Redox-Active Ferrocene Polymer for Electrode-Active Materials: Step-by-Step Synthesis on Gold Electrode Using Automatic Sequential Polymerization Equipment.

Redox-active polymers have garnered significant attention as promising materials for redox capacitors, which are energy-storage devices that rely on reversible redox reactions to store and deliver electrical energy. Our focus was on optimizing the electrochemical performance in the design and synthesis of redox-active polymer electrodes. In this study, a redox-active polymer was prepared through step-by-step synthesis on a gold electrode. To achieve this, we designed an automatic sequential polymerization equipment that minimizes human intervention and enables a stepwise polymerization reaction. The electrochemical properties of the polymer gold electrodes were investigated. The degree of polymerization of the polymer grown on the gold electrode can be controlled by adjusting the cycle of the sequential operation. As the number of cycles increases, the amount of accumulated charge increases proportionally, indicating the potential for enhanced electrochemical performance.

Control of Bandgaps and Energy Levels in Water-Soluble Discontinuously Conjugated Polymers through Chemical Modification.

Bandgap and energy levels are crucial for developing new electronic and photonic devices because photoabsorption is highly dependent on the bandgap. Moreover, the transfer of electrons and holes between different materials depends on their respective bandgaps and energy levels. In this study, we demonstrate the preparation of a series of water-soluble discontinuously π-conjugated polymers through the addition-condensation polymerization of pyrrole (Pyr), 1,2,3-trihydroxybenzene (THB) or 2,6-dihydroxytoluene (DHT), and aldehydes, including benzaldehyde-2-sulfonic acid sodium salt (BS) and 2,4,6-trihydroxybenzaldehyde (THBA). To control the energy levels of the polymers, varying amounts of phenols (THB or DHT) were introduced to alter the electronic properties of the polymer structure. The introduction of THB or DHT into the main chain results in discontinuous conjugation and enables the control of both the energy level and bandgap. Chemical modification (acetoxylation of phenols) of the polymers was employed to further tune the energy levels. The optical and electrochemical properties of the polymers were also investigated. The bandgaps of the polymers were controlled in the range of 0.5-1.95 eV, and their energy levels could also be effectively tuned.

Electrical Conductivities of Narrow-Bandgap Polymers with Two Types of π-Conjugated Post-Crosslinking.

Bandgap energy is one of the most important properties for developing electronic devices because of its influence on the electrical conductivity of substances. Many methods have been developed to control bandgap, one of which is the realization of conducting polymers using narrow-bandgap polymers; however, the preparation of these polymers is complex. In this study, water-soluble, narrow-bandgap polymers with reactive groups were prepared by the addition-condensation reaction of pyrrole (Pyr), benzaldehyde-2-sulfonic acid sodium salt (BS), and aldehyde-containing reactive groups (aldehyde and pyridine) for post-crosslinking. Two types of reactions, aldehyde with p-phenylenediamine and pyridine with 1,2-dibromoethylene, were carried out for the π-conjugated post-crosslinking between polymers. The polymers were characterized by proton nuclear magnetic resonance (1H-NMR), thermogravimetric/differential thermal analysis (TG/DTA), UltraViolet-Visible-Near InfraRed spectroscopy (UV-Vis-NIR), and other analyses. The bandgaps of the polymers, calculated from their absorption, were less than 0.5 eV. Post-crosslinking prevents resolubility and develops electron-conducting routes between the polymer chains for π-conjugated systems. Moreover, the post-crosslinked polymers maintain their narrow bandgaps. The electrical conductivities of the as-prepared polymers were two orders of magnitude higher than those before the crosslinking.

Synthesis of Reactive Water-Soluble Narrow-Band-Gap Polymers for Post-Crosslinking.

In this study, water-soluble, narrow-band-gap polymers containing reactive groups were prepared by the addition-condensation of pyrrole (Pyr), benzaldehyde-2-sulfonic acid sodium salt (BS), and terephthalaldehydic acid (TPA) or p-hydroxybenzaldehyde (p-HB). TPA and p-HB were used for the post-crosslinking reaction between polymers. The polymers were characterized by employing various analyses such as 1H-NMR, thermal gravimetric analysis (TGA), and UV-Vis-NIR. The Eg values of polymers estimated from the absorption edges were 0.55 and 0.62 eV. The post-crosslinking reaction is important for preventing resolubilization and for developing an electron conducting route between the polymer chains. Herein, the post-crosslinked polymer was observed to maintain its narrow-band-gap and conductivity was increased 46 times compared to that observed before crosslinking.

Bovine serum albumin-capped gold nanoclusters conjugating with methylene blue for efficient 1O2 generation via energy transfer.

Bovine serum albumin (BSA)-capped gold nanoclusters (BSA-Au NCs) are attractive photosensitizers for efficient singlet oxygen 1O2 generation owing to their high-water solubility, low toxicity, and the broad absorption from UV to visible wavelengths, and the long lifetime of the electronic excitations (of the order of microseconds). However, the 1O2 generation efficiency of BSA-Au NCs is relatively low. In the present study, a conjugate of BSA-Au NCs and methylene blue (MB) (BSA-Au NC-MB conjugate) has been developed to improve 1O2 generation for antimicrobial photodynamic therapy (aPDT). The BSA-Au NC-MB conjugate demonstrated enhanced 1O2 generation compared to the case of BSA-Au NCs and effective aPDT ability under white-light LED illumination for only 1min due to the resonance energy transfer from the Au NCs to the MB in the conjugate. To the best of my knowledge, this is first report of Au NCs on the resonance energy transfer application for efficient 1O2 generation. Therefore, the BSA-Au NC-MB conjugate is a novel photosensitizer for 1O2 generation that shows great potential for aPDT, and the present study also develops a very simple strategy to fabricate albumin-based nanoparticles for PDT.

Structure-controlled polymers prepared by pseudo-living addition-condensation polymerization and their application to light harvesting.

An A,B-block amphiphilic polymer and a branched polymer were prepared by using a new type of pseudo-living addition-condensation polymerization. The first polymer showed an interphase photoinduced energy transfer in a micellar system, while the second type showed efficient light-harvesting ability.

In situ sensitive fluorescence imaging of neurons cultured on a plasmonic dish using fluorescence microscopy.

A plasmonic dish was fabricated as a novel cell-culture dish for in situ sensitive imaging applications, in which the cover glass of a glass-bottomed dish was replaced by a grating substrate coated with a film of silver. Neuronal cells were successfully cultured over a period of more than 2 weeks in the plasmonic dish. The fluorescence images of their cells including dendrites were simply observed in situ using a conventional fluorescence microscope. The fluorescence from neuronal cells growing along the dish surface was enhanced using the surface plasmon resonance field. Under an epi-fluorescence microscope and employing a donut-type pinhole, the fluorescence intensity of the neuron dendrites was found to be enhanced efficiently by an order of magnitude compared with that using a conventional glass-bottomed dish. In a transmitted-light fluorescence microscope, the surface-selective fluorescence image of a fine dendrite growing along the dish surface was observed; therefore, the spatial resolution was improved compared with the epi-fluorescence image of the identical dendrite.