Chemosensors

13 pages, 3469 KiB

Open AccessArticle

An Integration of UPLC-Q-TOF-MS, GC-MS, Electronic Nose, Electronic Tongue, and Molecular Docking for the Study of the Chemical Properties and Flavor Profiles of Moringa oleifera Leaves

by Mingxiao Zhang, Mengjia Guo, Na Chen, Zhuqian Tang, Junjie Xiang, Lixin Yang, Guohua Wang, Bin Yang and Hua Li

Chemosensors 2024, 12(9), 199; https://doi.org/10.3390/chemosensors12090199 - 23 Sep 2024

Cited by 1 | Viewed by 1692

Abstract

Moringa oleifera leaves (MOLs) have gained significant attention due to their nutritional and biological activity. Therefore, this study aimed to examine its flavor characteristics and underlying compositions. In this study, we used ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), gas [...] Read more.

Moringa oleifera leaves (MOLs) have gained significant attention due to their nutritional and biological activity. Therefore, this study aimed to examine its flavor characteristics and underlying compositions. In this study, we used ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), gas chromatography-mass spectrometry (GC-MS), electronic nose, electronic tongue, and molecular docking to comprehensively investigate the chemical properties and flavor profiles of MOLs. UPLC-Q-TOF-MS and GC-MS were instrumental in identifying the 20 non-volatile and 19 volatile constituents of MOLs, respectively. The electronic nose and electronic tongue systems provided an objective evaluation of the sweet, bitter, and spicy attributes and flavor characteristics of MOLs. Concurrently, molecular docking was employed to elucidate the material basis of flavor profiles. It revealed that glucosinolates and flavonoids are probably the key components for the bitter taste of MOLs. The sweet taste may be attributed to glucosinolates and flavonoids. The spicy scent appears to be linked to the presence of glucosinolates and alkaloids. The integration of these techniques confers a thorough understanding of the chemical composition and sensory properties of MOLs. These findings have significant implications for innovative applications in the food industry as well as pharmaceuticals and agriculture sectors; furthermore, they contribute towards enhancing the perception of Moringa oleifera as a valuable natural resource. Full article

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

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21 pages, 20880 KiB

Open AccessArticle

Ceramic Nanotubes—Conducting Polymer Assemblies with Potential Application as Chemosensors for Breath Ammonia Detection in Chronic Kidney Disease

by Alexandru Florentin Trandabat, Romeo Cristian Ciobanu, Oliver Daniel Schreiner, Thomas Gabriel Schreiner and Sebastian Aradoaei

Chemosensors 2024, 12(9), 198; https://doi.org/10.3390/chemosensors12090198 - 23 Sep 2024

Cited by 1 | Viewed by 1413

Abstract

This paper describes the process of producing chemosensors based on hybrid nanostructures obtained from Al₂O₃, as well as ZnO ceramic nanotubes and the following conducting polymers: poly(3-hexylthiophene), polyaniline emeraldine-base (PANI-EB), and poly(3, 4-ethylenedioxythiophene)-polystyrene sulfonate. The process for creating ceramic [...] Read more.

This paper describes the process of producing chemosensors based on hybrid nanostructures obtained from Al₂O₃, as well as ZnO ceramic nanotubes and the following conducting polymers: poly(3-hexylthiophene), polyaniline emeraldine-base (PANI-EB), and poly(3, 4-ethylenedioxythiophene)-polystyrene sulfonate. The process for creating ceramic nanotubes involves three steps: creating polymer fiber nets using poly(methyl methacrylate), depositing ceramic films onto the nanofiber nets using magnetron deposition, and heating the nanotubes to 600 °C to burn off the polymer support completely. The technology for obtaining hybrid nanostructures from ceramic nanotubes and conducting polymers is drop-casting. AFM analysis emphasized a higher roughness, mainly in the case of PANI-EB, for both nanotube types, with a much larger grain size dimension of over 5 μm. The values of the parameter Rku were close or slightly above 3, indicating, in all cases, the formation of layers predominantly characterized by peaks and not by depressions, with a Gaussian distribution. An ink-jet printer was used to generate chemiresistors from ceramic nanotubes and PANI-EB structures, and the metallization was made with commercial copper ink for printed electronics. Calibration curves were experimentally generated for both sensing structures across a wider range of NH₃ concentrations in air, reaching up to 5 ppm. A 0.5 ppm detection limit was established. The curve for the ZnO:PANI-EB structure presented high linearity and lower resistance values. The sensor could be used in medical diagnosis for the analysis of breath ammonia and biomarkers for predicting CKD in stages higher than 1. The threshold value of 1 ppm represents a feasible value for the presented sensor, which can be defined as a simple, low-value and robust device for individual use, beneficial at the patient level. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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15 pages, 1471 KiB

Open AccessArticle

A Straightforward Electrochemical Approach for the Simultaneous Determination of Thymol and Carvacrol in Essential Oils

by Sabrina Antonella Maccio, Ruben Darío Alaniz, Gastón Darío Pierini, María Alicia Zon, Fernando Javier Arévalo, Héctor Fernández, Héctor Casimiro Goicoechea, Sebastian Noel Robledo and Mirta Raquel Alcaraz

Chemosensors 2024, 12(9), 197; https://doi.org/10.3390/chemosensors12090197 - 23 Sep 2024

Cited by 2 | Viewed by 1233

Abstract

A novel, simple, rapid, and non-expensive analytical method based on square wave voltammogram at Pt-microelectrode coupled with partial least square multivariate calibration was used for the simultaneous quantitation of thymol (THY) and carvacrol (CAR) in thyme and oregano essential oils. Results demonstrated that [...] Read more.

A novel, simple, rapid, and non-expensive analytical method based on square wave voltammogram at Pt-microelectrode coupled with partial least square multivariate calibration was used for the simultaneous quantitation of thymol (THY) and carvacrol (CAR) in thyme and oregano essential oils. Results demonstrated that the multivariate calibration method successfully exploited the first-order advantage, rendering highly satisfactory quantitative figures (average recoveries not statistically different than 100%). Moreover, the results agree well with those obtained from the official analytical method. Last, the method’s environmental sustainability was asserted using the AGREE metric, highlighting its eco-friendly nature. More importantly, the proposed analytical procedure does not require previous sample preparation or electrode surface modification. The results underscore the suitability of the method for determining THY and CAR in essential oils at low concentrations (LOD ~ 7.6 µM) with REP% below 5.6%, meeting the requirements of the green analytical chemistry. Full article

(This article belongs to the Special Issue Chemometrics for Analytical Chemistry: Second Edition)

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9 pages, 2559 KiB

Open AccessCommunication

Impact of Coffee Roasting and Grind Size on Acidity and Bitterness: Sensory Evaluation Using Electronic Tongue

by Masaaki Habara and Toshihide Horiguchi

Chemosensors 2024, 12(9), 196; https://doi.org/10.3390/chemosensors12090196 - 23 Sep 2024

Cited by 1 | Viewed by 2535

Abstract

Coffee flavor is profoundly influenced by numerous factors, including the origin’s terroir and variety, as well as post-harvest processing, drying, and sorting. Even specialty coffee beans, carefully selected for their high quality, can exhibit a wide range of flavor profiles depending on how [...] Read more.

