Editorial

2 pages, 167 KiB

Open AccessEditorial

by Maria Raposo and Paulo A. Ribeiro

Chemosensors 2019, 7(3), 37; https://doi.org/10.3390/chemosensors7030037 - 08 Aug 2019

Cited by 1 | Viewed by 2667

An increasing number of fields in everyday life require the development and application of ever more modern and efficient chemical sensors and biosensors, namely to be integrated in intelligent control system networks [...] Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

Research

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10 pages, 2992 KiB

Open AccessArticle

Electro-Optical Gas Sensor Consisting of Nanostructured Paper Coating and an Ultrathin Sensing Element

by Jawad Sarfraz, Emil Rosqvist, Petri Ihalainen and Jouko Peltonen

Chemosensors 2019, 7(2), 23; https://doi.org/10.3390/chemosensors7020023 - 01 May 2019

Cited by 8 | Viewed by 4479

Abstract

This work describes the use of a paper substrate for electro-optical detection of toxic hydrogen sulfide (H₂S) gas. For electrical detection, a chemiresistive type of gas sensor was developed. Ultrathin gold film electrodes (UTGFE) were produced by physical vapor deposition of [...] Read more.

This work describes the use of a paper substrate for electro-optical detection of toxic hydrogen sulfide (H₂S) gas. For electrical detection, a chemiresistive type of gas sensor was developed. Ultrathin gold film electrodes (UTGFE) were produced by physical vapor deposition of gold on nanostructured latex-coated paper substrate. The gas-sensing film was deposited on the electrodes by inkjet printing. The sensing films were characterized by atomic force microscopy, X-ray photoelectron spectroscopy and conductometry. The sensing films showed more than seven orders of magnitude change in resistance when exposed to as low as 1 part per million (ppm) H₂S gas at room temperature. Besides resistive response, the change in color of the sensing films was studied on a paper substrate, both as a function of print density of the sensing material and H₂S concentration. For quantification of the analyte the red, green and blue color deconvolution was performed on the pictures of the paper strip indicator using an open source software. A clear response was obtained from the blue channel. The inexpensive disposable color strips produced on the paper substrate can be used for qualitative and quantitative detection (as low as 1.5 ppm) of H₂S gas. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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13 pages, 4174 KiB

Open AccessArticle

Inkjet Printed Interdigitated Biosensor for Easy and Rapid Detection of Bacteriophage Contamination: A Preliminary Study for Milk Processing Control Applications

by Giulio Rosati, Arianna Cunego, Fabio Fracchetti, Antonio Del Casale, Matteo Scaramuzza, Alessandro De Toni, Sandra Torriani and Alessandro Paccagnella

Chemosensors 2019, 7(1), 8; https://doi.org/10.3390/chemosensors7010008 - 18 Feb 2019

Cited by 18 | Viewed by 4434

Abstract

Bacteriophages are responsible for significant material and time losses in the dairy industry. This because these viruses infect the selected lactic starter cultures used for milk fermentation, i.e., the first stage toward cheese production. Standard detection techniques are time- and labor-consuming, causing huge [...] Read more.

Bacteriophages are responsible for significant material and time losses in the dairy industry. This because these viruses infect the selected lactic starter cultures used for milk fermentation, i.e., the first stage toward cheese production. Standard detection techniques are time- and labor-consuming, causing huge costs related to production plant sanitation and product wasting. A new type of biosensor for early detection of bacteriophage contamination is highly demanded by the milk processing market, and inkjet-printed electrochemical sensors could be the answer. Inkjet printing is a well-known technology that has been revisited in recent years, using silver nanoparticle (AgNP) based inks for low-cost and easy fabrication of sensing and biosensing systems on flexible and eco-compatible substrates. In this research, we studied inkjet printing for the manufacturing of both interdigitated electrodes arrays (IDEAs), and a versatile system to monitor bacterial cultures by electrochemical impedance spectroscopy (EIS). In particular, we studied this biosensing system for the detection of bacteriophages by comparing its performance with standard microbiological methods. We performed electrical and morphological characterizations of the devices produced with a consumer-use inkjet printer with commercial AgNPs ink on flexible substrates, such as office paper, polyethylene (PET), and photo paper. We used light microscopy optical analysis, profilometry, atomic force microscopy (AFM), and scanning electron microscopy (SEM) imaging to define the objects resolution, their real dimensions, and thickness. We also investigated the devices’ conductivity and layout, by EIS measurements with a standard buffer solution, i.e., phosphate buffered saline (PBS). Finally, we tested our system by monitoring Lactococcus lactis cultures and bacteriophage infection. We compared the results to those obtained by two standard microbiological methods in terms of response time, proving that our technique requires less than half the time of other methods and no specialized personnel. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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14 pages, 4063 KiB

