Abstract
Tip-enhanced Raman spectroscopy (TERS), which offers a spatial resolution far beyond the limitations of the optical diffraction and detection sensitivity down to a single molecular level, has become one of the powerful techniques applied in current nanoscience and technology. However, the excellent performance of a TERS system is very much dependent on the quality of metallized probes used in TERS characterization. Thus, how to prepare higher-quality probes plays a vital role in the development and application of TERS technique. In this work, one simple wet-chemistry procedure was designed to fabricate atomic force microscopy-based TERS (AFM-TERS) probes. Through the controlled growth of a gold film on a commercial silicon AFM probe, TERS probes with different apex diameters were prepared successfully. A series of TERS results indicated that the probes with the apex size of 50~60 nm had the maximum TERS enhancement, and the Raman enhancement factor was in the range of 106 to 107. Compared with those prepared by other fabrication methods, our TERS probes fabricated by this wet-chemistry method have the virtues of good stability, high reproducibility, and strong enhancement effect.
Highlights
Atomic force microscopy (AFM) has been widely applied in nanoscience for its high lateral resolution, simple operation, and environmental adaptability
Tips Silanization Commercial Si AFM probe (VIT_P, NT-MDT Co., Moscow, Russia) was ozone cleaned for 30 s to render them hydroxylated, and the probe was immersed in a 0.25-mM 3-merraptnpropylt rimethnxysilane (MPTS, 95%, Sigma-Aldrich) methanol solution for 30 min
As no other material was introduced in this experiment, the size increase in probe apex could be ascribed to the growth of Au film on the probe surface
Summary
Atomic force microscopy (AFM) has been widely applied in nanoscience for its high lateral resolution, simple operation, and environmental adaptability. In AFM, the surface information of a sample is acquired via the interaction force between the tip and sample, which is converted into the motion of a small spring-like cantilever with the tip at the end. The motion is detected by deflection of a semiconductor laser illuminating on the back of the AFM cantilever. The topography and optical information of a sample can be characterized simultaneously with a nanoscale resolution when the metallized probe is scanning the sample surface. This is the principle of AFM-based tip-enhanced Raman spectroscopy (AFM-TERS).
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