Phase evolution, surface chemistry, and antimicrobial performance of Ni-incorporated vanadium pentoxide complex oxides

Nickel-incorporated vanadium pentoxide (V 2-2x Ni 3x O 5-δ , 0.03 ≤ x ≤ 0.06) microparticles were synthesized and structurally characterized, revealing a biphasic composition dominated by orthorhombic V 2 O 5 with Pmmn space group and a minor triclinic NiV 2 O 6 phase with cap <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:mi>P</m:mi> <m:mover accent="true"> <m:mn>1</m:mn> <m:mo>̅</m:mo> </m:mover> </m:mrow> </m:math> P̅1 space group, as confirmed by Rietveld refinement. With increasing Ni content, the orthorhombic lattice parameters expanded due to ionic substitution. At the same time, the emergence of a distinct peak at 2θ = 23.57° indicated the onset of NiV 2 O 6 phase formation, reaching 12.2 wt% at x = 0.05 and signifying a solubility-driven structural transition. X-ray photoelectron spectroscopy (XPS) revealed the presence of mixed oxidation states of Ni (Ni 1+ , Ni 2+, Ni 3+ ) and V (V 4+ , V 5+ ), along with a chemically diverse oxygen environment comprising lattice oxygen, surface hydroxyls, and adsorbed oxygen species. The as-prepared compounds exhibited potent and broad-spectrum antimicrobial activity, demonstrating significant inhibition against the Gram-negative bacterium Pseudomonas aeruginosa and effective activity against the Gram-positive bacteria Staphylococcus aureus and Escherichia coli . The antimicrobial mechanism is attributed to a synergistic interplay of reactive oxygen species (ROS) generation, redox-mediated metal ion toxicity, and physical disruption of microbial membranes. Moreover, the increasing molar fraction of Ni enhanced antimicrobial efficacy, supporting a concentration-dependent increase in ROS production and microbial interaction.