Chemosensors

14 pages, 1793 KiB

Open AccessArticle

Thiosemicarbazone- and Thiourea-Functionalized Calix[4]arenes in cone and 1,3-alternate Conformations: Receptors for the Recognition of Ions

by Andrés Ochoa, Belén Hernández-Arancibia, José Herrera-Muñoz, Horacio Gómez-Machuca and Claudio Saitz

Chemosensors 2025, 13(2), 48; https://doi.org/10.3390/chemosensors13020048 (registering DOI) - 3 Feb 2025

Abstract

In this research we have synthesized and evaluated five calix[4]arene-based receptors functionalized with thiosemicarbazone or thiourea groups, incorporating pyridinyl naphthalene or triazolopyridine chromophores in 1,3-alternate, pinched cone and cone conformations. The ion recognition capabilities of these receptors were investigated using UV-visible [...] Read more.

In this research we have synthesized and evaluated five calix[4]arene-based receptors functionalized with thiosemicarbazone or thiourea groups, incorporating pyridinyl naphthalene or triazolopyridine chromophores in 1,3-alternate, pinched cone and cone conformations. The ion recognition capabilities of these receptors were investigated using UV-visible and fluorescence spectroscopy. Receptor (I), which adopts a pinched cone conformation with thiosemicarbazone groups, demonstrated bifunctional sensing abilities by detecting both cations and anions. Receptors (II) and (III) showed remarkable selectivity and sensitivity for Cu²⁺ ions. Receptors (IV) and (V), in cone and 1,3-alternate conformations, respectively, where functionalized with a triazolo[1,5-a]pyridine fluorophore and exhibited highly sensitive ON-OFF fluorescence sensing for Co²⁺, Cu²⁺ and Ni²⁺ ions, with significant fluorescence quenching upon binding and a low detection limit of 2.94 µg/L for the Co²⁺ ion in receptor (IV). Ion receptor (I) demonstrates a strong performance in broad-spectrum ion detection, whereas the structural conformations of receptors (IV) and (V) play a pivotal role in their remarkable selectivity and sensitivity for specific transition metals in fluorescence-based sensing. Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensors: Current Status and Future Development)

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16 pages, 6076 KiB

Open AccessArticle

Facile Synthesis of Palladium Nanorods: Self-Assembly into Thin 2D Layers for SERS Sensing

by Mohammad Navvabpour, Safi Jradi, Pierre-Michel Adam and Suzanna Akil

Chemosensors 2025, 13(2), 47; https://doi.org/10.3390/chemosensors13020047 (registering DOI) - 3 Feb 2025

Abstract

This study presents a simple, high-throughput synthesis approach for fabricating palladium (Pd) nanomaterials with anisotropic shapes, specifically Pd nanorods, via a self-assembly process. This method avoids the use of reducing agents, surface functionalization, and stabilizing agents. Palladium–poly(methyl methacrylate) (Pd-PMMA) nanocomposites were successfully synthesized [...] Read more.

This study presents a simple, high-throughput synthesis approach for fabricating palladium (Pd) nanomaterials with anisotropic shapes, specifically Pd nanorods, via a self-assembly process. This method avoids the use of reducing agents, surface functionalization, and stabilizing agents. Palladium–poly(methyl methacrylate) (Pd-PMMA) nanocomposites were successfully synthesized using a vapor-induced phase separation (VIPS) method. The formation of Pd nanorods was controlled by tuning key parameters, such as the Pd precursor concentration, choice of solvents, and spin coating speed. Notably, the resulting nanorods exhibited high reproducibility and ultrasensitivity as a surface-enhanced Raman scattering (SERS) platform, achieving an enhancement factor of approximately 1.8 × 10⁵, despite the relatively weak plasmonic properties of Pd. This work represents a novel, facile strategy for Pd nanorod synthesis, offering new potential for the design of Pd-based nanosensors for chemical sensing applications. Full article

(This article belongs to the Special Issue Advanced Surface Plasmon Resonance Sensors)

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13 pages, 1533 KiB

Open AccessArticle

Protocol for the Determination of Total Iodine in Iodized Table Salts Using Ultra-High-Performance Liquid Chromatography

by Mohd Azerulazree Jamilan, Aswir Abd Rashed and Mohd Fairulnizal Md Noh

Chemosensors 2025, 13(2), 46; https://doi.org/10.3390/chemosensors13020046 (registering DOI) - 3 Feb 2025

Abstract

Potassium iodate and potassium iodide are commonly fortified in iodized table salt, which must be continuously monitored to maintain quality. Our study reported an optimized detection method for total iodine in iodized table salt using 0.5 M sodium bisulfite as the reducing agent. [...] Read more.

