Enhancement of luminescence signal by deuterated water – Practical implications

Deep Eutectic Solvent-Based Highly Sensitive Turn-On Fluorescent Probe for D2O

“…It is well established that the vibrational frequency of the O–H bond is more compared to the O–D bond owing to the decreased zero point vibrational energy (ZPVE), as a consequence of heavier mass of D . As was reported earlier, this decrease in vibrational frequency in O–D, in turn, reduces nonradiative energy losses in a fluorophore via vibrational relaxation and promotes fluorescence intensity. − …”

“…Deep eutectic solvents (DESs) are a class of solvents formed by mixing quaternary ammonium, phosphonium, or sulfonium salts with a hydrogen bond donor (HBD) in the eutectic molar ratio. − This further forms a low-melting liquid mixture whose melting point is even lower than that of the individual components, driven by strong hydrogen bonds that help to overcome the lattice energy of the pure components. − DESs offer a number of advantages, such as low volatility, broad liquid spectrum, low melting points, low/nonflammability, wide electrochemical window, and the ability to be tailored to specific use through judicious selection of ingredients. − Previously, our group has reported a novel, hydrophobic DES based on heptyltriphenylphosphonium bromide and decanoic acid, which exhibits excellent fluorescence (blue emission) endowed by distortion of phenyl ring pi-electron cloud driven by strong H-bonding between the HBD and hydrogen bond acceptor (HBA) upon excitation at 363 nm with a 23% quantum yield . We envisaged that such a fluorescent, H-bonded system containing a −COOH group may act as an ideal system for D 2 O sensing, since it is well established that the addition of D 2 O to a molecule containing functional groups with labile hydrogen, namely, −OH, −COOH, and −NH 2 , results in a rapid exchange of the labile proton with deuterium, leading to change in its fluorescence properties. − In fact, once exchanged, the low vibrational energy of the OD bond helps to reduce nonradiative energy losses due to vibrational relaxation, leading to increased radiative power for such luminescent systems with exchangeable labile protons. − This increase in the fluorescence yield of the DES in the presence of D 2 O was found to be useful for quantitative measurement of the D 2 O isotopic purity (IP), and the measurement was found to be at par with the established methods such as Fourier transformed infrared (FT-IR) spectroscopy.…”

Luminescence enhancement by deuterium

“…One especially valuable outcome of D 2 O augmented fluorescence was its use for dramatically improved resolution in fluorescence microscopy. [51][52][53][54] In one instance, for the microscopy dye Cy7, its fluorescence quantum yield using D 2 O was 2.6 times that of its fluorescence quantum yield in water. Also, the Cy7 fluorescence lifetime in D 2 O was 2.4 times that of its fluorescence lifetime in water.…”

“…Coincidently, a later section in this discussion is devoted to the role of deuterium in singlet oxygen chemiluminescence enhancement. One especially valuable outcome of D 2 O augmented fluorescence was its use for dramatically improved resolution in fluorescence microscopy 51–54 . In one instance, for the microscopy dye Cy7, its fluorescence quantum yield using D 2 O was 2.6 times that of its fluorescence quantum yield in water.…”

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

“…As the nonradiative transition of O–H is much larger than that of O–D, the presence of H 2 O will result in fluorescence quenching . Therefore, H 2 O can be distinguished from D 2 O by judging from the fluorescence intensity. − However, because the H–D exchange is time-dependent, the fluorescence intensity is unstable over time, thus misleading the detecting result for the exact content of D 2 O. By comparison, probe molecules based on the response mechanism of spectrographic wavelength shifting (in other words, the change of excited state energy levels) are seemed to be more reliable, as the intensity change that caused by the essential H–D exchange can be ignored.…”