Chemical sensor with an indicator dye

A chemical sensor for sensing a chemical in a variable humidity atmosphere comprising:

• an optical transmissive element comprising:
• an indicator dye having an optical attenuation characteristic responsive to the presence of said chemical;
• wherein said indicator dye comprises a triphenylmethane dye;
• a hygroscopic polymer permeable by said chemical for supporting said indicator dye within said hygroscopic polymer;
• said hygroscopic polymer comprising polyimide;
• and
• nanoparticles within said medium for enhancing the response of said indicator dye to said chemical;
• an optical source coupled to said optical transmissive element, said optical source providing light at a wavelength associated with said optical attenuation characteristic of said indicator dye;
• and
• an optical detector coupled to said optical transmissive element to receive said light transmitted through said optical transmissive element, said optical detector producing a signal responsive to said light transmitted through said optical transmissive element.

A method for preparing a sensing element for sensing a chemical, comprising the steps of:

• preparing a metal-solvent colloid comprising an organic solvent having metal nanoparticles suspended therein;
• combining said metal-solvent colloid with a solution containing a hygroscopic polymer and an indicator dye to yield a composite mixture, said indicator dye having an optical attenuation responsive to said chemical, said metal nanopartices adapted to enhance the response to said chemical of said optical attenuation;
• evaporating said solvent from said composite mixture to yield a polymer nanocolloid sensing element;
• wherein the polymer is a polyimide, and the indicator dye is a pH indicator dye;
• and
• wherein the pH indicator dye is a triphenylmethane dye.