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Article

Low-Cost Carbon Paste Cu(II)-Exchanged Zeolite Amperometric Sensor for Hydrogen Peroxide Detection

by
Delia Gligor
1,
Sanda Andrada Maicaneanu
2 and
Codruta Varodi
3,*
1
Department of Environmental Analysis and Engineering, Babes-Bolyai University, 30 Fantanele St., 400294 Cluj-Napoca, Romania
2
Madia Department of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, 421 North Walk, Indiana, PA 15705, USA
3
National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat St., 400293 Cluj-Napoca, Romania
*
Author to whom correspondence should be addressed.
Chemosensors 2024, 12(2), 23; https://doi.org/10.3390/chemosensors12020023
Submission received: 27 December 2023 / Revised: 30 January 2024 / Accepted: 31 January 2024 / Published: 4 February 2024
(This article belongs to the Special Issue Low-Cost Chemo/Bio-Sensors Based on Nanomaterials)
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Abstract

:
The aim of this work was to explore the possibility of using a Cu-exchanged zeolitic volcanic tuff (which is natural and easy to prepare and apply) for the preparation of a new low-cost carbon paste amperometric sensor for H2O2 detection. The properties of the zeolitic volcanic tuff were determined using chemical analysis, energy-dispersive X-ray spectroscopy, the specific surface area, electron microscopy, X-ray diffraction spectroscopy, and Fourier-transform infrared spectroscopy. The sensor was successfully built and operates at pH 7, at an applied potential of −150 mV Ag/AgCl/KClsat, presenting a sensitivity of 0.87 mA M−1, a detection limit of 10 µM and a linear domain up to 30 mM H2O2. These good electroanalytic parameters for H2O2 detection (a low detection limit and high sensitivity) support the possibility of using these sensors for the detection of many analytes in environmental, food and medical applications.

1. Introduction

Zeolites are widely used in the environmental remediation of soil or water to immobilize or remove toxic materials by cation exchange, e.g., Cu [1], due to their channel network and exchangeable cations. They have specific properties: their adsorption–desorption capacity, ion exchange capacity and catalytic properties [2]. Their ionic exchange capacity allows for the modification of natural or synthetic zeolites with metal ions. Such modification of zeolites opens up new ways in which they can be used.
Copper-modified zeolites have many applications: some modified electrodes prepared using an aqueous ion-exchange method on synthetic zeolites have been tested for their electrochemical stability [3]; other modified electrodes have been used as electrochemical sensors for the determination of dopamine, ascorbic acid and non-electroactive cations [4,5,6,7,8].
Hydrogen peroxide (H2O2) is a bleaching agent used in the textile and paper industries and shows oxidizing properties [9]. It is used as a disinfectant and antiseptic and as an oxidizer for solid rocket propulsion [10], and is produced naturally in organisms as a by-product of metabolism, regulating numerous states of oxidative stress [11,12].
Additionally, H2O2 has an important role in natural oxidation processes because it is found in air, water and solid foods. It is an analyte used in food [13], agricultural [14], pharmaceutical [15], clinical [16], industrial and environmental analyses [17,18]. Techniques for detecting H2O2 include colorimetry [19,20], spectrometry [21], chemiluminescence [22,23], titrimetry [24], spectrophotometry [25], fluorimetry [26,27,28,29,30,31,32], the use of fiber-optic devices [33] and chromatography [34], but most of these are time-consuming, use expensive reagents and suffer with interference from various species. As such, the use of electrochemical methods such as voltammetry and amperometry presents advantages, such as low detection limits and a rapid response time [35,36,37,38,39,40,41,42,43,44,45,46,47,48].
Taking into account all these considerations, the novelty of this work was to prepare a new, low-cost carbon paste amperometric sensor for H2O2 detection based on Cu-exchanged zeolitic volcanic tuff. The obtained amperometric sensor is low cost due to the natural materials used to create it (natural zeolite), and it is easy to prepare and apply. The advantages of this natural zeolite are its low energy consumption and the lack of pollutants created throughout its entire life cycle, as well as the fact that it is found in high quantities in the environment. Additionally, the chemical composition of the natural zeolite was the same for many samples that were used to prepare the H2O2 amperometric sensors, due to the high quality (homogeneity and zeolite content) of the deposit where the samples were collected from.
The modified electrodes show good electroanalytic parameters for H2O2 detection (a low detection limit and high sensitivity), which supports the possibility of using them to detect many analytes in environmental, food and medical applications.
The modified zeolite was characterized using different methods (chemical analysis, energy-dispersive X-ray spectroscopy, electron microscopy, X-ray diffraction spectroscopy and Fourier-transform infrared spectroscopy). The copper-exchanged zeolite-modified electrode was characterized using cyclic voltammetry and amperometry techniques.

2. Materials and Methods

2.1. Materials

Hydrogen peroxide, NaCl, CuSO4·5H2O and 25% ammonium solution were acquired from Reactivul, Bucharest, Romania, and graphite powder and paraffin oil were purchased from Fluka (Buchs, Switzerland).
For the preparation of phosphate-buffered solution, we employed K2HPO4·2H2O and KH2PO4·H2O from Merck (Darmstadt, Germany).

2.1.1. Preparation of the Modified Zeolite

The zeolitic tuff sample was collected from a natural outcrop in Macicas (Cluj County, Romania). To prepare the electrode material, the zeolitic tuff sample was ground to 0.2–0.4 mm (based on a previous test which showed that this fraction is the best for retaining metal ions in fixed-bed column experiments) via grinding and size separation, then washed with distilled water and dried at 105 °C. This physical treatment was followed by an alkaline treatment (NaCl 1 M), as described in a previous work [49].
Modification of the zeolitic tuff sample was realized by contact with a copper synthetic aqueous solution in dynamic conditions. The ionic exchange process took place, as shown in Equation (1), when copper solution (0.25–16.6 g Cu2+/L prepared from analytical-purity CuSO4·5H2O) was passed through a column containing 2.5 g of zeolitic volcanic tuff (flooded, di = 15 mm) at a flow rate of 0.07 mL/s, as previously described [2]. The experiments were realized at room temperature (22 ± 2 °C), without any pH adjustments, until exhaustion of the zeolite volcanic tuff sample took place. Samples obtained in this way were further subjected to drying at 105 °C for 6 h and calcination at 400 °C (in air) for 4 h. The amount of copper incorporated into the zeolite sample was determined using the initial and final concentrations of copper ions in solution, determined by spectrophotometric measurements (Jenway 6305 spectrophotometer, Vernon Hills, Illinois, USA, 25% ammonium solution, λmax = 440 nm):
2Z − Na + Cu2+ ⇆ Z2 − Cu + 2Na+
Cu–Z-modified zeolitic volcanic tuff was further used to prepare the modified carbon-paste electrodes.

