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17 pages, 2364 KB

Open AccessArticle

Exploring Electromagnetic Density of States Near Plasmonic Material Interfaces

by Rodolfo Cortés-Martínez, Ricardo Téllez-Limón, Cesar E. Garcia-Ortiz, Benjamín R. Jaramillo-Ávila and Gabriel A. Galaviz-Mosqueda

Surfaces 2025, 8(4), 71; https://doi.org/10.3390/surfaces8040071 - 10 Oct 2025

Viewed by 891

Abstract

The electromagnetic density of states (EM-DOS) plays a crucial role in understanding light–matter interactions, especially at metal–dielectric interfaces. This study explores the impact of interface geometry, material properties, and nanostructures on EM-DOS, with a focus on surface plasmon polaritons (SPPs) and evanescent waves. Using a combination of analytical and numerical methods, the behavior of EM-DOS is analyzed as a function of distance from metal–dielectric interfaces, showing exponential decay with penetration depth. The influence of different metals, including copper, gold, and silver, on EM-DOS is examined. Additionally, the effects of dielectric materials, such as Ti

O_{2}

, PMMA, and

{Al}_{2}

O_{3}

, on the enhancement of electromagnetic field confinement are discussed. The study also investigates the effect of nanostructures, like nanohole and nanopillar arrays, on EM-DOS by calculating effective permittivity and analyzing the interaction of quantum emitters with these structures. Results show that nanopillar arrays enhance EM-DOS more effectively than nanohole arrays, especially in the visible spectrum. The findings provide insights into optimizing plasmonic devices for applications in sensing, quantum technologies, and energy conversion. Full article

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14 pages, 2952 KB

Open AccessArticle

Highly Sensitive and Wide-Range Detection of Thiabendazole via Surface-Enhanced Raman Scattering Using Bimetallic Nanoparticle-Functionalized Nanopillars

by Hyunjun Park, Gayoung Kim, Woochang Kim, Eugene Park, Joohyung Park and Jinsung Park

Biosensors 2024, 14(3), 133; https://doi.org/10.3390/bios14030133 - 4 Mar 2024

Cited by 3 | Viewed by 3202

Abstract

Thiabendazole (TBZ) is a benzimidazole; owing to its potent antimicrobial properties, TBZ is extensively employed in agriculture as a fungicide and pesticide. However, TBZ poses environmental risks, and excessive exposure to TBZ through various leakage pathways can cause adverse effects in humans. Therefore, a method must be developed for early and sensitive detection of TBZ over a range of concentrations, considering both human and environmental perspectives. In this study, we used silver nanopillar structures (SNPis) and Au@Ag bimetallic nanoparticles (BNPs) to fabricate a BNP@SNPi substrate. This substrate exhibited a broad reaction surface with significantly enhanced surface-enhanced Raman scattering hotspots, demonstrating excellent Raman performance, along with high reproducibility, sensitivity, and selectivity for TBZ detection. Ultimately, the BNP@SNPi substrate successfully detected TBZ across a wide concentration range in samples of tap water, drinking water, juice, and human serum, with respective limits of detection of 146.5, 245.5, 195.6, and 219.4 pM. This study highlights BNP@SNPi as a promising sensor platform for TBZ detection in diverse environments and contributes to environmental monitoring and bioanalytical studies. Full article

(This article belongs to the Special Issue Advanced SERS Biosensors for Detection and Analysis)

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10 pages, 31066 KB

Open AccessArticle

Rebuildable Silver Nanoparticles Employed as Seeds for Synthesis of Pure Silver Nanopillars with Hexagonal Cross-Sections under Room Temperature

by Pengfei Yang, Yu Liang, Daxiao Zhang, Shaobo Ge, Shijie Li, Xichao Liang, Jin Zhang, Yingxue Xi, Yan Zhang and Weiguo Liu

Nanomaterials 2023, 13(7), 1263; https://doi.org/10.3390/nano13071263 - 3 Apr 2023

Cited by 1 | Viewed by 2325

Abstract

Silver nanopillars with strong plasmonic effects are used for localized electromagnetic field enhancement and regulation and have wide potential applications in sensing, bioimaging, and surface-enhanced spectroscopy. Normally, the controlled synthesis of silver nanopillars is mainly achieved using heterometallic nanoparticles, including Au nanobipyramids and Pd decahedra, as seeds for inducing nanostructure growth. However, the seed materials are usually doped in silver nanopillar products. Herein, the synthesis of pure silver nanopillars with hexagonal cross-sections is achieved by employing rebuildable silver nanoparticles as seeds. An environmentally friendly, stable, and reproducible synthetic route for obtaining silver nanopillars is proposed using sodium dodecyl sulfate as the surface stabilizer. Furthermore, the seed particles induce the formation of regular structures at different temperatures, and, specifically, room temperature is beneficial for the growth of nanopillars. The availability of silver nanoparticle seeds using sodium alginate as a carrier at different temperatures was verified. A reproducible method was developed to synthesize pure silver nanopillars from silver nanoparticles at room temperature, which can provide a strategy for designing plasmonic nanostructures for chemical and biological applications. Full article

