Electrochemical Sensing Platform Research Articles

Synthesis and Characterization of Palladium/Silver Modified Reduced Graphene Oxide–Nanocomposite Platform for Electrochemical Sensors

AbstractMetal nanoparticles incorporated into carbon nanostructures have tremendous applications in the field of nanosensors and other technologies. Herein, a nanohybrid of reduced graphene oxide modified with silver and/or palladium nanoparticles (Ag/Pd/rGO) was prepared by impregnation of Pd and Ag into the rGO platform and deposited on a glass carbon electrode. Palladium and silver nanoparticles improve the stability and durability of the sensor platform by preventing the agglomeration of graphene oxide sheets and providing chemical stability against environmental factors. This ensures long‐term reliability and repeatability of the sensor performance. The morphologies and microstructures of the as‐prepared nanohybrid were characterized by X‐ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, UV–visible and infrared spectroscopy. The average crystallite size of PdAgNPs was found to be between 12 and 15 nm and demonstrated good dispersion across reduced graphene oxide sheets with high‐loading capacities. Thorough investigation of the electrochemical properties of the nanomaterial surfaces through cyclic voltammetry (CV) experiments, revealed distinct redox peaks for Ag+/Ag0 and Pd2+/Pd0 processes and demonstrated the excellent electrochemical properties of the prepared nanocomposites. The rGO‐PdAgNPs‐GCE had a diffusion coefficient value of 1.14×10−14 cm2 s−1 which is acceptable for electrochemical sensors as it is indicative of a fast response time and enhanced sensitivity to changes in gas concentration. The results obtained through thorough characterizations contributes to the novelty of the research by offering a deeper understanding of the material properties and the potential of the nanohybrid material for a broad application scope.

A natural fibre based sustainable and high-performance platform for electrochemical sensors

Sugarcane skin natural fibre based sustainable electrochemical sensors developed for wide applicability ranging from glucose sensing to heavy metal detection.

Engineering an Antifouling Electrochemical Sensing Platform Based on an All-in-One Peptide and a Hierarchical β-Bi2O3-Au Microsphere for Vancomycin Detection in Food.

Challenges associated with interference aroused by nonspecific attachment of foulants in the food matrix steered the development of sensor surfaces capable of antifouling capacity. In this study, an antifouling electrochemical sensing platform based on an all-in-one peptide (DOPA3-PPPPEKDQDKKaa) with anchoring, antifouling, and recognition functions and a hierarchical β-Bi2O3-Au microsphere was proposed for vancomycin (Van) detection in food. The β-Bi2O3-Au with excellent conductivity was synthesized and introduced as an electrode modifier to accelerate electron transfer on the sensor surface, enhancing sensing response. Mussel organism-inspired oligo DOPA, that is, oligo 3,4-dihydroxyphenylalanine, was employed as the anchoring segment of the all-in-one peptide, which is versatile for surfaces with different materials. PPPPEKDQDK and Kaa as antifouling and recognition segments confer abilities to resist nonspecific adsorption of foulants and specifically bind Van on the sensor surface, respectively. Notably, the excellent antifouling performance of the proposed sensor has been verified in protein solutions, carbohydrate solutions, and even in diluted milk and honey. Molecular dynamics simulation was carried out to explain the antifouling mechanism of the all-in-one peptide. The proposed sensor can detect Van sensitively and selectively with a relatively wide linear range (0.1-100 ng mL-1) and a limit of detection (LOD) as low as 0.038 ng mL-1 and support the quantification of Van in milk, milk powder, and honey samples with satisfactory recoveries within 105.3-110.8%. This antifouling electrochemical sensing platform offers a feasible strategy to reduce matrix interference, which guarantees the accurate detection of Van in food samples.

Graphene-Based Electrochemical Sensing Platform for Rapid and Selective Ferulic Acid Quantification

Due to the multitude of physiological functions, ferulic acid (FA) has a wide range of applications in the food, cosmetic, and pharmaceutical industries. Thus, the development of rapid, sensitive, and selective detection tools for its assay is of great interest. This study reports a new electroanalytical approach for the quantification of ferulic acid in commercial pharmaceutical samples using a sulphur-doped graphene-based electrochemical sensing platform. The few-layer graphene material (exf-SGR) was prepared by the electrochemical oxidation of graphite, at a low applied bias (5 V), in an inorganic salt mixture of Na2S2O3/(NH4)2SO4 (0.3 M each). According to the morpho-structural characterization of the material, it appears to have a high heteroatom doping degree, as proved by the presence of sulphur lines in the XRD pattern, and the C/S ratio was determined by XPS investigations to be 11.57. The electrochemical performances of a glassy carbon electrode modified with the exf-SGR toward FA detection were tested by cyclic voltammetry in both standard laboratory solutions and real sample analysis. The developed modified electrode showed a low limit of detection (30.3 nM) and excellent stability and reproducibility, proving its potential applicability as a viable solution in FA qualitative and quantitative analysis.

