Colloidal Nano-apatite Particles with Active Luminescent and Magentic Properties for Biotechnology Applications

Colloidal Nano-apatite Particles with Active Luminescent and Magentic Properties for Biotechnology Applications. The synthesis of functional nano-materials is a burgeoning field that has produced remarkable and consistent breakthroughs over the last two decades. Individual particles have become smaller and shown potential for well defined functionality. However, there are still unresolved problems, a primary one being the loss of functionality and novelty due to uncontrolled aggregation driven by surface energy considerations. As such the first design criteria to harness the true potential of nanoparticles is to prevent unwanted agglomeration by: (1) improving, and, if possible, (2) controlling aggregation behavior. This requires specific knowledge of the chemistry of the immediate locale of the intended application; especially for biologically relevant applications. The latter criterion is also application driven but should be considered, generally, to diversify the range of functional properties that can be achieved. We have now reason to believe that such a novel system with multifunctional capabilities can be synthesized rather conveniently and have far reaching impact in biotechnology and other applications in the near future. We are presently experimenting with the syntheses of spheroidal, metal-doped, colloidal apatite nano-particles (~10 nm) for several potential biomedical applications.

Development of Vapor Deposited Silica Sol-Gel Particles for a Bioactive Materials System to Direct Osteoblast Behavior

Tissue engineering and regenerative medicine have emerged in an effort to generate replacement tissues capable of restoring native tissue structure and function, but because of the complexity of biologic system, this has proven to be much harder than originally anticipated. Silica based bioactive glasses are popular as biomaterials because of their ability to enhance osteogenesis and angiogenesis. Sol-gel processing methods are popular in generating these materials because it offers: 1) mild processing conditions; 2) easily controlled structure and composition; 3) the ability to incorporate biological molecules; and 4) inherent biocompatibility. The goal of this work was to develop a bioactive vaporization system for the deposition of silica sol-gel particles as a means to modify the material properties of a substrate at the nano- and micro- level to better mimic the instructive conditions of native bone tissue, promoting appropriate osteoblast attachment, proliferation, and differentiation as a means for supporting bone tissue regeneration. The size distribution, morphology and degradation behavior of the vapor deposited sol-gel particles developed here were found to be dependent upon formulation (H2O:TMOS, pH, Ca/P incorporation) and manufacturing (substrate surface character, deposition time). Additionally, deposition of these particles onto substrates can be used to modify overall substrate properties including hydrophobicity, roughness, and topography. Deposition of Ca/P sol particles induced apatite-like mineral formation on both two- and three-dimensional materials when exposed to body fluids. Gene expression analysis suggests that Ca/P sol particles induce upregulation osteoblast gene expression (Runx2, OPN, OCN) in preosteoblasts during early culture time points. Upon further modification-specifically increasing particle stability-these Ca/P sol particles possess the potential to serve as a simple and unique means to modify biomaterial surface properties as a means to direct osteoblast differentiation.

Laser ablation and induced nano-particle synthesis

Laser pulses are largely used for processing and analysis of materials and in particular for nano-particle synthesis. This paper addresses fundamentals of the generation of nano-materials following specific thermodynamic paths of the irradiated material. Computer simulations using the hydro code MULTI and the SESAME equation of state have been performed to follow the dynamics of a target initially heated by a short laser pulse over a distance comparable to the metal skin depth.

Influence of Abutment Design on Stiffness, Strength, and Failure of Implant-Supported Monolithic Resin Nano Ceramic (RNC) Crowns

BACKGROUND Recent technical development allows the digital manufacturing of monolithic reconstructions with high-performance materials. For implant-supported crowns, the fixation requires an abutment design onto which the reconstruction can be bonded. PURPOSE The aim of this laboratory investigation was to analyze stiffness, strength, and failure modes of implant-supported, computer-assisted design and computer-aided manufacturing (CAD/CAM)-generated resin nano ceramic (RNC) crowns bonded to three different titanium abutments. MATERIALS AND METHODS Eighteen monolithic RNC crowns were produced and loaded in a universal testing machine under quasi-static condition according to DIN ISO 14801. With regard to the type of titanium abutment, three groups were defined: (1) prefabricated cementable standard; (2) CAD/CAM-constructed individualized; and (3) novel prefabricated bonding base. Stiffness and strength were measured and analyzed statistically with Wilcoxon rank sum test. Sections of the specimens were examined microscopically. RESULTS Stiffness demonstrated high stability for all specimens loaded in the physiological loading range with means and standard deviations of 1,579 ± 120 N/mm (group A), 1,733 ± 89 N/mm (group B), and 1,704 ± 162 N/mm (group C). Mean strength of the novel prefabricated bonding base (group C) was 17% lower than of the two other groups. Plastic deformations were detectable for all implant-abutment crown connections. CONCLUSIONS Monolithic implant crowns made of RNC seem to represent a feasible and stable prosthetic construction under laboratory testing conditions with strength higher than the average occlusal force, independent of the different abutment designs used in this investigation.

