We report the controlled growth of Au25(SR)18 and Au38(SR)24 (where R=CH2CH2Ph) nanoclusters of molecular purity via size-focusing from the same crude product that contains a distribution of nanoclusters.In this method,gold salt was first mixed with tetraoctylammonium bromide (TOAB),and then reacted with excess thiol to form Au(I)-SR polymers in THF (as opposed to toluene in previous work),followed by NaBH 4 reduction.The resultant crude product contains polydisperse nanoclusters and was then used as the common starting material for controlled growth of Au25(SR)18 and Au38(SR)24,respectively.In Route I,Au25(SR)18 nanoclusters of molecular purify were produced from the crude product after 6 h aging at room temperature.In Route II,the crude product was isolated and further subjected to thermal thiol etching in a toluene solution containing excess thiol,and one obtained pure Au38(SR)24 nanoclusters,instead of Au25(SR)18.This work not only provides a robust and simple method to prepare both Au25(SR)18 and Au38(SR)24 nanoclusters,but also reveals that these two nanoclusters require different environments for the size-focusing growth process. We report the controlled growth of Au25 (SR) 18 and Au38 (SR) 24 (where R = CH2CH2Ph) nanoclusters of molecular purity via size-focusing from the same crude product that contains a distribution of nanoclusters. In this method, gold salt was first mixed with tetraoctylammonium bromide (TOAB), and then reacted with excess thiol to form Au (I) -SR polymers in THF (as opposed to toluene in work), followed by NaBH 4 reduction. The resulting crude product contains polydisperse nanoclusters and was used as the common starting material for controlled growth of Au25 (SR) 18 and Au38 (SR) 24, respectively. Route I, Au 25 (SR) 18 nanoclusters of molecular purify were produced from the crude product after 6 h aging at room temperature.In Route II, the crude product was isolated and further subjected to thermal thiol etching in a toluene solution containing excess thiol, and one obtained pure Au38 (SR) 24 nanoclusters, instead of Au25 (SR) 18.This work not only provides a robust and simple method to prepare bot h Au25 (SR) 18 and Au38 (SR) 24 nanoclusters, but also reveals these two nanoclusters require different environments for the size-focusing growth process.