Chemosensors

41 pages, 15347 KiB

Open AccessEditor’s ChoiceReview

Metal–Oxide Nanowire Molecular Sensors and Their Promises

by Hao Zeng, Guozhu Zhang, Kazuki Nagashima, Tsunaki Takahashi, Takuro Hosomi and Takeshi Yanagida

Chemosensors 2021, 9(2), 41; https://doi.org/10.3390/chemosensors9020041 - 22 Feb 2021

Cited by 31 | Viewed by 6608

Abstract

During the past two decades, one–dimensional (1D) metal–oxide nanowire (NW)-based molecular sensors have been witnessed as promising candidates to electrically detect volatile organic compounds (VOCs) due to their high surface to volume ratio, single crystallinity, and well-defined crystal orientations. Furthermore, these unique physical/chemical [...] Read more.

During the past two decades, one–dimensional (1D) metal–oxide nanowire (NW)-based molecular sensors have been witnessed as promising candidates to electrically detect volatile organic compounds (VOCs) due to their high surface to volume ratio, single crystallinity, and well-defined crystal orientations. Furthermore, these unique physical/chemical features allow the integrated sensor electronics to work with a long-term stability, ultra-low power consumption, and miniature device size, which promote the fast development of “trillion sensor electronics” for Internet of things (IoT) applications. This review gives a comprehensive overview of the recent studies and achievements in 1D metal–oxide nanowire synthesis, sensor device fabrication, sensing material functionalization, and sensing mechanisms. In addition, some critical issues that impede the practical application of the 1D metal–oxide nanowire-based sensor electronics, including selectivity, long-term stability, and low power consumption, will be highlighted. Finally, we give a prospective account of the remaining issues toward the laboratory-to-market transformation of the 1D nanostructure-based sensor electronics. Full article

(This article belongs to the Special Issue Nanomaterials-Based Sensors)

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14 pages, 1301 KiB

Open AccessArticle

A Paper-Based Ultrasensitive Optical Sensor for the Selective Detection of H₂S Vapors

by Alejandro P. Vargas, Francisco Gámez, Javier Roales, Tânia Lopes-Costa and José M. Pedrosa

Chemosensors 2021, 9(2), 40; https://doi.org/10.3390/chemosensors9020040 - 19 Feb 2021

Cited by 12 | Viewed by 3741

Abstract

A selective and inexpensive chemical paper-based sensor for the detection of gaseous H₂S is presented. The triggering of the sensing mechanism is based on an arene-derivative dye which undergoes specific reactions in the presence of H₂S, allowing for colorimetric [...] Read more.

A selective and inexpensive chemical paper-based sensor for the detection of gaseous H₂S is presented. The triggering of the sensing mechanism is based on an arene-derivative dye which undergoes specific reactions in the presence of H₂S, allowing for colorimetric analysis. The dye is embedded into a porous cellulose matrix. We passively exposed the paper strips to H₂S generated in situ, while the absorbance was monitored via an optic fiber connected to a spectrophotometer. The kinetics of the emerging absorbance at 534 nm constitute the sensor response and maintain a very stable calibration signal in both concentration and time dimensions for quantitative applications. The time and concentration dependence of the calibration function allows the extraction of unusual analytical information that expands the potential comparability with other sensors in the literature, as the limit of detection admissible within a given exposure time. The use of this specific reaction ensures a very high selectivity against saturated vapors of primary interferents and typical volatile compounds, including alkanethiols. The specific performance of the proposed sensor was explicitly compared with other colorimetric alternatives, including standard lead acetate strips. Additionally, the use of a smartphone camera to follow the color change in the sensing reaction was also tested. With this straightforward method, also affordable for miniature photodiode devices, a limit of detection below the ppm scale was reached in both colorimetric approaches. Full article

(This article belongs to the Section Optical Chemical Sensors)

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15 pages, 7373 KiB

Open AccessArticle

Colorimetric Chemosensor Array for Determination of Halides

by Michal Šídlo, Přemysl Lubal and Pavel Anzenbacher, Jr.

Chemosensors 2021, 9(2), 39; https://doi.org/10.3390/chemosensors9020039 - 18 Feb 2021

Cited by 10 | Viewed by 3388

Abstract

The halide anions are essential for supporting life. Therefore, halide anion analyses are of paramount importance. For this reason, we have performed both qualitative and quantitative ana- lyses of halides (chloride, bromide, iodide) using the Tl(III) complex of azodye, 4-(2-pyridylazo)re- sorcinol (PAR), a [...] Read more.

The halide anions are essential for supporting life. Therefore, halide anion analyses are of paramount importance. For this reason, we have performed both qualitative and quantitative ana- lyses of halides (chloride, bromide, iodide) using the Tl(III) complex of azodye, 4-(2-pyridylazo)re- sorcinol (PAR), a potential new chemical reagent/sensor that utilizes the substitution reaction whereas the Tl(III)PAR complex reacts with a halide to yield a more stable thallium(III)-halide while releasing the PAR ligand in a process accompanied by color change of the solution. The experimental conditions (e.g., pH, ratio metal ion-to-ligand ratio, etc.) for the substitution reaction between the metal complex and a halide were optimized to achieve increased sensitivity and a lower limit of detection (chloride 7 mM, bromide 0.15 mM, iodide 0.05 mM). It is demonstrated that this single chemosensor can, due to release of colored PAR ligand and the associated analyte-specific changes in the UV/VIS spectra, be employed for a multicomponent analysis of mixtures of anions (chloride + bromide, chloride + iodide, bromide + iodide). The spectrophotometric data evaluated by artificial neural networks (ANNs) enable distinguishing among the halides and to determine halide species concentrations in a mixture. The Tl(III)-PAR complex was also used to construct sensor arrays utilizing a standard 96-well plate format where the output was recorded at several wavelengths (up to 7) using a conventional plate reader. It is shown that the data obtained using a digital scanner employing only three different input channels may also be successfully used for a subsequent ANN analysis. The results of all approaches utilized for data evaluation were similar. To increase the practical utility of the chemosensor, we have developed a test paper strip indicator useful for routine naked-eye visual determination of halides. This test can also be used for halide anion determination in solutions using densitometer. The methodology described in this paper can be used for a simple, inexpensive, and fast routine analysis both in a laboratory as well as in a field setting. Full article

