Routine Femtogram-Level Chemical Analyses Using Vibrational Spectroscopy and Self-Cleaning Scanning Probe Microscopy Tips

Abstract

Simultaneous structural and chemical characterization of materials at the nanoscale is both an immediate need and an ongoing challenge. This article reports a route to address this need, which can be rapidly adopted by practitioners, by combining the benefits of widely available scanning probe microscopy and vibrational microspectrometry. In an atomic force microscope (AFM), the probe tip can provide a nanoscale topographic image. Here, we use a temperature-controlled probe tip to selectively acquire an analyte from a specified location and determine its mass in a thermogravimetric manner. The tip is then analyzed via complementary Raman and Fourier transform infrared microspectrometers, providing a molecular characterization of samples down to the femtogram level in minutes. The probe can be self-cleaned and employed for repeated use by rapidly heating it to vaporize the analyte. By combining the established analytical modalities of AFM and vibrational spectrometry, a complete physical and molecular characterization of nanoscale domains is possible: mass determination is facile, thermal analyses can be integrated on the probe, and the obtained spectral data can be related to existing knowledge bases.

High-resolution Fourier-transform infrared chemical imaging with multiple synchrotron beams

“…7). We estimated this to be ~100-fold better than with current instrumentation 16 and this compared favorably with the lowest detection limit reported 35 using destructive methods.…”

Infrared Spectroscopic Imaging: The Next Generation

“…Apertures have been employed for decades and the technology 26,27 has been essentially unaltered since the advent of Fourier transform infrared (FT-IR) microscopy. While scanning probes have received considerably more attention for nanoscale spectroscopic mapping, their use for microscale measurements 28–31 is generally useful only to localize signal from specific regions or samples 32 and not for large area mapping. IR imaging typically refers to the use of multichannel detectors to achieve spatial localization, which enables recording a reasonably sized image in short times.…”

In situ characterization of nanoscale contaminations adsorbed in air using atomic force microscopy

“…Several methods for tip characterization have been proposed, such as X-ray analysis, Raman spectroscopy, contact angle measurements, and scanning and transmission electron microscopy [ 33 – 36 ]. Since the tip may change quite frequently during AFM operation, ex situ methods may be quite inadequate and unproductive for many AFM experiments.…”