Coffee flavor is profoundly influenced by numerous factors, including the origin’s terroir and variety, as well as post-harvest processing, drying, and sorting. Even specialty coffee beans, carefully selected for their high quality, can exhibit a wide range of flavor profiles depending on how they are roasted and ground. Traditionally, the coffee industry has used the Brewing Control Chart, which considers total dissolved solids (TDS) and extraction (E), to guide professionals toward achieving consistent flavors. However, this chart has limitations in representing the complex chemical composition and its influence on the sensory attributes of coffee. This study explores a more comprehensive approach to evaluating coffee quality by utilizing a taste sensing system (electronic tongue) to measure acidity and bitterness for full-immersion brewing. We investigate the impact of brew ratio and grind size on these taste attributes, while also considering the influence of roast level. Our findings demonstrate that finer grind sizes significantly affect TDS and E, while roast level and grind size significantly affect sensory attributes, as measured by the taste sensing system. This approach complements the traditional Brewing Control Chart by providing a more nuanced understanding of how roast level and grind size influence coffee flavor. Full article

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

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20 pages, 5259 KiB

Open AccessArticle

Voltammetric Sensor Based on Titania Nanoparticles Synthesized with Aloe vera Extract for the Quantification of Dithiophosphates in Industrial and Environmental Samples

by Javier E. Vilasó-Cadre, Alondra Ramírez-Rodríguez, Juan Hidalgo, Iván A. Reyes-Domínguez, Roel Cruz, Mizraim U. Flores, Israel Rodríguez-Torres, Roberto Briones-Gallardo, Luis Hidalgo and Juan Jesús Piña Leyte-Vidal

Chemosensors 2024, 12(9), 195; https://doi.org/10.3390/chemosensors12090195 - 22 Sep 2024

Cited by 1 | Viewed by 1732

Abstract

In this work, TiO₂ spherical nanoparticles with a mean diameter of 10.08 nm (SD = 4.54 nm) were synthesized using Aloe vera extract. Rutile, brookite, and anatase crystalline phases were identified. The surface morphology of a carbon paste electrode does not change [...] Read more.

In this work, TiO₂ spherical nanoparticles with a mean diameter of 10.08 nm (SD = 4.54 nm) were synthesized using Aloe vera extract. Rutile, brookite, and anatase crystalline phases were identified. The surface morphology of a carbon paste electrode does not change in the presence of nanoparticles; however, the surface chemical composition does. The voltammetric response to dicresyl dithiophosphate was higher when the electrode was modified with TiO₂ nanoparticles. After an electrochemical response study from pH 1.0 to 12.0, pH 7.0 was selected for the electroanalysis. The electroactive area of the modified sensor was 0.036 cm², while it was 0.026 cm² for the bare electrode. The oxidation process showed mixed adsorption-diffusion control. The charge transfer resistance of the modified sensor (530.1 Ω, SD = 4.08 Ω) was much lower than that of the bare electrode (4298 Ω, SD = 8.53 Ω). The linear quantitative range by square wave voltammetry was from 5 to 150 μmol/L, with a limit of detection of 1.89 μmol/L and a limit of quantification of 6.26 μmol/L under optimal pulse parameters of 50 Hz frequency, 1 mV step potential, and 25 mV pulse amplitude. The sensor response was repeatable and reproducible over 30 days. The results on real flotation and synthetically contaminated soil samples were statistically equivalent to those obtained by UV-vis spectrophotometry. A dithiocarbamate showed an interfering effect on the sensor response to dithiophosphate. Full article

(This article belongs to the Special Issue Advances in Electrochemical Sensing and Analysis)

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14 pages, 7204 KiB

Open AccessArticle

Optimization by Hydrogen Plasma Treatment of a-CH and Hydrogen/Nitrogen-Assisted a-CH Layers for SAW Sensors

by Veronica Satulu, Mihai Paunica, Simona Brajnicov, Sorin Vizireanu, Gheorghe Dinescu, Bogdana Mitu and Cristian Viespe

Chemosensors 2024, 12(9), 194; https://doi.org/10.3390/chemosensors12090194 - 20 Sep 2024

Viewed by 3571

Abstract

The high toxicity of hydrogen sulfide combined with poor sensitivity at room operating temperature urge for the development of new sensitive materials for sensors complying with this requirement, as well as a fast response and low cost. In this work, we have successfully [...] Read more.

The high toxicity of hydrogen sulfide combined with poor sensitivity at room operating temperature urge for the development of new sensitive materials for sensors complying with this requirement, as well as a fast response and low cost. In this work, we have successfully developed materials for surface acoustic wave (SAW) sensors sensitive to H₂S gas that provide a reversible response at room temperature. The sensitive materials were created by plasma-enhanced chemical vapor deposition of a-CH films using methane as a precursor with argon and argon admixed with hydrogen or nitrogen and applied on piezoelectric quartz substrates. Smooth films, with an AFM root mean square below 1.5 nm, were obtained in all cases, although slight topographical variations were noted, depending on the gas types. XPS detected varying degrees of oxidation, indicating that the assisting gases played a crucial role in introducing oxygen-containing functional groups, thus influencing the material’s surface chemistry and sensitivity response. A hydrogen plasma treatment was applied on the a-CH deposited sensors as a further sensor preparation step. The hydrogen plasma treatment resulted in significant modifications in the topographical features, including roughness increase and notable variations in the surface aspect ratios, as confirmed through AFM data analysis, which involved advanced pixel height analysis and line profile processing. X-ray photoelectron spectroscopy (XPS) studies indicated the formation of new functional groups, increased defect density, and a significant reduction in electron transitions following hydrogen plasma treatment. The sensors demonstrated a reversible response to H₂S gas within 8 to 20 ppm concentration ranges, effectively detecting these levels. The sensitivity of the sensors was significantly enhanced, up to 39% through hydrogen plasma treatment, reaching an improved overall performance in detecting low concentrations of H₂S down to 0.9 ppm. These findings highlight a-CH thin films as an excellent candidate for next-generation SAW sensors. The study also suggests the potential for experimenting with various assisting gases during plasma deposition and additional plasma treatments to push detection capabilities to below ppm levels. Full article

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

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10 pages, 1876 KiB

Open AccessArticle

Chemiluminescence Immunoassay for Sensitive Detection of C-reactive Protein Using Graphene Oxide–Gold Nanoparticle–Luminol Hybrids as Enhanced Luminogenic Molecules

by Kyung Mi Kim, Phuong Thy Nguyen, Jeemin Kim, Seung Hoo Song, Jin Woo Park and Moon Il Kim

Chemosensors 2024, 12(9), 193; https://doi.org/10.3390/chemosensors12090193 - 20 Sep 2024

Cited by 4 | Viewed by 1830

Abstract

This study presents the development of luminol and gold nanoparticle co-functionalized graphene oxide (GO-AuNPs-L) hybrids as enhanced luminogenic signaling molecules in the chemiluminescence immunoassay (CLIA) for detecting C-reactive protein (CRP), a key biomarker of inflammation and cardiovascular diseases. When compared to free luminol, [...] Read more.

This study presents the development of luminol and gold nanoparticle co-functionalized graphene oxide (GO-AuNPs-L) hybrids as enhanced luminogenic signaling molecules in the chemiluminescence immunoassay (CLIA) for detecting C-reactive protein (CRP), a key biomarker of inflammation and cardiovascular diseases. When compared to free luminol, the GO-AuNPs-L hybrids significantly increased and prolonged the CL signal based on their synergistic enhancement in electron transfer during CL production. Based on the performance, the hybrids were employed as signaling molecules in both well plate-based and lateral flow CLIA platforms, showing substantial improvements in signal intensity and sensitivity in CRP detection. These results highlight the potential of GO-AuNPs-L hybrids as versatile and highly sensitive luminogenic molecules for immunological CRP detection, offering promising applications in clinical laboratory settings as well as in point-of-care diagnostics. Full article

(This article belongs to the Special Issue Rapid Point-of-Care Testing Technology and Application)

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14 pages, 5503 KiB

Open AccessArticle

A Study Based on the First-Principle Study of the Adsorption and Sensing Properties of Mo-Doped WSe₂ for N₂O, CO₂, and CH₄

by Mingqi Dong, Yingyu Wu, Shiqi Zhou, Shuai Zhang, Junzhe Peng, Shuangshuang Tian and Benli Liu

Chemosensors 2024, 12(9), 192; https://doi.org/10.3390/chemosensors12090192 - 19 Sep 2024

Cited by 1 | Viewed by 1201

Abstract

As industry continues to develop rapidly, the greenhouse effect is becoming increasingly severe. CO₂, CH₄, and N₂O are the three primary greenhouse gases, making their effective monitoring a crucial step in reducing emissions. This paper investigates the [...] Read more.

