From Molecule to Aggregate: Designing AIE Nanocrystals for Low‐Power Backward Third‐Harmonic Generation Angiography
Abstract
Abstract Organic materials featuring third harmonic generation (THG) hold great promise for deep‐tissue bioimaging due to their good biocompatibility and second near‐infrared excitation. However, minimizing photodamage from the incident light necessitates significant improvements in the third‐order nonlinear susceptibility. Herein, an organic luminogen called OTBP is developed as a backward THG (BTHG) contrast agent for second near‐infrared (NIR‐II) angiography. OTBP's intense absorption at 433 nm resonantly enhances its BTHG efficiency when excited by a 1300 nm femtosecond laser. In the aggregate state, the robust intermolecular interactions among OTBP molecules realize excellent crystallinity and the facile preparation of nanocrystals (NCs) with a high refractive index of 1.78. By leveraging Mie scattering theory, the best size of OTBP NCs for BTHG collection is attained. These integrated properties result in a high BTHG efficiency of OTBP NCs. Encapsulating the NCs with F‐127 enables ultralow‐power but high‐contrast 3D vasculature imaging with negligible photodamage and background interference. Further elevating the laser power to 60 mW enables the visualization of microvessels at 500 µm with a high SNR of 143. This study offers insights into material design strategies toward efficient organic BTHG contrast agents and paves the way for the materials‐oriented non‐linear optics.
Article Details
Authors (13)
Lidong Du
MOE Frontiers Science Center for Precision Oncology University of Macau Macau 999078 China
Hanchen Shen
Innovative Centre for Flexible Devices (iFLEX), Max Planck−NTU Joint Laboratory for Artificial Senses, School of Materials Science and Engineering
Changhuo Xu
Xinyan Zhu
Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Division of Life Science, and State Key Laboratory of Molecular Neuroscience
Bingnan Wang
School of Chemistry and Chemical Engineering Hainan University Haikou China
Qingqing Zhou
Beijing National Laboratory for Molecular Engineering, New Cornerstone Science Laboratory, College of Chemistry and Molecular Engineering
Chunxi Liu
Herman H. Y. Sung
Department of Chemistry
Ryan T. K. Kwok
Department of Chemistry, the Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biological Engineering, State Key Laboratory of Nervous System Disorders, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China
Jacky W. Y. Lam
Department of Chemistry, the Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biological Engineering, State Key Laboratory of Nervous System Disorders, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China
Quan Zhou
Tzu‐Ming Liu
MOE Frontiers Science Center for Precision Oncology University of Macau Macau 999078 China
Ben Zhong Tang
School of Science and Engineering, Guangdong Basic Research Center of Excellence for Aggregate Science, The Chinese University of Hong Kong (Shenzhen), Longgang, Shenzhen 518172, Guangdong, P. R. China