Chemosensors

13 pages, 2716 KiB

Open AccessArticle

Banana Flour Adulteration Key Marker Unravelled by Inductively Coupled Plasma Optical Emission Spectrometry Assisted by Chemometric Tools

by Silvio Luiz Fernandes Júnior, Paula Mothé Gonçalves, Diego Barros Batista, Aderval S. Luna, Fernanda Nunes Ferreira, Licarion Pinto and Jefferson Santos de Gois

Chemosensors 2025, 13(4), 153; https://doi.org/10.3390/chemosensors13040153 - 21 Apr 2025

Abstract

Green banana flour has been gaining prominence as a functional food due to its high nutritional value and health benefits. However, its increasing commercialization has also raised concerns about adulteration, which can compromise both product quality and consumer confidence. In this study, we [...] Read more.

Green banana flour has been gaining prominence as a functional food due to its high nutritional value and health benefits. However, its increasing commercialization has also raised concerns about adulteration, which can compromise both product quality and consumer confidence. In this study, we propose a simple method to detect adulteration in banana flour using ICP-OES combined with chemometric tools. A total of 73 samples, including authentic and adulterated flours, were analyzed for their mineral composition (B, Ca, Cu, Fe, Mn, P, K, Mg, and Na). The limit of detection was determined for all analytes, being 0.005 µg g⁻¹ (Ca), 0.007 µg g⁻¹ (K), 0.02 µg g⁻¹ (Mg), 0.04 µg g⁻¹ (Na), 0.001 µg g⁻¹ (P), 3 µg g⁻¹ (B), 1.4 µg g⁻¹ (Cu), 0.4 µg g⁻¹ (Fe), and 3 µg g⁻¹ (Mn). Applying chemometric techniques, such as Principal Component Analysis, Linear Discriminant Analysis, and Partial Least Squares Discriminant Analysis, allowed us to distinguish the authentic samples from the adulterated ones clearly. With the help of chemometric tools, it was found that K is a key marker to identify adulteration. The applied techniques demonstrated high precision in detecting adulterations and providing a confidence limit to identify banana flour fraud, proving to be a promising tool for ensuring the authenticity of green banana flour. Full article

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

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20 pages, 8464 KiB

Open AccessArticle

Influence of Different Synthesis Methods on the Defect Structure, Morphology, and UV-Assisted Ozone Sensing Properties of Zinc Oxide Nanoplates

by Pedro P. Ortega, João V. N. Palma, Ana L. Doimo, Laura Líbero, Gabriel F. Yamakawa, Leonnam G. Merízio, Ederson C. Aguiar, Luís F. Silva and Elson Longo

Chemosensors 2025, 13(4), 152; https://doi.org/10.3390/chemosensors13040152 - 20 Apr 2025

Abstract

In this work, room-temperature UV-assisted ozone detection was investigated using ZnO nanoplates synthesized via precipitation, ultrasound-, ultrasonic tip-, and microwave-assisted hydrothermal (MAH) methods. X-ray diffraction confirmed the formation of crystalline phases with an ~3.3 eV band gap, independent of the synthesis used. Raman [...] Read more.

In this work, room-temperature UV-assisted ozone detection was investigated using ZnO nanoplates synthesized via precipitation, ultrasound-, ultrasonic tip-, and microwave-assisted hydrothermal (MAH) methods. X-ray diffraction confirmed the formation of crystalline phases with an ~3.3 eV band gap, independent of the synthesis used. Raman spectroscopy revealed oxygen-related defects. Plate-like morphologies were observed, with the ultrasonic tip-assisted synthesis yielding ~17 nm-thick plates. Electrical measurements showed 10–170 ppb ozone sensitivity under UV. The sample synthesized via the MAH method (ZM) demonstrated superior conductance, with a baseline resistance of ~1.2% for the ultrasound (ZU) sample and less than 50% for the precipitation (ZA) and ultrasonic tip (ZP) samples. Despite the appreciable response in dark mode, the recovery was slow (>>30 min), except for the UV illumination condition, which reduced the recovery response to ~2 min. With top areas of ~0.0122 µm², ZP and ZU showed high specific surface areas (24.75 and 19.37 m²/g, respectively), in contrast to ZM, which exhibited the lowest value (15.32 m²/g) with a top area of ~0.0332 µm² and a thickness of 26.0 nm. The superior performance of ZM was attributed to the larger nanoplate sizes and the lower baseline resistance. The ultrasound method showed the lowest sensitivity due to the higher resistance and the depletion layer effect. The results indicate that the synthesis methods presented herein for the production of reactive ZnO nanoplates using NaOH as a growth-directing agent are reliable, simple, and cost-effective, in addition to being capable of detecting ozone with high sensitivity and reproducibility at concentrations as low as 10 ppb. Full article

(This article belongs to the Special Issue Recent Progress on Sensors and Smart Systems for In-Situ Gas Monitoring)

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21 pages, 14047 KiB

Open AccessArticle

Characteristics of Peanut Protein-Derived Carbon Dots and Their Application in Cell Imaging and Sensing of Metronidazole

by Junyan Liao, Zhixiong Hu, Weinong Zhang, Yanpeng Zhang, Jiangrong Xiao and Shenglan Lei

Chemosensors 2025, 13(4), 151; https://doi.org/10.3390/chemosensors13040151 - 19 Apr 2025

Viewed by 44

Abstract

In this paper, peanut protein (PP) was used as the sole raw material for the preparation of fluorescent carbon dots (PP-CDs) by hydrothermal method. The PP-CDs exhibit good dispersibility, spherical-like shapes, and uniform sizes; the average particle size of the PP-CDs was 3.18 [...] Read more.

In this paper, peanut protein (PP) was used as the sole raw material for the preparation of fluorescent carbon dots (PP-CDs) by hydrothermal method. The PP-CDs exhibit good dispersibility, spherical-like shapes, and uniform sizes; the average particle size of the PP-CDs was 3.18 ± 0.17 nm. The Fourier transform infrared spectroscopy (FTIR) results show that the surface of PP-CDs is rich in hydrophilic groups such as hydroxyl, carboxyl and amide groups. The PP-CDs exhibit good fluorescence emission properties and excitation wavelength dependence, with the optimal excitation wavelength and emission wavelength at 348 nm and 452 nm, respectively. According to the fluorescence quenching effect of metronidazole (MTZ) and tinidazole (TDZ) on PP-CDs, a highly linear fluorescence sensor was established, with a concentration range of 0.10–60.0 µM, and the detection limits of MTZ and TDZ are 32.0 nM and 48.0 nM, respectively. The result of CCK-8 test and imaging of HepG-2 cells and onion epidermal cells reveal that PP-CDs have good membrane permeability, biocompatibility and imaging ability. Full article

(This article belongs to the Section (Bio)chemical Sensing)

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18 pages, 4156 KiB

Open AccessArticle

Influence of P(V3D3-co-TFE) Copolymer Coverage on Hydrogen Detection Performance of a TiO₂ Sensor at Different Relative Humidity for Industrial and Biomedical Applications

by Mihai Brinza, Lynn Schwäke, Lukas Zimoch, Thomas Strunskus, Thierry Pauporté, Bruno Viana, Tayebeh Ameri, Rainer Adelung, Franz Faupel, Stefan Schröder and Oleg Lupan

Chemosensors 2025, 13(4), 150; https://doi.org/10.3390/chemosensors13040150 - 19 Apr 2025

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Abstract

The detection of hydrogen gas is crucial for both industrial fields, as a green energy carrier, and biomedical applications, where it is a biomarker for diagnosis. TiO₂ nanomaterials are stable and sensitive to hydrogen gas, but their gas response can be negatively [...] Read more.

