BiFeO3 nanocrystals for bio-imaging based on nonlinear optical harmonic generation

TL;DR

This study explores BiFeO3 nanocrystals' potential as bio-imaging biomarkers by investigating their second harmonic generation efficiency and magnetic properties, highlighting their suitability for multiphoton imaging and diagnostics.

Contribution

First investigation of SHG in BiFeO3 nanocrystals demonstrating high nonlinear optical efficiency and magnetic response for bio-imaging applications.

Findings

BiFeO3 nanocrystals exhibit high SHG efficiency with <d> coefficient of 79+-12 pm/V.

Nanocrystals show moderate magnetic response due to gamma-Fe2O3 impurities.

Potential for combined nonlinear optical and magnetic bio-imaging applications.

Abstract

Second Harmonic Generation (SHG) from BiFeO3 nanocrystals is investigated for the first time to determine their potential as biomarkers for multiphoton imaging. Nanocrystals are produced by an auto-combustion method with TRIS as a fuel. Stable colloidal suspensions with mean particle diameters in the range 100-120 nm are then obtained after wet-milling and sonication steps. SHG properties are determined using two complementary experimental techniques, Hyper Rayleigh Scattering and nonlinear polarization microscopy. BiFeO3 shows a very high second harmonic efficiency with an averaged <d> coefficient of 79+-12 pm/V. From the nonlinear polarization response of individual nanocrystals, relative values of the independent dij coefficients are also determined and compared with recent theoretical and experimental studies. Additionally, the particles show a moderate magnetic response, which is attributed to gamma-Fe2O3 impurities. A combination of high nonlinear optical efficiency and magnetic response within the same particle is of great interest for future bio-imaging and diagnostic applications.