Zinc　oxide　(ZnO)　flower-like　nanosheets　and　nanorods　were　synthesized　on　a　glass　substrate　with　an　Al　layer　by　a　simple　chemical　bath　method,　and　their　morphology　was　controlled　by　adjusting　the　pH　of　the　solution　without　the　assistance　of　an　additional　surfactant.　For　the　3D　nanostructures　of　the　annealed　nanosheets,　the　blue　light　emission　at　about　410　nm　disappeared,　which　may　be　due　to　the　defect　of　zinc　vacancy.　The　emission　of　the　yellow　band　at　about　550　nm　was　enhanced,　which　could　have　originated　from　the　interstitial　oxygen.　These　results　indicate　that　the　concentrations　or　types　of　the　dominant　defects　could　be　changed　because　of　the　diffusion　of　Al　substrates　during　the　course　of　annealing.　The　as-prepared　flower-like　nanostructures　of　nanorods　exhibited　a　high　UV　emission　peak　(at　about　380　nm).　After　the　samples　were　annealed,　the　green　emission　(at　about　500　nm)　was　also　enhanced　abnormally,　except　for　the　UV　emission　(at　380　nm),　indicating　that　the　crystalline　quality　could　not　be　improved　by　annealing　for　complex　nanostructures,　except　for　the　top　of　the　structures.　Our　results　present　a　simple,　reproducible,　and　cost-competitive　method　to　synthesize　ZnO　three-dimensional　flower-like　structures　and　would　provide　useful　information　for　the　fabrication　of　optoelectronic　devices　at　room　temperature.　©　2023　Author(s).