Chemosensors

16 pages, 2405 KiB

Open AccessArticle

Electrochemical Polymerization of Guaiacol in Organic Solvents and Analytical Performance of the Poly (Guaiacol) Modified Electrode Towards Phenol Antioxidants

by László Kiss, Péter Szabó and Sándor Kunsági-Máté

Chemosensors 2025, 13(6), 214; https://doi.org/10.3390/chemosensors13060214 - 11 Jun 2025

Abstract

The electrochemical polymerization of guaiacol was studied in different organic solvents. Significant electrode blocking was observed in dichloromethane. Microscopic studies verified the formation of a coherent deposit on the platinum electrode. In acetonitrile, the insulating deposit formation proceeded above 20 mM monomer concentration. [...] Read more.

The electrochemical polymerization of guaiacol was studied in different organic solvents. Significant electrode blocking was observed in dichloromethane. Microscopic studies verified the formation of a coherent deposit on the platinum electrode. In acetonitrile, the insulating deposit formation proceeded above 20 mM monomer concentration. The differences in layer formation performed in acetic acid or ethyl acetate only allowed us to make estimations in a narrow range of the composition of their binary solvent mixtures utilizing the shape of curves related to guaiacol electropolymerization. Guaiacol was therefore not reliable in solvent composition estimations within the entire range. Due to its apolar nature, a poly (guaiacol) modified platinum macroelectrode was assessed for analyses in solutions prepared with organic solvents. The analytical performance of the modified electrode was tested with butylhydroxyanisole and butylhydroxytoluene. Linear sweep voltammetry was applied under stirred conditions, and the noise of stirring diminished compared with the bare electrode, although lower sensitivity was noticed. Full article

(This article belongs to the Special Issue New Electrodes Materials for Electroanalytical Applications)

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11 pages, 1667 KiB

Open AccessCommunication

Analysis of Ergothioneine Using Surface-Enhanced Raman Scattering: Detection in Mushrooms

by Federico Puliga, Veronica Zuffi, Alessandra Zambonelli, Pavol Miškovský, Ornella Francioso and Santiago Sanchez-Cortes

Chemosensors 2025, 13(6), 213; https://doi.org/10.3390/chemosensors13060213 - 10 Jun 2025

Abstract

Surface-enhanced Raman scattering (SERS) spectroscopy is a straightforward analytical technique capable of providing detailed information about metabolites in biological samples. The objective of this study was to perform a SERS analysis of ergothioneine (EGT), an amino acid synthesized by microbes and fungi, across [...] Read more.

Surface-enhanced Raman scattering (SERS) spectroscopy is a straightforward analytical technique capable of providing detailed information about metabolites in biological samples. The objective of this study was to perform a SERS analysis of ergothioneine (EGT), an amino acid synthesized by microbes and fungi, across a range of pH values (acidic to alkaline) and concentrations (2 × 10⁻⁵ M to 2 × 10⁻⁷ M), to understand the dynamic interactions between EGT and silver (Ag) nanoparticles. Furthermore, SERS was applied in situ on mushroom fruiting bodies to detect the presence of EGT. The SERS spectra revealed that the interaction of EGT with Ag nanoparticles underwent significant alterations at varying pH levels, primarily due to isomerization. These changes were associated with modifications in the aromaticity and ionization of the imidazole ring, driven by both metal adsorption and alkaline conditions. Our results indicated the formation of distinct tautomeric forms of the imidazole group, namely the thione and thiol forms, in aqueous solution and on the Ag surface, respectively. Furthermore, the EGT spectra at different concentrations suggested that ionization occurred at lower concentrations. Notably, the SERS spectra of the mushroom fruiting bodies were dominated by prominent bands attributable to EGT, as corroborated by the comparison with the EGT fungal extract and EGT standard. These findings underscore the utility of SERS spectroscopy as a rapid and effective tool for obtaining comprehensive molecular fingerprints, even directly from complex biological matrices such as mushroom fruiting bodies. 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, 1050 KiB

Open AccessArticle

Green On-Site Diclofenac Extraction from Wastewater Matrices Using a 3D-Printed Device Followed by PTV-GC-MS Determination

by César Castro-García, Edwin Palacio, Rogelio Rodríguez-Maese, Luz O. Leal and Laura Ferrer

Chemosensors 2025, 13(6), 212; https://doi.org/10.3390/chemosensors13060212 - 9 Jun 2025

Abstract

A 3D-printed device was designed and printed by a stereolithographic technique (SLA) and coated with a highly selective solid phase extraction resin for on-site diclofenac extraction from wastewater, avoiding the transport and treatment of large volumes of samples in the laboratory. The best [...] Read more.

