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Chemosensors, Volume 9, Issue 11 (November 2021) – 35 articles

Cover Story (view full-size image): Tunable photophysical properties, coupled with facile and modular synthetic approaches to incorporate various recognition motifs, make squaraine dyes an attractive scaffold for designing versatile chemosensors. This review focuses on assembling squaraine-based optical sensors using readily available building blocks that contain chelating and chemocaging groups. Furthermore, synthetic strategies that take advantage of acid–base and electrophile–nucleophile interactions for optical sensing, as well as the possibilities of using metal-containing squaraine scaffolds for multi-analyte recognition, are highlighted. View this paper
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Article
Reconfigurable Modular Platform for Prolonged Sensing of Toxic Gases in Particle Polluted Environments
Chemosensors 2021, 9(11), 328; https://doi.org/10.3390/chemosensors9110328 - 22 Nov 2021
Cited by 1 | Viewed by 753
Abstract
The prolonged sensing of toxic gases in polluted particles and harsh environments is a challenging task that is also in high demand. In this work, the proof of principle of a sensitive, low-cost, and low-maintenance reconfigurable platform for filter-free and continuous ammonia (NH [...] Read more.
The prolonged sensing of toxic gases in polluted particles and harsh environments is a challenging task that is also in high demand. In this work, the proof of principle of a sensitive, low-cost, and low-maintenance reconfigurable platform for filter-free and continuous ammonia (NH3) sensing in polluted environments is simulated. The platform can be modified for the detection of various toxic gases and includes three main modules: a microfluidic system for in-line continuous dust filtering; a toxic gas adsorption module; and a low-frequency microwave split-ring resonator (SRR). An inertia-based spiral microfluidic system has been designed and optimized through simulation for the in-line filtration of small particles from the intake air. Zeolite Y is selected as the adsorbent in the adsorption module. The adsorption module is a non-metallic thin tube that is filled with zeolite Y powder and precisely fixed at the drilled through-hole into the 3D microwave system. For the sensing module, a low-frequency three-dimensional (3D) split-ring resonator is proposed and optimally designed. A microwave resonator continuously monitors the permittivity of zeolite Y and can detect small permittivity alterations upon the presence of ammonia in the intake air. The microwave resonator is optimized at a frequency range of 2.5–3 GHz toward the detection of ammonia under different ammonia concentrations from 400 to 2800 ppm. The microwave simulation results show a clear contrast of around 4 MHz that shifts at 2.7 GHz for 400 ppm ammonia concentration. The results show the proof of principle of the proposed microfluidic-microwave platform for toxic gas detection. Full article
(This article belongs to the Special Issue Microfluidic-Based Chemical and Biochemical Sensors)
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Article
Facile Detection and Quantification of Acetamiprid Using a Portable Raman Spectrometer Combined with Self-Assembled Gold Nanoparticle Array
Chemosensors 2021, 9(11), 327; https://doi.org/10.3390/chemosensors9110327 - 22 Nov 2021
Cited by 2 | Viewed by 766
Abstract
Rapid and facile determination of pesticides is critically important in food and environmental monitoring. This study developed a self-assembled gold nanoparticle array based SERS method for highly specific and sensitive detection of acetamiprid, a neonicotinoid pesticide that used to be difficult in SERS [...] Read more.
Rapid and facile determination of pesticides is critically important in food and environmental monitoring. This study developed a self-assembled gold nanoparticle array based SERS method for highly specific and sensitive detection of acetamiprid, a neonicotinoid pesticide that used to be difficult in SERS analysis due to its low affinity with SERS substrates. SERS detection and quantification of acetamiprid was conducted with self-assembled gold nanoparticle arrays at the interface of chloroform and water as the enhancing substrate. Since targets dissolved in chloroform (organic phase) also have access to the hot-spots of Au NP array, the developed method exhibited good sensitivity and specificity for acetamiprid determination. Under the optimal conditions, SERS intensities at Raman shifts of 631 cm−1 and 1109 cm−1 displayed a good linear relationship with the logarithm concentration of acetamiprid in the range of 5.0 × 10−7 to 1.0 × 10−4 mol/L (0.11335 ppm to 22.67 ppm), with correlation coefficients of 0.97972 and 0.97552, respectively. The calculated LOD and LOQ of this method were 1.19 × 10−7 mol/L (0.265 ppb) and 2.63 × 10−7 mol/L (0.586 ppb), respectively, using SERS signal at 631 cm−1, and 2.95 × 10−7 mol/L (0.657 ppb) and 3.86 × 10−7 mol/L (0.860 ppb) using SERS signal at 1109 cm−1, respectively. Furthermore, the developed SERS method was successfully applied in determining acetamiprid on the surface of apple and spinach. This method offers an exciting opportunity for rapid detection of acetamiprid and other organic pesticides considering its advantages of simple preparation process, good specificity and sensitivity, and short detection time (within 1 h). Full article
(This article belongs to the Section Optical Chemical Sensors)
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Review
Plasmonic Biosensors for the Detection of Lung Cancer Biomarkers: A Review
Chemosensors 2021, 9(11), 326; https://doi.org/10.3390/chemosensors9110326 - 21 Nov 2021
Viewed by 908
Abstract
Lung cancer is the most common and deadliest cancer type globally. Its early diagnosis can guarantee a five-year survival rate. Unfortunately, application of the available diagnosis methods such as computed tomography, chest radiograph, magnetic resonance imaging (MRI), ultrasound, low-dose CT scan, bone scans, [...] Read more.
