Ormosil, optical

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. 

Hie dye-doped ORMOSIL materials exhibit much higher photostability than the reported polymer-doped materials. For example, optical gain was reported for several coumarin dyes in PMMA (13), It is significant to note that the best dyes reported could only be used to several hundred pulses and that most of the coumarin dyes could not even oscillate for 100 pulses. The ORMOSIL gels thus represent an improvement of at least 1-2 orders of magnitude in photostability. Optical gain was also reported for R6G doped into modified poly(methyl methacrylate) (14L These materials exhibited loss of 20% output after 180 pump pulses (1 J/cm ) at 532 nm. The reported plots indicate that these materials would have dropped by 90% after 275-300 pulses due to rapid steady state photodegradation once the pulse count exceeded the critical pulse number. In this case the R6G doped ORMOSIL gel laser offers a useful lifetime improvement by a factor of more than 15 over the reported polymer material. 

It is known that the advantages of imprinted ormosils (organically modified silanes) over acrylic-based MIPs are their chemical stability, the high thermal stability of sol-gel materials, synthesis in mild temperature conditions, optical transparency, photo-, electro- and chemical stability, all properties that made these materials ideal for use in optical sensing approaches, particularly in aqueous samples.48 50 Although... 

In this chapter, recent progress in several key areas is reviewed. These areas are catagorized by material classification rather than by end-use application (1) bulk silica optics (2) optically active doped silica glasses (3) gel-polymer composites (4) organically modified silicates (ormosils) and (5) gradient-index glasses. These represent the five most significant developments in the area of bulk optical materials by the sol-gel process to date. 

Ormosils can possess excellent transparency when processing conditions are optimized. Moreover, they are typically nonporous. Their properties, as well as their low-temperature processing, make them ideal candidates as optical host media for a wide range of optically active species. These include laser dyes [51,53,55], photochromic molecules [52], second-harmonic-generating dielectric oxides [54], semiconductor quantum dots [53], and metallic quantum dots... 

Already, lasing, second-harmonic generation, and photochromism have been successfully demonstrated in ormosils. This new class of material has a bright future in bulk optical applications. 

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