Nanoparticle Micro-Extinction Spectroscopy (MExS)
Prof. Emilie Ringe
Optical Nanomaterials Group, Department of Materials Science and Metallurgy, University of Cambridge, UK
Background
Professor Emilie Ringe’s research is focused on optical nanomaterials, specifically how manipulating nanoscale attributes leads to changes in optical properties. Prof. Ringe further explained her work, “Currently we are really interested in plasmonic structures, which are basically metal nanoparticles, and these can resonate and have a light driven electron oscillation. There are only a few metals that can do that, gold and silver have traditionally been used, now we are exploring magnesium nanoparticles.”
“These metal nanostructures interact with light like an antenna and we think of them as ways to capture sunlight or NIR light and turn it into local energy for applications in sunlight driven catalysis or photothermal cancer therapy.”
“One of the best ways to understand how the nanoscale features affect the optical properties is to do single particle studies. With the correct illumination geometry and a sensitive enough detector, we can measure scattering from a single particle in darkfield. This scattering is a spectrum that represents the resonance in the particle, and we are developing techniques to make correlated single particle spectroscopy easier and statistically relevant.”
Figure 1: Transmission micro-extinction spectroscopy (MExS) characterization of transitional metal dichalcogenides (TMDs). The top row displays optical images of monolayers of (a) molybdenum disulphide (MoS2), (b) molybdenum diselenide (MoSe2), (c) tungsten disulfide (WS2), and (d) tungsten diselenide (WSe2). These images correspond to the spectral images in the bottom row, (e-h). The black squares show the location from where the spectrum was taken, spectra shown in (J), the TMD absorption spectra each labelled with exciton resonances A and B. Acquired with the ProEM EMCCD camera and the IsoPlane spectrometer, Teledyne Princeton Instruments.
Challenge
Prof. Ringe described the imaging and spectroscopy challenges she faces, “We illuminate with a darkfield condenser and collect the scattered light, that way we can measure one diffraction limited spot at a time. Then we also sample with electron microscopy sample with to see what nanostructure shape, size, or composition the spectra corresponds to. The challenge for us is having high spectral resolution, we have special gratings because we want the entire visible range at once.”
“We do a lot of push broom hyperspectral spectroscopy because we want to acquire a lot of particles from our sample. We developed a hyperspectral technique we call MExS or micro-extinction spectroscopy, which scans a line of pixels instead of going point by point, and this greatly reduces acquisition times, but we need suitable EMCCD cameras.”
IsoPlane spectrometers are obviously top of the line instruments, Their high throughput, high efficiency, and astigmatism-free design are unbeatable!
Prof. Emilie Ringe
Solution
The IsoPlane spectrometer, combined with 1024 x1024 PIXIS CCD cameras and a ProEM EMCCD camera, make the ideal solution for this imaging and spectroscopy application, thanks to a high spectral resolution, high sensitivity, and high throughput.
Prof. Ringe shared her experiences, “I have two IsoPlane spectrometers, three PIXIS spectroscopy cameras, and a ProEM 1k x 1k camera. One of our IsoPlane and PIXIS systems is for another application involving home-built Raman spectroscopy for chemical reaction tracking. We got the IsoPlane for that application specifically, where we can install the types of grating we need for high resolution Raman spectroscopy, and for the other IsoPlane we wanted a large spectral range for our MExS hyperspectral mapping of nanoparticles, so the IsoPlanes are very flexible.”
“The setup process is absolutely brilliant, the LightField software really makes it intuitive and easy. We can modify our hardware and the software control is always good. Some of our other software can struggle with the volume of data we obtain in each stack, but not LightField, that helps us turn our data into meaningful information. When we make changes, things don’t bug LightField, it’s a really solid piece of software and the instrumentation is just reliably working.”
“IsoPlane spectromters are obviously top of the line instruments, Their high throughput, high efficiency, and astigmatism-free design are unbeatable!. We also have an IntelliCal for calibration, which we absolutely love, it’s dead easy. You get a graphical user interface, and a nice calibration standard, it makes it accessible to any student who enters my lab.”
Figure 2: Microscope and spectroscope configuration from the lab of Professor Emilie Ringe: (a) Teledyne Princeton Instruments ProEM EMCCD camera, (b) Teledyne Princeton Instruments IsoPlane 320 spectrometer, (c) halogen lamp, (d) dark-field condenser, (e) piezo stage, (f) imaging camera, (g) LED lamp
References
Elabbadi M., Boukouvala C., Hopper E.R., Asselin J., and Ringe E., (2023) Synthesis of Controllable Cu Shells on Au Nanoparticles with Electrodeposition: A Systematic in Situ Single Particle Study, The Journal of Physical Chemistry C 2023 127 (10), 5044-5053, 10.1021/acs.jpcc.2c08910
Kumar, A., Villarreal, E., Zhang, X. et al. (2018) Micro-Extinction Spectroscopy (MExS): a versatile optical characterization technique. Adv Struct Chem Imag 4, 8. https://doi.org/10.1186/s40679-018-0057-6
Kumar A., Sebastian A., Das S., and Ringe E., (2018) In Situ Optical Tracking of Electroablation in Two-Dimensional Transition-Metal Dichalcogenides, ACS Applied Materials & Interfaces 2018 10 (47), 40773-40780, 10.1021/acsami.8b14585