Lung cancer is the most common and deadliest cancer type globally. Its early diagnosis can guarantee a five-year survival rate. Unfortunately, application of the available diagnosis methods such as computed tomography, chest radiograph, magnetic resonance imaging (MRI), ultrasound, low-dose CT scan, bone scans, positron emission tomography (PET), and biopsy is hindered due to one or more problems, such as phenotypic properties of tumours that prevent early detection, invasiveness, expensiveness, and time consumption. Detection of lung cancer biomarkers using a biosensor is reported to solve the problems. Among biosensors, optical biosensors attract greater attention due to being ultra-sensitive, free from electromagnetic interference, capable of wide dynamic range detection, free from the requirement of a reference electrode, free from electrical hazards, highly stable, capable of multiplexing detection, and having the potential for more information content than electrical transducers. Inspired by promising features of plasmonic sensors, including surface plasmon resonance (SPR), localised surface plasmon resonance (LSPR), and surface enhanced Raman scattering (SERS) such as ultra-sensitivity, single particle/molecular level detection capability, multiplexing capability, photostability, real-time measurement, label-free measurement, room temperature operation, naked-eye readability, and the ease of miniaturisation without sophisticated sensor chip fabrication and instrumentation, numerous plasmonic sensors for the detection of lung cancer biomarkers have been investigated. In this review, the principle plasmonic sensor is explained. In addition, novel strategies and modifications adopted for the detection of lung cancer biomarkers such as miRNA, carcinoembryonic antigen (CEA), cytokeratins, and volatile organic compounds (VOCs) using plasmonic sensors are also reported. Furthermore, the challenges and prospects of the plasmonic biosensors for the detection of lung cancer biomarkers are highlighted. Full article
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Article
Efficient Microwave-Assisted Extraction of Nitrites from Cured Meat and Their Voltammetric Detection at Chemically Modified Electrodes Based on Hexamethyl-p-Terphenyl Poly(methylatedbenzimidazolium) Incorporating Nitrogen-Doped Graphite Nanoplatelets
Chemosensors 2021, 9(11), 325; https://doi.org/10.3390/chemosensors9110325 - 19 Nov 2021
Viewed by 555
Abstract
We describe a fast and reliable procedure for the efficient extraction of nitrites in cured meat using microwave-assisted heat and report their in situ determination via voltammetry using an anion-exchanger ionene, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), and nitrogen-doped graphite nanoplatelets (NGNPs). Cyclic voltammetry and chronoamperometry [...] Read more.
We describe a fast and reliable procedure for the efficient extraction of nitrites in cured meat using microwave-assisted heat and report their in situ determination via voltammetry using an anion-exchanger ionene, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), and nitrogen-doped graphite nanoplatelets (NGNPs). Cyclic voltammetry and chronoamperometry were utilized to evaluate the concentration of the redox mediator within the film and apparent diffusion coefficient. To investigate the suitability of the composite material for sensing applications, HMT-PMBI/NGNPs were tested for their detection of nitrite in bacon samples without the need of any pretreatments or dilutions. HMT-PMBI/NGNP coated electrodes showed enhanced sensitivity in the detection of nitrite ions in bacon with a limit of detection (LoD) of 0.64 µM, sensitivity 0.52 µA µM−1 cm−2, and operating in a linear range between 1–300 μM. The results highlight that the determination of nitrites in cured meat using microwave extraction is in good agreement with standard procedures such as the ISO 2918 and the AOAC International 973.31 methods. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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Review
An overview of Structured Biosensors for Metal Ions Determination
Chemosensors 2021, 9(11), 324; https://doi.org/10.3390/chemosensors9110324 - 18 Nov 2021
Viewed by 566
Abstract
The determination of metal ions is important for nutritional and toxicological assessment. Atomic spectrometric techniques are highly efficient for the determination of these species, but the high costs of acquisition and maintenance hinder the application of these techniques. Inexpensive alternatives for metallic element [...] Read more.
The determination of metal ions is important for nutritional and toxicological assessment. Atomic spectrometric techniques are highly efficient for the determination of these species, but the high costs of acquisition and maintenance hinder the application of these techniques. Inexpensive alternatives for metallic element determination are based on dedicated biosensors. These devices mimic biological systems and convert biochemical processes into physical outputs and can be used for the sensitive and selective determination of chemical species such as cations. In this work, an overview of the proposed biosensors for metal ions determination was carried out considering the last 15 years of publications. Statistical data on the applications, response mechanisms, instrumentation designs, applications of nanomaterials, and multielement analysis are herein discussed. Full article
(This article belongs to the Special Issue Modern Directions in Ion Electroanalysis for Real World Applications)
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Article
Rapid Voltammetric Screening Method for the Assessment of Bioflavonoid Content Using the Disposable Bare Pencil Graphite Electrode
Chemosensors 2021, 9(11), 323; https://doi.org/10.3390/chemosensors9110323 - 18 Nov 2021
Cited by 2 | Viewed by 505
Abstract
Hesperidin (HESP) is a plant bioflavonoid found in various nutritional and medicinal products. Many of its multiple health benefits rely on the compound’s antioxidant ability, which is due to the presence of oxidizable hydroxyl groups in its structure. Therefore, the present study aimed [...] Read more.
Hesperidin (HESP) is a plant bioflavonoid found in various nutritional and medicinal products. Many of its multiple health benefits rely on the compound’s antioxidant ability, which is due to the presence of oxidizable hydroxyl groups in its structure. Therefore, the present study aimed to investigate the electrochemical behavior of HESP at a cheap, disposable pencil graphite electrode (PGE) in order to develop rapid and simple voltammetric methods for its quantification. Cyclic voltammetric investigations emphasized a complex electrochemical behavior of HESP. The influence of the electrode material, solution stability, supporting electrolyte pH, and nature were examined. HESP main irreversible, diffusion-controlled oxidation signal obtained at H type PGE in Britton Robinson buffer pH 1.81 was exploited for the development of a differential pulse voltammetry (DPV) quantitative analysis method. The quasi-reversible, adsorption-controlled reduction peak was used for HESP quantification by differential pulse adsorptive stripping voltammetry (DPAdSV). The linear ranges of DPV and DPAdSV were 1.00 × 10−7–1.20 × 10−5 and 5.00 × 10−8–1.00 × 10−6 mol/L with detection limits of 8.58 × 10−8 and 1.90 × 10−8 mol/L HESP, respectively. The DPV method was applied for the assessment of dietary supplements bioflavonoid content, expressed as mg HESP. Full article
(This article belongs to the Special Issue Applications of Chemosensors in Real-World Sample Analysis)
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Review
A Review of the Analytical Methods for the Determination of 4(5)-Methylimidazole in Food Matrices
Chemosensors 2021, 9(11), 322; https://doi.org/10.3390/chemosensors9110322 - 18 Nov 2021
Cited by 1 | Viewed by 866
Abstract
4(5)-Methylimidazole (4(5)MEI) is a product of the Maillard reaction between sugars and amino acids, which occurs during the thermal processing of foods. This compound is also found in foods with caramel colorants additives. Due to its prevalence in foods and beverages and its [...] Read more.
