Luminescent upconversion nanoparticles evaluating temperature-induced stress experienced by aquatic organisms owing to environmental variations

Abstract

Growing anthropogenic activities are significantly influencing the environment and especially aquatic ecosystems. Therefore, there is an increasing demand to develop techniques for monitoring and assessing freshwater habitat changes so that interventions can prevent irrevocable damage. We explore an approach for screening the temperature-induced stress experienced by aquatic organisms owing to environmental variations. Luminescent spectra of upconversion [Y2O3: Yb, Er] particles embedded within Caridina multidentata shrimps are measured, while ambient temperature gradient is inducing stress conditions. The inverse linear dependence of the logarithmic ratio of the luminescence intensity provides an effective means for temperature evaluation inside aquatic species in vivo. The measured luminescence shows high photostability on the background of the complete absence of biotissues' autofluorescence, as well as no obscuration of the luminescence signal from upconversion particles. Current approach of hybrid sensing has a great potential for monitoring variations in aquatic ecosystems driven by climate changes and pollution.

Keywords: Aquatic science; Environmental science; Physiology; Zoology.

Graphical abstract

Figure 1

Experimental protocol/measurements Schematic overview of the experimental protocol/measurements, utilizing standard laser diode as a light source (1) and portable spectrometer (2), equipped with the detecting optical fiber (3), dichroic mirror (4) and microscopy objective (5) to deliver light to/from the object of interest.

Figure 2

Luminescence spectrum of UCP and energy levels The luminescence spectra of UCP at 25°C with an excitation wavelength of 975 nm (A). Schematic representation of the energy levels and energy transfer in the [Y₂O₃: Yb³⁺, Er³⁺] crystal (B).

Figure 3

Luminescence spectra of water-suspended UCP and F-factor Luminescence spectra of water-suspended UCP in the red spectral range at different temperatures for an excitation wavelength of 975 nm (A). Temperature dependence of the F-factor for UCP suspended in pure water, with an excitation wavelength of 975 nm (B). The error bars are standard deviation values resulting from the averaging.

Figure 4

Images of CMS in vivo Images of CMS in vivo: before (A) and after (B) illumination with a 975 nm laser.

Figure 5

Luminescence spectra of the UPC inside CMS and F-factor (A) Typical luminescence spectra of the UPC inside CMS at 21°C (1, blue) and 45°C (2, green). Luminescence bands of the water-suspended UPC (3, red) at 22°C, and autofluorescence of the shrimp at 21 °C (4, black). (B) – Temperature dependence of the F-factor for UPC injected into CMS, with an excitation wavelength of 975 nm. The error bars are standard deviation values resulting from the averaging.