Boron-doped Diamond Electrode Research Articles

(Invited) Structure and Dynamics of Interfacial Species in Electrical Double Layer

Understanding electrochemical processes is of importance for many industrial and scientific fields. Especially, interfacial species, such as electrolyte ions and solvent significantly affect electrochemical reaction activity. Surface oxide species also promote or inhibit various electrode reactions; therefore, the oxidation processes of metal electrode have been investigated using in situ vibrational spectroscopy. Infrared (IR) spectroscopy is an important tool because it can detect the complementary vibrational modes of surface oxide species. However, observation of the low-frequency mode is restricted by infusible IR windows such as CaF2, that are generally used in the IR reflection absorption spectroscopy (IRAS). We developed a complementary IR method that can be used to avoid contamination by dissolved ions from window material. The fusible low-pass IR window can be applied to in-situ IRAS measurements [1,2]. The adsorbed hydroxide was observed on the single crystal Pt electrodes depending on the surface orientation, its coverage was correlated with the decrease in oxygen reduction reaction activity [3]. Recent time resolved X-ray diffraction measurements revealed that there is a delay in the approach of alkali metal cations to surface because the interfacial water causes a blocking effect [4]. Therefore, the kinetics of approaching step in the EDL is significantly different from that of migration in the bulk phase, and the adsorption rate depends on the hydration structure, ionic valence, and ionic size. Although X-ray diffraction provides a distribution of interfacial species, it does not provide sufficient information about species identification and molecular orientation. We investigated the coadsorption dynamics of metal cation and (bi)sulfate anion using time resolved IR measurement [5]. Boron doped diamond (BDD) is a promising material of which properties are significantly different from those of metals and other carbon materials. However, the complex atomic arrangement and oxidation state of the polycrystalline BDD surface inhibit an atomic level study on the relationship between the electrochemical response and surface structure. More detailed surface analyses are necessary for the investigation of the electrode surface of BDD. We applied in situ ATR−IR spectroscopy to reveal the oxidative species and dopamine oxidation on the BDD electrode [6,7].[1] M. Nakamura, Y. Nakajima, N. Hoshi, H. Tajiri, O. Sakata, ChemPhysChem, 14, 2426 (2013).[2] M. Nakamura, Y. Nakajima, K. Kato, O. Sakata, N. Hoshi, J. Phys. Chem. C, 119, 23586 (2015).[3] T. Kumeda, H. Tajiri, O. Sakata, N. Hoshi, M. Nakamura, Nat. Commun., 9, 4378 (2018).[4] M. Nakamura, H. Kaminaga, O. Endo, H. Tajiri, O. Sakata, N. Hoshi, J. Phys. Chem. C, 118, 22136 (2014).[5] M. Nakamura, T. Banzai, Y. Maehata, O. Endo, H. Tajiri. O. Sakata, N. Hoshi, Sci. Rep., 7, 914 (2017).[6] T. Ogose, S. Kasahara, N. Ikemiya, N. Hoshi, Y. Einaga, M. Nakamura, J. Phys. Chem. C, 122, 27456 (2018).[7] R. Hosoda, N. Kamoshida, N. Hoshi, Y. Einaga, M. Nakamura, Carbon, 171, 814 (2021).

