Jerome Wenger NanoBioPhotonics

Our latest work, published in ACS Photonics, introduces a new strategy to fabricate zero-mode waveguide (ZMW) nanoaperture arrays by sequential multi-step nanoimprint lithography.

ZMWs are powerful nanophotonic structures for single-molecule fluorescence detection, confining excitation light into extremely small volumes and enabling measurements at micromolar concentrations. However, their fabrication typically relies on electron-beam or focused-ion-beam lithography, limiting scalability and throughput.

Here, we exploit the controlled shrinkage of sol-gel materials during annealing to progressively reduce the aperture size over successive imprinting generations. Starting from a single master, four imprinting steps produce ZMWs from 230 nm down to just 115 nm in diameter, without requiring a new high-resolution master at each size.

The resulting structures combine sub-attoliter detection volumes with fluorescence brightness enhancements of up to 20× and more than one million detected photons per second per molecule under saturation. This work demonstrates a scalable route to progressively smaller nanophotonic structures, with strong potential for single-molecule fluorescence and large-area fabrication of nanoscale optical devices.

Beyond ZMW fabrication itself, this work demonstrates how sequential nanoimprint lithography can progressively generate smaller nanophotonic structures from a single master, offering a promising route toward scalable fabrication of nanoscale optical devices. 

Free open-access on ArXiv 2607.09141

Detecting polymer nanoparticles remains a significant challenge due to their weak optical contrast. In this work, we demonstrate a counterintuitive phenomenon: UV illumination enhances rather than bleaches the intrinsic autofluorescence of polystyrene (PS) nanoparticles. This enhancement enables the autofluorescence detection of individual PS nanoparticles down to 100 nm in diameter using a simple, cost-effective UV microscope setup.

Key Discoveries:
- Unexpected Behavior: Contrary to conventional photobleaching, the autofluorescence intensity of PS nanoparticles increases during UV exposure.
- Mechanism: The enhancement arises from reactive oxygen species (ROS)-mediated surface photodecomposition, which exposes fresh emissive domains of the nanoparticle.
- Performance: A 15× signal improvement pushes the limit of detection to 100 nm, enabling reliable single-particle imaging.
- Versatility: The phenomenon is preserved across various sizes and polymer materials (e.g., PMMA, melamine resin) and allows direct discrimination between polymer and metal nanoparticles.

By leveraging a simple UV microscope, this method offers a cost-effective and accessible alternative to more complex techniques like Raman spectroscopy or interferometric scattering microscopy. This approach unlocks new possibilities for high-sensitivity detection of polymer-based nanoparticles in fields such as analytical chemistry, biosensing and/or environmental monitoring.

Read the full paper on free repository: HAL-05686837

We are thrilled to announce that our latest research, "Single Nanoparticle Dynamics in Opto-Thermal Tweezers: Resolving the Temporal Resolution of Depletion Force Trapping", has been accepted for publication in ACS Nano!

In this work, we achieve a milestone by resolving the temporal dynamics of single 40 nm polystyrene nanoparticles in optothermal traps with sub-millisecond resolution. Using time-resolved fluorescence microscopy, we distinguish for the first time between transient localization and stable trapping, a critical ambiguity in previous studies that relied on ensemble averaging.

Our results reveal that residency times exceeding 1 second require PEG concentrations above 7% and IR intensities exceeding 6 mW/µm². Numerical simulations confirm our experimental observations, elucidating the interplay between thermophoresis and diffusiophoresis that governs nanoparticle motion.

This advance deepens our understanding of optothermal trapping mechanisms and paves the way for applications in single nanoparticle studies, nanoscale assembly, and drug delivery systems. We look forward to engaging with the community on these exciting findings!

We are thrilled to announce our latest publication in Advanced Functional Materials: "DNA-Origami-Assembled Rhodium Nanoantennas for Deep-UV Label-Free Single-Protein Detection" (DOI: 10.1002/adfm.202532006).

In this work, we pioneer a robust strategy for functionalizing rhodium nanocubes with DNA, enabling their assembly into programmable UV-plasmonic nanoantennas on DNA origami scaffolds. This breakthrough allows for the precise positioning of a single streptavidin protein within the plasmonic hotspot, achieving up to 22× brightness enhancement in deep-UV autofluorescence detection. Our approach overcomes the limitations of traditional UV-plasmonic materials by combining the chemical stability of rhodium with the addressability of DNA origami, opening new avenues for label-free, single-molecule spectroscopy in the deep-UV range.

This research marks a significant step toward deterministic, high-precision sensing of individual proteins without the need for fluorescent labels, with potential applications in structural biology and bioanalytical chemistry. It establishes label-free UV autofluorescence detection at the single protein level.

Read the full paper here.

Metal oxide nanoparticles play a pivotal role across many fields of nanoscience and nanotechnology, yet their detection remains challenging, requiring expensive SEM or TEM microscopies. Moreover, metal oxide nanoparticles generally form complex nanoaggregates of different sizes and morphologies, requiring experiments to be performed at the level of a single nanoaggregate to yield meaningful information.

In our recent article published in Particle & Particle Systems Characterization, we detail a novel application of ultraviolet (UV) microscopy for detecting metal oxide nanoparticles with high sensitivity and versatility. By leveraging the strong absorption of metal oxides in the UV spectral range, we demonstrate robust detection capabilities, validated through correlative electron microscopy and numerical simulations. Our results provide critical information characterizing the material and morphology parameters determining the UV response of metal oxide nanoaggregates

This work offers significant advancements for nanoparticle analysis, with potential applications spanning across material science, biotechnology, and environmental monitoring.