.8, and 9.4 nm, respectively. The mineralization ability of silicon ions can be enhanced using conditions with a higher acidity. The air electrodes fabricated using the yeast-SiO2 mesoporous composites exhibited remarkable electrocatalytic activity in oxygen reduction reaction under alkaline conditions. The mesoporous sample synthesized at pH 5.0 showed the highest electrocatalytic performance in the oxygen reduction reaction; this sample has the largest surface area and the highest total pore volume. It is supposed that the mesoporous structure of the nanocomposites predetermined by the yeast cell template significantly reduced the electrochemical polarization and improved mass transport in the air diffusion electrode.

K-shell X-ray transition energies of multi-electron ions of silicon and sulfur

Prompted by the detection of K-shell absorption or emission features in the spectra of plasma surrounding high mass X-ray binaries and black holes, recent measurements using the Livermore electron beam ion trap have focused on the energies of the n=2 to n=1 K-shell transitions in the L-shell ions of lithiumlike through fluorinelike silicon and sulfur. In parallel, we have made calculations of these transitions using the Flexible Atomic Code and the multi-reference Møller-Plesset (MRMP) atomic physics code. Using this code we have attempted to produce sets of theoretical atomic data with spectroscopic accuracy for all the L-shell ions of silicon and sulfur. We present results of our calculations for oxygenlike and fluorinelike silicon and compare them to the recent electron beam ion trap measurements as well as previous calculations.

Optical confinement achieved in zinc oxide modified by energetic silicon ions beams

Optical confinement was achieved in zinc oxide by silicon ions irradiation. Waveguide effects were found in all the irradiated samples. The optical properties and the field intensity distribution of the propagation mode, as well as the refractive index profile in the irradiated waveguide were studied and reconstructed accordingly. Achievement of optical waveguide structure in zinc oxide by silicon ions irradiation makes it possible to expand its application in modern optics and optical telecommunications in an attempt to control the propagation of light and to enhance the optical efficiency.

Development of multisubstituted hydroxyapatite nanopowders as biomedical materials for bone tissue engineering applications.

Ionic substitutions have been proposed as a tool to control the functional behavior of synthetic hydroxyapatite (HA), particularly for Bone Tissue Engineering applications. The effect of simultaneous substitution of different levels of carbonate (CO3 ) and silicon (Si) ions in the HA lattice was investigated. Furthermore, human bone marrow-derived mesenchymal stem cells (hMSCs) were cultured on multi-substituted HA (SiCHA) to determine if biomimetic chemical compositions were osteoconductive. Of the four different compositions investigates, SiCHA-1 (0.58 wt % Si) and SiCHA-2 (0.45 wt % Si) showed missing bands for CO3 and Si using FTIR analysis, indicating competition for occupation of the phosphate site in the HA lattice; 500°C was considered the most favorable calcination temperature as: (i) the powders produced possessed a similar amount of CO3 (2-8 wt %) and Si (<1.0 wt %) as present in native bone; and (ii) there was a minimal loss of CO3 and Si from the HA structure to the surroundings during calcination. Higher Si content in SiCHA-1 led to lower cell viability and at most hindered proliferation, but no toxicity effect occurred. While, lower Si content in SiCHA-2 showed the highest ALP/DNA ratio after 21 days culture with hMSCs, indicating that the powder may stimulate osteogenic behavior to a greater extent than other powders. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1775-1785, 2017.

Light emitting from the self‐interstitial clusters buried in the Si + self‐ion implanted Si films

The photoluminescence (PL) properties corresponding to different types of the interstitial clusters (or defects) in the silicon ion (Si+) self-implanted Si have been well reviewed. Given a brief of the conjectural origin, defect type, annealing temperature of the W (1218 nm), X (1193 nm) peak, R (1376 nm), and D bands concluded the present application of Si+ self-ion-implantation. The challenges for application of light-emitting Si and application prospects are also discussed.

Effect of plasma immersion ion beam processing on the structure–phase state and the properties of the surface layers in titanium nickelide samples

The formation of a microstructure in the surface layers of model samples made of a titanium nickelide–based alloy intended for medical application during plasma immersion processing by silicon ions is studied. Depending on technological conditions, either a silicon coating can be formed or a surface layer can be alloyed. The formed layers have a high microhardness and high adhesion to the base material.

A multifunctional bioactive material that stimulates osteogenesis and promotes the vascularization bone marrow stem cells and their resistance to bacterial infection.

The main limitation of tissue engineering lies in the inability to stimulate osteogenesis, angiogenesis of stem cells and broad-spectrum antimicrobial activity. However, the development of multifunctional bioactive materials with these capabilities remains a great challenge. In this study, we prepared mesoporous silica nanoparticles encapsulated with silver nanocrystals (AG-MSN) with uniform sphere size and mesopores. Platelet-derived growth factor BB (PDGF-BB) was effectively loaded in the AG-MSN mesopores (P-AG-MSN). The silicon ions (Si) released by P-AG-MSN stimulate osteogenic differentiation of bone marrow stromal cells (BMSC) by activating the alkaline phosphatase (ALP) activity of bone-related genes and increasing protein (OCN, RUNX2 and OPN) expression. Ag+ ions could be slowly released from the interior of the shell, highlighting their durable antibacterial activity. The sustained release of PDGF-BB from P-AG-MSN stimulated the angiogenic differentiation of BMSC, as indicated by the enhanced secretion of vascular endothelial growth factor (VEGF), HIF-1α, HGF and ANG-1 and protein expression. Our results show that P-AG-MSN can clearly promote BMSC osteostimulation and vascularization. This research serves as a preliminary study of the utilization of this multifunctional mixture to fabricate a new active biological scaffold that integrates BMSC osteostimulation, vascularization and bactericidal effects by 3D printing technology.

