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Chemosensors, Volume 11, Issue 2 (February 2023) – 80 articles

Cover Story (view full-size image): Fascinating optical properties of nano-metals, due to excitation of Surface Plasmon (SP) modes, have been applied in different fields. Label-free biological and chemical sensing is the most relevant for health, environmental and food safety fields. Engineering the spectral features by tuning geometric parameters of metal nanostructures, namely shape, size and distances among them, is a key route for improving the sensing performance of plasmonic sensors.  In the paper, a cost-effective nanofabrication technique, based on the self-assembly of a colloidal mask, is investigated. A fine tuning of mask geometrical features is reflected in a variety of plasmonic nanostructures with different functional abilities owing to a different distribution of the enhanced local field. A specific sensing application of interest in the agrifood sector is demonstrated. View this paper
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12 pages, 2202 KiB  
Article
Discovering a Dihydrofluorescein Analogue as a Promising Fluorescence Substrate to HRP
Chemosensors 2023, 11(2), 152; https://doi.org/10.3390/chemosensors11020152 - 20 Feb 2023
Cited by 2 | Viewed by 1525
Abstract
Horseradish peroxidase (HRP) combined with its fluorescence substrates is attracting increasing attention for biochemical analysis. Amplex red is the most widely used fluorescence substrate to HRP; however, it suffers from some drawbacks, such as nonspecific responsiveness toward carboxylesterases. Discovering a new small molecular [...] Read more.
Horseradish peroxidase (HRP) combined with its fluorescence substrates is attracting increasing attention for biochemical analysis. Amplex red is the most widely used fluorescence substrate to HRP; however, it suffers from some drawbacks, such as nonspecific responsiveness toward carboxylesterases. Discovering a new small molecular fluorescence substrate with improved sensitivity and selectivity for HRP is thus desired. Herein, three dihydrofluorescein derivatives (DCFHs) are presented to serve as HRP substrates through fluorescence turn-on methods. The most promising one, 2,7-dichloro-9-(2-(hydroxymethyl)phenyl)-9H-xanthene-3,6-diol (DCFH-1), exhibited excellent sensitivity in the detection of HRP. Moreover, DCFH-1 does not respond to carboxylesterase, thus holding advantages over Amplex red. In the further study, the detection reagent in the commercial ELISA kits was replaced with DCFH-1 to establish a new fluorescence ELISA, which works very well in the quantification of inflammatory cytokine biomarkers from in vitro models. Full article
(This article belongs to the Collection Advances of Chemical and Biosensors in China)
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12 pages, 4529 KiB  
Article
A Paper-Chip-Based Phage Biosensor Combined with a Smartphone Platform for the Quick and On-Site Analysis of E. coli O157:H7 in Foods
Chemosensors 2023, 11(2), 151; https://doi.org/10.3390/chemosensors11020151 - 20 Feb 2023
Cited by 2 | Viewed by 1503
Abstract
The rapid and specific point-of-care (POC) analysis of virulent pathogenic strains plays a key role in ensuring food quality and safety. In this work, a paper-based fluorescent phage biosensor was developed for the detection of the virulent E. coli O157:H7 strain (as the [...] Read more.
The rapid and specific point-of-care (POC) analysis of virulent pathogenic strains plays a key role in ensuring food quality and safety. In this work, a paper-based fluorescent phage biosensor was developed for the detection of the virulent E. coli O157:H7 strain (as the mode of virulent pathogens) in food samples. Firstly, phages that can specifically combine with E. coli O157:H7 (E. coli) were stained with SYTO-13 dye to prepare a novel fluorescent probe (phage@SYTO). Simultaneously, a micro-porous membrane filter with a pore size of 0.45 μm was employed as a paper chip so as to retain the E. coli-phage@SYTO complex (>1.2 μm) on its surface. The phage@SYTO (200 nm in size) was able to pass through the pores of the chip, and the complex could be retained on the paper chip using the free phage@SYTO probes. The E. coli-phage@SYTO could emit a visual fluorescent signal (excited at 365 nm; emitted at 520 nm) onto the chip, which could be detected by a smartphone to reflect the concentration of E. coli. Under optimized conditions, the detection limit was as low as 50 CFU/mL (S/N = 3) and exhibited a wide linear range from 102 to 106 CFU/mL. The sensor has potential application value for the quick and specific POCT detection of virulent E. coli in foods. Full article
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8 pages, 2271 KiB  
Communication
Direct Determination of Three PAHs in Drill Cuttings Recycling Products by Solid-Surface 3D Fluorescence Coupled with Chemometrics
Chemosensors 2023, 11(2), 150; https://doi.org/10.3390/chemosensors11020150 - 20 Feb 2023
Viewed by 1103
Abstract
In this work, the feasibility of solid-surface three-dimensional fluorescence (SSTF) in combination with chemometrics to rapidly and directly determine three PAHs in drill cuttings recycling products was studied for the first time. Due to the nondestructive characteristics of SSTF and the “mathematical separation” [...] Read more.
In this work, the feasibility of solid-surface three-dimensional fluorescence (SSTF) in combination with chemometrics to rapidly and directly determine three PAHs in drill cuttings recycling products was studied for the first time. Due to the nondestructive characteristics of SSTF and the “mathematical separation” of chemometric three-way calibration, neither time-consuming sample pretreatments nor toxic organic reagents were involved in the determination. By using the smart “mathematical separation” function of the parallel factor analysis (PARAFAC) algorithm, clear spectral profiles together with reasonable quantitative results for the three target PAHs were successfully extracted from the total SSTF signals of drill cuttings recycling products without the need for chromatographic separation. The linearity of the calibration models was good (R2 > 0.96) and the average spiked recoveries of three target PAHs were between 88.1–102.7% with a relative standard deviation less than 20%. Nevertheless, given the green, fast, low-cost, and nondestructive advantages of the proposed strategy, it has the potential to be used as a fast screening approach and allow for a quick survey of PAHs in drill cuttings recycling products. Full article
(This article belongs to the Special Issue Chemometrics for Analytical Chemistry)
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11 pages, 2579 KiB  
Article
Continuous Glucose Monitoring in Hypoxic Environments Based on Water Splitting-Assisted Electrocatalysis
Chemosensors 2023, 11(2), 149; https://doi.org/10.3390/chemosensors11020149 - 18 Feb 2023
Cited by 1 | Viewed by 2027
Abstract
Conventional enzyme-based continuous glucose sensors in interstitial fluid usually rely on dissolved oxygen as the electron-transfer mediator to bring electrons from oxidase to electrode while generating hydrogen peroxide. This may lead to several problems. First, the sensor may provide biased detection results owing [...] Read more.
