We have developed a platform that allows for real time optical sensing based on localized surface plasmon resonance (LSPR) readout inside a transmission electron microscope (TEM). With the TEM, we obtain insight into the structure and composition of materials by performing imaging and spectroscopy with atomic resolution [1]. However, the probed volume is rather small, and the beam-specimen interaction is often non-negligible and needs to be taken into account, usually by performing additional experiments. Thus, there is an increasing effort towards enabling simultaneous TEM probing and characterization with complementary techniques. Thanks to the strongly enhanced electric fields generated around metallic nanoantennas, LSPR-based sensing is a proven tool to study processes at the nanoscale [2], and an ideal complement to TEM since it probes a much larger volume of the specimen.

We have fabricated a TEM specimen holder hosting a miniaturized optical bench [3] that allows for sample illumination and spectroscopic readout. Specimens can be heated up to 1300 ºC, and the holder is compatible with differentially pumped environmental TEM (ETEM), with no prior modification to the microscope required. Comparison between signals obtained simultaneously by TEM and LSPR provides indication of the relevance of electron beam-induced effects. Moreover, we enable for the first time direct correlation of the LSPR response with changes in physical properties of the specimen. We investigate thermally-induced sintering of metal nanoparticles, a crucial process in deactivation of catalysts [4]. We envision the combination of LSPR sensing with probing by ETEM to become a versatile tool to study processes at the nanoscale, especially taking place on (photo)catalysts.