In the last couple of decades, biophotonics has become an important area of biomedical research. It has contributed to the improving understanding of biological phenomena. In this context the recent emergence of bio-imaging based on nonlinear microscopies (such as second harmonic generation and two-photon excited fluorescence) as a major topic of study, has been made possible by significant optimization of probes response.
The chemists play a major role in the design of new probes with improved spectroscopic properties for in-depth imaging of organisms, and high specificity for targeted compartments with a minimization of toxicity. This second issue of Display and Imaging (DI) is related to Novel Approaches for Linear and Nonlinear Optical Probes.
Kenji Kamada rationalizes the shapes of biphotonic spectra high energy parts of numerous non-centrosymmetric molecules with respect to corresponding linear spectra. He shows that the overlap between one-photon and two-photon spectra, generally observed for the lowest excited state, cannot be generalized at higher energy levels. This trend is interpreted on the basis of the study of different contributions in the theoretical two-photon absorption cross-section expression based on three-level model.
Frédéric Bolze et al reports molecular engineering work on diketopyrrolopyrrole derivatives for biological applications based on biphotonic microscopy. This paper presents the main advantages of this family, in terms of fluorescence quantum yield and photostability, which are relevant characteristics required for probes in the view of their use in bio-systems.
Anthony D’Aléo and Frédéric Fages present the state of art on solidstate emission properties of new dyes based on boron complexes of monoanionicbidentate ligands containing two coordinating heteroatoms, as alternative to the well-known borondipyrromethene (BODIPYs) families. The authors emphase the important role of π-π interactions, which could lead to aggregation induced enhanced emission (AIEE) effects to produce emission in the visible with a significant Stokes shift for imaging
Finally, Ileana Rau, François Kajzar et al describe spectroscopic, electronic and electrochemical properties of a conjugated natural anthocyanine, the maldivin molecule. This is a charge transfer non-centrosymmetric molecule, which presents a strong solvatochromism effect and photoluminescence interesting for display and imaging applications.
This issue contains innovative results on sensors engineering, which is actually a hot research area. Although it was difficult to obtain a wide sample of results in this field, I wish that this issue will illustrate some novel directions for bio-probes and imaging. I acknowledge deeply all the authors of this issue, and the editors of Display and Imaging, who gave me the opportunity to contribute to this issue.
May 23, 2014