4(5)-Methylimidazole (4(5)MEI) is a product of the Maillard reaction between sugars and amino acids, which occurs during the thermal processing of foods. This compound is also found in foods with caramel colorants additives. Due to its prevalence in foods and beverages and its potent carcinogenicity, 4(5)MEI has received federal and state regulatory agency attention. The aim of this review is to present the extraction procedures of 4(5)MEI from food matrices and the analytical methods for its determination. Liquid and gas chromatography coupled with mass spectrometry are the techniques most commonly employed to detect 4(5)MEI in food matrices. However, the analysis of 4(5)MEI is challenging due to the high polarity, water solubility, and the absence of chromophores. To overcome this, specialized sample pretreatment and extraction methods have been developed, such as solid-phase extraction and derivatization procedures, increasing the cost and the preparation time of samples. Other analytical methods for the determination of 4(5)MEI, include capillary electrophoresis, paper spray mass spectrometry, micellar electrokinetic chromatography, high-performance cation exchange chromatography, fluorescence-based immunochromatographic assay, and a fluorescent probe. Full article
(This article belongs to the Collection Recent Trend in Chromatography for Pharmaceutical Analysis)
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Article
Decoration of Ag Nanoparticle on ZnO Nanowire by Intense Pulsed Light and Enhanced UV Photodetector
Chemosensors 2021, 9(11), 321; https://doi.org/10.3390/chemosensors9110321 - 15 Nov 2021
Viewed by 602
Abstract
Zinc oxide (ZnO) nanowires (NWs) are wide-bandgap semiconductors that absorb ultraviolet (UV) radiation. Various post-treatment processes have been studied to improve the optical properties of the as-grown ZnO NWs. Among them, Ag nanoparticles (NPs) effectively improved the optical properties on the surface of [...] Read more.
Zinc oxide (ZnO) nanowires (NWs) are wide-bandgap semiconductors that absorb ultraviolet (UV) radiation. Various post-treatment processes have been studied to improve the optical properties of the as-grown ZnO NWs. Among them, Ag nanoparticles (NPs) effectively improved the optical properties on the surface of the ZnO NWs. In this study, ZnO NWs were synthesized via the hydrothermal synthesis method. ZnO NWs were decorated with Ag NPs on the surface of the ZnO NWs in a silver nitrate (AgNO3) aqueous solution by intense pulsed light (IPL) irradiation. Ag NPs were successfully decorated under the following conditions: aqueous AgNO3 solution of 100 nM, an energy of 1 J/cm2, and an exposure time of 8 ms. The responsivity and sensitivity of the ZnO NW UV photodetectors increased by 7.43 and 3.37 times, respectively. The IPL process makes it possible to decorate Ag NPs in a simple manner within an extremely short time. Full article
(This article belongs to the Special Issue Nanowire-Based Sensors)
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Communication
Enhanced Capacitive Humidity Sensing Performance at Room Temperature via Hydrogen Bonding of Cyanopyridone-Based Oligothiophene Donor
Chemosensors 2021, 9(11), 320; https://doi.org/10.3390/chemosensors9110320 - 15 Nov 2021
Cited by 3 | Viewed by 573
Abstract
Cyanopyridone-based oligothiophene donors with both hydrophobic and hydrophilic characters have been evaluated as active layers within simple capacitive devices for humidity sensing at room temperature. Surface studies using atomic force microscopy revealed a self-assembled nanofibrous network with a thin needle-like structure for the [...] Read more.
Cyanopyridone-based oligothiophene donors with both hydrophobic and hydrophilic characters have been evaluated as active layers within simple capacitive devices for humidity sensing at room temperature. Surface studies using atomic force microscopy revealed a self-assembled nanofibrous network with a thin needle-like structure for the terminal hydroxy example (CP6), devoid in the methyl example (CP1). The sensing performance of each sensor was investigated over a broad range of relative humidity levels as a function of capacitance at room temperature. The sensor CP6 demonstrated favourable features such as high sensitivity (12.2 pF/%RH), quick response/recovery (13 s/20.7 s), wide working range of relative humidity (10%–95% RH), low hysteresis (0.57%), outstanding recyclability, and excellent long-term stability. From the results obtained, hydrophilicity and hydrogen bonding appear to play a vital role in enhancing humidity sensing performance, leading to possible new design directions for simple organic semiconductor-based sensors. Full article
(This article belongs to the Special Issue Nanomaterials Based on Bio/Chemical Sensors)
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Article
Colorimetric Sensing of Benzoyl Peroxide Based on the Emission Wavelength-Shift of CsPbBr3 Perovskite Nanocrystals
Chemosensors 2021, 9(11), 319; https://doi.org/10.3390/chemosensors9110319 - 14 Nov 2021
Viewed by 680
Abstract
Using the ionic salt characteristics of CsPbBr3 perovskite nanocrystals (CsPbBr3 NCs), the fluorescence wavelength of CsPbBr3−xIx NCs could be changed by the halogen exchange reaction between CsPbBr3 NCs and oleylammonium iodide (OLAM-I). Under the excitation of a [...] Read more.
