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Volume 13
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Chemosensors, Volume 13, Issue 10 (October 2025) – 18 articles

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16 pages, 2760 KB  
Article
Simple Moisture Sensing Element Using Carbon Nanotube Composite Paper
by Takahide Oya, Tadashi Saito, Yuma Morita and Koya Arai
Chemosensors 2025, 13(10), 373; https://doi.org/10.3390/chemosensors13100373 - 16 Oct 2025
Abstract
We propose a unique moisture sensing element (including humidity sensor) using carbon nanotube (CNT) composite paper. The CNT composite paper is a composite material consisting of CNTs and cellulose paper, which can be easily produced using a method based on the Japanese washi [...] Read more.
We propose a unique moisture sensing element (including humidity sensor) using carbon nanotube (CNT) composite paper. The CNT composite paper is a composite material consisting of CNTs and cellulose paper, which can be easily produced using a method based on the Japanese washi papermaking process. Since this composite paper contains CNTs, it is a conductive paper. In addition, the cellulose fibers that make up the paper are known to show a volume change of up to 35% with humidity. The proposed moisture sensing element uses this volume change and the electrical resistance derived from the CNT network contained in the composite paper. Through various experiments, it was confirmed that the electrical resistance of the CNT composite paper changes in response to moisture of various sizes, such as water droplets and vapors (humidity). It was concluded that these changes were the result of the volume change of paper fibers due to moisture, which greatly affected the structure of the CNT network contained within the composite paper. The results of this study will be useful for the practical application of simple and flexible paper-based moisture sensing elements in the near future. Full article
(This article belongs to the Special Issue Application of Carbon Nanotubes in Sensing)
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12 pages, 1973 KB  
Article
A Simple Second-Derivative Image-Sharpening Algorithm for Enhancing the Electrochemical Detection of Chlorophenol Isomers
by Shuo Duan, Yong Wen, Fangquan Xia and Changli Zhou
Chemosensors 2025, 13(10), 372; https://doi.org/10.3390/chemosensors13100372 - 16 Oct 2025
Abstract
Electrochemical detection is widely used in environmental, health, and food analysis due to its portability, low cost, and high sensitivity. However, when analytes with similar redox potentials coexist, overlapping voltammetric signals often occur, which compromises detection accuracy and sensitivity. In this study, a [...] Read more.
Electrochemical detection is widely used in environmental, health, and food analysis due to its portability, low cost, and high sensitivity. However, when analytes with similar redox potentials coexist, overlapping voltammetric signals often occur, which compromises detection accuracy and sensitivity. In this study, a simple second-derivative image sharpening (IS) algorithm is applied to the electrochemical detection of chlorophenol (CP) isomers with similar redox behaviors. Specifically, a graphene-modified electrode was employed for the electrochemical detection of two chlorophenol isomers: ortho-CP (o-CP) and meta-chlorophenol (m-CP) in the range from 1.0 to 10.0 μmol/L. After image-sharpening, the peak potential difference between o- and m-CP increased from 0.08 V to 0.12 V. The limits of detection (LOD) for o-CP and m-CP decreased from 0.6 to 0.9 μmol/L to 0.12 and 0.31 μmol/L, respectively. The corresponding sensitivities also improved from 0.92 to 1.35 A/(mol L−1) to 4.11 and 3.71 A/(mol L−1), respectively. Moreover, the sharpened voltammograms showed enhanced peak resolution, facilitating visual discrimination of the two isomers. These results demonstrate that image sharpening can significantly improve peak shape, peak separation, sensitivity, and detection limit in electrochemical analysis. The obtained algorithm is computationally efficient (<30 lines of C++ (Version 6.0)/OpenCV, executable in <1 ms on an ARM-M0 microcontroller) and easily adaptable to various programming environments, offering a promising approach for data processing in portable electrochemical sensing systems. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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15 pages, 3319 KB  
Article
Next-Generation Airborne Pathogen Detection: Flashing Ratchet Potential in Action
by Yazan Al-Zain, Mohammad Bqoor, Maha Albqoor and Lujain Ismail
Chemosensors 2025, 13(10), 371; https://doi.org/10.3390/chemosensors13100371 - 16 Oct 2025
Abstract
A novel airborne pathogen detection method, based on Flashing Ratchet Potential (FRP) and Electric Current Spectroscopy (ECS), is presented. The system employs a precisely engineered asymmetric electrode array to generate controlled directional transport of oxygen ions (O2−•), produced via thermionic [...] Read more.
