【Angew.Chem.】吉林大学张红雨|突破固定输出！新型柔性有机晶体实现730-824 nm近红外光波导双模态智能调控#

FIGURE 1 Molecular structure, crystal morphology, mechanical properties, and optical characteristics of DPTD. (a) Chemical structure of the DPTD molecule. (b) Photographs of DPTD in dichloromethane solution, under daylight and 375 nm ultraviolet excitation. (c, d) Absorption and emission spectra of DPTD in solvents with different polarities. (e) Photographs of DPTD single crystals under daylight and 375 nm ultraviolet irradiation (scale bar: 5 mm). (f) Reversible elastic bending behavior of a DPTD single crystal under external force (scale bar: 5 mm). (g) Three-point bending test results of DPTD crystals. (h) Nanoindentation test results of DPTD crystals. (i) Absorption and emission spectra of DPTD crystals. (j) CIE 1931 chromaticity coordinates of DPTD crystal emission. (k) Time-resolved photoluminescence decay curve of a DPTD single crystal.#

FIGURE 2 The crystal structure, intermolecular interactions, and energy frameworks of DPTD single crystals. (a–c) Packing structures of DPTD single crystals. Dashed lines in different colors indicate π–π stacking interactions (red), C–H···N hydrogen-bonding interactions (blue), and C–H···O hydrogen-bonding interactions (green). (d, e) Energy framework calculated using CrystalExplorer. (f) Electrostatic potential map of the DPTD molecule.#

随后，研究人员对其光波导调控行为进行了深入探究。如图3所示，由于独特的自吸收效应，随着光传播距离的增加，高能光子被反复吸收并重新发射，导致波导输出峰值波长成功实现了从730 nm到824 nm的连续大幅度红移。此外，晶体还展现出杰出的光热转换效率。如图4所示，在660 nm激光照射下，晶体表面温度在4秒内迅速升至147°C以上，展现出极快的响应速度，并且在100次连续循环中保持了完美的结构完整性。

FIGURE 3 Optical waveguiding behavior and light propagation-based wavelength modulation in DPTD single crystals. (a, b) Optical waveguide images of straight (a) and bent (b) DPTD single crystals under 375 nm ultraviolet excitation. (c, d) Waveguide output spectra of straight and bent DPTD single crystals recorded at different light propagation distances. (e, f) Dependence of the intensity ratio between the output end and the excitation point (Itip/Ibody) on propagation distance for straight and bent DPTD single crystals. (g, h) Dependence of the waveguide output peak wavelength on propagation distance for straight and bent DPTD single crystals.#

最终，通过将光热效应与温度依赖性荧光淬灭机制相结合，研究团队构建了光热驱动的波导强度调制系统。如图5所示，晶体荧光强度在温度超过64.5°C后表现出明显的急剧淬灭。利用激光辐照功率精细调节晶体温度，使光激发生成荧光与光热引发荧光淬灭这两者相互竞争，成功实现了对波导输出强度的远程非接触式精密调制，该系统在200次交替切换循环中表现出极高的稳定性和耐用性。

FIGURE 4 Photothermal conversion of DPTD crystals under 660 nm laser irradiation. (a) Schematic arrangement of the experimental setup for photothermal measurements. (b) Infrared thermal images of a DPTD single crystal recorded under a laser irradiation intensity of 1.61 W·cm−2, showing the heating and cooling processes. (c) Temperature–time profile corresponding to the crystal heated by 660 nm laser of 1.61 W·cm−2. (d, e) Heating and cooling curves of a DPTD single crystal under different laser irradiation intensities. (f) Dependence of the maximum surface temperature on the laser irradiation intensity. (g) Heating rate calculated from the temperature–time profiles. (h) Photothermal durability test of a DPTD single crystal over 100 consecutive heating–cooling cycles under an irradiation intensity of 1.61 W·cm−2.#

FIGURE 5 Photothermal-driven modulation of waveguide output intensity in DPTD single crystals. (a) Schematic illustration and corresponding photograph of the experimental setup for thermal fluorescence quenching measurements. The scale bar is 5 mm. (b) Fluorescence spectra of a DPTD single crystal recorded at different temperatures. (c) Dependence of the fluorescence peak intensity on temperature, showing a two-stage quenching behavior with a well-defined threshold. (d) Schematic illustration of the photothermal modulation setup, where 375 nm ultraviolet light serves as the excitation source and a 660 nm laser is used for photothermal control. (e, f) Waveguide output spectra and corresponding intensity variations under different 660 nm laser irradiation intensities. (g) Schematic illustration and photograph of the experimental setup using only a 660 nm laser as both the excitation and photothermal source, and corresponding thermal image. The light transduction distance is 8 mm. (h, i) Waveguide output spectra and corresponding peak intensity variations under different laser irradiation intensities, revealing the competition between optical excitation and photothermal-induced quenching. (j) Stability of the waveguide output intensity during repeated switching of the laser irradiation intensity.#