Potassium iodate and potassium iodide are commonly fortified in iodized table salt, which must be continuously monitored to maintain quality. Our study reported an optimized detection method for total iodine in iodized table salt using 0.5 M sodium bisulfite as the reducing agent. The iodized table salt (0.5 g) was dissolved in 0.5 M sodium bisulfite solution prior to injection in ultra-high-performance liquid chromatography (UHPLC) coupled with a diode array detector using a weak anion-exchange column (2.1 mm × 150 mm, 5 μm). Iodide was eluted at 9.92 ± 0.06 min (λ = 223 nm) when an isocratic mobile phase of 1:1 (v/v) methanol/120 mM phosphate buffer mixed with tetrasodium pyrophosphate (pH 3.0) was running at 0.20 mL/min (15 min). Iodide was detected as total iodine from 10.0 to 50.0 mg/kg with a limit of detection (LOD) of 1.2 mg/kg and a limit of quantification (LOQ) of 3.7 mg/kg. The method was validated with relative standard deviations (RSDs) of 4.2%, 0.4%, 1.6%, and 0.8% for accuracy, repeatability, intermediate precision, and robustness, respectively. The determination of total iodine was successful on six (6) samples (n = 3), which recovered 87.2–106.9% of iodate and iodide spike. Thus, this study provides a validated protocol for the determination of total iodine in iodized table salt using 0.5 M sodium bisulfite. Full article

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

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21 pages, 5047 KiB

Open AccessArticle

Electrospun WO₃/TiO₂ Core–Shell Nanowires for Triethylamine Gas Sensing

by Wenhao Li, Bo Zhang, Xiangrui Dong, Qi Lu, Hao Shen, Yi Ni, Yuechen Liu and Haitao Song

Chemosensors 2025, 13(2), 45; https://doi.org/10.3390/chemosensors13020045 (registering DOI) - 2 Feb 2025

Abstract

In this work, WO₃/TiO₂ core–shell (C-S) nanowires (NWs) were successfully synthesized by the coaxial electrospinning method and subsequent high-temperature calcination treatment. After some microscopic structural characterizations, although the prepared WO₃–TiO₂ and TiO₂–WO₃ C-S NWs [...] Read more.

In this work, WO₃/TiO₂ core–shell (C-S) nanowires (NWs) were successfully synthesized by the coaxial electrospinning method and subsequent high-temperature calcination treatment. After some microscopic structural characterizations, although the prepared WO₃–TiO₂ and TiO₂–WO₃ C-S NWs displayed quite different surface morphologies, both of the shell coatings were uniform and their typical shell thicknesses were extremely close, with mean values of 22 and 20 nm, respectively. In gas sensing tests, WO₃/TiO₂ C-S NWs exhibited good selectivity towards triethylamine (TEA) without significant interfering gases. Compared with bare WO₃ and TiO₂ NWs, WO₃/TiO₂ C-S NWs showed better gas sensing performance. Specifically, the optimal operating temperature and response of TiO₂–WO₃ C-S NWs to 100 ppm TEA were 130 °C and 106, which were reduced by 70 °C and increased by 5.73 times compared to bare WO₃, respectively. Obviously, the C-S nanostructures contributed to improving the gas sensing performance of materials towards TEA. Finally, some hypothetical sensing mechanisms were proposed, which were expected to have important reference significance for the design of target products applied to TEA sensing. Full article

(This article belongs to the Special Issue Recent Progress in Nano Material-Based Gas Sensors)

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15 pages, 1611 KiB

Open AccessArticle

Towards the Measurement of Acute-Phase Proteins in Saliva in Farm Conditions: Development and Validation of a Lateral Flow Assay for the Measurement of C-Reactive Protein in Pigs

by Fernando Tecles, Asta Tvarijonaviciute, Simone Cavalera, Fabio Di Nardo, Claudio Baggiani, José Joaquín Cerón, Antonio González-Bulnes, María Elena Goyena, Silvia Martínez-Subiela, Lorena Franco-Martínez and Laura Anfossi

Chemosensors 2025, 13(2), 44; https://doi.org/10.3390/chemosensors13020044 (registering DOI) - 2 Feb 2025

Abstract

Point-of-care diagnostic tests, such as lateral-flow immunoassay (LFIA), have emerged as a fast diagnostic tool in both human and veterinary medicine. In this paper, a gold nanoparticle-based LFIA device was developed for the measurement of C-reactive protein (CRP) in porcine saliva, using a [...] Read more.

