Voltammetric carbon nanotubes based sensor for determination of tryptophan in the milk sample

Detection of cadmium heavy metal ions using a nanostructured green sensor in food, biological and environmental samples

Heavy metals are one of the most important pollutants in the environment due to their toxic properties, accumulation, and indestructibility. So that when the metals enter the body of plants from natural and artificial sources, they accumulate in the organs and tissues. Therefore, in the present study, a sensitive and selective strategy is reported for the detection of cadmium(II) ions. To achieve this purpose, first sodium aluminate nanostructures were synthesized using a sol-gel method and green route. Then, using the nanostructures, a modified nanostructured sensor was designed. The characterization of the nanostructures was performed using various techniques. Next, the electrochemical behavior of the modified nanostructured electrode was investigated. The studies show the environment-friendly sensor has an enhanced voltammetric response than the unmodified sensor for cadmium(II) ions. After confirming the performance of the modified sensor, the analysis of cadmium(II) ions at the surface of the nanostructured modified electrode was investigated. Then, by differential pulse voltammetry (DPV) technique, the detection limit of cadmium(II) ions in optimal conditions was obtained at 1.10 nM with a broad dynamic linear range of 0.02-20.00 μM and 20.00-900.00 μM. Finally, the performance of the modified nanostructure sensor was investigated in food, biological and environmental samples, and acceptable results were obtained using the proposed method.

Ultralow Detection of Mancozeb Using Two-Dimensional Cobalt Telluride (CoTe2)

Pesticides are crucial in modern agriculture because they reduce pests and boost yield, but they also represent major risks to human health and the environment; therefore, it is important to monitor their presence in food. Reliable and precise detection techniques are possible ways to address this issue. In this work, we utilize atomically thin (two-dimensional) cobalt telluride (CoTe2) with a high surface area and charge as a template material to detect mancozeb using spectroscopic and electrochemical techniques. When mancozeb (MNZ) molecules interact with 2D CoTe2, spectroscopic analyses reveal distinctive spectral shifts that clarify the underlying chemical interactions and binding mechanisms. Furthermore, CoTe2's electroactive sites and their manipulation for improved sensitivity and selectivity toward certain MNZ molecules are investigated by electrochemical studies. The CoTe2/GCE electrode exhibits enhanced electrochemical activity toward the electrooxidation of MNZ. The developed sensing electrode shows a linear range from 0.184 mM to 18.48 μM and a limit of detection of about 0.18 μM. In addition, we employ density functional theory (DFT) first-principles calculations to validate the experimental findings and comprehend the mechanism behind the interaction between CoTe2 and MNZ molecules. The study highlights the effectiveness of 2D CoTe2 as a dual-mode sensing platform for qualitative and quantitative assessment of MNZ pollutants, demonstrated by the integration of electrochemistry and spectroscopy and the critical role that 2D CoTe2-based sensors can play in accurate and efficient pesticide detection, which is required for agricultural safety protocols and environmental monitoring.

Electrochemical monitoring of bisphenol-s through nanostructured tin oxide/Nafion/GCE: A solution to environmental pollution

Over the past few decades, phenolic compounds have been broadly exploited in the industries to be utilized in several applications including polycarbonate plastic, food containers, epoxy resins, etc. One of the major compounds in phenolics is Bisphenol-S (BPS) which has dominantly replaced Bisphenol-A in several applications. Phenolic compounds are extensively drained into the environment without proper treatment and cause several health hazards. Thus, to tackle this serious problem an electrochemical sensor based on SnO₂/GCE has been successfully engineered to monitor the low-level concentration of BPS in water samples. The fabrication of SnO₂ nanoparticles (SnO₂ NPs) was confirmed through FTIR, XRD, and TEM to examine the size, crystallinity, internal texture, and functionalities of the prepared material. The fabricated material was exploited as a chemically modified sensor for the determination of BPS in water samples collected from different sources. Under optimal conditions such as scan sweep 100 mV/s, PBS electrolyte pH of 6, potential window (0.3-1.3 V), the proposed sensor manifested an excellent response for BPS. The LOD of the present method for BPS was calculated as 0.007 μM, respectively. Moreover, the stability and selectivity profile of SnO₂/GCE for BPS in the real matrix was examined to be outstanding.

