Figure 7.

Polydopamine deposition is compatible with a wide range of hair substrates. (A) Natural virgin red (1) and brown (3) hair and (B) hair dyed with a purple hair dye (5) were used as hair substrates. Dopamine oxidation was carried out using 3% NH₄OH as shown in Figure 2. (C) Virgin gray hair (7) was dyed using 3% NH₄OH (8) and 3% NH₄OH/100 mM H₂O₂ (as for sample 5 in Figure 4). In every case, reactions were carried out at 37–40 °C for 2 h and hair samples were washed five times with water and three times with a 10% shampoo solution prior to imaging/analysis.