Conventional enzyme-based continuous glucose sensors in interstitial fluid usually rely on dissolved oxygen as the electron-transfer mediator to bring electrons from oxidase to electrode while generating hydrogen peroxide. This may lead to several problems. First, the sensor may provide biased detection results owing to fluctuation of oxygen in interstitial fluid. Second, the polymer coatings that regulate the glucose/oxygen ratio can affect the dynamic response of the sensor. Third, the glucose oxidation reaction continuously produces corrosive hydrogen peroxide, which may compromise the long-term stability of the sensor. Here, we introduce an oxygen-independent nonenzymatic glucose sensor based on water splitting-assisted electrocatalysis for continuous glucose monitoring. For the water splitting reaction (i.e., hydrogen evolution reaction), a negative pretreatment potential is applied to produce a localized alkaline condition at the surface of the working electrode for subsequent nonenzymatic electrocatalytic oxidation of glucose. The reaction process does not require the participation of oxygen; therefore, the problems caused by oxygen can be avoided. The nonenzymatic sensor exhibits acceptable sensitivity, reliability, and biocompatibility for continuous glucose monitoring in hypoxic environments, as shown by the in vitro and in vivo measurements. Therefore, we believe that it is a promising technique for continuous glucose monitoring, especially for clinically hypoxic patients. Full article
(This article belongs to the Collection Advances of Chemical and Biosensors in China)
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15 pages, 2509 KiB  
Article
Tailoring Magnetic Properties and Magnetoimpedance Response in Nanocrystalline (Fe3Ni)81Nb7B12 Ribbons for Sensor Applications
Chemosensors 2023, 11(2), 148; https://doi.org/10.3390/chemosensors11020148 - 17 Feb 2023
Cited by 2 | Viewed by 1026
Abstract
Today, there is an increasing demand for progress in the magnetoimpedance (MI) response of cost-effective soft-magnetic materials for use in high-performance sensing devices. In view of this, we investigate here the field-annealing effects on soft-magnetic properties, magnetoimpedance response, and field sensitivity in the [...] Read more.
Today, there is an increasing demand for progress in the magnetoimpedance (MI) response of cost-effective soft-magnetic materials for use in high-performance sensing devices. In view of this, we investigate here the field-annealing effects on soft-magnetic properties, magnetoimpedance response, and field sensitivity in the nanocrystalline (Fe3Ni)81Nb7B12 alloy ribbons. We observe that within the low-frequency regime, between 2 and 5 MHz, the zero-field-annealed (ZFA) ribbons exhibit the highest magnetoimpedance values. By magneto-optical Kerr effect measurements, we show that this result stems from the formation of irregular transversally patched magnetic domains after annealing, which in turn explains the induced transverse anisotropy necessary to increase the GMI response. In addition, we discuss this increment in terms of skin effect. Moreover, we report that the highest sensitivity of ca. 189%/(kA/m)—15%/Oe—is achieved for the field-annealed samples whose magnetic field was applied transverse to the ribbon axis. These findings are of practical importance to develop and refine highly sensitive magnetic sensors. Full article
(This article belongs to the Special Issue Advances in Magnetic Sensors with Nanocomponents)
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12 pages, 3460 KiB  
Article
Different Diacetyl Perception Detected through MOX Sensors in Real-Time Analysis of Beer Samples
Chemosensors 2023, 11(2), 147; https://doi.org/10.3390/chemosensors11020147 - 16 Feb 2023
Cited by 1 | Viewed by 1211
Abstract
Beer is the most consumed alcoholic beverage; with 177.5 million kiloliters produced every year, it is one of the most relevant food products. Diacetyl is a typical byproduct of yeast metabolism that is formed during the fermentation inside breweries. The perception of this [...] Read more.
Beer is the most consumed alcoholic beverage; with 177.5 million kiloliters produced every year, it is one of the most relevant food products. Diacetyl is a typical byproduct of yeast metabolism that is formed during the fermentation inside breweries. The perception of this high volatile and butter-like flavor molecule varies according to the kind of beer, from a positive and highly sought characteristic to a characteristic that is avoided. Furthermore, its toxicity when inhaled has been proven. Typical diacetyl analysis includes voltametric detection and chromatographic analysis techniques. Using metal oxide sensors (MOS), this analysis can become fast and cost-effective, evaluating the differences in diacetyl concentrations through resistance variation. The S3+ (Nano Sensor Systems s.r.l.; Reggio Emilia, Italy; device can recognize volatile compounds through a tailormade array of different materials. The results can be shown on a PCA that is directly generated by the instruments and can be used to manage the productive process through an IoT integrated system. Testing different beer typology through electrochemical sensors allows for the validation of this new approach for diacetyl evaluation. The results have shown an excellent ability to detect diacetyl in different beer samples, perfectly discriminating among different concentrations. Full article
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14 pages, 32178 KiB  
Article
Study on Denoising Method of Photoionization Detector Based on Wavelet Packet Transform
Chemosensors 2023, 11(2), 146; https://doi.org/10.3390/chemosensors11020146 - 16 Feb 2023
Cited by 1 | Viewed by 1152
Abstract
Aiming at the task of noise suppression caused by the photoionization detector (PID) monitoring signal of volatile organic compounds (VOCs) due to local non-uniformity of the photocathode surface of PID in the ionization chamber, this paper proposes an analytical method of a PID [...] Read more.
Aiming at the task of noise suppression caused by the photoionization detector (PID) monitoring signal of volatile organic compounds (VOCs) due to local non-uniformity of the photocathode surface of PID in the ionization chamber, this paper proposes an analytical method of a PID signal with the adaptive weight of the small wave package decomposition node. The PID signal is transmitted to the upper machine software through the single-chip microcontroller. The appropriate wavelet packet decomposition level is determined according to the time frequency characteristics of the original signal of the PID, and the optimal wavelet packet base is selected through the polynomial fitting of the signal quality evaluation index. By comparing the quality of signals processed by the traditional wavelet packet denoising method and the denoising method presented in this paper, the superiority of the proposed method in the denoising signals of PID was verified. This method can eliminate the noise generated by local non-uniformity on the photocathode surface of the PID ionization chamber in a high humidity environment, which lays a foundation for the accurate monitoring of VOCs in a high humidity environment. Full article
(This article belongs to the Special Issue Chemical Sensors for Volatile Organic Compound Detection)
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16 pages, 3438 KiB  
Article
New ICT-Based Ratiometric Two-Photon near Infrared Probe for Imaging Tyrosinase in Living Cells, Tissues, and Whole Organisms
Chemosensors 2023, 11(2), 145; https://doi.org/10.3390/chemosensors11020145 - 16 Feb 2023
Viewed by 1657
Abstract
Melanoma is a type of highly malignant and metastatic skin cancer. In situ molecular imaging of endogenous levels of the melanoma biomarker tyrosinase (TYR) may decrease the likelihood of mortality. In this study, we proposed the weakly fluorescent probe 1-(4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenyl)-3-(4-hydroxybenzyl)urea (DCM-HBU), which releases [...] Read more.
