Time-temperature nanosensors for subsurface applications

A method of monitoring temperature in a reservoir, the method comprising:

• introducing a temperature monitoring composition into the reservoir, the temperature monitoring composition comprising a carrier fluid and at least one shape-changing nanoparticle,
• wherein the at least one shape-changing nanoparticle is configured to change shape upon exposure to elevated temperature for a period of time, and
• wherein the at least one shape-changing nanoparticle is selected from the group consisting of a silver nanoparticle, a gold nanoparticle, a platinum nanoparticle, and a palladium nanoparticle;
• after a predetermined period, producing a produced fluid from the reservoir;
• collecting samples of the produced fluid;
• measuring an optical property of the shape-changing nanoparticle;
• and
• based on the measured property of the shape-changing nanoparticle, determining a temperature of at least a portion of the reservoir.