2.1.2. Electrode Preparation

The zeolites were mixed with graphite (2:1, w/w) and paraffin oil to obtain carbon paste electrodes modified with zeolite (Z-CPEs) and carbon paste electrodes modified with Cu-enriched zeolite (Cu–Z-CPEs).
All the compounds were manually mixed in an agate mortar and pestle for 10 min and the resulting samples were introduced into a Teflon tube equipped with an electrical copper wire contact for external connection to the potentiostat/galvanostat. Finally, the electrode’s surface preparation included a polishing step, carried out multiple times using regular paper.

2.2. Methods

2.2.1. Physical and Chemical Characterization

The zeolitic volcanic tuff, in natural (Z) and modified (Cu–Z) forms, was characterized using chemical analysis, energy dispersive X-ray spectroscopy (EDS), specific surface area (BET), scanning and transmission electron microscopy (SEM, TEM), X-ray diffraction spectroscopy (XRD) and Fourier-transform infrared spectroscopy (FTIR).
Chemical analysis of the bulk sample was realized using specific analytical methods for silicate materials. Oxford Instruments EDS–Inca apparatus (Abingdon, United Kingdom) was used for surface elemental analysis (EDS).
Measurement of the BET surface area (SBET) and pore size distribution was performed using approximately 0.2 g of sample degassed in a vacuum at 106 °C for 20 h to remove all the adsorbed species. A Sorptomatic 1990 (Thermo Electron Corporation, Waltham, MA, USA) was used to record the nitrogen adsorption and desorption isotherms.
Powder X-ray diffraction was performed using a Siemens Bruker unit with a Cu Kα anticathode. Diffraction patterns were obtained in the 5° ÷ 50° 2θ range and the following analytical conditions: 20 kV, 40 mA and a step of 2 degrees. The mineral composition was determined using a semi-quantitative X-ray diffraction method.
SEM images were obtained from samples deposited on double adhesive carbon discs, covered with 10 nm Au in an Agar Automated Sputter Coater and examined using a Jeol JSM5510Lvscanning electron microscope (Peabody, MA, USA). TEM images were obtained from samples suspended in distilled water (ultrasonic bath), deposited on a 300-mesh electrolytic grid, covered with carbon film (freshly deposited in vacuum) and examined using a Jeol JEM1010 transmission electron microscope (Peabody, MA, USA)).
A Jasco 615 spectrophotometer (Tokyo, Japan) was used to collect the FTIR spectra in the 400–4000 cm−1 range, with a resolution of 2 cm−1, on KBr pellets (2 mg sample in 200 mg KBr).

2.2.2. Electrochemical Measurements

A PC-controlled electrochemical analyzer (Autolab-PGSTAT 10, EcoChemie, Utrecht, The Netherlands) managed by GPES 4.8 (General Purpose Electrochemical System software package) was used for cyclic voltammetry and amperometry measurements, while a EG&G rotator (Radiometer) was used to modulate the stirring rate of the working electrode. The carbon paste electrode (CPE) was the working electrode, the Ag/AgCl (3.0 mol L−1 KCl) was used as the reference electrode and a platinum electrode was used as a counter electrode.
A pH-meter (HI255, Hanna Instruments, Cluj-Napoca, Romania) equipped with a HI1131B glass electrode was used to adjust the pH during the addition of the phosphate buffer solutions.

3. Results and Discussion

3.1. Physical and Chemical Characterization of Natural and Modified Zeolite Samples

The zeolitic tuff samples were collected from an outcrop in Macicas (Cluj County, Romania). This deposit belongs to the Dej Tuff Level and it is of lower Badenian age. From a structural point of view, volcanic tuffs from Macicas are massive cinerites represented by vitric-crystal and vitric tuffs. The main petrographical component is represented by white-greyish or white-greenish volcanic tuff that may be interlayered with marls and clays. Depending on the level, volcanic tuff varies from fine microporous to compact macroporous [2].
The bulk chemical composition of the natural zeolitic tuff sample was determined to be as follows, in mass %: SiO2 63.91, Al2O3 14.45, Fe2O3 1.74, CaO 5.34, MgO 0.30, Na2O 1.02, K2O 0.86, TiO2 0.38 and loss of ignition at 1000 °C (L.O.I.) 12. The value of the L.O.I. indicates that secondary and hydrated materials (zeolite and clay minerals) are present in high amounts. The tuff samples collected from the studied area are remarkably homogeneous in their mineralogical and chemical composition [49,50].
Figure 1A, B presents the SEM–EDS spectra and atomic weight composition of the Z (A) and Cu–Z (B) samples. The EDS spectra for the natural sample indicates the following elemental composition: Si, Al, Na, K, Ca, Mg and O (Figure 1A). For the Cu–Z-modified sample, copper was identified alongside the main elements; Figure 1B. Several surface regions of the Cu–Z and Cu–Z-CPE samples were analyzed; copper amounts of between 1.3 and 6.6% (average 3.95%) were determined. A high quantity of carbon from graphite, up to 74.3%, was identified when the electrode material was subjected to EDS analysis.
According to N2 adsorption and desorption isotherm investigations, the BET specific surface area of the unmodified zeolitic volcanic tuff sample had an average value of 35.7 m2/g, while after modification, a small decrease was observed—most probably due to the thermal treatment applied (down to 30 m2/g). The adsorption–desorption isotherm, shown in Figure 2A, is of type II with a H3 type loop, typical of slit-shaped pores [51]. The pore size distribution, shown in Figure 2B, indicates that the considered samples had a multimodal distribution of mesopores in the small-size region (3–13 nm). For the modified sample, a change in the pore size distribution was observed, which can be attributed to the alteration of the pore size during the thermal treatment (pore volumes corresponding to small pores decreased, while new nodal positions appeared at higher pore diameters).
XRD powder diffractograms indicated that clinoptilolite was present in substantial amounts and was the main zeolite species present. Based on a semi-quantitative estimation, the zeolite—clinoptilolite—represented 70–80% of the crystallized fraction of the tuff. Quartz, plagioclase, biotite and montmorillonite were identified as accompanying minerals [2,49,50].
SEM and TEM images of the unmodified zeolitic volcanic tuff sample show that the zeolite was present as tabular clinoptilolite crystals, shown in Figure 3, which varied in size from 2 to 10 µm. Larger crystals were usually found in the pores of the bulk rock.
FTIR measurements were also used to characterize the samples of zeolitic volcanic tuff and confirm the presence of clinoptilolite. Spectra of the natural sample (Figure 4) confirmed the presence of specific zeolite peaks, identified in Table 1, in accordance with the literature data [2,52,53,54,55]. For the Cu–Z sample, some minor modifications—specifically, peak shifts (Figure 4)—were observed. This can be attributed to the partial destruction of the zeolite’s three-dimensional structure during the calcination process [2].
The breakthrough curve (time vs. concentration evolution) and cation exchange capacity during the ionic exchange process and modification of the zeolitic tuff sample, (up to 225 min, 900 mL copper solution) are presented in Figure 5. The cation exchange capacity (“practical capacity” or “operating capacity” obtained under working conditions) [56,57], in mg/g, was calculated by taking into consideration the initial concentration times t concentration and the zeolitic volcanic tuff mass placed in the column. Following the ionic exchange process evolution, shown in Figure 5A, it was observed that as the copper ion initial concentration decreased, the breakthrough curve slope angle was smaller, indicating that the ionic exchange reaction rate decreased and therefore that the ionic exchange capacity had a smaller value; Figure 5B. Additionally, when a concentrated copper ion solution made contact with the zeolitic volcanic tuff, the ionic exchange capacity increased abruptly—up to 262.6 mg/g—showing a high capacity of the sample to retain metal ions when mass transfer conditions are improved. The maximum calculated cation exchange capacity values are presented in Figure 6.

