Amperometric bromate-sensitive sensor via layer-by-layer assembling of metalloporphyrin and polyelectrolytes on carbon nanotubes modified surfaces

doi:10.1016/j.snb.2016.12.114

Sensors and Actuators B: Chemical

Volume 244, June 2017, Pages 157-166

https://doi.org/10.1016/j.snb.2016.12.114 Get rights and content

Highlights

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The BrO₃⁻ sensor was a novel design based on Fe(III)P and PSS integrated LbL assembly.
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The current cathodic response showed a maximum value at the two layers of Fe(III)P.
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The detection limit of BrO₃⁻ was 43 nM by using the proposed LbL sensor.
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The proposed LbL sensor has acceptable anti-interference property.

Abstract

A novel amperometric sensor for bromate (BrO₃⁻) was developed using the layer-by-layer (LbL) assembly process of iron(III)-porphyrin (Fe(III)P) and polyelectrolytes alongside oxidized multiwall carbon nanotubes (OMWCNTs) on a disposable screen-printed carbon electrode (SPCE). Positively charged Fe(III)P and negatively charged poly(sodium 4-styrenesulfonate) (PSS) were used as structure blocks for LbL assembly on the OMWCNTs modified SPCE. The electrocatalytic response by Fe(III)P from the amperometric LbL sensor for determining BrO₃⁻ concentration was characterized using cyclic voltammetry. Critical experimental parameters affecting the sensor’s performance were optimized, including the number of assembled layers, pH of the buffer solution, and concentration of Fe(III)P immobilized on the electrode surface. A linear response from 100 nM to 2.5 mM of BrO₃⁻ in 0.2 M SAB solution with a sensitivity of 115.2 μA mM⁻¹ and a detection limit of 43 nM were achieved with good selectivity. As a final demonstration, the proposed LbL sensor, [Fe(III)P-PSS]₁-Fe(III)P-OMWCNTs/SPCE, was applied to analyze BrO₃⁻ concentrations in tap water and mineral water samples.

Introduction

Chlorination and ozonation have emerged as two of the most promising methods for disinfection of drinking water [1], [2]. However, these disinfection methods tend to oxidize the bromide (Br⁻) present in natural water, such as seawater and freshwater, to bromate (BrO₃⁻), which presents a potential human health problem. The BrO₃⁻ is a bromine-based oxyhalide formed as a disinfection byproduct during chlorination or ozonation in water containing Br⁻ [3], [4], [5]. BrO₃⁻ has also been classified as a group B2 carcinogen and has an acceptable maximum contaminant level of 10 μg/L for BrO₃⁻ in global drinking water regulations to prevent the consumption of excess BrO₃⁻ [6], [7], [8]. Moreover, the significantly high concentration of BrO₃⁻ has been recently detected in natural water due to a chemical reaction of Br⁻ with sunlight and chlorine [9], [10].

Several studies have been carried out to determine the concentration of BrO₃⁻ in water samples using ion chromatography (IC) [11], [12], IC with inductively coupled plasma mass spectrometry [13], [14], liquid chromatography-mass spectrometry [15], gas chromatography-mass spectrometry [16], and spectrofluorometry [17]. However, these techniques require many pre-treatment procedures such the preparation of high levels of chloride in the sample matrix exchange sites [18], and the need to operate with complicated and expensive instruments. Therefore, the development of new methods for the simple, rapid, and inexpensive determination of BrO₃⁻ is required for environmental samples. Hence, electrochemical techniques have been introduced as reasonable, uncomplicated, and fast procedures to detect a wide range of BrO₃⁻ in water samples [19], [20], [21], [22], [23].

Iron(III)-porphyrin (Fe(III)P), the metalloporphyrin compounds of which have excellent electrocatalytic properties, has been applied in the detection of several major analytes, such as biocatalysts, molecular materials, and chemical mediators [24], [25], [26], due to their unique structural and electronic properties. However, most of the modified electrodes composed of Fe(III)P complexes have shown a number of problems such as loss of electron transfer mediators and short-term stability [21].

