Glyphosate (GP) is a broad-spectrum systemic herbicide which is used for killing a wide variety of harmful plants. Several recent studies indicate possible adverse health effects on humans. This work is focused on detection and adsorption studies of GP and its metabolite aminomethylphosphonic acid (AMPA) on silver-capped silicon nanopillars using surface-enhanced Raman spectroscopy (SERS). Density Functional Theory with the B3LYP functional was employed for the geometry optimization of ground state geometries and simulation of Raman and SERS spectra of the GP and AMPA. The theoretically calculated and experimentally observed vibrations of GP and AMPA free and attached to the Ag surface exhibited different Raman spectra revealing chemical interactions between the analysed molecules and the metal surface. DFT studies confirmed that the main Ag-GP interaction is with the oxygen from carboxylic and phosphate groups, and
for AMPA the main interaction is via a strong interaction between nitrogen from NH with the metal surface. In order to study the binding behavior, adsorption isotherm analysis between GP and AMPA on silver-capped silicon nanopillars (AgNPs) were performed. Finally, the obtained isotherms for GP and AMPA followed a negative cooperative binding mechanism.
Glyphosate, AMPA, silver nanopillars, adsorption, DFT
 Antier C, Kudsk P, Reboud X, Ulber L, Baret P, and Messéan A. Glyphosate use in the european agricultural sector. Sustainability. 12: 1–22, 2020.
 Helander M, Pauna A, Saikkonen K, and Saloniemi I. Glyphosate residues in soil affect crop plant germination and growth. Scientific reports. 9: 1–9, 2019.
 Mañas F, Peralta L, Raviolo J, García H, Ugnia L, Gonzalez M, and Gorla N. Genotoxicity of AMPA, the environmental metabolite of glyphosate, assessed by the Comet assay and cytogenetic tests. Ecotoxicology and environmental safety. 72: 834–837, 2009.
 Corbera M, Hidalgo M, Salvad V, and Wieczorek P. Determination of glyphosate and aminomethylphosphonic acid in natural water using the capillary electrophoresis combined with enrichment step. Analytica chimica acta. 540: 3–7, 2005.
 Bruggen V, He M, Shin K, Mai V, Jeong K, Finckh M, and Morris J. Environmental and health effects of the herbicide glyphosate. Science of the total environment. 617: 255–268, 2018.
 Benachour N and Seralini G. Glyphosate formulations induce apoptosis and necrosis in human umbilical, embryonic, and placental cells. Chemical research in toxicology.22: 97–105, 2009.
 url: https://www.theguardian.com/environment/2019/sep/04/germany-ban-glyphosateweedkiller- by-2023.
 ZhangW, Feng Y, Ma L, An J, Zhang H, Cao M, Zhu H, KangW, and Lian K. A method for determining glyphosate and its metabolite aminomethyl phosphonic acid by gas chromatography-flame photometric detection. Journal of chromatography. A.1589: 116–121, 2019.
 Costa J, Ando R, Sant’Ana C, and Corio P. Surface-enhanced Raman spectroscopy studies of organophosphorous model molecules and pesticides. Physical chemistry chemical physics. 14: 15645–15651, 2012.
 Frisch J, Trucks W, Schlegel B, Scuseria E, Robb A, Cheeseman R, Scalmani V, Mennucci B, Petersson A, Nakatsuji H, Caricato M, Li Hratchian X, Izmaylov F, Bloino J, Zheng G, Sonnenberg J, Hada M, Ehara M, Toyota K, Fukuda R, Hasegawa J, Ishida M, Nakajima T, Honda Y, Kitao O, Nakai H, Vreven T, Montgomery J, Peralta E, Ogliaro F, Bearpark M, Heyd J, Brothers E, Kudin K, Staroverov V, Kobayashi R, Normand J, Raghavachari K, Rendell A, Burant J, Iyengar S, Tomasi J, Cossi M, Rega N, Klene M, Ortiz J, Cioslowski J, and Fox D. Gaussian 09, revision a.1. Wallingford, CT.
url: https://gaussian.com/g09citation/. 2009.