Using the ionic salt characteristics of CsPbBr3 perovskite nanocrystals (CsPbBr3 NCs), the fluorescence wavelength of CsPbBr3−xIx NCs could be changed by the halogen exchange reaction between CsPbBr3 NCs and oleylammonium iodide (OLAM-I). Under the excitation of a 365 nm UV lamp and the increase of OLAM-I concentration, the content of iodine in CsPbBr3−xIx NCs increased, and the fluorescence emission wavelength showed a redshift from 511.6 nm to 593.4 nm, resulting in the fluorescence color change of CsPbBr3 NCs from green to orange-red. Since OLAM-I is a mild reducing agent and easily oxidized by benzoyl peroxide (BPO), a novel colorimetric sensing approach for BPO based on the fluorescence wavelength shift was established in this study. The linear relationship between the different wavelength shifts (Δλ) and the concentration of BPO (CBPO) is found to be in the range of 0 to 120 μmol L−1. The coefficient of alteration (R2) and the detection limit are 0.9933 and 0.13 μmol L−1 BPO, respectively. With this approach, the determination procedure of BPO in flour and noodle samples can be achieved in only a few minutes and exhibit high sensitivity and selectivity. Full article
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Review
Aptamer-Conjugated Quantum Dot Optical Biosensors: Strategies and Applications
Chemosensors 2021, 9(11), 318; https://doi.org/10.3390/chemosensors9110318 - 12 Nov 2021
Viewed by 664
Abstract
Quantum dots (QDs) represent the promising new generation of luminophores owing to their size-, composition-, and surface-dependent tunable photoluminescence (PL) and photochemical stability. The development of various QD composites with high PL and good biocompatibility has facilitated the use of aptamer-functionalized QD biosensors [...] Read more.
Quantum dots (QDs) represent the promising new generation of luminophores owing to their size-, composition-, and surface-dependent tunable photoluminescence (PL) and photochemical stability. The development of various QD composites with high PL and good biocompatibility has facilitated the use of aptamer-functionalized QD biosensors for highly sensitive and specific detection of molecules in clinical and environmental settings. In addition to describing the recent advances in aptamer-based QD biosensor technology for the detection of diverse chemicals and biomolecules, this review provides recent examples of sensing strategies based on optical signal enhancement and quenching of QDs. It also discusses potential strategies for the development of biosensors to widen their practical applications across various scientific and technological fields. Full article
(This article belongs to the Special Issue Quantum-Dots Sensors)
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Article
3D Printed Chromophoric Sensors
Chemosensors 2021, 9(11), 317; https://doi.org/10.3390/chemosensors9110317 - 09 Nov 2021
Viewed by 601
Abstract
Eight chromophoric indicators are incorporated into Sylgard 184 to develop sensors that are fabricated either by traditional methods such as casting or by more advanced manufacturing techniques such as 3D printing. The sensors exhibit specific color changes when exposed to acidic species, basic [...] Read more.
Eight chromophoric indicators are incorporated into Sylgard 184 to develop sensors that are fabricated either by traditional methods such as casting or by more advanced manufacturing techniques such as 3D printing. The sensors exhibit specific color changes when exposed to acidic species, basic species, or elevated temperatures. Additionally, material properties are investigated to assess the chemical structure, Shore A Hardness, and thermal stability. Comparisons between the casted and 3D printed sensors show that the sensing devices fabricated with the advanced manufacturing technique are more efficient because the color changes are more easily detected. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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Review
Metal-Organic-Frameworks: Low Temperature Gas Sensing and Air Quality Monitoring
Chemosensors 2021, 9(11), 316; https://doi.org/10.3390/chemosensors9110316 - 08 Nov 2021
Cited by 3 | Viewed by 996
Abstract
As an emerging class of hybrid nanoporous materials, metal-organic frameworks (MOFs) have attracted significant attention as promising multifunctional building blocks for the development of highly sensitive and selective gas sensors due to their unique properties, such as large surface area, highly diversified structures, [...] Read more.
As an emerging class of hybrid nanoporous materials, metal-organic frameworks (MOFs) have attracted significant attention as promising multifunctional building blocks for the development of highly sensitive and selective gas sensors due to their unique properties, such as large surface area, highly diversified structures, functionalizable sites and specific adsorption affinities. Here, we provide a review of recent advances in the design and fabrication of MOF nanomaterials for the low-temperature detection of different gases for air quality and environmental monitoring applications. The impact of key structural parameters including surface morphologies, metal nodes, organic linkers and functional groups on the sensing performance of state-of-the-art sensing technologies are discussed. This review is concluded by summarising achievements and current challenges, providing a future perspective for the development of the next generation of MOF-based nanostructured materials for low-temperature detection of gas molecules in real-world environments. Full article
(This article belongs to the Special Issue Gas Sensing beyond MOX Semiconductors)
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Communication
Concentration-Dependent Fluorescence Emission of Quercetin
Chemosensors 2021, 9(11), 315; https://doi.org/10.3390/chemosensors9110315 - 07 Nov 2021
Cited by 2 | Viewed by 583
Abstract
Quercetin (Q) is an important antioxidant with high bioactivity and the potential of being used as SARS-CoV-2 inhibitor. The fluorescence (FL) emission from Q solutions made with different polar and non-polar solvents (methanol, acetone, and chloroform) was measured and compared with the FL [...] Read more.
Quercetin (Q) is an important antioxidant with high bioactivity and the potential of being used as SARS-CoV-2 inhibitor. The fluorescence (FL) emission from Q solutions made with different polar and non-polar solvents (methanol, acetone, and chloroform) was measured and compared with the FL emission from Q powder and from Q crystals. In the FL spectra of the solutions with high Q concentration, as well as in the spectra of Q in solid state, two features, at 615 nm and 670 nm, were observed. As the solution concentration decreases, the intensity of those peaks decreases and a peak at 505 nm arises. The FL emission of low concentration solutions displayed only that peak. Calculations for the Q molecule in each solvent, performed using time-dependent density functional theory (TDDFT), show that the emission at 505 nm is associated with the excited state intramolecular proton transfer (ESIPT) of the –OH3 group proton. Our calculations also show that the feature at 615 nm, which is observed in solid state Q and also in the emission of the high concentrated solutions, is related to the –OH5 proton transfer. Full article
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Article
Rapid Screening of Butyl Paraben Additive in Toner Sample by Molecularly Imprinted Photonic Crystal
Chemosensors 2021, 9(11), 314; https://doi.org/10.3390/chemosensors9110314 - 06 Nov 2021
Viewed by 498
Abstract
In consideration of the endocrine disrupting effects caused by the butyl paraben (BP), a portable visual sensor has been developed based on the photonic crystal and molecular imprinting technology for the rapid screen of BP in toner sample which is a type of [...] Read more.
