Assessing quantum dot photoemissions

March 2, 2018, Kumamoto University
Kumamoto University's Professor Tetsuya Kida and team have shown that polyoxometalates may be used in a technique to assess quantum dot photoluminescence. Their research is highlighted on the cover of the January 2018 issue of Advanced Functional Materials. [Reprinted from Pramata, A. D., Suematsu, K., Quitain, A. T., Sasaki, M., & Kida, T. (2017). Synthesis of Highly Luminescent SnO2 Nanocrystals: Analysis of their Defect-Related Photoluminescence Using Polyoxometalates as Quenchers. Advanced Functional Materials, 28(4), 1704620. doi:10.1002/adfm.201704620 with permission from John Wiley and Sons] Credit: Professor Tetsuya Kida

Recent research from Kumamoto University in Japan has revealed that polyoxometalates (POMs), typically used for catalysis, electrochemistry, and photochemistry, may also be used in a technique for analyzing quantum dot (QD) photoluminescence (PL) emission mechanisms.

Quantum dots (QDs) are small, semiconducting nanocrystals or particles typically between two to ten nanometers in size. Discovered almost 40 years ago, their strong photoluminescent properties are a function of their size and shape making them useful for optical applications ranging from bioimaging to . Advances in high-quality QD research in the last ten years has produced highly luminescent but somewhat unstable QDs that also, unfortunately, use toxic or rare elements. Efforts to create stable QDs without these toxic or expensive elements has been a driving force in recent research.

To address these issues, researchers have been investigating how to change the size, morphology, and PL of tin dioxide (SnO2) to produce cheap, stable, and nontoxic colloidal semiconductor nanocrystals for various applications. Interestingly, the optical properties of SnO2 have been found to be effected by defects in both the bulk material and the QDs themselves.

Researchers from Professor Kida's Chemical Engineering Laboratory at Kumamoto University synthesized SnO2 QDs using a liquid phase method to produce QDs of various morphologies. The sizes of the QDs were controlled by changing the temperature during synthesis. All of the QDs produced a blue PL when exposed to UV light (370 nm) and QDs 2 nm in size produced the best intensity. To examine the PL properties and mechanisms related to defects in the synthesized QDs, the researchers used materials (POMs) that quench florescence through excited state reactions.

POMs quenched emissions of the SnO2 QDs at peak intensities (401, 438, and 464 nm) but, to the surprise of the researchers, a previously unseen peak at 410 nm was revealed.

"We believe that the at 410 nm is caused by a bulk defect, which cannot be covered by POMs, that causes what is known as radiative recombination—the spontaneous emission of a photon with a wavelength related to the released energy," said project leader Professor Tetsuya Kida. "This work has shown that our technique is effective in analyzing PL emission mechanisms for QDs. We believe it will be highly beneficial for future QD research."

Explore further: Quantum-emitting answer might lie in the solution

More information: Azzah Dyah Pramata et al, Synthesis of Highly Luminescent SnO2 Nanocrystals: Analysis of their Defect-Related Photoluminescence Using Polyoxometalates as Quenchers, Advanced Functional Materials (2017). DOI: 10.1002/adfm.201704620

Related Stories

Quantum-emitting answer might lie in the solution

November 28, 2017

Tapping into the quantum properties of photons for optoelectronics requires highly efficient light sources. Lead trihalide perovskite nanocrystals exhibit a number of properties that make them promising candidates as light ...

Extremely bright and fast light emission

January 10, 2018

An international team of researchers from ETH Zurich, IBM Research Zurich, Empa and four American research institutions have found the explanation for why a class of nanocrystals that has been intensively studied in recent ...

Many colours from a single dot

February 19, 2018

Physicists Bart van Dam and Katerina Newell (Dohnalova) from the UvA Institute of Physics, in collaboration with Emanuele Marino and Peter Schall as well as colleagues from the University of Twente and Jiljin University in ...

Recommended for you

Engineers produce smallest 3-D transistor yet

December 10, 2018

Researchers from MIT and the University of Colorado have fabricated a 3-D transistor that's less than half the size of today's smallest commercial models. To do so, they developed a novel microfabrication technique that modifies ...

New traffic rules in 'Graphene City'

December 6, 2018

In the drive to find new ways to extend electronics beyond the use of silicon, physicists are experimenting with other properties of electrons, beyond charge. In work published today (Dec 7) in the journal Science, a team ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.