A surface plasmon resonance mercury sensor was demonstrated by electroless reduction of silver nanoparticles on amorphous silicon thin films. Unlike the previous Ag/Au nanoparticle - Hg interaction investigations, which monitored the blue shift of the dipolar plasmon band of well-dispersed nanoparticles, the present work reveals and explores the red shift of the symmetric hybrid plasmon mode of the interacting nanoparticles in response to Hg vapor exposure. Sensitivity to Hg was explored with varying nanoparticle size, which could be controlled by the immersion time associated with the reduction process. The recovery of the hybrid plasmon band after the Hg exposure was also monitored which was observed to be slower than the recovery of the dipolar plasmon band for noninteracting particles.

Embedded piezoresistive microcantilever (EPM) sensors provide a tiny, low-cost, and robust platform for the detection of chemical or biological analytes. New sensing applications become potentially available as the design or synthesis of new sensing materials for EPM instruments are studies. In this study, we report on the detection of hydrogen fluoride gas (HF) in air, and in a medical application, the measurement of human hydration levels. Two sensing materials characterize these applications, thiolated gold nanoparticles in a keratin matrix (HF), and a crosslinked PVA-based hydrogel in the hydration application.

Microscale (MEMS) gas sensing devices for power plant and automobile exhaust gas are being developed. Bulk BaZrO3 has been previously found to be sensitive to H2O at high temperatures, but was never studied in a thin film form. This research thrust focuses on undoped BaZrO3 and doped BaZrO3 with Y.

Thin films were deposited on oxidized n-type silicon substrates at room temperature from ceramic targets with an Ar sputtering ambient. Various deposition pressures and deposition powers were used for the initial investigation. The structural and electrical properties of the deposited films were characterized to investigate their relationships to the deposition process parameters. X-ray diffraction (XRD) was used to measure the crystal structure of the deposited films, and in particular was used to determine if any crystallographic texture is present in the films. XRD results indicate the as-deposited films are amorphous before annealing. Films sputtered with and without oxygen in the ambient were compared. The crystal structure and morphology of BaZrO3 and BaZrO3 doped with Y after annealing were also determined. The materials changed from amorphous to crystalline after annealing at temperatures of 800 °C and 1000 °C for 3 hours in forming gas (2% H2 balanced with Ar gas) and oxygen. Temperature was found to dominate over deposition conditions in determining the final film structure. Atomic force microscopy was used to examine the morphology of the thin films. Gas sensor test structures using a Pt thin film metallization for interdigitated electrode structures were fabricated for gas sensing measurements. The experiments with the completed test structures measured the materials¡¦ resistivity as a function of temperature and gas concentration. Both materials decrease in resistance with increasing temperature, which is consistent with ionic conduction. Some experiments tested the gas sensitivity and selectivity of the films to the target gas H2O vapor (humidity) and possible cross sensitive gases H2 and CO2. Both materials need further development to evaluate their suitability for thin film sensors. First, the films were found to be highly resistive, making characterization of the electrical properties very difficult. Second, O2 ambient annealing gas will be applied to compare the crystal structure and morphology of both films with an Ar ambient annealing process.

The interest in semiconducting metal oxide nanowires for gas sensing devices is today very high. Besides common materials such as SnO2 or ZnO, also In2O3 has been obtained in this quasi-1D morphology . In the present work In2O3 nanowires have been grown by vapor transport process starting from 6N pure In. For a better knowledge of the fundamental properties and the sensing mechanism of In2O3 nanowires, the obtained samples have been investigated by different techniques, focusing mainly on the optical characterization. Their morphology and structure have been studied by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray diffraction. The optical properties have been investigated as well, mainly by means of photo- (PL) and Cathodo-luminescence (CL) both applied in the UV-Visible range. A complex emission spectrum has been revealed and assigned to specific defects thanks to a deep analysis of the bands as functions of temperature (varying from 20 to 300K) and to suitable thermal treatments (in oxygen rich atmosphere at 1000°C). Moreover, the effects of electron beam irradiation have been pointed out by performing CL spectra on a single In2O3 nanowire after different irradiation times. The possible influence of the substrate has been verified by measuring low temperature spectra on In2O3 nanowires grown both on alumina and silicon substrates.

Semiconducting oxides are widely known and commercially applied for their gas sensing properties. However, biochemical sensing has mostly depended on optical and electrochemical techniques that are more cumbersome. This work investigates the biosensing characteristics of ZnO nanobelts and ZnO thin films. Zinc oxide thin film sensors showed changes in conductivity after protein functionalization with rabbit IgG and hybridization with anti-rabbit IgG. Conductivity changes were also measured after coating the oxides with MCF-7 cancer cells and its antibodies. In another set of experiments, ZnO nanobelts showed systematic conductivity changes with rabbit IgG protein hybridization. The experimental results in this paper indicate that the conductimetric properties of nano and thin film oxides can be sensitized to protein and cancer cell hybridization reactions. This technique can also be applied to certain other pathogen proteins or toxic proteins from the environment leading to low-cost miniaturized wireless biosensors.

5,10,15,20 meso-tetraphenyl porphyrin (H2TPP) and copper phthalocyanine (CuPc) films have been deposited by means of a recently developed plasma based technique named glow discharge induced sublimation (GDS). The two macrocycles have been deposited by vacuum evaporation (VE) and H2TPP by spin coating (SPIN) as well for comparison. The physical properties of the films have been characterized by means of scanning electron microscopy (SEM) and nitrogen physisorption measurements. SEM images and physisorption isotherms highlight both the much higher surface roughness and specific surface area of GDS samples with respect to the VE and SPIN ones. Optical sensing measurements, performed in differently concentrated ethyl alcohol atmospheres, highlight that GDS samples yield much higher response intensities than SPIN and VE films, short response times and complete recovery.

In this paper, we present the electrochemically programmed release of immobilized IgG protein molecules that have been attached to gold coated surfaces via a thiol-gold linkage. Fluorescence microscopy has been used to image the release of fluorescently tagged IgGs in phosphate buffered saline. In this technique, the reductive desorption of self-assembled monolayers is employed for the release of proteins, which are immobilized on the surface either by non-covalent or covalent interactions. The voltage applied for the release of proteins is in a range of -1.5V to -60V.

We report efforts at enhancement of the surface area of a photonic crystal biosensor through incorporation of a porous titanium dioxide film into the device. The film possessing the structure of nanorods is deposited by the glancing angle deposition technique. Results for detection of polymer films, large proteins and small molecules indicate up to a four-fold enhancement of detected adsorbed mass density for high surface area sensors, compared with sensors without the high surface area coating.