A 3D-printed device was designed and printed by a stereolithographic technique (SLA) and coated with a highly selective solid phase extraction resin for on-site diclofenac extraction from wastewater, avoiding the transport and treatment of large volumes of samples in the laboratory. The best results in terms of chemical and mechanical resistance were obtained with Rigid 10K resin. The “stick-and-cure” impregnation technique was used to coat the 3D-printed device with Oasis^® HLB resin. The coated 3D-printed device can be reused up to eight times without losing extraction efficiency. The eluent and derivatization reagent volumes were optimized by a multivariate design. The proposed method allowed for the extraction and determination of diclofenac by PTV-GC-MS, achieving methodological detection and quantification limits of 0.019 and 0.055 μg L⁻¹, respectively, with a preconcentration factor of 46. The analysis time was 23 min per sample. To validate the proposed methodology, addition/recovery tests were carried out in different wastewater samples, obtaining recoveries above 90%. The methodology was applied at the wastewater treatment plant (WWTP) of Calvià (Mallorca, Spain), finding diclofenac in concentrations of 15.39 ± 0.07 μg L⁻¹ at the input of the primary decantation process, 4.48 ± 0.03 μg L⁻¹ at the output of the secondary decantation, and 0.099 ± 0.001 μg L⁻¹ at the output of the tertiary treatment, demonstrating the feasibility of the on-site extraction method in monitoring diclofenac over a wide concentration range. Finally, a greenness index of 0.58 for the proposed on-site sample preparation was achieved according to the AGREEprep metrics, making it an eco-friendly alternative for diclofenac monitoring. Full article

(This article belongs to the Special Issue GC, MS and GC-MS Analytical Methods: Opportunities and Challenges (Third Edition))

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10 pages, 1369 KiB

Open AccessCommunication

Electrochemical Assessment of Microbial Activity Using PEDOT:PSS-Immobilized Cells

by N. Vigués, C. Cantallops-Vilà and J. Mas

Chemosensors 2025, 13(6), 211; https://doi.org/10.3390/chemosensors13060211 - 9 Jun 2025

Abstract

This study presents a microbial sensing device that employs a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) matrix to immobilize viable and metabolically Escherichia coli cells. This device enables the monitoring of microorganism metabolic activity in response to external stimuli such as variations in carbon sources or [...] Read more.

This study presents a microbial sensing device that employs a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) matrix to immobilize viable and metabolically Escherichia coli cells. This device enables the monitoring of microorganism metabolic activity in response to external stimuli such as variations in carbon sources or exposure to inhibitory or toxic compounds. PEDOT:PSS, a conductive and chemically stable polymer, was electrodeposited onto screen-printed electrodes, successfully entrapping approximately 1.26 × 10⁷ cells per electrode. The confocal microscopy of Live/Dead-stained samples confirmed a uniform cell distribution and an average viability of ~78%. Ferricyanide respirometry validated the metabolic activity of the immobilized cells. The biosensor’s performance was evaluated using 3,5-dichlorophenol (3,5-DCP) as a reference toxicant. The observed inhibition of microbial activity correlated with 3,5-DCP concentration, yielding a half-maximal effective concentration (EC₅₀) of 9 ppm, consistent with the literature values. Full article

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

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19 pages, 3716 KiB

Open AccessArticle

Ultrafast and Ultrasensitive Simultaneous Molecular Recognition and Quantification of CA12-5, CA72-4, HER1, and AFP in Biological Samples

by Ruxandra-Maria Ilie-Mihai, Raluca-Ioana Stefan-van Staden and Bianca-Maria Tuchiu-Stanca

Chemosensors 2025, 13(6), 210; https://doi.org/10.3390/chemosensors13060210 - 9 Jun 2025

Abstract

Simultaneous molecular recognition and quantification of at least four biomarkers in biological samples may contribute to early and fast diagnosis of illnesses such as cancer. The electrodes able to reliably perform on-site these tests are the stochastic sensors. Therefore, three novel 3D stochastic [...] Read more.

