Graphene quantum dots (GQDs) with white fluorescence are synthesized by a microwave-assisted hydrothermal method using graphite as the precursor. A solution-processed white-light-emitting diode (WLED) is fabricated using the as-prepared white fluorescent GQDs (white-light-emitting graphene quantum dots, WGQDs) doped 4,4-bis(carbazol-9-yl)biphenyl as the emissive layer. White-light emission is obtained from the WLED with 10 wt% doping concentration of WGQDs, which shows a luminance of 200 cd m⁻² at the applied voltage of 11–14 V. Importantly, an external quantum efficiency of 0.2% is achieved, which is the highest among all the reported WLED based on GQDs or carbon dots. The results demonstrate that WGQDs as a novel phosphor may open up a new avenue to develop the environmentally friendly WLEDs for practical application in solid-state lighting.

A rapid, simple and cost-effective polyol method has been developed for the synthesis of silver nanowires with high aspect ratio and high purity. The aspect ratios of the silver nanowires as high as ca. 1000 (average length 40 µm and some even as long as 80 µm, diameter 50–100 nm) were obtained via optimizing the reaction conditions. Transparent electrodes with excellent optoelectronic performances (optical transmittance of 90%, sheet resistance of 23.2 Ω/□ and optical transmittance of 87%, sheet resistance of 19.7 Ω/□) comparable to commercial ITO were fabricated via simple spin coating the resulting silver nanowires onto the glass substrates. The high optoelectronic performances and the facile all-solution process of the as-prepared transparent electrodes render them rather promising candidates for use in cost-effective large-area optoelectronic devices.

A highly sensitive and selective, "turn-on" and simple Hg²⁺ biosensor is reported by using water-soluble graphene oxide (WSGO) and dye-labeled mercury(II)-specific oligonucleotide (MSO) probe. The probe is rich of thymine (T) and can readily form the stem-loop structure which consists of the T-Hg²⁺-T configuration. In the absence of Hg²⁺, the probe exists as a random coil conformation which can be readily adsorbed on the surface of WSGO by strong noncovalent binding of bases, as a result, the fluorescence of the dye labeled on the terminus of the MSO is strongly quenched by the efficient electron/energy transfer from the dye to WSGO. Upon addition of Hg²⁺, the formation of the T-Hg²⁺-T structure releases the MSO from the surface of WSGO, resulting in a restoration of the fluorescence of dye-labeled MSO probe. Based on this observation, a highly sensitive and selective Hg²⁺ sensor is developed, which can work with "turn-on" mode in aqueous solutions at room temperature. By using the fluorometric method, the limit of detection for Hg²⁺ can reach picomolar range (187 pmol·L⁻¹), and it is demonstrated that the biosensor is highly selective and only minimally perturbed by a wide range of non-specific metal ions.

We present herein a novel design and the efficient synthesis towards a “homogeneous” starburst fluorene system based on the novel 2,3,7,8,12,13-hexaaryltruxene scaffold. Controlled microwave heating provides a facile and powerful approach for each step in the synthesis of these bulky materials with large steric hindrance, suggesting an avenue to access structurally well-defined complex organic semiconductors (OSCs) rapidly and conveniently with high yield and purity. The resulting materials exhibited good thermal stability and an excellent glassy structure as revealed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) as well as wide-angle X-ray diffraction (WAXD) studies. Moreover, compared with their corresponding three-arm-substituted counterparts T1–T4, the introduction of the ortho substituents around the truxene core in Tr1–Tr4 results in significant blueshifts (of 7–24 nm) of the absorption maxima λ_max and higher energy optical gaps (E_g). Comparative studies with corresponding linear, rod-shaped oligofluorene counterparts (OFX) have revealed that the longest para-conjugated segment in the TrX (X=1–4) structures plays the dominant role in determining their electronic properties. UV/Vis data and cyclic voltammetry (CV) investigations have indicated that there is little electronic interaction between the arms, even for the shortest armed oligomer Tr1. A clear linear relationship of both 1/λ_max and E_g with the inverse of (n+1) for these branched systems was found. Our findings highlight a novel molecular design comprising an ortho-substituted, multiarmed architecture that would allow the introduction of isotropic physical and/or mechanical properties, while at the same time maintaining most of the important electronic properties of the rod-shaped constituents of a fully conjugated system.

Here, a detailed characterization of the optical gain properties of sky-blue-light-emitting pyrene-cored 9,9-dialkylfluorene starbursts is reported; it is shown that these materials possess encouragingly low laser thresholds and relatively high thermal and environmental stability. The materials exhibit high solid-state photoluminescence (PL) quantum efficiencies (>90%) and near-single-exponential PL decay transients with excited state lifetimes of ∼1.4 ns. The thin-film slab waveguide amplified spontaneous emission (ASE)-measured net gain reaches 75–78 cm⁻¹. The ASE threshold energy is found to remain unaffected by heating at temperatures up to 130 °C, 40 to 50 °C above T_g. The ASE remained observable for annealing temperatures up to 170 or 200 °C. 1D distributed feedback lasers with 75% fill factor and 320 nm period show optical pumping thresholds down to 38–65 Wcm⁻², laser slope efficiencies up to 3.9%, and wavelength tuning ranges of ∼40 nm around 471–512 nm. In addition, these lasers have relatively long operational lifetimes, with N_1/2 ≥ 1.1 × 10⁵ pulses for unencapsulated devices operated at ten times threshold in air.

To improve efficiency, processability, and stability, three novel poly-(p-phenylene vinylenes) (PPVs) derivatives (P_a, P_b, and P_c) with pendent 2,4-difluorophenyl and fluorenyl moieties were synthesized via Gilch reaction. Their structures were characterized by ¹H NMR, ¹³C NMR, and ELEM. ANAL. Compared with those of PPV and MEH-PPV, the absolute quantum efficiencies of these polymers showed remarkable improvement (measured at 38.7, 37.2, and 20.3%, respectively), which can be attributed to the presence of twisted multiaryl segments and fluorine atoms. TGA revealed that the inflection temperatures of their thermal decomposition curves were above 400 °C. Double-layered electroluminescent devices with these polymers as light-emitting layers [ITO/PEDOT:PSS/Polymer/Ba/Al] showed peak emissions at 493/515, 503, and 600 nm and maximum luminance of 2700, 450, and 4700 cd/m² for P_a, P_b, and P_c, respectively, with onset voltages of ∼4 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2500–2508, 2009