Gold Nanoparticles and Surfactant-Based Electrochemical Sensing Platform for the Detection and Electroanalysis of the Anticancer Drug Oxoplatin

In the current work surface of a glassy carbon electrode (GCE) is purposely modified with a suitable modifier to enhance its sensing characteristics. A composite of surfactant 1-(2, 4-initrophenyl)-dodecanoylthiourea (DAN) and gold nanoparticles (AuNPs) was employed as modified for the sensitive detection of oxoplatin (OXP), an extensively used anticancer drug. It enters into water bodies through improper handling in underdeveloped countries where drug disposal precautions are not fully respected. The designed platform (DAN/AuNPs/GCE) displays remarkable sensitivity 6.35 μA nM−1 and senses OXP with LOD of 14.5 pM under optimized conditions. The sensor was characterized by electrochemical techniques mainly cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry. The response of OXP was also examined in the artificial serum sample. The modified electrode was found to have extraordinary discrimination ability for the selected drug even in the presence of a 100-fold higher concentration of several interfering agents and displayed remarkable repeatability and reproducibility with RSD up to 3%. The role of the electrode modifier in enhancing the concentration of OXP near the transducer surface and consequently intensifying the oxidation signal of OXP was validated from experimental and computational studies.

Voltammetric Quantification of D-penicillamine by Using a Carbon Paste Electrode Modified with WO3 Nanorods and Ionic Liquid as an Efficient Electrochemical Sensing Platform

Voltammetric Quantification of D-penicillamine by Using a Carbon Paste Electrode Modified with WO3 Nanorods and Ionic Liquid as an Efficient Electrochemical Sensing Platform

Portable non‐enzymatic electrochemical biosensor based on caffeine for Alzheimer's disease diagnosis

AbstractCaffeine and its derivatives can effectively bind amyloid beta 16–22 (Aβ16–22) fragment of amyloid beta 1–42 (Aβ1–42), a biomarker for the early diagnosis of Alzheimer's disease (AD), by means of conformation selection, π–π stacking, van der Waals forces, and hydrogen bonding, so as to achieve high specificity and quantitative detection of Aβ1–42. In this study, 3‐mercaptopropionic acid (MPA), conductive polymer poly(thiophene‐3‐acetic acid) (PTAA), and pine‐like/Au pine PTAA (pine PTAA) were applied to modify the electrodes, and the non‐enzymatic caffeine was used as specific biorecognition element to study the analytical performance of the electrochemical sensor platform for Aβ1–42 oligomer (AβO). It was found that caffeine/pine PTAA‐based sensor with large surface area, high active sites, and excellent electrical conductivity demonstrated the widest linear range (10−8 to 100 nM) and highest sensitivity (743.77 Ω/log nM) in comparison. The prepared caffeine‐based sensor was afterward applied to cerebrospinal fluid and blood tests for real sample analysis, demonstrating its potential for practical use in detecting AβO at the attomolar level. Furthermore, the non‐enzymatic caffeine was constructed on the pine‐like PTAA‐modified screen‐printed electrodes for the rapid detection of AβO using portable meter.

Green Synthesis of Au Magnetic Nanocomposites Using Waste Chestnut Skins and Their Application as a Peroxidase Mimic Nanozyme Electrochemical Sensing Platform for Sodium Nitrite.

