Bis(thiena??2a??yl)a??2,1, <scp>3a??benzothiadiazolea??diketopyrrolopyrrole</scp> a??based <scp>acceptora??acceptor</scp> conjugated polymers: Design, synthesis, and the synergistic effect of the substituent on their solar cell properties

摘要： Three acceptor–acceptor conjugated copolymers (TBT-DPP, FTBT-DPP, and HFTBT-DPP) with different substituent groups have been synthesized with palladium-catalyzed Stille coupling condensation polymerization assisted with microwave. Polymer solar cells (PSCs) based on these copolymers as the electron donors and PC71BM as the acceptor have been fabricated. The synergistic effect of the substituent between two fluorine atoms and hexyl alkyl chains in bis(thien-2-yl)-2,1,3-benzothiadiazole fragment on their solar cell properties has been investigated. Both the fluorine atoms and the synergistic effect can improve the solubility of the polymers effectively while the excellent thermal stability properties are still retained. Two fluorine atoms (polymer FTBT-DPP) increased the power conversion efficiency of the PSCs twice compared with TBT-DPP (without substituent). The synergistic effect (polymer HFTBT-DPP) decreased that seriously to zero. Density function theory calculations showed that the conjugation level of the polymer backbone is one of key factors. It demonstrates that the synergistic effect of fluorine atoms and alkyl chains in the same fragment does not always work well in improving the PSCs performance.

Low-cost and high-resolution pressure sensors using highly stretchable polymer optical fibers

摘要： This letter reports on the development of a low-cost intensity variation-based pressure sensor using polymer optical fibers (POFs) with high flexibility fabricated through the light polymerization spinning process. The fibers were characterized by tensile tests that indicate a Young’s modulus of 18.11 MPa. The pressure response of the proposed system shows a sensitivity five times higher when compared with systems employing commercial POFs. Furthermore, results also show low hysteresis (3.5%) and resolution potentially higher than the systems with spectral based sensors.

Compact, a??Clickablea?? Quantum Dots Photoligated with Multifunctional Zwitterionic Polymers for Immunofluorescence and In-Vivo Imaging

摘要： We detail the preparation of highly fluorescent quantum dots (QDs), surface-engineered with multifunctional polymer ligands that are compact, readily compatible with strain-promoted click conjugation, and the use of these nanocrystals in immunofluorescence and in-vivo imaging. The ligand design combines the benefits of mixed coordination (i.e., thiol and imidazole) with molecular-scale zwitterion motifs, yielding sterically-stabilized and compact QDs that present a controllable number of azide groups, for easy conjugation to biomolecules via the efficient and selective click chemistry. The polymer coating was characterized using NMR spectroscopy to extract estimates of the diffusion coefficient, hydrodynamic size and ligand density. The azide-functionalized QDs were conjugated to anti-tropomyosin receptor kinase B antibody (α-TrkB), or to the brain-derived neurotrophic factor (BDNF). These conjugates were highly effective for labeling the tropomyosin receptor kinase B (TrkB) in pyramidal neurons within cortical tissue and for monitoring the BDNF induced activation of TrkB signaling in live neuronal cells. Finally, the polymer-coated QDs were applied for in vivo imaging of Drosophila Melanogaster embryo, where the QDs remain highly fluorescent and colloidally stable, with no measurable cytotoxicity. These materials would be of great use in various imaging applications, where small size, ease of conjugation and great colloidal stability for in vivo studies are needed.

MoS <sub/>2</sub> Assisted Self-Assembled Poly (3-hexylthiophene) Thin Films at Air/Liquid Interface for High-Performance Field-Effect Transistors under Ambient Condition

摘要： It is a key challenge to achieve long-range ordering in nanoscale morphology of π-conjugated polymers for efficient charge transport in organic electronic devices. The long-range ordering and aggregation in poly (3-hexylthiophene) (P3HT) has been accomplished by introducing two dimensional (2D) Molybdenum disulfide (MoS2) nanosheets in polymer matrix followed by ultrasonication in chloroform. Thin films of synthesized P3HT/MoS2 nanocomposites having various fractions of MoS2 in the P3HT matrix have been fabricated on the air/liquid interface. The UV visible absorption spectroscopy has been employed to investigate the nature of aggregation and exciton bandwidth in the resultant films deposited at the air/liquid interface. Moreover, grazing incidence X-ray diffraction (GIXD) analysis, and atomic force microscopy (AFM), reveal the long-range ordering and highly crystalline thin films with the edge-on orientation of polymer chains over the substrate. Further, the impact of aggregation, morphology, and orientation on macroscopic charge transport performance is elaborately estimated by fabricating organic field-effect transistors (OFETs). The hole mobility as high as 0.160 ± 0.007 cm2V-1s-1, has been achieved for P3HT/MoS2 (1%) nanocomposite under ambient condition.