A novel airborne pathogen detection method, based on Flashing Ratchet Potential (FRP) and Electric Current Spectroscopy (ECS), is presented. The system employs a precisely engineered asymmetric electrode array to generate controlled directional transport of oxygen ions (O2−•), produced via thermionic emission and three-body electron attachment. As these ions interact with airborne particles in the detection zone, measurable perturbations in the ECS profile emerge, yielding distinct spectral signatures that indicate particle presence. Proof-of-concept experiments, using standardized talcum powder aerosols as surrogates for viral-scale particles, established optimal operating parameters of 6 V potential and 600 kHz modulation frequency, with reproducible detection signals showing a relative shift of 4.5–13.4% compared to filtered-air controls. The system’s design concept incorporates humidity-resilient features, intended to maintain stability under varying environmental conditions. Together with the proposed size selectivity (50–150 nm), this highlights its potential robustness for real-world applications. To the best of our knowledge, this is the first demonstration of an open-air electro-ratchet transport system coupled with electric current spectroscopy for bioaerosol monitoring, distinct from prior optical or electrochemical airborne biosensors, highlighting its promise as a tool for continuous environmental surveillance in high-risk settings such as hospitals, airports, and public transit systems. Full article
(This article belongs to the Section (Bio)chemical Sensing)
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15 pages, 1511 KB  
Article
NIR and MIR Spectroscopy for the Detection of Adulteration of Smoking Products
by Zeb Akhtar, Ihtesham ur Rehman, Cédric Delporte, Erwin Adams and Eric Deconinck
Chemosensors 2025, 13(10), 370; https://doi.org/10.3390/chemosensors13100370 - 16 Oct 2025
Viewed by 46
Abstract
This study explores the application of Mid-Infrared (MIR) and Near-Infrared (NIR) spectroscopy combined with various multivariate calibration techniques to detect the presence of cannabis in tobacco samples and tobacco in herbal smoking products. Both MIR and NIR spectra were recorded for self-prepared samples, [...] Read more.
This study explores the application of Mid-Infrared (MIR) and Near-Infrared (NIR) spectroscopy combined with various multivariate calibration techniques to detect the presence of cannabis in tobacco samples and tobacco in herbal smoking products. Both MIR and NIR spectra were recorded for self-prepared samples, followed by data exploration using Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA), and the calculation of binary classification models with Soft Independent Modelling of Class Analogy (SIMCA) and Partial Least Squares-Discriminant Analysis (PLS-DA). PCA demonstrated a clear differentiation between tobacco samples containing and not containing cannabis. On the other hand, based on PCA, only NIR was able to distinguish herbal smoking products adulterated and not adulterated with tobacco. HCA further clarified these results by revealing distinct clusters within the data. Modelling results indicated that MIR and NIR spectroscopy, particularly when paired with preprocessing techniques like Standard Normal Variate (SNV) and autoscaling, demonstrated high classification accuracy in SIMCA and PLS-DA, achieving correct classification rates of 90% to 100% for external test sets. Comparison of MIR and NIR revealed that NIR spectroscopy resulted in slightly more accurate models for the screening of tobacco samples for cannabis and herbal smoking products for tobacco. The developed approach could be useful for the initial screening of tobacco samples for cannabis, e.g., in a night life setting by law enforcement, but also for inspectors visiting shops selling tobacco and/or herbal smoking products. Full article
(This article belongs to the Section Optical Chemical Sensors)
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20 pages, 5256 KB  
Article
Electrochemical Approach to the Determination of Gallic Acid with Bismuth-Based Carbon Electrodes
by Ivana Škugor Rončević, Marijo Buzuk, Josipa Dugeč, Jure Vasilj, Marija Pustak and Nives Vladislavić
Chemosensors 2025, 13(10), 369; https://doi.org/10.3390/chemosensors13100369 - 14 Oct 2025
Viewed by 317
Abstract
The synergistic combination of bismuth and its compounds with the exceptional properties of single-walled carbon nanotubes (SWCNT) was investigated as a sensing platform for the sensitive detection of gallic acid and as a standard for the determination of total phenol. Four bismuth-based electrodes [...] Read more.