A reusable and sensitive electrochemical sensor for determination of idarubicin in environmental and biological samples based on NiFe2O4 nanospheres anchored N-doped graphene quantum dots composite; an electrochemical and molecular docking investigation

An ultrasensitive and selective voltammetric sensor with ultra-trace level detection limit is introduced for idarubicin (IDA) determination in real samples. The as-synthesized nanocomposite was characterized by several techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, Energy-dispersive X-ray spectroscopy (EDX), and Field emission scanning electron microscopy (FE-SEM). The electrocatalytic performance of the developed electrode was observed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The limit of detection (LOD) of the developed sensor for idarubicin is 1.0 nM, and the response is found to be in the dynamic concentration range of 0.01-1.9 μmol/L in a Britton-Robinson buffer (B-R, pH = 6.0). Moreover, the fabricated electrode illustrated high selectivity with good repeatability and reproducibility for diagnosing idarubicin as an anthracycline antileukemic drug. Furthermore, to evaluate the validity of the recommended method, three real samples, including human plasma, urine, and water samples, were analyzed with satisfactory recovery and compared with high-performance liquid chromatography (HPLC). The minor groove-binding mode of interaction was also supported by docking simulation studies, emphasizing that IDA can bind to ds-DNA preferably and confirmed experimental results. The reduced assay time and the possibility of measuring a single sample with another anticancer drug without any interference are significant advantages compared to the HPLC. The developed and validated sensor could be a valuable point-of-care diagnostic tool for IDA quantification in patients.

A zinc oxide nanorods/molybdenum disulfide nanosheets hybrid as a sensitive and reusable electrochemical sensor for determination of anti-retroviral agent indinavir

This work aims to develop an electrochemical sensor for the reusable and selective detection of trace levels of indinavir (IDV) as an anti-retroviral drug by using zinc oxide nano-rods/molybdenum disulfide nanosheets on a screen-printed electrode (ZnO NRs/MoS₂ NSs/SPE). Quantitative IDV detection was achieved using differential pulse voltammetry (DPV). The assay specificity was illustrated using interfering species and exhibited high specificity toward the IDV. The developed displayed a wide dynamic range, from 0.01 to 0.66 and 0.66-7.88 μM in Britton-Robinson (B-R) buffer, with a 0.007 μM limit of detection. The fabricated ZnO NRs/MoS₂ NSs/SPE electrode exhibited high sensitivity, stability, good reproducibility, and repeatability towards the sensing of IDV. It turned out that the hybrid electrochemical sensor's sensing performance was remarkably improved due to the synergistic effect between MoS₂ NSs and ZnO NRs, where the former affords a large active surface area and quick electron transfer. The reported sensor provides a new alternative for electrochemical detection of IDV and could expand the applications of metal nanoparticles in emerging technologies for monitoring drugs in real samples.

A dimedone-phenylalanine-based fluorescent sensor for the detection of iron (III), copper (II), L-cysteine, and L-tryptophan in solution and pharmaceutical samples

