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Chemosensors, Volume 12, Issue 6 (June 2024) – 31 articles

Cover Story (view full-size image): Solid-contact ion-to-electron transducers for potentiometric sensors have been investigated for a long time to improve sensor robustness, paving the way for miniaturization and incorporation into portable platforms. This study reports a novel approach using graphene oxide (GO) in its native form as a transducer to develop all-solid-state nitrate electrodes based on an alkyl ammonium salt as the sensing element. The proposed sensors exhibited the absence of a water layer, contributing to their great potential stability and extended lifetime. Additionally, these sensors demonstrated an impressive reproducibility between equally prepared electrodes. The applicability was demonstrated by the accurate determination of nitrate levels in water samples. View this paper
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16 pages, 1353 KiB  
Article
Sensor Selection for an Electronic Tongue for the Rapid Detection of Paralytic Shellfish Toxins: A Case Study
by Mariana Raposo, Maria Teresa S. R. Gomes, Sara T. Costa, Maria João Botelho and Alisa Rudnitskaya
Chemosensors 2024, 12(6), 115; https://doi.org/10.3390/chemosensors12060115 - 19 Jun 2024
Viewed by 131
Abstract
The performance of an electronic tongue can be optimized by varying the number and types of sensors in the array and by employing data-processing methods. Sensor selection is typically performed empirically, with sensors picked up either by analyzing their characteristics or through trial [...] Read more.
The performance of an electronic tongue can be optimized by varying the number and types of sensors in the array and by employing data-processing methods. Sensor selection is typically performed empirically, with sensors picked up either by analyzing their characteristics or through trial and error, which does not guarantee an optimized sensor array composition. This study focuses on developing a method for sensor selection for an electronic tongue using simulated sensor data and Lasso regularization. Simulated sensor responses were calculated using sensor parameters such as sensitivity and selectivity, which were determined in the individual analyte solutions. Sensor selection was carried out using Lasso regularization, which removes redundant or highly correlated variables without much loss of information. The objective of the optimization of the sensor array was twofold, aiming to minimize both quantification errors and the number of sensors in the array. The quantification of toxins belonging to one of the groups of marine toxins—paralytic shellfish toxins (PSTs)—using arrays of potentiometric chemical sensors was used as a case study. Eight PSTs corresponding to the toxin profiles in bivalves due to the two common toxin-producing phytoplankton species, G. catenatum (dcSTX, GTX5, GTX6, and C1+2) and A. minitum (STX, GTX2+3), as well as total sample toxicity, were included in the study. Experimental validation with mixed solutions of two groups of toxins confirmed the suitability of the proposed method of sensor array optimization with better performance obtained for the a priori optimized sensor arrays. The results indicate that the use of simulated sensor responses and Lasso regularization is a rapid and efficient method for the selection of an optimized sensor array. Full article
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27 pages, 8711 KiB  
Review
Photoluminescence Sensing of Lead Halide Perovskite Nanocrystals and Their Two-Dimensional Structural Materials
by Yaning Huang, Chen Zhang, Xuelian Liu and Xi Chen
Chemosensors 2024, 12(6), 114; https://doi.org/10.3390/chemosensors12060114 - 17 Jun 2024
Viewed by 196
Abstract
In recent years, the development of new efficient, fast, and intuitive materials and methods for photoluminescence (PL) sensing has become a research hotspot in analytical chemistry. Lead halide perovskite (LHP) materials have the characteristics of adjustable PL properties, high PL efficiency, and a [...] Read more.
In recent years, the development of new efficient, fast, and intuitive materials and methods for photoluminescence (PL) sensing has become a research hotspot in analytical chemistry. Lead halide perovskite (LHP) materials have the characteristics of adjustable PL properties, high PL efficiency, and a variety of synthesis methods. Their PL is also sensitive to the change in specific factors in the environment. Based on these characteristics, LHP has shown good application prospects in the field of optical sensing. The study of the structural dimension, organic composition, or doped ions of LHP is helpful in exploring its sensing potential and proposing new sensing mechanisms, which have important research significance to promote sensing applications. In this review, the PL characteristics and sensing mechanisms, as well as their sensing applications of two- and three dimensional LHP, are discussed and summarized. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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23 pages, 10977 KiB  
Review
Advanced NIR-II Fluorescence Imaging Technology for Precise Evaluation of Nanomedicine Delivery in Cancer Therapy
by Meng Li, Tuanwei Li, Feng Wu, Feng Ren, Sumei Xue and Chunyan Li
Chemosensors 2024, 12(6), 113; https://doi.org/10.3390/chemosensors12060113 - 16 Jun 2024
Viewed by 302
Abstract
Tumors represent a significant threat to human health, underscoring the critical need for effective treatment strategies. However, conventional drug therapies are hampered by imprecise delivery, potentially leading to inadequate efficacy and severe side effects. The strategic development of nanomedicines is believed to harbor [...] Read more.
Tumors represent a significant threat to human health, underscoring the critical need for effective treatment strategies. However, conventional drug therapies are hampered by imprecise delivery, potentially leading to inadequate efficacy and severe side effects. The strategic development of nanomedicines is believed to harbor enormous potential for enhancing drug safety and efficacy, especially for precise, tumor-targeted therapies. Nevertheless, the fate of these nanomedicines within the human body is intricately governed by various physiological barriers and complex environments, posing challenges to predicting their behaviors. Near-infrared II (NIR-II, 1000–1700 nm) fluorescence imaging technology serves as a non-invasive, real-time monitoring method that can be applied for the precise evaluation of nanomedicine delivery in cancer therapy due to its numerous advantages, including high tissue penetration depth, high spatiotemporal resolution, and high signal-to-noise ratio. In this review, we comprehensively summarize the pivotal role of NIR-II fluorescence imaging in guiding the intratumoral precise delivery of nanomedicines and shed light on its current applications, challenges, and promising prospects in this field. Full article
(This article belongs to the Special Issue Nanoprobes for Biosensing and Bioimaging)
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15 pages, 2069 KiB  
Article
Batch-Injection Amperometric Determination of Glucose Using a NiFe2O4/Carbon Nanotube Composite Enzymeless Sensor
by Amanda B. Nascimento, Lucas V. de Faria, Tiago A. Matias, Osmando F. Lopes and Rodrigo A. A. Muñoz
Chemosensors 2024, 12(6), 112; https://doi.org/10.3390/chemosensors12060112 - 16 Jun 2024
Viewed by 387
Abstract
The development of sensitive and selective analytical devices for monitoring glucose levels (GLU) in biological fluids is extremely important for clinical diagnostics. In this work, we produced a new composite based on NiFe2O4 and multi-walled carbon nanotubes (MWCNT), called NiFe [...] Read more.
