Synthesis and Application of Time-Gated Fluorescent Tags for Tracing Downhole Fluids and Mineral Samples

Abstract

We have developed a nanoparticle (NP) composed of a polystyrene-vinyl benzoic acid copolymer via one-pot emulsion polymerization. This NP anchors a Eu³⁺ complex with a 1,10-phenanthroline antenna ligand (PS-VBA-Eu-Phen). With only 15 mol % of the Eu³⁺ ion relative to styrene, this low-cost and readily scalable NP exhibits the characteristic luminescence of ligand-to-metal charge transfer from the Eu³⁺ complex. We determined the lifetime and the intrinsic quantum yield of the strongest ⁵D₀ → ⁷F₂ luminescence for the Eu³⁺ complex inside the NPs. The long lifetime of the luminescence ensures clear detection of the PS-VBA-Eu-Phen NPs in complex oil-based mud (OBM) and on mineral samples (cuttings) recovered from the OBM using time-gated emission measurement. This method effectively reduces the background emission from minerals or additives in the mud and promises potential applications of the NP as a tracer or tag for tracking downhole fluids and cuttings.