Portable Electrochemical System Research Articles

Nafion/graphite-bismuth nanoplate with a vibration unit for portable heavy metal ion detection

Contamination of natural resources, particularly water sources, by heavy metal ions, even at low concentrations, poses a significant threat to ecosystems and human health, underscoring the importance of developing sensors with point-of-use (POU) applications. To that end, a vibration-unit-equipped portable electrochemical system (vPES) capable of extremely sensitive detection of Pb2+ and Cd2+ in water is reported herein. The vibration unit enhances sensitivity by facilitating sample diffusion, and its compactness makes it suitable for point-of-use applications through mobile phone connectivity. The system also integrates Nafion and a graphite/bismuth-nanoplate-functionalized screen-printed carbon electrode to detect heavy metals efficiently. The approach implemented in this study and validated through experiments and simulations suggests that vibration-based mixing leads to 540 % and 511 % higher Pb2+ and Cd2+ detection efficiencies, respectively, than those in the absence of vibration. Additionally, the sensor exhibits the limits of detection of 0.98 and 1.65 nM for Pb2+ and Cd2+, respectively, in laboratory environments. Samples collected from the Nakdong River in Korea and real environmental specimens—freshwater, soil, and serum—validate the detection performance. Overall, this study highlights the potential of vPES as a rapid, sensitive POU sensor for heavy metal detection, thereby bolstering environmental and public health monitoring efforts.

Portable Electrochemical System and Platform with Point-of-Care Determination of Urine Albumin-to-Creatinine Ratio to Evaluate Chronic Kidney Disease and Cardiorenal Syndrome.

The urine albumin (Alb)-to-creatinine (Crn) ratio (UACR) is a sensitive and early indicator of chronic kidney disease (CKD) and cardiorenal syndrome. This study developed a portable and wireless electrochemical-sensing platform for the sensitive and accurate determination of UACR. The developed platform consists of a carbon nanotube (CNT)-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)(ABTS)-based modified UACR sensor, a miniaturised potentiostat, a cup holder embedded with a magnetic stirrer and a smartphone app. The UACR sensing electrode is composed of two screen-printed carbon working electrodes, one screen-printed carbon counter electrode and a screen-printed AgCl reference electrode. The miniaturised potentiostat, which is controlled by the developed app, performs cyclic voltammetry and amperometry to detect Alb and Crn, respectively. Clinical trials of the proposed system by using spot urine samples from 30 diabetic patients indicate that it can accurately classify all three CKD risk statuses within 30 min. The high accuracy of our proposed sensing system exhibits satisfactory agreement with the commercial biochemical analyser TBA-25FR (Y = 0.999X, R2 = 0.995). The proposed UACR sensing system offers a convenient, reliable and affordable solution for personal mobile health monitoring and point-of-care urinalysis.

An enzyme-free and ratiometric biosensor for single nucleotide polymorphism with portable electrochemical system

Portable, low-cost and efficient biosensing systems are valuable for single nucleotide polymorphisms (SNPs) analysis, particularly in resource-limited fields. Herein, a rapid, enzyme-free and ratiometric SNPs biosensor with portable electrochemical system enabling simultaneous recognition and signal amplification is proposed. To demonstrate its versatility and effectiveness, we have selected the human cancer-related KRAS gene and the soybean mosaic virus resistance Rsv3 gene as our analysis models. Our biosensor is constructed based on a combination of strand displacement reactions and hybridization chain reactions (HCR). This unique design enables to differentiate between mutant (MT) and wild (WD) sequences based on the differential release of HCR products on the electrode surfaces. Importantly, this enzyme-free SNPs biosensor concurrently achieves both SNPs recognition and signal amplification, significantly reducing the reaction time to just 40 minutes. Furthermore, we have developed a miniaturized biosensor system that incorporates screen printed gold electrodes (SPGE) and smartphones. This system is integrated with a ratiometric strategy with an limit of detection as low as 1.2 fM, enhancing accuracy and eliminating external interference. This simple SNPs biosensing system possesses high reliability, positioning it as a versatile biosensor for the determination of various SNPs mutations.

