Graphene Oxide Nanohybrid Research Articles

Zeolite Containing Mortars Reinforced with Graphene Oxide Synthesized by Hydrolysis of Tetraethyl Orthosilicate

In the last decade, the use of nanomaterials such as graphene oxide (GO) with their noticeable potential for reinforcing cement derivatives has been considered. Unfortunately, the poor dispersion of graphene oxide in cement matrix due to the high alkalinity of the environment has disrupted the final performance of cementitious composites. In this study, GO was modified in a synthesis process with tetraethyl orthosilicate (TEOS) and was coated with Nano-SiO2 (NS) particles, and NS and GO (NS&GO) nanohybrid was prepared. The dispersion behavior of NS&GO nanohybrid was examined by Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and a map analysis. Also, natural zeolite with high pozzolanic activity was used in order to reduce the alkalinity of the cement environment. In order to compare single and hybrid effects of NS&GO, eight mortar mixtures were considered, and their mechanical, durability, and transfer properties were evaluated. The results showed that the mortar which contained NS&GO nanohybrid and 15% zeolite (by mass of cement) had the best results. These results indicate that the formation of covalent bonds between the silica coating and the carboxylate groups of GO reduces the agglomeration of GO nanosheets. Also, zeolite prevents the formation of O─ Ca─ O bonds by consuming portlandite and reducing Ca+2 ions in the cement environment. Finally, NS&GO nanohybrid through nucleation performance and zeolite through pozzolanic properties improved the durability properties of mortars.

Metal-doped Magnetic Graphene Oxide Nanohybrid for Solid-phase Microextraction of Copper from Environmental Samples

Metal-doped Magnetic Graphene Oxide Nanohybrid for Solid-phase Microextraction of Copper from Environmental Samples

Raman, TEM, EELS, and Magnetic Studies of a Magnetically Reduced Graphene Oxide Nanohybrid following Exposure to Daphnia magna Biomarkers.

A ternary nanocomposite made of nanomaghemite, nanoanatase, and graphene oxide has been successfully synthesized using an inorganic coprecipitation approach, and it has been systematically investigated by X-ray diffraction, transmission electron microscopy, and different spectrocopic techniques (electron energy loss, µ-Raman, and 57Fe Mössbauer) after interaction with an effluent containing Daphnia magna individuals. Specifically, the influence of the nanocomposite over the Daphnia magna carapace, administered in two doses (0.5 mg mL−1 and 1 mg mL−1), has been characterized using µ-Raman spectroscopy before and after laser burning protocols, producing information about the physicochemical interaction with the biomarker. The thermal stability of the nanocomposite was found to be equal to 500 °C, where the nanoanatase and the nanomaghemite phases have respectively conserved their structural identities. The magnetic properties of the nanomaghemite have also been kept unchanged even after the high-temperature experiments and exposure to Daphnia magna. In particular, the size, texture, and structural and morphological properties of the ternary nanocomposite have not shown any significant physicochemical modifications after magnetic decantation recuperation. A significant result is that the graphene oxide reduction was kept even after the ecotoxicological assays. These sets of observations are based on the fact that while the UV-Vis spectrum has confirmed the graphene oxide reduction with a localized peak at 260 nm, the 300-K and 15-K 57Fe Mössbauer spectra have only revealed the presence of stoichiometric maghemite, i.e., the two well-defined static magnetic sextets often found in the bulk ferrimagnetic counterpart phase. The Mössbauer results have also agreed with the trivalent-like valence state of Fe ions, as also suggested by electron energy loss spectroscopy data. Thus, the ternary nanocomposite does not substantially affect the Daphnia magna, and it can be easily recovered using an ordinary magnetic decantation protocol due to the ferrimagnetic-like character of the nanomaghemite phase. Consequently, it shows remarkable physicochemical properties for further reuse, such as cleaning by polluted effluents, at least where Daphnia magna species are present.