Melanoma is a type of highly malignant and metastatic skin cancer. In situ molecular imaging of endogenous levels of the melanoma biomarker tyrosinase (TYR) may decrease the likelihood of mortality. In this study, we proposed the weakly fluorescent probe 1-(4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenyl)-3-(4-hydroxybenzyl)urea (DCM-HBU), which releases a strong red-shifted fluorescent signal after a TYR-mediated oxidation followed by hydrolysis of the urea linkage. The large Stokes shift of the dye is owed to the recovery of the intramolecular charge transfer (ICT) effect. The resulting probe derivate shows a highly ratiometric fluorescence output. Furthermore, the simultaneous excitation by two near-infrared (NIR) photons of the released derivative of dicyanomethylene-4H-pyran (DCM-NH2) fluorophore could avoid the usual drawbacks, such as cellular absorption, autofluorescence, and light scattering, due to an usually short wavelength of the excitation light on biological systems, resulting in images with deeper tissue penetration. In addition, the probe is useful for the quantitative sensing of TYR activity in vivo, as demonstrated in zebrafish larvae. This new ratiometric two-photon NIR fluorescent probe is expected to be useful for the accurate detection of TYR in complex biosystems at greater depths than other one-photon excited fluorescent probes. Full article
(This article belongs to the Special Issue Advances in Fluorescence Sensing)
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22 pages, 6718 KiB  
Review
Trends in Molecularly Imprinted Polymers (MIPs)-Based Plasmonic Sensors
Chemosensors 2023, 11(2), 144; https://doi.org/10.3390/chemosensors11020144 - 15 Feb 2023
Cited by 3 | Viewed by 1842
Abstract
In recent years, plasmonic sensors have been used in various fields ranging from environmental monitoring, pharmaceutical analysis, medical diagnosis, and food quality assessment to forensics. A significant amount of information on plasmonic sensors and their applications already exists and there is a continuing [...] Read more.
In recent years, plasmonic sensors have been used in various fields ranging from environmental monitoring, pharmaceutical analysis, medical diagnosis, and food quality assessment to forensics. A significant amount of information on plasmonic sensors and their applications already exists and there is a continuing development of reliable, selective, sensitive, and low-cost sensors. Combining molecularly imprinting technology with plasmonic sensors is an increasingly timely and important challenge to obtain portable, easy-to-use, particularly selective devices helpful in detecting analytes at the trace level. This review proposes an overview of the applications of molecularly imprinted plasmonic chemosensors and biosensors, critically discussing the performances, pros, and cons of the more recently developed devices. Full article
(This article belongs to the Special Issue Molecularly Imprinted Plasmonic Sensor)
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15 pages, 5230 KiB  
Article
A Dinitrophenol-Based Colorimetric Chemosensor for Sequential Cu2+ and S2− Detection
Chemosensors 2023, 11(2), 143; https://doi.org/10.3390/chemosensors11020143 - 15 Feb 2023
Cited by 4 | Viewed by 1516
Abstract
A dinitrophenol-based colorimetric chemosensor sequentially sensing Cu2+ and S2−, HDHT ((E)-2-(2-(2-hydroxy-3,5-dinitrobenzylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium), was designed and synthesized. The HDHT selectively detected Cu2+ through a color change of yellow to colorless. The calculated detection limit of the HDHT [...] Read more.
A dinitrophenol-based colorimetric chemosensor sequentially sensing Cu2+ and S2−, HDHT ((E)-2-(2-(2-hydroxy-3,5-dinitrobenzylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium), was designed and synthesized. The HDHT selectively detected Cu2+ through a color change of yellow to colorless. The calculated detection limit of the HDHT for Cu2+ was 6.4 × 10−2 μM. In the interference test, the HDHT was not considerably inhibited by various metal ions in its detection of Cu2+. The chelation ratio of the HDHT to Cu2+ was determined as 1:1 by using a Job plot and ESI-MS experiment. In addition, the HDHT–Cu2+ complex showed that its color selectively returned to yellow only in the presence of S2−. The detection limit of the HDHT–Cu2+ complex for S2− was calculated to be 1.2 × 10−1 μM. In the inhibition experiment for S2−, the HDHT–Cu2+ complex did not significantly interfere with other anions. In the real water-sample test, the detection performance of the HDHT for Cu2+ and S2− was successfully examined. The detection features of HDHT for Cu2+ and the HDHT–Cu2+ for S2− were suggested by the Job plot, UV–Vis, ESI-MS, FT-IR spectroscopy, and DFT calculations. Full article
(This article belongs to the Special Issue Chemical Sensors and Analytical Methods for Environmental Monitoring)
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15 pages, 5615 KiB  
Article
Chemoresistive Properties of V2CTx MXene and the V2CTx/V3O7 Nanocomposite Based on It
Chemosensors 2023, 11(2), 142; https://doi.org/10.3390/chemosensors11020142 - 15 Feb 2023
Cited by 7 | Viewed by 1731 | Correction
Abstract
The in-situ Raman spectroscopy oxidation of the accordion-like V2CTx MXene has been studied. It was found that a nanocomposite of V2CTx/V3O7 composition was formed as a result. The elemental and phase composition, the [...] Read more.
The in-situ Raman spectroscopy oxidation of the accordion-like V2CTx MXene has been studied. It was found that a nanocomposite of V2CTx/V3O7 composition was formed as a result. The elemental and phase composition, the microstructure of the synthesized V2CTx powder and MXene film as well as the V2CTx/V3O7 nanocomposite obtained at a minimum oxidation temperature of 250 °C were studied using a variety of physical and chemical analysis methods. It was found that the obtained V2CTx and V2CTx/V3O7 films have an increased sensitivity to ammonia and nitrogen dioxide, respectively, at room temperature and zero humidity. It was shown that the V2CTx/V3O7 composite material is characterized by an increase in the response value for a number of analytes (including humidity) by more than one order of magnitude, as well as a change in their detection mechanisms compared to the individual V2CTx MXene. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes)
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13 pages, 2744 KiB  
Article
Electrochemical Sensing Platform Based on Renewable Carbon Modified with Antimony Nanoparticles for Methylparaben Detection in Personal Care Products
Chemosensors 2023, 11(2), 141; https://doi.org/10.3390/chemosensors11020141 - 15 Feb 2023
Cited by 5 | Viewed by 1341
Abstract
This paper describes for the first time the surface modification of glassy carbon (GC) electrodes with bamboo-based renewable carbon (RC) and antimony nanoparticles (SbNPs) for the determination of methylparaben (MePa) in personal care products (PCPs). The synthesized RC-SbNP material was successfully characterized by [...] Read more.
