Chemosensors

13 pages, 3284 KiB

Open AccessArticle

Fabrication of an All-Solid-State Carbonate Ion-Selective Electrode with Carbon Film as Transducer and Its Preliminary Application in Deep-Sea Hydrothermal Field Exploration

by Chuqing Zhang, Yang He, Jianbo Wu, Manqing Ai, Wei Cai, Ying Ye, Chunhui Tao, Pingping Zhang and Quan Jin

Chemosensors 2021, 9(8), 236; https://doi.org/10.3390/chemosensors9080236 - 23 Aug 2021

Cited by 3 | Viewed by 2468

Abstract

Real-time measurements of carbonate ion concentrations in the ocean are critical to advancing marine environmental monitoring and research into deep-sea hydrothermal activity. Herein, we report the first example of deep-sea hydrothermal field exploration using a carbonate ion-selective electrode (ISE). The novel carbonate ISE [...] Read more.

Real-time measurements of carbonate ion concentrations in the ocean are critical to advancing marine environmental monitoring and research into deep-sea hydrothermal activity. Herein, we report the first example of deep-sea hydrothermal field exploration using a carbonate ion-selective electrode (ISE). The novel carbonate ISE was composed of a Ni wire as substrate, carbon film as transducers and carbonate-selective membrane layers. This paper describes the preparation process of the electrode and characterises its performance via scanning electron microscopy (SEM) and electrochemical analysis. The detection limit of the electrode for CO₃²⁻ is 2.821 × 10⁻⁶ mol/L, the linear response range is 1.0 × 10⁻⁵–1.0 × 10⁻¹ mol/L and the Nernst slope was −30.4 mV/decade. In April 2021, the carbonate ISE was mounted on multi-parameter sensors with pH and Eh (redox) electrodes for the search of hydrothermal activity at the Southwest Indian Ridge. The simultaneous potential anomalies appeared at this carbonate electrode with the pH and Eh electrodes when passing through the hydrothermal field. The study of the hydrothermal field was supported by the in situ camera video and the sulphide samples. Additionally, the carbonate electrode provides enhanced information of water chemistry for the study of the hydrothermal field. Full article

(This article belongs to the Special Issue Sensors for Water Quality Monitoring)

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13 pages, 3551 KiB

Open AccessArticle

Evaluating TiO₂ Photocatalysis Performance in Microtubes on Paper Background by Smartphone: Principles and Application Examples

by Xian Liu, Chengxiang Xu, Shiwei Xie, Lei Zhu and Xun Wang

Chemosensors 2021, 9(8), 235; https://doi.org/10.3390/chemosensors9080235 - 23 Aug 2021

Cited by 5 | Viewed by 1878

Abstract

Titanium dioxide (TiO₂) photocatalysis is a popular and promising technology in water treatment, but the performance evaluation usually depends on expensive equipment. In this study, using a smartphone for colorimetric detection, a self-invented method based on paper and microtubes (PMTs) is [...] Read more.

Titanium dioxide (TiO₂) photocatalysis is a popular and promising technology in water treatment, but the performance evaluation usually depends on expensive equipment. In this study, using a smartphone for colorimetric detection, a self-invented method based on paper and microtubes (PMTs) is proposed to test the photocatalytic performance of TiO₂. Firstly, the study has identified that PMTs achieved a correlation coefficient of above 0.9 between the greyscale values and concentrations during the physical process of different color dyes (i.e., rhodamine B (RhB), reactive yellow (RY), methylene blue (MB), and mixtures of the two or three dyes). The results indicate that when the principle of solution color follows the CMYK (Cyan, Magenta, Yellow, Black) color model, its photo color on white paper background conforms to the RGB (Red, Green, Blue) color model. Compared to the results obtained from the absorbance method, the PMTs method showed high reliabilities up to 99.36% on the monitoring of the photocatalytic process of the different dye solutions. Interestingly, the colorless solution of salicylic acid (SA) could also be analyzed by the PMTs after complexed with Fe(III) ion to develop a purple solution. These results suggest that the PMTs could be an alternative analysis method to evaluating physical and chemical reaction processes when the high-tech analysis equipment is unviable. Full article

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

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17 pages, 1756 KiB

Open AccessArticle

A Novel Dialkylamino GFP Chromophore as an Environment-Polarity Sensor Reveals the Role of Twisted Intramolecular Charge Transfer

by Cheng Chen, Sean A. Boulanger, Anatolii I. Sokolov, Mikhail S. Baranov and Chong Fang

Chemosensors 2021, 9(8), 234; https://doi.org/10.3390/chemosensors9080234 - 23 Aug 2021

Cited by 12 | Viewed by 3290

Abstract

We discovered a novel fluorophore by incorporating a dimethylamino group (–NMe₂) into the conformationally locked green fluorescent protein (GFP) scaffold. It exhibited a marked solvent-polarity-dependent fluorogenic behavior and can potentially find broad applications as an environment-polarity sensor in vitro and in [...] Read more.

We discovered a novel fluorophore by incorporating a dimethylamino group (–NMe₂) into the conformationally locked green fluorescent protein (GFP) scaffold. It exhibited a marked solvent-polarity-dependent fluorogenic behavior and can potentially find broad applications as an environment-polarity sensor in vitro and in vivo. The ultrafast femtosecond transient absorption (fs-TA) spectroscopy in combination with quantum calculations revealed the presence of a twisted intramolecular charge transfer (TICT) state, which is formed by rotation of the –NMe₂ group in the electronic excited state. In contrast to the bright fluorescent state (FS), the TICT state is dark and effectively quenches fluorescence upon formation. We employed a newly developed multivariable analysis approach to the FS lifetime in various solvents and showed that the FS → TICT reaction barrier is mainly modulated by H-bonding capability instead of viscosity of the solvent, accounting for the observed polarity dependence. These deep mechanistic insights are further corroborated by the dramatic loss of fluorogenicity for two similar GFP-derived chromophores in which the rotation of the –NMe₂ group is inhibited by structural locking. Full article

(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)

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12 pages, 1374 KiB

Open AccessArticle

Evaluation of Photosensitive Paper Coatings as Detectors for Instrumentation-Free UV Photometric Analysis Based on Photography-Based Photometry

by Tatiana G. Choleva, Afroditi Sfakianaki, Athanasios G. Vlessidis and Dimosthenis L. Giokas

Chemosensors 2021, 9(8), 233; https://doi.org/10.3390/chemosensors9080233 - 20 Aug 2021

Cited by 2 | Viewed by 2128

Abstract

Photography-based photometry is a technique developed to perform high throughput UV photometric analysis without instrumental detectors in resource-limited settings. Its principle relies on the illumination of a sample with UV irradiation and then capturing the transmitted irradiation on a photosensitive paper surface. Therefore, [...] Read more.

