Quantum dots research benefits from neutron scattering
12 May 2026 - Peter Hurrell
An international team of researchers have demonstrated a new approach to precisely controlling the size of indium chloride quantum dots. Such quantum dots (QDs) are used in lighting and displays, as well as in medical imaging, photonics and as sensors.
The team also showed that the ligands used during the process could be isolated and reused following a simple crystallisation, improving the sustainability of the process. Small angle neutron scattering on the SANS2D instrument at ISIS, together with small angle X-ray scattering, confirmed the size and morphology of the quantum dots produced.
Reducing environmental harm
III–V Quantum Dots are semiconductor crystals that range from just a few nanometres up to tens of nanometres in size. They can emit light, with the wavelength emitted corresponding to their size. As a result, manufacturers need to be able to precisely control the manufacturing process if they are to produce high quality, consistent QDs for applications such as screens and low energy lighting.
Many QDs are manufactured from toxic metals such as cadmium. To shift to less environmentally damaging substances such as indium, researchers need to refine the manufacturing process. To address this, most previous studies have focussed on the phosphorus precursor. However, the researchers from the University of Keele, Politecnico di Milano and ISIS decided to look at the indium source instead.
Sustainable and cost-effective
For their study, the team investigated indium chloride (InCl3) as well as four triarylphosphine adducts of InCl3. For each, the indium precursor was mixed with oleylamine and heated. At this stage, the indium forms monomers, which then start nucleating to form the quantum dots. The second stage of the process involved the growth of the QDs to the required size. Separating these processes in time is key to controlling QD production.
During the experiment the researchers measured change in light spectrum emitted over a two-hour period from samples drawn from the experimental setup. They found these samples emitted light of increasing wavelengths over time, as expected from growth of the QDs. All the indium precursors showed rapid growth in the first ten minutes of the reaction, followed by a decreasing growth rate until the experiment concluded after two hours. Using the triarylphosphine adducts increased the initial speed of growth, but all five resulted in QDs of similar size by the end of the experiment.
Once the full two-hour period was over, the team used neutron and X-ray small angle scattering experiments to confirm the size and morphology of the QDs produced. Small angle scattering is ideal for studying structure at nanometre length scales for samples suspended in solution. This study also exploited the use of both SANS and SAXS, as SANS is more sensitive to the adduct structure, whereas SAXS is more sensitive to the indium molecules. Using both techniques combined allowed the researchers to probe the complete structure of the quantum dots.
This was my first time working with the scientists at ISIS, and we had a fantastic time. They were very supportive with carrying out the experiments and collecting and analysing the data. The entire experience was very smooth. The SANS data enabled us to develop a better understanding of how the precursors influence the size of our QDs and was a very powerful technique for us. ISIS is truly a unique operation and we’re excited to plan our next experiments on the beamline.
Dr Peter Matthews, Keele University
They found that all five adducts resulted in QDs of similar size after two hours, confirming their earlier results. The morphology in all cases was shown to be core-shell spheres that are able to aggregate to form clusters.
The results confirm that researchers and manufacturers could precisely control indium chloride quantum dot growth by choosing the right triarylphosphine ligand and controlling the time the reaction is allowed to run for. The researchers were also able to recover around 90% of the triarylphosphine ligand through simple crystallisation, providing manufacturers with a more sustainable and cost-effective process.
Related publication: Precise control of InP quantum dot growth via recyclable indium adducts – Nanoscale (RSC Publishing)