(This article belongs to the Special Issue Feature Papers – Chemical Sensors for Industrial Applications, Environmental, and Food Monitoring)

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10 pages, 1816 KiB

Open AccessCommunication

Pb(II) Determination in a Single Drop Using a Modified Screen-Printed Electrode

by Nika Žurga, David Majer and Matjaž Finšgar

Chemosensors 2021, 9(2), 38; https://doi.org/10.3390/chemosensors9020038 - 18 Feb 2021

Cited by 4 | Viewed by 2952

Abstract

This work presents the development and validation of an electroanalytical method for Pb(II) determination in a single drop. The electrochemical sensors used were an unmodified screen-printed electrode (SPE) and a Bi-film SPE (BiFSPE). Anodic square wave stripping voltammetry (SWASV) was performed at an [...] Read more.

This work presents the development and validation of an electroanalytical method for Pb(II) determination in a single drop. The electrochemical sensors used were an unmodified screen-printed electrode (SPE) and a Bi-film SPE (BiFSPE). Anodic square wave stripping voltammetry (SWASV) was performed at an accumulation potential of −1.5 V vs. Ag/AgCl and an accumulation time of 60 s. Electroanalysis with an unmodified SPE did not yield satisfactory results, whereas the BiFSPE was a much better analysis method. The linear concentration using the BiFSPE was in the range of 138.8–162.5 µg/L. The accuracy and precision were evaluated for different spiked concentrations, but the method using the unmodified SPE was neither accurate nor precise. Using the BiFSPE, the method was found to be both accurate and precise for Pb(II) determination at a concentration of 140.0 μg/L, with recovery and relative standard deviation (RSD) of 106.6% and 12.1%, respectively. In addition, using the BiFSPE, LOD and LOQ values of 1.2 μg/L and 3.3 μg/L were obtained, respectively. The possible interference effect on Pb(II) stripping signal was checked in the presence of Cd(II), Zn(II), Cu(II), Sn(IV), Sb(III), Hg(II), Fe(III), As(V), K(I), I⁻, Ca(II), and NO_3⁻. Electrochemical impedance spectroscopy measurements were also performed for the unmodified SPE and BiFSPE. The application of single drop Pb(II) analysis was tested by real water sample analysis. Full article

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

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13 pages, 3550 KiB

Open AccessArticle

Gold Nanoframe Array Electrode for Straightforward Detection of Hydrogen Peroxide

by Agnes Purwidyantri, Ya-Chung Tian, Gardin Muhammad Andika Saputra, Briliant Adhi Prabowo, Hui-Ling Liu, Chia-Ming Yang and Chao-Sung Lai

Chemosensors 2021, 9(2), 37; https://doi.org/10.3390/chemosensors9020037 - 16 Feb 2021

Cited by 8 | Viewed by 4050

Abstract

The nanostructuring of a sensing membrane is performed through colloidal nanosphere lithography (NSL) techniques with a tiny polystyrene nanobead template 100 nm in size. The solvent ratio adjustment has been proven to be effective in assisting the monolayer deposition of small templating particles [...] Read more.

The nanostructuring of a sensing membrane is performed through colloidal nanosphere lithography (NSL) techniques with a tiny polystyrene nanobead template 100 nm in size. The solvent ratio adjustment has been proven to be effective in assisting the monolayer deposition of small templating particles with minimal defects. Two distinct structures, namely, a billowy gold nanostructure (BGN) where the nanobead template is left unetched and a gold nanoframe array (GNA) with a regular ring-like structure after template removal, are used for the extended-gate field-effect transistor (EGFET) electrodes. The GNA structure generates an electroactive surface area significantly (~20%) larger than its geometrical area as well as a greater surface roughness than the BGN. When integrated with the portable constant voltage–constant current (CVCC) FET circuitry for pH screening to determine the optimized measurement conditions for H₂O₂ sensing, the GNA sensing membrane also shows more improved Nernstian sensitivity at ~50 mV/pH than the BGN electrode. The more optimized sensitivity is then proven using the GNA in the detection of H₂O₂, the most common representative reactive oxygen species (ROS) involved in the environment, food, and neurodegenerative diseases, such as Parkinson´s and Alzheimer´s diseases. The GNA electrode has a sensitivity of 70.42 mV/log µM [H₂O₂] and a limit of detection (LoD) of 1.183 µM H₂O₂. The integrated ion sensing system employing unique, highly ordered gold array gate electrodes and a portable CVCC circuit system has shown a stable real-time output voltage signal, representing an alternative to bulky conventional FET devices for potential on-site H₂O₂ detection. Full article

(This article belongs to the Special Issue Selected Papers from the International Electron Devices & Materials Symposium 2020 (IEDMS 2020))

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11 pages, 4320 KiB

Open AccessArticle

AgNWs@TiO₂ and AgNPs@TiO₂ Double-Layer Photoanode Film Improving Light Capture and Application under Low Illumination

by Jung-Chuan Chou, Yu-Che Lin, Chih-Hsien Lai, Po-Yu Kuo, Yu-Hsun Nien, Ruei-Hong Syu, Zhen-Rong Yong and Yi-Ting Wu

Chemosensors 2021, 9(2), 36; https://doi.org/10.3390/chemosensors9020036 - 11 Feb 2021

Cited by 7 | Viewed by 2625

Abstract

In this article, silver nanowires (AgNWs) were prepared and introduced into the double-layer photoanode of dye-sensitized solar cells (DSSCs). Silver nanowires with a diameter of about 50–60 nm and a length of 1–2 mm were prepared by the polyol method. The power conversion [...] Read more.

