High Quantum Yield Water‐Dispersed Near‐Infrared In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots with Robust Stability for Bioimaging

• Published in: Advanced materials interfaces Vol. 7; no. 22
• Main Authors: Lim, Kang Rui Garrick, Darwan, Daryl, Wijaya, Hadhi, Lim, Zhi Chiaw, Shanmugam, Janaki, Wang, Tian, Lim, Li Jun, Ang, Wee Han, Tan, Zhi‐Kuang
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.11.2020
• Subjects: Aqueous solutions; Attenuation; core–shell quantum dots; Cytotoxicity; Dispersion; Emitters; fluorescence bioimaging; Fluorescent dyes; ligand‐exchange; Line spectra; Medical imaging; near‐infrared; Photoluminescence; Quantum dots; Robustness; Spectral emittance; Stability; Toxicity; water‐dispersible; Zinc sulfide
• ISSN: 2196-7350; 2196-7350
• DOI: 10.1002/admi.202000920

Fluorescent dyes with a high photoluminescence quantum yield (PLQY) and photostability are favored in bioimaging as they offer better imaging signals at lower dye loading, circumventing issues of cytotoxicity and biological pathway interference. Quantum dots (QDs) are efficient emitters with narrow spectral line‐widths, but often employ toxic heavy‐metals, and show significantly diminished PLQY and poor stability after phase‐transfer into aqueous media. Here, the preparation of nontoxic, water‐dispersed giant‐shell In(Zn)As–In(Zn)P–GaP–ZnS QDs that emit in the near‐infrared (NIR) at 828 nm is demonstrated. The QDs exhibit a remarkable PLQY of 75% when initially synthesized in a hydrophobic medium, and retains a high PLQY of 60% after ligand‐exchange and phase‐transfer into water. The water‐dispersed QDs show robust photostability with negligible photoluminescence (PL) attenuation after 3 h of laser irradiation, suggesting that the giant shell is effective in reducing nonradiative recombination that may be caused by photoinduced defects. The water‐dispersed QDs also exhibit high aqueous colloidal stability, retaining a high PLQY of 53% without QD agglomeration after 14 months of storage at 4 °C at a high loading concentration of 20 mg mL−1. The QDs are also successfully incorporated into HeLa cells for confocal bioimaging with no practical signs of cytotoxicity. No near‐infrared (NIR) quantum dot (QD) is clinically approved due to cytotoxicity from poor QD encapsulation and toxic heavy metal usage. An NIR giant‐shell QD with a tiny In(Zn)As core encapsulated by three thicker shells is prepared, limiting arsenic content to 2%. The QDs possess a high aqueous quantum yield and colloidal stability for bioimaging with no signs of cytotoxicity.