Highly concentrated amino group-functionalized graphite encapsulated magnetic nanoparticles fabricated by a one-step arc discharge method

In this work, we apply a one-step direct current arc discharge method to synthesize graphite-encapsulated magnetic nanoparticles functionalized with a high concentration of amino groups uniformly without further modification or any other pre/post-treatment procedures. The synthesis was accomplished by adding different molar ratios of NH3 into He/CH4 gas mixture under various gas pressures. The optimized number of functionalized amino groups is evaluated to be ∼3.22 × 105 per nanoparticle prepared at 50 Torr with 0.1% of NH3. As the molar ratios of NH3 decrease from 1.0% to 0.1%, the optical emission peaks of CN and NH are intensified gradually, and the surface structural integrities also increase. These results indicate that NH3 not only provides -NH or -NH2 fragment species to introduce amino groups incorporating with the dangling bonds activated by H radicals, but also constructs networks to flatten the outmost graphitic surfaces of encapsulated nanoparticles. As the working gas pressure changes from 25 to 100 Torr, the outmost shells formed by the dissociated CH4/NH3 molecules tend to be relatively less disordered.

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