The detection of hydrogen gas is crucial for both industrial fields, as a green energy carrier, and biomedical applications, where it is a biomarker for diagnosis. TiO₂ nanomaterials are stable and sensitive to hydrogen gas, but their gas response can be negatively affected by external factors such as humidity. Therefore, a strategy is required to mitigate these influences. The utilization of organic–inorganic hybrid gas sensors, specifically metal oxide gas sensors coated with ultra-thin copolymer films, is a relatively novel approach in this field. In this study, we examined the performance and long-term stability of novel TiO₂-based sensors that were coated with poly(trivinyltrimethylcyclotrisiloxane-co-tetrafluoroethylene) (P(V3D3-co-TFE)) co-polymers. The P(V3D3-co-TFE)/TiO₂ hybrid sensors exhibit high reliability even for more than 427 days. They exhibit excellent hydrogen selectivity, particularly in environments with high humidity. An optimum operating temperature of 300 °C to 350 °C was determined. The highest recorded response to H₂ was approximately 153% during the initial set of measurements at a relative humidity of 10%. The developed organic–inorganic hybrid structures open wide opportunities for gas sensor tuning and customization, paving the way for innovative applications in industry and biomedical fields, such as exhaled breath analysis, etc. Full article

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

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20 pages, 5758 KiB

Open AccessReview

Innovative Microfluidic Technologies for Rapid Heavy Metal Ion Detection

by Muhammad Furqan Rauf, Zhenda Lin, Muhammad Kamran Rauf and Jin-Ming Lin

Chemosensors 2025, 13(4), 149; https://doi.org/10.3390/chemosensors13040149 - 18 Apr 2025

Viewed by 185

Abstract

Heavy metal ion (HMI) contamination poses significant threats to public health and environmental safety, necessitating advanced detection technologies that are rapid, sensitive, and field-deployable. While conventional methods like atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) remain prevalent, their limitations—including [...] Read more.

Heavy metal ion (HMI) contamination poses significant threats to public health and environmental safety, necessitating advanced detection technologies that are rapid, sensitive, and field-deployable. While conventional methods like atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) remain prevalent, their limitations—including high costs, complex workflows, and lack of portability—underscore the urgent need for innovative alternatives. This review consolidates advancements in the last five years in microfluidic technologies for HMI detection, emphasizing their transformative potential through miniaturization, integration, and automation. We critically evaluate the synergy of microfluidics with cutting-edge materials (e.g., graphene and quantum dots) and detection mechanisms (electrochemical, optical, and colorimetric), enabling ultra-trace detection at parts-per-billion (ppb) levels. We highlight novel device architectures, such as polydimethylsiloxane (PDMS)-based labs-on-chip (LOCs), paper-based microfluidics, 3D-printed systems, and digital microfluidics (DMF), which offer unparalleled portability, cost-effectiveness, and multiplexing capabilities. Additionally, we address persistent challenges (e.g., selectivity and scalability) and propose future directions, including AI integration and sustainable fabrication. By bridging gaps between laboratory research and practical deployment, this review provides a roadmap for next-generation microfluidic solutions, positioning them as indispensable tools for global HMI monitoring. Full article

(This article belongs to the Special Issue Feature Review Papers in Chemical/Bio-Sensors and Analytical Chemistry in 2025)

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22 pages, 17549 KiB

Open AccessArticle

Monitoring of Indoor Air Quality in a Classroom Combining a Low-Cost Sensor System and Machine Learning

by Ioannis D. Apostolopoulos, Eleni Dovrou, Silas Androulakis, Katerina Seitanidi, Maria P. Georgopoulou, Angeliki Matrali, Georgia Argyropoulou, Christos Kaltsonoudis, George Fouskas and Spyros N. Pandis

Chemosensors 2025, 13(4), 148; https://doi.org/10.3390/chemosensors13040148 - 18 Apr 2025

Viewed by 149

Abstract

Monitoring indoor air quality in schools is essential, particularly as children are highly vulnerable to air pollution. This study evaluates the performance of the low-cost sensor-based air quality monitoring system ENSENSIA, during a 3-week campaign in an elementary school classroom in Athens, Greece. [...] Read more.

Monitoring indoor air quality in schools is essential, particularly as children are highly vulnerable to air pollution. This study evaluates the performance of the low-cost sensor-based air quality monitoring system ENSENSIA, during a 3-week campaign in an elementary school classroom in Athens, Greece. The system measured PM_2.5, CO, NO, NO₂, O₃, and CO₂. High-end instrumentation provided the reference concentrations. The aim was to assess the sensors’ performance in estimating the average day-to-day exposure, capturing temporal variations and the degree of agreement among different sensor units, with particular attention to the impact of machine learning (ML) calibration. Using the factory calibration settings, the CO₂ and PM_2.5 sensors showed strong inter-unit consistency for hourly averaged values. The other sensors, however, exhibited inter-unit variability, with differences in the reported average day-to-day concentrations ranging from 20% to 160%. ML-based calibration was investigated for the CO, NO, NO₂, and O₃ sensors using measurements by reference instruments for training and evaluation. Among the eleven ML algorithms tested, the Support Vector Regression performed better for the calibration of the CO, NO₂, and O₃ sensors. The NO sensor was better calibrated using the Elastic Net algorithm. The inter-unit variability was reduced by a factor of two after the ML calibration. The daily average error compared to the reference measured was also reduced by approximately 15–50% depending upon the sensor. Full article

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

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12 pages, 2088 KiB

Open AccessArticle

Enzyme Inhibition-Mediated Distance-Based Paper Biosensor for Organophosphate Pesticide Detection in Food Samples

by Yulin Liu, Longzhan Dong, Qiognzheng Hu, Jingbo Chen and Mashooq Khan

Chemosensors 2025, 13(4), 147; https://doi.org/10.3390/chemosensors13040147 - 16 Apr 2025

Viewed by 196

Abstract

Organophosphate pesticides (OPs) enter the environment through various avenues, posing significant health risks. This highlights the need to monitor OPs in food and environmental samples. This study introduces an enzyme inhibition-mediated distance-based paper (EIDP) biosensor designed for naked-eye visual detection of OPs in [...] Read more.

Organophosphate pesticides (OPs) enter the environment through various avenues, posing significant health risks. This highlights the need to monitor OPs in food and environmental samples. This study introduces an enzyme inhibition-mediated distance-based paper (EIDP) biosensor designed for naked-eye visual detection of OPs in food samples. We synthesized a copper alginate (Cu-Alg) hydrogel that traps water within the gel and restricts water flow on pH paper. When incubated with acetylcholinesterase (AChE) and acetylthiocholine (ATCh), the enzyme activity of AChE on ATCh generates thiocholine, which interacts with the Cu²⁺ ions in the gel. This interaction alters the gel’s 3D structure, releasing the trapped water onto the pH paper. Conversely, when AChE is exposed to OPs, its activity is inhibited, limiting the water flow from the gel. As a result, OPs are quantified by measuring the reduction in water flow distance within a linear range of 18 to 105 ng/mL, with a lower detection limit of 18 ng/mL. The EIDP biosensor exhibits high selectivity for OP detection and successfully analyzes OPs in pumpkin and rice samples, achieving percent recoveries ranging from 93% to 103%. This method offers a straightforward, portable, instrument-free, and cost-effective solution for detecting OPs in food samples. Full article

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

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18 pages, 3643 KiB

Open AccessReview

Engineered Intelligent Electrochemical Biosensors for Portable Point-of-Care Diagnostics

by Jiamin Lin, Yuanyuan Chen, Xiaohui Liu, Hui Jiang and Xuemei Wang

Chemosensors 2025, 13(4), 146; https://doi.org/10.3390/chemosensors13040146 - 16 Apr 2025

Viewed by 189

Abstract

The development of cost-effective, rapid-response, and user-friendly biosensing platforms has become paramount importance for achieving precise biomarker quantification in early disease detection. Implementing timely diagnostic interventions through accurate biomarker analysis not only significantly improves treatment outcomes but also enables effective disease management strategies, [...] Read more.

