Chapter 8
Red and Near-IR Fluorescent
Two-Photon Absorption Dyes
Tsutomu Ishi-i
Abstract The two-photon excitation technique has several advantages such as
reduced autofluorescence and deeper penetration in tissues, less photodamage and
photobleaching, and higher three-dimensional resolution, which cannot be achieved
by linear one-photon excitation. Because of these advantages, two-photon absorption
(TPA) of organic molecules has been developed in biological and materials science
fields. In particular, fluorescent TPA dyes have attracted the attention of chemists
as well as biologists because of their application in biological imaging. At present,
various types of fluorescent TPA dyes that have large TPA cross sections as well
as good fluorescence quantum yields are accessible. However, the fluorescent color
has mostly been restricted to the shorter wavelength region of blue and green light,
which competes with the autofluorescence from intrinsic biomolecules. To achieve
efficient two-photon imaging, the longer wavelength emission of red and near-IR
light is required for two-photon excitation because this light lies in the biological
optical window. In this chapter, we focus first on fluorescent TPA dyes that have
red and near-IR light-emitting properties. Then, we summarize the recent advances
made in the development of these dyes for applications in biological systems. In the
last section, the unique features of two-photon absorption in aggregate systems are
summarized.
Keywords Two-photon absorption · Red fluorescence · Near-IR fluorescence ·
Biological imaging · Aggregation
8.1 Introduction
Two-photon absorption (TPA) is a nonlinear optical phenomenon (Marder 2006). In
contrast to linear one-photon absorption, two photons that are approximately twice
the wavelength (or approximately half the energy) are simultaneously absorbed upon
photoexcitation (Fig. 8.1). Thus, the red and near-infrared (IR) light regions can be
T. Ishi-i (B)
Department of Biochemistry and Applied Chemistry, National Institute of Technology, Kurume
College, 1-1-1 Komorino, Kurume 830-8555, Japan
e-mail: ishi-i@kurume-nct.ac.jp
© Springer Nature Singapore Pte Ltd. 2021
Y. Ooyama and S. Yagi (eds.), Progress in the Science of Functional Dyes,
https://doi.org/10.1007/978-981-33-4392-4_8
283
Red and Near-IR Fluorescent
Two-Photon Absorption Dyes
Tsutomu Ishi-i
Abstract The two-photon excitation technique has several advantages such as
reduced autofluorescence and deeper penetration in tissues, less photodamage and
photobleaching, and higher three-dimensional resolution, which cannot be achieved
by linear one-photon excitation. Because of these advantages, two-photon absorption
(TPA) of organic molecules has been developed in biological and materials science
fields. In particular, fluorescent TPA dyes have attracted the attention of chemists
as well as biologists because of their application in biological imaging. At present,
various types of fluorescent TPA dyes that have large TPA cross sections as well
as good fluorescence quantum yields are accessible. However, the fluorescent color
has mostly been restricted to the shorter wavelength region of blue and green light,
which competes with the autofluorescence from intrinsic biomolecules. To achieve
efficient two-photon imaging, the longer wavelength emission of red and near-IR
light is required for two-photon excitation because this light lies in the biological
optical window. In this chapter, we focus first on fluorescent TPA dyes that have
red and near-IR light-emitting properties. Then, we summarize the recent advances
made in the development of these dyes for applications in biological systems. In the
last section, the unique features of two-photon absorption in aggregate systems are
summarized.
Keywords Two-photon absorption · Red fluorescence · Near-IR fluorescence ·
Biological imaging · Aggregation
8.1 Introduction
Two-photon absorption (TPA) is a nonlinear optical phenomenon (Marder 2006). In
contrast to linear one-photon absorption, two photons that are approximately twice
the wavelength (or approximately half the energy) are simultaneously absorbed upon
photoexcitation (Fig. 8.1). Thus, the red and near-infrared (IR) light regions can be
T. Ishi-i (B)
Department of Biochemistry and Applied Chemistry, National Institute of Technology, Kurume
College, 1-1-1 Komorino, Kurume 830-8555, Japan
e-mail: ishi-i@kurume-nct.ac.jp
© Springer Nature Singapore Pte Ltd. 2021
Y. Ooyama and S. Yagi (eds.), Progress in the Science of Functional Dyes,
https://doi.org/10.1007/978-981-33-4392-4_8
283