Uniform electroactive fiber-like micelle nanowires for organic electronics

AbstractMicelles formed by the self-assembly of block copolymers in selective solvents have attracted widespread attention and have uses in a wide variety of fields, whereas applications based on their electronic properties are virtually unexplored. Herein we describe studies of solution-processable, low-dispersity, electroactive fibre-like micelles of controlled length from π-conjugated diblock copolymers containing a crystalline regioregular poly(3-hexylthiophene) core and a solubilizing, amorphous regiosymmetric poly(3-hexylthiophene) or polystyrene corona. Tunnelling atomic force microscopy measurements demonstrate that the individual fibres exhibit appreciable conductivity. The fibres were subsequently incorporated as the active layer in field-effect transistors. The resulting charge carrier mobility strongly depends on both the degree of polymerization of the core-forming block and the fibre length, and is independent of corona composition. The use of uniform, colloidally stable electroactive fibre-like micelles based on common π-conjugated block copolymers highlights their significant potential to provide fundamental insight into charge carrier processes in devices, and to enable future electronic applications.</jats:p

Factors Affecting the Growth and Fragmentation of Polyferrocenylsilane Diblock Copolymer Micelles

Polyferrocenylsilane (PFS) diblock copolymers self-assemble in selective solvents to form one-dimensional micelles for a broad range of polymer compositions and experimental conditions, driven by the crystallization of the PFS block that forms the micelle core. The most striking feature of these micelles is that they remain active for further growth. They can be extended in length when additional polymer, dissolved in a good solvent, is added to a solution of the pre-existing micelles. This thesis describes several studies investigating the factors that affect the growth and fragmentation of PFS diblock copolymer micelles in solution, with a particular emphasis on polyisoprene-PFS (PI-PFS) diblock copolymers. The goal of my research was trying to provide deeper understanding of this crystallization-driven self-assembly (CDSA) process. In an attempt to understand the growth kinetics of the PI-PFS cylindrical micelles, I added tiny amount of short micelle seeds into supersaturated solution of the same polymer, and followed the micelle growth by light scattering. The data analysis showed that the increase of micelle length could be described by an expression with two exponential decay terms. In another attempt to examine the factors that may affect the growth behavior of the PI-PFS micelles, I found that PI-PFS long micelles underwent fragmentation when they were subjected to external stimuli, e.g. addition of polar solvent, or heating. During the course of studying the effect of heating on the micelles, I developed a new approach to generate cylindrical micelles with controllable and uniform length, a one-dimensional analogue of self-seeding of crystalline polymers. I carried out a systematic study to investigate the self-seeding behavior of PFS block copolymers.Ph

Fabrication of Novel Magnetic Nanoparticles of Multifunctionality for Water Decontamination

Efficient and powerful water purifiers are in increasing need because we are facing a more and more serious problem of water pollution. Here, we demonstrate the design of versatile magnetic nanoadsorbents (M-QAC) that exhibit excellent disinfection and adsorption performances at the same time. The M-QAC is constructed by a Fe₃O₄ core surrounded by a polyethylenimine-derived corona. When dispersed in water, the M-QAC particles are able to interact simultaneously with multiple contaminants, including pathogens and heavy metallic cations and anions, in minutes. Subsequently, the M-QACs along with those contaminants can be easily removed and recollected by using a magnet. Meanwhile, the mechanisms of disinfection are investigated by using TEM and SEM, and the adsorption mechanisms are analyzed by XPS. In a practical application, M-QACs are applied to polluted river water 8000-fold greater in mass, producing clean water with the concentrations of all major pollutants below the drinking water standard of China. The adsorption ability of M-QAC could be regenerated for continuous use in a facile manner. With more virtues, such as low-cost fabrication and easy scaling up, the M-QAC have been shown to be a very promising multifunctional water purifier with rational design and to have great potential for real water purification applications

Interaction between Organic Compounds and Catalyst Steers the Oxidation Pathway and Mechanism in the Iron Oxide-Based Heterogeneous Fenton System

In the past decades, extensive efforts have been devoted to the mechanistic understanding of various heterogeneous Fenton reactions. Nevertheless, controversy still remains on the oxidation mechanism/pathway toward different organic compounds in the classical iron oxide-based Fenton reaction, largely because the role of the interaction between the organic compounds and the catalyst has been scarcely considered. Here, we revisited the classic heterogeneous ferrihydrite (Fhy)/H2O2 system toward different organic compounds on the basis of a series of degradation experiments, alcohol quenching experiments, theoretical modeling, and intermediate analysis. The Fhy/H2O2 system exhibited highly selective oxidation toward the group of compounds that bear carboxyl groups, which tend to complex with the surface Fe(III) sites of the Fhy catalyst. Such interaction results in a nonradical inner sphere electron transfer process, which seizes one electron from the target compound and features negligible inhibition by the radical quencher. In contrast, for the oxidation of organic compounds that could not complex with the catalyst, the traditional HO· process makes the main contribution, which proceeds via hydroxyl addition reaction and could be readily suppressed by the radical quencher. This study implies that the interaction between the organic compounds and the catalyst plays a decisive role in the oxidation pathway and mechanism of the target compounds and provides a holistic understanding on the iron oxide-based heterogeneous Fenton system

