Far infrared micro-spectroscopy: an innovative method to detect individual metal-organic framework particles

The purpose of this study is to extend the spectral range of a differential method of infrared micro-spectroscopy in order to allow the accurate detection of nanoparticles of interest for biomedical applications. Among these, metal-organic framework (MOF) nanoparticles have attracted increasing interest due to their capacity to incorporate high drug payloads, biodegradability, and possibility of tailoring their surfaces by grafting specific ligands. However, MOF particle detection in biological media without grafting or incorporating fluorescent molecules is challenging. We took advantage here of the presence of the specific absorption bands of nanoscale MOFs in far infrared in order to individually discriminate them. Here we show that single MOF nanoparticles can be imaged with a spatial resolution of a few tens of nanometers.