Chemosensors

13 pages, 992 KiB

Open AccessReview

The Application of Molecularly Imprinted Polymers in Forensic Toxicology: Issues and Perspectives

by Susan Mohamed, Simone Santelli, Arianna Giorgetti, Guido Pelletti, Filippo Pirani, Paolo Fais and Jennifer P. Pascali

Chemosensors 2024, 12(12), 279; https://doi.org/10.3390/chemosensors12120279 - 23 Dec 2024

Cited by 5 | Viewed by 1670

Abstract

Molecularly imprinted polymers (MIPs) are synthetic receptors designed to selectively bind specific molecules, mimicking natural antibody–antigen interactions. Produced through polymerization around a target molecule (template), MIPs create imprints that confer high specificity and binding affinity upon template removal. Initially developed in the 1970s [...] Read more.

Molecularly imprinted polymers (MIPs) are synthetic receptors designed to selectively bind specific molecules, mimicking natural antibody–antigen interactions. Produced through polymerization around a target molecule (template), MIPs create imprints that confer high specificity and binding affinity upon template removal. Initially developed in the 1970s with organic polymers, MIPs now play critical roles in separation sciences, catalysis, drug delivery, and sensor technology. In forensic science, MIPs offer potential for sample preparation, pre-concentration, and analyte detection, especially with complex biological and non-biological matrices. They exhibit superior stability under extreme conditions, enabling their use in challenging forensic contexts such as detecting new psychoactive substances or trace explosives. Despite advantages like reusability and high selectivity, MIPs face limitations in forensic analysis due to their complex synthesis, potential template leakage, and non-specific binding. Moreover, the lack of standardized protocols limits their mainstream adoption, as forensic applications require validated, reproducible methods. This review systematically assesses MIPs in forensic toxicology, focusing on their current capabilities, limitations, and potential for broader integration into forensic workflows. Future research should address standardization and evaluate MIPs’ effectiveness in diverse forensic applications to realize their full potential. Full article

(This article belongs to the Special Issue Chemical Sensing and Analytical Methods for Forensic Applications)

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9 pages, 1940 KiB

Open AccessCommunication

Electrochemical Detection of Microplastics in Water Using Ultramicroelectrodes

by Changhui Lee, Sangwon Han and Jun Hui Park

Chemosensors 2024, 12(12), 278; https://doi.org/10.3390/chemosensors12120278 - 23 Dec 2024

Cited by 5 | Viewed by 2352

Abstract

Herein, a method for detecting microplastics in water using single-entity electrochemistry is presented, with a focus on the interaction between microplastics in aqueous solution and the surface of an ultramicroelectrode (UME). Polystyrene and polypropylene, two commonly used plastics that were ground and dispersed [...] Read more.

Herein, a method for detecting microplastics in water using single-entity electrochemistry is presented, with a focus on the interaction between microplastics in aqueous solution and the surface of an ultramicroelectrode (UME). Polystyrene and polypropylene, two commonly used plastics that were ground and dispersed in aqueous solution, served as the detection target materials. The collisional contact of microplastics with the UME was transduced into a discernible signal. To detect microplastics in solution using an UME, redox species (e.g., ferrocyanide) were continuously oxidized at the electrode, and the resulting steady-state current was monitored. Collisional contact followed by adsorption of microplastics on the UME disturbed the diffusional flux of redox species, resulting in an immediate change in the steady-state current. Detection sensitivity was further enhanced by optimizing the electrolyte composition to induce a migration effect. COMSOL Multiphysics simulations were employed to analyze the magnitude of the current changes as a function of microplastic size. The size distribution obtained from the simulations closely matched measurements from dynamic light scattering (DLS). Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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13 pages, 3624 KiB

Open AccessArticle

Improvement of Laser-Induced Breakdown Spectroscopy Quantitative Performance Using Minimizing Signal Uncertainty as Signal Optimization Target: Taking the Ambient Pressure as an Example

by Kaifan Zhang, Jianxun Ji, Zhitan Liu, Zongyu Hou and Zhe Wang

Chemosensors 2024, 12(12), 277; https://doi.org/10.3390/chemosensors12120277 - 21 Dec 2024

Cited by 1 | Viewed by 1253

Abstract

Quantitative analysis performance is considered the Achilles’ heel of laser-induced breakdown spectroscopy. Improving the raw spectral signal is fundamental to achieving accurate quantification. Signal-to-noise ratio enhancement and uncertainty reduction are two targets to improve the raw spectral signal. Most LIBS studies choose the [...] Read more.

Quantitative analysis performance is considered the Achilles’ heel of laser-induced breakdown spectroscopy. Improving the raw spectral signal is fundamental to achieving accurate quantification. Signal-to-noise ratio enhancement and uncertainty reduction are two targets to improve the raw spectral signal. Most LIBS studies choose the maximum signal-to-noise ratio as the target to optimize the signal. However, there are no precise conclusions about how to optimize signal until now. It has been insisted by our group that the lowest signal uncertainty should be the optimization criterion, which is verified in this article. This study performed quantitative analysis on brass samples at three typical pressures: atmospheric pressure (100 kPa), pressure corresponding to the maximal signal-to-noise ratio (60 kPa), and pressure corresponding to the lowest signal uncertainty (5 kPa) under the optimal spatiotemporal window at each pressure based on a previous study. The results indicate that a pressure of 60 kPa led to a decrease in the accuracy and an increase in the precision of the quantitative analysis; the pressure of 5 kPa led to the highest accuracy and the best precision of the quantitative analysis. Reasons for changes in quantitative analysis are analyzed in detail through matrix effects and signal uncertainty. Therefore, selecting the pressure that corresponds to the lowest signal uncertainty can better improve the LIBS quantitative analysis performance. Signal uncertainty reduction is recommended as a more important direction for the LIBS community. Full article

(This article belongs to the Special Issue Application of Laser-Induced Breakdown Spectroscopy, 2nd Edition)

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Graphical abstract

19 pages, 3172 KiB

Open AccessReview

Origami-Inspired Biosensors: Exploring Diverse Applications and Techniques for Shape-Changing Sensor Platforms

by Shikha Patil, Shariq Suleman, Nigar Anzar, Jagriti Narang, Roberto Pilloton, Suna Timur, Emine Guler Celik, Chandra S. Pundir and Sudheesh K. Shukla

Chemosensors 2024, 12(12), 276; https://doi.org/10.3390/chemosensors12120276 - 21 Dec 2024

Cited by 3 | Viewed by 2394

Abstract

Biosensors are widely used across industries such as healthcare, food safety, and environmental monitoring, offering high stability and sensitivity compared to conventional methods. Recently, origami—the art of folding 2D structures into 3D forms—has emerged as a valuable approach in biosensor development, enabling the [...] Read more.