In consideration of the endocrine disrupting effects caused by the butyl paraben (BP), a portable visual sensor has been developed based on the photonic crystal and molecular imprinting technology for the rapid screen of BP in toner sample which is a type of aqueous cosmetic to soften the face skin. By integrating the self-reporting and molecular recognition properties, the molecular imprinting photonic crystal (MIPC) sensor can display obvious color changes regularly according to the concentration of BP. Based on the “color guide”, the content of BP in toner sample can be estimated directly with the naked eye. In addition, the Bragg diffraction spectrum of MIPC can red shift linearly with the increase of the concentration of BP in sample solution with correlation coefficient as 0.9968. The quantitative determination of BP can be achieved through the optical fiber spectrometer with detection limit as 0.022 mmol·L−1. With good selectivity, this MIPC film can recognize BPs against the complex sample matrix, showing a standard addition recovery of 107% for the real samples. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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Article
Laser Illumination Adjustments for Signal-to-Noise Ratio and Spatial Resolution Enhancement in Static 2D Chemical Images of NbOx/IGZO/ITO/Glass Light-Addressable Potentiometric Sensors
Chemosensors 2021, 9(11), 313; https://doi.org/10.3390/chemosensors9110313 - 04 Nov 2021
Cited by 1 | Viewed by 410
Abstract
In a previous study, a thin In-Ga-Zn-oxide light addressable potentiometric sensor (IGZO LAPS) was indicated to have the advantages of low interference from ambient light, a high photocurrent and transfer efficiency, and a low cost. However, illumination optimization to obtain two-dimensional (2D) chemical [...] Read more.
In a previous study, a thin In-Ga-Zn-oxide light addressable potentiometric sensor (IGZO LAPS) was indicated to have the advantages of low interference from ambient light, a high photocurrent and transfer efficiency, and a low cost. However, illumination optimization to obtain two-dimensional (2D) chemical images with better spatial resolutions has not been fully investigated. The trigger current and AC-modulated frequency of a 405-nm laser used to illuminate the fabricated IGZO LAPS were modified to check the photocurrent of the sensing area and SU8–2005 masking area, obtaining spatial resolution-related functions for the first time. The trigger current of illumination was adjusted from 0.020 to 0.030 A to compromise between an acceptable photocurrent and the integrity of the SU8–2005 masking layer. The photocurrent (PC) and differential photocurrent (DPC) versus scanning length (SL) controlled by an X-Y stage were used to check the resolved critical dimensions (CDs). The difference between resolved CD and optically measured CD (e.g., delta CD) measured at an AC frequency of 500 Hz revealed overall smaller values, supporting precise measurement in 2D imaging. The signal-to-noise ratio (SNR) has an optimized range of 2.0 to 2.15 for a better resolution for step spacings of both 10 and 2 μm in the scanning procedure to construct static 2D images. Under illumination conditions with a trigger current of 0.025 A and at an AC frequency of 500 Hz, the spatial resolution can be reduced to 10 μm from the pattern width of 6 μm. This developed methodology provides a quantitative evaluation with further optimization in spatial resolution without an extra cost for applications requiring a high spatial resolution, such as single-cell activity. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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Article
Single Fiber Reflectance Spectroscopy for the Monitoring of Cement Paste
Chemosensors 2021, 9(11), 312; https://doi.org/10.3390/chemosensors9110312 - 04 Nov 2021
Viewed by 551
Abstract
Reinforced concrete structures are an essential part of our modern society, and monitoring their structural health is of paramount importance. Early detection of decay allows for the reduction of repair costs and, more importantly, the prevention of catastrophic failure. For this purpose, a [...] Read more.
Reinforced concrete structures are an essential part of our modern society, and monitoring their structural health is of paramount importance. Early detection of decay allows for the reduction of repair costs and, more importantly, the prevention of catastrophic failure. For this purpose, a single fiber reflectance spectrometer was embedded in cement paste samples for the monitoring of water at the fiber tip through its sensitivity to changes in the refractive index. It monitored the curing of samples with different water-to-cement ratios (w/c), between 0.45 and 0.60, measuring the water exhaust during the hardening of the cement paste. It also measured the capillary coefficient from cement paste samples of 0.50, 0.55 and 0.60 w/c: 0.668 ± 0.002 mm/√h, 1.771 ± 0.052 mm/√h and 6.360 ± 0.269 mm/√h, respectively. The capillary coefficient values agree with gravimetric measurements of sorptivity and are further confirmed through porosity measurements made with a scanning electron microscope. Thus, single fiber reflectance spectroscopy can be a gateway to inexpensively measure the entire life cycle of cement, from its curing until its eventual decay, assessing, in situ, its durability through the capillary coefficient. Full article
(This article belongs to the Section Optical Chemical Sensors)
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Article
Ultrasensitive Leaky Surface Acoustic Wave Immunosensor for Real-Time Detection of Alpha-Fetoprotein in Biological Fluids
Chemosensors 2021, 9(11), 311; https://doi.org/10.3390/chemosensors9110311 - 04 Nov 2021
Viewed by 609
Abstract
We propose an ultrasensitive leaky surface acoustic wave (LSAW) immunosensor based on molybdenum disulfide @ cuprous oxide—gold (MoS2@Cu2O-Au) nanoparticles and subsequent gold staining for the detection of alpha-fetoprotein (AFP). MoS2@Cu2O-Au nanoparticles, with their large specific [...] Read more.