An electrochemical sensor with high sensitivity for the detection of sodium nitrite was constructed based on the peroxidase-like activity of Au magnetic nanocomposites (Au@Fe3O4). The Au@Fe3O4 composite nanoparticles were green-synthesized via the reduction of gold nanoparticles (AuNPs) from waste chestnut skins combined with the sonochemical method. The nanoparticles have both the recoverability of Fe3O4 and the advantage of being able to amplify electrical signals. Furthermore, the synergistic effect of green reduction and sonochemical synthesis provides a functional approach for the preparation of Au@Fe3O4 with significant peroxidase-like activities. The physicochemical properties were characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), the Brunauer-Emmett-Teller (BET) method, and Fourier transform infrared spectroscopy (FT-IR). The electrochemical properties of sodium nitrite were determined with cyclic voltammetry (CV) and chronoamperometry (i-t). The results revealed that Au@Fe3O4 acted as a peroxidase mimic to decompose hydrogen peroxide to produce free radicals, while ·OH was the primary free radical that promoted the oxidation of sodium nitrite. With the optimal detection system, the constructed electrochemical sensor had a high sensitivity for sodium nitrite detection. In addition, the current response had a good linear relationship with the sodium nitrite concentration in the range of 0.01-100 mmol/L. The regression equation of the working curve was y = 1.0752x + 4.4728 (R2 = 0.9949), and the LOD was 0.867 μmol/L (S/N = 3). Meanwhile, the constructed detection system was outstanding in terms of recovery and anti-interference and had a good detection stability of more than 96.59%. The sensor has been successfully applied to a variety of real samples. In view of this, the proposed novel electrochemical analysis method has great prospects for application in the fields of food quality and environmental testing.

Copper oxide anchored polyaniline modified glassy carbon electrode: A new sensor platform for the Amperometric determination of Chlorpyrifos

This work aims to develop an electrochemical sensor platform for the estimation of the insecticide, Chlorpyrifos (CPF), using copper oxide (CuxO) anchored Polyaniline (PANI) modified glassy carbon electrode (GCE) [CuxO-PANI/GCE]. Even though both the bare and PANI modified GCEs were responsive to the pesticide, CuxO-PANI-GCE was more effective towards the detection of CPF. During the cyclic voltammetric measurements, the modified electrode shows one anodic and two cathodic peaks in the bare phosphate buffer solution (PBS) which were found to be the characteristics of CuxO. After stabilizing the peak currents by running multiple cyclic voltammograms, the pesticide was introduced into the solution, which binds with the Cu in the polymer resulting in an enhancement of the peak currents. This confirms the electrocatalytic activity of the electrode against CPF. The current values of anodic as well as cathodic peaks vary linearly in the concentration range of 1-12 µM. The regression coefficient values are 0.9903 and 0.9808 for anodic and cathodic curves respectively. Using the amperometric protocols, the sensitivity of the electrode is evaluated, and we conclude that the electrode is able to produce a linear variation in the sensitivity in the concentration range of 1-11 pM with the regression coefficient value, 0.9940. The sensitivity, limit of detection (LOD), and limit of quantification (LOQ) of the electrode against the pesticide are 0.028 µA/pM, 0.54 pM, 1.8 pM respectively. The selectivity of the electrode was evaluated in the presence of other possible interfering substances and determined that the modified electrode was selective towards the estimation of CPF. The electrode was employed for the determination of CPF in honey samples to analyse its performance in real samples.

Electrochemical Sensing Platform Based on the Modification of Carbon-Ceramic Electrode with Bimetallic Fe/Mn-MOF Applied in the Determination of Nifedipine in Human Serum Samples

Background: Nifedipine, known as a calcium channel blocker, is widely used for the treatment of cardiovascular diseases such as hypertension and angina pectoris. However, its high doses are toxic and may result in a heartbeat, nausea, vomiting, etc. Methods: In the present research, the bimetallic Fe/Mn-MOF modified carbon-ceramic electrode (CCE) was used for studying the electrochemical behavior and determination of nifedipine. The presence of Fe/Mn-MOF on the surface of the CCE as an efficient modifier caused an increase in the current density of nifedipine oxidation. In this way, optimization of some effective parameters consisting of buffer type, pH, modifier concentration, etc. was successfully performed. Moreover, other analytical parameters including reproducibility, repeatability, stability, and selectivity were investigated. Results: The relative standard deviation (RSD) of peak current was 3.2 % for 10 µmol.L-1 nifedipine. Meantime, the linear range of 1-200 µmol.L-1. Additionally, limit of detection (LOD) and limit of quantification were obtained 0.24 μmol.L-1 and 0.82 µmol.L-1 respectively. The results showed that the modified electrode has a good electro-oxidation capability for nifedipine. Finally, for investigating the accuracy of the fabricated sensing assay, the determination of nifedipine in drug and human serum samples was performed. The recoveries and the related RSDs% were obtained 96.4-102% and 2.2-3.6% respectively. Conclusion: This modified electrode exhibited appropriate stability, low cost, simple preparation, fast response time, high repeatability, and good sensitivity. The obtained results clearly demonstrate the applicability of the proposed sensing assay in various matrix effects which does not affect the electrochemical response.

Electrochemical Sensing Platform Based on Carbon Dots for the Simultaneous Determination of Theophylline and Caffeine in Tea.