Simultaneous molecular recognition and quantification of at least four biomarkers in biological samples may contribute to early and fast diagnosis of illnesses such as cancer. The electrodes able to reliably perform on-site these tests are the stochastic sensors. Therefore, three novel 3D stochastic sensors employing carbon-based powders (graphite, graphene, nanographene) treated with N-(2-mercapto-1H-benzo[d]imidazole-5-yl) oleamide solution were used for screening tests of whole blood, gastric tumoral tissue, urine, and saliva for molecular recognition and quantification of CA12-5, CA72-4, HER1, and AFP. The best performance was achieved for the sensor based on graphene, when the highest sensitivities were recorded, on wide working concentration ranges of: 8.37 × 10⁻¹⁴–8.37 U mL⁻¹ for CA12-5, 4.00 × 10⁻¹¹–4.00 × 10⁻³ U mL⁻¹ for CA72-4, 3.90 × 10⁻¹⁶–3.90 × 10⁻⁶ g mL⁻¹ for HER1, and 3.00 × 10⁻²⁰–3.00 × 10⁻⁶ g mL⁻¹ for AFP. The wide linear concentration ranges cover levels of biomarkers found in gastric cancer patients from early to late stages. The recovery values were higher than 98.00 with %, RSD lower than 1.00%. Full article

(This article belongs to the Special Issue Innovative Analytical Methods in Pharmaceutical and Biomedical Analysis)

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30 pages, 4171 KiB

Open AccessReview

Two-Dimensional Materials for Biosensing: Emerging Bio-Converged Strategies for Wearable and Implantable Platforms

by Ki Ha Min, Koung Hee Kim and Seung Pil Pack

Chemosensors 2025, 13(6), 209; https://doi.org/10.3390/chemosensors13060209 - 8 Jun 2025

Abstract

The development of functional biosensors is rapidly advancing in response to the growing demand for personalized and continuous healthcare monitoring. Two-dimensional (2D) nanostructured materials have attracted significant attention for next-generation biosensors due to their exceptional physicochemical properties, including a high surface-to-volume ratio, excellent [...] Read more.

The development of functional biosensors is rapidly advancing in response to the growing demand for personalized and continuous healthcare monitoring. Two-dimensional (2D) nanostructured materials have attracted significant attention for next-generation biosensors due to their exceptional physicochemical properties, including a high surface-to-volume ratio, excellent electrical conductivity, and mechanical flexibility. The integration of 2D materials with biological recognition elements offers synergistic improvements in sensitivity, stability, and overall sensor performance. These unique properties make 2D materials particularly well-suited for constructing wearable and implantable biosensors, which require conformal contact with soft tissues, mechanical adaptability to body movement, and reliable operation under physiological conditions. This review highlights recent advances in functionalized and composite 2D materials for wearable and implantable biosensing applications. We focus on key strategies in surface modification and hybrid nanostructure engineering aimed at optimizing performance in dynamic, body-integrated environments. Finally, we discuss current challenges and future directions for clinical translation, emphasizing the potential of 2D-material-based biosensors to drive progress in personalized and precision medicine. Full article

(This article belongs to the Special Issue Emerging 2D Materials for Sensing Applications)

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14 pages, 2913 KiB

Open AccessArticle

Sensitive Gold Nanostar-Based Adsorption Sensor for the Determination of Dexamethasone

by Riccarda Thelma MacDonald, Keagan Pokpas, Emmanuel Iwuoha and Candice Cupido

Chemosensors 2025, 13(6), 208; https://doi.org/10.3390/chemosensors13060208 - 7 Jun 2025

Abstract

Herein, a novel, highly efficient electrochemical adsorption method is introduced for detection of the potent anti-inflammatory synthetic corticosteroid, dexamethasone (DEX). Unlike conventional electrochemical techniques that rely on high reduction potentials, the proposed sensor offers an alternative adsorption-based mechanism with a gold nanostar-modified glassy [...] Read more.

Herein, a novel, highly efficient electrochemical adsorption method is introduced for detection of the potent anti-inflammatory synthetic corticosteroid, dexamethasone (DEX). Unlike conventional electrochemical techniques that rely on high reduction potentials, the proposed sensor offers an alternative adsorption-based mechanism with a gold nanostar-modified glassy carbon electrode (AuNS|GCE). This enables DEX detection at a less negative or moderate reduction potential of +200 mV, circumventing potential window limitations of a GCE and providing a suitable microenvironment for detection in biological media. DEX is known to effectively prevent or suppress symptoms of inflammation due to its small applied dosage; however, an overdose thereof in the human body could lead to adverse drug effects such as gastrointestinal perforation, seizures, and heart attacks. Therefore, a sensitive method is essential to monitor DEX concentration in biofluids such as urine. NMGA-capped AuNSs were leveraged to enhance the active surface area of the sensing platform and allow adsorption of DEX onto the gold surfaces through its highly electronegative fluorine atom. Under optimized experimental conditions, the developed AuNS|GCE sensor showed excellent analytical performance with a remarkably low limit of detection (LOD) of 1.11 nM, a good sensitivity of 0.187 µA.nM⁻¹, and a high percentage recovery of 92.5% over the dynamic linear range of 20–120 nM (linear regression of 0.995). The favourable electrochemical performance of this sensor allowed for successful application in the sensitive determination of DEX in synthetic urine (20% v/v in PBS, pH 7). Full article

