Upconverting nanoparticles as tracers for production and well monitoring

A method of monitoring well production, the method comprising:

• introducing an upconverting nanoparticle into a wellbore penetrating a subterranean formation, the upconverting nanoparticle having a host material, a dopant, and a surface modification comprising modified oleic acid functional groups, such that the upconverting nanoparticle is soluble or dispersible in (i) water, (ii) a hydrocarbon oil, or (iii) a combination thereof;
• producing an emulsion from the subterranean formation;
• contacting the upconverting nanoparticle with the produced emulsion in the wellbore;
• exposing the upconverting nanoparticle to an excitation radiation from an electromagnetic radiation source;
• measuring an optical property of the upconverting nanoparticle in the produced emulsion, and
• identifying a zone that produces the emulsion or monitoring an amount of water or oil in the produced emulsion,
• wherein the host material of the upconverting nanoparticle comprises NaYF4, NaGdF4, LiYF4, YF3, CaF2, Gd2O3, LaF3, Y2O3, ZrO2, Y2O2S, La2O2S, Y2BaZnO5, or Gd2BaZnO5;
• and
• the dopant comprises about 5 mol % to about 30 mol % of Yb3+ and about 1 mol % to about 3 mol % of one or more of the following:
• Tm3+, Ho3+, or Er3+, each based on the total mole of the upconverting nanoparticle.