The development of cost-effective, rapid-response, and user-friendly biosensing platforms has become paramount importance for achieving precise biomarker quantification in early disease detection. Implementing timely diagnostic interventions through accurate biomarker analysis not only significantly improves treatment outcomes but also enables effective disease management strategies, ultimately leading to substantial reductions in patient mortality rates. These clinical imperatives have consequently driven the innovation of portable point-of-care (POC) diagnostic systems. Electrochemical biosensors are attractive in the early diagnosis of diseases due to their low cost, simple operation, and high sensitivity. This review examines prevalent material innovations in electrode functionalization for electrochemical biosensing platforms, with specific emphasis on their translational applications in early-stage disease detection. The analysis included three important early diagnostic biomarker types: proteins, nucleic acids, and small molecule metabolites. Furthermore, the work proposes novel research trajectories for next-generation biosensor development, advocating the synergistic integration of artificial intelligence-driven analytics, Internet of Medical Things (IoMT)-enabled diagnostic networks, and advanced micro/nanofabrication techniques. Full article

(This article belongs to the Special Issue Electrochemical Sensing in Medical Diagnosis)

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40 pages, 12301 KiB

Open AccessReview

Luminescent Pyrene-Derivatives for Hg²⁺ and Explosive Detection

by Muthaiah Shellaiah, Kien-Wen Sun, K. Anandan, Arumugam Murugan, Vijayaraj Venkatachalam, Mayank Bhushan, Mani Sivakumar, E. Manikandan, Kumaravel Kaliaperumal and Wen-Tai Li

Chemosensors 2025, 13(4), 145; https://doi.org/10.3390/chemosensors13040145 - 14 Apr 2025

Viewed by 266

Abstract

Mercury and explosives are well-known hazards that affect the environment and threaten society. Mercury generally exists as inorganic mercuric (Hg²⁺) salts, and its detection via fluorometric response is highly notable. Likewise, mainstream explosives contains a nitro (−NO₂) moiety as [...] Read more.

Mercury and explosives are well-known hazards that affect the environment and threaten society. Mercury generally exists as inorganic mercuric (Hg²⁺) salts, and its detection via fluorometric response is highly notable. Likewise, mainstream explosives contains a nitro (−NO₂) moiety as a functional unit, and numerous reports have quantified them using fluorescence quenching. Among the available literature, there are still noticeable concerns about the environmental and biological applicability of luminescent pyrene derivaives-tunedfluorometric detection of Hg²⁺ and explosives. In the presence of Hg²⁺ ions, pyrene derivatives tend to form excimers, which can be tuned to the chelation-enhanced fluorescence (CHEF), photo-induced electron transfer (PET), or fluorescence resonance energy transfer (FRET), etc., to exhibit “Turn-On” or “Turn-Off” fluorescence responses. On the other hand, π-π stacking of emissive pyrene-derivatives may lead to J- or H-type aggregation via self-excimers (Py-Py*), which has been found to be quenched/enhanced by explosive hazards. In fact, −NO₂-containing explosives interact with pyrene derivatives, leading to exceptional fluorescence quenching or enhancement. This review details the use of pyrene derivatives toward the sensing of Hg²⁺ and explosives with demonstrated applications. Further, the design requirements, sensory mechanisms, advantages, limitations, and the future scope of using the reported pyrene derivatives in Hg²⁺ and explosives sensing are discussed. Full article

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

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10 pages, 1406 KiB

Open AccessArticle

A Photochemical Vapor Generation Method for the Determination of Hg and Pb in Imitation Jewelry by Inductively Coupled Plasma Optical Emission Spectrometry

by Fernanda P. Braga and Jefferson Santos de Gois

Chemosensors 2025, 13(4), 144; https://doi.org/10.3390/chemosensors13040144 - 14 Apr 2025

Viewed by 152

Abstract

The monitoring of contaminants in imitation jewelry has become important nowadays due to the high amount of products sold worldwide. Due to the complexity of the sample matrix (composed mainly of metals in high concentration), sample analysis can be very challenging. One interesting [...] Read more.

The monitoring of contaminants in imitation jewelry has become important nowadays due to the high amount of products sold worldwide. Due to the complexity of the sample matrix (composed mainly of metals in high concentration), sample analysis can be very challenging. One interesting alternative for this purpose is the use of photochemical vapor generation coupled to inductively coupled plasma optical emission spectrometry (PVG-ICP-OES) due to the ability of separating the analytes from the sample solution prior to analysis; additionally, it is considered an eco-friendly approach if compared to other vapor generation techniques. Thus, this work presents the development and application of a PVG-ICP-OES system for the determination of Hg and Pb in imitation jewelry after sample dissolution in hydrochloric acid. The PVG system was built with two UV lamps (254 nm), a quartz capillary reactor, and a glass gas-liquid separator. Acetic acid concentration and UV exposure time were optimized using a central composite design, as well as the carrier gas flow rate and the radiofrequency (RF) power for the ICP-OES. The optimum conditions were achieved at 30% v/v acetic acid, 60 s reaction time, 0.035 L min⁻¹ carrier gas flow rate, and 1310 W for RF power. The influence of the sample matrix and chemical modifiers were studied, where it was found that the presence of the sample matrix may cause suppression of the analytical signal. The accuracy of the method was evaluated by recovery tests, which ranged from 88 to 102%. The detection limits ranged from 1 to 3 mg g⁻¹, allowing the monitoring of Hg and Pb in imitation jewelry. Full article

(This article belongs to the Special Issue Green Analytical Methods for Environmental and Food Analysis)

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20 pages, 3507 KiB

Open AccessReview

Biosensors for Micro- and Nanoplastics Detection: A Review

by Maria Daoutakou and Spyridon Kintzios

Chemosensors 2025, 13(4), 143; https://doi.org/10.3390/chemosensors13040143 - 14 Apr 2025

Viewed by 288

Abstract

Microplastics (MPs) and nanoplastics (NPs), which are widespread in many habitats as the byproducts of various industrial processes, pose considerable environmental and health hazards. However, current, conventional methods for detecting and characterizing them are considerably lacking in throughput, sensitivity, reliability, and field deployability. [...] Read more.

Microplastics (MPs) and nanoplastics (NPs), which are widespread in many habitats as the byproducts of various industrial processes, pose considerable environmental and health hazards. However, current, conventional methods for detecting and characterizing them are considerably lacking in throughput, sensitivity, reliability, and field deployability. In the current report, we review the state of the art in biosensor-based MP/NP detection, in particular, describing advances in optical and electrochemical approaches, along with the development of novel biorecognition elements and the application of bioinformatics tools. Full article

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

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17 pages, 7423 KiB

Open AccessArticle

Development of Polyphenol–Metal Film-Modified Colored Porous Microspheres for Enhanced Monkeypox Antigen Detection

by Wei-Zhi Zhang, Chen-Fei Zhang and Shou-Nian Ding

Chemosensors 2025, 13(4), 142; https://doi.org/10.3390/chemosensors13040142 - 12 Apr 2025

Viewed by 203

Abstract

The Monkeypox virus (MPXV), a DNA virus classified under the Orthpoxvirus genus alongside variola virus, has recently garnered significant global health attention due to its increasing transmission and emerging genomic mutations. Point-of-care testing is essential for effective clinical response and outbreak mitigation. In [...] Read more.

