A reagent-free phosphate chemiresistive sensor using carbon nanotubes functionalized with crystal violet

Patel, Vinay; Akbar, Ali; Kruse, Peter; Selvaganapathy, P. Ravi

doi:10.1039/d3an00622k

Cited by 2 publications

(3 citation statements)

References 33 publications

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“…Carbon-based materials such as graphene (single layer and few layer), graphene oxide, and carbon nanotubes (singlewalled and multiwalled) are some of the best substrates that have been demonstrated for transducer films in aqueous chemiresistive sensing. 23,24,28,37 Fabrication of a stable and uniform film is the key requirement for sensitive chemiresistive sensing, as the film directly interacts with water and any analyte present in the solution. FLG from the exfoliation of graphite presents a simple and economical way of producing resistive films.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…22 Typically, a small bias voltage is applied between the contacts of a chemiresistor and then the change in conductivity of the sensing element is monitored as a function of changes in the chemical environment. 22 Carbon-based materials such as carbon nanotubes, 23 graphene, 24,25 graphenelike carbon, 26 and graphite 27 have been used as the transducing element for monitoring pH, 28 heavy metals, 24 and disinfectants 26,29 in water. Single-element disinfectant sensors are effective when only one disinfectant with a known identity is present.…”

Section: ■ Introductionmentioning

confidence: 99%

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Continuous Monitoring of Monochloramine in Water, and Its Distinction from Free Chlorine and Dichloramine Using a Functionalized Graphene-Based Array of Chemiresistors

Akbar,

Selvaganapathy,

Kruse

2024

ACS EST Water

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Monochloramine (MCA) is commonly added to drinking water as a disinfectant to prevent pathogen growth. The generation of MCA at the treatment plant requires tight control over both pH and the ratio of free chlorine (FC) to ammonia to avoid forming undesirable byproducts such as dichloramine (DCA) and trichloramine (TCA), which can impart odor and toxicity to the water. Therefore, continuous monitoring of MCA is essential to ensuring drinking water quality. Currently, standard colorimetric methods to measure MCA rely on the use of reagents and are unsuitable for online monitoring. In addition, other oxidants can interfere with MCA measurement. Here, we present a solid-state, reagent-free MCA sensing method using an array of few-layer graphene (FLG) chemiresistors. The array consists of exfoliated FLG chemiresistors functionalized with specific redox-active molecules that have differential responses to MCA, FC, and DCA over a range of concentrations. Chemometric methods were employed to separate the analytes’ responses and to generate multivariate calibration for quantification. A minimum of three sensors are required in the array to maintain full functionality. The array has been demonstrated to quantify MCA in buffered and tap water as a low-cost, reagent-free approach to continuous monitoring.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Continuous Monitoring of Monochloramine in Water, and Its Distinction from Free Chlorine and Dichloramine Using a Functionalized Graphene-Based Array of Chemiresistors

Akbar,

Selvaganapathy,

Kruse

2024

ACS EST Water

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“…We have previously reported chemiresistive sensors for continuous monitoring of free chlorine in drinking water utilizing nanocarbon-based films doped with redox-active aniline oligomers. , Facile fabrication, rapid prototyping, low cost, and availability of high precision resistance measurement circuits make chemiresistors a good choice for sensor applications. − Carbon nanotube (CNT) films are suitable chemiresistive substrates since their electrical properties are affected by the adsorption of electron-donating or electron-accepting species acting as dopants. − Redox-active molecules dope CNTs by forming charge-transfer complexes, the nature of which is susceptible to the oxidation state of the molecule . Thus, the doping state of the CNTs is related to the oxidation state of the molecules .…”

Section: Introductionmentioning

confidence: 99%

Identification and Quantification of Aqueous Disinfectants Using an Array of Carbon Nanotube-Based Chemiresistors

Akbar,

Sharif,

Selvaganapathy

et al. 2023

ACS Appl. Eng. Mater.

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Disinfection of water is essential to prevent the growth of pathogens, but at high levels, it can cause harm to human health. Therefore, accurate monitoring of disinfectant concentrations in water is essential to ensure safe drinking water. The use of multiple disinfectants at different stages in water treatment plants makes it necessary to also identify the type and concentrations of all of the disinfectant species present. Here, we demonstrate an effective approach to identify and quantify multiple disinfectants (using the example of free chlorine and potassium permanganate) in water using single-walled carbon nanotube (SWCNT)-based reagent-free chemiresistive sensing arrays. Facile fabrication of chemiresistive devices makes them a popular choice for the implementation of sensor arrays. Our sensing array consists of functionalized and unfunctionalized (blank) SWCNT sensors to distinguish the disinfectants. The distinct responses from the different sensors at varying concentrations and pH can be fitted to the mathematical model of a Langmuir adsorption isotherm separately for each sensor. Blank and functionalized sensors respond through different mechanisms that result in varying responses that are concentration-and pH-dependent. Chemometric techniques such as principal component analysis (PCA) and partial least-squares-discriminant analysis (PLS-DA) were used to analyze the sensor data. PCA showed an excellent separation of the analytes over five different pHs (5.5, 6.5, 7.5, 8.5, and 9.5). PLS-DA provided excellent separability as well as good predictability with a Q 2 of 94.26% and an R 2 of 95.67% for the five pH regions of the two analytes. This proof-of-concept solid-state chemiresistive sensing array can be developed for specific disinfectants that are commonly used in water treatment plants and can be deployed in water distribution and monitoring facilities. We have demonstrated the applicability of chemiresistive devices in a sensor array format for the first time for aqueous disinfectant monitoring.

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A reagent-free phosphate chemiresistive sensor using carbon nanotubes functionalized with crystal violet

Abstract: This is the first study to report a solid-state and reagent-free chemiresistive sensor for phosphate measurements. The sensor exhibited a working range from 0.1 to 10 mM at a working pH 8 and potentially for hydroponics or aquaponics systems.

Cited by 2 publications

References 33 publications

Continuous Monitoring of Monochloramine in Water, and Its Distinction from Free Chlorine and Dichloramine Using a Functionalized Graphene-Based Array of Chemiresistors

Continuous Monitoring of Monochloramine in Water, and Its Distinction from Free Chlorine and Dichloramine Using a Functionalized Graphene-Based Array of Chemiresistors

Identification and Quantification of Aqueous Disinfectants Using an Array of Carbon Nanotube-Based Chemiresistors

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