Tryptophan (TRY) is an essential amino acid associated with neurotransmitters and some particular syndromes. For that reason, the detection of Try levels in the food samples is necessary. In recent ...years electrochemical sensors exhibit inherent effect to detect the amino acids because it has more benefits such as high sensitivity, simplicity, celerity, and economy compared to other traditional methods. Some bimetal oxides have emerged as good candidates for the trace-level detection of amino acids due to their large surface area and high conductivity. As the carbon-based materials, importantly reduced graphene oxide (RGO) have large surface areas to increase the conductivity of the electrodes. In this present work, we demonstrate the detection of TRY by using an electrochemical sensor based on a bimetal oxide with RGO nanocomposite material. We synthesized a manganese tungstate-nanoplates-encapsulated reduced graphene oxide nanocomposite (MnWO4/RGO) using a facile hydrothermal method. Morphological and structural characterization of the nanocomposite MnWO4/RGO was performed using various spectroscopic techniques and analytical methods. The resulting MnWO4/RGO/GCE could be used for the quick and selective determination of TRY in the presence of other interfering bioanalytes. Under optimum conditions, this electrochemical sensor exhibited maximum performance toward TRY determination with good linearity in a broad linear range of 0.001–120 μM with a remarkable lower detection limit of 4.4 nM. The newly proposed sensor was used for the precise determination of TRY in milk samples with satisfactory results.
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•MnWO4/RGO nanocomposite prepared by the facile hydrothermal route without external reducing agent and surfactants.•MnWO4 nanoplates encapsulated on RGO nanosheets modified electrode is an efficient nanocatalyst for the detection of Tryptophan.•MnWO4/RGO sensor exhibit lower detection limit, wide linear range and good recoveries for Tryptophan in Milk samples.
Due to recent legalization of marijuana across many states in the U.S., there is an increased concern of users driving while impaired/intoxicated with Δ9‐tetrahydrocannabinol (Δ9‐THC), the principal ...psychoactive constituent of cannabis/marijuana. Hence, there is a need for a rapid roadside detection of this drug that can be used to accurately screen drivers. Current field sobriety tests rely on a series of physical and mental exercises administered during DUI investigations to help determine a driver's level of impairment. Due to their portability and effectiveness, screen printed carbon electrodes (SPCEs) are ideal to work with when it comes to devising a low‐cost screening device for roadside testing. SPCE's can potentially detect low levels of Δ9‐THC in an individual's saliva via electrochemical oxidation of Δ9‐THC. Herein we report a fast, cheap, and accurate approach to electrochemically detect 1–20 μM Δ9‐THC in a 1 mL sample of artificial oral fluid (AF‐OF) diluted to 50 % with a buffer/electrolyte solution using differential pulse voltammetry (DPV) at the surface of a small SPCE. Implications for the use of this method to screen intoxicated drivers are discussed.
A three-dimensional g-C3N4/MWNTs/GO hybrid modified electrode was constructed as an electrochemical sensor for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). ...Due to the high conductivity of MWCNTs and the strong synergy between g-C3N4 and GO, the combination of the three effectively improved the electrocatalytic activity of the modified electrode for the oxidation of AA, DA, and UA, and solved the problems such as overlapping anodic peaks. The electrochemical performance of the as-constructed sensor was investigated and optimized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The linear response range of AA, DA, and UA in the optimal condition was 0.2–7.5 mM, 2–100 μM, and 4–200 μM, respectively. The detection limits (S/N = 3) of AA, DA, and UA were 96, 0.22, and 1.36 μM, respectively. The recoveries of AA, DA and UA in serum samples from three groups were 92.82–106.50%, and the relative standard deviations were less than 2%. The results show that the as-constructed g-C3N4/MWNTs/GO modified electrode has the advantages of simplicity, high sensitivity and good selectivity, and can simultaneously determine AA, DA, and UA.
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•A three-dimensional g-C3N4/MWNTs/GO hybrid electrode was constructed as an electrochemical sensor.•g-C3N4/MWNTs/GO hybrid sensor can simultaneously determine DA, AA, and UA.•The recoveries of DA, AA and UA in serum samples from three groups were 92.82–106.50%.•g-C3N4/MWNTs/GO hybrid sensor has the advantages of simplicity, high sensitivity and good selectivity.
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•A quantitative POCT system is developed for simultaneous detection of multiple metal ions.•The system consists of a hand-held electrochemical analyzer, a smartphone, and a customized ...SPCE.•The customized SPCE was prepared by successive modification of SPCE with rGO, the SMOF and PEI.•Smartphones installed with APP DHMI can realize two-way communication with electrochemical analyzer.•Quantitation results of this POCT system correlate well with ICP-MS measurements.