The synergistic combination of bismuth and its compounds with the exceptional properties of single-walled carbon nanotubes (SWCNT) was investigated as a sensing platform for the sensitive detection of gallic acid and as a standard for the determination of total phenol. Four bismuth-based electrodes were used for this purpose: SWCNT with bismuth (SWCNT/Bi) or bismuth (III) oxide (SWCNT/Bi2O3) and bismuth or bismuth (III) oxide electrodeposited on a glassy carbon electrode (ELF/Bi and ELF/Bi2O3), which were morphologically characterized by scanning electron microscopy. Cyclic voltammetry in phosphate electrolyte at different pH values revealed that the SWCNT/Bi2O3 electrode exhibited optimal performance for the analytical determination of gallic acid at pH 3. Surface-active carbon nanotubes facilitate the adsorption and accumulation of gallic acid, while the addition of Bi2O3 improves electron transfer, resulting in a synergistic enhancement of the oxidation signal. Square-wave voltammetry with SWCNT/Bi2O3 electrodes also provided reliable and accurate results and proved to be suitable for the quantitative determination of gallic acid with wide linearity (0.2–80 µM) and sensitivities of 12.5, 2.35, and 0.385 µA µmol−1 dm3 for low, medium, and high concentration ranges, respectively. The limit of detection was 0.06 µmol dm−3. Finally, the electrode was successfully applied for gallic acid determination in various seeds. Full article
(This article belongs to the Special Issue Progress of Photoelectrochemical Analysis and Sensors)
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17 pages, 3452 KB  
Article
Room Temperature Sub-ppm NO2 Gas Sensor Based on Ag/SnS2 Heterojunction Driven by Visible Light
by Ding Gu, Jun Dong, Wei Liu and Xiaogan Li
Chemosensors 2025, 13(10), 368; https://doi.org/10.3390/chemosensors13100368 - 10 Oct 2025
Viewed by 453
Abstract
As industrial waste gas, nitrogen dioxide (NO2) is a serious hazard to air pollution and human health, and there is a pressing demand for developing high-performance NO2 gas sensors. Tin disulfide (SnS2), a representative two-dimensional metal sulfide characterized [...] Read more.
As industrial waste gas, nitrogen dioxide (NO2) is a serious hazard to air pollution and human health, and there is a pressing demand for developing high-performance NO2 gas sensors. Tin disulfide (SnS2), a representative two-dimensional metal sulfide characterized by a significant specific surface area, a suitable electron band gap, and an easily tunable layered structure, shows a broad application prospect in gas sensing applications. Nevertheless, SnS2-based gas sensors suffer from poor sensitivity, which seriously hinders their application in room temperature gas sensing. In this study, Ag/SnS2 heterojunction nanomaterials were synthesized by an in situ reduction approach. The findings reveals that the gas-sensitive response of the Ag/SnS2 nanocomposites at room temperature under visible light irradiation can achieve 10.5 to 1 ppm NO2, with a detection limit as low as 200 ppb, which realizes the room-temperature detection of Sub-ppm NO2. Meanwhile, the sensor exhibits good selectivity, reproducibility (cyclic stability > 95%). The improved gas sensitivity of the Ag/SnS2 sensor can be due to the synergistic effect of the carrier separation at the Ag/SnS2 Schottky junction and the localized surface plasmon resonance (LSPR) of Ag nanoparticles. The LSPR effect significantly enhances light absorption and surface-active site density, facilitating trace NO2 detection at room temperature. This study provides the foundation for the subsequent development of room temperature layered metal sulfide gas sensors. Full article
(This article belongs to the Special Issue Advanced Chemical Sensors in Gas Detection)
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36 pages, 3836 KB  
Review
Carbon Nanotube-Based Chemical Sensors: Sensing Mechanism, Functionalization and Applications
by Jie Tang, Ruirui Li, Subhan Mahmood, Jiying Li and Shun Yao
Chemosensors 2025, 13(10), 367; https://doi.org/10.3390/chemosensors13100367 - 10 Oct 2025
Viewed by 578
Abstract
Carbon nanotubes (CNTs) have opened new routes in the field of chemical sensing due to their unparalleled electrical conductivity, high surface area, and versatile functionalization capabilities. This review systematically examined the latest advancements in CNT-based chemical sensors, with a focus on their sensing [...] Read more.
