OICC Press International Journal of Nano Dimension 2228-5059 17 2 2026 04 10 Band Gap Enhancement and Violet Luminescence from Chemically Synthesized Copper Oxide Nanospindles and Its Antimicrobial Activity Against S. Aureus and K. Pneumoniae 10.57647/ijnd-2026-1702-08 EN Suvayan Mandal Department of Physics, Midnapore College (Autonomous), Paschim Medinipur, West Bengal, India; Department of Physics, Raiganj University, Uttar Dinajpur, West Bengal, India https://orcid.org/0000-0002-5757-5791 Pinaki Chakraborty Department of Physics, Raiganj University, Uttar Dinajpur, West Bengal, India https://orcid.org/0000-0002-2858-535X Pijus Kanti Samanta Department of Physics, Prabhat Kumar College, Contai, Purba Medinipur, West Bengal, India https://orcid.org/0000-0001-9330-713X Journal Article 2026 04 10 A simple wet-chemical method has been deployed to synthesize copper oxide (CuO) nanostructures. FESEM images revealed the formation of uniform-sized, spindle-like nanostructures. The TEM image revealed that the nanospindles are composed of several small crystallites. The distinct diffraction peaks in the XRD pattern confirm well-crystalline nanostructures and the average crystallite size was ~10 nm. FTIR spectra revealed the formation of Cu-O bonds. The band gap of the nanocrystals was calculated from the absorption spectra and was estimated to be 3.28 eV. Quantum confinement effect is therefore found to be very significant in these nanocrystals, manifested by the band gap enhancement. The synthesized CuO nanospindles exhibit strong photoluminescence peaked at ~ 407 nm owing to band-to-band transition. This emission peak is due to the transition associated with low energy peaks at ~ 461 nm due to shallow levels created below the bottom of the conduction band. The nanostructure showed significant antimicrobial activity against S. Aureus (Gram-positive) and K. Pneumoniae (Gram-negative) bacteria as studied by agar well diffusion technique. The zone of inhibition depends on the concentration of nanoparticles as revealed from the study. Therefore, the synthesized CuO is of immense potential for optoelectronics and biomedical applications.