Triclosan Detection in Aqueous Environmental Matrices by Thin-Films Sensors

Triclosan (TCS), a bacteriostatic detected in water bodies, have inauspicious effects in human and biota. Consequently, there is a critical need of monitoring these type of compounds in aqueous matrices. In this sense, sensors, based on polyethyleneimine and polysodium 4-styrenesulfonate layer-by-layer thin-films adsorbed on supports with gold interdigitated electrodes deposited, were developed. The aim was analyze the sensitivity of discrimination of TCS (10−15 M to 10−5 M) in deionized water, Luso® and in an effluent, by measuring the impedance spectra. LbL films can distinguish TCS concentrations in EF, while in LW was achieved an acceptable sensibility when interdigitated electrodes without films were used.

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Polyelectrolyte Based Sensors as Key to Achieve Quantitative Electronic Tongues: Detection of Triclosan on Aqueous Environmental Matrices

Nanomaterials ◽

10.3390/nano10040640 ◽

2020 ◽

Vol 10 (4) ◽

pp. 640

Author(s):

Cátia Magro ◽

Paulo Zagalo ◽

João Pereira-da-Silva ◽

Eduardo Pires Mateus ◽

Alexandra Branco Ribeiro ◽

...

Keyword(s):

Continuous Monitoring ◽

Mineral Water ◽

Electronic Tongue ◽

Principal Component ◽

Electrical Impedance Spectroscopy ◽

Layer By Layer ◽

Environmental Matrices ◽

Film Stability ◽

Lbl Films ◽

Water And Wastewater

Triclosan (TCS) is a bacteriostatic used in household items that promotes antimicrobial resistance and endocrine disruption effects both to humans and biota, raising health concerns. In this sense, new devices for its continuous monitoring in complex matrices are needed. In this work, sensors, based on polyelectrolyte layer-by-layer (LbL) films prepared onto gold interdigitated electrodes (IDE), were studied. An electronic tongue array, composed of (polyethyleneimine (PEI)/polysodium 4-styrenesulfonate (PSS))5 and (poly(allylamine hydrochloride/graphene oxide)5 LbL films together with gold IDE without coating were used to detect TCS concentrations (10−15–10−5 M). Electrical impedance spectroscopy was used as means of transduction and the obtained data was analyzed by principal component analysis (PCA). The electronic tongue was tested in deionized water, mineral water and wastewater matrices showing its ability to (1) distinguish between TCS doped and non-doped solutions and (2) sort out the TCS range of concentrations. Regarding film stability, strong polyelectrolytes, as (PEI/PSS)n, presented more firmness and no significant desorption when immersed in wastewater. Finally, the PCA data of gold IDE and (PEI/PSS)5 sensors, for the mineral water and wastewater matrices, respectively, showed the ability to distinguish both matrices. A sensitivity value of 0.19 ± 0.02 per decade to TCS concentration and a resolution of 0.13 pM were found through the PCA second principal component.

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Detection of Triclosan in Tuned Solutions by pH and Ionic Strength Using PAH/PAZO Thin Films

Proceedings ◽

10.3390/proceedings2019015025 ◽

2019 ◽

Vol 15 (1) ◽

pp. 25

Author(s):

Paulo M. Zagalo ◽

Cátia Magro ◽

João Pereira-da-Silva ◽

Benachir Bouchikhi ◽

Nezha El Bari ◽

...

Keyword(s):

Thin Films ◽

Ionic Strength ◽

Sodium Salt ◽

Personal Care Products ◽

Electronic Tongue ◽

Layer By Layer ◽

Personal Care ◽

Electrical Parameters ◽

Adsorbed Amount ◽

Lbl Films

The electronic tongue concept based on layer-by-layer (LbL) films can be used to the detection in water of triclosan (TCS), a pernicious molecule used in personal care products and widely released in the environment. In this work, we analyzed the adsorption of TCS on poly(allylaminehydrochloride) (PAH) and poly[1-[4-(3-carboxy-4hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) layers of PAH/PAZO LbL films. We demonstrate that the adsorbed amount is strongly dependent of pH, the efficiency of adsorption of TCS on PAH layer is higher, and, when PAZO is the outmost layer, the electrical parameters can discriminate the ionic strength on solutions of TCS.

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Voltammetric Detection of Caffeine in Beverages at Nafion/Graphite Nanoplatelets Layer-by-Layer Films

Nanomaterials ◽

10.3390/nano9020221 ◽

2019 ◽

Vol 9 (2) ◽

pp. 221 ◽

Cited By ~ 3

Author(s):

Sandra Hernandez-Aldave ◽

Afshin Tarat ◽

James D. McGettrick ◽

Paolo Bertoncello

Keyword(s):

