Optical sensors for vapors, liquids, and biological molecules based on porous silicon technology (original) (raw)
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Resonant cavity enhanced optical microsensor for molecular interactions based on porous silicon
physica status solidi (a), 2006
The molecular binding between the glutamine binding-protein (GlnBP) from Escherichia coli and Lglutamine (Gln) is detected by means of an optical biosensor based on porous silicon technology. The binding event is optically transduced in the wavelength shift of the porous silicon optical microcavity (PSMC) reflectivity spectrum. The hydrophobic interaction links the GlnBP, which acts as a molecular probe for Gln, to the hydrogenated porous silicon surface area. We can thus avoid any preliminary surface functionalization process. The protein infiltrated PSMC results stable to oxidation at least for few cycles of wet measurements. The penetration of the proteins into the pores of the porous silicon matrix has been optimized: a strong base post-etch process increases the pore size and removes any nanostructure on top and inside the porous silicon multilayer while does not degrade the optical response and the quality of the microcavity.
Smart Optical Sensors for Chemical Substances Based on Porous Silicon Technology
Applied Optics, 2004
A simple geometry optical sensor based on porous silicon technology is theoretically and experimentally studied. We expose some porous silicon optical microcavities with different porous structures to several substances of environmental interest: Very large red shifts in the single transmission peak in the reflectivity spectrum due to changes in the average refractive index are observed. The phenomenon can be ascribed to capillary condensation of vapor phases in the silicon pores. We numerically compute the peak shifts as a function of the liquid volume fraction condensed into the stack by using the Bruggeman theory. The results presented are promising for vapor and liquid detection and identification.
Porous Silicon Microcavities as Optical and Electrical Chemical Sensors
Physica Status Solidi (a), 2000
The optical and electrical properties of porous silicon microcavities are strongly dependent on the environment. For highly luminescent samples both the luminescence intensity and the peak position are affected by organic substances, which also strongly modify the electrical conductivity, giving the possibility to obtain a multi-parametric optical/electrical sensor. The peak position depends on the refractive index of the organic compound, whereas the luminescence intensity depends on its low frequency dielectric constant. Electrical properties depend on the dipole moment of the molecules. This allows discriminating between different organic substances.
Photonics, Devices, and Systems II, 2003
Photoluminescence quenching response of as prepared and surface modified porous silicon sensors in presence of organic analytes in gas phase was studied. Surface modification aimed at increasing of operational stability and modification of sensoric response was performed by a hydrosilylation reaction with various organic compoundsmethy l lO-undecenoate, haemin, cinchonine and quinine. These sensors were tested for a homological set of aliphatic alcoho ls from methanol to hexanol. We have systematically measured changes in porous silicon photoluminescence inte nsity as a function of concentration of detected analytes and evaluated sensitivity, detection limit and linear dynamic range of our sensors. Speed of the sensoric response was of the order of seconds. The obtained sensoric parameters were correlated with chemical and physical properties of both the compounds used for derivatization and the detected analytes.