Field Determination and Spatial Distribution of Se (IV) in Coastal Seawater of China

A portable electrochemical system based on rGO/AuNPs/Nafion was constructed for selenium (IV) field determination in coastal seawater of the North Yellow Sea, East China Sea and South China Sea. This system demonstrated a low determination limit (0.03 μg/L), a wide linear range of concentration (0.1–30 μg/L), exceptional reproducibility and repeatability, and excellent selectivity. Each individual, entire test could be accomplished within 8 min. In Yantai Sishili Bay, the Se (IV) concentrations ranged from 0.16–3.59 μg/L (average 1.43 μg/L). In Shengshan Island, the Se (IV) concentrations ranged from 0.20–5.18 μg/L (average 2.06 μg/L). In Zhelin Bay, the Se (IV) concentrations ranged from 0.87–4.87 μg/L (average 3.13 μg/L). The average concentrations of Se (IV) in surface seawater showcased an increasing trend from the north to the south of China, suggesting Zhelin Bay > Shengshan Island > Sishili Bay. The system develops a new, competitive method for water quality assessment, and contributes to the accurate study of the biogeochemical cycles of selenium.

Competitive smartphone-based portable electrochemical aptasensor system based on an MXene/cDNA-MB probe for the determination of Microcystin-LR

A competitive smartphone-based portable electrochemical aptamer sensing system was developed for MC-LR detection. The platform was composed with a smartphone-controlled portable electrochemical system, a smartphone with custom application and a screen-printed carbon electrode (SPCE). The portable electrochemical system consisted a homemade ARM STM32 with chronoamperometry (CA), cyclic voltammetry (CV) and square wave voltammetry (SWV) modules that had a similar performance to commercial electrochemical workstations. The control of the portable electrochemical system, reception and visualization of the assay results were implemented by a smartphone. SPCE was modified by in situ electrodeposition with gold nanoparticles (AuNPs) and reduced graphene oxide (rGO). Subsequently, the aptamer was incubated onto the SPCE through Au-S bonds. The complementary DNA labeled with methylene blue (cDNA-MB) was conjugated onto the surface of MXene to form the probe for signal amplification. The competitive aptasensor was accomplished when the probe was complemented with the aptamer. The fabricated system exhibited the outstanding capability for the determination of MC-LR over a range of 0.0001–5 nM with a limit of detection of 4 × 10−5 nM. Furthermore, the system demonstrated acceptable stability, reproducibility, specificity and high recovery rate. The smartphone-based competitive aptasensor system exhibited the merits of portability, low-cost and fast-response to satisfy the demand for on-site detection of MC-LR.

Dual nanocatalysts co-decorated three-dimensional, laser-induced graphene hybrid nanomaterials integrated with a smartphone portable electrochemical system for point-of-care non-enzymatic glucose diagnosis

Non-enzymatic biosensors based on various nanomaterials with large surface-volume ratios and high catalytic efficiencies have been proposed to compensate for the non-stability and high cost of enzymatic biosensors. However, the construction of a stable, highly sensitive, flexible, three-dimensional (3D), microstructured, non-enzymatic biosensor integrated with a smartphone-based portable system has been challenging. Herein, highly conductive laser-induced graphene (LIG) array with a honeycomb-like 3D microstructure co-decorated with copper(I) oxide and gold nanocatalysts was developed via simple and green electro-deposition and chemical reduction approaches for a miniaturized electrochemical flexible non-enzymatic biosensor. SEM, XRD, Raman and XPS analyzations indicated that the Cu2O and Au nanocatalysts co-decorated three-dimensional, laser-induced graphene hybrid nanomaterials were developed successfully. The signal of the biosensor was improved by more than 10 fold compared to the LIG alone due to the co-decorated with copper(I) oxide and gold nanocatalysts. The fabricated electrochemical biochip was integrated with a smartphone-based microstation for glucose monitoring, presenting a larger linear interval of 1–20 mM with an excellent sensitivity of 236 μA/mM/cm2 and a relatively low detection limit of 0.31 μM. Noticeably, the biochip could measure blood sugar on curved surfaces and still deliver stable sensing signals after being bent back-and-forth 25 times. The novel biosensor is a potentially valuable flexible electronic device. The hybrid nanomaterials developed in this work may be applicable to other biosensing, catalytic, and energy devices (supercapacitors and batteries).

