Near infrared fluorescent nanomaterials for biosensing applications

Nanomaterials have novel properties due to quantum confinement and high surface areas and are therefore interesting for both fundamental studies and applications. One important property of many nanomaterials is fluorescence, which provides insights into electronic structure and local chemical processes. Additionally, fluorescence is a valuable tool to detect biomolecules. We are interested in 1D and 2D near infrared (NIR) fluorescent materials because this region of the spectrum (800 nm -1700 nm) promises ultra-low background and scattering. One example are semiconducting single-walled carbon nanotubes (SWCNTs). We developed different non-covalent concepts and quantum defects to tailor the organic phase around SWCNTs and tune both molecular interactions and photophysics. It allowed us to understand mechanistically how conformational changes of the organic phase affects the NIR fluorescence spectra of the SWCNTs. These functionalized SWCNTs can be used to detect and label (bio)molecules over multiple length scales: Single proteins, release of signaling molecules such as neurotransmitters from cells and stress (reactive oxygen species) in plants. Another example are 2D NIR fluorescent silicate nanosheets that have size-dependent fluorescence lifetimes in the µs range and enable lifetime-encoded fluorescence microscopy and detection methods. In summary, we present fundamental insights into the engineering of NIR fluorescent materials and their interfaces and the potential for biosensing.