Thin Films ◽

Hydrogen Bonding ◽

Hydrophobic Interactions ◽

Carbon Electrodes ◽

Layer By Layer ◽

Graphite Nanoplatelets ◽

Glassy Carbon Electrodes ◽

X Ray ◽

Voltammetric Detection ◽

Lbl Films

We report for the first time a procedure in which Nafion/Graphite nanoplatelets (GNPs) thin films are fabricated using a modified layer-by-layer (LbL) method. The method consists of dipping a substrate (quartz and/or glassy carbon electrodes) into a composite solution made of Nafion and GNPs dissolved together in ethanol, followed by washing steps in water. This procedure allowed the fabrication of multilayer films of (Nafion/GNPs)n by means of hydrogen bonding and hydrophobic‒hydrophobic interactions between Nafion, GNPs, and the corresponding solid substrate. The average thickness of each layer evaluated using profilometer corresponds to ca. 50 nm. The as-prepared Nafion/GNPs LbL films were characterized using various spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), FTIR, and optical microscopy. This characterization highlights the presence of oxygen functionalities that support a mechanism of self-assembly via hydrogen bonding interactions, along with hydrophobic interactions between the carbon groups of GNPs and the Teflon-like (carbon‒fluorine backbone) of Nafion. We showed that Nafion/GNPs LbL films can be deposited onto glassy carbon electrodes and utilized for the voltammetric detection of caffeine in beverages. The results showed that Nafion/GNPs LbL films can achieve a limit of detection for caffeine (LoD) of 0.032 μM and linear range between 20‒250 μM using differential pulse voltammetry, whereas, using cyclic voltammetry LoD and linear range were found to be 24 μM and 50‒5000 μM, respectively. Voltammetric detection of caffeine in beverages showed good agreement between the values found experimentally and those reported by the beverage producers. The values found are also in agreement with those obtained using a standard spectrophotometric method. The proposed method is appealing because it allows the fabrication of Nafion/GNPs thin films in a simple fashion using a single-step procedure, rather than using composite solutions with opposite electrostatic charge, and also allows the detection of caffeine in beverages without any pre-treatment or dilution of the real samples. The proposed method is characterized by a fast response time without apparent interference, and the results were competitive with those obtained with other materials reported in the literature.

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Selective Hydrogen Bonding Controls Temperature Response of Layer-by-Layer Upper Critical Solution Temperature Micellar Assemblies

Soft Matter ◽

10.1039/d0sm01997f ◽

2021 ◽

Author(s):

Aliaksei Aliakseyeu ◽

Victoria Albright ◽

Danielle Yarbrough ◽

Samantha Hernandez ◽

Qing Zhou ◽

...

Keyword(s):

Hydrogen Bonding ◽

Methacrylic Acid ◽

Temperature Response ◽

Solution Temperature ◽

Layer By Layer ◽

Critical Solution Temperature ◽

Hydrogen Bonding Interactions ◽

Upper Critical Solution Temperature ◽

Lbl Films

This work establishes a correlation between the selectivity of hydrogen-bonding interactions and the functionality of micelle-containing layer-by-layer (LbL) assemblies. Specifically, we explore LbL films formed by assembly of poly(methacrylic acid)...

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Thermally Stimulated Desorption Optical Fiber-Based Interrogation System: An Analysis of Graphene Oxide Layers’ Stability

Photonics ◽

10.3390/photonics8030070 ◽

2021 ◽

Vol 8 (3) ◽

pp. 70

Author(s):

Maria Raposo ◽

Carlota Xavier ◽

Catarina Monteiro ◽

Susana Silva ◽

Orlando Frazão ◽

...

Keyword(s):

Graphene Oxide ◽

Optical Fiber ◽

Optical Fiber Sensor ◽

Layer By Layer ◽

Film Stability ◽

A Value ◽

Device Reliability ◽

Sensor Devices ◽

Lbl Films ◽

The Stability

Thin graphene oxide (GO) film layers are being widely used as sensing layers in different types of electrical and optical sensor devices. GO layers are particularly popular because of their tuned interface reflectivity. The stability of GO layers is fundamental for sensor device reliability, particularly in complex aqueous environments such as wastewater. In this work, the stability of GO layers in layer-by-layer (LbL) films of polyethyleneimine (PEI) and GO was investigated. The results led to the following conclusions: PEI/GO films grow linearly with the number of bilayers as long as the adsorption time is kept constant; the adsorption kinetics of a GO layer follow the behavior of the adsorption of polyelectrolytes; and the interaction associated with the growth of these films is of the ionic type since the desorption activation energy has a value of 119 ± 17 kJ/mol. Therefore, it is possible to conclude that PEI/GO films are suitable for application in optical fiber sensor devices; most importantly, an optical fiber-based interrogation setup can easily be adapted to investigate in situ desorption via a thermally stimulated process. In addition, it is possible to draw inferences about film stability in solution in a fast, reliable way when compared with the traditional ones.

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Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

Nanomaterials ◽

10.3390/nano11071631 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1631

Author(s):

Qiang Zhang ◽

Yohanes Pramudya ◽

Wolfgang Wenzel ◽

Christof Wöll

Keyword(s):

Thin Films ◽

Surface Roughness ◽

Deposition Rate ◽

Layer Growth ◽

Coarse Grained ◽

Structural Defects ◽

Effect Of Temperature ◽

Layer By Layer ◽

Reactant Concentration ◽

Metal Organic

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations.

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