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Title: Pushing The Sample-Size Limit Of Infrared Vibrational Nano-Spectroscopy: From Monolayer Towards Single molecule sensitivity

Abstract

While scattering-scanning near-field optical microscopy (s-SNOM) has demonstrated its potential to extend infrared (IR) spectroscopy into the nanometer scale, it has not yet reached its full potential in terms of spectroscopic sensitivity. We combine broadband femtosecond mid-IR excitation with an optimized spectral irradiance of 2 W/cm2/ cm–1 (power/area/bandwidth) and a combination of tip- and substrate enhancement to demonstrate single-monolayer sensitivity with exceptional signal-to-noise ratio. Using interferometric time domain detection, the near-field IR s-SNOM spectral phase directly reflects the molecular vibrational resonances and their intrinsic line shapes. We probe the stretching resonance of 1000 carbonyl groups at 1700 cm–1 in a self-assembled monolayer of 16-mercaptohexadecanoic acid (MHDA) on an evaporated gold substrate with spectroscopic contrast and sensitivity of 100 vibrational oscillators. From these results we provide a roadmap for achieving true single-molecule IR vibrational spectroscopy in s-SNOM by implementing optical antenna resonant enhancement, increased spectral pump power, and improved detection schemes.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1047406
Report Number(s):
PNNL-SA-88335
36406; KP1704020; TRN: US201216%%265
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry Letters, 3(13):1836-1841
Additional Journal Information:
Journal Volume: 3; Journal Issue: 13
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANTENNAS; CARBONYLS; DETECTION; EXCITATION; GOLD; MOLECULES; OPTICAL MICROSCOPY; OSCILLATORS; POTENTIALS; RADIANT FLUX DENSITY; RESONANCE; SENSITIVITY; SIGNAL-TO-NOISE RATIO; SPECTROSCOPY; SUBSTRATES; femtosecond near-field infrared spectroscopy; vibrational nano-spectroscopy; chemical imaging; near-field microscopy; self-assembled monolayer; Environmental Molecular Sciences Laboratory

Citation Formats

Xu, Xiaoji G, Rang, Matthias, Craig, Ian M, and Rashcke, Markus B. Pushing The Sample-Size Limit Of Infrared Vibrational Nano-Spectroscopy: From Monolayer Towards Single molecule sensitivity. United States: N. p., 2012. Web. doi:10.1021/jz300463d.
Xu, Xiaoji G, Rang, Matthias, Craig, Ian M, & Rashcke, Markus B. Pushing The Sample-Size Limit Of Infrared Vibrational Nano-Spectroscopy: From Monolayer Towards Single molecule sensitivity. United States. doi:10.1021/jz300463d.
Xu, Xiaoji G, Rang, Matthias, Craig, Ian M, and Rashcke, Markus B. Mon . "Pushing The Sample-Size Limit Of Infrared Vibrational Nano-Spectroscopy: From Monolayer Towards Single molecule sensitivity". United States. doi:10.1021/jz300463d.
@article{osti_1047406,
title = {Pushing The Sample-Size Limit Of Infrared Vibrational Nano-Spectroscopy: From Monolayer Towards Single molecule sensitivity},
author = {Xu, Xiaoji G and Rang, Matthias and Craig, Ian M and Rashcke, Markus B},
abstractNote = {While scattering-scanning near-field optical microscopy (s-SNOM) has demonstrated its potential to extend infrared (IR) spectroscopy into the nanometer scale, it has not yet reached its full potential in terms of spectroscopic sensitivity. We combine broadband femtosecond mid-IR excitation with an optimized spectral irradiance of 2 W/cm2/ cm–1 (power/area/bandwidth) and a combination of tip- and substrate enhancement to demonstrate single-monolayer sensitivity with exceptional signal-to-noise ratio. Using interferometric time domain detection, the near-field IR s-SNOM spectral phase directly reflects the molecular vibrational resonances and their intrinsic line shapes. We probe the stretching resonance of 1000 carbonyl groups at 1700 cm–1 in a self-assembled monolayer of 16-mercaptohexadecanoic acid (MHDA) on an evaporated gold substrate with spectroscopic contrast and sensitivity of 100 vibrational oscillators. From these results we provide a roadmap for achieving true single-molecule IR vibrational spectroscopy in s-SNOM by implementing optical antenna resonant enhancement, increased spectral pump power, and improved detection schemes.},
doi = {10.1021/jz300463d},
journal = {Journal of Physical Chemistry Letters, 3(13):1836-1841},
number = 13,
volume = 3,
place = {United States},
year = {2012},
month = {6}
}