(This article belongs to the Special Issue Electrochemical Bio/Sensors for Biological and Pharmaceutical Analysis)

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16 pages, 2702 KiB

Open AccessArticle

Air-Assisted Liquid–Liquid Microextraction (AALLME) as an Alternative Sample Pre-Treatment for Isolating Tetrahydrocannabinol (THC) from Hair

by Laura Blanco-García, Pamela Cabarcos-Fernández, Iván Álvarez-Freire, María Jesús Tabernero-Duque, Antonio Moreda-Piñeiro and Ana María Bermejo-Barrera

Chemosensors 2025, 13(6), 207; https://doi.org/10.3390/chemosensors13060207 - 6 Jun 2025

Abstract

Cannabis remains the most widely used illicit drug worldwide, identifying it is a routine procedure in forensic toxicology. Due to its widespread use, there is a need for analytical methods that can detect it in biological samples. Hair is of particular interest in [...] Read more.

Cannabis remains the most widely used illicit drug worldwide, identifying it is a routine procedure in forensic toxicology. Due to its widespread use, there is a need for analytical methods that can detect it in biological samples. Hair is of particular interest in forensic toxicology as it is the only biological sample that enables retrospective analysis of consumption. In addition, collecting hair is non-invasive, and the specimens can be stored at room temperature. However, the sample preparation process for hair is tedious and multi-step. To address this issue, this study introduces a novel approach to preparing hair samples for analysis, based on air-assisted liquid–liquid microextraction (AALLME). This technique is a modification of dispersive liquid–liquid microextraction (DLLME), which eliminates the need for dispersants and chlorinated organic solvents as extractants. Both techniques offer sustainable alternatives to conventional liquid–liquid extraction (LLE) and solid-phase extraction (SPE), making them of interest in forensic toxicology. This study is the first to report the application of AALLME to the hair matrix. A mixture of cyclohexane and ethyl acetate (9:1) was used as the extractant solvent. Gas chromatography–mass spectrometry (GC–MS) was then used to determine and quantify THC. The method was validated according to FDA guidelines and demonstrated good linearity within the 0.01–4 ng/mg range. The limits of detection (LOD) and quantification (LOQ) were 0.008 and 0.01 ng/mg, respectively. Finally, the applicability of the method was evaluated by analyzing hair samples received by the Forensic Toxicology Service. Full article

(This article belongs to the Special Issue Mass Spectroscopy in Analytical and Bioanalytical Chemistry)

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15 pages, 2594 KiB

Open AccessArticle

Eliminating Assay Background of a Low-Cost, Colorimetric Glutamine Biosensor by Engineering an Alternative Formulation of Cell-Free Protein Synthesis

by Joseph P. Talley, Tyler J. Free, Tyler P. Green, Dallin M. Chipman and Bradley C. Bundy

Chemosensors 2025, 13(6), 206; https://doi.org/10.3390/chemosensors13060206 - 5 Jun 2025

Abstract

Glutamine is an essential biomolecule that plays a pivotal role in many diseases, such as cancer, where it can serve as fuel for rapid proliferation. Treatments for these diseases can be monitored and optimized through the detection of glutamine, though standard glutamine detection [...] Read more.

Glutamine is an essential biomolecule that plays a pivotal role in many diseases, such as cancer, where it can serve as fuel for rapid proliferation. Treatments for these diseases can be monitored and optimized through the detection of glutamine, though standard glutamine detection procedures are costly and require complex instrumentation. Cell-free protein synthesis (CFPS) has recently enabled a paper-based, colorimetric glutamine sensor that carries the potential to increase test accessibility while dramatically reducing consumer cost to enable at-home, rapid treatment monitoring. Test sensitivity remained limited by residual assay background, thus motivating this work where CFPS reactions traditionally formulated with glutamate salts were compared to systems using alternative salts, including aspartate, acetate, citrate, and sulfate, to reduce the background generation of glutamine. This led to the discovery of a novel aspartate-based CFPS system that boasts a high signal strength and indetectable background noise over 225 min. Acetate-, citrate-, and sulfate-based systems also yielded zero background glutamine detection but at a lower signal response compared to the aspartate-based system. These findings mark crucial advancements in producing a cost-effective, simple glutamine monitor while simultaneously showcasing the adaptability of CFPS’s open reaction environment for solving complex challenges in next-generation biosensor development. Full article

(This article belongs to the Special Issue Progress in Enzyme Sensing Technology)

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25 pages, 1376 KiB

Open AccessReview

Applications of Gas Chromatography and Gas Chromatography-Mass Spectrometry for the Determination of Illegal Drugs Used in Drink Spiking

by Hesham Kisher, Oliver Gould and Kevin C. Honeychurch

Chemosensors 2025, 13(6), 205; https://doi.org/10.3390/chemosensors13060205 - 5 Jun 2025

Abstract

Drink spiking is a significant public safety issue, often linked to crimes such as theft and sexual assault. The detection of drugs used in these incidents is challenging due to the low concentrations (<ng) and complex matrices involved. This review explores the application [...] Read more.

