In this contribution, we combine for the first time tip-enhanced Raman spectroscopy (TERS) and photoinduced force microscopy (PiFM) synergistically and examine this instrumental approach on the 2D material molybdenum disulfide (MoS2). In a first step the PiFM technique was applied to map the electrical field distribution of the incident light field with nanometer resolution according to the plasmon resonance of the TERS tip. This experiment provides a fast and nondestructive characterization of the TERS tips focus interaction and is in good agreement with theoretical models. Subsequently, combined TERS and PiFM experiments on a MoS2 monolayer finally demonstrate a correlation of maximum TERS signal enhancement and the corresponding PiFM image with respect to the depth and lateral position of the focal laser spot. Hence, the results indicate a significantly improved route toward the alignment efficiency of TERS experiments and establish MoS2 as an outstandingly suitable TERS test sample.

An amendment to this paper has been published and can be accessed via the original article.

We study the optical properties of aggregates of hollow gold nanoparticles: monodisperse and bidisperse random gas particles and fractal cluster-cluster aggregates consisting of 1000 particles. We use the coupled-dipole equations to describe the interaction of the electromagnetic wave with particles. We find that the particle core volume fraction can be tuned to minimize the full width at half-maximum (FWHM) and to considerably shift the peak of the absorption spectrum. We find that the redshift, but not the FWHM of the peak, has a monotonic dependence on the particle core volume fraction. High pass, low pass and band rejection filters can be realized with random and fractal aggregates of hollow particles. In the case of fractal clusters, particle size dispersion has a deep influence on the overall shape of the spectrum. Thus, the aggregates of hollow nanoparticles are superior to the aggregates of solid nanoparticles: their absorption spectrum can be easily engineered by hollow size.