Point-of-care diagnostic tests, such as lateral-flow immunoassay (LFIA), have emerged as a fast diagnostic tool in both human and veterinary medicine. In this paper, a gold nanoparticle-based LFIA device was developed for the measurement of C-reactive protein (CRP) in porcine saliva, using a monoclonal anti-porcine CRP antibody. The dilution ratio for the saliva samples was optimized at 1:5 with an assay buffer. The reaction time was optimized to 20 min, since this provided a positive signal with high CRP concentration saliva samples, but a negative result with an assay buffer or samples with a low CRP concentration. Linear results were observed when two samples with a high CRP concentration were serially diluted. Also, a linear relationship was observed with a validated quantitative method. The assay was precise when samples with high CRP concentration were measured five times in a single assay run. No overlap was observed when samples from healthy and diseased animals were analyzed. The LFIA allowed the detection of high CRP concentrations in porcine saliva samples. The intensity of the result was proportional to the CRP concentration obtained with the quantitative method, allowing for the possible use of the test for semiquantitative purposes. Full article

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

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20 pages, 4604 KiB

Open AccessArticle

Graphene-Modified Electrode for Linear Sweep Voltammetric Sensing of Catechol

by Florina Pogăcean, Lidia Măgeruşan, Alexandru Turza and Stela Pruneanu

Chemosensors 2025, 13(2), 43; https://doi.org/10.3390/chemosensors13020043 (registering DOI) - 1 Feb 2025

Abstract

A graphene sample (EGr) was obtained in a single-step synthesis by electrochemical exfoliation of graphite rods. A combination of 0.05 M ammonium sulfate and 0.05 M ammonium thiocyanate was employed, leading to a graphene sample composed of few-layer, multi-layer and graphene oxide flakes. [...] Read more.

A graphene sample (EGr) was obtained in a single-step synthesis by electrochemical exfoliation of graphite rods. A combination of 0.05 M ammonium sulfate and 0.05 M ammonium thiocyanate was employed, leading to a graphene sample composed of few-layer, multi-layer and graphene oxide flakes. Due to the mild exfoliation conditions, large sheets with linear sizes in the range of tens to hundreds of micrometers were produced. The LSV technique gave information about the effect of catechol concentration on the electrochemical signal of bare and graphene-modified electrodes. Based on the resulting calibration plots, the corresponding analytical parameters (linear range, sensitivity, limit of quantification and limit of detection) were calculated for each electrode. In the case of the EGr/GC electrode the linear range was from 6 × 10⁻⁷ to 1 × 10⁻⁴ M catechol. The detection limit was low (1.82 × 10⁻⁷ M) while the quantification limit was 6 × 10⁻⁷ M. The sensitivity was five times higher than that corresponding to bare GC, proving the excellent electro-catalytic properties of the graphene-modified electrode. The practical applicability of the graphene-modified electrode was tested in tap water, obtaining an excellent recovery of 102%. Full article

(This article belongs to the Special Issue Electrochemical Biosensors: Advances and Prospects)

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14 pages, 4532 KiB

Open AccessArticle

Research on Enhancement of LIBS Signal Stability Through the Selection of Spectral Lines Based on Plasma Characteristic Parameters

by Yunfeng Xia, Honglin Jian, Qishuai Liang and Xilin Wang

Chemosensors 2025, 13(2), 42; https://doi.org/10.3390/chemosensors13020042 (registering DOI) - 1 Feb 2025

Abstract

Laser-induced breakdown spectroscopy (LIBS) is widely used for online quantitative analysis in industries due to its rapid analysis and minimal damage. However, challenges like signal instability, matrix effects, and self-absorption hinder the measurement accuracy. Recent approaches, including the internal standard method and crater [...] Read more.

Laser-induced breakdown spectroscopy (LIBS) is widely used for online quantitative analysis in industries due to its rapid analysis and minimal damage. However, challenges like signal instability, matrix effects, and self-absorption hinder the measurement accuracy. Recent approaches, including the internal standard method and crater limitation method, aim to improve the stability but suffer from high computational demands or complexity. This study proposes a method to enhance LIBS stability by utilizing craters formed from laser ablation without external cavity assistance. It first improves the plasma temperature calculation reliability using multiple elemental spectral lines, after which electron density calculations are performed. By fitting plasma parameter curves based on laser pulse counts and using a laser confocal microscope for crater analysis, stable plasma conditions were found within crater areas of 0.400 mm² to 0.443 mm² and depths of 0.357 mm to 0.412 mm. Testing with elemental spectral lines of Ti II, K II, Ca I, and Fe I showed a significant reduction in the relative standard deviation (RSD) of the LIBS spectral line intensity, demonstrating an improved signal stability within specified crater dimensions. Full article

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

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12 pages, 950 KiB

Open AccessPerspective

Handheld Laser-Induced Breakdown Spectroscopy (hLIBS) Applied to On-Site Mine Waste Analysis/Evaluation in View of Its Recycling/Reuse

by Giorgio S. Senesi

Chemosensors 2025, 13(2), 41; https://doi.org/10.3390/chemosensors13020041 (registering DOI) - 1 Feb 2025

Abstract

Nowadays, the recovery/recycling/reuse of mining and mineral processing wastes is considered the best approach to support the circular economy and sustainability of mining and metal extraction industries. Mine wastes can be used to restore surface and subsurface land damaged by mining operations, generate [...] Read more.

