Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with Fe_3O_4 particles

In order to investigate the impedance matching properties of microwave absorbers,the ternary nanocomposites of GO/PANI/Fe3O4（GPF） are prepared via a two-step method,GO/PANI composites are synthesized by dilute polymerization in the presence of aniline monomer and GO,and GO/PANI/Fe3O4 is prepared via a co-precipitation method.The obtained nanocomposites are characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,and Fourier transform infrared spectroscopy（FTIR）,respectively.The microwave absorbability reveals enhanced microwave absorption properties compared with GO,PANI,and GO/PANI.The maximum reflection loss of GO/PANI/Fe3O4 is up to-27 dB at 14 GHz with its thickness being 2 mm,and its absorption bandwidths exceeding-10 dB are more than 11.2 GHz with its thickness values being in the range from 1.5 mm-4 mm.It provides that GO/PANI/Fe3O4 can be used as an attractive candidate for microwave absorbers.

Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with gold nanoparticles

A composite of graphene/PANI/GAunano is synthesized using the co-blend method. The morphologies and microstructures of samples are examined by transition electron microscopy(TEM) and Fourier transform infrared spectroscopy(FTIR). Moreover, the microwave absorption properties of both graphene/PANI and GO/PANI/ GAunano composites are investigated in a microwave frequency band from 1 GHz to 18 GHz. The maximum reflection loss(RL) of GO/PANI/GAunano with a thickness of 2 mm is up to-24.61 d B at 15.45 GHz, and the bandwidth corresponding to RL at-10 d B can reach 4.08 GHz(from 13.92 GHz to 18.00 GHz) for a 2-mm-thick layer. The electromagnetic data demonstrate that GO/PANI/GAunano can be used as an attractive candidate for microwave absorbers.

Ultra-high sensitivity fiber optic microphone with corrugated graphene-oxide diaphragm for voice recognition

To avoid interference from unexpected background noises and obtain high fidelity voice signal,acoustic sensors with high sensitivity,flat frequency response,and high signal-to-noise ratio(SNR)are urgently needed for voice recognition.Grapheneoxide(GO)has received extensive attention due to its advantages of controllable thickness and high fracture strength.However,low mechanical sensitivity(SM)introduced by undesirable initial stress limits the performance of GO material in the field of voice recognition.To alleviate the aforementioned issue,GO diaphragm with annular corrugations is proposed.By means of the reusable copper mold machined by picosecond laser,the fabrication and transfer of corrugated GO diaphragm are realized,thus achieving a Fabry–Perot(F–P)acoustic sensor.Benefitting from the structural advantage of the corrugated GO diaphragm,our F–P acoustic sensor exhibits high S_(M)(43.70 nm/Pa@17 kHz),flat frequency response(−3.2 to 3.7 dB within 300–3500 Hz),and high SNR(76.66 dB@1 kHz).In addition,further acoustic measurements also demonstrate other merits,including an excellent frequency detection resolution(0.01 Hz)and high time stability(output relative variation less than 6.7% for 90 min).Given the merits presented before,the fabricated F–P acoustic sensor with corrugated GO diaphragm can serve as a high-fidelity platform for acoustic detection and voice recognition.In conjunction with the deep residual learning framework,high recognition accuracy of 98.4%is achieved by training and testing the data recorded by the fabricated F–P acoustic sensor.

Structure-guided Capacitance Relationships in Oxidized Graphene Porous Materials Based Supercapacitors

Supercapacitors formed from porous carbon and graphene-oxide(GO)materials are usually dominated by either electric double-layer capacitance,pseudo-capacitance,or both.Due to these combined features,reduced GO materials have been shown to offer superior capacitance over typical nanoporous carbon materials;however,there is a significant variation in reported values,ranging between 25 and 350 F g^(−1).This undermines the structure(e.g.,oxygen functionality and/or surface area)-performance relationships for optimization of cost and scalable factors.This work demonstrates important structure-controlled charge storage relationships.For this,a series of exfoliated graphene(EG)derivatives are produced via thermal-shock exfoliation of GO precursors and following controlled graphitization of EG(GEG)generates materials with varied amounts of porosity,redox-active oxygen groups and graphitic components.Experimental results show significantly varied capacitance values between 30 and 250 F g^(−1)at 1.0 A g^(−1)in GEG structures;this suggests that for a given specific surface area the redox-active and hydrophilic oxygen content can boost the capacitance to 250–300%higher compared to typical mesoporous carbon materials.GEGs with identical oxygen functionality show a surface area governed capacitance.This allows to establish direct structure-performance relationships between 1)redox-active oxygen functional concentration and capacitance and 2)surface area and capacitance.

