Multifunctional Harmonic Nanoparticles: Synthesis, Optical Properties and Recent Applications in Bio-Imaging

Dear Colleagues,

Non-centrosymmetric metal oxide nanocrystals, also called “harmonic nanoparticles” (HNPs) because of the great richness of their non-linear optical (NLO) response, have attracted substantial interest over the last decade as new exogenous bio-labeling probes as they can be excited in the three biological transparency windows, circumventing the limitations (low penetration depth, photo-bleaching, blinking, optically resonant conditions, etc.) of most fluorescent probes. Based on the known NLO performances of their bulk counterparts, BaTiO₃, KTiOPO₄ (KTP) and LiNbO₃ nanocrystals were first developed and used for several bio-imaging proof-of-concept studies. More recently, other nanocrystals such as BiFeO₃, ZnO, La(IO₃)₃, KNbO₃, etc., have been synthesized and studied with the goal of better assessing their spectral NLO response (second, third, or higher-order harmonic generation), increasing their biocompatibility and adding new optical and chemical functionalities. In terms of synthesis methods, various solution-based techniques have been tested, but challenges are still ahead as understanding/controlling the nucleation and growth mechanisms is a prerequisite to the large-scale preparation of HNPs showing size and shape control (in the 5-500 nm range), high crystal quality, colloidal stability, and well-characterized optical properties.

This Special Issue of Nanomaterials will highlight different aspects of HNPs spanning from their chemical preparation to their specific optical properties but will also focus on more recent breakthroughs. Research articles and reviews can thus address (but are not limited to) the wet-chemical routes leading to the HNP synthesis, their growth mechanisms, the preparation of new non-centrosymmetric hosts, the incorporation of luminescent species opening additional properties like up-conversion processes, scattering of harmonic signals from suspensions or at the single-particle level, Mie and plasmonic resonances, surface functionalization, bio-imaging, and multi-photon microscopy studies.

Dr. Yannick Mugnier
Dr. Geraldine Dantelle
Guest Editors

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• non-centrosymmetric metal oxides
• synthesis and growth mechanisms
• size and shape control
• second and third harmonic scattering
• spectroscopy
• luminescence from rare-earth ions
• up-conversion
• plasmonic enhancement
• polarization-resolved studies
• multi-photon microscopy