Nowadays, the recovery/recycling/reuse of mining and mineral processing wastes is considered the best approach to support the circular economy and sustainability of mining and metal extraction industries. Mine wastes can be used to restore surface and subsurface land damaged by mining operations, generate fuel for power plants, further extract their component minerals, and as building materials additives. The aim of this perspective paper is to briefly highlight and focus on the most recent analytical potential and performance achieved by handheld laser-induced breakdown spectroscopy (hLIBS) instrumentation in the perspective of its future application in the mine waste sector to quickly identify on-site the presence of useful chemical elements for their possible sustainable recovery. Full article

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

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11 pages, 1129 KiB

Open AccessArticle

An Electronic Nose Analysis of the Headspace from Extra-Virgin Olive Oil–Saliva Interactions and Its Ability to Differentiate Between Individuals Based on Body Mass Index

by Alessandro Genovese, Andrea Balivo, Nicola Caporaso and Raffaele Sacchi

Chemosensors 2025, 13(2), 40; https://doi.org/10.3390/chemosensors13020040 - 29 Jan 2025

Abstract

The interaction between fatty foods and saliva in individuals of different body weights may lead to differences in the release of volatile compounds in the mouth. This study investigates the ability of an electronic nose (E-nose) to discriminate between the headspace profiles of [...] Read more.

The interaction between fatty foods and saliva in individuals of different body weights may lead to differences in the release of volatile compounds in the mouth. This study investigates the ability of an electronic nose (E-nose) to discriminate between the headspace profiles of extra-virgin olive oil (EVOO) mixed with the saliva of 55 subjects of different body mass indices (BMI). The resulting data were analysed using linear discriminant analysis (LDA) and principal component analysis (PCA) to evaluate the E-nose’s ability to discriminate between groups. W5S, W1S, W2S, and W2W sensors exhibited the greatest variation in response intensity; in particular, they highlighted differences between obese and non-obese subjects. The LDA plot demonstrated a clear separation of samples corresponding to three BMI groups, with the first and second components accounting for 61.25% and 23.97% of the variance, respectively. Overall, the percentage of correct classification in the cross-validation results was 87.3%. These results highlight the potential of an electronic nose for use as a rapid and objective tool for screening olfactory profiles associated with food matrix–saliva interaction in different BMI groups, providing valuable insight for further research on food–saliva interactions. Full article

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

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Graphical abstract

13 pages, 6451 KiB

Open AccessArticle

Insight into Reduction Process of Diquat on Silver and Copper Electrodes Studied Using SERS

by María Rosa López-Ramírez, Lucas Olivares-Fernández and Santiago Sanchez-Cortes

Chemosensors 2025, 13(2), 39; https://doi.org/10.3390/chemosensors13020039 - 27 Jan 2025

Abstract

A surface-enhanced Raman scattering (SERS) study of diquat (DQ) on silver and copper electrodes is presented in this work in order to complete previous studies on the SERS of DQ on metal nanoparticles. We supported the experimental results with theoretical calculations of different [...] Read more.

A surface-enhanced Raman scattering (SERS) study of diquat (DQ) on silver and copper electrodes is presented in this work in order to complete previous studies on the SERS of DQ on metal nanoparticles. We supported the experimental results with theoretical calculations of different species of DQ, analyzing the most important molecular differences and their corresponding Raman spectra. DQ SERS spectra on Ag and Cu electrodes were obtained at different excitation wavelengths. An analysis of the SERS spectra revealed that at more positive electrode potentials, the interaction of DQ with the metal formed a charge-transfer complex via the chloride anion previously adsorbed on the surface; additionally, at more negative potentials, other species of diquat, such as DQ²⁺, could be directly adsorbed on the metal’s surface. Finally, we detected new SERS bands corresponding to DQ at negative electrode potentials that were sensitive to the excitation wavelength, suggesting that lateral interactions between radical cation species on the electrode surface lead to intramolecular dimerization and a possible multilayer of the adsorbate. Full article

(This article belongs to the Special Issue Surface-Enhanced Raman Spectroscopy for Bioanalytics)

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19 pages, 2711 KiB

Open AccessArticle

Implementing an Analytical Model to Elucidate the Impacts of Nanostructure Size and Topology of Morphologically Diverse Zinc Oxide on Gas Sensing

by Sanju Gupta and Haiyang Zou

Chemosensors 2025, 13(2), 38; https://doi.org/10.3390/chemosensors13020038 - 26 Jan 2025

Abstract

The development of state-of-the-art gas sensors based on metal oxide semiconductors (MOS) to monitor hazardous and greenhouse gas (e.g., methane, CH₄, and carbon dioxide, CO₂) has been significantly advanced. Moreover, the morphological and topographical structures of MOSs have significantly [...] Read more.