 Sharma G, Carmichael E, and Mccall D. Vibrational spectroscopy fabrication of SERS substrate for the detection of rhodamine 6G, glyphosate, melamine and salicylic acid. Vibrational spectroscopy. 83: 159–169, 2016.
 Torul H, Boyaci , and Tamer U. Attomole detection of glyphosate by surface-enhanced Raman spectroscopy using gold nanorods. Journal of pharmaceutical science. 35: 179–184, 2010.
 Jin M, Hong Z, Chang M, Liu C, and Cheng H. Metal carbonyl-gold nanoparticle conjugates for highly sensitive SERS detection of organophosphorus pesticides. Biosensors and bioelectronics. 96: 167–172, 2017.
 Lopez–Ramirez M, Guerrini L, and Garcia-Ramos V. Vibrational analysis of herbicide diquat: a normal Raman and SERS study on Ag nanoparticles. Vibrational spectroscopy. 48: 58–64, 2008.
 Bonora S, Benassi E, Maris A, Tugnoli V, Ottani S, and Di Foggia M. Raman and SERS study on atrazine, prometryn and simetryn triazine herbicides. Journal of molecular structure. 1040: 139–148, 2013.
 Feis A, Gellini C, Ricci M, Tognaccini L, Becucci M, and Smulevich G. Surfaceenhanced Raman scattering of glyphosate on dispersed silver nanoparticles: a reinterpretation based on model molecules. Vibrational spectroscopy. 108: 1–8, 2020.
 Emonds G, Mignolet B, Malherbe C, Monbaliu J, Remacle F, and Eppe G. Understanding chemical interaction between phosphonatederivative molecules and silver surface cluster in SERS: a combined experimental and computational approach. Physical chemistry Chemical Physics. 21: 22180–22187, 2019.
 Tu Q, Yang T, Qu Y, Gao S, Zhang Z, Zhang Q, Wang Y, Wang J, and He L. In situ colorimetric detection of glyphosate on plant tissues using cysteamine-modified gold nanoparticles. Analyst. 144: 2017–2025, 2019.
 Johnson P and Christy R. Optical constants of the noble metals. Physical review. B.6: 4370–4379, 1972.
 Aspnes D and Studna D. Dielectric functions and optical parameters of Si, Ge, GaP, GaAs, GaSb, InP, InAs, and InSb from 1.5 to 6.0 eV. Physical review. B.27: 985–1009, 1983.
 O’Boyle A, Tenderholt L, and Langner K. Cclib: a library for package-independent computational chemistry algorithms. Journal of computational chemistry. 29: 839–845, 2008.
 Scott A and Radom L. Harmonic vibrational frequencies: an evaluation of Hartree– Fock, Moller–Plesset, quadratic configuration interaction, density functional theory, and semiempirical scale factors. Journal of physical chemistry. 100: 16502–16513, 1996.
 Weiss J. The Hill equation revisited: uses and misuses. FASEB journal. 11: 835–841, 1997.
 Castillo J, Rindzevicius T, Rozo C, and Boisen A. Adsorption and vibrational study of folic acid on gold nanopillar structures using surface-enhanced Raman scattering spectroscopy. Nanomaterials and nanotechnology. 5: 1–8, 2015.
 Ascolani J, Fuhr J, Bocan G, Millone A, Tognalli N, Santos M, and Martiarena M. Abiotic degradation of glyphosate into aminomethylphosphonic acid in the presence of metals. Journal of agricultural food chemistry. 62: 9651–9656, 2014.
 Tang J, Chen W, and Ju H. Rapid detection of pesticide residues using a silver nanoparticles coated glass bead as nonplanar substrate for SERS sensing. Sensors and actuators b: chemical. 287: 576–583, 2019.
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