Perylene Dyes

Perylene dyes refer to the materials that use perylene as chromophore, and perylene diimide (PDI) and its derivatives are mostly researched. Perylene dye is a kind of compound with conjugated planar structure, strong π-π interaction, good thermal stability and high fluorescence quantum efficiency. The main absorption peaks of perylene dyes range from 400 nm to 600 nm, and the maximum molar absorption coefficient is 9.5L / (mol•cm). Due to the unique molecular structure, the solubility of perylene dyes is poor. Introducing large substituents on the N atoms of imines or bay region can increase the solubility. The optical properties and luminous efficiency of perylene dyes can be regulated by means of self-assembly, expansion of aromatic nucleus and selection of solvents.

Applications:

• Fluorescent probe field: Perylene dyes can be designed as metal ion fluorescent probes, DNA fluorescent probes and protein molecular fluorescent probes with high sensitivity, high selectivity and rapid response. For example, Fe³⁺ is a toxic metal ion that can cause harm to the nervous system, hematopoietic system and kidneys. Fluorescent probes designed by perylene dyes can realize the detection of Fe³⁺.

Figure 1. A Fe³⁺ fluorescent probe designed by perylene dye.

• Tumor therapy field: In the field of tumor therapy, perylene dyes can be designed as drug carriers, antitumor agents and fluorescent tracers. As drug carriers, perylene dyes could be self-assembled into nanoparticles and loaded with drugs. Specific groups, such as polyethylene glycol (PEG), can be introduced to transport the drugs to the corresponding lesions. By in vivo or in vitro stimulation, targeted release could be realized. Therefore, drugs concentration in the lesions will be improved and anti-tumor effect will be enhanced. In addition, real-time monitoring of drugs could be performed by the fluorescence of perylene dyes themselves.

Figure 2. An example of perylene dye used in tumor therapy.

• Solar cell field: Perylene dyes have excellent chemical stability, light resistance and high electron affinity, and the π-π stack between molecules results in high electron mobility along the stack direction. Furthermore, the energy levels of perylene dyes could be adjusted by chemical modification to meet the requirements of energy level as photovoltaic receptor materials. Therefore, this compound is one of the best N-type materials in the field of solar cells.

Figure 3. An example of perylene dye used in solar cell.

• Organic electroluminescence materials field: Organic electroluminescence materials are characterized by low cost, low toxicity, light quality, low starting voltage, and flexible device preparation. Due to excellent photothermal stability, chemical stability, adjustable luminescence color, high fluorescence quantum yield and excellent electronic transmission characteristics, perylene dyes have become a hot spot in the field of organic electroluminescence materials.

Figure 4. An example of perylene dye applied as organic electroluminescence material.

• The others: In addition to those mentioned above, perylene dyes could be applied in a variety of fields, such as liquid crystal materials.

Classification:

According to the solubility, perylene dyes can be classified into water-soluble, amphiphilic and water-insoluble perylene dyes.

• Water-soluble perylene dyes: Water-soluble perylene dyes have good solubility in water phase, which is helpful for biological applications.
• Amphiphilic perylene dyes: Amphiphilic perylene dyes can be constructed by introducing both hydrophilic and hydrophobic groups into the molecular structure. This type molecules play an important role in self-assembly.
• Water-insoluble perylene dyes: Water-insoluble perylene dyes have poor solubility in water phase, which limits the applications in biological environment.

References:

1. Głowacki E D, Irimia-Vladu M, Bauer S, et al. Hydrogen-bonds in molecular solids – from biological systems to organic electronics[J]. Journal of Materials Chemistry B, 2013.
2. Fan Q, Cheng K, Yang Z, et al. Perylene‐Diimide‐Based Nanoparticles as Highly Efficient Photoacoustic Agents for Deep Brain Tumor Imaging in Living Mice[J]. Advanced Materials, 2015.