Biosensors are widely used across industries such as healthcare, food safety, and environmental monitoring, offering high stability and sensitivity compared to conventional methods. Recently, origami—the art of folding 2D structures into 3D forms—has emerged as a valuable approach in biosensor development, enabling the creation of shape-changing devices. These origami-based biosensors are particularly useful in precision medicine, rapid diagnostics, and resource-limited settings, offering affordable, highly precise, and portable solutions with diverse applications. Paper and biological substrates like DNA have been integrated with origami techniques to develop biosensors with enhanced functionality. The incorporation of aptamer origami into both paper and DNA biosensors further increases sensitivity and specificity for target detection. The concept of paper-based origami biosensors originated from using paper as a platform for biological assays, leading to significant advancements in design and functionality. These devices employ folding techniques to create channels and wells for manipulating samples and detecting target molecules through reactions with specific reagents. Similarly, DNA origami, introduced in 2006, has revolutionized biosensors by enabling the creation of precise molecular systems with tunable properties. Paper-based and DNA origami biosensors have immense potential to transform biosensing technologies in healthcare, food safety, and environmental monitoring. This review explores diverse origami-based biosensor techniques and their applications, including the role of aptamer origami in paper and DNA biosensors. Full article

(This article belongs to the Special Issue Feature Review Papers in Chemical/Bio-Sensors and Analytical Chemistry in 2024)

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24 pages, 8219 KiB

Open AccessArticle

Prediction of Potato Rot Level by Using Electronic Nose Based on Data Augmentation and Channel Attention Conditional Convolutional Neural Networks

by Jiayu Mai, Haonan Lin, Xuezhen Hong and Zhenbo Wei

Chemosensors 2024, 12(12), 275; https://doi.org/10.3390/chemosensors12120275 - 20 Dec 2024

Viewed by 1104

Abstract

This study introduces a novel approach for predicting the decay levels of potato by integrating an electronic nose system combined with feature-optimized deep learning models. The electronic nose system was utilized to collect volatile gas data from potatoes at different decay stages, offering [...] Read more.

This study introduces a novel approach for predicting the decay levels of potato by integrating an electronic nose system combined with feature-optimized deep learning models. The electronic nose system was utilized to collect volatile gas data from potatoes at different decay stages, offering a non-invasive method to classify decay levels. To mitigate data scarcity and improve training model robustness, a Gaussian Mixture Embedded Generative Adversarial Network (GMEGAN) was used to generate synthetic data, resulting in augmented datasets that increased diversity and improved model performance. Several machine learning and deep learning models, including traditional classifiers (SVM, LR, RF, ANN) and advanced neural networks (CNN, ECA-CNN, CAM-CNN, Conditional CNN), were trained and evaluated. Models incorporating feature-optimized channel attention modules (f-CAM, f-ECA) achieved a classification accuracy of up to 90.28%, significantly outperforming traditional machine learning models (72–77%) and standard CNN models (83.33%). The inclusion of GMEGAN-generated datasets further enhanced classification performance, especially for feature-optimized Conditional CNN models, with an observed increase in accuracy of up to 5.55%. A comprehensive evaluation of the GMEGAN-generated data, including feature mapping consistency, data distribution similarity, and quality metrics, demonstrated that the generated data closely resembled real data, thereby effectively enhancing dataset diversity. The proposed approach shows significant potential in improving classification accuracy and robustness for agricultural quality assessment, particularly in predicting the decay levels of potatoes. Full article

(This article belongs to the Special Issue Advanced Real-Time On-Site Sensing Technologies for Food and Environment Analysis: 2nd Edition)

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27 pages, 4617 KiB

Open AccessReview

A Review on Analytical Techniques for Quantitative Detection of Biogenic Amines in Aquatic Products

by Zixin Chen, Jing Xie and Jun Mei

Chemosensors 2024, 12(12), 274; https://doi.org/10.3390/chemosensors12120274 - 20 Dec 2024

Cited by 3 | Viewed by 2125

Abstract

Aquatic products contain a large amount of protein, which can promote the production of a variety of biogenic amines through the function of microorganisms. Biogenic amines are a broad category of organic substances that contain nitrogen and have a low molecular weight. The [...] Read more.

Aquatic products contain a large amount of protein, which can promote the production of a variety of biogenic amines through the function of microorganisms. Biogenic amines are a broad category of organic substances that contain nitrogen and have a low molecular weight. The presence of biogenic amines can cause the deterioration and excessive accumulation of aquatic products, which can cause damage to human health. Therefore, it is essential to discover a fast, convenient, and easy to operate method for the determination of biogenic amines in aquatic products. In this paper, the function and research significance of biogenic amines are analyzed from the aspects of their formation, toxicological properties, harm to the human body, and control methods. Several common direct detection techniques and indirect techniques for biogenic amines are briefly introduced especially sensors. This review provides references for efficient detection in the future. Full article

(This article belongs to the Special Issue Feature Review Papers in Chemical/Bio-Sensors and Analytical Chemistry in 2024)

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14 pages, 3144 KiB

Open AccessArticle

Fabrication of a Near-Infrared Upconversion Nanosensor for the Ultrasensitive Detection of eARGs Using a Dual-Amplification Strategy

by Yuqi Zhang, Mengmeng Li, Yan Zhang, Xinli Shi, Yujun Sun, Chunping Ge, M. Haris Mahmood, Zhaomei Sun, Xinyue Song and Shusheng Zhang

Chemosensors 2024, 12(12), 273; https://doi.org/10.3390/chemosensors12120273 - 19 Dec 2024

Cited by 1 | Viewed by 1335

Abstract

Extracellular antibiotic resistance genes (eARGs) have emerged as significant environmental contaminants due to their role in the transmission and proliferation of antibiotic-resistant bacteria, posing a major threat to global health. Traditional detection methods for eARGs require complicated equipment, lengthy analysis times, and relatively [...] Read more.

Extracellular antibiotic resistance genes (eARGs) have emerged as significant environmental contaminants due to their role in the transmission and proliferation of antibiotic-resistant bacteria, posing a major threat to global health. Traditional detection methods for eARGs require complicated equipment, lengthy analysis times, and relatively low selectivity. Furthermore, eARGs are present in low concentrations in surface water samples, which presents considerable challenges to the sensitivity of detection assays. Therefore, there is an urgent need to develop more accessible, stable, and sensitive detection methods. In this work, we developed an ultrasensitive upconversion nanosensor utilizing a dual-amplification strategy for the detection of trace eARGs (bla_-TEM). The upconversion nanosensor was activated upon the capture of bla_-TEM and subsequently enriched through magnetic separation. Following this, a cascade nicking-polymerization amplification process occurred in a single reaction facilitated by a magnetic capture probe, an upconversion recognition probe, and the relevant enzymes. The upconversion nanosensor functions as both the direct target-recognizing moieties and signal reporters, replacing the energy donor in conventional luminescence resonance energy transfer-based upconversion nanosensors. Ultimately, the strategy demonstrated excellent sensitivity with a limit of detection (LOD) of 0.093 aM, rapid detection in less than one hour, good selectivity, and high accuracy compared to conventional polymerase chain reaction (PCR) assays. These findings provide valuable insights for the development of ultrasensitive detection assays for emerging environmental pollutants. Full article

(This article belongs to the Special Issue Dedicated to Professor Huangxian Ju and Professor Xueji Zhang on the Occasion of Their 60th Birthday for Their Outstanding Contributions to the Field of Chemical/Bio Sensors)

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16 pages, 6729 KiB

Open AccessArticle

A Practical Approach to Triclosan Detection: A Novel Y₂O₃@GCN-Modified Carbon Paste Electrode for Sensitive and Selective Detection in Environmental and Consumer Products

by Aleksandar Mijajlović, Miloš Ognjanović, Vesna Stanković, Tijana Mutić, Slađana Đurđić, Branka B. Petković and Dalibor M. Stanković

Chemosensors 2024, 12(12), 272; https://doi.org/10.3390/chemosensors12120272 - 19 Dec 2024

Cited by 1 | Viewed by 1135

Abstract

This study presents the development of a novel electrochemical sensor for the sensitive and selective detection of triclosan (TSC) on a carbon paste electrode (CPE) modified with graphitic carbon nitride (GCN) and doped with yttrium oxide nanoparticles (Y₂O₃). The [...] Read more.