The development of fluorescence molecules for the fast and effective detection of L-tryptophan (L-Trp) has attracted a lot of attention because it is an important amino acid for baby growth, nitrogen equilibrium in adults, improving sleep, and mood regulation. A dimedone-phenylalanine-based chiral sensor (SDPA) was synthesized and exhibited a strong fluorescence quenching by Fe³⁺ and Cu²⁺ in a water/DMSO (3/7) solution with a detection limit of 2.29 × 10^-6 M and 6.37 × 10^-6 M, respectively. The factors affecting fluorescence sensings, such as the pH and competing cations, were studied. The sensor can be reused at least five times after being treated with EDTA. The Job plot, ESI-MS spectra, ¹H NMR spectra, absorbance, and fluorescence titration experiments were investigated to study the mechanism of SDPA-Fe³⁺ and SDPA-Cu²⁺ complexation. The SDPA-Cu²⁺ complex can detect L-tryptophan and L-cysteine at trace levels by turn-on fluorescence with a detection limit of 9.35 × 10^-6 M and 8.86 × 10^-6 M, respectively. Moreover, applying the SDPA-Cu²⁺ complex for quantitative analysis of L-tryptophan in real sleep-improving capsules resulted in good recovery. The L-tryptophan level of the Elining capsule was determined at 190.8 ± 10.5 mg/g (mg L-tryptophan/g medicine), which is close to the announced quantity of 180 mg/g. Besides, the SDPA-Cu²⁺ complex can selectively detect free L-Try molecules and L-Try residues in proteins.

Molecularly Imprinted Polymer-Amyloid Fibril-Based Electrochemical Biosensor for Ultrasensitive Detection of Tryptophan

A tryptophan (Trp) sensor was investigated based on electrochemical impedance spectroscopy (EIS) of a molecularly imprinted polymer on a lysozyme amyloid fibril (MIP-AF). The MIP-AF was composed of aniline as a monomer chemically polymerized in the presence of a Trp template molecule onto the AF surface. After extracting the template molecule, the MIP-AF had cavities with a high affinity for the Trp molecules. The obtained MIP-AF demonstrated rapid Trp adsorption and substantial binding capacity (50 µM mg⁻¹). Trp determination was studied using non-Faradaic EIS by drop drying the MIP-AF on the working electrode of a screen-printed electrode. The MIP-AF provided a large linear range (10 pM–80 µM), a low detection limit (8 pM), and high selectivity for Trp determination. Furthermore, the proposed method also indicates that the MIP-AF can be used to determine Trp in real samples such as milk and cancer cell media.

Plant extract-based green fabrication of nickel ferrite (NiFe2O4) nanoparticles: An operative platform for non-enzymatic determination of pentachlorophenol

Environmental pollution has become a major human concern with the extensive exploitation of pesticides. Pentachlorophenol (PCP) is the most hazardous of all chlorophenols which are being used as pesticide, fungicide, and wood preservative. Thus, the fabrication of ultrasensitive electrochemical methods for the determination of pesticides is of great significance. In the present experiment, a simple, green, and sensitive electrochemical sensor was constructed for the determination of PCP by using a chemically modified nickel ferrite glassy carbon electrode (NiFe₂O₄/GCE). The fabricated nanoparticles were primarily characterized by several analytical tools to confirm the functionalities, surface texture, crystallinity, and elemental composition. For the investigation of conductive nature, the proposed NiFe₂O₄/GCE was exploited to the primary electrochemical characterization tools e.g. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ultra-sensitive determination of PCP was carried out under the linear dynamic range from 0.01 to 90 μM at the pulse amplitude of 80 mV/s in BRB buffer pH of 4. The limit of detection of the developed methods for PCP was calculated to be 0.0016 μM. The analytical applicability of the fabricated sensor was tested in different water samples depicting the acceptable recovery values.

A review of boron removal from aqueous solution using carbon-based materials: An assessment of health risks

Carbon-based compounds have gained attention of researchers for use in boron removal due to their properties, which make them a viable and low cost adsorbent with a high availability, as well as environmental friendliness and high removal efficiency. The removal of boron utilizing carbon-based materials, including activated carbon (AC), graphene oxide (GO), and carbon nanotubes (CNTs), is extensively reviewed in this paper. The effects of the operating conditions, kinetics, isotherm models, and removal methods are also elaborated. The impact of the modification of the lifetime of carbon-based materials has also been explored. Compared to unmodified carbon-based materials, modified materials have a significantly higher boron adsorption capability. It has been observed that adding various elements to carbon-based materials improves their surface area, functional groups, and pore volume. Tartaric acid, one of these doped elements, has been employed to successfully improve the boron removal and adsorption capabilities of materials. An assessment of the health risk posed to humans by boron in treated water utilizing carbon-based materials was performed to better understand the performance of materials in real-world applications. Furthermore, the boron removal effectiveness of carbon-based materials was evaluated, as well as any shortcomings, future perspectives, and gaps in the literature.