The development of state-of-the-art gas sensors based on metal oxide semiconductors (MOS) to monitor hazardous and greenhouse gas (e.g., methane, CH₄, and carbon dioxide, CO₂) has been significantly advanced. Moreover, the morphological and topographical structures of MOSs have significantly influenced the gas sensors by means of surface catalytic activities. This work examines the impact of morphological and topological networked assembly of zinc oxide (ZnO) nanostructures, including microparticles and nanoparticles (0D), nanowires and nanorods (1D), nanodisks (2D), and hierarchical networks of tetrapods (3D). Gas sensors consisting of vertically aligned ZnO nanorods (ZnO–NR) and topologically interconnected tetrapods (T–ZnO) of varying diameter and arm thickness synthesized using aqueous phase deposition and flame transport method on interdigitated Pt electrodes are evaluated for methane detection. Smaller-diameter nanorods and tetrapod arms (nanowire-like), having higher surface-to-volume ratios with reasonable porosity, exhibit improved sensing behavior. Interestingly, when the nanorods’ diameter and interconnected tetrapod arm thickness were comparable to the width of the depletion layer, a significant increase in sensitivity (from 2 to 30) and reduction in response/recovery time (from 58 s to 5.9 s) resulted, ascribed to rapid desorption of analyte species. Additionally, nanoparticles surface-catalyzed with Pd (~50 nm) accelerated gas sensing and lowered operating temperature (from 200 °C to 50 °C) when combined with UV photoactivation. We modeled the experimental findings using a modified general formula for ZnO methane sensors derived from the catalytic chemical reaction between methane molecules and oxygen ions and considered the structural surface-to-volume ratios (S/V) and electronic depletion region width (L_d) applicable to other gas sensors (e.g., SnO₂, TiO₂, MoO₃, and WO₃). Finally, the effects of UV light excitation reducing detection temperature help to break through the bottleneck of ZnO-based materials as energy-saving chemiresistors and promote applications relevant to environmental and industrial harmful gas detection. Full article

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

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29 pages, 10155 KiB

Open AccessArticle

Quantification of Argan Oil (Argania spinosa L.) Adulterated with Avocado, Flaxseed, Walnut, and Pumpkin Oils Using Fourier-Transform Infrared Spectroscopy and Advanced Chemometric and Machine Learning Techniques

by Linda Gjonaj, Oliver B. Generalao, Arnold Alguno, Roberto Malaluan, Arnold Lubguban and Gerard G. Dumancas

Chemosensors 2025, 13(2), 37; https://doi.org/10.3390/chemosensors13020037 - 26 Jan 2025

Abstract

The increasing trend in the popularity of argan oil (AGO), a multi-beneficial health and cosmetic product, can leave it prone to adulteration. The overall goal of this study was to utilize an attenuated total reflectance Fourier-transform infrared spectroscopic and chemometric methods, including partial [...] Read more.

The increasing trend in the popularity of argan oil (AGO), a multi-beneficial health and cosmetic product, can leave it prone to adulteration. The overall goal of this study was to utilize an attenuated total reflectance Fourier-transform infrared spectroscopic and chemometric methods, including partial least squares (PLS), principal component regression (PCR), and artificial neural network (ANN) for the authentication of AGO in the presence of other oil adulterants, avocado oil (AVO), pumpkin seed oil (PSO), flaxseed oil (FSO), and walnut seed oil (WNO). All three chemometrics methods were able to effectively quantify the FSO adulterant concentration across all statistical models, with the most optimal results in the ANN model as applied in the testing set data (RMSEP = 1.454 %v/v, R² = 0.821). Comparable results were also obtained for PLS (RMSEP = 1.727 %v/v, R² = 0.807) and PCR (RMSEP = 1.731 %v/v, R² = 0.846). Full article

(This article belongs to the Special Issue Chemometrics Tools Used in Chemical Detection and Analysis)

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21 pages, 7142 KiB

Open AccessArticle

Implicit Measurement of Sweetness Intensity and Affective Value Based on fNIRS

by Jiayu Mai, Siying Li, Zhenbo Wei and Yi Sun

Chemosensors 2025, 13(2), 36; https://doi.org/10.3390/chemosensors13020036 - 26 Jan 2025

Abstract

This study explores the effectiveness of functional near-infrared spectroscopy (fNIRS) as an implicit measurement tool for evaluating sweetness intensity and affective value. Thirty-two participants tasted sucrose solutions at concentrations of 0.15 M, 0.3 M, and 0.6 M, while both their neural responses were [...] Read more.

