Abstract
Molecular-level spectroscopy is crucial for sensing and imaging applications, yet detecting and quantifying minuscule quantities of chemicals remain a challenge, especially when they surface adsorb in low numbers. Here, we introduce a photothermal spectroscopic technique that enables the high selectivity sensing of adsorbates with an attogram detection limit. Our approach utilizes the Seebeck effect in a microfabricated nanoscale thermocouple junction, incorporated into the apex of a microcantilever. We observe minimal thermal mass exhibited by the sensor, which maintains exceptional thermal insulation. The temperature variation driving the thermoelectric junction arises from the nonradiative decay of molecular adsorbates’ vibrational states on the tip. We demonstrate the detection of photothermal spectra of physisorbed trinitrotoluene (TNT) and dimethyl methylphosphonate (DMMP) molecules, as well as representative polymers, with an estimated mass of 10-18 g.
| Original language | English |
|---|---|
| Pages (from-to) | 7883-7889 |
| Number of pages | 7 |
| Journal | Nano Letters |
| Volume | 23 |
| Issue number | 17 |
| DOIs | |
| State | Published - Sep 13 2023 |
Funding
This work was supported by the School of Engineering and Applied Sciences (SEAS) University at Buffalo, The State University of New York, and NSF Award 2226614. A.P. acknowledges partial support from the Office of Biological and Environmental Research (BER) in the U.S. Department of Energy (DOE) Office of Science. ORNL is managed by UT-Battelle, LLC, for the US DOE under Contract DE-AC05-00OR22725. The authors acknowledge Drs. A. Ciric and M. Medic, the Institute of Nuclear Sciences, the University of Belgrade, for help with the physical vapor deposition setup and Dr. A. Chand from AppNano for fruitful discussions.
Keywords
- calorimetry
- infrared sensor
- microfabricated thermocouple
- molecular recognition
- photothermal spectroscopy