An electrochemical molecularly imprinted sensor based on CuBi2O4/rGO@MoS2 nanocomposite and its utilization for highly selective and sensitive for linagliptin assay

The molecularly imprinted polymers (MIP) is an outstanding electrochemical tool that demonstrates good chemical sensitivity and stability. These main advantages, coupled with the material's vast microfabrication flexibility, make molecularly imprinted sensors an attractive sensing device. Herein, it was aimed to develop a state-of-art molecularly imprinted sensor based on CuBi₂O₄/rGO@MoS₂ nanocomposite to be utilized for the detection of linagliptin (LNG), a novel hypoglycemic drug. The electrochemical characterizations of linagliptin on the surface of the modified electrode was examined via cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Several characterization methods including transmission electron microscope (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and Energy-dispersive X-ray spectroscopy(EDX), were utilized for electrode characterization. The LNG imprinted voltammetric sensor was developed in 80.0 mM phenol containing 20.0 mM LNG. CuBi₂O₄/rGO@MoS₂ nanocomposite on LNG imprinted screen-printed carbon electrode (SPCE) (MIP/CuBi₂O₄/rGO@MoS₂ nanocomposite/SCPE) exhibited a linear relationship between peak current and LNG concentration in the range 0.07-0.5 nM with a detection limit of 0.057 nM. In the existence of interfering substances, an LNG imprinted electrode was utilized to analyze urine, human plasma, and tablet samples with adequate selectivity. The developed sensor was also illustrated for stability, repeatability, reproducibility, and reusability.

Highly sensitive voltammetric determination of NADH based on N-CQDs decorated SnO2/ionic liquid/carbon paste electrode

A highly sensitive and selective modified electrode was successfully developed for the monitoring of nicotinamide adenine dinucleotide (NADH) in the presence of folic acid. In this regard, a carbon paste electrode (CPE) was functionalized by the nitrogen-doped carbon quantum dots/tin oxide (N-CQDs/SnO₂) nanocomposite and 1-butyl-2,3-dimethyl imidazolium hexafluorophosphate ([C₄DMIM][PF₆]) ionic liquid (IL). The structure and surface morphology of the nanocomposite were characterized by various methods, including field emission scanning electron microscopy, energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and x-ray diffraction (XRD). The modified electrode displayed powerful and long-lasting electron mediating activity, with well-separated NADH and folic acid oxidation peaks. The sensing response of the developed [C₄DMIM][PF₆]/N-CQDs/SnO₂/CPE platform was evaluated by determining NADH via the voltammetric technique under the optimized operating conditions. The current peaks of the square wave voltammograms of NADH and folic acid increased linearly with enhancing its concentrations within the ranges of 0.003-275μM NADH and 0.4-380μM folic acid. The detection limits for NADH and folic acid were obtained at 0.8 nM and 0.1μM, respectively. Interference species such as glucose, urea, tryptophan, glycine, methionine, and vitamin B₁₂had no influence on the ability of the fabricated modified electrode to detect the target species. The low detection limit, high sensitivity, excellent selectivity, superior stability, and cost-effectiveness made it suitable for the quantification of NADH in the real biological samples with the recovery percent values in the range of 97.5%-103%.

