Jerome Wenger NanoBioPhotonics

The Institut Fresnel and IM2NP (Marseille, France), in collaboration with SolNil, offer a 5–6 month Master 2 internship focused on optimizing the nanofabrication of zero-mode waveguide (ZMW) nanoaperture arrays for single-molecule fluorescence detection.

The project combines sol-gel nanoimprint lithography, HF vapor etching and advanced characterization techniques, including electron microscopy and single-molecule fluorescence measurements. The goal is to improve the quality, reproducibility and performance of a cost-effective, high-throughput nanofabrication process.

Candidate profile: Master 2 students with experimental background in nanosciences, nanotechnology or micro/nanofabrication. Previous cleanroom or etching experience is an advantage.

Location: Marseille, France (Saint-Jérôme campus).

Eligibility: EU citizenship or residency required. Grants will be allocated for internships longer than 8 weeks, in accordance with current regulations.

PicoQuant has recently published two articles and an application note highlighting the use of our zero-mode waveguide (ZMW) nanoapertures with their Luminosa single-molecule fluorescence microscope.

ZMWs reduce the fluorescence observation volume to the attoliter range (10^-18 L or 0.001 µm³) enabling single-molecule measurements at concentrations far beyond the limits of conventional confocal microscopy. In recent work, we developed scalable ZMW arrays with 230 nm apertures and observation volumes of 10 aL.

Integrated with the Luminosa platform, these nanoapertures enable FCS measurements at micromolar concentrations, with enhanced molecular brightness and automated measurements across many individual ZMWs. In a demonstration, 88 ZMWs were measured automatically in ~85 minutes.

This collaboration marks an important step toward making nanophotonic single-molecule spectroscopy more accessible, quantitative and scalable. It also demonstrates the straightforward implementation of our nanophotonic ZMWs devices into a commercial confocal microscope.

Read the two PicoQuant articles:

• Zero-Mode Waveguides: Extending single-molecule fluorescence to higher concentrations
• FCS with Zero-Mode Waveguides: From individual nanoapertures to automated measurements

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!