Layer-by-Layer Naphthalenediimide/Zn Phosphonate Hybrid Films Grown from Aqueous Solutions by a Simple Deposition Technique

Abstract

Hybrid thin films containing N,N′-bis­(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) and zinc cations (PNDI/Zn films) were built on silicon and indium tin oxide (ITO) substrates by a simple layer-by-layer deposition process. Silicon substrates primed with a layer of phosphonate groups were immersed alternately into zinc nitrate and PNDI aqueous solutions, yielding PNDI/Zn films containing up to 40 layers. ITO substrates, on the other hand, were used without priming, and the deposition sequence began with a PNDI layer. All film growth steps were conducted at room temperature, using aqueous solutions, thus assuring an environmentally clean process. The PNDI/Zn films were studied by X-ray reflectivity and grazing angle X-ray diffraction, using synchrotron radiation source. The films were constituted by crystallites, containing zinc phosphonate layers oriented nearly parallel to the substrate. PNDI/Zn films on ITO were reduced to stable free radicals, which were observed by UV–visible spectroscopy. Moreover, PNDI/Zn bulk materials with structural analogy with the films were produced.

Radical Anions and Dianions of Naphthalenediimides Generated within Layer-by-Layer Zirconium Phosphonate Thin Films

“…35 These results indicate that film growth involves nanocrystal nucleation, rather than the formation of the plane, segregated layers suggested in the idealized representation of Figure 1. However, our recent results with the analogue Zn/PNDI films 37 showed that a layered structure was indeed present in the interior of a Values in parentheses are the molar absorptivity coefficients (M −1 cm −1 ). b The most intense peaks are in bold characters.…”

“…Our group has synthesized N , N ′-bis­(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI), a NDI derivative substituted with phosphonic acid groups at the imide nitrogens (Scheme ), which is suitable for the construction of metal phosphonate films. Layer-by-layer zirconium and zinc phosphonate thin films have been grown from PNDI aqueous solutions and studied by ellipsometry, cyclic voltammetry, and X-ray scattering methods. − Those studies, however, were mainly focused on PNDI in the ground state. In the present report, we constructed a 25-layer PNDI zirconium phosphonate film on quartz (NDIZP film) (Figure ) and then reduced the imide with sodium dithionite, resulting in metal phosphonate films doped with stable radical anion and dianion species.…”

Photocatalyst–Mediator Interface Modification by Surface-Metal Cations of a Dye-Sensitized H2 Evolution Photocatalyst

“…Although the AQY and STH values of dye-sensitized photocatalysts (DSPs) are still lower than those of their metal-oxide-based counterparts, the dye-sensitization technique offers a unique advantage. Indeed, further modification at the dye–semiconductor interface is possible by co-absorption and/or multilayering of functional molecules, as evidenced by recent studies in dye-sensitized solar (DSSCs) and electrochemical (DSPECs) cells. − Meyer et al demonstrated one-directional energy transfer in a bilayer film composed of two different Ru­(II) dyes. − Hanson et al reported that the lifetime of the charge-separated state can be controlled by introducing an organic spacer molecule into the dye–semiconductor interface with various metal cation linkages. − Furthermore, several research groups have reported that the host–guest interaction is useful for softly immobilizing dyes and catalyst molecules on the semiconductor surface. − However, the literature on the further modification of the dye–semiconductor interface in the field of DSP for water splitting remains limited.…”

Construction of Multifunctional and Adjustable Langmuir–Blodgett Composite Films Containing Black Phosphorus with High Stability for Optically Electrical Applications

“…Various supramolecular nanostructures include one-dimensional (1D) rods, tubes, and fibers, 2D layered sheets, and 3D vesicles can be obtained through molecular self-assembly. − In order to obtain a supramolecular polymer system with a specific structure and function, the specific noncovalent interactions are introduced into the molecular building blocks to drive the entire self-assembly process, including π–π bond interactions, hydrogen bonds, and metal–ligand interaction. The methods of preparing ordered ultrathin films mainly include Langmuir–Blodgett (LB) technology, self-assembled monolayer technology, and layer-by-layer assembly technology (LbL). , Compared with the traditional LbL, the thin film with controllable thickness and internal molecular structure can be prepared by the LB technology, and the film molecules are arranged in a high degree of order. In addition, the obtained LB film can better realize polymerization and high molecular weight and achieve assembly at the molecular level.…”

“…The methods of preparing ordered ultrathin films mainly include Langmuir− Blodgett (LB) technology, self-assembled monolayer technology, and layer-by-layer assembly technology (LbL). 21,22 Compared with the traditional LbL, the thin film with controllable thickness and internal molecular structure can be prepared by the LB technology, and the film molecules are arranged in a high degree of order. In addition, the obtained LB film can better realize polymerization and high molecular weight and achieve assembly at the molecular level.…”