Etching and ellipsometry studies on CL-VPE grown GaN epilayer

Abstract The surface morphological characteristics of wet chemical etched GaN layers grown at different temperatures on (0 0 0 1) sapphire substrates by Chloride-Vapor Phase Epitaxy (Cl-VPE) have been studied using optical microscope. Significant surface morphology changes have been observed in correlation to the growth temperature and etching time. Also optical properties of the as grown and high-energy silicon (Si) ion irradiated gallium nitride (GaN) epilayers were studied using monochromatic ellipsometry. The effect of ion fluences on the refractive index of the GaN has been investigated and it has been found to decrease with an increase of ion fluence. This decrease is attributed to irradiation-induced defects and polycrystallization which plays an important role in determining the optical properties of silicon (Si) ion irradiated GaN layers.

Intra-bone marrow injection of trace elements co-doped calcium phosphate microparticles for the treatment of osteoporotic rat.

Osteoporotic femur fractures are the most common fragility fracture and account for approximately one million injuries per year. Local intervention by intra-marrow injection is potentially a good choice for preventing osteoporotic bone loss when the osteoporotic femoral fracture was treated. Previously, it was shown that trace element co-doped calcium phosphate (teCaP) implants could stimulate osteoporotic bone marrow mesenchymal stem cell activity in vitro and bone regeneration in femoral bone defects in osteoporotic animal models. They hypothesized that local intra-marrow injection of teCaP particles could improve bone function because the teCaP can sustain release of biologically essential inorganic minerals and improve bone remodeling in osteoporosis. The teCaP and CaP particles were synthesized in simulated body fluid with and without adding silicon, zinc and strontium ions. Female rats (8 months) were ovariectomized (OVX) or sham-operated, and then intervened in the femoral marrow space at 12 months old. Groups include: (1) saline water; (2) CaP particles; and (3) teCaP particles. After 2-3 months of intervention, the sham groups showed higher bone mineral density (MBD) in the femur, and teCaP group increased the BMD in the OVX groups. The compressive strength of the OVX-teCaP group was significantly higher than that in the OVX-CaP group. Significant differences between OVX-teCaP and OVX-CaP groups were found for bone mineral microarchitecture, bone mineral density, and trace mineral content, but not for feces composition. These results confirm the teCaP particles could suppress osteoporotic bone loss by local intramarrow injection. Therefore, this biomaterial could be used as a next-generation combination treatment for osteoporotic trauma and osteoporosis itself. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1422-1432, 2017.

Effect of lanthanum species on the physicochemical properties of La/SAPO-11 molecular sieve

La/SAPO-11 was synthesized via one-pot method. Lanthanum ions protect framework from distortion under the severe thermal (600°C, 4h) and hydrothermal (800°C, 4h) conditions. A higher retention of Brønsted acid sites (45.5%) is obtained after hydrothermal treatment. Lanthanum ions enhance the depolymerization of phosphorus species and interaction with phosphorus and aluminum species. In the coexistence of silicon and lanthanum ions, lanthanum ions could not incorporate into zeolite framework. LaPO4 preserves framework structure from steam attack. In addition, [La(OH)2]+ ions compensate structure tensions and increase the bond strength of Al–O inhibiting the desilication reaction during the thermal treatment. The hydrolyzed species of Si (4Al) and Si (3Al) can be recovered by dehydroxylation. In the cracking reaction of n-dodecane, La/SAPO-11 molecular sieve possessing moderate acid sites enhance isomerization reaction (increasing iso-paraffin by 9.5%) and inhibit cracking. The narrow pore has restriction for di-molecular reactions (e.g., hydrogen transfer reaction).

RhBMP-2 loaded 3D-printed mesoporous silica/calcium phosphate cement porous scaffolds with enhanced vascularization and osteogenesis properties

A major limitation in the development of effective scaffolds for bone regeneration has been the limited vascularization of the regenerating tissue. Here, we propose the development of a novel calcium phosphate cement (CPC)-based scaffold combining the properties of mesoporous silica (MS) with recombinant human bone morphogenic protein-2 (rhBMP-2) to facilitate vascularization and osteogenesis. Specifically, the development of a custom MS/CPC paste allowed the three-dimensional (3D) printing of scaffolds with a defined macroporous structure and optimized silicon (Si) ions release profile to promote the ingrowth of vascular tissue at an early stage after implantation in support of tissue viability and osteogenesis. In addition, the scaffold microstructure allowed the prolonged release of rhBMP-2, which in turn significantly stimulated the osteogenesis of human bone marrow stromal cells in vitro and of bone regeneration in vivo as shown in a rabbit femur defect repair model. Thus, the combination MS/CPC/rhBMP-2 scaffolds might provide a solution to issues of tissue necrosis during the regeneration process and therefore might be able to be readily developed into a useful tool for bone repair in the clinic.