Microplasma Controlled Nanogold Sensor for SERS of Aliphatic and Aromatic Explosives with PCA-KNN Recognition

TY - JOUR

T1 - Microplasma Controlled Nanogold Sensor for SERS of Aliphatic and Aromatic Explosives with PCA-KNN Recognition

AU - Olenik, Jaka

AU - Shvalya, Vasyl

AU - Modic, Martina

AU - Vengust, Damjan

AU - Cvelbar, Uroš

AU - Walsh, James L.

N1 - Publisher Copyright: © 2024 The Authors. Published by American Chemical Society.

PY - 2024/12/24

Y1 - 2024/12/24

N2 - Nanogold is an emerging material for enhancing surface-enhanced Raman scattering (SERS), which enables the detection of hazardous analytes at trace levels. This study presents a simple, single-step plasma synthesis method to control the size and yield of Au nanoparticles by using plasma-liquid redox chemistry. The pin-based argon plasma reduces the Au3+ precursor in under 5 min, synthesizing Au spherical particles ranging from ∼20 nm at 0.025 mM to ∼90 nm at 1.0 mM, in addition to plate-like particles occurring at concentrations of 0.25-1.0 mM. The enhanced SERS responses correlated with the UV-vis absorption and reflectance profiles, which can be attributed to synergistic plasmonic hotspots created by the sphere-sphere, plate-sphere, and plate-plate nanogold interactions. This nanogold mixture, combined with gold-plated CPU grid pin arrays, facilitated the detection of trace explosives, including aromatic (TNT, TNB, and TNP) and aliphatic (RDX, PETN, and HMX) compounds. We demonstrate that stabler aliphatic analytes, associated with lower vapor pressure (10-8-10-11 atm), exhibit smaller signal fluctuations (RSD ∼ 6-10%) compared to their more volatile (10-5 atm) aromatic (RSD ∼ 12-17%) counterparts at similar analyte concentrations. The calculated limit of detection (LoD) was found to be ∼2-6 nM and ∼600-900 pM for aromatic and aliphatic explosives, respectively. Finally, we show that the poorer performance of aromatic explosives under the same sensing conditions affects SERS-PCA separation, which can then be improved either by a machine learning approach (PCA with k-NN classification) or by consideration of a specific NO2 symmetric stretching fingerprint range.

AB - Nanogold is an emerging material for enhancing surface-enhanced Raman scattering (SERS), which enables the detection of hazardous analytes at trace levels. This study presents a simple, single-step plasma synthesis method to control the size and yield of Au nanoparticles by using plasma-liquid redox chemistry. The pin-based argon plasma reduces the Au3+ precursor in under 5 min, synthesizing Au spherical particles ranging from ∼20 nm at 0.025 mM to ∼90 nm at 1.0 mM, in addition to plate-like particles occurring at concentrations of 0.25-1.0 mM. The enhanced SERS responses correlated with the UV-vis absorption and reflectance profiles, which can be attributed to synergistic plasmonic hotspots created by the sphere-sphere, plate-sphere, and plate-plate nanogold interactions. This nanogold mixture, combined with gold-plated CPU grid pin arrays, facilitated the detection of trace explosives, including aromatic (TNT, TNB, and TNP) and aliphatic (RDX, PETN, and HMX) compounds. We demonstrate that stabler aliphatic analytes, associated with lower vapor pressure (10-8-10-11 atm), exhibit smaller signal fluctuations (RSD ∼ 6-10%) compared to their more volatile (10-5 atm) aromatic (RSD ∼ 12-17%) counterparts at similar analyte concentrations. The calculated limit of detection (LoD) was found to be ∼2-6 nM and ∼600-900 pM for aromatic and aliphatic explosives, respectively. Finally, we show that the poorer performance of aromatic explosives under the same sensing conditions affects SERS-PCA separation, which can then be improved either by a machine learning approach (PCA with k-NN classification) or by consideration of a specific NO2 symmetric stretching fingerprint range.

KW - explosives

KW - gold nanoparticles

KW - machine learning

KW - plasma synthesis

KW - SERS

UR - http://www.scopus.com/inward/record.url?scp=85213017817&partnerID=8YFLogxK

U2 - 10.1021/acssensors.4c02651

DO - 10.1021/acssensors.4c02651

M3 - Article

AN - SCOPUS:85213017817

SN - 2379-3694

JO - ACS sensors

JF - ACS sensors

ER -