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Papers by Henrique Baltar

The Journal of Physical Chemistry C, 2018

Despite the progress in understanding the properties of plasmonic nanostructures, the design of s... more Despite the progress in understanding the properties of plasmonic nanostructures, the design of structures with specific optical characteristics still poses a challenge. In order to better understand how material and various geometrical parameters affect the response of the nanostructures, we analysed, theoretically and experimentally, the optical properties and their tunability in diverse configurations of a two-dimensional periodic array of silver nanocylinders and dimers, with or without an underlying thin silver layer. We show the tuning of the surface plasmon resonances can be approximated by affine equations at the regions we worked on. The controllable parameters that can be used for tuning include nanoparticle-metal layer distance, index of refraction of the surrounding dielectric material, cap layer thickness and cylinder diameter. We also calculated the enhancement of the average square electric field at the top surface, useful for surface-enhanced spectroscopies. Enhanced optical transmission not due to propagating surface plasmon was also observed.

Plasmonics - Principles and Applications, 2012

Tuning resonant modes in a plasmonic array of nanocylinders by a mirror

ABSTRACT In order to advance in the development of nanodevices, we simulated silver nanocylinders... more ABSTRACT In order to advance in the development of nanodevices, we simulated silver nanocylinders arrays over mirrors and compared with experimental data. They match and we can tune resonant modes by modifying environmental and geometric properties.

Detection of specific strains of viable bacterial pathogens by using RNA bead assays and flow cytometry with 2100 Bioanalyzer

Bead assays are an emerging microbial detection technology with the capability for rapid detectio... more Bead assays are an emerging microbial detection technology with the capability for rapid detection of extremely low levels of viable pathogens. Such technologies are of high value in clinical settings and in the food industry. Here, we perform a bead assay for extracted 16S rRNA from Escherichia coli (strain K12) with the flow cytometry readout on a 2100 Bioanalyzer, a highly accurate, small-scale flow cytometer system.

Metal-enhanced fluorescence in the life sciences: Here, now and beyond

We discuss the phenomenon of enhanced fluorescence in the proximity of metal nanostructures addre... more We discuss the phenomenon of enhanced fluorescence in the proximity of metal nanostructures addressing the question of how much fluorescence signal can be obtained from fluorophores in such altered environments. We review its applicability for the methodologies used in the life science, such as immunoassays, flow cytometry and bioimaging. Experimental and theoretical scenarios employing various metal nanostructures - such as homogeneous enhancing substrates, fluorescence-enhancing microbeads, and metal core-dielectric shell nanocomposites - are described.

Dense Two-Dimensional Silver Single and Double Nanoparticle Arrays with Plasmonic Response in Wide Spectral Range

Langmuir, 2012

We report the properties of plasmons in dense planar arrays of silver single and double nanostruc... more We report the properties of plasmons in dense planar arrays of silver single and double nanostructures with various geometries fabricated by electron beam lithography (EBL) as a function of their size and spacing. We demonstrate a strong plasmon coupling mechanism due to near-field dipolar interactions between adjacent nanostructures, which produces a major red shift of the localized surface plasmon resonance (LSPR) in silver nanoparticles and leads to strong maximum electric field enhancements in a broad spectral range. The extinction spectra and maximum electric field enhancements are theoretically modeled by using the finite element method. Our modeling revealed that strong averaged electric field enhancements of up to 60 in visible range and up to 40 in mid-infrared result from hybridization of multipolar resonances in such dense nanostructures; these are important for applications in surface enhanced spectroscopies.

Analytical Chemistry, 2011

Bead assays are an important rapid microbial detection technology suitable for extremely low path... more Bead assays are an important rapid microbial detection technology suitable for extremely low pathogen levels. We report a bead assay for rRNA extracted from Escherichia coli K12 that does not require amplification steps and has readout on an Agilent 2100 Bioanalyzer flow cytometry system. Our assay was able to detect 125 ng of RNA, which is 16 times less than reported earlier. The specificity was extremely high, with no binding to a negative control organism (Bacillus subtilis). We discuss challenges faced during optimization of the key assay components, such as varying amounts of RNA in the samples, number of beads, aggregation, and reproducibility.

Plasmonically enhanced optical nonlinearities in anisotropic arrays of gold nanorods supported in polymeric film

Latin America Optics and Photonics Conference, 2016

The nonlinear optical properties of gold nanorods in a polyvinyl alcohol film are studied as a fu... more The nonlinear optical properties of gold nanorods in a polyvinyl alcohol film are studied as a function of the anisotropy. We have experimentally studied the effect on the nonlinear absorptive and refractive nanomaterial’s response using the Z-scan technique.