Tin disulfide-graphene oxide-β-cyclodextrin mediated electro-oxidation of melatonin hormone: an efficient platform for electrochemical sensing

Ultrasensitive detection of chlortetracycline in animal-origin food using molecularly imprinted electrochemical sensor based on SnS2/ZnCo-MOF and AuNPs

The chlortetracycline (CTC) residue in food poses a threat to human health. Therefore, developing sensitive, convenient and selective analytical methods for CTC detection is crucial. This study innovatively uses tin disulfide/bimetallic organic framework (SnS2/ZnCo-MOF) nanocomposites in conjunction with gold nanoparticles (AuNPs) to co-modify a glassy carbon electrode (GCE). Further, a molecularly imprinted polymer (MIP)-based electrochemical sensing platform Au-MIP/SnS2/ZnCo-MOF/Au/GCE (AZG) was fabricated for selective CTC detection. SnS2/ZnCo-MOF enhanced the stability and surface area of the AZG sensor. The presence of AuNPs facilitated electron transport between the probe and the electrode across the insulating MIP layer. The fixation of AuNPs and MIP via electropolymerization enhanced the selective recognition of this sensor and amplified its output signal. The AZG sensor demonstrated a wide linear detection range (0.1-100 μM), low detection limit (0.072 nM), and high sensitivity (0.830 μA μM-1). It has been used for detecting CTC in animal-origin food with good recovery (96.08%-104.60%).

Development of an impedimetric sensor for susceptible detection of melatonin at picomolar concentrations in diverse pharmaceutical and human specimens

Our investigation aimed to create and manufacture an electrochemical impedance sensor with the purpose of improving the detection efficiency of melatonin (ME). To achieve this objective, we employed gold nanoparticles coated on polydopamine formed in glassy carbon electrodes (AuNPs/PDA/GCE) as a means to enhance the sensor's capabilities. A novel approach employing the signal-off strategy and electrochemical impedance spectroscopy (EIS) technique was utilized to determine ME. When the AuNPs/PDA/GCE electrode was immersed in a buffered solution containing ME, and the oxidation current of AuNPs was recorded, it was observed that the oxidation current of AuNPs decreased upon the introduction of ME molecules. The decrease in electrical current can be ascribed to the inhibitory impact of ME molecule adsorption on the electrode surface with applying -0.2 V for 150 s in acetate buffer solution (ABS) (pH, 5) through various mechanisms, which hinders the electron transfer process crucial for AuNPs oxidation. Consequently, by utilizing EIS, various concentrations of ME were quantified spanning from 1 to 18 pM. Moreover, the ME sensor achieved an impressive detection limit of 0.32 pM, indicating its remarkable sensitivity in detecting low concentrations of ME. Importantly, these novel sensors demonstrated exceptional attributes in terms of sensitivity, specificity, stability, and repeatability. The outstanding performance of these sensors, coupled with their desirable attributes, establishes their considerable potential for a wide range of practical applications. These applications encompass various fields such as clinical diagnostics, pharmaceutical analysis, environmental monitoring, and industrial quality control, where accurate and sensitive detection of ME is of utmost importance.

Electrochemical sensor for simultaneous determination of trifluoperazine and dopamine in human serum based on graphene oxide-carbon nanotubes/iron-nickel nanoparticles

Trifluoperazine (TFLP) is an important psychiatric medication that balances the dopamine (DA) level in the brain for patients suffering from neurological disorder diseases. An efficient electrochemical sensor is developed for detecting TFLP in real human serum samples. The sensor is fabricated by casting the GC surface with two consecutive thin layers, namely a graphene oxide-carbon nanotubes mixture (GRO-CNT), and iron-nickel nanoparticles (Fe-Ni). The diffusion-controlled oxidation process of TFLP at the composite surface includes one electron transfer process. Under optimized conditions, the sensor in human serum shows excellent catalytic effect for simultaneous determination of TFLP and dopamine (DA) in the same concentration range (0.5 μM to 18 μM) with low detection limits of 0.13 μM and 0.32 μM respectively. The combined effect of a large conductive surface area and the excellent catalytic activity of the nanocomposite improves the sensor's performance. The sensor exhibits a stable current response over four weeks, excellent reproducibility, and insignificant interference from common species present in human serum samples. The reliability test of using the sensor in serum samples shows good recovery of TFLP.