The Monkeypox virus (MPXV), a DNA virus classified under the Orthpoxvirus genus alongside variola virus, has recently garnered significant global health attention due to its increasing transmission and emerging genomic mutations. Point-of-care testing is essential for effective clinical response and outbreak mitigation. In this article, we developed a novel class of colored microspheres designed for application in a lateral flow immunoassay (LFIA) platform targeting MPXV-specific biomarkers. Polystyrene-maleic anhydride (SMA-MAA) microspheres were synthesized with a high-temperature soap-free emulsion polymerization optimized in our lab. Subsequent alkali and acid treatments were employed to introduce porosity into the microsphere matrix. Solvent Red 27 and Disperse Red 60 were incorporated via solvent-swelling and thermal-swelling methods, respectively, to generate high brightness (HB) carriers. A surface coating composed of a tannic acid–iron (TA–Fe³⁺) coordination complex was applied to form a stable metal–polyphenol film (MPF). This coating not only minimized dye leaching by establishing a robust shell but also improved dye distribution, thereby enhancing overall color intensity. The final HB-LFIA system, configured in a sandwich immunoassay format, demonstrated favorable sensitivity and linear detection range for Monkeypox antigen, indicating strong potential for clinical diagnostic use. Full article

(This article belongs to the Special Issue Application of Luminescent Materials for Sensing, 2nd Edition)

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12 pages, 3153 KiB

Open AccessArticle

Sensitive Detection of Aflatoxin B1 in Foods Using Aptasensing Based on FGO-Mediated CdTe QDs

by Puye Liang, Sihan Liu, Qinqing Han, Kaixuan Zhou, Tiange Li, Xianqing Huang, Lianjun Song and Tianlin Wang

Chemosensors 2025, 13(4), 141; https://doi.org/10.3390/chemosensors13040141 - 11 Apr 2025

Viewed by 212

Abstract

Aflatoxin B₁ (AFB₁) exhibits high toxicity and has the potential to induce cancer, deformities, and mutations. It is therefore highly desirable that sensitive and straightforward methods for detecting AFB₁ be developed. In this study, due to the high specific [...] Read more.

Aflatoxin B₁ (AFB₁) exhibits high toxicity and has the potential to induce cancer, deformities, and mutations. It is therefore highly desirable that sensitive and straightforward methods for detecting AFB₁ be developed. In this study, due to the high specific adsorption capacity of AFB₁ aptamers, we applied a sensing strategy based on quantum dots (QDs) and carboxyl-functionalized graphene oxide (FGO) to construct a simple fluorescence quenching platform. FGO and CdTe QDs modified with AFB₁ aptamers cause a FRET effect that produces CdTe QDs with yellow-green fluorescence quenching. When AFB₁ is present, aptamers form complexes with it and CdTe QDs leave the quenching platform, resulting in fluorescence recovery. In this study, we used a fluorescence aptasensor with a wide detection range of 0.05 to 150 ng/mL and a low limit of detection (LOD) of 8.2 pg/mL. The average recoveries of AFB₁ in peanut and pure milk samples ranged from 94.5% to 107.0%. The aptasensor also exhibited the advantages of simple operation, low cost, and good stability. The sensing strategy reported here can thus serve as a potential candidate for the rapid detection of AFB_1. Full article

(This article belongs to the Special Issue Advanced Biosensors for Point-of-Care Testing in Analytical Chemistry)

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20 pages, 3366 KiB

Open AccessArticle

Design, Fabrication and Validation of Chemical Sensors for Detecting Hydrocarbons to Facilitate Oil Spillage Remediation

by Perpetual Eze-Idehen and Krishna Persaud

Chemosensors 2025, 13(4), 140; https://doi.org/10.3390/chemosensors13040140 - 11 Apr 2025

Viewed by 205

Abstract

To address the environmental hazards posed by oil spills and the limitations of conventional hydrocarbon monitoring techniques, a cost-effective and user-friendly gas sensor system was developed for the real-time detection and quantification of hydrocarbon contaminants in soil. This system utilizes carbon black (CB)-filled [...] Read more.

To address the environmental hazards posed by oil spills and the limitations of conventional hydrocarbon monitoring techniques, a cost-effective and user-friendly gas sensor system was developed for the real-time detection and quantification of hydrocarbon contaminants in soil. This system utilizes carbon black (CB)-filled poly(methyl methacrylate) (PMMA) and poly(vinyl chloride) (PVC) nanocomposites to create chemoresistive sensors. The CB-PMMA and CB-PVC composites were synthesized and deposited as thin films onto interdigitated electrodes, with their morphologies characterized using scanning electron microscopy. The composites, optimized at a composition of 10% w/w CB and 90% w/w polymer, exhibited a sensitive response to hydrocarbon vapors across a tested range from C₂₀ (99 ppmV) to C₈ (8750 ppmV). The sensor’s response mechanism is primarily attributed to the swelling-induced resistance change of the amorphous polymer matrix in hydrocarbon vapors. These findings demonstrate the potential use of CB–polymer composites as field-deployable gas sensors, providing a rapid and efficient alternative to traditional gas chromatography methods for monitoring soil remediation efforts and mitigating the environmental impact of oil contamination. Full article

(This article belongs to the Special Issue 10th Anniversary of Chemosensors—Section 'Materials for Chemical Sensing')

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14 pages, 2621 KiB

Open AccessArticle

Silica Optical Fibers Connected via a Micro MIP-Core Waveguide to Build Optical-Chemical Sensors

by Rosalba Pitruzzella, Chiara Marzano, Francesco Arcadio, Filipa Sequeira, Alessandra Cutaia, Catarina Cardoso Novo, Ricardo Oliveira, Maria Pesavento, Luigi Zeni, Rogerio Nunes Nogueira, Nunzio Cennamo and Giancarla Alberti

Chemosensors 2025, 13(4), 139; https://doi.org/10.3390/chemosensors13040139 - 10 Apr 2025

Viewed by 243

Abstract

Molecularly imprinted polymers (MIPs) can be combined with optical fibers (OFs) to create various sensor configurations, yielding low-cost and highly sensitive extrinsic and intrinsic sensors. In this work, an MIP-based extrinsic optical fiber sensor is obtained by two silica OFs connected via an [...] Read more.

