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▼ [13p-A41-7] Fabrication of highly concentrated amino group-functionalized graphite encapsulated magnetic nanoparticles by one-step arc discharge method
Keywords:arc discharge, surface modification, amino functional groups
Since then, many researchers focus on the fabrication and surface functionalization of metallic nanoparticles by plasma processing. As reported in our previous papers, we have successfully fabricated graphite-encapsulated magnetic nanoparticles (GEMNPs) and graphite-encapsulated gold nanoparticles by direct current (DC) arc discharge method and functionalized their surfaces with amino functional groups using radio frequency inductively-coupled plasma. The uniform treatment of the entire surfaces of nanoparticles was quite difficult because the amino modification would occur only on the top side of the samples. We also greatly enhanced the surface interaction between GEMNPs and activated species of plasma by employing the particle explosion technique where the nanoparticles were ion-sputtered via a negative pulsed biasing of the sample stage during the plasma treatment. However, sputtered magnetic nanoparticles would be agglomerated and still less exposed to the plasma. The fabrication of GEMNPs functionalized by amino groups uniformly using plasma technique is one of the challenges in this field. The motivation of our research stems from the need for direct fabrication of amino-functionalized GEMNPs by one-step plasma synthetic process.
In this study, a versatile one-step DC arc discharge method was applied to fabricate GEMNPs functionalized by large amount of amino groups uniformly in the working gas mixture of He/CH4/NH3. By changing the NH3 gas mixture ratios from 0% to 5.0% (Fig. 1) and the working gas pressures from 25 Torr to 100 Torr (Fig. 2), different numbers of modified amino groups are quantitatively confirmed by the chemical derivatization method. The optimized condition of this one-step fabrication process for effective functionalization of amino groups is achieved. It shows that at 50 Torr with 0.1% of NH3, amino groups are fully functionalized on the surface with a number of ~3.22×105 per nanoparticle, which is about 6.7 times higher than the number of carbon atoms on the outmost layer of one nanoparticle. The surface structural integrity of outmost layers of GEMNPs increases as the NH3 gas mixture ratios decrease from 1.0% to 0.1%. The adding NH3 not only provides –NH or -NH2 fragment species to introduce amino groups incorporating with the dangling bonds activated by H radicals, but also performs the construction of networks to flatten the surfaces of GEMNPs. This present work suggests that one-step arc discharge method is desirable and easily controllable for the fabrication of amino-functionalized GEMNPs while maintaining their original bulk structures, which can be also used to synthesize other metallic nanoparticles efficiently for various applications.
In this study, a versatile one-step DC arc discharge method was applied to fabricate GEMNPs functionalized by large amount of amino groups uniformly in the working gas mixture of He/CH4/NH3. By changing the NH3 gas mixture ratios from 0% to 5.0% (Fig. 1) and the working gas pressures from 25 Torr to 100 Torr (Fig. 2), different numbers of modified amino groups are quantitatively confirmed by the chemical derivatization method. The optimized condition of this one-step fabrication process for effective functionalization of amino groups is achieved. It shows that at 50 Torr with 0.1% of NH3, amino groups are fully functionalized on the surface with a number of ~3.22×105 per nanoparticle, which is about 6.7 times higher than the number of carbon atoms on the outmost layer of one nanoparticle. The surface structural integrity of outmost layers of GEMNPs increases as the NH3 gas mixture ratios decrease from 1.0% to 0.1%. The adding NH3 not only provides –NH or -NH2 fragment species to introduce amino groups incorporating with the dangling bonds activated by H radicals, but also performs the construction of networks to flatten the surfaces of GEMNPs. This present work suggests that one-step arc discharge method is desirable and easily controllable for the fabrication of amino-functionalized GEMNPs while maintaining their original bulk structures, which can be also used to synthesize other metallic nanoparticles efficiently for various applications.