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A WS 2 /GdCoO 3 nanocomposite was successfully prepared using hydrothermal-assisted synthesis. Our prepared WS 2 /GdCoO 3 nanocomposite was fabricated on a glassy carbon electrode (GCE) for the detection of quercetin (QCT). The WS 2 /GdCoO 3 nanomaterial was characterized by powder XRD, micro-Raman, FT-IR, XPS, FE-SEM, and HR-TEM, which proved that WS 2 nanoplates were finely dispersed on the surface of the GdCoO 3 nanoflakes. The electrocatalytic performance of WS 2 /GdCoO 3 was investigated by the EIS technique, and it exhibited a small semi-circle, which confirms that it has a large active surface area and high electrical conductivity. The electrochemical behavior of QCT at the WS 2 /GdCoO 3 sensor was explored by using the CV and DPV methods. The proposed electrochemical sensor exhibited excellent electrochemical response toward QCT with a wide linear range of 0.001 to 329 µM, low limit of detection (LOD) of 0.003 µM, and limit of quantification (LOQ) of 0.0101 µM. The sensor also displayed excellent selectivity, sensitivity, reproducibility, and stability. Additionally, the WS 2 /GdCoO 3 sensor was utilized for the detection of QCT in apple juice and grape juice samples, and it exhibited good recovery results., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Selective and sensitive dopamine (DPA) sensor was developed using hydrothermally prepared functionalized multi-walled carbon nanotube-coated bismuth molybdate (f-MWCNT@BMO). The f-MWCNT@BMO-reinforced electrode exhibited an outstanding electrocatalytic activity towards DPA oxidation. The nanocomposite-reinforced electrode displayed a rapid response towards DPA sensing and possessed the minimized potential of (E pa  + 0.285 V vs Ag/AgCl) in 0.1 M phosphate buffer (PB). The electrochemical results of prepared sensors were analyzed using the differential pulse voltammetry method (DPV). As a result, the f-MWCNT@BMO-reinforced electrode exhibited a widelinear range of 10 nM - 814 μM with a very low detection limit of 3.4 nM towards DPA oxidation. The developed sensor shows excellent selectivity in presence of similar functional group biomolecules. The detection of DPA in real samples was evaluated in human serum, as the results of the proposed sensor possessed good recoveries., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Detection of anticancer drug (doxorubicin) using an electrochemical sensor is developed based on a transition metal vanadate's related carbon composite material. With an environmentally friendly process, we have synthesized a metal oxide composite of iron vanadate nanoparticle assembled with sulfur-doped carbon nanofiber (FeV/SCNF). The FeV/SCNF composite was characterized using XRD, TEM, FESEM with elemental mapping, XPS and EDS. In contrast to other electrodes reported in the literature, a much-improved electrochemical efficiency is shown by FeV/SCNF composite modified electrodes. Amperometric technique has been employed at 0.25 V (vs. Ag/AgCl) for the sensitive detection of DOX within a wide range of 20 nM-542.5 μM and it possesses enhanced selectivity in presence of common interferents. The modified electrochemical sensors show high sensitivity of 46.041 μA μM -1  cm -2 . The newly developed sensor could be used for the determination of doxorubicin in both blood serum and drug formulations with acceptable results, suggesting its feasibility for real-time applications., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The highly selective and sensitive electrochemical detection of highly toxic fungicide carbendazim (CBZ) by the iron (Fe)-doped copper vanadate (CuVO 4 ; CuV) is discussed. The Fe-doped copper vanadate (Fe-CuV) is prepared by the simple co-precipitation method followed by an annealing process which produced high crystallinity. The material properties of Fe-CuV are characterized by XRD, Raman spectrometry, XPS analysis, HRTEM, and SAED pattern. The electrochemical characterization of Fe-CuV towards CBZ detection are done by CV and DPV techniques. The Fe-CuV/GCE exhibits good electroanalytical activity towards the electro-oxidation of CBZ at the potential of 0.81 V vs Ag/AgCl. The developed sensor electrode revealed a linear range of 0.01 to 83.1 μM and a limit of detection of about 5 nM. In addition, Fe-CuV/GCE reveals good storage stability (RSD = 2.63%) and reproducibility (RSD = 2.85%) for the electro-oxidation of CBZ. The electrode material was applied to the detection of CBZ in apple juice and soy milk samples, and the results were discussed. Thus, our projected Fe-CuV/GCE can be employed as electrode material in a rapid onsite sensor for the detection and determination of noxious pollutants., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The one-step synthesis of heteroatom-doped porous carbons is reported with the in situ formation of cobalt oxide nanoparticles for dual electrochemical applications (i.e., electrochemical sensor and supercapacitor). A single molecular template of zeolitic imidazole framework-67 (ZIF-67) was utilized for the solid-state synthesis of cobalt oxide nanoparticle-decorated nitrogen-doped porous carbon (Co 3 O 4 @NPC) nanocomposite through a facile calcination treatment. For the first time, Co 3 O 4 @NPC nanocomposite derived from ZIF-67 has been applied as an electrode material for the efficient electrochemical detection of anticancer drug flutamide (FLU). The cyclic voltammetry studies were performed in the operating potential from 0.15 to - 0.65 V (vs. Ag/AgCl). Interestingly, the fabricated drug sensor exhibited a very low reduction potential (- 0.42 V) compared to other  reported sensors. The fabricated sensor exhibited good analytical performance in terms of low detection limit (12 nM), wide linear range (0.5 to 400 μM), and appreciable recovery results (~ 98%, RSD 1.7% (n = 3)) in a human urine sample. Hereafter, we also examined the supercapacitor performance of the Co 3 O 4 @NPC-modified Ni foam in a 1M KOH electrolyte, and noticeable a specific capacitance of 525 F g -1 at 1.5 A g -1 was attained, with long-term cycling stability. The Co 3 O 4 @NPC nanocomposite supercapacitor experiments outperform the associated MOF-derived carbons and the Co 3 O 4 -based nanostructure-modified electrodes.