Carbon nanotubes (CNTs) have opened new routes in the field of chemical sensing due to their unparalleled electrical conductivity, high surface area, and versatile functionalization capabilities. This review systematically examined the latest advancements in CNT-based chemical sensors, with a focus on their sensing mechanism, functionalization strategies, and applications. A spotlight was cast on the wide-ranging applications of CNT-based chemical sensors, spanning environmental analysis, drug detection, healthcare, food quality control, gases detection, strain sensing, etc. Finally, through a comprehensive SWOT analysis, the strengths, weaknesses, opportunities, and existing threats, along with emerging trends of CNTs in the sensing field, were elucidated. This review systematically summarized the applications of CNTs across six major fields, highlighting more than 60 CNT-based sensing materials. We aim to provide a forward-looking perspective on how CNTs will continue to shape the future of chemical sensing. Full article
(This article belongs to the Special Issue Application of Carbon Nanotubes in Sensing)
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16 pages, 5153 KB  
Article
Fabrication and Characterization of a Portable and Electrochemical System for Field Determination of Nitrate in Coastal Seawater
by Xiaoling He, Hong Wei, Tian Ouyang, Ziwen Xu, Taoda Liu, Ying Cheng, Ziman Ma, Wenyan Tao and Dawei Pan
Chemosensors 2025, 13(10), 366; https://doi.org/10.3390/chemosensors13100366 - 9 Oct 2025
Viewed by 405
Abstract
Nitrate, as one of the important nutrients in seawater, influences the constant ratio of nitrogen to phosphorus, which is closely related to phytoplankton survival. In this work, a Cu-nanosphere-modified gold microwire electrode was used as the working electrode for determining nitrate in an [...] Read more.
Nitrate, as one of the important nutrients in seawater, influences the constant ratio of nitrogen to phosphorus, which is closely related to phytoplankton survival. In this work, a Cu-nanosphere-modified gold microwire electrode was used as the working electrode for determining nitrate in an artificial seawater sample with salinity of 35‰ by a differential pulse voltammetry technique. Under the optimized conditions, the detection linear range is from 1 μM to 2000 μM, the limit of detection is 0.33 μM, and the response time for a single sample is 5 min. Then, to reduce the influence of factors such as temperature, humidity, and microbial environment during sample transporting on the nitrate concentration in real seawater, a portable electrochemical system was introduced for on-site detection. Rapid field determination results show that nitrate levels correlate with tides, proving the portable system’s reliability. Full article
(This article belongs to the Special Issue Photoelectrochemical and Surface Plasmon Resonance Sensors: Current Status and Future Perspectives)
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16 pages, 2895 KB  
Article
Reverse Titration Using Tablets for Accurate Water Hardness Measurement with Improved Resistance to Interference
by Chinonso Henry Ezeoke, Zubi Sadiq, Seyed Hamid Safiabadi Tali and Sana Jahanshahi-Anbuhi
Chemosensors 2025, 13(10), 365; https://doi.org/10.3390/chemosensors13100365 - 8 Oct 2025
Viewed by 345
Abstract
We report a novel tablet-based reverse titration system for rapid, point-of-use measurement of water hardness, overcoming key limitations of conventional EDTA titration. Reagents are encapsulated in pullulan matrix giving two separate tablets. The first tablet contains the Eriochrome black T (EBT) and N [...] Read more.
We report a novel tablet-based reverse titration system for rapid, point-of-use measurement of water hardness, overcoming key limitations of conventional EDTA titration. Reagents are encapsulated in pullulan matrix giving two separate tablets. The first tablet contains the Eriochrome black T (EBT) and N-cyclohexyl-3-aminopropanesulfonic acid (CAPS) buffer, while the second encapsulates ethylenediaminetetraacetic acid (EDTA) disodium salt dihydrate. The system employs a trimodal detection strategy: qualitative screening via immediate color change with the EBT tablet, semi-quantitative estimation through combined tablet dissolution and adjusting the sample volume to a reference level, and quantitative determination using reverse titration, where water is gradually added until the red wine endpoint appears. This approach enhances interference tolerance from competing metal ions and improves accuracy over traditional methods. Testing with real water samples showed excellent agreement with standard titration. The tablets remain stable for over seven months, and the system eliminates the need for skilled personnel, laboratory equipment, or bulky instrumentation. This low-cost, user-friendly, and interference-tolerant platform enables rapid and accurate water hardness assessment at the point of use. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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16 pages, 2105 KB  
Article
Synthesis of CSA-Capped Poly(aniline-co-aniline-2-sulfonic acid) Spherical Nanoparticles for Gas Sensor Applications
by Ki-Hyun Pyo, Ji-Sun Kim, Yoon Hee Jang and Jin-Yeol Kim
Chemosensors 2025, 13(10), 364; https://doi.org/10.3390/chemosensors13100364 - 4 Oct 2025
Viewed by 329
Abstract
We synthesized emeraldine salts of poly(aniline-co-aniline-2-sulfonic acid) capped with camphorsulfonic acid (CSA), forming spherical nanoparticles (NPs), i.e., CSA-capped P(ANi-co-ASNi), and demonstrated their efficacy as gas sensor elements. The synthesized core–shell spherical NPs, averaging 265 nm in diameter, feature a CSA shell with a [...] Read more.