MEH-PPV photophysics: insights from the influence of a nearby 2D quencher

摘要： The effect of 2D quenching on single chain photophysics was investigated by spin coating 13 nm thick films of polystyrene lightly doped with MEH-PPV onto CVD grown graphene and observing the changes in several photoluminescent (PL) observables. With 99% of the PL quenched, we found a 60% drop in the PL lifetime, along with a significant blue-shift of the PL emission due to the preferential quenching of emission at longer wavelengths. During photo-bleaching, the blue spectral shift observed for isolated polymers was eliminated in the presence of the quencher up until 70% of the polymer was photo-bleached. Results were interpreted using a static disorder induced conjugation length distribution model. The quencher, by opening up a new non-radiative decay channel, ensures that excitons do not have sufficient time to migrate to nearby lower energy chromophores. The reduction of energy transfer into the lowest-energy chromophores thus reduces their rate of photo-bleaching. Finally, the difference between the quenched and non-quenched spectra allows the rate of energy transfer along the polymer backbone to be estimated at ～2 ns?1.

UV irradiation induce NLO modulation in photochromic Styrylquinoline-Based Polymers: Computational and Experimental Studies

摘要： Functionalized photochromic materials have attracted a growing interest during the last few decades since they are promising materials to be used in optoelectronics and photonics. In this paper, the results of the nonlinear optical (NLO) investigation (second and third harmonic generation) of spin deposited high-quality thin films of styrylquinoline containing methacrylic polymers studied by using Maker fringes technique employing 30 ps laser pulses at fundamental wavelength of 1064 nm are presented. Photochromic styrylquinoline units were oriented in the thin films by corona poling technique promoting second order NLO activity. Strong dependence of the NLO response upon the structure of the polymers has been found, which is related to the different charge transfer within the styrylquinoline fragments. These investigations were completed by theoretical studies using HOMO-LUMO energy levels theory and the first and second order hyperpolarizability values. Good compatibility has been achieved between the theoretical and experimental results. Studied styrylquinoline-based polymers showed the contrast in NLO response after their trans-cis photoisomerization making them interesting for using in photonic devices.

Nanoplumbing with 2D Metamaterials

摘要： Nanoplumbing with 2D Metamaterials Saroj Dangi and Robert Riehn* Complex manipulations of DNA in a nanofluidic device require channels with branches and junctions. However, the dynamic response of DNA in such nanofluidic networks is relatively unexplored. Here, the transport of DNA in a 2D metamaterial made by arrays of nanochannel junctions is investigated. The mechanism of transport is explained as Brownian motion through an energy landscape formed by the combination of the confinement free energy of DNA and the effective potential of hydrodynamic flow, which both can be tuned independently within the device. For the quantitative understanding of DNA transport, a dynamic mean-field model of DNA at a nanochannel junction is proposed. It is shown that the dynamics of DNA in a nanofluidic device with branched channels and junctions is well described by the model.

Hybrid quantum dot-based theranostic nanomedicines for tumor-targeted drug delivery and cancer imaging

摘要： Quantum dots (QDs) are considered one of the most efficient tools used in theranostic applications for diagnosis and therapy due to their unique physiochemical characteristics. QDs are semiconductor crystals in the nano-scale range of 2–10 nm which exhibit unique photoluminescence characteristics as well as electronic properties such as tunable emission from visible to near infrared wavelengths and superior light stability. QDs possess strong photoluminescence with high molar extinction coefficient values, which make them the best candidates for cell labeling and detection of cancer biomarkers. QDs are characterized by symmetric narrow-emission spectra and broad-absorption spectra. However, some fears have been raised regarding the toxicity of QDs, especially Cd-containing QDs, due to the release of Cd ions and the generation of reactive oxygen species. Therefore, strategies have been developed to reduce their toxicity and enhance their biocompatibility through hybridization with other moieties such as polymers, proteins, polysaccharides or lipids, offering efficient tumor targeting in addition to inhibiting their release into the systemic circulation. This article discusses QD-based nanohybrids for delivery of anticancer drugs in combination with cancer imaging.

Conducting Polymers || Electrical Properties of Polymer Light-Emitting Devices

摘要： In this chapter, we present a brief introduction to semiconducting properties of conjugated polymers and the motivation to apply this class of materials in electronic/optoelectronic devices such as polymer light-emitting diodes (PLEDs). We describe, in detail, the operating mechanisms of PLEDs, with particular focus on the effects of charge injection and transport and their dependence on the external electric field and temperature. The mechanisms of current injection from the electrodes into the organic semiconductor are initially treated using traditional models for thermionic emission and tunnelling injection. More recent models considering the influence of metal/semiconductor interface recombination and of energetic and spatial disorder in the injection currents are also introduced and discussed. In addition, models considering space-charge-limited currents and trap-filling-limited currents are employed to describe the charge transport characteristics in the bulk. Furthermore, we present a brief discussion on ideas concerning the effects of the disorder on the charge-carrier transport behaviour.

A Library of PPYPs with Unique Fluorescence Properties