Surface plasmon enhanced linear and nonlinear optical properties of lycopene bioconjugated silver nanoparticles

The synthesis of lycopene@silver nanoparticle bioconjugates by pulsed laser ablation in liquid was studied. The ablation product was characterised by UV-Vis optical absorption, Raman spectroscopy and transmission electron microscopy (TEM). The experimental results were confirmed by the computational studies. Furthermore, to assess the influence of the surface plasmon on nonlinear optical (NLO) responses, in this work, we investigated the NLO properties of lycopene@silver systems using the density functional theory (DFT) approach at the M062X/6-311 + G(d,p)/LANL2DZ level. In addition to molecular descriptors, the static and dynamic (at the working wavelengths of the device, 1064 nm and 532 nm) polarizability (α), first hyperpolarizability (β), and second hyperpolarizability (γ) were calculated. Compared to the lycopene molecule, results of the lycopene@Ag₈ system show increased values of + 3.95 D, 63.3 × 10^-24 esu, 135.97 × 10^-30 esu, and 5.85 × 10^-34 esu, for μ, α₀, β₀, and γ₀, respectively. We found that the static (ω = 0) enhancement results from Ag-lycopene interaction induced dipole modification, whereas the dynamic response (ω = 532 nm > ω = 1064 nm) exhibits wavelength-dependent plasmonic modification, being stronger at resonance (532 nm) due to localised field enhancement and weaker off-resonance (1064 nm) via higher-order effects. These findings allow us to hypothesise that the lycopene@Ag NPs could be used as third-order NLO materials with improved stability, high flexibility in molecular engineering, and flexible photonic devices. Bioconjugated lycopene with Ag NPs enhances local field effects, boosting both linear and NLO attributes.