Langmuir–Blodgett Films of Self-Assembled (Alkylether-Derivatized Zn Phthalocyanine)–(C₆₀ Imidazole Adduct) Dyad with Controlled Intermolecular Distance for Photoelectrochemical Studies

Abstract

A multilayer Langmuir-Blodgett (LB) film of the self-assembled electron donor-acceptor dyad of Zn phthalocyanine, appended with four long-chain aliphatic ether peripheral substituents, and an imidazole adduct of C60 was prepared and applied as a photoactive material in a photoelectrochemical cell. Changes in the simultaneously recorded surface pressure and surface potential vs area per molecule compression isotherms for Langmuir films of the dyad and, separately, of its components helped to identify phase transitions and mutual interactions of molecules in films. The Brewster angle microscopy (BAM) imaging of the Langmuir films showed circular condensed phase domains of the dyad molecules. The determined area per molecule was lower than that estimated for the dyad and its components, separately. The multilayer LB films of the dyad were transferred onto hydrophobized fluorine-doped tin oxide-coated (FTO) glass slides under different conditions. The presence of both components in the dyad LB films was confirmed with the UV-vis spectroscopy measurements. For the LB films transferred at different surface pressures, the PM-IRRAS measurements revealed that the phthalocyanine macrocycle planes and ether moieties in films were tilted with respect to the FTO surface. The AFM imaging of the LB films indicated formation of relatively uniform dyad LB films. Then, the femtosecond transient absorption spectral studies evidenced photoinduced electron transfer in the LB film. The obtained transient signals corresponding to both Zn(TPPE)(•+) and C60im(•-) confirmed the occurrence of intramolecular electron transfer. The determined rate constants of charge separation, kcs = 2.6 × 10(11) s(-1), and charge recombination, kcr = 9.7 × 10(9) s(-1), indicated quite efficient electron transfer within the film. In the photoelectrochemical studies, either photoanodic or photocathodic current was generated depending on the applied bias potential when the dyad LB film-coated FTO was used as the working electrode and ascorbic acid or methylviologen, respectively, as the charge mediator in an aqueous solution.

Tetrakis(4-pyridylphenyl)ethylene-based Zinc Metal–Organic Framework with Aggregation-Induced Chemiluminescence Emission on a Paper Platform for Formaldehyde Detection in Breath

“…From the FTIR results in Figure 1D, the adsorption peaks of Zn-Py-TPE at 1116 and 1568 cm −1 corresponded to C−H in-plane vibrations of benzene ring and bending vibrations of C�C, respectively. 29,30 The peak at 1489 cm −1 was assigned to asymmetric aromatic ring stretching vibrations, 29 and the adsorption peak at 1598 cm −1 confirmed the pyridine group in the Py-TPE ligand. 31 The peaks at 650−910 cm −1 in the fingerprint area reflected different substituent regions of the phenyl ring.…”

Chlorin e6 sensitized photovoltaic cells: effect of co-adsorbents on cell performance, charge transfer resistance, and charge recombination dynamics

“…3(b), strong peak at 582 nm, that was absent for pristine chlorin e6 was observed providing evidence for charge injection from the singlet excited state of chlorin e6 to the conduction band of TiO 2 , an observation similar to that reported earlier for FTO∕TiO 2 ∕porphyrin and phthalocyanine-based solar cells. 23,31,32 The time profile of this peak could be fitted satisfactorily to a biexponential decay fit resulting in time constants of 0.88 and 24.7 ps. The rate of charge injection, k CI , and charge recombination, k CR , evaluated from these time constants were found to be 1.14 × 10 12 and 4.05 × 10 10 s −1 , respectively.…”

“…The magnitude of these values was close to that reported for porphyrin-based solar cells. 23,[31][32][33] Figures 8(c) and 8(d) show transient spectra of FTO∕TiO 2 ∕chlorin e6þcholic acid and FTO∕TiO 2 ∕chlorin e6þdeoxycholic acid electrodes. The spectral features were quite similar to that gathered for the FTO∕TiO 2 ∕chlorin e6 electrode suggesting that the co-adsorbent does not directly interact with the sensitizer to change the spectral features.…”