(This article belongs to the Topic Synthesis and Applications of Nanowires)

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12 pages, 2523 KB

Open AccessArticle

Machine Learning Assisted Real-Time Label-Free SERS Diagnoses of Malignant Pleural Effusion due to Lung Cancer

by Jayakumar Perumal, Pyng Lee, Kapil Dev, Hann Qian Lim, U. S. Dinish and Malini Olivo

Biosensors 2022, 12(11), 940; https://doi.org/10.3390/bios12110940 - 28 Oct 2022

Cited by 14 | Viewed by 3749

Abstract

More than half of all pleural effusions are due to malignancy of which lung cancer is the main cause. Pleural effusions can complicate the course of pneumonia, pulmonary tuberculosis, or underlying systemic disease. We explore the application of label-free surface-enhanced Raman spectroscopy (SERS) as a point of care (POC) diagnostic tool to identify if pleural effusions are due to lung cancer or to other causes (controls). Lung cancer samples showed specific SERS spectral signatures such as the position and intensity of the Raman band in different wave number region using a novel silver coated silicon nanopillar (SCSNP) as a SERS substrate. We report a classification accuracy of 85% along with a sensitivity and specificity of 87% and 83%, respectively, for the detection of lung cancer over control pleural fluid samples with a receiver operating characteristics (ROC) area under curve value of 0.93 using a PLS-DA binary classifier to distinguish between lung cancer over control subjects. We have also evaluated discriminative wavenumber bands responsible for the distinction between the two classes with the help of a variable importance in projection (VIP) score. We found that our label-free SERS platform was able to distinguish lung cancer from pleural effusions due to other causes (controls) with higher diagnostic accuracy. Full article

(This article belongs to the Special Issue Surface-Enhanced Raman Scattering Biosensors)

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10 pages, 1623 KB

Open AccessCommunication

Highly Sensitive Biosensor Based on Partially Immobilized Silver Nanopillars in the Terahertz Band

by Shuo Liu, Lin Li and Zhenxu Bai

Photonics 2021, 8(10), 438; https://doi.org/10.3390/photonics8100438 - 13 Oct 2021

Cited by 9 | Viewed by 2552

Abstract

In this paper, a highly sensitive biosensor based on partially immobilized silver nanopillars is proposed. The working frequency of this sensor is in the terahertz band, and the range of the detected refractive index is 1.33 to 1.38. We set air holes of two different sizes on the cross-section of the optical fiber and arranged them into a hexagon. In order to improve the sensitivity, silver nanopillars were immobilized on part of the surface of the fiber cladding. The method for detecting the change of refractive index of the bio-analyte was based on local surface plasmon resonance properties of noble metal. The research recorded valuable data about the values of loss peak and full width at half maximum as well as resonance frequency shift under different setting conditions. The data present the biosensor’s final sensitivity as 1.749 THz/RIU. Full article

(This article belongs to the Special Issue Optical Sensing)

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20 pages, 6922 KB

Open AccessArticle

Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors

by Akram A. Khosroabadi, Palash Gangopadhyay, Steven Hernandez, Kyungjo Kim, Nasser Peyghambarian and Robert A. Norwood

Materials 2015, 8(8), 5028-5047; https://doi.org/10.3390/ma8085028 - 7 Aug 2015

Cited by 4 | Viewed by 7565

Abstract

We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) structures, with feature sizes below 100 nm and a controlled surface architecture. The optical and electrical properties of these core shell electrodes, including the surface plasmon frequency, can be tuned by suitably changing the order and thickness of the dielectric layers. By varying the dimensions of the nanopillars, the surface plasmon wavelength of the nanopillar Ag can be tuned from 650 to 690 nm. Adding layers of ITO to the structure further shifts the resonance wavelength toward the IR region and, depending on the sequence and thickness of the layers within the structure, we show that such structures can be applied in sensing devices including enhancing silicon as a photodetection material. Full article

(This article belongs to the Special Issue Plasmonic Materials)

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