Molybdenum disulfide (MoS 2 ) surface functionalization was performed with a catechol-containing polymer sodium alginate (SA) and dopamine (DA) through simultaneous MoS 2 exfoliation and self-polymerization of DA. The MoS 2 /SA-PDA nanocomposite was characterized using spectroscopic, microscopic, and electroanalytical techniques to evaluate its electrocatalytic performance. The electrocatalytic behavior of the MoS 2 /SA-PDA nanocomposite modified electrode for the detection of acebutolol (ACE), a cardio-selective β-blocker drug was explored  through cyclic voltammetric and differential pulse voltammetric techniques. The influence of scan rate, concentration, and pH value on the oxidation peak current of ACE was investigated  to optimize the deducting condition. The electrochemical activity of the MoS 2 /SA-PDA nanocomposite electrode was attributed to the existence of reactive functional groups being contributed from SA, PDA, and MoS 2 exhibiting a synergic effect. The MoS 2 /SA-PDA nanocomposite modified electrode exhibits admirable electrocatalytic activity with a wide linear response range (0.009 to 520 μM), low detection limit (5 nM), and high sensitivity (0.354 μA μM -1  cm -2 ) also in the presence of similar (potentially interfering) compounds. The fabricated MoS 2 /SA-PDA nanocomposite modified electrode can be useful for the detection of ACE in pharmaceutical analysis.

Metastable and rarely reported GO warped tetragonal phase t-lanthanum vanadate nanocomposites (GO@LaVO 4 -NCs) are reported for the sensitive electrochemical determination of antifungal drug Clioquinol (CQ). The hydrothermal method was adopted for synthesis of GO@LaVO 4 -NCs. The electrochemical performance of CQ was examined using cyclic voltammetry (CV) and differential plus voltammetry (DPV) at GO@LaVO 4 -NCs modified glassy carbon electrode (GCE). The electrocatalytic oxidation of CQ at the GO@LaVO 4 -NCs/GCE shows the highest anodic peak current at a potential of +0.51 V vs. Ag/AgCl. The proposed sensor provides excellent sensitivity of 4.1894 μA μM -1  cm -2 , a very low detection limit (LOD) of 2.44 nM, and a wide range of 25 nM to 438.52 μM towards CQ detection. Finally, the detection of CQ in biological media was successfully done using the GO@LaVO 4 -NCs/GCE and possesses recoveries of 94.67-98.0%.

The low-temperature synthesis of the graphene oxide-wrapped perovskite-type strontium titanate nanocomposites (GO@SrTiO 3 -NC) is reported for the electrochemical sensing of organochlorine pesticide 2,4,6-trichlorophenol (TCP) detection. The as-prepared GO@SrTiO 3 nanocomposites provide a large surface area, excellent conductivity, and active sites, which are more favorable to the catalysis of TCP. The synergistic effect between the GO and the perovskite SrTiO 3 results in the extended working range of 0.01 to 1.47 and 1.47 to 434.4 μM with a very low detection limit of 3.21 nM towards TCP detection. Moreover, the prepared sensor possessed good selectivity and long-term stability. Finally, the practical applicability of the sensor was tested in environmental samples of river water and soil, exhibiting adequate recovery values.

