Boron-Doped Diamond Electrodes: Recent Developments and Advances in View of Electrochemical Drug Sensors

The cathodically pretreated boron-doped diamond electrode as an environmentally friendly electrochemical tool for the detection and monitoring of mesotrione in food samples

Excessive pesticide use can harm human health, making it essential to develop new techniques to monitor hazardous pesticides in food. Our study focuses on detecting mesotrione (MST) using an unmodified boron-doped diamond (BDD) electrode. This was the first application of cathodically pretreated BDD electrode for the detection of MST, based on its oxidation at a high potential value of +1.4 V. We theoretically examined the oxidation mechanism of MST trough the utilization of density functional theory (DFT) methodology. The utilized DPV method achieved a detection limit of 0.45 μM and showed satisfactory selectivity. The practical application of this method was demonstrated by examining corn-based food products. To ensure practical application of the method, MST was deliberately added to the samples to evaluate the accuracy of the proposed method. The effectiveness of the method was confirmed by using HPLC method. This environmentally-friendly approach can establish a solid foundation for future use in food analysis.

Electrochemical Evaluation of Cd, Cu, and Fe in Different Brands of Craft Beers from Quito, Ecuador

The presence of heavy metals in craft beers can endanger human health if the total metal content exceeds the exposure limits recommended by sanitary standards; in addition, they can cause damage to the quality of the beer. In this work, the concentration of Cd(II), Cu(II), and Fe(III) was determined in 13 brands of craft beer with the highest consumption in Quito, Ecuador, by differential pulse anodic stripping voltammetry (DPASV), using as boron-doped diamond (BDD) working electrode. The BDD electrode used has favorable morphological and electrochemical properties for the detection of metals such as Cd(II), Cu(II), and Fe(III). A granular morphology with microcrystals with an average size between 300 and 2000 nm could be verified for the BDD electrode using a scanning electron microscope. Double layer capacitance of the BDD electrode was 0.01412 μF cm^-2, a relatively low value; Ip_ox/Ip_red ratios were 0.99 for the potassium ferro-ferricyanide system in BDD, demonstrating that the redox process is quasi-reversible. The figures of merit for Cd(II), Cu(II), and Fe(III) were; DL of 6.31, 1.76, and 1.72 μg L^-1; QL of 21.04, 5.87, and 5.72 μg L^-1, repeatability of 1.06, 2.43, and 1.34%, reproducibility of 1.61, 2.94, and 1.83% and percentage of recovery of 98.18, 91.68, and 91.68%, respectively. It is concluded that the DPASV method on BDD has acceptable precision and accuracy for the quantification of Cd(II), Cu(II), and Fe(III), and it was verified that some beers did not comply with the permissible limits of food standards.

In Vitro Biofouling Performance of Boron-Doped Diamond Microelectrodes for Serotonin Detection Using Fast-Scan Cyclic Voltammetry

Neurotransmitter release is important to study in order to better understand neurological diseases and treatment approaches. Serotonin is a neurotransmitter known to play key roles in the etiology of neuropsychiatric disorders. Fast-scan cyclic voltammetry (FSCV) has enabled the detection of neurochemicals, including serotonin, on a sub-second timescale via the well-established carbon fiber microelectrode (CFME). However, poor chronic stability and biofouling, i.e., the adsorption of interferent proteins to the electrode surface upon implantation, pose challenges in the natural physiological environment. We have recently developed a uniquely designed, freestanding, all-diamond boron-doped diamond microelectrode (BDDME) for electrochemical measurements. Key potential advantages of the device include customizable electrode site layouts, a wider working potential window, improved stability, and resistance to biofouling. Here, we present a first report on the electrochemical behavior of the BDDME in comparison with CFME by investigating in vitro serotonin (5-HT) responses with varying FSCV waveform parameters and biofouling conditions. While the CFME delivered lower limits of detection, we also found that BDDMEs showed more sustained 5-HT responses to increasing or changing FSCV waveform-switching potential and frequency, as well as to higher analyte concentrations. Biofouling-induced current reductions were significantly less pronounced at the BDDME when using a "Jackson" waveform compared to CFMEs. These findings are important steps towards the development and optimization of the BDDME as a chronically implanted biosensor for in vivo neurotransmitter detection.

A Portable Wireless Intelligent Nanosensor for 6,7-Dihydroxycoumarin Analysis with A Black Phosphorene and Nano-Diamond Nanocomposite-Modified Electrode

In this work, a novel portable and wireless intelligent electrochemical nanosensor was developed for the detection of 6,7-dihydroxycoumarin (6,7-DHC) using a modified screen-printed electrode (SPE). Black phosphorene (BP) nanosheets were prepared via exfoliation of black phosphorus nanoplates. The BP nanosheets were then mixed with nano-diamond (ND) to prepare ND@BP nanocomposites using the self-assembly method, achieving high environmental stability. The nanocomposite was characterized by SEM, TEM, Raman, XPS and XRD. The nanocomposite was used for the modification of SPE to improve its electrochemical performances. The nanosensor displayed a wide linear range of 0.01-450.0 μmol/L with a low detection limit of 0.003 μmol/L for 6,7-DHC analysis. The portable and wireless intelligent electrochemical nanosensor was applied to detect 6,7-DHC in real drug samples by the standard addition method with satisfactory recoveries, which extends the application of BP-based nanocomposite for electroanalysis.