Effects of rGO incorporation on structural and magnetic properties of Ni-Zn ferrite nanostructures

Ni0.5Zn0.5Fe2O4 (NZ)/reduced graphene oxide (rGO) nanohybrids were prepared by surfactant assisted citric acid mediated sol–gel auto combustion method. Samples were analyzed by various characterization techniques to acquire information about the structural, morphological, thermal and magnetic properties. X-ray diffraction results confirm the successful synthesis of NZ/rGO nanocomposite. Transmission electron microscopic images reveal that the NZ nanostructures are well decorated on the rGO matrix. Few of them are also sandwiched within the rGO sheets. Samples were thermally characterized by thermo-gravimetric setup. Raman spectroscopic technique was also employed for the analysis of the samples. The room temperature Mössbauer spectra of the samples were fitted into a doublet and two sextets owing to the presence of two magnetic sites. Room temperature (300 K), as well as low temperature (10 K) M−H loops of the samples were recorded by SQUID magnetometer. Enhancement in the value of coercivity of the NZ/rGO sample with comparison to the pure NZ, has established that the incorporation of rGO has effectively influenced the magnetic property of pure NZ.

Synergistic effect of cellulose nanocrystals-graphene oxide as an effective nanofiller for enhancing properties of solventless polymer nanocomposites

The solution mixing approach-based cellulose nanocrystals (CNCs) decorated graphene oxide (GO) nanohybrids (CNC@GO) was prepared and their effect over on the solventless polymer (SLP) called waterborne epoxy system was analyzed. The as-prepared GO, CNC and CNC@GO were scrutinized by several characterization techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman Analysis, Fourier transform infra-red (FT-IR), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) for identifying their quality. The GO-SLP, CNC-SLP and CNC@GO-SLP nanocomposites mechanical and thermal properties were analyzed in detail. The highest tensile strength was observed at the lowest loading content (0.2 wt %) of CNC@GO incorporated SLP nanocomposites, as compared with other (0.2 wt % of (GO-SLP and CNC-SLP)) nanocomposites. Also, the thermo-mechanical analysis of CNC@GO nanohybrids incorporated SLP system exposes a notable improvement in the tan delta and storage modulus values at lower nanofiller concentration (0.2 wt %). The successful decoration of CNC on the GO surface promotes to the uniform dispersion, strong hydrogen bonding and outstanding interaction between the introduced nanofillers within the SLP system which leads to the better results in the mechanical and thermal properties. Besides, it was observed that the numerical simulation responses were in good deal with the laboratory values for both ultimate stress and strain. Thus, the as-prepared nanohybrids could possibly enrich the mechanical and thermal properties of the SLP system.

CTAB Enhanced Room-Temperature Detection of NO2 Based on MoS2-Reduced Graphene Oxide Nanohybrid

A new NO2 nanohybrid of a gas sensor (CTAB-MoS2/rGO) was constructed for sensitive room-temperature detection of NO2 by 3D molybdenum disulfide (MoS2) and reduced graphene oxide (rGO), assisted with hexadecyl trimethyl ammonium bromide (CTAB). In comparison with MoS2 and MoS2/rGO, the BET and SEM characterization results depicted the three-dimensional structure of the CTAB-MoS2/rGO nanohybrid, which possessed a larger specific surface area to provide more active reaction sites to boost its gas-sensing performance. Observations of the gas-sensing properties indicated that the CTAB-MoS2/rGO sensor performed a high response of 45.5% for 17.5 ppm NO2, a remarkable selectivity of NO2, an ultra-low detection limit of 26.55 ppb and long-term stability for a 30-day measurement. In addition, the response obtained for the CTAB-MoS2/rGO sensor was about two to four times that obtained for the MoS2/rGO sensor and the MoS2 sensor toward 8 ppm NO2, which correlated with the heterojunction between MoS2 and rGO, and the improvement in surface area and conductivity correlated with the introduction of CTAB and rGO. The excellent performance of the CTAB-MoS2/rGO sensor further suggested the advantage of CTAB in assisting a reliable detection of trace NO2 and an alternative method for highly efficiently detecting NO2 in the environment.

