In this study, we demonstrate the synthesis of stable large copper nanosheets using fast reduction at room temperature. Nanosheets are synthesized by reducing Cu(OH)42- with hydrazine hydrate in the presence of CTAB at room temperature. The size of the nanosheet is critically dependent on the concentration of NaOH and reducing agent, and an optimum concentration range has been determined experimentally. The large nanosheets may be centrifuged and dried into a powder and re-dispersed without any apparent size or shape change. Additional impurities (nano-rods, nano-particles) produced in the sub-optimal process is readily removed by the precipitation-re-dispersion process. While re-dispersing in chloroform, it was observed that the smaller nanosheets assembled like a pack of cards due to a high centrifugal field to form large nanosheets. © The Royal Society of Chemistry 2016.