A simple and selective method for the determination of caffeine (CAF) and theophylline (THEO) has been developed for a glassy carbon electrode (GCE) modified with a composite including carbon dots (CDs) and chitosan (CS). To our knowledge, there are no previous studies that analyze a CDs-modified GCE for the presence of CAF and THEO. The electrochemical behavior of a GCE modified with a CDs-CS composite was studied in acidic medium by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Considering the sensor analytical parameters, the same linear concentrations range was found for CAF and THEO ranging from 1 × 10-5 to 5 × 10-3 mol L-1 with the same detection limit (LOD) of 1 × 10-6 mol L-1. The reproducibility and repeatability data were satisfactory in terms of RSD%. Moreover, the storage stability was evaluated, evidencing good results whatever the experimental conditions used. The developed sensor was applied for the simultaneous determination of CAF and THEO in tea and drug, and results were compared with those obtained with HPLC-ESI-MS in SIR mode as an independent method optimized on purpose. The electrochemical sensor presents the undoubled advantages in terms of cheapness, portability, and ease of use, since it does not require skilled personnel.

Toll-like receptor-immobilized carbon paste electrodes with plasma functionalized amine termination: Towards real-time electrochemical based triaging of gram-negative bacteria

Chronic wounds caused due to bacterial biofilms are detrimental to a patient, and an immediate diagnosis of these bacteria can aid in an effective treatment, which is still an unmet clinical need. An instant and accurate identification of bacterial type could be made by utilizing the Toll-Like Receptors (TLRs) combined with Myeloid Differentiation factor 2 (MD-2). Given this, we have developed an electrochemical sensing platform to identify the gram-negative (gram-ve) bacteria using TLR4/MD-2 complex. The nonthermal plasma (NTP) technique was utilized to functionalize amine groups onto the carbon surface to fabricate cost-effective carbon paste working electrodes (CPEs). The proposed electrochemical sensor platform with a specially engineered electrochemical cell (E-Cell) identified the Escherichia coli (E. coli) in a wide linear range of 1.5×10° - 1.5×106 C.F.U./mL, accounting for a very low detection limit of 0.087 C.F.U./mL. The novel and cost-effective sensor platform identified gram-ve bacteria predominantly in a mixture of gram positive (gram+ve) bacteria and fungi. Further, towards real-time detection of bacteria and point-of-care (PoC) applications, the effect of the pond water matrix was studied, which was minimal, and the sensor could identify E. coli concentrations selectively, showing the potential application of the proposed platform towards real-time bacterial detection.

Modified electrochemical sensor via supramolecular structural functionalized graphene oxide for ultra-sensitive detection of gallic acid

Gallic acid (GA) is a synthetic polyphenolic compound that has been increasing interest due to its diverse biological activities, including anti-inflammatory, antioxidant, anti-tumor, scavenging free radicals, protecting cardiovascular diseases, and hypertension-lowering properties. The precise and rapid determination of GA content holds significant importance for human health. In this study, we present a cost-effective and highly sensitive electrochemical sensor employing a nanocomposite material, diester calix[4]arene functionalized graphene oxide (DEC4/GO) for the ultrasensitive detection of GA. The characterization of the as-synthesized nanocomposite material was carried out using various techniques, such as Fourier-Transform infrared (FT-IR), Raman spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Tunneling Electron Microscopy (TEM), to ascertain its chemical composition, crystalline nature, phase purity, and structural morphology. The uniform deposition of DEC4/GO on the surface of a bare glass carbon electrode (GCE) was achieved via a drop casting method. In addition, the developed sensor DEC4/GO/GCE exhibits exceptional electrochemical response towards GA under optimized conditions, such as pH -7 phosphate-buffered saline (PBS) as a supporting electrolyte, a scan rate of 110 mV/s, and an applied potential window between −0.2 V and 0.8 V. The as-developed sensor demonstrated a wide linear dynamic range of 10–100 μM, resulting a brilliant linear calibration obtained for GA. Furthermore, the limit of detection (LOD) and quantification (LOQ) of the developed sensor were calculated as 0.01 and 0.03 μM respectively, lower than those reported for the other GA sensors. To validate the feasibility of our developed method, we analyzed the GA content in wine and green tea samples, achieving good recovery results. Overall, this study presents a promising electrochemical sensor platform for ultrasensitive detection of GA holding potential implications for various applications in health monitoring and food analysis.

