Radojković Nikolina, Spasojević Jelena, Kačarević-Popović Zorica, Stamenović Una, Vodnik Vesna, Roglić Goran, Radosavljević Aleksandra
Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, University of Belgrade, Mike Petrovića Alasa 12-14, Vinča, 11351 Belgrade, Serbia.
Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade, Serbia.
Polymers (Basel). 2024 Dec 5;16(23):3416. doi: 10.3390/polym16233416.
Hydrogel nanocomposites that respond to external stimuli and possess switchable electrical properties are considered as emerging materials with potential uses in electrical, electrochemical, and biological devices. This work reports the synthesis and characterization of thermo-responsive and electroconductive hydrogel nanocomposites based on poly(-isopropylacrylamide) (PNiPAAm) and gold nanoparticles (nanospheres-AuNPs and nanorods-AuNRs) using two different synthetic techniques. Method I involved γ-irradiation-induced crosslinking of a polymer matrix (hydrogel), followed by radiolytic formation of gold nanoparticles, while Method II included the chemical synthesis of nanoparticles, followed by radiolytic formation of a polymer matrix around the gold nanoparticles. UV-Vis spectral studies revealed the presence of local surface plasmon resonance (LSPR) bands characteristic of nanoparticles of different shapes, confirming their formation and stability inside the polymer matrix. Morphological, structural, and physicochemical analyses indicated the existence of a stable porous polymer matrix, the formation of nanoparticles with a face-centered cubic structure, increased swelling capacity, and a slightly higher volume phase transition temperature (VPTT) for the hydrogel nanocomposites. Comparative electrochemical impedance spectroscopy (EIS) showed an increase in conductivity for the nano Au-PNiPAAm hydrogel nanocomposites compared to the PNiPAAm hydrogel, with a considerable rise detected above the VPTT. By reverting to room temperature, the conductivity decreased, indicating that the investigated hydrogel nanocomposites exhibited a remarkable reversible "on-off" thermo-switchable mechanism. The highest conductivity was observed for the sample with rod-shaped gold nanoparticles. The research findings, which include optical, structural, morphological, and physicochemical characterization, evaluation of the efficiency of the chosen synthesis methods, and conductivity testing, provide a starting point for future research on the given nanocomposite materials with integrated multifunctionality.
能够响应外部刺激并具有可切换电学性质的水凝胶纳米复合材料被认为是在电气、电化学和生物设备中具有潜在用途的新兴材料。这项工作报道了基于聚（N-异丙基丙烯酰胺）（PNiPAAm）和金纳米颗粒（纳米球-AuNPs和纳米棒-AuNRs）的热响应性和导电水凝胶纳米复合材料的合成与表征，采用了两种不同的合成技术。方法I涉及聚合物基质（水凝胶）的γ射线辐射诱导交联，随后通过辐射分解形成金纳米颗粒，而方法II包括纳米颗粒的化学合成，随后在金纳米颗粒周围通过辐射分解形成聚合物基质。紫外-可见光谱研究揭示了不同形状纳米颗粒特有的局部表面等离子体共振（LSPR）带的存在，证实了它们在聚合物基质中的形成和稳定性。形态学、结构和物理化学分析表明存在稳定的多孔聚合物基质，形成了具有面心立方结构的纳米颗粒，水凝胶纳米复合材料的溶胀能力增加，体积相变温度（VPTT）略高。比较电化学阻抗谱（EIS）表明，与PNiPAAm水凝胶相比，纳米金-PNiPAAm水凝胶纳米复合材料的电导率有所增加，在VPTT以上检测到显著上升。恢复到室温后，电导率下降，表明所研究的水凝胶纳米复合材料表现出显著的可逆“开-关”热切换机制。对于具有棒状金纳米颗粒的样品，观察到最高电导率。这些研究结果，包括光学、结构、形态和物理化学表征、所选合成方法效率的评估以及电导率测试，为未来对具有集成多功能性的给定纳米复合材料的研究提供了一个起点。