A high-performance imipramine (IMPR) sensor has been developed  based on metal chalcogenide-carbon composite materials. The antimony telluride-graphite nanofiber (Sb 2 Te 3 -GNF, hereafter SBT-GNF) composite was synthesized by the hydrothermal method and confirmed by X-ray powder diffraction (XRD) pattern. The morphology, crystalline lattice, and chemical states were characterized by HRTEM, SAED, and XPS analysis. The characterizations confirmed the formation of an effective composite, SBT-GNF. The SBT-GNF was fabricated as a disposable sensor electrode with a screen-printed carbon electrode (SPCE) and examined for the detection of IMPR by differential pulse voltammetry (DPV). The electroanalytical results of SBT-GNF are compared with the SBT and GNF, and the rational design of effective composite is discussed. SBT-GNF/SPCE showed a good linear range (0.01‑51.8 μM), sensitivity (1.35 ± 0.1 μA μM -1  cm -2 ), and low LOD (4 ± 2 nM). Moreover, the SBT-GNF/SPCE revealed high selectivity and high tolerance limit against potential interfering compounds in blood serum and urine samples. Therefore, this electrochemical sensor can be applicable for the detection of tricyclic antidepressant drug IMPR in clinical and pharmaceutical analysis.

Two-dimensional (2D) MoS 2 core-shell nanoparticles were synthesized using an eco-friendly surface functionalization-agent with L-glutathione and cystamine (L-GSH-MoS 2 -CYS) using ultrasonic frequency of 20-25 kHz. The novel modified electrode was evaluated for the electrochemical detection of doxorubicin (DOX), through cyclic and differential pulse voltammetric techniques. The electro-catalytic oxidation currents of DOX exhibited a linear relationship in the concentration ranges 0.1-78.3 and 98.3-1218 μM, with a detection limit of 31 nM. A sensitivity of 0.017μA μM -1  cm -2 was acquired at 0.48 V. The fabricated L-GSH-MoS 2 -CYS modified electrode showed excellent precision, selectivity, repeatability, and reproducibility during the determination of DOX levels in blood serum samples. Thus, the fabricated L-GSH-MoS 2 -CYS/GCE modified electrode has potential for clinical applications for optimization of chemotherapeutic drugs owing to its selectivity, ease of preparation, and long-term stability. Graphical abstract.

A needle-shaped perovskite, barium stannate (BaSnO 3 ), was synthesized via a co-precipitation technique for the simultaneous electrochemical determination of antibiotic drug nitrofurantoin (NFTO) and pericardial drug nifedipine (NFP). The spectroscopic and microscopic result confirms that as-prepared BaSnO 3 particles formed with desired crystalline nature, functional group, pore size, pore diameter, and fine needle-like morphology. The simultaneous electrochemical detection of the two pharmaceutical compounds was examined via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) technique using BaSnO 3 -modified glassy carbon electrode (BaSnO 3 /GCE) at a potential range from +0.4 to - 1.2 V. The discrete and simultaneous detection of NFTO and NFP at the BaSnO 3 sensor exhibits higher catalytic activity in terms of cathodic current and cathodic potential compared to bare GCE. DPV results of the BaSnO 3 sensor provide improved linear ranges and limits of detection for NFTO (0.01-42.65 µM; 42.65-557.65 μM, 0.062 μM, respectively) and NFP (0.01-697.65 μM, 0.0168 μM, respectively). Besides, the BaSnO 3 -fabricated sensor exhibits good sensitivity, reproducibility, and repeatability. The modified electrode shows excellent recoveries of NFTO (97.0-100.7%) and NFP (98.7-101.3%) in plasma, urine, and milk samples with an acceptable relative standard deviation (RSD) of 1.6-4.8%. Graphical abstract Needle-shaped BaSnO 3 perovskite material for simultaneous electrochemical sensing of pharmaceutical drugs.