Smartphone-Assisted Flexible Electrochemical Sensor Platform by a Homology DNA Nanomanager Tailored for Multiple Cancer Markers Field Inspection.

In this work, an ingenious sensor technology was established by integrating the EBFCs on a flexible paper strip carrier (PE) that was used for simultaneous detection of tumor markers in complex samples. Adopting high performance ultrathin graphdiyne (U-GDY) as the substrate can increase the enzyme load, accelerate the electron transfer rate, and significantly enhance the detection sensitivity. A homologous DNA nanomanager strategy cleverly uses signal switches to recycle and amplify target miRNAs, while the smartphone receives real-time instantaneous current values to realize multivariate detection. Electrochemical data show that the detection limits (LODs) of miRNA-21 and miRNA-155 are 0.09 and 0.15 fM in the wide concentration range. The results confirm that the tailored sensor platform provides a strategy for the early cancer diagnosis and lays the foundation for the construction of a flexible wearable platform.

Disposable Miniaturized Electrochemical Sensing Platform With Laser-Induced Reduced Graphene Oxide Electrodes for Multiplexed Biochemical Analysis.

Metabolic biomarkers, such as Dopamine (DA), Uric acid (UA), and Ascorbic acid (AA), have significant roles in determining the physiological functioning of the human body. These are often analyzed through clinical lab-based procedures which are bulky and require skilled technicians. In view of this, the design, development, and fabrication of a portable, cost-effective, user-friendly, and disposable device for electro-analytical detection, leading to point-of-care (POC) detection of these metabolic biomarkers is a pressing need. This work reports a laser-induced reduced graphene oxide (LIrGO) based miniaturized paper device fabricated by laser ablation of a lab-grade paper using a blue diode laser (450 nm). A three-electrode electrochemical platform was designed with the LIrGO electrodes, whereby bare rGO electrodes were employed as working and counter electrodes, and Ag/AgCl ink-coated rGO was used as the reference electrode. The device was characterized morphologically by Scanning Electron Microscopy (SEM) and electrochemically by a potentiostat. The prepared device was subjected to electrochemical sensing of Dopamine (DA), Uric Acid (UA), and Ascorbic Acid (AA). Furthermore, the effects of several sensory parameters, such as concentration, pH, and interference, were analyzed. A linear range of 10- [Formula: see text] was obtained for all three analytes with the limit of detection (LoD) being [Formula: see text], [Formula: see text], [Formula: see text], and the limit of quantification (LoQ) being [Formula: see text], [Formula: see text], [Formula: see text] for DA, UA and AA, respectively. Finally, the device was tested for non-interference with co-analytes and validated by testing a real sample of human blood serum. This work demonstrates a proof-of-principle of utilizing bare LIrGO for selective sensing which will open door to multiplexed and POC sensing.

Nonenzymatic Electrochemical Sensing Platform Based on 2D Isomorphic Co/Ni-Metal-Organic Frameworks for Glucose Detection.

Two-dimensional metal-organic framework (MOF) crystalline materials possess promising potential in the electrochemical sensing process owing to their tunable structures, high specific surface area, and abundant metal active sites; however, developing MOF-based nonenzymatic glucose (Glu) sensors which combine electrochemical activity and environmental stability remains a challenge. Herein, utilizing the tripodic nitrogen-bridged 1,3,5-tris(1-imidazolyl) benzene (TIB) linker, Co2+ and Ni2+, two 2D isomorphic crystalline materials, including Co/Ni-MOF {[Co (TIB)]·2BF4} (CTGU-31) and {[Ni(TIB)]·2NO3} (CTGU-32), with a binodal (3, 6)-connected kgd topological net were firstly synthesized and fabricated with conducting acetylene black (AB). When modified on a glassy carbon electrode, the optimized AB/CTGU-32 (1:1) electrocatalyst demonstrated a higher sensitivity of 2.198 μA μM-1 cm-2, a wider linear range from 10 to 4000 μM, and a lower detection limit (LOD) value (0.09 μM, S/N = 3) compared to previously MOF-based Glu sensors. Moreover, AB/CTGU-32 (1:1) exhibited desirable stability for at least 2000 s during the electrochemical process. The work indicates that MOF-based electrocatalysts are a promising candidate for monitoring Glu and demonstrate their potential for preliminary screening for diabetes.

Copper Nanoparticles and Reduced Graphene Oxide as an Electrode Modifier for the Development of an Electrochemical Sensing Platform for Chloroquine Phosphate Determination.