The development of sensitive and selective analytical devices for monitoring glucose levels (GLU) in biological fluids is extremely important for clinical diagnostics. In this work, we produced a new composite based on NiFe2O4 and multi-walled carbon nanotubes (MWCNT), called NiFe2O4@MWCNT, to be applied as a non-enzymatic amperometric sensor for GLU. Both NiFe2O4 and NiFe2O4@MWCNT composites were properly characterized by XRD, SEM, FTIR, and Raman spectroscopy, which confirmed that the composite was successfully prepared. A glassy-carbon electrode (GCE) modified with NiFe2O4@MWCNT was investigated by cyclic voltammetry and applied for the amperometric GLU detection using batch-injection analysis (BIA). A linear working range between 50 and 600 µmol L−1 GLU with a significant increase in sensitivity (3-fold) in comparison with MWCNT/GCE was verified, with a detection limit of 36 µmol L−1. Inter-electrode measurements (n = 4, RSD = 10%) indicated that the sensor fabrication is reproducible. Furthermore, the proposed non-enzymatic sensor was selective even in the presence of other biomarkers found in urine. When applied to synthetic urine samples, recovery levels between 84 and 95% confirmed analytical accuracy and the absence of sample matrix effect. Importantly, the developed approach is simple (free of biological modifiers), fast (77 injections per hour), and practical (high-performance tool), which are suitable features for routine analyses. Full article
(This article belongs to the Special Issue Advanced Glucose Biosensors)
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16 pages, 2866 KiB  
Article
SO2 Detection over a Wide Range of Concentrations: An Exploration on MOX-Based Gas Sensors
by Arianna Rossi, Elena Spagnoli, Alan Visonà, Danial Ahmed, Marco Marzocchi, Vincenzo Guidi and Barbara Fabbri
Chemosensors 2024, 12(6), 111; https://doi.org/10.3390/chemosensors12060111 - 14 Jun 2024
Viewed by 408
Abstract
Noxious gases such as sulfur-containing compounds can inflict several different adverse effects on human health even when present at extremely low concentrations. The accurate detection of these gases at sub-parts per million levels is imperative, particularly in fields where maintaining optimal air quality [...] Read more.
Noxious gases such as sulfur-containing compounds can inflict several different adverse effects on human health even when present at extremely low concentrations. The accurate detection of these gases at sub-parts per million levels is imperative, particularly in fields where maintaining optimal air quality is crucial. In this study, we harnessed the capabilities of nanostructured metal-oxide semiconducting materials to detect sulfur dioxide, since they have been extensively explored starting from the last decades for their effectiveness in monitoring toxic gases. We systematically characterized the sensing performance of seven chemoresistive devices. As a result, the SnO2:Au sensor demonstrated to be the most promising candidate for sulfur dioxide detection, owing to its highly sensitivity (0.5–10 ppm), humidity-independent behavior (30 RH% onwards), and selectivity vs. different gases at an operating temperature of 400 °C. This comprehensive investigation facilitates a detailed performance comparison to other devices explored for the SO2 sensing, supporting advancements in gas detection technology for enhanced workplace and environmental safety. Full article
(This article belongs to the Special Issue Gas Sensors and Electronic Noses for the Real Condition Sensing)
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12 pages, 4711 KiB  
Article
CoNiTe2 Nanomaterials as an Efficient Non-Enzymatic Electrochemical Sensing Platform for Detecting Dopamine
by Zhi-Yuan Wang, Chi-Hung Shen, Shih-Hao Yang, Han-Wei Chang and Yu-Chen Tsai
Chemosensors 2024, 12(6), 110; https://doi.org/10.3390/chemosensors12060110 - 13 Jun 2024
Viewed by 240
Abstract
Dopamine (DA) is an important catecholamine neurotransmitter in the mammalian central nervous system that affects many physiological functions. Hence, a highly sensitive and selective sensing platform is necessary for quantification of DA in the human body. In this study, ternary transition metal tellurides [...] Read more.
Dopamine (DA) is an important catecholamine neurotransmitter in the mammalian central nervous system that affects many physiological functions. Hence, a highly sensitive and selective sensing platform is necessary for quantification of DA in the human body. In this study, ternary transition metal tellurides of CoNiTe2 were successfully synthesized using the hydrothermal method. The proposed CoNiTe2 nanomaterials were dispersed well in Nafion to form a well-dispersed suspension and, when dropped on a glassy carbon electrode (GCE) as the working electrode (CoNiTe2/Nafion/GCE) for electrochemical non-enzymatic DA sensing, displayed excellent electrocatalytic activity for dopamine electrooxidation. The morphology and physical/chemical properties of CoNiTe2 nanomaterials were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In order to obtain the best electrochemical response to DA from the fabricated CoNiTe2/Nafion/GCE, the experimental conditions of electrochemical sensing, including the CoNiTe2 loading amounts and pH values of the phosphate buffer solution (PBS), were explored to achieve the best electrochemical sensing performance. Under optimal conditions (2 mg of CoNiTe2 and pH 6.0 of PBS), the fabricated CoNiTe2/Nafion/GCE showed excellent electrocatalytic activity of DA electrooxidation. The CoNiTe2/Nafion/GCE sensing platform demonstrated excellent electrochemical performance owing to the optimal structural and electronic characteristics originating from the synergistic interactions of bimetallic Co and Ni, the low electronegativity of Te atoms, and the unique morphology of the CoNiTe2 nanorod. It exhibited a wide linear range from 0.05 to 100 μM, a high sensitivity of 1.2880 µA µM−1 cm−2, and a low limit of detection of 0.0380 µM, as well as acceptable selectivity for DA sensing. Therefore, the proposed CoNiTe2/Nafion/GCE could be considered a promising electrode material for electrochemical non-enzymatic DA sensing. Full article
(This article belongs to the Special Issue Nanomaterial-Based Chemosensors and Biosensors for Smart Sensing)
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17 pages, 3787 KiB  
Article
Preparation, Characterization and Electrochemical Response of Nanostructured TiAlV with Potentiostatically Deposited IrOx as a pH Sensor for Rapid Detection of Inflammation
by Jitřenka Jírů, Vojtěch Hybášek, Alena Michalcová, Klára Korbelová, Lukáš Koláčný and Jaroslav Fojt
Chemosensors 2024, 12(6), 109; https://doi.org/10.3390/chemosensors12060109 - 11 Jun 2024
Viewed by 282
Abstract
Electrochemical pH sensors have a wide range of industrial applications such as in medicine due to their fast response and high sensitivity to pH changes. This work focuses on the preparation of samples based on the nanostructure of TiO2 with potentiostatically deposited [...] Read more.
Electrochemical pH sensors have a wide range of industrial applications such as in medicine due to their fast response and high sensitivity to pH changes. This work focuses on the preparation of samples based on the nanostructure of TiO2 with potentiostatically deposited particles of iridium and its oxides (IrO2), using a Ti-6Al-4V alloy as the base material, and subsequent surface characterization. Transmission electron microscopy and secondary ion mass spectroscopy showed Ir particles distributed in the nanotubes. Using a potentiostatic method, a stable pH sensor was prepared. By monitoring the open circuit potential, it was shown that this sensor is usable even without being kept in a storage medium and does not react to changes in the redox potential of the solution. Full article
(This article belongs to the Collection pH Sensors, Biosensors and Systems)
12 pages, 1935 KiB  
Article
Upcycled Graphene Oxide Nanosheets for Reversible Room Temperature NO2 Gas Sensor
by Vien Trinh, Kai Xu, Hao Yu, Nam Ha, Yihong Hu, Muhammad Waqas Khan, Rui Ou, Yange Luan, Jiaru Zhang, Qijie Ma, Guanghui Ren and Jian Zhen Ou
Chemosensors 2024, 12(6), 108; https://doi.org/10.3390/chemosensors12060108 - 10 Jun 2024
Viewed by 652
Abstract
Graphene oxide (GO) nanosheets, as one of the most studied graphene derivatives, have demonstrated an intrinsically strong physisorption-based gas–matter behavior, owing to its enhanced volume–surface ratio and abundant surface functional groups. The exploration of efficient and cost-effective synthesis methods for GO is an [...] Read more.
