A Reusable Route to Trace Uranyl Detection
A magnetic SERS platform combines selective uranyl enrichment, portable Raman detection, substrate regeneration, and interpretable spectral classification.
A reusable magnetic SERS platform has been developed for trace uranyl detection, combining selective enrichment with portable Raman analysis and automated spectral interpretation.
The sensor pairs magnetic microspheres and gold nanoparticles with a covalent organic polymer that binds uranyl, the most common soluble form of uranium in environmental waters. That polymer layer concentrates the ions close to plasmonic hotspots around the gold, where their otherwise weak Raman signal can be amplified.
After a 20-minute enrichment step, the platform detected uranyl down to 1 × 10⁻⁷ mol·L⁻¹ through its characteristic Raman band near 850 cm⁻¹. The signal remained selective in the presence of common dissolved ions, and a flow-through test reproduced the same detection limit under moving-sample conditions.
“Our goal was to create a sensing material that can not only capture trace uranyl ions efficiently, but also produce reliable spectral signals that can be interpreted automatically,” said corresponding author Zhenli Sun in a recent press release.
Uranyl could also be removed with sodium carbonate, allowing the substrate to be reused; its characteristic SERS signal remained detectable after six adsorption–desorption cycles. A convolutional neural network classified spectra before and after uranyl adsorption with 100 percent accuracy in the study dataset. Grad-CAM analysis showed that the model relied primarily on the chemically meaningful 850 cm⁻¹ uranyl band rather than unrelated spectral features.
Because the classifier focused on the uranyl-specific Raman feature, the automated decision retained a clear chemical basis rather than functioning as a purely statistical distinction. The authors argue that combining that regeneration with portable Raman readout could make the platform more practical for repeated environmental monitoring.
A Panoramic View of the Infarcted Heart
The six-camera platform distinguishes healthy, border-zone, and scar tissue while tracking excitation and repolarization across infarcted hearts.
Scar tissue and electrical activity have been mapped together across the surface of infarcted hearts using a panoramic system that combines hyperspectral imaging with optical voltage measurements.
The George Washington University team used hyperspectral imaging to distinguish healthy muscle, infarct scar, and the border zone between them, allowing electrical behavior to be interpreted in its local structural context. The six-camera system combined a line-scan hyperspectral camera with four high-speed cameras for membrane-potential mapping and a separate camera for reconstructing the heart’s three-dimensional surface.
Ultraviolet excitation produced endogenous fluorescence from tissue components including collagen, while a voltage-sensitive dye recorded changes in transmembrane potential. The datasets were then registered onto a common panoramic surface map.
The researchers tested the approach on perfused rat hearts four weeks after experimentally induced myocardial infarction. Collagen-associated fluorescence between 400 and 520 nm distinguished infarcted and border-zone tissue, classifying the mapped surface into the three tissue types. Histology supported the tissue assignments.
Combining those maps with the electrical recordings showed how scar altered excitation. Premature ventricular contractions and reentrant activity appeared in three of the four hearts during pacing, with premature beats originating near the infarct border and propagating around the scar. Electrical activity also persisted longest in infarcted tissue, was shorter in the border zone, and shortest in healthy myocardium.
By combining panoramic hyperspectral tissue classification with electrical mapping across the entire heart surface, the system linked structural damage with changes in excitation and repolarization. The authors describe it as the first panoramic platform to bring those measurements together in a living perfused heart, providing a more complete view of how infarct architecture shapes arrhythmic behavior.
A Better Benchmark for Optical Sensors
Multilayer optical phantoms reproduce how increasing pigmentation attenuates blood-related hyperspectral signals.
Optical skin phantoms spanning lighter to darker skin tones have reproduced how pigmentation changes the visibility of blood-related signals in hyperspectral measurements, offering a controlled way to test light-based medical devices across a broader range of skin properties.
Researchers from the VTT Technical Research Centre of Finland created multilayer silicone phantoms representing the epidermis, deeper tissue, and subcutaneous fat, then embedded artificial vessels beneath the surface. A miniature pump circulated a blood-like liquid through the channels, allowing pigmentation and subsurface flow to be varied within the same controlled model.
The team then used hyperspectral imaging to compare vessel-containing regions with nearby vessel-free areas across a broad wavelength range. The resulting reflectance spectra closely matched the wavelength-dependent patterns reported for human skin, with the models spanning tones broadly comparable to those reported across European, South Asian, and African populations.
The measurements also showed how strongly pigmentation affected signal recovery. Blood-associated spectral contrast was readily visible in the lighter phantoms but weakened progressively as pigmentation increased. In the darkest model, the upper pigmented layer obscured much of the optical signature from the flowing fluid beneath it.
That attenuation is relevant to devices such as pulse oximeters and wearable optical sensors, which rely on light reaching vascular tissue and returning with enough contrast to support a reliable measurement. By varying pigmentation while keeping vessel geometry, flow, and other conditions controlled, the phantoms provide a way to isolate how skin tone influences device response without relying solely on comparisons between human volunteers.
The models also remained optically stable over nine months, supporting repeated or longer-term testing. The researchers plan to extend the range of skin tones represented and compare the phantom measurements directly with human skin, with the aim of providing a more consistent benchmark for evaluating optical-device performance across pigmentation levels.
The Inner Life of a 16th-Century Altarpiece
Robotic terahertz spectroscopy reveals subsurface changes in a 16th-century wooden altarpiece before and after conservation.
A 16th-century wooden altarpiece has been examined before and after restoration with robotic terahertz spectroscopy, revealing subsurface changes hidden beneath its painted surface.
The team studied the centerpiece of the Marienaltar at Isenhagen Monastery in Germany, where limewood had been weakened by common furniture beetle damage, fungal activity, and earlier interventions. A structured-light scan first reconstructed the sculpture’s three-dimensional surface, allowing a robotic arm to guide the terahertz measurement head safely across selected regions on the figures of Mary and the infant Jesus.
Terahertz pulses can pass through many non-metallic conservation materials and return reflected echoes from interfaces, voids, cracks, and other subsurface features. As the authors note, this provides “a tool to map the three-dimensional internal structure of the object,” allowing changes beneath the polychromy to be compared before and after restoration.
The analysis revealed both newly appearing and disappearing subsurface reflections near cracks and treated regions. In several areas, those patterns followed the expected spread of injected consolidant, while shifts in reflection arrival time pointed to changes in refractive index and material thickness. On the infant Jesus figure, for example, increased optical density was consistent with consolidation, while a separate region showed reduced density after surface contamination was removed.
Laboratory THz measurements of limewood and restoration materials helped interpret the in-situ data. Materials with refractive indices close to wood produced relatively weak contrast, while more strongly absorbing fillers could mask deeper layers, particularly at higher terahertz frequencies.
Robotic THz-TDS detected millimeter-scale structural changes introduced during conservation and distinguished several treatment effects beneath painted surfaces. Although moisture and strongly absorbing materials can limit penetration, the method provides a non-contact way to monitor whether restoration has altered subsurface structure as intended.
Newsletters
Receive the latest analytical science news, personalities, education, and career development – weekly to your inbox.