Molecularly imprinted polymers (MIPs) can be combined with optical fibers (OFs) to create various sensor configurations, yielding low-cost and highly sensitive extrinsic and intrinsic sensors. In this work, an MIP-based extrinsic optical fiber sensor is obtained by two silica OFs connected via an optical waveguide using an MIP as a core of micrometer size (micro OF-MIP-OF sensor). The proposed sensing approach can be used only with MIP receptors and implements an intensity-based sensor configuration. MIPs present several advantages over bio-receptors and can be exploited to realize novel sensing methods. The MIP used in this work is specifically designed for 2-furaldehyde (2-FAL) detection, and the experimental results demonstrate that the micro-probe performs well in terms of sensitivity and selectivity, with capabilities applicable to several application fields. In particular, a nanomolar detection range, from 1.5 nM to 150 nM, has been achieved. Moreover, the results are comparable to or better than those of other previously proposed MIP optical fiber sensors for 2-FAL, which employ more complex sensing principles or fabrication steps. Full article

(This article belongs to the Special Issue The Recent Progress and Applications of Optical Chemical Sensors)

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13 pages, 3236 KiB

Open AccessArticle

Detection of Ammonia Nitrogen in Neutral Aqueous Solutions Based on In Situ Modulation Using Ultramicro Interdigitated Array Electrode Chip

by Yuqi Liu, Nan Qiu, Zhihao Zhang, Yang Li and Chao Bian

Chemosensors 2025, 13(4), 138; https://doi.org/10.3390/chemosensors13040138 - 9 Apr 2025

Viewed by 243

Abstract

In this study, an in situ electrochemical modulation method based on an ultramicro interdigitated array electrode (UIAE) sensor chip was developed for the detection of ammonia nitrogen (NH₃-N) in neutral aqueous solutions. One comb of the UIAE was used as the [...] Read more.

In this study, an in situ electrochemical modulation method based on an ultramicro interdigitated array electrode (UIAE) sensor chip was developed for the detection of ammonia nitrogen (NH₃-N) in neutral aqueous solutions. One comb of the UIAE was used as the working electrode for both the modulating and sensing functions, while the other comb was used as the counter electrode. Utilizing its enhanced mass transfer and proximity effects, the feasibility of in situ modulation of the solution environment near the UIAE chip to generate an electrochemical response for NH₃-N was investigated using electrochemical methods. The proposed method enhances the concentration of hydroxide ions and active chloride in the local solution near the sensor chip. These reactive species play a key role in improving the sensor’s electrocatalytic oxidation capability toward ammonia nitrogen, facilitating the sensitive detection of ammonia nitrogen in neutral environments. A linear relationship was displayed, ranging from 0.15–2.0 mg/L (as nitrogen) with a sensitivity of 3.7936 µA·L·mg⁻¹ (0.0664 µA µM⁻¹ mm⁻²), which was 2.45 times that in strong alkaline conditions without modulation. Additionally, the relative standard deviation of the measurement remained below 2.9% over five days of repeated experiments, indicating excellent stability. Full article

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

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21 pages, 7498 KiB

Open AccessArticle

Evaluating the Intensity of Bitter–Astringent Interactive Perception in Green Tea Based on the Weber–Fechner Law

by Siying Li, Dongdong Du, Shaoming Cheng and Zhenbo Wei

Chemosensors 2025, 13(4), 137; https://doi.org/10.3390/chemosensors13040137 - 9 Apr 2025

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Abstract

This study aimed to quantify the bitter–astringent interactive perceived intensity (BAIPI) of green tea based on the Weber–Fechner law by two-alternative forced choice test. Caffeine, (-)-epigallocatechin-3-gallate (EGCG), and Quercetin-3-o-rutinoside (Que-rut) were identified as the key bitter–astringent compounds. Then, BAIPI values were assessed based [...] Read more.

This study aimed to quantify the bitter–astringent interactive perceived intensity (BAIPI) of green tea based on the Weber–Fechner law by two-alternative forced choice test. Caffeine, (-)-epigallocatechin-3-gallate (EGCG), and Quercetin-3-o-rutinoside (Que-rut) were identified as the key bitter–astringent compounds. Then, BAIPI values were assessed based on the concentration ratios and ranges of caffeine, EGCG, and Que-rut in green tea according to the Weber–Fechner law. The BAIPI values were further fitted to a logarithmic curve:

y_{B A I P I v a l u e} = a \times \ln (x_{concentration of caffeine} - b) - c + {I V}_{i n i t i a l B A I P I v a l u e} - 1

. The constant terms

a

,

b

, and

c

were derived from the ratio of caffeine to EGCG, as the slope and X-intercept of the curves correlated exponentially with this ratio. The initial BAIPI value (IV) was calculated as:

{I V}_{i n i t i a l B A I P I v a l u e} = 18.7960 - 0.3956 q_{(t h e r a t i o o f c a f f e i n e t o Q u e - r u t)}

. Validation showed a standard error of 1.5865 between estimated and actual BAIPI values. This method enables the estimation of bitter–astringent intensity in green tea by analyzing the concentrations of caffeine, EGCG, and Que-rut. Full article

(This article belongs to the Topic Advances in Analysis of Flavors and Fragrances: Chemistry, Properties and Applications in Food Quality Improvement)

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13 pages, 2428 KiB

Open AccessArticle

Small Acetone Sensor with a Porous Colorimetric Chip for Breath Acetone Detection Using the Flow–Stop Method

by Yuto Muramatsu, Sota Watanabe, Mahiro Osada, Kohsuke Tajima, Akihiro Karashima and Yasuko Yamada Maruo

Chemosensors 2025, 13(4), 136; https://doi.org/10.3390/chemosensors13040136 - 8 Apr 2025

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Abstract

Acetone is a well-known biogas involved in lipid metabolism and is considered a potential biomarker for diabetes. However, the conventional detection methods for acetone face the limitations of large size, complex usage, and cross-sensitivity. In this study, we developed a portable device comprising [...] Read more.

Acetone is a well-known biogas involved in lipid metabolism and is considered a potential biomarker for diabetes. However, the conventional detection methods for acetone face the limitations of large size, complex usage, and cross-sensitivity. In this study, we developed a portable device comprising a porous colorimetric acetone analytical chip composed of 2-nitrophenyl hydrazine and porous glass. The analytical chip was highly sensitive and selective for acetone because it was based on the chemical reaction between acetone and hydrazine in a nanoporous material, which provides a large surface area. The device consisted of a 450 nm laser light source and a photodiode detector with a volume of less than 40 mL. Acetone gas was measured in the atmosphere for 10 min using the developed flow–stop method. The measurable acetone concentration ranged from 0 to 6.0 ppm with a detection limit of 0.22 ppm. We successfully conducted a feasibility study using human exhaled breath and analyzed the relationship between exercise and the acetone concentration in the breath. An upward trend in exhaled acetone levels was seen post-exercise for each individual. Full article

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

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12 pages, 2386 KiB

Open AccessArticle

Preparation of Au-CeO₂ Nanocubes as a New SERS Substrate and Efficient Detection of Organic Compounds

by Xin Tian, Li Ren, Jie Huang, Guangcheng Xi, Feifan Chang and Guoying Wei

Chemosensors 2025, 13(4), 135; https://doi.org/10.3390/chemosensors13040135 - 7 Apr 2025

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Abstract

Surface-enhanced Raman scattering (SERS) is extensively employed for detecting organics, where its sensitivity and selectivity are strongly influenced by the properties of the SERS substrates. In this work, a simple hydrothermal synthesis followed by a subsequent reduction was used to prepare Au-CeO₂ [...] Read more.