Determination of sensoric parameters of porous silicon in sensing of organic vapors
Materials Science and Engineering: C, 2002
Ž. Ž. Photoluminescence PL properties of as-prepared and surface derivatized porous silicon PS in the presence of organic compounds in gas phase were studied. Surface derivatization, aimed at increasing stability of porous silicon properties, was performed by Lewis acid mediated hydrosilylation with methyl 10-undecenoate. We have systematically measured changes in photoluminescence intensity for a set of alcohols from C to C. From the variation of the photoluminescence quenching response as a function of alcohol concentration, we 1 6 determine the sensitivities and detection limits of our porous silicon sensors and these correlate with physical and chemical properties of studied species. For methyl 10-undecenoate derivatized PS samples, we have observed a remarkable enhancement of the selectivity for
Porous silicon-based optical biosensors and biochips
Physica E: Low-dimensional Systems and Nanostructures, 2007
Porous silicon multilayered microstructures have unique optical and morphological properties that can be exploited in chemical and biological sensing. The large specific surface of nanostructured porous silicon can be chemically modified to link different molecular probes (DNA strands, enzymes, proteins and so on), which recognize the target analytes, in order to enhance the selectivity and specificity of the sensor device. We designed fabricated and characterized several photonic porous silicon-based structures, which were used in sensing some specific molecular interactions. The next step is the integration of the porous silicon-based optical transducer in biochip devices: at this aim, we have tested an innovative anodic bonding process between porous silicon and glass, and its compatibility with the biological probes. r
Porous Silicon Based Sensor for Organic Vapors
Acta Physica Polonica A, 2015
Porous silicon (PS) has been an attractive material for enhancing optical properties of silicon. Its large surface area for sensor applications and compatibility with silicon-based technologies has been a driving force for further technology development. In this study, ability of PS to sense at room temperature organic vapors such as acetone, trichloroethylene and hexane, which are harmful to human health, has been investigated. Electrical (DC) and photo-luminescence (PL) measurements in a controlled atmosphere (nitrogen gas and an organic vapor mix) were performed to test the sensor response towards the organic vapors. It was found that PS surface is very sensitive against these vapors. The experimental results also suggested that PS can be used as a new electro-optical material to sense harmful vapors.
Rationally designed porous silicon as platform for optical biosensors
Thin Solid Films, 2012
Optical porous silicon multilayer structures are able to work as sensitive chemical sensors or biosensors based in their optical response. An algorithm to simulate the optical response of these multilayers was developed, considering the optical properties of the individual layers. The algorithm allows designing and customizing the porous silicon structures according to a given application. The results obtained by the simulation were experimentally verified; for this purpose different photonic structures were prepared, such as Bragg reflectors and microcavities. Some of these structures have been derivatized by the introduction of aminosilane groups on the porous silicon surface. The algorithm also permits to simulate the effects produced by a non uniform derivatization of the multilayer.
Transmittance correlation of porous silicon multilayers used as a chemical sensor platform
Sensors and Actuators B: Chemical, 2015
This work presents a system of two optical microcavities made of mesoporous silicon that have been analyzed as a platform for either chemical sensing or biosensing. When a porous microcavity is exposed to an analyte, the effective refractive index of its layers change, and its optical transmittance shifts towards lower wavenumbers. We constructed a device that employs two identical porous silicon microcavities, one of them is allowed to be in contact with the analyte, whereas the other remains unexposed. The transmitted intensity of the system results in the integrated product of the transmittances of both multilayers, which can be approximated to the autocorrelation function of the transmittance of the microcavity. Its value depends on the analyte concentration, so it can be used for sensing purposes. This results in a sensor that requires neither a wavelength-sensitive detector nor a monochromatic source of illumination, and is robust to changes in temperature, because it only depends on the relative changes in the microcavities. The sensor's response can be optimized by modifying the angular position of the second microcavity. A sensor based on this principle is demonstrated for isopropyl alcohol detection. The minimum concentration change that can be measured is about 30 ppm, which is equivalent to a minimum measurable change of refractive index of 5 x10-5 .
Porous silicon and polymer materials for optical chemical sensors
SPIE Newsroom, 2010
The optical characteristics of porous materials depend on their structural properties (porosity, pore size, and pore distribution). Specifically in materials with air-filled pores, the effective refractive index is a weighted average of the refractive indices of the relevant material and air, which is thus directly related to the material's porosity. Mesoporous materials, such as porous silicon and porous polymers, have therefore been exploited to create photonic devices, from simple interference filters to exotic photonic-bandgap (PBG) structures. 1, 2 In addition, the high internal surface area of porous materials provides an excellent host medium to immobilize analyte-specific recognition elements through sequestration. 3 Interactions of the analyte molecules with the sequestered recognition elements often alter the effective index or other optical properties. These optical variations can be employed as a simple and straightforward transduction approach in optical sensing.