Sensors

101 KiB

Open AccessArticle

by C. Baratto, G. Faglia, G. Sberveglieri, Z. Gaburro, L. Pancheri, C. Oton and L. Pavesi

Sensors 2002, 2(3), 121-126; https://doi.org/10.3390/s20300121 - 11 Apr 2002

Cited by 82 | Viewed by 10418

We investigated the possibility of using several sensing parameters from porous silicon in order to improve gas selectivity. By fabricating porous silicon optical microcavities, three independent quantities can be measured, i.e. the electrical conductance, the photoluminescence intensity, and the wavelength of the optical resonance. We monitored the change of these three parameters as a function of NO₂ (0.5-5 ppm), ethanol (300-15000 ppm) and relative humidity (0-100%). Preliminary results confirm that the examined species affect the parameters in a different way, both as a relative change and as dynamic. Full article

(This article belongs to the Special Issue Nano-Porous Sensor Material)

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3894 KiB

Open AccessArticle

Nanoporous Platforms for Cellular Sensing and Delivery

by Lara Leoni, Darlene Attiah and Tejal A. Desai

Sensors 2002, 2(3), 111-120; https://doi.org/10.3390/s20300111 - 20 Mar 2002

Cited by 22 | Viewed by 7748

Abstract

In recent years, rapid advancements have been made in the biomedical applications of micro and nanotechnology. While the focus of such technology has primarily been on in vitro analytical and diagnostic tools, more recently, in vivo therapeutic and sensing applications have gained attention. This paper describes the creation of monodisperse nanoporous, biocompatible, silicon membranes as a platform for the delivery of cells. Studies described herein focus on the interaction of silicon based substrates with cells of interest in terms of viability, proliferation, and functionality. Such microfabricated nanoporous membranes can be used both in vitro for cell-based assays and in vivo for immunoisolation and drug delivery applications. Full article

(This article belongs to the Special Issue Nano-Porous Sensor Material)

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2264 KiB

Open AccessArticle

Room Temperature Ammonia and Humidity Sensing Using Highly Ordered Nanoporous Alumina Films

by Elizabeth C. Dickey, Oomman K. Varghese, Keat G. Ong, Dawei Gong, Maggie Paulose and Craig A. Grimes

Sensors 2002, 2(3), 91-110; https://doi.org/10.3390/s20300091 - 18 Mar 2002

Cited by 130 | Viewed by 12339

Abstract

The effect of pore size and uniformity on the response of nanoporous alumina, formed on aluminum thick films through an anodization process, to ammonia and humidity at room temperature is reported. Pore sizes examined range from 13 nm to 48 nm, with pore size standard deviations ranging from 2.6 nm to 7.8 nm. The response of the material to ammonia and humidity is a strong function of pore size and operating frequency. At 5 kHz an alumina sensor with an average pore size of 13.6 nm, standard deviation 2.6 nm, exhibits a factor of two change in impedance magnitude as it is cycled between an ammonia and argon environment. At 5 kHz the same sensor exhibits a well-behaved change in impedance magnitude of 10³ over 20% to 90% relative humidity. Cole-Cole plots of the 5 Hz to 13 MHz measured impedance spectra, modeled using equivalent circuits, are used to resolve the effects of adsorption and ion migration. Full article

(This article belongs to the Special Issue Nano-Porous Sensor Material)

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201 KiB

Open AccessArticle

Mass Transfer in Amperometric Biosensors Based on Nanocomposite Thin Films of Redox Polymers and Oxidoreductases

by Michael V. Pishko, Alexander Revzin and Aleksandr L. Simonian

Sensors 2002, 2(3), 79-90; https://doi.org/10.3390/s20300079 - 12 Mar 2002

Cited by 23 | Viewed by 9830

Abstract

Mass transfer in nanocomposite hydrogel thin films consisting of alternating layers of an organometallic redox polymer (RP) and oxidoreductase enzymes was investigated. Multilayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monolayer of 11-mercaptoundecanoic acid, followed by the electrostatic binding of a cationic redox polymer, poly[vinylpyridine Os(bis-bipyridine)2Clco-allylamine], and an anionic oxidoreductase. Surface plasmon resonance spectroscopy, Fourier transform infrared external reflection spectroscopy (FTIR-ERS), ellipsometry and electrochemistry were employed to characterize the assembly of these nanocomposite films. Simultaneous SPR/electrochemistry enabled real time observation of the assembly of sensing components, changes in film structure with electrode potential, and the immediate, in situ electrochemical verification of substrate-dependent current upon the addition of enzyme to the multilayer structure. SPR and FTIR-ERS studies also showed no desorption of polymer or enzyme from the nanocomposite structure when stored in aqueous environment occurred over the period of three weeks, suggesting that decreasing in substrate sensitivity were due to loss of enzymatic activity rather than loss of film compounds from the nanostructure. Full article

(This article belongs to the Special Issue Nano-Porous Sensor Material)

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1211 KiB

Open AccessArticle

The Preparation of ZnGa₂O₄ Nano Crystals by Spray Coprecipitation and Its Gas Sensitive Characteristics

by Zheng Jiao, Gang Ye, Feng Chen, Mingqiang Li and Jinhuai Liu

Sensors 2002, 2(3), 71-78; https://doi.org/10.3390/s20300071 - 12 Mar 2002

Cited by 41 | Viewed by 10222

Abstract

ZnGa₂O₄ nano crystals were prepared by an improved coprecipitation method, which we call ‘spray coprecipitation’. XRD results shows the resulting crystal size using the new method is under 10nm, whereas the powder prepared by ordinary coprecipitation is about 30nm. XRD results also shows ZnO peaks exists in ZnGa₂O₄ powder prepared by traditional coprecipitation, but disappears in ZnGa₂O₄ nano crystal prepared by spraying coprecipitation. SEM and TEM were used to analysis the structural characteristics of ZnGa₂O₄ nano crystals. The gas sensitive characteristics of ZnGa₂O₄ nano crystals are reported. Full article

(This article belongs to the Special Issue Nano-Porous Sensor Material)

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Sensors, Volume 2, Issue 3 (March 2002) – 5 articles , Pages 71-126

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