This study presents the development of a novel electrochemical sensor for the sensitive and selective detection of triclosan (TSC) on a carbon paste electrode (CPE) modified with graphitic carbon nitride (GCN) and doped with yttrium oxide nanoparticles (Y₂O₃). The materials and proposed electrode were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The modified sensor exhibited significantly enhanced electrocatalytic activity towards TSC compared to the unmodified CPE. The sensor demonstrated a wide linear detection range, which was obtained using square wave voltammetric method (SWV), with a low limit of detection (LOD) of 0.137 µM and a low limit of quantification (LOQ) of 0.455 µM. The sensor also exhibited excellent selectivity towards TSC in the presence of various interfering substances. The practical applicability of the sensor was evaluated through real-sample analysis, where it was successfully used to determine TSC levels in tap water and toothpaste samples. The sensor demonstrated high recovery rates and minimal matrix effects, indicating its suitability for real-world applications. In conclusion, the developed CPE/Y₂O₃@GCN sensor offers a promising approach for the sensitive, selective, and reliable detection of triclosan in environmental and consumer products. Full article

(This article belongs to the Special Issue Electrochemical Sensors and Biosensors for Environmental Detection)

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30 pages, 10673 KiB

Open AccessReview

Advancing Biosensing and Imaging with DNA-Templated Metal Nanoclusters: Synthesis, Applications, and Future Challenges—A Review

by Jiacheng Li, Sidra Parvez and Tong Shu

Chemosensors 2024, 12(12), 271; https://doi.org/10.3390/chemosensors12120271 - 19 Dec 2024

Cited by 1 | Viewed by 1400

Abstract

Metal nanoclusters (MNCs) are emerging as a novel class of luminescent nanomaterials with unique properties, bridging the gap between individual atoms and nanoparticles. Among these, DNA-templated MNCs have gained significant attention due to the synergistic combination of MNCs’ properties (such as exceptional resistance [...] Read more.

Metal nanoclusters (MNCs) are emerging as a novel class of luminescent nanomaterials with unique properties, bridging the gap between individual atoms and nanoparticles. Among these, DNA-templated MNCs have gained significant attention due to the synergistic combination of MNCs’ properties (such as exceptional resistance to photostability, size-tunable emission, and excellent optical characteristics) with the inherent advantages of DNA, including programmability, functional modification, molecular recognition, biocompatibility, and water solubility. The programmability and biocompatibility of DNA offer precise control over the size, shape, and composition of MNCs, leading to tunable optical, electrical, and magnetic properties. This review delves into the complex relationship between DNA sequence, structure, and the resulting MNC properties. By adjusting parameters such as DNA sequence, length, and conformation, the size, morphology, and composition of the corresponding MNCs can be fine-tuned, enabling insights into how DNA structure influences the optical, electrical, and magnetic properties of MNCs. Finally, this review highlights the remarkable versatility and latest advancements of DNA-templated MNCs, particularly in biosensing and imaging, and explores their future potential to revolutionize biomedical applications. Full article

(This article belongs to the Special Issue Dedicated to Professor Huangxian Ju and Professor Xueji Zhang on the Occasion of Their 60th Birthday for Their Outstanding Contributions to the Field of Chemical/Bio Sensors)

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16 pages, 4300 KiB

Open AccessArticle

A Simple Green Method for the Determination of Hydrogen Peroxide and Fe(III)/Fe(II) Species Based on Monitoring the Decolorization Process of Polymethine Dye Using an Optical Immersion Probe

by Arina Skok, Yaroslav Bazel and Maksym Fizer

Chemosensors 2024, 12(12), 270; https://doi.org/10.3390/chemosensors12120270 - 19 Dec 2024

Cited by 1 | Viewed by 1053

Abstract

We have found that the dye 1,3,3-trimethyl-2-((1′E,3′E,5′E)-5’-(1″,3″,3″-trimethylindol-(2′E)-ylidene)-penta-1″,3″-dien-1″-yl)-3H-indol-1-ium (DTMI-5) can be successfully used for the simple green determination of H₂O₂ and Fe(III)/Fe(II) species. The dye is characterized by a successful combination of spectral, protolytic, and redox properties, [...] Read more.

We have found that the dye 1,3,3-trimethyl-2-((1′E,3′E,5′E)-5’-(1″,3″,3″-trimethylindol-(2′E)-ylidene)-penta-1″,3″-dien-1″-yl)-3H-indol-1-ium (DTMI-5) can be successfully used for the simple green determination of H₂O₂ and Fe(III)/Fe(II) species. The dye is characterized by a successful combination of spectral, protolytic, and redox properties, and the process of its decolorization in the Fenton reaction is monitored using an optical immersion probe. Theoretical calculations of the reactive sites in the DTMI-5 molecule under free radical attack reveal that the methine groups of the penta-1′,3′-dien-1′-yl linker serve as the primary reactive centers in Fe³⁺ or Fenton-type oxidation conditions. Density functional theory (DFT) calculations indicate that the redox potentials of the examined structures range from 0.34 to 1.65 eV. The experimentally observed broad peak at 340–360 nm, which appears after the interaction of DTMI-5 with the Fenton reagent, is attributed to the formation of aldehyde-type oxidation products, whose theoretical CIS(D) absorption maxima were 358.1 and 337.4 nm. The influence of various factors on the course of the reaction was experimentally investigated. The most important analytical characteristics of the methods, such as linearity intervals of calibration graphs, precision, LOD and LOQ values, selectivity coefficients, etc., were determined. The developed methods were applied to model and real samples (water, oxidation emulsion, and fertilizer). Full article

(This article belongs to the Special Issue Low-Cost Chemosensors for Applications in Environment, Health, Food, and Industry Process Control)

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Graphical abstract

22 pages, 1085 KiB

Open AccessReview

Recent Progress in Saliva-Based Sensors for Continuous Monitoring of Heavy Metal Levels Linked with Diabetes and Obesity

by Liliana Anchidin-Norocel, Wesley K. Savage, Alexandru Nemțoi, Mihai Dimian and Claudiu Cobuz

Chemosensors 2024, 12(12), 269; https://doi.org/10.3390/chemosensors12120269 - 19 Dec 2024

Cited by 4 | Viewed by 1439

Abstract

Sensors are versatile technologies that provide rapid and efficient diagnostic results, making them invaluable tools in public health for measuring and monitoring community exposure to environmental contaminants. Heavy metals such as lead, mercury, and cadmium, commonly found in food and water, can accumulate [...] Read more.

Sensors are versatile technologies that provide rapid and efficient diagnostic results, making them invaluable tools in public health for measuring and monitoring community exposure to environmental contaminants. Heavy metals such as lead, mercury, and cadmium, commonly found in food and water, can accumulate in the body and have toxic effects, contributing to the development of conditions like obesity and diabetes. Traditional methods for detecting these metals often require invasive blood samples; however, sensors can utilize saliva, offering a noninvasive and simplified approach for public health screening. The use of saliva as a diagnostic fluid represents a major advance in population health monitoring due to its low cost, noninvasiveness, and ease of collection. Recent advances in sensor technology have enabled the development of diagnostic tests that link heavy metal levels in saliva with the risk of developing obesity and diabetes. Optimizing these sensors could facilitate the identification of individuals or groups at risk, enabling targeted, personalized preventive measures. Sensors that use saliva for detecting heavy metals hold promise for diagnosing and preventing metabolic diseases, providing valuable insights into the link between heavy metal exposure and metabolic health. Full article

(This article belongs to the Special Issue Low-Cost Chemosensors for Applications in Environment, Health, Food, and Industry Process Control)

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16 pages, 5091 KiB

Open AccessArticle

Novel Sequential Detection of NO₂ and C₂H₅OH in SnO₂ MEMS Arrays for Enhanced Selectivity in E-Nose Applications

by Mahaboobbatcha Aleem, Yilu Zhou, Swati Deswal, Bongmook Lee and Veena Misra

Chemosensors 2024, 12(12), 268; https://doi.org/10.3390/chemosensors12120268 - 19 Dec 2024

Viewed by 4886

Abstract

This study explores the surface chemistry and electrical responses of ultra-high-sensitivity SnO₂ MEMS arrays to enable a novel sequential detection methodology for detecting nitrogen dioxide (NO₂) and ethanol (C₂H₅OH) as a route to achieve selective gas [...] Read more.

