Fluorescent Probes with Variable Intramolecular Charge Transfer: Constructing Closed-Circle Plots for Distinguishing D₂O from H₂O

Abstract

It is difficult to distinguish between H 2 O and D 2 O due to their very similar properties. Triphenylimidazole derivatives with carboxyl groups (TPI-COOH-2R) show intramolecular charge transfer that responds to polarities and pH of solvents. Here, a series of TPI-COOH-2R with very high photoluminescence quantum yields (73−98%) were synthesized to distinguish D 2 O from H 2 O by the method of wavelength-changeable fluorescence. In a mixed THF/water solution, the increase of H 2 O and D 2 O contents will separately induce different pendulum-type fluorescence variations and form plots of closed circles with the same starting and ending points from which a THF/water ratio that displays the most different emission wavelengths (up to 53 nm with an LOD of 0.064 vol %) can be determined to further distinguish D 2 O from H 2 O. This is proved to be originated from the various Lewis acidities between H 2 O and D 2 O. The results of theoretical calculations and experiments suggest that, for different substituent groups in TPI-COOH-2R, an appropriate electron-donating effect is beneficial to distinguish between H 2 O and D 2 O, while the electron-pulling effect is adverse. Moreover, because the potential hydrogen/deuterium exchange does not affect the as-responsive fluorescence, this method is reliable. And this work provides a new strategy for the design of fluorescent probes for D 2 O.

Dual-Color Visual Ratiometric Fluorescence Sensing for H2O and D2O Mixtures Using a Hexanuclear Ln(III) Cluster-Based Metal–Organic Framework

“…Similar to that at full-range variation ratios, the emission intensities at 618 and 546 nm intensified but with better dependency (Figure S14a,b). As can be seen in Figure e, the correlation between the I 546 / I 618 values and H 2 O fractions (0–10%) in D 2 O was fitted to obey y = 0.114 x + 1.84 with high relativity ( R 2 = 0.994); therefore, the LOD was determined to be 0.039% (v/v %), which was higher than that observed in most studies. ,,, Moreover, the fluorescence emission spectra of Eu 0.5 Tb 0.5 -TZB-MOF in H 2 O with low D 2 O fractions varying from 0 to 10% were obtained to determine the LOD value of D 2 O in H 2 O (Figure S15a,b), which was calculated to be 0.111% (Table S3). These fluorescence titration experiments demonstrate that Eu 0.5 Tb 0.5 -TZB-MOF can be used to detect both trace H 2 O in D 2 O and trace D 2 O in H 2 O quantitatively with high sensitivity.…”

“…Heavy water (D 2 O) is an important strategic material owing to its vital role as a neutron moderator in nuclear reactors and extensive application in chemical synthesis, analysis, and spectral characterization . However, the physical and chemical properties of D 2 O are extremely similar to those of H 2 O and are responsible for the high hygroscopicity that hampers its practical use .…”