Modified Graphene Nanoplatelets Research Articles

Incorporation of surface modified graphene nanoplatelets for development of shape memory PLA nanocomposite

In this study, a temperature sensitive shape memory polymer (SMP) system based on polylactic acid (PLA) has been developed and the effect of graphene nanoplatelets (GNPs) on the shape memory properties was evaluated. Dispersion of GNPs in PLA was improved with the aid of a zwitterionic surfactant. X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the surface modified graphene nanoplatelets (SMGNPs) were exfoliated and homogenously dispersed in the PLA matrix due to enhancement of the polymer-graphene interaction. Mechanical properties of the samples namely stiffness and elasticity were increased upon incorporation of graphene nanoplatelets accompanied by their good dispersion in the PLA matrix. Furthermore, differential scanning calorimetry (DSC) revealed that the nucleation effect of graphene promote the crystallization and noticeably enhanced the degree of crystallinity. Finally, prominent mechanical properties along with high degree of crystallization due to fine dispersion of surface modified graphenes, resulted in drastic improvement in shape memory performance.

Antibiotic amoxicillin removal from aqueous solution using magnetically modified graphene nanoplatelets

The removal of antibiotic amoxicillin (AA) from aqueous solution was investigated using magnetically modified graphene nanoplatelets (M-GNPs). M-GNPs were prepared by mixing GNPs with freshly prepared magnetite nanopartilcles, and characterized using TEM, and XRD. The characterization results revealed the homogenous distribution of the magnetite nanopartilcles over the surface of transparent platelet-like graphene platlets. The M-GNPs proved to possess superior adsorption capacity compared with the pristine GNPs and the magnetite nanopartilces. The effects of different operational parameters which affect the removal process were explored; adsorbent amounts, contact time, initial pH, temperature, and the initial concentration of AA. The results showed the great affinity of the M-GNPs toward the AA and the maximum adsorption capacity was found to be 14.10mgg−1. The adsorption mechanism of AA by the M-GNPs involved π–π stacking and electrostatic interaction. The adsorption was studied kinetically and thermodynamically, and was found to mainly follow pseudo-second-order kinetic model, and was spontaneous and exothermic in nature.

Generation of nitrile groups on graphites in a nitrogen RF-plasma discharge

Graphite particles were treated in a nitrogen radio frequency-plasma (RF-plasma) at different excitation power. The morphological as well as chemical surface modifications were investigated by Raman spectroscopy, SEM, and XPS. Changes of the sp2/sp3 bonding ratio and selective surface terminations by functional groups were achieved. Especially, a direct functionalization of the graphites with nitrile groups was evidenced by a characteristic signal at 2240cm−1 in the Raman spectra after a high energy RF-nitrogen plasma treatment. A total nitrogen content of up to 11at.% was reached by the applied conditions. The increased polarity of the surfaces was confirmed by contact angle measurements. The nitrile functionalization may serve as synthetic scaffold for the development of new routes towards the chemical surface modification of carbon substrates. Furthermore, the modified graphites can be processed by common exfoliation techniques yielding nitrogen modified graphene nanoplatelets directly in polar and non-polar solvents.

Size sorting of chemically modified graphene nanoplatelets

Size-sorted graphene nanoplatelets are highly desired for fundamental research and technological applications of graphene. Here we show a facile approach for fabricating size-sorted graphene oxide (GO) nanoplatelets by a simple centrifugal method using different dispersion solvents. We found that the small-sized GO nanoplatelets were more effectively separated when dispersed in water or dimethylformamide (DMF) than in an alkali aqueous solution. After several iterations of the centrifugation, the sizes of GO in the supernatant solution were mostly several micrometers. We found that the GO area was not strongly correlated with the C-O content of the GO dispersed in water. However, the size-sorted GO nanoplatelets in DMF showed different C-O content, since DMF can reduce GO nanoplatelets during exfoliation and centrifugation processes.

Simultaneous enhancements in damping and static dissipation capability of polyetherimide composites with organosilane surface modified graphene nanoplatelets

Polyetherimide (PEI) possesses excellent thermal resistance and advanced mechanical properties, for which it has been used as interior materials in various transportation structures. Multifunctional PEI nanocomposites, in particular, with high damping properties and satisfactory static dissipation capability, will be more significant for those applications. In this study, PEI/graphene nanoplatelet (GNP) nanocomposites were fabricated via solution processing. Effects of GNP loading and surface silanization of GNPs on damping capacity and static dissipation properties were studied. The addition of the GNPs effectively increased the storage modulus of PEI, especially storage modulus at higher temperature (200 °C). The silanization of GNPs, on one hand, improved the dispersion quality; on the other hand, provided strong interfacial bonding with PEI matrix, which benefited the stress transfer within the composites. The superior damping capacity enhancements for the resulting nanocomposites are: with the loading of 3.0 wt% silanized GNP, the storage modulus of PEI increased approximately 4 times and 200 times at 30 °C and 200 °C, respectively, and the damping factor is 3 times higher than PEI. In addition, with the addition of 3.0 wt% GNPs, both low electrical resistivity (∼10 6 Ω∗cm) and low dielectric constant (∼7) were realized, corresponding to excellent volume static dissipation capability, however, silanization resulting in good interfacial bonding did not cause invisible impact on the electrical and dielectric properties of the nanocomposites. The superior damping capacity and static dissipation property make them suitable for intra-structure materials for airplane and transportation.