Synthesis, characterisation and corrosion inhibition assessment of a novel ionic liquid-graphene oxide nanohybrid

A novel ionic liquid, L-proline nitrate and graphene oxide nanohybrid (IL-GO), was synthesized and characterised by FTIR, UV-–Vis,1H NMR,13C NMR and HR-TEM. The corrosion inhibition potency of IL-GO nanohybrid for mild steel in 1 M HCl was examined by gravimetric measurements, electrochemical methods supplemented with SEM-EDS, XPS, contact angle measurement, and FTIR. The experimental results supported that IL-GO endowed fairly good corrosion inhibition response in the temperature range 303–353 K. Inhibition efficiency raised with inhibitor concentration, reaching 86.5% at 250 ppm and falling above 333 K. Adsorption of IL-GO over mild steel surface suited well with Langmuir model involving both chemisorption and physisorption interactions. Electrochemical results demonstrated that IL-GO remarkably resisted charge transfer process across the mild steel–solution interface and functioned as mixed-type inhibitor. SEM-EDS and XPS studies verified the adsorption of IL-GO nanohybrid and fabrication of a physical barrier film at the metal surface.

Mesoporous Fe3O4/graphene oxide nanohybrid for catalytic Ozonation: Preparation, characterization and process modeling by neural network

BackgroundCatalytic activity of graphene and its related compounds have been reported in the ozonation process. In addition, Fe3O4 has a good catalytic activity in the ozonation process. Fabrication of high porosity Fe3O4/graphene oxide nanohybrids can improve the production of reactive oxygen species. MethodsMesoporous Fe3O4/ graphene oxide nanohybrid was prepared by coprecipitation method. The catalytic activity of nanohybrid was investigated in ozonation degradation of acid red88 in the simulated wastewater. The progress of degradation process was determined using reactive oxygen species scavengers. The process was modeled by the artificial neural network. Significant FindingsThe mesoporous nanohybrid has a specific surface area of 252.7 m2/g, total pore volume of 0.353 cm3/g and mean pore diameter of 5.6 nm. Fe3O4/ graphene oxide showed superior catalytic activity compared to Fe3O4 and graphene oxide. Hydroxyl (OH·) and superoxide radicals (O2·−) were identified the main radical reactive species. The influence of ozone dosage, pH, dye and catalyst concentration, on the acid red88 degradation rate was investigated. The degradation process was pH dependent, and acidic condition was more favorable to mineralization of acid red88 than neutral or basic mediums. Chemical oxygen demand removal has reached 69% in the catalytic ozonation process, while it reached only 25% in single ozonation process. A very good agreement (R = 0.99) was observed between the calculated and experimental degradation efficiency. The results demonstrated that mesoporous nanohybrid is a promising catalyst for ozonation process, especially treating water polluted by azo dyes.

Electroactive calcium-alginate/polycaprolactone/reduced graphene oxide nanohybrid hydrogels for skeletal muscle tissue engineering

Graphene derivatives such as reduced graphene oxide (rGO) are used as components of novel biomaterials for their unique electrical properties. Electrical conductivity is a crucial factor for muscle cells, which are electrically active. This study reports the development of a new type of semi-interpenetrated polymer network based on two biodegradable FDA-approved biomaterials, sodium alginate (SA) and polycaprolactone (PCL), with Ca2+ ions as SA crosslinker. Several drawbacks such as the low cell adhesion of SA and weak structural stability can be improved with the incorporation of PCL. Furthermore, this study demonstrates how this semi-IPN can be engineered with rGO nanosheets (0.5% and 2% wt/wt rGO nanosheets) to produce electroactive nanohybrid composite biomaterials. The study focuses on the microstructure and the enhancement of physical and biological properties of these advanced materials, including water sorption, surface wettability, thermal behavior and thermal degradation, mechanical properties, electrical conductivity, cell adhesion and myogenic differentiation. The results suggest the formation of a complex nano-network with different interactions between the components: bonds between SA chains induced by Ca2+ ions (egg-box model), links between rGO nanosheets and SA chains as well as between rGO nanosheets themselves through Ca2+ ions, and strong hydrogen bonding between rGO nanosheets and SA chains. The incorporation of rGO significantly increases the electrical conductivity of the nanohybrid hydrogels, with values in the range of muscle tissue. In vitro cultures with C2C12 murine myoblasts revealed that the conductive nanohybrid hydrogels are not cytotoxic and can greatly enhance myoblast adhesion and myogenic differentiation. These results indicate that these novel electroactive nanohybrid hydrogels have great potential for biomedical applications related to the regeneration of electroactive tissues, particularly in skeletal muscle tissue engineering.

