Resumen de The applications of cvd grown graphene in surface-enhanced raman scattering and förster resonance energy transfer
In this thesis, the surface-enhanced Raman scattering(SERS) performance of graphene-related substrates and continuous modulation of Förster resonance energy transfer(FRET) between thin films of the molecules have been studied.
SERS is a promising method that enlarges the applicability of Raman microscope. By applying the SERS substrate, the intensity of the Raman signal is extremely enhanced and the more detailed information of the molecules can be observed. To better understand the mechanisms of the SERS, the Au nano-discs/single-layer graphene(Au NDs/SLG) and single-layer graphene/Au nano-holes(SLG/Au NHs) substrates were designed and fabricated. By applying Au NDs/SLG and SLG/Au NHs in SERS experiments, the Raman signals of the probe molecules were remarkably enhanced due to the light interaction between light the metallic nanostructures. The spatial Raman mapping was applied to study the distribution of the Raman intensity obtained from the Au NDs/SLG substrate with 2.5 μm NDs diameter. From the spatial Raman mapping, it revealed that the rim region of the Au NDs showed larger SERS signals. This result proved the electrical mechanism(EM) of SERS.
For the purpose of getting high-performance SERS substrates, the 3-dimensional(3D) Ag nanoparticles/single-layer graphene/Ag nano-discs(Ag NPs/SLG/Ag NDs) substrate have been designed and fabricated. In this 3D structure, not only the horizontal space but also the vertical space was fully used to generate the plasmon structure. So, the integrated Ag NPs/SLG/Ag NDs substrate exhibited extremely large SERS performance. Also, the spatial Raman mapping revealed that the rim of the Ag NDs mainly dominated the SERS signals due to the larger plasmon effect between Ag NPs and the edge of Ag NDs.
To quantify the defects in chemical vapor deposition(CVD) grown graphene, the Au nanoparticles/single-layer graphene/Au nano-holes(Au NPs/SLG/Au NHs) substrates have been designed and fabricated. By applying the plasmonic nanostructures, the defects-induced Raman signals of SLG have been extremely enhanced which provided an opportunity to measure the D and D´ band of SLG. The general and empirical formulas have been applied to quantify graphene defects nano-crystallite (La) through the Raman intensity ratios of ID/IG and ID´/IG.
FRET process is a very important process in measuring the conformational distribution and dynamics of molecules. FERT has been widely applied in polymer science, biochemistry, and structural biology. In this thesis, a method of continuously modulating the FRET between two thin films of the molecules have been exhibited. By applying the SLG as an intermediate material between the molecules thin films of rhodamine 6g(R6G) and fluorescein, the FRET efficiency has been continuously tuned by shifting the Fermi level(EF) of graphene.
In summary, graphene as the next century material possesses promising applicable potentials. By combing graphene with plasmon nanostructures, the integrated structure illustrated high SERS performance. By electrically shifting the Fermi level of graphene, we could permit or inhibit the FERT between emitters and SLG. These applications indicated its applicable potentials in practice.
