Graphene/SnO 2 nanocomposite-modified electrode for electrochemical detection of dopamine

Development of ZnO/SnO2/rGO hybrid nanocomposites for effective photocatalytic degradation of toxic dye pollutants from aquatic ecosystems

The impact of ZnO/SnO₂/reduced graphene oxide nanocomposites (ZnO/SnO₂/rGO NCs) for improved photocatalytic degradation of organic dye pollution is examined in this study. The developed ternary nanocomposites had a variety of characteristics that were detected, such as crystallinity, recombination of photogenerated charge carriers, energy gap, and surface morphologies. When rGO was added to the mixture, the optical band gap energy of ZnO/SnO₂ was lowered, which improved the photocatalytic activity. Additionally, in comparison to ZnO, ZnO/rGO, SnO₂/rGO samples, the ZnO/SnO₂/rGO nanocomposites demonstrated exceptional photocatalytic effectiveness for the destruction of orange II (99.8%) and reactive red 120 dye (97.02%), respectively after 120 min exposure to sunlight. The high electron transport properties of the rGO layers, which make it feasible to efficiently separate electron-hole pairs, are attributed to the enhanced photocatalytic activity of the ZnO/SnO₂/rGO nanocomposites. According to the results, synthesized ZnO/SnO₂/rGO nanocomposites are a cost-efficient option for removing dye pollutants from an aqueous ecosystem. Studies show that ZnO/SnO₂/rGO nanocomposites are effective photocatalysts and may one day serve as the ideal material to reduce water pollution.

Neuro-nanotechnology: diagnostic and therapeutic nano-based strategies in applied neuroscience

Artificial, de-novo manufactured materials (with controlled nano-sized characteristics) have been progressively used by neuroscientists during the last several decades. The introduction of novel implantable bioelectronics interfaces that are better suited to their biological targets is one example of an innovation that has emerged as a result of advanced nanostructures and implantable bioelectronics interfaces, which has increased the potential of prostheses and neural interfaces. The unique physical-chemical properties of nanoparticles have also facilitated the development of novel imaging instruments for advanced laboratory systems, as well as intelligently manufactured scaffolds and microelectrodes and other technologies designed to increase our understanding of neural tissue processes. The incorporation of nanotechnology into physiology and cell biology enables the tailoring of molecular interactions. This involves unique interactions with neurons and glial cells in neuroscience. Technology solutions intended to effectively interact with neuronal cells, improved molecular-based diagnostic techniques, biomaterials and hybridized compounds utilized for neural regeneration, neuroprotection, and targeted delivery of medicines as well as small chemicals across the blood-brain barrier are all purposes of the present article.

Antibacterial and in vivo toxicological studies of Bi2O3/CuO/GO nanocomposite synthesized via cost effective methods

In this research work, Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO nanocomposites have been synthesized via an eco-friendly green synthesis technique, solgel route and co-precipitation method respectively for the assessment of antibacterial activity as well as in vivo toxicity. The XRD patterns confirm the formation of Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO nanocomposites showing monoclinic structures. Crystallite size and lattice strain are calculated by Scherrer equation, Scherrer plot and Willimson Hall plot methods. Average crystallite size measured for Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO nanocomposites by Scherrer equation, Scherrer plot and WH-plot methods are (5.1, 13.9, 11.5)nm, (5.4, 14.2, 11.3)nm and (5.2, 13.5, 12.0)nm respectively. Optical properties such as absorption peaks and band-gap energies are studied by UV–vis spectroscopy. The FTIR peaks at 513 cm⁻¹, 553 cm⁻¹ and 855 cm⁻¹ confirms the successful synthesis of Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO nanocomposites. The antibacterial activity of synthesized Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO nanocomposites is examined against two gram-negative (Escherichia coli and pseudomonas) as well as gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) at dose 25 mg/kg and 40 mg/kg by disk diffusion technique. Zone of inhibition for Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO at dose 40 mg/kg against E. coli (gram − ve) are 12 mm, 17 mm and 18 mm respectively and against Pseudomonas (gram − ve) are 28 mm, 19 mm and 21 mm respectively. While the zone of inhibition for Bi₂O₃/GO and Bi₂O₃/CuO/GO at dose 40 mg/kg against B. cereus (gram + ve) are 8 mm and 8.5 mm respectively and against S. aureus (gram + ve) are 5 mm and 10.5 mm respectively. These amazing results reveal that Bi₂O₃, Bi₂O₃/GO and Bi₂O₃/CuO/GO nanocomposite as a kind of antibacterial content, have enormous potential for biomedical applications. In addition, the in vivo toxicity of synthesized Bi₂O₃/CuO/GO nanocomposite is investigated on Swiss Albino mice at dose of 20 mg/kg by evaluating immune response, hematology and biochemistry at the time period of 2, 7, 14 and 30 days. No severe damage is observed in mice during whole treatment. The p value calculated by statistical analysis of hematological and biochemistry tests is nonsignificant which ensures that synthesized nanocomposites are safe and non-toxic as they do not affect mice significantly. This study proves that Bi₂O₃/CuO/GO nanocomposites are biocompatible and can be explored further for different biomedical applications.