Drink spiking is a significant public safety issue, often linked to crimes such as theft and sexual assault. The detection of drugs used in these incidents is challenging due to the low concentrations (<ng) and complex matrices involved. This review explores the application of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) to identify drugs in spiked beverages. GC-MS offers high sensitivity and specificity, and is capable of detecting drugs at ng/mL levels and distinguishing between compounds with similar structures. This review highlights the advantages of GC-MS, including its ability to simultaneously analyze multiple substances and provide detailed molecular information. Various methods for detecting gamma-hydroxybutyrate (GHB), benzodiazepines, and other drugs in beverages are discussed, emphasizing the importance of derivatization to enhance their volatility and the method’s chromatographic performance. The paper also addresses the challenges of analyzing complex beverage matrices and the need for continuous improvement in detection techniques to keep pace with the evolving drug market. Overall, GC and GC-MS are powerful tools for forensic analysis in drink spiking cases, offering reliable and accurate results, which are essential for legal and investigative processes. Full article

(This article belongs to the Special Issue GC, MS and GC-MS Analytical Methods: Opportunities and Challenges (Third Edition))

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37 pages, 2458 KiB

Open AccessReview

Limonene Detection in the Exhaled Human Breath Providing an Early Diagnosis Method of Liver Diseases

by Erich Kny, Christoph Kleber and Wiktor Luczak

Chemosensors 2025, 13(6), 204; https://doi.org/10.3390/chemosensors13060204 - 3 Jun 2025

Abstract

This review aims to summarize possible methods for the detection of limonene in the gas phase at low to very low concentrations. Limonene has historically been of interest as a fragrance in cosmetics, the food industry, pharmaceutics, and the production of solvents. The [...] Read more.

This review aims to summarize possible methods for the detection of limonene in the gas phase at low to very low concentrations. Limonene has historically been of interest as a fragrance in cosmetics, the food industry, pharmaceutics, and the production of solvents. The development of analytical methods for limonene was initially driven by its use in relevant industries such as chemical, pharmaceutics, cosmetics, food, agriculture, and forestry. More recently, it has been recognized as a potent biomarker for human metabolic conditions, such as liver disease and certain cancers. The interest in improved limonene detection in exhaled human breath has increased, particularly from the medical field, which demands high reliability, very low detection limits in the parts per billion (ppb) and even parts per trillion (ppt) range, and excellent selectivity against other exhaled volatile organic compounds (VOC). In addition, the detection methods should be portable and affordable to facilitate potential mass screening. This review paper aims to explore all possible detection methods by evaluating their proven analytical capabilities for limonene or discussing their potential usefulness, benefits, and applicability for limonene detection. Full article

(This article belongs to the Special Issue Chemical Sensors for Bio-Medical and Environmental Applications, 2nd Edition)

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18 pages, 3501 KiB

Open AccessArticle

Recognition of Tea Infusions by Optical “Smart-Tongue” Based on Microparticles Incorporated with Metalloporphyrins

by Aleksandra Kossakowska, Natalia Jędryka and Patrycja Ciosek-Skibińska

Chemosensors 2025, 13(6), 203; https://doi.org/10.3390/chemosensors13060203 - 3 Jun 2025

Abstract

Tea contains bioactive components that provide many health benefits, but overdoses can also cause health problems related to fluorosis, among other things. The analysis of tea quality is complicated due to its diverse chemical composition, and also depends on multistep processing of raw [...] Read more.

Tea contains bioactive components that provide many health benefits, but overdoses can also cause health problems related to fluorosis, among other things. The analysis of tea quality is complicated due to its diverse chemical composition, and also depends on multistep processing of raw tea leaves. In this work, chemosensitive microparticles incorporated with various metalloporphyrins that are sensitive to fluoride and chloride ions were developed. A set of seven types of microparticle suspensions was used to form an optical “smart tongue” applied for the recognition of tea infusions. Using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) for the analysis of the spectrophotometric and spectrofluorimetric responses of the microparticles, the infusions were identified with high accuracy. Moreover, the “smart tongue” enabled the discrimination according to the fluorine content and fermentation status. These results highlight the potential of chemosensitive microparticles as versatile tests in assessing tea quality. Full article