Graphene oxide (GO) nanosheets, as one of the most studied graphene derivatives, have demonstrated an intrinsically strong physisorption-based gas–matter behavior, owing to its enhanced volume–surface ratio and abundant surface functional groups. The exploration of efficient and cost-effective synthesis methods for GO is an ongoing task. In this work, we explored a novel approach to upcycle inexpensive polyethylene terephthalate (PET) plastic waste into high-quality GO using a combination of chemical and thermal treatments based on a montmorillonite template. The obtained material had a nanosheet morphology with a lateral dimension of around ~2 µm and a thickness of ~3 nm. In addition, the GO nanosheets were found to be a p-type semiconductor with a bandgap of 2.41 eV and was subsequently realized as a gas sensor. As a result, the GO sensor exhibited a fully reversible sensing response towards ultra-low-concentration NO2 gas with a limit of detection of ~1.43 ppb, without the implementation of an external excitation stimulus including elevating the operating temperature or bias voltages. When given a thorough test, the sensor maintained an impressive long-term stability and repeatability with little performance degradation after 5 days of experiments. The response factor was estimated to be ~11% when exposed to 1026 ppb NO2, which is at least one order of magnitude higher than that of other commonly seen gas species including CH4, H2, and CO2. Full article
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14 pages, 5355 KiB  
Article
SnO2 Nanowire/MoS2 Nanosheet Composite Gas Sensor in Self-Heating Mode for Selective and ppb-Level Detection of NO2 Gas
by Jin-Young Kim, Ali Mirzaei and Jae-Hun Kim
Chemosensors 2024, 12(6), 107; https://doi.org/10.3390/chemosensors12060107 - 9 Jun 2024
Viewed by 488
Abstract
The development of low-cost and low-power gas sensors for reliable NO2 gas detection is important due to the highly toxic nature of NO2 gas. Herein, initially, SnO2 nanowires (NWs) were synthesized through a simple vapor–liquid–solid growth mechanism. Subsequently, different amounts [...] Read more.
The development of low-cost and low-power gas sensors for reliable NO2 gas detection is important due to the highly toxic nature of NO2 gas. Herein, initially, SnO2 nanowires (NWs) were synthesized through a simple vapor–liquid–solid growth mechanism. Subsequently, different amounts of SnO2 NWs were composited with MoS2 nanosheets (NSs) to fabricate SnO2 NWs/MoS2 NS nanocomposite gas sensors for NO2 gas sensing. The operation of the sensors in self-heating mode at 1–3.5 V showed that the sensor with 20 wt.% SnO2 (SM-20 nanocomposite) had the highest response of 13 to 1000 ppb NO2 under 3.2 V applied voltage. Furthermore, the SM-20 nanocomposite gas sensor exhibited high selectivity and excellent long-term stability. The enhanced NO2 gas response was ascribed to the formation of n-n heterojunctions between SnO2 NWs and MoS2, high surface area, and the presence of some voids in the SM-20 composite gas sensor due to having different morphologies of SnO2 NWs and MoS2 NSs. It is believed that the present strategy combining MoS2 and SnO2 with different morphologies and different sensing properties is a good approach to realize high-performance NO2 gas sensors with merits such as simple synthesis and fabrication procedures, low cost, and low power consumption, which are currently in demand in the gas sensor market. Full article
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18 pages, 4842 KiB  
Article
Quantitative Analysis of Chlorogenic Acid during Coffee Roasting via Raman Spectroscopy
by Deborah Herdt, Tobias Teumer, Shaun Paul Keck, Thomas Kunz, Victoria Schiwek, Sarah Kühnemuth, Frank-Jürgen Methner and Matthias Rädle
Chemosensors 2024, 12(6), 106; https://doi.org/10.3390/chemosensors12060106 - 9 Jun 2024
Viewed by 421
Abstract
Tracking coffee roasting at an industrial scale for quality control is challenging. Bean color is a practical gauge for monitoring and regulating the process but only occurs before and after the process. This study highlights the feasibility of monitoring the process throughout using [...] Read more.
Tracking coffee roasting at an industrial scale for quality control is challenging. Bean color is a practical gauge for monitoring and regulating the process but only occurs before and after the process. This study highlights the feasibility of monitoring the process throughout using Raman spectroscopy. Strecker degradation and the Maillard reaction contribute to various aromatic compounds that can serve as markers in quality monitoring. Among these are chlorogenic acids (CGAs), recognized as pivotal factors determining the desired aroma. Here, drum and fluidized bed roaster processes were monitored, capitalizing on the chemical alterations induced by high temperatures (140–200 °C), particularly through the Maillard reaction. These chemical changes manifest in the scattered light signal. For real-time monitoring, Raman spectra were taken every 10 ms in selected ranges, with an average calculated every second. Utilizing a calibration matrix from a High-Pressure Liquid Chromatography (HPLC) method, CGA concentration becomes the control variable for assessing roasting progress. This study reveals the potential of Raman spectroscopy for tracking CGA during roasting. It establishes a correlation between inelastic scattered light and CGA validated through laboratory measurements and fixed roasting conditions, resulting in a theoretical CGA concentration that can be used as a process termination criterion. Full article
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20 pages, 4116 KiB  
Article
Quick Plant Sample Preparation Methods Using a Micro-Homogenizer for the Detection of Multiple Citrus Pathogens
by Chia-Wei Liu, Sohrab Bodaghi, Georgios Vidalakis and Hideaki Tsutsui
Chemosensors 2024, 12(6), 105; https://doi.org/10.3390/chemosensors12060105 - 8 Jun 2024
Viewed by 295
Abstract
Effective pathogen detection is essential for plant disease control. However, plant sample preparation for downstream assays, such as quantitative polymerase chain reaction (qPCR), is challenging to perform outside of a laboratory. This paper reports two sample preparation methods featuring chemical and mechanical lysis [...] Read more.