Electrochemical Synthesis of Selected λ3- and λ5-Iodanes

Numerous λ3- and λ5-iodanes are used as highly selective oxidants in organic synthesis and are considered as a green alternative to classical metal based (CrVI, MnVII, ...) oxidants. The main advantage of iodanes is substantially lower toxicity and environmental footprint. However, their synthesis is based on chemical oxidation of iodobenzenes which usually involves handling toxic or at least potentially unstable oxidants (e.g. bromate, chlorine, persulfate or percarboxylic acids). This represents safety issue which becomes significant especially when scale-up of the process beyond laboratory level is required. Application of electrochemical synthesis of iodanes offers substantial advantage over the classical chemical approach in a sence no chemical oxidants are required. However, up to this point, no cheap, sustainable and easily scalable process for electrochemical synthesis of λ3-iodanes has been published. The main problems is that majority of the authors use environmentally unfriendly solvents and often workup of the product is complicated or even missing. In the case of electrochemical synthesis of λ5-iodanes, the situation is even worse since there is just handfull of publications on the topic.In the present contribution, a process of electrochemical synthesis of selected λ3- and λ5-iodanes (based on our previous publications [1-3]) including solid product workup, will be presented. In particular, the electrochemical process is based on anodic oxidation of 2-iodobenzoic acid to 2-iodosylbenzoic acid and 2-iodylbenzoic acid (IBX) using boron-doped diamond electrode. This step proceeds with high current efficiency, selectivity and product yield. Separation involves precipitation, crystallisation and filtration. No product washing with organic solvents is required. It is important to note that during the process development the attention was paid to minimisation of the environmental footprint of the process (high atom efficiency, low amount of waste, absence of toxic chemicals), low price of the chemicals and process scalability.

Electrochemical Sensing of 2,4-Dinitrotoluene on Boron-Doped Carbon Nanowall Electrodes in Seawater

50 000 tons of chemical weapons and 500 000 tons of conventional weapons, containing nitroexplosive compounds such as 2,4,6-trinitrotoluene (TNT) have been dumped in the Baltic Sea since the end of World War II. In addition, many wrecks from World War II are still laying at the bottom of the Baltic Sea. The marine environment, due to the content of chloride ions, shows high corrosion aggressiveness. As a result, the degradation of metal ammunition casings, fuel tanks and other metal elements causes the successive release of toxic substances into the ecosystem. Uncontrolled emission of those chemicals hinders the development of biological life and poisons fish living in the sea, which later as food posing a real threat to human health.TNT is a highly energetic material commonly utilized as a filling of shell casting and mines, thus it is used in large quantities in armed conflicts. 2,4-dinitrotoluene (2,4-DNT) is the decomposition product of TNT and has a similar structure (2,4-DNT has two nitro groups (-NO2) and TNT three). Exposure to high 2,4-DNT concentrations may cause lung and liver complications as well as reproductive problems. 2,4-DNT is spread all over the world and is found in air, surface water, groundwater, and soil [1]. Therefore, environmental monitoring of DNT using an effective sensor is essential. The development of DNT sensors able to effectively work in marine water with the required sensitivity is extremely necessary and remains a challenge.Carbon nanomaterials have been used in various fields, such as electronic, optoelectronic, photovoltaic, and electrochemical applications, owing to their excellent electrical, electrochemical and mechanical properties. Boron-doped carbon nanowall (B:CNW) electrodes are characterized by excellent charge transfer and compared to for example boron-doped diamond electrodes exhibit highly developed active surface area [2]. Moreover, these electrodes showed a sensitive and selective response to nitroaromatic compounds, such as TNT and 2,4,6-trinitroanisole (TNA) [3].In this study, we propose a 2,4-DNT electrochemical sensor based on a boron-doped carbon nanowall electrode prepared in a one-step process using a chemical vapor deposition technique. The determination of 2,4-dinitrotoluene was performed using differential pulses voltammetry (DPV) and cyclic voltammetry (CV) in saline water matrices on B:CNW electrodes, using a three-electrode setup. The objective of this work is to test the influence of water salinity level on the 2,4-dinitrotoluene detection sensitivity. For this purpose, water containing various levels of salinity (from 2 – 20 ‰) was investigated. Furthermore, real-sample measurements were conducted using the Baltic See water from the Gulf of Gdansk. The levels of salinity were selected based on average salinity of the Baltic Sea (7.5‰).Literature:[1] D. E. Rickert, et al., CRC Critical Reviews in Toxicology. (1984) 13:3 217-234[2] M. Sobaszek, et al., J. Phys. Chem. C. 121 (2017) 20821–20833[3] A. Dettlaff, et al., J. Hazard. Mater. 387 (2020) 121672Acknowledgements:The research leading to these results has received funding from the Norway Grants 2014-2021 via the National Centre for Research and Development within research grant no. NOR/SGS/NITROsens/0011/2020-00.

