Gebrekrstos Amanuel, Madras Giridhar, Bose Suryasarathi
Department of Chemical Engineering and Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India.
ACS Omega. 2018 May 17;3(5):5317-5326. doi: 10.1021/acsomega.8b00237. eCollection 2018 May 31.
Herein, graphene oxide (GO) was suitably functionalized to obtain carboxylated and fluorinated GO (GOCOOH and GOF) derivatives, respectively, via the Hunsdiecker reaction. Electrospun mats of poly(vinylidene fluoride) (PVDF)/GO, PVDF/GOCOOH, and PVDF/GOF fibers were then prepared by electrospinning from well-dispersed GO derivatives. The piezoelectric coefficient ( ), as measured using piezoelectric force measurement (PFM), enhanced by more than 2 folds with respect to the control PVDF spun mat. The piezoelectric coefficient though enhanced upon the addition of GO and GOCOOH, however, enhanced significantly in the case of GOF. For instance, a drastic increase in piezoelectric response from 30 pm V(electrospun neat PVDF) to 63 pm V (for electrospun PVDF/GOF) was observed as revealed from PFM results. The phase transformation in these fibers was systematically investigated by various techniques such as Fourier transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (XRD), Raman spectroscopy, and PFM. FTIR and XRD results revealed that the electrospun fiber mats showed predominantly β-PVDF. Interestingly, the highest β content was obtained in the presence of GOF. The drastic enhancement in β phase is due to the presence of highly electronegative fluorine. The addition of GOCOOH and GOF in PVDF not only increases the polar β phase but also changes the piezoelectric response significantly. More interestingly, PVDF/GOF films exhibited higher energy density and dielectric permittivity when compared with the control PVDF samples. These findings will help guide the researchers working in this field from both theoretical understanding and practical view point for energy storing device and charge storage electronics.
在此，通过洪斯迪克尔反应对氧化石墨烯（GO）进行适当功能化处理，分别获得羧基化和氟化的GO（GOCOOH和GOF）衍生物。然后，通过静电纺丝从分散良好的GO衍生物中制备聚偏二氟乙烯（PVDF）/GO、PVDF/GOCOOH和PVDF/GOF纤维的静电纺丝垫。使用压电力测量（PFM）测量的压电系数相对于对照PVDF纺丝垫提高了2倍以上。虽然添加GO和GOCOOH后压电系数有所提高，但在GOF的情况下显著提高。例如，从PFM结果可以看出，压电响应从30 pm V（静电纺纯PVDF）急剧增加到63 pm V（静电纺PVDF/GOF）。通过傅里叶变换红外光谱（FTIR）、广角X射线衍射（XRD）、拉曼光谱和PFM等各种技术系统地研究了这些纤维中的相变。FTIR和XRD结果表明，静电纺纤维垫主要呈现β-PVDF。有趣的是，在GOF存在的情况下获得了最高的β含量。β相的急剧增强归因于高电负性氟的存在。在PVDF中添加GOCOOH和GOF不仅增加了极性β相，还显著改变了压电响应。更有趣的是，与对照PVDF样品相比，PVDF/GOF薄膜表现出更高的能量密度和介电常数。这些发现将从理论理解和实际应用的角度帮助指导该领域的研究人员开发储能装置和电荷存储电子器件。