(This article belongs to the Special Issue Novel Nanocarriers-Based (Bio)Chemical Sensors in Medicine)

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27 pages, 11167 KiB

Open AccessArticle

Integrating In Situ Non-Destructive Techniques and Colourimetric Analysis to Evaluate Pigment Ageing and Environmental Effects on Tibetan Buddhist Murals

by Xiyao Li, Erdong She, Jingqi Wen, Yan Huang and Jianrui Zha

Chemosensors 2025, 13(6), 202; https://doi.org/10.3390/chemosensors13060202 - 2 Jun 2025

Abstract

The colour degradation of murals presents a significant challenge in the conservation of architectural heritage. Previous research has often concentrated on localized pigment changes while paying insufficient attention to the interaction between colour variation and indoor environmental conditions. Although non-destructive analytical techniques are [...] Read more.

The colour degradation of murals presents a significant challenge in the conservation of architectural heritage. Previous research has often concentrated on localized pigment changes while paying insufficient attention to the interaction between colour variation and indoor environmental conditions. Although non-destructive analytical techniques are widely used in heritage studies, their integrated application in combination with colourimetry has been limited, particularly in the context of Tibetan Buddhist murals in highland continental climates. This study investigates the murals of Liuli Hall in Meidai Lamasery, Inner Mongolia, as a representative case. We employed a comprehensive methodology that combines non-destructive analytical tools, gas chromatography–mass spectrometry, and quantitative colour analysis to examine pigment composition, binding material, and surface deterioration. Through joint analysis using the CIE Lab and CIE LCh colour space systems, we quantified mural colour changes and explored their correlation with material degradation and environmental exposure. The pigments identified include cinnabar, atacamite, azurite, and chalk, with animal glue and drying oils as binding materials. Colourimetric results revealed pronounced yellowing on the east and west walls, primarily caused by the ageing of organic binders. In contrast, a notable reduction in brightness on the south wall was attributed to dust accumulation. These findings support tailored conservation measures such as regular surface cleaning for the south wall and antioxidant stabilization treatments for the east and west walls. Initial cleaning efforts proved effective. The integrated approach adopted in this study provides a replicable model for mural diagnostics and conservation under complex environmental conditions. Full article

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

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16 pages, 3337 KiB

Open AccessArticle

Fabrication of Palladium-Decorated Zinc Oxide Nanostructures for Non-Enzymatic Glucose Sensing

by Reagan Aviha, Anju Joshi and Gymama Slaughter

Chemosensors 2025, 13(6), 201; https://doi.org/10.3390/chemosensors13060201 - 1 Jun 2025

Abstract

The growing global burden of diabetes necessitates the development of glucose sensors that are not only reliable and sensitive but also cost-effective and amenable to point-of-care use. In this work, we report a non-enzymatic electrochemical glucose sensor based on laser-induced graphene (LIG), functionalized [...] Read more.

The growing global burden of diabetes necessitates the development of glucose sensors that are not only reliable and sensitive but also cost-effective and amenable to point-of-care use. In this work, we report a non-enzymatic electrochemical glucose sensor based on laser-induced graphene (LIG), functionalized with zinc oxide (ZnO) and palladium (Pd) nanostructures. The ZnO nanostructures were systematically optimized on the LIG surface by varying electrochemical deposition parameters, including applied potential, temperature, and deposition time, to enhance the electrocatalytic oxidation of glucose in alkaline medium. Subsequent modification with Pd nanostructures further improved the electrocatalytic activity and sensitivity of the sensor. The performance of the LIG/ZnO/Pd sensor was investigated using chronoamperometric and cyclic voltammetric analysis in 0.1 M NaOH at an applied potential of 0.65 V. The sensor exhibited a wide dynamic range (2–10 mM; 10–24 mM) with a limit of detection of 130 μM, capturing hypo- and hyperglycemia conditions. Moreover, a sensitivity of 25.63 µA·mM⁻¹·cm⁻² was observed. Additionally, the sensor showcased selective response towards glucose in the presence of common interferents. These findings highlight the potential of the LIG/ZnO/Pd platform for integration into next-generation, non-enzymatic glucose monitoring systems for clinical and point-of-care applications. Full article

(This article belongs to the Special Issue Advanced Nanomaterials-Based (Bio)sensors for Electrochemical Detection and Analysis)

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12 pages, 9594 KiB

Open AccessArticle

An Electrochemical Sensor Based on AuNPs@Cu-MOF/MWCNTs Integrated Microfluidic Device for Selective Monitoring of Hydroxychloroquine in Human Serum

by Xuanlin Feng, Jiaqi Zhao, Shiwei Wu, Ying Kan, Honemei Li and Weifei Zhang

Chemosensors 2025, 13(6), 200; https://doi.org/10.3390/chemosensors13060200 - 1 Jun 2025

Abstract

Hydroxychloroquine (HCQ), a cornerstone therapeutic agent for autoimmune diseases, requires precise serum concentration monitoring due to its narrow therapeutic window. Current HCQ monitoring methods such as HPLC and LC-MS/MS are sensitive but costly and complex. While electrochemical sensors offer rapid, cost-effective detection, their [...] Read more.