Photography-based photometry is a technique developed to perform high throughput UV photometric analysis without instrumental detectors in resource-limited settings. Its principle relies on the illumination of a sample with UV irradiation and then capturing the transmitted irradiation on a photosensitive paper surface. Therefore, the photosensitive surface acts as a detector for the determination of the concentration of analytes in the sample. This work aims to investigate the optimum photosensitive paper coatings for capturing the transmitted UV irradiation. To this end, photosensitive coatings based on silver, iron, and dichromate salts were tested using three assays of pharmaceutical and biochemical interest. The results from both calibrations, using standard solutions and the application in real samples, show that photosensitive coatings based on iron salts provide the best results. Importantly, the detection limits and the linear range of the calibration curves were better than those obtained with standard photometry. Based on these findings, cyanotype green papers, are proposed as optimum detectors for photography-based photometry. This finding simplifies the operation of the technique enabling the fabrication of prototype readers for analytical assays performed in resource limited settings, point-of-need applications or in the field. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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27 pages, 3246 KiB

Open AccessReview

Advances in Antimicrobial Resistance Monitoring Using Sensors and Biosensors: A Review

by Eduardo C. Reynoso, Serena Laschi, Ilaria Palchetti and Eduardo Torres

Chemosensors 2021, 9(8), 232; https://doi.org/10.3390/chemosensors9080232 - 19 Aug 2021

Cited by 23 | Viewed by 6036

Abstract

The indiscriminate use and mismanagement of antibiotics over the last eight decades have led to one of the main challenges humanity will have to face in the next twenty years in terms of public health and economy, i.e., antimicrobial resistance. One of the [...] Read more.

The indiscriminate use and mismanagement of antibiotics over the last eight decades have led to one of the main challenges humanity will have to face in the next twenty years in terms of public health and economy, i.e., antimicrobial resistance. One of the key approaches to tackling antimicrobial resistance is clinical, livestock, and environmental surveillance applying methods capable of effectively identifying antimicrobial non-susceptibility as well as genes that promote resistance. Current clinical laboratory practices involve conventional culture-based antibiotic susceptibility testing (AST) methods, taking over 24 h to find out which medication should be prescribed to treat the infection. Although there are techniques that provide rapid resistance detection, it is necessary to have new tools that are easy to operate, are robust, sensitive, specific, and inexpensive. Chemical sensors and biosensors are devices that could have the necessary characteristics for the rapid diagnosis of resistant microorganisms and could provide crucial information on the choice of antibiotic (or other antimicrobial medicines) to be administered. This review provides an overview on novel biosensing strategies for the phenotypic and genotypic determination of antimicrobial resistance and a perspective on the use of these tools in modern health-care and environmental surveillance. Full article

(This article belongs to the Special Issue Chemical and Biosensors: A Theme Issue in Honor of Professor Otto S. Wolfbeis)

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16 pages, 2279 KiB

Open AccessArticle

Phenolic Compounds from Irradiated Olive Wastes: Optimization of the Heat-Assisted Extraction Using Response Surface Methodology

by Joana Madureira, Bruno Melgar, Celestino Santos-Buelga, Fernanda M. A. Margaça, Isabel C. F. R. Ferreira, Lillian Barros and Sandra Cabo Verde

Chemosensors 2021, 9(8), 231; https://doi.org/10.3390/chemosensors9080231 - 19 Aug 2021

Cited by 13 | Viewed by 2491

Abstract

Olive pomace, an environmentally detrimental residue generated during olive oil extraction, contains bioactive compounds in demand by the food industry. To valorize this waste product a suitable yield for the extraction process is required. Heat-assisted extraction of bioactive compounds from olive pomace was [...] Read more.

Olive pomace, an environmentally detrimental residue generated during olive oil extraction, contains bioactive compounds in demand by the food industry. To valorize this waste product a suitable yield for the extraction process is required. Heat-assisted extraction of bioactive compounds from olive pomace was optimized by a circumscribed central composite design and response surface methodology. Our previous studies indicated that irradiation could improve 2.4-fold the extractability of the main phenolic compounds from olive pomace. The effect of extraction time, temperature and solvent concentration on the yield of polyphenols from irradiated olive pomace at 5 kGy was tested. Hydroxytyrosol-1-β-glucoside, hydroxytyrosol, tyrosol and caffeic acid were quantified by High Performance Liquid Chromatography to calculate the total polyphenol content. The optimal general conditions by RSM modeling were extraction time of 120 min, temperature of 85 °C, and 76% of ethanol in water. Using these selected conditions, 19.04 ± 1.50 mg/g dry weight, 148.88 ± 8.73 mg/g extract of total polyphenols were obtained, representing a yield of 13.7%, which was consistent with the value predicted by the model. This work demonstrated the potential of residues from the olive oil industry as a suitable alternative to obtain compounds that could be used as ingredients for the food industry. Full article

(This article belongs to the Special Issue Application of Response Surface Methodology for Food Optimization Processes)

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16 pages, 4735 KiB

Open AccessArticle

Highly Sensitive Quartz-Based Sensing System for the Detection of Subpercentage Changes in the Relative Permittivity of Liquids Flowing in Microchannels

by Vojko Matko and Miro Milanovič

Chemosensors 2021, 9(8), 230; https://doi.org/10.3390/chemosensors9080230 - 18 Aug 2021

Viewed by 1876

Abstract

We describe a highly sensitive quartz sensor for measuring changes in the relative permittivity of liquids flowing in microchannels. The proposed method uses a highly stable oscillator and capacitance-dependent quartz crystal together with a capacitance-sensitive element attached along the microchannel. A change in [...] Read more.

We describe a highly sensitive quartz sensor for measuring changes in the relative permittivity of liquids flowing in microchannels. The proposed method uses a highly stable oscillator and capacitance-dependent quartz crystal together with a capacitance-sensitive element attached along the microchannel. A change in the relative permittivity of the fluid induces a change in the capacitance of the sensitive element in the aF range, which is detected as a change in the resonant frequency. The advantages of the proposed measurement technique are the extreme sensitivity (changes in the relative permittivity as low as 0.01% can be detected), the temperature independence of the setup between 10 and 40 °C, the stability (the frequency reading fluctuates within 0.025 Hz), and the low cost compared with the methods that use impedance analyzers or lock-in amplifiers. We present the use of the method to detect changes in mixtures of liquids if the temperature, volume fractions, or properties of one liquid change. The method presents a useful tool for applications in biology, chemistry, pharmacy, and technology in general wherever accurate monitoring of compositions of fluids is required and where changes, for example, due to temperature variation or mixture aging, need to be detected in real time. Full article

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20 pages, 4051 KiB

Open AccessArticle

Gold Nanoparticles/Carbon Nanotubes and Gold Nanoporous as Novel Electrochemical Platforms for L-Ascorbic Acid Detection: Comparative Performance and Application

by Cristina Tortolini, Federico Tasca, Mary Anna Venneri, Cinzia Marchese and Riccarda Antiochia

Chemosensors 2021, 9(8), 229; https://doi.org/10.3390/chemosensors9080229 - 16 Aug 2021

Cited by 9 | Viewed by 2651

Abstract

Herein, the effects of nanostructured modifications of a gold electrode surface in the development of electrochemical sensors for L-ascorbic acid detection have been investigated. In particular, a bare gold electrode has been modified by electrodeposition of gold single-walled carbon nanotubes (Au/SWCNTs) and by [...] Read more.