We synthesized emeraldine salts of poly(aniline-co-aniline-2-sulfonic acid) capped with camphorsulfonic acid (CSA), forming spherical nanoparticles (NPs), i.e., CSA-capped P(ANi-co-ASNi), and demonstrated their efficacy as gas sensor elements. The synthesized core–shell spherical NPs, averaging 265 nm in diameter, feature a CSA shell with a porous thin-film morphology, characterized by the uneven distribution of fine particulate domains across the outer surface of the positively charged P(ANi-co-ASNi) cores. This uniquely heterogeneous shell architecture facilitates stable charge transport at the core–shell interface, enhances resistance to ambient humidity, and promotes efficient interaction with organic gas molecules. The CSA-capped P(ANi-co-ASNi) sensors reliably detected low concentrations of acetone (1–5 ppm) and water vapor (1–28% RH) under ambient conditions. Furthermore, the sensors exhibited superior stability across varying temperature, humidity, and cyclic performance, outperforming conventional pure PANiNi. Full article
(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors and Humidity Sensors)
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15 pages, 1190 KB  
Article
Tropical Weathering Effects on Neat Gasoline: An Analytical Study of Volatile Organic Profiles
by Khairul Osman, Naadiah Ahmad Mazlani, Gina Francesca Gabriel, Noor Hazfalinda Hamzah, Rogayah Abu Hassan, Dzulkiflee Ismail and Wan Nur Syuhaila Mat Desa
Chemosensors 2025, 13(10), 363; https://doi.org/10.3390/chemosensors13100363 - 3 Oct 2025
Viewed by 400
Abstract
Gasoline is the most common ignitable liquid used to initiate fires, making its detection and identification in fire debris crucial for determining incendiary origins. Fire debris is typically collected after extinguishment and safety clearance, often resulting in gasoline weathering, especially when delayed. Most [...] Read more.
Gasoline is the most common ignitable liquid used to initiate fires, making its detection and identification in fire debris crucial for determining incendiary origins. Fire debris is typically collected after extinguishment and safety clearance, often resulting in gasoline weathering, especially when delayed. Most research on gasoline weathering has been conducted in controlled laboratory settings in temperate climates. However, the effects of tropical conditions on the rate of gasoline weathering and the resulting chemical composition of volatiles remain largely unexplored. Understanding how tropical environmental factors alter gasoline weathering is essential for accurate fire debris interpretation in such regions. This study investigates how tropical climates impact gasoline weathering indoors and outdoors. Weathered samples were prepared by volume reduction method, gradually evaporating gasoline from 10% to 95%. Indoor samples were exposed to room temperature, while outdoor samples were left in open space under natural tropical conditions. Gas Chromatography/Mass Spectrometry (GC-MS) analysis revealed chromatographic shifts in heavier compounds (C3–C4 alkylbenzenes) compared to lighter ones like toluene as weathering progressed. Correlation between indoor and outdoor samples was high (>0.970) at 10–50% weathering but declined (<0.600) at 90–95%, indicating differing patterns. All target compounds remained detectable across all samples. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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13 pages, 4976 KB  
Article
Nanostructured CeO2-C Derived from Ce-BDC Precursors for Room-Temperature Ammonia Sensing
by Liang Wang, Manyi Liu, Shan Ren, Xiankang Zhong, Bofeng Bai, Shouning Chai, Chi He and Xinzhe Li
Chemosensors 2025, 13(10), 362; https://doi.org/10.3390/chemosensors13100362 - 3 Oct 2025
Viewed by 407
Abstract
The prompt and reliable detection of NH3 leakage at room temperature (RT) is considered important for safety assurance and sustainable production. Although chemiresistive NH3 sensors feature low cost and structural simplicity, their practical application is hindered by high operating temperatures and [...] Read more.
