## 2 Results and Discussion
### Interactions and Dispersion Stability of Anion-\(\pi\) Type PNPs with CuPc and CB  
Five PNPs were mixed with pigment CuPc at a mass ratio of 5:1. The interactions between these PNPs and CuPc were investigated using a series of methods. Firstly, electrostatic interactions can induce alterations in the ultraviolet-visible (UV-Vis) absorption peaks [37]. No absorption peaks of these PNPs were observed in the range of 400-800 nm (Figure S9). As shown in Figure 3a, the two distinct absorption peaks at 640 and 725 nm were attributed to the Q bands of CuPc. Compared to CuPc, the absorption peaks of the mixed samples were all blue-shifted. The order of blue-shifted distances was as follows: CuPc + PNPs-1 > CuPc + PNPs-3 > CuPc + PNPs-2 \(\geq\) CuPc + PNPs-4 > CuPc + PNPs-5 (Figure 3b). Generally, a lower dissociation constant (p\(K_{\mathrm{a}}\)) value of the corresponding acid suggests a higher negative charge of these PNPs, resulting in stronger electrostatic interactions with the pigments [29]. The predicted values of p\(K_{\mathrm{a}}\) in water for the acids corresponding to these PNPs were as follows: 2.44 (PNPs-1), 4.03 (PNPs-2), 3.6 (PNPs-3), 3.38 (PNPs-4), and 2.99 (PNPs-5) (Figure 3c) [38; 39; 40]. Theoretically, the electrostatic interactions were postulated to be stronger in the mixtures of CuPc with PNPs-4 or PNPs-5. However, this was not consistent with the order of blue-shifted distances in the absorption peaks observed in the experiments. It was assumed that stronger intermolecular interactions, particularly \(\pi\)-\(\pi\) interactions, were present within the two mixtures, which led to the red-shift of the absorption peaks. To confirm this assumption, UV-Vis spectra of CuPc in ethanol with different contents of the oil phase monomer St added were measured. Results showed that the absorption peaks of the mixtures of CuPc and St gradually red-shifted with increasing St content (Figure 3d). This indicated the presence of \(\pi\)-\(\pi\) interactions between the benzene ring in the chain segment of PNPs and CuPc. Consequently, the smaller blue-shifted distances of the absorption peaks indicated that PNPs-4 and PNPs-5 exhibited stronger \(\pi\)-\(\pi\) interactions with CuPc. Next, the interaction strengths between these PNPs and CuPc was investigated using XPS spectra. The high-resolution XPS spectrum of N 1s for CuPc can be deconvoluted into four peaks: N=C at 399.05 eV, N-C at 400.47 eV, and two N-Cu coordination peaks at 402.91 and 405.74 eV, respectively (Figure S10). As shown in Figure 3e, the binding energies of the N=C peak after mixing with these PNPs were 398.70, 398.96, 398.88, 398.61, and 398.56 eV (Figure S10), respectively [41]. This noticeable shift of the N=C peak towards lower binding energies provided additional evidence of the \(\pi\)-\(\pi\) interactions between these PNPs and CuPc [42]. The interaction between PNPs-5 and CuPc was the strongest, which was consistent with UV-Vis spectra results. In addition, two peaks of N-Cu coordination were shifted to lower binding energies (Figure 3f), suggesting electron transfer from these PNPs to CuPc. In the high-resolution XPS spectrum of Cu 2p for CuPc, two spin-orbit peaksat around 935.35 and 955.30 eV were ascribed respectively to Cu 2p\({}_{3/2}\) and Cu 2p\({}_{1/2}\) of Cu\({}^{2+}\). In addition, two satellite peaks were located around 943.98 and 963.94 eV, while two peaks at around 936.92 and 957.14 eV were assigned to the Cu-N coordination (Figure S11). Since the satellite peaks were less relevant to the main interactions between these PNPs and CuPc, their variations were neglected (Figure S12). Two peaks of Cu-N coordination also shifted to lower binding energies after mixing these PNPs (Figure 3g), which was consistent with the XPS results of N 1s. The Cu 2p\({}_{3/2}\) and Cu 2p\({}_{1/2}\) peaks in each case shifted toward lower binding energies (Figure 3h), confirming that electrostatic interactions facilitated electron transfer from these anions to CuPc.