W. Wang, Z. Pan
Aramco Services Company,
Keywords: up-conversion luminescence, long-persistent luminescence, near infrared luminescence, nanoparticles, bio-imaging, crude oil sensing
Summary:In vivo fluorescence imaging suffers from suboptimal signal-to-noise ratio and shallow detection depth, which is caused by the strong tissue autofluorescence under constant external excitation and the scattering and absorption of short-wavelength light in tissues. Here we address these limitations by using two types of special optical imaging nanoprobes, photostimulable near-infrared (NIR) persistent luminescence nanoparticles (PLNPs) and NIR upconversion nanoparticles (UCNPs), which allow optical imaging to be performed in an autofluorescence-free manner. Our studies reveal promising potential of these nanoprobes in cell tracking and tumor targeting, exhibiting exceptional sensitivity and penetration that far exceed those afforded by conventional fluorescence imaging. Similarly, in oil industry, current fluorescent nanoparticles-based tracer sensing techniques for oilfield applications also suffer from insufficient sensitivity, which is mainly caused by the interference of the background fluorescence from the organic residues in crude oil-brine mixture under constant external excitation. The unique optical properties of PLNPs and UCNPs enable a background fluorescence-free measurement condition for ultrahigh-sensitivity crude oil sensing. By using novel near-infrared persistent luminescent nanoparticles as a tracer nanoagent, we achieved a tracer detection limit at the single-digit ppb level of nanoparticles concentration in high oil fraction oil-water mixtures via a convenient, CCD camera based imaging technique without any pretreatment or phase separation of the fluid samples. This detection limit is about four to five orders of magnitude lower than that obtained using conventional spectral methods. Our research demonstrated that the new luminescent nanoagents and imaging detection method have wide application from fundamental bio-imaging study to potential industrial practice in crude oil sensing.