In this article, silver nanowires (AgNWs) were prepared and introduced into the double-layer photoanode of dye-sensitized solar cells (DSSCs). Silver nanowires with a diameter of about 50–60 nm and a length of 1–2 mm were prepared by the polyol method. The power conversion efficiency of the double-layer photoanode DSSC made of AgNWs@TiO₂ and AgNPs@TiO₂ composite materials is 6.38%. Compared with the unmodified DSSC, the composite double-layer photoanode combined with AgNWs and AgNPs increased the efficiency of DSSC by 58.7%. This increased efficiency was mainly due to the localized surface plasmon resonance effect caused by AgNPs and AgNWs. The increased light collection was caused by the plasma effect of AgNPs, and it increased the short-circuit photocurrent density (J_SC). The conductive properties of AgNWs improved interface charge transfer and delay charge recombination. The effect of a low light environment on DSSC efficiency was also investigated, and the best photovoltaic conversion efficiency under an irradiance of 10 mW/cm² was found to be 8.78%. Full article

(This article belongs to the Special Issue Selected Papers from the International Electron Devices & Materials Symposium 2020 (IEDMS 2020))

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22 pages, 7697 KiB

Open AccessArticle

Graphite Studded with Facile-Synthesized Cu₂O Nanoparticle-Based Cubes as a Novel Electrochemical Sensor for Highly Sensitive Voltametric Determination of Mebeverine Hydrochloride

by Ahmed H. Naggar, Ahmed Kotb, Ahmed A. Gahlan, Mahmoud H. Mahross, Abd El-Aziz Y. El-Sayed and Adel A. Abdelwahab

Chemosensors 2021, 9(2), 35; https://doi.org/10.3390/chemosensors9020035 - 9 Feb 2021

Cited by 6 | Viewed by 2374

Abstract

Herein, a feasible chemical reduction method followed by intensive mixing was applied for the preparation of an attractive material based on graphite studded with cuprous oxide nanoparticle-based cubes (Cu₂ONPs–C@G). Transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and [...] Read more.

Herein, a feasible chemical reduction method followed by intensive mixing was applied for the preparation of an attractive material based on graphite studded with cuprous oxide nanoparticle-based cubes (Cu₂ONPs–C@G). Transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV) were utilized for characterization. Cuprous oxide nanoparticles (Cu₂ONPs), with a diameter range mainly distributed from 4 to 20 nm, aggregate to form microcubes (Cu₂ONPs–C) with an average diameter of about 367 nm. Paste electrode was prepared using Cu₂ONPs–C@G (Cu₂ONPs–C@G/PE) for voltametric quantification of the musculotropic antispasmodic drug: mebeverine hydrochloride (MEB). The electrochemical behavior of MEB was studied using CV, and the optimum analytical parameters were investigated using square wave adsorptive anodic stripping voltammetry (SWAdASV). Moreover, density functional theory (DFT) was used to emphasize the ability of MEB to form a complex with Cu²⁺, confirming the suggested electrochemical behavior of MEB at Cu₂ONPs–C@G/PE. With good stability and high reproducibility, SWAdASV of Cu₂ONPs–C@G/PE shows successful quantification of MEB over the concentration range of 5.00 × 10⁻¹¹–1.10 × 10⁻⁹ M with lower limit of detection (LOD) and lower limit of quantification (LOQ) values of 2.41 × 10⁻¹¹ M and 8.05 × 10⁻¹¹ M, respectively. Finally, accurate quantification of MEB in dosage forms (tablets) and biological fluids (spiked human urine and plasma samples) was achieved using Cu₂ONPs-C@G/PE. Full article

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

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14 pages, 6464 KiB

Open AccessArticle

Nanocrystalline Oxides Ni_xCo_3−xO₄: Sub-ppm H₂S Sensing and Humidity Effect

by Kseniya Prikhodko, Abulkosim Nasriddinov, Svetlana Vladimirova, Marina Rumyantseva and Alexander Gaskov

Chemosensors 2021, 9(2), 34; https://doi.org/10.3390/chemosensors9020034 - 7 Feb 2021

Cited by 7 | Viewed by 2602

Abstract

In this work, p-type oxide semiconductors, Co₃O₄ and complex oxides Ni_xCo_3−xO₄ (x = 0.04, 0.07, 0.1), were studied as materials for sub-ppm H₂S sensing in the temperature range of 90–300 [...] Read more.