Effective pathogen detection is essential for plant disease control. However, plant sample preparation for downstream assays, such as quantitative polymerase chain reaction (qPCR), is challenging to perform outside of a laboratory. This paper reports two sample preparation methods featuring chemical and mechanical lysis and nucleic acid extraction using a micro-homogenizer, followed by serial dilution or nucleic acid purification with a paper disk before assay. Five minutes of lysis and extraction resulted in DNA and RNA yields of up to 76.5% and 63.3%, respectively, compared to mortar and pestle controls. Crude lysates were unsuitable for direct use in qPCR assays; however, serial dilution or quick wash using chromatography paper rendered samples ready for such assays. Additionally, the nucleic acids stored on paper disks under various storage conditions remained stable for one month. These methods can facilitate the in-field preparation of citrus samples and allow for both onsite and mail-in diagnostics for growers. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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14 pages, 1089 KiB  
Article
Bimetallic Fe3O4@Co3O4/CN as a Nanozyme with Dual Enzyme-Mimic Activities for the Colorimetric Determination of Mercury(II)
by Yanyan Xing, Pingping He, Deyong Wang, Yuan Liang, Xing Gao and Xiaohong Hou
Chemosensors 2024, 12(6), 104; https://doi.org/10.3390/chemosensors12060104 - 7 Jun 2024
Viewed by 362
Abstract
Colorimetric biosensor-based nanozymes have received considerable attention in various fields thanks to the advantages of the simple preparation, good stability, and regulable catalytic activity of nanozymes. In this study, a bimetallic nanozyme Fe3O4@Co3O4/CN was prepared [...] Read more.
Colorimetric biosensor-based nanozymes have received considerable attention in various fields thanks to the advantages of the simple preparation, good stability, and regulable catalytic activity of nanozymes. In this study, a bimetallic nanozyme Fe3O4@Co3O4/CN was prepared via the high-temperature calcination of Fe3O4-PVP@ZIF-67. The material retained its skeletal structure before calcination, which prevented the aggregation of nanoparticles and exposed more active sites of the nanozyme, substantially enhancing the intrinsic dual enzyme-mimetic activities, including peroxidase- and oxidase-like activities. In particular, Fe3O4@Co3O4/CN with oxidase-like activity catalyzed the colorless tetramethylbenzidine (TMB) to become blue oxTMB with oxygen. Reducing glutathione (GSH) could inhibit the above oxidation reaction. In contrast, with respect to the existence of mercury(II), GSH bound to mercury(II) due to the strong affinity between mercury(II) and -SH, thus eliminating the inhibition and restoring the oxTMB signal. A simple and effective colorimetric sensor was fabricated to detect mercury(II) based on the above principles. The proposed measurement had a linear range of 0.1–15 μM and a limit of detection (LOD) of 0.017 μM. It was shown that the established colorimetric sensing system could be successfully applied to detect mercury(II) in water samples, and the Fe3O4@Co3O4/CN nanozyme proved to be a promising candidate for biosensing application. Full article
(This article belongs to the Special Issue Chemosensors in Biological Challenges, Volume II)
12 pages, 4772 KiB  
Article
Synthesis of Bismuth Film Assembly on Flexible Carbon Cloth for the Electrochemical Detection of Heavy Metal Ions
by Yujie Cao, Xiangyu Zhou, Ziling Wang, Yi Li, Minglei Yan, Yun Zeng, Jie Xiao, Yang Zhao and Jun-Heng Fu
Chemosensors 2024, 12(6), 103; https://doi.org/10.3390/chemosensors12060103 - 6 Jun 2024
Viewed by 391
Abstract
The utilization of bismuth as a sensing material for the detection of heavy metal ions has gained significant attention due to its exceptional interfacial activity and selective absorption properties. However, it also poses challenges in terms of agglomeration and its inferior electrical conductivity [...] Read more.
The utilization of bismuth as a sensing material for the detection of heavy metal ions has gained significant attention due to its exceptional interfacial activity and selective absorption properties. However, it also poses challenges in terms of agglomeration and its inferior electrical conductivity during the synthesis process. This paper employed a facile in situ synthesis and electrodeposition approach to uniformly grow a bismuth film on a conductive carbon cloth, designated as Bi/Ag@CC. The Bi/Ag@CC electrode material exhibited benign electrochemical properties, enabling its application for detecting Pb2+ in tap water and lake water samples. Furthermore, this work investigated the impact of electrochemical parameters, including electrolyte pH, deposition potential and pre-enrichment time, on the detection performance. The results demonstrated the sensor’s wide linear range (from 20 to 400 ppb) and detection limits (0.15 ppb) for heavy metal ion detection, along with excellent anti-interference capabilities and satisfactory repeatability, with an RSD of less than 2.31% (n = 6). This paper offers a novel strategy for positioning the bismuth-based composite as a promising candidate for practical electrochemical sensing applications. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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12 pages, 3439 KiB  
Article
Interaction of the Polymeric Layer Derived from 3-(4-Trifluoromethyl)-phenyl)-thiophene with Synthetic Stimulants on the Phase Boundary
by Tatiana V. Shishkanova, Natalie Štěpánková, Gabriela Broncová and Martin Vrňata
Chemosensors 2024, 12(6), 99; https://doi.org/10.3390/chemosensors12060099 - 5 Jun 2024
Viewed by 329
Abstract
Modification of an electrode surface with a selective layer leads to amplification of the electrochemical signal. A film derived from electrochemically oxidized 3-(4-trifluoromethyl)-phenyl)-thiophene deposited on a graphite electrode (ThPhCF3/G) was used to estimate the affinity for synthetic stimulants (2-aminoindane, buphedrone, naphyrone) [...] Read more.
Modification of an electrode surface with a selective layer leads to amplification of the electrochemical signal. A film derived from electrochemically oxidized 3-(4-trifluoromethyl)-phenyl)-thiophene deposited on a graphite electrode (ThPhCF3/G) was used to estimate the affinity for synthetic stimulants (2-aminoindane, buphedrone, naphyrone) using a combination of square wave voltammetry and electrochemical impedance spectroscopy. The modified surface was characterized using Raman spectroscopy, which confirmed that the presence of the –PhCF3 group is important for the recognition of synthetic stimulants. The determined values of the adsorption constants (Kads) showed the significance of charge–transfer and/or hydrogen bond interactions between—PhCF3 groups in the polymeric film and the analyte of interest: buphedrone (9.79 × 105) < naphyrone (1.57 × 106) < 2-AI (1.87 × 106). Compared to electrodes modified with nanomaterial, PThPhCF3/G-electrodes showed the highest sensitivity in concentration range of 1–11 μmol L−1 at neutral pH and a possibility of detection of 0.43–0.56 μg mL−1 (sr = 0.05–0.12). The analytical performance of ThPhCF3/G promises good perspectives for the detection of synthetic stimulants in forensic samples without prior pretreatment. Full article
(This article belongs to the Special Issue Advances in Electrochemical Sensing and Analysis)
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11 pages, 944 KiB  
Article
Portable Sensing Platform for the Visual Detection of Iodide Ions in Food and Clinical Samples
by Aizaz Khan, Ali Turab Jafry, Huma Ajab, Asim Yaqub, Shahaab Jilani, Dildar Hussain and Naseem Abbas
Chemosensors 2024, 12(6), 102; https://doi.org/10.3390/chemosensors12060102 - 5 Jun 2024
Viewed by 395
Abstract
The detection of iodide ions (I), despite challenges due to low concentrations and potential masking, is crucial for studying physiological processes and diagnosing diseases. A colorimetric sensor was developed to improve I ion monitoring and facilitate on-site detection based on [...] Read more.
