Molecular rotor dynamics influenced by the elastic modulus of polyethylene nanocomposites

Abstract

We observed that the excited-state twisting motion of 3,3′-diethyloxacarbocyanine in polymer nanocomposites (PNCs) depends strongly on the elastic modulus of medium. PNCs consist of low density polyethylene dispersed with surface-functionalized nanodiamonds with various alkyl groups. The mechanical properties of the PNCs were measured by a nanoindentation method, and the photoisomerization processes of the cyanine dye doped in the composites were investigated by time-resolved fluorescence spectroscopy. It was found that the molecular rotor dynamics in rigid media should be quantitatively describable by the elastic modulus of polymer.

Kinetics of Bacterial Fluorescence Staining with 3,3′-Diethylthiacyanine

“…The molecular structure of THIA elucidates the sensitivity of its fluorescence quantum yield to the viscosity of the environment. For cyanine dyes and other molecular rotors with extended π conjugation, the viscosity of the surrounding microenvironment modulates the kinetics of non-radiative decay, which is reflected by changes in the fluorescence quantum yields. − …”

“…An increase in the media viscosity slows down such molecular motions that allow for exploration of the conformational space. As a corollary of the increase in the media viscosity, a decrease in the likelihood of conformational changes leading to non-radiative deactivation results in an increase in the fluorescence quantum yield of the cyanine dye. − …”

Conformational Control of Ultrafast Molecular Rotor Property: Tuning Viscosity Sensing Efficiency by Twist Angle Variation

“…Viscosity is an important parameter which governs solution-phase reaction rate of virtually all chemical and biological reactions. − Due to the heterogeneous nature of complex chemical and biological systems, the diffusion-controlled bimolecular reactions are mainly governed by the viscosity at microscopic and nanoscopic length scale. − Design and development of an efficient viscosity sensor based on a fluoroscent molecular rotor is key to map the viscosity of the nanoscopic compartments of chemical and biological environments. − …”

“…Excellent sensitivity along with the ease of fluorescence measurement technique has made UMR-based sensing modality an attractive tool for microrigidity mapping of chemical and biological systems. In recent years, molecular-rotor-based fluorescence sensors and imaging agents gained widespread interest toward viscosity mapping of chemical systems such as sol–gel transition or elastic modulus of polymer nanocomposites. , Prof. Theodorakis and co-workers have developed several molecular rotors based on DCVJ and explored microscopic fluidity of several complex chemical and biological materials. − Employing fluorescence lifetime imaging microscopic (FLIM) technique, Prof. Kuimova and co-workers have extensively used BODIPY and porphyrin-based molecular rotors to map the viscosity of different compartments of cell, aerosol surface, lipids, and so on. − Local viscosity measurements of heterogeneous chemical systems have been explored using different molecular rotors. − Cationic molecular rotors such as thioflavin-T and auramine-O are being extensively used as excellent viscosity reporters, not only for biomolecules but also for complex chemical fluids. − The excellent fluorescence sensitivity of the molecular rotor is due to occurrence of ultrafast nonradiative-torsion-induced emission quenching in nonviscous medium and different degree of inhibition of the nonradiative process depending on surrounding viscosity. To develop an efficient viscosity sensor, it is necessary to underpin the influencing factors which govern torsional speed of a molecular rotor.…”

“…In recent years, molecular-rotor-based fluorescence sensors and imaging agents gained widespread interest toward viscosity mapping of chemical systems such as sol−gel transition or elastic modulus of polymer nanocomposites. 33,34 Prof. Theodorakis and co-workers have developed several molecular rotors based on DCVJ and explored microscopic fluidity of several complex chemical and biological materials. 16−22 Employing fluorescence lifetime imaging microscopic (FLIM) technique, Prof. Kuimova and co-workers have extensively used BODIPY and porphyrin-based molecular rotors to map the viscosity of different compartments of cell, aerosol surface, lipids, and so on.…”