This study explores the surface chemistry and electrical responses of ultra-high-sensitivity SnO₂ MEMS arrays to enable a novel sequential detection methodology for detecting nitrogen dioxide (NO₂) and ethanol (C₂H₅OH) as a route to achieve selective gas sensing in electronic nose (E-nose) applications. Utilizing tin oxide (SnO₂) thin films deposited via atomic layer deposition (ALD), the array achieves the lowest reported detection limits of 8 parts per billion (ppb) for NO₂. The research delves into the detection mechanisms of NO₂ and C₂H₅OH, both individually and in subsequent exposures, assessing the sensor’s dynamic response across various operating temperatures. It demonstrates rapid response and recovery times, with averages of 48 s and 277 s for NO₂ and 40 and 48 for C₂H₅OH. Understanding the role of individual gases on the SnO₂ surface chemistry is paramount in discerning subsequent gas exposure behavior. The oxidizing behavior of C₂H₅OH following NO₂ exposure is attributed to interactions between NO₂ and oxygen vacancies on the SnO₂ surface, which leads to the formation of nitrate or nitrite species. These species subsequently influence interactions with C₂H₅OH, inducing oxidizing properties, and need to be carefully considered. Principal component analysis (PCA) was used to further improve the sensor’s capability to precisely identify and quantify gas mixtures, improving its applicability for real-time monitoring in complex scenarios. Full article

(This article belongs to the Special Issue Electronic Nose and Electronic Tongue for Substance Analysis)

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26 pages, 2108 KiB

Open AccessReview

Sustainable Biopolymer-Based Electrochemical Sensors for Trace Heavy Metal Determination in Water: A Comprehensive Review

by Rabiaa Helim, Ali Zazoua and Hafsa Korri-Youssoufi

Chemosensors 2024, 12(12), 267; https://doi.org/10.3390/chemosensors12120267 - 17 Dec 2024

Cited by 1 | Viewed by 2387

Abstract

The growing concern over heavy metal contamination in environmental and industrial settings has intensified the need for sensitive, selective, and cost-effective detection technologies. Electrochemical sensors, due to their high sensitivity, rapid response, and portability, have emerged as promising tools for detecting heavy metals. [...] Read more.

The growing concern over heavy metal contamination in environmental and industrial settings has intensified the need for sensitive, selective, and cost-effective detection technologies. Electrochemical sensors, due to their high sensitivity, rapid response, and portability, have emerged as promising tools for detecting heavy metals. Recent years have seen significant progress in utilizing biopolymer-based materials to enhance the performance of these sensors. Biopolymers, derived from renewable raw materials, have garnered considerable interest in both science and industry. These biopolymer-based composites are increasingly recognized as superior alternatives to conventional non-biodegradable materials because of their ability to degrade through environmental exposure. This review provides a comprehensive overview of recent advancements in biopolymer-based electrochemical sensors for heavy metal detection. It discusses various types of biopolymers and bio-sourced polymers, their extraction methods, and chemical properties. Additionally, it highlights the state of the art in applying biopolymers to electrochemical sensor development for heavy metal detection, synthesizing recent advances and offering insights into design principles, fabrication strategies, and analytical performance. This review underscores the potential of biopolymer-based sensors as cost-effective, eco-friendly, and efficient tools for addressing the pressing issue of heavy metal contamination in water and discusses their advantages and limitations. It also outlines future research directions to further enhance the performance and applicability of these sensors. Full article

(This article belongs to the Special Issue Feature Review Papers in Chemical/Bio-Sensors and Analytical Chemistry in 2024)

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15 pages, 2271 KiB

Open AccessArticle

Determination of Methotrexate Using an Electrochemical Sensor Based on Carbon Paste Electrode Modified with NiO Nanosheets and Ionic Liquid

by Peyman Mohammadzadeh Jahani, Somayeh Tajik, Hadi Beitollahi, Fariba Garkani Nejad and Zahra Dourandish

Chemosensors 2024, 12(12), 266; https://doi.org/10.3390/chemosensors12120266 - 17 Dec 2024

Cited by 3 | Viewed by 1266

Abstract

In this paper, the application of NiO nanosheets (NiO NSs) for the detection of methotrexate (MTX) is described. The NiO NSs were synthesized using a hydrothermal method. The electrocatalytic activity of two modifiers, ionic liquid (IL) and NiO NSs, was examined on a [...] Read more.

In this paper, the application of NiO nanosheets (NiO NSs) for the detection of methotrexate (MTX) is described. The NiO NSs were synthesized using a hydrothermal method. The electrocatalytic activity of two modifiers, ionic liquid (IL) and NiO NSs, was examined on a carbon paste electrode (CPE) in relation to MTX, utilizing voltammetry methods such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), and chronoamperometry at 0.1 M phosphate buffer solution (PBS) pH = 7.0. The anodic peak currents for MTX on the NiO NSs/IL/CPE were approximately 3.5 times greater than those on unmodified CPE. Based on DPV measurements, the electrochemical sensor demonstrated a linear response in the concentration range (LDR: 0.01 µM to 160.0 µM), with a limit of detection (LOD: 0.003 µM). Moreover, the NiO NSs/IL/CPE sensor demonstrated good stability, repeatability, reproducibility, and selectivity, which were of importance in the electroanalysis of compounds. Lastly, the practicality of the NiO NSs/IL/CPE sensor was assessed by analyzing MTX levels in urine samples and pharmaceutical formulation, yielding satisfactory recovery rates of 97.1% to 103.3%. Full article

(This article belongs to the Special Issue Progress of Photoelectrochemical Analysis and Sensors)

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16 pages, 3550 KiB

Open AccessArticle

Investigation of Microbial Fermentation Degree of Pu-Erh Tea Using Deep Learning Coupled Colorimetric Sensor Array via Prediction of Total Polyphenols

by Min Liu, Cui Jiang, Md Mehedi Hassan, Xinru Zhang, Runxian Wang, Renyong Cao, Wei Sheng and Huanhuan Li

Chemosensors 2024, 12(12), 265; https://doi.org/10.3390/chemosensors12120265 - 16 Dec 2024

Viewed by 1176

Abstract

The degree of tea fermentation is crucial as it ultimately indicates the quality of the tea. Hence, this study developed a total polyphenol prediction system for Pu-erh tea liquid using eight porphyrin dyes and one pH dye in a printed colorimetric sensor array [...] Read more.