The detection of iodide ions (I), despite challenges due to low concentrations and potential masking, is crucial for studying physiological processes and diagnosing diseases. A colorimetric sensor was developed to improve I ion monitoring and facilitate on-site detection based on filter paper, which is a cost-effective platform. The sensor observed color changes in response to the exposure of hydrogen peroxide (H2O2), 3,3′,5,5′-tetramethylbenzidine (TMB), from colorless to yellowish brown. The sensor demonstrated a detection limit of 0.125 × 10−6 M for I ions in a relatively wide range of 0.01 to 15 × 10−6 M under optimized conditions including gel concentration, temperature, incubation time, TMB and H2O2 concentration, and pH. Furthermore, the proposed sensor was successfully employed in a variety of applications, such as biological (urine and blood serum), food (egg yolk and snacks), and environmental samples (tap water). The study established effective recoveries in complex media for visual on-site I ion monitoring, indicating the developed assay as a potent, affordable, and practical platform. Full article
(This article belongs to the Special Issue Rapid Point-of-Care Testing Technology and Application)
13 pages, 3117 KiB  
Communication
Thermal Modulation of Resistance Gas Sensor Facilitates Recognition of Fragrance Odors
by Ran Sui, Erpan Zhang, Xiaoshui Tang, Wenjun Yan, Yun Liu and Houpan Zhou
Chemosensors 2024, 12(6), 101; https://doi.org/10.3390/chemosensors12060101 - 5 Jun 2024
Viewed by 316
Abstract
Herein, we prepared two different MOS-based gas sensors with integrated micro-hotplates. The two sensors were employed to detect various fragrances (cedar, mandarin orange, rose A, and rose B), exhibiting similarly great sensing performances. The gas sensing properties of the MOS-based sensor depend on [...] Read more.
Herein, we prepared two different MOS-based gas sensors with integrated micro-hotplates. The two sensors were employed to detect various fragrances (cedar, mandarin orange, rose A, and rose B), exhibiting similarly great sensing performances. The gas sensing properties of the MOS-based sensor depend on the sensor’s operating temperature. In addition to isothermal operation, various pulse heating modes were applied to investigate the gas sensing performances with respect to the four fragrances. Multivariate gas sensing features of the four fragrances were obtained under different operating modes, which were utilized for the recognition of fragrance odors successfully, based on the long short-term memory (LSTM) algorithm. Full article
(This article belongs to the Section Applied Chemical Sensors)
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13 pages, 912 KiB  
Article
Improved Affinity: A Customized Fluorescent Probe for the Rapid Detection of Butyrylcholinesterase
by Wei Wang, Xiao-Fei Chen, Yi Zhang, Yang Ran, Long Jin, Shuai Li and Bai-Ou Guan
Chemosensors 2024, 12(6), 100; https://doi.org/10.3390/chemosensors12060100 - 5 Jun 2024
Viewed by 352
Abstract
This article presents the distinctive butyrylcholinesterase (BChE) fluorescent probe P5, designed via a targeting-site method. This method was proposed to enhance the affinity of the probe for BChE by targeting the peripheral anionic site (PAS) of BChE. By mimicking the natural substrate [...] Read more.
This article presents the distinctive butyrylcholinesterase (BChE) fluorescent probe P5, designed via a targeting-site method. This method was proposed to enhance the affinity of the probe for BChE by targeting the peripheral anionic site (PAS) of BChE. By mimicking the natural substrate butyrylcholine, the structure of the probe was optimized by introducing a positive charge. Fluorescent probe P5, selected from a series of designed fluorescent probes P1P6, exhibited excellent affinity and specificity towards BChE, enabling rapid detection within 5 min with a low detection limit of 16.7 ng/mL. Furthermore, this probe can distinguish between normal cells and Alzheimer’s disease (AD) model cells, and demonstrated good imaging results in a P12 cell AD model. The results of this study indicate that this novel fluorescent probe could serve as a promising tool for the rapid detection of BChE and accurate AD diagnosis. Full article
(This article belongs to the Special Issue Fluorescent Probe and Imaging for Biological Analysis)
15 pages, 2750 KiB  
Article
A Flow-Through Biosensor System Based on Pillar[3]Arene[2]Quinone and Ferrocene for Determination of Hydrogen Peroxide and Uric Acid
by Dmitry Stoikov, Insiya Shafigullina, Dmitry Shurpik, Ivan Stoikov and Gennady Evtugyn
Chemosensors 2024, 12(6), 98; https://doi.org/10.3390/chemosensors12060098 - 4 Jun 2024
Viewed by 249
Abstract
Simple and reliable electrochemical sensors are highly demanded in medicine and pharmacy for the fast determination of metabolites and biomarkers of diseases. In this work, a flow-through biosensor system was developed on the base of a screen-printed carbon electrode modified with pillar[3]arene[2]quinone and [...] Read more.
Simple and reliable electrochemical sensors are highly demanded in medicine and pharmacy for the fast determination of metabolites and biomarkers of diseases. In this work, a flow-through biosensor system was developed on the base of a screen-printed carbon electrode modified with pillar[3]arene[2]quinone and ferrocene implemented in carbon black. The modification was performed in a single step and resulted in the formation of a stable layer with good operation characteristics. Uricase was immobilized on the inner walls of a replaceable reactor by carbodiimide binding. A flow-through cell was manufactured by 3D printing from poly(lactic acid). The flow-through system was first optimized on the hydrogen peroxide assay and then used for the determination of 1 nM–0.1 mM uric acid (limit of detection 0.3 nM, 20 measurements per hour). Implementation of ferrocene resulted in a synergetic increase in the cathodic current of H2O2 reduction measured by flow switching in chronoamperometric mode. The developed system was tested on the determination of uric acid in artificial urine and Ringer–Locke solution and showed a recovery rate of 96–112%. In addition, the possibility of determination of H2O2 in commercial disinfectants was shown. Easy assembly, fast and reliable signal and low consumption of the reagents make the system developed attractive for routine clinical analysis of metabolites. Full article
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13 pages, 4596 KiB  
Article
Polyaniline-Based Flexible Sensor for pH Monitoring in Oxidizing Environments
by Liam Bignall, Claire Magnenet, Catheline Ramsamy, Sophie Lakard, Simon Vassal and Boris Lakard
Chemosensors 2024, 12(6), 97; https://doi.org/10.3390/chemosensors12060097 - 3 Jun 2024
Viewed by 365
Abstract
Measuring pH in oxidizing solutions is a crucial issue in areas such as aquaculture, water treatment, industrial chemistry, and environmental analysis. For this purpose, a low-cost potentiometric flexible sensor using a polymer film as a pH-sensitive material has been developed in this study. [...] Read more.