Open AccessArticle

Resistive Low-Temperature Sensor Based on the SiO₂ZrO₂ Film for Detection of High Concentrations of NO₂ Gas

by Tatiana N. Myasoedova, Tatiana S. Mikhailova, Galina E. Yalovega and Nina K. Plugotarenko

Chemosensors 2018, 6(4), 67; https://doi.org/10.3390/chemosensors6040067 - 19 Dec 2018

Cited by 10 | Viewed by 3414

Abstract

The SiO₂ZrO₂ composite films were prepared by means of sol-gel technology and characterized by scanning electron microscopy, energy dispersive X-ray (EDX) analysis, and X-ray diffraction. The presence of the stable monoclinic ZrO₂ with an impurity of tetragonal phases is [...] Read more.

The SiO₂ZrO₂ composite films were prepared by means of sol-gel technology and characterized by scanning electron microscopy, energy dispersive X-ray (EDX) analysis, and X-ray diffraction. The presence of the stable monoclinic ZrO₂ with an impurity of tetragonal phases is shown. The film surface is characterized by the presence of ZrOCl₂·6H₂O or ZrCl(OH)/ZrCl(OH)₂ grains. The crystallite size negligibly depends on the annealing temperature of the film and amount to 10–12 nm and 9–12 nm for the films thermally treated at 200 °C and 500 °C, respectively. The film’s resistance is rather sensitive to the presence of NO₂ impurities in the air at a low operating temperature (25 °C). Accelerated stability tests of the initial resistance showed high stability and reproducibility of the sensor based on the SiO₂ZrO₂ film thermally treated at 500 °C. Full article

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8 pages, 1779 KiB

Open AccessArticle

Fluorinated Chromium Phthalocyanine Thin Films: Characterization and Ammonia Vapor Detection

by Hikmat Adnan Banimuslem and Burak Y. Kadem

Chemosensors 2018, 6(4), 63; https://doi.org/10.3390/chemosensors6040063 - 06 Dec 2018

Cited by 6 | Viewed by 3119

Abstract

Thin films of fluorinated chromium phthalocyanine were prepared using spin coating techniques and annealed at 100, 200, 300, and 400 °C. The prepared films were investigated using UV-Visible absorption spectroscopy, Raman spectroscopy, and atomic force microscopy. The band gap characteristics were evaluated to [...] Read more.

Thin films of fluorinated chromium phthalocyanine were prepared using spin coating techniques and annealed at 100, 200, 300, and 400 °C. The prepared films were investigated using UV-Visible absorption spectroscopy, Raman spectroscopy, and atomic force microscopy. The band gap characteristics were evaluated to study the difference electronic transitions between the prepared thin films under different annealing temperatures. Films were exposed to ammonia vapor in a concentration range of 40–100 ppm to demonstrate the gas sensing activity of prepared devices. Resistance versus voltage behavior was investigated upon the exposure of ammonia gas and the samples show an increase in the resistance towards the existence of ammonia molecules. The dependency of the sensors on time was studied to evaluate the response and recovery time, which were found to be 10 and 13 s respectively. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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15 pages, 1930 KiB

Open AccessArticle

Broad-Range Hydrogel-Based pH Sensor with Capacitive Readout Manufactured on a Flexible Substrate

by Krister Hammarling, Magnus Engholm, Henrik Andersson, Mats Sandberg and Hans-Erik Nilsson

Chemosensors 2018, 6(3), 30; https://doi.org/10.3390/chemosensors6030030 - 25 Jul 2018

Cited by 12 | Viewed by 4673

Abstract

Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, [...] Read more.

Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, there is a need for new sensors and sensor systems that suits these type of measurements. However, the diversity of sensors suitable for low, battery powered- and large area sensor systems are limited. We have manufactured and characterized a flexible pH sensor using laser processing and blade coating techniques that is able to measure pH between 2.94 and 11.80. The sensor consists of an interdigital capacitance with a pH sensitive hydrogel coating. Thin sensors can reach 95% of their final value value within 3 min, and are stable after 4 min. Good repeatability was achieved in regard to cycling of the sensor with different pH and multiple measurements from dry state. We have also studied the relation between an interdigital capacitance penetration depth and hydrogels expansion. We believe that our passive sensor is suitable to be used in low power and large area sensor networks. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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11 pages, 881 KiB

Open AccessArticle

Synthesis, Curing Behavior and Swell Tests of pH-Responsive Coatings from Acryl-Terminated Oligo(β-Amino Esters)

by Krister Hammarling, Mats Sandberg, Magnus Engholm, Henrik Andersson and Hans-Erik Nilsson

Chemosensors 2018, 6(1), 10; https://doi.org/10.3390/chemosensors6010010 - 23 Feb 2018

Cited by 4 | Viewed by 4280

Abstract

The ability of acryl-terminated oligo(

β

-amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of [...] Read more.

The ability of acryl-terminated oligo(

β

-amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of AOBAEs used as a pH-responsive coating material in sensor applications. Here we present an investigation of the synthesis, curing behavior and swell tests of AOBAEs. AOBAEs were synthesized from reacting an excess of asymmetric diacrylates with piperazine without the use of any solvents. They were then cross-linked to an insoluble network by UV-curing. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the AOBAEs. NMR was used to clarify the irregular structure of the AOBAE. FTIR was used to monitor the effects of UV-curing dose and air exposure on monomer conversion during curing. An interferometric technique was used to monitor the swelling behavior of the coating in response to pH variations. Swell experiments showed that the AOBAE also responded to pH variations after polymerization. Therefore, AOBAE is an interesting class of material with potential use as a pH responsive coating in optical-and printed electronics pH-sensors applications. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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Review

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23 pages, 1386 KiB

Open AccessEditor’s ChoiceReview

Thin Films Sensor Devices for Mycotoxins Detection in Foods: Applications and Challenges

by Andréia O. Santos, Andreia Vaz, Paula Rodrigues, Ana C. A. Veloso, Armando Venâncio and António M. Peres

Chemosensors 2019, 7(1), 3; https://doi.org/10.3390/chemosensors7010003 - 04 Jan 2019

Cited by 20 | Viewed by 5941

Abstract

Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of [...] Read more.

Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of mycotoxins include gas chromatography and high-performance liquid chromatography coupled with mass spectrometry or other detectors (fluorescence or UV detection), thin layer chromatography and enzyme-linked immunosorbent assay. These techniques are generally straightforward and yield reliable results; however, they are time-consuming, require extensive preparation steps, use large-scale instruments, and consume large amounts of hazardous chemical reagents. Rapid detection of mycotoxins is becoming an increasingly important challenge for the food industry in order to effectively enforce regulations and ensure the safety of food and feed. In this sense, several studies have been done with the aim of developing strategies to detect mycotoxins using sensing devices that have high sensitivity and specificity, fast analysis, low cost and portability. The latter include the use of microarray chips, multiplex lateral flow, Surface Plasmon Resonance, Surface Enhanced Raman Scattering and biosensors using nanoparticles. In this perspective, thin film sensors have recently emerged as a good candidate technique to meet such requirements. This review summarizes the application and challenges of thin film sensor devices for detection of mycotoxins in food matrices. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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