Quantum Dots for Photodetectors
The near-infrared photodetectors used in biomedical sensing, defense, and security detect multiple wavelengths of light on a single chip. Quantum dots—nanoscale semiconductor particles—are ideal for this purpose, owing to their tunable optics, and can be engineered to absorb different light wavelengths. However, depositing quantum dots as a uniform film on textured, irregular chips has been a challenge.
In a January 16, 2025, paper published in Nanoscale, Livermore researchers describe a method they used to deposit quantum dots as a thin, consistent film. Electrophoretic deposition drove charged particles through a solution, and the dots migrated toward an electrode and assembled as a film. Switching the field on or off started or stopped the deposition, enabling selective coating of defined areas on a patterned chip. Through synthesizing the dots with short ligands (molecules that bind to and stabilize the dots in solution), the team reduced production time and obviated postprocessing. Livermore scientist and lead author Xiaojie Xu says, “By combining in-solution ligand exchange with electrophoretic deposition, this paper explains that dense, conformal and electronically functional quantum-dot films can be deposited in a single step.”
Contact: Xiaojie Xu (925) 423-9269 (xu17 [at] llnl.gov (xu17[at]llnl[dot]gov)).
Resolving X-ray Motion Blur
X-ray radiography is a useful, nondestructive tool to visualize the internal components of a structure. Time-integrated dynamic x-ray radiography enables the study of events occurring millions of times faster than the blink of an eye, such as high-explosive detonations. When radiography exposure time is long, interfaces between regions of differing densities blur and extend, making identifying the precise location of interfaces challenging, if not impossible.
In the October 26, 2024, issue of Scientific Reports, a Livermore team developed a methodology to quantify motion blur in dynamic events that addresses this problem. The researchers used the time-stepped outputs from Livermore’s hydrodynamics simulation code (ALE3D) as inputs to the radiographic ray-tracing simulation code (HADES) and simulated motion blur that closely matched experimental results.
Livermore researchers used data from gas-gun experiments at Argonne National Laboratory’s Dynamic Compression Center to test their simulation methodology, which is applicable to any geometry or sample material, provided its thermodynamic properties are known, and to any dynamic x-ray radiography platform at any energy range, given properties such as x-ray spectrum and exposure time. This successful demonstration of the methodology benefits large-scale, system-level experiments that are difficult to repeat and can serve as a reliable simulation tool for adjusting input parameters before an experiment to optimize image quality and extract physical parameters of interest.
Contact: Mukul Kumar (925) 422-0600 (kumar3 [at] llnl.gov (kumar3[at]llnl[dot]gov)).
Finding New Antifungals
Filamentous fungi are microorganisms characterized by hyphae or tubular filaments that can blight crops, spoil goods, foul industrial equipment, and trigger deadly infection in the immunocompromised. These fungi are common, thriving worldwide and increasingly resistant to the small number of available antifungal treatments. In an August 2025 study in Journal of Microbiological Methods, researchers at Lawrence Livermore introduced the Disk Diffusion Assay for Filamentous Fungi Susceptibility (DAFFS) test—a straightforward way to screen chemicals for fungicidal efficacy in potential treatments and drugs.
Using DAFFS, researchers deposited a fungus at the center of a plate to observe outward growth. Different antifungals were added to disks and placed on the plate to test the inhibition of the fungi’s outward growth.
With only one standardized fungal test currently available (for Aspergillus) the need for additional methods is high. Now, by using DAFFS, researchers can assay many filamentous strains more efficiently. Lead author Salustra Urbin observes, “We have many assays for various chemicals to understand whether they’re antibacterial, but not whether they’re antifungal. Our method doesn’t require sophisticated equipment and can be widely used.”
Contact: Salustra Urbin (925) 422-9320 (urbin2 [at] llnl.gov (urbin2[at]llnl[dot]gov)).