Structure Evolution of Iron (Hydr)oxides under Nanoconfinement and Its Implication for Water Treatment

In the development of nanoenabled technologies for large-scale water treatment, immobilizing nanosized functional materials into the confined space of suitable substrates is one of the most effective strategies. However, the intrinsic effects of nanoconfinement on the decontamination performance of nanomaterials, particularly in terms of structural modulation, are rarely unveiled. Herein, we investigate the structure evolution and decontamination performance of iron (hydr)­oxide nanoparticles, a widely used material for water treatment, when confined in track-etched (TE) membranes with channel sizes varying from 200 to 20 nm. Nanoconfinement drives phase transformation from ferrihydrite to goethite, rather than to hematite occurring in bulk systems, and the increase in the nanoconfinement degree from 200 to 20 nm leads to a significant drop in the fraction of the goethite phase within the aged products (from 41% to 0%). The nanoconfinement configuration is believed to greatly slow down the phase transformation kinetics, thereby preserving the specific adsorption of ferrihydrite toward As­(V) even after 20-day aging at 343 K. This study unravels the structure evolution of confined iron hydroxide nanoparticles and provides new insights into the temporospatial effects of nanoconfinement on improving the water decontamination performance

Nanoconfinement-triggered oligomerization pathway for efficient removal of phenolic pollutants via a Fenton-like reaction

Abstract Heterogeneous Fenton reaction represents one of the most reliable technologies to ensure water safety, but is currently challenged by the sluggish Fe(III) reduction, excessive input of chemicals for organic mineralization, and undesirable carbon emission. Current endeavors to improve the catalytic performance of Fenton reaction are mostly focused on how to accelerate Fe(III) reduction, while the pollutant degradation step is habitually overlooked. Here, we report a nanoconfinement strategy by using graphene aerogel (GA) to support UiO-66-NH2-(Zr) binding atomic Fe(III), which alters the carbon transfer route during phenol removal from kinetically favored ring-opening route to thermodynamically favored oligomerization route. GA nanoconfinement favors the Fe(III) reduction by enriching the reductive intermediates and allows much faster phenol removal than the unconfined analog (by 208 times in terms of first-order rate constant) and highly efficient removal of total organic carbon, i.e., 92.2 ± 3.7% versus 3.6 ± 0.3% in 60 min. Moreover, this oligomerization route reduces the oxidant consumption for phenol removal by more than 95% and carbon emission by 77.9%, compared to the mineralization route in homogeneous Fe2++H2O2 system. Our findings may upgrade the regulatory toolkit for Fenton reactions and provide an alternative carbon transfer route for the removal of aqueous pollutants

Self-carbon-thermal-reduction strategy for boosting the Fenton-like activity of single Fe-N4 sites by carbon-defect engineering

Abstract Carbon-defect engineering in metal single-atom catalysts by simple and robust strategy, boosting their catalytic activity, and revealing the carbon defect-catalytic activity relationship are meaningful but challenging. Herein, we report a facile self-carbon-thermal-reduction strategy for carbon-defect engineering of single Fe-N4 sites in ZnO-Carbon nano-reactor, as efficient catalyst in Fenton-like reaction for degradation of phenol. The carbon vacancies are easily constructed adjacent to single Fe-N4 sites during synthesis, facilitating the formation of C-O bonding and lowering the energy barrier of rate-determining-step during degradation of phenol. Consequently, the catalyst Fe-NCv-900 with carbon vacancies exhibits a much improved activity than the Fe-NC-900 without abundant carbon vacancies, with 13.5 times improvement in the first-order rate constant of phenol degradation. The Fe-NCv-900 shows high activity (97% removal ratio of phenol in only 5 min), good recyclability and the wide-ranging pH universality (pH range 3-9). This work not only provides a rational strategy for improving the Fenton-like activity of metal single-atom catalysts, but also deepens the fundamental understanding on how periphery carbon environment affects the property and performance of metal-N4 sites

Fluorous Cylindrical Micelles of Controlled Length by Crystallization-Driven Self-Assembly of Block Copolymers in Fluorinated Media

Fluorous solvents have recently found broad applications in medical treatments as well as catalytic transformations, yet the controlled self-assembly of nanomaterials in fluorinated media has remained a challenge. Herein, we report the synthesis of block copolymers containing a crystalline polyferrocenylsilane metalloblock and a highly fluorinated coil block and their controlled self-assembly in fluorinated media. Using the crystallization-driven self-assembly approach, cylindrical micelles have been prepared with controlled lengths and narrow length polydispersities by self-seeding. Finally, by partial functionalization of these block copolymers with fluorescent dye molecules, we show that well-defined, functional nanomaterials can be obtained in the fluorous phase