One-Pot Synthesis of SnO2-rGO Nanocomposite for Enhanced Photocatalytic and Anticancer Activity

Metal oxide and graphene derivative-based nanocomposites (NCs) are attractive to the fields of environmental remediation, optics, and cancer therapy owing to their remarkable physicochemical characteristics. There is limited information on the environmental and biomedical applications of tin oxide-reduced graphene oxide nanocomposites (SnO₂-rGO NCs). The goal of this work was to explore the photocatalytic activity and anticancer efficacy of SnO₂-rGO NCs. Pure SnO₂ NPs and SnO₂-rGO NCs were prepared using the one-pot hydrothermal method. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), UV–Vis spectrometry, photoluminescence (PL), and Raman scattering microscopy were applied to characterize the synthesized samples. The crystallite size of the SnO₂ NPs slightly increased after rGO doping. TEM and SEM images show that the SnO₂ NPs were tightly anchored onto the rGO sheets. The XPS and EDX data confirmed the chemical state and elemental composition of the SnO₂-rGO NCs. Optical data suggest that the bandgap energy of the SnO₂-rGO NCs was slightly lower than for the pure SnO₂ NPs. In comparison to pure SnO₂ NPs, the intensity of the PL spectra of the SnO₂-rGO NCs was lower, indicating the decrement of the recombination rate of the surfaces charges (e⁻/h⁺) after rGO doping. Hence, the degradation efficiency of methylene blue (MB) dye by SnO₂-rGO NCs (93%) was almost 2-fold higher than for pure SnO₂ NPs (54%). The anticancer efficacy of SnO₂-rGO NCs was also almost 1.5-fold higher against human liver cancer (HepG2) and human lung cancer (A549) cells compared to the SnO₂ NPs. This study suggests a unique method to improve the photocatalytic activity and anticancer efficacy of SnO₂ NPs by fusion with graphene derivatives.

Metal-Oxide Nanomaterials Synthesis and Applications in Flexible and Wearable Sensors

Metal-oxide nanomaterials (MONs) have gained considerable interest in the construction of flexible/wearable sensors due to their tunable band gap, low cost, large specific area, and ease of manufacturing. Furthermore, MONs are in high demand for applications, such as gas leakage alarms, environmental protection, health tracking, and smart devices integrated with another system. In this Review, we introduce a comprehensive investigation of factors to boost the sensitivity of MON-based sensors in environmental indicators and health monitoring. Finally, the challenges and perspectives of MON-based flexible/wearable sensors are considered.

Graphene and Carbon Nanotube-based Electrochemical Sensing Platforms for Dopamine

Dopamine (DA) is an important neurotransmitter, which is created and released from the central nervous system. It plays a crucial role in human activities, like cognition, emotions, and response to anything. Maladjustment of DA in human blood serum results in different neural diseases, like Parkinson's and Schizophrenia. Consequently, researchers have started working on DA detection in blood serum, which is undoubtedly a hot research area. Electrochemical sensing techniques are more promising to detect DA in real samples. However, utilizing conventional electrodes for selective determination of DA encounters numerous problems due to the coexistence of other materials, such as uric acid and ascorbic acid, which have an oxidation potential close to DA. To overcome such problems, researchers have put their focus on the modification of bare electrodes. The aim of this review is to present recent advances in modifications of most used bare electrodes with carbonaceous materials, especially graphene, its derivatives, and carbon nanotubes, for electrochemical detection of DA. A brief discussion about the mechanistic phenomena at the electrode interface has also been included in this review.

