Hamaamin Othman K, Ghareeb Hewa O, Mohammed Sewara J
Department of Chemistry, College of Science, University of Sulaimani, Kurdistan Regional Government, Qlyasan Street, Sulaymaniyah, 46001, Iraq.
Department of Anesthesia, College of Health Sciences, Cihan University Sulaimaniya, Sulaymaniyah City, Kurdistan, Iraq.
Sci Rep. 2025 Aug 7;15(1):28891. doi: 10.1038/s41598-025-14206-6.
This study presents an eco-friendly strategy to enhance the optical and structural properties of polyvinyl alcohol (PVA) films through doping with eggplant peel dye (EPPD), a natural pigment extracted from agricultural waste via a green aqueous synthesis (~ 33% yield from 30 g of peel). EPPD was uniformly dispersed in PVA films (PVA-D1, PVA-D2, PVA-D3) using an ultrasonic-assisted solution casting technique, with chitosan (CS) added to prevent fungal growth. Comprehensive characterization (Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), ultraviolet-visible spectroscopy (UV-Vis), and differential scanning calorimetry (DSC)) confirmed successful integration of EPPD, revealing its polyhydric alcohol content, amorphous nature, and uniform distribution within the polymer matrix. Doping with EPPD significantly reduced the optical band gap from 6.314 eV (pure PVA) to 1.8 eV (PVA-D3), introducing localized states that enhanced light absorption (peaking at 554 nm in PVA-D3), as supported by Tauc's model (transition type: direct allowed → direct forbidden) and dielectric loss analysis. Additionally, the refractive index increased from 1.165 to 1.27, while the optical dielectric constant (ε₁) improved from 1.366 to 1.609 due to enhanced charge carrier density. XRD analysis revealed a decrease in crystallinity from 30.50% (pure PVA) to 18.11% (PVA-D3), leading to a reduction in the glass transition temperature (from 30.5 °C to 25 °C) and melting temperature (from 240 °C to 194 °C). The Urbach energy (Eu), an indicator of structural disorder, increased from 0.43 eV (pure PVA) to 0.62 eV (PVA-D3), reflecting a higher density of localized states in the amorphous matrix and broader tail states in the band structure. These tunable optoelectronic properties position EPPD-doped PVA films as promising candidates for various applications, including UV-protective textiles, smart packaging, biomedical dressings, and energy-efficient optoelectronic devices.
本研究提出了一种环保策略，通过掺杂茄子皮染料（EPPD）来增强聚乙烯醇（PVA）薄膜的光学和结构性能。EPPD是一种从农业废弃物中提取的天然色素，采用绿色水相合成法（30克果皮的产率约为33%）。使用超声辅助溶液浇铸技术将EPPD均匀分散在PVA薄膜（PVA-D1、PVA-D2、PVA-D3）中，并添加壳聚糖（CS）以防止真菌生长。综合表征（傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、场发射扫描电子显微镜（FESEM）、紫外可见光谱（UV-Vis）和差示扫描量热法（DSC））证实了EPPD的成功整合，揭示了其多元醇含量、无定形性质以及在聚合物基质中的均匀分布。掺杂EPPD显著降低了光学带隙，从6.314电子伏特（纯PVA）降至1.8电子伏特（PVA-D3），引入了局域态，增强了光吸收（在PVA-D3中于554纳米处达到峰值），这得到了陶克模型（跃迁类型：直接允许→直接禁戒）和介电损耗分析的支持。此外，由于载流子密度增加，折射率从1.165提高到1.27，光学介电常数（ε₁）从1.366提高到1.609。XRD分析表明结晶度从30.50%（纯PVA）降至18.11%（PVA-D3），导致玻璃化转变温度降低（从30.5℃降至25℃）和熔点降低（从240℃降至194℃）。乌尔巴赫能量（Eu）是结构无序的指标，从0.43电子伏特（纯PVA）增加到0.62电子伏特（PVA-D3），反映了非晶基质中局域态密度更高，能带结构中尾部态更宽。这些可调节的光电性能使掺杂EPPD的PVA薄膜成为各种应用的有前途的候选材料，包括紫外线防护纺织品、智能包装、生物医学敷料和节能光电器件。
