Synthesis and Characterization of C₆₀-Anchored Multiarmed Polymers with Well-Defined Structures

A multistep procedure for preparing novel C60-anchored multiarmed polymers with well-defined structures was developed. First, di-, tetra- and octabromo-functionalized molecules with a malonate ester core were synthesized and used as functional initiators for growing two-, four-, and eight-armed poly(tert-butyl acrylate) (PtBA) with well-controlled molecular weight, by atom transfer radical polymerization. Then, C60-anchored polymers were synthesized by the effective Bingel reaction between C60 and the malonate ester core of the multiarmed polymers. The NMR analyses of the products demonstrated that C60 had been covalently bonded to the polymers and UV−vis studies of these polymers revealed strong characteristics of “closed” 6−6-ring-bridged methanofullerene derivatives. As indicated by GPC chromatograms, the molecular weights of the polymers were comparable before and after they are attached to C60 molecules, suggesting that these polymers were monosubstituted C60 derivatives. Furthermore, the C60 contents in these polymers were determined from their light absorbance at 326 nm based on Beer's law and were found to be very close to the theoretical value based on the assumption that C60-derived polymer was a monoadduct. Additionally, highly water-soluble C60-anchored multiarmed poly(acrylic acid) were obtained in quantitative yield by the hydrolysis of the C60-anchored multiarmed PtBA in the presence of trifluoroacetic acid at room temperature

Conducting Polymer Composite Films with Core−Shell-like Nanostructure Prepared from Terthiophene-Terminated Starburst Poly(<i>n</i>-butyl acrylate)

Conducting Polymer Composite Films with Core−Shell-like Nanostructure Prepared from Terthiophene-Terminated Starburst Poly(n-butyl acrylate

Controlled Self-Aggregation of C₆₀-Anchored Multiarmed Polyacrylic Acids and Their Cytotoxicity Evaluation

Controlled Self-Aggregation of C60-Anchored Multiarmed Polyacrylic Acids and Their Cytotoxicity Evaluatio

Mechanistic Insights into the Effect of Polymer Regioregularity on the Thermal Stability of Polymer Solar Cells

Thermal stability is a bottleneck toward commercialization of polymer solar cells (PSCs). The effect of PCBM aggregation on a multilength scale on the bulk-heterojunction (BHJ) structure, performance, and thermal stability of PSCs is studied here by grazing-incidence small- and wide-angle X-ray scattering. The evolution of hierarchical BHJ structures of a blend film tuned by regioregularity of polymers from the as-cast state to the thermally unstable state is systematically investigated. The thermal stability of PSCs with high polymer regioregularity values can be improved because of the good mutual interaction between polymer crystallites and fullerene aggregates. The insights obtained from this study provide an approach to manipulate the film structure on a multilength scale and to enhance the thermal stability of P3HT-based PSCs

Synthesis and Direct Visualization of Electroactive Unimolecular Core−Shell Nanoparticle

Synthesis and Direct Visualization of Electroactive Unimolecular Core−Shell Nanoparticl

Effect of Fullerene Passivation on the Charging and Discharging Behavior of Perovskite Solar Cells: Reduction of Bound Charges and Ion Accumulation

Ion accumulation of organometal halide perovskites (OHPs) induced by electrode polarization of perovskite solar cells (PSCs) under illumination has been intensely studied and associated with a widely observed current–voltage hysteresis behavior. This work is dedicated to the investigation of the behavior of charged species at the compact TiO₂/OHP interface with respect to electrode polarization in PSC devices. By providing a comprehensive discussion of open-circuit voltage (<i>V</i>_OC) buildup and <i>V</i>_OC decay under illumination and in the dark for the PSCs modified with [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) at the TiO₂/OHP interface and their corresponding electrochemical impedance spectroscopies (EISs), a justified mechanism is proposed attempting to elucidate the dynamics of interfacial species with respect to the time and frequency domains. Our results demonstrate that the retarded <i>V</i>_OC buildup and decay observed in PSC devices are related to the formation of bound charges in TiO₂, which is essential to neutralize the oppositely charged ions accumulating at the OHP side. Besides, inserting a thicker PCBM at the TiO₂/OHP interface as a passivation layer can alleviate the electrode polarization more efficiently as verified by the low dielectric constant measured from EIS. Moreover, photoluminescence measurements indicate that PCBM at the TiO₂/OHP interface is capable of passivating a trap state and improving charge transfer. However, with respect to the time scale investigated in this work, the reduction of the hysteresis behavior on a millisecond scale is more likely due to less bound charge formation at the interface rather than shallow trap-state passivation by PCBM. After all, this work comprehensively demonstrates the interfacial properties of PSCs associated with PCBM passivation and helps to further understand its impact on charging/discharging as well as device performance