This study explores the effectiveness of functional near-infrared spectroscopy (fNIRS) as an implicit measurement tool for evaluating sweetness intensity and affective value. Thirty-two participants tasted sucrose solutions at concentrations of 0.15 M, 0.3 M, and 0.6 M, while both their neural responses were recorded with a 24-channel fNIRS system and their self-reported assessments of sweetness intensity and affective value were collected. The neural fNIRS data were converted into oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) concentrations using the modified Beer–Lambert Law, and analyzed through univariate activation analysis and multivariable decoding analysis to identify neural activation patterns associated with sweetness perception. The results showed significant activation in the dorsolateral prefrontal cortex (dlPFC) and orbitofrontal cortex (OFC) in response to varying levels of sweetness intensity and affective value, with channels 8, 10, 12, 13, 14, 15, and 17 consistently activated across all sucrose concentrations. As sweetness concentration increased from 0.15 M to 0.6 M, the number of significantly activated channels rose from seven to eleven, indicating stronger and more widespread neural responses corresponding to higher sweetness intensity. The multivariable decoding analysis further demonstrated the capability of fNIRS in accurately distinguishing positive affective responses, with up to 72.1% accuracy. The moderate positive correlation between explicit self-reports and implicit fNIRS data regarding sweetness intensity further supports the validity of fNIRS as a reliable tool for assessing taste perception. This study highlights the potential of fNIRS in sensory neuroscience, demonstrating its effectiveness in capturing the neural mechanisms underlying sweet taste perception. Full article

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

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13 pages, 7211 KiB

Open AccessArticle

Electrochemical Sensor for Cu(II) Based on Carbon Nanotubes Functionalized with a Rationally Designed Schiff Base

by Alejandro Tamborelli, Michael López Mujica, Gustavo Servetti, Diego Venegas-Yazigi, Patricio Hermosilla-Ibáñez, Pablo Dalmasso and Gustavo Rivas

Chemosensors 2025, 13(2), 35; https://doi.org/10.3390/chemosensors13020035 - 25 Jan 2025

Abstract

This work proposes a new strategy for the electrochemical quantification of Cu(II) using glassy carbon electrodes (GCEs) modified with a nanohybrid of multiwall carbon nanotubes (MWCNTs) non-covalently functionalized with a rationally designed Schiff base containing different groups (SB-dBA). The principle of sensing was [...] Read more.

This work proposes a new strategy for the electrochemical quantification of Cu(II) using glassy carbon electrodes (GCEs) modified with a nanohybrid of multiwall carbon nanotubes (MWCNTs) non-covalently functionalized with a rationally designed Schiff base containing different groups (SB-dBA). The principle of sensing was the complexation of Cu(II) by the Schiff base that supports the MWCNTs at the open-circuit potential, followed by a reduction step at −0.600 V and further linear sweep anodic stripping voltammetry (LSASV) in a 0.200 M acetate buffer solution of pH 5.00. The linear range goes from 10 to 200 μg L⁻¹, with a sensitivity of (0.79 ± 0.07) µA L µg⁻¹ (R² = 0.991), a detection limit of 3.3 μg L⁻¹, and a reproducibility of 8.0% for the same nanohybrid (nine electrodes) and 9.0% for four different nanohybrids. The proposed sensor was very selective for Cu(II) even in the presence of Pb(II), Fe(II), As(III), Cr(III), Cd(II), and Hg(II), and it was successfully used for the quantification of Cu(II) in different water samples (tap, groundwater, and river) without any pretreatment. Full article

(This article belongs to the Special Issue Carbon Nanotubes for Electrochemical Sensing: Sensors and Platforms)

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17 pages, 4209 KiB

Open AccessArticle

Sensitive Electrochemical Sensor Based on Amino-Functionalized Graphene Oxide/Polypyrrole Composite for Detection of Pb²⁺ Ions

by Priyanka C. Zine, Vijaykiran N. Narwade, Shubham S. Patil, Masira T. Qureshi, Meng-Lin Tsai, Tibor Hianik and Mahendra D. Shirsat

Chemosensors 2025, 13(2), 34; https://doi.org/10.3390/chemosensors13020034 - 24 Jan 2025

Abstract

In this work, an amino-functionalized graphene oxide/polypyrrole (AMGO/PPy) composite-based novel sensing platform was established to monitor lead ions (Pb²⁺) at high sensitivity. AMGO was synthesized through a hydrothermal process and later formed a composite with PPy at varying concentrations. A physicochemical [...] Read more.