The prompt and reliable detection of NH3 leakage at room temperature (RT) is considered important for safety assurance and sustainable production. Although chemiresistive NH3 sensors feature low cost and structural simplicity, their practical application is hindered by high operating temperatures and inadequate selectivity. Metal–organic frameworks (MOFs) and their derivatives offer a promising approach to address these limitations. In this work, Ce-BDC precursors with tunable particle sizes and crystallinity were synthesized by adjusting the raw material concentration. Controlled pyrolysis yielded a series of CeO2-C-X (X = 0.5, 1, 1.5, 2) materials with nanosized particles. Among them, the CeO2-C-1 sensor delivered a high response of 82% toward NH3 under 40% relative humidity at RT. Moreover, it possessed excellent selectivity, repeatability, and rapid response-recovery behavior compared with the other samples. CeO2-C-1 also remained stable under varying oxygen and humidity conditions, demonstrating high applicability. The superior sensing properties may be attributed to its high specific surface area and optimized mesoporous structure, which facilitated efficient gas adsorption and reaction. These findings demonstrated that precise control of MOF precursors and the structure in CeO2 nanomaterials was critical for achieving high-performance gas sensing and established Ce-MOF-derived CeO2 as a promising sensing material for NH3 detection at RT. Full article
(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors)
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12 pages, 980 KB  
Article
HS-SPME-GC-MS Volatile Profile of “Aglio Rosso di Sulmona” (Sulmona Red Garlic) Floral Scape
by Samantha Reale, Rossella Ferretti, Alessandra Biancolillo, Valter Di Cecco, Luciano Di Martino, Marco Di Santo and Angelo Antonio D’Archivio
Chemosensors 2025, 13(10), 361; https://doi.org/10.3390/chemosensors13100361 - 2 Oct 2025
Viewed by 389
Abstract
Garlic (Allium Sativum L.) is a source of organosulphur compounds with well-known sensorial and biological activity. Organosulphur precursors of garlic aroma are also detected in the plant leaves, but limited literature on this subject is available. This study is aimed at the [...] Read more.
Garlic (Allium Sativum L.) is a source of organosulphur compounds with well-known sensorial and biological activity. Organosulphur precursors of garlic aroma are also detected in the plant leaves, but limited literature on this subject is available. This study is aimed at the characterization of the volatile profile of the floral scapes of Sulmona red garlic (aglio rosso di Sulmona) cultivated in the Abruzzo region (Italy). Floral scapes are manually removed from the plant before flowering and used as an ingredient of local gastronomy. The organosulphur volatile profile of the scapes is investigated by HS-SPME-GC-MS and compared to that provided by the clove. The GC-MS chromatogram of garlic clove, which is characterized by the predominant contribution of a few organosulphur organic compounds, is significantly more intense than that of the scapes. Almost all the organosulphur compounds contributing to the clove aroma were detected in the scape volatile profile, which, however, exhibits a more balanced contribution of major and minor organo sulphur compounds. Moreover, a significantly higher relative abundance of terpenes and aldehydes is observed in the scape aroma. The geographical/varietal origin of clove seeds (Sulmona versus Spain or France) and cultivation area interactively influence the aroma profile of Sulmona red garlic scapes. Full article
(This article belongs to the Special Issue GC, MS and GC-MS Analytical Methods: Opportunities and Challenges (Fourth Edition))
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13 pages, 2151 KB  
Article
Profiling Hydrogen-Bond Conductance via Fixed-Gap Tunnelling Sensors in Physiological Solution
by Biao-Feng Zeng, Canyu Yan, Ye Tian, Yuxin Yang, Long Yi, Shiyang Fu, Xu Liu, Cuifang Kuang and Longhua Tang
Chemosensors 2025, 13(10), 360; https://doi.org/10.3390/chemosensors13100360 - 2 Oct 2025
Viewed by 371
Abstract
Hydrogen bonding, a prevalent molecular interaction in nature, is crucial in biological and chemical processes. The emergence of single-molecule techniques has enhanced our microscopic understanding of hydrogen bonding. However, it is still challenging to track the dynamic behaviour of hydrogen bonding in solution, [...] Read more.
