The discovery of C60 at Rice University has boosted the development of nanotechnology in the past decades. Materials at nanoscale possess distinct and excellent properties as compared to their bulk counterparts. Endowed with advantageous physical, chemical and electronic properties, nanomaterials have found promising applications in fields such as electronics, energy conversion, and energy storages. The performance of nanomaterial is usually correlated with its size, elemental constitution and hierarchical structure. My thesis begins with the investigation of zero dimensional nanomaterials in Chapter 1, which mainly focuses on the discovery and purification of graphene quantum dots (GQDs) from an abundant source: coal. I further explore of GQD applications as optical materials with tunable bandgap, and as electrocatalysts for the oxygen reduction reaction. Chapter 2 discusses the synthesis and applications of two dimensional nanomaterials, which includes the use of graphene-based hybrid and layered transition metal dichalcogenides in electrocatalysis. Finally, Chapter 3 studies the nanomaterials in three dimensional porous structures, namely laser-induced graphene. This chapter discloses the formation of hierarchical-structured graphene on commercial polymers and iii natural materials, and develops various applications in energy storage and energy conversion.