## 3 Results
The EPD process resulted in the formation of continuous films at voltages of 20-80 V. The microstructure of the films formed at 20 V showed a large number of fibers with a typical length of 5-10 \(\upmu\)m and diameters of about 0.5 \(\upmu\)m. Fiber formation can result from self-assembly of water-insoluble hydrophobic CBXH\({}_{2}\) molecules. The formation of fibrous particles by electrochemical self-assembly was observed in other experiments on anodic electrodeposition of other small organic molecules [36; 37]. Such fibers were not observed at higher voltages. The increase of voltage above 80V in the water-ethanol solvent resulted in pinholes. Therefore, the EPD from aqueous suspensions was limited to voltages not higher than 15 V, whereas the deposition from ethanol-water suspensions was performed at voltages below 80 V. It is important to note that the selection of a solvent is important for the fabrication of stable suspensions for EPD. Therefore, in this investigation EPD of different materials was performed in aqueous or ethanol-water suspensions in order to achieve good suspension stability for each material. The deposition mechanism of carbon materials and PTFE involved CBX\({}^{2-}\) adsorption; the adsorbed CBX\({}^{2-}\) makes the materials negatively charged and facilitates EPD from stable suspensions. Figure 3 shows microstructures of films containing diamond and nanodiamond, as well as the XRD patterns of the films. Electron microscopy showed the formation of continuous films, which were crack-free and contained diamonds (Figure 3A). Nanodiamond particles showed poor dispersion in water. However, relatively stable suspensions were obtained in ethanol-water solvent, which facilitated nanodiamond dispersion in the  
Figure 2: SEM images of films, deposited from 1 g L\({}^{-1}\) CBXNa\({}_{2}\) solutions in water at (**A**) 5 V, (**B**) 15 V and in ethanol-water solvent (5% water) at (**C**) 20 V and (**D**) 80 V.  
presence of CBXNa\({}_{2}\). Electron microscopy studies showed some agglomerates on the film surface (Figure 3B). The size of the primary particles in such agglomerates was significantly larger than the size of the nanodiamond particles. The agglomeration of the nanodiamond particles can result from their lower zeta-potential (Supplementary material, Table S1). The incorporation of diamond and nanodiamond in the films was confirmed by XRD (Figure 3C), which showed peaks (111), (220) and (113) of diamond. The peak broadening for nanodiamond resulted from its small size (Figure 3C). The feasibility of diamond deposition by EPD from their dispersion in CBXNa\({}_{2}\) solutions indicated that CBX\({}^{2-}\) adsorbed on chemically inert diamond surfaces. It was hypothesized that the hydrophobic interactions allowed for adsorption of amphiphilic CBX\({}^{2-}\) on the diamond particles. It was found that other carbon materials, such as carbon dots and graphene, can also be deposited from their dispersions in the CBXNa\({}_{2}\) solutions. Figure 4 shows that continuous and crack-free films were deposited. The SEM image shows relatively large graphene particles. The incorporation of carbon dots into the CBXH\({}_{2}\) films was verified by FTIR. Figure 4: SEM images of films, prepared from (**A**) 0.5 gL\({}^{-1}\) CBXNa\({}_{2}\) with 0.5 gL\({}^{-1}\) carbon dots in water at 15 V and (**B**) 1 gL\({}^{-1}\) CBXNa\({}_{2}\) with 1 gL\({}^{-1}\) graphene in water at 10 V.  
Figure 3: (**A**,**B**) SEM and (**C**) XRD data for films prepared from 1 gL\({}^{-1}\) CBXNa\({}_{2}\) solutions with (**A**,**C**(a)) 1 gL\({}^{-1}\) diamond at 7 V in water and (**B**,**C**(b)) 1 gL\({}^{-1}\) nanodiamond at 70 V in ethanol-water (5% water) solvent. The FTIR spectrum of CBXNa\({}_{2}\) (Figure 5A(a)) presents peaks at 1397 and 1564 cm\({}^{-1}\), owing to symmetric and asymmetric vibrating of salified carboxylic groups, respectively [38].