Herein, the effects of nanostructured modifications of a gold electrode surface in the development of electrochemical sensors for L-ascorbic acid detection have been investigated. In particular, a bare gold electrode has been modified by electrodeposition of gold single-walled carbon nanotubes (Au/SWCNTs) and by the formation of a highly nanoporous gold (h-nPG) film. The procedure has been realized by sweeping the potential between +0.8 V and 0 V vs. Ag/AgCl for 25 scans in a suspension containing 5 mg/mL of SWCNTs in 10 mM HAuCl₄ and 2.5 M NH₄Cl solution for Au/SWCNTs modified gold electrode. A similar procedure was applied for a h-nPG electrode in a 10 mM HAuCl₄ solution containing 2.5 M NH₄Cl, followed by applying a fixed potential of −4 V vs. Ag/AgCl for 60 s. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the properties of the modified electrodes. The developed sensors showed strong electrocatalytic activity towards ascorbic acid oxidation with enhanced sensitivities of 1.7 × 10⁻² μA μM⁻¹cm⁻² and 2.5 × 10⁻² μA μM⁻¹cm⁻² for Au/SWCNTs and h-nPG modified electrode, respectively, compared to bare gold electrode (1.0 × 10⁻² μA μM⁻¹cm⁻²). The detection limits were estimated to be 3.1 and 1.8 μM, respectively. The h-nPG electrode was successfully used to determine ascorbic acid in human urine with no significant interference and with satisfactory recovery levels. Full article

(This article belongs to the Special Issue Applications of Probe Sensing in Medicine)

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11 pages, 1572 KiB

Open AccessArticle

Botulinum Neurotoxin-C Detection Using Nanostructured Porous Silicon Interferometer

by Dashananda Nanda Kumar, Zina Baider, Daniel Elad, Shlomo E. Blum and Giorgi Shtenberg

Chemosensors 2021, 9(8), 228; https://doi.org/10.3390/chemosensors9080228 - 16 Aug 2021

Cited by 3 | Viewed by 1732

Abstract

Botulinum neurotoxins (BoNT) are the most potent toxins, which are produced by Clostridium bacteria and cause the life-threatening disease of botulism in all vertebrates. Specifically, animal botulism represents a serious environmental and economic concern in animal production due to the high mortality rates [...] Read more.

Botulinum neurotoxins (BoNT) are the most potent toxins, which are produced by Clostridium bacteria and cause the life-threatening disease of botulism in all vertebrates. Specifically, animal botulism represents a serious environmental and economic concern in animal production due to the high mortality rates observed during outbreaks. Despite the availability of vaccines against BoNT, there are still many outbreaks of botulism worldwide. Alternative assays capable of replacing the conventional in vivo assay in terms of rapid and sensitive quantification, and the applicability for on-site analysis, have long been perused. Herein, we present a simple, highly sensitive and label-free optical biosensor for real-time detection of BoNT serotype C using a porous silicon Fabry–Pérot interferometer. A competitive immunoassay coupled to a biochemical cascade reaction was adapted for optical signal amplification. The resulting insoluble precipitates accumulated within the nanostructure changed the reflectivity spectra by alternating the averaged refractive index. The augmented optical performance allowed for a linear response within the range of 10 to 10,000 pg mL⁻¹ while presenting a detection limit of 4.8 pg mL⁻¹. The practical aspect of the developed assay was verified using field BoNT holotoxins to exemplify the potential use of the developed optical approach for rapid bio-diagnosis of BoNT. The specificity and selectivity of the assay were successfully validated using an adjacent holotoxin relevant for farm animals (BoNT serotype D). Overall, this work sets the foundation for implementing a miniaturized interferometer for routine on-site botulism diagnosis, thus significantly reducing the need for animal experimentation and shortening analysis turnaround for early evidence-based therapy. Full article

(This article belongs to the Special Issue Silicon-Based Optical Biosensors)

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11 pages, 2134 KiB

Open AccessCommunication

Nitrogen Dioxide Gas Sensor Based on Ag-Doped Graphene: A First-Principle Study

by Qichao Li, Yamin Liu, Di Chen, Jianmin Miao, Xiao Zhi, Shengwei Deng, Shujing Lin, Han Jin and Daxiang Cui

Chemosensors 2021, 9(8), 227; https://doi.org/10.3390/chemosensors9080227 - 14 Aug 2021

Cited by 15 | Viewed by 3221

Abstract

High-performance tracking trace amounts of NO₂ with gas sensors could be helpful in protecting human health since high levels of NO₂ may increase the risk of developing acute exacerbation of chronic obstructive pulmonary disease. Among various gas sensors, Graphene-based sensors have [...] Read more.

High-performance tracking trace amounts of NO₂ with gas sensors could be helpful in protecting human health since high levels of NO₂ may increase the risk of developing acute exacerbation of chronic obstructive pulmonary disease. Among various gas sensors, Graphene-based sensors have attracted broad attention due to their sensitivity, particularly with the addition of noble metals (e.g., Ag). Nevertheless, the internal mechanism of improving the gas sensing behavior through doping Ag is still unclear. Herein, the impact of Ag doping on the sensing properties of Graphene-based sensors is systematically analyzed via first principles. Based on the density-functional theory (DFT), the adsorption behavior of specific gases (NO₂, NH₃, H₂O, CO₂, CH₄, and C₂H₆) on Ag-doped Graphene (Ag–Gr) is calculated and compared. It is found that NO₂ shows the strongest interaction and largest Mulliken charge transfer to Ag–Gr among these studied gases, which may directly result in the highest sensitivity toward NO₂ for the Ag–Gr-based gas sensor. Full article

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

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59 pages, 14207 KiB

Open AccessReview

Application of Metal-Organic Framework-Based Composites for Gas Sensing and Effects of Synthesis Strategies on Gas-Sensitive Performance

by Bo Huang, Yanqiong Li and Wen Zeng

Chemosensors 2021, 9(8), 226; https://doi.org/10.3390/chemosensors9080226 - 14 Aug 2021

Cited by 18 | Viewed by 4636

Abstract

Gas sensing materials, such as semiconducting metal oxides (SMOx), carbon-based materials, and polymers have been studied in recent years. Among of them, SMOx-based gas sensors have higher operating temperatures; sensors crafted from carbon-based materials have poor selectivity for gases and longer response times; [...] Read more.

Gas sensing materials, such as semiconducting metal oxides (SMOx), carbon-based materials, and polymers have been studied in recent years. Among of them, SMOx-based gas sensors have higher operating temperatures; sensors crafted from carbon-based materials have poor selectivity for gases and longer response times; and polymer gas sensors have poor stability and selectivity, so it is necessary to develop high-performance gas sensors. As a porous material constructed from inorganic nodes and multidentate organic bridging linkers, the metal-organic framework (MOF) shows viable applications in gas sensors due to its inherent large specific surface area and high porosity. Thus, compounding sensor materials with MOFs can create a synergistic effect. Many studies have been conducted on composite MOFs with three materials to control the synergistic effects to improve gas sensing performance. Therefore, this review summarizes the application of MOFs in sensor materials and emphasizes the synthesis progress of MOF composites. The challenges and development prospects of MOF-based composites are also discussed. Full article

(This article belongs to the Special Issue Nanotechnology for Sensing, Medical and Environmental Application)

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42 pages, 16060 KiB

Open AccessReview

Preparation and Application of 2D MXene-Based Gas Sensors: A Review

by Qingting Li, Yanqiong Li and Wen Zeng

Chemosensors 2021, 9(8), 225; https://doi.org/10.3390/chemosensors9080225 - 14 Aug 2021

Cited by 71 | Viewed by 10699

Abstract

Since MXene (a two-dimensional material) was discovered in 2011, it has been favored in all aspects due to its rich surface functional groups, large specific surface area, high conductivity, large porosity, rich organic bonds, and high hydrophilicity. In this paper, the preparation of [...] Read more.