This study describes the use of copper nanoparticles (CuNPs) and reduced graphene oxide (rGO) as an electrode modifier for the determination of chloroquine phosphate (CQP). The synthetized rGO-CuNPs composite was morphologically characterized using scanning electron microscopy and electrochemically characterized using cyclic voltammetry. The parameters were optimized and the developed electrochemical sensor was applied in the determination of CQP using square-wave voltammetry (SWV). The analytical range for the determination of CQP was 0.5 to 110 μmol L-1 (one of the highest linear ranges for CQP considering electrochemical sensors), with limits of detection and quantification of 0.23 and 0.78 μmol L-1, respectively. Finally, the glassy carbon (GC) electrode modified with rGO-CuNPs was used for quantification of CQP in tap water; a study was carried out with interferents using SWV and obtained great results. The use of rGO-CuNP material as an electrode modifier was thus shown to be a good alternative for the development of low-cost devices for CQP analysis.

MOFs-based Fe@YAU-101/GCE electrochemical sensor platform for highly selective detecting trace multiplex heavy metal ions

The construction of sensors with specific recognition functions can easily, sensitively and efficiently detect heavy metal ions, which is a demand in the field of electrochemical sensing and an important topic in the detection of environmental pollutants. An electrochemical sensor based on MOFs composites was developed for sensing of multiplex metal ions. The large surface area, adjustable porosities and channels in MOFs facilitate successful loading of sufficient quantities highly active units. The active units and pore structures of MOFs are regulated and synergetic with each other to enhance the electrochemical activity of MOFs composites. Thus, the selectivity, sensitivity and reproducibility of MOFs composites have been improved. Fortunately, after characterization, Fe@YAU-101/GCE sensor with strong signal was successfully constructed. In the presence of target metal ions in solution, the Fe@YAU-101/GCE can efficiently and synchronously identify Hg2+, Pb2+, and Cd2+. The detection limits (LOD) are 6.67 × 10−10 M(Cd2+), 3.33 × 10−10 M(Pb2+) and 1.33 × 10−8 M (Hg2+), and are superior to the permissible limits set by the National Environmental Protection Agency. The electrochemical sensor is simple without sophisticated instrumentation and testing processes, hence promising for practical applications.

ZIFs-derived Hollow CoS2/N-doped Mesoporous Graphite Carbon Nanocages as an Electrochemical Sensing Platform for Hydrazine Detection in Food

The design and construction of a promising electrode is attractive for the sensitive and selective detection of hydrazine. In this paper, hollow CoS2/N-doped mesoporous graphite carbon nanocages (CoS2/HNGC) were synthesized derived from ZIF-8@ZIF-67 by annealing and sulfidation. In situ nitrogen coordination and self-compounding porous carbon with hollow structure can effectively improve electrocatalytic performance and electron transfer rate of catalyst electrode. The sensor has good performance for hydrazine with a wide linear range of 1 μM − 3 mM, high sensitivity of 2384 μA mM−1 cm−2, and detection limit of 0.272 μM (S/N = 3). In addition, the fine selectivity and the application of this sensor in food hydrazine detection suggest that CoS2/HNGC can be used as an efficient electrochemical detection material for hydrazine.

Craft-and-Stick Xurographic Manufacturing of Integrated Microfluidic Electrochemical Sensing Platform

An innovative modular approach for facile design and construction of flexible microfluidic biosensor platforms based on a dry manufacturing "craft-and-stick" approach is developed. The design and fabrication of the flexible graphene paper electrode (GPE) unit and polyethylene tetraphthalate sheet (PET)6/adhesive fluidic unit are completed by an economic and generic xurographic craft approach. The GPE widths and the microfluidic channels can be constructed down to 300 μm and 200 μm, respectively. Both units were assembled by simple double-sided adhesive tapes into a microfluidic integrated GPE (MF-iGPE) that are flexible, thin (<0.5 mm), and lightweight (0.4 g). We further functionalized the iGPE with Prussian blue and glucose oxidase for the fabrication of MF-iGPE glucose biosensors. With a closed-channel PET fluidic pattern, the MF-iGPE glucose biosensors were packaged and sealed to protect the integrated device from moisture for storage and could easily open with scissors for sample loading. Our glucose biosensors showed 2 linear dynamic regions of 0.05-1.0 and 1.0-5.5 mmol L-1 glucose. The MF-iGPE showed good reproducibility for glucose detection (RSD < 6.1%, n = 6) and required only 10 μL of the analyte. This modular craft-and-stick manufacturing approach could potentially further develop along the concept of paper-crafted model assembly kits suitable for low-resource laboratories or classroom settings.