Measuring pH in oxidizing solutions is a crucial issue in areas such as aquaculture, water treatment, industrial chemistry, and environmental analysis. For this purpose, a low-cost potentiometric flexible sensor using a polymer film as a pH-sensitive material has been developed in this study. The sensor consists in a polyaniline film electrodeposited from a sulfuric acid solution on a gold electrode previously deposited on a flexible polyimide substrate. The resulting polyaniline-based pH sensors showed an interesting performance detection in aqueous solution, leading to sensitive (73.4 mV per unit pH) and reproducible (standard deviation of 1.75) responses over the entire pH range from 3 to 8. On the contrary, they were inoperative in the presence of oxidizing hypochlorite ions. Thus, other polyaniline films were electrodeposited in the presence of cetyltrimethylammonium bromide or Tritonx100 surfactant in an attempt to improve the sensing performance of the pH sensors in oxidizing solutions. The pH sensors based on polyaniline and Tritonx100 surfactant were then found to be sensitive (62.3 mV per unit pH) and reproducible (standard deviation of 1.52) in aqueous solutions containing hypochlorite ions. All polyaniline films were also characterized by profilometry and electronic microscopy to correlate the physicochemical features with the performance of the sensors. Full article
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27 pages, 8110 KiB  
Review
A Review on Low-Temperature Protonic Conductors: Principles and Chemical Sensing Applications
by Sofia R. Mendes, Georgenes M. G. da Silva, Evando S. Araújo and Pedro M. Faia
Chemosensors 2024, 12(6), 96; https://doi.org/10.3390/chemosensors12060096 - 2 Jun 2024
Viewed by 310
Abstract
Proton conductors are ceramic materials with a crystalline or amorphous structure, which allow the passage of an electrical current through them exclusively by the movement of protons: H+. Recent developments in proton-conducting ceramics present considerable promise for obtaining economic and sustainable [...] Read more.
Proton conductors are ceramic materials with a crystalline or amorphous structure, which allow the passage of an electrical current through them exclusively by the movement of protons: H+. Recent developments in proton-conducting ceramics present considerable promise for obtaining economic and sustainable energy conversion and storage devices, electrolysis cells, gas purification, and sensing applications. So, proton-conducting ceramics that combine sensitivity, stability, and the ability to operate at low temperatures are particularly attractive. In this article, the authors start by presenting a brief historical resume of proton conductors and by exploring their properties, such as structure and microstructure, and their correlation with conductivity. A perspective regarding applications of these materials on low-temperature energy-related devices, electrochemical and moisture sensors, is presented. Finally, the authors’ efforts on the usage of a proton-conducting ceramic, polyantimonic acid (PAA), to develop humidity sensors, are looked into. Full article
(This article belongs to the Section Applied Chemical Sensors)
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12 pages, 962 KiB  
Article
Real-Time Potentiometric Monitoring of Tetrachloroaurate(III) with an Ion-Selective Electrode and Its Applications to HAuCl4 Iodide-Catalyzed Reduction by Hydroxylamine
by Carmen María Almagro-Gómez, José Ginés Hernández-Cifre and Joaquín Ángel Ortuño
Chemosensors 2024, 12(6), 95; https://doi.org/10.3390/chemosensors12060095 - 1 Jun 2024
Viewed by 219
Abstract
Ion-selective electrodes for tetrachloroaurate(III) have been developed for potentiometric monitoring of the reduction reaction of tetrachloroaurate(III). Three different plasticized polyvinyl chloride membranes containing tridodecymethylammonium chloride as an anion exchanger were investigated. These membranes differ in the plasticizer used, either 2-nitrophenyl octyl ether (NPOE) [...] Read more.
Ion-selective electrodes for tetrachloroaurate(III) have been developed for potentiometric monitoring of the reduction reaction of tetrachloroaurate(III). Three different plasticized polyvinyl chloride membranes containing tridodecymethylammonium chloride as an anion exchanger were investigated. These membranes differ in the plasticizer used, either 2-nitrophenyl octyl ether (NPOE) or tricresyl phosphate (TCP) or bis-(2-ethylhexyl) sebacate (DOS). The potentiometric response of the electrodes to the tetrachloroaurate(III) concentration was studied by two methods. In the first method, commonly used in the calibration of ion-selective electrodes, successive tetrachloroaurate(III) concentration increments were used and the potential was allowed to stabilize after each concentration step. The second method was developed to mimic the tetrachloroaurate(III) reduction reaction in which there is a continuous decrease in the concentration of tetrachloroaurate(III). This was achieved by continuously diluting an initial concentration of tetrachloroaurate(III) by pumping a diluent solution while keeping the sample volume constant. This method gave an excellent linear response to the tetrachloroaurate(III) concentration. The calibrated electrodes were used for the potentiometric monitoring of the kinetics of a newly observed reaction: the reduction of tetrachloroaurate(III) by hydroxylamine catalyzed by iodide. A mechanism for this reaction is proposed on the basis of the experimental results obtained. Full article
(This article belongs to the Special Issue State-of-the-Art Chemical Sensors in Spain)
16 pages, 764 KiB  
Article
Combining PDMS Composite and Plasmonic Solid Chemosensors: Dual Determination of Ammonium and Hydrogen Sulfide as Biomarkers in a Saliva Single Test
by Belen Monforte-Gómez, Sergio Mallorca-Cebriá, Carmen Molins-Legua and Pilar Campíns-Falcó
Chemosensors 2024, 12(6), 94; https://doi.org/10.3390/chemosensors12060094 - 31 May 2024
Viewed by 170
Abstract
In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination [...] Read more.
In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination of ammonium and hydrogen sulfur in saliva using two colorimetric chemosensors. The ammonia reacts with 1,2-Naftoquinone 4 sulphonic acid (NQS) entrapped in polydimethylsiloxane (PDMS) and the hydrogen sulfide with AgNPs retained in a nylon membrane. The color changed from orange to brown in the case of ammonia chemosensors and from yellow to brown in the H2S. The experimental conditions to be tested have been established. Both analytes have been determined from their gaseous form; these are ammonia from ammonium and hydrogen sulfur from hydrogen sulfur. Good figures of merit have been obtained by using both measuring strategies (reflectance diffuse and digitalized images). The acquired results show that both sensors can be used and provide good selectivity and sensitivity for the determination of these biomarkers in saliva. Both measurement strategies have provided satisfactory results for the real saliva samples (n = 15). Recoveries on spiked samples were between 70 and 100%. This methodology can lead to possible in situ diagnosis and monitoring of certain diseases and pathologies related with NH4+ and/or H2S, in a fast, simple, cheap and non-invasive way. Full article
14 pages, 4090 KiB  
Article
Pt-Embedded Metal–Organic Frameworks Deriving Pt/ZnO-In2O3 Electrospun Hollow Nanofibers for Enhanced Formaldehyde Gas Sensing
by Lei Zhu, Ze Wang, Jianan Wang, Jianwei Liu, Jiaxin Zhang and Wei Yan
Chemosensors 2024, 12(6), 93; https://doi.org/10.3390/chemosensors12060093 - 31 May 2024
Viewed by 203
Abstract
Functionalization by noble metal catalysts and the construction of heterojunctions are two effective methods to enhance the gas sensing performance of metal oxide-based sensors. In this work, we adopt the porous ZIF-8 as a catalyst substrate to encapsulate the ultra-small Pt nanoparticles. The [...] Read more.
