Localized surface plasmon

Surface plasmon resonance

Plasmon

Physics

Surface plasmon

Resonance (particle physics)

Nanoparticle

Nanotechnology

Atomic physics

Materials science

Silver nanoparticle

Optoelectronics

Nano-Structures & Nano-Objects

Silver (Ag) and silver-polyvinylpyrrolidone (Ag-PVP) nanoparticles (NPs) were effectively synthesized by a green synthesis method using Moringa oleifera with various PVP concentrations (1.70, 2.55 and 4.25 ppm). The localized surface plasmon resonance (LSPR) behavior of the Ag-PVP NPs was investigated using the Kretschmann configuration with a layer arrangement of prism/Au/Ag-PVP NPs/air. The Ag NPs were spherical with a face-centered cubic crystal structure and a dispersed particle size of 22 nm. The size of the NPs decreased to 20, 19 and 15 nm with increasing PVP concentrations. PVP plays a vital role in crystallite size regulation; the higher the concentration of PVP, the narrower the particle size distribution. The UV–visibleabsorption spectra showed an LSPR band at 326 nm which blue-shifted to 325, 323 and 321 nm as the PVP concentration increased. This is because the size of the NPs decreased with increasing PVP concentration. Fourier-transform infrared spectra verified the intermolecular interaction between PVP and the Ag NPs, as indicated by the peaks at 3,326–3,330 cm −1 , corresponding to the hydroxyl group, and the sharp and strong peaks at 1,633–1,638 cm −1 , corresponding to the carbonyl group. PVP compounds containing nitrogen (N) and oxygen (O) atoms were coordinated with Ag + , forming a closed layer on the particle surface, which inhibited agglomeration and shifted the wavelength to a lower value. The results showed that the LSPR angle shifted toward a larger incidence angle due to the Ag-PVP NPs. Increasing the PVP concentration caused a large shift in the LSPR angle owing to the change in the size and thickness of the PVP layer of NPs, which changed the dielectric constant of the NPs. This proves that the use of PVP can help control the microstructural and LSPR properties of green synthesized Ag-PVP NPs and potentially optimize the performance of SPR-based sensors in the future.

Localized surface plasmon resonance properties of green synthesized silver nanoparticles