Luminescent Materials

• OLED

• Iridium Complexes

• Ruthenium Complexes

• Photoluminescent Materials

• NLO Optical Materials

• AIE Materials

Introduction

Luminescent materials are materials that can absorb energy in a way then convert it into light radiation (non-equilibrium radiation). The process in which a substance absorbs energy from the outside and converts it into light energy is called luminescence. There are various luminescence modes of luminescent materials, including photoluminescence, cathodoluminescence, electroluminescence, thermo luminescence, photoluminescence, radioluminescence and so on.

Fig.1 The application of luminescent materials

Categories

Common and widely studied luminescent materials can be divided into electroluminescent materials (organic light-emitting diode is the main representative), photoluminescent materials, nonlinear optical materials, etc. according to the excitation mode.

• Organic light-emitting devices (OLED) materials: Organic electroluminescence refers to the phenomenon that organic semiconductor materials emit light when stimulated by an electric field, realizing the transformation from electric energy to light energy. Based on this phenomenon, OLED can be constructed with specific organic materials. OLED materials have many advantages such as low cost, no backlight, wide viewing Angle, good temperature adaptability, fast response, simple preparation process, light weight and flexible wear. Therefore, OLED products have been widely used in our daily life.

Fig.2 OLED materials in displayer, illumination and medical fields

• Photoluminescence materials: Photoluminescence refers to that an object depends on the external light source irradiation, so as to obtain energy and produce the phenomenon of excitation leading to luminescence. It roughly goes through three main stages: absorption, energy transfer and light emission. The absorption and emission of light all occur in the transition between energy levels and pass through the excited state. And the energy transfer is due to the motion of the excited state. Photoluminescence can be caused by ultraviolet, visible and infrared radiation, such as phosphorescence and fluorescence.

Fig.3 Photoluminescence materials: fluorescent powder

• Nonlinear optical materials (NLO): Nonlinear optical material refers to a kind of material whose frequency, phase and amplitude change under the action of external light field, electric field and strain field, thus causing changes in refractive index, light absorption and light scattering. They are capable of light wave frequency conversion and light signal processing. Therefore, these materials are widely used in laser frequency conversion, four-wave mixing, beam steering, image amplification, optical information processing, optical storage, optical fiber communication, underwater communication, laser countermeasures and nuclear fusion and also are important materials for future optoelectronic technology. They are mainly divided into second order nonlinear optical materials and third order nonlinear optical materials.

Fig.4 The application of Nonlinear optical materials in fiber-optic and nuclear fusion field

Alfa chemistry provides intermediates and related services for the above kinds of luminescent materials. If you do not find the product you need in the catalog, please contact us immediately, we will provide more detailed service. It is particularly noted that the complex of iridium and ruthenium, the transition metal, occupies an important position in the research of luminescent materials. In order to make it easier for customers to find, we assign the complex of iridium and ruthenium separately, hoping to bring you a better ordering experience.

Case Study

One-step Hydrothermal Synthesis of Hydrophilic Lanthanide UCNP

Zhou, Jing, et al. Chemical reviews. 2015;115(1):395-465.

In this paper, an one-step synthesis strategy is developed, which consists of a hydrothermal pathway assisted by binary synergistic ligands to prepare water-dispersed surface functionalized lanthanide UCNP.
Preparation scheme
• It involves the introduction of hydrophilic 6-aminocaproic acid and hydrophobic OA as binary synergistic ligands to control the nucleation and crystal growth of small nanoparticles.
• The water solubility of UCNP can be fine-tuned by changing the molar ratio of 6-aminocaproic acid to oleic acid.
• In addition, other compounds, such as polyethylene glycol bis (carboxymethyl) ether, can also be used as OA binary synergistic ligands for the preparation of hydrophilic UCNP.

Anti-Stokes Shift Luminescent Materials for Biological Applications

Zhu, Xingjun, et al. Chemical Society Reviews. 2017;46(4):1025-39.

