Luminescent upconversion nanoparticles are used as alternate fluorescence tracers to overcome the interference of organic molecules in the analysis of flowback waters. Upconversion nanoparticles use low-energy excitation at approximately 980 nm with high-energy emissions in the region of 200 to 950 nm. Emission properties of the nanoparticles are tuned by selective doping, and their dispersiblity in water and oil are altered through appropriate functionalization. The flow experiments used stable crude oil emulsions in API brine with the mixture of two different emission upconversion tracer nanoparticles. Data from these experiments suggest that the nanoparticle tracers can flow through the porous media and distinguish between each other, even in the presence of organics in an emulsion. This capability can open new avenues in in-situ reservoir communication and understanding.