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Special Issue "New Materials, Technology and Application of Refractive Index Based Sensing"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: 20 November 2023 | Viewed by 4421

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Special Issue Editors

Dr. Katerina Lazarova

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Guest Editor

Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Interests: optical sensors; thin films; nanomaterials

Dr. Biliana Georgieva

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Guest Editor

Institute of Optical Materials and Technologies “Acad. J. Malinowski”, Bulgarian Academy of Sciences, Akad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria
Interests: transmission electron microscopy; nanomaterials; optical sensors; thin films

Special Issue Information

Dear Colleagues,

Recently, there has been increasing interest in sensors based on color change upon exposure to the tested analyte. New materials which change their optical characteristics under the influence of an external stimulus are being researched widely. As optical refractive index sensors are based on detection that can convert changes in refractive index into detectable optical information, new possibilities are being sought for the easy, fast and cheap implementation of sensitive media in these sensors - in the form of thin films, photonic crystals, etc.

The purpose of this Special Issue is to cover the development of technologies in this direction, and to bring together the results of the latest research, solutions, challenges and applications based on materials with changing optical characteristics.

Potential topics for this Special Issue include, but are not limited to:

Optical sensors;
Photonic crystals;
Thin films;
Optical properties;
Refractive index changing materials;
Biomedical sensors;
Wearable sensors based on color change;
Nanosensors;
Color indicators for VOCs.

Dr. Katerina Lazarova
Dr. Biliana Georgieva
Guest Editors

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Keywords

optical sensors
color indicators
optical materials
thin films
photonic crystals
refractive index

Published Papers (3 papers)

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Research

Open AccessArticle

Improving the Angular Visibility of Photopolymer-Based Reflection Holograms for Sensing Applications

and

Sensors 2023, 23(9), 4275; https://doi.org/10.3390/s23094275 - 25 Apr 2023

Cited by 1 | Viewed by 1120

Abstract

Volume reflection hologram-based sensors are designed to visibly change colour in response to a target stressor or analyte. However, reflection holograms fabricated in thick photopolymer films are highly angularly selective, making these sensors challenging to view and interpret by non-experts. Here, the use of speckle holography to improve the visibility of reflection holograms is presented. A novel recording approach combining speckle recording techniques with Denisyuk reflection recording geometry is described. The recorded speckle reflection grating operates as a series of multiplexed reflection gratings with a range of spatial frequencies, capable of reflecting light at a wider range of angles. A comparative study of the angular and wavelength selectivity of speckle and standard reflection gratings was conducted. The FWHM of the angular selectivity curves of the speckle reflection gratings is doubled (4°) in comparison to standard 4500 lines/mm reflection gratings (2°). The wavelength selectivity FWHM is also doubled from 4.2 to 8.6 nm. The comparative ability of the speckle and standard reflection gratings to act as colour-changing compressional pressure sensors in the 0.88–5.31 MPa range is described. Finally, we present a prototype reflection hologram viewer which enables the easy observation of angularly specific reflection holograms by non-experts. Full article

(This article belongs to the Special Issue New Materials, Technology and Application of Refractive Index Based Sensing)

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Open AccessArticle

Binding of SARS-CoV-2 Structural Proteins to Hemoglobin and Myoglobin Studied by SPR and DR LPG

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Sensors 2023, 23(6), 3346; https://doi.org/10.3390/s23063346 - 22 Mar 2023

Viewed by 2065

Abstract

One of the first clinical observations related to COVID-19 identified hematological dysfunctions. These were explained by theoretical modeling, which predicted that motifs from SARS-CoV-2 structural proteins could bind to porphyrin. At present, there is very little experimental data that could provide reliable information about possible interactions. The surface plasmon resonance (SPR) method and double resonance long period grating (DR LPG) were used to identify the binding of S/N protein and the receptor bind domain (RBD) to hemoglobin (Hb) and myoglobin (Mb). SPR transducers were functionalized with Hb and Mb, while LPG transducers, were only with Hb. Ligands were deposited by the matrix-assisted laser evaporation (MAPLE) method, which guarantees maximum interaction specificity. The experiments carried out showed S/N protein binding to Hb and Mb and RBD binding to Hb. Apart from that, they demonstrated that chemically-inactivated virus-like particles (VLPs) interact with Hb. The binding activity of S/N- and RBD proteins was assessed. It was found that protein binding fully inhibited heme functionality. The registered N protein binding to Hb/Mb is the first experimental fact that supports theoretical predictions. This fact suggests another function of this protein, not only binding RNA. The lower RBD binding activity reveals that other functional groups of S protein participate in the interaction. The high-affinity binding of these proteins to Hb provides an excellent opportunity for assessing the effectiveness of inhibitors targeting S/N proteins. Full article

(This article belongs to the Special Issue New Materials, Technology and Application of Refractive Index Based Sensing)

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Open AccessArticle

Blending Approach Preparation of PVA-g-PMA Films with Embedded “Green” Synthesized Silver Nanoparticles for Acetone Optical Detection

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Sensors 2023, 23(6), 2941; https://doi.org/10.3390/s23062941 - 08 Mar 2023

Viewed by 924

Abstract

The blending approach (also known as the ex-situ approach) was used for the deposition of thin composite films comprising poly(vinyl alcohol-graft-methyl acrylate) (PVA-g-PMA) and silver nanoparticles (AgNPs). Firstly, the copolymer aqueous dispersion was synthesized through the redox polymerization of methyl acrylate (MA) on poly(vinyl alcohol) (PVA) using ammonium cerium (IV) nitrate as the initiator. Then, AgNPs were synthesized through a “green” method using the water extract of lavender based on by-products of the essential oil industry, and then they were blended with the polymer. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine nanoparticle size, along with their stability over time in suspension, during the 30-day period. Thin films of the PVA-g-PMA copolymer, with different AgNP volume fractions varying between 0.008 and 0.260%, were deposited via the spin-coating method on Si substrates, and their optical properties were explored. UV-VIS-NIR spectroscopy and non-linear curve fitting were used for the determination of the refractive index, extinction coefficient, and thickness of the films, while photoluminescence measurements at room temperature were conducted for studying the emission of the films. The concentration dependence of film thickness was observed and showed that thickness increased linearly from 31 nm to 75 nm when the nanoparticles’ weight content increased from 0.3 wt% to 2.3 wt%. The sensing properties toward acetone vapors were tested in a controlled atmosphere by measuring reflectance spectra before and during exposure to the analyte molecules in the same film spot; the swelling degree of films was calculated and compared to the corresponding undoped samples. It was shown that the concentration of AgNPs of 1.2 wt% in the films is optimal for the enhancement of the sensing response toward acetone. The influence of AgNPs on the films’ properties was revealed and discussed. Full article

(This article belongs to the Special Issue New Materials, Technology and Application of Refractive Index Based Sensing)

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