We propose an ultrasensitive leaky surface acoustic wave (LSAW) immunosensor based on molybdenum disulfide @ cuprous oxide—gold (MoS2@Cu2O-Au) nanoparticles and subsequent gold staining for the detection of alpha-fetoprotein (AFP). MoS2@Cu2O-Au nanoparticles, with their large specific surface area and good biocompatibility, not only capture the secondary antibodies (Ab2) but also amplify the mass loading effect of the acoustic wave sensor in the detection of AFP. The immunosensor signals are further amplified upon injection of gold staining solution. The developed immunosensor achieved a low detection limit of 5.5 and 25.0 pg/mL with and without gold staining, respectively. The immunosensor demonstrated its efficiency for the quantitative detection of AFP in complex biological fluids, including human serum and saliva samples, with excellent selectivity and long-term stability, showing great potential for the quantification of AFP in clinical diagnosis. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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Communication
“Green” Three-Electrode Sensors Fabricated by Injection-Moulding for On-Site Stripping Voltammetric Determination of Trace In(III) and Tl(I)
Chemosensors 2021, 9(11), 310; https://doi.org/10.3390/chemosensors9110310 - 03 Nov 2021
Cited by 1 | Viewed by 465
Abstract
This work reports the fabrication of a new environmentally friendly three-electrode electrochemical sensor suitable for on-site voltammetric determination of two toxic emerging ‘technology-critical elements’ (TCEs), namely indium and thallium. The sensor is fully fabricated by injection-moulding and features three conductive polymer electrodes encased [...] Read more.
This work reports the fabrication of a new environmentally friendly three-electrode electrochemical sensor suitable for on-site voltammetric determination of two toxic emerging ‘technology-critical elements’ (TCEs), namely indium and thallium. The sensor is fully fabricated by injection-moulding and features three conductive polymer electrodes encased in a plastic holder; the reference electrode is further coated with AgCl or AgBr. The sensor is applied to the determination of trace In(III) and Tl(I) by anodic stripping voltammetry using a portable electrochemical set-up featuring a miniature smartphone-based potentiostat and a vibrating device for agitation. For the analysis, the sample containing the target metal ions is spiked with Bi(III) and a bismuth film is electroplated in situ forming an alloy with the accumulated target metals on the working electrode of the sensor; the metals are stripped off by applying a square-wave anodic voltametric scan. Potential interferences in the determination of In(III) and Tl(I) were alleviated by judicious selection of the solution chemistry. Limits of quantification for the target ions were in the low μg L−1 range and the sensors were applied to the analysis of lake water samples spiked with In(III) and Tl(I) with recoveries in the range of 95–103%. Full article
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Article
An Aptamer-Array-Based Sample-to-Answer Biosensor for Ochratoxin A Detection via Fluorescence Resonance Energy Transfer
Chemosensors 2021, 9(11), 309; https://doi.org/10.3390/chemosensors9110309 - 30 Oct 2021
Cited by 3 | Viewed by 605
Abstract
Food toxins are a hidden threat that can cause cancer and tremendously impact human health. Therefore, the detection of food toxins in a timely manner with high sensitivity is of paramount importance for public health and food safety. However, the current detection methods [...] Read more.
Food toxins are a hidden threat that can cause cancer and tremendously impact human health. Therefore, the detection of food toxins in a timely manner with high sensitivity is of paramount importance for public health and food safety. However, the current detection methods are relatively time-consuming and not practical for field tests. In the present work, we developed a novel aptamer-chip-based sample-to-answer biosensor (ACSB) for ochratoxin A (OTA) detection via fluorescence resonance energy transfer (FRET). In this system, a cyanine 3 (Cy3)-labeled OTA-specific biotinylated aptamer was immobilized on an epoxy-coated chip via streptavidin-biotin binding. A complementary DNA strand to OTA aptamer at the 3′-end was labeled with a black hole quencher 2 (BHQ2) to quench Cy3 fluorescence when in proximity. In the presence of OTA, the Cy3-labeled OTA aptamer bound specifically to OTA and led to the physical separation of Cy3 and BHQ2, which resulted in an increase of fluorescence signal. The limit of detection (LOD) of this ACSB for OTA was 0.005 ng/mL with a linearity range of 0.01–10 ng/mL. The cross-reactivity of ACSB against other mycotoxins, ochratoxin B (OTB), aflatoxin B1 (AFB1), zearalenone (ZEA), or deoxynilvalenol (DON), was less than 0.01%. In addition, this system could accurately detect OTA in rice samples spiked with OTA, and the mean recovery rate of the spiked-in OTA reached 91%, with a coefficient of variation (CV) of 8.57–9.89%. Collectively, the ACSB may represent a rapid, accurate, and easy-to-use platform for OTA detection with high sensitivity and specificity. Full article
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Editorial
Editorial: Organic Fluorescent Materials as Chemical Sensors
Chemosensors 2021, 9(11), 308; https://doi.org/10.3390/chemosensors9110308 - 28 Oct 2021
Viewed by 434
Abstract
The last two decades have witnessed a significant development of fluorescent chemosensors with high sensitivity and selectivity, fast response and in situ detection [...] Full article
(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)
Article
Electrochemical Development of an Immunosensor for Detection Polychlorinated biphenyls (PCBs) for Environmental Analysis
Chemosensors 2021, 9(11), 307; https://doi.org/10.3390/chemosensors9110307 - 28 Oct 2021
Cited by 1 | Viewed by 746
Abstract
Polychlorinated biphenyls (PCBs) are a highly toxic family of synthetic chemical compounds. PCBs are widely spread in the environment and their toxicity can cause serious ailments to living organisms such as cancer; therefore, developing a device for the detection of PCBs in the [...] Read more.
Polychlorinated biphenyls (PCBs) are a highly toxic family of synthetic chemical compounds. PCBs are widely spread in the environment and their toxicity can cause serious ailments to living organisms such as cancer; therefore, developing a device for the detection of PCBs in the environment is significant. In this paper, polyclonal primary anti-PCB antibodies were immobilized onto a gold screen-printed electrode with the purpose of creating an electrochemical immunosensor for the detection of Aroclor 1254. It was modified with 11-mercaptoundecanoic acid (11-MUA) and the activation of the carboxylic acid terminal was performed by cross-linking 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hyrodsuccinmide (NHS) on the electrode surface. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle measurement were employed to characterize SAM development on the gold electrode. Using a competitive assay, a 0.09 ng/mL−1 limit of detection and a linear range of 0.101–220 ng/mL−1 were determined. The self-assembled monolayers (SAM) were successful in encapsulating the PCBs on the immunosensor. The electrochemical detection showed better resolution when compared to traditional methods such as the ELISA optical technique. The novel electrochemical immunosensor approach that is discussed in this paper has the potential to offer rapid sample screening in a portable, disposable format and could contribute to the effective control and prevention of PCBs in the environment. Full article
(This article belongs to the Special Issue Electrochemical Immunosensor)
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Review
Group 4 Metal-Based Metal—Organic Frameworks for Chemical Sensors
Chemosensors 2021, 9(11), 306; https://doi.org/10.3390/chemosensors9110306 - 28 Oct 2021
Cited by 4 | Viewed by 1107
Abstract
Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 [...] Read more.
Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 metal-based (e.g., zirconium, titanium, hafnium, and cerium) MOFs, have become especially of interest for the sensors requiring the operations in aqueous media owing to their remarkable chemical stability in water. Research efforts have been made to utilize these group 4 metal-based MOFs in chemosensors such as luminescent sensors, colorimetric sensors, electrochemical sensors, and resistive sensors for a range of analytes since 2013. Though several studies in this subfield have been published especially over the past 3–5 years, some challenges and concerns are still there and sometimes they might be overlooked. In this review, we aim to highlight the recent progress in the use of group 4 metal-based MOFs in chemical sensors, and focus on the challenges, potential concerns, and opportunities in future studies regarding the developments of such chemically robust MOFs for sensing applications. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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Review
Gold and Silver Nanoparticle-Based Colorimetric Sensors: New Trends and Applications
Chemosensors 2021, 9(11), 305; https://doi.org/10.3390/chemosensors9110305 - 26 Oct 2021
Cited by 3 | Viewed by 722
Abstract
Gold and Silver nanoparticles (AuNPs and AgNPs) are perfect platforms for developing sensing colorimetric devices thanks to their high surface to volume ratio and distinctive optical properties, particularly sensitive to changes in the surrounding environment. These characteristics ensure high sensitivity in colorimetric devices. [...] Read more.
Gold and Silver nanoparticles (AuNPs and AgNPs) are perfect platforms for developing sensing colorimetric devices thanks to their high surface to volume ratio and distinctive optical properties, particularly sensitive to changes in the surrounding environment. These characteristics ensure high sensitivity in colorimetric devices. Au and Ag nanoparticles can be capped with suitable molecules that can act as specific analyte receptors, so highly selective sensors can be obtained. This review aims to highlight the principal strategies developed during the last decade concerning the preparation of Au and Ag nanoparticle-based colorimetric sensors, with particular attention to environmental and health monitoring applications. Full article
(This article belongs to the Special Issue Progress of Nanomaterials for Colorimetric Sensing)
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Review
Enantioresolution and Binding Affinity Studies on Human Serum Albumin: Recent Applications and Trends
Chemosensors 2021, 9(11), 304; https://doi.org/10.3390/chemosensors9110304 - 25 Oct 2021
Viewed by 711
Abstract
The interaction between proteins and drugs or other bioactive compounds has been widely explored over the past years. Several methods for analysis of this phenomenon have been developed and improved. Nowadays, increasing attention is paid to innovative methods, such as high performance affinity [...] Read more.
The interaction between proteins and drugs or other bioactive compounds has been widely explored over the past years. Several methods for analysis of this phenomenon have been developed and improved. Nowadays, increasing attention is paid to innovative methods, such as high performance affinity liquid chromatography (HPALC) and affinity capillary electrophoresis (ACE), taking into account various advantages. Moreover, the development of separation methods for the analysis and resolution of chiral drugs has been an area of ongoing interest in analytical and medicinal chemistry research. In addition to bioaffinity binding studies, both HPALC and ACE al-low one to perform other type of analyses, namely, displacement studies and enantioseparation of racemic or enantiomeric mixtures. Actually, proteins used as chiral selectors in chromatographic and electrophoretic methods have unique enantioselective properties demonstrating suitability for the enantioseparation of a large variety of chiral drugs or other bioactive compounds. This review is mainly focused in chromatographic and electrophoretic methods using human serum albumin (HSA), the most abundant plasma protein, as chiral selector for binding affinity analysis and enantioresolution of drugs. For both analytical purposes, updated examples are presented to highlight recent applications and current trends. Full article
(This article belongs to the Collection Recent Trend in Chromatography for Pharmaceutical Analysis)
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Article
Development of a New Screen-Printed Transducer for the Electrochemical Detection of Thiram
Chemosensors 2021, 9(11), 303; https://doi.org/10.3390/chemosensors9110303 - 25 Oct 2021
Cited by 1 | Viewed by 717
Abstract
A new transducer based on a screen-printed carbon electrode has been developed for the quantification of thiram. Detection of this fungicide is based on the performance of two enzymes: (1) aldehyde dehydrogenase catalyzes the aldehyde oxidation using NAD+ as a cofactor and [...] Read more.
A new transducer based on a screen-printed carbon electrode has been developed for the quantification of thiram. Detection of this fungicide is based on the performance of two enzymes: (1) aldehyde dehydrogenase catalyzes the aldehyde oxidation using NAD+ as a cofactor and simultaneously, (2) diaphorase reoxidizes the NADH formed in the first enzymatic process due to the presence of hexacyanoferrate(III) which is reduced to hexacyanoferrate(II). Taking into account that aldehyde dehydrogenase is inhibited by thiram, the current decreases with pesticide concentration and thiram can be electrochemically quantified below legal limits. The transducer proposed in this work involves the modification of the carbon WE with the co-factors (NAD+ and hexacyanoferrate(III)) required in the enzymatic system. The new device employed in this work allows the detection of 0.09 ppm thiram, a concentration below legal limits (Maximum Residue Limits 0.1–10 ppm). Full article
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Review
Squaraine-Based Optical Sensors: Designer Toolbox for Exploring Ionic and Molecular Recognitions
Chemosensors 2021, 9(11), 302; https://doi.org/10.3390/chemosensors9110302 - 25 Oct 2021
Cited by 2 | Viewed by 849
Abstract
Small molecule-based chromogenic and fluorogenic probes play an indispensable role in many sensing applications. Ideal optical chemosensors should provide selectivity and sensitivity towards a variety of analytes. Synthetic accessibility and attractive photophysical properties have made squaraine dyes an enticing platform for the development [...] Read more.