3.2. Electrochemical and H2O2 Electrocatalytic Measurements

The electrochemical characterization of the newly obtained modified electrodes was realized in different experimental conditions to determine the electrochemical parameters and to study the influence of the supporting electrolyte pH and scan rate on the voltammetric response.
The obtained electrodes were first electrochemically tested in a phosphate buffer solution to observe their voltammetric response. As can be seen in Figure 7A, in phosphate buffer solution as the supporting electrolyte, at 7 pH and a scan rate of 10 mV s−1, the copper-enriched zeolite-modified electrodes (Cu–Z-CPEs) showed better voltammetric signals than the carbon paste electrodes modified with zeolites (Z-CPEs) and unmodified carbon paste electrodes (CPEs). The redox peak pair can be atributed to the oxidation and reduction of the copper available in the modified natural zeolite. The electrochemical parameters for Cu–Z-CPEs are as follows: the anodic peak potential Epa = −235 mV vs. Ag/AgCl/KClsat; the cathodic peak potential Epc = −5 mV vs. Ag/AgCl/KClsat; the formal standard potential (calculated as average of anodic and cathodic peak potential) E0′ = −120 mV vs. Ag/AgCl/KClsat; the Ipa/Ipc ratio = 3.12; surface coverage Γ = 2.2·10−7 mol cm−2, according to [58].
All further experiments were realized with phosphate buffer as the supporting electrolyte, with different pH values. As was expected, the E0′ values were dependent on the supporting electrolyte pH in the case of the obtained carbon paste electrodes. The slope of the linear regression corresponding to the E0′ vs. pH dependence (Figure 7B) was close to 0.059 V/ΔpH, which indicates that a transfer of 2e−/2H+ was involved in the redox process and that the transfer electrons varied with the pH. This pH influence on the voltammetric response of the newly obtained electrodes will be useful for further investigations on H2O2 electrocatalytic activity.
Cyclic voltammetric measurements were recorded at increased electrode potential scan rates (Figure S1) to determine the kinetic parameters of the copper electron transfer, using the method proposed by Laviron [59]. From the influence of the formal standard potential E0′ on the log of the scan rate (Figure 7C), the rate constant of the heterogeneous electron transfer ks of 1.74 s−1 and the transfer coeficient α of 0.74 were evaluated for the obtained modified electrodes (Cu–Z-CPEs). This value of the heterogeneous electron transfer rate constant proves that copper can be used as an efficient mediator for electron transfer.
Additionally, the scan rate influence on the peak current was studied by recording the voltammograms at different potential scan rates. The cyclic voltammograms measurements performed at different potential scan rates, between 0.01 and 1.8 V s−1, and showed a linear dependence of anodic and cathodic peak current intensity (Ipa and Ipc) on the potential scan rate (v). At different supporting electrolyte pHs, the slopes of the log Ip vs. log v dependence were close to 0.5, confirming the existance of a diffusion control (Table 2).
The electrocatalytic characterization of H2O2 reduction was first studied using cyclic voltammetric measurements, to determine the electrocatalytic efficiency.
The cyclic voltammograms recorded in phosphate buffer solution at pH 7 and a scan rate of 10 mV s−1 for the obtained carbon paste electrodes (Cu-Z-CPEs), in the absence and in the presence of H2O2 solution at two concentrations (1 mM and 5 mM; Figure 8), proved the presence of good electrocatalytic activity towards H2O2 reduction, as characterized by: (i) decreasing of the H2O2 reduction overpotential (~200 mV, estimated by the difference of cathodic peak potentials); (ii) a good electrocatalytic efficiency (ratio of ((Ipeak)[H2O2] = 5 mM − (Ipeak)[H2O2] = 0)/(Ipeak)[H2O2] = 0), at an applied potential of −400 mV vs. Ag/AgCl/KClsat; 1.95. Overpotential decreases are advantageous, as this lowers the applied potential for further amperometric measurements to very close to 0 mV vs. Ag/AgCl/KClsat. The obtained electrodes present good electrocatalytic efficiency and suggest again that they are improved by the presence of the copper that was introduced into the zeolite sample [52]. These characteristics prove the the newly prepared electrodes can be used as efficient amperometric sensors for H2O2 detection.
Once the voltammetric electrocatalytic characterization of the newly obtained modified electrodes was completed, measurements with rotating disk electrodes were realized at different supporting electrolyte pH values, in 0.1 M phosphate buffer containing 20 mM H2O2 at a rotation speed of 800 rpm, to estimate the electroanalytic parameters of the electrocatalytic reduction of H2O2. Thus, the optimum applied potential was determined from the dependence of the H2O2 electrocatalytic current on the applied potential (Figure 9A–C).
As can be seen in Figure 9A–C, the optimum value of applied potential was −50 mV vs. Ag/AgCl/KClsat for pH 3, −150 mV vs. Ag/AgCl/KClsat for pH 7 and −400 mV vs. Ag/AgCl/KClsat for pH 9. For pH 3, the optimum value of applied potential was chosen as the higher value, while for pH 7 and pH 9, the optimum values were chosen on the plateau of the graph, because after this plateau, the values of the H2O2 electrocatalytic currents dramatically decreased. All these values were used in further electroanalytical measurements.
Figure 10 presents the calibration curves obtained from the amperometric measurements recorded in Figure S2, for the new modified electrodes Cu–Z-CPEs in 0.1 M phosphate buffer solutions with different pH values (3, 7 and 9), at increased values of H2O2 concentrations (between 10−5 to 10−1 M H2O2), rotation speeds of 800 rpm and using the values of applied potential determined above: −50 mV vs. Ag/AgCl/KClsat (pH 3), −150 mV vs. Ag/AgCl/KClsat (pH 7) and −400 mV vs. Ag/AgCl/KClsat (pH 9).
The electroanalytical parameters were obtained from Figure 10 and Figure S2 and are presented in Table 3. The sensitivity (calculated as the ratio of Imax/KM, mA M−1, according to Michaelis–Menten treatment [60]) was 0.75 (pH 3) < 0.87 (pH 7) < 27.8 (pH 9); in almost all cases, the linear domain reached up to 1 mM; the detection limit (calculated as a ratio of signal/noise of 3) was 10 μM (pH 3 and pH 7) and 31 μM (pH 9); in all cases, the response time was less than 1 min. Even at pH 9, the sensitivity was high and the applied potential was very low. The electroanalytical parameters determined at pH 7 are of interests due to the applied potential being close to 0 mV vs. Ag/AgCl/KClsat and due to the possibility of the sensor for use in the detection of many analytes in environmental, food and medical applications in neutral pH media. The detection limit is better compared with other results already published for H2O2 sensors based on electrodes modified with zeolites [61,62,63] and are comparable with other H2O2 sensors based on carbon paste [64,65,66].
The durability of the H2O2 sensor was studied in different ways, to test their repeatability and reproducibility: (i) The voltammetric response of the modified electrode in the presence of 5 mM H2O2 over 100 cycles (Figure 11A) was tested, as well as the stability of the catalytic current of the modified electrode over 7 days (Figure 11B). In both cases, a decrease of less than 5% of the catalytic current was observed; (ii) Five modified electrodes were tested at the same H2O2 concentration (5 mM) and a small difference between signals occurred (5.4%; Figure 11C).

