A novel series of semiconducting conjugated copolymers, derived from alkyl-substituted fluorene, 4,7-diselenophen-2‘-yl-2,1,3-benzothiadiazole (SeBT), and 4,7-diselenophen-2‘-yl-2,1,3-benzoselenadiazole (SeBSe), was synthesized by a palladium-catalyzed Suzuki coupling reaction with various feed ratios. The optical band gap of copolymers is very low, 1.87 eV for SeBT and 1.77 eV for SeBSe. The efficient fast energy transfer from fluorene segments to narrow-band-gap sites was observed. The emission of photoluminescence and electroluminescence is dominated by narrow-band-gap species and peaked at 670−790 nm, in the range from deep-red to near-infrared (NIR). The external electroluminescent (EL) quantum efficiencies reached 1.1% and 0.3% for devices from these two types of copolymers, respectively. Bulk−heterojunction polymer photovoltaic cells (PPVCs) made from composite thin film of the copolymer 9,9-dioctylfluorene and SeBT (PFO−SeBT) in blend with fullerene derivative [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as an active layer show promising performances. The energy conversion efficiency (ECE) is up to 1% under AM1.5 solar simulator (78.2 mW/cm2). The spectral response is extended up to 675 and 750 nm for PPVCs from PFO−SeBT and PFO−SeBSe, respectively.

A novel series of light-emitting copolymers derived from 9,9-dioctylfluorene (DOF) and 2,1,3benzoselenadiazole (BSeD) is prepared by means of palladium-catalyzed Suzuki coupling reaction. The feed ratios of DOF to BSeD were 50:50, 85:15, 92:8, and 98:2, respectively. All of the copolymers are soluble in common organic solvents and highly fluorescent in solid state. Devices from such copolymers emit orange-red light with λmax ) 570-600 nm. The maximal EL emissions of the devices slightly redshifted gradually with increasing BSeD's contents. The maximal external quantum efficiency of the polymer light-emitting devices (PLED) reaches 1.0%, which indicates that this new seleno-containing EL polymer based on fluorene and benzoselenadiazole is a promising candidate for fabricating PLEDs.

Large-scale, substrate-free graphene, with few-layered sheets, is synthesized by the CVD of methane over cobalt supported on magnesium oxides at 1000 -C in a gas flow of argon. Typically, 50 mg of the few-layered graphene materials over 500 mg of the Co/MgO catalysts are synthesized under our experimental conditions. Randomly aggregated, thin, crumpled graphene sheets stacked closely together are produced. Both carbon (94.6 at.-%) and oxygen (5.4 at.-%) are present in the graphene sheets. The oxygen may originate from air adsorbed on the graphene sheets. Our results indicate the presence of localized sp 3 defects within the sp 2 carbon network and small sp 2 domains in the few-layered graphene particles.

An ultraviolet-emitting conjugated polymer, poly(9,9'-alkyl-3,6-silafluorene) with a wide band gap of 4.0 eV, has been synthesized and characterized.

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