Project Leader: Dr. Eng. Marcin Szalkowski
The synthesis and study of nanomaterial properties constitute a highly important branch of modern science, intensively developed at the intersection of several disciplines. Among numerous nanomaterials, two stand out for their particularly broad application potential: metallic nanoparticles (MNs) and inorganic nanocrystals doped with rare-earth ions (NCs). Both materials share high stability, biocompatibility, and the possibility of tuning their optical properties during chemical synthesis. Additionally, they offer extensive opportunities for surface functionalization, further expanding their range of possible applications.
Metallic nanoparticles are distinguished by their ability to exhibit plasmon resonance, i.e., collective oscillations of the electron gas, which results in strong electromagnetic field concentration around them. This allows significant influence on nearby emitters, enabling precise control of their emission—from strong enhancement to complete quenching. Moreover, such materials can be used as efficient converters of light energy into heat. The optical properties of MNs depend on their size and shape, which can be precisely controlled during chemical synthesis.
In the second material, lanthanide-doped nanocrystals, an up-conversion (UC) process occurs, in which the energy of two absorbed photons is subsequently emitted as a single photon of higher energy. This allows activation by near-infrared light, a range for which biological tissue transmission is high. Combined with the mentioned high stability and biocompatibility, NCs become a useful tool for bioimaging and the construction of biosensors enabling non-contact investigations of biological structures. A particular type of UC is avalanche emission, characterized by extreme sensitivity to changes in excitation power—small variations can lead to emission intensity changes spanning several orders of magnitude. Materials exhibiting avalanche emission, while retaining all the advantages of conventional up-converters, open new possibilities, including super-resolution imaging beyond the diffraction limit, optical logic operations, optical memory, highly sensitive temperature measurements, and more.
The influence of plasmonic excitations on avalanche emission parameters remains largely unexplored. However, evidence suggests that combining these effects could be advantageous—nanoscale control of the electric field distribution provided by properly designed metallic nanostructures could enable precise stimulation of avalanche emission in NCs. Achieving this requires not only matching the spectral parameters of interacting materials but also maintaining appropriate spacing between them. This can be achieved via chemical surface modification of both materials, enabling their assembly into structures with predetermined geometry. Furthermore, introducing suitable chemical groups allows specific attachment of additional components—chemical compounds or biomolecules—to such hybrids.
The aim of the project is to conduct fundamental studies of interactions between MNs and NCs exhibiting avalanche emission and, through understanding the functioning of such systems, to create multifunctional nanoassemblies. These assemblies will enable bioimaging and temperature measurements, as well as pave the way for therapeutic applications and infrared light stimulation of biological or chemical structures.