Anti-Stokes shift luminescence materials have attracted much attention because of their unique ability to convert long-wavelength (low-energy) excited photons into biological applications, because long-wavelength light (i.e. near-infrared light, NIR) can penetrate deeper into biological samples, and unusual anti-Stokes shift luminescence avoids background fluorescence interference.
• Anti Stokes luminescent materials for biological imaging: Among tropical absorbing materials, rhodamine derivatives are mainly used for cell imaging to detect intracellular temperature or hazardous metal ions. The unique anti Stokes shift up conversion luminescence also enables rare earth probes to work together with other fluorescent species. There are few examples of using TTA based upconversion materials for cell imaging. Li et al. achieved blue light cell imaging using TTA based silica nanoparticles at low power density of 532 nm laser.
• Anti Stokes luminescent materials for biological detection: The molecular structure of tropical absorbing dyes is commonly used in the design of chemical dosimeters and can be easily modified to meet the needs of biological detection. For example, the designed NRH chemical dosimeter combines near-infrared (NIR) upconversion luminescent rhodamine derivatives and hydrazine cyclization reaction sites, which provide selective and sensitive turn-on response to copper (II) ions. The sensing system shows an extremely low detection limit, as low as 3.2 ppb.
• Anti Stokes luminescent material as a micro temperature reporter: One of the main characteristics of anti Stokes luminescence process is that the emission intensity is temperature dependent. Based on this principle, Prasad and his colleagues used the anti Stokes luminescence of Rhodamine 101 to measure cell temperature under a confocal microscope system.

Functionalization of Pyrene To Prepare Luminescent Materials

Feng, X., Hu, J. Y., Redshaw, C., et al. Chemistry–A European Journal. (2016, 22(34), 11898-11916.

Due to its large planar conjugated aromatic system, pyrene exhibits a high tendency for p-stacking and quasi molecular formation in condensed media, and is prone to quenching emission, resulting in a low photoluminescence quantum yield (PLQY). Therefore, in order to further improve its optical properties, recent research has mainly focused on functionalizing it.
Functionalization of Pyrene
• Formylation/Acetylation of Pyrene: Miyazawa developed a step-by-step synthesis route for 4,5,9,10-tetramethylpyrene using carbal-dehyde 7 as the starting material. Reduction of 7 with LiAlH4 in ether afforded 2,7-di-tert-butyl-4-methylyrene in 87% yield. Subsequently, treatment of 10 with Cl2CHOCH3 in the presence of TiCl4 as catalyst gave a mixture of methylpyrene 11-13. By repeating the two steps of reduction and formylation, a single 2,7-di-tert-butyl-4,5,9-trimethylpyrrole was obtained, which could further participate in formylation and reduction to obtain 20. This method provides a clear strategy to methylate the pyrene building blocks through a Lewis acid-catalyzed process in the K region, i.e., 4-, 5-, 9-, and 10-positions.
• Bromination of pyrene: In the presence of iron powder, 2,7-di-tert-butylpyrene undergoes bromination reactions with 1.1 mole equivalents and 2.2 mole equivalents of bromine, respectively, to obtain a mixture of 1-bromo-2,7-di-tert-butylpyrene (45) and 1,6-dibromo-2,7-di-tert-butylpyrene (46) and 1,8-dibromo-2,7-di-tert-butylpyrene (47), with contents of 85% and 73%, respectively. These compounds can be further brominated with excess bromine under iron catalytic conditions to obtain 44.
• Oxidation of pyrenes: Using RuCl3 as a catalyst and NaIO4 to oxidize pyrene (R=H and tBU) in CH2Cl2 medium, diketone 77 and tetraketone 78 were obtained at different stoichiometric ratios of bromine reagents. This route uses highly valuable RuCl3.
• Borylation of Pyrene: Since Marder and his colleagues first reported a new boronation reaction method for the one-step catalytic synthesis of pyrene-2-boronate ester 102, and pyrene-2,7-bis(boronate) ester 103 with yields of 68% and 97%, many new 2,7-di substituted pyrene compounds have been reported. Liu reported on the regioselective addition of 2,4,7-bis (boronic) ester 103 to the B2 n-hexane of B2 in n-hexane, resulting in a yield of 62% to obtain 2,4,7-triazine pyrene 104. Similarly, under the same conditions, the boronation reaction of 2,7-tert-butylpyran resulted in a yield of 45% to obtain 4-Bpin-2,7-di-tert-butylpyrene 105.