Showing papers by "Nathan S. Lewis published in 1999"

Electronic techniques for analyte detection

Abstract: Techniques are used to detect and identify analytes. Techniques are used to fabricate and manufacture sensors to detect analytes. An analyte (1810) is sensed by sensors (1820) that output electrical signals in response to the analyte. The electrical signals are preprocessed (1830) by filtering and amplification. In an embodiment, this preprocessing includes adapting the sensor and electronics to the environment in which the analyte exists. The electrical signals are further processed (1840) to classify and identify the analyte, which may be by a neural network.

Trace level detection of analytes using artificial olfactometry

Abstract: The present invention provides a device (20) for detecting the presence of an analyte, including: a sample chamber (22) having a fluid inlet port (24) for the influx of the analyte; a fluid concentrator (23) in flow communication with the sample chamber (22) wherein the fluid concentrator (23) has an absorbent material capable of absorbing the analyte and capable of desorbing a concentrated analyte; and an array of sensors (26) in fluid communication with the concentrated analyte. Methods for detection of various medical conditions, including halitosis and periodontal disease are also disclosed.

Methods of use for sensor based fluid detection devices

Abstract: A sensor (Fig 1) for detecting an analyte in a fluid comprising a substrate having a first organic material and a second organic material (21) that has a response to an analyte. The sensor has information storage and processing equipment (Fig 14a), and a fluid delivery appliance. This device compares a response (Fig 13) from the detector with a stored ideal response to detect the presence of analyte. Methods for use for the above system are described where the first organic material and the second organic material are sensed and the analyte is detected. The method provides for a device, which delivers fluid to the sensor and measures the response of the sensor with the detector. Further, the response is compared to a stored ideal response for the analyte to determine the presence of the analyte. In different embodiments, the fluid measured may be a gas, a liquid, or a fluid extracted from a solid.

Stabilization of Si photoanodes in aqueous electrolytes through surface alkylation

Abstract: A two-step chlorination/alkylation technique used to introduce alkyl groups, —C n H 2n+1 (n=1-6), functionally onto single-crystal, ( 111 )-oriented, n-type Si surfaces. H-terminated Si photoanodes were unstable under illumination in contact with an aqueous 0.35 M K 4 Fe(CN) 6 -0.05 MK 3 Fe(CN) 6 electrolyte. Such electrodes displayed low open-circuit voltages and exhibited a pronounced time-dependent deterioration in their current density vs potential characteristics due to anodic oxidation. In contrast, Si surfaces functionalized with —CH 3 and —C 2 H 5 groups displayed significant improvements in stability while displaying excellent electrochemical properties when used as photoelectrodes in the aqueous Fe(CN) 6 3−/4− electrolyte.

Colloidal particles used in sensing arrays

Abstract: Chemical sensors for detecting analytes in fluids comprising a plurality of alternating nonconductive regions (comprising a nonconductive material) and conductive regions (comprising a conductive material). In preferred embodiments, the conducting region comprises a nanoparticle. Variability in chemical sensitivity from sensor to sensor is provided by qualitatively or quantitatively varying the composition of the conductive and/or nonconductive regions. An electronic nose for detecting an analyte in a fluid may be constructed by using such arrays in conjunction with an electrical measuring device electrically connected to the conductive elements of each sensor.

Method and system for determining analyte activity

Abstract: Chemical sensors for detecting the activity of a molecule or analyte of interest is provided. The chemical sensors comprise an array or plurality of chemically-sensitive resistors that are capable of interacting with the molecule of interest, wherein the interaction provides a resistance fingerprint. The fingerprint can be associated with a library of similar molecules of interest to determine the molecule's activity.

Method of resolving analytes in a fluid

Abstract: A statistical metric, based on the magnitude and standard deviations along linear projections of clustered array response data, is utilized to facilitate an evaluation of the performance of detector arrays in various vapor classification tasks. This approach allows quantification of the ability of arrays of different types including carbon black-insulating polymer composite chemiresistor sensors, tin oxide sensors and bulk conducting organic polymer sensors to distinguish between analytes. The evaluation of questions such as the optimal number of detectors required for a specific task, whether improved performance is obtained by increasing the number of detectors in a detector array, and how to assess statistically the diversity of a collection of detectors in order to understand more fully which properties are underrepresented in a particular set of array elements, are addressed.