Bottom-up strategy of multi-level structured boron-doped diamond for the durable electrode in water purification

Long-term exposition of electrodes to aqueous media inevitably results in biofouling and adhesion of bacteria, reducing the electrolysis efficiency of electrodes for water treatment. To ensure technically efficient antifouling of materials for durable electrodes, hierarchical micro-/nano structured boron-doped diamond (BDD) electrodes were designed and synthesized. Multi-level structured BDD was coated on titanium mesh by a bottom-up strategy, based on a combination of self-assembly seeding and hot filament chemical vapor deposition (HFCVD) growth. The morphology of the BDD coating can be controlled by manipulating the seeding density and boron doping concentration. The designed micro/nano hierarchical structure of the BDD electrode suppressed bacterial adhesion greatly and exhibited excellent anti-biofouling efficiency with an antibacterial rate of ∼ 93 %, which entails simplified self-cleaning and durable BDD-coated electrodes. The BDD-coated electrodes were employed to electrochemically treat Escherichia coli-contaminated water, killing virtually all bacteria (≥99.9 %) in 1 min. Finally, real river water was electrochemically treated, reducing the chemical oxygen demand (COD) down to 5 mg/L in 4 h. The excellent performance shows the great potential of the structured BDD electrodes for long-term water purification.

Simultaneous voltammetric determination of female hormones using different carbonaceous electrodes in a non-aqueous environment

An undemanding electroanalytical method for the simultaneous determination of estrogens, namely 17β-estradiol (E2) or synthetic 17α-ethinylestradiol (EE2), with dienogest (DGN) has been developed for the analysis of oral contraceptives and hormone replacement therapy products. This approach is based on their anodic oxidation at carbonaceous electrode materials in pure acetonitrile using square-wave voltammetry. The electrochemical behaviour of these hormones at a glassy carbon electrode (GCE) in a nonaqueous environment was investigated using cyclic voltammetry to verify their reaction mechanisms. As part of the optimisation, commercially available GCE and boron-doped diamond electrodes were found to provide similar analytical performance, characterized by a wide linear range (>100 μmolL−1) with limits of quantification approximately 1.6 μmolL−1 for each hormone. A satisfactory precision (relative standard deviation < 4%) has been achieved for a mixture of 10 μmolL−1 E2 and DGN. Finally, the developed electroanalytical method was applied to the determination of female hormones present in pharmaceutical preparations and the results acquired were comparable to those obtained by a reference method employing reversed-phase high-performance liquid chromatography coupled to a diode array detector, which confirmed the practical use of this method in routine pharmaceutical analysis.

Laser-patterned boron-doped diamond electrodes with precise control of sp2/sp3 carbon lateral distribution

A thorough study on sp3 to sp2 carbon conversion in undoped and boron-doped diamond (BDD) thin (≈ 500 nm) layers leading to the desired sp2/sp3 carbon ratio and lateral distribution, which utilizes boron atom incorporation and infrared (IR) material laser processing has been performed. Polycrystalline as-grown (AG) or chem-mechanically polished (CMP) undoped diamond/BDD layers were investigated with respect to boron content and laser wavelength (800, 1030 nm). Boron incorporation leads to an increase in IR optical absorption and reduction of required energy fluence (Fth≈ 1 J cm−2) needed for sp3 to sp2 carbon conversion. Raman spectroscopy was performed to identify carbon conversion stages and to tailor the ideal parameters for other IR laser sources and required sp2/sp3 carbon ratio. Electrochemical parameters (ΔEp and IAp/ICp ratio) were obtained from cyclic voltammetry measurements of outer-([Ru(NH3)6]3＋/2＋) and inner-([Fe(CN)6]3−/4−) sphere redox markers. Values of ΔEp and IAp/ICp are mainly influenced after conversion of 10% of sp3 to sp2 carbon. This trend is most pronounced for the [Fe(CN)6]3−/4− redox marker, by decrease or increase of these parameters on AG or CMP BDD electrodes respectively. Electrochemical findings were supported by electrochemical impedance spectroscopy where Rct keeps the same trend as ΔEp values and double layer capacitance profoundly increases between 10 and 25% of surface conversion.