Production of 3D-printed disposable electrochemical sensors for glucose detection using a conductive filament modified with nickel microparticles

Three-dimensional printing techniques have been widely used in the fabrication of new materials applied to energy, sensing and electronics due to unique advantages, such as fast prototyping, reduced waste generation, and multiple fabrication designs. In this paper, the production of a conductive 3D-printing filament composed of Ni(OH)2 microparticles and graphene within a polylactic acid matrix (Ni-G-PLA) is reported. The nanocomposite was characterized by thermogravimetric, energy-dispersive X-ray spectroscopic, scanning electronic microscopic, Raman spectroscopic and electrochemical techniques. Characteristics such as printability (using fused deposition modelling), electrical conductivity and mechanical stability of the polymer nanocomposite were evaluated before and after 3D printing. The novel 3D-printed disposable electrode was applied for selective detection of glucose (enzyme-less sensor) with a detection limit of 2.4 μmol L−1, free from the interference of ascorbic acid, urea and uric acid, compounds typically found in biological samples. The sensor was assembled in a portable electrochemical system that enables fast (160 injection h−1), precise (RSD < 5%) and selective determination of glucose without the need of enzymes (electrocatalytic properties of the Ni-G-PLA nanocomposite). The obtained results showed that Ni-G-PLA is a promising material for the production of disposable sensors for selective detection of glucose using a simple and low-cost 3D-printer.

A multi-functional minimally-disruptive portable electrochemical system based on yeast/Co3O4/Au/SPEs for blood lead (II) measurement

A minimally-disruptive portable electrochemical system is constructed by combining a hand-held syringe as reservoir with disposable screen-printed electrodes (SPEs) modified with a simple and efficient yeast/Co3O4/Au material for lead determination by a square-wave voltammetry (SWV) method. Not only can it preserve the operation and advantages of the conventional electrochemical procedure, but it also integrates sampling, filtering and analysis to make the determination of lead convenient and effective at higher and lower concentration levels. This is the first report of a microbial biosensor based on active yeast crosslinked to Co3O4/Au particles using glutaraldehyde as the crosslinking agent. The determination process is simplified by introducing a fiber filter and takes only 150 s with the developed system, which illustrates its simplicity, speed and detection accuracy. Also, the design shows a wide log-linear dynamic range (LDR) from 10−8 to 10−14 g·L−1, with a limit of detection (LOD) of 3.45 × 10−15 g·L−1 (S/N = 3). Additionally, the proposed system was used to determine lead in blood samples, which demonstrated the potential of this biosensor for use in practical applications. Furthermore, this study provides a basis for the development of microscale blood devices for lead measurement.

A Portable Electrochemical System for the On-Site Detection of Heavy Metals in Farmland Soil Based on Electrochemical Sensors

In this paper, a portable electrochemical system for the on-site detection of heavy metals (HMs) in farmland soil is developed, characterized, and evaluated. The system has a three-electrode configuration and includes a signal acquisition and processing device and a computer, which integrates a microcontroller-based potentiostat to implement square-wave anodic stripping voltammetry at a bismuth-film-modified glassy carbon electrode. In addition, three analysis methods, namely, the standard addition method, the bivariate regression model, and double-stripping voltammetry, were integrated into this system for the on-site detection of HMs to meet different analysis requirements. One unique characteristic of the system is its custom software, which enables calculations based on all three analysis methods. Moreover, stripping peak currents and background currents can be identified and acquired automatically by two of the developed algorithms. The system was assessed by applying it to detect Pb(II) and Cd(II) in an acetate buffer solution and acetic acid soil extracts. The interference of Cu(II) can be inhibited by adding 0.1-mM ferrocyanide to the real sample exacts by complexation. The results indicate that the system was sensitive, effective, and reliable and has broad application prospects in the field of on-site analysis. In addition, the system can be used by non-specialist personnel.

