ORMOSILs sensors

Figure 6. Tip of the 20-pm tip of a fiber optic oxygen microsensor. The tip is coated with a ormosil-type of sol-gel doped with a ruthenium indicator for oxygen that display red luminescence. The sensor measures its decay time as a function of oxygen partial pressure.

An optical sensor for the measurement of carbon dioxide in modified atmosphere packaging (MAP) applications was developed89. It was based on the fluorescent pH indicator l-hydroxypyrene-3,6,8-trisulfonate (HPTS) immobilized in a hydrophobic organically modified (ormosil) matrix. The CO2 sensor was stable over a period of at least 7 months and its output was in excellent agreement with a standard reference method for carbon dioxide analysis. 

The formulation of the ORMOSIL precursor is chosen in the light of screening experiments (Figure 6.13). For the recognition of ovalbumin, for example, the precursor is a 55 mol% TEOS, 2 mol% 3-aminopro-pyltriethoxysilane (APTES), 3 mol% n-octyItrimethoxysi 1 ane (C8-TMOS) and 40 mol% bis(2-hydroxyethyl)aminopropyltriethoxysilane (HAPTS) mixture. The resulting microarray sensor exhibits analytical... 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

The confinement of a relatively large number of dye molecules in the small volume of a nanoparticle may trigger collective phenomena otherwise not observable in bulk solution. This has been demonstrated by Prasad and coworkers in the case of an ORMOSIL pH sensor.69 The PEBBLEs contain a naphthalenylvinylpyridine derivative (NVP) as pH-sensitive fluorescent dye which has been functionalized with a triethoxysilane anchor by reaction with an excess of (3-isocyanatopropyl)triethoxysi-lane (ICTES). The sol-gel polymerization in aqueous micellar solution of the NVP-ICTES derivative with VTES gives spherically shaped 33 nm silica nanoparticles in which the dye is covalently linked to the silica matrix and uniformly distributed in the nanoparticle volume. The NVP dye responds ratiometrically to protons, with a... 

Fig. 16.8 Typical intensity-based Stern-Volmer plots for the [Ru(dpp)3]2+-doped pin-printed class II ORMOSIL-based sensor elements...

Figure 5. Calibration curves for the analysis of Na and NHf ions using ion sensor made from bilayer of ferrocene-linked ormosil and dibenzo-18-crown-6 incorporated plasticized poly (vinyl chloride) matrix membrane.

Conclusion. The new ormosil derived from optimized two silane out of four differ t typed of aUcoxysilane precursors are repotted particularly for the ccmstuction of ncm-mediated glucose biosensor, a solid-state icm sensor and mediated biosensor and the new material are prennising for the construction of other senscxrs/bios scM. ... 

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