The degree of tea fermentation is crucial as it ultimately indicates the quality of the tea. Hence, this study developed a total polyphenol prediction system for Pu-erh tea liquid using eight porphyrin dyes and one pH dye in a printed colorimetric sensor array (CSA) coupled with a convolutional neural network (CNN) during microbial fermentation. Firstly, the Box–Behnken sampling method was applied to optimize the degree of microbial fermentation of Pu-erh tea liquid using the response surface methodology. Under optimized conditions, the polyphenol degradation rate reached up to 66.146%. CSA images were then collected from the volatile compounds of Pu-erh tea-reacted CSA sensors. Subsequently, six chemometric approaches were comparatively investigated, and CNN achieved the best results for predicting total polyphenol content. Therefore, the results suggest that the proposed approach can be used to predict the degree of fermentation by measuring total polyphenols in microbial-fermented Pu-erh tea liquid. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Sensors for Food Analysis)

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15 pages, 1379 KiB

Open AccessReview

Investigating Sepsis-Associated Delirium Through Optical Neuroimaging: A New Frontier in Critical Care Research

by Shixie Jiang, Matthew Gunther, Jose R. Maldonado, Philip A. Efron, Steven T. DeKosky and Huabei Jiang

Chemosensors 2024, 12(12), 264; https://doi.org/10.3390/chemosensors12120264 - 15 Dec 2024

Cited by 1 | Viewed by 1901

Abstract

Sepsis is a life-threatening syndrome consisting of physiological, pathological, and biochemical abnormalities induced by infection which continues to be a major public health burden. It remains one of the most common reasons for intensive care unit (ICU) admission. Delirium precipitated by sepsis in [...] Read more.

Sepsis is a life-threatening syndrome consisting of physiological, pathological, and biochemical abnormalities induced by infection which continues to be a major public health burden. It remains one of the most common reasons for intensive care unit (ICU) admission. Delirium precipitated by sepsis in the intensive care setting is one of its most common neuropsychiatric complications that leads to prolonged hospitalization, increased mortality, and an increased risk of incident dementia. Understanding the pathophysiology and neurobiological mechanisms of sepsis-associated delirium is difficult; neuroimaging biomarkers are lacking due to difficulties with imaging critically ill patients. Optical imaging techniques, including near-infrared spectroscopy and diffuse optical tomography are potentially promising approaches for investigating this pathophysiology due to their portability and high spatiotemporal resolution. In this review, we examine the emergence of optical neuroimaging techniques for the study of sepsis-associated delirium in the ICU and how they can further advance our knowledge and lead to the development of improved preventative, predictive, and therapeutic strategies. Full article

(This article belongs to the Special Issue Feature Review Papers in Chemical/Bio-Sensors and Analytical Chemistry in 2024)

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54 pages, 7881 KiB

Open AccessReview

Spectroscopy-Based Methods and Supervised Machine Learning Applications for Milk Chemical Analysis in Dairy Ruminants

by Aikaterini-Artemis Agiomavriti, Maria P. Nikolopoulou, Thomas Bartzanas, Nikos Chorianopoulos, Konstantinos Demestichas and Athanasios I. Gelasakis

Chemosensors 2024, 12(12), 263; https://doi.org/10.3390/chemosensors12120263 - 13 Dec 2024

Cited by 1 | Viewed by 2258

Abstract

Milk analysis is critical to determine its intrinsic quality, as well as its nutritional and economic value. Currently, the advancements and utilization of spectroscopy-based techniques combined with machine learning algorithms have made the development of analytical tools and real-time monitoring and prediction systems [...] Read more.

Milk analysis is critical to determine its intrinsic quality, as well as its nutritional and economic value. Currently, the advancements and utilization of spectroscopy-based techniques combined with machine learning algorithms have made the development of analytical tools and real-time monitoring and prediction systems in the dairy ruminant sector feasible. The objectives of the current review were (i) to describe the most widely applied spectroscopy-based and supervised machine learning methods utilized for the evaluation of milk components, origin, technological properties, adulterants, and drug residues, (ii) to present and compare the performance and adaptability of these methods and their most efficient combinations, providing insights into the strengths, weaknesses, opportunities, and challenges of the most promising ones regarding the capacity to be applied in milk quality monitoring systems both at the point-of-care and beyond, and (iii) to discuss their applicability and future perspectives for the integration of these methods in milk data analysis and decision support systems across the milk value-chain. Full article

(This article belongs to the Special Issue Artificial Intelligence (AI)/Machine Learning (ML)-Assisted Chemical Sensors)

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20 pages, 5553 KiB

Open AccessArticle

Investigation of Long-Term Performance of a Proposed Cost-Effective HCl Non-Dispersive Infrared Analyzer at Real Stationary Sources

by Byeong-Gyu Park, Trieu-Vuong Dinh, Sang-Woo Lee, In-Young Choi, Byung-Chan Cho, Da-Hyun Baek, Jong-Choon Kim and Jo-Chun Kim

Chemosensors 2024, 12(12), 262; https://doi.org/10.3390/chemosensors12120262 - 13 Dec 2024

Cited by 1 | Viewed by 1118

Abstract

The zero drift, interference, and sensitivity of an HCl analyzer based on a non-dispersive infrared (NDIR) technique can be improved to develop a cost-effective solution for continuous emission monitoring systems (CEMSs). To achieve these improvements, the same bandpass filter technique, negligible interference bandpass [...] Read more.

The zero drift, interference, and sensitivity of an HCl analyzer based on a non-dispersive infrared (NDIR) technique can be improved to develop a cost-effective solution for continuous emission monitoring systems (CEMSs). To achieve these improvements, the same bandpass filter technique, negligible interference bandpass filter, and optimal path length are applied to the analyzer. Laboratory inspections and long-term field trials are conducted to evaluate the performance of the analyzer. A metalworking factory and a cement factory are selected for field trials. In laboratory inspections, the relative error of the analyzer is less than 1%, aligning closely with the results obtained from standard ion chromatography methods. Moreover, the basic specifications of the proposed analyzer are comparable to those of commercial HCl analyzers. In field trials, the NDIR analyzer shows a significant bias compared to the standard method. However, when considering the difference between HCl emission levels and HCl emission standards, the relative errors are less than 10%. These results suggest the proposed NDIR analyzer is a practical option for the CEMS of metalworking and cement factories. However, seasonal variations should be considered when the temperatures of gas emissions are low. Full article

(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)

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12 pages, 5960 KiB

Open AccessArticle

CRDS Technology-Based Integrated Breath Gas Detection System for Breath Acetone Real-Time Accurate Detection Application

by Jing Sun, Dongxin Shi, Le Wang, Xiaolin Yu, Binghong Song, Wangxin Li, Jiankun Zhu, Yong Yang, Bingqiang Cao and Chenyu Jiang

Chemosensors 2024, 12(12), 261; https://doi.org/10.3390/chemosensors12120261 - 13 Dec 2024

Cited by 1 | Viewed by 1302

Abstract

The monitoring of acetone in exhaled breath is expected to provide a noninvasive and painless method for dynamic monitoring of summarized physiological metabolic status during obesity treatment. Although the commonly used Mass Spectrometry (MS) technology has high accuracy, the long detection time and [...] Read more.

