Kwaśniewska Anita, Orzechowska Katarzyna, Rząd Klaudia, Ceresa Luca, Figiel Małgorzata, Hoser Anna A, Nowak Maurycy E, Karcz Dariusz, Gładyszewska Bożena, Gładyszewski Grzegorz, Srebro-Hooper Monika, Matwijczuk Arkadiusz
Department of Applied Physics, Faculty of Mechanical Engineering, Lublin University of Technology, Nadbystrzycka 38, Lublin, 20-618, Poland.
Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, Kraków, 30-387, Poland.
Sci Rep. 2024 Dec 28;14(1):31350. doi: 10.1038/s41598-024-82853-2.
Physical and photophysical properties of starch-based biopolymer films containing 5-(4-nitrophenyl)-1,3,4-thiadiazol-2-amine (NTA) powder as a nanofiller were examined using atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), stationary UV-Vis and fluorescence spectroscopy as well as resonance light scattering (RLS) and time-resolved measurements, and where possible, analyzed with reference to pristine NTA solutions. AFM studies revealed that the addition of NTA into the starch biopolymer did not significantly affect surface roughness, with all examined films displaying similar Sq values ranging from 70.7 nm to 79.7 nm. Similarly, Young's modulus measurements showed no significant changes after incorporating the 1,3,4-thiadiazole. Adhesion force and water contact angle assessments demonstrated that the films maintained high hydrophilicity (water wetting) across all examined films. Color analysis corroborated the anticipated trend, showing that increasing additive content resulted in decreased lightness and increased yellowness. Interestingly, however, while in polar isopropanol solvent at low concentration, NTA shows a typical single-band emission, centered at 410 nm and a slight enhancement of the band on the long-wavelength side around 530 nm, its incorporation into the biopolymer matrices results in the appearance of dual fluorescence signal with maxima at 430 and 530 nm. Concentration-dependence emission experiments, demonstrating that with even a slight increase of the amount of NTA in solution, an additional, weak long-wavelength emission band emerged within the spectral range corresponding to the intensive band in the biopolymer film, along with results of the performed quantum-chemical studies, including both the monomeric and aggregated (dimer and trimer) models, conclusively unveil that the dual fluorescence observed in starch/NTA films is due to molecular aggregation effects resulting in aggregation-induced emission. This study underscores the potential of NTA as an additive in biobased polymer films, furnishing them with new photophysical features without substantially altering their surface properties and thus enabling their extended applications.
使用原子力显微镜（AFM）、傅里叶变换红外光谱（FTIR）、稳态紫外 - 可见光谱和荧光光谱以及共振光散射（RLS）和时间分辨测量方法，研究了含有5 - （4 - 硝基苯基） - 1,3,4 - 噻二唑 - 2 - 胺（NTA）粉末作为纳米填料的淀粉基生物聚合物薄膜的物理和光物理性质，并在可能的情况下，参照原始NTA溶液进行分析。AFM研究表明，向淀粉生物聚合物中添加NTA对表面粗糙度没有显著影响，所有检测的薄膜显示出相似的Sq值，范围在70.7 nm至79.7 nm之间。同样，杨氏模量测量显示在掺入1,3,4 - 噻二唑后没有显著变化。附着力和水接触角评估表明，所有检测的薄膜都保持了高亲水性（水湿润性）。颜色分析证实了预期趋势，表明添加剂含量增加导致明度降低和黄度增加。然而，有趣的是，虽然在低浓度的极性异丙醇溶剂中，NTA显示出典型的单带发射，中心波长为410 nm，并且在530 nm左右的长波长侧带略有增强，但将其掺入生物聚合物基质中会导致出现双荧光信号，最大值分别在43（此处原文有误，应为430）和530 nm。浓度依赖性发射实验表明，即使溶液中NTA的量略有增加，在与生物聚合物薄膜中的强带相对应的光谱范围内也会出现一个额外的、较弱的长波长发射带，同时进行的量子化学研究结果，包括单体和聚集（二聚体和三聚体）模型，最终揭示淀粉/NTA薄膜中观察到的双荧光是由于分子聚集效应导致的聚集诱导发射。这项研究强调了NTA作为生物基聚合物薄膜添加剂的潜力，为它们赋予新的光物理特性，而基本上不改变其表面性质，从而实现其扩展应用。
