Showing papers in "Sensor Letters in 2010"

Nanosensor Device for Breath Acetone Detection

Abstract: Nanosensor Device for Breath Acetone Detection L. Wang1, K. Kalyanasundaram2, M. Stanacevic3, and P. Gouma4 ∗ 1Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, BC V6T1Z4, Canada 2Sensitron Semiconductor, Deer Park, NY 11729, USA 3Department of Electrical and Computer Engineering, SUNY Stony Brook, Stony Brook, NY 11794, USA 4Center for Nanomaterials and Sensor Development, SUNY Stony Brook, Stony Brook, NY 11794-2275, USA

Antibodies and their replicae in microfluidic sensor systems-labelfree quality assessment in food chemistry and medicine

Abstract: Sesame protein is one of the most potent food allergens making it an interesting topic for analytical chemistry and sensor approaches. Within this paper, we compare different strategies to obtain sensitive layers for this purpose: immobilizing natural anti-sesame IgY on the gold electrodes of a quartz crystal microbalance (QCM) leads to appreciable sensor responses with selectivity factors of about four towards brazil nut protein, which shows cross reactions in sesame allergy patients. Molecularly imprinted polymers (MIP) generated directly from sesame protein yield the same selectivity, but sensitivity is increased by a factor of three as compared to the natural antibodies. Synthesizing antisesame IgY MIP nanoparticles and utilizing these as templates in a surface imprinting procedure yields cavities exposing “copies” of the initial immunoglobulin molecules on their surfaces. On QCM, these materials again show the same selectivity as the natural one, but sensitivity is increased by a factor of ten. Therefore, the templating process does not only yield rugged, robust materials but also gives way to substantially increased sensor responses due to the higher surface density of selective recognition sites on the respective sensor surface.

Hydrogen Sensing with a Single Palladium Nanowire

Abstract: We describe the properties of single nanocrystalline palladium (Pd) nanowires for the resistancebased detection of hydrogen gas (H2). These Pd nanowires were prepared on glass surfaces using the Lithographically Patterned Nanowire Electrodeposition (LPNE) method. Pd nanowires had a mean grain size of 15 (±3) nm and a height and width in the range from 11 to 48 nm and 36–93 nm, respectively. Sensors consisting of a single Pd nanowire and an evaporated gold electrical contact demonstrated a limit-of-detection for H2 of 2 ppm and withstood repeated exposures to 10% H2 without fracturing. Response and recovery times for nanowires were directly correlated with their lateral dimensions. The reproducibility of the resistance response to H2 and the stability of the resistance baseline were both excellent.

Directly Grown Nanocrystalline Diamond Field-Effect Transistor Microstructures

Abstract: Nanocrystalline diamond microscopic structures (5 m width) are grown directly on Si/SiO2 substrates by patterning of a nucleation layer using photolithography prior to the diamond growth. The diamond in a thickness of 300 nm is grown by a microwave chemical vapor deposition on the nucleation patterns. Morphology and material composition of the microstructures are characterized by scanning electron microscopy and atomic force microscopy. The diamond microstructures exhibit clear transistor characteristics in both solid-state and solution-gated field-effect transistor configurations. The conductivity is generated by a transfer doping of hydrogen-terminated diamond surface. Gating of the transistors is realized by a deposition of Al electrode or by an immersion into a pH buffer in contact with Ag/AgCl electrode. The solution-gated field-effect transistors are sensitive to pH.

Electrochemical Impedance Immunosensor for the Detection of C-Reactive Protein in Aqueous Solution

Abstract: A label-free electrochemical impedance immunosensor is reported by immobilizing protein antibody, αCRP-Ab, through a self assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) using a cross linker, Bis[sulfosuccinimidyl] suberate (BS3), on indium tin oxide (ITO) coated glass electrode. The immunosensor (αCRP-Ab/BS3/APTES/ITOglass) was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical techniques. The electrochemical performance of the immunosensor was studied by electrochemical impedance spectroscopy. The results showed an increasing electron-transfer resistance with the immobilization of CRP antibody (αCRP-Ab) on the modified ITO coated glass electrode surface and on their coupling with protein CRP antigen (αCRP-Ag) at the immunosensor surface in the presence of [Fe(CN)6]3−/4− as redox probe. The immunosensor exhibits an electrochemical impedance response to antigen, αCRP-Ab, concentrations in a linear range from 8.5 ng to 9.12 μg mL−1 a with a lowest detection limit of 3.5 ng mL−1 antigen.