ABSTRACT:The improved performance of polyalkylfluorene light-emitting device has been achieved through the optimization of processing conditions and device configuration. The current density, brightness, power efficiency, and operation lifetime of polymer light-emitting device (PLED) were strongly dependent on the surface treatment of anode, the film thickness of light-emitting polymer (LEP), and the cathode configuration. The anode surface treated with O 2 plasma exhibited a higher current density and brightness than the CF 4 plasma treated device. However, better operation stability was obtained for the CF 4 plasma treated device than for the O 2 plasma treated device. The maximum of brightness and power efficiency has been achieved for the PLED with an LEP thickness of 80 nm. The PLED with LiF/Ca/Al cathode possesses a better power efficiency and operation stability than does the Ca/Al or LiF/Al based PLED. The influences of device fabrication conditions and device configuration on the performance of a polyalkylfluorene-based PLED are discussed in detail.

An amphiphilic block copolymer (BCP) which contains both photoresponsive and thermoresponsive blocks was synthesized by the atom transfer radical polymerization approach. Meanwhile, a new core/shell type of the upconversion nanoparticle (UCNP) LiYF 4 :Yb 3+ 0.25 ,Tm 3+ 0.01 @LiYF 4 :Yb 3+ 0.2 was successfully synthesized. By encapsulating UCNPs inside the micelles of the BCP and incorporating Nile red (NR) into the UCNP@BCP hybrid nanoparticles as a model drug, controlled release of the drug by the dual-stimuli BCP could be studied. After exposing the UCNP-loaded micellar solution to near-infrared (NIR) light, it was found that the UV light pumped from UCNPs could disrupt the polymer micelles and the fluorescence intensity of NR decreased with the increase of the irradiation time of the NIR light. The thermoresponsive study indicated that the fluorescence intensity of NR decreased with the increase of temperature of the micellar solution because of the release of NR into water arising from the contraction of the amphiphilic BCP.

The early adhesions of cells to various biopolymers are important to their growths and proliferations. Here, the adhesion of cells (e.g., fibroblasts) on the electrode of a quartz crystal microbalance (QCM) that was coated by PCL or PEG/PCL and further adsorbed by chitosan (CS) or CS/hyaluronic acid (HA) layers, was examined by cell-counting technique, QCM method and MTS assay under a serum-free condition for 3 h. The surfaces on electrodes of the QCM were confirmed to have been modified by measuring their contact angles, FT-IR spectra and the weights of biopolymers affected the frequency shifts of the QCM. Among tested surfaces on electrodes, the adhesion of fibroblasts on a HA/CS/PCL surface was the most (e.g., 3.08 × 10(5) cells/cm(2)) while that on a PEG/PCL surface was the least (e.g., 0.7 × 10(5) cells/cm(2)), as determined by cell-counting technique. The frequency shift and the mass of adhering fibroblasts on HA/CS/PCL electrodes were -3,537 ± 770 Hz and 3.78 ± 0.22 μg (n = 3), respectively, that were significantly exceeded those on other electrodes (-393 ± 58 Hz and 0.32 ± 0.06 μg, n = 3, respectively, for PEG/PCL electrodes). These results were consistent with cell-counting technique. Although MTS assay yielded similar results, it was less sensitive than the two aforementioned methods. In conclusion, modified electrodes of a QCM provide a convenient and sensitive method for examining the early adhesion of cells (e.g., 3 h) to biopolymer surfaces.

ABSTRACT:The electroluminescence properties of polymer light-emitting devices with and without an ultraviolet (UV)-shielding filter were studied. The polymer light-emitting devices were fabricated with poly(2-methoxy-5,2Ј-ethylhexyloxy-1,4-phenylene vinylene) as the light emitter and poly(ethylenedioxy thiophene) as the hole-transporting material. The UV-shielding filter was composed of alternating TiO 2 and SiO 2 dielectric multilayers made by a physical vacuum deposition process. The current density, brightness, and photometric efficiency decreased significantly for the polymer light-emitting device without the UV-shielding filter after irradiation by UV light. The decay of PLEDs due to UV degradation was greatly reduced by the UV-shielding filter.

In this study, we prepared the reduced graphene oxide (rGO)-CdSe/ZnS quantum dots (QDs) hybrid films on a three-layer scaffold that the QD layer was sandwiched between the two rGO layers. The photocurrent was induced by virtue of the facts that the rGO quenched the photoluminescence of QDs and transferred the excited energy. The quenching mechanism was attributed to the surface energy transfer, supported in our experimental results. We found that the optoelectronic conversion efficiency of the hybrid films can be significantly improved by incorporating the silver nanowires (AgNWs) into the QD layer. Upon increasing AgNW content, the photocurrent density increased from 22.1 to 80.3 μA cm−2, reaching a near 3.6-fold enhancement compared to the pristine rGO-QD hybrid films. According to the analyses of photoluminescence spectra, shape effect, and electrochemical impedance spectra, the enhancement on the optoelectronic conversion efficiency arise mainly from the strong quenching ability of silver and the rapid electron transfer of AgNWs.