In this work, an amino-functionalized graphene oxide/polypyrrole (AMGO/PPy) composite-based novel sensing platform was established to monitor lead ions (Pb²⁺) at high sensitivity. AMGO was synthesized through a hydrothermal process and later formed a composite with PPy at varying concentrations. A physicochemical investigation of the synthesized materials was carried out using various characterization tools, while the electrochemical properties were examined by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods. The AMGO/PPy composite was deposited on a glassy carbon electrode (GCE), which was used for the real-time electrochemical detection of Pb²⁺. The AMGO/PPy sensor exhibited lower limits of detection (LOD) of 0.91 nM. In addition, the developed Pb²⁺ sensor exhibited excellent reproducibility, repeatability, selectivity, sensitivity, and long-term stability for 25 days. The AMGO/PPy composite emerges as a ground-breaking material for the electrochemical detection of Pb²⁺, holding significant potential for environmental monitoring and the protection of human health. Full article

(This article belongs to the Special Issue Nanomaterial-Based Sensors: Design, Development and Applications)

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11 pages, 702 KiB

Open AccessArticle

Stretching the Limits of Refractometric Sensing in Water Using Whispering-Gallery-Mode Resonators

by Kevin Soler-Carracedo, Antonia Ruiz, Susana Ríos, Sergio de Armas-Rillo, Leopoldo L. Martín, Martin Hohmann, Inocencio R. Martín and Fernando Lahoz

Chemosensors 2025, 13(2), 33; https://doi.org/10.3390/chemosensors13020033 - 24 Jan 2025

Abstract

A novel application of microresonators for refractometric sensing in aqueous media is presented. To carry out this approach, microspheres of different materials and sizes were fabricated and doped with Nd³⁺ ions. Under 532 nm excitation, the microspheres presented typical NIR Nd³⁺ [...] Read more.

A novel application of microresonators for refractometric sensing in aqueous media is presented. To carry out this approach, microspheres of different materials and sizes were fabricated and doped with Nd³⁺ ions. Under 532 nm excitation, the microspheres presented typical NIR Nd³⁺ emission bands with superimposed sharp peaks, related to the Whispering Gallery Modes (WGMs), due to the geometry of the microspheres. When the microspheres were submerged in water with increasing concentrations of glycerol, spectral shifts for the WGMs were observed as a function of the glycerol concentration. These spectral shifts were studied and calibrated for three different microspheres and validated with the theoretical shifts, obtained by solving the Helmholtz equations for the electromagnetic field, considering the geometry of the system, and also by calculating the extinction cross-section. WGM shifts strongly depend on the diameter of the microspheres and their refractive index (RI) difference compared with the external medium, and are greater for decreasing values of the diameter and lower values of RI difference. Experimental sensitivities ranging from 2.18 to 113.36 nm/RIU (refractive index unit) were obtained for different microspheres. Furthermore, reproducibility measurements were carried out, leading to a repeatability of 2.3 pm and a limit of detection of 5 × 10⁻⁴ RIU. The proposed sensors, taking advantage of confocal microscopy for excitation and detection, offer a robust, reliable, and contactless alternative for environmental water analysis. Full article

(This article belongs to the Special Issue Sensors for Food Testing, Environmental Analysis, and Medical Diagnostics)

13 pages, 3826 KiB

Open AccessArticle

Non-Invasive Detection of Interferon-Gamma in Sweat Using a Wearable DNA Hydrogel-Based Electrochemical Sensor

by Yang Dai, Xiuran Mao, Maimaiti A. Abulaiti, Qianyu Wang, Zhihao Bai, Yifeng Ding, Shuangcan Zhai, Yang Pan and Yue Zhang

Chemosensors 2025, 13(2), 32; https://doi.org/10.3390/chemosensors13020032 - 24 Jan 2025

Abstract

Monitoring of immune factors, including interferon-gamma (IFN-γ), holds great importance for understanding immune responses and disease diagnosis. Wearable sensors enable continuous and non-invasive detection of immune markers in sweat, drawing significant attention to their potential in real-time health monitoring and personalized medicine. Among [...] Read more.