4. Conclusions

Cu-exchanged zeolitic volcanic tuff was structurally and morphologically characterized using chemical analysis, energy dispersive X-ray spectroscopy, electron microscopy, X-ray diffraction spectroscopy and Fourier-transform infrared spectroscopy. A copper-exchanged zeolite-modified electrode was prepared by mixing copper–zeolite, graphite powder and paraffin oil to obtain new, low-cost amperometric sensors for H2O2 detection. Using cyclic voltammetry and amperometry techniques, the electrochemical reduction of hydrogen peroxide at the modified electrodes was investigated. The influence of pH and scan rate on the voltammetric response, characteristic of the modified electrodes, was studied and the optimum operating conditions were established. The new H2O2 amperometric sensor was electroanalytically characterized by the following parameters: a sensitivity of 0.87 mA/M, detection limit of 10 μM and linear domain up to 0.3 mM for H2O2 detection at pH 7, proving the possibility of its use for the detection of many analytes in environmental, food and medical applications.
Moreover, this natural material, which was used to obtain the H2O2 amperometric sensor—Cu-exchanged natural zeolite—is low-cost, decreases energy consumption and avoids pollution in many ways, over its whole life cycle. It is good for environmental applications due to the above-mentioned properties, and also for detecting different pollutants in various environmental media.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/chemosensors12020023/s1, Figure S1: Cyclic voltammograms corresponding to obtained Cu–Z-CPEs electrodes, recorded at increased scan rates of the electrode potential (between 5 mV/s and 320 mV/s), in 0.1 M phosphate buffer solution, pH 7, and Figure S2: The amperometric response of the modified electrodes Cu–Z-CPEs in 0.1 M phosphate buffer solutions with different pH values pH 7.0 (A), pH 3.0 (B) and pH 9.0 (C), at increased values of H2O2 concentrations (between 10−5 and 10−1 M H2O2), a rotation speed of 800 rpm and using the values of applied potential determined above: −50 mV vs. Ag/AgCl/KClsat (pH 3), −150 mV vs. Ag/AgCl/KClsat (pH 7) and −400 mV vs. Ag/AgCl/KClsat (pH 9).