Direct acidic graphene oxide enabled fabrication of three-dimensional molybdenum trisulfide and reduced graphene oxide nanohybrid aerogels with simultaneous energy storage and electrocatalytic capability

To confront the ever-growing energy and environmental concerns, the rational design and development of newer yet high-performance energy storage and conversion materials are highly desirable. Herein, we proposed a scalable and simplistic approach to prepare a three-dimensional (3D) MoS3/reduced graphene oxide (RGO) aerogel as an efficient electroactive material. Under a benign in-situ hydrothermal method, an acidic graphene oxide was directly used as support and catalyst to form uniformly dispersed MoS3 nanoparticles within porous 3D RGO architecture. Owing to its unique synergy of plentiful exposed active sites and highly porous conductive network, the resulting nanohybrid was successfully used as a supercapacitor electrode and electrocatalyst for hydrogen evolution reaction (HER). The as-obtained 3D MoS3/RGO nanohybrid-based electrode provides a higher specific capacitance of 576.5 F·g−1, more significant than the pristine MoS3 electrode (206.4 F g−1). Likewise, an asymmetric supercapacitor (ASC) device assembled using the MoS3/RGO and activated carbon (AC) delivers a maximum energy density of 35.2 Wh kg−1 at a power density of 528 W kg−1, over a voltage window of 1.5 V. Moreover, remarkable cycling stability accompanied by 92% capacitance retention was also observed. Similarly, the resulting 3D MoS3/RGO nanohybrids display significant HER activity, requiring a smaller overpotential of only 0.121 V to accomplish a current density of 10 mA·g−1 in conjunction with a smaller Tafel slope value of 60 mV dec−1 in 0.5 M H2SO4. Such remarkable electrocatalytic activity is accredited to its unique porous nanoarchitecture, sulfur-rich active centers, and improved conductivity. Overall, the implemented optimal methodology offers technological scalability in the fabrication of low-cost 3D nanohybrids electrodes composed of graphene and TMDs for various energy-related applications.

Directed aromatic C–H functionalization of N-arylcarbamates and quinazolinones catalyzed by palladium nanoparticles supported on nitrogen-doped graphene

Pd nanoparticle‑nitrogen doped reduced graphene oxide (Pd/N-RGO) nanohybrid was successfully utilized for the C-H-acyloxylation of N-arylcarbamates and the CH halogenation of quinazolinones with N-halosuccinimides. The use of the catalyst was shown to be a highly efficient, less time-consuming and recyclable procedure for two different types of CH functionalization; it was even better than Pd(OAc)2 as its homogeneous counterpart. Additionally, the effect of introducing nitrogen into the graphene lattice on the catalytic activities of palladium was evaluated by synthesizing Pd nanoparticles-reduced graphene oxide. The catalyst exhibited no significant palladium leaching; so, it was successfully recovered and reused in ten consecutive runs without any noticeable decrease in its catalytic activity.

Preparation of Silver Decorated Reduced Graphene Oxide Nanohybrid for Effective Photocatalytic Degradation of Indigo Carmine Dye

Background: Even though silver decorated reduced graphene oxide (Ag-rGO) shows maximum absorptivity in the UV region, most of the research on the degradation of dyes using Ag-rGO is in the visible region. Therefore the present work focused on the photocatalytic degradation of indigo carmine (IC) dye in the presence of Ag-rGO as a catalyst by UV light irradiation. Methods: In this context, silver-decorated reduced graphene oxide hybrid material was fabricated and explored its potential for the photocatalytic degradation of aqueous IC solution in the UV region. The decoration of Ag nanoparticles on the surface of the rGO nanosheets is evidenced by TEM analysis. The extent of mineralization of the dye was measured by estimating chemical oxygen demand (COD) values before and after irradiation. Results: The synthesized Ag-rGO binary composites displayed excellent photocatalytic activity in 2 Χ 10-5 M IC concentration and 5mg catalyst loading. The optical absorption spectrum of Ag-rGO showed that the energy band-gap was found to be 2.27 eV, which is significantly smaller compared to the band-gap of GO. 5 mg of Ag-rGO was found to be an optimum quantity for the effective degradation of IC dye. The degradation rate increases with the decrease in the concentration of the dye at alkaline pH conditions. The photocatalytic efficiency was 92% for the second time. Conclusion: The impact of the enhanced reactive species generation was consistent with higher photocatalytic dye degradation. The photocatalytic mechanism has been proposed and the hydroxyl radical was found to be the reactive species responsible for the degradation of dye. The feasibility of reusing the photocatalyst showed that the photocatalytic efficiency was very effective for the second time.

