Optochemical sensors for the detection of low pressure vapors based on porous semiconductors and emissive organics
A chemical sensor for detecting organic or inorganic target vapors and comprising a silicon member having a silicon surface with semiconductor pores therein, at least one luminescent sensory material entrapped in the semiconductor pores. The luminescent spectral material is exposed to the target vapors, wherein an excitation of the at least one luminescent sensory material results in a luminescent spectral response due to emission interference. The change in the luminescent spectral response is measured during this exposure.
1. A method of detecting a target vapor employing at least one luminescent sensory material entrapped in semiconductor porous structure, comprising the steps of: excitation said at least one luminescent sensory material resulting in a narrow luminescent peak;
wherein the narrow luminescent peak is the result of sufficient or deep infiltration of sensory material inside the porous structure so that the sensory material fills at least 20% of the depth of the porous structure; wherein the bandwidth of the luminescent peak is in the range of 0.5-25 nm; exposing the luminescent sensory material to the target vapor; and measuring the change of the luminescent peak during such exposure.
2. The method of claim 1 wherein the step of measuring the luminescent peak includes measuring the change of the luminescent intensity at least at two different wavelengths from the luminescent peak.
3. The method of claim 2 wherein said luminescent peak is caused by the emission of the sensory material only.
4. The method of claim 1 wherein the luminescent peak is selected from one of Fabry-Perot fringes of a porous monolayer or the resonance peak of microcavity fabricated by multiple layers of alternating low and high porosity, wherein the first layer has porosity lower than 48% and the second layer has porosity higher than 55% to provide a sufficient or deep infiltration of sensory material inside porous microcavity.
5. The method of claim 1 wherein the step of measuring relies on, not only a spectral shift of the luminescent peak, but also from a simultaneous change of the luminescence intensity as a result of the binding of target molecules to luminescent sensory material entrapped inside the semiconductor pores.
6. The method of claim 1 wherein the step of measuring includes the real-time monitoring of the emission intensity upon the analyte exposure at different wavelengths selected from the luminescent peak.
7. The method of claim 1 wherein the intensity of the luminescence is concurrently monitored on a real-time basis as time traces during the vapor exposure at least at two different wavelengths of the luminescent peak.
8. The method of claim 7 including monitoring the time traces of the luminescent intensity as relates to at least one factor affecting luminescent peak including the spectral shift due to a change of the refractive index upon vapor exposure.
9. The method of claim 7 including monitoring the time traces of the luminescent intensity as relates to at least one factor affecting luminescent peak including luminescence quenching or enhancing due to specificity (selective binding) of target vapors to luminescent sensory material.
10. The method of claim 1 wherein the luminescent peak is caused by the emission of the sensory material only, due to multiple light reflection and interference inside the semiconductor pores.
11. The method of claim 1 wherein the luminescent peak is caused by Fabry-Perot fringes of porous monolayer or narrow peak of microcavity fabricated by multiple layers of alternating porosity.
12. The method of claim 11 wherein the luminescent peak is the result of a significant narrowing of the broad luminescence bandwidth of the luminescent sensory material entrapped deep in the semiconductor pores of microcavity.
13. The method of claim 1 , wherein said luminescent sensory material entrapped in the semiconductor pores is selected from emissive sensory polymers; emissive sensory molecules or quantum dots; organic emissive molecules or quantum dots blended with non-emissive sensory polymer.
14. The method of claim 1 , wherein said semiconductor pores have size in the range of 2-500 nm and made in semiconductor bulk material to provide the light interference for reflected and emissive light.
15. The method of claim 1 , wherein porous microcavity or porous monolayer are situated on a top of the bulk semiconductor material and from which they are fabricated.
16. The method of claim 1 , wherein porous microcavity or porous monolayer are prepared as a free standing membrane.
17. The method of claim 14 , wherein the porous semiconductor is selected from the group consisting of Group II/VI semiconductors, Group III/V semiconductors and Group IV semiconductors.
18. The method of claim 17 , wherein the semiconductor is selected from the group consisting of Cds, CdSe, InP, GaAs, Ge, Si and doped Si.
19. The method of claim 1 which provides an enhanced selectivity over the sensor comprising the same luminescent sensory material deposited onto a flat substrate (and do not possessing the narrow luminescent peak) because of multiple intensity monitoring at different detecting wavelengths.