Intermediate band materials for more efficient solar energy use: quantum modelling and experimental realizations

The intermediate band (IB) solar cell (Fig. 1) has been proposed [1] to increase photovoltaic efficiency by a factor above 1.5, based on the absorption of two sub-bandgap photons to promote an electron across the bandgap. To realize this principle, that can be applied also to obtain efficient photocatalysis with sunlight, we proposed in recent years several materials where a metal or heavy element, substituting for an electropositive atom in a known semiconductor that has an appropriate band gap width (around 2 eV), forms inside the gap the partially filled levels needed for this aim

Crack mechanical failure in ceramic materials under ion irradiation: case of lithium niobate crystal

Swift heavy ion irradiation (ions with mass heavier than 15 and energy exceeding MeV/amu) transfer their energy mainly to the electronic system with small momentum transfer per collision. Therefore, they produce linear regions (columnar nano-tracks) around the straight ion trajectory, with marked modifications with respect to the virgin material, e.g., phase transition, amorphization, compaction, changes in physical or chemical properties. In the case of crystalline materials the most distinctive feature of swift heavy ion irradiation is the production of amorphous tracks embedded in the crystal. Lithium niobate is a relevant optical material that presents birefringence due to its anysotropic trigonal structure. The amorphous phase is certainly isotropic. In addition, its refractive index exhibits high contrast with those of the crystalline phase. This allows one to fabricate waveguides by swift ion irradiation with important technological relevance. From the mechanical point of view, the inclusion of an amorphous nano-track (with a density 15% lower than that of the crystal) leads to the generation of important stress/strain fields around the track. Eventually these fields are the origin of crack formation with fatal consequences for the integrity of the samples and the viability of the method for nano-track formation. For certain crystal cuts (X and Y), these fields are clearly anisotropic due to the crystal anisotropy. We have used finite element methods to calculate the stress/strain fields that appear around the ion- generated amorphous nano-tracks for a variety of ion energies and doses. A very remarkable feature for X cut-samples is that the maximum shear stress appears on preferential planes that form +/-45º with respect to the crystallographic planes. This leads to the generation of oriented surface cracks when the dose increases. The growth of the cracks along the anisotropic crystal has been studied by means of novel extended finite element methods, which include cracks as discontinuities. In this way we can study how the length and depth of a crack evolves as function of the ion dose. In this work we will show how the simulations compare with experiments and their application in materials modification by ion irradiation.

Comportamiento de morteros de cemento con nano adiciones sometidos a ciclos hielo-deshielo.

El objetivo de este trabajo es determinar la influencia de la incorporación de nanoSiO2, nanoAl2O3 así como la mezcla de ambas adiciones, en morteros de cemento cuando son sometidos a ciclos de hielo-deshielo, e interpretar dicho comportamiento a través de los cambios microestructurales. Para ello se fabricaron cuatro morteros de cemento con distintas adiciones. Un mortero de cemento CEM I 52,5R normalizado de acuerdo a la Norma Europea EN 196-1:2005 como control. Otro de igual composición, al que se incorporó un 5% de nano-SiO2 respecto a la cantidad total de cemento, un tercero con un 5% de nano-Al2O3 y un cuarto con un 2,5% de nano-SiO2 y un 2,5% de nano-Al2O3. La relación agua/material cementante de 0,47. Para cada mortero, se fabricaron 4 probetas de 15x15x15 cm con el fin de determinar su resistencia a ciclos de hielodeshielo de acuerdo a la UNE-CEN/TS 12390-9 EX. Además, se caracterizaron microestructuralmente mediante porosimetría por intrusión de mercurio, análisis termogravimétrico y micrografía electrónica. Los resultados de la caracterización microestructural ponen de manifiesto un refinamiento de la matriz porosa, con aumento de la cantidad de geles hidratados. Las imágenes de SEM revelan cambios en la morfología de los productos hidratados de la matriz cementicia, siendo notables tanto en la portlandita como en la ettringita. Los cambios producidos por la adición de nano sílice muestran una gran influencia en la estructura porosa y determinan una mejora muy significativa en el comportamiento de estos morteros bajo ciclos hielo-deshielo. The rise of nanotechnology in the last two decades has been of scientific interest considerable for the construction industry due to the high potential in the use of nano-particles in cementitious materials. These allow a reengineering of existing products and the design of new high-performance materials. In this line there are many works in which we study the effect of additions of nano-particles in mortars and concretes. However, were very few scientific papers in which we study the behavior of these materials under freeze-thaw cycles. The aim of this study was to determine the influence of incorporating nano-SiO2, nano-Al2O3 and the mixture of both additions in cement mortar when subjected to freeze-thaw cycles, and interpret such behavior through microstructural changes.For this purpose four cement mortars have been fabricated with different additions. A cement mortar CEM I 52,5 R normalized according to the European standard EN 196-1:2005 was manufactured as control . Another mortar with a 5% nano-SiO2 in respect to the total amount of cement, other with 5% nano-Al2O3 and for last a mortar with 2.5% of nano-SiO2 and 2.5% of nano-Al2O3. The water/binder ratio was 0.47. For each mortar, four specimens were made of 150x150x150 mm in order to determine its behavior under freeze-thaw cycles according to UNE-CEN/TS EX 12390-9. Furthermore, the mortars were characterized microstructurally by mercury intrusion porosimetry, thermogravimetric analysis and electron micrograph. The microstructural characterization results show a refinement of the porous matrix, with increased amount of hydrated gels. The SEM images show changes in the morphology of the products of the hydrated cement matrix being remarkable both in the portlandite as in the ettringite. The changes produced by the addition of nanosilica show a great influence on the porous structure and determine a significant improvement in the behavior of these mortars under freeze-thaw cycles.

