Computational Study of the One‐ and Two‐Dimensional Infrared Spectra of a Proton‐Transfer Mode in a Hydrogen‐Bonded Complex Dissolved in a Polar Nanocluster

The signatures of nanosolvation on the one‐ and two‐dimensional (1D and 2D) IR spectra of a proton‐transfer mode in a hydrogen‐bonded complex dissolved in polar solvent molecule nanoclusters of varying size are elucidated by using mixed quantum–classical molecular dynamics simulations. For this particular system, increasing the number of solvent molecules successively from N=7 to N=9 initiates the transition of the system from a cluster state to a bulk‐like state. Both the 1D and 2D IR spectra reflect this transition through pronounced changes in their peak intensities and numbers, but the time‐resolved 2D IR spectra also manifest spectral features that uniquely identify the onset of the cluster‐to‐bulk transition. In particular, it is observed that in the 1D IR spectra, the relative intensities of the peaks change such that the number of peaks decreases from three to two as the size of the cluster increases from N=7 to N=9. In the 2D IR spectra, off‐diagonal peaks are observed in the N=7 and N=8 cases at zero waiting time, but not in the N=9 case. It is known that there are no off‐diagonal peaks in the 2D IR spectrum of the bulk version of this system at zero waiting time, so the disappearance of these peaks is a unique signature of the onset of bulk‐like behavior. Through an examination of the trajectories of various properties of the complex and solvent, it is possible to relate the emergence of these off‐diagonal peaks to an interplay between the vibrations of the complex and the solvent polarization dynamics.     

Colorimetric and bare-eye determination of fluoride using gold nanoparticle agglomeration probes

We report on a sensitive detection scheme for fluoride that is based on a quinone-methide-type of rearrangement reaction to trigger a color change among cloaked gold nanoparticle agglomeration probes. Fluoride ions remove silyl moieties from phenol groups on the surface of the probes, and this causes a quinone-methide-type of rearrangement reaction to occur. This is accompanied by the release of a dithiol in a spontaneous and irreversible reaction at room temperature in aqueous medium. The released dithiol causes aggregation of the AuNPs which leads to a color change from pink-red to violet-blue that can easily be seen with bare eyes.. The generation of color by this cascade reactions is only caused by fluoride and not interfered by any other anions. The assay platform developed here offers a sensitive colorimetric assay for fluoride. The lower limit of detection is 120 μM, and the dynamic concentration range is from 120 μM to 1.5 mM.

Synthesis and properties of thermoresponsive magnetic polymer composites and their electrospun nanofibers

The thermoresponsive magnetic polymer composites and nanofibers were fabricated. Their thermal and magnetic properties were also investigated. Fe₃O₄ nanoparticles were prepared by coprecipitation method. Further condensation reaction was used to fabricate the double‐layer lauric acid modified Fe₃O₄ (DLF) nanoparticles dispersed well in water. Thermal properties of poly(N‐isopropylacrylamide) (PNIPAAm) and DLF/PNIPAAm composites and their aqueous solutions were measured by TGA and DSC. With the increasing of DLF content, the interaction between DLF and PNIPAAm caused the lower critical solution temperature (LCST) of polymer solution to shift from 33 to 31.25 °C. The effects of concentration and pH on LCST were also studied. The DLF/PNIPAAm nanofibers were fabricated by electrospinning. Their diameters were around 100–250 nm. Magnetization curves of DLF/PNIPAAm composite and nanofibers were overlapped and the saturated magnetizations were the same. Magnetic attraction behaviors of DLF/PNIPAAm polymer solution at temperatures below and above LCST were different. Aggregation of DLF/PNIPAAm above LCST enhanced magnetic moment density as well as magnetic attraction ability. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 848–856     

Solution‐processable and thermally cross‐linkable fluorene‐cored triple‐triphenylamines with terminal vinyl groups to enhance electroluminescence of MEH‐PPV: Synthesis,curing, and optoelectronic properties

This study reports the synthesis, curing, and optoelectronic properties of a solution‐processable, thermally cross‐linkable electron‐ and hole‐blocking material containing fluorene‐core and three periphery N‐phenyl‐N‐(4‐vinylphenyl)benzeneamine ( FTV ). The FTV exhibited good thermal stability with T_d above 478 °C in nitrogen atmosphere. The FTV is readily cross‐linked via terminal vinyl groups by heating at 160 °C for 30 min to obtain homogeneous film with excellent solvent resistance. Multilayer PLED device [ITO/PEDOT:PSS/cured‐ FTV /MEH‐PPV/Ca (50 nm)/Al (100 nm)] was successfully fabricated using solution processed. Inserting cured‐ FTV is between PEDOT:PSS and MEH‐PPV results in simultaneous reduction in hole injection from PEDOT:PSS to MEH‐PPV and blocking in electron transport from MEH‐PPV to anode. The maximum luminance and maximum current efficiency were enhanced from 1810 and 0.27 to 4640 cd/m² and 1.08 cd/A, respectively, after inserting cured‐ FTV layer. Current results demonstrate that the thermally cross‐linkable FTV enhances not only device efficiency but also film homogeneity after thermal curing. FTV is a promising electron‐ and hole‐blocking material applicable for the fabrication of multilayer PLEDs based on PPV derivatives. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012     

A novel route for preparation of multifunctional polymeric nanocarriers for stimuli‐triggered drug release

Fluorescence‐incorporated, crosslinker‐free, pH‐ and thermoresponsive nanocarriers were prepared by the incorporation of drug molecules into the thermoresponsive nanocapsules, which composed of poly(N‐isopropylacrylamide) (PNIPAAm) with carboxylic acid end groups via temperature induced self‐assembling method. Well‐defined, pH‐responsive carboxylic acid group‐ended PNIPAAm homopolymer (HOOC? PNIPAAm? COOH) was synthesized by reversible addition fragmentation chain transfer polymerization with S,S′‐bis(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate (CMP) as a chain transfer agent. Rhodamine 6G (R6G), the model drug, was used for three kinds of application: First, the nanostructure fixing; second, the fluorescence‐labeling; and last, the controlled release modeling. The transmission electron microscope images showed the solution type dosing led to the encapsulation of drug molecules into the nanocarriers, while the powder‐type drug‐loading process significantly contributed to the structure preservation of nanocarriers. The controlled release behaviors with various pH values and temperatures were evaluated. These multifunctional nanocarriers have potential to be applied for the biomedical therapy by stimuli‐responsive controlled release. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 561–571