Infrared (IR) and Raman spectroscopy are powerful vibrational techniques that provide label-free molecular information through characteristic vibrational fingerprints. Their surface-enhanced variants, surface-enhanced infrared absorption (SEIRA) and surface-enhanced Raman scattering (SERS), exploit plasmonic nanostructures to overcome intrinsically weak signals. While SEIRA and SERS offer complementary vibrational information, their simultaneous implementation on the same sensing platform remains challenging due to the distinct plasmonic requirements of IR and visible resonances. This thesis addresses the challenge of integrating SEIRA and SERS on a single substrate by combining top-down and bottom-up nanofabrication strategies. Top-down approaches, based on electron-beam lithography, enable the reproducible fabrication of IR-resonant nanoantennas, while bottom-up colloidal synthesis provides plasmonic nanoparticles with plasmon resonances in the visible spectrum for Raman. To that end we explore synthetic growth procedures of gold nanostructures, with a particular focus on gold nanostars, and identify key molecular parameters governing their formation. Building on this knowledge, hybrid plasmonic platforms were developed by integrating colloidal nanoparticles with lithographically defined IR antennas. Initial designs based on spiked antenna architectures revealed a fundamental trade-off: while nanoscale roughness and spikes strongly enhanced SERS, they simultaneously degraded IR resonances, significantly reducing SEIRA performance. To overcome this limitation, a modular strategy was implemented in which gold nanospheres of different sizes were selectively placed onto IR-resonant antennas. This approach enabled the coexistence of visible and IR plasmon bands on the same substrate location enabling collection of SEIRA and SERS from the same substrate location with enhanced signal opposed to single structures that are not combined. The thesis further presents a systematic comparison of SEIRA measurements in transmission and reflection geometries. The results establish that the antenna design is a key factor in determining the most suitable measurement configuration. These insights lead to practical guidelines for designing SEIRA-based which will be relevant for broader plasmonic sensing applications. Overall, this work establishes design principles and fabrication strategies for integrating SEIRA and SERS on a single substrate. By combining complementary nanofabrication approaches and carefully balancing plasmonic responses, it lays a foundation for design of multimodal plasmonic sensors.