Hydrogen bonding, a prevalent molecular interaction in nature, is crucial in biological and chemical processes. The emergence of single-molecule techniques has enhanced our microscopic understanding of hydrogen bonding. However, it is still challenging to track the dynamic behaviour of hydrogen bonding in solution, particularly under physiological conditions where interactions are significantly weakened. Here, we present a nanoscale-confined, functionalised quantum mechanical tunnelling (QMT) probe that enables continuous monitoring of electrical fingerprints of single-molecule hydrogen bonding interactions for over tens of minutes in diverse solvents, including polar physiological solutions, which reveal reproducible multi-level conductance distributions. Moreover, the functionalised QMT probes have successfully discriminated between L(+)- and D(−)-tartaric acid enantiomers by resolving the conductance difference. This work uncovers dynamic single-molecule hydrogen bonding processes within confined nanoscale spaces under physiological conditions, establishing a new paradigm for probing molecular hydrogen-bonding networks in supramolecular chemistry and biology. Full article
(This article belongs to the Special Issue Advancements of Chemosensors and Biosensors in China—2nd Edition)
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17 pages, 2793 KB  
Article
Full-Spectrum LED-Driven Underwater Spectral Detection System and Its Applications
by Yunfei Li, Jun Wei, Shaohua Cheng, Tao Yu, Hong Zhao, Guancheng Li and Fuhong Cai
Chemosensors 2025, 13(10), 359; https://doi.org/10.3390/chemosensors13100359 - 1 Oct 2025
Viewed by 422
Abstract
Spectral detection technology offers non-destructive, in situ, and high-speed capabilities, making it widely applicable for detecting biological and chemical samples and quantifying their concentrations. Water resources, essential to life on Earth, are widely distributed across the planet. The application of spectral technology to [...] Read more.
Spectral detection technology offers non-destructive, in situ, and high-speed capabilities, making it widely applicable for detecting biological and chemical samples and quantifying their concentrations. Water resources, essential to life on Earth, are widely distributed across the planet. The application of spectral technology to underwater environments is useful for wide-area water resource monitoring. Although spectral detection technology is well-established, its underwater application presents challenges, including waterproof housing design, power supply, and data transmission, which limit widespread application of underwater spectral detection. Furthermore, underwater spectral detection necessitates the development of compatible computational methods for sample classification or regression analysis. Focusing on underwater spectral detection, this work involved the construction of a suitable hardware system. A compact spectrometer and LEDs (400 nm–800 nm) were employed as the detection and light source modules, respectively, resulting in a compact system architecture. Extensive tests confirmed that the miniaturized design-maintained system performance. Further, this study addressed the estimation of total phosphorus (TP) concentration in water using spectral data. Samples with varying TP concentrations were prepared and calibrated against standard detection instruments. Subsequently, classification algorithms applied to the acquired spectral data enabled the in situ underwater determination of TP concentration in these samples. This work demonstrates the feasibility of underwater spectral detection for future in situ, high-speed monitoring of aquatic biochemical indicators. In the future, after adding UV LED light source, more water quality parameter information can be obtained. Full article
(This article belongs to the Special Issue Spectroscopic Techniques for Chemical Analysis)
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22 pages, 3094 KB  
Article
Enhanced NO2 Detection in ZnO-Based FET Sensor: Charge Carrier Confinement in a Quantum Well for Superior Sensitivity and Selectivity
by Hicham Helal, Marwa Ben Arbia, Hakimeh Pakdel, Dario Zappa, Zineb Benamara and Elisabetta Comini
Chemosensors 2025, 13(10), 358; https://doi.org/10.3390/chemosensors13100358 - 1 Oct 2025
Viewed by 444
Abstract
NO2 is a toxic gas mainly generated by combustion processes, such as vehicle emissions and industrial activities. It is a key contributor to smog, acid rain, ground-level ozone, and particulate matter, all of which pose serious risks to human health and the [...] Read more.