The monitoring of acetone in exhaled breath is expected to provide a noninvasive and painless method for dynamic monitoring of summarized physiological metabolic status during obesity treatment. Although the commonly used Mass Spectrometry (MS) technology has high accuracy, the long detection time and large equipment size limit the application of daily bedside detection. As for the real-time and accurate detection of acetone, the gas sensor has become the best choice of gas detection technology, but it is easy to be disturbed by water vapor in breath gas. An integrated breath gas detection system based on cavity ring-down spectroscopy (CRDS) is reported in this paper, which is a laser absorption spectroscopy technique with high-sensitivity detection and absolute quantitative analysis. The system uses a 266 nm single-wavelength ultraviolet laser combined with a breath gas pretreatment unit to effectively remove the influence of water vapor. The ring-down time of this system was 1.068 μs, the detection sensitivity was 1 ppb, and the stability of the system was 0.13%. The detection principle of the integrated breath gas detection system follows Lambert–Beer’s law, which is an absolute measurement with very high detection accuracy, and was further validated by Gas Chromatography–Mass Spectrometer (GC-MS) testing. Significant differences in the response of the integrated breath gas detection system to simulated gases containing different concentrations of acetone indicate the potential of the system for the detection of trace amounts of acetone. Meanwhile, the monitoring of acetone during obesity treatment also signifies the feasibility of this system in the dynamic monitoring of physiological indicators, which is not only important for the optimization of the obesity treatment process but also promises to shed further light on the interaction between obesity treatment and physiological metabolism in medicine. Full article

(This article belongs to the Special Issue Advanced Chemical Sensors for Gas Detection)

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11 pages, 5810 KiB

Open AccessArticle

Reading Dye-Based Colorimetric Inks: Achieving Color Consistency Using Color QR Codes

by Ismael Benito-Altamirano, Laura Engel, Ferran Crugeira, Miriam Marchena, Jürgen Wöllenstein, Joan Daniel Prades and Cristian Fàbrega

Chemosensors 2024, 12(12), 260; https://doi.org/10.3390/chemosensors12120260 - 13 Dec 2024

Cited by 2 | Viewed by 1252

Abstract

Color consistency when reading colorimetric sensors is a key factor for this technology. Here, we demonstrate how the usage of machine-readable patterns, like QR codes, can be used to solve the problem. We present our approach of using back-compatible color QR codes as [...] Read more.

Color consistency when reading colorimetric sensors is a key factor for this technology. Here, we demonstrate how the usage of machine-readable patterns, like QR codes, can be used to solve the problem. We present our approach of using back-compatible color QR codes as colorimetric sensors, which are common QR codes that also embed a set of hundreds of color references as well as colorimetric indicators. The method allows locating the colorimetric sensor within the captured scene and to perform automated color correction to ensure color consistency regardless of the hardware used. To demonstrate it, a

C O_{2}

-sensitive colorimetric indicator was printed on top of a paper-based substrate using screen printing. This indicator was formulated for Modified Atmosphere Packaging (MAP) applications. To verify the method, the sensors were exposed to several environmental conditions (both in gas composition and light conditions). And, images were captured with an 8M pixel digital camera sensor, similar to those used in smartphones. Our results show that the sensors have a relative error of 9% when exposed with a

C O_{2}

concentration of 20%. This is a good result for low-cost disposable sensors that are not intended for permanent use. However, as soon as light conditions change (2500–6500 K), this error increases up to $ϵ_{20}$ = 440% (rel. error at 20%

C O_{2}

concentration) rendering the sensors unusable. Within this work, we demonstrate that our color QR codes can reduce the relative error to $ϵ_{20}$ = 14%. Furthermore, we show that the most common color correction, white balance, is not sufficient to address the color consistency issue, resulting in a relative error of $ϵ_{20}$ = 90%. Full article

(This article belongs to the Special Issue Novel Gas Sensing Approaches: From Fabrication to Application)

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21 pages, 16297 KiB

Open AccessReview

Silsesquioxanes as Promising Materials for the Development of Electrochemical (Bio)Sensors

by Felipe Zahrebelnei, Ariane Caroline Ribicki, Aline Martins Duboc Natal, Sérgio Toshio Fujiwara, Karen Wohnrath, Dhésmon Lima and Christiana Andrade Pessôa

Chemosensors 2024, 12(12), 259; https://doi.org/10.3390/chemosensors12120259 - 12 Dec 2024

Viewed by 1419

Abstract

Silsesquioxanes (SSQs) comprise an interesting and versatile class of three-dimensional organosilicate oligomers with diverse structural arrangements and interesting physicochemical properties. SSQs are of considerable technological interest, with applications that include the development of electrochemical detection devices. The presence of functional groups on their [...] Read more.

Silsesquioxanes (SSQs) comprise an interesting and versatile class of three-dimensional organosilicate oligomers with diverse structural arrangements and interesting physicochemical properties. SSQs are of considerable technological interest, with applications that include the development of electrochemical detection devices. The presence of functional groups on their structures enables the anchoring of different electroactive and conductive species, such as complexes, metal nanoparticles and carbon nanomaterials, and biomolecules, including enzymes, nucleic acids, and antibodies, which boosts the sensitivity and selectivity of the obtained (bio)sensors. These materials can also be incorporated into conductive matrices using a range of methods, which enhances their versatility. This mini review provides an overview of the most recent applications of hybrid organic–inorganic SSQs in the preparation of modified electrodes for the development of electrochemical sensors and biosensors. Special focus is placed on the incorporation of nanomaterials in their polymeric structure and on the design and fabrication of electrochemical devices using different strategies. Full article

(This article belongs to the Special Issue Electrochemical Sensors and Biosensors for Food, Environmental and Biomedical Analysis)

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14 pages, 2120 KiB

Open AccessArticle

Flexible Polymer-Based Electrodes for Detecting Depression-Related Theta Oscillations in the Medial Prefrontal Cortex

by Rui Sun, Shunuo Shang, Qunchen Yuan, Ping Wang and Liujing Zhuang

Chemosensors 2024, 12(12), 258; https://doi.org/10.3390/chemosensors12120258 - 10 Dec 2024

Viewed by 1259

Abstract

This study investigates neural activity changes in the medial prefrontal cortex (mPFC) of a lipopolysaccharide (LPS)-induced acute depression mouse model using flexible polymer multichannel electrodes, local field potential (LFP) analysis, and a convolutional neural network-long short-term memory (CNN-LSTM) classification model. LPS treatment effectively [...] Read more.

This study investigates neural activity changes in the medial prefrontal cortex (mPFC) of a lipopolysaccharide (LPS)-induced acute depression mouse model using flexible polymer multichannel electrodes, local field potential (LFP) analysis, and a convolutional neural network-long short-term memory (CNN-LSTM) classification model. LPS treatment effectively induced depressive-like behaviors, including increased immobility in the tail suspension and forced swim tests, as well as reduced sucrose preference. These behavioral outcomes validate the LPS-induced depressive phenotype, providing a foundation for neurophysiological analysis. Flexible polymer-based electrodes enabled the long-term recording of high-quality LFP and spike signals from the mPFC. Time-frequency and power spectral density (PSD) analyses revealed a significant increase in theta band (3–8 Hz) amplitude under depressive conditions. Using theta waveform features extracted via empirical mode decomposition (EMD), we classified depressive states with a CNN-LSTM model, achieving high accuracy in both training and validation sets. This study presents a novel approach for depression state recognition using flexible polymer electrodes, EMD, and CNN-LSTM modeling, suggesting that heightened theta oscillations in the mPFC may serve as a neural marker for depression. Future studies may explore theta coupling across brain regions to further elucidate neural network disruptions associated with depression. Full article

(This article belongs to the Special Issue Advancements of Chemosensors and Biosensors in China—2nd Edition)

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22 pages, 6425 KiB

Open AccessReview

Photoacoustic Imaging of pH-Sensitive Optical Sensors in Biological Tissues

by Hyunjun Kye, Dongyoung Jo, Sanghwa Jeong, Chulhong Kim and Jeesu Kim

Chemosensors 2024, 12(12), 257; https://doi.org/10.3390/chemosensors12120257 - 9 Dec 2024

Cited by 1 | Viewed by 1906

Abstract

Photoacoustic imaging is an emerging biomedical imaging technique that enables non-invasive visualization of the optical absorption properties of biological tissues in vivo. Although numerous studies have used contrast agents to achieve high-contrast imaging in deep tissues, targeting specific areas remains a challenge when [...] Read more.

