title: Green synthesis of titanium dioxide nanoparticles using Psidium guajava extract and its antibacterial and antioxidant properties.
abstract: OBJECTIVE
  To determine the efficacies of antibacterial and antioxidant activities of aqueous leaf extract of Psidium guajava mediated biosynthesis of titanium dioxide nanoparticles (TiO2 NPs).
  
  
  METHODS
  Synthesized TiO2 NPs were tested by disc diffusion method against against human pathogenic bacteria. The total antioxidant activity and phenolic content (Folin-Ciocalteau method) of synthesized TiO2 NPs and aqueous plant extract were determined. The scavenging radicals were estimated by DPPH method. The synthesized TiO2 NPs were characterized by XRD, FTIR, FESEM and EDX.
  
  
  RESULTS
  FTIR spectra of synthesized TiO2 NPs exhibited prominent peaks at 3 410 cm(-1) (alkynes), 1 578 cm(-1), 1 451 cm(-1) (alkanes), and 1 123 cm(-1)(C-O absorption). The morphological characterization of synthesized TiO2 NPs was analysed by FESEM which showed spherical shape and clusters with an average size of 32.58 nm. The maximum zone of inhibition was observed in the synthesized TiO2 NPs (20 μg/mL) against Staphylococcus aureus (25 mm) and Escherichia coli (23 mm). The synthesized TiO2 NPs showed more antibacterial activity than the standard antibiotic disk, tetracycline which drastically reduces the chances for the development of antibiotics resistance of bacterial species. The plant aqueous extract and synthesized TiO2 NPs were found to possess maximum antioxidant activity when compared with ascorbic acid. The content of phenolic compounds (mg/g) in leaf aqueous extract and synthesized TiO2 NPs were found to be 85.4 and 18.3 mgTA/g, respectively.
  
  
  CONCLUSIONS
  Green synthesized TiO2 NPs provides a promising approach can satisfy the requirement of large-scale industrial production bearing the advantage of low-cost, eco-friendly and reproducible.
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India.
authors.forename: Thirunavukkarasu
authors.initials: T
authors.lastname: Santhoshkumar
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India. Electronic address: abdulrahuman6@hotmail.com.
authors.forename: Abdul Abdul
authors.initials: AA
authors.lastname: Rahuman
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India.
authors.forename: Chidambaram
authors.initials: C
authors.lastname: Jayaseelan
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India.
authors.forename: Govindasamy
authors.initials: G
authors.lastname: Rajakumar
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India.
authors.forename: Sampath
authors.initials: S
authors.lastname: Marimuthu
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India.
authors.forename: Arivarasan Vishnu
authors.initials: AV
authors.lastname: Kirthi
authors.affiliation: Unit of Nanotechnology and Bioactive Natural Products, Post Graduate and Research Department of Zoology, C. Abdul Hakeem College, Melvisharam - 632 509, Vellore District, Tamil Nadu, India.
authors.forename: Kanayairam
authors.initials: K
authors.lastname: Velayutham
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore 632 014. Tamil Nadu, India.
authors.forename: John
authors.initials: J
authors.lastname: Thomas
authors.affiliation: Department of Chemistry, Pukyong National University, Busan - 608 737, Republic of Korea.
authors.forename: Jayachandran
authors.initials: J
authors.lastname: Venkatesan
authors.affiliation: Department of Chemistry, Pukyong National University, Busan - 608 737, Republic of Korea.
authors.forename: Se-Kwon
authors.initials: SK
authors.lastname: Kim
keywords: Antibacterial activity; Antioxidant activity; Electron microscopy; FTIR; Psidium guajava; TiO(2) nanoparticles