Optimizing the Limit of Detection of Waveguide-Based Interferometric Biosensor Devices.

Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ∼ 10 - 8 RIU with a silicon nitride sensor operating at telecom wavelengths.

Nuevos biomateriales: estudio in vivo del carburo de silicio como material osteointegrador / New biomaterials: in vivo study of silicon carbide as boneintegration material

Objetivo: Evaluar, mediante ensayos in vivo, la biocompatibilidad y el grado de penetración ósea en la microestructura porosa del carburo de silicio (SiC). Material y métodos: se implantaron en cóndilos femorales de conejos cilindros de SiC obtenidos a partir de maderas de pino y sapeli. Como material de referencia fueron utilizados cilindros de titanio. El sacrificio de los animales se realizó a las 12 semanas de implantación y se procedió al examen histológico de las muestras. Resultados: Comprobamos un crecimiento de trabéculas óseas, tanto en la superficie del implante como a través de su estructura porosa, sin apreciarse signos de inflamación ni aparición de tejido fibroso alrededor de la muestra. Estos resultados son confirmados mediante microscopía electrónica de barrido (SEM) y análisis de rayos X por dispersión de energías. Conclusión: El carburo de silicio biomórfico es una cerámica con excelentes propiedades mecánicas y porosidad interconectada que le confiere un especial atractivo de cara a sus aplicaciones biomédicas en implantes ortopédicos (AU)

Objective: To evaluate, using in vivo tests, the biocompatibility and the degree of bone penetration into the porous microstructure of silicon carbide (SiC). Material and methods: For this purpose cylindres of SiC obatained from wood of pine and sapeli were implanted in femoral condyles of rabbits. As reference material we used titanium cylinders. The slaughter of animals was performed at 12 weeks of implantation and proceeded to the histological examination of the samples. Results: We see a growth of bone trabeculae, both on the surface of the implant and through its porous structure, without signs of inflammation or appearance of fibrous tissue around the samples. These results are confirmed by scanning electron microscopy scanning (SEM) and X-ray analysis by dispersion of energies (EDS). Conclusion: Biomorphic silicon carbide (SiC) is a ceramic with excellent mechanical properties and interconnected porosity which gives a special attraction for their biomedical applications in orthopaedic implants (AU)

Redox tuning and species distribution in Maya Blue-type materials: a reassessment.

Maya Blue-type specimens prepared from indigo (1 wt %) plus kaolinite, montmorillonite, palygorskite, sepiolite, and silicalite are studied. Liquid chromatography with diode array detection, ultra-performance liquid chromatography coupled with mass spectrometry, and pyrolysis-silylation gas chromatography-mass spectrometry analyses of the extracts from these specimens combined with spectral and solid-state voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy techniques provide evidence for the presence of a significant amount of dehydroindigo and isatin accompanying indigo and other minority organic compounds in all samples. Solid-state electrochemistry data permits the estimatation of indigo loading in archeological Maya Blue, which is in the range of 0.2 to 1.5 wt %. These results support a view of 'genuine' Maya Blue-type materials as complex polyfunctional organic-inorganic hybrids.

Recycling silicon wire-saw slurries: separation of silicon and silicon carbide in a ramp settling tank under an applied electrical field.

UNLABELLED: The growing demand for silicon solar cells in the global market has greatly increased the amount of silicon sawing waste produced each year. Recycling kerf Si and SiC from sawing waste is an economical method to reduce this waste. This study reports the separation of Si and SiC using a ramp settling tank. As they settle in an electrical field, small Si particles with higher negative charges have a longer horizontal displacement than SiC particles in a solution of pH 7, resulting in the separation of Si and SiC. The agreement between experimental results and predicted results shows that the particles traveled a short distance to reach the collection port in the ramp tank. Consequently, the time required for tiny particles to hit the tank bottom decreased, and the interference caused by the dispersion between particles and the fluid motion during settling decreased. In the ramp tank, the highest purities of the collected SiC and Si powders were 95.2 and 7.01 wt%, respectively. Using a ramp tank, the recycling fraction of Si-rich powders (SiC < 15 wt%) reached 22.67% (based on the whole waste). This fraction is greater than that achieved using rectangular tanks. IMPLICATIONS: Recycling Si and SiC abrasives from the silicon sawing waste is regarded as an economical solution to reduce the sawing waste. However, the separation of Si and SiC is difficult. This study reports the separation of Si and SiC using a ramp settling tank under an applied electrical field. As they settle in an electrical field, small Si particles with higher negative charges have a longer horizontal displacement than SiC particles in a solution of pH 7, resulting in the separation of Si and SiC. Compared with the rectangular tanks, the recycling fraction of Si-rich powders using a ramp tank is greater, and the proposed ramp settling tank is more suitable for industrial applications.

Comparative chemistry of isolable divalent compounds of silicon, germanium, and tin.

Recent studies of the synthesis, structures, spectroscopic properties, and reactions of a series of isolable metallylenes (R2E:, E = Si (1), Ge (2), and Sn (3); R2 = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) are summarized. Because these group-14 metallylenes bear the same helmet-like ligand, a straightforward discussion of the element-dependence of the intrinsic properties of the group-14 element divalent compounds is possible. All these metallylenes were monomeric both in solution and in the solid state, indicating the effective steric protection by the ligand against dimerization. A small sigma-pi conjugation between C-Si(substituent) sigma orbitals and the vacant npz orbitals of divalent atoms in R2E: exists and the extent decreases in the order E = Si > Ge > Sn, as evidenced by UV-vis and NMR spectroscopies and X-ray crystallography. However, the extent of the sigma-pi conjugation in metallylenes 1-3 was much smaller than the electron-donating effects of neighboring nitrogen atoms in known stable cyclic diamino-substituted metallylenes, and hence metallylenes 1-3 are regarded as the least electronically perturbed. Comparative studies of the unique reactions among these metallylenes are also discussed.

A simple method for the synthesis of silicon carbide nanorods.

SiC nanorods were synthesized by a reaction at a temperature of 1200 degrees C, under an argon gas atmosphere, from silicon and amorphous carbon powders mixed by ball milling. The reaction product, which contain SiC nanorods and nanoparticles, has been characterized by high-resolution transmission electron microscopy, X-ray diffraction, and micro-Raman spectroscopy. The synthesized nanorods are more than 1 micron long with a mean diameter of about 10-30 nm. The nanorods possess a well-defined crystalline structure with a thin layer of amorphous SiO2 on the surface. Raman shifts of SiC nanorods and the role of structural defects are discussed.