Benzoselenadiazole Fluorescent Probes – Near-IR Optical and Ratiometric Fluorescence Sensor for Fluoride Ion

A highly selective and sensitive near-IR optical sensor, benzoselenadiazole based diarylamine (<b>TBS-HN</b>), for fluoride (F^–) has been designed and synthesized. <b>TBS-HN</b> also shows turn-on ratiometric fluorescence signaling in the presence of F^– by inhibiting the excited state intramolecular proton transfer (ESIPT) processes

Thermochromism of a Poly(phenylene vinylene): Untangling the Roles of Polymer Aggregate and Chain Conformation

We report reversible thermochromism of a conjugated polymer, poly{2,5-bis[3-(N,N-diethylamino)-1-oxapropyl]-1,4-phenylenevinylene} (DAO-PPV), in diluted solutions of toluene and 1,2-dichlorobenzene. By means of temperature- and solvent-dependent steady-state spectroscopy, picosecond time-resolved photoluminescence spectroscopy, and dynamic light scattering, we provide new insights into the role of polymer aggregates in defining the thermochromic behavior of PPVs. We find DAO-PPV to exhibit a low temperature state with vibronically structured red visible absorption and emission spectra. Structurally, this low temperature state is a densely packed and disordered polymer aggregate, which contains a fraction of well-ordered, packed polymer chains. These ordered regions serve as low energy trap sites for the more disordered regions in the aggregate, thus regulating the final emission of the aggregate and imposing a vibronically resolved emission spectrum, which is usually associated with emission from one or a few chromophores. The high temperature state of DAO-PPV is a loose aggregate, with structureless absorption and emission spectra in the green visible range. Structurally, the loose aggregate is a well-solvated aggregate retaining the physical dimension of the dense aggregate but for which interchain interactions are diminished with the increase of temperature. As a result, the spectroscopic behavior of the loose aggregate is very similar if not identical to that of the single polymer chain. Increased solubility untangles polymer aggregates into single, dispersed, polymer chains, as we demonstrate here for DAO-PPV in 1,2-dichlorobenzene and at high temperature

C₆₀(OH)₁₂ and Its Nanocomposite for High-Performance Lithium Storage

Organic carbon materials, such as graphene and nanotubes, with a high specific capacity show promise in improving the energy density for lithium ion batteries (LiBs). Here, we report on the synthesis and characterization of C60(OH)12 and the C60(OH)12/graphene oxide (GO) composite and demonstrate their use as anode materials in LiBs. We find that the C60(OH)12/GO composite forms due to the chemical reactions between the carboxyl and epoxy groups of GO and the hydroxyl of C60(OH)12 nanoparticles and that C60(OH)12 uniformly grows on the surface of GO nanosheets. Using a suite of spectroscopy probes, we unequivocally show the mixing between C60(OH)12 and GO at the molecular level, which leads to superior battery performances. This composite has a reversible capacity of 1596 mAh g–1 at 0.2 A g–1, higher than the capacities of C60(OH)12 and GO. This composite has a superior cycling stability and excellent rate performance, making it a promising organic anode material for high-performance LiBs

[60]Fulleropyrrolidines Bearing π‑Conjugated Moiety for Polymer Solar Cells: Contribution of the Chromophoric Substituent on C₆₀ to the Photocurrent

Two fullerene-terthiophene dyads without hexyl chains (3T-C60) and with hexyl chains (3TH-C60) on the terthiophene substituent are synthesized by 1,3-dipolar cycloaddition of corresponding azomethine ylides to C60. The cyclic voltammetry studies indicate no apparent electronic communication between the terthiophene pendent group and the fulleropyrrolidine core in the ground state. However, a significant florescence quenching is observed for 3T-C60 and 3TH-C60, compared to their fluorescent terthiophene (3T) and 3TH precursors, respectively, suggesting the occurrence of strong intramolecular electron/energy transfers in the photoexcited state. Furthermore, these new fulleropyrrolidine derivatives are applied as electron acceptors to fabricate poly­(3-hexylthiophene) (P3HT) based bulk heterojunction solar cells. The incident photon-to-current efficiency (IPCE) value of the P3HT/3T-C60 device is significantly higher than that of the P3HT/PCBM cell in wavelengths of 350–420 nm. This finding provides direct evidence for the contribution of 3T excitons to the photocurrent. Replacing 3T-C60 with 3TH-C60 effectively improves the morphology of the photoactive layer and widens the window of optimal D/A ratios, raising the power conversion efficiency (PCE) from 2.14% to 2.54%. Importantly, these devices exhibit superior stability of PCE against high-temperature aging