The In2O3 thin film nanosensors were fabricated by dropping In(OH)3 sol on nano gap electrode with 0.1-2.5 micron of gap size, dried, and calcined at various temperatures. The grain size of In2O3 and thus the number of In2O3 grains were changed by calcining at 600-850 °C. The size of grain was increased from 15 nm at 600 °C to 55 nm at 850 °C, and thus the number of grains in 0.3 micron gap was decreased from 19 to 5.3. Contrary to the expectation, the small resistance changes to both 1 ppm Cl2 (resistance increase) and 0.5 ppm Cl2 (resistance decrease) were obtained for In2O3 nanosensors calcined at 700-850 °C. These were contributed to the changes in the surface and interface chemical state to suppress the adsorption of or substitution with Cl2 molecule.

In this paper we present results of intrinsic/non doped zinc oxide deposited at room temperature by rf magnetron sputtering able to be used as a semiconductor material on electronic devices, like for example ozone gas sensors and ultra-violet detectors. The produced films are polycrystalline with a c-axis preferential orientation parallel to the substrate. The films present a resistivity that varies from 4.0×10−2 Ωcm to 1.0×109 Ωcm depending on the deposition conditions used in this study (rf power density and oxygen partial pressure) without changing the optical properties (an average transmittance of 85 % and an optical band gap energy ≈3.44 eV). When exposed to UV light the sensor response exceeds more than 5 orders of magnitude recovering to the initial state in the presence of ozone. The sensitivity of the films is improved when the oxygen partial pressure increases and the rf power density decreases which are directly related to the structural properties of the films.

An algorithm for compensating water vapor pressure in CO detection is proposed here and tested on SnO2 thick-film gas sensors. For each sensor working at a fixed temperature, the conductance, G, is fitted by an analytical surface, whose expression can be inverted to determine the CO concentration once the water partial pressure is measured. As soon as the rate of water-vapor pressure change is slower than about 300 Pa/min, G is a function of the temperature, water vapor and CO concentration. If quicker water vapor variations occur instead, the sensing film undergoes a non-negligible transitory phenomenon during which G assumes different values even at fixed water vapor pressure and temperature. This phenomenon prevents the compensation from working properly. An explanation of the behavior is offered by the interpretation of kinetics equations at surface.

We have used embedded piezoresistive microcantilever (EPM) sensors in the detection of hydrogen cyanide gas. EPM sensors are small, MEMS-based devices consisting of a tiny piezoresistive microcantilever partially embedded into a “sensing material” designed to respond volumetrically when exposed to the desired analyte. These EPM sensors may be very small, operate on simple and inexpensive support electronics, are highly resistant to movement or shock, may be operated by hardwire connection or wirelessly in large numbers, and are capable of detecting many different analytes. In this study, we have used EPM sensors to detect hydrogen cyanide gas. Preliminary results indicate that the EPM sensors provide a fast response (less than 5 seconds) to levels of HCN that may be lethal to humans.

Gas sensors based on tin dioxide nanoparticles show high sensitivity to reducing and oxidizing gases. Dry aerosol synthesis applying the flame spray pyrolysis was used for manufacture and directly (in-situ) deposit nanoparticles on sensor substrates. For the first time this technique has been used to synthesize a combination of two stacked porous layers for gas sensor fabrication. Compared to state-of-the-art techniques, aerosol technology provides a direct and versatile method to produce homogeneous nanoparticle films. Two different sensing layers were deposited directly on interdigital ceramic substrates. These porous bottom layers consisted either of pure tin dioxide or palladium doped tin dioxide. The top layer was a palladium doped alumina nanoparticle film which served as a chemical filter. The fabricated gas sensors were tested with methane, CO and ethanol. In case of CH4 detection, the pure tin dioxide sensor with the Pd/Al2O3 filter layer showed higher sensor signals and significantly improved analyte selectivity with respect to water vapor compared to single tin dioxide films. At temperatures up to 250°C the Pd-doping of the tin dioxide strongly increased the sensitivity to all gases. At higher temperatures the sensor signal significantly decreased for the Pd/SnO2 sensor with a Pd/Al2O3 filter on top indicating high catalytic activity.

SnO2 nanowires have been recently employed in the “gas-sensors” field and excellent results of conductometric and optical tests on SnO2 nanowires-based gas sensors have been reported.