Functionalization by noble metal catalysts and the construction of heterojunctions are two effective methods to enhance the gas sensing performance of metal oxide-based sensors. In this work, we adopt the porous ZIF-8 as a catalyst substrate to encapsulate the ultra-small Pt nanoparticles. The Pt/ZnO-In2O3 hollow nanofibers derived from Pt/ZIF-8 were prepared by a facile electrospinning method. The 25PtZI HNFs sensor possessed a response value of 48.3 to 100 ppm HCHO, 2.7 times higher than the pristine In2O3, along with rapid response/recovery time (5/22 s), and lower theoretical detection limit (74.6 ppb). The improved sensing properties can be attributed to the synergistic effects of electron sensitization effects and catalytic effects of Pt nanoparticles, and the high surface O absorbing capability of heterojunctions. The present study paves a new way to design high performance formaldehyde gas sensors in practical application. Full article
(This article belongs to the Special Issue Functional Nanomaterial-Based Gas Sensors)
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32 pages, 3921 KiB  
Review
Biosensors for Food Mycotoxin Determination: A Comparative and Critical Review
by Aurelia Magdalena Pisoschi, Florin Iordache, Loredana Stanca, Elena Mitranescu, Liliana Bader Stoica, Ovidiu Ionut Geicu, Liviu Bilteanu and Andreea Iren Serban
Chemosensors 2024, 12(6), 92; https://doi.org/10.3390/chemosensors12060092 - 30 May 2024
Viewed by 196
Abstract
The need for performant analytical methodologies to assess mycotoxins is vital, given the negative health impact of these compounds. Biosensors are analytical devices that consist of a biological element for recognizing the analyte and a transducer, which translates the biorecognition event into a [...] Read more.
The need for performant analytical methodologies to assess mycotoxins is vital, given the negative health impact of these compounds. Biosensors are analytical devices that consist of a biological element for recognizing the analyte and a transducer, which translates the biorecognition event into a signal proportional to the analyte concentration. The biorecognition elements can be enzymes, antibodies, or DNA fragments. The modalities of detection can be optical, electrochemical, thermal, or mass-sensitive. These analytical tools represent viable alternatives to laborious, expensive traditional methods and are characterized by specificity given by the biorecognition element, sensitivity, fast response, portability, multi-modal detection, and the possibility of in situ application. The present paper focuses on a comprehensive view, enriched with a critical, comparative perspective on mycotoxin assay using biosensors. The use of different biorecognition elements and detection modes are discussed comparatively. Nanomaterials with optical and electrochemical features can be exploited in association with a variety of biorecognition elements. Analytical parameters are reviewed along with a broad range of applications. Full article
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19 pages, 5421 KiB  
Article
A “Turn-Off” Pyrene-Based Ligand as a Fluorescent Sensor for the Detection of Cu2+ and Fe2+ Ions: Synthesis and Application in Real Water Samples, Logic Gate Construction, and Bio-Imaging
by Bhavana G. Gowda, Muzaffar Iqbal and Shiva Prasad Kollur
Chemosensors 2024, 12(6), 91; https://doi.org/10.3390/chemosensors12060091 - 30 May 2024
Viewed by 235
Abstract
Herein, we report the synthesis and characterization of a novel Schiff base ligand, (Z)-5-((pyren-1-ylmethylene)amino)-2,4-dihydro-3H-pyrazol-3-one (PMDP). The characterization of ligand PMDP was carried out using ESI-MS, 1H NMR, and UV–Visible spectroscopic techniques. As a probe, PMDP displayed a detectable, colorimetric colour [...] Read more.
Herein, we report the synthesis and characterization of a novel Schiff base ligand, (Z)-5-((pyren-1-ylmethylene)amino)-2,4-dihydro-3H-pyrazol-3-one (PMDP). The characterization of ligand PMDP was carried out using ESI-MS, 1H NMR, and UV–Visible spectroscopic techniques. As a probe, PMDP displayed a detectable, colorimetric colour shift in the presence of Cu2+ and Fe2+ ions. The solution was seen to have a light brown colour and to exhibit a fluorometric “turn off” response when Cu2+ and Fe2+ ions were present in a DMSO solution (HEPES 0.01 M, pH = 7.4) at room temperature. Job’s plot revealed that the PMDP binding ratio to Cu2+ and Fe2+ ions was in 1:2 ratio. In contrast to the other metal ions (Cd2+, Mn2+, Co2+, Na+, Ni2+, Cu+, Fe3+, Hg2+, Mg2+, Zn2+, K+, and V5+), the synthesised probe showed exceptional sensitivity and selectivity for detecting Cu2+ and Fe2+ metal ions. The results indicate that the detection limits for Cu2+ and Fe2+ are 0.42 μM and 0.51 μM, respectively. Furthermore, PMDP was efficiently utilised for the quantitative analysis of Cu2+ and Fe2+ in real water samples, RGB colour values in smart phones, logic gate construction, and cell imaging in HeLa cells. Full article
16 pages, 1426 KiB  
Article
Enhancement of H2 Gas Sensing Using Pd Decoration on ZnO Nanoparticles
by Jin-Young Kim, Kyeonggon Choi, Seung-Wook Kim, Cheol-Woo Park, Sung-Il Kim, Ali Mirzaei, Jae-Hyoung Lee and Dae-Yong Jeong
Chemosensors 2024, 12(6), 90; https://doi.org/10.3390/chemosensors12060090 - 27 May 2024
Viewed by 372
Abstract
Hydrogen (H2) gas, with its high calorimetric combustion energy and cleanness, is a green source of energy and an alternative to fossil fuels. However, it has a small kinetic diameter, with high diffusivity and a highly explosive nature. Hence, the reliable [...] Read more.
Hydrogen (H2) gas, with its high calorimetric combustion energy and cleanness, is a green source of energy and an alternative to fossil fuels. However, it has a small kinetic diameter, with high diffusivity and a highly explosive nature. Hence, the reliable detection of H2 gas is essential in various fields such as fuel cells. Herein, we decorated ZnO nanoparticles (NPs) with Pd noble metal NPs, using UV irradiation to enhance their H2 gas-sensing performance. The synthesized materials were fully characterized in terms of their phases, morphologies, and chemical composition. Then, the sensing layer was deposited on the electrode-patterned glass substrate to make a transparent sensor. The fabricated transparent gas sensor was able to detect H2 gas at various temperatures and humidity levels. At 250 °C, the sensor exhibited the highest response to H2 gas. As a novelty of the present study, we successfully detected H2 gas in mixtures of H2/benzene and H2/toluene gases. The enhanced H2 gas response was related to the catalytic effect of Pd, the formation of heterojunctions between Pd and ZnO, the partial reduction of ZnO to Zn in the presence of H2 gas, and the formation of PdHx. With a high performance in a high response, good selectivity, and repeatability, we believe that the sensor developed in this study can be a good candidate for practical applications where the detection of H2 is necessary. Full article
(This article belongs to the Special Issue Gas Sensors and Electronic Noses for the Real Condition Sensing)
17 pages, 3076 KiB  
Article
Superoxide Dismutase Detection on Silver Nanostructured Substrates through Surface-Enhanced Spectroscopic Techniques
by Anastasia Kanioura, Georgia Geka, Ioannis Kochylas, Vlassis Likodimos, Spiros Gardelis, Anastasios Dimitriou, Nikolaos Papanikolaou, Sotirios Kakabakos and Panagiota Petrou
Chemosensors 2024, 12(6), 89; https://doi.org/10.3390/chemosensors12060089 - 25 May 2024
Viewed by 357
Abstract
Oxidative stress refers to the overproduction of reactive oxygen species and is often associated with numerous pathological conditions. Superoxide dismutase (SOD) is a widely used enzyme for evaluating oxidative stress, with numerous methods being developed for its detection in biological specimens like blood, [...] Read more.