This paper describes for the first time the surface modification of glassy carbon (GC) electrodes with bamboo-based renewable carbon (RC) and antimony nanoparticles (SbNPs) for the determination of methylparaben (MePa) in personal care products (PCPs). The synthesized RC-SbNP material was successfully characterized by scanning electron microcopy, energy-dispersive X-ray spectroscopy and cyclic voltammetry. The proposed sensor was applied in the detection of MePa using the optimized parameters by differential pulse voltammetry (DPV). The analytical range for detection of MePa was 0.2 to 9.0 µmol L−1, with limits of detection and quantification of 0.05 µmol L−1 and 0.16 µmol L−1, respectively. The determination of MePa in real PCP samples was performed using the proposed GC/RC-SbNP sensor by DPV and UV-vis spectrophotometry as comparative methodology. The use of RC-SbNP material for the development of electrochemical sensors brings a fresh approach to low-cost devices for MePa analysis. Full article
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14 pages, 10865 KiB  
Article
Formaldehyde Gas Sensing Characteristics of ZnO-TiO2 Gas Sensors
Chemosensors 2023, 11(2), 140; https://doi.org/10.3390/chemosensors11020140 - 14 Feb 2023
Cited by 2 | Viewed by 1388
Abstract
Since the increase in the emission of various Volatiles Organic Compounds, gas and formaldehyde gas have had a harmful effect on the human body, and gas sensors that can measure those gases were fabricated in this study. After Pt coating was performed on [...] Read more.
Since the increase in the emission of various Volatiles Organic Compounds, gas and formaldehyde gas have had a harmful effect on the human body, and gas sensors that can measure those gases were fabricated in this study. After Pt coating was performed on the alumina substrate, Zn seed layers were fabricated. Nanostructures were formed through sonochemical synthesis by varying the ratio of ZnO and TiO2. Thereafter, the reactivity and recovery properties were compared and evaluated according to the concentrations of formaldehyde and toluene gas. The ZnO(99%)-TiO2(1%) gas sensor showed meaningful selectivity of about 40% or more at a concentration ranging from 5 to 20 ppm (high concentration) of formaldehyde and toluene gas, and showed a low selectivity of about 5% or more for a concentration ranging from 0.1 to 1 ppm (low concentration) of formaldehyde and toluene gas. This sensor can be optimized to have a meaningful selectivity of formaldehyde gas compared to other Volatiles Organic Compounds gases by optimizing the ZnO-TiO2 nanostructure. Full article
(This article belongs to the Special Issue Gas Sensors and Electronic Noses for the Real Condition Sensing)
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17 pages, 4051 KiB  
Article
Ion Mobility Spectrometry for the Metabolomic Study of Inflammatory Bowel Disease Using the Volatile Organic Compounds Profile in Human Serum and Urine
Chemosensors 2023, 11(2), 139; https://doi.org/10.3390/chemosensors11020139 - 14 Feb 2023
Cited by 1 | Viewed by 1334
Abstract
Inflammatory bowel disease (IBD) is an immune-mediated disease characterized by chronic mucosal inflammation of the digestive tract. The IBD diagnosis is currently based on the results of imaging, clinical, and histopathological tests. The gold standard diagnostic method is endoscopy, an invasive imaging technique [...] Read more.
Inflammatory bowel disease (IBD) is an immune-mediated disease characterized by chronic mucosal inflammation of the digestive tract. The IBD diagnosis is currently based on the results of imaging, clinical, and histopathological tests. The gold standard diagnostic method is endoscopy, an invasive imaging technique that requires patient sedation and prior bowel preparation and is expensive. In the present work, monitoring the volatile compound fingerprint of serum and urine by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) is presented as a rapid and reliable diagnostic complementary test for patients with IBD. The analytical method was optimized and applied for the analysis of serum (118) and urine (123) samples from patients with IBD (in remission and active phase of the disease) and healthy volunteers without IBD. Orthogonal partial least square discriminant analysis was performed using all the integrated markers present in the topographic maps of each sample type, allowing the differentiation between healthy IBD volunteers and IBD patients and between IBD status (remission or active). The individual study of markers allowed the identification and quantification of twelve and six compounds in urine and serum samples, respectively. This information was further used to perform a one-way analysis of variance to compare the different categories. Full article
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19 pages, 5795 KiB  
Article
Microplotter Printing of Hierarchically Organized NiCo2O4 Films for Ethanol Gas Sensing
Chemosensors 2023, 11(2), 138; https://doi.org/10.3390/chemosensors11020138 - 14 Feb 2023
Cited by 6 | Viewed by 1382
Abstract
Using a combination of chemical coprecipitation and hydrothermal treatment of the resulting dispersed system, a hierarchically organized NiCo2O4 nanopowder was obtained, consisting of slightly elongated initial oxide nanoparticles self-organized into nanosheets about 10 nm thick, which in turn are combined [...] Read more.
Using a combination of chemical coprecipitation and hydrothermal treatment of the resulting dispersed system, a hierarchically organized NiCo2O4 nanopowder was obtained, consisting of slightly elongated initial oxide nanoparticles self-organized into nanosheets about 10 nm thick, which in turn are combined into hierarchical cellular agglomerates of about 2 μm. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HR-TEM) allowed to confirm the formation of NiCo2O4 powder with the desired crystal structure via additional heat treatment of the intermediate product. Energy-dispersive X-ray spectroscopy (EDX) was used to confirm the target metal ratio, and the uniform distribution of the elements (Ni, Co and O) was shown by mapping. The resulting nanopowder was employed to prepare functional inks suitable for microplotter printing of the NiCo2O4 film. It was found that an oxide film morphology is fully inherited from the hierarchically organized oxide nanopowder used. Atomic force microscopy (AFM) revealed the film thickness (15 μm) and determined the maximum height difference of 500 nm over an area of 25 μm2. Kelvin probe force microscopy (KPFM) showed that the surface potential was shifted to the depths of the oxide film, and the work function value of the material surface was 4.54 eV, which is significantly lower compared to those reported in the literature. The electronic state of the elements in the NiCo2O4 film under study was analyzed by X-ray photoelectron spectroscopy (XPS). Chemosensor measurements showed that the printed receptor layer exhibited selectivity and high signal reproducibility for ethanol detection. As the relative humidity increases from 0 to 75%, the response value is reduced; however, the sensor response profile and signal-to-noise ratio remain without significant changes. Full article
(This article belongs to the Special Issue The State-of-the-Art Gas Sensor)
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11 pages, 2560 KiB  
Communication
Investigation of the Colorimetric Characteristics of VX in Squaraine-Based Solutions
Chemosensors 2023, 11(2), 137; https://doi.org/10.3390/chemosensors11020137 - 14 Feb 2023
Viewed by 1122
Abstract
Colorimetry is an important on-site detection method for organophosphorus compounds. O-Ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate (VX) is recognized as one of the deadliest organophosphorus chemical agents, and the rapid on-site detection of VX is of great significance to public safety. In this paper, [...] Read more.
