Improving Quantum Yield of a NIR‐II Dye by Phenylazo Group

Abstract

Understanding structure‐fluorescence correlation is very helpful for the design of fluorescent probes. In this paper, a donor‐acceptor‐donor (D‐A‐D) type NIR‐II fluorophore with benzobisthiadiazole as the acceptor and triphenyl amine as the donor, and its three derivatives bearing respectively amino, tert‐butyloxycarbonyl amino and phenylazo groups in donor moieties, are synthesized. Their electronic structures and optical properties are investigated via theoretical and experimental studies. It is found that all the three types of substituents significantly influence its fluorescent properties and the phenylazo groups dramatically enhance its quantum yield (QY). To achieve biological applications and maintain high QY in aqueous environments, the phenylazo‐containing fluorophore is encapsulated in polystyrene‐co‐poly(ethylene glycol) micelles. The obtained fluorescent micelles have a QY of ≈3.51% in 1000–1500 nm in aqueous medium that is among the highest of the organic NIR‐II probes reported so far for biological imaging. The high QY enables the in vivo imaging of the micelle‐administered mice to be conducted with high speed and quality. As an application example, ultrafast NIR‐II imaging of intravenously injected mice is performed and used to determine their cardiac cycle and heart rate. The micelles also significantly accumulate in tumors after tail‐vein injection and exhibit great application potentials in tumor detection.

Small Molecular NIR-II Fluorophores for Cancer Phototheranostics

“… 96 TPB-AZO PS-PEG / 690/909 1.562% (850–1,500 nm); 0.351% (1,000–1,500 nm) FLI / Determining cardiac cycle and heart rate; tumor detection Zhang et al. 97 SYL DSPE-mPEG 5k / 765/976 N.A. FLI/PAI PTT Tumor imaging and imaging-guided PTT Zhang et al.…”

Surgical Navigation for Malignancies Guided by Near‐Infrared‐II Fluorescence Imaging

“…[ 54 ] Also, dye optical properties can be tuned by designing variable donor and acceptor combinations. [ 55,56 ] However, many of these dyes, such as the first‐generation D‐A‐D NIR‐II hydrophobic dye, CH1055 (Figure 2), CHS2, [ 57 ] and SCH1100, [ 58 ] generally suffer with low QYs. To improve the QYs, Cheng et al.…”

Activatable NIR‐II Fluorescent Probes Applied in Biomedicine: Progress and Perspectives

“…With the continuous emergence of excellent NIR‐II AFPs, the application of NIR‐II biological imaging technology in biomedical field has made considerable progress. Here, certain significant researches that associated with NIR‐II bioimaging of NIR‐II AFPs are presented, including precise tissue bioimaging, [90–94] dynamic bioimaging for monitoring [95–98] and multiplexed bioimaging [99–102] …”

“…Wu et al. fabricated fluorescent micelles based on a NIR‐II fluorophore with the D‐A‐D structure, which utilized phenylazo‐triphenylamine and benzobisthiadiazole as the donor and acceptor, respectively [96] . By injecting the fluorescent micelle into veins of mice, the heart rate and cardiac cycle of mice were measured to achieve NIR‐II window bioimaging.…”