Hormigón autocompactante con nano-adiciones de sílice y alúmina

El presente Trabajo Fin de Máster tiene por objeto principal el estudio de la influencia que tienen las adiciones tanto de Nano-Alúmina como de Nano-Sílice en el Hormigón Autocompactante (HAC). Para ello se realizará una comparativa de ensayos con un hormigón patrón cuya publicación versa en el artículo de referencia “Construction and Building Materials 55 (2014) 274–288 (On the mechanical properties and fracture behavior of polyolefin fiber-reinforced self compacting concrete)”, y con idéntica dosificación que el del presente Trabajo, pero con presencia de nano-adiciones, y comparando los ensayos de resistencia a compresión simple, módulo de elasticidad, resistencia a tracción indirecta, resistencia a flexotracción y durabilidad (índice de penetración de agua). El desarrollo del presente trabajo consta de diferentes capítulos, los cuáles se pueden englobar a grandes rasgos dentro de los siguientes tres grandes puntos: - Se elabora un pequeño estudio del estado del conocimiento, referente a hormigones autocompactantes, describiendo su elaboración convencional del mismo y en particular comentando todas los posibles aditivos y adiciones y en concreto, la descripción específica del objeto de este presente Trabajo Fin de Máster, que son las adiciones de nano-sílice y de nano-alúmina, encontrándose todo lo anterior en la literatura existente y referenciada a lo largo del presente Trabajo. El fin de lo anteriormente descrito, es el de revisar un marco teórico, que nos permitirá introducir el conocimiento de partida del presente Trabajo Fin de Máster, tomándolo a su vez como una metodología que sirva de base para el desarrollo del mismo y para futuras líneas de investigación. - Emprender una campaña experimental de laboratorio que nos permita familiarizarnos con los materiales comprendidos dentro del hormigón a tratar (HAC), pasando por cada uno de sus procedimientos de fabricación y curado, así como también conocer y desarrollar los pertinentes ensayos tanto para su estado fresco como para el estado endurecido. - Finalmente, analizar resultados obtenidos de los diferentes ensayos de laboratorio, comparando los mismos y realizando unas conclusiones y futuras líneas de investigación dentro del campo objeto del presente Trabajo Fin de Máster.

Study of the increase in bending stiffness on timber beams reinforced with composite materials

It is common to find structures that need to be reinforced due to deterioration or because the function of the building changes. The economic cost involved in these forms of interventions is considerable. Therefore, it is interesting to progress in the existing strengthening techniques and the study of new reinforcement systems. This paper analyses the behaviour of timber beams reinforced with carbon and basalt fiber composite materials. The main objective of this study is to test the stiffness increase produced by the carbon and basalt FRP on reinforced beams. The results show the stiffness increase produced by the different types of reinforcement.

