Tomáš Lednický Develops Low-Cost Optical Sensors for ­Environmental and Health Analysis

Whether it’s contaminated drinking water or harmful gases, many pollutants enter the environment unnoticed and are difficult to detect. Their identification often requires specialized laboratories, expensive measuring instruments, and lengthy analysis times. As a result, regular environmental monitoring remains a challenge in many parts of the world. Tomáš Lednický is working on an alternative: optical sensors based on gold nanoparticles that aim to detect water and air quality more precisely, quickly, and affordably.

A sensor that detects pollutants using light – compact, cost-effective, and, in the future, possibly usable outside specialized laboratories with portable measurement systems: In his postdoctoral project at Leibniz IPHT, Dr. Tomáš Lednický is researching how gold nanoparticles can be fabricated into optical sensors and optimized for various applications.

Tomáš Lednický studied physical engineering and nanotechnology in Brno, Czech Republic, and completed research stays in France and Austria. With a Marie Skłodowska-Curie Fellowship (MSCA) from the EU, he came to Leibniz IPHT in Jena for his postdoctoral project DESIRE. “The institute offers me the opportunity to collaborate with international partners and further develop my research on LSPR sensors,” says Tomáš Lednický. An interdisciplinary approach that combines nanofabrication and biosensor technology is particularly important for him.

Gold as a Precision Tool

Gold is more than a precious metal – at the nanoscale, it becomes a powerful sensor. Gold nanoparticles interact with light, and their optical properties change depending on their immediate surroundings – a phenomenon known as localized surface plasmon resonance (LSPR). “The idea is simple: the sensors work like optical litmus paper,” explains Tomáš Lednický. “When a molecule binds to the gold surface, the transmitted light changes – and we can measure that.”

However, the sensor does not respond specifically to individual substances, but rather to any change in its surroundings – such as changes in the refractive index. “Our sensors are very sensitive, but not inherently selective,” says Tomáš Lednický. “To detect specific compounds, we need to functionalize them.” To do this, suitable molecules can be coupled to the gold nanoparticles: such as DNA sequences that bind only to complementary genetic information – for example, from viruses or bacteria. “We can also use molecules that detect hormones, pharmaceutical residues, or heavy metals. This functionalization makes our sensors extremely versatile.”

High-Sensitivity Sensors – Without High Costs

The production of ordered nanostructures smaller than 100 nanometers over large areas is labor-intensive and costly. Electron beam lithography, a technique for precise nanostructuring, can drive production costs up to ten thousand euros per wafer. Tomáš Lednický has developed an alternative method that drastically reduces these costs.

This involves creating a self-organized, honeycomb-like oxide layer on aluminum, which is then removed. This results in a fine network of nanoscale indentations, which serves as a template for a gold layer. When heated, nanoparticles form through dewetting. “Even at relatively low temperatures, tiny gold droplets form – similar to water droplets when a thin layer of ice melts,” says Tomáš Lednický. The result: highly sensitive sensors that can be produced for less than five euros per square centimeter.

More Precise Sensitivity Evaluation

An important step in sensor development is evaluating their sensitivity. Plasmonic sensors are often calibrated with liquids of different refractive indices. However, on the nanoscale, this method can lead to inaccuracies – for example, due to the formation of thin adsorption layers.

To improve this, Tomáš Lednický, together with other researchers, developed a new approach for objectively evaluating plasmonic sensors in 2024 – demonstrated with gas sensors. “Until now, there has been no standardized way to compare the performance of such sensors,” he explains. Their model takes into account the sensitivity drop from the nanoparticle surface and the thickness of the measured layer. “This allows us to quantify for the first time which sensors are actually more sensitive – regardless of the detection medium.”

Gas detection is a particularly challenging test field. “Gases are difficult to detect, mainly because of their stability and low refractive index,” says Tomáš Lednický. To address this challenge, he is working on coating the gold nanoparticles with ultra-thin layers of well-known gas-reactive materials like tungsten or zinc oxide. This allows the sensors to respond selectively to specific gases. A major advantage over many commercial gas sensors: they work at room temperature and allow remote detection – at significantly lower costs.

International Collaboration for Global Solutions

Tomáš Lednický collaborates with researchers from around the world, including Hungary, Portugal, and the Czech Republic. Last year, he presented his research findings at the IEEE Nano Conference in Spain and the Eurosensors Conference in Hungary. “Many laboratory techniques that are standard in Europe are not available elsewhere,” says Tomáš Lednický. “If we develop a technology that is precise, affordable, and easy to apply, we could make environmental and health analysis more accessible to many people.”

Original publication: https://doi.org/10.1021/acsami.4c11102