Jan 22, 2019
(Nanowerk News) Nanotechnology and nanoscience are disciplines in which minute molecular structures with special physical and chemical properties are designed, manufactured and studied. One of the types of particles that are studied in these disciplines are quantum dots; they are semiconductor nanocrystals the size of which ranges between 2 nm and 10 nm and which have excellent optical and electronic properties. Worthy of mention is the fact that they emit light in different colours depending on their size, in other words, "the emission wavelength is varied just by varying the size of the nanocrystal, without modifying its composition," explained Alicia de San Luis, a POLYMAT researcher and author of this work (Israel Journal of Chemistry, "PS/PMMA-CdSe/ZnS Quantum Dots Hybrid Nanofibers for VOCs Sensors").
Microscopic image of quantum dots (dark points) encapsulated in polymer particles. (Image: Dr Mariano Barrado / UPV/EHU)
The properties of quantum dots render them potentially useful for a range of applications, such as detection in biomedicine, the production of solar panels and LEDs, their use as sensors of volatile organic compounds (VOCs), and as photosensitizers. Yet, "their drawbacks also need to be taken into consideration: they are difficult to handle owing to their small size, and are toxic, given that the quantum dots of higher quality mostly consist of heavy metals," pointed out the researcher.
To get the most out of the excellent optical properties of these nanoparticles, while not forgetting the toxicity problems they have, at the UPV/EHU's Polymat institute of research they have managed to efficiently encapsulate commercial quantum dots into polymer particles dispersed in water while maintaining the fluorescence of the quantum dots over long periods of time.
"The main aim was to encapsulate the quantum dots into slightly larger polymer particles to protect them and, at the same time, be able to handle them without them losing their properties," as the author of the research pointed out. "We have implemented a simple method yielding good results: polymer particles with fluorescence stable over a minimum of 9 months," she added.