Diamond as Insulation for Conductive Diamond—A Spotted Pattern Design for Miniaturized Disinfection Devices

Boron-doped diamond (BDD) electrodes are well known for the in situ production of strong oxidants. These antimicrobial agents are produced directly from water without the need of storage or stabilization. An in situ production of reactive oxygen species (ROS) used as antimicrobial agents has also been used in recently developed medical applications. Although BDD electrodes also produce ROS during water electrolysis, only a few medical applications have appeared in the literature to date. This is probably due to the difficulties in the miniaturization of BDD electrodes, while maintaining a stable and efficient electrolytic process in order to obtain a clinical applicability. In this attempt, a cannula-based electrode design was achieved by insulating the anodic diamond layer from a cathodic cannula, using a second layer of non-conducting diamond. The undoped diamond (UDD) layer was successfully grown in a spotted pattern, resulting in a perfectly insulated yet still functional BDD layer, which can operate as a miniaturized flow reactor for medical applications. The spotted pattern was achieved by introducing a partial copper layer on top of the BDD layer, which was subsequently removed after growing the undoped diamond layer via etching. The initial analytical observations showed promising results for further chemical and microbial investigations.

An Interference-Free Voltammetric Method for the Detection of Sulfur Dioxide in Wine Based on a Boron-Doped Diamond Electrode and Reaction Electrochemistry.

This paper describes a new, simple, and highly selective analytical technique for the detection of sulfur dioxide in wine, as a real sample with a relatively complicated matrix. The detection of the above analyte was based on the electrogeneration of iodine from iodide on a boron-doped diamond electrode, without modifications, in the presence of 0.1 mol dm-3 HClO4 as a supporting electrolyte. The electrogenerated iodine reacted with sulfur dioxide, forming iodide ions and sulfuric acid (i.e., a Bunsen reaction). The product of this reaction, the iodide ion, diffused back to the surface of the boron-doped diamond electrode and oxidized itself again. This chemical redox cycling enhanced the voltammetric response of the boron-doped diamond electrode. The selectivity of the determination was assured using NaOH and formaldehyde during sample preparation, and a blank was also measured and taken into account. The detection limit was estimated to be 10-6-10-7 mol dm-3. However, the content of sulfur dioxide in wine is significantly higher, which can lead to more accurate and reliable results.

Surface morphology-assisted electrochemical conversion of carbon dioxide to formic acid via nanocrystalline boron-doped diamond electrodes

Due to its unmatched corrosion stability and overall versatility, boron-doped diamond (BDD) has superb potential as an electrode material for the production of valuable chemicals via electrochemical reduction of carbon dioxide (CO2). To advance its practical application, it is necessary to explore ways to achieve cost-effective fabrication of BDD electrodes, which can enable significant selectivity for product formation during CO2 electroreduction. Here, BDD electrodes of nanocrystalline form were fabricated employing two distinct chemical vapor deposition (CVD) techniques, which allow for substantial upscaling of electrode dimensions to match industrial/wafer-size standards. Thin (<400 nm) nanocrystalline BDD layers were fabricated at various synthesis temperatures to investigate its effect on the electrical, structural, and electrochemical characteristics. Furthermore, modification of the BDD layer crystallinity and morphology has been performed to significantly alter the overall electrode structure and sp3/sp2-carbon phase-composition. Finally, when employed as cathodes in electrochemical CO2 reduction, nanocrystalline BDD electrodes of modified structure demonstrated enhanced values of faradaic efficiency (FE) towards production of formic acid (HCOOH), surpassing FEHCOOH values observed for microcrystalline form of BDD cathodes. Reported findings present a basis for further development of BDD cathodes, including their design, structure, and composition, which leverages the advantages of scalable and cost-effective synthesis of BDD electrodes.