In this work, p-type oxide semiconductors, Co₃O₄ and complex oxides Ni_xCo_3−xO₄ (x = 0.04, 0.07, 0.1), were studied as materials for sub-ppm H₂S sensing in the temperature range of 90–300 °C in dry and humid air. Nanocrystalline Co₃O₄ and Ni_xCo_3−xO₄ (x = 0.04, 0.07, 0.1) were prepared by coprecipitation of cobalt and nickel oxalates from nitrate solutions and further annealing at 300 °C. The surface reactivity of the obtained materials toward H₂S both in dry and humid atmosphere (relative humidity at 25 °C R.H. = 60%) was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Sensor measurements showed a decrease in sensor signal toward 1 ppm H₂S with an increase in Ni content because of a decrease in chemisorbed surface oxygen species. On the other hand, sensor signal increases for all samples with increasing the relative humidity that depends on reactivity of the surface hydroxyl groups, which stimulate the decomposition of surface sulfites and provide better surface regeneration at higher temperature. This assumption was additionally confirmed by the faster saturation of the conductivity curve and a decrease in the sensor response time in humid air. Full article

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

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17 pages, 1161 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Optical, Electrochemical and Field Effect pH Sensors

by Federico Vivaldi, Pietro Salvo, Noemi Poma, Andrea Bonini, Denise Biagini, Lorenzo Del Noce, Bernardo Melai, Fabio Lisi and Fabio Di Francesco

Chemosensors 2021, 9(2), 33; https://doi.org/10.3390/chemosensors9020033 - 5 Feb 2021

Cited by 43 | Viewed by 7713

Abstract

Although its first definition dates back to more than a century ago, pH and its measurement are still studied for improving the performance of current sensors in everyday analysis. The gold standard is the glass electrode, but its intrinsic fragility and need of [...] Read more.

Although its first definition dates back to more than a century ago, pH and its measurement are still studied for improving the performance of current sensors in everyday analysis. The gold standard is the glass electrode, but its intrinsic fragility and need of frequent calibration are pushing the research field towards alternative sensitive devices and materials. In this review, we describe the most recent optical, electrochemical, and transistor-based sensors to provide an overview on the status of the scientific efforts towards pH sensing. Full article

(This article belongs to the Collection pH Sensors, Biosensors and Systems)

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9 pages, 2259 KiB

Open AccessCommunication

Silica Layer Used in Sensor Fabrication from a Low-Temperature Silane-Free Procedure

by Pei-Cheng Jiang, Yu-Ting Chow, Chi-Wei Chien, Cheng-Hsun-Tony Chang and Chii-Ruey Lin

Chemosensors 2021, 9(2), 32; https://doi.org/10.3390/chemosensors9020032 - 4 Feb 2021

Cited by 4 | Viewed by 2838

Abstract

Silica (SiO_2, silicon dioxide—a dielectric layer commonly used in electronic devices) is widely used in many types of sensors, such as gas, molecular, and biogenic polyamines. To form silica films, core shell or an encapsulated layer, silane has been used as a [...] Read more.

Silica (SiO_2, silicon dioxide—a dielectric layer commonly used in electronic devices) is widely used in many types of sensors, such as gas, molecular, and biogenic polyamines. To form silica films, core shell or an encapsulated layer, silane has been used as a precursor in recent decades. However, there are many hazards caused by using silane, such as its being extremely flammable, the explosive air, and skin and eye pain. To avoid these hazards, it is necessary to spend many resources on industrial safety design. Thus, the silica synthesized without silane gas which can be determined as a silane-free procedure presents a clean and safe solution to manufactures. In this report, we used the radio frequency (rf = 13.56 MHz) plasma-enhanced chemical vapor deposition technique (PECVD) to form a silica layer at room temperature. The silica layer is formed in hydrogen-based plasma at room temperature and silane gas is not used in this process. The substrate temperature dominates the silica formation, but the distance between the substrate and electrode (D_STE) and the methane additive can enhance the formation of a silica layer on the Si wafer. This silane-free procedure, at room temperature, is not only safer and friendlier to the environment but is also useful in the fabrication of many types of sensors. Full article

(This article belongs to the Special Issue Selected Papers from the International Electron Devices & Materials Symposium 2020 (IEDMS 2020))

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14 pages, 9323 KiB

Open AccessArticle

Identification of Mint Scents Using a QCM Based E-Nose

by Salih Okur, Mohammed Sarheed, Robert Huber, Zejun Zhang, Lars Heinke, Adnan Kanbar, Christof Wöll, Peter Nick and Uli Lemmer

Chemosensors 2021, 9(2), 31; https://doi.org/10.3390/chemosensors9020031 - 4 Feb 2021

Cited by 32 | Viewed by 5069

Abstract

Mints emit diverse scents that exert specific biological functions and are relevance for applications. The current work strives to develop electronic noses that can electronically discriminate the scents emitted by different species of Mint as alternative to conventional profiling by gas chromatography. Here, [...] Read more.

Mints emit diverse scents that exert specific biological functions and are relevance for applications. The current work strives to develop electronic noses that can electronically discriminate the scents emitted by different species of Mint as alternative to conventional profiling by gas chromatography. Here, 12 different sensing materials including 4 different metal oxide nanoparticle dispersions (AZO, ZnO, SnO₂, ITO), one Metal Organic Frame as Cu(BPDC), and 7 different polymer films, including PVA, PEDOT:PSS, PFO, SB, SW, SG, and PB were used for functionalizing of Quartz Crystal Microbalance (QCM) sensors. The purpose was to discriminate six economically relevant Mint species (Mentha x piperita, Mentha spicata, Mentha spicata ssp. crispa, Mentha longifolia, Agastache rugosa, and Nepeta cataria). The adsorption and desorption datasets obtained from each modified QCM sensor were processed by three different classification models, including Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and k-Nearest Neighbor Analysis (k-NN). This allowed discriminating the different Mints with classification accuracies of 97.2% (PCA), 100% (LDA), and 99.9% (k-NN), respectively. Prediction accuracies with a repeating test measurement reached up to 90.6% for LDA, and 85.6% for k-NN. These data demonstrate that this electronic nose can discriminate different Mint scents in a reliable and efficient manner. Full article

(This article belongs to the Special Issue Organic-Inorganic Hybrid Chemo- and Bio-Sensors)

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32 pages, 33096 KiB

Open AccessReview

Recent Advances in Perylene Diimide-Based Active Materials in Electrical Mode Gas Sensing

by Salman Ali, Akhil Gupta, Mahnaz Shafiei and Steven J. Langford

Chemosensors 2021, 9(2), 30; https://doi.org/10.3390/chemosensors9020030 - 1 Feb 2021

Cited by 27 | Viewed by 5328

Abstract

This review provides an update on advances in the area of electrical mode sensors using organic small molecule n-type semiconductors based on perylene. Among small organic molecules, perylene diimides (PDIs) are an important class of materials due to their outstanding thermal, chemical, [...] Read more.

