The resonant wave modes in monomodal and multimodal planar Surface Plasmon Resonance (SPR) sensors and their response to a bidimensional array of gold nanoparticles (AuNPs) are analyzed both theoretically and experimentally, to investigate the parameters that rule the correct nanoparticle counting in the emerging metal nanoparticle-amplified surface plasmon resonance (PA-SPR) spectroscopy. With numerical simulations based on the Finite Element Method (FEM), we evaluate the error performed in the determination of the surface density of nanoparticles σ when the Maxwell-Garnett effective medium theory is used for fast data processing of the SPR reflectivity curves upon nanoparticle detection. The deviation increases directly with the manifestations of non-negligible scattering cross-section of the single nanoparticle, dipole-dipole interactions between adjacent AuNPs and dipolar interactions with the metal substrate. Near field simulations show clearly the set-up of dipolar interactions when the dielectric thickness is smaller than 10 nm and confirm that the anomalous dispersion usually observed experimentally is due to the failure of the effective medium theories. Using citrate stabilized AuNPs with a nominal diameter of about 15 nm, we demonstrate experimentally that Dielectric Loaded Waveguides (DLWGs) can be used as accurate nanocounters in the range of surface density between 20 and 200 NP/µm2, opening the way to the use of PA-SPR spectroscopy on systems mimicking the physiological cell membranes on SiO2 supports.

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The influence of a dielectric shell on metallic spherical nanoparticles [core-shell nanoparticles (CSNps)] in the resonant modal response of a surface plasmon resonance (SPR)-type sensor is presented. The planar multilayer sensor structure, based on the Kretschmann and surface plasmon coupled emission (SPCE) configurations, is coupled to a periodic array of these nanoparticles. In the first configuration, the CSNps are considered as a homogeneous layer with effective permittivity given by the Clausius-Mossotti mixing formula and polarizability of a core shell for a quasi-static scattering regime. In the second configuration, it performed an evaluation via the discrete complex image method (DCIM). Electromagnetic wave propagation is evaluated by the generalized reflection coefficient for multilayer structures. The analytical results are validated by numerical simulations performed via finite element method and also by experimental data. We observed that the dielectric shell thickness affects considerably the sensibility of the sensor when analyzing the change in other parameters of the CSNps array.Resonance 186

An alternative approach to classical surface plasmon resonance spectroscopy is dielectric-loaded waveguide (DLWG) spectroscopy, widely used in the past decades to investigate bio-interaction kinetics. Despite their wide application, a successful and clear approach to use the DLWGs for the one-step simultaneous determination of both the thickness and refractive index of organic thin films is absent in the literature. We propose here, for the first time, an experimental protocol based on the multimodal nature of DLWGs to be followed in order to evaluate the optical constants and thickness of transparent thin films with a unique measurement. The proposed method is general and can be applied to every class of transparent organic materials, with a resolution and accuracy which depend on the nature of the external medium (gaseous or liquid), the geometrical characteristics of the DLWG, and the values of both the thickness and dielectric constant of the thin film. From the experimental point of view, the method is demonstrated in a nitrogen environment with an accuracy of about 3%, for the special case of electroluminescent thin films of Eu3+β-diketonate complexes, with an average thickness of about 20 nm. The high value of the refractive index measured for the thin film with the Eu­(btfa)3(t-bpete) complex was confirmed by the use of a spectroscopic model based on the Judd–Ofelt theory, in which the magnetic dipole transition 5D0 → 7F1 (Eu3+) for similar films containing Eu3+ complexes is taken as a reference. The DLWGs are finally applied to control the refractive index changes of the organic thin films under UVA irradiation, with potential applications in dosimetry and monitoring light-induced transformation in organic thin films.

Resumo-Neste artigo analisa-se teoricamente um sensor tipo SPR, cuja estrutura multicamada é baseada na configuração Kretschmann, acoplado à um arranjo periódico de nanopartículas de ouro cobertas por casca dielétrica (core-shell). A modelagem analítica considera o arranjo de nanopartículas como uma camada homogênea com permissividade efetiva dada pela fórmula de Clausius-Mossotti e a polarizabilidade de um coreshell obtida para um regime de espalhamento quase estático. A propagação da onda eletromagnética é avaliada pelo coeficiente de reflexão generalizado para estruturas multicamadas. Os resultados analíticos são comparados com resultados numéricos obtidos por simulação em geometria 3D no software COMSOL R .

Resumo -O controle preditivo baseado no modelo é uma técnica muito utilizada para lidar com os desafios do controle de conversores de potência empregados como interface entre energias renováveis e a rede elétrica. Essa técnica combina o controle em malha fechada com minimização do erro e do esforço de controle, mas a sintonia de forma sistemática ainda é um desafio em aberto e pouco se conhece sobre os efeitos dos parâmetros desse controlador no desempenho em malha fechada de conversores fonte de tensão conectados à rede.Neste artigo um controlador preditivo com modulação é aplicado no referencial síncrono a um conversor de potência com filtro indutivo. Como proposta de sintonia do controlador, primeiro avalia-se os polos de malha fechada para limitar os parâmetros e garantir a estabilidade. Depois o desempenho em malha fechada é refinado mapeando o desempenho do sistema de controle considerando simultaneamente horizontes de tempo do modelo preditivo e os fatores de peso da função custo. Os ajustes propostos para o controlador foram validados experimentalmente em uma bancada de baixa potência e comparados com o preditivo Finite Control Set. Os resultados corroboram o projeto do controlado com desempenho comparável e até superior a outras técnicas de controle avançado.Palavras-chave -Controle preditivo.Controle de corrente.Conversor CC-CA. Conversor com filtro L. Conversor conectado à rede. Projeto do controle preditivo.MPC design control modulation using performance map applied to VCS-grid converter with L filter

Model predictive control (MPC) is a powerful and widely used technique to address the control challenges in power converters as the grid interface for renewable energy systems. This technique combines closed-loop control with error and control effort minimization; however, its design is challenging, and we know little about how the controller parameters affect the closed-loop performance of grid-connected voltage source converters. In this study, we applied an MPC direct power control with modulation for a grid-connected power converter with an inductive filter. For the controller design, we proposed an initial set based on the power converter's nominal setup. Then, we define the range of settings to guarantee stability by analyzing the closed-loop poles of the system. The fine-tuning to improve the performance can be identified visually using the performance maps built from simulations of the control system, simultaneously sweeping the time horizons of the predictive model and the weight factors of the cost function. Experimental results on a low-power bench demonstrate the excellent performance of the designed controller, following and even outperforming the classical proportional-integral (PI) controller and other advanced control techniques.INDEX TERMS Direct power control, grid-connected VSC, model predictive control, MPC with PWM modulation, weight factors design.The associate editor coordinating the review of this manuscript and approving it for publication was Qi Zhou.