From 1945 to 2002, the use of nutrients and fertilizers for agriculture has increased 20-fold in the US alone1. Nitrate and phosphate based nutrients in groundwater are associated with serious health problems and eutrophication. Detection of these ions is a prominent field of research2. Zhang et al. reported fluorescence detection of nitrite ion in water3. Probes with fluorescent detection in the IR range were examined, including the nanoparticles described by Reineck4 IR range was selected cause it provided lower background signal from scatter when propagating through tissues compared to visible wavelength. Gold nanoshells were purchased from Nanocomposix, Egyptian blue solution was prepared by dispersing 2.5 g Egyptian blue (Kremer Pigment) in 40 mL of HPLC water. Photosystem1 (PS1) solution (75nmol/L) was prepared in water. The original extraction of PS1 from spinach was described in Ciesielski et al.5 A silica:gold core:shell nanoparticle solution with a concentratio of 0.05 mg/mL was prepared in HPLC water. Sodium nitrate and sodium phosphate with different concentrations were added to the reporter solution. Fluorescent emission was measured using Horiba Fluorolog3 spectrometer. As shown, in figure 1, Egyptian blue has a fluorescent peak at 900 nm at excitation wavelength of 532 nm. PS1 has a strong peak at 700 nm and a small peak at 1360 nm at excitation wavelength of 532 nm. Silica:gold nanoparticles showed less intense peaks; one at 900 nm and other one at 1800 nm at excitation wavelength of 789 nm. As can be seen in figure 2 the fluorescent peak at 900 nm decreased as the concentration of sodium nitrate increased. As shown in figure 2, the fluorescent peak at 680nm decreased in the presence of sodium phosphate.

IR fluorescent probe for water-based agricultural nutrients

255th National Meeting (2018)

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