研究目的
To propose a straightforward and purely experimental method to access quantitative information of the plasmon resonance and near-field temperature experienced exclusively by the molecules directly contributing to the TERS signal.
研究成果
The study provides access to unprecedented molecular-level information on physical parameters that crucially affect experiments under TERS conditions. The study thereby improves the usability of TERS in day-to-day operation. The obtained information is of central importance for any experimental plasmonic investigation and for the application of TERS in the field of nanoscale thermometry.
研究不足
The technical and application constraints of the experiments include the complexity of the obtained spectral information and the lack of knowledge about crucial parameters affecting day-to-day experiments. Potential areas for optimization include the tuning of the laser with respect to the plasmon resonance.
1:Experimental Design and Method Selection:
The study uses standard TERS experimental equipment to simultaneously probe the Stokes and anti-Stokes spectral intensities.
2:Sample Selection and Data Sources:
Self-assembled 16-mercaptohexadodecanoic acid monolayers covalently bonded to an ultra-flat gold surface were used as a demonstrator.
3:List of Experimental Equipment and Materials:
A 532 nm laser excitation (Cobolt 04-01 series, Sweden), a Raman spectrometer (SP300, Princeton Instruments, USA) equipped with a CCD camera (PIXIS400, Princeton Instruments), and an AFM head (NanoWizard 2, JPK, Germany) mounted on an inverted microscope with a ×100 oil-immersion objective (NA
4:30, Olympus, Japan). Experimental Procedures and Operational Workflow:
The system used a 532 nm laser excitation with a power of 100 μW at the sample. Ag-coated AFM tips are first positioned in the focus of the laser spot by optimizing the amplitude of the silicon signal using the tip scanner. The sample scanning option is used to control the sample position during the experiments to preserve the tip/laser focus positioning.
5:Data Analysis Methods:
The plasmon frequency and width, as well as the near-field temperature, were evaluated with the help of Eq. (4) programmed in Mathematica (Wolfram, USA) software.
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