A novel electrochemical immunosensor based on SnS2/NiCo metal-organic frameworks loaded with gold nanoparticles for cortisol detection

In this work, a label-free electrochemical immunosensor using tin sulfide/nickel cobalt metal-organic frameworks (SnS₂/NiCo MOFs) was established for the sensitive etection of cortisol. First, SnS₂/NiCo MOFs were synthesized by doping SnS₂ with NiCo MOF nanocubes by a hydrothermal method. Then, gold nanoparticles (AuNPs) were grown in situ on SnS₂/NiCo MOFs for electrochemical detection. The use of SnS₂/NiCo MOFs promoted the electron transfer rate of AuNPs and enhanced the electrochemical sensing performance of AuNPs@SnS₂/NiCo MOFs-modified electrodes. The large specific surface area of AuNPs@SnS₂/NiCo MOFs provides more active sites for antibody loading. After the prepared immunosensor was incubated with the target analyte, cortisol, the electron transfer impedance increased and the amperometric response decreased, thus establishing a highly sensitive immunosensing method. The sensor had a linear range of 100 fg/mL to 100 ng/mL and a low detection limit of 29 fg/mL. The sensor showed good accuracy and practicability and could be used for the determination of cortisol in saliva.

Bimetallic Cu5Zn8 alloy-embedded hollow porous carbon nanocubes derived from 3D-Cu/ZIF-8 as efficient electrocatalysts for environmental pollutant detection in water bodies

Excessive use of nitrofurantoin (NFT) and its residues can be harmful to the ecosystem, and to mitigate this, rapid and cost-effective detection of NFT in water bodies is needed. In this regard, we prepared a three-dimensional (3D) copper-zeolitic imidazole framework (Cu/ZIF-8)-derived bimetallic Cu₅Zn₈ alloy-embedded hollow porous carbon nanocubes (Cu₅Zn₈/HPCNC) for electrochemical detection of NFT. The resultant material is characterized using suitable spectrophotometry and voltammetry methods. Cu₅Zn₈/HPCNC is an effective electrocatalyst with high electrical conductivity and a fast electron transfer rate. It also has more catalytic active sites for improved electrochemical reduction of NFT. Fabricated Cu₅Zn₈/HPCNC-modified screen-printed electrode (SPE) for NFT reduction have a wide linear range with a low detection limit, and high sensitivity (15.343 μA μМ^-1 cm^-2), appreciable anti-interference ability with related nitro compounds, storage stability, reproducibility, and repeatability. Also, the practicability of Cu₅Zn₈/HPCNC/SPE can be successfully employed in NFT monitoring in water bodies (drinking water, pond water, river water, and tap water) with satisfactory recoveries.

Synthesis and Applications of Dimensional SnS2 and SnS2/Carbon Nanomaterials

Dimensional nanomaterials can offer enhanced application properties benefiting from their sizes and morphological orientations. Tin disulfide (SnS₂) and carbon are typical sources of dimensional nanomaterials. SnS₂ is a semiconductor with visible light adsorption properties and has shown high energy density and long cycle life in energy storage processes. The integration of SnS₂ and carbon materials has shown enhanced visible light absorption and electron transmission efficiency. This helps to alleviate the volume expansion of SnS₂ which is a limitation during energy storage processes and provides a favorable bandgap in photocatalytic degradation. Several innovative approaches have been geared toward controlling the size, shape, and hybridization of SnS₂/Carbon composite nanostructures. However, dimensional nanomaterials of SnS₂ and SnS₂/Carbon have rarely been discussed. This review summarizes the synthesis methods of zero-, one-, two-, and three-dimensional SnS₂ and SnS₂/Carbon composite nanomaterials through wet and solid-state synthesis strategies. Moreover, the unique properties that promote their advances in photocatalysis and energy conversion and storage are discussed. Finally, some remarks and perspectives on the challenges and opportunities for exploring advanced SnS₂/Carbon nanomaterials are presented.