Use of a lab-made screen-printed sensor with chemically deposited boron-doped diamond for simple and selective electrochemical detection of the synthetic cathinone N-ethylpentylone in forensic samples

N-ethylpentylone (NEP), also known as ephylone, is a synthetic cathinone (SC) that has been banned worldwide since 2019 due to alarming cases of intoxication. However, preliminary identification of this drug is of interest in the forensic scenario. Here, a new forensic application using a lab-made screen-printed sensor with chemically deposited boron-doped diamond electrode (LM-SP/BDDE) for the detection of SCs is presented. We present, for the first time, the electrochemical behavior of NEP and its detection in forensic samples using a versatile, robust, low-cost, and simple sensor that requires a small sample volume (30 µL) for the analysis. NEP presented three irreversible and independent redox processes (O1 at +0.88 V, R1 at –1.3 V and R2 at –1.45 V), and a dependent reduction R3 at –1.6 V vs. Ag/AgCl. The proposed method for NEP detection on LM-SP/BDDE was optimized by adsorptive stripping differential pulse voltammetry (AdSDPV). The use of LM-SP/BDDE with AdSDPV provided a good stability of NEP electrochemical responses using the same electrode (n = 5), with RSD < 4.0% for all redox processes. Furthermore, wide linear ranges for NEP determination (1.0 – 100.0 µmol L − 1) with a low LOD (0.66 µmol L − 1) were obtained. Interference studies have been performed for common adulterants and other illicit drugs (semi-synthetics, amphetamines, and other SCs), and a highly selective response for NEP detection was observed. Therefore, LM-SP/BDDE combined with AdSDPV is an alternative tool for selective screening of NEP in on-site forensic analysis, providing rapid and simple preliminary identification.

Inkjet Printing-Manufactured Boron-Doped Diamond Chip Electrodes for Electrochemical Sensing Purposes.

Fabrication of patterned boron-doped diamond (BDD) in an inexpensive and straightforward way is required for a variety of practical applications, including the development of BDD-based electrochemical sensors. This work describes a simplified and novel bottom-up fabrication approach for BDD-based three-electrode sensor chips utilizing direct inkjet printing of diamond nanoparticles on silicon-based substrates. The whole seeding process, accomplished by a commercial research inkjet printer with piezo-driven drop-on-demand printheads, was systematically examined. Optimized and continuous inkjet-printed features were obtained with glycerol-based diamond ink (0.4% vol/wt), silicon substrates pretreated by exposure to oxygen plasma and subsequently to air, and applying a dot density of 750 drops (volume 9 pL) per inch. Next, the dried micropatterned substrate was subjected to a chemical vapor deposition step to grow uniform thin-film BDD, which satisfied the function of both working and counter electrodes. Silver was inkjet-printed to complete the sensor chip with a reference electrode. Scanning electron micrographs showed a closed BDD layer with a typical polycrystalline structure and sharp and well-defined edges. Very good homogeneity in diamond layer composition and a high boron content (∼2 × 1021 atoms cm-3) was confirmed by Raman spectroscopy. Important electrochemical characteristics, including the width of the potential window (2.5 V) and double-layer capacitance (27 μF cm-2), were evaluated by cyclic voltammetry. Fast electron transfer kinetics was recognized for the [Ru(NH3)6]3+/2+ redox marker due to the high doping level, while somewhat hindered kinetics was observed for the surface-sensitive [Fe(CN)6]3-/4- probe. Furthermore, the ability to electrochemically detect organic compounds of different structural motifs, such as glucose, ascorbic acid, uric acid, tyrosine, and dopamine, was successfully verified and compared with commercially available screen-printed BDD electrodes. The newly developed chip-based manufacture method enables the rapid prototyping of different small-scale electrode designs and BDD microstructures, which can lead to enhanced sensor performance with capability of repeated use.