As industry continues to develop rapidly, the greenhouse effect is becoming increasingly severe. CO₂, CH₄, and N₂O are the three primary greenhouse gases, making their effective monitoring a crucial step in reducing emissions. This paper investigates the gas sensing performance of Mo-doped WSe₂ for these three gases, through a theoretical study. First, using first-principles calculations, the doping behavior of Mo in WSe₂ is examined. Subsequently, the adsorption properties of Mo-WSe₂ for CO₂, CH₄, and N₂O are analyzed by calculating adsorption energy, charge transfer, the electron localization function (ELF), Hirshfeld partition (IGMH), and the density of states (DOSs), culminating in an analysis of its sensing properties. The results indicate that when Mo is positioned above the upper Se atom, the structure is most stable. Therefore, this position is selected as the optimal adsorption site for studying the adsorption of the three gases. The adsorption energies for CO₂, CH₄, and N₂O are 1.349 eV, −1.194 eV, and −0.528 eV, respectively, with corresponding charge transfers of 0.418, 0.450, and 0.115. In the N₂O and CO₂ adsorption systems, significant adsorption energy and charge transfer are observed, leading to relatively better adsorption compared to the CH₄ system. Additionally, considering the adsorption performance, Mo-WSe₂ demonstrates good sensor response and desorption times for N₂O and CO₂ at temperatures above 298 K. The findings of this research provide theoretical guidance for the application of Mo-WSe₂ as a gas sensing material for detecting greenhouse gases. Full article

(This article belongs to the Section Nanostructures for Chemical Sensing)

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14 pages, 4940 KiB

Open AccessArticle

Near-Infrared Multiwavelength Raman Anti-Stokes/Stokes Thermometry of Titanium Dioxide

by Veronica Zani, Roberto Pilot, Danilo Pedron and Raffaella Signorini

Chemosensors 2024, 12(9), 191; https://doi.org/10.3390/chemosensors12090191 - 17 Sep 2024

Viewed by 1405

Abstract

The use of multiple wavelengths to excite Titanium Dioxide Raman scattering in the near-infrared was investigated for optical nanothermometry. Indeed, Raman spectroscopy can be a very interesting technique for this purpose, as it offers non-disruptive contactless measurements with a high spatial resolution, down [...] Read more.

The use of multiple wavelengths to excite Titanium Dioxide Raman scattering in the near-infrared was investigated for optical nanothermometry. Indeed, Raman spectroscopy can be a very interesting technique for this purpose, as it offers non-disruptive contactless measurements with a high spatial resolution, down to a few µm. A method based on the ratio between the anti-Stokes and Stokes peaks of Anatase Titanium Dioxide was proposed and tested at three different wavelengths, 785, 800 and 980 nm, falling into the first biological transparency window (BTW-I). Using a temperature-controller stage, the temperature response of the sample was measured between 20 and 50 °C, allowing the thermal sensitivity for this range to be estimated. The use of sufficiently high laser power results in the generation of local heating. A proof of concept of the proposed thermometric method was performed by determining the extent of local heating induced by increasing laser power. By exciting with an 800 nm laser at low power intensities, a temperature equal to room temperature (RT) was found, while a maximum temperature increase of 15 °C was detected using the anti-Stokes/Stokes method. Full article

(This article belongs to the Special Issue Recent Advances in Optical Chemo- and Biosensors)

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11 pages, 1944 KiB

Open AccessArticle

O₂-Sensitive Inks for Measuring Total (Aerobic) Viable Count Using Micro-Respirometry

by Sean Cross, Dilidaer Yusufu, Christopher O’Rourke and Andrew Mills

Chemosensors 2024, 12(9), 190; https://doi.org/10.3390/chemosensors12090190 - 15 Sep 2024

Viewed by 1097

Abstract

The popular method of micro-respirometry (μR) for measuring total viable (aerobic) count (TVC) utilises luminescence-based O₂ sensors that are difficult to fabricate and therefore expensive. A simple method is described for making inexpensive, ink-based potential substitutes that utilise the same O₂ [...] Read more.

The popular method of micro-respirometry (μR) for measuring total viable (aerobic) count (TVC) utilises luminescence-based O₂ sensors that are difficult to fabricate and therefore expensive. A simple method is described for making inexpensive, ink-based potential substitutes that utilise the same O₂-sensitive dyes. The sensitivity of such inks is readily increased by using dyes with a long lifetime in the absence of O₂, τ_o, and/or an ink resin/polymer with a high O₂ permeability, P_m(O₂). Response modelling of the μR-based TVC system and subsequent testing using a range of O₂ sensors of different sensitivity show that there is little to be gained by making the O₂ sensor either very sensitive or insensitive, and that the best O₂ sensors are dyes such as Pt(II) tetraphenyltetrabenzoporphyrin (PtBP), with τ_o = ca. 40–50 μs. Further work shows that a simple-to-make PtBP ink can be used as a direct replacement for the expensive O₂ sensor used in commercial instruments for measuring TVC based on μR. In addition, the PtBP can be replaced by an even less expensive O₂-sensitive dye, Pt(II) meso-tetra(pentafluorophenyl)porphyrin (PtTFPP). The potential use of inexpensive O₂-sensitive inks as an alternative to any expensive commercial counterpart based on the same O₂-sensitive dye is discussed briefly. Full article

(This article belongs to the Special Issue Recent Advances in Optical Chemo- and Biosensors)

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20 pages, 3791 KiB

Open AccessReview

Research Progress of Taste Biosensors in Simulating Taste Transduction Mechanism

by Jingjing Liu, Jiale Kuang, Yan Zhang, Yizhou Chen, Shikun Liu, Yanfeng Li, Lixin Qiao, Zhenbo Wei, Shui Jiang and Jie Meng

Chemosensors 2024, 12(9), 189; https://doi.org/10.3390/chemosensors12090189 - 14 Sep 2024

Cited by 2 | Viewed by 2229

Abstract

The simulation of human sensory functions is a key trend in the field of sensor development. In taste sensing, taste biosensors emulate taste perception using biorecognition elements that participate in taste transduction, such as taste receptors, cells, tissues, etc. This approach obtains high [...] Read more.

The simulation of human sensory functions is a key trend in the field of sensor development. In taste sensing, taste biosensors emulate taste perception using biorecognition elements that participate in taste transduction, such as taste receptors, cells, tissues, etc. This approach obtains high selectivity and a wide detection range of human taste perception, making taste biosensors widely used in food analysis and taste perception studies. By combining biorecognition elements with suitable data processing and analysis techniques, the taste information generated during the process of taste transduction, obtained by the sensing elements of the sensor, can be accurately captured. In this paper, we explore current available solutions to stability and sensitivity, and other challenges in taste biosensors using taste receptors, cells, and tissues as sensing elements. We also outline the applied signal processing techniques based on the signal characteristics from different types of taste biosensors. Finally, it is proposed that the development of taste biosensing sensors will further promote the application of intelligent sensory evaluation and human perception analysis systems in food, medicine, and other fields. Full article

(This article belongs to the Special Issue Electrochemical Sensor Array for Food Detection and Human Perception)

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13 pages, 2594 KiB

Open AccessArticle

Evaluation of an Enzyme-Linked Magnetic Electrochemical Assay for Hepatitis a Virus Detection in Drinking and Vegetable Processing Water

by Cristine D’Agostino, Rocco Cancelliere, Antonio Ceccarelli, Danila Moscone, Loredana Cozzi, Giuseppina La Rosa, Elisabetta Suffredini and Laura Micheli

Chemosensors 2024, 12(9), 188; https://doi.org/10.3390/chemosensors12090188 - 14 Sep 2024

Cited by 1 | Viewed by 1753

Abstract

Globally, waterborne viral infections significantly threaten public health. While current European Union regulations stipulate that drinking water must be devoid of harmful pathogens, they do not specifically address the presence of enteric viruses in water used for irrigation or food production. Traditional virus [...] Read more.

