Permeable nanoparticle reflector

Abstract

An optically-responsive multilayer reflective article is formed by applying a dilute solution or suspension of metallic nanoparticles to an optically-responsive detection layer. The solution or suspension is allowed to dry to form a semicontinuous liquid- or vapor-permeable light-reflective layer that will permit a liquid or vapor analyte to pass through the light-reflective layer to cause an optically-responsive change in the detection layer in the presence of the analyte.

1 . A method for forming an optically-responsive multilayer reflective article, which method comprises applying a dilute solution or suspension of metallic nanoparticles to an optically-responsive detection layer and allowing the solution or suspension to dry to form a semicontinuous liquid- or vapor-permeable light-reflective layer that will permit a liquid or vapor analyte to pass through the light-reflective layer to cause an optically-responsive change in the detection layer in the presence of the analyte. 
     
     
         2 . A method according to  claim 1  wherein the dilute solution or suspension has a solids level less than 30%. 
     
     
         3 . A method according to  claim 1  wherein the dilute solution or suspension has a solids level less than 10%. 
     
     
         4 . A method according to  claim 1  wherein the dilute solution or suspension has a solids level less than 5%. 
     
     
         5 . A method according to  claim 1  wherein the nanoparticles comprise silver or an alloy containing silver. 
     
     
         6 . A method according to  claim 1  wherein the nanoparticles comprise nickel, gold, platinum, palladium or an alloy containing any of the foregoing. 
     
     
         7 . A method according to  claim 1  wherein the nanoparticles have an average particle diameter of about 3 to about 50 nm. 
     
     
         8 . A method according to  claim 1  wherein the light-reflective layer has a thickness less than about 200 nm. 
     
     
         9 . A method according to  claim 1  wherein the light-reflective layer has a thickness less than about 100 nm. 
     
     
         10 . A method according to  claim 1  wherein the light-reflective layer is discontinuous. 
     
     
         11 . A method according to  claim 1  wherein the light-reflective layer is semicontinuous. 
     
     
         12 . A method according to  claim 1  wherein the light-reflective layer has a reflectance of at least about 20% at 500 nm. 
     
     
         13 . A method according to  claim 1  wherein the light-reflective layer has a reflectance of at least about 50% at 500 nm. 
     
     
         14 . A method according to  claim 1  further comprising sintering the light-reflective layer. 
     
     
         15 . A method according to  claim 1  wherein the detection layer is porous. 
     
     
         16 . A method according to  claim 15  wherein the detection layer comprises porous silica. 
     
     
         17 . A method according to  claim 1  further comprising forming the detection layer by plasma-activated chemical vapor deposition. 
     
     
         18 . A method according to  claim 1  wherein the detection layer comprises a polymer of intrinsic microporosity. 
     
     
         19 . A method according to  claim 18  wherein the detection layer comprises a polymer of bis-catechol and a fluorinated arene. 
     
     
         20 . A method according to  claim 1  wherein the detection layer exhibits a change in optical thickness in the presence of an analyte. 
     
     
         21 . A method according to  claim 1  wherein the detection layer exhibits a change in light phase shift, polarization, birefringence or transmission in the presence of an analyte.