Design and Synthetic Scheme of Water Dispersible Graphene Oxide-Coumarin Complex for Ultra-Sensitive Fluorescence Based Detection of Copper (Cu2+) Ion in Aqueous Environment

Copper oxides and its salts are now widely used as pesticides to control fungal and bacterial diseases of field crops. Copper toxicity is often a major contributor of human health problems caused through accumulation of excess copper ions in various organs via drinking water, fruits and vegetables. So, detection and estimation of cupric ions in biological organs, drinking water, fruits and vegetables are extremely important. Recently, a fluorescence based sensor using coumarin dye (high quantum yield) has been proposed to detect micromolar Cu++ ion in biological organs. But major problem with coumarin dye is that it is insoluble in water and undergoes dye-dye aggregation in organic solvents. We proposed here a synthetic scheme of preparation of graphene oxide conjugated coumarin dye derivative which would be water dispersible and expected to be an ideal candidate for Cu2+ ion estimation in biological organs and drinking water.

Effect of Counterparts and Applied Load on the Tribological Behavior of the Graphene–Nickel Matrix Self-Lubricating Composite

Graphene-oxide (GO) has been recognized as an excellent lubrication material owing to its two-dimensional structure and weak interlayer interactions. However, the functional groups of GO that can contribute to anti-friction, anti-wear, and superlubricity are yet to be elucidated. Hence, further improvement in GO-family materials in tribology and superlubricity fields is impeded. In this study, macroscale superlubricity with a coefficient of friction of less than 0.01 is achieved by exploiting the high adhesive force between amino groups within aminated GO (GO–NH_(2)) nanosheets and SiO_(2). It was observed that GO–NH_(2) nanosheets form a robust adsorption layer on the worn surfaces owing to the high adsorption of amino groups. This robust GO–NH_(2) adsorption layer not only protects the contact surfaces and contributes to low wear, but also causes the shearing plane to transform constantly from solid asperities (high friction) into GO–NH_(2) interlayers (weak interlayer interactions), resulting in superlubricity. A SiO_(2)-containing boundary layer formed by tribochemical reactions and a liquid film are conducive to low friction. Such macroscale liquid superlubricity provides further insights into the effect of functional groups within functionalized GO materials and a basis for designing functionalized GO materials with excellent tribological performances.

Simultaneous removal of Congo red and cadmium(Ⅱ) from aqueous solutions using graphene oxide–silica composite as a multifunctional adsorbent

Graphene oxide is a very high capacity adsorbent due to its functional groups and π-π interactions with other compounds. Adsorption capacity of graphene oxide, however, can be further enhanced by having synergistic effects through the use of mixed-matrix composite. In this study, silica-decorated graphene oxide(SGO) was used as a high-efficiency adsorbent to remove Congo red(CR) and Cadmium(Ⅱ) from aqueous solutions. The effects of solution initial concentration(20 to 120 mg/l), solution pH(pH 2 to 7), adsorption duration(0 to 140 min) and temperature(298 to 323 K) were measured in order to optimize the adsorption conditions using the SGO adsorbent. Morphological analysis indicated that the silica nanoparticles could be dispersed uniformly on the graphene oxide surfaces. The maximum capacities of adsorbent for effective removal of Cd(Ⅱ) and CR were 43.45 and 333.33 mg/g based on Freundlich and Langmuir isotherms, respectively. Langmuir and Freundlich isotherms displayed the highest values of Q max for CR and Cd(Ⅱ) adsorption in this study, which indicated monolayer adsorption of CR and multilayer adsorption of Cd(II) onto the SGO, respectively. Thermodynamic study showed that the enthalpy( H) and Gibbs free energy( G) values of the adsorption process for both pollutants were negative, suggesting that the process was spontaneous and exothermic in nature. This study showed active sites of SGO( π-π, hydroxyl, carboxyl, ketone, silane-based functional groups) contributed to an enormous enhancement in simultaneous removal of CR and Cd(Ⅱ) from an aqueous solu-tion, Therefore, SGO can be considered as a promising adsorbent for future water pollution control and removal of hazardous materials from aqueous solutions.