Since MXene (a two-dimensional material) was discovered in 2011, it has been favored in all aspects due to its rich surface functional groups, large specific surface area, high conductivity, large porosity, rich organic bonds, and high hydrophilicity. In this paper, the preparation of MXene is introduced first. HF etching was the first etching method for MXene; however, HF is corrosive, resulting in the development of the in situ HF method (fluoride + HCl). Due to the harmful effects of fluorine terminal on the performance of MXene, a fluorine-free preparation method was developed. The increase in interlayer spacing brought about by adding an intercalator can affect MXene’s performance. The usual preparation methods render MXene inevitably agglomerate and the resulting yields are insufficient. Many new preparation methods were researched in order to solve the problems of agglomeration and yield. Secondly, the application of MXene-based materials in gas sensors was discussed. MXene is often regarded as a flexible gas sensor, and the detection of ppb-level acetone at room temperature was observed for the first time. After the formation of composite materials, the increasing interlayer spacing and the specific surface area increased the number of active sites of gas adsorption and the gas sensitivity performance improved. Moreover, this paper discusses the gas-sensing mechanism of MXene. The gas-sensing mechanism of metallic MXene is affected by the expansion of the lamellae and will be doped with H₂O and oxygen during the etching process in order to become a p-type semiconductor. A p-n heterojunction and a Schottky barrier forms due to combinations with other semiconductors; thus, the gas sensitivities of composite materials are regulated and controlled by them. Although there are only several reports on the application of MXene materials to gas sensors, MXene and its composite materials are expected to become materials that can effectively detect gases at room temperature, especially for the detection of NH₃ and VOC gas. Finally, the challenges and opportunities of MXene as a gas sensor are discussed. Full article

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

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17 pages, 19500 KiB

Open AccessArticle

Gas Chromatography Multiresidue Method for Enantiomeric Fraction Determination of Psychoactive Substances in Effluents and River Surface Waters

by Ivan Langa, Maria Elizabeth Tiritan, Diana Silva and Cláudia Ribeiro

Chemosensors 2021, 9(8), 224; https://doi.org/10.3390/chemosensors9080224 - 13 Aug 2021

Cited by 7 | Viewed by 2390

Abstract

Determination of psychoactive substances (PAS) and/or their metabolites in surface waters is crucial for environmental risk assessment, and disclosure of their enantiomeric fractions (EF) allows discrimination between consumption, direct disposal, and synthesis pathways. The aim of this study was to develop and validate [...] Read more.

Determination of psychoactive substances (PAS) and/or their metabolites in surface waters is crucial for environmental risk assessment, and disclosure of their enantiomeric fractions (EF) allows discrimination between consumption, direct disposal, and synthesis pathways. The aim of this study was to develop and validate an indirect method by gas chromatography coupled to mass spectrometry (GC–MS) based on derivatization using (R)-(−)-α-methoxy-α-(trifluoromethyl) phenylacetyl chloride as chiral derivatization reagent, for enantiomeric quantification of amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxymethamphetamine (MDMA), norketamine, buphedrone (BPD), butylone, 3,4-dimethylmethcathinone (3,4-DMMC), 3-methylmethcathinone, and quantification of 1-benzylpiperazine and 1-(4-metoxyphenyl)-piperazine. The method allowed to evaluate the occurrence, spatial distribution, and the EF of the target chiral PAS in Portuguese surface waters and in effluents from 2 wastewater treatment plants (WWTP). For that, water samples were pre-concentrated by solid phase extraction using OASIS^® MCX cartridges, derivatized and further analyzed by GC–MS. Both enantiomers of AMP, (R)-MDMA, (S)-MAMP, and the first eluted enantiomer of BPD (configuration not assigned) were found in surface waters, while effluent samples showed both enantiomers of MDMA, (S)-MAMP, (R)-AMP, and the first eluted enantiomer of BPD and 3,4-DMMC. According to our knowledge, this is the first multiresidue analytical method by CG–MS enrolling cathinones, amphetamines, and piperazines. The presence of illicit synthetic cathinones in Douro River estuary is here reported for the first time, along with other amphetamine derivatives. The potential of the method to monitor consumption of the target PAS was demonstrated. Full article

(This article belongs to the Collection Recent Trend in Chromatography for Pharmaceutical Analysis)

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18 pages, 3208 KiB

Open AccessArticle

Selective Enhancement of SERS Spectral Bands of Salicylic Acid Adsorbate on 2D Ti₃C₂T_x-Based MXene Film

by Sonata Adomavičiūtė-Grabusovė, Simonas Ramanavičius, Anton Popov, Valdas Šablinskas, Oleksiy Gogotsi and Arūnas Ramanavičius

Chemosensors 2021, 9(8), 223; https://doi.org/10.3390/chemosensors9080223 - 13 Aug 2021

Cited by 23 | Viewed by 3452

Abstract

In this research, we have demonstrated that 2D Ti₃C₂X_n-based MXene (MXene) films are suitable for the design of surface-enhanced Raman spectroscopy (SERS)-based sensors. The enhanced SERS signal was observed for a salicylic acid molecule on Ti₃ [...] Read more.

In this research, we have demonstrated that 2D Ti₃C₂X_n-based MXene (MXene) films are suitable for the design of surface-enhanced Raman spectroscopy (SERS)-based sensors. The enhanced SERS signal was observed for a salicylic acid molecule on Ti₃C₂T_x-based MXene film. Confirmation of the adsorption of the salicylic acid molecule and the formation of a salicylic acid–MXene complex were determined by experimental SERS-based spectral observations such as greatly enhanced out-of-plane bending modes of salicylic acid at 896 cm⁻¹ and a band doublet at 681 cm⁻¹ and 654 cm⁻¹. Additionally, some other spectral features indicate the adsorption of salicylic acid on the MXene surface, namely, a redshift of vibrational modes and the disappearance of the carboxyl deformation spectral band at 771 cm⁻¹. The determined enhancement factor indicates the value that can be expected for the chemical enhancement mechanism in SERS of 220 for out-of-plane vibrational modes. Theoretical modeling based on density functional theory (DFT) calculations using B3LYP/6311G++ functional were performed to assess the formation of the salicylic acid/MXene complex. Based on the calculations, salicylic acid displays affinity of forming a chemical bond with titanium atom of Ti₃C₂(OH)₂ crystal via oxygen atom in hydroxyl group of salicylic acid. The electron density redistribution of the salicylic acid–MXene complex leads to a charge transfer effect with 2.2 eV (428 nm) and 2.9 eV (564 nm) excitations. The experimentally evaluated enhancement factor can vary from 220 to 60 when different excitation wavelengths are applied. Full article

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

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14 pages, 3058 KiB

Open AccessCommunication

Aptamer-Sensitized Nanoribbon Biosensor for Ovarian Cancer Marker Detection in Plasma

by Yuri D. Ivanov, Kristina A. Malsagova, Tatyana O. Pleshakova, Rafael A. Galiullin, Andrey F. Kozlov, Ivan D. Shumov, Vladimir P. Popov, Svetlana I. Kapustina, Irina A. Ivanova, Arina I. Isaeva, Fedor V. Tikhonenko, Nikolay E. Kushlinskii, Alexander A. Alferov, Vadim Yu. Tatur, Vadim S. Ziborov, Oleg F. Petrov, Alexander V. Glukhov and Alexander I. Archakov

Chemosensors 2021, 9(8), 222; https://doi.org/10.3390/chemosensors9080222 - 13 Aug 2021

Cited by 4 | Viewed by 2325

Abstract

The detection of CA 125 protein in buffer solution with a silicon-on-insulator (SOI)-based nanoribbon (NR) biosensor was experimentally demonstrated. In the biosensor, sensor chips, bearing an array of 12 nanoribbons (NRs) with n-type conductance, were employed. In the course of the analysis with [...] Read more.