Monitoring of Butylated Hydroxyanisole in Food and Wastewater Samples Using Electroanalytical Two-Fold Amplified Sensor

A high performance and fast response sensor was fabricated as a monitoring system for the determination of butylated hydroxyanisole (BHA) in food and wastewater samples. In this regard, a carbon paste electrode (CPE) that was amplified with platinum-decorated single wall carbon nanotubes (Pt/SWCNTs) and 1-Butyl-3-methylimidazolium chloride ([C4mim][Cl]) was investigated as a new electroanalytical sensor for the monitoring of BHA in aqueous solution. The [C4mim][Cl]/Pt/SWCNTs/CPE offered an excellent catalytic activity on oxidation signal of BHA and enhanced its oxidation current about 5.51 times. In the final step, the standard addition results confirmed the powerful ability of [C4mim][Cl]/Pt/SWCNTs/CPE to the monitoring of BHA in different water and food samples with acceptable recovery data.

Monitoring of atropine anticholinergic drug using voltammetric sensor amplified with NiO@Pt/SWCNTs and ionic liquid

In this work, the synergic impact of 1-ethyl-3-methylimidazolium methyl sulfate (EMMS) and NiO doped Pt decorated SWCNTs (NiO@Pt/SWCNTs) in carbon paste matrix was examined as an analytical tool for investigating electrochemical behavior of atropine. The voltammetric results revealed that NiO@Pt/SWCNTs/EMMS/CPE exhibited an excellent electrocatalytic activity towards redox reaction of atropine in aqueous solution pH = 10.0. The NiO@Pt/SWCNTs/EMMS/CPE offered the best electro-analytical conditions for monitoring of atropine in the concentration range of 4.0 nM-220 μM with an increase in oxidation current about 5.93 times. On the other hand, NiO@Pt/SWCNTs/EMMS/CPE displayed a long time stability (about 60 days) for monitoring of atropine. The ability of NiO@Pt/SWCNTs/EMMS/CPE as an electroanalytical tool for monitoring of atropine was investigated, and the recovery range was detected as to be 97.6%-104.25% for this goal.

Recent advances in Ponceau dyes monitoring as food colorant substances by electrochemical sensors and developed procedures for their removal from real samples

Ponceau dyes are one of the food coloring materials that are added to various pharmaceutical, health and food products and give them an appearance. These dyes contain contaminants such as Benzidine, 4-Aminobiphenyl, and 4-Aminoazobenzene that are safe in small amounts, but they are not approved by the US Food and Drug Administration (US-FDA) for human consumption. This study comprehensively was reviewed the properties, applications, chemistry, and toxicity of Ponceau dyes as food colorant substances. Electroanalysis of Ponceau dyes was discussed in detail, and the various electrochemical sensors used to detect and monitor these dyes as food colorant were examined. The applied methods of removing and degradation of these dyes in municipal and industrial wastes were also discussed. Conclusions and future perspectives to motivate future research were also explored.

Voltammetric sensor based on bimetallic nanocomposite for determination of favipiravir as an antiviral drug

A novel and sensitive voltammetric nanosensor was developed for the first time for trace level monitoring of favipiravir based on gold/silver core–shell nanoparticles (Au@Ag CSNPs) with conductive polymer poly (3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) and functionalized multi carbon nanotubes (F-MWCNTs) on a glassy carbon electrode (GCE). The formation of Au@Ag CSNPs/PEDOT:PSS/F-MWCNT composite was confirmed by various analytical techniques, including X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and field-emission scanning electron microscopy (SEM). Under the optimized conditions and at a typical working potential of + 1.23 V (vs. Ag/AgCl), the Au@Ag CSNPs/PEDOT:PSS/F-MWCNT/GCE revealed linear quantitative ranges from 0.005 to 0.009 and 0.009 to 1.95 µM with a limit of detection 0.46 nM (S/N = 3) with acceptable relative standard deviations (1.1-4.9 %) for pharmaceutical formulations, urine, and human plasma samples without applying any sample pretreatment (1.12–4.93%). The interference effect of antiviral drugs, biological compounds, and amino acids was negligible, and the sensing system demonstrated outstanding reproducibility, repeatability, stability, and reusability. The findings revealed that this assay strategy has promising applications in diagnosing FAV in clinical samples, which could be attributed to the large surface area on active sites and high conductivity of bimetallic nanocomposite.