Surface-enhanced Raman scattering (SERS) is extensively employed for detecting organics, where its sensitivity and selectivity are strongly influenced by the properties of the SERS substrates. In this work, a simple hydrothermal synthesis followed by a subsequent reduction was used to prepare Au-CeO₂ composite nanocubes as a new SERS substrate, in which the side length of the CeO₂ cubes was 20~30 nm and the diameter of the Au nanoparticles was 5~25 nm. Using methylene blue (MB) and crystal violet (CV) as probe molecules, the lowest detection limit (LDL) of methylene blue (MB) on the Au-CeO₂ composite nanocubes substrate was 10⁻⁷ M, and the maximum SERS enhancement factor (EF) was 2.6 × 10⁵. As a result, the lowest detection limit (LDL) of crystal violet (CV) was 10⁻⁷ M, and the maximum enhancement factor (EF) was 3.7 × 10⁴. The above results proved that the Au-CeO₂ composite nanocubes had a quite good Raman enhancement effect, which could be used as a SERS substrate. Finally, a Raman enhancement mechanism is proposed for the Au-CeO₂ nanucubes. Full article

(This article belongs to the Special Issue The Application of Surface-Enhanced Raman Spectroscopy (SERS) Platform)

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14 pages, 4453 KiB

Open AccessArticle

Research on Taste and Aroma Characteristics of Dahongpao Tea with Different Grades

by Xiaomin Pang, Jishuang Zou, Pengyao Miao, Weiting Cheng, Zewei Zhou, Xiaoli Jia, Haibin Wang, Yuanping Li, Qi Zhang and Jianghua Ye

Chemosensors 2025, 13(4), 134; https://doi.org/10.3390/chemosensors13040134 - 7 Apr 2025

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Abstract

This study aimed to thoroughly investigate the quality differences and influencing factors of Dahongpao tea of different grades. Through sensory evaluation, electronic nose analysis, electronic tongue analysis, biochemical component analysis, and HS-SPME-GC-MS, the taste and aroma characteristics of Dahongpao samples of different grades [...] Read more.

This study aimed to thoroughly investigate the quality differences and influencing factors of Dahongpao tea of different grades. Through sensory evaluation, electronic nose analysis, electronic tongue analysis, biochemical component analysis, and HS-SPME-GC-MS, the taste and aroma characteristics of Dahongpao samples of different grades (superfine, first, and second grades) were comprehensively studied. The results showed that there were significant differences in sensory quality, aroma components, and taste components among Dahongpao of different grades. Superfine Dahongpao has a rich aroma and mellow taste, containing a higher content of esters and aromatic hydrocarbons such as benzaldehyde (2-hydroxy-5-methoxy), hexyl benzoate, and cyclohexanecarboxylic acid 2,3-dichlorophenyl ester, which endow it with fruity, floral, and woody characteristics. In contrast, first- and second-grade Dahongpao contain more alkanes, pyrazines, and furans such as benzene (1-ethyl-1-propenyl), dodecane (2,6,10-trimethyl), and pyrazine (2,6-dimethyl), which impart floral, roasted, and nutty flavors. Moreover, superfine Dahongpao has a more bitter and astringent taste, but the bitterness and astringency dissipate more quickly, while the taste of first- and second-grade Dahongpao is relatively bland. These differences provide a scientific basis for the grade classification of Dahongpao tea and offer references for improving tea quality and standardized production. Full article

(This article belongs to the Special Issue Electrochemical Sensor for Food Analysis)

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16 pages, 4767 KiB

Open AccessArticle

Non-Enzymatic Electrochemical Sensing of Glucose with Silver Nanoparticles Supported on Poly(3-aminobenzoic acid)

by América Susana Mares-García, Claudia Alejandra Hernández-Escobar, Sonia Kimberly Enriquez-Durán, Anayansi Estrada-Monje, Erasto Armando Zaragoza-Contreras and Claudia Ivone Piñón-Balderrama

Chemosensors 2025, 13(4), 133; https://doi.org/10.3390/chemosensors13040133 - 6 Apr 2025

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Abstract

This study explores the development of a non-enzymatic electrochemical glucose sensor based on poly(3-aminobenzoic acid) (P3ABA) combined with silver nanoparticles (AgNPs). Incorporating AgNPs into the P3ABA matrix enhances the sensor’s electrocatalytic properties, leading to a system with greater stability. Cyclic voltammetry and chronoamperometry [...] Read more.

This study explores the development of a non-enzymatic electrochemical glucose sensor based on poly(3-aminobenzoic acid) (P3ABA) combined with silver nanoparticles (AgNPs). Incorporating AgNPs into the P3ABA matrix enhances the sensor’s electrocatalytic properties, leading to a system with greater stability. Cyclic voltammetry and chronoamperometry were employed to evaluate the sensor’s performance, demonstrating a sensitivity of 50.71 µA mM⁻¹ cm⁻² and a limit of detection (LOD) of 0.2 µM. The sensor exhibited a linear response over a broad concentration range (1 to 16 mM), with a coefficient of determination (R²) of 0.998, indicating good reproducibility and precision. These results highlight the potential of the P3ABA/AgNP composite for glucose sensing applications, offering an extended linear range, allowing for the quantification of glucose concentrations from very low to significantly high levels, covering both physiological and pathological conditions. Full article

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

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14 pages, 1340 KiB

Open AccessArticle

An Innovative Real-Time Cell Viability Analysis: A Cutting-Edge Flexible Bioimpedance Sensor

by Thien-Luan Phan, Hsin-Yu Chou, Hui-Xuan Huang, Chia-Hung Kuo, Congo Tak Shing Ching and Hui-Min David Wang

Chemosensors 2025, 13(4), 132; https://doi.org/10.3390/chemosensors13040132 - 6 Apr 2025

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Abstract

There are many compounds used to treat cancer, but still, only 20% of proposed anticancer agents have been commercialized after clinical trials due to serious side effects and unsatisfactory results. To screen potential drugs precisely and quickly, this study develops a flexible bioimpedance [...] Read more.

There are many compounds used to treat cancer, but still, only 20% of proposed anticancer agents have been commercialized after clinical trials due to serious side effects and unsatisfactory results. To screen potential drugs precisely and quickly, this study develops a flexible bioimpedance sensor. The sensor positively detects the half maximal inhibitory concentration (IC50) of drugs in real time by analyzing phase angle changes during cell mortality. The best results are achieved using a probe separation of A12B34 at logarithmic frequencies of 163 Hz and 77.87 kHz. At these two frequencies, there is a linear relationship with the phase angle at 0% and 50% of the dead cells. Dividing the phase angle at the two frequencies shows a 17.98% change in the phase angle, which allows self-correction and insensitivity to the number of cells. A custom phase angle measurement device is developed for detection at 163 Hz and 77.87 kHz, respectively. This study develops a novel sensor that is precise and fast and allows high-throughput analysis to detect the inhibition of cancer in real time. This sensor is an alternative to traditional chemical detection methods because it is faster, cheaper, and more accurate. Full article

(This article belongs to the Special Issue Feature Papers in the Section "Analytical Methods, Instrumentation and Miniaturization")

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17 pages, 6261 KiB

Open AccessArticle

Pushing Peak Shapes to Perfection by High-Temperature Focus GC-IMS

by Lukas Bodenbender, Sascha Rohn and Philipp Weller

Chemosensors 2025, 13(4), 131; https://doi.org/10.3390/chemosensors13040131 - 4 Apr 2025

Viewed by 339

Abstract

Gas chromatography–ion mobility spectrometry (GC-IMS) is a powerful technique in the field of food and flavor analysis specifically, as well as for the determination of volatile organic compounds (VOCs) in general. It offers high sensitivity and selectivity, combined with a robust design. Sample [...] Read more.