A miniaturized electrochemical system for high sensitive determination of chromium(VI) by screen-printed carbon electrode with gold nanoparticles modification

Chromium(VI) has been known as a toxic heavy metal ion that can cause adverse effects to human health, including carcinogenic effects. An approach that can detect chromium(VI) in a rapid, sensitive and portable manner is of great importance. This paper presents a miniaturized portable electrochemical system for chromium(VI) determination based on a screen-printed carbon electrode with gold nanoparticles modification. The miniaturized electrochemical system is composed of an analyzer, a detection module integrated with a screen-printed carbon electrode and a laptop or smartphone. Gold nanoparticles were modified on the working electrode in screen-printed carbon electrode to implement high sensitive detection of chromium(VI). The effect of pH, different supporting electrolyte and scan rate were studied. With the optimized conditions, the calibration curve for chromium(VI) shows a sensitivity of 1.1 nA(μg/L)−1 and a linearity of 0.999 from 20 μg/L to 200 μg/L with a limit of detection of 5.4 μg/L. The results suggest that this system could provide a promising platform for in-situ, rapid and sensitive detection of chromium (VI) in water.

Portable electrochemical system using screen-printed electrodes for monitoring corrosion inhibitors

This work presents a portable electrochemical system for the continuous monitoring of corrosion inhibitors in a wide range of matrices including ethanol, seawater and mineral oil following simple dilution of the samples. Proof-of-concept is demonstrated for the sensing of 2,5-dimercapto-1,3,5-thiadiazole (DMCT), an important corrosion inhibitor. Disposable screen-printed graphitic electrodes (SPGEs) associated with a portable batch-injection cell are proposed for the amperometric determination of DMCT following sample dilution with electrolyte (95% v/v ethanol + 5% v/v 0.1molL-1 H2SO4 solution). This electrolyte was compatible with all samples and the organic-resistant SPGE could be used continuously for more than 200 injections (100µL injected at 193µLs-1) free from effects of adsorption of DMCT, which have a great affinity for metallic surfaces, and dissolution of the other reported SPGE inks which has hampered prior research efforts. Fast (180h-1) and precise responses (RSD < 3% n = 10) with a detection limit of 0.3µmolL-1 was obtained. The accuracy of the proposed method was attested through recovery tests (93–106%) and the reasonable agreement of results of DMCT concentrations in samples analyzed by both proposed and spectrophotometric (comparative) methods.

A Compact Batch Injection Analysis Cell for Screen Printed Electrodes: A Portable Electrochemical System for On‐site Analysis

AbstractHerein, a compact batch injection analysis cell for screen printed electrodes (BIASPE cell) is reported. The proposed system shows several requirements of a portable system that include easy‐to‐operate (“user‐friendly”), high‐speed quantitative and qualitative analysis, excellent cost effectiveness, and low‐power requirements (all auxiliary components are battery‐powered). Similar to analytical microsystems, small volumes of samples (5 to 100 μL) are required for analysis, however, the robustness of the system here proposed is considerably higher. The combination of the BIASPE cell with battery‐powered accessories (electronic micropipette, potentiostat and tablet or laptop computer) can be considered as a robust portable electroanalytical system. Electrochemical methods with portable characteristics can be now easily developed.

Combination of screen-printed electrodes and batch injection analysis: A simple, robust, high-throughput, and portable electrochemical system

To date, both screen-printed electrodes (SPEs) and batch injection analysis (BIA) systems are separately used in the development of analytical methods with portable characteristics. In this work, for the first time, a BIA cell was designed to adapt SPEs for use as a robust portable electroanalytical system. This system in combination with other battery-powered components (electronic pipette, mini-potentiostat, and laptop computer) can be operated outside a laboratory, in the absence of an external power supply. The performance of the portable system has been evaluated using diclofenac, hydrogen peroxide and metals (Pb, Cu, and Hg) as model analytes. In addition to the portability characteristics (low cost, low-power requirements, quick response, simplicity, robustness, and minimal sample size requirements), the proposed approach also allows the implementation of simple and effective strategies to prevent or minimize the gradual fouling of the electrode surface (common limitation of solid electrodes). Therefore, the proposed portable electrochemical system offers promise to increase the use of electrochemical methods for point-of-care or on-site analysis.