A 3D flexible domestic waste styrofoam is reported as a surface enhanced Raman scattering (SERS) substrate loaded with BiOCl-BiOBr@Pt/Au semiconductor-plasmonic composites. The hydrothermally prepared BiOCl-BiOBr nanocomposite is thoroughly characterized for its crystal structure using X-Ray diffraction, morphology through scanning electron microscopy, and electronic states of the elements using X-ray photoelectron spectroscopy. The alpha cypermethrin (ACM) is chosen as a model pesticide analyte for SERS investigation. The BiOCl-BiOBr@Pt/Au loaded foam substrate exhibited a high enhancement factor (10 6 ) and low limit of detection (10 -10  M) upon SERS investigation. The unique architecture of the semiconductor-plasmonic composite enables an efficient charge transfer capability and plasmonic hotspots which aids in the enhancement of target analytes. In order to better demonstrate the versatility towards other pesticides, SERS detection of glyphosate and paraquat pesticides are also performed using the fabricated SERS substrate. The stability of the substrate has been investigated in detail for 30 days and the substrate was highly stable. The BiOCl-BiOBr@Pt/Au-based foam substrate also performed well in rapid real-time sensing of alpha cypermethrin on the kiwi fruit exocarp at lower level concentrations. Graphical abstract.

Graphitic carbon nitrides supported cuprous oxide architecture is reported as an efficient electrode material for supercapacitors, especially due to its high charge-transfer conductivity of the electrochemical devices. Herein, we present an electrochemical sensor to specifically detect 8-hydroxy-2'-deoxyguanosine (8-HDG) oxidative stress biomarker using graphitic carbon nitrides that decorate a cuprous oxide cubes modified electrode. The fabricated electrochemical sensor was characterized and proved by electrochemical methods, EDX, FESEM, and amperometry (i-t). In the presence of 8-hydroxy-2'-deoxyguanosine (8-HDG), the effective interaction between graphitic carbon nitrides and 8-HDG favors the accumulation on the Cu 2 O/g-C 3 N 4 /GCE, which increases the electrocatalytic property and amperometric response. The proposed electrochemical sensor exhibits a wide linear range for 8-HDG in 0.1 M phosphate buffer (pH 7.0) from 25 nM to 0.91 mM, and the limit of detection (LOD) is 4.5 nM. The stability of the Cu 2 O/g-C 3 N 4 /GCE is improved when stored at 4 °C. The repeatability and reproducibility of this electrochemical sensor is good and the sensor retains its  current response for 8-HDG detection also after long time storage. The modified sensor proved high selectivity and sensitivity for 8-HDG, which made it possible to determine 8-HDG in biological samples. Furthermore, the Cu 2 O/g-C 3 N 4 /GCE offered a favorable electron transfer between the Cu 2 O/g-C 3 N 4 and the electrode interface compared to Cu 2 O/GCE, g-C 3 N 4 /GCE, and unmodified GCE. Graphical abstract Electrochemical detection of oxidative stress marker based on Cu 2 O@g-C 3 N 4 materials modified electrode.

The synthesis and fabrication of oval-shaped tantalum carbide (Ta-C) integrated functionalized-multiwalled carbon nanotube (Ta-C/f-MWCNT) as an electrocatalyst for the electrochemical determination of nitrofurantoin (NFT) is described. The Ta-C/f-MWCNT composite was prepared using the soft-template method followed by the ultrasonication process. The as-prepared Ta-C/f-MWCNT composite was characterized using powder X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS) analysis. The electrochemical properties of Ta-C/f-MWCNT were investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The Ta-C/f-MWCNT-modified glassy carbon electrode (Ta-C/f-MWCNT/GCE) was successfully utilized as an active electrocatalyst for the detection of NFT in the presence of 0.384 mM NFT containing 0.05 M phosphate buffer (pH 7) at a scan rate of 50 mV/s. The Ta-C/f-MWCNT/GCE exhibited a wide linear response range (0.04-1047 μM) and a low detection limit (0.0011 μM). Further, the Ta-C/f-MWCNT/GCE showed appreciable results for repeatability, reproducibility, and long-term cyclic stability towards NFT sensing. The Ta-C/f-MWCNT/GCE was applied to real sample analysis such as a commercial tablet and human urine samples. The Ta-C/f-MWCNT/GCE exhibited good recovery values for the tablet (105 to 115%) and urine (101-107%) samples. The above electrochemical results suggest that the Ta-C/f-MWCNT is a promising electrocatalyst for the electrochemical sensing of NFT drug. Graphical abstract .

