Optical sensors for downhole tools and related systems and methods

A method of determining a concentration of hydrogen sulfide in a fluid within a subterranean formation, the method comprising:

• locating a sensor comprising optically sensitive materials comprising at least one of chromophores, fluorophores, and nanoparticles dispersed within a permeable matrix material proximate at least one component of downhole equipment in a wellbore extending through one or more subterranean formations, the sensor operably coupled through at least one fiber optic cable to a radiation source configured to provide electromagnetic radiation to the sensor;
• contacting the sensor with a fluid within at least one of the downhole equipment or the wellbore;
• transmitting electromagnetic radiation from the radiation source through the sensor and to a detector operably coupled to the at least one fiber optic cable;
• and
• determining, with the detector, a change in an optical characteristic of at least one of the optically sensitive materials of the sensor responsive to contact of the sensor with the fluid.

A downhole optical sensor assembly, comprising:

• a sensor operably coupled to at least one component of downhole equipment, the sensor including optically sensitive materials comprising one of chromophores, fluorophores, metal nanoparticles, or metal oxide nanoparticles disposed within a permeable optically transparent matrix material;
• a radiation source coupled to the sensor through a fiber optic cable, the radiation source configured to generate electromagnetic radiation for transmission through at least one optical fiber of the fiber optic cable;
• and
• a detector coupled to the sensor through a fiber optic cable, the detector configured to measure at least one of an absorbance spectrum, an emission spectrum, a maximum absorption intensity, or a maximum emission intensity of electromagnetic radiation passing through the sensor.