nanoparticles into a hexagonal array, while maintaining the photoluminescence of the nanoparticles. This patterning technique illustrates a simple example of directed deposition where the lateral distribution of the nanoparticles in a thin film can be manipulated rapidly by use of a capillary force. This deposition process is quite versatile since both the size of the nanoparticles and the diameter of the nanopores can easily be changed. In addition, if symmetric copolymers are used, where the morphology is lamellar as opposed to cylindrical, then an assembly of the nanoparticles into nanoscopic channels can be attained. Further, if an electron beam were used to crosslink the PS and degrade the PMMA, then a pattern could be written on the surface and nanoparticles of one size could be selectively placed within the exposed pattern. Subsequent exposure of this film to e-beam or UV radiation would allow the placement of nanoparticles with a different diameter to be placed elsewhere on the surface, resulting in the fabrication of a patterned heterogeneous structure. Furthermore, by placing appropriate functionality on the ligands attached to the nanoparticles, we will be able to impart favorable interactions between the particles and the bottom of the pores to further enhance the deposition process. The simplicity, generality, versatility, and speed of this deposition process make it amenable to the fabrication of complex structures and to large-scale commercial processes. ExperimentalNanoparticle Preparation: Cadmium selenide (CdSe) nanoparticles were prepared according to literature procedures, following the method of Peng and coworkers [25]. Nanoparticles of various diameters were prepared, all of which were capped with an organic shell of phosphorous-containing surfactants, such as tri-n-octylphosphine oxide (TOPO). These hydrophobic nanoparticles could be readily dissolved or dispersed in common organic solvents used in these experiments.Template Preparation: Templates were prepared by anchoring a random copolymer of PS and PMMA containing 58 % styrene onto a silicon wafer onto which a 60±100 nm layer of SiO was evaporated; the coated templates were then annealed for 3 days. Non-anchored random copolymer was rinsed from the surface, and a very thin film of P(S-b-MMA) diblock copolymer with a thickness of L 0 was spin-coated onto this surface, then annealed at 170 C overnight. The film was then exposed to UV light under vacuum, and immersed in glacial acetic acid to selectively remove the degraded PMMA from the PS matrix. Subsequent inspection by atomic force microscopy (AFM) showed hexagonally ordered cylindrical pores normal to the substrate. These templates were then dipped vertically into heptane solutions of nanoparticles at various nanoparticle concentrations. The withdrawal rates varied from fast (~1200 cm min ±1 ) to slow (~2 cm min ±1 ). The impregnated templates were cut into small pieces, and removed from the silicon wafer by etching and floating on 5 % HF in water. The templates were retrieved with a ...

Several devices using a europium complex Eu͑TTA͒ 3 ͑DPPz͒(TTAϭ2-thenoyltrifluoroacetonate, DPPzϭdipyrido͓3,2-a:2Ј,3Ј-c͔phenazine) as dopant emitter were fabricated. The performances of these devices are among the best reported for devices incorporating a europium complex as a red emitter. One such device with structure TPD ͑50 nm͒/Eu:CBP ͑4.5%, 30 nm͒/BCP ͑30 nm͒/Alq ͑25 nm͒ exhibits an external quantum efficiency 2.1%, current efficiency 4.4 cd/A, power efficiency 2.1 lm/W, and brightness 1670 cd/m 2 .

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An idealized bipolar host material and dopant are synthesized for deep‐red phosphorescent organic light‐emitting diodes (PhOLEDs). The host material exhibits a low‐lying lowest unoccupied molecular orbital and high thermal and morphological stability, while the dopant emits sharply at 616 nm with a full width at half‐maximum of only 39 nm. The new host/guest combination for the deep‐red device yields the highest device efficiencies to date.

Several substituted phenanthrolines (L = pyrazino[2,3‐f][1,10]phenanthroline (PyPhen), 2‐methylpyrazino[2,3‐f][1,10]phenanthroline (MPP), dipyrido[3,2‐a:2′,3′‐c]phenazine (DPPz), 11‐methyldipyrido[3,2‐a:2′,3′‐c]phenazine (MDPz), 11,12‐dimethyldipyrido[3,2‐a:2′,3′‐c]phenazine (DDPz), and benzo[i]dipyrido[3,2‐a:2,3‐c]phenazine (BDPz)) were successfully prepared and europium complexes Eu(TTA)3L (Eu‐L) based on these ligands were synthesized from EuCl3, 2‐thenoyltrifluoroacetone (TTA) and L in good yields. Irradiation at the absorption band between 320–390 nm of all these europium complexes, except Eu‐BDPz, in solution or in the solid state leads to the emission of a sharp red band at ∼ 612 nm, a characteristic Eu3+ emission due to the transition 5D0 → 7F2. No emission from the ligands was found. The result indicates that complete energy transfer from the ligand to the center Eu3+ ion occurs for these europium complexes. In contrast, the photoluminescence spectrum of Eu‐BDPz exhibits a strong emission at around 550 nm from the coordinated BDPz ligand and a weak emission at 612 nm from the central europium ion. Incomplete energy transfer from the ligand to the central Eu3+ ion was observed for the first time. Several electroluminescent devices (A–I) using Eu‐PyPhen, Eu‐MPP, Eu‐DPPz, and Eu‐DDPz as dopant emitters with the device configuration: TPD or NPB (50 nm)/Eu:CBP (1.7–7 %, 30 nm)/BCP (20–30 nm)/Alq (25–35 nm) (where TPD: 4,4′‐bis[N‐(p‐tolyl)‐N‐phenylamino]biphenyl; NPB: 4,4′‐bis[1‐naphthylphenylamino]biphenyl; CBP: 4,4′‐N,N′‐dicarbazole biphenyl; BCP: 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline; Alq: tris[8‐hydroxyquinoline]aluminum) were fabricated. Some of these devices emit saturated red light and are the only europium complex‐based devices that show a brightness of more than 1000 cd m–2.

Cellulose separated from corncob was used as a new cellulose resource to produce esterified cellulose nanofiber (E-CNF) with hexanoyl chloride through one-step mechanochemical esterification by ball milling. The result showed that corncob cellulose was easily disintegrated and esterified to achevie a high DS, and then, thin nanofiber was compared to the common pulp cellulose resource. The DS of E-CNF was as high as 0.95, and the diameter was about 1.5–2.8 nm. Then, E-CNF was formed to nanopaper by vacuum filtration showing high optical transparency up to 89% at 550 nm. The transparent nanopaper had a Young’s modulus of 5.5 GPa and tensile strength of 110–125 MPa. Due to the introduction of alkyl chain, the wetting property of the nanopaper was changed from hydrophilicity to hydrophobicty. So, it may still work well in a humid environment.

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