Effect of Polymer Composition on the Optical Properties of a New Aggregation-Induced Emission Fluorophore: A Combined Experimental and Computational Approach.

Nowadays, fluorophores with a tetraphenylethylene (TPE) core are considered interesting due to the aggregation-induced emission (AIE) behavior that enables their effective use in polymer films. We propose a novel TPE fluorophore (TPE-BPAN) bearing two dimethylamino push and a 4-biphenylacetonitrile pull moieties with the typical AIE characteristics in solution and in the solid state, as rationalized by DFT calculations. Five different host polymer matrices with different polarity have been selected: two homopolymers of poly(methylmethacrylate) (PMMA) and poly(cyclohexyl methacrylate) (PCHMA) and three copolymers at different compositions (P(MMA-co-CHMA) 75:25, 50:50, and 25:75 mol%). The less polar comonomer of CHMA appeared to enhance TPE-BPAN emission with the highest quantum yield (QY) of about 40% measured in P(MMA-co-CHMA) 75:25. Further reduction in polymer polarity lowered QY and decreased the film stability and adhesion to the glass surface. LSC performances were not significantly affected by the matrix's polarity and resulted in around one-third of the state-of-the-art due to the reduced QY of TPE-BPAN. The theoretical investigation based on density functional theory (DFT) calculations clarified the origin of the observed AIE and the role played by the environment in modulating the photophysical behavior.

Organic compounds for solid state luminescence enhancement/aggregation induced emission: a theoretical perspective.

Organic luminophores displaying one or more forms of luminescence enhancement in solid state are extremely promising for the development and performance optimization of functional materials essential to many modern key technologies. Yet, the effort to harness their huge potential is riddled with hurdles that ultimately come down to a limited understanding of the interactions that result in the diverse molecular environments responsible for the macroscopic response. In this context, the benefits of a theoretical framework able to provide mechanistic explanations to observations, supported by quantitative predictions of the phenomenon, are rather apparent. In this perspective, we review some of the established facts and recent developments about the current theoretical understanding of solid-state luminescence enhancement (SLE) with an accent on aggregation-induced emission (AIE). A description of the macroscopic phenomenon and the questions it raises is accompanied by a discussion of the approaches and quantum chemistry methods that are more apt to model these molecular systems with the inclusion of an accurate yet efficient simulation of the local environment. A sketch of a general framework, building from the current available knowledge, is then attempted via the analysis of a few varied SLE/AIE molecular systems from literature. A number of fundamental elements are identified offering the basis for outlining design rules for molecular architectures exhibiting SLE that involve specific structural features with the double role of modulating the optical response of the luminophores and defining the environment they experience in solid state.

Electron induced efficient dechlorination of trichlorethylene with S doped Fe2B: The enhancement mechanism of S.

In this work, S doped Fe2B (Fe2B-S) was synthesized by sintering method and applied for the enhanced dechlorination of trichlorethylene (TCE). The degradation ratio (D) of TCE was 99.8% with reaction rate constant (kobs) of 0.956 h-1 by 10.0at% S doped Fe2B (corresponding to Fe2B-S10.0), compared to D and kobs values 37.3% and 0.067 h-1 by Fe2B, respectively. The major dechlorination products of acetylene, ethene, ethane and C3-C6 hydrocarbon compounds were observed from a reductive ß-elimination pathway. S doped and undoped Fe2B could form the first-level in-situ galvanic cell, and the returned S provided a second-level galvanic cell to further enhance electron transfer. The doped S worked as electron donor to increase the density of localized unpaired electrons, and the electron enriched Fe atoms leading to stronger reducibility were verified by the density functional theory (DFT) calculation. This work provides a complete insight into the enhancement mechanism of S doped Fe2B and guides the potential design of zero-valent iron (ZVI) with properties tailored for chlorinated hydrocarbons dechlorination.

Oxygen defect-induced localized surface plasmon resonance at the WO3-x quantum dot/silver nanowire interface: SERS and photocatalysis.

Oxygen defects play a crucial role in a variety of functional transition metal oxides, ranging from photocatalytic materials to photoelectric devices. Tungsten oxide (WO3-x) is a type of transition metal oxide that has rich substoichiometric compositions and possesses oxygen defects. These oxygen defects determine the photon-electron interactions in the WO3-x structures. Therein, WO3-x quantum dots (QDs) exhibit fast carrier-transport for photon-electron interactions due to their strong quantum-size effects. Here, we report the use of non-stoichiometric WO3-x QDs, as a model material, in combination with silver nanowires (Ag NWs) to study photon-electron interactions on the nanoscale. We demonstrate that the incident photon-to-electron conversion efficiency can be increased by 8.5% and that the dye photodegradation performance was improved by 40% in a WO2.72 QD@Ag NW (WO2.72 QDs supported on AgNWs) composite compared to those of individual WO2.72 QDs under simulated AM 1.5G light. Furthermore, the WO3-x QD@Ag NW composite exhibits both photocatalytic activity and surface-enhanced Raman scattering (SERS) features, and the WO3-x QDs can be switched between a "photocatalytic state" and a "SERS state" by changing the stoichiometric ratio. The synergistic effects are ascribed to the "plasmonic state" of WO2.72 QDs upon light irradiation. This work provides new insight into the design of highly efficient transition metal oxide/plasmonic metal nanocomposites for photoelectric devices.