Xiaoji Xu

Our group focuses on advancing nanoscale imaging and spectroscopy techniques to study the chemical and physical properties of materials at the nanometer scale. Our current focus is on deeply integrating atomic force microscopy (AFM) with advanced laser spectroscopy techniques. We are innovating and utilizing AFM-based photothermal action spectroscopy (AFM-IR) and scattering-type scanning near-field optical microscopy (s-SNOM) to study a wide range of materials, including soft matter, photovoltaics, two-dimensional polariton and quantum materials, catalytic nanostructures, and biomacromolecules. We are particularly interested in exploring nanoscale phenomena inaccessible to conventional optical spectroscopy, which is limited by Abbe’s diffraction limit in spatial resolution. We are especially focused on combining time-domain two-dimensional infrared (AFM-2DIR) spectroscopy with AFM photothermal action detection. We are actively developing AFM-based 2DIR techniques to investigate light-matter interactions and energy transfer at material interfaces. In addition to AFM-based infrared techniques, our group is developing and refining Kelvin probe force microscopy (KPFM) to study nanoscale surface electrical potential at material interfaces.

•  Amirhossein Zahmatkeshsaredorahi, Ruben Millan-Solsona, Devon S. Jakob,
  
  Liam Collins, and Xiaoji G. Xu “Kelvin probe force microscopy under ambient
  
  conditions”; Nature Reviews Methods Primers, 5, 35, (2025)

• Qing Xie, Yu Zhang, Eli Janzen, James H. Edgar, and Xiaoji G. Xu “Atomic-force-
  
  microscopy-based time-domain two-dimensional infrared nanospectroscopy”
  
  Nature Nanotechnology, 19, 1108-1115 (2024)

• Le Wang, Haomin Wang, and Xiaoji G. Xu “Principle and Applications of Peak
  
  Force Infrared Microscopy” Chemical Society Reviews, 51, 5268 - 5286 (2022)

•  Haomin Wang, Joseph M. González-Fialkowski, Wenqian Li, Qing Xie, Yan Yu,
  
  and Xiaoji G. Xu “Liquid-Phase Peak Force Infrared Microscopy for Chemical
  
  Nano-imaging and Spectroscopy” Analytical Chemistry, 93, 7, 3567-3575 (2021)

•  Devon S. Jakob, Haomin Wang, Guanghong Zeng, Daniel E. Otzen, Yong Yan,
  
  and Xiaoji G. Xu “Peak Force Infrared – Kelvin Probe Force Microscopy”
  
  Angewandte Chemie Int. Ed., 59, 16083 (2020)

•  Devon S. Jakob, Haomin Wang, and Xiaoji G. Xu “Pulsed Force Kelvin Probe
  
  Force Microscopy” ACS Nano, 14, 4, 4839-4848 (2020)

• Haomin Wang, Le Wang, Devon S. Jakob, and Xiaoji G. Xu “Tomographic and
  
  Multimodal Scattering-Type Scanning Near-field Optical Microscopy with Peak
  
  Force Tapping Mode” Nature Communications, 9:2005 (2018)

• Le Wang, Haomin Wang, Martin Wagner, Yong Yan, Devon S. Jakob and Xiaoji
  
  G. Xu “Nanoscale Simultaneous Chemical and Mechanical Imaging via Peak
  
  Force Infrared Microscopy” Science Advances, 3, 6, e1700255 (2017)

• Haomin Wang, Le Wang and Xiaoji G. Xu “Scattering-type Scanning Near-field Optical Microscopy with Low Repetition Rate Pulsed Light Source through Phase-domain Sampling” Nature Communications, 7:13212 (2016)

• Le Wang and Xiaoji G. Xu “Scattering Type Scanning Near-field Optical
  
  Microscopy with Reconstruction of Vertical Interaction” Nature Communications,
  
  6:8973 (2015).

For a full list of publications, please see here

2025, Richard Van Duyne Early Career Award in Experimental Physical Chemistry, ACS PHYS Division

2025, Danser Distinguished Faculty Chair in Chemistry, Lehigh University

2025, Senior Member, National Academy of Inventors

2021, Camille Dreyfus Teacher-Scholar Award, Camille and Henry Dreyfus Foundation

2020-2022, Class of ’61 Professorship, Lehigh University

2020, Sloan Research Fellowship, Alfred P. Sloan Foundation

2019, NSF CAREER, National Science Foundation

2018, Beckman Young Investigator, Arnold and Mabel Beckman Foundation