Multiband MgAl_0.05Ge_0.95O₃:0.3%Pr³⁺ Persistent Phosphor as Efficient Tracers in Crude Oil Emulsions

The use of fluorescent nanoparticles (NPs) for tracing purposes in oilfields encounters challenges due to background interferences under constant external excitation caused by organic residues present in crude oil. This results in insufficient sensitivity and lower tracer detection limits in the crude oil/water emulsions. In this study, we present the synthesis of persistent luminescent NPs, showcasing their remarkable application as tracers in crude oil. The multiband MgAl_0.05Ge_0.95O₃:0.3%Pr³⁺ persistent NPs were synthesized via the sol-gel method. Through meticulous experimentation and analysis, our study unveils a novel avenue for efficient and lasting traceability in crude oil. The synthesized NPs emit light across the visible, near-infrared, and shortwave infrared regions, allowing for versatile detection. The unique luminescent properties of these NPs, particularly their ability to persist in emitting light without a continuous external excitation, enable their effective use as tracers in crude oil/water emulsions where background fluorescence typically poses a significant challenge. By employing these persistent NPs in background fluorescence-free conditions, we achieve ultrahigh sensitivity in detecting these NPs in crude oil. Our research reveals that the doping of Al³⁺ ions significantly enhances both the afterglow intensity of MgGeO₃:0.3%Pr³⁺ phosphor and the afterglow decay time of Pr³⁺ emission. This characteristic enables the re-excitation of MgAl_0.05G_0.95O:0.3%Pr³⁺ NPs within the emulsion, allowing for repeated spectral and imaging acquisition. This high sensitivity not only facilitates precise imaging of NPs in crude oil but also enables long-term monitoring in real-time, offering valuable insights for oilfield operations.