NO2 is a toxic gas mainly generated by combustion processes, such as vehicle emissions and industrial activities. It is a key contributor to smog, acid rain, ground-level ozone, and particulate matter, all of which pose serious risks to human health and the environment. Conventional resistive gas sensors, typically based on metal oxide semiconductors, detect NO2 by resistance modulation through surface interactions with the gas. However, they often suffer from low responsiveness and poor selectivity. This study investigates NO2 detection using nanoporous zinc oxide thin films integrated into a resistor structure and floating-gate field-effect transistor (FGFET). Both Silvaco-Atlas simulations and experimental fabrication were employed to evaluate sensor behavior under NO2 exposure. The results show that FGFET provides higher sensitivity, faster response times, and improved selectivity compared to resistor-based devices. In particular, FGFET achieves a detection limit as low as 89 ppb, with optimal performance around 400 °C, and maintains stability under varying humidity levels. The enhanced performance arises from quantum well effects at the floating-gate Schottky contact, combined with NO2 adsorption on the ZnO surface. These interactions extend the depletion region and confine charge carriers, amplifying conductivity modulation in the channel. Overall, the findings demonstrate that FGFET is a promising platform for NO2 sensors, with strong potential for environmental monitoring and industrial safety applications. Full article
(This article belongs to the Special Issue Functionalized Material-Based Gas Sensing)
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16 pages, 2914 KB  
Article
Colorimetric Chemosensor for Determination of Loratadine Based on Bromocresol Purple–Cationic Polyacrylamide Copolymer System
by Andriy B. Vishnikin, Anna Chernyavskaya and Yaroslav Bazel
Chemosensors 2025, 13(10), 357; https://doi.org/10.3390/chemosensors13100357 - 1 Oct 2025
Viewed by 399
Abstract
A new sensor system for the determination of nitrogen-containing pharmaceutical substances has been proposed. It is based on the use of an ion association complex formed between cationic polyacrylamide (CPAA) and sulfonephthalein dye as a reagent. Bromocresol purple (BCP) interacts with CPAA to [...] Read more.
A new sensor system for the determination of nitrogen-containing pharmaceutical substances has been proposed. It is based on the use of an ion association complex formed between cationic polyacrylamide (CPAA) and sulfonephthalein dye as a reagent. Bromocresol purple (BCP) interacts with CPAA to form a complex through hydrophobic interaction as well as electrostatic interaction. In the pH range from 3.5 to 5.5, this leads to an increase in the intensity of the dianionic form BCP band at 590 nm. The interaction between the polymer and the dye leads to an increase in the acidic properties of BCP, causing its pKa2 to shift from 6.3 to 3.75. Subsequently, when loratadine (LOR) is added to the CPAA/BCP system, the strong electrostatic interaction between the BCP monoanion and the protonated form of LOR leads to a decrease in the intensity of the band at 590 nm and an increase in the absorbance of the band at 432 nm, which is related to the dye monoanion. Here, we have demonstrated that this facile methodology can enable the rapid, reliable, and selective determination of LOR with a detection limit of 1.6 mg L−1 and a linear range from 5.0 to 120 mg L−1. The environmental friendliness of the developed method was assessed using the AGREE metric and is characterized by a high score of 0.83. The developed method represents a new approach to the creation of extraction-free spectrophotometric methods based on ionic associates of anionic dyes with protonated forms of nitrogen-containing medicinal compounds. The method was successfully applied to the determination of LOR in pharmaceutical preparations with satisfactory precision and accuracy. Overall, the results obtained indicate that this method has great potential for application in pharmaceutical analysis. Full article
(This article belongs to the Special Issue Electrochemical and Optical Sensing: Progress, Perspectives and Challenges)
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Article
Impact of Annealing Treatment on the Potential Stability of SUS316L and Its Possibility for Realizing a Quasi-Reference Electrode
by Kyosuke Sawada, Shinji Okazaki, Tatsuki Inaba and Motohiro Sakuma
Chemosensors 2025, 13(10), 356; https://doi.org/10.3390/chemosensors13100356 - 1 Oct 2025
Viewed by 350
Abstract
This work demonstrates the use of SUS316L stainless steel as a new material for the fabrication of quasi-reference electrodes (QREs) intended to replace conventional reference electrodes (REs) in electrochemical sensors. The present study examined the potentials generated by SUS316L specimens annealed in air [...] Read more.
This work demonstrates the use of SUS316L stainless steel as a new material for the fabrication of quasi-reference electrodes (QREs) intended to replace conventional reference electrodes (REs) in electrochemical sensors. The present study examined the potentials generated by SUS316L specimens annealed in air at 400 °C and above for 1 h or more. Annealing above 500 °C increased the proportion of Cr in surface oxide films, hence reducing the stability of the potential. Samples annealed at 400 °C for 5 h produced the most stable electrode potential, which was attributed to a higher concentration of Fe in the oxide layer. The potential of such specimens increased by only 28.3 mV between test durations of 24 and 168 h, and potential data acquired at 30 s intervals had a standard deviation of less than 2 µV. Applying a surface treatment prior to immersion in the simulated tap water evidently stabilized the electrode potential, as a consequence of the formation of an inner oxide layer together with an outer layer consisting primarily of iron oxides. Full article
(This article belongs to the Special Issue Electrochemical Sensors and Biosensors: Recent Progress, Challenges, and Future Perspectives)
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