Variable-Temperature Time-Resolved Emission Spectra Studies of Random Pyrene Urethane Methacrylate Copolymers with High Pyrene Incorporation

Total Emission Time Resolved Decay: a Method for Measurement and Resolution of Broad-Band Emission

This article reports a time-resolved fluorescence data acquisition technique termed as "Total Emission Time Resolved Decay" (TETRD). TETRD is recorded by using zero-order diffraction of emission grating in TCSPC instrument. TETRD decay curve has entire wavelength dependent decay information buried in it. Cut-off filters are used to avoid scattering contamination. Two existing approaches are used for analysing the interconnected TETRD data. (i) First, global analysis: for discretely decaying multiple components, TETRD dataset is analyzed using global analysis. The normalized pre-exponentials (α_i) and relative amplitudes (f_i) recovered from global analysis reflect the individual component emission more faithfully and resembles with steady-state spectral data as well. (ii) Second, stretched exponential fitting (StrEF): for continuous lifetime distribution systems, StrEF (I(t) = I₀ exp[-(t/τ)^1/h]) has been used to analyse TETRD data. The average lifetime (τ) of StrEF matches well with the average lifetime of multi-exponential fitting, the heterogeneity factor (h) of StrEF is an additional parameter, which informs about local heterogeneity in the system. It is shown that the lifetimes obtained with TETRD matches well with the lifetimes obtained using conventional time resolved emission spectra (TRES). TETRD holds advantage in rapid data acquisition and facilitates inclusion of another variable (like concentration, solvent composition, pH, excitation wavelength etc.) into experimental design. Further, with the use of an appropriate data analysis tool, the multi-component decay profiles can be resolved conveniently.

Amphiphilic dendrons with a pyrene functional group at the focal point: synthesis, self-assembly and generation-dependent DNA condensation

Dendritic amphiphiles with a dual-functional pyrene as a fluorescent probe and hydrophobe at the focal point exhibited generation-dependent self-assembly and DNA condensation.

Towards a new FRET system via combination of pyrene and perylene bisimide: synthesis, self-assembly and fluorescence behavior

A new fluorescent derivative of cholesterol, N,N'-(N-(2-(3β-cholest-5-en-3yl-formamido)ethyl) pyrene-1-sulfonamido)ethyl perylene-3,4:9,10-tetracarboxylic acid bisimide (CPPBI), was designed and synthesized. In the design, pyrene (Py) and perylene bisimide (PBI) were specially chosen as the energy donor and the acceptor, respectively. Fluorescence studies revealed that (1) CPPBI shows a strong tendency to form supra-molecular assemblies, (2) the assemblies possess a high efficiency of fluorescence resonance energy transfer (FRET) via intermolecular interactions, and (3) the profile and position of its fluorescence emission are highly dependent upon the nature of its medium, but the medium shows little effect on the efficiency of the energy transfer, suggesting that the chromophores including both Py and PBI units enjoy some rotational and/or translational mobility in the aggregated state of the compound. Temperature- and concentration-dependent (1)H NMR spectroscopy studies revealed that both hydrogen-bonding and π-π stacking play a great role in stabilizing the assemblies of the compound, and confirmed the existence of π-π stacking between the Py moieties and between the PBI residues of the compound, of which the donor and the acceptor may have arranged in an appropriate orientation and at a suitable distance which are the key factors to determine the FRET efficiency. Moreover, the CPPBI-based film possesses unusual photochemical stability, and its emission is sensitive to the presence of some organic vapors, in particular aniline.