An Electrochemical Sensor for Quantitation of the Oral Health Care Agent Chlorogenic Acid Based on Bimetallic Nanowires with Functionalized Reduced Graphene Oxide Nanohybrids.

Chlorogenic acid (CGA), a phenolic acid from coffee, has been regarded as a powerful ingredient against oxidative stress and inflammation. Meanwhile, its healing feature to interfere with periodontal disease (PD) makes it a promising drug candidate. However, the existing methods for chlorogenic acid detection limit its practical application in purification and further pharmacological study in stomatology due to their lack of accuracy and productivity. Therefore, it is crucial to find a forceful approach to precisely evaluate CGA for an in-depth anti-PD study. In this work, we reported a facile and controllable synthesis of Pt@Pd nanowires (NWs) in a non-compacted core–shell structure with high electrocatalytic activity. In addition, polyethylenimine (PEI)-capped reduced graphene oxide (rGO) nanoflakes provided large binding sites for a network structure composed of interweaved Pt@Pd nanowires and protected hemin from self-destruction, which empowered Pt@Pd NWs-Hemin-PEI-rGO nanohybrids to own a large electroactive surface area and great electrochemical property for CGA detection. The enzyme-free electrochemical sensor based on Pt@Pd NWs-Hemin-PEI-rGO displayed a favorable capacity for trace CGA detection with a detection limit of 7.8 nM and a wide linear range of 0.5 μM to 4 mM. The exceptional sensitivity and selectivity of the sensor made it accomplish the measurements of chlorogenic acid in soft drinks and coffee with high consistency of HPLC results. The satisfactory performance of the obtained sensor enables it to be used for quality control and study of drug metabolism in PD treatments.

Constructing efficient and recyclable composite absorbent based on the modification of polymer skeleton with in situ assembled mesoporous silica/graphene oxide nanohybrid

Polymers functionalized with hybrid nanoparticles are very popular for the preparation of composite absorbents with large surface area and good absorption capacity. However, the weak physical interactions between different nanoparticles allow for the easy destruction of the hybrid structure, which will greatly reduce the advantages of the hybrid nanoparticles as building blocks for the composite absorbent and decrease the stability of the composite absorbent in practical use. Here, in situ chemically boned mesoporous SiO2 (mSiO2)/graphene oxide (GO) nanohybrid (GO-mSiO2) was first synthesized by hydrolysis and condensation of tetraethylorthosilicate on the GO sheets, on which mSiO2 with the diameter of ca. 5 nm was uniformly distributed. Subsequently, a ternary absorbent with large surface area and very good water repellency was constructed by first impregnating commercial poly(melamine-formaldehyde) (MF) foam into GO-mSiO2 and then into polydimethylsiloxane (as cement and low surface energy source) solution. Because of the dually roughened skeleton surface with hybrid nanoparticles and the channel structure of mSiO2, the GO-mSiO2 modified hydrophobic MF (m-MF) foam possessed large surface area and high selective absorption ability for different oils and organic solvents from water, showing an absorption capacity that was up to 172 times its own weight. Moreover, m-MF can be recycled via the continued extrusion/sorption method. Taken together, these results suggest that the thus-prepared ternary absorbent can be applied as a potential candidate for the cleanup of oil spillage and toxic chemical leakage.