Electrochemical oxidation of a real effluent using selective cathodic and anodic strategies to simultaneously produce high value-added compounds: Green hydrogen and carboxylic acids

In this work, the simultaneous production of green hydrogen (H2) and carboxylic acids from the electrochemical treatment of washing machine effluent is demonstrated for the first time. The electrochemical treatment of the effluent was carried out using a solar-powered polymer electrolyte membrane (PEM-type) cell with a boron-doped diamond (BDD) electrode as anode and a Ni-Fe-based SS (stainless steel) mesh as the cathode with two types of electrolytes (0.1 mol/L H2SO4 and 0.1 mol/L Na2SO4), by applying different current densities (j). A synthetic and non-destructive effluent transformation strategy was implemented by controlling the operating conditions in order to regulate precursor-intermediates, oxidants, and •OH production. The results show the formation of high value-added products (carboxylic acids) and energy sources (green H2) in the anodic and cathodic compartments, respectively, with the possibility of selective electroconversion to acetic acid depending on the electrolyte and j. The green H2 production rate is also influenced by the pH conditions, the electrolyte, and the anodic j. The technology proposed here may constitute a promising, efficient and sustainable route towards the United Nations’ Sustainable Development Goals (SDGs) 6 and 7.

Degradation of levofloxacin from antibiotic wastewater by pulse electrochemical oxidation with BDD electrode

Antibiotic-containing wastewater is a typical biochemical refractory organic wastewater and general treatment methods cannot effectively and quickly degrade the antibiotic molecules. In this study, a novel boron-doped diamond (BDD) pulse electrochemical oxidation (PEO) technology was proposed for the efficient removal of levofloxacin (LFXN) from wastewater. The effects of current density (j), initial pH (pH0), frequency (f), electrolyte types and initial concentration (c0(LFXN)) on the degradation of LFXN were systematically investigated. The degradation kinetics under four different processes have also been studied. The possible degradation mechanism of LFXN was proposed by Density functional theory calculation and analysis of degradation intermediates. The results showed that under the optimal parameters, the COD removal efficiency (η(COD)) was 94.4% and the energy consumption (EEC) was 81.43 kWh·m−3 at t = 120 min. The degradation of LFXN at pH = 2.8/c(H2O2) followed pseudo-first-order kinetics. The apparent rate constant was 1.33 × 10−2 min−1, which was much higher than other processes. The degradation rate of LFXN was as follows: pH = 2.8/c(H2O2) > pH = 2.8 > pH = 7/c(H2O2) > pH = 7. Ten aromatic intermediates were formed during the degradation of LFXN, which were further degraded to F−, NH4+, NO3−, CO2 and H2O. This study provides a promising approach for efficiently treating LFXN antibiotic wastewater by pulsed electrochemical oxidation with a BDD electrode without adding H2O2.

Boron doped diamond electrode for efficient persulfate generation: The modulation of boron doping level on interfacial electron transfer

The inefficient Faradaic efficiency of electro-synthesis of sodium persulfate (Na2S2O8) hinders its industrial application. In this work, modulated high-performance boron-doped-diamond (BDD) electrodes were used to Na2S2O8 electro-synthesis. The effect of boron doping level of BDD electrode on Na2S2O8 generation was studied for the first time. Based on electro-synthesis results, BDD (0.05% B) electrode produced more Na2S2O8 (41.85 mM at 120 min) with the Faradaic efficiency of 90% that is the highest value reported in the literatures. Na2S2O8 was generated by ·OH mediated indirect oxidation, and the BDD (0.05% B) electrode produced more ·OH. Furthermore, the less C-O functional groups on the BDD (0.05% B) electrode surface inhibited the interfacial electron transfer of H2O to O2, and therefore promoted ·OH formation. These findings highlight the relationship between boron doping level, surface functional groups, interfacial electron transfer process and Na2S2O8 generation, providing a theoretical guidance for efficient Na2S2O8 electro-synthesis.

Platinum and palladium nanoparticles on boron-doped diamond for the electrochemical detection of hydrogen peroxide: a comparison study.