Globally, waterborne viral infections significantly threaten public health. While current European Union regulations stipulate that drinking water must be devoid of harmful pathogens, they do not specifically address the presence of enteric viruses in water used for irrigation or food production. Traditional virus detection methods rely on molecular biology assays, requiring specialized personnel and laboratory facilities. Here, we describe an electrochemical sandwich enzyme-linked immunomagnetic assay (ELIME) for the detection of the hepatitis A virus (HAV) in water matrices. This method employed screen-printed electrodes as the sensing platform and utilized commercially available pre-activated magnetic beads to provide a robust foundation for the immunological reaction. The ELIME assay demonstrated exceptional analytical performance in only 185 min achieving a detection limit of 0.5 genomic copies per milliliter (g.c./mL) and exhibiting good reproducibility with a relative standard deviation (RSD) of 7% in HAV-spiked drinking and processing water samples. Compared with the real-time RT-qPCR method described in ISO 15216-1, the ELIME assay demonstrated higher sensitivity, although the overall linearity of the method was moderate. These analytical attributes highlight the potential of the ELIME assay as a rapid and viable alternative for HAV detection in water used for agriculture and food processing. Full article

(This article belongs to the Special Issue Electrochemical Sensors for Food Control, Environmental Analysis, and Diagnosis in Medicine)

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14 pages, 5745 KiB

Open AccessArticle

The Efficient and Sensitive Detection of Serum Dopamine Based on a MOF-199/Ag@Au Composite SERS Sensing Structure

by Yuyu Peng, Chunyan Wang, Gen Li, Jianguo Cui, Yina Jiang, Xiwang Li, Zhengjie Wang and Xiaofeng Zhou

Chemosensors 2024, 12(9), 187; https://doi.org/10.3390/chemosensors12090187 - 13 Sep 2024

Cited by 2 | Viewed by 1593

Abstract

In this study, a MOF-199/Ag@Au SERS sensing structure was successfully synthesized by combining metal–organic frameworks (MOFs) with surface-enhanced Raman scattering (SERS) technology for the efficient detection of dopamine (DA), a biomarker for neurological diseases, in serum. Using electrochemical methods, a copper-based MOF (MOF-199) [...] Read more.

In this study, a MOF-199/Ag@Au SERS sensing structure was successfully synthesized by combining metal–organic frameworks (MOFs) with surface-enhanced Raman scattering (SERS) technology for the efficient detection of dopamine (DA), a biomarker for neurological diseases, in serum. Using electrochemical methods, a copper-based MOF (MOF-199) was synthesized in situ on copper substrates and further deposited with silver nanoparticles (AgNPs). Subsequently, gold nanoshells were encapsulated around these silver cores by in situ chemical deposition. This preparation process is simple, controllable, and inexpensive. Furthermore, a novel Azo reaction-based DA SERS method was proposed to detect 1 pM DA, which represents an improvement in sensitivity by two orders of magnitude compared to previous unlabeled SERS detection methods and by four orders of magnitude compared to another SERS approach proposed in this work. There was an excellent linear relationship (R² = 0.976) between the SERS signal at 1140 cm⁻¹ and the DA concentration (0.001 M~1 pM). The results indicate that the MOF-199/Ag@Au sensor structure can successfully achieve both the qualitative and quantitative detection of DA in serum, thus providing a robust technical basis for the application of SERS technology in the field of clinical neurological disease screening. Full article

(This article belongs to the Special Issue Chemical and Biosensors Based on Metal-Organic Frames (MOFs))

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14 pages, 4077 KiB

Open AccessArticle

Sensitive Detection of Fungicide Folpet by Surface-Enhanced Raman Scattering: Experimental and Theoretical Approach

by Oumaima Douass, Bousselham Samoudi and Santiago Sanchez-Cortes

Chemosensors 2024, 12(9), 186; https://doi.org/10.3390/chemosensors12090186 - 12 Sep 2024

Viewed by 1151

Abstract

In this work, Surface-Enhanced Raman Spectroscopy (SERS) was employed as an effective detection technique for folpet, characterized by its notable specificity and sensitivity. The investigation involved the use of UV–Vis, Raman, and SERS spectroscopy of folpet at different concentrations for a comprehensive study [...] Read more.

In this work, Surface-Enhanced Raman Spectroscopy (SERS) was employed as an effective detection technique for folpet, characterized by its notable specificity and sensitivity. The investigation involved the use of UV–Vis, Raman, and SERS spectroscopy of folpet at different concentrations for a comprehensive study of plasmon-driven effects such as plasmon resonance, plasmon hybridization, and electric field enhancement resulting in the SERS’ intensification. Specifically, SERS detection of folpet solutions at concentrations below 100 µM is presented in detail by using Ag nanoparticles prepared with hydroxylamine reduction. The experimentation encompassed diverse conditions to optimize the detection process, with Raman spectra acquired for both folpet powder and aqueous solution of folpet at the natural pH. SERS analyses were conducted across a concentration range of 9.5 × 10⁻⁸ to 1.61 × 10⁻⁴ M, employing 532 nm excitation. The differences in the spectral profiles observed for folpet Raman powder and SERS are ascribed to N–S cleavage; these changes are attributed to plasmon catalysis induced by the used Ag nanoparticles. Transmission electron microscopy (TEM) was also important in the present analysis to better understand which mechanism of nanoparticles aggregation is more favorable for the SERS detection regarding the formation of hot spots in the suspension. Complementing the experimental data, the molecular structure and theoretical Raman spectra of the folpet molecule were calculated through density functional theory (DFT) methods. The outcomes of these calculations were crucial in the elucidation of folpet’s vibrational modes. The culmination of this research resulted in the successful detection of folpet, achieving a notable limit of detection at 4.78 × 10⁻⁸ M. This comprehensive approach amalgamates experimental and theoretical methodologies, offering significant insights into the detection capabilities and molecular characteristics of folpet via SERS analysis. Full article

(This article belongs to the Special Issue Raman and Surface-Enhanced Raman Scattering Techniques in Analytical and Biomedical Fields)

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26 pages, 6242 KiB

Open AccessArticle

Wireless Sensor Node for Chemical Agent Detection

by Zabdiel Brito-Brito, Jesús Salvador Velázquez-González, Fermín Mira, Antonio Román-Villarroel, Xavier Artiga, Satyendra Kumar Mishra, Francisco Vázquez-Gallego, Jung-Mu Kim, Eduardo Fontana, Marcos Tavares de Melo and Ignacio Llamas-Garro

Chemosensors 2024, 12(9), 185; https://doi.org/10.3390/chemosensors12090185 - 11 Sep 2024

Viewed by 1466

Abstract

In this manuscript, we present in detail the design and implementation of the hardware and software to produce a standalone wireless sensor node, called SensorQ system, for the detection of a toxic chemical agent. The proposed wireless sensor node prototype is composed of [...] Read more.

