Electrochemical properties of biogenic silver nanoparticles synthesized using Hagenia abyssinica (Brace) JF. Gmel. medicinal plant leaf extract

Abstract

The biogenic/green silver nanoparticles (g-Ag NPs) were synthesised by using the extract of indigenous medicinal plant of Ethiopia, Hagenia abyssinica (Brace) JF. Gmel. leaf extract for the first time, to investigate the synergistic effect of biomolecules towards the enhancement of electrochemical properties of NPs. The synthesized g-Ag NPs were characterized by UV-visible, UV-DRS, FT-IR, XRD, SEM, EDXA, TEM, HRTEM and SAED techniques. The maximum absorbance, λ _max was found to be 461 nm for g-Ag NPs due to surface plasmon resonance. The energy gap, E _g of NPs, was found to be 2.31 eV. FTIR spectrum confirmed the presence of bioactive compounds responsible for possible capping and stabilisation of g-Ag NPs. The XRD analysis revealed that the g-Ag NPs are highly crystalline exhibiting sharp peaks for (111), (200), (220) and (311) planes in the diffraction pattern. SEM and TEM micrographs showed differently shaped Ag particles in addition to spherical shape. The average particle size of NPs was found to be 24.08 nm using imageJ analysis. EDX analysis confirmed the presence of Ag in the g-Ag NPs. In addition, the SAED pattern of g-Ag NPs presented concentric patterns for 4 major planes of crystalline silver. The d-spacing values of 0.2428 nm, 0.2126 nm, 0.1483 nm and 0.1263 nm corresponds to d _111 Ag, d _200 Ag, d _220 Ag and d _311 Ag lattice fringes respectively. The cyclic voltammetry (CV) results suggest that g-Ag NPs possess better electrochemical properties due to its lower charge transfer resistance value of 17 Ω. EIS studies too revealed better stability of g-Ag NPs as electrode materials.

Keywords

• green synthesis
• Hagenia abyssinica (Brace) JF. Gmel
• g-Ag NPs
• EIS
• charge transfer resistance