Hydrogen peroxide (H2O2) plays a role in many facets - a household item, an important industrial chemical, a biomarker in vivo, and several others. For this reason, its measurement and quantification in a variety of media are important. While spectroscopic detection is primarily used for H2O2, electrochemical methods offer advantages in versatility, cost, and sensitivity. In this work, we investigate a 2-step surface metal nanoparticle (NP) modification for platinum (Pt) and palladium (Pd) on boron-doped diamond (BDD) electrodes for the detection of H2O2. Several parameters such as the metal salt concentration and electrodeposition charge in the 2-step modification were varied to find an optimum. Using cyclic voltammetry (CV), the BDD-PdNP electrode types were found to yield a sharper, more well-resolved H2O2 oxidation peak compared to the BDD-PtNP electrodes. Both metal NP electrode types significantly improved the response compared to the bare BDD electrode; a 150-200× improvement in sensitivity was observed across all modified electrode types. Calibration experiments were completed at both low and high concentration ranges in stagnant and flow-based solutions. The lowest limit of detection (LOD) obtained was 50 nM (5E-08 M) on a BDD-PdNP electrode modified with 1.0 mM PdCl2 to 5.0 mC in the wet chemical seeding and electrodeposition steps. 0.25 mM PdCl2 to 3.23 mC and 0.25 mM HPtCl6- to 3.23 mC also yielded a sufficient response for low-level H2O2, with LODs around 100 nM (1E-07 M). Overall, this work exemplifies the wide applicability of BDD and achieves sub-μM H2O2 LODs with a non-enzymatic electrode material.

Cloud point extraction of carbendazim fungicide from strawberry samples and amperometric detection with boron doped diamond

The cloud point extraction (Tergitol® surfactant) method was used for the first time to extract and preconcentrate the fungicide carbendazim (CBZ) from strawberry samples, while electrochemical detection (boron doped diamond electrode) in association with high performance liquid chromatography (HPLC-EC) was used for the determination of CBZ. The variables of bath temperature, ultrasonic stirring time, mass of NaCl and amount of surfactant were investigated using a 24 full factorial design. Limits of detection (LOD, S/N = 3) and quantification (LOQ) of 3.42 × 10−8 mol/L (or 6.54 µg/L) and 6.84 × 10−8 mol/L (or 13.1 µg/L), respectively, were obtained for the CPE processes, considering the value of the preconcentration factor obtained (9.12). The method was validated based on linearity, intra-day and inter-day recovery tests, accuracy and precision. The proposed method was applied to strawberry samples from local commercial establishments and different procedures for washing and sanitizing strawberry fruits were also evaluated.

Morphology modulation on boron-doped diamond electrodes and its effect on boosting the conversion of CO2-to-CO

Boron-doped diamond (BDD) electrodes have achieved excellent selectivity and switchable product formation for electrochemical CO2 reduction reaction (eCO2RR), although the current should be improved. Surface morphology modulation is a promising approach for improving it by exposing a larger electroactive area. Herein, we fabricated a porous 1 % BDD film (p-BDD) and a rough-surfaced 1 % BDD film (r-BDD) by modifying the surface of a flat 1 % BDD film (f-BDD). Fundamental electrochemical properties, including potential window, differential capacitance, and active area were examined, followed by eCO2RR activity evaluation. The synthetic r-BDD electrode enabled approximately 1.7-fold increases in current density and yield rate (17.6 μmol h−1) toward CO production compared to f-BDD (10.3 μmol h−1). This improvement in eCO2RR is ascribed to the larger electroactive area with a comparable kinetic performance, in comparison to f-BDD. On the other hand, p-BDD possesses the largest real area, but showed the lowest activity for eCO2RR (1.2 μmol h−1 for CO), which could result from hindered diffusion of CO2 inside the pores. X-rays photoelectron spectroscopy and electrochemical impedance spectroscopy were employed to disentangle the morphological structure effect from the chemical reactivity of the electrode surface.