Photoacoustic imaging is an emerging biomedical imaging technique that enables non-invasive visualization of the optical absorption properties of biological tissues in vivo. Although numerous studies have used contrast agents to achieve high-contrast imaging in deep tissues, targeting specific areas remains a challenge when using agents that are continuously activated. Recent research has focused on developing triggered contrast agents that are selectively activated in target areas. This review delves into the use of pH-triggered contrast agents in photoacoustic imaging, which take advantage of the lower pH of the tumor microenvironment compared to normal tissues. The paper discusses the mechanisms of pH-triggered contrast agents that contribute to improving depth and contrast in photoacoustic tumor imaging. In addition, the integration of functionalities, such as photothermal therapy and drug delivery monitoring, into these agents demonstrates significant potential for biomedical applications. Full article

(This article belongs to the Collection pH Sensors, Biosensors and Systems)

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19 pages, 8894 KiB

Open AccessArticle

The Effect of Doping rGO with Nanosized MnO₂ on Its Gas Sensing Properties

by Mohamed Ayoub Alouani, Juan Casanova-Chafer, Santiago de Bernardi-Martín, Alejandra García-Gómez, Foad Salehnia, José Carlos Santos-Ceballos, Alejandro Santos-Betancourt, Xavier Vilanova and Eduard Llobet

Chemosensors 2024, 12(12), 256; https://doi.org/10.3390/chemosensors12120256 - 6 Dec 2024

Cited by 4 | Viewed by 1606

Abstract

Manganese dioxide (MnO₂) has drawn attention as a sensitiser to be incorporated in graphene-based chemoresistive sensors thanks to its promising properties. In this regard, a rGO@MnO₂ sensing material was prepared and deposited on two different substrates (silicon and Kapton). The [...] Read more.

Manganese dioxide (MnO₂) has drawn attention as a sensitiser to be incorporated in graphene-based chemoresistive sensors thanks to its promising properties. In this regard, a rGO@MnO₂ sensing material was prepared and deposited on two different substrates (silicon and Kapton). The effect of the substrate nature on the morphology and sensing behaviour of the rGO@MnO₂ material was thoroughly analysed and reported. These sensors were exposed to different dilutions of NO₂ ranging from 200 ppb to 1000 ppb under dry and humid conditions (25% RH and 70% RH) at room temperature. rGO@MnO₂ deposited on Kapton showed the highest response of 6.6% towards 1 ppm of NO₂ under dry conditions at RT. Other gases or vapours such as NH₃, CO, ethanol, H₂ and benzene were also tested. FESEM, HRTEM, Raman, XRD and ATR-IR were used to characterise the prepared sensors. The experimental results showed that the incorporation of nanosized MnO₂ in the rGO material enhanced its response towards NO₂. Moreover, this material also showed very good responses toward NH₃ both under dry and humid conditions, with the rGO@MnO₂ sensor on silicon showing the highest response of 18.5% towards 50 ppm of NH₃ under 50% RH at RT. Finally, the synthetised layers showed no cross-responsiveness towards other toxic gases. Full article

(This article belongs to the Special Issue Advanced Chemical Sensors for Gas Detection)

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32 pages, 8812 KiB

Open AccessReview

Recent Progress in Surface Acoustic Wave Sensors Based on Low-Dimensional Materials and Their Applications

by Qinhao Lin, Chunxia Zhao, Mingyu Li and Hao Xu

Chemosensors 2024, 12(12), 255; https://doi.org/10.3390/chemosensors12120255 - 5 Dec 2024

Cited by 1 | Viewed by 2429

Abstract

Benefitting from high sensitivity, rapid response, and cost-effectiveness, surface acoustic wave (SAW) sensors have found extensive applications across various fields, including biomedical diagnostics, environmental monitoring, and industrial automation. Recently, low-dimensional materials have shown great potential in enhancing the performance of SAW sensors due [...] Read more.

Benefitting from high sensitivity, rapid response, and cost-effectiveness, surface acoustic wave (SAW) sensors have found extensive applications across various fields, including biomedical diagnostics, environmental monitoring, and industrial automation. Recently, low-dimensional materials have shown great potential in enhancing the performance of SAW sensors due to their exceptional physical, optical, and electronic properties. This review explores recent advancements in the fundamental mechanisms, design, fabrication and applications of SAW sensors based on low-dimensional materials. Specifically, the utilization of low-dimensional materials, including zero-, one- and two-dimensional materials, as sensing materials in SAW sensors are summarized. Their applications in SAW-based gas sensing, ultraviolet light sensing, humidity sensing, as well as biosensing are discussed. Furthermore, major challenges and future perspectives regarding employing low-dimensional materials to enhance SAW sensors are highlighted, providing valuable insights for future research and development in this field. Full article

(This article belongs to the Special Issue Current Trends on Surface Acoustic Wave Sensors and Humidity Sensors)

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11 pages, 5146 KiB

Open AccessCommunication

Achieving Optical Ozone Sensing with Increased Response and Recovery Speed by Using Highly Dispersed CdSe/ZnS Quantum Dots in Porous Glass

by Masanori Ando, Hideya Kawasaki, Satoru Tamura and Yasushi Shigeri

Chemosensors 2024, 12(12), 254; https://doi.org/10.3390/chemosensors12120254 - 5 Dec 2024

Viewed by 1532

Abstract

CdSe/ZnS quantum dots (QDs) that were highly dispersed in porous glass showed a rapid decrease in the intensity of their photoluminescence (PL) in response to ozone at concentrations of 0–200 ppm in air (at room temperature and atmospheric pressure), followed by a similarly [...] Read more.

CdSe/ZnS quantum dots (QDs) that were highly dispersed in porous glass showed a rapid decrease in the intensity of their photoluminescence (PL) in response to ozone at concentrations of 0–200 ppm in air (at room temperature and atmospheric pressure), followed by a similarly rapid recovery to full PL in air with no ozone. The response time of the PL quenching in the presence of ozone, and the recovery time to full PL in air after the ozone was removed, showed little dependence on the ozone concentration. Compared to conventional CdSe/ZnS QD films on planar glass substrates, the speed of ozone-induced decrease in the PL intensity of QDs increased, and the recovery speed of the PL intensity, once the ozone was removed from the air, was even more rapid compared to the recovery on planar glass. The 100% PL intensity recovery time in air was reduced to about 10% for CdSe/ZnS QDs that were dispersed in porous glass compared to CdSe/ZnS QD films on planar glass substrates. We hypothesize that this reflects the fact that ozone molecules that are adsorbed on the QD-layer-lined pore surfaces are quickly desorbed in ozone-free air, because the layer of CdSe/ZnS QDs is much thinner in the pores of porous glass than on a planar glass substrate. Thus, CdSe/ZnS QDs that were dispersed in porous glass showed a rapid response to ozone and a similarly rapid recovery in ozone-free air, which has not been seen in previous QD ozone gas sensors, indicating that they are promising as high-performance optical ozone sensor materials. Full article

(This article belongs to the Special Issue Functionalized Material-Based Gas Sensing)

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39 pages, 6112 KiB

Open AccessReview

The Optical Sensing of Volatile Organic Compounds Using Porphyrins

by Elizaveta V. Ermakova and Alla Bessmertnykh-Lemeune

Chemosensors 2024, 12(12), 253; https://doi.org/10.3390/chemosensors12120253 - 3 Dec 2024

Viewed by 2170

Abstract

The detection of volatile organic compounds (VOCs) is a rapidly growing research area due to the importance of VOCs in environmental pollution, human health assessment, food quality control, and homeland security. Optical sensing materials based on porphyrins are particularly appealing for VOCs detection, [...] Read more.

