Optical Nanoantennas for Multiband Surface-Enhanced Infrared and Raman Spectroscopy

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Incident wavelength resolved resonant SERS on Au sphere segment void (SSV) arrays

Sphere segment void (SSV) arrays allow the reproducible engineering of plasmon-polariton modes from the near infrared to the ultraviolet through the tuning of the void height and diameter. The wavelength dependence of surface-enhanced Raman scattering (SERS) can then in principle be controlled by selecting these parameters. Using 4-mercaptopyridine as a covalently bonded nonresonant molecular probe, we report a detailed study of such wavelength dependence of SERS in Au SSV arrays as a function of void diameter and height. We conclude that the SERS mechanism on SSV arrays depends on the plasmonic properties of the substrates and also that additional effects contribute significantly to the observed enhancement including a chemical contribution related to the molecular probe and a nanostructuring induced surface plasmon localization existent for the smaller cavity dimensions

Quantitative electrochemical SERS of flavin at a structured silver surface

In situ electrochemical surface enhanced Raman spectra (SERS) for an immobilized monolayer of a flavin analogue (isoalloxazine) at nanostructured silver surfaces are reported. Unique in the present study, the flavin is not directly adsorbed at the Ag surface but is attached through a chemical reaction between cysteamine adsorbed on the Ag surface and methylformylisoalloxazine. Even though the flavin is held away from direct contact with the metal, strong surface enhancements are observed. The nanostructured silver surfaces are produced by electrodeposition through colloidal templates to produce thin (<1 ?m) films containing close-packed hexagonal arrays of uniform 900 nm sphere segment voids. The sphere segment void (SSV) structured silver surfaces are shown to be ideally suited to in situ electrochemical SERS studies at 633 nm, giving stable, reproducible surface enhancements at a range of electrode potentials, and we show that the SER spectra are sensitive to subfemtomole quantities of immobilized flavin. Studies of the SER spectra as a function of the electrode potential show clear evidence for the formation of the flavin semiquinone at the electrode surface at cathodic potential

Magneto-Optical Enhancement by Plasmon Excitations in Nanoparticle/Metal Structures

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Abiotic Degradation of Glyphosate into Aminomethylphosphonic Acid in the Presence of Metals

Glyphosate [N-phosphono-methylglycine (PMG)] is the most used herbicide worldwide, particularly since the development of transgenic glyphosate-resistant (GR) crops. Aminomethylphosphonic acid (AMPA) is the main glyphosate metabolite, and it may be responsible for GR crop damage upon PMG application. PMG degradation into AMPA has hitherto been reckoned mainly as a biological process, produced by soil microorganisms (bacteria and fungi) and plants. In this work, we use density functional calculations to identify the vibrational bands of PMG and AMPA in surface-enhanced Raman spectroscopy (SERS) and attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectra experiments. SERS shows the presence of AMPA after glyphosate is deposited from aqueous solution on different metallic surfaces. AMPA is also detected in ATR–FTIR experiments when PMG interacts with metallic ions in aqueous solution. These results reveal an abiotic degradation process of glyphosate into AMPA, where metals play a crucial role.Fil: Ascolani Yael, Julian Esteban. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Fuhr, Javier Daniel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bocan, Gisela Anahí. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Daza Millone, Maria Antonieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Tognalli, N.. Centro de Innovación Tecnológica Empresarial y Social S.A.; ArgentinaFil: Dos Santos Afonso, María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Martiarena, María Luz. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

SERS in PAH-Os and gold nanoparticle self-assembled multilayers

We present a detailed structural and surface-enhanced Raman scattering (SERS) study of poly(allylamine) modified with Os (byp)2 ClPyCHO (PAH-Os) and gold nanoparticles self-assembled multilayers [PAH-Os+ (Au-nanoparticlesPAH-Os)n, n=1 and 5]. Atomic force microscopy and variable-angle spectroscopic ellipsometry measurements indicate that the first nanoparticle layer grows homogenously by partially covering the substrate without clustering. Analyzing the sample thickness and roughness we infer that the growth process advances thereafter by filling with nanoparticles the interstitial spaces between the previously adsorbed nanoparticles. After five immersion steps the multilayers reach a more compact structure. The interaction between plasmons of near-gold nanoparticles provides a new optical absorption around 650 nm which, in addition, allows a more effective SERS process in that spectral region than at the single-plasmon resonance (∼530 nm). We compare the electronic resonance Raman and SERS amplification mechanisms in these self-assembled multilayers analyzing Raman resonance scans and Raman intensity micromaps. As a function of nanoparticle coverage we observe large changes in the Raman intensity scans, with maxima that shift from the electronic transitions, to the plasmon resonance, and finally to the coupled-plasmon absorption. The Raman micromaps, on the other hand, evidence huge intensity inhomogeneities which we relate to "hot spots." Numerical discrete dipole approximation calculations including the interaction between gold nanoparticles are presented, providing a qualitative model for the coupled-plasmon absorption and redshifted Raman hot spots in these samples. © 2005 American Institute of Physics.Fil:Calvo, E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Bonazzola, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Abiotic Degradation of Glyphosate into Aminomethylphosphonic Acid in the Presence of Metals

Glyphosate [<i>N</i>-phosphono-methylglycine (PMG)] is the most used herbicide worldwide, particularly since the development of transgenic glyphosate-resistant (GR) crops. Aminomethylphosphonic acid (AMPA) is the main glyphosate metabolite, and it may be responsible for GR crop damage upon PMG application. PMG degradation into AMPA has hitherto been reckoned mainly as a biological process, produced by soil microorganisms (bacteria and fungi) and plants. In this work, we use density functional calculations to identify the vibrational bands of PMG and AMPA in surface-enhanced Raman spectroscopy (SERS) and attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectra experiments. SERS shows the presence of AMPA after glyphosate is deposited from aqueous solution on different metallic surfaces. AMPA is also detected in ATR–FTIR experiments when PMG interacts with metallic ions in aqueous solution. These results reveal an abiotic degradation process of glyphosate into AMPA, where metals play a crucial role