Then 18 mg annealed pN-C was added to the mixture, sonicated to obtain a homogeneous solution and further stirred for 10 min in r.t. Then 1 mL 1 M HCl was added to the above solution, which was stirred for another 10 min. The final product was obtained by centrifuging the reaction mixture and washed with EtOH for 3 times.