Effects of Molecular Geometry on the STM Image Contrast of Methyl- and Bromo-Substituted Alkanes and Alkanols on Graphite

Abstract: Scanning tunneling microscopy (STM) images have been collected for a series of substituted alkanes and alkanols that form ordered overlayers at room temperature on highly ordered pyrolytic graphite surfaces. Molecules that have been imaged possess an internal bromide, with or without terminal alcohol groups (HO(CH2)9CHBr(CH2)10OH and H3C(CH2)16CHBr(CH2)16CH3), an internal −OH group (H3C(CH2)16CHOH(CH2)16CH3), and an internal methyl group (H3C(CH2)16CHCH3(CH2)16CH3). These data allow comparison to the STM image contrast reported previously for molecules in which −OH, −Br, and −CH3 groups were located in terminal positions of alkane chains adsorbed onto graphite surfaces. When the functional groups were in gauche positions relative to the alkyl chain, and thus produced molecular features that protruded toward the tip, the functional groups were observed to produce bright regions in a constant current STM image, regardless of the STM contrast behavior observed for these same functional groups when they were ...

Conductive organic sensors, arrays and methods of use

Abstract: The present invention provides a class of sensors prepared from regions of conducting organic materials and conducting materials that show an increased sensitivity detection limit for amines. The present class of sensors have applications in the detection of spoiled food products and in testing for diseases, such as cholera and lung cancer, which have amines as biomarkers.

Method for validating that the detection ability of a sensor array mimics a human nose detection ability

Abstract: The present invention relates to methods for matching and validating the response intensity of a sensor array to an odorant with the detection threshold of a human nose.

Tunneling mechanism implications from an stm study of h3c(ch2)15hc=c=ch(ch2)15ch3 on graphite and c14h29oh on mos2

Abstract: The observations reported herein confirm that the bright spots in high-resolution STM images of adsorbed alkanes and alkanols are predominantly due to the electronic and topographic structure of th...

Techniques and system for analyte detection

Abstract: Techniques are used to detect and identify analytes. Techniques are used to fabricate and manufacture sensors to detect analytes. An analyte ( 810 ) is sensed by sensors ( 820 ) that output electrical signals in response to the analyte. The electrical signals may be preprocessed ( 830 ) by filtering and amplification. In one embodiment, a plurality of sensors are formed on a single integrated circuit. The sensors may have diverse compositions.

Simulations of the Steady-State Current Density vs Potential Characteristics of Semiconducting Electrodes

Abstract: A series of digital simulations has been performed to obtain insight into the steady-state current density vs potential behavior of semiconductor/liquid interfaces. The ToSCA program, incorporating all of the key kinetic parameters involved with the generation, transport, and recombination of charge carriers both in the semiconductor and across the semiconductor/liquid interface, has been used for this purpose. The simulations confirmed conclusions obtained previously from a simplified analytical model, which state that for ideal behavior of a nondegenerately doped semiconducting electrode the photovoltage of an n-type semiconductor/liquid interface should not change if the concentration of the reduced form of the redox species, A-, is held constant but the concentration of the oxidized form of the redox species, A, is varied. The simplified analytical model also predicts that the photovoltage will be independent of variation in [A-] if [A] is held constant. In contrast, recent work has asserted that idea...

Polymer/plasticizer based sensors

Abstract: This invention relates to a novel class of vapor sensors with tunable properties. More particularly, this invention relates to vapor sensors modified by the addition of a compatible small molecule of low volatility, i.e., a plasticizer. In certain aspects, the invention relates to a sensor for detecting an analyte in a fluid comprising: an organic polymer; a plasticizer combined with the organic polymer; and detector operatively associated with the organic polymer.

Reactions of Etched, Single Crystal (111)B-Oriented InP To Produce Functionalized Surfaces with Low Electrical Defect Densities

Abstract: Synthetic routes have been developed that allow attachment of a variety of functional groups to etched, single-crystal InP surfaces. Benzyl halides, alkyl halides, silyl halides, and esters reacted readily with InP to yield covalently attached overlayers on the semiconductor surface. High-resolution X-ray photoelectron spectroscopy (XPS) revealed that the functionalization chemistry was consistent with the reactivity of surficial hydroxyl groups. Analysis of the XP spectra of the (111)B-oriented (P-rich) face in ultrahigh vacuum revealed signals ascribable to a monolayer of oxidized P atoms on the etched (111)B InP surface. The lack of reactivity of the (111)A-oriented (In-rich) face with these same functionalization reagents is therefore attributed to the difference in the nucleophilicity and acidity of the In and P oxides that are present on the (111)A and (111)B faces, respectively. The coverage of benzylic groups obtained through functionalization of (111)B-oriented InP with benzyl halides was estimat...

