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    Home > New achievement of cooperation between academician Tang benzhong of Hong Kong University of science and technology and Professor Ding Dan of Nankai University: intramolecular movement induced photothermal transformation (imipt)

    New achievement of cooperation between academician Tang benzhong of Hong Kong University of science and technology and Professor Ding Dan of Nankai University: intramolecular movement induced photothermal transformation (imipt)

    • Last Update: 2019-02-28
    • Source: Internet
    • Author: User
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    In recent years, Dr Zhao Zheng has been a research hotspot in the field of controlling the movement of molecules in excited state to construct advanced optical functional materials Related works such as molecular motor of light response, intelligent polymer materials of light control and stimulating response fluorescent materials have been reported However, how to realize the movement of active molecules in nanoparticles and solid state and apply it to biomedical field is still a challenge Recently, the research group of Professor Tang benzhong of Hong Kong University of science and technology and Professor Ding Dan of Nankai University have proposed a new concept of molecular design, which uses molecular motion in solid state to promote non radiative transition heat production to build efficient photothermal materials The molecular design concept is based on the concept of aggregation induced emission (AIE) proposed by academician Tang benzhong in 2001, but it is different from AIE Therefore, they proposed a new concept and named it intramolecular motion induced photothermal (imipt) Relevant achievements were published in nature communications (DOI: 10.1038 / s41467-019-08722-z) under the title of "highly efficient photothermal nanoagent achieved by harvestingenergy via exclusive state intramolecular motion within Nanoparticals" Fig 1 Schematic diagram of the comparison of aggregation induced luminescence and intramolecular motion induced photothermal conversion (source: Nat Commun.) AIE refers to a kind of phenomenon that molecules rich in rotating primitives do not emit light in the dissolution state but enhance fluorescence in the aggregation state The mechanism behind this phenomenon is: in the excited state, the monodisperse form of molecules in the solution makes it possible to dissipate the excited state energy in the form of heat through the non radiative relaxation pathway through the active intramolecular movement; in the aggregated state, the intramolecular movement is limited, and the energy is released in the form of luminescence through the radiative transition pathway For a long time, the research of AIE materials has been focused on how to effectively control and utilize their radiative transition pathways, but little attention has been paid to the utilization of their non radiative pathways This work is a reverse thinking of the concept of AIE Compared with AIE type molecules trying to inhibit molecular movement to open the radiation transition path and emit fluorescence, this work aims to maximize the molecular movement in the solid state to enhance the non radiation transition, so as to convert light energy into heat energy (Figure 1) Previous reports have shown that the introduction of strong donor acceptor structure and distorted AIE motifs can effectively promote the intramolecular movement and non radiative transition, but in the solid state, the non radiative transition pathway is often inhibited due to the restriction of intramolecular movement In this work, on the basis of previous molecular design, the author introduces long alkyl bifurcated side chains to overcome the inhibition of molecular motion in solid state (Fig 2), to realize the aggregation, the active molecular motion in solid state and the efficient non radiation transition This result is obviously different from the previous case that TPE molecule is introduced to convert planar molecule into AIE molecule, which proves the rationality and effectiveness of the design of imipt molecule with long alkyl side chain Figure 2 Molecular design of imipt and photophysical properties of molecules in solution and aggregation state (source: Nat Commun.) are shown in Figure 2 Compared with ndta molecules, two molecules containing TPE units do not emit light in solution, nano aggregate or solid film The ultrafast spectrum experiments show that with the introduction of TPE, the singlet lifetime of 2tpe-ndta and 2tpe-2ndta molecules is shorter than that of ndta (nanosecond level) to picosecond level, and the non radiative transition of exciton is dominant Low temperature experiments and solvation effects show that both molecules exhibit strong fluorescence emission at 800-900 nm in the near-infrared region when the molecular motion is inhibited at 77 K and in non-polar solvents Figure 3 Solid state NMR data (source: Nat Commun.) shows that 2tpe-ndta and 2tpe-2ndta show very short relaxation time compared with typical AIE compounds TPE (Figure 3) Relaxation time can be used to characterize the movement of molecules in solid state The length of relaxation time corresponds to the speed and slowness of the movement of molecules in solid state respectively This shows that 2tpe-ndta and 2tpe-2ndta have very fast molecular motion in the solid state, which is consistent with their non luminescent characteristics in the solid state Figure 4 Photothermal conversion efficiency of imipt molecule (source: Nat Commun.) photothermal conversion efficiency test shows that (Figure 4), compared with star semiconductor molecule SPNs reported in the literature, imipt type molecule shows higher photothermal conversion efficiency (54.9%) than SPNs (27.5%) Photoacoustic signal test shows that, compared with the commercial methylene blue (MB) and the known star semiconductor polymer SPNs, the nanoparticles prepared by imipt type molecules show stronger photoacoustic signal and excellent optical stability Finally, the nanoparticles prepared by imipt type molecules were successfully used in in vivo near-infrared photoacoustic imaging Compared with normal muscle tissue, tumor tissue showed better imaging contrast Figure 5 Near infrared photoacoustic imaging (source: Nat Commun.) The significance of this work lies in: from the perspective of application, the author puts forward a new idea of using molecular motion to build advanced functional materials, not limited to the precise control of molecular motion; from the mechanism, the author reversely confirms the rationality and universality of the aggregation induced luminescence mechanism, and confirms that the excited state molecular motion regulation is developing multifunctional π Material feasibility The first authors of this work are Dr Zhao Zheng, postdoctoral student of Hong Kong University of science and technology, Chen Chao, doctoral student of Nankai University and Wu Wenting, doctoral student of Shanghai Institute of organic science, Chinese Academy of Sciences The corresponding authors are academician Tang benzhong and Professor Ding Dan of Nankai University Dr Wang fanfen of Nankai University and Professor Sun Pingchuan also helped in solid-state NMR experiment and analysis; Dr Du Lili of Hong Kong University and Professor Phillips helped in ultrafast spectrum experiment and analysis Researcher Gao Xike from Shanghai organic Research Institute provided important help and suggestions for this work The research is supported by NSFC, ITC, RGC and other projects in Hong Kong The author of the paper: Zheng Zhao Chen, Wenting Wu, Fenfen Wang, Lili Du, Xiaoyan Zhang, Yu Xiong, Xuewen he, Yuanjing Cai, Ryan K Kwok, Jacky W.Y Lam, Xike Gao, Pingchuan sun, David Lee Phillips, Dan Ding * & Ben Zhong Tang * Review of previous reports: academician Tang benzhong of Hong Kong University of science and technology and Professor Yu Xiaoqiang of Shandong University: new ultra-low concentration AIE materials for specific two-photon lipid droplet imaging Tang benzhong, academician team of Hong Kong University of science and technology and Yu Xiaoqiang, Professor team of Shandong University: nonreactive mitochondrial fluorescence probe capable of tracking mitochondria over a long period of time Mate.: academician Tang benzhong of Hong Kong University of science and technology has developed a dual-functional AIE material that can be used to monitor and kill multidrug-resistant bacteria Academician Tang benzhong of Hong Kong University of science and technology starts from aggregation induced luminescence - silver ion probe, fluorescent silver staining and dynamic monitoring of silver ion release Academician Tang benzhong of Hong Kong University of science and technology: aggregation induced luminescence emission, AIE)
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