Voltammetric determination of antipsychotic drug flupentixol HCl in human serum at a boron-doped diamond electrode

This study aims to offer a voltammetric method for determining the antipsychotic drug flupentixol from serum samples. According to pH and scan rate studies, the oxidation behavior of flupentixol at boron-doped diamond electrode was found as irreversible and diffusion-controlled. In order to determine flupentixol from bulk form and serum samples, differential pulse voltammetry was preferred as the working method because of the repeatability. Linear responses were obtained in the range of 6.0×10-7 – 8.0×10-6 M and 8.0×10-7 – 1.0×10-5 M for bulk form and serum samples in pH 2.0 Britton-Robinson buffer solution, with detection limit values of 1.09×10-7 M and 1.08×10-7 M, respectively. Required validation parameters were also studied and according to recovery from serum samples (99.91 %) and precision studies, it can be said that developed method was accurate and precise.

In situ voltammetric analysis of 2,4-dichlorophenoxyacetic acid in environmental water using a boron doped diamond electrode and an adapted unmanned air vehicle sampling platform

In the present work a voltammetric method was developed for in situ detection of 2,4-dichlorophenoxyacetic acid (2,4-D) in environmental water samples, using a compact and lightweight electrochemical cell using a fused deposition modeling (FDM) 3D printer with biodegradable polylactic acid filament, and a boron-doped diamond electrode (BDDE). The samples were collected by an adapted unmanned aerial vehicle (UAV) with a micropump and a miniature solenoid valve powered by an open source microcontroller. After optimizing the supporting electrolyte, pH and parameters of the square wave voltammetry (SWV) a linear analytical curve for 2,4-D in 0.5 mol L^-1 Na₂SO₄ (pH = 2.0 regulated using 0.5 mol L^-1 H₂SO₄ solution) in a concentration range from 100 nmol L^-1 to 911 nmol L^-1 with 34 nmol L^-1 as the limit of detection was obtained. The same samples in situ analyzed by SWV were sent to the laboratory for gas chromatography-mass spectrometry (GC-MS) analysis; and there was no statistical difference from the concentration of 2,4-D in any of the samples at a 95% confidence level. Therefore, the method developed for quantification of 2,4-D in water provides an important environmental monitoring tool since it enables access to difficult areas in a fast, practical and safe way. This is the first time that an adapted UAV with these features has been used to collect environmental water for in situ electrochemical analysis as a screening tool to alert the presence of environmental hazard compounds, such as 2,4-D. Thus, this method can be used by environmental and sanitary control agencies to monitor or to supervise environmental water quality with response in real time.

Diamond Structures for Tuning of the Finesse Coefficient of Photonic Devices

Finesse coefficient is one of the most important parameters describing the properties of a resonant cavity. In this research, a mathematical investigation of the application of diamond structures in a fiber-optic Fabry–Perot measurement head to assess their impact on the finesse coefficient is proposed. We present modeled transmission functions of cavities utilizing a nitrogen-doped diamond, a boron-doped diamond, nanocrystalline diamond sheet and a silver mirror. The diamond structures were deposited using a microwave plasma-assisted chemical vapor deposition system. A SEM investigation of surface morphology was conducted. The modeling took into consideration the fiber-optic Fabry–Perot setup working in a reflective mode, with an external cavity and a light source of 1550 nm. A comparison of the mathematical investigation and experimental results is presented.

Diamond-Based Electrodes for Detection of Metal Ions and Anions

Diamond electrodes have long been a well-known candidate in electrochemical analyte detection. Nano- and micro-level modifications on the diamond electrodes can lead to diverse analytical applications. Doping of crystalline diamond allows the fabrication of suitable electrodes towards specific analyte monitoring. In particular, boron-doped diamond (BDD) electrodes have been reported for metal ions, anions, biomolecules, drugs, beverage hazards, pesticides, organic molecules, dyes, growth stimulant, etc., with exceptional performance in discriminations. Therefore, numerous reviews on the diamond electrode-based sensory utilities towards the specified analyte quantifications were published by many researchers. However, reviews on the nanodiamond-based electrodes for metal ions and anions are still not readily available nowadays. To advance the development of diamond electrodes towards the detection of diverse metal ions and anions, it is essential to provide clear and focused information on the diamond electrode synthesis, structure, and electrical properties. This review provides indispensable information on the diamond-based electrodes towards the determination of metal ions and anions.