The incorporation of metalloporphyrin (i.e. Fe(III)P) into electrode materials has previously been shown to enhance the sensitivity of electrochemical sensors for various chemical compounds [21], [25], [27], [28], [29]. For instance, Fe(III)P and multiwalled carbon nanotubes composites on glassy carbon electrodes have been employed to detect ascorbic acid, dopamine, uric acid, and nitrite at concentrations as low as 3, 0.09, 0.3, and 0.5 μM, respectively [25]. Since pristine multiwalled carbon nanotubes (MWCNTs) on the surface are stable, it is somewhat difficult to modify their surface directly. Hence, the oxidized multiwalled carbon nanotubes (OMWCNTs), which are inserted branches on the surfaces of the MWCNTs, significantly increase the surface activity of MWCNTs, which increases the linkage between some functional groups (such as carboxylic acid groups) and MWCNTs for modification of the MWCNTs [30]. Thus, the OMWCNT is a promising material as it possesses excellent interchangeability and electrochemical conductivity, and is able to immobilize various substances on its external and internal surfaces [31], [32].

In this paper, we introduce a newly developed, novel, and highly sensitive amperometric sensor design based on the layer by layer (LbL) assembly technique of Fe(III)P and polyelectrolytes for resolving the disadvantages of Fe(III)P. We then demonstrate its usefulness in the sensitive and selective detection of BrO₃⁻. Carballo et al. determined the LbL assembly is utilizing metalloporphyrin in combination with a polyelectrolyte on an electrode surface [33]. However, there has not been any reported research done on the Fe(III)P with polyelectrolytes and OMWCNTs on a disposable SPCE for developing bromate sensor.

In our approach, negatively charged OMWCNTs were assembled on a SPCE, followed by sequential electrostatic adsorption of positively charged Fe(III)P and negatively charged poly(sodium 4-styrenesulfonate) (PSS) electrolytes. The performance of the LbL sensor for detecting BrO₃⁻, including its sensitivity, reproducibility, and long-term stability, were evaluated using cyclic voltammetry (CV). In this study, the design parameters are optimized and include the number of Fe(III)P layers and the concentration of Fe(III)P. In addition, a comparison is given with the LbL assembled on SPCEs. Finally, the Fe(III)P and the polyelectrolyte integrated with the LbL sensor were employed to analyze BrO₃⁻ concentrations in chlorinated water (i.e. tap water) and ozonated water (i.e. mineral water) samples. The result was validated using ultraviolet-visible (UV–vis) spectroscopy measurements.

Section snippets

Reagents

The MWCNTs with 90% purity (5–20 nm diameter) and <10 μm length were obtained from local company (Carbon Nanomaterial Technology Co., Ltd, Korea). Fe(III)P and PSS were purchased from Sigma-Aldrich (St. Louis, USA) and used without further purification. Analytical grade potassium bromate (KBrO₃) was also purchased from Sigma-Aldrich (Missouri, USA). A predetermined concentration of BrO₃⁻ solutions was completed with the supporting electrolyte (0.2 M sodium acetate buffer (SAB), pH 7) for the daily

Estimation of electroactive surface area of modified SPCEs

The sufficiently electroactive surface area of the modified SPCE configuration was evaluated using the CV of the well-known reference redox couple, Fe(CN)₆^4−/3− (Fig. 2). Although this measurement is a general evaluation of the electroactive surface area of each electrode configuration, it can also be estimated theoretically. The electroactive surface area of the electrode configuration was determined using the Randles-Sevcik Eq. (1) [42], [43]:I_p = (2.69 × 10⁵)n^3/2 D^1/2 v^1/2 ACwhere I_p is the peak

Conclusion

An in-situ disposable electrochemical sensor for determining BrO₃⁻ concentration was developed by depositing Fe(III)P, PSS, and OMWCNTs on an SPCE. The proposed LbL sensor enables fast, selective, and sensitive determination of BrO₃⁻ concentration in water samples. CV revealed that the linear responses were in a BrO₃⁻ concentration range of from 100 nM to 2.5 mM and the minimum detectable BrO₃⁻ concentration was 43 nM. Furthermore, the proposed LbL sensor has excellent selectivity for BrO₃⁻ over

Acknowledgements

This research was supported by basic research program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (NRF-2014R1A2A2A03007000), Republic of Korea.

Yong-Gu Lee received his B.S. degree from Chungnam National University in 2010 followed by M.S. degree from the Gwangju Institute of Science and Technology in 2012. He is currently a Ph.D. student at the Graduate School of Water Resources, the Sungkyunkwan University, Republic of Korea. His research interests focus on the development of electrochemical sensor using novel nanocomposites for the determination of disinfection by-products and heavy metals in water.