The detection of CA 125 protein in buffer solution with a silicon-on-insulator (SOI)-based nanoribbon (NR) biosensor was experimentally demonstrated. In the biosensor, sensor chips, bearing an array of 12 nanoribbons (NRs) with n-type conductance, were employed. In the course of the analysis with the NR biosensor, the target protein was biospecifically captured onto the surface of the NRs, which was sensitized with covalently immobilized aptamers against CA 125. Atomic force microscopy (AFM) and mass spectrometry (MS) were employed in order to confirm the formation of the probe–target complexes on the NR surface. Via AFM and MS, the formation of aptamer–antigen complexes on the surface of SOI substrates with covalently immobilized aptamers against CA 125 was revealed, thus confirming the efficient immobilization of the aptamers onto the SOI surface. The biosensor signal, resulting from the biospecific interaction between CA 125 and the NR-immobilized aptamer probes, was shown to increase with an increase in the target protein concentration. The minimum detectable CA 125 concentration was as low as 1.5 × 10⁻¹⁷ M. Moreover, with the biosensor proposed herein, the detection of CA 125 in the plasma of ovarian cancer patients was demonstrated. Full article

(This article belongs to the Special Issue Aptasensors: Applications in Life Science and Environmental Technology)

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14 pages, 4148 KiB

Open AccessArticle

Ultrathin Leaf-Shaped CuO Nanosheets Based Sensor Device for Enhanced Hydrogen Sulfide Gas Sensing Application

by Ahmad Umar, Hassan Algadi, Rajesh Kumar, Mohammad Shaheer Akhtar, Ahmed A. Ibrahim, Hasan Albargi, Mohsen A. M. Alhamami, Turki Alsuwian and Wen Zeng

Chemosensors 2021, 9(8), 221; https://doi.org/10.3390/chemosensors9080221 - 11 Aug 2021

Cited by 7 | Viewed by 2438

Abstract

Herein, a simple, economical and low temperature synthesis of leaf-shaped CuO nanosheets is reported. As-synthesized CuO was examined through different techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), fourier [...] Read more.

Herein, a simple, economical and low temperature synthesis of leaf-shaped CuO nanosheets is reported. As-synthesized CuO was examined through different techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), fourier transform infrared spectroscopic (FTIR) and Raman spectroscopy to ascertain the purity, crystal phase, morphology, vibrational, optical and diffraction features. FESEM and TEM images revealed a thin leaf-like morphology for CuO nanosheets. An interplanar distance of ~0.25 nm corresponding to the (110) diffraction plane of the monoclinic phase of the CuO was revealed from the HRTEM images XRD analysis indicated a monoclinic tenorite crystalline phase of the synthesized CuO nanosheets. The average crystallite size for leaf-shaped CuO nanosheets was found to be 14.28 nm. Furthermore, a chemo-resistive-type gas sensor based on leaf-shaped CuO nanosheets was fabricated to effectively and selectively detect H₂S gas. The fabricated sensor showed maximum gas response at an optimized temperature of 300 °C towards 200 ppm H₂S gas. The corresponding response and recovery times were 97 s and 100 s, respectively. The leaf-shaped CuO nanosheets-based gas sensor also exhibited excellent selectivity towards H₂S gas as compared to other analyte gases including NH₃, CH₃OH, CH₃CH₂OH, CO and H₂. Finally, we have proposed a gas sensing mechanism based upon the formation of chemo-resistive CuO nanosheets. Full article

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

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15 pages, 2821 KiB

Open AccessArticle

Theoretical and Experimental Research on Ammonia Sensing Properties of Sulfur-Doped Graphene Oxide

by Yao Yu, Zhijia Liao, Fanli Meng and Zhenyu Yuan

Chemosensors 2021, 9(8), 220; https://doi.org/10.3390/chemosensors9080220 - 11 Aug 2021

Cited by 8 | Viewed by 2167

Abstract

In this paper, gas sensing characteristics of sulfur-doped graphene oxide (S-GO) are firstly presented. The results of the sensing test revealed that, at room temperature (20 °C), S-GO has the optimal sensitivity to NH₃. The S-GO gas sensor has a relatively [...] Read more.

In this paper, gas sensing characteristics of sulfur-doped graphene oxide (S-GO) are firstly presented. The results of the sensing test revealed that, at room temperature (20 °C), S-GO has the optimal sensitivity to NH₃. The S-GO gas sensor has a relatively short response and recovery time for the NH₃ detection. Further, the sensing limit of ammonia at room temperature is 0.5 ppm. Theoretical models of graphene and S-doped graphene are established, and electrical properties of the graphene and S-doped graphene are calculated. The enhanced sensing performance was ascribed to the electrical properties’ improvement after the graphene was S-doped. Full article

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

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10 pages, 4058 KiB

Open AccessArticle

UV-Light-Driven Enhancement of Peroxidase-Like Activity of Mg-Aminoclay-Based Fe₃O₄/TiO₂ Hybrids for Colorimetric Detection of Phenolic Compounds

by Yoon Jung Jang, Vu Khac Hoang Bui, Phuong Thy Nguyen, Young-Chul Lee and Moon Il Kim

Chemosensors 2021, 9(8), 219; https://doi.org/10.3390/chemosensors9080219 - 11 Aug 2021

Cited by 6 | Viewed by 2333

Abstract

Light-activated nanozymes possess several advantages, such as light-mediated activity regulation, utilization of molecular oxygen as a green oxidant, and highly enhanced activity; however, the types of light-activated nanozymes are still limited. In this study, we found that Mg aminoclay-based Fe₃O₄ [...] Read more.

Light-activated nanozymes possess several advantages, such as light-mediated activity regulation, utilization of molecular oxygen as a green oxidant, and highly enhanced activity; however, the types of light-activated nanozymes are still limited. In this study, we found that Mg aminoclay-based Fe₃O₄/TiO₂ hybrids (MgAC-Fe₃O₄/TiO₂) exhibited peroxidase-like catalytic activity to catalyze the oxidation of the peroxidase substrate 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) in the presence of H₂O₂, which was significantly enhanced under ultraviolet (UV)-light irradiation. Compared with MgAC-Fe₃O₄ and MgAC-TiO₂, MgAC-Fe₃O₄/TiO₂ showed around three-fold enhancement in the absorption intensity corresponding to the oxidized ABTS under UV-light irradiation, presumably due to the synergistic effect between Fe₃O₄ and TiO₂, thereby facilitating photocatalytic electron transfer during the catalytic action. In addition, the MgAC-Fe₃O₄/TiO₂ showed vivid stability enhancement in wide range of pH and temperature values compared with natural peroxidase. The UV-light-driven MgAC-Fe₃O₄/TiO₂-based system was successfully applied for the colorimetric detection of phenolic compounds, including pyrocatechol and resorcinol, in a dynamic linear range of 0.15–1.30 mg/mL with a limit of detection as low as 0.1 mg/mL. Further, the system could successfully determine the phenolic compounds in spiked tap water, and thus, it can be used for practical applications. We believe that the UV-light-driven enhancement in the peroxidase-like catalytic performances highlights the potential of MgAC-Fe₃O₄/TiO₂ for detecting phenolic compounds as well as other clinically and environmentally important substances. Full article

(This article belongs to the Collection Sensing Materials: Advances in Synthesis, Functionalities, and Applications)

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9 pages, 980 KiB

Open AccessCommunication

Bovine Serum Albumin Protein Detection by a Removable SPR Chip Combined with a Specific MIP Receptor

by Francesco Arcadio, Luigi Zeni, Chiara Perri, Girolamo D’Agostino, Giudo Chiaretti, Giovanni Porto, Aldo Minardo and Nunzio Cennamo

Chemosensors 2021, 9(8), 218; https://doi.org/10.3390/chemosensors9080218 - 11 Aug 2021

Cited by 17 | Viewed by 2919

Abstract

Nowadays, the development of simple, fast, and low-cost selective sensors to detect substances of interest is of great importance in several application fields. Among this kind of sensors, those based on surface plasmon resonance (SPR) represent a promising category, since they are highly [...] Read more.