This review provides an update on advances in the area of electrical mode sensors using organic small molecule n-type semiconductors based on perylene. Among small organic molecules, perylene diimides (PDIs) are an important class of materials due to their outstanding thermal, chemical, electronic, and optical properties, all of which make them promising candidates for a wide range of organic electronic devices including sensors, organic solar cells, organic field-effect transistors, and organic light-emitting diodes. This is mainly due to their electron-withdrawing nature and significant charge transfer properties. Perylene-based sensors of this type show high sensing performance towards various analytes, particularly reducing gases like ammonia and hydrazine, but there are several issues that need to be addressed including the selectivity towards a specific gas, the effect of relative humidity, and operating temperature. In this review, we focus on the strategies and design principles applied to the gas-sensing performance of PDI-based devices, including resistive sensors, amperometric sensors, and operating at room temperature. The device properties and sensing mechanisms for different analytes, focusing on hydrazine and ammonia, are studied in detail, and some future research perspectives are discussed for this promising field. We hope the discussed results and examples inspire new forms of molecular engineering and begin to open opportunities for other rylene diimide classes to be applied as active materials. Full article

(This article belongs to the Collection pH Sensors, Biosensors and Systems)

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9 pages, 1502 KiB

Open AccessCommunication

Quantitative Fiber-Enhanced Raman Sensing of Inorganic Nitrogen Species in Water

by Hugo Kerdoncuff, Lisa C. Deleebeeck and Mikael Lassen

Chemosensors 2021, 9(2), 29; https://doi.org/10.3390/chemosensors9020029 - 31 Jan 2021

Cited by 1 | Viewed by 2644

Abstract

Fast and efficient water quality monitoring is essential in the pursuit of reducing the impact of human activities on the environment. We address this issue by presenting a sensing system and method based on Raman spectroscopy in liquid-filled capillaries, that enables quantitative measurement [...] Read more.

Fast and efficient water quality monitoring is essential in the pursuit of reducing the impact of human activities on the environment. We address this issue by presenting a sensing system and method based on Raman spectroscopy in liquid-filled capillaries, that enables quantitative measurement of polyatomic anions in solution. We demonstrate quantitative measurement of nitrate concentrations in water via multivariate analysis with partial least squares regression. We achieve a limit of detection of 0.13 millimolar for a measurement time of 30 s. Our Raman method is compared with gravimetrically measured concentration with good agreement and reproducibility. The Raman monitoring method can be performed in a continuous manner, thus suitable for fast continuous monitoring of water and wastewater quality. Full article

(This article belongs to the Special Issue Surface-Enhanced Raman Spectroscopy: New Perspectives and Future Directions)

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13 pages, 3894 KiB

Open AccessArticle

Quantification of Pharmaceutical Bitterness Using a Membrane Electrode Based on a Hydrophobic Tetrakis [3,5-Bis (trifluoromethyl) phenyl] Borate

by Xiao Wu, Takeshi Shiino, Yusuke Tahara, Hidekazu Ikezaki and Kiyoshi Toko

Chemosensors 2021, 9(2), 28; https://doi.org/10.3390/chemosensors9020028 - 31 Jan 2021

Cited by 5 | Viewed by 2642

Abstract

Technologies for quantifying bitterness are essential for classifying medicines. As previously reported, taste sensors with lipid polymer membranes can respond to bitter hydrochloride substances in pharmaceuticals. However, the acid hydrolysis reaction between the lipid phosphoric acid di-n-decyl ester (PADE) and the plasticizer tributyl [...] Read more.

Technologies for quantifying bitterness are essential for classifying medicines. As previously reported, taste sensors with lipid polymer membranes can respond to bitter hydrochloride substances in pharmaceuticals. However, the acid hydrolysis reaction between the lipid phosphoric acid di-n-decyl ester (PADE) and the plasticizer tributyl o-acetylcitrate (TDAB) led to a deterioration in sensor responses during storage. Given the cost of transportation and preservation for commercialization, membrane components that maintain physical and chemical stability during long-term storage are needed. Here we present a membrane electrode based on hydrophobic tetrakis [3,5-bis (trifluoromethyl) phenyl] borate (TFPB) and a plasticizer 2-nitrophenyl octyl ether (NPOE) for the quantification of pharmaceutical bitterness; they maintain a stable response before and after accelerated deterioration, as well as high selectivity and sensitivity. It is a first attempt to use a completely dissociative substance to replace non-completely dissociative lipids. Our work offsets the long-term stability issue of a bitterness sensor with a negatively charged hydrophobic membrane. Meanwhile, we provide the opportunity to select surface charge modifiers for a membrane surface using ester plasticizers containing oppositely charged impurities. Full article

(This article belongs to the Special Issue Gustatory and Olfactory Sensing Technologies and Applications)

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13 pages, 3668 KiB

Open AccessArticle

Optimization of ZnO Nanorods Concentration in a Micro-Structured Polymeric Composite for Nanogenerators

by Andreia dos Santos, Filipe Sabino, Ana Rovisco, Pedro Barquinha, Hugo Águas, Elvira Fortunato, Rodrigo Martins and Rui Igreja

Chemosensors 2021, 9(2), 27; https://doi.org/10.3390/chemosensors9020027 - 31 Jan 2021

Cited by 13 | Viewed by 4414

Abstract

The growing use of wearable devices has been stimulating research efforts in the development of energy harvesters as more portable and practical energy sources alternatives. The field of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), especially employing zinc oxide (ZnO) nanowires (NWs), has [...] Read more.