However, the mechanism that controls the gas-sensing effect in metal oxides nanowires is not fully understood yet. Here the authors present the first results of an in-depth study about the influence of post growth treatments on the physical and gas sensing properties of SnO2 nanowires.

In particular, SnO2 nanowires grown by a vapour transport technique were annealed in a oxygen-rich atmosphere and then characterized by different techniques to assess the influence of the treatment on the nanowires properties.

The annealing in oxygen atmosphere is shown to strongly affect the PL and CL spectra, the electrical resistivity as well as the gas sensing properties of the nanowires. The obtained results are consistent with a reduction of the oxygen vacancies concentration induced by the O2 treatment and seem to confirm the role of these defects in affecting the gas response of SnO2 nanowires-based sensors.

The swelling behavior of chitosan hydrogels in ionic liquid–water binary systems was studied using hydrophilic room-temperature ionic liquids (RTILs) to elucidate the swelling properties of chitosan hydrogels. It was confirmed that chitosan hydrogels are much stiffer after immersing in a pure RTIL because the water existing inside the chitosan polymer network is extracted into the RTIL. The pH of the binary system changes when the RTIL is in contact with water. The chitosan hydrogels were fully dissociated at a 90% water content in the BMI-BF4-water binary system. The equilibrium binary system content behavior of the chitosan hydrogels depended upon the amount of free water present. The water behavior in a pure RTIL was examined using differential scanning calorimetry.

Biosensing property and functionalization of In2O3 nanowire and carbon nanotube field effect transistor were investigated. Low-density lipoproteins adsorbed on their surface were found to give complementary effects on their electrical property, e.g., enhanced conductance in NW and suppressed conductance in CNT. Prostate specific antigen was selectively detected by functionalizing the sensors with PSA antibody via linker molecules. It was found that the exposure to 0.14 nM (5 ng/ml) PSA increases the conductance of In2O3 nanowire by 1.3 %, while 1.4 nM (50 ng/ml) PSA decreases that of carbon nanotube by 2 %. Additionally, selective functionalization of Indium Tin Oxide thin film and In2O3 NWs with probe DNA single strand was achieved by selectively converting hydroquinone into quinone using electrochemistry, as confirmed by the fluorescence study.

Nanocomposites of iron /iron oxide/ polyoxocarbosilane were prepared by the IR co-pyrolysis of Fe(CO)5 and HMDSO. Their morphologies, chemical content and thermal behavior were studied by different analytical techniques. For examining the sensing capabilities of the low-polymer content nanocomposite thick films, the variation of the electrical resistance to CO and CH4 gases was tested. A promising behavior as concerning the sensitivity and the selectivity was found.

Composite fibers composed of chitosan and single-wall carbon nanotubes (CNTs) have been fabricated using a wet spinning method. The dispersion was improved by the sonic agitation of the CNTs in a chitosan solution followed by centrifugation to remove tube aggregates and any residual catalyst. The mechanical behavior was investigated using a dynamic mechanical analyzer (DMA). The mechanical tests showed a dramatic increase in Young's modulus for the chitosan/CNT composite fibers fabricated using the improved dispersion method. The strain on the microfibers was determined from tensile load measurements during pH switching in acidic or basic electrolyte solutions. The microfibers showed a general actuation behavior of expanding at pH = 2 and contracting at pH = 7 under low tensile loads. However, a reverse of this actuation behavior was exhibited under high tensile loads. This anomalous pH actuation is both new and surprising. It was explained from an analysis of the differences in sample stiffness and Poisson’s ratio under tensile load in electrolyte solutions with different pH values.

Rapid, multiplexed, high throughput detection of proteins is essential for the development of protein biomarkers as sensors. Electrical alignment and detection is a non-invasive, label free technique for rapid identification of bimolecular. We present here a micro fabricated platform based detector for rapidly identifying protein biomarkers present in atherosclerotic plaque for rapid clinical diagnosis of arterial obstruction. This is achieved by electrical assembly of polystyrene beads functionalized with specific antibody receptors (anti-C-reactive protein) .The electrical assembly is achieved using electrophoresis. The polystyrene “bridge” micro structure formed due to electrical assembly aids in the amplification of the antibody-antigen binding event. Antigen (C-reactive protein) at nanogram / ml concentration was detected when binding of the antigen resulted in an amplification of the electrical signal that was measured from the base microelectrode platform. This technique is a demonstration of the application of microscale technology (electrodes) in nanoscale (protein) electrical detection.

