Optical sensor for hydrogen bonding gaseous molecules

1. An optical system for obtaining a quantity of hydrogen bonding gaseous molecules, the optical system comprising

an optically transparent matrix comprising a molecule containing a hydroxyazobenzene group embedded in the matrix;

an isomerizing light source;

at least one light detector for measuring absorbance changes from the optically transparent matrix; and

measurement control electronics configured to control the isomerizing light source, the at least one light detector, and optionally a second light source, wherein the measurement control electronics are configured to

control the isomerizing light source to illuminate the optically transparent matrix with isomerizing light capable of inducing trans-cis isomerization in the hydroxyazobenzene group,

control the at least one light detector to measure absorbance changes from the optically transparent matrix at a single or multiple wavelength(s) to obtain a thermal cis-trans isomerization time constant, and

obtain the quantity of the hydrogen bonding gaseous molecules by using a dependency of the thermal cis-trans isomerization time constant on the quantity of the hydrogen bonding gaseous molecules.

2. The optical system of claim 1 , wherein the molecule containing a hydroxyazobenzene group comprises the hydroxyazobenzene of Formula (I):

wherein all R 1 -R′ 6 and R′ 2 -R′ 5 are selected from —H, —OH, —(CH 2 ) x CH 3 , —O(CH 2 ) x CH 3 , —NO 2 , —CN, —F, —CF 3 and —NH 2 , wherein the hydroxyazobenzene of Formula (I) includes at least one —OH group.

3. The optical system of claim 1 , wherein the molecule containing a hydroxyazobenzene group is 4-hydroxyazobenzene.

4. The optical system of claim 1 , wherein the molecule containing a hydroxyazobenzene group is 4-octyl-4′-hydroxyazobenzene.

5. The optical system of claim 1 , wherein the molecule containing a hydroxyazobenzene group is 4-ethyl-4′-hydroxyazobenzene.

6. The optical system of claim 1 , wherein the matrix comprises organic polymer.

7. The optical system of claim 1 , wherein the matrix comprises poly(4-vinyl pyridine).

8. The optical system of claim 1 , wherein the hydroxyazobenzene group is hydrogen bonded to the matrix.

9. The optical system of claims 1 , wherein the hydroxyazobenzene group is part of a larger molecule or a polymer.

10. The optical system of claim 1 , wherein the optically transparent matrix further comprises a second molecule containing a hydroxyazobenzene group embedded in the matrix.

11. The optical system of claim 1 , wherein the optically transparent matrix further comprises a second isomerizing molecule or a thermochromic molecule embedded in the matrix.

12. The optical system of claim 11 , wherein the optical system is arranged to measure temperature.

13. The optical system of claim 1 , wherein the at least one light detector comprises one or more light intensity detector(s).

14. The optical system of claim 1 , comprising a second light source as a measurement light.

15. The optical system of claim 1 , wherein the isomerizing light source or the second light source is selected from a light-emitting diode and a laser.

16. The optical system of claim 15 , wherein the isomerizing light source or the second light source provides light at a wavelength in the ultra violet range.

17. The optical system of claim 1 , wherein the measurement control electronics are configured to obtain the quantity of hydrogen bonding gaseous molecules by using the dependency of the thermal cis-trans isomerization time constant on the quantity of the hydrogen bonding gas molecules based on one or more calibration curve(s).

18. The optical system of claim 1 , comprising one or more optical fibers.

19. The optical system of claim 1 , wherein the hydrogen bonding gaseous molecules are selected from at least one of the following: water, methanol, ethanol, and acetic acid.

20. The optical system of claim 1 , wherein the optical system is arranged to measure humidity.

21. A method for measuring the quantity of hydrogen bonding gaseous molecules, the method comprising

providing an optically transparent matrix comprising a molecule containing a hydroxyazobenzene group embedded in the matrix or the optical system of claim 1 ;

illuminating the optically transparent matrix with isomerizing light capable of inducing trans-cis isomerization in the hydroxyazobenzene group;

measuring absorbance changes from the optically transparent matrix at a single or multiple wavelength(s) to obtain a thermal cis-trans isomerization time constant; and

obtaining the quantity of the hydrogen bonding gaseous molecules by using a dependency of the thermal cis-trans isomerization time constant on the quantity of the hydrogen bonding gaseous molecules.

22. The method of claim 21 , wherein the molecule containing a hydroxyazobenzene group comprises the hydroxyazobenzene of Formula (I):

wherein all R 1 -R′ 6 and R′ 2 -R′ 5 are selected from —H, —OH, —(CH 2 ) x CH 3 , —O(CH 2 ) x CH 3 , —NO 2 , —CN, —F, —CF 3 and —NH 2 , wherein the hydroxyazobenzene of Formula (I) includes at least one —OH group.

23. The method of claim 21 , wherein the molecule containing a hydroxyazobenzene group is 4-hydroxyazobenzene.

24. The method of claim 21 , wherein the molecule containing a hydroxyazobenzene group is 4-octyl-4′-hydroxyazobenzene.

25. The method of claim 21 , wherein the molecule containing a hydroxyazobenzene group is 4-ethyl-4′-hydroxyazobenzene.

26. The method of claim 21 , wherein the matrix comprises organic polymer.

27. The method of claim 21 , wherein the matrix comprises poly(4-vinyl pyridine).

28. The method of claim 21 , wherein the hydroxyazobenzene group is hydrogen bonded to the matrix.

29. The method of claim 21 , wherein the hydroxyazobenzene group is part of a larger molecule or a polymer.

30. The method of claim 21 , wherein the optically transparent matrix further comprises a second molecule containing a hydroxyazobenzene group embedded in the matrix.

31. The method of claim 21 , wherein the optically transparent matrix further comprises a second isomerizing molecule or a thermochromic molecule embedded in the matrix.

32. The method of claim 31 , wherein the method is a method for measuring temperature.

33. The method of claim 21 , wherein the hydrogen bonding gaseous molecules are being adsorbed into the optically transparent matrix.

34. The method of claim 21 , wherein the hydrogen bonding gaseous molecules are selected from at least one of the following: water, methanol, ethanol, and acetic acid.

35. The method of claim 21 , wherein the method is a method for measuring humidity.