The growing use of wearable devices has been stimulating research efforts in the development of energy harvesters as more portable and practical energy sources alternatives. The field of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), especially employing zinc oxide (ZnO) nanowires (NWs), has greatly flourished in recent years. Despite its modest piezoelectric coefficient, ZnO is very attractive due to its sustainable raw materials and the facility to obtain distinct morphologies, which increases its multifunctionality. The integration of ZnO nanostructures into polymeric matrices to overcome their fragility has already been proven to be fruitful, nevertheless, their concentration in the composite should be optimized to maximize the harvesters’ output, an aspect that has not been properly addressed. This work studies a composite with variable concentrations of ZnO nanorods (NRs), grown by microwave radiation assisted hydrothermal synthesis, and polydimethylsiloxane (PDMS). With a 25 wt % ZnO NRs concentration in a composite that was further micro-structured through laser engraving for output enhancement, a nanogenerator (NG) was fabricated with an output of 6 V at a pushing force of 2.3 N. The energy generated by the NG could be stored and later employed to power small electronic devices, ultimately illustrating its potential as an energy harvesting device. Full article

(This article belongs to the Special Issue Nanomaterials-Based Sensors)

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12 pages, 4168 KiB

Open AccessEditor’s ChoiceArticle

Development of an ImmunoFET for Analysis of Tumour Necrosis Factor-α in Artificial Saliva: Application for Heart Failure Monitoring

by Daiva Vozgirdaite, Hamdi Ben Halima, Francesca G. Bellagambi, Albert Alcacer, Francisio Palacio, Nicole Jaffrezic-Renault, Nadia Zine, Joan Bausells, Abdelhamid Elaissari and Abdelhamid Errachid

Chemosensors 2021, 9(2), 26; https://doi.org/10.3390/chemosensors9020026 - 29 Jan 2021

Cited by 26 | Viewed by 5412

Abstract

Assessing tumour necrosis factor-α (TNF-α) levels in the human body has become an essential tool to recognize heart failure (HF). In this work, label-free, rapid, easy to use ImmunoFET based on an ion-sensitive field effect transistor (ISFET) was developed for the detection of [...] Read more.

Assessing tumour necrosis factor-α (TNF-α) levels in the human body has become an essential tool to recognize heart failure (HF). In this work, label-free, rapid, easy to use ImmunoFET based on an ion-sensitive field effect transistor (ISFET) was developed for the detection of TNF-α protein. Monoclonal anti-TNF-α antibodies (anti-TNF-α mAb) were immobilized on an ISFET gate made of silicon nitride (Si₃N₄) after salinization with 11-(triethoxysilyl) undecanal (TESUD). The obtained ISFET functionalized with the mAbs (ImmunoFET) was used to detect TNF-α protein in both phosphate buffer saline (PBS) and artificial saliva (AS). The change in the threshold voltage of the gate (∆V_T) showed approximately linear dependency on the concentration of the antigens in the range 5–20 pg/mL for both matrixes. The cross-selectivity study showed that the developed ImmunoFET demonstrated to be selective towards TNF-α, when compared to other HF biomarkers such as N-terminal pro-brain natriuretic peptide (NT-proBNP), interleukin-10 (IL-10), and cortisol, even if further experiments have to be carried out for decreasing possible unspecific absorption phenomena. To the best of our knowledge, this is the first ImmunoFET that has been developed based on Si₃N₄ for TNF-α detection in AS by electrical measurement. Full article

(This article belongs to the Section Applied Chemical Sensors)

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13 pages, 3027 KiB

Open AccessEditor’s ChoiceArticle

Carbon Dots Fluorescence-Based Colorimetric Sensor for Sensitive Detection of Aluminum Ions with a Smartphone

by Wei Wei, Juan Huang, Wenli Gao, Xiangyang Lu and Xingbo Shi

Chemosensors 2021, 9(2), 25; https://doi.org/10.3390/chemosensors9020025 - 29 Jan 2021

Cited by 31 | Viewed by 4868

Abstract

In this work, blue emission carbon dots (CDs) are synthesized in the one-pot solvothermal method using naringin as precursor. The CDs are used to develop a ratiometric fluorescence sensor for the sensitive analysis of Al³⁺ with a detection limit of 113.8 nM. [...] Read more.

In this work, blue emission carbon dots (CDs) are synthesized in the one-pot solvothermal method using naringin as precursor. The CDs are used to develop a ratiometric fluorescence sensor for the sensitive analysis of Al³⁺ with a detection limit of 113.8 nM. A fluorescence emission peak at 500 nm gradually appears, whereas the original fluorescence peak at 420 nm gradually decreases upon the increase in the Al³⁺ concentration. More importantly, the obvious color change of the CDs probe from blue to green under a 360 nm UV lamp can be identified by a smartphone and combined with the RGB (red/green/blue) analysis. This results in a visual and sensitive analysis of Al³⁺ with a detection limit of 5.55 μM. Moreover, the high recovery is in the 92.46–104.10% range, which demonstrates the high accuracy of this method for actual samples’ analysis. The use of a smartphone and the RGB analysis greatly simplifies the operation process, saves equipment cost, shortens the detection time, and provides a novel method for the instant, on-site, visual detection of Al³⁺ in actual samples. Full article