It is of great significance to develop versatile and cost-effective point-of-care testing (POCT) systems for simultaneous quantitation of multiple analytes on-site. This work reports on: 1) the customized electrodes which exhibit good analytical performance for simultaneous detection of Cd2+, Cu2+, Hg2+, Pb2+ with low detection limits (Cd2+, 0.296 μM; Cu2+, 0.055 μM; Hg2+, 0.351 μM; and Pb2+, 0.025 μM) and wide dynamic ranges (Cd2+, 0.50–12.5 μM; Cu2+, 0.10–9.50 μM; Hg2+, 0.50–12.5 μM; and Pb2+, 0.10–12.5 μM) using differential pulse voltammetry (DPV) measurements. 2) a hand-held electrochemical analyzer which can realize two-way communication with a smartphone and implement DPV measurements; its cost, weight and power consumption are ~$10.0, ~30 g and ~ 253 mW, respectively; 3) a self-developed APP DHMI which can control the analyzer, receive data from the analyzer, and plot the voltammograms on smartphone’s screen in real-time. This quantitative POCT system has been successfully demonstrated for simultaneous quantitation of Cd2+, Cu2+, Hg2+, Pb2+ in tap water, mineral water and Pearl River water, and the quantitation results correlated well with ICP-MS measurements. The features of cost-effectiveness, ease-to-use and reliability make this quantitative POCT system useful for on-site monitoring of multiple heavy metal ions, especially in resource-constrained environments.
n-Doped conjugated polymers usually show low electrical conductivities and low thermoelectric power factors, limiting their applications in n-type organic thermoelectrics. Here, we report the ...synthesis of a new diketopyrrolopyrrole (DPP) derivative, pyrazine-flanked DPP (PzDPP), with the deepest LUMO level in all the reported DPP derivatives. Based on PzDPP, a donor–acceptor copolymer, P(PzDPP-CT2), is synthesized. The polymer displays a deep LUMO energy level and strong interchain interaction with a short π–π stacking distance of 3.38 Å. When doped with n-dopant N-DMBI, P(PzDPP-CT2) exhibits high n-type electrical conductivities of up to 8.4 S cm–1 and power factors of up to 57.3 μW m–1 K–2. These values are much higher than previously reported n-doped DPP polymers, and the power factor also ranks the highest in solution-processable n-doped conjugated polymers. These results suggest that PzDPP is a promising high-performance building block for n-type organic thermoelectrics and also highlight that, without sacrificing polymer interchain interactions, efficient n-doping can be realized in conjugated polymers with careful molecular engineering.
•An electrochemical sensor was fabricated based on ionic surfactant modified graphene paste electrode.•Ability of surfactant modified graphene paste electrode for the individual and simultaneous ...analysis of vanillin and caffeine.•Developed electrode was characterized by LSV, CV, FESEM, and DPV technique.•The practicality of the developed electrode has been determined.
This paper describes a simple approach for the determination of vanillin (VN) based on the ionic surfactant modified graphene paste electrode. The electrochemical behavior of VN at the modified electrode is investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), suggests the modified electrode exhibits excellent electrochemical activity towards VN compared to the bare electrode. VN shows an irreversible behavior, and the nature of the electrode response was noticed to be adsorption controlled. Under the optimized conditions, the anodic peak current for VN was proportional to VN concentration from 4 × 10−6 to 1.5 × 10−5 M and 2 × 10−5 to 7 × 10−5 M with a limit of detection 1.29 µM. The developed method was effectively applied in the determination of VN in commercial food samples with good recovery.
Electrochemical methods have low toxicity, fast response and, easy operation. By modifying electrochemical sensors with a conductive and porous modifier, their sensitivity and selectivity can be ...improved. Nanomaterials with new and extraordinary properties are a new approach in science and especially in electrochemical sensors. In this study, UiO66-NH2/mesoporous carbon nitride (M − C3N4) composite provides a porous structure for decorated Au nanoparticles (AuNPs) to prepare a potent modifier for carbon paste electrode (CPE). Due to environmental toxicity of methotrexate, its sensitive, fast and, low-cost determination in workplace environments is of great interest. So, the modified CPE was applied as a sensitivity analysis approach for methotrexate in plasma samples. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as techniques to optimize the analysis and measurement of methotrexate. To measure this drug, several effective parameters were optimized and a calibration curve was drawn under optimal conditions. The calibration curve showed a linear range from 0.5 to 150 μM with a detection limit of 0.15 μM for methotrexate. Examining the repeatability of the response of one electrode and multiple electrodes under optimal conditions shows the high precision of the developed method. Finally, this developed method based on UiO66-NH2/M-gC3N4/AuNPs|CPE was used to determine the methotrexate in the plasma sample using the standard addition method.
