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In the last decade, tip-enhanced optical spectroscopy has emerged as a powerful analytical tool for hyperspectral chemical imaging of 2D materials at the nanoscale. In this talk, I will present the basic principles of tip-enhanced optical spectroscopy and discuss how tip-enhanced Raman spectroscopy (TERS) can be used to visualize structural defects in pristine single-layer graphene [1,2] and determine the level and location of molecular disorder in chemically functionalized few-layer graphene [3], carboxyl-modified graphene oxide [4] and graphene nanoribbons [5]. Furthermore, application of hyperspectral tip-enhanced photoluminescence (TEPL) microscopy to probe excitonic processes in single-layer MoS2 [6], visualize optoelectronic behavior of grain boundaries grain boundaries in single-layer WSe2 [7] and probe nanoscale exciton funneling at wrinkles of twisted bilayer MoS2 [8] will be presented.

References:

S. Mignuzzi, N. Kumar, B. Brennan, I. S. Gilmore, D. R. Richards, A. J. Pollard, D. Roy “Probing individual point defects in graphene via near-field Raman scattering” Nanoscale 2015, 9, 19413-19418W. Su†, N. Kumar†, N. Dai, D. Roy “Nanoscale chemical mapping of intrinsic defects in graphene using tip-enhanced Raman spectroscopy” Chemical Communications 2016, 52, 8227-8230E. L. Legge, K. R. Paton, M. Wywijas, G. McMahon, R. Pemberton, N. Kumar et al. “Determining the level and location of functional groups on few-layer graphene and their effect on the mechanical properties of nanocomposites” ACS Applied Materials & Interfaces, 2020, 12, 13481-13493W. Su, N. Kumar, A. Krayev, M. Chaigneau “In situ topographical chemical and electrical imaging of carboxyl graphene oxide at the nanoscale Nature Communications 2018, 9: 2891W. Su, A. Esfandiar, O. Lancry, J. Shao, N. Kumar, M. Chaigneau "Visualising structural modification of patterned graphene nanoribbons using tip-enhanced Raman spectroscopy" Chemical Communications, 2021, 57, 6895-6898W. Su†, N. Kumar†, S. Mignuzzi, J. Crain, D. Roy “Nanoscale mapping of excitonic processes in single layer MoS2 using tip-enhanced photoluminescence microscopy” Nanoscale 2016, 8, 10564-10569W. Su, N. Kumar, H. Shu, O. Lancry, M. Chaigneau “In situ Visualization of Optoelectronic Behavior of Grain Boundaries in Monolayer WSe2 at the Nanoscale” The Journal of Physical Chemistry C, 2021, 125, 26883-26891J. Shao, F. Chen, W. Su, N. Kumar, Y. Zeng, L. Wu, H. W. Lu “Probing Nanoscale Exciton Funneling at Wrinkles of Twisted Bilayer MoS2 Using Tip-Enhanced Photoluminescence Microscopy” The Journal of Physical Chemistry Letters, 2022, 13, 3304-3309