Red/NIR/SWIR multi-band persistent luminescent nanoparticles as ultrasensitive multi-channel tracers in water and crude oil/water emulsions

We report the use of CaTiO₃:Pr³⁺ multiband persistent luminescent nanoparticles, which can simultaneously emit red (610 nm), near-infrared (893 nm), and short-wave infrared (1040 nm) photoluminescence and persistent luminescence, as the tracer nanoagents for water tracer sensing. By using a spectrofluorometer, an Si charge-coupled device (CCD) camera and an InGaAs array camera as the detection tools, we evaluated the sensing capabilities of the three emission bands of CaTiO₃:Pr³⁺ nanoparticles in brine water solutions and crude oil/brine water emulsions in both photoluminescence mode and persistent luminescence mode. Among these different detection combinations, the persistent luminescence-based Si CCD camera imaging exhibits the best sensing performance with the detection limits being at a single-digit ppb level for the 610 and 893 nm bands and about 100–200 ppb for the 1040 nm band in both water solutions and crude oil/water emulsions, while the photoluminescence-based Si CCD camera imaging has a much higher detection limit of ~ 10 ppm in water solutions and of ~ 200 ppm in oil/water emulsions. The persistent luminescence-based InGaAs array camera imaging to the 1040 nm band has the worst performance with the detection limits higher than 200 ppm for both solutions. The sensing performances of the spectrofluorometer to photoluminescence signals and persistent luminescence signals in the two solutions are about the same, with the detection limits being around 100–200 ppm.