ORIGINAL PAPER Gum Acacia Modified Ni Doped CuO Nanoparticles: An Excellent Antibacterial Material Lalit Mohan Dwivedi 1 • Neelam Shukla 1 • Kirti Baranwal 1 • Surabhi Gupta 1 • Shehala Siddique 1 • Vandana Singh 1 Received: 15 November 2019 Ó Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Ni doped CuO Nps (Ni 0.1 CuO-GA) grown in gum acacia (GA) medium behaved as an efficient antibacterial material. The antibacterial activity of Ni 0.1 CuO-GA was much higher than the control antibiotic (Amplicillin) and simple Ni doped CuO Nps. Different concentrations of GA were used (as the growth medium) to tune the material’s bioactivity. Among the synthesized Ni 0.1 CuO-GA samples (G 1 –G 4 ), G 3 sample (synthesized using 1.5% (w/v) GA) showed optimum antibacterial activity. The corresponding undoped sample (CuO-GA) was less active. The structural, morphological, compositional and optical properties of G 3 have been determined by FTIR, XRD, FESEM, HR-TEM and UV–visible analyses. It exhibited excellent antibacterial activity for Enterobacter, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus bacterial strains (ZOI being 27 mm, 28.75 mm, 27.50 mm and 26.50 mm respectively). ZOI for the reference antibiotic for respective bacterial strains were 17.50 mm, 18.50 mm, 18.25 mm and 19.50 mm respectively, while ZOI for neat CuO Nps, G 1 ,G 2 ,G 4 and CuO-GA samples ranged between 21 and 24 mm for the same doses. The advantage Ni doping combined with the usage of GA as growth medium is evident by the excellent antibacterial behaviour of G 3 . Keywords Gum acacia Á Nickel Á CuO Á Nanoparticles Á Antibacterial activity Introduction Assemblies of hetero- or homo-nanostructures are of great interest [1] as they exhibit unusual physical, chemical and biological properties, different from the respective bulk materials [2]. The confluence of nanotechnology and biology has been utilized to address several biomedical issues [3]. Noble metal nanoparticles have been extensively investi- gated for their antibacterial effects [4]. Cu and CuO nanos- tructures are the economical alternatives of noble metal nanoparticles. Copper oxide is considered as one of the important metal oxide because of its low cost, abundant availability and peculiar properties. It is an important p-type transition metal oxide semiconductor material which has a narrow band gap of 1.2 eV. It finds use in photocatalytic and antibacterial applications [5], electrochemical sensors [6], light emitters [7], gas sensors [8], super capicitors [9], magnetic storage media [10], thermoelectric materials [11], photovoltaic cells [12], and catalysis [13]. Various physical and chemical routes are known for synthesizing CuO nanostructures such as reactive ion sputtering [14], electro deposition [15], pulsed laser evaporation [16], hydrothermal process [17], sonochemical synthesis [18], microwave combustion [19], and chemical methods [20], [21]. Amongst these techniques, the co-precipitation process has attracted substantial attention as this method is simple and cost effective. It requires low amounts of energy and can be carried out at ambient temperature. CuO nanoparticles are also known to have antimicrobial properties [22]; however their efficacy depends upon the size, stability and concentration of the nanoparticles which can be tuned by using certain growth mediums. Copper oxide nanoparticles (CuO and Cu 2 O) cause severe damage to the bacterial cell envelope. The toxicity of cuprous oxide (Cu 2 O) is because of the formation of copper(I)–peptide complex while cupric oxide (CuO) generate free radicals that harm the bacterial cells [23]. & Vandana Singh vschemau@gmail.com 1 Department of Chemistry, University of Allahabad, Allahabad 211002, India 123 Journal of Cluster Science https://doi.org/10.1007/s10876-020-01779-7