Modulation of charge transfer by N-alkylation to control photoluminescence energy and quantum yield

Abstract

A versatile N-alkylation strategy controls the presence of charge-transfer excited states and the emission colour of N-heterocyclic chromophores.

From phosphorescence to delayed fluorescence in one step: tuning photophysical properties by quaternisation of an sp2-hybridised nitrogen atom

“…The triflate salt was the main focus of our investigation as the absorption and photoluminescence profiles for the salts with different counter-ions were very similar. As expected from our previous work 4 there was a significant red shift in the absorption spectra in going from the Q1 and Q2 compounds to their respective The absorption spectra for Q1 and Q2 in most solvents demonstrate two strong bands corresponding to p-p* transitions with several additional smaller peaks (Fig. 1 and Fig.…”

“…[5][6][7][8] Initially TADF was observed in Eosin-Y (hence also being known as E-type delayed fluorescence), 9 a material that, similar to quinine, has a protonation site. Protonation and quaternisation have been shown 4,10 to have a significant impact on the behaviour of the charge-transfer (CT) states-states that are crucial to TADF. Quaternisation, therefore, provides an attractive means to explore the control and modification of delayed fluorescence in quinine and similar compounds such as quinoline.…”

Secondary through-space interactions facilitated single-molecule white-light emission from clusteroluminogens

“…It is noteworthy that TSCT state with the (n,π*) feature may quench the emission of some fluorogens in the solution state due to spatially weak electron overlap and low oscillator strength 52 , 53 . Since the TSCT effect was not reflected in the absorption spectra of the three compounds (Fig.…”

Optical Detection of Acetone Using “Turn-Off” Fluorescent Rice Straw Based Cellulose Carbon Dots Imprinted onto Paper Dipstick for Diabetes Monitoring

“…The form and size of NCDs were examined using TEM (JEOL1230; Japan). At an excitation of 365 nm, eq 1 was employed to determine the QY of NCDs in an aqueous solution of H 2 SO 4 (0.1 M) using quinine sulfate as a standard reference (QY of 54%) 87 where r is the standard sample, η is the refractive index of solvent, A is the absorbance intensity, and I is the emission intensity.…”