Micro electrochemical sensor with copper nanoclusters for nitrate determination in freshwaters

A microsensor chip was fabricated by micro electromechanical system technology, and a portable electrochemical system for nitrate determination in freshwaters was developed. As the electrocatalyst material, copper was electrodeposited onto the working-electrode of the microsensor by the cyclic voltammetry method. It was found that the deposited layer was porous and constructed by copper nanoclusters. The electrochemical response of the modified microsensor for nitrate under acidic conditions (pH=2.0) was characterised by linear sweep voltammetry. Calibration in standard nitrate samples in the range of 6.25–300 µmol/l yielded straight lines: y1 [µA]=−0.0526x–3.905 (R12=0.9993), while in the range of 300–3500 µmol/l yielded straight lines: y2 [µA]=−0.0353x–13.653 (R22=0.9918). It was found that the modified microsensor performed at higher sensitivity in nitrate detection than previous works and the limit of detection is 5 µmol/l (S/N≥3). Interference analysis with nine kinds of ions (NO2−, Cl−, HPO42−/PO43−, SO42−, HCO3−/CO32−, Na+ and K+) commonly found in water indicated that only NO2− causes reasonable interference (i.e. 10% signal distortion). Based on the modified microsensor, the developed portable electrochemical system was employed for nitrate determination in three freshwater samples. The results were in good agreement with the data obtained by the ultraviolet spectrophotometric method.

Fabrication of a microfluidic Ag/AgCl reference electrode and its application for portable and disposable electrochemical microchips

This report describes a convenient method for the fabrication of a miniaturized, reliable Ag/AgCl reference electrode with nanofluidic channels acting as a salt bridge that can be easily integrated into microfluidic chips. The Ag/AgCl reference electrode shows high stability with millivolt variations. We demonstrated the application of this reference electrode in a portable microfluidic chip that is connected to a USB-port microelectrochemical station and to a computer for data collection and analysis. The low fabrication cost of the chip with the potential for mass production makes it disposable and an excellent candidate for real-world analysis and measurement. We used the chip to quantitatively analyze the concentrations of heavy metal ions (Cd(2+) and Pb(2+)) in sea water. We believe that the Ag/AgCl reference microelectrode and the portable electrochemical system will be of interest to people in microfluidics, environmental science, clinical diagnostics, and food research.

Simultaneous determination of dihydroxybenzene isomers using disposable screen-printed electrode modified by multiwalled carbon nanotubes and gold nanoparticles

A disposable electrode, modified with multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs), was developed to serve as a sensor for the simultaneous determination of dihydroxybenzene isomers (hydroquinone, catechol and resorcinol). The modified electrode was fabricated by electrodepositing AuNPs on a MWCNTs decorated screen-printed electrode (SPE), then it was characterized in morphology and electrochemical properties and utilized to determine the isomers of dihydroxybenzene in water samples. Compared with bare SPE, AuNPs-modified SPE, and MWCNTs-modified SPE, the fabricated SPE has much stronger electrocatalytic activity for the oxidation of dihydroxybenzenes with the increase of the peak current and the decrease of the potential difference (△Ep) between the anodic and cathodic peaks. By using differential pulse voltammetry (DPV), the three isomers can be determined simultaneously and sensitively at the modified SPE. For hydroquinone, catechol and resorcinol, the oxidation peak currents are linear to the concentrations at the range of 2.0 × 10−6∼7.3 × 10−4 M, 2.0 × 10−6∼7.3 × 10−4 M and 3.0 × 10−6∼9.6 × 10−4 M with the detection limits of 3.9 × 10−7 M, 2.6 × 10−7 M and 7.2 × 10−7 M, respectively. Moreover, a rapid on-filed determination is convenient to be performed at this disposable modified SPE incorporated in a portable electrochemical system. These results reveal that the presented sensor can be used for the simultaneous and sensitive on-field determination of dihydroxybenzene isomers.