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Citation Excerpt :
All electrochemical measurements for BrO3− were performed at room temperature. The detailed fabrication procedures for the metalloporphyrin, polyelectrolyte, and oxidized multiwalled carbon nanotubes (OMWCNTs) based layer by layer (LbL) assembled bromate sensor was the same as those in our previous studies [23,24]. As briefly explained, the fabrication process of the sensor for detection bromate as follows: the OMWCNTs modified screen-printed carbon chip (SPCC) was alternately dipped in 2 mM iron(III) porphyrin (Fe(III)P) and 2 mM poly(sodium 4-styrenesulfonate) (PSS) solution for 30 min each, followed by rinsing with 0.2 M SAB solution (pH 7.0) and drying under N2 gas.
One of the problems of BrO₃⁻ detection using the electrochemical method, such as a cyclic voltammetry (CV) is that it is impressionable to interferences from Humic acid (HA). The objective of this study was to determine the effect of HA on electrochemical detection of BrO₃⁻ using metalloporphyrin-based multilayer sensor under different pH conditions in the presence of FeCl₃. The effect of HA interference on chemical interaction at the electrode surface in the presence of FeCl₃ was determined based on Fourier transform infrared spectrum. CV was used to measure the concentration of BrO₃⁻ in the solution containing HA with or without different concentrations of FeCl₃. Results of CV revealed a dynamic linear concentration range of BrO₃⁻ from 10 to 100 μg/L in 0.1 to 1 mg/L of HA solution (pH 9). The detection limit for BrO₃⁻ concentration was 8.9 μg/L in 0.1 mg/L of HA solution.

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Hye Jin Lee received her B.Sc. from Dankook University in 1991 followed by M.Sc. from Sogang University in 1994. She obtained her Ph.D. in 1999 from the Ecole Polytechnique Federale de Lausanne with Prof. Girault on creating micro liquid/liquid interfaces for use as ion-selective sensors. Following postdoctoral research at the University of Wisconsin-Madison, she undertook an Associate Researcher position at the University of California-Irvine where she developed a series of surface enzymatic amplification methods that enable the direct detection of biomolecules down to fM concentrations. She then joined Kyungpook National University as an Assistant Professor in 2008, and promoted to Associate Professor in 2012. Her primary research focus is the design and application of highly sensitive and selective biosensors integrating emerging nanotechnologies. Prof. Lee has published over 100 research papers in refereed journals with an h-index of 38 and 5 book chapters and filed four U.S. patents.

Am Jang received his Ph.D. in Environmental Science and Engineering from the Gwangju Institute Science and Technology (GIST), Gwangju, Republic of Korea, in 2002. Before he joined the faculty of the Graduate School of Water Resources at the Sungkyunkwan University (SKKU) in 2011, he worked at the University of Cincinnati as a Postdoctoral Fellow (2003–2006) and an Assistant Professor for Research (2006–2010). His research interests blur the disciplinary boundaries among molecular-scale phenomena, electrochemistry, and bioprocess engineering. At this interface, the development and deployment of state-of-the-art environmental monitoring sensors, measuring DO, pH, ORP, nitrate, phosphate, and heavy metals, provide a virtually endless supply of new information about environmental processes on a fundamental, nano scale to either make it more operationally efficient and/or improve water quality monitoring. Currently, he has participated in desalination researches, including forward osmosis/reverse osmosis hybrid system. He is the project leader of the research project entitled by The study on FO-RO mechanism investigation & advanced operation technology for water quality control, which is financially supported by Ministry of Land, Infrastructure and Transport of Korean government. He has been a director of Korea Society of Water and Wastewater Association (since 2014) and an academic director of Membrane Society of Korea (since 2015). In addition, he has been a vice manager and manager of the Korea Society of Environmental Engineers (KSEE) since 2014.

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Amperometric bromate-sensitive sensor via layer-by-layer assembling of metalloporphyrin and polyelectrolytes on carbon nanotubes modified surfaces

Highlights

Abstract

Introduction

Section snippets

Reagents

Estimation of electroactive surface area of modified SPCEs

Conclusion

Acknowledgements

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Electrochim. Acta

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