Improved Hummers Method Research Articles

Fabrication of non-enzymatic and highly sensitive electrochemical ascorbic acid sensor based on GO/Ag/PMMA nanocomposites

In the present study, Graphene Oxide–Silver–Poly(methyl methacrylate) (GO/Ag/PMMA) nanocomposites were fabricated and investigated for Ascorbic Acid sensing without using any enzyme. First, the graphene oxide was prepared by improved Hummers method. The tri-phase nanocomposites were also prepared by sonication and solution casting method with the ratio of Graphene Oxide (1, 2, 3, 4, and 5 %). The composites were characterized by FTIR, X-ray Diffraction (XRD), TGA, and scanning electron microscopy (SEM) analysis. The electrochemical studies/characterizations of ascorbic acid oxidation were carried out in the acidic medium and the new sensor was found to be a better electrochemical ascorbic acid sensor. The fabricated sensor is highly sensitive to ascorbic acid and shows its sensitivity (778.532 µA mM−1 cm−2), it has a broad linear range (from 0.1 to 6 mM), it is selective, and it shows tolerance towards endogenous species such as glucose, uric acid, hydrogen peroxide, and dopamine.

Molecular insights into the interaction between graphene oxide and β-galactosidase: From multispectral experiment, enzyme kinetics experiment to computational simulations

β-galactosidase has potential applications in various scientific disciplines, including the food industry, genetic engineering, and enzyme engineering. In this study, multi-spectral experiments combined with enzyme kinetics experiments and computational simulation were used to explore the interaction mechanism, structural and functional changes, and effects on the microenvironment of graphene oxide and β-galactosidase. Graphene oxide was synthesized using the improved Hummer method, and the characterization experiments demonstrated that the structure was flat and free of cracks, and the functional groups satisfied the required amount. Zeta potential experiments and molecular docking results jointly confirmed that graphene oxide and β-galactosidase were combined by van der Waals forces, electrostatic forces, and hydrophobic forces. Fluorescence quenching experiments showed that the quenching constant decreased from 2.90 × 1012 mLμg-1s−1 to 1.76 × 1012 mLμg−1 s−1 with the increase of temperature, indicating that the quenching mode was static quenching, accompanied by increased polarity and decreased hydrophilicity of β-galactosidase. Circular Dichroism Spectrum, Fourier Transform infrared spectroscopy, the ONPG experiment, and molecular dynamics simulation proved that the stability and activity of β-galactosidase were improved after binding with graphene oxide. These findings provide support for the potential applications of β-galactosidase in addressing lactose intolerance, optimizing gene expression efficiency, and developing innovative biosensors or bioprocessing systems.

Standalone Highly Efficient Graphene Oxide as an Emerging Visible Light-Driven Photocatalyst and Recyclable Adsorbent for the Sustainable Removal of Organic Pollutants.

Carbon-based nanostructures are promising eco-friendly multifunctional nanomaterials because of their tunable surface and optoelectronic properties for a variety of energy and environmental applications. The present study focuses on the synthesis of graphene oxide (GO) with particular emphasis on engineering its surface and optical properties for making it an excellent adsorbent as well as a visible light-active photocatalyst. It was achieved by modifying the improved Hummers method through optimizing the synthesis parameters involved in the oxidation process. This controlled synthesis allows for systematic tailoring of structural, optical, and surface functionality, leading to improved adsorption and photocatalytic properties for the sustainable removal of organic pollutants in water treatment. Several spectroscopic and microscopic characterization techniques, such as XRD, SEM, Raman, UV-visible, FTIR, TEM, XPS, BET, etc. were employed to analyze the degree of oxidation, surface chemistry/functionalization, morphological, optical, and structural properties of the synthesized GO nanostructures. The analyses showed excellent surface functionality with surface active sites for better adsorptive removal and a tunable band gap from 2.51 to 2.76 eV exhibiting excellent natural sunlight activity (>99%) for photocatalytic removal of the organic pollutant. Various adsorption isotherms have been studied with excellent adsorption capability (Qmax = 454.54 mg/g) as compared to the literature. The study introduces GO both as a proficient stand-alone (sole) nanoadsorbent as well as a nanophotocatalyst for the efficient removal of organic dye pollutants in water treatment. Additionally, the article highlights the sustainable solar light-induced green chemistry aspects of GO as an excellent recyclable adsorbent as a result of its self-cleaning ability under natural sunlight, demonstrating its potential in real eco-friendly environmental and practical applications.

