Cleumar da Silva Moreira

This work investigates the intrinsic sensitivity limits of surface plasmon resonance (SPR) sensors for detecting acetone concentrations relevant to breath-based diagnostics. Fresnel multilayer simulations are combined with experiments using a Kretschmann–Raether configuration with a PMMA prism and a 50-nm gold film. Sensor performance is evaluated through resonance shift, full width at half maximum (FWHM), sensitivity, and figure of merit (FOM). Simulations predict clear reflectivity variations and resonance redshift with increasing acetone concentration. Experiments with aqueous acetone solutions from 1.8 to 90 ppm confirm the simulated trends. Measurable SPR variations are observed down to approximately 9 ppm. Baseline noise analysis indicates a theoretical limit of detection near 1 ppm, while practical detection is limited by instrumental resolution. These results establish a benchmark for bulk refractive-index SPR sensing.

A prism-coupled surface plasmon resonance (SPR) platform was assessed for detecting dilute acetone in liquid samples representative of condensed exhaled breath. The study combines transfer-matrix Fresnel calculations with wavelength-interrogated experiments performed with a PMMA prism and a nominal 50 nm Au layer. The numerical analysis was used to examine the resonance position, line broadening, minimum reflectance, sensitivity, and figure of merit as a function of optical and material parameters. Experimentally, aqueous acetone solutions spanning 1.8–90 ppm were analyzed. The resonance band shifted systematically toward longer wavelengths as the acetone content increased, and reproducible spectral changes were obtained for concentrations down to approximately 9 ppm using the present optical setup. From the measured spectral slope and baseline fluctuations, the statistical limit of detection was estimated to be close to 1 ppm, whereas the practical limit was governed mainly by spectrometer resolution and low-concentration signal separation. These results establish a reproducible reference for non-functionalized Au/PMMA SPR sensing of acetone in condensed breath-like aqueous media.

Research focused on improving the sensitivity of SPR analytical technology has led to the investigation of different electric field enhancement elements for incorporation with classic sensor structures. Over the past ten years, considerable attention has been given to ceramic, metal oxide, and 2D materials that not only improve the magnitude of the field but are also used as affinity layers for improved adsorption of molecules. However, focusing on the improvements these materials deliver can lead designers to explore only some of themultiple dependencies associated with sensitivity. When using the angular interrogation mode, the impacts of working with different wavelengths are generally disregarded, as a fixed value of λ=633 nm is commonly adopted. Choosing 633 nm is often justified for achieving near-zero reflectivity and good sensitivity. However, newer SPR designs lack the determination of optimal wavelength-dependent sensitivity points. This article numerically investigates sensitivity as a function of wavelength for SPR sensors. We systematically study the effects of operating outside λ=633 nm and show that the signature produced by bare metal sensors does not always resemble the signatures produced by field-enhanced designs. Examinations are based on Graphene and BaTiO ₃ . Furthermore, we demonstrate how imposing thresholds on optimization targets can be leveraged to sustain high-sensitivity results, and we elaborate on the pertinent tradeoffs. Our approach shows further performance improvements in designs for which highly efficient benchmarks have already been demonstrated.

A numerical investigation of a sensor for acetone monitoring using surface plasmon resonance (SPR) is proposed. We evaluate the effects of polyaniline (PANI), graphene, or chitosan acting as a chemisorption binding layer for the selective sensing of acetone. Our findings suggest that these materials present suitable responses when applied as an overlayer to the sensor. Their thicknesses, however, should be maintained close to a monolayer level to preserve performance.

A numerical investigation of a sensor for acetone monitoring in exhaled breath condensate (EBC) using surface plasmon resonance principle is proposed. We use the Kretschmann-Raether (K-R) setup and the Fresnel multilayer model for the theoretical analysis. Three figures of merit, i.e., resonance angle (RA), minimum reflectance at resonance (MRR), and full width at half maximum (FWHM) are used for performance analysis. Firstly, the sensor performance for different plasmonic metals and substrates is evaluated. Results using gold, silver, and copper as the plasmonic metals and polycarbonate the substrate, showed narrow SPR curves with an FWHM of less than 1.8 degrees. Achieved values for MRR parameter are close to zero (< 0.001). Subsequently, we evaluate the effects of adding polyaniline (PANI), graphene, or chitosan as a chemisorption binding layer for the selective sensing of acetone. Our findings suggest that these materials present suitable responses when applied as an overlay to the sensor. Their thicknesses, however, should be kept close to a single monolayer level to preserve performance. The overall best result occurs when polycarbonate is the substrate, silver, is the metal, and chitosan, is the reception layer.

Graphene, molybdenum disulfide (MoS2), and zinc oxide (ZnO) are proposed here to enhance the evanescent field of an optical fiber Surface Plasmon Resonance (SPR) sensor. Gold and silver are the plasmonic materials and the fiber core material is polymethylmethacrylate (PMMA). A Fresnel equations-based analysis is used, and the obtained results pointed out higher values of sensitivity, figure of merit, and FWHM (Full-Width at Half Maximum) when compared to conventional SPR sensors. In despite of silver-only based SPR sensor has a better performance, oxidation occurs, and the sensor's lifetime is reduced. The addition of graphene layers leads to sensitivity values 50% higher than the conventional sensor. On the other hand, the MoS2-based sensor improves the interaction of the sensor with the bio-recognition molecules, which is attractive for biomedical applications. When ZnO was added to the silver-based sensor a highest sensitivity, 4,740.9 nm/RIU, was obtained. Graphene-based silver SPR exhibit the highest FOM values.

This paper presents an in silico and in vitro study concerning the application of a trapezoidal prism-based surface plasmon resonance chip to detect colorectal cancer by analyzing the mucosa tissue. The sensor is a multilayered structure and works in the wavelength interrogation mode. Performance parameters related to the metallic film characteristics, such as thickness and type of metal were determined. For the analyzed noble metals, the silver film of 40 nm has the highest sensitivity of 6,454.12 nm/RIU, and the 60 nm-thick presents the best values for full width at half maximum and χ parameter (20.20 nm and 286.63 RIU ^–1 ). The palladium nanolayer deposition enhanced the sensitivity by 10.81% for copper film and peaks at 6,497.04 nm/RIU for the silver film. The palladium nanolayer also provokes deeper dips in the reflectance spectrum. Tissue phantoms were used to study the sensor response to solid surrounding medium to show the feasibility and the correctness of the proposed methodology.