The two-step microwave method was used to synthesize zinc oxide nanostars linked to graphene oxide (GO) nanosheets. The material was used to modify a screen printed carbon electrode (SPCE) and then explored as a binder-free electrocatalyst for the electrochemical determination of methyl parathion (MP). The morphology and crystallinity of the material were characterized by various techniques. The modified SPCE shows extraordinary electrochemical performances for sensitive determination of MP. Figures of merit include (a) a wide linear dynamic range (0.03-670 μM), (b) a low detection limit (1.2 nM; at S/N = 3), (c) a comparably low working voltage (-0.69 V vs. Ag/AgCl); and (d) an excellent sensitivity (16.5 μA μM -1  cm -2 ) that surpasses other modified electrodes. The sensor was successfully applied to the determination of MP, even in the presence of other common electroactive interference, in (spiked) fruits and vegetables. Graphical abstractGraphene oxide anchored three-dimensional zinc oxide nanostars were used to coat electrode for the sensing of methyl parathion (MP) by voltammetry.

Urchin-like CuS was grown on xanthan gum-derived carbon nanofibers to obtain a sensor for enzyme-free electrochemical sensing of glucose. The unique nanostructure of the sensor provides a large specific surface, more electrocatalytically active sites, and high electrical conductivity. The voltammetric response to glucose, best measured at around 57 mV (vs. Ag/AgCl (E/V)) in 0.1 M NaOH solution, covers two linear ranges, one from 0.1-125 μM, another from 0.16 to 1.2 mM. The sensitivity is quite high (23.7 μA mM -1  cm -2 ), and the detection limit is low (19 nM at S/N = 3). The sensor has high selectivity against potentially interfering molecules such as fructose, appreciable operational stability, excellent durability, and good repeatability (with relative standard deviations of 2.3%). It was successfully applied to the determination of glucose in diluted serum samples. Graphical abstractSchematic representation of electrochemical detection of glucose based on the use of a screen printed carbon electrode (SPCE) modified with CuS and xanthan gum-derived carbon nanofibers (XGCNFs).

Lanthanum oxide nanomaterials were decorated with carbon black (CB) and grafted with a poly(acrylic acid) nanogel to obtain a composite material (CB-g-PAA/La 2 O 3 ) for simultaneous determination of acetaminophen (AMP), naproxen (NPX), and theophylline (TPH). The nanogel was synthesized by in-situ free radical polymerization. The composite was dropped onto a glassy carbon electrode (GCE), and the modified GCE displays robust electrocatalytic activity towards AMP, NPX, and TPH, with voltammetric signals that are enhanced compared to a bare GCE. Features of merit for AMP, NPX, and TPH, respectively, include (a) peak potentials of 0.42, 0.85 and 0.12 V (vs. Ag/AgCl), (b) linear ranges from 0.05-887, 0.05-884, and 0.02-888 μM, and (c) detection limits of 20, 35, and 15 nM. The practical applicability of the CB-g-PAA/La 2 O 3 /GCE was illustrated by analyzing serum and urine samples. Graphical abstract Schematic presentation of simultaneous electrochemical sensing of acetaminophen (AMP), naproxen (NPX), and theophylline (TPH) in real sample analysis using poly(acrylic acid) nanogel covalently grafted onto a carbon black/La 2 O 3 composite (CB-g-PAA/La 2 O 3 /GCE).

Cerium vanadate resembling the shape of a hedgehog were interconnected with carbon nanofibers to give a heterostructure (referred to as CeV/CNF) that exhibits efficient catalytic activity for the electrochemical detection of the drug nilutamide (NLT). The heterostructure material and its modification were characterized by XRD, Raman spectra, XPS, FESEM, TEM, SAED, and EDX. A glassy carbon electrode was modified with the CeV/CNF nanocomposite. Best operated at -0.52 V (vs. Ag/AgCl), it exhibits a very low detection limit (2.0 nM), wide linear range (0.01-540 μM), high sensitivity (1.36 μA μM -1  cm -2 ) and rapid response towards NLT. It was applied to the determination of NLT in spiked human urine. Graphical abstractSchematic presentation of cerium vanadate interconnected with carbon nanofiber heterostructure for electrochemical determination of prostate cancer drug nilutamide in biological samples.

A screen-printed carbon electrode (SPCE) was modified with chitosan (Chit) supported on carbon aerogel (CA) to obtain an electrochemical sensor for the tuberculosis drug isoniazid (INZ). The interconnected mesoporous structure of Chit/CA provides a large surface area (S BET  = 461 m 2  g -1 ) and good porosity (V Tot  = 0.69 cm 3  g -1 ). Besides, the modified SPCE displayed enhanced electrocatalytic activity due to the presence of numerous active sites (such as >C=O, -NH-, -NH 2 , -OH). Figures of merit include (a) a typical working voltage of 0.28 V (vs. Ag/AgCl), (b) high sensitivity (8.09 μA μM -1  cm -2 ), (c) a wide linear response to INZ (0.01-115 μM) and (d) a low detection limit (8 nM). The modified electrode has successfully been applied to the determination of INZ in spiked serum and urine, and recoveries ranged from 97.8 to 99.8%. Graphical abstract Schematic illustration of preparation and applications of a nanocomposite consisting of chitosan (Chit; CS) supported on carbon aerogel (CA) for electrochemical detection of isoniazid.

