Self-Assembly and Catalytic Activity of Metal Nanoparticles Immobilized in Polymer Membrane Prepared via Layer-by-Layer Approach

Densely packed nanoparticles distributed in a stable and robust thin film is a highly preferred system for utilizing the various applications of nanoparticles. Here, we report covalent bond mediated layer-by-layer (LbL) self-assembled thin films of nanoparticles embedded in polymer membrane. Polymer with complementary functional group is utilized for fabrication of thin film via covalent bonding. UV–visible spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to monitor the growth of LbL thin film. Subsequently, the composite thin film is used for catalysis of an organic electron transfer reaction of <i>p</i>-nitrophenol to <i>p</i>-aminophenol by sodium borohydride. The catalytic activity of these composite films is assayed multiple times, proving its applicability as a catalyst. The kinetic data obtained by monitoring reduction of <i>p</i>-nitrophenol suggest that the reaction rates are directly related to the sizes of the nanoparticle and porosity of the membrane

Correlation between Optical Properties and Nanomorphology of Fluoranthene-Based Conjugated Copolymer

Nanoparticles of conjugated polymers are receiving attention due to their interesting optical properties. Here we report nanoparticles of fluoranthene-based conjugated copolymer prepared by the Suzuki coupling reaction. The copolymer forms nanoparticles by the spontaneous self-assembly after evaporation of organic solvent. The mean diameter of the nanoparticles can be manipulated by varying solvent composition. We investigated the parameters that govern the nanostructured morphology of polymer by systematic variation of good and poor solvent. The UV–vis and time-resolved fluorescence spectroscopy measurement reveal the use of poor solvent in the organization of nanostructures. Furthermore, transmission electron microscopy highlights the importance of rigidity of the polymer backbone in morphological development

Investigation of Ion-Mediated Charge Transport in Methylammonium Lead Iodide Perovskite

We have investigated the origin of ionic conductivity in methylammonium lead iodide (MAPbI₃) by positron annihilation lifetime spectroscopy (PALS), supplemented by coincidence Doppler broadening spectroscopic (CDBS) techniques which reveal the presence of methylammonium (MA⁺) defects in the perovskite crystal lattice. Crystallinity and the defect concentration vary with the perovskite synthesis process, which in turn governs the magnitude of ionic conductivity. Single-crystalline perovskite contains lesser defects with equal probability of developing both cationic and anionic (halide) vacancies, whereas the polycrystalline perovskite sample developed through mechanical process carries mainly cationic, i.e., MA⁺ vacancy (<i>V</i>′_MA) in its crystal lattice as indicated by direct current (dc) polarization experiment

Investigation of Ion-Mediated Charge Transport in Methylammonium Lead Iodide Perovskite

We have investigated the origin of ionic conductivity in methylammonium lead iodide (MAPbI₃) by positron annihilation lifetime spectroscopy (PALS), supplemented by coincidence Doppler broadening spectroscopic (CDBS) techniques which reveal the presence of methylammonium (MA⁺) defects in the perovskite crystal lattice. Crystallinity and the defect concentration vary with the perovskite synthesis process, which in turn governs the magnitude of ionic conductivity. Single-crystalline perovskite contains lesser defects with equal probability of developing both cationic and anionic (halide) vacancies, whereas the polycrystalline perovskite sample developed through mechanical process carries mainly cationic, i.e., MA⁺ vacancy (<i>V</i>′_MA) in its crystal lattice as indicated by direct current (dc) polarization experiment

Modulation of Electronic and Self-Assembly Properties of a Donor–Acceptor–Donor-Based Molecular Materials via Atomistic Approach

The performance of molecular materials in optoelectronic devices critically depends upon their electronic properties and solid-state structure. In this report, we have synthesized sulfur and selenium based (<b>T4BT</b> and <b>T4BSe</b>) donor–acceptor–donor (D–A–D) organic derivatives in order to understand the structure–property correlation in organic semiconductors by selectively tuning the chalcogen atom. The photophysical properties exhibit a significant alteration upon varying a single atom in the molecular structure. A joint theoretical and experimental investigation suggests that replacing sulfur with selenium significantly reduces the band gap and molar absorption coefficient because of lower electronegativity and ionization potential of selenium. Single-crystal X-ray diffraction analysis showed differences in their solid-state packing and intermolecular interactions. Subsequently, difference in the solid-state packing results variation in self-assembly. Micorstructural changes within these materials are correlated to their electrical resistance variation, investigated by conducting probe atomic force microscopy (<b>CP-AFM</b>) measurements. These results provide useful guidelines to understand the fundamental properties of D–A–D materials prepared by atomistic modulation