Dendrimers finally have what it takes to break into the laser scene

May 07, 2020

Tsukuba, Japan - The advances in optical devices that we expect as consumers must be supported by the development of new materials. Microcrystallites of luminescent organic compounds can act as tiny laser sources for such devices, for example for use in displays and other components. Dendrimers offer numerous advantages as luminescent materials, however so far they have not been used as microcrystallites owing to their fragility and poor crystallinity. Now a team of researchers has produced dendrimers that form robust crystals with lasing properties. Their findings are published in Angewandte Chemie.

Dendrimers are polymers that grow out from a core through the addition of small molecules to form extended branches--which explains their name, derived from the Greek word for tree. Dendrimers have many advantages that make them interesting luminescent materials. They are highly soluble, which makes them easy to incorporate into systems; they have high quantum yields, meaning you get a lot of the light you put in back again; they are good at harvesting light; and they tend to show relatively low luminescence loss when condensed into a solid.

The researchers made a family of dendrimers--getting larger in size as the generation number increased--made up of carbazole units forming the branches around a highly fluorescent core. The dendrimers formed stable single crystals even when the solvent was removed, and could be analyzed by single crystal X-ray analysis. In fact, the third generation dendrimer, which has a molecular weight of 4,600 Da, is the largest organic dendrimer ever to have been analyzed in this way.

"Our dendrimers have two key parts," study corresponding author Professor Yohei Yamamoto explains. "The branches are made up of aromatic molecules that act as light harvesting antennas, collecting light made up of waves in many different planes, which is known as non-polarized light. This light is then transferred to the fluorescent core, whose structure leads to polarized light--light with waves in a single plane--being generated."

When the dendrimer crystals were subjected to strong optical pumping--the process used to amplify the signal in laser materials--they produced amplified spontaneous emission and lasing with little damage to the structure of the material or the optical properties.

"The family of dendrimers we produced remedies a number of issues that have prevented the properties of these materials being exploited. We therefore expect them to make a significant contribution to the development of organic materials for laser optics," says Professor Yamamoto. "The robust properties and laser emission of the crystals will be useful for components such as full-color optical displays and micro-optical circuits."
-end-


University of Tsukuba

Related Crystals Articles from Brightsurf:

A new method to measure optical absorption in semiconductor crystals
Tohoku University researchers have revealed more details about omnidirectional photoluminescence (ODPL) spectroscopy - a method for probing semiconducting crystals with light to detect defects and impurities.

Fat crystals trigger chronic inflammation
A congenital disorder of the fat metabolism can apparently cause chronic hyperreaction of the immune system.

First ever observation of 'time crystals' interacting
For the first time ever, scientists have witnessed the interaction of a new phase of matter known as 'time crystals'.

'Blinking" crystals may convert CO2 into fuels
Imagine tiny crystals that ''blink'' like fireflies and can convert carbon dioxide, a key cause of climate change, into fuels.

Laser takes pictures of electrons in crystals
Microscopes of visible light allow to see tiny objects as living cells and their interior.

Rubies on sapphire: Recipe for making crystals in flux
The effect of the holding temperature and solubility curve of rubies was elucidated, for Al2O3:Cr in MoO3 from 1050 to 1200.

Transparency discovered in crystals with ultrahigh piezoelectricity
Use of an AC rather than a DC electric field can improve the piezoelectric response of a crystal.

New photonic liquid crystals could lead to next-generation displays
A new technique to change the structure of liquid crystals could lead to the development of fast-responding liquid crystals suitable for next generation displays -- 3D, augmented and virtual reality -- and advanced photonic applications such as mirrorless lasers, bio-sensors and fast/slow light generation, according to an international team of researchers from Penn State, the Air Force Research Laboratory and the National Sun Yat-sen University, Taiwan.

The secret behind crystals that shrink when heated
Scientists at Brookhaven Lab have new experimental evidence and a predictive theory that solves a long-standing materials science mystery: why certain crystalline materials shrink when heated.

Engineered protein crystals make cells magnetic
If scientists could give living cells magnetic properties, they could perhaps manipulate cellular activities with external magnetic fields.

Read More: Crystals News and Crystals Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.