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•UiO66-NH2/mesoporous carbon nitride composite provides decorated AuNPs.•A sensitive electrochemical sensor is used for analysis of methotrexate.•The ability of the developed method to measure methotrexate and acetaminophen in real plasma samples was investigated.
•Incorporation of AC with CoWO4 to improve inherent redox activity towards oxidation of TBPA.•Utilization of ANN modeling for predictive assessment of DPV based TBPA sensing.•DFT based confirmation ...of non-covalent interaction between TBPA and CoWO4.
The escalating levels of environmental pollution, particularly from commercially used products, highlight the imperative of efficient sensor technologies to facilitate timely and effective remediation strategies. Herein, a simple method is proposed to enhance the electrochemical performance of CoWO4 structures by coupling them with activated carbon (AC) for direct tetrabromobisphenol A (TBPA) oxidation. The systematic comparison shows that incorporation of AC with CoWO4 not only improves the overall effective surface area (ESA) of the catalyst by 1.8-fold but also improves the cyclic voltammetry (CV) based irreversible oxidation current by 2.0-fold owing to improved conductivity and surface characteristics. Differential pulse voltammetry (DPV) based optimization of the sensory characteristics confirmed robust electrocatalytic TBPA oxidation within a 0.1 to 1.0 µM concentration range, achieving a 0.024 µM detection limit within PBS (0.1 M) (pH 5.0). Moreover, density functional theory (DFT) analysis confirms the non-covalent interaction favorability between TBPA and CoWO4 surface, validating TBPA’s easy adsorption onto the catalytic surface and, thus, facilitated electron mobility between the molecule and the catalyst during the surface oxidation process. The DPV sensing interpreted using machine learning (ML) algorithms confirmed the detection accuracy of the developed sensor. Among the adopted models, artificial neural networks (ANN) achieved the highest R2 score (0.9659) and the lowest values across Mean Squared Error (MSE), Mean Absolute Error (MAE), and Root Mean Squared Error (RMSE) error matrices confirming its suitability in deciphering DPV correlations.
Integrating ANN with DPV based electrocatalytic oxidation sensing underscores machine learning’s potential in analyzing complex electrochemical signatures, thus advancing intelligent sensing for precise environmental monitoring.
A nanocomposite is described that consists of TmPO
and graphene oxide (GO) and is used to modify a glassy carbon electrode (GCE) to obtain a sensor for simultaneous determination of ascorbic acid ...(AA), dopamine (DA) and uric acid (UA). GO and TmPO
were synthesized via the Hummers method and by a hydrothermal method, respectively. The nanocomposite was characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical properties of the modified GCE were studied by electrochemical impedance spectroscopy and cyclic voltammetry. The good performance of the modified GCE results from the synergistic effects between GO with its good electrical conductivity and of TmPO
as the electron mediator that accelerates the electron transfer rate. Compared to a bare GCE, a GO/GCE and a TmPO
/GCE, the GO/TmPO
/GCE exhibits three well-defined and separated oxidation peaks (at -0.05, +0.13 and + 0.26 V vs. SCE). Responses to AA, DA and UA are linear in the 0.1-1.0 mM, 2-20 μM and 10-100 μM concentration ranges, respectively. Graphical abstract Schematic presentation of a nanocomposite that consists TmPO
and graphene oxide (GO) and is used to modify a glassy carbon electrode (GCE) to obtain a sensor for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA).
A new alpha-fetoprotein-MIP (AFP-MIP) immunosensor based on glass carbon electrode (GCE) modified with polythionine (PTh) and gold nanoparticles (AuNPs) was successfully prepared for the sensitive ...detection of AFP. The AFP-MIP immunosensor presented a facile preparation, low sample consumption, and good stability, and could become a new promising method for the detection of AFP.
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A new α-fetoprotein-MIP (AFP-MIP) immunosensor based on glass carbon electrode (GCE) modified with polythionine (PTh) and gold nanoparticles (AuNPs) was successfully fabricated for sensitive detection of α-fetoprotein (AFP). Through controlling electropolymerization, A “polydopamine (PDA)-AFP” complex was achieved applying AFP as template and dopamine (DA) as imprinted monomers. After elution, the specific cavities can adsorb the target molecules. Using differential pulse voltammetry (DPV) detection, the peak current decreased with the increase in concentration of AFP, and the linear response range of the AFP-MIP immunosensor was from 0.001 ng/mL to 800 ng/mL with the detection limit as low as 0.8138 pg/mL. The MIP immunosensor could become a new promising method for the detection of AFP. Furthermore, this MIP sensor was demonstrated in testing AFP in human serum samples with satisfactory results.
