A new low-cost optical sensor could make it easier to detect airborne nanoparticles in workplaces and research settings. Using luminescent paper and a simple UV flashlight, the method offers a practical alternative to expensive laboratory-based exposure screening. If validated further, it could support safer handling of nanomaterials and improve workplace monitoring. 

Cost-effective detection of airborne nanoparticles  

Italian scientists developed a low-cost, paper-based luminescent sensor that can indicate the presence of airborne nanoparticles in the workplace using a UV flashlight. This provides a promising solution to the challenge of detecting nanomaterials in research and industrial settings. Current methods typically rely on expensive, time-consuming, laboratory-based methods that require specialised equipment and trained personnel. This makes routine screening difficult and expensive.  

A sensor based on luminescent paper 

The sensor is based on a simple principle. Cellulose filters (essentially paper) are coated with a polyvinyl alcohol (PVA) solution containing luminescent material. When nanoparticles come into contact with the coated paper, the intensity of the emitted light decreases. This change can be detected using a spectrofluorometer, but it can also be seen directly under ultraviolet (UV) light. In the reported experiments, the researchers used a standard, commercially available UV flashlight.  

Detection of particles of different sizes and compositions  

The study showed that the sensor could detect a broad range of airborne nanoparticles and provide a qualitative indication of particle size. In tests with silica nanoparticles, smaller particles (12 or 55 nm) formed continuous darkened regions on the sensor surface, while larger ones (500 nm) appeared as more isolated spots. The particle deposition and qualitative size indications were confirmed by electron microscopy. The system also successfully detected other particles such as zinc oxide nanoparticles and graphene despite having a different chemical composition. Importantly, the luminescent dye used in the sensor was found to be photostable at temperatures up to 60 °C for 24 hours and at humidity levels between 30 and 60%. 

Reflection by RIVM  

The concept of using luminescence-based sensors for detecting nanomaterials is not entirely new. Previous studies have used carbon nanodots. Due to their unique structure and properties, these sensors emit light that can be quenched upon contact with nanoparticles. Also, cellulose-based supports have been functionalised using a patented method designed for smart sensing of nanoparticles under UV illumination. However, the Italian scientists compared the performance of carbon dot-based sensors with that of luminescent dye-based sensors and found that the latter were more sensitive, photostable, and, unlike carbon dot-based sensors, suitable for large-scale production.   

In general, the use of optical sensors, including this luminescent-based technique, offers an attractive alternative to time-consuming laboratory-based spectroscopic methods that require a high degree of expertise. These sensors enable simple, cost-effective detection of nanoparticle contamination in the work environment. Before these sensors can be used in practice, a validation study is needed to determine both the lower and upper detection limits. Once validated, this luminescent-based sensor can be used as a screening tool to identify sources of nanoparticles in the workplace and to evaluate control intervention methods with immediate visualisation of results. Both of these applications are important for promoting worker safety in the nanomaterial manufacturing industry and for researchers handling and producing nanomaterials.