Effect of nano-Si2O and nano-Al2O3 on cement mortars for use in agriculture and livestock production

The effect of nano-silica, nano-alumina and binary combinations on surface hardness, resistance to abrasion and freeze-thaw cycle resistance in cement mortars was investigated. The Vickers hardness, the Los Angeles coefficient (LA) and the loss of mass in each of the freeze–thaw cycles to which the samples were subjected were measured. Four cement mortars CEM I 52.5R were prepared, one as control, and the other three with the additions: 5% nano-Si, 5% nano-Al and mix 2.5% n-Si and 2.5% n-Al. Mortars were tested at 7, 28 and 90 d of curing to determine compression strength, total porosity and pore distribution by mercury intrusion porosimetry (MIP) and the relationship between the CSH gel and Portlandite total by thermal gravimetric analysis (TGA). The capillary suction coefficient and an analysis by a scanning electron microscope (SEM) was made. There was a large increase in Vickers surface hardness for 5% n-Si mortar and a slight increase in resistance to abrasion. No significant difference was found between the mortars with nano-particles, whose LA was about 10.8, classifying them as materials with good resistance to abrasion. The microstructure shows that the addition of n-Si in mortars refines their porous matrix, increases the amount of hydrated gels and generates significant changes in both Portlandite and Ettringite. This produced a significant improvement in freeze–thaw cycle resistance. The effect of n-Al on mortar was null or negative with respect to freeze–thaw cycle resistance.

Galvanic Corrosion of High-Temperature Low-Sag (HTLS) High Voltage Conductors: New Materials - New Challenges

High-Temperature Low-Sag (HTLS) high voltage overhead conductors offer higher operating temperatures, reduced resistance and less sag than conventional designs. With up to twice the current capacity for the same diameter conductor, they may help ease the power shortage in the constantly increasing electricity demand, but there might be some concerns about their corrosion resistance. These new conductors use materials relatively new to the power industry, such as advanced carbon fiber polymer matrix composites and unique metal matrix composites/nano-composites predominantly used in aerospace industries. This study has made an initial assessment of potential galvanic corrosion problems in three very different HTLS designs: ACCC (Aluminum Conductor Composite Core), ACCR (Aluminum Conductor Composite Reinforced) and ACSS (Aluminum Conductor Steel Supported). In particular the ACCC design was evaluated for its resistance to corrosion and compared to the other designs. The study concludes that all three designs can develop galvanic corrosion under certain circumstances. While the results are not sufficient to make service life predictions of any of the tested conductors, they point out the necessity of thorough corrosion testing of all new conductor designs.

Nano-biocomposite films with modified cellulose nanocrystals and synthesized silver nanoparticles

Ternary nano-biocomposite films based on poly(lactic acid) (PLA) with modified cellulose nanocrystals (s-CNC) and synthesized silver nanoparticles (Ag) have been prepared and characterized. The functionalization of the CNC surface with an acid phosphate ester of ethoxylated nonylphenol favoured its dispersion in the PLA matrix. The positive effects of the addition of cellulose and silver on the PLA barrier properties were confirmed by reductions in the water permeability (WVP) and oxygen transmission rate (OTR) of the films tested. The migration level of all nano-biocomposites in contact with food simulants were below the permitted limits in both non-polar and polar simulants. PLA nano-biocomposites showed a significant antibacterial activity influenced by the Ag content, while composting tests showed that the materials were visibly disintegrated after 15 days with the ternary systems showing the highest rate of disintegration under composting conditions.

Combined effects of cellulose nanocrystals and silver nanoparticles on the barrier and migration properties of PLA nano-biocomposites

Poly(lactic acid) (PLA)-based high performance nano-biocomposites were prepared to be used in active food packaging. Pristine (CNC) and surfactant modified cellulose nanocrystals (s-CNC) with silver (Ag) nanoparticles were used as the matrix modifiers. Binary and ternary systems were prepared. Morphological investigations revealed the good distribution of silver nanoparticles in PLA ternary systems. The combination of s-CNC and Ag nanoparticles increased the barrier effect of the produced films while the results of overall migration for the PLA nano-biocomposites revealed that none of the samples exceeded the overall migration limit, since results were well below 60 mg kg−1 of simulant.

SERS Active Surface in Two Steps, Patterning and Metallization

Robust and reproducible metallized nano/microstructured surfaces of polymeric surfaces have been successfully prepared by direct laser interference patterning (DLIP) of commercial polymeric films followed by sputtering of metallic thin films. The SERS spectra for 2-thioaniline adsorbed on a structured polycarbonate surfaces covered with a gold or platinum film showed a ca. three order of magnitude enhancement over a flat surface with the same metal film. The method here reported is suitable for mass production of substrates for SERS since large areas (several cm2) can be structured in ca. 1–5 s.