Polyaniline–graphene quantum dots (PANI–GQDs) are considered as an important candidate for applications in photovoltaic cells. In this work, GQDs were prepared using sono-Fenton reagent from reduced graphene oxide (rGO). PANI–GQD hybrid was also synthesized using the chemical in situ polymerization method. The synthesized materials were characterized using UV–visible (UV–Vis) spectroscopy, photoluminescence (PL) spectroscopy, current–voltage (I–V) characteristic, thermal gravimetric analysis (TGA), Raman spectroscopy, and X-ray difraction (XRD). Dynamic light scattering was also used to estimate the lateral size of GQDs. The enhanced visible-light absorbance in the hybrid was confrmed by UV–Vis analysis and the decrease in intensity around 3461 cm−1 in FT-IR spectra was due to the interaction between functional groups of PANI with GQDs. This led to improved thermal stability and conductivity as observed from TGA and I–V analysis, respectively.
Moreover, the Raman spectrum for PANI–GQDs showed a decrease in the peak at ~1348 and ~1572 cm−1 as compared to PANI and GQDs. Similarly, from the XRD profle of PANI–GQDs, a shift in peak was observed due to an alteration in the microstructure. A sandwich device with cell structure glass/ITO/PANI–GQDs/Al was fabricated and its application was tested. Current density–voltage (J–V) curve of the device was measured with a Keithley SMU 2400 unit under an illumina�tion intensity of 100 Wm−2 simulating the AM 1.5 solar spectrum. The hybrid exhibited photovoltaic properties, and 0.857% efciency was observed in response to the applied voltage. This work suggests that PANI can be used as an alternative material for photovoltaic cells.
Chemical incorporation of epoxy-modifed graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-mod�ifed GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modifed GO to the resin matrices resulted in a hybrid composite with high thermal characteristics.
Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray dif�fraction, and Raman spectroscopy were used for approving modifcation of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modifcation with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modifed GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modifed GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modifed GO.
In this paper, we report graphene composite membranes prepared by transfer of a layer of chemical vapor deposition graphene onto porous anodic alumina (AA) substrates with nominal pore size 20 and 30 nm, referred as 20AA and 30AA. The coated and uncoated substrates were characterized using optical and electron microscopy techniques. The bare substrates exhibited a smooth surfaces with a well-organized array of hexagonal pores, displaying an average pore size of 17±3 (20AA) and 23±3 nm (30AA). The scanning electron microscopy and atomic force microscopy analyses confrmed the successful transfer of graphene layer onto the target substrates. The molecular transport study was performed by introducing 0.5 M potassium chloride (KCl) and deionized water in a Side-bi-Side Franz difusion cell. The graphene/20AA specimen blocked 66% ions transport, and graphene/30AA membrane about 64%. The ions blockage exceeded 90%, near the characteristics of defect�free graphene when the defects of the transferred graphene were sealed with Nylon 6,6. The results of this study suggest the potential use of graphene on AA substrates for water desalination and gas purifcation applications.
Spinnable mesophase pitch precursor containing more than 98% mesophase content was successfully prepared from FCC-DO (fuid catalytic cracking-decant oil) without hydrogenation or catalytic reaction. The preparation method involved thermal condensation, vacuum treatment, and annealing treatment. Petroleum mesophase pitch-based carbon fbers are produced by melt spinning of pitch precursors, followed by stabilization and carbonization. The resulting carbon fber exhibited good mechanical performances up to tensile strength of 2.1 GPa and tensile modulus of 212 GPa, with strain-to-failure higher than 1.0%. These properties ensuring that the automotive grade carbon fbers can be successfully prepared from FCC-DO derived petroleum mesophase pitches through the cost-competitive processes.
