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Synthesis and phosphorescent properties of the copolymers of N-vinylcarbazole, methyl methacrylate and iridium complex

100%

Wang W. , Zhou M. , Liang L. , Lin M. , Ling M.

tom Vol. 32, No. 2

206--213

The copolymers containing carbazole unit and iridium complexes, such as (Ir(bpy)2Cl, Ir(mbpy)2Cl and Ir(Brbpy)2Cl, were synthesized via radical copolymerization of N-vinylcarbazole, methyl methacrylate and iridium complex. The synthesized copolymers were characterized by FT-IR, UV-Vis absorption spectroscopy and photoluminescence (PL) spectroscopy, respectively. According to the results, the copolymers (Ir(Brbpy)2Cl/PVK and Ir(mbpy)2Cl/PVK) exhibit yellow phosphorescence with an emission peak at around 553 nm under UV-visible light in the solid state. The results also reveal almost complete energy transfer from the host carbazole segments to the guest Ir complex in the copolymer film when the Ir content reaches 1.0 wt.%. The synthesized copolymers are good candidates as blue or yellow phosphorescent materials for PLED applications.

Comparison of jasmine antioxidant system responses to different degrees and durations of shade

100%

Deng Y. , Jia X. , Sun X. , Liang L. , Su J.

nr 02

Jasmine [Jasminum sambac (L.) Aiton] growth and development is affected by long-term shade. To determine the effects of short-term shade on jasmine physiology, the contents of soluble proteins, malondialdehyde (MDA) and antioxidative enzymes were comparatively investigated during 24 h (short-term, ST) and 7 days (medium-term, MT) of varying light regimes. The results showed that the protein content exhibited two peaks under ST treatment, and shade postponed the first peak 2 h later than full light. On the whole, protein synthesis was reduced by ST shade and induced by MT shade, whereas MDA content decreased during all shade treatments. Under ST shade, superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) activities were enhanced, but catalase (CAT) activity was repressed by limited irradiances. However, the antioxidant enzymes responded differently—SOD activity increased after 2 h of shading and then kept on a high level, whereas POD, APX and CAT activities increased mainly during the first hour and deceased subsequently. Under MT shade, these antioxidative enzymes responded differently to varying light irradiances, too. In general, POD and CAT activities were repressed, SOD activity was induced by weak (50% irradiance) shade and reduced by moderate (20% irradiance) and severe (5% irradiance) shade. APX activity was rather more complicated and irregularly responded to different degrees and durations of shade, meaning it might not be the main enzyme to remove ROS in jasmine plants under shading condition. The increase protein content with prolonged shade represents the sound adaptive ability of jasmine plants to restricted irradiances. At the same time, rapid changes in proteins and antioxidants reflect the efficient metabolic apparatus of the plant in response to shade. Therefore, the jasmine cultivar is shade tolerant. Furthermore, shade could help the plants protect themselves from full light, and some degrees of shade were beneficial to their antioxidant system. However, severe shade (5% of irradiance) is only suggested for a few hours to protect the plants at solar noon. If the plants are continuously shaded for 3–7 days, weak (20%) to moderate (50%) level of irradiance should be applied.