Chemiresistive sensor based on PMMA/rGO composite for detection ammonia

Reduced graphene oxide (rGO) has been a promising material in sensing applications. However, rGO-based sensors have very high recovery time at room temperature (RT). Therefore, various materials combination needs to explored to address this issue. We have developed chemiresistive sensor based on a composite of Poly (methyl methacrylate) (PMMA) and rGO for detection of ammonia (NH3). To prepare more oxidized graphene oxide (GO), peroxidation of graphite oxide (PGO) was used from graphite by following Improved Hummer’s Method (IHM). Due to PGO, synthesized rGO was more conductive and high charge capacity. Synthesized PMMA/rGO composite was drop cast on fabricated interdigitated copper electrodes. Various characterization tools were used for materials confirmation. The chemiresistive sensor based on PMMA/rGO exhibited very good sensing behaviour towards NH3 analytes. The range of detection was 1–10 ppm with very good reproducibility. It was far below the Occupational Safety and Health Administration Permissible Exposer Limit (OSHA PEL) of NH3. A chemiresistive sensor based on PMMA/rGO composite revealed better sensing results than a pristine rGO sensor. The response time and recovery time for rGO based sensor was 122 s and 168 s respectively at 2 ppm of NH3 whereas for PMMA/rGO based sensor it was 50 s and 75 s respectively. Moreover, the PMMA/rGO based sensor exhibited repeatability at 2 ppm for NH3 at RT. This type of PMMA/rGO sensor will be very much useful for the detection of hazardous gases in chemical laboratories and industrial areas.

Graphene Oxide as Novel Visible Light Active Photocatalyst: Synthesis, Modification by Nitrogen and Boron Doping, and Photocatalytic Application

Graphene oxide (GO) has become one of the emerging and important sole photocatalyst nanomaterials in recent years due to its exceptional/tunable optoelectronic properties, multifunctionality, and eco‐friendly nature. However, challenges remain in tuning surface chemistry, tailoring the band gap, developing doping strategies, and understanding the sole photocatalytic mechanism. This contribution investigated the synthesis of GO via the improved Hummers method by varying the ratio of the oxidizing agents (K2Cr2O7:KMnO4), as well as modifications by nitrogen (N) and boron (B) doping in view of its applications in photocatalytic degradation of organic dye pollutants. Furthermore, changes in surface chemistry, optical, compositional, morphological, and structural properties are investigated to understand the photocatalytic mechanism. The synthesized GO showed a broad spectrum of light absorption with a tunable band gap of 2.4–4.3 eV and exhibited more than 91% degradation of methylene blue dye under direct sunlight. However, the photocatalytic activity decreased after N and B doping attributed to reduced oxygen‐containing functional groups, low surface area, and dopants‐induced bonding configurations within the GO structure. This study provides a new insight into replacing metallic semiconductor photocatalysts with highly affordable, environmentally friendly, and potent metal‐free GO photocatalysts.

Quick responding humidity sensor based on polyaniline/reduced graphene oxide composite

The relative humidity sensing response of the Polyaniline/ reduced Graphene Oxide (PRGO) composites has been explored in this present research work. For these observations, polyaniline (PANI), synthesised by the chemical oxidative polymerisation process, was physically blended using the different mass ratios of reduced graphene oxide (rGO). By the improved hummers method, graphene oxide (GO) is prepared, adding the minimal quantity of selenium power, and the GO was effectively and facilely reduced to rGO. By adding different weight per cent (wt%) of reduced Graphene oxide (rGO) to the polymer matrix, PRGO composites were prepared. Structural and morphological properties of rGO were confirmed by XRD, RAMAN, FTIR, SEM, EDX, and HR-TEM (elementary mapping) characterisations. XRD, FTIR SEM and EDX proficiencies were employed to characterise the PRGO composites. For the humidity sensing determination, the sensing film of the PANI, rGO, and PRGO composites is groomed by loading the sample on an IDT substrate through a drop casting technique. The PRGO-3 composite has shown an epitome response and recovery of 3 and 4 s, respectively. The PRGO-3 composite has the most minored and less real sensitivity with a lower limit of detection (LOD). Also, the prepared PRGO composites have recorded less hysteresis and good linearity and depicted exact stability over PANI and other PRGO composites. The physical parameters for PRGO composites were also calculated to determine the potentiality of a perfect sensor. The sensing mechanism also hashed out based on establishing chemisorption and physisorption layers.