The detection of volatile organic compounds (VOCs) is a rapidly growing research area due to the importance of VOCs in environmental pollution, human health assessment, food quality control, and homeland security. Optical sensing materials based on porphyrins are particularly appealing for VOCs detection, owing to availability of porphyrins, their exceptional optical and binding properties, as well as their photo and chemical stability. As research and technology continue to advance, optical sensors involving these materials are expected to play an increasing role in various applications. This article presents an overview of porphyrin-based sensing materials developed for use as optical sensors for VOCs in a gaseous phase. First, sensing films composed exclusively of porphyrin molecules are discussed, followed by the materials obtained by grafting or the incorporation of porphyrins into organic and inorganic polymer matrices. Considering the growing interest in multianalyte analysis with porphyrin-based sensor arrays, special attention is devoted to this area. Full article

(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes, 2nd Edition)

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14 pages, 3995 KiB

Open AccessArticle

An Intensity-Variation RI Sensor for Multi-Variant Alcohol Detection with Twisted Structure Using Polymer Optical Fiber

by Abdul Ghaffar, Rehan Mehdi, Irfan Mehdi, Bhagwan Das, Vicky Kumar, Sadam Hussain, Gul Sher, Kamran Ali Memon, Sikandar Ali, Mujahid Mehdi and Khurram Karim Qureshi

Chemosensors 2024, 12(12), 252; https://doi.org/10.3390/chemosensors12120252 - 3 Dec 2024

Cited by 1 | Viewed by 1222

Abstract

This research introduces an RI sensor for detecting various alcohol species with a designed twisted polymer optical fiber (POF) sensor. The sensor is developed via a straightforward twisting technique to form an effective coupling mechanism. The sensor works on intensity variation where coupled [...] Read more.

This research introduces an RI sensor for detecting various alcohol species with a designed twisted polymer optical fiber (POF) sensor. The sensor is developed via a straightforward twisting technique to form an effective coupling mechanism. The sensor works on intensity variation where coupled intensity varies when different types of alcohol are added. The structure relies on the twisting of two fibers, where one fiber is used as the illuminating fiber and the other fiber is used as the receiving fiber. Five different types of alcohol are tested (methanol, ethanol, propanol, butanol, and pentanol) as a substant. The experimental results reveal that the sensor is able to detect all five distinct substants effectively by optical power intensity variation. Moreover, the sensor’s sensitivity is analyzed with different factors such as the influence of the bending radius and the coupling length, which reveals that the sensing parameters could be customized depending on specific requirements. The sensor demonstrated consistent responses in repeatability tests, with minimal variation across multiple measurements, highlighting its stability. Additionally, the study explores temperature’s influence, revealing a sensitivity shift for every degree Celsius of change. This POF-based alcohol sensor represents a significant leap forward in optical sensing technology. Full article

(This article belongs to the Special Issue Advanced Chemical Sensors for Gas Detection)

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11 pages, 1227 KiB

Open AccessArticle

Sampling and Comparison of Extraction Techniques Coupled with Gas Chromatography–Mass Spectrometry (GC-MS) for the Analysis of Substrates Exposed to Explosives

by Himanshi Upadhyaya, Alexis J. Hecker and John V. Goodpaster

Chemosensors 2024, 12(12), 251; https://doi.org/10.3390/chemosensors12120251 - 29 Nov 2024

Viewed by 1702

Abstract

Explosive-detecting canines (EDCs) show high sensitivity in detecting explosives that they are trained to detect. The ability of canines to detect explosive residues to the parts per trillion level can sometimes result in nuisance alerts. These nuisance alerts can occur when various materials [...] Read more.

Explosive-detecting canines (EDCs) show high sensitivity in detecting explosives that they are trained to detect. The ability of canines to detect explosive residues to the parts per trillion level can sometimes result in nuisance alerts. These nuisance alerts can occur when various materials (i.e., substrates) are exposed to volatile organic compounds (VOCs) present in explosive mixtures, leading to contamination—the unintended absorption or adsorption of VOCs by the substrate. Chemical constituents such as taggant, plasticizer, and residual solvent in explosives are often composed of VOCs that canines are trained on to detect explosives. Composition C-4 (C4) is a common explosive that EDCs are trained to detect and hence is this study’s focus. Common VOCs of interest emitted from C4 include 2,3-dimethyl-2,3-dinitrobutane (DMNB), 2-ethyl-1 hexanol (2E1H), and cyclohexanone. In this study, we developed a protocol for comparing different substrates such as cotton, cardboard, wood, sheet metal, and glass that were exposed to volatiles from C4. 1-bromooctane (1-BO) was used as a single-odor compound to compare the complex odor originating from C4. Triplicates of substrates such as cotton, wood, cardboard, sheet metal, and glass were exposed to 1 g of C4 in a paint can for one week and the substrates were then extracted using various extraction methods such as liquid injection, direct SPME, and headspace analysis coupled with gas chromatography–mass spectrometry. An extraction time study was performed to determine the optimal extraction time for SPME analysis, and it was found to be 20 min. Comparison of extraction methods revealed that SPME surpassed other techniques as DMNB was found on all substrates using SPME. It was observed that porous substrates such as wood and cardboard have a higher retention capacity for volatiles in comparison to non-porous substrates such as sheet metal and glass. Finally, swabbing was evaluated as a sampling technique for the substrates of interest and the extracts were analyzed using the total vaporization–solid phase microextraction (TV-SPME) technique. No volatiles associated with C4 were identified on conducting a GC-MS analysis, suggesting that swabbing is not an ideal technique for analysis of substrates exposed to C4. Full article

(This article belongs to the Special Issue Detection of Volatile Organic Compounds in Complex Mixtures)

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15 pages, 4984 KiB

Open AccessArticle

Fast-Response Hydrogen Sensor Based on γ-Al₂O₃-Modified Graphene

by Bin Shen, Qinglan Zhang, Xinlei Liu, Jiazhe Li, Yu Guan and Dan Xiao

Chemosensors 2024, 12(12), 250; https://doi.org/10.3390/chemosensors12120250 - 28 Nov 2024

Viewed by 1112

Abstract

The fast response of H₂ sensors plays an important role in the early warning of H₂ leakage; in this work, a nanoscale

γ

-Al₂O₃ carrier material was prepared using the precipitation method and a new hydrogen sensor was [...] Read more.

The fast response of H₂ sensors plays an important role in the early warning of H₂ leakage; in this work, a nanoscale

γ

-Al₂O₃ carrier material was prepared using the precipitation method and a new hydrogen sensor was prepared by doping and modifying it with graphene. During the detecting part of the experiment, the voltage–current–temperature detecting system was designed based on the principle of voltage division and shunt, and the theoretical operating temperature computational model was established in parallel. After testing, it was shown that the sensor had a good linear relationship for the range of 1000–10,000 ppm H₂; the operating temperature was only 176 °C at 1.4 V operating voltage, the T₉₀ response time was 6.69 s, and the average sensitivity and temperature rise characteristics were 28.23 mV/1% H₂ and 36.77 °C/1% H₂, respectively. Moreover, the calculated theoretical operating temperature and the measured temperature were basically consistent. This work provides a useful reference for further exploration of H₂ sensors. Full article

(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)

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