Core–mantle nanohybrids were prepared via grafting the multi-walled carbon nanotubes (MWCNTs) with polyaniline (PANI). Core–mantle–shell supramolecules were then designed by crystallization of poly(3-hexylthiophene) (P3HT) and poly[benzodithiophene-bis(decyltetradecyl-thien) naphthothiadiazole] (PBDT-DTNT) conductive polymers onto core (CNT)– mantle (PANI) nanostructures. Supramolecules were thoroughly investigated and applied in active layers of P3HT:phenyl�C71-butyric acid methyl ester (PC71BM) solar cells. Efcacies of 5.71% and 6.02% were acquired for photovoltaics based on nanostructures having PBDT-DTNT and P3HT shells, respectively. Diameters of core(CNT)–mantle(PANI), core(CNT)– mantle(PANI)–shell(P3HT), and core(CNT)–mantle(PANI)–shell(PBDT-DTNT) supramolecules ranged in 75–90 nm, 145– 160 nm, and 120–130 nm, respectively. The highest efciency (=6.02%) was achieved for P3HT:PC71BM:CNT-graft-PANI/ P3HT systems without any post-treatment (13.42 mA/cm2 , 0.68 V, and 66%). Charge mobilities were also very high for corresponding electron-only (µe =9.8×10−3 cm2 /V s) and hole-only (µh=5.0×10−3 cm2 /V s) devices. PANI mantle may act as both acceptor and donor in core–mantle–shell supramolecules. Core(CNT)–mantle(PANI)–shell(PBDT-DTNT) nano�structures also elevated photovoltaic efciency up to 5.71% (13.12 mA/cm2 , 0.67 V, 65%, 4.7×10−3 cm2 /V s, and 9.0×10−3 cm2 /V s). Results acquired for core(CNT)–mantle(PANI)–shell(P3HT)-based systems were somehow higher than those recorded for core(CNT)–mantle(PANI)–shell(PBDT-DTNT)-based ones. It could be assigned to consistency of P3HT shells and P3HT host chains in bulk of P3HT:PC71BM active layer. P3HT backbones owing to their simpler chemical structures were also capable of arranging more ordered shells, leading to larger charge mobilities and currents.
The reduced graphene oxide/single-wall carbon nanotubes composites are coated onto the polyurethane substrate using spray coating technique to produce a stretchable and semi-transparent supercapacitor. The electrochemical properties of the stretch�able and semi-transparent full device as a function of stretching cycles are characterized using electrochemical impedance spectroscopy (EIS), cyclic voltammetry and galvanostatic charge/discharge tests. The EIS and charge/discharge curves of the stretchable and semi-transparent supercapacitor exhibit good capacitive behavior even after prolonged stretching cycles up to 100. The highest capacitance value of the stretchable and semi-transparent supercapacitor (unbent) is 21.4 F g−1. The capacitance value of the stretchable and semi-transparent supercapacitor is retained 62% after 100th stretching with applica�tion of 3000th galvanostatic charge/discharge cycles.
A novel approach was presented for deposition of nickel–graphene nanocomposite coating on copper. Unlike conventional methods, graphene and graphene oxide nanosheets were not used. The basis of the method is to synthesize graphene oxide by oxidation of graphite anode during the electrochemical deposition process. The obtained graphene oxide sheets were reduced during the deposition in the cathode and co-formed with the nickel deposition in the coating. The pulsed ultrasonic force was applied during the deposition process. When the ultrasonic force stops, the deposition process begins. Scanning electron microscopy, Raman spectroscopy, atomic force microscopy, X-ray difraction and X-ray photoelectron spectros�copy confrmed the presence of graphene nanosheets in the coating. The amount of graphene nanosheets increases up to a maximum of 14.8 wt% by increasing the time of applying ultrasonic force to 6 s. In addition, with the presence of graphene in the nickel coating, the wear rate dramatically decreased.
We report potentiometric performances of ion-to-electron transducer based on reduced graphene oxide (RGO) for applica�tion of all-solid-state potassium ion sensors. A large surface area and pore structure of RGO are obtained by a hydrothermal self-assembly of graphene oxide. The extensive electrochemical characterization of RGO solid contact at the interface of ion�selective membrane and gold electrode shows that the potassium ion-selective electrode based on RGO had a high sensitivity (53.34 mV/log[K+]), a low detection of limit (−4.24 log[K+], 0.06 mM) a good potential stability, and a high resistance to light and gas interferences. The potentiometric K+-sensor device was fabricated by combining of screen-printed electrodes and a printed circuit board. The K+-sensor device accurately measures the ion concentration of real samples of commercial sports drinks, coke and orange juice, and then transfers the collected data to a mobile application through a Bluetooth module.