(This article belongs to the Special Issue Near-Infrared Fluorophores for Biomedical Research)

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22 pages, 3781 KiB

Open AccessArticle

Gold-Platinum Core-Shell Nanoparticles with Thiolated Polyaniline and Multi-Walled Carbon Nanotubes for the Simultaneous Voltammetric Determination of Six Drug Molecules

by Shaopei Li, Jiayun Zhou, Meissam Noroozifar and Kagan Kerman

Chemosensors 2021, 9(2), 24; https://doi.org/10.3390/chemosensors9020024 - 28 Jan 2021

Cited by 21 | Viewed by 3995

Abstract

In this proof-of-concept study, a novel nanocomposite of the thiolated polyaniline (tPANI), multi-walled carbon nanotubes (MWCNTs) and gold–platinum core-shell nanoparticles (Au@Pt) (tPANI-Au@Pt-MWCNT) was synthesized and utilized to modify a glassy carbon electrode (GCE) for simultaneous voltammetric determination of six over-the-counter (OTC) drug molecules: [...] Read more.

In this proof-of-concept study, a novel nanocomposite of the thiolated polyaniline (tPANI), multi-walled carbon nanotubes (MWCNTs) and gold–platinum core-shell nanoparticles (Au@Pt) (tPANI-Au@Pt-MWCNT) was synthesized and utilized to modify a glassy carbon electrode (GCE) for simultaneous voltammetric determination of six over-the-counter (OTC) drug molecules: ascorbic acid (AA), levodopa (LD), acetaminophen (AC), diclofenac (DI), acetylsalicylic acid (AS) and caffeine (CA). The nanocomposite (tPANI-Au@Pt-MWCNT) was characterized with transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Using the sensor (GCE-tPANI-Au@Pt-MWCNT) in connection with differential pulse voltammetry (DPV), the calibration plots were determined to be linear up to 570.0, 60.0, 60.0, 115.0, 375.0 and 520.0 µM with limit of detection (LOD) of 1.5, 0.25, 0.15, 0.2, 2.0, and 5.0 µM for AA, LD, AC, DI, AS and CA, respectively. The nanocomposite-modified sensor was successfully used for the determination of these redox-active compounds in commercially available OTC products such as energy drinks, cream and tablets with good recovery yields ranging from 95.48 ± 0.53 to 104.1 ± 1.63%. We envisage that the electrochemical sensor provides a promising platform for future applications towards the detection of redox-active drug molecules in pharmaceutical quality control studies and forensic investigations. Full article

(This article belongs to the Special Issue Carbon Nanomaterials and Related Materials for Sensing Applications)

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10 pages, 1895 KiB

Open AccessCommunication

A Novel Multi-Ionophore Approach for Potentiometric Analysis of Lanthanide Mixtures

by Julia Ashina, Vasily Babain, Dmitry Kirsanov and Andrey Legin

Chemosensors 2021, 9(2), 23; https://doi.org/10.3390/chemosensors9020023 - 27 Jan 2021

Cited by 8 | Viewed by 2279

Abstract

This work aims to discuss quantification of rare earth metals in a complex mixture using the novel multi-ionophore approach based on potentiometric sensor arrays. Three compounds previously tested as extracting agents in reprocessing of spent nuclear fuel were applied as ionophores in polyvinyl [...] Read more.

This work aims to discuss quantification of rare earth metals in a complex mixture using the novel multi-ionophore approach based on potentiometric sensor arrays. Three compounds previously tested as extracting agents in reprocessing of spent nuclear fuel were applied as ionophores in polyvinyl chloride (PVC)-plasticized membranes of potentiometric sensors. Seven types of sensors containing these ionophores were prepared and assembled into a sensor array. The multi-ionophore array performance was evaluated in the analysis of Ln³⁺ mixtures and compared to that of conventional monoionophore sensors. It was demonstrated that a multi-ionophore array can yield RMSEP (root mean-squared error of prediction) values not exceeding 0.15 logC for quantification of individual lanthanides in binary mixtures in a concentration range 5 to 3 pLn³⁺. Full article

(This article belongs to the Special Issue Chemical Sensors for the Determination of Persistent and Emerging Contaminants)

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2 pages, 174 KiB

Open AccessEditorial

Chemosensors Comes of Age

by Igor L. Medintz

Chemosensors 2021, 9(2), 22; https://doi.org/10.3390/chemosensors9020022 - 27 Jan 2021

Viewed by 1750

Abstract

It has now been just over eight years since I had the pleasure of introducing Chemosensors to the world [...] Full article

13 pages, 3092 KiB

Open AccessArticle

Fabrication of Zinc Protoporphyrin-Modified Gold Electrode for Sensitive and Fast Detection of Vascular Endothelial Growth Factor

by Hung-Yu Lin, Chin-Cheng Liao and Mu-Yi Hua

Chemosensors 2021, 9(2), 21; https://doi.org/10.3390/chemosensors9020021 - 23 Jan 2021

Cited by 3 | Viewed by 3633

Abstract

Vascular endothelial growth factor (VEGF) is directly related to cancer growth and its distant spread, and thus, it is considered a promising biomarker for diagnosis and post-treatment monitoring of patients with malignancies. Zinc protoporphyrin (ZnPP) is a zinc-centered raw purple compound (protoporphyrin) that [...] Read more.

