Abstract
Organic-molecule fluorophores with emission wavelengths in the second near-infrared window (NIR-II, 1000–1700 nm) have attracted substantial attention in the life sciences and in biomedical applications because of their excellent resolution and sensitivity. However, adequate theoretical levels to provide efficient and accurate estimations of the optical and electronic properties of organic NIR-II fluorophores are lacking. The standard approach for these calculations has been time-dependent density functional theory (TDDFT). However, the size and large excitonic energies of these compounds pose challenges with respect to computational cost and time. In this study, we used the GW approximation combined with the Bethe-Salpeter equation (GW-BSE) implemented in many-body perturbation theory approaches based on density functional theory. This method was used to perform calculations of the excited states of two NIR molecular fluorophores (BTC980 and BTC1070), going beyond TDDFT. In this study, the optical absorption spectra and frontier molecular orbitals of these compounds were compared using TDDFT and GW-BSE calculations. The GW-BSE estimates showed excellent agreement with previously reported experimental results.
Highlights
Fluorescence imaging in the second near-infrared window (NIR-II, 1000–1700 nm) has shown strong potential in biological tissues compared with fluorescence imaging in the ultraviolet (UV), visible (400–700 nm), and first near-infrared window (NIR-I, 700–1000 nm) regions because of reduced scattering of photons and self-luminescence [8,9,10,11,12,13,14]
We looked fordesigned, the state-of-the-art computational stand and predict their measured photophysical and electronic properties that result from a chain to accurately excited states for cyanine NIR fluorophores systems, constituting extending their2 conjugated chains and adjusting their terminal groups
The GGA/GW approximation combined with the Bethe-Salpeter equation (GW-Bethe-Salpeter equation (BSE)) showed a high vertical absorption wavelength gap value compared to the experimental longest absorption wavelength with 13 nm
Summary
Organic fluorescent dyes have received intense attention because of their high fluorescence quantum efficiency, easy synthesis, and adjustable luminescence spectrum [1,2,3,4,5,6,7].Recently, fluorescence imaging in the second near-infrared window (NIR-II, 1000–1700 nm) has shown strong potential in biological tissues compared with fluorescence imaging in the ultraviolet (UV), visible (400–700 nm), and first near-infrared window (NIR-I, 700–1000 nm) regions because of reduced scattering of photons and self-luminescence [8,9,10,11,12,13,14]. Organic fluorescent dyes have received intense attention because of their high fluorescence quantum efficiency, easy synthesis, and adjustable luminescence spectrum [1,2,3,4,5,6,7]. NIR-II fluorophores are mainly based on two architectures that extend the absorption emission wavelength range: donor-acceptor-donor (DAD) fluorophores and polymethine cyanines [15,16]. The wavelength of cyanine fluorophores can be tuned by installing terminal benzothiopyrylium heterocycles at different positions of the electron diethylamino particles. The benzothiopyrylium pentamethine cyanines (BTCs) overcome the phenomenon of solvatochromism in polar solvents, which is the key to obtaining various anti-quenching dyes with high brightness and superior photostability in aqueous solution.
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