Hydroxychloroquine (HCQ), a cornerstone therapeutic agent for autoimmune diseases, requires precise serum concentration monitoring due to its narrow therapeutic window. Current HCQ monitoring methods such as HPLC and LC-MS/MS are sensitive but costly and complex. While electrochemical sensors offer rapid, cost-effective detection, their large chambers and high sample consumption hinder point-of-care use. To address these challenges, we developed a microfluidic electrochemical sensing platform based on a screen-printed carbon electrode (SPCE) modified with a hierarchical nanocomposite of gold nanoparticles (AuNPs), copper-based metal–organic frameworks (Cu-MOFs), and multi-walled carbon nanotubes (MWCNTs). The Cu-MOF provided high porosity and analyte enrichment, MWCNTs established a 3D conductive network to enhance electron transfer, and AuNPs further optimized catalytic activity through localized plasmonic effects. Structural characterization (SEM, XRD, FT-IR) confirmed the successful integration of these components via π-π stacking and metal–carboxylate coordination. Electrochemical analyses (CV, EIS, DPV) revealed exceptional performance, with a wide linear range (0.05–50 μM), a low detection limit (19 nM, S/N = 3), and a rapid response time (<5 min). The sensor exhibited outstanding selectivity against common interferents, high reproducibility (RSD = 3.15%), and long-term stability (98% signal retention after 15 days). By integrating the nanocomposite-modified SPCE into a microfluidic chip, we achieved accurate HCQ detection in 50 μL of serum, with recovery rates of 95.0–103.0%, meeting FDA validation criteria. This portable platform combines the synergistic advantages of nanomaterials with microfluidic miniaturization, offering a robust and practical tool for real-time therapeutic drug monitoring in clinical settings. Full article

(This article belongs to the Special Issue Feature Papers on Luminescent Sensing (Second Edition))

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11 pages, 2359 KiB

Open AccessArticle

String-Shaped Electrodes for Aβ₄₂ Detection Towards Early Diagnosis of Alzheimer’s Disease

by Bianca Seufert, Sylvia Thomas and Arash Takshi

Chemosensors 2025, 13(6), 199; https://doi.org/10.3390/chemosensors13060199 - 1 Jun 2025

Abstract

Alzheimer’s disease (AD) affects a significant portion of humanity’s elderly population across the globe. Recent studies have identified Amyloid-Beta 42 (Aβ₄₂) as a key biomarker for AD. In this research, we examined the feasibility of using string-shaped electrodes to develop a [...] Read more.

Alzheimer’s disease (AD) affects a significant portion of humanity’s elderly population across the globe. Recent studies have identified Amyloid-Beta 42 (Aβ₄₂) as a key biomarker for AD. In this research, we examined the feasibility of using string-shaped electrodes to develop a potentially wearable biosensor for the early detection of AD. Two types of flexible electrochemical electrodes were fabricated using a commercial thread (25% cotton-75% polyester) and an electrospun nanofiber-based string. Decorating the strings with either gold or SiC nanoparticles, several different electrodes were tested to explore their responses to Aβ₄₂. Our results show that the nanofiber-based electrode decorated with gold nanoparticles had the highest sensitivity of 1.71 µA/pg.cm and the best limit of detection (LoD) of 8.36 pg/mL. These findings highlight the importance of the string structure in designing highly sensitive sensors. Full article

(This article belongs to the Special Issue Low-Cost Chemosensors for Applications in Environment, Health, Food, and Industry Process Control, 2nd Edition)

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15 pages, 1993 KiB

Open AccessArticle

Compact Dual-Wavelength Optical Fiber Sensor for the Simultaneous Measurement of the Refractive Index and Temperature of Liquid Samples

by Karla Ivonne Serrano-Arévalo, Erika Rodríguez-Sevilla, Monserrat Alonso-Murias, Héctor Pérez-Aguilar and David Monzón-Hernández

Chemosensors 2025, 13(6), 198; https://doi.org/10.3390/chemosensors13060198 - 28 May 2025

Abstract

This study proposes the development of a dual-wavelength optical fiber sensor (DWOFS) that integrates two optical fiber structures in a multimode transmission line to measure the refractive index and temperature of a liquid concurrently. One structure is based on a refractive index sensor [...] Read more.