Palladium-copper nanoparticles were placed on activated carbon to give a nanocomposite for electrochemical sensing of riboflavin (vitamin B 2 ). The activated carbon was produced by pyrolysis of natural waste of pistachio nutshells after KOH activation and under a nitrogen atmosphere. The carbons possess a large surface area and micro/meso-porosity. The nanocomposite was characterized by a variety of techniques to confirm structures and morphology. A screen-printed electrode modified with the composite was examined by EIS, CV, DPV, and amperometry. The effects of pH value, scan rate, and stability of the modified electrode were studied. Under optimized conditions, vitamin B 2 displays a well-expressed oxidation peak at -0.15 V (vs. Ag/AgCl) in solutions with a pH value of 7.0. The voltammetric signal increases linearly in the 0.02 to 9 μM concentrations range and a lower detection limit of 7.6 pM. The sensor was successfully applied to the determination of vitamin B 2 even in the presence of other common vitamins and in (spiked) raw milk samples. Graphical abstract A highly porous carbon was modified with palladium-copper alloy nanoparticles and used to coat an electrode for sensing of riboflavin (vitamin B 2 ) by voltammetry.

A carbon nanofiber functionalized with ruthenium(II)-tetrasulfonato phenyl porphine (CNF/Ru-TSPP) is shown to be viable sensor for amperometric determination of the antipsychotic drug chlorpromazine (CPZ). The hollow platelet structured Ru-TSPP combines with the hollow cylindrical tube-like structure of the CNF via π stacking interaction. The morphological and electro conductive properties of the electrode were characterized by spectrophotometric techniques. The CNF/Ru-TSPP modified electrode displays a large surface-to-volume ratio, good electron transport and good electrocatalytic activity. The amperometric sensor, typically operated at a potential 0.63 V (vs. Ag/AgCl) exhibits a linear response in the 0.6 nM to 1.1 mM CPZ concentration range, has a 0.2 nM detection limit, and a remarkably good electrochemical sensitivity (2.405 μA μM -1  cm -2 ). The sensor is selective, repeatable and reproducible. It was successfully applied to the determination of CPZ in spiked serum samples. Graphical abstract Schematic presentation of carbon nanofiber/ tetrasulfonatophenyl Ruthenium(II)porphine (CNF/Ru-TSPP) nanocomposite synthesis and application for the electrochemical determination of chlorpromazine (CPZ).

An efficient non-enzymatic electrochemical sensor for hydrogen peroxide (H 2 O 2 ) was constructed by modifying a glassy carbon electrode (GCE) with a nanocomposite prepared from cobalt nanoparticle (CoNP) and tungsten carbide (WC). The nanocomposite was prepared at low temperature through a simple technique. Its crystal structure, surface morphology and elemental composition were investigated via X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed the composite to be uniformly distributed and that the CoNP are well attached to the surface of the flake-like WC. Electrochemical studies show that the modified GCE has an improved electrocatalytic activity toward the reduction of H 2 O 2 . H 2 O 2 can be selectively detected, best at a working voltage of -0.4 V (vs. Ag/AgCl), with a 6.3 nM detection limit over the wide linear range from 50 nM to 1.0 mM. This surpasses previously reported non-enzymatic H 2 O 2 sensors. The sensor was successfully applied to the determination of H 2 O 2 in contact lens solutions and in spiked serum samples. Graphical abstract Schematic presentation of a method for electrochemical sensing of hydrogen peroxide in real samples using cobalt nanoparticle decorated tungsten carbide (WCC) modified glassy carbon electrode (GCE).

A rapid voltammetric method is described for the determination of the organophosphorus pesticide paraoxon-ethyl (PEL). A glassy carbon electrode (GCE) was modified with a composite consisting of a poly(N-isopropylacrylamide)-chitosan microgel with incorporated palladium nanoparticles. The microgel was characterized by FE-SEM, EDX, XPS, FTIR, XRD, and EIS. The modified GCE is shown to enable direct electro-reductive determination of PEL by using differential pulse voltammetry. The method works in pH 7 solution and in the 0.01 μM to 1.3 mM PEL concentration range. At a typical working potential of -0.66 V (vs. Ag/AgCl) (at 50 mV/s), the detection limit is as low as 0.7 nM, and the electrochemical sensitivity is 1.60 μA μM -1  cm -2 . Intriguingly, the modified GCE displays good recovery when applied to bok choy and water samples. Graphical abstract Schematic of an electrochemical method for determination of paraoxon ethyl (PEL) in bok choy extract and water by using poly(N-isopropyl acrylamide)-chitosan microgel decorated with palladium nanoparticle-modified glassy carbon electrodes (PdNPs/PNIPAM-CT microgel/GCE).