Graphene enhanced α-MnO2 for photothermal catalytic decomposition of carcinogen formaldehyde

Formaldehyde (HCHO) causes increasing concerns due to its ubiquitously found in indoor air and being irritative and carcinogenic to humans. Photothermal-catalysis developed in recent years has been considered as a significant strategy for enhancing catalytic activity. Manganese oxides, compared with its strong thermocatalytic activity, generally suffer from much lower photocatalytic activity make its photochemical properties less concerned. Herein, α-MnO2 nanowires were composited with the graphene oxide (GO) via mechanical grinding and co-precipitating method, respectively. α-MnO2/GO nanohybrids prepared by co-precipitating method exhibits excellent activity, achieving 100% decomposition of HCHO with the solar-light irradiation at ambient temperature. It is found that, besides the photo-driven thermocatalysis, the photocatalysis mechanism made a major contribution to the decomposition of HCHO. The incorporation of GO, on the one hand, is beneficial to improve the optical absorption capacity and photothermal conversion efficiency; on the other hand, is conductive to electron transfer and effective separation of electrons and holes. These synergistic effects significantly improve the catalytic activity of α-MnO2/GO nanohybrids. This work proposes a new approach for the utilization of solar energy by combining manganese oxides, and also develops an efficient photothermal-catalyst to control HCHO pollution in indoor air.

Facile synthesis of Al substituted Cu-ferrite infused reduced graphene oxide (rGO) nanohybrid for improving microwave absorption at gigahertz frequencies

This work mainly deals with the synthesis of Al substituted copper ferrite infused reduced graphene oxide (rGO) as a microwave absorbing material in a frequency ranging from 8.2 to 12.4 GHz (X-band). Firstly, Al substituted copper ferrite (CAF) infused rGO was synthesized using the solvothermal method. Then it mixed in the epoxy media to fabricate lightweight nanocomposites for their potential uses as competent electromagnetic wave absorbers. The structural analysis using XRD validates the successful substitution of Al into copper ferrite lattice. TEM results showed that copper-Al-ferrite's spherical morphology with size ~20–30 nm is well infused on rGO in the as-synthesized nanohybrid. BET analysis confirmed numerous pore formations in the nanohybrid that created during CAF over rGO. Furthermore, the effect of rGO-loaded/and unloaded nanohybrid on the microwave absorption properties was also studied. Notably, it is seen that the strategy to infuse CAF on rGO was found more effective in enhancing the absorption capacity of pure CAF. Remarkably, the CAF-rGO/epoxy nanocomposite exhibited excellent microwave absorption capacity as the reflection loss (RL) value of − 35.7 dB (99.973% absorption) is achieved with 3.55 GHz of broad − 10 dB (90% absorption) bandwidths under the low filler content of 20 wt% and small matching thickness of 2.2 mm. Besides, the possible microwave absorption mechanisms in the nanohybrid composite are also disclosed. Therefore, our results could be helpful to manufacture the rGO based dielectric-magnetic hybrid nanocomposites for the highly efficient and lightweight microwave absorber exclusively for X band application, i.e., in the high gigahertz range.

Porous perovskite CaMnO3/rGO hybrid as an efficient electrocatalyst in lithium-oxygen batteries.

In this work, we demonstrate a facile route for synthesizing a novel CaMnO3/reduced graphene oxide (CaMnO3/rGO) nanohybrid as a cathode catalyst in Li-O2 batteries. The experimental results show that the CaMnO3/rGO hybrid exhibits superior electrochemical properties compared to bare CaMnO3 perovskite oxide. Li-O2 batteries assembled with a CaMnO3/rGO cathode catalyst show a remarkable initial discharge capacity of 19 000 mA h g-1 at a high current density of 1000 mA g-1. Excellent cycling stability is achieved within 200 cycles at a restricted charge/discharge capacity of 2000 mA h g-1. The enhanced catalytic performance proposes the hybrid of mesoporous CaMnO3 perovskite oxide and rGO nanosheets as a potential electrocatalyst for next-generation Li-O2 batteries.

Fabrication of a polyoxotungstate/metal-organic framework/phosphorus-doped reduced graphene oxide nanohybrid modified glassy carbon electrode by electrochemical reduction and its electrochemical properties.

