Silicon wafers are cut into pieces, rinsed with water and ethanol, and dried under a nitrogen stream. The substrates are cleaned and activated by plasma cleaning with oxygen plasma for 20 min and subsequently functionalized by vapor deposition of APTES (0.1 mL) in a desiccator under vacuum overnight. Next, they are rinsed and dried again and the initiator (BiBB) is coupled by reaction in a solution consisting of 100 mL of toluene, 1 mL of TEA, and 1 mL of BiBB for 3 h. The reaction mixture is vigorously stirred to prevent settling of aggregates on the substrates. After the reaction, the samples are thoroughly rinsed and dried once again.