Effect of surface species on the alcohol-acid adsorption from FTS wastewater on graphene: A structure-capacity study

Fischer-Tropsch synthesis (FTS) wastewater retaining low-carbon alcohols and acids are organic pollutants as a limiting factor for FTS industrialization. In this work, the structure-capacity relationships between alcohol-acid adsorption and surface species on graphene were reported, shedding light into their intricate interactions. The graphene oxide (GO) and reduced graphene oxide (rGO) were synthesized via improved Hummers method with flake graphite (G). The physicochemical properties of samples were characterized via SEM, XRD, XPS, FT-IR, and Raman. The alcohol-acid adsorption behaviors and adsorption quantities on G, GO, and rGO were measured via theoretical and experimental method. It was revealed that the presence of COOH, C=O and CO species on graphene occupy the adsorption sites and increase the interactions of water with graphene, which are unfavorable for alcohol-acid adsorption. The equilibrium adsorption quantities of alcohols and acids grow in pace with carbon number. The monolayer adsorption occurs on graphene was verified via model fitting. rGO has the highest FTS modeling wastewater adsorption quantity (110 mg/g) due to the reduction of oxygen species. These novel findings provide a foundation for the alcohol-acid wastewater treatment, as well as the design and development of high-performance carbon-based adsorbent materials.

Large-scale Production of Few-Layer Reduced Graphene Oxide by the Rapid Thermal Reduction of Graphene Oxide and Its Structural Characterization

Graphene, a carbon allotrope, is a two-dimensional honeycomb of carbon atoms. Although graphene is a thin material, it is the strongest material known on Earth thanks to the strong carbon bonds in its structure. It is stated that the strength of these carbon bonds in graphene is about 100 times stronger than steel. In this study, graphite was first converted into graphene oxide (GO) by the Improved Hummers method, which is one of the methods suitable for large-scale production. Reduced graphene oxide (RGO) was obtained from the synthesized GOs by thermal reduction. TGA, FTIR, XRD, XPS, Raman, BET, and SEM analyses were used to characterize GO produced using the improved Hummers method and RGO reduced by thermal methods. TGA measurements show that RGO produced using the thermal approach had a lower mass loss than graphite oxidized using the improved Hummers process. This shows that the GO sample prepared using the improved Hummers approach contains a considerable number of distinct oxygen-containing groups. The novelty of the modified Hummers' method lies in its enhanced efficiency in producing graphene oxide through reduced thermal reaction times and improved scalability compared to the original approach in the literature. The C:O ratio of the GO and RGO samples was determined by XPS to be 1.88 and 11.17, respectively. The ID/IG ratio obtained by Raman analysis was 0.973. In addition, RGO's BET surface area was discovered to be 543.6 m2 g-1. These findings demonstrated that graphite was successfully oxidized by an improved Hummers method, and the resulting GO was thermally converted to few-layer RGO.

An improved Hummers method derived graphene oxide wrapped ZIF-8 polyhedron derived porous heterostructure for symmetric supercapacitor performance

By exposing more interfaces, utility of heterostructured electrodes in capacitance retention has been further expanded to devices with a large-scale 3D network. IGO@ZIF-8-NC was described as a symmetric supercapacitor device which paves the way forward for sustainable capacitive devices.