Colorimetry is an important on-site detection method for organophosphorus compounds. O-Ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate (VX) is recognized as one of the deadliest organophosphorus chemical agents, and the rapid on-site detection of VX is of great significance to public safety. In this paper, a squaraine derivative was synthesized as probe molecules, and the sensing characteristics of VX in a colorimetric solution system containing tetrabutylammonium fluoride (TABF) were studied with UV−Vis spectroscopy, nuclear magnetic resonance (1H NMR), and mass spectrometry. The results showed that the binding of the thiol moiety of VX to the quaternary ring of the squaraine probe changed the molecular conjugation system, and that the rapid colorimetric detection of micro-trace VX was achieved based on color change before and after interaction with squaraine, enabling the detection limit of VX to be as low as 0.4 μg/mL. Moreover, the colorimetry method also possessed satisfactory sensitivity and could detect VX from other organophosphorus pesticides (e.g., parathion and dichlorvos), phosphorus-containing reagents (e.g., diethyl chlorophosphate and dimethyl methylphosphonate), a benzene series (e.g., toluene), and acid and base agents (e.g., acetic acid and triethylamine, respectively), which demonstrated that squaraine-based colorimetry could provide fast, on-site measurement results for VX detection. The strategy of this research could be extended as a common approach for the detection of other organophosphorus nerve agents or organophosphorus pesticides. Full article
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17 pages, 3501 KiB  
Article
Comparison of Surface and Spectral Properties of Optical Sensor Layers Prepared by Spin/Spray Coating and Printing Techniques
Chemosensors 2023, 11(2), 136; https://doi.org/10.3390/chemosensors11020136 - 13 Feb 2023
Viewed by 1015
Abstract
This study investigated the surface properties of optical sensor layers prepared using sol-gel technology and their response to dissolved NH3. A glass substrate was used to fabricate the optical sensor layers. The sol-gel solution was applied to the glass substrate using [...] Read more.
This study investigated the surface properties of optical sensor layers prepared using sol-gel technology and their response to dissolved NH3. A glass substrate was used to fabricate the optical sensor layers. The sol-gel solution was applied to the glass substrate using three different techniques: spin coating (SC), inkjet printing (IP), and spray coating (SP). In this work, we have attempted to investigate the effects of the different techniques for producing the sensor layers and to determine their response in the presence of ammonia. The surface properties (surface free energy—SFE and surface chemical composition—XPS) and spectral properties (response to ammonia and real-time response) of the prepared optical sensor layers were characterised. The results show that the sensor layers prepared by different techniques have similar SFE and XPS values, but different responses to dissolved NH3 solution and different responses in real-time measurements (exposure to fresh fish). Sensor layers prepared with a spray coating (SP) are the most responsive, the most sensitive, and have a higher response over time and the biggest colour change compared to SC and IP sensor layers. Full article
(This article belongs to the Section Optical Chemical Sensors)
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14 pages, 4438 KiB  
Article
Inhibitors of the RBD-ACE-2 Found among a Wide Range of Dyes by the Immunoassay Method
Chemosensors 2023, 11(2), 135; https://doi.org/10.3390/chemosensors11020135 - 13 Feb 2023
Cited by 1 | Viewed by 1393
Abstract
Angiotensin-converting enzyme 2 (ACE2), the functional receptor of SARS-CoV-2, plays a crucial role in the pathogenesis of COVID-19. ACE2 targeting holds the promise for preventing and inhibiting SARS-CoV-2 infection. In this work, we describe the development and use of a test system based [...] Read more.
Angiotensin-converting enzyme 2 (ACE2), the functional receptor of SARS-CoV-2, plays a crucial role in the pathogenesis of COVID-19. ACE2 targeting holds the promise for preventing and inhibiting SARS-CoV-2 infection. In this work, we describe the development and use of a test system based on competitive ELISA for the primary screening of potential antiviral compounds. We studied the activity of the library of dyes of different groups. Several dyes (ortho-cresolphthalein, eosin (free acid), eosin (Na salt)) that inhibited the interaction of ACE2 with the spike proteins of SARS-CoV-2 have been identified among the candidates. A potential antiviral drug, methylene blue, did not show activity in our study. We believe that our results can help in the further search for inhibitors of interaction between the coronavirus spike protein and ACE2 receptor. Full article
(This article belongs to the Special Issue Chemosensors in Biological Challenges)
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25 pages, 3760 KiB  
Review
Formaldehyde Gas Sensors Fabricated with Polymer-Based Materials: A Review
Chemosensors 2023, 11(2), 134; https://doi.org/10.3390/chemosensors11020134 - 13 Feb 2023
Cited by 4 | Viewed by 1770
Abstract
Formaldehyde has been regarded as a common indoor pollutant and does great harm to human health, which has caused the relevant departments to pay attention to its accurate detection. At present, spectrophotometry, gas chromatography, liquid chromatography, and other methods have been proposed for [...] Read more.
Formaldehyde has been regarded as a common indoor pollutant and does great harm to human health, which has caused the relevant departments to pay attention to its accurate detection. At present, spectrophotometry, gas chromatography, liquid chromatography, and other methods have been proposed for formaldehyde detection. Among them, the gas sensor is especially suitable for common gaseous formaldehyde detection with the fastest response speed and the highest sensitivity. Compared with the formaldehyde sensors based on small molecules, the polymer-based sensor has higher selectivity but lower sensitivity because the polymer-based sensor can realize the specific detection of formaldehyde through a specific chemical reaction. Polymer-related formaldehyde sensors can be very versatile. They can be fabricated with a single polymer, molecularly imprinted polymers (MIP), polymer/metal-oxide composites, different polymers, polymer/biomass material composites, polymer/carbon material composites, and polymer composites with other materials. Almost all of these sensors can detect formaldehyde at ppb levels under laboratory conditions. Moreover, almost all polymer nanocomposite sensors have better sensitivity than single polymer sensors. However, the sensing performance of the sensor will be greatly reduced in a humid environment due to the sensitive coating on the gaseous formaldehyde sensor, which is mostly a hydrophilic polymer. At present, researchers are trying to improve the sensitive material or use humidity compensation methods to optimize the gaseous formaldehyde sensor. The improvement of the practical performance of formaldehyde sensors has great significance for improving indoor living environments. Full article
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14 pages, 1933 KiB  
Article
Validation of a HS–GC–FID Method for the Quantification of Sevoflurane in the Blood, Urine, Brain and Lungs for Forensic Purposes
Chemosensors 2023, 11(2), 133; https://doi.org/10.3390/chemosensors11020133 - 13 Feb 2023
Cited by 1 | Viewed by 1662
Abstract
Background: Sevoflurane is a polyfluorinated compound extensively used as an inhalation anesthetic in patients undergoing surgery. If administered outside the operating room, sevoflurane is dangerous and potentially lethal, and toxicologists may be asked to investigate its presence in biological matrices for forensic purposes. [...] Read more.