The screen-printed ion sensors based on RGO solid contact show a great potential for real-time monitoring and point-of-care devices in human health care, water-treatment process, and environmental and chemical industries.
The study presented in the article is focused on use of graphene obtained by novel microwave-enhanced chemical vapor deposition (MECVD) method as a construction material for 3D porous structures—aerogels and sponges. MECVD gra�phene nanoplatelets-based aerogels were obtained by mixing MECVD graphene nanoplatelets and chitosan, dissolved in 3% acetic acid followed by its freeze drying and carbonization at 800° in inert medium. Surface morphology of aerogels was characterized by SEM. MECVD graphene nanoplatelets-based aerogels are characterized by a porous structure; they are superhydrophobic and possess high sorption capacity with regard to organic liquids of diferent densities. Polyurethane sponges coated with MECVD graphene can serve as an alternative to aerogels. The process of their obtaining is cheaper and less complicated. They were obtained by facile “dip-coating” method, modifying its surface to increase its hydrophobicity.
The resulting sponges are superhydrophobic and superoleophilic, and demonstrate high rate of sorption of organic liquids and can be easily regenerated by squeezing. In addition, they can be used as a separating material in conjunction with vacuum system for continuous and selective collection of organic liquids from the surface of water.
For applications in cement-based materials, studies on carbon-based nanomaterials have been almost exclusively on carbon nanotubes, carbon nanofbers, and graphite oxide. Graphene sheets (GPs), as a kind of carbon-based nanomaterials, show unusual mechanical, electrical, optical, and other properties. In this paper, the main focus is to enhance the efect of GPs by improving dispersion through ultrasonication and use of surfactant. Then, dispersion and stability are quantitatively measured by comparing absorbance spectra through spectrophotometry and qualitatively observed through digital imaging and SEM imaging. Therefore, the dispersing protocol is optimized and the most efective and stable dispersion is achieved. At last, the piezoresistivities under compressive load of GPs/cement composites pastes at diferent additions of GPs are studied by comparing with plain cement paste.
Increasing demand for fossil fuels is associated with massive atmospheric CO2 levels. Considering that numerous studies have been published with CO2 capturing techniques, utilizing techniques are yet in early stage with fnancial or technical issues. As a part of chemical conversion in CO2 utilization, this paper investigated the performance of a CO2 and H2O mixture (CHM) onto activated carbon fbers (ACF) for surface modifcation. CHM-treated ACF samples were prepared at a pressure of 20 bar with 100 °C of water vapor and 750 μL of CO2 for 1 h through the gas-phase, and labeled as C-ACF850. For the control sample, N-ACF850 was also prepared by the impregnation of nitric acid. Physiochemical analyses revealed that the overall characteristics of C-ACF850 lay between ACF850 and N-ACF850. C-ACF850 experienced minimized surface area decrement (21.92% better than N-ACF850), but increased surface functional groups (50.47% better than ACF850). C-ACF850 also showed preferable adsorption efciency on selected metals, in which case both physical and chemical properties of adsorbent afect the overall adsorption efciency. In this regard, a novel applicability of CHM may present an appealing alternative to traditionally used strong acids.
The reduced graphene oxide (rGO)/activated carbon (AC) composites are coated on the aluminum substrate using spray coat�ing technique to fabricate nanocarbon-based supercapacitor. Polymer-based solid-state xanthan-gum/Na2SO4 electrolyte is also introduced to increase stability of the supercapacitor. The electrochemical properties of the supercapacitor are evaluated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge tests. The highest capacitance value of the rGO/AC composite-based supercapacitor is 120 F/g. The rGO/AC composite-based supercapacitor has also retained~85% of its initial capacitance value after 3000 galvanostatic charge/discharge cycles.