Nowadays, the development of simple, fast, and low-cost selective sensors to detect substances of interest is of great importance in several application fields. Among this kind of sensors, those based on surface plasmon resonance (SPR) represent a promising category, since they are highly sensitive, versatile, and label-free. In this work, an SPR probe, based on a poly(methyl methacrylate) (PMMA) slab waveguide covered by a gold nanofilm, combined with a specific molecularly imprinted polymer (MIP) receptor for bovine serum albumin (BSA) protein, has been realized and experimentally characterized. The obtained experimental results have shown a limit of detection (LOD) equal to about 8.5 × 10⁻⁹ M. This value is smaller than the one achieved by another SPR probe, based on a D-shaped plastic optical fiber (POF), functionalized with the same MIP receptor; more specifically, the obtained LOD was reduced by about three orders of magnitude with respect to the POF configuration. Moreover, concerning the D-shaped POF configuration, no manufacturing process is present in the proposed sensor configuration. In addition, fibers are used only to connect the simple sensor chip with a light source and a detector, promoting a bio-chemical sensing approach based on disposable, low-cost, and removable chips. Full article

(This article belongs to the Section Optical Chemical Sensors)

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11 pages, 20763 KiB

Open AccessArticle

Fluorescence Enhancement via Dual Coupling of Dye Molecules with Silver Nanostructures

by Vien Thi Tran and Heongkyu Ju

Chemosensors 2021, 9(8), 217; https://doi.org/10.3390/chemosensors9080217 - 10 Aug 2021

Cited by 5 | Viewed by 2258

Abstract

We demonstrate the enhancement of fluorescence emitted from dye molecules coupled with two surface plasmons, i.e., silver nanoparticles (AgNPs)-induced localized surface plasmons (LSP) and thin silver (Ag) film supported surface plasmons. Excitation light is illuminated to a SiO₂ layer that contains both [...] Read more.

We demonstrate the enhancement of fluorescence emitted from dye molecules coupled with two surface plasmons, i.e., silver nanoparticles (AgNPs)-induced localized surface plasmons (LSP) and thin silver (Ag) film supported surface plasmons. Excitation light is illuminated to a SiO₂ layer that contains both rhodamine 110 molecules and AgNPs. AgNPs enhances excitation rates of dye molecules in their close proximity due to LSP-induced enhancement of local electromagnetic fields at dye excitation wavelengths. Moreover, the SiO₂ layer on one surface of which a 50 nm-thick Ag film is coated for metal cladding (air on the other surface), acts as a waveguide core at the dye emission wavelengths. The Ag film induces the surface plasmons which couple with the waveguide modes, resulting in a waveguide-modulated version of surface plasmon coupled emission (SPCE) for different SiO₂ thicknesses in a reverse Kretschmann configuration. We find that varying the SiO₂ thickness modulates the fluorescent signal of SPCE, its modulation behavior being in agreement with the theoretical simulation of thickness dependent properties of the coupled plasmon waveguide resonance. This enables optimization engineering of the waveguide structure for enhancement of fluorescent signals. The combination of LSP enhanced dye excitation and the waveguide-modulated version of SPCE may offer chances of enhancing fluorescent signals for a highly sensitive fluorescent assay of biomedical and chemical substances. Full article

(This article belongs to the Special Issue Photonics and Plasmonics: New Challenges for Optical Nanostructured Materials in Sensing)

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14 pages, 9110 KiB

Open AccessArticle

2,12-Diaza[6]helicene: An Efficient Non-Conventional Stereogenic Scaffold for Enantioselective Electrochemical Interphases

by Francesca Fontana, Benedetta Bertolotti, Sara Grecchi, Patrizia Romana Mussini, Laura Micheli, Roberto Cirilli, Matteo Tommasini and Simona Rizzo

Chemosensors 2021, 9(8), 216; https://doi.org/10.3390/chemosensors9080216 - 10 Aug 2021

Cited by 4 | Viewed by 2104

Abstract

The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racemate and the enantiomers were separated in an enantiopure state by semi-preparative HPLC on chiral stationary phase. Under selected alkylation conditions it was possible to obtain both the enantiopure 2-N-mono- and [...] Read more.

The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racemate and the enantiomers were separated in an enantiopure state by semi-preparative HPLC on chiral stationary phase. Under selected alkylation conditions it was possible to obtain both the enantiopure 2-N-mono- and di-N-ethyl quaternary iodides. Metathesis with bis(trifluoromethanesulfonyl)imide anion gave low-melting salts which were tested as inherently chiral additives to achiral ionic liquids for the electrochemical enantiodiscrimination of chiral organic probes in voltammetric experiments. Remarkable differences in the oxidation potentials of the enantiomers of two probes, a chiral ferrocenyl amine and an aminoacid, were achieved; the differences increase with increasing additive concentration and number of alkylated nitrogen atoms. Full article

(This article belongs to the Collection Novel Chirogenic Systems and Sensing Materials for Stereoselective Sensors Development)

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20 pages, 4191 KiB

Open AccessReview

Perovskite@Graphene Nanohybrids for Breath Analysis: A Proof-of-Concept

by Juan Casanova-Chafer, Rocio Garcia-Aboal, Pedro Atienzar, Carla Bittencourt and Eduard Llobet

Chemosensors 2021, 9(8), 215; https://doi.org/10.3390/chemosensors9080215 - 08 Aug 2021

Cited by 4 | Viewed by 2734

Abstract

Nanohybrids comprising graphene loaded with perovskite nanocrystals have been demonstrated as a potential option for sensing applications. Specifically, their combination presents an interesting synergistic effect owing to greater sensitivity when bare graphene is decorated with perovskites. In addition, since the main drawback of [...] Read more.

Nanohybrids comprising graphene loaded with perovskite nanocrystals have been demonstrated as a potential option for sensing applications. Specifically, their combination presents an interesting synergistic effect owing to greater sensitivity when bare graphene is decorated with perovskites. In addition, since the main drawback of perovskites is their instability towards ambient moisture, the hydrophobic properties of graphene can protect them, enabling their use for ambient monitoring, as previously reported. However not limited to this, the present work provides a proof-of-concept to likewise employ them in a potential application as breath analysis for the detection of health-related biomarkers. There is a growing demand for sensitive, non-invasive, miniaturized, and inexpensive devices able to detect specific gas molecules in human breath. Sensors gathering these requirements may be employed as a screening tool for reliable and fast detection of potential health issues. Moreover, perovskite@graphene nanohybrids present additional properties highly desirable as the capability to be operated at room temperature (i.e., reduced power consumption), reversible interaction with gases (i.e., reusability), and long-term stability. Within this perspective, the combination of both nanomaterials, perovskite nanocrystals and graphene, possibly includes the main requirements needed, being a promising option to be employed in the next generation of sensing devices. Full article

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

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13 pages, 4106 KiB

Open AccessArticle

On the Radiolytic Stability of Potentiometric Sensors with Plasticized Polymeric Membranes

by Julia Savosina, Marina Agafonova-Moroz, Maria Khaydukova, Andrey Legin, Vasiliy Babain, Peter Tolstoy and Dmitry Kirsanov

Chemosensors 2021, 9(8), 214; https://doi.org/10.3390/chemosensors9080214 - 08 Aug 2021

Cited by 2 | Viewed by 1553

Abstract

There is not much known on the stability of plasticized polymeric sensor membranes against ionizing radiation. While recent studies have indicated the applicability of potentiometric sensors with such membranes for quantification of actinides and lanthanides in spent nuclear fuel reprocessing solutions, the real [...] Read more.