Background: Sevoflurane is a polyfluorinated compound extensively used as an inhalation anesthetic in patients undergoing surgery. If administered outside the operating room, sevoflurane is dangerous and potentially lethal, and toxicologists may be asked to investigate its presence in biological matrices for forensic purposes. The aim of the present study is to develop and validate a method for the detection and the quantification of sevoflurane in biological fluids and organs through gas chromatography coupled to flame ionization detection (GC–FID). Methods: The method was optimized based on the maximization of the signal-to-noise ratio. The GC–FID instrument was equipped with a Zebron capillary column ZB-624 (30 m, 0.32 mm ID, 1.80 µm film thickness). Results: The method was validated over a concentration range of 1.0–304.0 µg/mL (blood and urine) and µg/g (brain, lungs). The lower limit of quantitation was 1.0 µg/mL or µg/g. Both the intra- and interassay imprecision and inaccuracy were ≤15% at all quality control concentrations in all the matrices. The method was successfully applied to measure the sevoflurane concentrations for 20 negative controls and for a real forensic case. Conclusions: The present method is suitable for the identification and quantification of sevoflurane in fluids and organs and can be a reliable tool in forensic casework. Full article
(This article belongs to the Special Issue GC, MS and GC-MS Analytical Methods: Opportunities and Challenges)
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25 pages, 4063 KiB  
Article
Facile Electrodeposition-Based Chemosensors Using PANI and C-Hybrid Nanomaterials for the Selective Detection of Ammonia and Nitrogen Dioxide at Room Temperature
Chemosensors 2023, 11(2), 132; https://doi.org/10.3390/chemosensors11020132 - 13 Feb 2023
Cited by 4 | Viewed by 1461
Abstract
Sensor systems for monitoring indoor air quality are vital for the precise quantification of the mechanisms which lead to the deterioration of human health, with a typical person spending an average of 20 h a day in an enclosed space. Thus, a series [...] Read more.
Sensor systems for monitoring indoor air quality are vital for the precise quantification of the mechanisms which lead to the deterioration of human health, with a typical person spending an average of 20 h a day in an enclosed space. Thus, a series of layered chemoresistive sensors, obtained by the facile electrodeposition of carbon nanomaterial-enhanced PANI composites, have been tested for the selective detection of two core indoor pollutants: ammonia and nitrogen dioxide. The sensors were tested with respect to sensitivity and selectivity to the target gasses, with performance being assessed based on response linearity and repeatability at room temperature. Of the tested sensors, two have been identified as having an adequate performance on ammonia, with sensitivities of up to 96.99% and resolutions of up to 0.85 ppm being observed, while on nitrogen dioxide, despite the successful sensor having a lower sensitivity, 10.71%, it has shown high resolution, 1.25 ppm, and linearity over a large concentration domain. These high performances highlight the viability of multi-layers chemosensors based on the electrodeposition of nanomaterial-enhanced conductive polymers for the detection of pollutant gasses, with finetuning of the detection layer allowing the accurate monitoring of a wide range of gasses. Full article
(This article belongs to the Special Issue Carbon Nanomaterials and Related Materials for Sensing Applications)
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11 pages, 1905 KiB  
Article
Bipolar Electrochemical Analysis of Chirality in Complex Media through Miniaturized Stereoselective Light-Emitting Systems
Chemosensors 2023, 11(2), 131; https://doi.org/10.3390/chemosensors11020131 - 13 Feb 2023
Cited by 4 | Viewed by 1391
Abstract
Environmentally relevant contaminants endowed with chirality may include pharmaceutical compounds, flame retardants, perfluoroalkyl chemicals, pesticides, and polychlorinated biphenyls. Despite having similar physicochemical properties, enantiomers may differ in their biochemical interactions with enzymes, receptors, and other chiral molecules leading to different biological responses. In [...] Read more.
Environmentally relevant contaminants endowed with chirality may include pharmaceutical compounds, flame retardants, perfluoroalkyl chemicals, pesticides, and polychlorinated biphenyls. Despite having similar physicochemical properties, enantiomers may differ in their biochemical interactions with enzymes, receptors, and other chiral molecules leading to different biological responses. In this work, we have designed a wireless miniaturized stereoselective light-emitting system able to qualitatively detect a chiral contaminant (3,4-dihydroxyphenylalanine, DOPA) dissolved in reduced volumes (in the microliters range), through bipolar electrochemistry. The diastereomeric environment was created by mixing the enantiomers of an inherently chiral inductor endowed with helical shape (7,8-dipropyltetrathia[7]helicene) and the chiral probe (DOPA) in micro-solutions of a commercial ionic liquid. The synergy between the inductor, the applied electric field, and the chiral pollutant was transduced by the light emission produced from a miniaturized light-emitting diode (LED) exploited in such an approach as a bipolar electrode. Full article
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19 pages, 3908 KiB  
Article
Synthesis and Characterization of a Multiporous SnO2 Nanofibers-Supported Au Nanoparticles-Based Amperometric Sensor for the Nonenzymatic Detection of H2O2
Chemosensors 2023, 11(2), 130; https://doi.org/10.3390/chemosensors11020130 - 10 Feb 2023
Cited by 3 | Viewed by 1849
Abstract
The challenges of a heme protein and enzyme-based H2O2 sensor was subdued by developing a highly sensitive and practically functional amperometric gold nanoparticles (Au NPs)/SnO2 nanofibers (SnO2 NFs) composite sensor. The composite was prepared by mixing multiporous SnO [...] Read more.
