Spectral and temporal luminescent properties of Eu(III) in humic substance solutions from different origins.

摘要: Abstract Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on origins. The information the difference in structure these complexes scarce. To participate filling this lack, study spectral and temporal evolution Eu(III) luminescence implied substance (HS) presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) (SRHA), Leonardite HA (LHA) from International Humic Substances Society (USA), Gorleben (GohyHA), Kleiner Kranichsee bog (KFA, KHA) Germany, purified commercial Aldrich (PAHA), were made contact with Eu(III). Eu(III)-HS time-resolved compared aqueous Eu3+ at pH 5. Using an excitation wavelength 394 nm, typical bi-exponential decay common all samples. components τ1 τ2 are same order magnitude samples, i.e., 40 ≤ τ1 (μs) ≤ 60, 145 ≤ τ2 (μs) ≤ 190, but significantly different. It shown that spectra obtained groups Terrestrial extract one hand, i.e. LHA/GohyHA, plus PAHA, purely aquatic extracts other SRFA/SRHA/KFA/KHA, induce inner coherent luminescent within each group. 5D0 → 7F2 transition exhibits most striking differences. A slight blue shift observed (λmax = 615.4 nm), samples share almost λmax ≈ 614.5 nm. main differences between reside shoulder around λ ≈ 612.5 nm, modelled by mixed Gaussian–Lorentzian band λ ≈ 612 nm. SRFA shows intense intensity ratio I612.5/I614.7 = 1.1, KFA/KHA/SRHA I612.5/I614.7 = 1.2–1.3, whilst LHA/GohyHA/PAHA group has I612.5/I614.5 = 1.5–1.6. This two complexes, despite comparable complexing properties, slightly symmetries awaited.