In this manuscript, we present in detail the design and implementation of the hardware and software to produce a standalone wireless sensor node, called SensorQ system, for the detection of a toxic chemical agent. The proposed wireless sensor node prototype is composed of a micro-controller unit (MCU), a radio frequency (RF) transceiver, a dual-band antenna, a rechargeable battery, a voltage regulator, and four integrated sensing devices, all of them integrated in a package with final dimensions and weight of 200 × 80 × 60 mm and 0.422 kg, respectively. The proposed SensorQ prototype operates using the Long-Range (LoRa) wireless communication protocol at 2.4 GHz, with a sensor head implemented on a hetero-core fiber optic structure supporting the surface plasmon resonance (SPR) phenomenon with a sensing section (L = 10 mm) coated with titanium/gold/titanium and a chemically sensitive material (zinc oxide) for the detection of Di-Methyl Methyl Phosphonate (DMMP) vapor in the air, a simulant of the toxic nerve agent Sarin. The transmitted spectra with respect to different concentrations of DMMP vapor in the air were recorded, and then the transmitted power for these concentrations was calculated at a wavelength of 750 nm. The experimental results indicate the feasibility of detecting DMMP vapor in air using the proposed optical sensor head, with DMMP concentrations in the air of 10, 150, and 150 ppm in this proof of concept. We expect that the sensor and wireless sensor node presented herein are promising candidates for integration into a wireless sensor network (WSN) for chemical warfare agent (CWA) detection and contaminated site monitoring without exposure of armed forces. Full article

(This article belongs to the Collection Recent Advances in Multifunctional Sensing Technology for Gas Analysis)

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14 pages, 9642 KiB

Open AccessArticle

Accurate Prediction of Tea Catechin Content with Near-Infrared Spectroscopy by Deep Learning Based on Channel and Spatial Attention Mechanisms

by Mingzan Zhang, Tuo Zhang, Yuan Wang, Xueyi Duan, Lulu Pu, Yuan Zhang, Qin Li and Yabing Liu

Chemosensors 2024, 12(9), 184; https://doi.org/10.3390/chemosensors12090184 - 11 Sep 2024

Cited by 1 | Viewed by 1521

Abstract

The assessment of catechin content stands as a pivotal determinant of tea quality. In tea production and quality grading, the development of accurate and non-destructive techniques for the accurate prediction of various catechin content is paramount. Near-infrared spectroscopy (NIRS) has emerged as a [...] Read more.

The assessment of catechin content stands as a pivotal determinant of tea quality. In tea production and quality grading, the development of accurate and non-destructive techniques for the accurate prediction of various catechin content is paramount. Near-infrared spectroscopy (NIRS) has emerged as a widely employed tool for analyzing the chemical composition of tea. Nevertheless, the spectral information obtained from NIRS faces challenges when discerning different types of catechins in black tea, owing to their similar physical and chemical properties. Moreover, the vast number of NIRS wavelengths exceeds the available tea samples, further complicating the accurate assessment of catechin content. This study introduces a novel deep learning approach that integrates specific wavelength selection and attention mechanisms to accurately predict the content of various catechins in black tea simultaneously. First, a wavelength selection algorithm is proposed based on feature interval combination sensitivity segmentation, which effectively extracts the NIRS feature information of tea. Subsequently, a one-dimensional convolutional neural network (CNN) incorporating channel and spatial–sequential attention mechanisms is devised to independently extract the key features from the selected wavelength variables. Finally, a multi-output predictor is employed to accurately predict the four main catechins in tea. The experimental results demonstrate the superiority of the proposed model over existing methods in terms of prediction accuracy and stability (R² = 0.92, RMSE = 0.018 for epicatechin; R² = 0.96, RMSE = 0.11 for epicatechin gallate; R² = 0.97, RMSE = 0.14 for epigallocatechin; R² = 0.97, RMSE = 0.32 for epigallocatechin gallate). This innovative deep learning approach amalgamates wavelength selection with attention mechanisms, provides a new perspective for the simultaneous assessment of the major components in tea, and contributes to the advancement of precision management in the tea industry’s production and grading processes. Full article

(This article belongs to the Special Issue Advanced Spectroscopy Technology for Chemical Qualitative and Quantitative Analysis)

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15 pages, 4617 KiB

Open AccessArticle

Voltammetric Investigation of Paracetamol Detection in Acidic Conditions by Using Cork-Modified Carbon Paste Electrodes

by Mayra K. S. Monteiro, Mayara M. S. Monteiro, João M. M. Henrique, Carlos A. Martínez-Huitle, Sergio Ferro and Elisama Vieira dos Santos

Chemosensors 2024, 12(9), 183; https://doi.org/10.3390/chemosensors12090183 - 10 Sep 2024

Cited by 3 | Viewed by 1493

Abstract

Developing new products that satisfy performance and durability expectations while also addressing environmental concerns is possible through the reuse of residues produced by industrial processes, aiming to fulfill the principles of circular economy. In this study, we improved the performance of a carbon [...] Read more.

Developing new products that satisfy performance and durability expectations while also addressing environmental concerns is possible through the reuse of residues produced by industrial processes, aiming to fulfill the principles of circular economy. In this study, we improved the performance of a carbon paste sensor by incorporating untreated (RC) and regranulated/thermally treated (RGC) cork, which are considered biomass residues from the cork industry. We explored the electroanalytical behavior of paracetamol in sulfuric acid solutions using cyclic voltammetry and differential pulse techniques. The cork-modified carbon paste sensors showed greater sensitivity towards paracetamol. Both modified sensors allowed for an excellent resolution in distinguishing the voltammetric responses of paracetamol in sulfuric acid, showing for both an increase in peak currents compared to the unmodified carbon paste electrode. The quantification of paracetamol without interference has proved to be a feasible operation for the RC- and RGC-modified carbon paste sensors; notably, the first showed the most favorable limits of detection (LD = 2.4112 µM) and quantification (LQ = 8.0373 µM) for paracetamol in the sulfuric acid solution, performing significantly better than the second (LD = 10.355 µM, and LQ = 34.518 µM). Finally, the practical utility of the proposed sensors was assessed by analyzing paracetamol in pharmaceutical samples, obtaining satisfactory results that were in line with those obtainable using high-performance liquid chromatography. Full article

(This article belongs to the Special Issue Carbon Nanomaterials and Related Materials for Sensing Applications, Volume II)

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12 pages, 8684 KiB

Open AccessCommunication

The Time Is Ripe: Olive Drupe Maturation Can Be Simply Evidenced by a Miniaturized, Portable and Easy-to-Use MicroNIR Green Sensor

by Giuseppina Gullifa, Chiara Albertini, Marialuisa Ruocco, Roberta Risoluti and Stefano Materazzi

Chemosensors 2024, 12(9), 182; https://doi.org/10.3390/chemosensors12090182 - 10 Sep 2024

Viewed by 1283

Abstract

The analytical study described in this work, based on NIR spectroscopy with a handheld device, allowed the development of a chemometric prediction model that has been validated for the objective evaluation of the ripening of olive drupes. The miniaturized, portable NIR spectrometer is [...] Read more.