The challenges of a heme protein and enzyme-based H2O2 sensor was subdued by developing a highly sensitive and practically functional amperometric gold nanoparticles (Au NPs)/SnO2 nanofibers (SnO2 NFs) composite sensor. The composite was prepared by mixing multiporous SnO2 NFs (diameter: 120–190 nm) with Au NPs (size: 3–5 nm). The synthesized Au NPs/SnO2 NFs composite was subsequently coated on a glassy carbon electrode (GCE) and displayed a well-defined reduction peak during a cyclic voltammetry (CV) analysis. The SnO2 NFs prevented the aggregation of Au NPs through its multiporous structure and enhanced the catalytic response by 1.6-fold. The SnO2 NFs-supported GCE/Au NPs/SnO2 NFs composite sensor demonstrated a very good catalytic activity during the reduction of hydrogen peroxide (H2O2) that displayed rapid amperometric behavior within 6.5 s. This sensor allowed for highly sensitive and selective detection. The sensitivity was 14.157 µA/mM, the linear detection range was from 49.98 µM to 3937.21 µM (R2 = 0.99577), and the lower limit of detection was 6.67 µM. Furthermore, the developed sensor exhibited acceptable reproducibility, repeatability, and stability over 41 days. In addition, the Au NPs/SnO2 NFs composite sensor was tested for its ability to detect H2O2 in tap water, apple juice, Lactobacillus plantarum, Bacillus subtilis, and Escherichia coli. Therefore, this sensor would be useful due to its accuracy and sensitivity in detecting contaminants (H2O2) in commercial products. Full article
(This article belongs to the Special Issue Advanced Electrochemical Sensors or Biosensors Based on Nanomaterial)
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19 pages, 1835 KiB  
Article
A Factorial Design and Simplex Optimization of a Bismuth Film Glassy Carbon Electrode for Cd(II) and Pb(II) Determination
Chemosensors 2023, 11(2), 129; https://doi.org/10.3390/chemosensors11020129 - 10 Feb 2023
Viewed by 792
Abstract
This work presents the use of a fractional two-level factorial design to determine the influence of different factors involved in the development of the square-wave anodic stripping voltammetry method. A fractional factorial design of eight different electrodes using a bismuth film glassy carbon [...] Read more.
This work presents the use of a fractional two-level factorial design to determine the influence of different factors involved in the development of the square-wave anodic stripping voltammetry method. A fractional factorial design of eight different electrodes using a bismuth film glassy carbon electrode (BiFGCE) was formulated, and the impact of the factors on the analytical performance of the electrodes was determined. The impact of six factors (deposition potential, deposition time, potential step, amplitude, frequency, and the concentration of Bi(III)) was tested for Cd(II) and Pb(II) determination. Next, simplex optimization was carried out to improve the electroanalytical performance of the BiFGCE. The objective of simplex optimization was to simultaneously obtain a low limit of quantification, a wide linear concentration range, high sensitivity, high accuracy, and good precision for the new BiFGCE developed. By employing the latter approach, an optimization criterion was improved by several orders of magnitude. Moreover, the possible interference effect of different species was tested using two optimized BiFGCE. Furthermore, a real sample analysis of tap water with two optimized BiFGCEs was also carried out. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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12 pages, 1647 KiB  
Article
Analyzing the Electrochemical Interaction of the Angiogenesis Inhibitor Batimastat by Surface-Enhanced Raman Spectroscopy
Chemosensors 2023, 11(2), 128; https://doi.org/10.3390/chemosensors11020128 - 10 Feb 2023
Viewed by 1188
Abstract
This is the first work to describe the vibrational properties of the anticancer drug batimastat (BB-94) as an inhibitor of extracellular matrix metalloproteinase with a broad spectrum of activity. In addition, the adsorption of this molecule onto a silver roughened electrode surface using [...] Read more.
This is the first work to describe the vibrational properties of the anticancer drug batimastat (BB-94) as an inhibitor of extracellular matrix metalloproteinase with a broad spectrum of activity. In addition, the adsorption of this molecule onto a silver roughened electrode surface using surface-enhanced Raman spectroscopy (SERS) was studied. This research provides a complete account of the influence of applied electrode potential and excitation wavelengths at the molecule-metal interface. Although vibrational assignment becomes more difficult as the molecule size increases, we performed density functional theory (DFT) at the B3LYP/6-31G(d,p) level of theory to calculate molecular geometry in the equilibrium state and Raman frequencies to clarify the nature of vibrational modes. The greatest amplification of the SERS signal occurs for the electrode potential of −0.3 V for the 532 nm excitation line and shifts as moves to the near-infrared laser line at 785 nm. The conclusion is that the mercaptothiophene part and one of the amide groups interact with the metal surface. This results in a charge transfer resonant process in the SERS of this molecule, which has been found by analyzing the charge transfer SERS profiles. Finally, there is the possibility of the formation of different adsorption species or metal complexes on the surface that could contribute to the whole signal observed in the SERS spectra. Full article
(This article belongs to the Special Issue Recent Trends in SERS: Sensing and DFT Application)
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20 pages, 6397 KiB  
Article
The Influence of Surfactants on the Deposition and Performance of Single-Walled Carbon Nanotube-Based Gas Sensors for NO2 and NH3 Detection
Chemosensors 2023, 11(2), 127; https://doi.org/10.3390/chemosensors11020127 - 09 Feb 2023
Cited by 3 | Viewed by 1625
Abstract
Solid-state chemiresistive gas sensors have attracted a lot of researchers’ attention during the last half-century thanks to their ability to detect different gases with high sensitivity, low power consumption, low cost, and high portability. Among the most promising sensitive materials, carbon nanotubes (CNTs) [...] Read more.
Solid-state chemiresistive gas sensors have attracted a lot of researchers’ attention during the last half-century thanks to their ability to detect different gases with high sensitivity, low power consumption, low cost, and high portability. Among the most promising sensitive materials, carbon nanotubes (CNTs) have attracted a lot of interest due to their large active surface area (in the range of 50–1400 m2/g, depending on their composition) and the fact that they can operate at room temperature. In this study, single-walled carbon nanotube (SWCNT)-based sensing films were prepared and deposited by spray deposition for the fabrication of gas sensors. For the deposition, various SWCNTs were prepared in deionized water with the addition of specific surfactants, i.e., carboxymethyl cellulose (CMC) and sodium dodecyl sulfate (SDS), which act as dispersing agents to create a suitable ink for deposition. This study aims to elucidate the possible differences in the sensing performance of the fabricated devices due to the use of the two different surfactants. To achieve this goal, all the devices were tested versus ethanol (C2H5OH), carbon monoxide (CO), nitrogen dioxide (NO2), and ammonia (NH3). The produced devices demonstrated high selectivity towards NH3 and NO2. The different sensors, prepared with different deposition thicknesses (from 0.51 nm to 18.41 nm), were tested in dry and wet conditions (40% humidity), highlighting an enhanced response as a function of relative humidity. In addition, sensor performance was evaluated at different working temperatures, showing the best performance when heated up to 150 °C. The best sensing conditions we found were against NO2, sensors with 10 layers of deposition and an operating temperature of 150 °C; in this condition, sensors showed high responses compared those found in the literature (62.5%—SDS-based and 78.6%—CMC-based). Finally, cross-sensitivity measurements showed how the produced sensors are good candidates for the practical and selective detection of NO2, even in the presence of the most important interfering gases identified, i.e., NH3. Full article
(This article belongs to the Special Issue Gas Sensing beyond MOX Semiconductors)
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15 pages, 3595 KiB  
Article
Design of a Decision Support System to Operate a NO2 Gas Sensor Using Machine Learning, Sensitive Analysis and Conceptual Control Process Modelling
Chemosensors 2023, 11(2), 126; https://doi.org/10.3390/chemosensors11020126 - 08 Feb 2023
Cited by 3 | Viewed by 1976
Abstract
The most advantageous method for detecting dangerous gases and reducing the risk of potential environmental toxicity effects is the use of innovative gas sensing systems. However, designing effective sensors requires a complex process of synthesizing functional nanoparticles, which is a costly process. Additionally, [...] Read more.