Hybrid nanocomposites based on polyoxometalates (POMs), metal–organic frameworks (MOFs), and graphene oxide (GO) have a unique set of properties. They have specific properties such as high acidity, oxygen-rich surface, and good redox capability from POMs. In contrast, they do not have weaknesses of POMs such as a low surface area, and high solubility in aqueous media. Herein, a novel organic–inorganic nanohybrid compound based on H3PW12O40 (PW12), a Co-based MOF, and GO was prepared. The prepared hybrid nanocomposite (PW12/MOF/GO) was characterized using different techniques. Then, a PW12/MOF/GO nanocomposite modified glassy carbon electrode (GCE) was fabricated by the drop-casting method and next was dried at room temperature. Then, the PW12/MOF/GO/GCE was subjected to electrochemical reduction at a constant potential of −1.5 V, in 0.1 M H3PO4 solution containing 0.10% w/v PW12/MOF/GO additive. The morphology, electrochemical activity, and stability of the modified electrode (PW12/MOF/P@ERGO/GCE) were studied with FE-SEM coupled with EDS, CV, and amperometry. The obtained results confirmed that the PW12/MOF/P@ERGO/GCE could be effective in hydrogen evolution reaction (HER). The electrochemical activity of the PW12/MOF/P@ERGO/GCE due to the desirable microstructure of the electrocatalyst (e.g. high active surface area and homogeneous distribution of the PW12/MOF/P@ERGO), and also the synergistic effect of the blocks, is more than those of PW12/GCE, MOF/GCE, PW12/MOF/GCE, and P@ERGO/GCE. Moreover, the PW12/MOF/P@ERGO/GCE showed an excellent long-term stability under the air atmosphere.

Hydrothermal fabrication of MoS2/reduced graphene oxide nanohybrid composite for the electrochemical sensing of Hg(II) in green tea

Heavy metal contamination is a standout among the most genuine ecological issues: toxicity, persistence, bioaccumulation, and biomagnification through food chains. The present work aims at the synthesis of abundant, fast-sensing electrochemical sensors MoS2 and MoS2@rGO composite by the hydrothermal method to develop electrochemical sensors for the detection of Mercury (Hg-II). The synthesized material was characterized and conformed to a hierarchical spherical sponge-like structure with a high surface-to-volume ratio. The electrochemical sensor conditions were observed at ambient conditions to detect Hg (II) (0.5, 1, 1.5, 2, 2.5, 3, 3.5 µm L−1 was used) and the results showed very promisingly. The limit of detection (LOD) was found to be 2.0 × 10−7 µg/mL for MoS2, 1.22 × 10−8 µg/mL for composite. The heavy metals were spiked in green tea extract to observe the sensor ability of the material. The sensor ability for the material for real-time detection of green tea was found to be LOD-2.12 × 10−7 µg/mL (MoS2) and 1.21 × 10−9 µg/mL (MoS2@rGO).

Preparation and third order nonlinear optical properties of corrole functionalized GO nanohybrids

Three novel corroles, 5,15-bis(phenyl)-10-(3-methoxy-4-hydroxylphenyl)- corrole PC, 5,15-bis(naphthyl)-10-(3-methoxy-4-hydroxylphenyl)-corrole NAPC and 5,15-bis(pyrenyl)-10-(3-methoxy-4-hydroxylphenyl)-corrole PYPC, were designed and synthesized. Their graphene oxide (GO) nanohybrids, PC-GO, NAPC-GO and PYPC-GO, were prepared by a covalent functionalization method and characterized by various spectroscopic techniques. The third order nonlinear optical (NLO) behavior of the corroles and their corresponding nanohybrids was investigated using open aperture Z-scan technique at 532 nm with 4 ns laser pulses. The nanohybrids showed enhanced NLO properties in comparison to the corresponding corroles. In addition, the NLO properties of nanohybrids increase in the order of NAPC-GO < PC-GO < PYPC-GO, while the corrole molecules exhibit NLO performance in the same order of NAPC < PC < PYPC, implying the NLO response originating from the corrole moiety play a more important role in the NLO properties of the nanohybrids than that arising from the photo-induced electron or energy transfer process between GO and corrole molecules. Importantly, at same transmission intensity, all the corroles showed typical nonlinear reverse saturation absorption (RSA) behavior, while all the nanohybrids exhibited a flip over behavior from saturation absorption (SA) to RSA. The different NLO response between the corrole molecules and their nanohybrids implies their promising applications as NLO materials.