Author Contributions

Conceptualization, D.G. and C.V.; investigation, D.G., S.A.M. and C.V.; resources, D.G., S.A.M. and C.V.; data curation, S.A.M. and C.V.; writing—original draft preparation, D.G. and S.A.M.; writing—review and editing, D.G., S.A.M. and C.V.; project administration, C.V.; funding acquisition, C.V. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by grants from the Ministry of Research, Innovation and Digitization, CNCS/CCCDI—UEFISCDI, projects number PN-III-P1-1.1-TE-2021-0358.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the authors.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Elsayed-Ali, O.H.; Abdel-Fattah, T.; Elsayed-Ali, H.E. Copper cation removal in an electrokinetic cell containing zeolite. J. Hazard. Mater. 2011, 185, 1550–1557. [Google Scholar] [CrossRef]
  2. Maicaneanu, A.; Bedelean, H.; Stanca, M. Zeoliti Naturali. Caracterizare si Aplicatii in Protectia Mediului; Editura Presa Universitara Clujeana: Cluj-Napoca, Romania, 2008; pp. 21–40. ISBN 9789736106736. [Google Scholar]
  3. Oliver-Tolentino, M.A.; Guzmán-Vargas, A.; Arce-Estrada, E.M.; Ramírez-Rosales, D.; Manzo-Robledo, A.; Lima, E. Understanding electrochemical stability of Cu+ on zeolite modified electrode with Cu-ZSM5. J. Electroanal. Chem. 2013, 692, 31–39. [Google Scholar] [CrossRef]
  4. He, P.; Wang, W.; Du, L.; Dong, F.; Deng, Y.; Zhang, T. Zeolite A functionalized with copper nanoparticles and graphene oxide for simultaneous electrochemical determination of dopamine and ascorbic acid. Anal. Chim. Acta 2012, 739, 25–30. [Google Scholar] [CrossRef]
  5. dos Santos, M.P.; Rahim, A.; Fattori, N.; Kubota, L.T.; Gushikem, Y. Novel amperometric sensor based on mesoporous silica chemically modified with ensal copper complexes for selective and sensitive dopamine determination. Sens. Actuators B Chem. 2012, 171–172, 712–718. [Google Scholar] [CrossRef]
  6. Rohani, T.; Taher, M.A. A new method for electrocatalytic oxidation of ascorbic acid at the Cu (II) zeolite-modified electrode. Talanta 2009, 78, 743–747. [Google Scholar] [CrossRef]
  7. Parpot, P.; Teixeira, C.; Almeida, A.M.; Ribeiro, C.; Neves, I.C.; Fonseca, A.M. Redox properties of (1-(2-pyridylazo)-2-naphthol)copper(II) encapsulated in Y Zeolite. Microporous Mesoporous Mater. 2009, 117, 297–303. [Google Scholar] [CrossRef]
  8. Walcarius, A. Factors affecting the analytical applications of zeolite modified electrodes: Indirect detection of nonelectroactive cations. Anal. Chim. Acta 1999, 388, 79–91. [Google Scholar] [CrossRef]
  9. Holkar, C.R.; Jadhav, A.J.; Pinjari, D.V.; Mahamuni, N.M.; Pandit, A.B. A critical review on textile wastewater treatments: Possible approaches. J. Environ. Manag. 2016, 182, 351–366. [Google Scholar] [CrossRef]
  10. Kopacz, W.; Okninski, A.; Kasztankiewicz, A.; Nowakowski, P.; Rarata, G.; Maksimowski, P. Hydrogen peroxide—A promising oxidizer for rocket propulsion and its application in solid rocket propellants. Fire Phys. Chem. 2022, 2, 56–66. [Google Scholar] [CrossRef]
  11. Sies, H. Role of metabolic H2O2 generation: Redox signaling and oxidative stress. J. Biol. Chem. 2014, 289, 8735–8741. [Google Scholar] [CrossRef] [PubMed]
  12. Mihailova, I.; Krasovska, M.; Sledevskis, E.; Gerbreders, V.; Mizers, V.; Ogurcovs, A. Assessment of oxidative stress by detection of H2O2 in Rye samples using a CuO- and Co3O4-nanostructure-based electrochemical sensor. Chemosensors 2023, 11, 532. [Google Scholar] [CrossRef]
  13. Miyamoto, F.; Saeki, M.; Yoshizawa, T. Improved protocol for an oxygen electrode method for determining hydrogen peroxide in foods. J. AOAC Int. 1997, 3, 681–687. [Google Scholar] [CrossRef]
  14. Shariati-Rad, M.; Narges, S.; Farzaneh, J. Determination of hydrogen sulfide and hydrogen peroxide in complex samples of milk and urine by spectroscopic standard addition data and chemometrics methods. RSC Adv. 2017, 46, 28626–28636. [Google Scholar] [CrossRef]
  15. Cibati, A.; Gonzalez-Olmos, R.; Rodriguez-Mozaz, S.; Buttiglieri, G. Unravelling the performance of UV/H2O2 on the removal of pharmaceuticals in real industrial, hospital, grey and urban wastewaters. Chemosphere 2022, 290, 133315–133323. [Google Scholar] [CrossRef] [PubMed]
  16. Liu, X.; Xu, Y.; Ma, X.; Li, G. A third-generation hydrogen peroxide biosensor fabricated with hemoglobin and Triton X-100. Sens. Actuators B Chem. 2005, 106, 284–288. [Google Scholar] [CrossRef]
  17. Wulansarie, R.; Rozaq, M.; Bismo, S.; Dyah, W.; Rengg, P. Degradation of Congo Red dye in wastewater using ozonation method with H2O2 catalyst. J. Ilmu Lingkung. 2024, 22, 150–154. [Google Scholar] [CrossRef]
  18. Xin, S.; Huo, S.; Zhang, C.; Ma, X.; Liu, W.; Xin, Y.; Gao, M. Coupling nitrogen/oxygen self-doped biomass porous carbon cathode catalyst with CuFeO2/biochar particle catalyst for the heterogeneous visible-light driven photo-electro-Fenton degradation of tetracycline. Appl. Catal. B-Environ. 2022, 305, 121024–121040. [Google Scholar] [CrossRef]
  19. Ito, Y.; Tonogai, Y.; Suzuki, H.; Ogawa, S.; Yokoyama, T.; Hashizume, T.; Santo, H.; Tanaka, K.I.; Nishigakki, K.; Iwaida, M. Improved 4-Aminoantipyrine Colorimetry for Detection of Residual Hydrogen Peroxide in Noodles, Fish Paste, Dried Fish, and Herring Roe. J. Assoc. Off. Anal. Chem. 1981, 64, 1448–1452. [Google Scholar] [CrossRef]
  20. Vinayagam, R.; Nagendran, V.; Goveas, L.C.; Narasimhan, M.K.; Varadavenkatesan, T.; Chandrasekar, N.; Selvaraj, R. Structural characterization of marine macroalgae derived silver nanoparticles and their colorimetric sensing of hydrogen peroxide. Mater. Chem. Phys. 2024, 313, 128787–128795. [Google Scholar] [CrossRef]
  21. Monakhova, Y.B.; Diehl, W.K. Rapid 1H NMR determination of hydrogen peroxide in cosmetic products and chemical reagents. Anal. Methods 2016, 8, 4632–4639. [Google Scholar] [CrossRef]
  22. Lu, J.; Lau, C.; Morizono, M.; Ohta, K.; Kai, M. A chemiluminescence reaction between hydrogen peroxide and acetonitrile and its applications. Anal. Chem. 2001, 73, 5979–5983. [Google Scholar] [CrossRef]
