Restriction of Molecular Twisting on a Gold Nanoparticle Surface

Abstract

To understand the photophysical properties of intramolecular charge transfer (ICT) and twisted intramolecular charge transfer (TICT) states on a gold nanoparticle (Au NP) surface, we have designed and synthesized a new coumarin molecule (C3) that exists both as ICT and TICT states in its excited state in a polar environment. On a Au NP surface, an excited C3 molecule only exists as an ICT state owing to restricted molecular rotation of a diethylamino group; as a result, no conversion from the ICT to TICT state was observed. Selection of the preferential state of a molecule with dual emitting states can be helpful for selected biological applications.

An Insight of Molecular Twisting of Coumarin Dyes

“…Experimental results suggest energy transfer from C343 to Au NP takes place KGaA. [64] because of good spectral overlap. In C343/Au NP system the energy transfer process can be attribute to nonradiative energy transfer (NERT) where C343 is energy donor and Au NP is energy acceptor.…”

“…Solvatochromic study of newly synthesized C1, C2 and C3 molecules were also conducted by using optical absorption and emission measurement. [63,64] The optical absorption and emission spectra related photophysical data of C1, C2 and C3 molecules in different solvent are summarized in Table 1. While absorption features are quite similar to those of C343 and D1421, the emission features differ, especially for the TICT dyes ( Figure 3).…”

“…The emission decay trace of C2 in water at ICT position can be fitted multi-exponentially with time constants τ 1 = 0.05 ns (80.8%), τ 2 = 0.22 ns (16.5%) and τ 3 = 3.15 ns (2.7%) with τ av = 0.16 ns KGaA. [63,64] while in TICT position the fitted time constants are τ 1 = 0.05 ns (87.6%), τ 2 = 0.18 ns (11.4%) and τ 3 = 2.24 ns (1%) with τ av = 0.09 ns. The fitted time constants show majority of the emission (> 80%) decays in pulse width limited timescale in water which is mainly due to non-radiative decay.…”

“…[74] absorption and emission spectroscopy. [64,76] Citrate capped Au NP was synthesized following modified Turkevich method. [77][78][79] Figure 9A compares the optical absorption spectra of Au NP, C343 and the composite of C343/Au.…”

A colorimetric and fluorogenic probe for bisulfite using benzopyrylium as the recognition unit

“…Compound 3 was synthesized according to the reported protocol . 1 H NMR (400 MHz, DMSO‐d 6 ) δ (ppm): 10.26 (d, J = 6.8 Hz, 1H), 8.36 (s, 1H), 7.66 (d, J = 6.8 Hz, 1H), 7.39 (d, J = 9.2 Hz, 1H), 6.64 (d, J = 8.4 Hz, 1H), 6.47 (s, 1H), 3.46 (q, J = 6.8 Hz, 4H), 1.24 (t, J = 6.8 Hz, 6H).…”