We succeeded in bridging unzipped graphene nanoribbons (GNRs) and separating them from unwanted single-walled carbon nanotubes (SWNTs) using a frequency-dependent dielectrophoresis (DEP) method by varying the frequency and applied voltage used for future assembly. Atomic force micrographs and Raman spectra proved that unzipped GNRs were successfully bridged by the DEP method at frequencies higher than 13 MHz. The theoretical calculation also supported the finding that only GNRs were collected from a mixture of SWNTs/GNRs suspensions.

Removal of heavy metal ions (Co2+, Cu2+, Zn2+, Fe2+, Mn2+, and Ni2+) from artificial wastewater has been successfully perfomed by adsorption process using magnetic ferrite (MFe2O4; M=Co2+, Mg2+, Zn2+, Fe2+, Mn2+, and Ni2+) nanoparticles. Ferrite nanoparticles were synthesized using coprecipitation method and used as absorbent in heavy metal ions removal with concentration of 5 g/L and 10 g/L. The adsorption and desorption ability of each ferrite nanoparticles, the effect of heavy metal ion in adsorption and desorption process, and the endurance of ferrite nanoparticles were investigated using atomic absorption spectroscopy (AAS). The removal process has been conducted for wastewater at pH 7.It showed the presence of heavy metal precipitate in solution. The result shows that MgFe2O4 has the highest adsorption ability than other ferrite and MnFe2O4 is the lowest. Desorption ability of all ferrites is high except for Fe ion removal. Desorption of Fe ion shows very low result which might due to FeO bond from Fe ion reaction in acid solution. The endurance of MnFe2O4 and Fe3O4 as adsorbent after repeated adsorption and desorption process is up to 4 times and more than 6 times. The MnFe2O4 nanoparticles show a stability in adsorption ability after 4 times repetition adsorption and desorption process.