  23. Tahirovic, A.; Copra, A.; Omanovic-Miklicanin, E.; Kalcher, K. A chemiluminescence sensor for the determination of hydrogen peroxide. Talanta 2007, 72, 1378–1385. [Google Scholar] [CrossRef] [PubMed]
  24. Klassen, N.V.; Marchington, D.; McGowan, H.C. H2O2 determination by the I3-method and by KMnO4 titration. Anal. Chem. 1994, 66, 2921–2925. [Google Scholar] [CrossRef]
  25. Rubio-Clemente, A.; Cardona, A.; Chica, E.; Peñuela, G.A. Sensitive Spectrophotometric Determination of Hydrogen Peroxide in Aqueous Samples from Advanced Oxidation Processes: Evaluation of Possible Interference. Afinidad 2017, LXXIV, 579. Available online: https://raco.cat/index.php/afinidad/article/view/328470 (accessed on 4 December 2023).
  26. Li, J.; Dasgupta, P.K.; Tarver, G.A. Pulsed excitation source multiplexed fluorometry for the simultaneous measurement of multiple analytes. Continuous measurement of atmospheric hydrogen peroxide and methyl hydroperoxide. Anal. Chem. 2003, 75, 1203–1210. [Google Scholar] [CrossRef] [PubMed]
  27. Oh, W.K.; Jeong, Y.S.; Kim, S.; Jang, J. Fluorescent polymer nanoparticle for selective sensing of intracellular hydrogen peroxide. ACS Nano 2012, 6, 8516–8524. [Google Scholar] [CrossRef] [PubMed]
  28. Geng, Y.; Wang, Z.; Zhou, J.; Zhu, M.; Liu, J.; James, T.D. Recent progress in the development of fluorescent probes for imaging pathological oxidative stress. Chem. Soc. Rev. 2023, 52, 3873–3926. [Google Scholar] [CrossRef] [PubMed]
  29. Ye, S.; Hu, J.J.; Zhao, Q.A.; Yang, D. Fluorescent probes for in vitro and in vivo quantification of hydrogen peroxide. Chem. Sci. 2020, 11, 11989–11997. [Google Scholar] [CrossRef] [PubMed]
  30. Sun, H.; Xu, Q.; Ren, M.; Kong, F. A biocompatible chitosan-based fluorescent polymer for efficient H2O2 detection in living cells and water samples. Int. J. Biol. Macromol. 2024, 257, 128760–128769. [Google Scholar] [CrossRef]
  31. Li, H.; Wu, Y.; Xu, Z.; Wang, Y. In situ anchoring Cu nanoclusters on Cu-MOF: A new strategy for a combination of catalysis and fluorescence toward the detection of H2O2 and 2,4-DNP. Chem. Eng. J. 2024, 479, 147508–147517. [Google Scholar] [CrossRef]
  32. Rajamanikandan, R.; Ilanchelian, M.; Ju, H. Highly selective uricase-based quantification of uric acid using hydrogen peroxide sensitive poly-(vinylpyrrolidone) templated copper nanoclusters as a fluorescence probe. Chemosensors 2023, 11, 268. [Google Scholar] [CrossRef]
  33. Botero-Cadavid, J.F.; Brolo, A.G.; Wild, P.; Djilali, N. Detection of hydrogen peroxide using an optical fiber-based sensing probe. Sens. Actuators B Chem. 2013, 185, 166–173. [Google Scholar] [CrossRef]
  34. Tarvin, M.; McCord, B.; Mount, K.; Sherlach, K.; Miller, M.L. Optimization of two methods for the analysis of hydrogen peroxide: High performance liquid chromatography with fluorescence detection and high performance liquid chromatography with electrochemical detection in direct current mode. J. Chromatogr. A 2010, 1217, 7564–7572. [Google Scholar] [CrossRef] [PubMed]
  35. Zhang, Y. An amperometric hydrogen peroxide sensor based on reduced graphene oxide/carbon nanotubes/Pt NPs modified glassy carbon electrode. Int. J. Electrochem. Sci. 2020, 15, 8771–8785. [Google Scholar] [CrossRef]
  36. Zhou, C.; Cheng, R.; Liu, B.; Fang, Y.; Nan, K.; Wu, W.; Xu, Y. Cascade selective recognition of H2O2 and ascorbic acid in living cells using carbon-based nanozymes with peroxidase-like activity. Sens. Actuators B Chem. 2024, 402, 135118–135128. [Google Scholar] [CrossRef]
  37. Wang, G.; Liu, J.; Dong, H.; Geng, L.; Sun, J.; Liu, J.; Dong, J.; Guo, Y.; Sun, X. A dual-mode biosensor featuring single-atom Fe nanozyme for multi-pesticide detection in vegetables. Food Chem. 2024, 437, 137882–137893. [Google Scholar] [CrossRef] [PubMed]
  38. Yang, Z.; Tian, Z.; Zhang, X.; Qi, C. A novel strategy for realizing highly sensitive nonenzymatic detection of H2O2 based on regulating crystallinity of CoO nanosheets. Microchem. J. 2023, 195, 109540–109547. [Google Scholar] [CrossRef]
  39. Ates, A.; Oskay, K.O. Evaluation of iron containing biochar composites prepared by different preparation methods for H2O2 sensing. J. Taiwan Inst. Chem. E 2023, 152, 105180–105195. [Google Scholar] [CrossRef]
  40. He, Z.; Jin, Y.; Yuan, X.; Xue, K.; Hu, J.; Xiong, X. ZIF in situ transformation hollow porous self-supporting CoZn-LDH@CuO electrode for electrochemical sensing of glucose and H2O2. Microchem. J. 2023, 195, 109457–109467. [Google Scholar] [CrossRef]
  41. Ahsan, M.; Dutta, A.; Akermi, M.; Alam, M.M.; Nizam Uddin, S.M.; Khatun, N.; Hasnat, M.A. Sulfur adlayer on gold surface for attaining H2O2 reduction in alkaline medium: Catalysis, kinetics, and sensing activities. J. Electroanal. Chem. 2023, 934, 117281–117290. [Google Scholar] [CrossRef]
  42. Zhang, A.; Liu, Y.; Wu, J.; Zhu, J.; Cheng, S.; Wang, Y.; Hao, Y.; Zeng, S. Electrocatalytic selectivity to H2O2 enabled by two-electron pathway on Cu-deficient Au@Cu2−xS-CNTs electrocatalysts. Chem. Eng. J. 2023, 454, 140317–140329. [Google Scholar] [CrossRef]
  43. Jiang, L.; Wang, H.; Rao, Z.; Zhu, J.; Li, G.; Huang, Q.; Wang, Z.; Liu, H. In situ electrochemical reductive construction of metal oxide/metal-organic framework heterojunction nanoarrays for hydrogen peroxide sensing. J. Colloid Interface Sci. 2022, 622, 871–879. [Google Scholar] [CrossRef]
  44. Han, J.; Kim, J.; Kim, B.-K.; Park, K. Hydrogel-based electrodeposition of copper nanoparticles for selective detection for hydrogen peroxide. Chemosensors 2023, 11, 384. [Google Scholar] [CrossRef]
  45. Oliveira, M.R.F.; Herrasti, P.; Furtado, R.F.; Melo, A.M.A.; Alves, C.R. Polymeric composite including magnetite nanoparticles for hydrogen peroxide detection. Chemosensors 2023, 11, 323. [Google Scholar] [CrossRef]
  46. Yang, Z.; Gao, Y.; Zuo, L.; Long, C.; Yang, C.; Zhang, X. Tailoring heteroatoms in conjugated microporous polymers for boosting oxygen electrochemical reduction to hydrogen peroxide. ACS Catal. 2023, 13, 4790–4798. [Google Scholar] [CrossRef]
