Controlling metal-protein interactions : the effect of molecular spacer and encapsulin on picocavities

The food and pharmaceutical industries demand sensitive detection techniques as impurity could be harmful to human health. Surface-enhanced Raman spectroscopy is such a technique detecting molecular vibrations by amplifying the Raman signal utilizing localized surface plasmon resonance. This thesis substrate consisted of 80 nm gold nanoparticles on a 100 nm gold film. The enhanced electric field of this substrate and laser light cause adatoms to extrude from the surface and localize light in volumes of less than 1 nm³, referred to as picocavities. Picocavities introduce time-fluctuations in the Raman signal by changing the number and variety of vibrational modes of molecules. The dependence of picocavities on the alkanethiol self-assembled monolayer length spacing equine spleen ferritin from the gold nanoparticle monolayer and the effect of encapsulation were investigated. Firstly, the Raman signal of encapsulin and the ferritin-like protein overlapped. Secondly, the high enhancement of Raman peaks by picocavity events at self-assembled monolayer lengths of 1.3 and 1.7 nm was remarkable, can revolutionize our understanding of picocavities, and enables bio-sensing possibilities. Finally, the picocavity and flare presence plateaued at 1 nm, resulting in an optimal self-assembled monolayer length of 1 nm.