The analytical study described in this work, based on NIR spectroscopy with a handheld device, allowed the development of a chemometric prediction model that has been validated for the objective evaluation of the ripening of olive drupes. The miniaturized, portable NIR spectrometer is proposed here as an easy-to-use sensor able to estimate the best harvesting time for ripening of olive drupes. The MicroNIR/chemometrics approach was developed for on-site identification of olive drupe ripening directly on plants, avoiding collection and successive laboratory analysis steps. A supporting parallel characterization by chromatographic techniques validated the spectroscopic prediction. The novelty of this approach consists in the possibility of investigating the olive drupe maturation point by collecting spectra in the near-infrared region and processing them using a chemometric model. The fast and accurate device allows one to easily follow the spectrum profile changes of olive drupes during ripening, thus preserving the fruits from being harvested too early or too late. The results of this study demonstrate the possibility of using the MicroNIR/chemometrics approach to determine the optimal ripening time of olives regardless of the plant variety, age and cultivation location. The results consequently demonstrated that the MicroNIR/chemometrics approach can be proposed as a new method to perform on-site evaluation of ripening by a single-click device. It can be conveniently used by any operator, who does not necessarily have to be expert but must simply be trained to use spectroscopy and a prediction model. Full article

(This article belongs to the Special Issue Recent Advances in Optical Chemo- and Biosensors)

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13 pages, 8362 KiB

Open AccessArticle

Low-Drift NO₂ Sensor Based on Polyaniline/Black Phosphorus Composites at Room Temperature

by Bolun Tang, Yunbo Shi, Jijiang Liu, Canda Zheng, Kuo Zhao, Jianhua Zhang and Qiaohua Feng

Chemosensors 2024, 12(9), 181; https://doi.org/10.3390/chemosensors12090181 - 5 Sep 2024

Cited by 2 | Viewed by 1252

Abstract

In this paper, a room-temperature NO₂ sensor based on a polyaniline (PANI)/black phosphorus (BP) composite material was proposed to solve the power consumption problem of traditional metal-oxide sensors operating at high temperatures. PANI was synthesized by chemical oxidative polymerization, whereas BP was [...] Read more.

In this paper, a room-temperature NO₂ sensor based on a polyaniline (PANI)/black phosphorus (BP) composite material was proposed to solve the power consumption problem of traditional metal-oxide sensors operating at high temperatures. PANI was synthesized by chemical oxidative polymerization, whereas BP was synthesized by low-pressure mineralization. The PANI/BP composite materials were prepared via ultrasonic exfoliation and mixing. Various characterization techniques, including scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), confirmed the successful preparation of the PANI/BP composites and their excellent structural properties. The sensor demonstrated outstanding gas sensitivity in the NO₂ concentration range of 2–60 ppm. In particular, the sensor showed a response exceeding 2200% at 60 ppm NO₂ concentration when using a 1:1 mass ratio of PANI to BP in the composite material. Full article

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

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15 pages, 4910 KiB

Open AccessArticle

Point-of-Care Testing Kit for the Detection of Hexavalent Chromium by Carbohydrazide-Derived Graphitic Carbon Nitride

by Muniyandi Maruthupandi and Nae Yoon Lee

Chemosensors 2024, 12(9), 180; https://doi.org/10.3390/chemosensors12090180 - 5 Sep 2024

Cited by 2 | Viewed by 1842

Abstract

Hexavalent chromium (Cr(VI)) ions are among the most common hazardous metals that pose a serious risk to human health, causing human carcinogenesis and chronic kidney damage. In this study, a point-of-care testing (POCT) kit is proposed for Cr(VI) ions detection at room temperature. [...] Read more.

Hexavalent chromium (Cr(VI)) ions are among the most common hazardous metals that pose a serious risk to human health, causing human carcinogenesis and chronic kidney damage. In this study, a point-of-care testing (POCT) kit is proposed for Cr(VI) ions detection at room temperature. The kit contains a hydrophobic parafilm, a nylon membrane to resist outflow, and a hydrophilic Whatman filter paper suitable for coating the fluorescent graphitic carbon nitride sheet (g-C₃N₄). Crystalline, nano-porous, blue-emitting g-C₃N₄ was produced by pyrolysis utilizing carbohydrazide. The electrostatic interactions between the g-C₃N₄ and Cr(VI) ions inhibit the fluorescence behavior. The POCT kit can be used for on-site Cr(VI) ion detection dependent upon the blue emission value. The detection limit was attained at 4.64 nM of Cr(VI) ions. This analytical methodology was utilized on real samples from tap, pond, river, and industrial wastewater. This POCT kit can be a useful alternative for on-site detection of Cr(VI) ions. Full article

(This article belongs to the Special Issue Rapid Point-of-Care Testing Technology and Application)

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13 pages, 2553 KiB

Open AccessArticle

Carbon-Based FET-Type Gas Sensor for the Detection of ppb-Level Benzene at Room Temperature

by Risheng Cao, Zhengyu Lu, Jinyong Hu and Yong Zhang

Chemosensors 2024, 12(9), 179; https://doi.org/10.3390/chemosensors12090179 - 4 Sep 2024

Cited by 2 | Viewed by 1618

Abstract

Benzene, as a typical toxic gas and carcinogen, is an important detection object in the field of environmental monitoring. However, it remains challenging for the conventional resistance-type gas sensor to effectively detect low-concentration (ppb-level) benzene gas molecules, owing to their insufficient reaction activation [...] Read more.

Benzene, as a typical toxic gas and carcinogen, is an important detection object in the field of environmental monitoring. However, it remains challenging for the conventional resistance-type gas sensor to effectively detect low-concentration (ppb-level) benzene gas molecules, owing to their insufficient reaction activation energy, especially when operating at room temperature. Herein, a field-effect transistor (FET)-type gas sensor using carbon nanotubes as a channel material is proposed for the efficient detection of trace benzene, where carbon nanotubes (CNTs) with high semiconductor purity act as the main channel material, and ZnO/WS₂ nanocomposites serve as the gate sensitive material. On the basis of the remarkable amplification effect in CNTs-based FET, the proposed gas sensor manifests desirable sensitive ability with the detection limit as low as 500 ppb for benzene even working at room temperature, and the sensor also exhibits fast response speed (90 s), high consistency with a response deviation of less than 5%, and long-term stability of up to 30 days. Furthermore, utilizing Tenax TA as the screening unit, the as-proposed gas sensor can achieve the feasible selective detection of benzene. These experimental results demonstrate that the strategy proposed here can provide significant guidance for the development of high-performance gas sensors to detect trace benzene gas at room temperature. Full article

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

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14 pages, 3199 KiB

Open AccessArticle

Gas Sensing with Nanoporous In₂O₃ under Cyclic Optical Activation: Machine Learning-Aided Classification of H₂ and H₂O

by Dominik Baier, Alexander Krüger, Thorsten Wagner, Michael Tiemann and Christian Weinberger

Chemosensors 2024, 12(9), 178; https://doi.org/10.3390/chemosensors12090178 - 3 Sep 2024

Viewed by 1378

Abstract

Clean hydrogen is a key aspect of carbon neutrality, necessitating robust methods for monitoring hydrogen concentration in critical infrastructures like pipelines or power plants. While semiconducting metal oxides such as In₂O₃ can monitor gas concentrations down to the ppm range, [...] Read more.

Clean hydrogen is a key aspect of carbon neutrality, necessitating robust methods for monitoring hydrogen concentration in critical infrastructures like pipelines or power plants. While semiconducting metal oxides such as In₂O₃ can monitor gas concentrations down to the ppm range, they often exhibit cross-sensitivity to other gases like H₂O. In this study, we investigated whether cyclic optical illumination of a gas-sensitive In₂O₃ layer creates identifiable changes in a gas sensor’s electronic resistance that can be linked to H₂ and H₂O concentrations via machine learning. We exposed nanostructured In₂O₃ with a large surface area of 95 m² g⁻¹ to H₂ concentrations (0–800 ppm) and relative humidity (0–70%) under cyclic activation utilizing blue light. The sensors were tested for 20 classes of gas combinations. A support vector machine achieved classification rates up to 92.0%, with reliable reproducibility (88.2 ± 2.7%) across five individual sensors using 10-fold cross-validation. Our findings suggest that cyclic optical activation can be used as a tool to classify H₂ and H₂O concentrations. Full article

(This article belongs to the Collection Recent Advances in Multifunctional Sensing Technology for Gas Analysis)

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18 pages, 1911 KiB

Open AccessArticle

An Optimization of the Extraction of Phenolic Compounds from Grape Marc: A Comparison between Conventional and Ultrasound-Assisted Methods

by Ziyao Liu, Hanjing Wu, Brendan Holland, Colin J. Barrow and Hafiz A. R. Suleria

Chemosensors 2024, 12(9), 177; https://doi.org/10.3390/chemosensors12090177 - 2 Sep 2024

Cited by 6 | Viewed by 3125

Abstract

The green extraction of total phenolic compounds, flavonoids, anthocyanins, and tannins from grape marc was optimized using response surface methodology. The extracts were characterized and analyzed using LC-ESI-QTOF-MS/MS, and free radical scavenging capacity was evaluated. An efficient green extraction method is crucial for [...] Read more.

