Osaka University researchers develop a tunable luminescent mixture that changes color and reversibly switches from a solution to a suspension when heated
Depending on their solubility, solids can completely dissolve in liquids to form clear solutions, or form suspensions that still contain undissolved solid. Solutions of polymers often have a lower critical solution temperature; only below this temperature is the polymer completely soluble at all concentrations.
These are pictures of LCST system under UV light irradiation at low temperature (left), high temperature (center), and during the course of decreasing temperature (right).
Credit: Osaka University
However, it is rare for non-polymeric mixtures to have a lower critical solution temperature because small molecules usually become more soluble as they are heated.
Osaka University researchers have now created a mixture of small organic and inorganic molecules that has a lower critical solution temperature. Their luminescent mixture is easily switched from a solution to a suspension and back again, simply by changing the temperature. The system, which has a different emission color depending on whether it is in the solution or suspension state, will be useful for the development of new thermo-responsive materials that change color when heated. The study was recently published in the journal Advanced Materials.
"This behavior is usually only observed in polymer systems," says Associate Professor Akinori Saeki, corresponding author of the study, "because they undergo structural changes at high temperatures that reduce their solubility. This is the first example of a luminescent molecule/ion-based lower critical solution temperature system."
The researchers based their system on methyl ammonium lead bromide nanoparticles, which have been used to develop new-generation LEDs and lasers. Noting that these nanoparticles are reversibly broken apart into their molecular components in the presence of certain amines, the researchers prepared a mixture of the nanoparticles with methylamine and other organic molecules.
At room temperature, the mixture was a clear solution that emitted blue light when it was irradiated under UV light. When the researchers heated this clear solution, however, it became white and cloudy, and then formed a yellow suspension above a critical temperature. The yellow suspension emitted green light when irradiated with UV light.
"Using X-ray diffraction, we found that the clear solution contained soluble 1D wires made up of lead bromide, methylamine and oleic acid," Dr Saeki says. "As the solution was heated, these wires rearranged into a co-crystal containing lead bromide and methylamine, which was insoluble in the solvent."
The intermediate co-crystal was an essential step before formation of the yellow nanoparticles at higher temperatures, and its assembly and fragmentation were mediated by the organic molecules oleic acid and methylamine.
Tuning the system by varying the concentrations of the organic molecules or adjusting the ratio of halide ions (chloride, bromide and iodide) in the nanoparticles, the researchers have developed a series of multicolored systems with the same luminescent behavior, and hope to use them in new-generation photomaterials.
Saori Obayashi | EurekAlert!
Game-changing finding pushes 3D-printing to the molecular limit
20.06.2018 | University of Nottingham
Creating a new composite fuel for new-generation fast reactors
20.06.2018 | Lobachevsky University
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
21.06.2018 | Earth Sciences
21.06.2018 | Life Sciences
21.06.2018 | Earth Sciences