The most advantageous method for detecting dangerous gases and reducing the risk of potential environmental toxicity effects is the use of innovative gas sensing systems. However, designing effective sensors requires a complex process of synthesizing functional nanoparticles, which is a costly process. Additionally, practical operation of the toxic gas sensors always carries a significant cost along with a considerable risk of hazardous gas emissions. Machine learning algorithms may be used to accurately automate the behavior of the sensors to eliminate the abovementioned deficiencies. In the present research, there are three different factors involved in the optimization of NO2 sensing by means of the response surface methodology (RSM). Two main functions of sensor efficiency, namely sensitivity and response time, are predicted according to the Fe3O4 additive (%), input NO2 (ppm), and response time/sensitivity, and moreover, the execution of a controlling system of the sensor network using the Jacobson model is proposed. The machine learning computations are implemented by Meta.RegressionByDiscretization, M5.Rules, Lazy KStar, and Gaussian Processes algorithms. The outcomes illustrate that the best gas sensor efficiency predictions are related to M5.Rules and Lazy KStar, with a correlation coefficient of more than 96%. The best performance of machine learning computations can be found in the range of 8–10-fold in training and testing arrangements. Meanwhile, the ANOVA assessment confirmed that the most important features in the prediction of response time and sensitivity are NO2 concentration and response time, respectively, with the lowest p-value recorded. The outcomes illustrated that with combinations of RSM, machine learning, and the Jacobson model as a controller, a decision support system can be presented for the NO2 gas sensor system. Full article
(This article belongs to the Special Issue Analytical and Computational Systems in Biosensing)
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38 pages, 19287 KiB  
Review
Recent Advance in Nucleus-Targeted Fluorescent Probes for Bioimaging, Detection and Therapy
Chemosensors 2023, 11(2), 125; https://doi.org/10.3390/chemosensors11020125 - 07 Feb 2023
Cited by 6 | Viewed by 2161
Abstract
The nucleus is not only the control hub of cell life activities, but also the center of storing and controlling genetic information. The morphology of the nucleus can be used to judge the cell vitality and health. The various biological molecules contained in [...] Read more.
The nucleus is not only the control hub of cell life activities, but also the center of storing and controlling genetic information. The morphology of the nucleus can be used to judge the cell vitality and health. The various biological molecules contained in the nucleus are closely related to the normal life activities, occurrence and development of diseases. In recent years, fluorescence imaging has gained increasing attention due to its advantages of being intuitive, in situ and visual. The development of fluorescent probes for high-resolution imaging of the nucleus and detection of biomolecules in the nucleus is of great value for understanding the normal physiological processes of cells or organisms, as well as for disease diagnosis and treatment. In this review, we mainly introduce the current general strategies for designing nucleus-targeted fluorescent probes, as well as their applications in nucleus-targeted imaging, intranuclear biomolecular detection and therapy. Moreover, we also discuss the current challenges and opportunities of nucleus-targeted fluorescent probes in terms of selectivity, design strategies and so on. Full article
(This article belongs to the Special Issue Fluorescent Probe and Biosensing)
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14 pages, 5608 KiB  
Article
PEDOT:PSS/PEDOT Film Chemiresistive Sensors for Hydrogen Peroxide Vapor Detection under Ambient Conditions
Chemosensors 2023, 11(2), 124; https://doi.org/10.3390/chemosensors11020124 - 07 Feb 2023
Cited by 11 | Viewed by 1570
Abstract
Hydrogen peroxide (aqueous solution of H2O2) is one of the most used reagents i n medical sterilization, environmental disinfection, food storage, and other fields. However, hydrogen peroxide has the potential to cause serious harm to biological health and environmental [...] Read more.
Hydrogen peroxide (aqueous solution of H2O2) is one of the most used reagents i n medical sterilization, environmental disinfection, food storage, and other fields. However, hydrogen peroxide has the potential to cause serious harm to biological health and environmental safety. There are many methods (especially electrochemistry) for H2O2 detection in liquid phase systems, but a lack of methods for vapor detection. This is due to its colorless and tasteless nature, as well as the oxidative activity of the molecule and its coexistence with humidity. In this study, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), one of the most commercially successful and widely used conductive polymers, was employed to fabricate an all-organic chemiresistive sensor for simple, real-time, and on-site sensing of hydrogen peroxide vapor (HPV) at room temperature. In comparison with pristine PEDOT:PSS film, the PEDOT:PSS/PEDOT film was prepared by in situ electrochemical polymerization. Upon exposure to different concentrations of HPV, it was found that the hydrophobic and porous PEDOT layer could weaken the interference of humidity in HPV sensing, resulting in a more sensitive and accurate response. At 1.0 ppm HPV concentration, the resistance signal response was increased by nearly 89% compared with the pristine PEDOT:PSS film. This PEDOT-film-based chemiresistive sensor showcases the possibility for further development of nonenzymatic HPV monitoring technology. Full article
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12 pages, 5078 KiB  
Communication
Measuring Water Vapor Sorption Hysteresis of Cement Paste through an Optical Fiber Sensor
Chemosensors 2023, 11(2), 123; https://doi.org/10.3390/chemosensors11020123 - 07 Feb 2023
Cited by 1 | Viewed by 914
Abstract
Water vapor sorption is a powerful tool for the analysis of cement paste, one of the most used substances by mankind. The monitoring of cementitious materials is fundamental for the improvement of infrastructure resilience, which has a deep impact on the economy, the [...] Read more.
Water vapor sorption is a powerful tool for the analysis of cement paste, one of the most used substances by mankind. The monitoring of cementitious materials is fundamental for the improvement of infrastructure resilience, which has a deep impact on the economy, the environment, and on society. In this work, a multimode fiber was embedded in cement paste for real-time monitoring of cement paste water vapor sorption. Changes in the reflected light intensity due to the build-up of water in the cement paste’s pores were exploited for this purpose. The sample was 7-day moist cured, and the relative humidity was controlled between 8.9% and 97.6%. Reflected light intensity was converted into a specific surface area of cement paste (133 m2/g) and thickness of water through the Brunauer-Emmett-Teller (BET) method and into a pore size distribution through the Barret-Joyner-Halenda (BJH) method. The results achieved through reflected light intensity agree with those found in the literature, validating the usage of this setup for the monitoring of water vapor sorption, breaking away from standard gravimetric measurements. Full article
(This article belongs to the Section Optical Chemical Sensors)
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