A Sandwich-Type Electrochemical Immunosensor for Insulin Detection Based on Au-Adhered Cu5 Zn8 Hollow Porous Carbon Nanocubes and AuNP Deposited Nitrogen-Doped Holey Graphene

Rapid, accurate, and sensitive insulin detection is crucial for managing and treating diabetes. A simple sandwich-type electrochemical immunosensor is engineered using gold nanoparticle (AuNP)-adhered metal-organic framework-derived copper-zinc hollow porous carbon nanocubes (Au@Cu₅ Zn₈ /HPCNC) and AuNP-deposited nitrogen-doped holey graphene (NHG) are used as a dual functional label and sensing platform. The results show that identical morphology and size of Au@Cu₅ Zn₈ /HPCNC enhance the electrocatalytic active sites, conductivity, and surface area to immobilize the detection antibodies (Ab₂ ). In addition, AuNP/NHG has the requisite biocompatibility and electrical conductivity, which facilitates electron transport and increases the surface area of the capture antibody (Ab₁ ). Significantly, Cu₅ Zn₈ /HPCNC exhibits necessary catalytic activity and sensitivity for the electrochemical reduction of H₂ O₂ using (i-t) amperometry and improves the electrochemical response in differential pulse voltammetry. Under optimal conditions, the immunosensor for insulin demonstrates a wide linear range with a low detection limit and viable specificity, stability, and reproducibility. The platform's practicality is evaluated by detecting insulin in human serum samples. All these characteristics indicate that the Cu₅ Zn₈ /HPCNC-based biosensing strategy may be used for the point-of-care assay of diverse biomarkers.

A bio-analytic nanoplatform based on Au post-functionalized CeFeO3 for the simultaneous determination of melatonin and ascorbic acid through photo-assisted electrochemical technology

Both melatonin and ascorbic acid could perform an irreplaceable role in maintaining the ecological balance of the human body and fighting cardiovascular diseases. Herein, a dual-channel photo-assisted electrochemical sensor has been fabricated based on Au post-functionalized CeFeO₃ nanospheres to simultaneously monitor melatonin and ascorbic acid for the first time. Briefly, CeFeO₃ nanospheres are prepared through a hydrothermal and annealing process, and then the reduced Au nanoclusters are anchored on the surface of spheres to afford the CeFeO₃@Au bi-nanospherical sensing probe. Impressively, the pre-fabricated sensor can produce a current signal 11% higher under light than that produced in a dark environment during the electrochemical measurements. Subsequently, the sensor fabricated by our strategy has achieved the simultaneous determination of melatonin and ascorbic acid with the wide detecting ranges of 1 nM-5 μM and 1 nM to 2 μM, and low detection limits of 0.8 nM and 0.4 nM by electrochemical measurements with the presence of the sunlight, and has shown satisfactory recoveries in the real sample measurements, demonstrating that the CeFeO₃@Au bi-nanospherical sensing probe will be an auspicious candidate of advanced electrode material in photo-assisted electrochemical sensing applications.

A novel electrochemical sensor based on β-cyclodextrin functionalized carbon nanosheets@carbon nanotubes for sensitive detection of bactericide carbendazim in apple juice

Carbendazim (CBZ) abuse always causes the over-standard of pesticide residues in agricultural products, which has adverse effects on human health. Herein, a novel electrochemical sensor was firstly fabricated based on the β-cyclodextrin (β-CD) functionalized carbon nanosheets@carbon nanotubes (CNS@CNT) for the CBZ determination. CNS@CNT combined large surface area of CNS and excellent electrical conductivity of CNT, which significantly enhanced the electrocatalytic performance. Moreover, β-CD possessed excellent host-gest supramolecular recognition ability, which could improve the selective recognition and enrichment capability of CBZ. Thanks to the synergistic interaction of CNS@CNT and β-CD, the β-CD/CNS@CNT/GCE sensor exhibited a low limit of detection of 9.4 nM in the linear CBZ concentration range of 0.03-30 μM. The fabricated sensor presented favorable stability, high sensitivity (30.86 μA μM^-1 cm^-2), and reliable reproducibility (RSD = 3.6%). Especially, the β-CD/CNS@CNT/GCE sensor could show pretty practical feasibility for the detection of CBZ in apple juice with recoveries of 97.1%-99.4%.

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.