Vapor sensing with arrays of carbon black-polymer composites

Abstract: Thin films of carbon black-organic polymer composites have been deposited across two metallic leads, with swelling- induced resistance changes of the films signaling the presence of vapors. To identify and classify vapors, arrays of such vapor-sensing elements have been constructed, with each element containing a different organic polymer as the insulating phase. The differing gas-solid partition coefficients for the various polymers of the sensor array produce a pattern of resistance changes that can be used to classify vapors and vapor mixtures. This type of sensor array has been shown to resolve all organic vapors that have been analyzed, and can even resolve H2O from D2O. Blends of poly(vinyl acetate) and poly(methyl methacrylate) have been used to produce a series of sensor that response to vapors with a change in resistance of a magnitude that is not simply a linear combination of the responses of the pure polymers. These compatible blend composite detectors provided additional analyte discrimination information relative to a reference detector array that only contained composites formed using the pure polymer phases. Vapor signatures from chemicals used in land mine explosives, including TNT, DNT, and DNB, have been detected in air in short sampling time and discriminated from each other using these sensor arrays.

Sensor arrays for resolution of enantiomers

Abstract: The present invention relates to an array of sensors useful for constructing 'electronic noses' for analyzing chiral analytes and producing a sample output. The array comprises compositionally different sensors, wherein a sensor comprises a chiral region. The analyte generates a differential electrical response across the sensor thereby being detected.

Simultaneous determination of equilibrium and kinetic properties

Abstract: Method of using a sensor array for simultaneously determining a partition coefficient and a diffusion coefficient of analytes. At least two sensors comprising the same polymer composition, but with differing predetermined polymer thicknesses, are used to measure the time lag difference between the sensors. This measurement is used to determine both equilibrium or steady state parameters as well as kinetic or diffusion coefficient information. The steady-state data can be used for analyte determination, whereas the kinetic data can be used for sensor array optimization and design.

Mimicking the sense of olfaction: A conducting-polymer-based electronic nose

Abstract: — We describe herein the construction of a simple, low-power, broadly responsive vapor sensor. Carbon-black-organic-polymer composites have been shown to swell reversibly upon exposure to vapors. Thin films of carbon-black-organic-polymer composites have been deposited across two metallic leads, with swelling-induced resistance changes of the films signaling the presence of vapors. To identify and classify vapors, arrays of such vapor-sensing elements have been constructed, with each element containing a different organic polymer as the insulating phase. The differing gas-solid partition coefficients for the various polymers of the sensor array produce a pattern of resistance changes that can be used to classify vapors and vapor mixtures. This type of sensor array has been shown to resolve all organic vapors that have been analyzed, and can even resolve H2O from D2O.

Determination simultaneees proprietes cinetiques et d'equilibre

Abstract: L'invention concerne un procede d'utilisation d'une mosaique de capteurs de facon a determiner simultanement un coefficient de distribution et un coefficient de diffusion d'analytes. Afin de mesurer la difference de decalage temporel entre au moins deux capteurs, on utilise des capteurs comportant la meme composition polymere mais d'epaisseur differente. On utilise cette mesure pour determiner aussi bien les parametres d'equilibre, ou parametres d'etat stationnaire, que les donnees relatives au coefficient de diffusion ou au coefficient cinetique. Les donnees concernant l'etat stationnaire sont utilisees pour la determination d'analytes, alors que les donnees cinetiques sont utilisees pour l'optimisation et la conception de la mosaique de capteurs.

Sensing and Discrimination of Vapors by an Array of Conducting Carbon Black‐Polymer Composites

Abstract: We describe herein the construction of a simple, low-power, broadly responsive vapor sensor. Carbon black-organic polymer composites have been shown to swell reversibly upon exposure to vapors. Thin films of carbon black-organic polymer composites have been deposited across two metallic leads, with swelling-induced resistance changes of the films signaling the presence of vapors. To identify and classify vapors, arrays of such vapor-sensing elements have been constructed, with each element containing a different organic polymer as the insulating phase. The differing gas-solid partition coefficients for the various polymers of the sensor array produce a pattern of resistance changes that can be used to classify vapors and vapor mixtures. This type of sensor array has been shown to resolve all organic vapors that have been analyzed, and can even resolve H2O from D2O.

Procede et systeme pour detecter l'activite d'un analyte

Abstract: L'invention concerne des capteurs chimiques permettant de detecter l'activite d'une molecule ou d'un analyte recherche. Ces capteurs chimiques comprennent un groupement de plusieurs resistances chimiquement sensibles capables d'interagir avec la molecule recherchee, cette interaction produisant une empreinte de resistance. Cette empreinte peut etre associee a une banque de molecules recherchees analogues, permettant ainsi de determiner l'activite de cette molecule.