Sensor gold film

The sensor ch consists of a glass de on to which a SO-nm thick gold film has been deposited. The gold film is then covered with a linker-layer to which a matrix of carboxylated dextran is attached. The dextran, which extends typically 100 nm out fi om the sur6ce, provides a hydrophilic, activatable and flexible polymer to which biomolecules can be coupled throu amine, sulphydryl, carboxyl and other groups. 

L. Ping and P. K. Dasgupta, Determination of Total Mercury in Water and Urine by a Gold Film Sensor Following Fenton s Reagent Digestion, Anal. Chem. 1989,61, 1230. 

Very few immunosensors are commercially available. The commercial immunosensors are either the detector or bioanalyzer types. The PZ 106 immunosensor from Universal Sensors Inc. (New Orleans, LA) has been used as a detector to measure antibody-antigen reaction. Ohmicron (Newtown, PA) developed a series of pesticide immuno-bioanalyzers that have been used in field tests. Pharmacia Biosensor USA (Piscataway, NJ) recently introduced BIAcore immunodetection system. A combination of a unique flow injection device and surface plasmon resonance (SPR) detection technique provides a real time analysis. A carboxylmethyldextran layer added to plasmon generating gold film is a hydrophobic, activatable, and flexible polymer that provides high antibody and low non-specific bindings. System demonstration at the Institute of Food Technologists (IFT) 1994 meeting in Atlanta drew attention of food scientists. It should easily be adapted for food protein characterization. 

Two disparate translation methods are investigated for the measurement of sulfur dioxide. Both involve interaction with an aqueous solution. In the first, collected S(IV) is translated by the enzyme sulfite oxidase to which is then measured by an enzymatic fluorometric method. The method is susceptible to interference from i CWg) efforts to minimize this interference is discussed. The second method involves the translation of SO2 into elemental Hg by reaction with aqueous mercurous nitrate at an air/liquid interface held in the pores of hydrophobic membrane tubes. The liberated mercury is measured by a conductometric gold film sensor. Both methods exhibit detection limits of 100 pptv with response times under two minutes. Ambient air measurements for air parcels containing sub-ppbv levels of SO2 show good correlation between the two methods. 

Fig. 11. Schematic diagram of continuous flow apparatus and structure of an enzymatically coupled FET. (a) Schematic diagram of continuous flow apparams S, enzymatically coupled FET sensor SC, sensor cell WB, water bath D, drtdnage P, peristaltic pump TV, three-way joint EV, electrical valve VC, valve controller WS, washing solution AS, analyte solution, (b) Detailed structure of flow-through cell OR, rubber O-ring. (c) Structure of enzymatically coupled FET (electrical insulation with epoxy resin is not shown here for simplicity) ISFET, ion-sensitive FET EM, enzyme membrane G, thin gold film TC, card edge connector. (Reproduced from Shiono et al. (9), with permission.)...

Ping L, Dasgupta PK. 1989. Determination of total mercury in water and urine by a gold film sensor following Fenton s reagent digestion. Anal Chem 61(11) 1230-1235. 

The sensor shown in Figure 2 A was developed by stripping and cleaving F-MLD multimode fibers obtained from Newport Corporation with a 100 pm core and a 140 pm cladding diameter and then evaporating a very thin gold film (4-8 nm) on the fiber tips Electron-beam evaporation process was employed for carrying out the... 

Another technique used for the analysis of receptor-ligand interaction is surface plasmon resonance (SPR), with its first commercially available application in the BIAcore instruments [44] (Fig. 5.8). Like PCS, it allows the determination of kinetics by monitoring the association and dissociation of a receptor-ligand complex in real time. The interaction partners do not necessarily have to be labeled, which is an advantage of the technique. The principle of SPR measurements is based on an optical phenomenon. The core unit in this technique is a sensor chip consisting of a thin gold film with a modified surface attached on one side. One reactant is attached to the modified sensor surface, whereas the other reaction partner flows past this surface in solution. When the two interaction partners form a com-... 

Fig. 5.8 Schematic setup of the surface plasmon resonance (SPR) detection unit in a Bia-core instrument. One interaction partner is immobilized on a modified gold surface, whereas the other flows by in solution. On the other side of the sensor chip, a beam of polarized light is reflected by the gold film. The optical phenomenon SPR leads to a re-...

For thin-film metallization, a thin metallic film is first deposited onto the surface of the substrate. The deposition can be accomplished by thermal evaporation, electronic-beam- or plasma-assisted sputtering, or ion-beam coating techniques, all standard microelectronic processes. A silicon wafer is the most commonly used substrate for thin-film sensor fabrication. Other substrate materials such as glass, quartz, and alumina can also be used. The adhesion of the thin metallic film to the substrate can be enhanced by using a selected metallic film. For example, the formation of gold film on silicon can be enhanced by first depositing a thin layer of chromium onto the substrate. This procedure is also a common practice in microelectronic processing. However, as noted above, this thin chromium layer may unintentionally participate in the electrode reaction. 

The process for the thennal sensor network is as follows. Organic diodes, to be used as sheet-type thermal sensors, are manufactured on an ITO-coated PEN film. A 30-mn thick p-type semiconductor of copper phthalocyanine (CuPc) and a 50-nm thick n-type semiconductor of 3,4,9,10-perylene-tetracarboxylic-diimide (PTCDI) are deposited by vacuum sublimation. A 150-mn thick gold film is then deposited to form cathode electrodes having an area of 0.19 mm. The film with the organic diodes is coated with a 2-pm thick parylene layer and the electronic interconnections are made by the method similar to that mentioned before. The diode film is also mechanically processed to form net-shaped structures. Finally, to complete the thermal sensor network, we laminated the transistor and diode net films together with silver paste patterned by a microdispenser. This is shown in Figure 6.3.11. 

Fig. 5 Instrumental contribution to sensitivity S0r/Sn f as a fimction of wavelength for SPR sensors with angular modulation and prism coupler or grating coupler and three different grating periods. Prism-hased sensor configuration BK7 glass prism, gold film, and a non-dispersive dielectric (refractive index 1.32). Grating-based sensor configuration a non-dispersive dielectric (refractive index 1.32) and gold grating...

Fig. 14 The maximum bulk refractive index sensitivity as a function of wavelength for SPR sensors with intensity modulation and a prism coupler exciting a conventional sim-face plasmon (SP) at the interface of gold and a non-dispersive dielectric (refractive index 1.32) and coupled symmetric (SSP) and antisymmetric (ASP) surface plasmons on a thin gold film (thickness 20 nm) simroimded by two identical non-dispersive dielectrics (refractive index 1.32)...

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