RESUMO
Two-dimensional-zero-dimensional plasmonic hybrids involving defective graphene and transition metals (DGR-TM) have drawn significant interest due to their near-field plasmonic effects in the wide range of the UV-vis-NIR spectrum. In the present work, we carried out extensive investigations on resonance Raman spectroscopy (RRS) and localized surface plasmon resonance (LSPR) from the various DGR-TM hybrids (Au, Ag, and Cu) using micro-Raman, spatial Raman mapping analysis, high-resolution transmission electron microscopy (HRTEM), and LSPR absorption measurements on defective CVD graphene layers. Further, electric field (E) mappings of samples were calculated using the finite domain time difference (FDTD) method to support the experimental findings. The spatial distribution of various in-plane and edge defects and defect-mediated interaction of plasmonic nanoparticles (NPs) with graphene were investigated on the basis of the RRS and LSPR and correlated with the quantitative analysis from HRTEM, excitation wavelength-dependent micro-Raman, and E-field enhancement features of defective graphene and defective graphene-Au hybrids before and after rapid thermal annealing (RTA). Excitation wavelength-dependent surface-enhanced Raman scattering (SERS) and LSPR-induced broadband absorption from DGR-Au plasmonic hybrids reveal the electron and phonon interaction on the graphene surface, which leads to the charge transfer from TM NPs to graphene. This is believed to be responsible for the reduction in the SERS signal, which was observed from the wavelength-dependent Raman spectroscopy/mappings. We implemented defective graphene and DGR-Au plasmonic hybrids as efficient SERS sensors to detect the Fluorescein and Rhodamine 6G molecules with a detection limit down to 10-9 M. Defective graphene and Au plasmonic hybrids showed an impressive Raman enhancement in the order of 108, which is significant for its practical application.
RESUMO
Poly(3-hexylthiophene) (P3HT) degrades in organic solvents containing dissolved molecular oxygen when irradiated with ultraviolet light. Hence, it is important to develop strategies that can enhance the photostability of P3HT and enhance the device performance. In this work, we report that preparing composites of P3HT with appropriate amounts of multiwalled carbon nanotube (MWCNT) results in superior photostability of P3HT. UV-visible and fluorescence spectroscopy have been used as primary tools to study the photostability of P3HT and its composites. Scanning electron microscopy (SEM) images of the composites display dispersed CNTs being well coated by P3HT. Transmission electron microscopy (TEM) micrographs along with SAED patterns reveal that P3HT coats the CNTs, which is the reason for superior dispersion of the composite. ESR spectroscopy was also performed to pursue and follow the degradation of P3HT. Ten weight percent of MWCNTs in P3HT was found to be the optimum loading amount that results in maximum photostability of the P3HT as compared to the other ratios. This enhanced photostability of P3HT on preparing composites with MWCNT in addition to its easy processability directly from solution makes these composites immensely important for optoelectronic applications.
