Novel nanomaterials have attracted considerable attention in nanophononics, aiming to advance the development of light-driven applications. Metallic plasmonic nanoparticles offer highly tunable optical properties and create energetic electron-hole pairs, making them ideal for building blocks of light-harvesting applications such as solar cells and photocatalysis. To efficiently use these unique properties and engineer plasmon-based devices, it is essential to understand the optical properties and dynamics of such plasmonic nanostructures and their hybrid heterostructures. In this thesis, I studied the optical properties and ultrafast dynamics of novel nanomaterials, including emerging aluminum nanostructures, gold nanorods, and novel gold nanorod-semiconductor core-shell heterostructures. I utilized single-particle microscopy and transient ultrafast spectroscopy techniques that allow for detailed investigation of transient dynamics and optical properties of individual nanoobjects. In the first part of this thesis, aluminum nanostructures are studied as a great plasmonic candidate due to their broad wavelength tunability and high natural abundance. I investigated the ultrafast dynamics of single aluminum nanocrystals and discovered the effects of crystallinity on their coherent phonon modes, resulting from substantially varying degrees of nanoparticle crystallinity. Based on the strong dependence on crystallinity, I established that highly crystalline aluminum nanoparticles are the best candidates for applications based on the optomechanical properties of plasmonic nanoparticles. Next, I investigated the radiative optical properties of plasmonic gold nanorod using correlated single-particle dark-field scattering and photoluminescence spectroscopy techniques. I demonstrated the effect of size on the photoluminescence of gold nanorods and determined that enhanced intraband transitions in the smallest gold nanorods yield the largest photoluminescence quantum yields. I established that single-particle photoluminescence spectroscopy can be used to probe hot carrier distributions and their relaxation pathway. In the third part of the thesis, I investigated the charge transfer mechanism in metal-semiconductor heterostructures by combining their ultrafast transient dynamics and steady-state optical properties. The results acquired in this part revealed the critical details regarding electron transfer pathways from metal to the semiconductor and their injection efficiencies. I quantified the relative contribution of the sequential transfer of hot electrons and direct metal-to-semiconductor interfacial charge transfer pathways. I conclusively showed the direct electron transfer pathway through chemical interface damping and found that about 50% of the total injected electrons are transferred through this direct pathway. These results are crucial for advancing our understanding of electron transfer in metal-semiconductor heterostructures, holding a great promise for improving the efficiency of light-harvesting systems towards generating currents or driving chemical reactions with visible illumination.