Vascular endothelial growth factor (VEGF) is directly related to cancer growth and its distant spread, and thus, it is considered a promising biomarker for diagnosis and post-treatment monitoring of patients with malignancies. Zinc protoporphyrin (ZnPP) is a zinc-centered raw purple compound (protoporphyrin) that has unique optical and electrochemical characteristics. In this study, we used a ZnPP-modified gold electrode to generate a chemical bond with Avastin by self-assembly and fabricate a Au/ZnPP/Avastin electrode. Bovine serum protein (BSA) was added to the electrode to prevent non-specific linkage with biomolecules. The prepared Au/ZnPP/Avastin/BSA electrodes were used for the detection of VEGF by cyclic voltammetry and amperometry. The optical properties of ZnPP were analyzed with an ultraviolet/visible/near-infrared spectrometer and a photoluminescence spectrometer. The structural and hydrophilic/hydrophobic properties of the ZnPP-modified gold electrodes were investigated by Fourier-transform infrared spectroscopy and contact angle gauge, respectively. VEGF was detected with the Au/ZnPP/Avastin/BSA electrodes prepared either with (w/LT) or without light treatment (w/o LT). The w/LT electrode showed a linear range and a sensitivity of 0.1 pg/mL–10 ng/mL and 6.52 μA/log(pg/mL)-cm², respectively; the corresponding values for the w/o LT electrode were 10 pg/mL–10 ng/mL and 3.15 μA/log(pg/mL)-cm², respectively. The w/LT electrode had good specificity for VEGF and was minimally influenced by other molecules. The excellent detection range, high sensitivity, and high selectivity for VEGF detection indicate that Au/ZnPP/Avastin electrodes have great potential for diagnostic and prognostic applications in patients with malignancies. Full article

(This article belongs to the Special Issue Selected Papers from the International Electron Devices & Materials Symposium 2020 (IEDMS 2020))

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12 pages, 1495 KiB

Open AccessArticle

Combining Chemical Functionalization and FinFET Geometry for Field Effect Sensors as Accessible Technology to Optimize pH Sensing

by Dipti Rani, Serena Rollo, Wouter Olthuis, Sivashankar Krishnamoorthy and César Pascual García

Chemosensors 2021, 9(2), 20; https://doi.org/10.3390/chemosensors9020020 - 21 Jan 2021

Cited by 11 | Viewed by 3243

Abstract

Field Effect Transistors (FETs) have led the progress of applications measuring the acidity in aqueous solutions thanks to their accuracy, ease of miniaturization and capacity of multiplexing. The signal-to-noise ratio and linearity of the sensors are two of the most relevant figures of [...] Read more.

Field Effect Transistors (FETs) have led the progress of applications measuring the acidity in aqueous solutions thanks to their accuracy, ease of miniaturization and capacity of multiplexing. The signal-to-noise ratio and linearity of the sensors are two of the most relevant figures of merit that can facilitate the improvements of these devices. In this work we present the functionalization with aminopropyltriethoxysilane (APTES) of a promising new FET design consisting of a high height-to-width aspect ratio with an efficient 2D gating architecture that improves both factors. We measured the transistor transfer and output characteristics before and after APTES functionalization, obtaining an improved sensitivity and linearity in both responses. We also compared the experimental results with a site-biding model of the surface buffering capacity of the APTES functionalized layers. Full article

(This article belongs to the Special Issue Nanomaterials-Based Sensors)

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17 pages, 3777 KiB

Open AccessArticle

Functionalized Surfaces as a Tool for Virus Sensing: A Demonstration of Human mastadenovirus Detection in Environmental Waters

by Juliana Schons Gularte, Roana de Oliveira Hansen, Meriane Demoliner, Jacek Fiutowski, Ana Karolina Antunes Eisen, Fagner Henrique Heldt, Paula Rodrigues de Almeida, Daniela Müller de Quevedo, Horst-Günter Rubahn and Fernando Rosado Spilki

Chemosensors 2021, 9(2), 19; https://doi.org/10.3390/chemosensors9020019 - 21 Jan 2021

Cited by 2 | Viewed by 3884

Abstract

The main goal of this study was to apply magnetic bead surface functionalization in the form of immunomagnetic separation (IMS) combined with real-time polymerase chain reaction (qPCR) (IMS-qPCR) to detect Human mastadenovirus species C (HAdV-C) and F (HAdV-F) in water samples. The technique [...] Read more.

The main goal of this study was to apply magnetic bead surface functionalization in the form of immunomagnetic separation (IMS) combined with real-time polymerase chain reaction (qPCR) (IMS-qPCR) to detect Human mastadenovirus species C (HAdV-C) and F (HAdV-F) in water samples. The technique efficiency was compared to a nonfunctionalized method (ultracentrifugation) followed by laboratory detection. Tests were carried out to standardize IMS parameters followed by tests on 15 water samples concentrated by IMS and ultracentrifugation. Microscopic analyses detected a successful beads–antibody attachment. HAdV was detected up to dilutions of 10⁻⁶ by IMS-qPCR, and samples concentrated by IMS were able to infect cell cultures. In water samples, HAdV-C was detected in 60% (monoclonal) and 47% (polyclonal) by IMS-qPCR, while 13% of samples concentrated by ultracentrifugation gave a positive result. HAdV-F was positive in 27% of samples by IMS-qPCR (polyclonal) and ultracentrifugation and 20% by IMS-qPCR (monoclonal). The rate of detection varied from 4.55 × 10² to 5.83 × 10⁶ genomic copies/L for IMS-qPCR and from 2.00 × 10² to 2.11 × 10³ GC/L for ultracentrifugation. IMS showed to be a more effective concentration technique for HAdV than ultracentrifugation, improving the assessment of infectious HAdV in water resources. Full article

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

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Chemosensors, Volume 9, Issue 2 (February 2021) – 23 articles

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