Paper presents results of investigation aimed at the development of tin dioxide nanodimensional film gas sensors (NDFGS) with high sensitivity to hydrogen. Specifics of the performed research consist in the approach based on the combination of utilization nanodimensional metal oxide film, as gas sensitive element of device, and group electron technology methods that allows to arranging from small to large scale manufacturing of given NDFGS.

Gas sensitive nanodimensional film (NDF) had been formatted by means of chemical spray pyrolysis method on the both ceramic substrate for study and optimization of electrophysical and gas sensitive characteristics and “chip” of gas sensor (GS) preliminarily produced through group electron technology. Films were deposited at the temperatures in interval 400-500°C from water solutions of SnCl4.5H2O precursor. The thickness of SnO2 films was varied in the range 40-80 nm.

Study of electrophysical characteristics of obtained layers has shown that the last one possess resistance on the level 105-106 Ohm/ at the working temperatures of GS. Gas sensitivity was determined as ratio of SnO2 film resistance in the pure air and in the presence of gas impurity in atmosphere (S=Rgas/Rair). Values of R were determined through Van-der-Pauw method.

X-ray and SEM investigation has allowed establishing the interconnection between technologic parameters, nanostructure and gas sensitive characteristics of obtained films.

Gas sensitivity S of the deposited undoped films has amounted 9-10 relative units to the 100 ppm of hydrogen in air. Modification of gas sensitive properties of tin dioxide NDF through bulk and surface doping with Pd has allowed to increasing hydrogen sensitivity up to almost 104 rel. units, providing the detection of hydrogen at the concentration on the level 1 ppm and shift of the sensitivity maximum from 350°C (in the case of undoped films) to 150°C (Pd doped NDF).

Performed sensor chip thermal regimes modeling has allowed developing of the NDFGS topology with reduced power consumption (< 30 mW).

In this presentation, we discuss the development of nanostructured sensor materials based on nanoparticulate metal-oxide suspensions deposited onto MEMS μHPs by microprinting. The preparation of the suspensions is described; the precise control over the thickness of the films through the composition of the metal-oxide suspensions is demonstrated. The procedure of microprinting is described. The deposited films are evaluated as chemical sensors. The sensor performance of the microsensors – sensitivity, stability, speed of operation, and selectivity – is compared with that of analogous traditional thick-film sensors.

This paper summarizes the results of experimental investigations of the feasibility of applying electrowetting-induced droplet self-oscillations to induce rapid mixing of small quantities of liquids. The concept was tested using video microscopy to monitor the mixing of passive colored dyes, of spatially-separated reactants that change color upon reaction, and of fluorescent DNA oligomers whose light emission vanishes upon hybridization with appropriately-functionalized complementary DNA strands. Droplet self-oscillation was found to increase the rate of mixing by factors ranging from 15 to 100 as compared with the rate of passive diffusion in undisturbed droplets. This demonstrates that self-oscillation-induced mixing is a viable method for substantially enhancing the speed of chemical reactions in general, and biochemical assays in particular, when performed in small volumes of liquids.

Tungsten oxide nanofibers have been successfully fabricated in a way based on electrospinning technique. A DMF solution of Poly(Vinyl Acetate)(PVAc, Mw=500,000) was mixed with tungsten isopropoxide to form a viscous precursor solution. Composite nanofibers were obtained by electrspinning this viscous solution. By calcination of the composite fibers, pure tungsten oxide nanofibers were obtained with controllable diameters of around 100 nm. Morphology of the fibers has been characterized by SEM and TEM. The relationship between solution concentration and ceramic nanofiber morphology has been studied. The detailed structure evolution process has been investigated by synchrotron based in-situ XRD. Specific phases of the oxide nanofibers at various calcination temperatures have been obtained from the in-situ XRD spectrum.

