The wide variety of novel properties provided by various nanomaterials has striking implications for future applications. However, adoption of new materials is hindered by challenges in material definition, reproducibility, and characterization. While a specific application will define a set of desired properties, the development of a new material that addresses each need often proves challenging particularly when addressed in a linear fashion. With the development of libraries of nanomaterial building blocks and chemical reagents it would be possible to develop a modular approach to the discovery phase. This dissertation describes the development of two such approaches and explores how the challenges of materials definition and characterization may be addressed through the development of characterization sets that afford both corroborative and commentary approaches. The appropriate characterization of any nanomaterial is challenging regardless of the properties being investigated. Considering characterization during the design of new materials greatly benefits the speed at which new materials may be explored. In addition to addressing characterization challenges, issues of reproducibility are considered early in the discovery phase in order to maximize the utility of the materials produced. A modular method for the construction of new nanomaterials is illustrated in two different approaches. The design and synthesis of functional gold nanoparticles that were water-soluble and contained tailored reactive group densities for use as chemical reagents is provided. These nanoparticle reagents are intended to take advantage of the benefits of "click" chemistry, namely the use of readily prepared modular reagents with appropriate functionality compatible with a wide range of synthetic conditions. The direct synthesis method demonstrated here allows for the one-step functionalization of the gold core with both an ethylene glycol diluent ligand for solubility and stability along with functional groups to be used in subsequent azide-alkyne coupling reactions. In the final illustrative approach, functionalized gold nanoparticles were used as building blocks in the construction of a functional nanomaterial assembly. A dilute ozone treatment to remove part of the ligand shell allows for the benefits of ligand-protected nanoparticles while still allowing the properties to the core to be utilized. This dissertation includes previously published and unpublished co-authored material.