Oxidative stress refers to the overproduction of reactive oxygen species and is often associated with numerous pathological conditions. Superoxide dismutase (SOD) is a widely used enzyme for evaluating oxidative stress, with numerous methods being developed for its detection in biological specimens like blood, urine, and saliva. In this study, a simple metal-assisted chemical etching method was employed for the fabrication of nanostructured silicon surfaces decorated with either silver dendrites or silver aggregates. Those surfaces were used as substrates for the immunochemical determination of SOD in synthetic saliva through surface-enhanced Raman spectroscopy (SERS) and surface-enhanced fluorescence (SEF). The immunoassay was based on a 3-step competitive assay format, which included, after the immunoreaction with the specific anti-SOD antibody, a reaction with a biotinylated secondary antibody and streptavidin. Streptavidin labeled with peroxidase was used in combination with a precipitating tetramethylbenzidine substrate for detection through SERS, whereas for SEF measurements, streptavidin labeled with the fluorescent dye Rhodamine Red-X was utilized. Both immunoassays were sensitive, with a detection limit of 0.01 μg/mL and a linear dynamic range from 0.03 to 3.3 μg/mL, enabling the evaluation of the oxidative stress status of an organism. Full article
(This article belongs to the Special Issue Application of Luminescent Materials for Sensing)
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18 pages, 3372 KiB  
Review
The Developments on Lateral Flow Immunochromatographic Assay for Food Safety in Recent 10 Years: A Review
by Peng Wang, Jinyan Li, Lingling Guo, Jiaxun Li, Feng He, Haitao Zhang and Hai Chi
Chemosensors 2024, 12(6), 88; https://doi.org/10.3390/chemosensors12060088 - 24 May 2024
Viewed by 379
Abstract
Food safety inspections are an essential aspect of food safety monitoring. Rapid, accurate, and low-cost food analysis can considerably increase the efficiency of food safety inspections. The lateral flow immunochromatographic assay (LFIA) technique has recently grown in popularity due to its ease of [...] Read more.
Food safety inspections are an essential aspect of food safety monitoring. Rapid, accurate, and low-cost food analysis can considerably increase the efficiency of food safety inspections. The lateral flow immunochromatographic assay (LFIA) technique has recently grown in popularity due to its ease of use and high efficiency. It is currently commonly utilized in food inspection. In this review, we briefly introduce the principle and classification of LFIA, critically discuss the recent application status of LFIA in food contaminantion detection, and finally propose that artificial intelligence and information technology will further advance the development of LFIA in the field of food safety monitoring. Full article
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13 pages, 3005 KiB  
Article
Controlled Insertion of Silver Nanoparticles in LbL Nanostructures: Fine-Tuning the Sensing Units of an Impedimetric E-Tongue
by Maria Helena Gonçalves, Maria Luisa Braunger, Anerise de Barros, Rafael C. Hensel, Julianna G. Dalafini, Italo O. Mazali, Leonardo M. Corrêa, Daniel Ugarte, Antonio Riul Jr and Varlei Rodrigues
Chemosensors 2024, 12(6), 87; https://doi.org/10.3390/chemosensors12060087 - 24 May 2024
Viewed by 420
Abstract
Silver nanoparticles (AgNPs) possess unique characteristics ideal for enhancing device sensitivity, primarily due to their high surface-to-volume ratio facilitating heightened interaction with analytes. Integrating AgNPs into polymers or carbon-based materials results in nanocomposites with synergistic properties, enabling the detection of minute changes in [...] Read more.
Silver nanoparticles (AgNPs) possess unique characteristics ideal for enhancing device sensitivity, primarily due to their high surface-to-volume ratio facilitating heightened interaction with analytes. Integrating AgNPs into polymers or carbon-based materials results in nanocomposites with synergistic properties, enabling the detection of minute changes in the environment across various applications. In this study, we investigate the adsorption kinetics of AgNPs within multilayered layer-by-layer (LbL) structures, specifically examining the impact of AgNPs concentration in the LbL film formation that is further explored as sensing units in an impedimetric microfluidic e-tongue. Although absorption kinetic studies are infrequent, they are crucial to optimize the AgNPs adsorption and distribution within LbL structures, significantly influencing upcoming applications. Through systematic variation of AgNPs concentration within identical LbL architectures, we applied the films as sensing units in a microfluidic e-tongue capable of distinguishing food enhancers sharing the umami taste profile. Across all tested scenarios, our approach consistently achieves robust sample separation, evidenced by silhouette coefficient, principal component analyses, and long-term stability. This work contributes to exploring controlled nanomaterial-based developments, emphasizing the importance of precise parameter control for enhanced sensor performance across diverse analytical applications. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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16 pages, 2698 KiB  
Article
All-Solid-State Potentiometric Sensor Based on Graphene Oxide as Ion-to-Electron Transducer for Nitrate Detection in Water Samples
by Renato L. Gil, Laura Rodriguez-Lorenzo, Begoña Espiña and Raquel B. Queirós
Chemosensors 2024, 12(6), 86; https://doi.org/10.3390/chemosensors12060086 - 22 May 2024
Viewed by 632
Abstract
Graphene oxide (GO) was used as an ion-to-electron transducer for all-solid-state nitrate electrodes based on an alkyl ammonium salt as the sensing element. Commercially available carbon screen-printed electrodes modified with GO were used as conductive substrates, whose morphology and distribution along the surface [...] Read more.
Graphene oxide (GO) was used as an ion-to-electron transducer for all-solid-state nitrate electrodes based on an alkyl ammonium salt as the sensing element. Commercially available carbon screen-printed electrodes modified with GO were used as conductive substrates, whose morphology and distribution along the surface were evaluated by scanning electron microscopy and Raman spectroscopy. The potentiometric performance of the GO-based electrodes revealed a Nernstian slope of −53.5 ± 2.0 mV decade−1 (R2 = 0.9976 ± 0.0015) in the range from 3.0 × 10−6 to 10−2 M and a lower limit of detection of 1.9 × 10−6 M. An impressive reproducibility between equally prepared electrodes (n = 15) was demonstrated by a variation of <6% for the calibration parameters. Constant current chronopotentiometry and water layer tests were used to evaluate the potential signal stability, providing similar performance to previously published works with graphene-based ion-selective electrodes. Notably, the GO-based sensors showed the absence of a water layer, a long-term drift of 0.3 mV h−1, and a stable performance (LOD and sensitivity) over 3 months. The applicability of the proposed sensors was demonstrated in determining nitrate levels in water samples with great accuracy, yielding recovery values from 87.8 to 107.9%, and comparable (p > 0.05) results to a commercial nitrate probe. These findings demonstrate the use of GO as an alternative ion-to-electron transducer for the fabrication of all-solid-state potentiometric electrodes. Full article
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