Chromium-doped (0.5-10 % Cr:Ti molar ratio) nanocrystalline titania (5–6 nm) prepared via sol-gel method was examined by synchrotron-based wide angle x-ray scattering (WAXS) for crystal structure determination. Atomic pair-distribution functions (PDF) for both raw and heat-treated samples were obtained by Fourier transforms of the WAXS data. The PDF data were fitted using structural models of nanocrystalline titania that considered phase compositions, lattice parameters, atomic positions and thermal factors. The unit cell of Cr-doped nanocrystalline titania expanded 1-2 % with respect to bulk titania as a consequence of the substitution of Ti by Cr and the generation of oxygen vacancies. We observed a lattice contraction after heat-treatment that may be caused by the redistribution of Cr atoms to nanoparticle surfaces during phase transformation and particle coarsening.

To detect biological events, biosensors require a transducer part where specific biomolecular binding events at a bioreceptor part is converted to measurable quantitative signals. Currently, most of biosensors adopt a fluorescent or radioactive probing technique as a transducer. However, such approaches require expensive and sophisticated analysis procedures with laboratory-based equipment.

In this work, we propose a novel method for optically detecting hybridization results in a deoxyribonucleic acid (DNA) chip using an anchoring transition of liquid crystal (LC) alignment. To investigate the effects of structural changes of DNA on the LC alignment, we used a functional substrate on which single-stranded oligonucleotide DNA (ssDNA) was selectively immobilized to a Biotin Chip substrate. In our experiment, we used a 19-mer oligoDNA or p53 tumor suppressor as a bioreceptor and its complementary partner oligoDNA as a target material.

Before hybridization, surface nematic LC (NLC) molecules on the immobilized ssDNAs are homeotropically aligned by a steric interaction between the freely penetrated NLC molecules and the ssDNA. After hybridization, the penetration of the NLC molecules is hindered by the double strand DNA (dsDNA) due to their increased packing density. Such an interface condition makes the surface ordering of the NLC molecules very weak, as a result, the NLC in the bulk has a planar inhomogeneous orientation. Although hybridization events of the DNA and the subsequent molecular interaction between the immobilized DNA and the NLC molecules takes place within a layer whose thickness is in the tens of nm, such binding events can be communicated to the NLC bulk beyond a distance of tens of μm though the long-range elastic deformation of the NLC molecules. Thus, the hybridization event is converted to amplified optical signals via birefringent nature of the NLC between crossed polarizers. Our NLC-based DNA chip array showed that the extinction ratio of transmitted light depending on the hybridization results was approximately four, which could be read by the naked eye. Since such anchoring behaviors on the immobilized DNA are very similar to those on the conventional amphiphilic homeotropic surfactant of LCs, it is expected that quantitative analysis of hybridization events can be explored with our simple system.

Sol-gel derived silica particles are candidates for vehicles for injectable controlled drug-delivery. In this study, Proteinase K was the model biomolecule encapsulated in the silica xerogel, ambigel, and aerogel particles. The surface area and average pore diameter of these particles are reported. Both the amount of Proteinase K released from the particles and the activity of the released Proteinase K were measured as a function of time. The primary finding of this study is the effect of pore diameter on the specific activity of Proteinase K released from these particles.

In this study an analysis is made of the adsorption properties of nanocrystalline SnO2 containing a metallic dopant. The analysis is based on semi-empirical Hartree-Fock and scattering theories and the structures considered are SnO2 grains with a rutile lattice and a size comparable with the experimental ones. The grains contain rows of gold atoms located on the grain surface or in an endohedral position, in the grain interior, and the adsorbed system is generated by depositing a CO molecule on the grain surface. The calculations illustrate the dependence of the binding energies and ofthe conductance on the grain size, on the location of the metallic additives in both the clean and in the CO-adsorbed grains. New mechanisms of adsorption and of current transport are proposed.

The paper reports experimental data on growth, morphology, NO sensitivity and electrophysical properties of A1Bi3C6 thin films obtained by means of simple vacuum technology. The investigated samples were condensed onto the glass substrates under deposition rate 0.1-0.5 nm/s at T = 300 K and vacuum level P = 10-3 Pa. AFM investigations of the film surface before and after interaction with aggressive environment demonstrated sufficient sensitivity of the film relief to the aggressive component. Room-temperature electric field-induced characteristics were investigated for metal-semiconductor (MS) Cr/NaBiTe2 structures.