The green extraction of total phenolic compounds, flavonoids, anthocyanins, and tannins from grape marc was optimized using response surface methodology. The extracts were characterized and analyzed using LC-ESI-QTOF-MS/MS, and free radical scavenging capacity was evaluated. An efficient green extraction method is crucial for improving the recovery rates of these high-value phytochemicals and for sustainably reusing wine by-products. Our study optimized parameters for both conventional and ultrasound-assisted extraction methods, including solution pH, extraction temperature, liquid-to-solvent ratio, and ultrasonic amplitude. The optimized conditions for conventional extraction were identified as 60% ethanol with a pH of 2, a solvent-to-solid ratio of 50:1, extraction time of 16 h at a temperature of 49.2 °C. For ultrasound-assisted extraction, the optimized conditions were determined as 60% ethanol with a pH of 2, a solvent-to-solid ratio of 50:1, and an amplitude of 100% for 5.05 min at a temperature of 60 °C. We also demonstrated that lowering the temperature to 49.5 °C improves the energy efficiency of the extraction process with a minor reduction in recovery rates. Considering all factors, ultrasound-assisted extraction is more suitable for efficiently recovering bioactive compounds from grape marc. Full article

(This article belongs to the Special Issue Green Analytical Chemistry: Current Trends and Future Developments)

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14 pages, 3965 KiB

Open AccessArticle

A Novel Colorimetric Biosensor for the Detection of Catalase-Positive Staphylococcus aureus Based on an Onion-like Carbon Nanozyme

by Yining Fan, Guanyue Gao and Jinfang Zhi

Chemosensors 2024, 12(9), 176; https://doi.org/10.3390/chemosensors12090176 - 2 Sep 2024

Cited by 1 | Viewed by 1497

Abstract

Staphylococcus aureus is one of the leading causes of skin and soft tissue infections, and it is even life-threatening if it enters the bloodstream, lung or heart. In the present work, we proposed a novel colorimetric biosensor for the detection of S. aureus [...] Read more.

Staphylococcus aureus is one of the leading causes of skin and soft tissue infections, and it is even life-threatening if it enters the bloodstream, lung or heart. In the present work, we proposed a novel colorimetric biosensor for the detection of S. aureus through hydrogen peroxide consumption. An onion-like carbon nanozyme with high peroxidase-like activity was prepared, which competed with the endogenous catalase of S. aureus in consuming hydrogen peroxide. This reaction was further characterized by the colorimetric reaction of 3,3′,5,5′-tetramethylbenzidine. The results showed that our approach allowed for the simple and rapid determination of S. aureus, with a linear range of 2 × 10⁴ to 2 × 10⁷ CFU/mL. Moreover, our method displayed good selectivity, with Bacillus subtilis and Escherichia coli showing negligible responses at the concentration of 2 × 10⁵ CFU/mL. The application of the as-prepared biosensor to analyze S. aureus in real water samples yielded recovery rates ranging from 95% to 112%, with relative standard deviations less than 7%. The method demonstrated good accuracy and specificity, which offers a novel approach for the simple and selective detection of S. aureus. Full article

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

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15 pages, 2780 KiB

Open AccessArticle

Enhanced Sensitivity and Homogeneity of SERS Signals on Plasmonic Substrate When Coupled to Paper Spray Ionization–Mass Spectrometry

by Adewale A. Adehinmoye, Ebenezer H. Bondzie, Jeremy D. Driskell, Christopher C. Mulligan and Jun-Hyun Kim

Chemosensors 2024, 12(9), 175; https://doi.org/10.3390/chemosensors12090175 - 2 Sep 2024

Cited by 1 | Viewed by 1769

Abstract

This work reports on the development of an analyte sampling strategy on a plasmonic substrate to amplify the detection capability of a dual analytical system, paper spray ionization–mass spectrometry (PSI-MS) and surface-enhanced Raman spectroscopy (SERS). While simply applying only an analyte solution to [...] Read more.

This work reports on the development of an analyte sampling strategy on a plasmonic substrate to amplify the detection capability of a dual analytical system, paper spray ionization–mass spectrometry (PSI-MS) and surface-enhanced Raman spectroscopy (SERS). While simply applying only an analyte solution to the plasmonic paper results in a limited degree of SERS enhancement, the introduction of plasmonic gold nanoparticles (AuNPs) greatly improves the SERS signals without sacrificing PSI-MS sensitivity. It is initially revealed that the concentration of AuNPs and the type of analytes highly influence the SERS signals and their variations due to the “coffee ring effect” flow mechanism induced during sampling and the degree of the interfacial interactions (e.g., van der Waals, electrostatic, covalent) between the plasmonic substrate and analyte. Subsequent PSI treatment at high voltage conditions further impacts the overall SERS responses, where the signal sensitivity and homogeneity significantly increase throughout the entire substrate, suggesting the ready migration of adsorbed analytes regardless of their interfacial attractive forces. The PSI-induced notable SERS enhancements are presumably associated with creating unique conditions for local aggregation of the AuNPs to induce effective plasmonic couplings and hot spots (i.e., electromagnetic effect) and for repositioning analytes in close proximity to a plasmonic surface to increase polarizability (i.e., chemical effect). The optimized sampling and PSI conditions are also applicable to multi-analyte analysis by SERS and MS, with greatly enhanced detection capability and signal uniformity. Full article

(This article belongs to the Special Issue Raman and Surface-Enhanced Raman Scattering Techniques in Analytical and Biomedical Fields)

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14 pages, 2785 KiB

Open AccessArticle

Machine Learning-Assisted 3D Flexible Organic Transistor for High-Accuracy Metabolites Analysis and Other Clinical Applications

by Caizhi Liao, Huaxing Wu and Luigi G. Occhipinti

Chemosensors 2024, 12(9), 174; https://doi.org/10.3390/chemosensors12090174 - 1 Sep 2024

Cited by 1 | Viewed by 1781

Abstract

The integration of advanced diagnostic technologies in healthcare is crucial for enhancing the accuracy and efficiency of disease detection and management. This paper presents an innovative approach combining machine learning-assisted 3D flexible fiber-based organic transistor (FOT) sensors for high-accuracy metabolite analysis and potential [...] Read more.