  47. Ma, X.; Tang, K.-L.; Lu, K.; Zhang, C.; Shi, W.; Zhao, W. Structural engineering of hollow microflower-like CuS@C hybrids as versatile electrochemical sensing platform for highly sensitive hydrogen peroxide and hydrazine detection. ACS Appl. Mater. Interfaces 2021, 13, 40942–40952. [Google Scholar] [CrossRef] [PubMed]
  48. Li, Z.; Jiang, G.; Wang, Y.; Tan, M.; Cao, Y.; Tian, E.; Zhang, L.; Chen, X.; Zhao, M.; Jiang, Y.; et al. Detecting residual chemical disinfectant using an atomic Co–Nx–C anchored neuronal-like carbon catalyst modified amperometric sensor. Environ. Sci. Nano 2022, 9, 1759–1769. [Google Scholar] [CrossRef]
  49. Bedelean, H.; Maicaneanu, A.; Burca, S.; Stanca, M. Investigations on some zeolitic volcanic tuffs from Cluj County (Romania), used for zinc ions removal from aqueous solution. Stud. Univ. Babes-Bolyai Geol. 2010, 55, 9–15. [Google Scholar] [CrossRef]
  50. Maicaneanu, A.; Bedelean, H.; Burca, S.; Stanca, M. Evaluation of ammonium removal performances of some zeolitic volcanic tuffs from Transylvania, Romania. Sep. Sci. Technol. 2011, 46, 1621–1630. [Google Scholar] [CrossRef]
  51. Rouquerol, E.; Rouquerol, J.; Sing, K. Adsorption by Powders and Porous Solids. Principles, Methodology and Applications; Academic Press: San Diego, CA, USA, 1999; pp. 18–20. [Google Scholar] [CrossRef]
  52. Gligor, D.; Varodi, C.; Maicaneanu, A.; Muresan, L.M. Carbon Nanotubes-Graphite Paste Electrode Modified with Cu(II)-Exchanged Zeolite for H2O2 Detection. Stud. Univ. Babsş-Bolyai Chem. 2010, 55, 293–302. Available online: https://chem.ubbcluj.ro/~studiachemia/issues/chemia2006_2015/Chemia2010_2T2.pdf (accessed on 4 December 2023).
  53. Bedelean, I.; Stoici, S. Zeoliti; Technical Publishing House: Bucharest, Romania, 1984; pp. 59–120. [Google Scholar]
  54. Abreu, N.J.; Valdés, H.; Zaror, C.A.; Azzolina-Jury, F.; Meléndrez, M.F. Ethylene adsorption onto natural and transition metal modified Chilean zeolite: An operando DRIFTS approach. Microporous Mesoporous Mater. 2018, 274, 138–148. [Google Scholar] [CrossRef]
  55. Ma, Y.-K.; Rigolet, S.; Michelin, L.; Paillaud, J.-L.; Mintova, S.; Khoerunnisa, F.; Daou, T.J.; Ng, E.-P. Facile and fast determination of Si/Al ratio of zeolites using FTIR spectroscopy technique. Microporous Mesoporous Mater. 2021, 311, 110683–110687. [Google Scholar] [CrossRef]
  56. Inglezakis, V.J. The concept of “capacity” in zeolite ion-exchange systems. J. Colloid Interface Sci. 2005, 281, 68–79. [Google Scholar] [CrossRef] [PubMed]
  57. Fanfan, P.N.; Mabon, N.; Thonart, P.; Lognay, G.; Copin, A.; Barthelemy, J.-P. Investigations on Cationic Exchange Capacity and Unused Bed Zone According to Operational Conditions in a Fixed bed Reactor for Water Lead Removal by a Natural Zeolite. Biotechnol. Agron. Soc. Environ. 2006, 10, 93–99. Available online: https://popups.uliege.be/1780-4507/index.php?id=1160 (accessed on 4 December 2023).
  58. Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2000. [Google Scholar]
  59. Laviron, E. General expression of the linear potential sweep voltammogram in the case of diffusionless electrochemical systems. J. Electroanal. Chem. 1979, 101, 19–28. [Google Scholar] [CrossRef]
  60. Makino, N.; Mochizuki, Y.; Bannai, S.; Sugit, Y. Kinetic Studies on the Removal of Extracellular Hydrogen Peroxide by Cultured Fibroblasts. J. Biol. Chem. 1994, 269, 1020–1025. Available online: https://pubmed.ncbi.nlm.nih.gov/8288557 (accessed on 4 December 2023). [CrossRef] [PubMed]
  61. Maicaneanu, A.; Varodi, C.; Bedelean, H.; Gligor, D. Physical-chemical and electrochemical characterization of Fe-exchanged natural zeolite applied for obtaining of hydrogen peroxide amperometric sensors. Chem. Erde Geochem. 2014, 74, 653–660. [Google Scholar] [CrossRef]
  62. Xue, F.; Qin, R.; Zhu, R.; Zhou, X. Sn species modified mesoporous zeolite TS-1 with oxygen vacancy for enzyme-free electrochemical H2O2 detecting. Dalton Trans. 2022, 51, 18169–18175. [Google Scholar] [CrossRef]
  63. Muresan, L.M. Zeolite-modified electrodes with analytical applications. Pure Appl. Chem. 2011, 83, 325–343. [Google Scholar] [CrossRef]
  64. Mosquera, N.; Aguirre, M.J.; Domingo, R.-L.; García, C.; Arce, R.; Bollo, S. Co2SnO4/carbon paste electrode as electrochemical sensor for hydrogen peroxide. J. Chil. Chem. Soc. 2017, 62, 3525–3528. [Google Scholar] [CrossRef]
  65. Norouzi, B.; Malekan, A.; Moradian, M. Nickel-zeolite modified carbon paste electrode as electrochemical sensor for hydrogen peroxide. Russ. J. Electrochem. 2016, 52, 330–339. [Google Scholar] [CrossRef]
  66. Rostami, S.; Azizi, S.N.; Ghasemi, S. Using of silver nanoparticles incorporated in nanoporous ZSM-5 hierarchical zeolite prepared from bagasse as a new sensor for electrocatalytic determination of H2O2 in biological samples. J. Electroanal. Chem. 2017, 799, 583–594. [Google Scholar] [CrossRef]
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Figure 1. SEM–EDS spectra and atomic weight composition of the Z (A) and Cu–Z (B) samples.
Figure 1. SEM–EDS spectra and atomic weight composition of the Z (A) and Cu–Z (B) samples.
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Figure 2. N2 adsorption–desorption isotherm for an unmodified sample, Z (A) and BJH pore size distribution (B) for an unmodified (Z) and Cu-modified sample (Cu–Z).
Figure 2. N2 adsorption–desorption isotherm for an unmodified sample, Z (A) and BJH pore size distribution (B) for an unmodified (Z) and Cu-modified sample (Cu–Z).
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Figure 3. SEM (A) of TEM (B, scale 500 nm) images of the unmodified zeolitic volcanic tuff.
Figure 3. SEM (A) of TEM (B, scale 500 nm) images of the unmodified zeolitic volcanic tuff.
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Figure 4. FTIR spectra of the unmodified Z and copper modified Cu–Z zeolitic volcanic.
Figure 4. FTIR spectra of the unmodified Z and copper modified Cu–Z zeolitic volcanic.