An electrochemical sensor is described for the determination of nilutamide (NLM) in biological fluids. A flexible mat of nitrogen-doped carbon nanofibers (NCNFs) was prepared by electrospinning. This was followed by carbonization and the growth of one-dimensional vanadium tetrasulfide (VS 4 ) nanorods in the circumference of the NCNFs by a solvothermal route. The material was used to modify a glassy carbon electrode (GCE). Cyclic voltammetry and amperometry revealed an excellent electrocatalytic activity of the VS 4 /NCNF mat towards NLM at a working potential of - 0.57 V (vs Ag/AgCl). The modified GCE has a wide linear range (0.001-760 μM), a low limit of detection (90 pM), good stability, and fast response. It was used to detect NLM in spiked serum and urine samples. Graphical abstract Schematic presentation of a glassy carbon electrode (GCE) composed of free-standing nitrogen-doped carbon nanofibers decorated with vanadium tetrasulfide (Patronite) nanorods (VS 4 /NCNF). It was fabricated by electrospinning followed by stabilization and carbonization. The GCE responds to nilutamide (NLM) with excellent selectivity and nanomolar sensitivity.

A hydrothermal route is reported for the preparation of a composite consisting of sheet-like glucose-derived carbon and nickel oxide nanoparticles. The nanocomposites were prepared at different annealing temperatures and exploited as electrode materials for amperometric (i-t) determination of hydrazine (N 2 H 4 ) and hydrogen peroxide (H 2 O 2 ) at trace levels. The performances of the sensors were assessed by cyclic voltammetry and amperometry detection using a rotating disk electrode (RDE) technique. The modified electrode annealed at ca. 300 °C was found to exhibit the best electrocatalytic performance in terms of sensitive and selective detection of N 2 H 4 and H 2 O 2 even in the presence of interfering species. The electrode is inexpensive, robust, easy to prepare in large batches, highly stable, and has a low overpotential. H 2 O 2 can be sensed, best at a working voltage of typically 0.13 V vs Ag/AgCl; rotationg speed 1200 rpm) over a wide concentration range (0.01 to 3.9 µM) with a detection limit of 1.5 nM. N 2 H 4 can be sensed, best at a working voltage of typically 0.0 V within the concentration range from 0.5 μM to 12 mM with an excellent detection limit of 1.5 µM. Thus, this cost-effective and robust modified electrode, which may be readily prepared in large batch quantity, represents a practical platform for industrial sensing. Graphical abstract Schematic of the hydrothermal method for synthesis of carbon and nickel oxide nanoparticle composites (GCD/NiO-150, GCD/NiO-300, and GCD/NiO-450). The composite was used for the electro-oxidation of hydrazine (N 2 H 4 ) and hydrogen peroxide (H 2 O 2 ) by cyclic voltammetry and amperometry (i-t).

A glassy carbon electrode (GCE) was modified with a nanocomposite prepared from carboxylated multiwalled carbon nanotubes (c-MWCNT) and titanium nitride (TiN) nanoparticles to obtain a sensor for nitrite. The nanocomposite was characterized by transmission electron microscopy, elemental mapping, X-ray diffraction, and Raman spectroscopy. Electrochemical studies results show the modified GCE to possess a low electrochemical resistance (Rct = 7 Ω) and a large electroactive surface (A = 0.112 cm 2 ). The heterogeneous electron transfer rate (k s ) is found to be 1.26 × 10 -2  cm s -1 . Due to the excellent synergistic effect of c-MWCNT and TiN, the GCE displays and excellent performance in terms of nitrite sensing. At a typical working voltage of +0.8 V (vs. Ag/AgCl), the limit of detection (LOD) is as low as 4 nM, and the useful analytical range extends from 6 nM to 950 μM. This is much better than the LODs of previously reported nitrite sensors. The sensor is fast (response time 4 s), selective, and long-term stable. It was applied to the determination of nitrite in spiked water and meat samples and gave good recoveries. Graphical abstract Schematic presentation of electrochemical determination of nitrite using carboxylated multiwalled carbon nanotubes modified with titanium nitride nanoparticles modified electrode.