There is not much known on the stability of plasticized polymeric sensor membranes against ionizing radiation. While recent studies have indicated the applicability of potentiometric sensors with such membranes for quantification of actinides and lanthanides in spent nuclear fuel reprocessing solutions, the real industrial application of such sensors will require their stability in ionizing radiation fields. The present study explores this problem and evaluates the stability of potentiometric sensitivity towards lanthanides and actinides for a variety of plasticized polymeric membranes based on different neutral ligands. We demonstrate that most of the studied sensor compositions retain their sensitivity up to 50–100 kGy of the absorbed gamma radiation dose. The higher doses lead to the gradual loss of sensitivity due to the radiolysis of ligands and a polymer membrane matrix as confirmed by electrochemical impedance and nuclear magnetic resonance studies. Full article

(This article belongs to the Section Applied Chemical Sensors)

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20 pages, 5024 KiB

Open AccessArticle

Evaluating the Effect of a Brewery By-Product as Feed Supplementation on the Quality of Eggs by Means of a Human Panel and E-Tongue and E-Nose Analysis

by Juan Pablo Aguinaga Bósquez, Zoltan Kovacs, Zoltán Gillay, György Bázár, Csaba Palkó, Hajnalka Hingyi, Éva Csavajda, Márta Üveges, Zsuzsanna Jókainé Szatura, Iuliana Diana Barbulescu, Mihaela Begea and Tamás Tóth

Chemosensors 2021, 9(8), 213; https://doi.org/10.3390/chemosensors9080213 - 06 Aug 2021

Cited by 8 | Viewed by 2558

Abstract

The objective of our research was to evaluate the possible alteration of the organoleptic properties of eggs produced by hens (Lohmann Brown-Classic) fed with diets containing different doses of an industrial by-product enriched with organic zinc (Zincoppyeast, ZP): Control 0%, ZP [...] Read more.

The objective of our research was to evaluate the possible alteration of the organoleptic properties of eggs produced by hens (Lohmann Brown-Classic) fed with diets containing different doses of an industrial by-product enriched with organic zinc (Zincoppyeast, ZP): Control 0%, ZP 2.5%, and ZP 5.0%. Eggs were collected after 30 days (batch 1) and 60 days (batch 2) of feeding with the experimental diets and subjected to chemical, microbiological, human sensory, e-nose, and e-tongue analyses. There was no significant difference among the microbiological status of eggs of the three groups, but there were significant differences (p < 0.05) in the fat (9.5% vs. 9.3%) and protein contents (12.7% vs. 13.4%) of the Control and ZP 5.0% groups, respectively. Human sensory analysis showed no clear change in the organoleptic characteristics of the eggs. Using linear discriminant analysis (LDA), the e-tongue could recognize the three groups of eggs in batch 1 and batch 2 with 95.9% and 100% accuracy and had a prediction accuracy of 64.8% and 56.2%, respectively. When the eggs were incubating at 50 °C or 80 °C before the e-nose analysis, the groups of eggs could be recognized with 98.0% and 82.7% accuracy, and predicted with 68.5% and 62.2% accuracy, respectively, using principal component analysis-based discriminant analysis (PCA–DA). The aroma compounds and respective sensory descriptors showing changes among the different groups of eggs (batch, storage, and feeding) were identified based on the e-nose analysis. The supplementation of laying hens’ feed with the investigated industrial by-product can be applied without any substantial effect on egg quality, which can, however, be detected with advanced analytical methods. Full article

(This article belongs to the Special Issue Applications of Chemosensors in Real-World Sample Analysis)

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38 pages, 8664 KiB

Open AccessReview

Functionalization Strategies of PEDOT and PEDOT:PSS Films for Organic Bioelectronics Applications

by Gonzalo E. Fenoy, Omar Azzaroni, Wolfgang Knoll and Waldemar A. Marmisollé

Chemosensors 2021, 9(8), 212; https://doi.org/10.3390/chemosensors9080212 - 06 Aug 2021

Cited by 32 | Viewed by 8446

Abstract

Organic bioelectronics involves the connection of organic semiconductors with living organisms, organs, tissues, cells, membranes, proteins, and even small molecules. In recent years, this field has received great interest due to the development of all kinds of devices architectures, enabling the detection of [...] Read more.

Organic bioelectronics involves the connection of organic semiconductors with living organisms, organs, tissues, cells, membranes, proteins, and even small molecules. In recent years, this field has received great interest due to the development of all kinds of devices architectures, enabling the detection of several relevant biomarkers, the stimulation and sensing of cells and tissues, and the recording of electrophysiological signals, among others. In this review, we discuss recent functionalization approaches for PEDOT and PEDOT:PSS films with the aim of integrating biomolecules for the fabrication of bioelectronics platforms. As the choice of the strategy is determined by the conducting polymer synthesis method, initially PEDOT and PEDOT:PSS films preparation methods are presented. Later, a wide variety of PEDOT functionalization approaches are discussed, together with bioconjugation techniques to develop efficient organic-biological interfaces. Finally, and by making use of these approaches, the fabrication of different platforms towards organic bioelectronics devices is reviewed. Full article

(This article belongs to the Special Issue Organic Thin-Film Transistor towards Biomedical Applications)

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23 pages, 4425 KiB

Open AccessReview

Current Progress of Magnetoresistance Sensors

by Songlin Yang and Jin Zhang

Chemosensors 2021, 9(8), 211; https://doi.org/10.3390/chemosensors9080211 - 05 Aug 2021

Cited by 26 | Viewed by 6384

Abstract

Magnetoresistance (MR) is the variation of a material’s resistivity under the presence of external magnetic fields. Reading heads in hard disk drives (HDDs) are the most common applications of MR sensors. Since the discovery of giant magnetoresistance (GMR) in the 1980s and the [...] Read more.

Magnetoresistance (MR) is the variation of a material’s resistivity under the presence of external magnetic fields. Reading heads in hard disk drives (HDDs) are the most common applications of MR sensors. Since the discovery of giant magnetoresistance (GMR) in the 1980s and the application of GMR reading heads in the 1990s, the MR sensors lead to the rapid developments of the HDDs’ storage capacity. Nowadays, MR sensors are employed in magnetic storage, position sensing, current sensing, non-destructive monitoring, and biomedical sensing systems. MR sensors are used to transfer the variation of the target magnetic fields to other signals such as resistance change. This review illustrates the progress of developing nanoconstructed MR materials/structures. Meanwhile, it offers an overview of current trends regarding the applications of MR sensors. In addition, the challenges in designing/developing MR sensors with enhanced performance and cost-efficiency are discussed in this review. Full article

(This article belongs to the Special Issue Advances in Magnetic Sensors with Nanocomponents)

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13 pages, 3454 KiB

Open AccessArticle

Development of Neutral Red as a pH/pCO₂ Luminescent Sensor for Biological Systems

by Megan N. Ericson, Sindhu K. Shankar, Laya M. Chahine, Mohammad A. Omary, Ione Hunt von Herbing and Sreekar B. Marpu

Chemosensors 2021, 9(8), 210; https://doi.org/10.3390/chemosensors9080210 - 05 Aug 2021

Cited by 6 | Viewed by 5146

Abstract

Neutral Red (NR), a eurhodin dye, is often used for staining living cells, but we demonstrated for the first time that NR can also serve as a CO₂ sensor, because of NR’s unique optical properties, which change with dissolved carbon dioxide (dCO [...] Read more.