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Figure 5. (A) Evolution over time of copper exchange capacity values (corresponding to the breakthrough curve) and (B) cation exchange capacity during the ionic exchange process; C1 = 16.6 g Cu2+/L, C2 = 1.10 g Cu2+/L, C3 = 0.50 g Cu2+/L, C4 = 0.25 g Cu2+/L, grain size 0.2–0.4 mm, flow rate 0.055 mL/min.
Figure 5. (A) Evolution over time of copper exchange capacity values (corresponding to the breakthrough curve) and (B) cation exchange capacity during the ionic exchange process; C1 = 16.6 g Cu2+/L, C2 = 1.10 g Cu2+/L, C3 = 0.50 g Cu2+/L, C4 = 0.25 g Cu2+/L, grain size 0.2–0.4 mm, flow rate 0.055 mL/min.
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Figure 6. Maximum copper exchange capacity values on the zeolitic volcanic tuff sample; C1 = 16.5 g Cu2+/L, C2 = 1.10 g Cu2+/L, C3 = 0.50 g Cu2+/L, C4 = 0.25 g Cu2+/L.
Figure 6. Maximum copper exchange capacity values on the zeolitic volcanic tuff sample; C1 = 16.5 g Cu2+/L, C2 = 1.10 g Cu2+/L, C3 = 0.50 g Cu2+/L, C4 = 0.25 g Cu2+/L.
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Figure 7. Cyclic voltammograms corresponding to the obtained modified electrodes (A); pH dependence of formal standard potential (B) and experimental dependence of (Ep − E0′) on the logarithm of the scan rate (C) corresponding to Cu–Z–CPEs. Experimental conditions: starting potential,—1000 mV vs. Ag/AgCl/KClsat; scan rate, 10 mV s—1 (A); 50 mV s—1 (B); supporting electrolyte, 0.1 M phosphate buffer solution, pH 7 (A,C).
Figure 7. Cyclic voltammograms corresponding to the obtained modified electrodes (A); pH dependence of formal standard potential (B) and experimental dependence of (Ep − E0′) on the logarithm of the scan rate (C) corresponding to Cu–Z–CPEs. Experimental conditions: starting potential,—1000 mV vs. Ag/AgCl/KClsat; scan rate, 10 mV s—1 (A); 50 mV s—1 (B); supporting electrolyte, 0.1 M phosphate buffer solution, pH 7 (A,C).
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Figure 8. Cyclic voltammograms recorded with Cu–Z–CPE electrodes in 0.1 M phosphate buffer (pH 7.0) and in solution containing two H2O2 concentrations.
Figure 8. Cyclic voltammograms recorded with Cu–Z–CPE electrodes in 0.1 M phosphate buffer (pH 7.0) and in solution containing two H2O2 concentrations.
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Figure 9. The influence of the applied potential on the H2O2 electrocatalytic current, recorded with Cu–Z–CPEs electrodes at different pHs of supporting electrolyte of pH 3.0 (A), pH 7.0 (B) and pH 9.0 (C).
Figure 9. The influence of the applied potential on the H2O2 electrocatalytic current, recorded with Cu–Z–CPEs electrodes at different pHs of supporting electrolyte of pH 3.0 (A), pH 7.0 (B) and pH 9.0 (C).
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Figure 10. Calibration curves for H2O2 of Cu–Z-CPEs electrodes, at different pHs of phosphate buffer solution.
Figure 10. Calibration curves for H2O2 of Cu–Z-CPEs electrodes, at different pHs of phosphate buffer solution.
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Figure 11. The durability of Cu–Z-CPEs sensor in the presence of 5 mM H2O2: repeatability over100 cycles (A) and 7 days (B); reproducibility of 5 electrodes (C).
Figure 11. The durability of Cu–Z-CPEs sensor in the presence of 5 mM H2O2: repeatability over100 cycles (A) and 7 days (B); reproducibility of 5 electrodes (C).
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Table 1. The infrared bands of the Z and Cu–Z samples.
Table 1. The infrared bands of the Z and Cu–Z samples.
SampleShift bIR Signal Attribution
ZCu–ZZ a
Wavenumber (cm−1)362036203610-O–H bond stretching
34463446--O–H bond stretching
163716371635-H–O–H angular deformation
1209shoulder1210↓↓(Si, Al)–O asymmetric internal stretching
105510741070↑(Si, Al)–O asymmetric external stretching
796788790↓(Si, Al)–O external symmetric stretching
733726740↓(Si, Al)–O external symmetric stretching
669674670↑(Si, Al)–O external symmetric stretching
606607602↑ring-coupled (Si, Al)–O external vibration
467459465↓O–(Si, Al)–O angular deformation
a literature data [2,53,54,55]. b IR band shift—↑ towards higher values, ↓ towards smaller values—Z vs. Cu–Z.
Table 2. Parameters of the log linear regression corresponding to the peak current dependence on the potential scan rate for Cu–Z-CPEs. Experimental conditions as in Figure 7.
Table 2. Parameters of the log linear regression corresponding to the peak current dependence on the potential scan rate for Cu–Z-CPEs. Experimental conditions as in Figure 7.
pHSlopeR/No. of Exp. Points
OxidationReductionOxidationReduction
30.56 ± 0.020.62 ± 0.030.995/90.992/9
50.34 ± 0.010.51 ± 0.030.996/130.985/13
70.41 ± 0.020.60 ± 0.020.990/100.994/14
90.40 ± 0.030.57 ± 0.020.970/120.995/15
Table 3. Electroanalytical parameters corresponding to Cu–Z-CPEs. Experimental conditions as in Figure 10.
Table 3. Electroanalytical parameters corresponding to Cu–Z-CPEs. Experimental conditions as in Figure 10.
pHEappl (mV)Detection Limit
(μM)		Linear Domain (M)S
(mA/M)		Chi2R2
3−501010−5–5·10−30.751.8·10−130.989
7−1501010−5–3·10−20.874.1·10−140.999
9−400312·10−5–10−327.81.0·10−110.999
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Gligor, D.; Maicaneanu, S.A.; Varodi, C. Low-Cost Carbon Paste Cu(II)-Exchanged Zeolite Amperometric Sensor for Hydrogen Peroxide Detection. Chemosensors 2024, 12, 23. https://doi.org/10.3390/chemosensors12020023

AMA Style

Gligor D, Maicaneanu SA, Varodi C. Low-Cost Carbon Paste Cu(II)-Exchanged Zeolite Amperometric Sensor for Hydrogen Peroxide Detection. Chemosensors. 2024; 12(2):23. https://doi.org/10.3390/chemosensors12020023

Chicago/Turabian Style

Gligor, Delia, Sanda Andrada Maicaneanu, and Codruta Varodi. 2024. "Low-Cost Carbon Paste Cu(II)-Exchanged Zeolite Amperometric Sensor for Hydrogen Peroxide Detection" Chemosensors 12, no. 2: 23. https://doi.org/10.3390/chemosensors12020023

APA Style

Gligor, D., Maicaneanu, S. A., & Varodi, C. (2024). Low-Cost Carbon Paste Cu(II)-Exchanged Zeolite Amperometric Sensor for Hydrogen Peroxide Detection. Chemosensors, 12(2), 23. https://doi.org/10.3390/chemosensors12020023

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