Electrochemical evaluation and voltammetric determination of some phenolic acids on the boron-doped diamond electrode

A simple, sensitive, and rapid method of determining phenolic acids, i.e. caffeic, ferulic, syringic, and vanillic using boron-doped diamond electrode (BDDE) by differential pulse voltammetry (DPV) was described. To the best of our knowledge, this is the first presentation of an electrochemical method to determine these compounds on BDDE. Under the conditions presented, the mentioned analytes undergo irreversible oxidation controlled by diffusion. The measurement conditions and composition of the supporting electrolyte were developed and optimized. Optimal measurement parameters ensure the usage of 0.02 mol L−1 ammonium citrate buffer pH 3.0 as a supporting electrolyte. The calibration graphs were linear with a correlation coefficient (r) >0.9959. The detection limits for the phenolic acids were within 0.01–0.03 mg L−1. Repeatability in all experiments, expressed by RSD%, was better than 5 %. The influence of interfering metal ions, such as Bi3+, Cd2+, Cu2+, Pb2+ and Tl+, was studied. The proposed method was successfully verified by measuring recoveries of phenolic acids in the model wine solution. The standard addition method was also applied in the determination of syringic acid in homemade and commercially available products: walnuts, walnut tincture, fresh and dried thyme. Effective application of the described analytical approach with the usage of BDDE not only enables the electrochemical detection of these four phenolic acids but also helps to reduce operational costs.

Electro-oxidation: An Effective Alternative for the Degradation of Textile Dyes and Reduction of Toxicity in Industrial Effluents

Purpose: This study aims to evaluate the efficiency of electro-oxidation as a treatment option for textile effluents containing industrial dyes, with the goal of minimizing their environmental impact. Theoretical framework: The textile industry is known for its high water demand and generation of effluents containing dyes, posing an environmental challenge. Electro-oxidation is a promising technology for the degradation of pollutants that are difficult to mineralize. Method: The treatment process and operational conditions were described, utilizing a Boron-Doped Diamond (BDD) electrode. Three ranges of electric current (6, 12, and 18 mA cm-2) were tested to degrade the Procion Yellow (PY) dye. The removal of the dye, energy consumption, reduction in Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and effluent toxicity were evaluated. Results and conclusion: The treatment resulted in the removal of 91.4% of the dye, with an energy consumption of 88.4 kWh/m³ for a concentration of 150 mg/L of PY, following a first-order kinetics. Significant reductions in COD (74%) and TOC (85.2%) were observed. The effluent toxicity decreased at currents of 6 and 12 mA cm-2 but increased at 18 mA cm-2. Electro-oxidation proved to be a promising option for treating textile effluents containing industrial dyes. Research implications: The results contribute to the advancement of science and socio-environmental management practices in the textile industry, providing a viable option for effluent treatment and reduction of environmental impact. Originality/value: This study highlights the efficiency of electro-oxidation in the degradation of industrial dyes present in textile effluents, presenting relevant results on dye removal, energy consumption, COD and TOC reduction, as well as the evaluation of treated effluent toxicity.

Electrochemical Disinfection of Root Canals Bears No Risk of Damaging Periapical Tissues in a Dog Model

Boron-doped diamond (BDD) electrodes have been advocated as a potential treatment alternative to the established methods for root canal disinfection. As healing of periapical tissue is important in this context, the associated risk of host tissue damage was to be evaluated. Following in vitro cell culture experiments (HeLa cells), root canal treatment was performed in an animal trial comparing BDD electrode application and the currently used rinsing media with respect to cell viability and host tissue damage. Statistical analyses comparing the size of radiolucency were based on Kruskal-Wallis and Nemenyi’s All Pairs tests (α = 0.05). The direct application of BDD electrodes had a time-dependent effect on cell viability comparable to H2O2, NaOCl, and CHX application. In contrast to the chemical treatment, the effect of BDD electrodes was transient. Conventionally treated teeth and teeth additionally treated with BDD electrodes did not significantly differ from each other with respect to the size of the periapical radiolucency as observed radiographically (vertical p = 0.998 and horizontal p = 0.878) and histologically (vertical p = 0.940 and horizontal p = 0.862). While showing greater disinfection efficiency, the application of BDD electrodes for the electrochemical disinfection of root canals does not have a greater risk of host tissue damage compared to the conventional treatment.