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In situ SERS detection of dissolved nitrate on hydrated gold substrates

The accurate and fast measurement of nitrate in seawater is important for monitoring and controlling water quality to prevent ecologic and economic disasters. In this work we show that the in situ detection of nitrate in aqueous solution is feasible at nanomolar concentrations through surface enhanc...

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Autores principales: Küster, Timo, Bothun, Geoffrey D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: RSC 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9418535/
https://www.ncbi.nlm.nih.gov/pubmed/36132825
http://dx.doi.org/10.1039/d1na00156f
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author Küster, Timo
Bothun, Geoffrey D.
author_facet Küster, Timo
Bothun, Geoffrey D.
author_sort Küster, Timo
collection PubMed
description The accurate and fast measurement of nitrate in seawater is important for monitoring and controlling water quality to prevent ecologic and economic disasters. In this work we show that the in situ detection of nitrate in aqueous solution is feasible at nanomolar concentrations through surface enhanced Raman spectroscopy (SERS) using native nanostructured gold substrates without surface functionalization. Spectra were analyzed as collected or after standard normal variate (SNV) normalization, which was shown through Principal Component Analysis (PCA) to reduce spectral variations between sample sets and improve Langmuir adsorption model fits. An additional normalization approach based on the substrate silicon template showed that silicon provided an internal standard that accounted for the spectral variance without the need for SNV normalization. Nitrate adsorption was well-described by the Langmuir adsorption model, consistent with an adsorbed monolayer, and a limit of detection of 64 nM nitrate was obtained in ultrapure water, representing environmentally relevant concentrations. Free energy calculations based on the Langmuir adsorption constants, approximating equilibrium adsorption constants, and calculated self-energy arising from image charge, accounting for electrostatic interactions with a polarizable nanostructured substrate, suggest that nitrate adsorption was partially driven by an entropy gain presumably due to dehydration of the gold substrate and/or nitrate ion. This work is being extended to determine if similar statistical and normalization methods can be applied to nitrate detection in complex natural waters where non-target ions and molecules are expected to interfere.
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spelling pubmed-94185352022-09-20 In situ SERS detection of dissolved nitrate on hydrated gold substrates Küster, Timo Bothun, Geoffrey D. Nanoscale Adv Chemistry The accurate and fast measurement of nitrate in seawater is important for monitoring and controlling water quality to prevent ecologic and economic disasters. In this work we show that the in situ detection of nitrate in aqueous solution is feasible at nanomolar concentrations through surface enhanced Raman spectroscopy (SERS) using native nanostructured gold substrates without surface functionalization. Spectra were analyzed as collected or after standard normal variate (SNV) normalization, which was shown through Principal Component Analysis (PCA) to reduce spectral variations between sample sets and improve Langmuir adsorption model fits. An additional normalization approach based on the substrate silicon template showed that silicon provided an internal standard that accounted for the spectral variance without the need for SNV normalization. Nitrate adsorption was well-described by the Langmuir adsorption model, consistent with an adsorbed monolayer, and a limit of detection of 64 nM nitrate was obtained in ultrapure water, representing environmentally relevant concentrations. Free energy calculations based on the Langmuir adsorption constants, approximating equilibrium adsorption constants, and calculated self-energy arising from image charge, accounting for electrostatic interactions with a polarizable nanostructured substrate, suggest that nitrate adsorption was partially driven by an entropy gain presumably due to dehydration of the gold substrate and/or nitrate ion. This work is being extended to determine if similar statistical and normalization methods can be applied to nitrate detection in complex natural waters where non-target ions and molecules are expected to interfere. RSC 2021-06-12 /pmc/articles/PMC9418535/ /pubmed/36132825 http://dx.doi.org/10.1039/d1na00156f Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by/3.0/
spellingShingle Chemistry
Küster, Timo
Bothun, Geoffrey D.
In situ SERS detection of dissolved nitrate on hydrated gold substrates
title In situ SERS detection of dissolved nitrate on hydrated gold substrates
title_full In situ SERS detection of dissolved nitrate on hydrated gold substrates
title_fullStr In situ SERS detection of dissolved nitrate on hydrated gold substrates
title_full_unstemmed In situ SERS detection of dissolved nitrate on hydrated gold substrates
title_short In situ SERS detection of dissolved nitrate on hydrated gold substrates
title_sort in situ sers detection of dissolved nitrate on hydrated gold substrates
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9418535/
https://www.ncbi.nlm.nih.gov/pubmed/36132825
http://dx.doi.org/10.1039/d1na00156f
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