dome (Division of Microbial Ecology, University of Vienna) invited Prof. Ji-Xin Cheng (Boston University) as opening presenter to their yearly lecture series.
Ji-Xin Cheng developed the technique now marketed as optical-PTIR by Photothermal Specotroscopy Corp. Like PTIR/AFM-IR, o-PTIR is an absorption spectroscopy technique that leverages the local thermal expansion upon illumination with a infrared laser to improve spatial resolution beyond the limit of diffraction. While PTIR uses an AFM cantilever to read out the local thermal expansion, o-PTIR uses an optical read-out using a visible laser. Hence o-PTIR shares some of the properties of PTIR - mainly that additional sensitivity factors are added to the measurement. However, due the optical read out in o-PTIR the spatial resolution is tied probe laser (in the visible) while it is mostly determined by the AFM tip radius and thermal properties in PTIR.
Talking just about o-PTIR, however, would not do justice to Ji-Xin’s talk. In the broadest sense, his area of expertise is spectroscopy by shooting small things with lasers as fast as possible. His talk encompassed using stimulated Raman spectroscopy for high speed, high resolution, lable free bio imaging, rapid hyperspectral coherent anti-Stokes Raman spectroscopy based imaging using custom electronic, o-PTIR large scale imaging, photoacoustics, and targeted use of light to kill bacteria. All in all a testament to the versatility of spectroscopy for bio-analysis.
At a lunch after his talk, together with Arno Schintlmeister and Michael Wagner, Ji-Xin talked more about the vision for his future research - to make fast Raman imaging more broadly accessible to other researchers and to push the envelope with regards to spatial resolution and acquisition speed.