Neutral Red (NR), a eurhodin dye, is often used for staining living cells, but we demonstrated for the first time that NR can also serve as a CO₂ sensor, because of NR’s unique optical properties, which change with dissolved carbon dioxide (dCO₂) concentrations. In the present study, optical sensitivity of NR was quantified as a function of changes in absorption and emission spectra to dCO₂ in a pH 7.3 buffer medium at eight dCO₂ concentrations. NR exhibited a response time of two minutes for equilibration in pure N₂ to 100% CO₂ with an ~200% percent change (%∆) in emission intensity and >400%∆ in absorbance, with full reversibility. Important to its application to biological systems, NR exhibited zero sensitivity to dissolved oxygen, which has routinely caused interference for CO₂ measurements. NR exhibited pH sensitive emission and excitation energies with dual excitation wavelengths at 455 nm and 540 nm, and a single emission at 640 nm. The CO₂ sensing properties of NR were benchmarked by a comparison to pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt) (HPTS). Future studies will evaluate the feasibility of NR as an intracellular in vivo pCO₂ sensor in aquatic organisms critically impacted by increasing global CO₂ levels. Full article

(This article belongs to the Section Optical Chemical Sensors)

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19 pages, 1870 KiB

Open AccessArticle

MOS Sensors Array for the Discrimination of Lung Cancer and At-Risk Subjects with Exhaled Breath Analysis

by Davide Marzorati, Luca Mainardi, Giulia Sedda, Roberto Gasparri, Lorenzo Spaggiari and Pietro Cerveri

Chemosensors 2021, 9(8), 209; https://doi.org/10.3390/chemosensors9080209 - 05 Aug 2021

Cited by 18 | Viewed by 3050

Abstract

Lung cancer is characterized by a tremendously high mortality rate and a low 5-year survival rate when diagnosed at a late stage. Early diagnosis of lung cancer drastically reduces its mortality rate and improves survival. Exhaled breath analysis could offer a tool to [...] Read more.

Lung cancer is characterized by a tremendously high mortality rate and a low 5-year survival rate when diagnosed at a late stage. Early diagnosis of lung cancer drastically reduces its mortality rate and improves survival. Exhaled breath analysis could offer a tool to clinicians to improve the ability to detect lung cancer at an early stage, thus leading to a reduction in the associated survival rate. In this paper, we present an electronic nose for the automatic analysis of exhaled breath. A total of five a-specific gas sensors were embedded in the electronic nose, making it sensitive to different volatile organic compounds (VOCs) contained in exhaled breath. Nine features were extracted from each gas sensor response to exhaled breath, identifying the subject breathprint. We tested the electronic nose on a cohort of 80 subjects, equally split between lung cancer and at-risk control subjects. Including gas sensor features and clinical features in a classification model, recall, precision, and accuracy of 78%, 80%, and 77% were reached using a fourfold cross-validation approach. The addition of other a-specific gas sensors, or of sensors specific to certain compounds, could improve the classification accuracy, therefore allowing for the development of a clinical tool to be integrated in the clinical pipeline for exhaled breath analysis and lung cancer early diagnosis. Full article

(This article belongs to the Special Issue State-of-the-Art in Electronic Nose Based on Optoelectronic/Electrochemical Sensors)

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13 pages, 1401 KiB

Open AccessArticle

One-Class Drift Compensation for an Electronic Nose

by Xiuxiu Zhu, Tao Liu, Jianjun Chen, Jianhua Cao and Hongjin Wang

Chemosensors 2021, 9(8), 208; https://doi.org/10.3390/chemosensors9080208 - 04 Aug 2021

Cited by 4 | Viewed by 1502

Abstract

Drift compensation is an important issue in an electronic nose (E-nose) that hinders the development of E-nose’s model robustness and recognition stability. The model-based drift compensation is a typical and popular countermeasure solving the drift problem. However, traditional model-based drift compensation methods have [...] Read more.

Drift compensation is an important issue in an electronic nose (E-nose) that hinders the development of E-nose’s model robustness and recognition stability. The model-based drift compensation is a typical and popular countermeasure solving the drift problem. However, traditional model-based drift compensation methods have faced “label dilemma” owing to high costs of obtaining kinds of prepared drift-calibration samples. In this study, we have proposed a calibration model for classification utilizing a single category of drift correction samples for more convenient and feasible operations. We constructed a multi-task learning model to achieve a calibrated classifier considering several demands. Accordingly, an associated solution process has been presented to gain a closed-form classifier representation. Moreover, two E-nose drift datasets have been introduced for method evaluation. From the experimental results, the proposed methodology reaches the highest recognition rate in most cases. On the other hand, the proposed methodology demonstrates excellent and steady performance in a wide range of adjustable parameters. Generally, the proposed method can conduct drift compensation with limited one-class calibration samples, accessing the top accuracy among all presented reference methods. It is a new choice for E-nose to counteract drift effect under cost-sensitive conditions. Full article

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

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19 pages, 5007 KiB

Open AccessArticle

MEMS-Based Cantilever Sensor for Simultaneous Measurement of Mass and Magnetic Moment of Magnetic Particles

by Wilson Ombati Nyang’au, Tamara Kahmann, Thilo Viereck and Erwin Peiner

Chemosensors 2021, 9(8), 207; https://doi.org/10.3390/chemosensors9080207 - 04 Aug 2021

Cited by 3 | Viewed by 2379

Abstract

This study presents a measurement approach suitable for the simultaneous determination of both the mass m_p and magnetic moment µ_p of magnetic particles deposited on a micro electro mechanical system (MEMS) resonant cantilever balance, which is operated in parallel to an [...] Read more.

This study presents a measurement approach suitable for the simultaneous determination of both the mass m_p and magnetic moment µ_p of magnetic particles deposited on a micro electro mechanical system (MEMS) resonant cantilever balance, which is operated in parallel to an external magnetic field-induced force gradient F′(z). Magnetic induction B(z) and its second spatial derivative δ²B/δz² is realized, beforehand, through the finite element method magnetics (FEMM) simulation with a pair of neodymium permanent magnets configured in a face-to-face arrangement. Typically, the magnets are mounted in a magnet holder assembly designed and fabricated in-house. The resulting F′ lowers the calibrated intrinsic stiffness k₀ of the cantilever to k₀-F′, which can, thus, be obtained from a measured resonance frequency shift of the cantilever. The magnetic moment µ_p per deposited particle is determined by dividing F′ by δ²B/δz² and the number of the attached monodisperse particles given by the mass-induced frequency shift of the cantilever. For the plain iron oxide particles (250 nm) and the magnetic polystyrene particles (2 µm), we yield µ_p of 0.8 to 1.5 fA m² and 11 to 19 fA m² compared to 2 fA m² and 33 fA m² nominal values, respectively. Full article

(This article belongs to the Special Issue Advances in Magnetic Sensors with Nanocomponents)

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Chemosensors, Volume 9, Issue 8 (August 2021) – 49 articles

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