β-Cyclodextrin functionalized 3D reduced graphene oxide composite-based electrochemical sensor for the sensitive detection of dopamine

A three-dimensional reduced graphene oxide nanomaterial with β-cyclodextrin modified glassy carbon electrode (3D-rGO/β-CD/GCE) was constructed and used to detect the electrochemical behavior of dopamine (DA). The nanocomposite materials were characterized by scanning electron microscopy (SEM), infrared spectrometry (FT-IR), Raman spectrogram and thermogravimetric analysis (TGA), which showed that β-CD was well modified on 3D graphene with a porous structure. The electrochemical properties of different modified electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), proving the highest electron transfer rate of the 3D-rGO/β-CD modified electrode. The experimental conditions such as scan rate, pH, enrichment time and layer thickness were optimized. Under the best experimental conditions, DA was detected by differential pulse voltammetry (DPV) by 3D-rGO/β-CD/GCE with excellent electrocatalytic ability and satisfactory recognition ability, resulting in a wide linear range of 0.5-100 μM and a low detection limit (LOD) of 0.013 μM. The modified electrode based on 3D-rGO/β-CD nanocomposites is promising in the field of electrochemical sensors due to its high sensitivity and other excellent properties.

Rational Confinement of Yttrium Vanadate within Three-Dimensional Graphene Aerogel: Electrochemical Analysis of Monoamine Neurotransmitter (Dopamine)

Real-time monitoring of neurotransmitter levels is of tremendous technological demand, which requires more sensitive and selective sensors over a dynamic concentration range. As a use case, we report yttrium vanadate within three-dimensional graphene aerogel (YVO/GA) as a novel electrocatalyst for detecting dopamine (DA). This synergy effect endows YVO/GA nanocomposite with good electrochemical behaviors for DA detection compared to other electrodes. Benefiting from tailorable properties, it provides a large specific surface area, rapid electron transfer, more active sites, good catalytic activity, synergic effect, and high conductivity. The essential analytical parameters were estimated from the calibration plot, such as a limit of detection (1.5 nM) and sensitivity (7.1 μA μM^-1 cm^-2) with the YVO/GA sensor probe electrochemical approach. The calibration curve was fitted with the correlation coefficient of 0.994 in the DA concentration range from 0.009 to 83 μM, which is denoted as the linear working range. We further demonstrate the proposed YVO/GA sensor's applicability to detect DA in human serum sample with an acceptable recovery range. Our results imply that the developed sensor could be applied to the early analysis of dementia, psychiatric, and neurodegenerative disorders.

Graphene Oxide Bulk-Modified Screen-Printed Electrodes Provide Beneficial Electroanalytical Sensing Capabilities

We demonstrate a facile methodology for the mass production of graphene oxide (GO) bulk-modified screen-printed electrodes (GO-SPEs) that are economical, highly reproducible and provide analytically useful outputs. Through fabricating GO-SPEs with varying percentage mass incorporations (2.5%, 5%, 7.5% and 10%) of GO, an electrocatalytic effect towards the chosen electroanalytical probes is observed, which increases with greater GO incorporated compared to bare/graphite SPEs. The optimum mass ratio of 10% GO to 90% carbon ink produces an electroanalytical signal towards dopamine (DA) and uric acid (UA) which is ca. ×10 greater in magnitude than that achievable at a bare/unmodified graphite SPE. Furthermore, 10% GO-SPEs exhibit a competitively low limit of detection (3σ) towards DA at ca. 81 nM, which is superior to that of a bare/unmodified graphite SPE at ca. 780 nM. The improved analytical response is attributed to the large number of oxygenated species inhabiting the edge and defect sites of the GO nanosheets, which are able to exhibit electrocatalytic responses towards inner-sphere electrochemical analytes. Our reported methodology is simple, scalable, and cost effective for the fabrication of GO-SPEs that display highly competitive LODs and are of significant interest for use in commercial and medicinal applications.

Electrochemical Oxidation of an Organic Dye Adsorbed on Tin Oxide and Antimony Doped Tin Oxide Graphene Composites

Electrochemical regeneration suffers from low regeneration efficiency due to side reactions like oxygen evolution, as well as oxidation of the adsorbent. In this study, electrically conducting nanocomposites, including graphene/SnO2 (G/SnO2) and graphene/Sb-SnO2 (G/Sb-SnO2) were successfully synthesized and characterized using nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Thereafter, the adsorption and electrochemical regeneration performance of the nanocomposites were tested using methylene blue as a model contaminant. Compared to bare graphene, the adsorption capacity of the new composites was ≥40% higher, with similar isotherm behavior. The adsorption capacity of G/SnO2 and G/Sb-SnO2 were effectively regenerated in both NaCl and Na2SO4 electrolytes, requiring as little charge as 21 C mg−1 of adsorbate for complete regeneration, compared to >35 C mg−1 for bare graphene. Consecutive loading and anodic electrochemical regeneration cycles of the nanocomposites were carried out in both NaCl and Na2SO4 electrolytes without loss of the nanocomposite, attaining high regeneration efficiencies (ca. 100%).