Small molecule-based chromogenic and fluorogenic probes play an indispensable role in many sensing applications. Ideal optical chemosensors should provide selectivity and sensitivity towards a variety of analytes. Synthetic accessibility and attractive photophysical properties have made squaraine dyes an enticing platform for the development of chemosensors. This review highlights the versatility of modular assemblies of squaraine-based chemosensors and chemodosimeters that take advantage of the availability of various structurally and functionally diverse recognition motifs, as well as utilizing additional recognition capabilities due to the unique structural features of the squaraine ring. Full article
(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)
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Article
Highly Fluorescent Carbon Dots as a Potential Fluorescence Probe for Selective Sensing of Ferric Ions in Aqueous Solution
Chemosensors 2021, 9(11), 301; https://doi.org/10.3390/chemosensors9110301 - 25 Oct 2021
Cited by 3 | Viewed by 857
Abstract
This paper’s emphasis is on the development of a fluorescent chemosensor for Fe3+ ions in an aqueous solution, using hydrophilic carbon dots (O-CDs). A simple, cost-effective, and environmentally friendly one-step hydrothermal synthesis method was used to synthesize fluorescent hydrophilic O [...] Read more.
This paper’s emphasis is on the development of a fluorescent chemosensor for Fe3+ ions in an aqueous solution, using hydrophilic carbon dots (O-CDs). A simple, cost-effective, and environmentally friendly one-step hydrothermal synthesis method was used to synthesize fluorescent hydrophilic O-CDs from Oxalis corniculata (Family; Oxalidaceae). The graphitic structure and size distribution of the O-CDs was verified by X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy studies. The resulting O-CDs had a near-spherical shape and an adequate degree of graphitization at the core, with an average diameter of 4.5 nm. X-ray photoelectron and Fourier transform infrared spectroscopy methods revealed the presence of several hydrophilic groups (carbonyl, amine, carboxyl, and hydroxyl, along with nitrogen and oxygen-rich molecules) on the surface of O-CDs. The synthesized hydrophilic O-CDs with excitation wavelength-dependent emission fluorescence characteristics showed a high quantum yield of about 20%. Besides this, the hydrophilic O-CDs exhibited a bright and controllable fluorescence with prolonged stability and photo-stability. These fluorescent hydrophilic O-CDs were used as a nanoprobe for the fluorometric identification of Fe3+ ions in an aqueous solution, with high sensitivity and selectivity. By quenching the blue emission fluorescence of this nanosensor, a highly sensitive Fe3+ ion in the range of 10–50 µM with a minimum detection limit of 0.73 µM was achieved. In addition, the developed nanosensor can be used to sense intracellular Fe3+ ions with high biocompatibility and cellular imaging capacity, and it has a lot of potential in biomedical applications. Full article
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Article
Effect of Al and Mg Doping on Reducing Gases Detection of ZnO Nanoparticles
Chemosensors 2021, 9(11), 300; https://doi.org/10.3390/chemosensors9110300 - 24 Oct 2021
Cited by 3 | Viewed by 785
Abstract
In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg1% doped ZnO, Al5% doped ZnO and (Al5%, Mg1%) co-doped ZnO [...] Read more.
In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg1% doped ZnO, Al5% doped ZnO and (Al5%, Mg1%) co-doped ZnO nanoparticles (NPs) were synthesized by a modified sol-gel method. The structural characterization showed the hexagonal crystalline structure of the prepared samples. Morphological characterizations confirmed the nanometric sizes of the NPs (27–57 nm) and elemental composition investigation proved the existence of Al and Mg with low concentrations. The optical characterization showed the high absorbance of the synthesized samples in the UV range. The gas sensing performances of the synthesized samples, prepared in the form of thick films, were investigated. Sensing tests demonstrated the high influence of the Al and Mg on the sensing performances towards H2 and CO gas, respectively. The 5A1MZO-based sensor exhibits high sensitivity and low detection limits to H2 (<2 ppm) and CO (<1 ppm). It showed a response around 70 (at 250 °C) towards 2000 ppm H2 and 2 (at 250 °C) towards CO. Full article
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Review
The Challenges of Developing Biosensors for Clinical Assessment: A Review
Chemosensors 2021, 9(11), 299; https://doi.org/10.3390/chemosensors9110299 - 24 Oct 2021
Cited by 2 | Viewed by 1067
Abstract
Emerging research in biosensors has attracted much attention worldwide, particularly in response to the recent pandemic outbreak of coronavirus disease 2019 (COVID-19). Nevertheless, initiating research in biosensing applied to the diagnosis of diseases is still challenging for researchers, be it in the preferences [...] Read more.
Emerging research in biosensors has attracted much attention worldwide, particularly in response to the recent pandemic outbreak of coronavirus disease 2019 (COVID-19). Nevertheless, initiating research in biosensing applied to the diagnosis of diseases is still challenging for researchers, be it in the preferences of biosensor platforms, selection of biomarkers, detection strategies, or other aspects (e.g., cutoff values) to fulfill the clinical purpose. There are two sides to the development of a diagnostic tool: the biosensor development side and the clinical side. From the development side, the research engineers seek the typical characteristics of a biosensor: sensitivity, selectivity, linearity, stability, and reproducibility. On the other side are the physicians that expect a diagnostic tool that provides fast acquisition of patient information to obtain an early diagnosis or an efficient patient stratification, which consequently allows for making assertive and efficient clinical decisions. The development of diagnostic devices always involves assay developer researchers working as pivots to bridge both sides whose role is to find detection strategies suitable to the clinical needs by understanding (1) the intended use of the technology and its basic principle and (2) the preferable type of test: qualitative or quantitative, sample matrix challenges, biomarker(s) threshold (cutoff value), and if the system requires a mono- or multiplex assay format. This review highlights the challenges for the development of biosensors for clinical assessment and its broad application in multidisciplinary fields. This review paper highlights the following biosensor technologies: magnetoresistive (MR)-based, transistor-based, quartz crystal microbalance (QCM), and optical-based biosensors. Its working mechanisms are discussed with their pros and cons. The article also gives an overview of the most critical parameters that are optimized by developing a diagnostic tool. Full article
(This article belongs to the Special Issue Chemical Sensors for Bio-Medical and Environmental Applications)
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