Carlos A. Martínez

Synthesis of nanoparticles of tantalum (V) oxide in presence of D-galactose 3,6 anhydro-L-galactose

In this work tantalum oxide nanoparticles were synthesised by controlled hydrolysis of tantalum ethoxide in presence of a linear polysaccharide (1-3 linked β-D galactapyranose and 1,4 linked 3,6 anyhdro-α-L-galactopyranose). Nanoparticles of 100–600 nm were obtained when the polysaccharide was used. The nanoparticles were characterised by scanning electron microscopy (SEM), and retrodispersive energy spectroscopy (EDAX).

Synthesis of Cobalt Ferrite Nanowires Using FeOOH as a Template

In this work, cobalt ferrite nanowires were chemically synthesized using FeOOH array a template. The FeOOH nanoarray was obtained by the hydrolysis and precipitation of Fe+3, from FeCl3.4 H2O. The cobalt ion (Co+2) was added in order to make it interact with FeOOH nanorods of 20 nm of diameter and 150 nm of length. These nanorods are grouped into packages having different orientations due to the interaction with the cobalt ions. The arrays were calcinated at 700 and 800 °C to obtain cobalt ferrite nanowires with 70 nm of diameter and some micrometers of length. The morphology and the average size of the nanorods and nanowires were determined using Field Emission Scanning Electron Microscopy (FESEM). The Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction.

Composites of Bromobenzenethiol Functionalized Gold Nanoparticles and the Fluorescent Poly(Phenylene Ethynylene) pPET3OC12-sqS for Optical Biosensors

Bromobenzenethiol passivated gold nanoparticles were mixed with a poly(phenylene ethynylene) bearing thioester flexible sequences in order to obtain a fluorescent composite for optical biosensors. The particles and the composite were characterized by 1H, 13C NMR, UV-Vis and fluorescence spectroscopy, TEM and STEM. The particles are homogeneously dispersed in the polymer matrix as observed by electron microscopy. The NMR spectra suggest that the gold particles and the poly(phenylene ethynylene) are probably interacting through the sulfur atoms of the –C(O)S- and –CH2-S-CH2- moieties of the flexible sequences of the polymer as well as through  interactions between the aromatic ring of 4-bromobenzenthiol and the conjugated backbone of pPET3OC12-sqS. The quantum yield of the composite both in solution and in solid state films is slightly lower than that of pPET3OC12-sqS because of the quenching effect of gold. Nonetheless, a change of the fluorescence intensity of the composite films can be detected as a consequence of the contact with microorganisms. Preliminary microbiological assays indicate an antimicrobial effect of the composite film with the E. coli bacteria.

Fabrication of a MZI device based on waveguides of SiN for biological detection

Integrated Optical (IO) devices have been gained much attention for chemical or biological sensing applications due to high sensibility, mechanical stability and the integration in Silicon [1–3]. In addition, the Si technology in conjunction with techniques of micromachining has enabled the creation of a variety of novel functions in Micro-Opto-Electro-Mechanical Systems (MOEMS). biological sensing uses the evanescent wave theory for detecting change in the refractive index or light absorption induced by the analyte contact. Spectrophotometric analysis is used to determine the concentration or amount of a particular component in an analyte [6]. Usually, the samples need to be sent to a laboratory for the analysis, and the results take time. The need for rapid and on-line measurements led to the development of microsystems with the substance, the detection and the readout electronics circuits all integrated in a single system with advantages that include: small sample volume, system integration, automation of measurement, short response time, improved analytical performance and reduction of time and cost. The most IO devices based in MZI have been fabricated SiN using high temperature (750–900°C) process in LPCVD system, which results in a challenge for the optical-electronic device integration. In contrast, PECVD SiN films for the MZI waveguides used in this work were fabricated at low temperature (∼300 °C) with some similar optical properties to LPCVD and without requirements of a post-annealing temperature. In this work is presented a simple sensor based in Mach-Zehnder Interferometric (MZI) configuration using silicon nitride waveguides deposited by Plasma Enhanced Chemical Vapor Deposition. The aim of this work is to use this micro-interferometer device for biological sensing using the absorbance of light. The light travels through an area of an arm of the waveguide called micro-cavity where the analyte under study is attached. This light is compared with a reference arm of the waveguide, which contain the reference substance. The device was fabricated by standard CMOS technology and using bulk micromachining in order to obtain the micro-cavities. The low temperature deposition of SiN thin films for the waveguide is attractive to have an integrated optic device with the read out circuits. The waveguide showed attenuation of 3% at 0.632¼m. The integrated interferometric sensor is a two arm multilayered optical integrated waveguide structure with a core layer of SiN film. For sensing purposes, in the MZI device one arm is used as the reference arm and the other arm is the sensing arm, with two micro-cavities between those, one for the analyte to be measured and the other used for a reference substance or a “blank” solution. The schematic of this simple MZI sensor is depicted in Figure 1. The micro-cavities, placed in each arm of the MZI were fabricated using KOH as an anisotropic etching solution (45% solution at 80°C) which results in an etch rate of 1.2 mm per min, in this way for the (111) substrate a membrane with a thickness of 50 mm could be produced from a wafer with a nominal thickness of 300 mm. The thermal oxide layer served as an etch-mask. The final micro-interferometric device has a total length of about 10mm, width of 4mm, with a separation of the reference and measuring arms of 3.5mm, as is shown in the figure 2.

Sol Gel Preparation of Ta 2 O 5 Nanorods Using DNA as Structure Directing Agent

Transition metal oxides are being considered as the next generation materials in field such as electronics and advanced catalysts; between them is Tantalum (V) Oxide; however, there are few reports for the synthesis of this material at the nanometer size which could have unusual properties. Hence, in this work we present the synthesis of Ta 2 O 5 nanorods by sol gel method using DNA as structure directing agent, the size of the nanorods was of the order of 40 to 100 nm in diameter and several microns in length; this easy method can be useful in the preparation of nanomaterials for electronics, biomedical applications as well as catalysts.