Congratulations to Chen Jingya's article published in Small!

       Due to the high penetrability and non-invasiveness of near-infrared light (NIR), materials scientists have developed a variety of NIR first-zone nanomaterials for photodynamic therapy/photothermal therapy (PDT). /PTT), these materials include carbon nanomaterials, organic small molecule/polymer semiconductors, transition metal compounds, metal nanomaterials, black phosphorus and biomolecular self-assembled materials, etc. Compared with inorganic nanomaterials, organic nanomaterials have the advantages of adjustable absorption wavelength, good biodegradability, low cost, and fast metabolism of biological tissues. Although conjugated polymers dominate the field, their synthesis and purification are relatively difficult, as well as batch-to-batch variability and quality control difficulties. Compared with conjugated polymers, organic small molecules have the advantages of well-defined chemical structure, high purity, good reproducibility, and easy modification and processing. Although many PTT organic small-molecule nanomaterials for 808 nm laser have been reported, only a few materials can be applied to PDT. In addition, the mechanism of action of PDT under NIR conditions is unclear. Designing and synthesizing triplet materials with efficient intersystem crossing (ISC) is the key to realize efficient PDT. According to perturbation theory, the rate constant (kISC) of ISC depends on two important parameters, the spin-orbit coupling (SOC) constant (ξ) and the energy gap (ΔEST) between singlet and triplet states. A large ξ can improve kISC. The heavy atom effect is a common method to achieve large ξ, however heavy atoms are harmful to humans. At the same time, a small ΔEST is also beneficial to improve kISC. To reduce ΔEST, a strategy of donor (D)-acceptor (A) structure and twisted conformation can be adopted. However, the conformational twist usually results in a blue-shift of the absorption and a decrease in the extinction coefficient, making it difficult to achieve strong absorption under 808 nm laser light. Therefore, it is challenging to design small-molecule high-efficiency near-infrared PTT/PDT nanomaterials without heavy atoms.

Professor Huang Hui from the School of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, and Professor Zhang Shiming from Nanjing University of Technology collaborated to achieve efficient near-infrared light by designing and synthesizing small molecule nanomaterials with electron-deficient large π-conjugated cores and twisted conformations Thermal and photodynamic effects. By introducing large π-conjugated electron-deficient units and D-A structures in organic small-molecule materials, it is ensured that they have strong absorption at 808 nm. By introducing the D-A structure and twisted conformation, the energy gap (ΔEST) between the singlet state and the triplet state is reduced, effective intersystem crossing is achieved, and the PDT effect is improved. At the same time, the mechanism is discussed through experimental and theoretical evidence, which provides a new strategy for designing efficient PDT/PTT small molecule near-infrared materials.

    The relevant results were published on Small (DOI: 10.1002/smll.202000909). Jingya Chen, a master student (joint training) from Nanjing University of Technology, is the first author of the paper, and Kaikai Wen, a doctoral student from the University of Chinese Academy of Sciences, is the co-first author of the paper.

Link：https://onlinelibrary.wiley.com/doi/full/10.1002/smll.202000909
          DOI: 10.1002/smll.202000909