Highly Selective Chemiresistive SO2 Sensor Based on a Reduced Graphene Oxide/Porphyrin (rGO/TAPP) Composite

AbstractThe emergence of toxic pollutants due to heavy human intervention in the ecosystem causes serious environmental problems. Therefore, sensors based on material having a strong affinity towards specific environmental gaseous pollutants are urgently needed. The present study deals with chemiresistive gas sensors for the detection of sulfur dioxide (SO2) based on a composite of reduced graphene oxide (rGO) and 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP). The improved Hummers method was used to synthesize graphene oxide (GO); it was further thermally reduced to rGO. The pattern of the copper electrode was coated on glass slides with a shadow mask using thermal evaporation. Then, GO was drop-cast between the two copper electrodes, thermally reduced to obtain rGO, and then modified by TAPP. The spectroscopic, structural, morphological, electrical, and optical studies were carried out using Fourier transform infrared spectroscopy, x-ray diffraction, Raman spectroscopy, atomic force microscopy, field emission scanning electron microscopy, current–voltage (I–V) and UV–visible spectroscopy, respectively. The developed sensor shows high selectivity towards SO2 gas analytes among exposed gaseous analytes. It exhibited reproducible response from 50 ppm to 200 ppm with enhanced repeatability at 50 ppm. The rGO/TAPP sensor exhibited a significant response (57 s) and recovery time (61 s), with a 5 ppm limit of detection. Graphical Abstract

Efficient adsorptive removal of Co2+ from aqueous solution using graphene oxide.

This study aimed to utilize synthesized graphene oxide (GO) for adsorptive removal of cobalt ions and investigate the adsorption mechanism using advanced techniques such as X-ray absorption spectra (XAFS). The GO was synthesized via an improved Hummers method, resulting in high surface area (93.7 m2/g) and abundant oxygen-containing functional groups. Various characterizations, including SEM, TEM, Raman, FT-IR, TG, potentiometric titrations, and N2 sorption-desorption measurements, were employed to characterize the GO. The adsorption behavior of GO towards Co2+ was investigated, and the results showed that the adsorption process followed a pseudo-second-order kinetic model and the Langmuir model, with a maximum sorption capacity of 93.7 mg/g. The adsorption process was chemisorption and endothermic, with GO showing adsorption selectivity order of Co2+ > Sr2+ > Cs+. Based on various characterizations such as X-ray absorption near-edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), FT-IR, and XPS, the sorption mechanism of Co2+ onto GO was discussed, with the results indicating that coordination and electrostatic interaction were the primary adsorption mechanisms, with oxygen-containing functional groups playing a vital role. The first coordinating atom for Co2+ was O, and the coordination environment was similar to that of cobalt acetate and CoO. Overall, this study provides comprehensive understanding of the adsorption behavior and mechanism of Co2+ onto GO, highlighting its potential as an effective adsorbent for removing nuclides from aqueous solution.

Conduction mechanism in hot-pressed Poly(vinylidene fluoride)/Graphene Oxide composites

Poly(vinylidene fluoride)/Graphene Oxide (PVDF/GO) composites were prepared by solvent casting and processed by hot pressing. Filler GO is synthesized by the improved Hummers method and purified by centrifuging. GO is characterized by XRD, FTIR, RAMAN, SEM, and TEM. XRD, FTIR, and DSC techniques were employed to characterize composites. AC conductivity data of PVDF and PVDF/GO composites with varying GO content were fitted with Jonscher’s power law at different temperatures, and the obtained DC conductivity was used to find the activation energy of the samples. The frequency exponent in power law is analyzed to identify the conduction mechanism in the composites. The frequency and temperature dependence of the exponent value and the nature of the frequency exponent with temperature confirm the overlapping large polaron tunneling as the responsible mechanism of conduction in PVDF/GO composites.

Heterogenity of graphite oxide particles obtained with wet oxidative exfoliation

Wet oxidative exfoliation of graphite is one of the most frequently applied techniques to obtain aqueous dispersions of hydrophilic graphene derivatives as required, e.g., in 3D printing, wet spinning or film casting. Due to the harsh conditions of the process, the resulting suspension is a mixture of particles with a wide distribution range both of physical dimensions and chemical properties. An aqueous graphite oxide suspension was obtained by an improved Hummers method and separated into five fractions by controlled centrifugation. The fractions were characterized and compared by various methods, revealing their diversity in size, chemical properties and application-related viscosity. The characterization methods (powder XRD, Raman spectroscopy, ATR-FTIR spectroscopy, XPS, potentiometric titration, rheology) exhibited subtle but measurable differences that exceeded the standard deviation of the techniques employed, but no systematic trend was found across the fractions in any of the properties investigated. The conditions of our centrifugal separation hardly meet the constrains of the ideal of Stokes’s law, the polydispersity of the high aspect ratio particles as well as their concentration close to the percolation limit challenge the independent sedimentation of the platelets.