This study proposes the development of a dual-wavelength optical fiber sensor (DWOFS) that integrates two optical fiber structures in a multimode transmission line to measure the refractive index and temperature of a liquid concurrently. One structure is based on a refractive index sensor that utilizes surface plasmon resonance, comprising a 5 mm long single-mode fiber (SMF) section coated with chromium/gold (Cr/Au) films. The secondary structure employs a multimode interferometer with a 29 mm long no-core fiber (NCF) section covered with a thick layer of polydimethylsiloxane (PDMS) to measure temperature. The measurements obtained reveal two distinct drops in the transmission spectrum at approximately 600 nm and 1550 nm, respectively, enabling precise measurement of the two parameters. The sensor demonstrates a high degree of sensitivity to both refractive index and temperature, spanning the visible (

2770.30 n m / R I U

) and infrared

(- 0.178 n m / ° C

) regions of the spectra, respectively. Furthermore, the thermo-optical coefficient for water

({- 0.9928 \times 10}^{- 4} R I U / ° C)

was estimated. The proposed sensor offers a compact solution for the simultaneous measurement of refractive index and temperature in liquid samples for a variety of applications, including biological, environmental, and healthcare research. Full article

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

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14 pages, 2039 KiB

Open AccessArticle

Carbon and Nitrogen Surface Contamination Contributions in ZnO Nanowire Based Hydrogen Sensing

by Aurelian Marcu, Sorin Vizireanu, Razvan Mihalcea, Veronica Satulu, Maria Balan, Marius Dumitru, Valentin Craciun, Catalin Constantin and Cristian Viespe

Chemosensors 2025, 13(6), 197; https://doi.org/10.3390/chemosensors13060197 - 27 May 2025

Abstract

Hexagonal ZnO nanowires were grown using the PLD/VLS technique on a SAW sensor active area for hydrogen sensing. The influence of different carbon and nitrogen surface contaminant concentrations on sensor output was investigated for three active area cases: a few weeks’ exposure to [...] Read more.

Hexagonal ZnO nanowires were grown using the PLD/VLS technique on a SAW sensor active area for hydrogen sensing. The influence of different carbon and nitrogen surface contaminant concentrations on sensor output was investigated for three active area cases: a few weeks’ exposure to free ambient air contamination, 3 h at 600 °C thermal desorption of carbon, and (room temperature) plasma-activated nitrogen and carbon contamination. Correlations between sensing performance and contamination element concentration were established. To understand the adsorption versus absorption mechanisms, similar studies were further performed on circular ZnO nanowires morphology, which have a different surface-area-to-volume ratio. Comparative results show that, while a 20% carbon surface contamination variation generates a variation of 3–5% in nanostructure hydrogen sorption, nitrogen surface contamination influence depends on nanostructure morphology. Thus, in our comparative studies, for the case of a nanowire hexagonal cross-section a 12% nitrogen surface contamination variation generates a 5–7% increase in hydrogen adsorption and also an increase of 6–8% in hydrogen absorption. Consequently, the catalytic effect of nitrogen could enlarge the linear response of nanowire-based (SAW) sensors over a wider hydrogen concentration range. Full article

(This article belongs to the Special Issue Novel Materials for Gas Sensing)

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12 pages, 6918 KiB

Open AccessArticle

Differentiation of Species and Provenance of Palm-Leaf Manuscripts Using Fourier Transform Infrared Spectroscopy and Chemometrics

by Lucas F. Voges, Nils Horn, Giovanni Ciotti and Stephan Seifert

Chemosensors 2025, 13(6), 196; https://doi.org/10.3390/chemosensors13060196 - 27 May 2025

Abstract

For authentication and interpretation of palm-leaf manuscripts, material analyses are required that enable identification of specific characteristics of written artefacts. In this study, we apply infrared spectroscopy (DRIFTS) in combination with principal component analysis (PCA) as a fingerprinting technique for the analysis of [...] Read more.

For authentication and interpretation of palm-leaf manuscripts, material analyses are required that enable identification of specific characteristics of written artefacts. In this study, we apply infrared spectroscopy (DRIFTS) in combination with principal component analysis (PCA) as a fingerprinting technique for the analysis of eleven palm-leaf manuscripts. We demonstrate that manuscript-specific information is obtained and that a differentiation regarding the taxonomic species of palm leaves used for production and of their geographical origin in South and Southeast Asia is possible. The results show the potential of infrared spectroscopy for fingerprinting and authentication of written artefacts. Full article

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

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