A core-shell molybdenum nanoparticles entrapped f-MWCNTs hybrid nanostructured material based non-enzymatic biosensor for electrochemical detection of dopamine neurotransmitter in biological samples

Dopamine (DA) is a critical neurotransmitter and has been known to be liable for several neurological diseases. Hence, its sensitive and selective detection is essential for the early diagnosis of diseases related to abnormal levels of DA. In this study, we reported novel molybdenum nanoparticles self-supported functionalized multiwalled carbon nanotubes (Mo NPs@f-MWCNTs) based core-shell hybrid nanomaterial with an average diameter of 40–45 nm was found to be the best for electrochemical DA detection. The Mo NPs@f-MWCNTs hybrid material possesses tremendous superiority in the DA sensing is mainly due to the large surface area and numerous electroactive sites. The morphological and structural characteristics of the as-synthesized hybrid nanomaterial were examined by XRD, Raman, FE-SEM, HR-TEM, EDX. The electrochemical characteristics and catalytic behavior of the as-prepared Mo NPs@f-MWCNTs modified screen-printed carbon electrode for the determination of DA were systematically investigated via electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The results demonstrate that the developed DA biosensor exhibit a low detection limit of 1.26 nM, excellent linear response of 0.01 µM to 1609 µM with good sensitivity of 4.925 µA µM⁻¹ cm⁻². We proposed outstanding appreciable stability sensor was expressed to the real-time detection of DA in the real sample analysis of rat brain, human blood serum, and DA hydrochloride injection.

Electroanalysis of Catecholamine Drugs using Graphene Modified Electrodes

Background:

Catecholamine drugs are a family of electroactive pharmaceutics, which are widely analyzed through electrochemical methods. However, for low level online determination and monitoring of these compounds, which is very important for clinical and biological studies, modified electrodes having high signal to noise ratios are needed. Numerous materials including nanomaterials have been widely used as electrode modifies for these families during the years. Among them, graphene and its family, due to their remarkable properties in electrochemistry, were extensively used in modification of electrochemical sensors.

Objective:

In this review, working electrodes which have been modified with graphene and its derivatives and applied for electroanalyses of some important catecholamine drugs are considered.

Cobalt Oxide Nanoparticles/Graphene/Ionic Liquid Crystal Modified Carbon Paste Electrochemical Sensor for Ultra-sensitive Determination of a Narcotic Drug

Purpose: Drug-abuse, namely morphine (MO) affects the metabolism of neurotransmitters such as dopamine (DA). Therefore, it is crucial to devise a sensitive sensing technique to simultaneously determine both compounds in real samples. Methods: The fabrication of the sensor is based on in situ modification of a carbon paste (CP) electrode with cobalt oxide nanoparticles, graphene, and ionic liquid crystal in presence of sodium dodecyl sulfate; CoGILCCP-SDS. The modified sensor is characterized using scanning electron microscopy, electrochemical impedance spectroscopy and voltammetry measurements. Results: Electron transfer kinetics and analytical performance of the proposed sensor were enhanced due to the synergistic role of all the modifiers. The simultaneous determination of MO and DA achieved low detection limits of 0.54 nmol L-1 and 0.25 nmol L-1, respectively. Besides, a carbon-based electrochemical sensor is fabricated for the nano-molar determination of MO in real samples and formulations. The sensor showed fouling resistance and anti-interference ability in presence of other species in human fluids. The real sample analysis of MO was successfully achieved with good recovery results in urine samples and pharmaceutical tablets. Linear dynamic range, sensitivity, detection limit and quantification limit of MO in urine were 5 nmol L-1 to 0.6 μmol L-1, 6.19 μA/μmol L-1, 0.484 nmol L-1 and 1.61 nmol L-1, respectively. Conclusion: This sensor has great ability to be extended for electrochemical applications in assaying of many drugs.

Fabrication of photo-electrochemical biosensors for ultrasensitive screening of mono-bioactive molecules: the effect of geometrical structures and crystal surfaces

The controlled design of hierarchical CN-ST flowers is a key feature for creating biosensor surface electrodes for photo-electrochemical, ultrasensitive screening of mono-bioactive molecules.

Synthesis of carbon nanoparticle embedded graphene for sensitive and selective determination of dopamine and ascorbic acid in biological fluids

We have prepared carbon nanoparticle embedded graphene (CNEG) by carbonizing a ternary composite of GO/melamine-formaldehyde resin/Zn(OAc)₂.