Ni(OH)2 nanosheets and highly stable Ni(OH)2/GO nanocomposite for its improved OER performance

In this work, Ni(OH)2/GO nanocomposite is synthesized using an improved hummers method followed by a hydrothermal method. The oxygen evolution reaction of the Ni(OH)2/GO nanocomposite is studied. The prepared nanocomposite is characterized by XRD, SEM, TEM, XPS, and Raman techniques. The Ni(OH)2 nanosheets are well dispersed on the surface of the graphene oxide layers, which improves the surface area. The nanocomposite is able to withstand high overpotential with a negligible current loss for 12 h. The Ni(OH)2/GO nanocomposite shows an improved oxygen evolution reaction (OER) performance with a low overpotential of 1.61 V (vs. RHE) at 10 mA cm−2. The nanocomposite shows a low Tafel slope of 89.1 mV dec−1, nearly one by third of bare Ni(OH)2 nanosheets 307.1 (mV dec−1). Also, the Ni(OH)2/GO nanocomposite shows improved electrochemical stability than the bare Ni(OH)2.

Green synthesis of reduced graphene oxide by shallots

An environment-friendly and low-cost green reducing agent shallots are used for the facile and effective synthesis of partially reduced Graphene Oxide (prGO). The improved hummers method is used for the synthesis of GO. Synthesis of reduced graphene oxide (rGO) using green reducing agents is recognized as one of the most economical, environmentally friendly, facile and efficient approaches. At the same time, partially reduced graphene oxide have the advantages and convenience of both GO and rGO and can be facilitated for more advanced applications. X-Ray Diffraction, RAMAN spectroscopy, SEM, UV Visible and FTIR spectroscopy are used for the analysis of structural and surface properties of prGO. FTIR analysis established that most of the oxygen-containing functional groups such as hydroxyl, carboxyl carbonyl, and epoxy groups are removed partially during the reduction process. XRD peak is observed at 2θ = 22.5°, and ID/IG ratio in Raman spectra is about 0.92. From all the above studies we got clear information regarding the facile and effective partial reduction of graphene oxide using shallots.

Study on the damage resistance and deterioration behavior of GO concrete under the harsh environment.

To exploretheeffects of physical, mechanical, anti-deterioration properties of graphene oxide (GO) on cement-based cementitious materials, GO sheet dispersions areprepared by the improved Hummers method and ultrasonic dispersion method. The influence of theGO content on the compressive and flexural strengths of cement paste is investigated, and the penetration process of chloride ions in graphene oxide concrete is discussed by the electric accelerated erosion method. Combined with the rapid freeze-thaw test, the deterioration of graphene oxide concrete ismethodically analyzed. Theobtained results reveal that an appropriate amount of GO improves both the compressive and flexural strengths of cement pastev. In the chloride environment, the chloride diffusion coefficient of 0.03% GO concrete is 18.75% less than that of ordinary concrete.Under the action of freeze-thaw cycles, with the increase of salt freezing times, the deterioration mode of GO concrete is a combination of mortar shedding, micro-crack expansion, denudation, and block shedding; The stress-strain curve of the specimen tends to be flat with the growth of salt freezing times. The peak stress gradually lessens, the peak strain gradually grows, and the elastic modulus remarkably reduces. Compared with ordinary cement paste, theGO is capable of promoting the growth of cement paste hydration crystals, changing the size and shape of crystals, and realizingthe regulation of cement paste microstructure. Incorporating an appropriate amount of theGO could promote the cement hydration process and enhance the chemical water-binding amount in the cement paste. The optimal GO content is reported to be 0.03% of the cement mass.

Sandwich nanoarchitectonics of heterogenous CB/CNTs honeycomb composite for impedance matching design and microwave absorption

Sandwich structure composite is one of the most potential and effective materials to comprehensively realize microwave absorption in wide frequency range and structural lightweight function. Here, honeycomb (HC) composites were fabricated by immersion method, consisting of a carbon nanotubes/carbon black/polyurethane (CNTs/CB/PU) absorbing layer and an aramid HC core. The using CNTs and CB were both modified by improved Hummers method with a heterogeneous structural surface to enhance the dielectric properties of the carbon materials. The sandwich honeycomb (SHC) absorber showed excellent broadband absorption performance with an effective absorption bandwidth (RL<−10 dB) of 15.5 GHz. Furthermore, the compressive stress of the absorber reached 3.69 MPa. With the integrated high microwave absorption and load-bearing performance, the as-prepared SHC absorber demonstrated promising future for applications in avionics.

