A General Approach to Synthesize Metal Nanostructures by Using Cucurbit[7]uril

Various metal (iron, copper, zinc, platinum)-based nanostructures were synthesized by a simple, green, and one-pot reaction of respective metal precursor and a cucurbit[7] uril (CB7) in an aqueous alkaline mixture at room temperature. The metal nanostructures (MNS) were obtained without adding any additional traditional reducing or protecting agents and/or external energy sources. Further, we could be able to tune the size and shape of the MNS just by varying the experimental conditions such as reaction concentration. Depending on the metal salts and reaction conditions, we could be able to produce different sizes and shapes of nanostructures. For example, the diameter of the CuO and iron nanoparticles (NP) was observed as similar to 1 nm (even < 1 nm) which suggests the inclusion mechanism. However, the particle size of zinc and platinum was over 2 nm which suggests the capping mechanism for the well-dispersed nanoparticles. It is worth mentioning that the CB7 acts as both reducing and protecting agent for the preparation of various MNS at ambient conditions. This one-pot and green approach for the preparation of MNS in aqueous solution has various advantages due to its mild synthesis condition and no toxic materials were used or produced, which is an important aspect for the exploration of biomedical applications and environmental influence of several metal nanoparticles that are presently prepared in organic solvents.