A voltammetric sensor is described for the quantitation of propyl gallate (PG). A screen-printed carbon electrode (SPCE) was modified with reduced graphene sheets that were decorated with cobalt diselenide nanoparticles (CoSe 2 @rGO). The material was hydrothermally prepared and characterized by several spectroscopic techniques. The modified SPCE displays excellent electrocatalytic ability towards PG. Differential pulse voltammetry, with a peak voltage at 0.34 V (vs. Ag/AgCl) has a sensitivity of 12.84 μA·μM -1 ·cm -2 and a detection limit as low as 16 nM. The method is reproducible, selective, and practical. This method was applied to the determination of PG in spiked meat samples, and the result showed an adequate recovery. Graphical abstract Schematic of a new method for fast and sensitive electrochemical determination of the food additive propyl gallate in meat.

A voltammetric sensor is described for the determination the antibiotic sulfamethoxazole (SMZ). It is based on the use of a glassy carbon electrode (GCE) modified with a nanocomposite prepared from graphitic carbon nitride and zinc oxide (g-C 3 N 4 /ZnO). The nanorod-like ZnO nanostructure were synthesized sonochemically. The g-C 3 N 4 /ZnO nanocomposite was then prepared by mixing g-C 3 N 4 with ZnO, followed by ultrasonication. The morphology and structure of the nanocomposite were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy and transmission electron microscopy. Under the optimal conditions, the response of the electrode, typically measured between 0.8 and 0.9 V (vs. Ag/AgCl), increases linearly in the 20 nM to 1.1 mM SMZ concentration range, and the lower detection limit is 6.6 nM. This is better than that of many previously reported sensors for SMZ. The modified electrode is highly selective, well reproducible and maintains its activity for at least 4 weeks. It was applied to the determination of SMZ in spiked human blood serum samples in with satisfactory results. Graphical abstract Schematic presentation of the voltammetric sensor for sulfamethoxazole. It consists of a glassy carbon electrode modified with a nanocomposite prepared from graphitic carbon nitride (g-C 3 N 4 /ZnO) that was supported with zinc oxide nanorods.

Nitrogen-doped multiwalled carbon nanotubes modified with nickel nanoparticles (Ni/N-MWCNT) were prepared by a thermal reduction process starting from urea and Ni(II) salt in an inert atmosphere. The nanocomposite was deposited on a screen printed electrode and characterized by X-ray diffraction, scanning and transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectroscopy, and thermogravimetric analyses. The performance of the composite was investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The numerous active metal sites with fast electron transfer properties result in enhanced electrocatalytic activity towards the individual and simultaneous detection of catechol (CC) and hydroquinone (HQ), best at 0.21 V for CC and 0.11 V for HQ (vs. Ag/AgCl). For both targets the detection limit (S/N of 3) was 9 nM (CC) and 11 nM (HQ), and the Ni/N-MWCNT-electrode showed linear response from 0.1-300 μM CC, and 0.3-300 μM HQ. The electrode is selective over many potentially interfering ions. It was applied to the analysis of spiked water samples and gave satisfactory recoveries. It also is sensitive for CC (5.396 μA·μM -1  cm -2 ) and HQ (5.1577 μA·μM -1  cm -2 ), highly active, durable, acceptably repeatable and highly reproducible. Graphical abstract Voltammetric determination of catechol and hydroquinone using nitrogen-doped multiwalled carbon nanotubes modified with nickel nanoparticles.

A new type of manganese diselenide nanoparticles (MnSeNPs) was synthesized by using a hydrothermal method. Their surface morphology, crystallinity and elemental distribution were characterized by using transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy which scrutinize the formation of the NPs. The NPs were coated on a glassy carbon electrode (GCE), and electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were applied to study the electroanalytical properties towards the oxidation of the food additive capsaicin. The modified GCE displays lower charge transfer resistance (R ct  = 29.52 Ω), a larger active surface area (0.089 cm 2 /g, and more efficient electrochemical oxidation of capsaicin compared to a MnS 2 /GCE and a bare GCE. The oxidation peak potential is 0.43 V (vs. Ag/AgCl) which is lower than that of previously reported GCEs. The sensor has a detection limit as low as 0.05 μM and an electrochemical sensitivity of 2.41 μA μM -1  cm -2 . The method was applied to the determination of capsaicin in pepper samples. Graphical abstract Electrochemical determination of capsaicin in pepper extract by using MnSeNPs modified electrode.