Structural Properties of Regenerated Carbon Graphene Oxide (GO) Synthesized through Hummers and Improved Hummer's Method

AbstractGraphene oxide (GO) is an oxidized form of graphene, laced with oxygen‐containing groups. In recent years, the cost‐effective and efficient synthesis of GO remains a significant issue. Hummer's method has become popular due to its simple top‐down synthesis, however, there is an issue due to the release of nitrate gaseous which is harmful to the environment. This research is carried out using regenerated carbon from waste tire as a source of synthesize process through the Hummers Method (HM) and Improved Hummers Method (IHM). The Raman peaks of IHM GO show that the D band and G band are at 1369.12 and 1583 cm−1, respectively and the intensity ratio of the D band relative to the G band (ID/IG) is 0.84. The morphology and structure of graphene oxide show that a nanosize particle stalked together on the surface of the sample structure, bumping pieces, and a coarse surface. The elemental composition of carbon (C) is higher than the oxygen (O) element which showed a good composition of graphene oxide. The XRD spectroscopy indicates the crystal structure of the material and the interlayer spacing between the material and atoms. In this study, the improved method is used by replacing sodium nitrate (NaNO3) with phosphoric acid (H3PO4) during the synthesis process to help increase interlayer distance and helps oxidation on the basal planes. This result confirms that the graphene oxide can be synthesized from regenerated carbon from waste tire using an improved Hummer's method.

Surface interaction of tetrabromobisphenol A, bisphenol A and phenol with graphene-based materials in water: Adsorption mechanism and thermodynamic effects

Carbon-based materials, especially graphene nanocomposites (GNS) have attracted wide attention in recent years. In this study, graphene oxide (GO) and reduced graphene oxide (rGO) were prepared using the Improved Hummers method and were investigated for their adsorption behavior of emerging contaminants such as tetrabromobisphenol A (TBBPA), bisphenol A (BPA), and a conventional contaminant, phenol. The adsorption capacity seemed to slightly increase with increasing reduction degree of GO, highlighting its hydrophobic effect. The adsorption kinetics and isotherms were well delineated using pseudo-second-order and Langmuir equations respectively. At higher temperatures, the adsorption of these selected organic contaminants on GO and rGO slightly increased, also indicating the slight effect of temperature on the adsorption in the environment. From a thermodynamic analysis, the endothermic and spontaneous reaction was observed. The adsorption mechanisms included hydrophobicity, π- π interactions and π electron acceptor and donor ones. GNS can suspend in water even after adsorbing pollutants at the water interface. This would enhance the transport of these contaminants with nanomaterials in the environment. These findings are valuable to elucidate the interaction mechanism between phenol, BPA, and TBBPA on GNS while further understanding the physicochemical behavior of these organic contaminants in the environment.Summary: Adsorption capacities of emerging contaminants, BPA and TBBPA, as well as phenol on graphene oxide (GO) and reduced GO (rGO), were similar. Higher temperatures slightly increased the adsorption of these phenolic compounds on GO and rGO, which also indicated an endothermic and spontaneous process.

Graphite Oxide as a Catalyst for Dehydration of Alcohols

Background: The methods of dehydration of alcohols frequently suffer from the following drawbacks: high reaction temperature, toxic catalysts, high catalyst loading, and difficulty to remove catalysts. Therefore, the development of a new catalyst for the dehydration of alcohols is still of importance. Methods: Graphite oxide is used as a catalyst for dehydration of alcohols. Results: Graphite oxide is used as a catalyst for dehydrating tertiary and secondary alcohols to the corresponding alkenes as well as dehydrating primary alcohols and diols to the corresponding ethers and cycloethers in moderate to excellent conversion rates and good selectivity. Conclusion: In these reactions, GO prepared by the improved Hummers method showed high catalytic activity. As an efficient catalyst, GO is easily available, cheap, weakly acidic with low toxicity, and well tolerant to various functional groups.