Monitoring of immune factors, including interferon-gamma (IFN-γ), holds great importance for understanding immune responses and disease diagnosis. Wearable sensors enable continuous and non-invasive detection of immune markers in sweat, drawing significant attention to their potential in real-time health monitoring and personalized medicine. Among these, electrochemical sensors are particularly advantageous, due to their excellent signal responsiveness, cost-effectiveness, miniaturization, and broad applicability, making them ideal for constructing wearable sweat sensors. In this study, we present a flexible and sensitive wearable platform for the detection of IFN-γ, utilizing a DNA hydrogel with favorable loading performance and sample collection capability, and the application of mobile software achieves immediate data analysis and processing. This platform integrates three-dimensional DNA hydrogel functionalized with IFN-γ-specific aptamers for precise target recognition and efficient sweat collection. Signal amplification is achieved through target-triggered catalytic hairpin assembly (CHA), with DNA hairpins remarkably enhancing sensitivity. Ferrocene-labeled reporting strands immobilized on a screen-printed carbon electrode are displayed via CHA-mediated strand displacement, leading to a measurable reduction in electrical signals. These changes are transmitted to a custom-developed mobile application via a portable electrochemical workstation for real-time data analysis and recording. This wearable sensor platform combines the specificity of DNA aptamers, advanced signal amplification, and the convenience of mobile data processing. It offers a high-sensitivity approach to detecting low-abundance targets in sweat, paving the way for new applications in point-of-care diagnostics and wearable health monitoring. Full article

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

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28 pages, 2338 KiB

Open AccessReview

Current and Future Diagnostics for Hepatitis C Virus Infection

by Hussein Zilouchian, Omair Faqah, Md Alamgir Kabir, Dennis Gross, Rachel Pan, Shane Shaifman, Muhammad Awais Younas, Muhammad Abdul Haseeb, Emmanuel Thomas and Waseem Asghar

Chemosensors 2025, 13(2), 31; https://doi.org/10.3390/chemosensors13020031 - 23 Jan 2025

Abstract

Hepatitis C virus (HCV), a member of the Flaviviridae family, is an RNA virus enclosed in an envelope that infects approximately 50 million people worldwide. Despite its significant burden on public health, no vaccine is currently available, and many individuals remain unaware of [...] Read more.

Hepatitis C virus (HCV), a member of the Flaviviridae family, is an RNA virus enclosed in an envelope that infects approximately 50 million people worldwide. Despite its significant burden on public health, no vaccine is currently available, and many individuals remain unaware of their infection due to the often asymptomatic nature of the disease. Early detection of HCV is critical for initiating curative treatments, which can prevent long-term complications such as cirrhosis, liver cancer, and decompensated liver disease. However, conventional diagnostic approaches available, such as enzyme immunoassays (EIAs) and polymerase chain reaction (PCR)-based methods, are often costly, time-intensive, and challenging to be implemented in resource-limited settings. This review provides an overview of HCV disease and the structural components of the virus, illustrating how different diagnostic methods target various parts of the viral structure. It examines current diagnostic tests and assays, highlighting their mechanisms, applications, and limitations, which necessitates the development of improved detection methods. Additionally, the paper explores emerging technologies in HCV detection that could offer affordable, accessible, and easy-to-use diagnostic solutions, particularly for deployment in low-resource and point-of-care settings. These advancements have the potential to contribute significantly to achieving the World Health Organization’s (WHO) target of eliminating HCV as a public threat by 2030. Full article

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

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13 pages, 2802 KiB

Open AccessArticle

Profiling of Australian Stingless Bee Honey Using Multivariate Data Analysis of High-Performance Thin-Layer Chromatography Fingerprints

by Mariana Mello dos Santos, Christina Jacobs, Kevin Vinsen, Md Khairul Islam, Tomislav Sostaric, Lee Yong Lim and Cornelia Locher

Chemosensors 2025, 13(2), 30; https://doi.org/10.3390/chemosensors13020030 - 22 Jan 2025

Abstract

The complex chemical composition of honey presents significant challenges for its analysis with variations influenced by factors such as botanical source, geographical location, bee species, harvest time, and storage conditions. This study aimed to employ high-performance thin-layer chromatography (HPTLC) fingerprinting, coupled with multivariate [...] Read more.

The complex chemical composition of honey presents significant challenges for its analysis with variations influenced by factors such as botanical source, geographical location, bee species, harvest time, and storage conditions. This study aimed to employ high-performance thin-layer chromatography (HPTLC) fingerprinting, coupled with multivariate data analysis, to characterise the chemical profiles of Australian stingless bee honey samples from two distinct bee species, Tetragonula carbonaria and Tetragonula hockingsi. Using a mobile phase composed of toluene:ethyl acetate:formic acid (6:5:1) and two derivatisation reagents, vanillin–sulfuric acid and natural product reagent/PEG, HPTLC fingerprints were developed to reveal characteristic patterns within the samples. Multivariate data analysis was employed to explore the similarities in the fingerprints and identify underlying patterns. The results demonstrated that the chemical profiles were more closely related to harvest time rather than bee species, as samples collected within the same month clustered together. The quality of the clustering results was assessed using silhouette scores. The study highlights the value of combining HPTLC fingerprinting with multivariate data analysis to produce valuable data that can aid in blending strategies and the creation of reference standards for future quality control analyses. Full article

(This article belongs to the Special Issue Chemometrics for Food, Environmental and Biological Analysis)

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