Gas chromatography–ion mobility spectrometry (GC-IMS) is a powerful technique in the field of food and flavor analysis specifically, as well as for the determination of volatile organic compounds (VOCs) in general. It offers high sensitivity and selectivity, combined with a robust design. Sample preparation is typically not required, and operating principles under ambient conditions facilitate routine analysis and usage at points of care. As of now, a plethora of applications of GC-IMS exist in the fields of food analysis, primarily for determining flavors and evaluating the authenticity of food. However, the general issue of peak tailing has, so far, not been addressed in IMS. Typical drift tube applications (DTIMS) are designed with emphasis to high detection sensitivities and feature large void volumes. This study aimed to develop an optimized IMS instrument design (“focus IMS”) which allows for signal mapping of eluting compounds. Due to an optimized flow architecture of sample and drift gases, in combination with an increased drift tube temperature, peak tailing is decreased significantly. In this study, the influence of drift gas flow and IMS cell temperature on the peak shape of several relevant allergenic terpenes was investigated. The peak quality optimization of DTIMS approaches for especially high-boiling substances facilitates the analysis of complex matrices, such as cosmetics, Citrus peel, and essence oils, as well as terpenes and terpenoids in general. 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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17 pages, 8911 KiB

Open AccessArticle

Study on Hybrid Assemblies of Graphene and Conducting Polymers with Embedded Gold Nanoparticles for Potential Electrode Purposes

by Alexandru F. Trandabat, Oliver Daniel Schreiner, Thomas Gabriel Schreiner, Olga Plopa and Romeo Cristian Ciobanu

Chemosensors 2025, 13(4), 130; https://doi.org/10.3390/chemosensors13040130 - 4 Apr 2025

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Abstract

This article outlines the method of creating electrodes for electrochemical sensors using hybrid nanostructures composed of graphene and conducting polymers with insertion of gold nanoparticles. The technology employed for graphene dispersion and support stabilization was based on the chemical vapor deposition technique followed [...] Read more.

This article outlines the method of creating electrodes for electrochemical sensors using hybrid nanostructures composed of graphene and conducting polymers with insertion of gold nanoparticles. The technology employed for graphene dispersion and support stabilization was based on the chemical vapor deposition technique followed by electrochemical delamination. The method used to obtain hybrid nanostructures from graphene and conductive polymers was drop-casting, utilizing solutions of P3HT, PANI-EB, and F8T2. Additionally, the insertion of gold nanoparticles utilized an innovative dip-coating technique, with the graphene-conducting polymer frameworks submerged in a HAuCl₄/2-propanol solution and subsequently subjected to controlled heating. The integration of gold nanoparticles differs notably, with P3HT showing the least adhesion of gold nanoparticles, while PANI-EB exhibits the highest. An inkjet printer was employed to create electrodes with metallization accomplished through the use of commercial silver ink. Notable variations in roughness (grain size) result in unique behaviors of these structures, and therefore, any potential differences in the sensitivity of the generated sensing structures can be more thoroughly understood through this spatial arrangement. The electrochemical experiments utilized a diluted sulfuric acid solution at three different scan rates. The oxidation and reduction potentials of the structures seem fairly alike. Nevertheless, a notable difference is seen in the anodic and cathodic current densities, which appear to be largely influenced by the active surface of gold nanoparticles linked to the polymeric grains. The graphene–PANI-EB structure with Au nanoparticles showed the highest responsiveness and will be further evaluated for biomedical applications. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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14 pages, 3362 KiB

Open AccessArticle

A Microelectrode Sensor Chip for Detecting Mercury and Arsenic with Wide Concentration Ranges

by Zhihao Zhang, Yuqi Liu, Yang Li and Chao Bian

Chemosensors 2025, 13(4), 129; https://doi.org/10.3390/chemosensors13040129 - 3 Apr 2025

Viewed by 189

Abstract

Traditional detection methods such as atomic absorption spectroscopy offer high sensitivity and accuracy for heavy metal ion detection; however, they are often limited to laboratory environments due to bulky equipment and complex procedures. To meet the demand for rapid on-site detection, this study [...] Read more.

Traditional detection methods such as atomic absorption spectroscopy offer high sensitivity and accuracy for heavy metal ion detection; however, they are often limited to laboratory environments due to bulky equipment and complex procedures. To meet the demand for rapid on-site detection, this study employs electrochemical analysis and utilizes Micro-Electro-Mechanical Systems (MEMS) technology to fabricate a microelectrode sensor chip for the electrochemical detection of heavy metal ions, Hg(II) and As(III). Nano-gold particles were electrodeposited on the sensing area of the working electrode of this chip using a constant-potential deposition method. Uniform distribution of the nanoparticles was obtained, which enhanced the effective specific surface area and electrochemical activity of the working electrode. Therefore, wide detection concentration ranges for Hg(II) of 5 to 1000 µg/L and for As(III) of 5 to 5000 µg/L were displayed, with detection limits of 1.4 µg/L and 2.4 µg/L, respectively. Moreover, the sensor exhibited satisfactory reproducibility, stability and anti-interference capability. These characteristics enable the developed microelectrode sensor chip to be utilized in the monitoring of a diverse range of pollution sources. Full article

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

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16 pages, 4066 KiB

Open AccessArticle

Development of a Reliable Device for ‘Fluorokinetic’ Analysis Based on a Portable Diode Array MEMS Fluorimeter

by Domingo González-Arjona and Germán López-Pérez

Chemosensors 2025, 13(4), 128; https://doi.org/10.3390/chemosensors13040128 - 3 Apr 2025

Viewed by 240

Abstract

A device was developed to study the evolution of fluorescence spectra as a function of time. A previously designed fluorimeter based on the diode array mini-spectrometer CM12880MA was used. The control and measurement were carried out by programming a SAM21D microcontroller. Considerations regarding [...] Read more.

A device was developed to study the evolution of fluorescence spectra as a function of time. A previously designed fluorimeter based on the diode array mini-spectrometer CM12880MA was used. The control and measurement were carried out by programming a SAM21D microcontroller. Considerations regarding the optimization of acquisition speed, memory, and computer interface have been analyzed and optimized. As a result, a very versatile device with great adaptability, reduced dimensions, portability, and a low budget (under EUR 500) has been built. The sensitivity, controlled by the integration time of the photodiodes, can be adjusted between 10 µs and 20 s, thus allowing sampling times ranging from 10 ms to more than 10 h. Under these conditions, chemical rate constants from 20 s⁻¹ to 10⁻⁸ s⁻¹ can be experimentally determined. It has a very wide operating range for the kinetic rate constant determination, over six orders of magnitude. As proof of the system performance, the oxidation reaction of Thiamine in a basic medium to form fluorescent Thiochrome has been employed. The evolution of the emission spectrum has been followed, and the decomposition rate constant has been measured at 2.1 × 10⁻³ s⁻¹, a value which matches those values reported in the literature for this system. A Thiochrome calibration curve has also been performed, obtaining a detection limit of 13 nM, consistent with literature data. Additionally, the stability of Thiochrome has been tested, being the photo-decomposition rate constants 1.8 × 10⁻⁴ s⁻¹ and 3.0 × 10⁻⁷ s⁻¹, in the presence and absence of UV light (365 nm), respectively. Finally, experiments have been designed to obtain, in a single measurement, the values of both rate constants: the formation of Thiochrome from Thiamine and its photo-decomposition under UV light to a non-fluorescent product. The rate constant values obtained are in good agreement with those previously obtained through independent experiments under the same experimental conditions. These results show that, under these conditions, Thiochrome can be considered an unstable intermediate in a chemical reaction with successive stages. Full article

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

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25 pages, 8266 KiB

Open AccessReview

Challenges and Applications of Bio-Sniffers for Monitoring Volatile Organic Compounds in Medical Diagnostics

by Yang Wang, Xunda Zhou, Siying Mao, Shiwei Chen and Zhenzhong Guo

Chemosensors 2025, 13(4), 127; https://doi.org/10.3390/chemosensors13040127 - 3 Apr 2025

Viewed by 333

Abstract

Bio-sniffers represent a novel detection technology that demonstrates significant potential in medical diagnostics. Specifically, they assess disease conditions and metabolic status through the detection of volatile organic compounds (VOCs) in exhaled breath. Unlike conventional methods such as gas chromatography-mass spectrometry (GC-MS) and gas [...] Read more.