The integration of advanced diagnostic technologies in healthcare is crucial for enhancing the accuracy and efficiency of disease detection and management. This paper presents an innovative approach combining machine learning-assisted 3D flexible fiber-based organic transistor (FOT) sensors for high-accuracy metabolite analysis and potential diagnostic applications. Machine learning algorithms further enhance the analytical capabilities of FOT sensors by effectively processing complex data, identifying patterns, and predicting diagnostic outcomes with 100% high accuracy. We explore the fabrication and operational mechanisms of these transistors, the role of machine learning in metabolite analysis, and their potential clinical applications by analyzing practical human blood samples for hypernatremia syndrome. This synergy not only improves diagnostic precision but also holds potential for the development of personalized diagnostics, tailoring treatments for individual metabolic profiles. Full article

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

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12 pages, 4934 KiB

Open AccessArticle

Resolution of Glycerol, Ethanol and Methanol Employing a Voltammetric Electronic Tongue

by João Pedro Jenson de Oliveira, Marta Bonet-San-Emeterio, Acelino Cardoso de Sá, Xavier Cetó, Leonardo Lataro Paim and Manel del Valle

Chemosensors 2024, 12(9), 173; https://doi.org/10.3390/chemosensors12090173 - 1 Sep 2024

Viewed by 1619

Abstract

This paper reports the use of nanoparticles (NPs)-modified voltammetric sensors for the rapid determination of glycerol in the presence of ethanol and methanol, which are used in the transesterification reaction of biodiesel production. Two different modified electrodes have been prepared to form the [...] Read more.

This paper reports the use of nanoparticles (NPs)-modified voltammetric sensors for the rapid determination of glycerol in the presence of ethanol and methanol, which are used in the transesterification reaction of biodiesel production. Two different modified electrodes have been prepared to form the electronic tongue (ET): copper hexacyanoferrate NPs obtained by chemical synthesis and mixed into graphite/epoxy (GEC) electrode, and nickel hydroxide NPs electrodeposited in reduced graphene oxide onto a GEC electrode. The response characteristics of these electrodes were first evaluated by building the respective calibration against glycerol, ethanol, and methanol. The electrodes demonstrated good stability during their analytical characterization, while principal component analysis confirmed the differentiated response against the different alcohols. Finally, the quantification of mixtures of these substances was achieved by a genetic algorithm-artificial neural networks (GA-ANNs) model, showing satisfactory agreement between expected and obtained values. Full article

(This article belongs to the Special Issue An Exciting Journey of Chemical Sensors and Biosensors: A Theme Issue in Honor of Professor Ingemar Lundström)

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21 pages, 4181 KiB

Open AccessArticle

Detection of Harmful H₂S Concentration Range, Health Classification, and Lifespan Prediction of CH₄ Sensor Arrays in Marine Environments

by Kai Zhang, Yongwei Zhang, Jian Wu, Tao Wang, Wenkai Jiang, Min Zeng and Zhi Yang

Chemosensors 2024, 12(9), 172; https://doi.org/10.3390/chemosensors12090172 - 29 Aug 2024

Viewed by 1424

Abstract

Underwater methane (CH₄) detection technology is of great significance to the leakage monitoring and location of marine natural gas transportation pipelines, the exploration of submarine hydrothermal activity, and the monitoring of submarine volcanic activity. In order to improve the safety of [...] Read more.

Underwater methane (CH₄) detection technology is of great significance to the leakage monitoring and location of marine natural gas transportation pipelines, the exploration of submarine hydrothermal activity, and the monitoring of submarine volcanic activity. In order to improve the safety of underwater CH₄ detection mission, it is necessary to study the effect of hydrogen sulfide (H₂S) in leaking CH₄ gas on sensor performance and harmful influence, so as to evaluate the health status and life prediction of underwater CH₄ sensor arrays. In the process of detecting CH₄, the accuracy decreases when H₂S is found in the ocean water. In this study, we proposed an explainable sorted-sparse (ESS) transformer model for concentration interval detection under industrial conditions. The time complexity was decreased to O (n log_n) using an explainable sorted-sparse block. Additionally, we proposed the Ocean X generative pre-trained transformer (GPT) model to achieve the online monitoring of the health of the sensors. The ESS transformer model was embedded in the Ocean X GPT model. When the program satisfied the special instructions, it would jump between models, and the online-monitoring question-answering session would be completed. The accuracy of the online monitoring of system health is equal to that of the ESS transformer model. This Ocean-X-generated model can provide a lot of expert information about sensor array failures and electronic noses by text and speech alone. This model had an accuracy of 0.99, which was superior to related models, including transformer encoder (0.98) and convolutional neural networks (CNN) + support vector machine (SVM) (0.97). The Ocean X GPT model for offline question-and-answer tasks had a high mean accuracy (0.99), which was superior to the related models, including long short-term memory–auto encoder (LSTM–AE) (0.96) and GPT decoder (0.98). Full article

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

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16 pages, 6134 KiB

Open AccessArticle

Fiber Optic-Based Portable Sensor for Rapid Evaluation and In Situ Real-Time Sensing of Scale Formation in Geothermal Water

by Takuma Matsuura, Takuya Okazaki, Kazuto Sazawa, Ai Hosoki, Akira Ueda and Hideki Kuramitz

Chemosensors 2024, 12(9), 171; https://doi.org/10.3390/chemosensors12090171 - 25 Aug 2024

Cited by 2 | Viewed by 1549

Abstract

The formation of scale in hot springs and geothermal brines can be detected quickly and easily using optical fiber-based scale sensors. This paper describes the development of a portable sensor for the in situ detection of scale in geothermal water. This sensor was [...] Read more.

The formation of scale in hot springs and geothermal brines can be detected quickly and easily using optical fiber-based scale sensors. This paper describes the development of a portable sensor for the in situ detection of scale in geothermal water. This sensor was used to detect the formation of calcium carbonate and silica scale and to assess the effectiveness of their inhibitors. The performance of the sensor was evaluated using calcium carbonate scale. In laboratory experiments using both the newly developed sensor and a conventional nonportable sensor, the strength of the transmitted signal was found to decrease significantly as the amount of scale increased. It was considered that this sensor can accurately evaluate only scale formation without being affected by turbidity. The scale that was deposited on each material (optical fiber core, glass plate, polyvinyl chloride (PVC), and SUS304) was observed using a shape analysis laser microscope. Based on these observations, we concluded that this sensor could be used to predict the amount of scale deposited in real time. In situ evaluation of the sensor was conducted at a blowout carbonated hot spring on Rishiri Island, which is located off the coast of Hokkaido, Japan. The results obtained from experiments using hot spring water showed a similar sensor response within a comparable time range as those obtained from the laboratory experiments. The results of this study thus demonstrate that this novel portable scale sensor is suitable for use in geothermal power plants and investigating effectiveness of inhibiters under different conditions. Full article

(This article belongs to the Section Optical Chemical Sensors)

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9 pages, 2754 KiB

Open AccessCommunication

Circular Dichroism Reflectance Anisotropy of Chiral Atomically Thin Films

by Ilaria Tomei, Filippo Pierucci, Beatrice Bonanni, Anna Sgarlata, Massimo Fanfoni, Seong-Jun Yang, Cheol-Joo Kim and Claudio Goletti

Chemosensors 2024, 12(9), 170; https://doi.org/10.3390/chemosensors12090170 - 24 Aug 2024

Viewed by 1403

Abstract

Recently, a technical modification of a Reflectance Anisotropy Spectroscopy (RAS) spectrometer has been proposed to investigate the circular dichroism (CD) of samples instead of the normally studied linear dichroism. CD-RAS measures the anisotropy of the optical properties of a sample under right-handed and [...] Read more.

Recently, a technical modification of a Reflectance Anisotropy Spectroscopy (RAS) spectrometer has been proposed to investigate the circular dichroism (CD) of samples instead of the normally studied linear dichroism. CD-RAS measures the anisotropy of the optical properties of a sample under right-handed and left-handed circularly polarized light. Here, we present the application of CD-RAS to measure the circular dichroism of a twisted bilayer of graphene, purposely prepared as a possible substrate for the adsorption of thin molecular layers, in air, in liquid or in a vacuum. This result demonstrates the performance of the apparatus and shows interesting perspectives for the investigation of chiral organic assemblies deposited in solid film. Full article

(This article belongs to the Special Issue An Exciting Journey of Chemical Sensors and Biosensors: A Theme Issue in Honor of Professor Ingemar Lundström)

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