Abstract
Silicon nanopost arrays (NAPA) are used in trace analysis by mass spectrometry (MS) because they enable highly efficient ion production from small molecules and thin tissue sections by UV laser desorption ionization (LDI). Such nanophotonic ionization of adsorbates relies on localized interactions between a nanostructured substrate and laser radiation. In LDI from NAPA, only the component of the oscillating electric field vector that is parallel with the posts couples the laser energy into the nanostructure. Enhancements in control over adsorbate ionization and fragmentation are expected if the surface-parallel component can also interact with the nanostructure. Here, an alternative nanophotonic ionization platform is introduced for LDI-MS, the elevated bowtie (EBT) array by adding triangular chromium features on top of silicon post pairs to form bowties. Compared to NAPA, the threshold fluence for ionization from EBT is lower, and at low laser fluences the ionization efficiency is increased by a factor of ≈17. The EBT platform with optimized apex angle exhibits a higher survival yield for molecular ions produced from biomolecules and xenobiotics and allows more control over fragmentation by adjusting the fluence. These unique nanophotonic ionization attributes are utilized for trace analysis and reaction monitoring in complex biological samples.
| Original language | English |
|---|---|
| Article number | 1801730 |
| Journal | Advanced Functional Materials |
| Volume | 28 |
| Issue number | 29 |
| DOIs | |
| State | Published - Jul 18 2018 |
Funding
A.V., L.R.C., and S.A.S conceived the study, and S.A.S, L.R.C, A.R.K., and S.T.R. performed the nanofabrication of the EBT and NAPA substrates. S.A.S. and X.A.H., conducted the experiments. S.A.S. and A.V. performed the data analysis and the computational modeling, and S.A.S, A.R.K., and A.V. wrote the manuscript. Research was sponsored by the U.S. Army Research Office and the Defense Advanced Research Projects Agency and was accomplished under Cooperative Agreement Number W911NF-14-2-0020. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office, DARPA, or the U.S. Government. Application of the developed methods to mass spectrometry imaging was supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant DE-FG02-01ER15129. S.A.S. is grateful for the scholarship award from the Achievement Rewards for College Scientists Foundation, Inc. (ARCS). The NAPA and EBT structures were nanofabricated, and a portion of the mass spectrometry data was obtained in the framework of a User Agreement (CNMS2013-309) at Oak Ridge National Laboratory's Center for Nanophase Materials Sciences, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The authors thank Dr. Christina Brantner for her help with the EDX measurements and SEM imaging and the Nanofabrication and Imaging Center of the The George Washington University for instrument access. A.V., L.R.C., and S.A.S conceived the study, and S.A.S, L.R.C, A.R.K., and S.T.R. performed the nanofabrication of the EBT and NAPA substrates. S.A.S. and X.A.H., conducted the experiments. S.A.S. and A.V. performed the data analysis and the computational modeling, and S.A.S, A.R.K., and A.V. wrote the manuscript. Research was sponsored by the U.S. Army Research Office and the Defense Advanced Research Projects Agency and was accomplished under Cooperative Agreement Number W911NF-14-2-0020. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office, DARPA, or the U.S. Government. Application of the developed methods to mass spectrometry imaging was supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant DE-FG02-01ER15129. S.A.S. is grateful for the scholarship award from the Achievement Rewards for College Scientists Foundation, Inc. (ARCS). The NAPA and EBT structures were nanofabricated, and a portion of the mass spectrometry data was obtained in the framework of a User Agreement (CNMS2013-309) at Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The authors thank Dr. Christina Brantner for her help with the EDX measurements and SEM imaging and the Nanofabrication and Imaging Center of the The George Washington University for instrument access.
Keywords
- bowtie arrays
- laser desorption
- mass spectrometry
- nanophotonic ionization
- nanopost arrays