A team from the University of Toronto Engineering has developed dye-sensitized nanoparticles capable of detecting subtle chemical differences, according to a September 14, 2026, report. The particles use upconversion to emit bright green light when exposed to near-infrared lasers, enabling precise detection of low-concentration chemicals and structural isomers. Created by Professor Kai Huang’s team, the breakthrough addresses a long-standing challenge in chemical sensing: distinguishing between molecules with nearly identical structures. By absorbing low-energy photons and re-emitting high-energy ones, the particles overcome limitations of traditional fluorophores, which only convert high-energy to low-energy light.
What makes our dye-sensitized nanoparticles special is that they are capable of upconversion, meaning that they can absorb light in the form of low-energy photons and emit higher-energy ones, Huang said
Solving the Back-Energy Transfer Bottleneck
The breakthrough hinges on solving a critical issue: back-energy transfer. When ytterbium ions are packed too densely, they absorb both incoming and outgoing energy, preventing erbium ions from emitting light. Jiaze Wu, a doctoral student in Huang’s lab and lead author of the new paper, explained that this back-energy transfer caused energy to bounce back to the ytterbium relay and never reach the surface.
To resolve this, the team redesigned the nanoparticle matrix. Instead of sodium, yttrium, and fluorine, they used lithium, lutetium, and fluorine. They also altered the shape of the particles, from flat hexagons to a more diamond-shaped 3D structure, and gave them multiple layers: a dense core surrounded by an inner shell, which in turn is surrounded by an outer shell. The concentration of embedded ytterbium ions gets denser as you go through each layer, with the core being the most dense, Wu said. This gradient allowed energy to flow almost entirely in one direction, inward toward the erbium ions.
Atomic Simulations and 150-Fold Brightness Boosts
The new structure significantly boosts brightness. According to Phys.org, the emitted light is roughly 150 times brighter than that of upconversion nanoparticles that haven’t been dye-sensitized and about 50 times brighter than some of the most optimized conventional structures previously reported under the same excitation conditions.
That’s how we showed that this core-shell-shell structure could actually function as a one-directional energy tunnel for incoming light,
Wu said.
The team’s simulations, led by undergraduate student Weixiang Ben, played a crucial role. Using Monte Carlo simulations and density functional theory, they tested dozens of formulations and geometries virtually before manufacturing the nanoparticles in the lab.
We used Monte Carlo simulations and density functional theory to simulate how the energy would interact between different parts of the nanoparticle, right down to the atomic or even subatomic level,
Ben said. This approach reduced trial-and-error and accelerated development.
Targeting Pharmaceutical Purity and Groundwater Safety
The nanoparticles’ sensitivity could revolutionize pharmaceutical manufacturing and environmental monitoring. They can detect structural isomers—molecules made of the exact same set of atoms but arranged slightly differently—which is critical for drug safety. If 10% of a batch is the wrong structural isomer, it can make the drug less effective or, worse, lead to side effects that you definitely don’t want, Wu said. Current detection methods rely on very expensive analytical tests, but the nanoparticles enable low-cost, small-sample analysis using low-cost lasers and a very small sample.
The technology also shows promise for groundwater pollution detection. By binding to trace chemical pollutants, the particles emit detectable green light, offering a non-invasive method for environmental monitoring. Huang compared the process to turning off the sun to see faint signals, noting that shifting the excitation frequency lower produces a zero-autofluorescence background in the samples you are analyzing, while the luminescent nanoprobes keep shining; it is like turning off the sun, so you can see the stars better.
Scaling Up for Industrial Implementation
While the proof-of-concept is complete, scaling production remains a challenge. We’re working on this already, in fact. We think it's feasible, but it requires a very long road map,
Huang said. The team’s design allows customization for any molecule you might want to detect, a feature he called something entirely new.
The research, published in the Journal of the American Chemical Society on September 14, 2026, marks a step toward practical applications. As Huang noted, In the meantime, this model serves as proof of concept; with this technique, we can produce a very high-performance upconversion nanoparticle that could be customized to any molecule you might want to detect.
The next phase will focus on refining manufacturing processes to meet industrial demands.
The nanoparticles’ design includes a transmission electron microscope image showing the 3D diamond shape of the new nanoparticles created by Huang, Wu, Ben and the rest of the team. The team’s work highlights a shift from previous flat-hexagon structures to layered, 3D geometries, improving both efficiency and applicability in real-world scenarios.