Bio-sniffers represent a novel detection technology that demonstrates significant potential in medical diagnostics. Specifically, they assess disease conditions and metabolic status through the detection of volatile organic compounds (VOCs) in exhaled breath. Unlike conventional methods such as gas chromatography-mass spectrometry (GC-MS) and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS), bio-sniffers provide rapid, sensitive, and portable detection capabilities. In this review, we examine the metabolic pathways and detection methods of specific VOCs in the human body, and their roles as disease biomarkers, and focus on the detection principles, performance characteristics, and medical applications of two bio-sniffer types: electrical and optical sensors. Finally, we systematically discuss the current challenges facing bio-sniffers in VOC monitoring, outline future development directions, and provide suggestions for improving sensitivity and reducing environmental interference. Full article

(This article belongs to the Special Issue Feature Review Papers in Chemical/Bio-Sensors and Analytical Chemistry in 2025)

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15 pages, 6078 KiB

Open AccessArticle

Developing a Quantitative Profiling Method for Detecting Free Fatty Acids in Crude Lanolin Based on Analytical Quality by Design

by Sihan Liu, Shaohua Wu, Hao Zhang and Xingchu Gong

Chemosensors 2025, 13(4), 126; https://doi.org/10.3390/chemosensors13040126 - 3 Apr 2025

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Abstract

In this study, a quantitative profiling method for detecting free fatty acids in crude lanolin based on the Quality by Design (QbD) concept was developed. High-performance liquid chromatography (HPLC) equipped with a charged aerosol detector (CAD) and a Proshell 120 EC C18 column [...] Read more.

In this study, a quantitative profiling method for detecting free fatty acids in crude lanolin based on the Quality by Design (QbD) concept was developed. High-performance liquid chromatography (HPLC) equipped with a charged aerosol detector (CAD) and a Proshell 120 EC C18 column was employed for the separation of crude lanolin components. Initially, the analytical target profile and critical method attributes were defined. Potential critical method parameters, including column temperature, flow rate, isocratic run time, gradient end organic phase ratio, and gradient time, were identified using fishbone diagrams and single-factor experiments. The definitive screening design (DSD) was then utilized to screen and optimize these parameters. Stepwise regression was applied to establish quantitative models between the critical method attributes and the method parameters. Subsequently, the method operable design region (MODR) was calculated and was successfully verified. The analytical conditions established were configured with 0.1% formic acid in water and 0.1% formic acid in acetonitrile serving as the mobile phases. The flow rate was set at 0.8 mL/min, and the column temperature was maintained at 35 °C with the evaporation tube temperature also set at 35 °C. An injection volume of 10 μL was used for each analysis. The gradient elution conditions were as follows: from 0 to 30 min, 75% of solvent B was used, and from 30 to 60 min, the proportion of solvent B was increased from 75% to 79%. Ten components, including 12-hydroxystearic acid, 2-hexyldecanoic acid, and palmitic acid, were identified by mass spectrometry, and seven common peaks were found in the fingerprints. The contents of palmitic acid, oleic acid, and stearic acid in the crude lanolin were quantitatively determined. Both the fingerprint and quantitative analysis methods were validated. The method was applied to analyze 15 batches of crude lanolin from different sources. The new established quantitative profiling method for free fatty acids can be potentially used for industrial applications to enhance the quality control of crude lanolin. Full article

(This article belongs to the Special Issue Spectroscopic Techniques for Chemical Analysis)

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18 pages, 3563 KiB

Open AccessArticle

Polydopamine-Coated Magnetite as a Sensing Material for the Optical Detection of Cationic Surfactants

by Alberto Fernández-Núñez, Francisco Pérez-Pla, Maria Ángeles Úbeda, Pedro Amorós and José V. Ros-Lis

Chemosensors 2025, 13(4), 125; https://doi.org/10.3390/chemosensors13040125 - 2 Apr 2025

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Abstract

The sensing of surfactants is a topic of interest for industrial and environmental purposes. Polydopamine-coated magnetite (Fe₃O₄@PDA) can be a relevant support for the detection of cationic surfactants in water samples. The negative charge in the surface of the [...] Read more.

The sensing of surfactants is a topic of interest for industrial and environmental purposes. Polydopamine-coated magnetite (Fe₃O₄@PDA) can be a relevant support for the detection of cationic surfactants in water samples. The negative charge in the surface of the PDA material favors the interaction with cationic molecules and allows the design of a chemoreagent for the detection of cationic surfactants by displacement or competition with methylene blue (MB). Magnetite nanoparticles with single and double PDA coating have been prepared and characterized. The PDA surface effectively coats magnetite nanoparticles with a thickness of 5 or 19 nm and a Z potential of −30 mV. The adsorption of MB follows second-order kinetics, and up 33 mg of dye can be loaded in 1 g of the support. The cationic surfactants can displace MB from the Fe₃O₄@PDA surface, coloring the solution. Thus, it can be applied for the analysis of water samples. The system is selective towards cationic molecules with long alkyl chains, but the response is influenced by high concentrations of divalent cations. The material can be used following diverse sensing protocols with a detection range from 4 × 10⁻⁶ to 2 × 10⁻⁴ M. The simplicity of its handling together with the naked eye detection allows its application in kits for field analysis with screening purposes. Full article

(This article belongs to the Section Applied Chemical Sensors)

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12 pages, 1205 KiB

Open AccessArticle

Chloride Catalytic Determination as Potential Tool to Assess Metal Ion Bioavailability in Water

by Mafalda G. Pereira, Justyna Paluch, Raquel B. R. Mesquita and António O. S. S. Rangel

Chemosensors 2025, 13(4), 124; https://doi.org/10.3390/chemosensors13040124 - 2 Apr 2025

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Abstract

This paper focuses on the development of an environmentally friendly sequential injection (SI) method for the determination of chloride in water samples from dynamic water systems. Chloride quantification is highly relevant, as it may affect metal ion bioavailability and potential toxicity to the [...] Read more.

This paper focuses on the development of an environmentally friendly sequential injection (SI) method for the determination of chloride in water samples from dynamic water systems. Chloride quantification is highly relevant, as it may affect metal ion bioavailability and potential toxicity to the environment. The approach was established based on the catalytic reaction of chloride ions in the colorimetric reaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide. Optimisation studies were performed regarding several parameters such as reaction pH, reagent volume and concentration, reaction time, and flow rates. As such, it was possible to obtain a wide dynamic range of 60 to 1000 mM, with a limit of detection and quantification of 17 and 58 mM, respectively, and a relative standard deviation of 7%. Validation was performed by analysing 13 water samples from dynamic water systems, namely seawater, estuarine water, and estuarine harbour water, with the SI method developed and by comparing the results obtained to potentiometric titration as the reference method. The relative error of these comparisons was not significant (<10%). Interference studies were also performed and showed no significant effect on the performance of the system (interference percentage < 10%), proving that a robust and sensitive system was developed. Full article

(This article belongs to the Special Issue Green Analytical Methods for Environmental and Food Analysis)

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