On February 23rd, MATERIALS HORIZONS published the latest research results from Prof. Mingqiang Zhu's group at Wuhan National Laboratory for Optoelectronics, “AIE-based universal super-resolution imaging for inorganic and organic nanostructures”.
Due to the diffraction of light, the resolution limit of the conventional optical microscope is about 200 nm, it is difficult to clearly observe the structure within 200 nm in size. Super-resolution Optical Microscopy based on single-molecule localization has broken the resolution limit of optical microscopes over the past 20 to 30 years, and it has become one of the most significant breakthroughs in the field of optical microscopy imaging in this century. However, the development of super-resolution imaging probes and new imaging mechanisms is progressed relatively slowly, limiting the practical application of super-resolution optical imaging. So it is of great scientific significance and application value to develop a widely applicable universal super-resolution imaging probe and technology.
In view of this, Professor Zhu Mingqiang's group at Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, integrate the induced emission phenomenon (AIE) effect and the electrostatic interaction mechanism, proposing a universal super-resolution imaging method for no matter synthesizing inorganic, organic materials or natural biomaterials. In the past, super-resolution microscopy technology must use light stimulation or even other auxiliary agents to produce fluorescent switch events. In contrast, this method here uses only one AIE-active fluorescent (OF+) probe with multiple positive charges. Through the dynamic electrostatic interaction between the anions and cations, the OF+ molecules will dynamically combine with the negatively charged material (emission of AIE fluorescence) and detachment (fluorescence quenching), realizing stochastic photoswitching of the fluorophores in the surface of the observed object, and thus become one of the necessary conditions of super resolution imaging.
AIE super-resolution probe OF+ synthesized by GCC reaction
Schematic of super resolution imaging using OF+
They choose silver nanowires, bacterial and anionic polystyrene-b-polyacrylic acid (PSt-b-PAA) self assembly nanocellulose with negative charges on the surface as a representative for nanostructures, and used the cationic AIE-active fluorescent molecule OF+ as the super-resolution probe. Taking silver nanowires as an example, the morphologies of silver nanowires under the same region of a conventional fluorescence microscope and super-resolution imaging, respectively, was campared. The conventional fluorescent imaging results in silver nanowire images with blurred shapes, showing a full width at half maximum (FWHM) of hundreds of nanometers which is significantly higher than the actual size of silver nanowires. Significantly, the super-resolution images shows the silver nanostructures with clear sketches inith a diameter distribution of 35.43 ± 11.72 nm, which is closely consistant with that measured in SEM images (31.75 ± 9.96 nm) but avoiding use of the rigorous conditions of SEM, demonstrating the effectiveness and powerfulness of this method.
Super-resolution imaging of silver nanowires. (a) Bright field image. (b) Conventional fluorescence image. (c) Super-resolution image corresponding to the same field as the fluorescence image. (d) The diameter distribution of the silver nanowires based on the FWHM measured in (c). (e) The photon count distribution at each event. (f) Conventional fluorescence and super-resolution imaging cross-sectional profiles of a single silver nanowire. (g) SEM image of the silver nanowires. (h) The diameter distribution of the silver nanowires based on the SEM image.
The greatest significance of this research is that it proposes a new universal super-resolution imaging probe and principle which use electrostatic interaction to control the behavior of AIE to achieve a stochastic switching of fluorescence and finally a resolution of sub-30 nm is obtained. Also, as a prospect in the end of the article, the authors claims that any other similar dynamic fluorescence switching behaviors derived or extended from aggregation-induced fluorescence (AIE) can be further developed into novel super-resolution imaging microscope technologies.
This work was completed by Qi-yuan Zhou, Cheng Fan (co-first authors), Chong Li (corresponding author), Ya-Long Wang, Ze-Qiang Chen, Qi Yu and Ming-qiang Zhu (corresponding author) from the Energy Photonics Functional Laboratory of Wuhan National Center for Optoelectronics. This work was supported by the National Basic Research Program (973) of China, the National Science Foundation of China, the Fundamental Research Funds for Central Universities, and the Director Fund of WNLO.
Full text link http://pubs.rsc.org/en/content/articlelanding/2018/mh/c8mh00089a#!divAbstract.
