Songnan Qu

A Biocompatible Fluorescent Ink Based on Water‐Soluble Luminescent Carbon Nanodots

Carbon nanodots (C-dots) are fascinating carbon materialsthat are attracting increasing interest because they possessdistinct benefits, such as chemical inertness, a lack of opticalblinking, low photobleaching, low cytotoxicity, and excellentbiocompatibility, compared with organic dyes and othersemiconductor nanodots with heavy metal cores.

Toward Efficient Orange Emissive Carbon Nanodots through Conjugated sp2‐Domain Controlling and Surface Charges Engineering

A strategy of achieving efficient orange emissive carbon nanodots (CNDs) with large sized conjugated sp(2) -domain is achieved in a solvothermal synthetic route using dimethylformamide as solvent, which is the basis of orange bandgap emission; enhanced orange emission with photoluminescent quantum yield of 46% is realized through surface charges engineering by surface metal-cation-functionalization.

Towards efficient solid-state photoluminescence based on carbon-nanodots and starch composites

A new type of environmentally friendly phosphor based on carbon nanodots (CDs) has been developed through the dispersion of CDs by integrating the CDs with starch particles. The starch particles contain large numbers of hydroxyl groups around the surfaces, which can effectively absorb the CDs, whose surfaces are functionalized by lots of carboxyl and amide groups, through hydrogen bonding. Effective dispersion of CDs on the surfaces of starch particles can suppress the non-radiative decay processes and photoluminescence (PL) quenching induced by aggregation of CDs. The starch matrix neither competes for absorbing excitation light nor absorbs the emissions of CDs, which leads to efficient PL emitting. As a result, the starch/CD phosphors with a quantum yield of ∼50% were obtained. The starch/CD phosphors show great potential in phosphor-based light emitting diodes, temperature sensors, and patterning.

Highly Sensitive Ultraviolet Photodetectors Fabricated from ZnO Quantum Dots/Carbon Nanodots Hybrid Films

Ultraviolet photodetectors have been fabricated from ZnO quantum dots/carbon nanodots hybrid films, and the introduction of carbon nanodots improves the performance of the photodetectors greatly. The photodetectors can be used to detect very weak ultraviolet signals (as low as 12 nW/cm2). The detectivity and noise equivalent power of the photodetector can reach 3.1 × 1017 cmHz1/2/W and 7.8 × 10−20 W, respectively, both of which are the best values ever reported for ZnO-based photodetectors. The mechanism for the high sensitivity of the photodetectors has been attributed to the enhanced carrier-separation at the ZnO/C interface.

Brightly fluorescent red organic solids bearing boron-bridged π–conjugated skeletons

Two π-conjugated organoboron complexes 1 and 2 with highly efficient red (632 nm) and deep red (670 nm) solid-state fluorescence have been constructed and qualified as potential non-doped red emitters accompanied by excellent electron-transport ability. X-ray crystal analysis demonstrated that the two side phenyl groups coordinated to each boron atom effectively keep the luminescent units apart. As a result, these red fluorophores are brightly fluorescent in the solid state (fluorescence quantum yields: 0.30 for 1 and 0.41 for 2). In addition, these boron complexes possess good thermal stability and high electron-transport ability. Organic light-emitting diodes employing 1 or 2 as non-doped emitters with simple device configuration exhibit bright red and near-infared electroluminescence.

Supra-(carbon nanodots) with a strong visible to near-infrared absorption band and efficient photothermal conversion

A novel concept and approach to engineering carbon nanodots (CNDs) were explored to overcome the limited light absorption of CNDs in low-energy spectral regions. In this work, we constructed a novel type of supra-CND by the assembly of surface charge-confined CNDs through possible electrostatic interactions and hydrogen bonding. The resulting supra-CNDs are the first to feature a strong, well-defined absorption band in the visible to near-infrared (NIR) range and to exhibit effective NIR photothermal conversion performance with high photothermal conversion efficiency in excess of 50%.

Evolution from Lyotropic Liquid Crystal to Helical Fibrous Organogel of an Achiral Fluorescent Twin-Tapered Bi-1,3,4-oxadiazole Derivative

We report an unprecedented hierarchical self-assembly of an achiral twin-tapered bi-1,3,4-oxadiazole derivative (2,2-bis(3,4,5-trioctanoxyphenyl)-bi-1,3,4-oxadiazole, BOXD-T8). This molecule can form a layer-structured lyotropic liquid crystal and further forms a helical fibrous organogel in DMF at concentrations above 0.6 wt %. The self-assembly process of BOXD-T8 in DMF is accompanied by a change in its fluorescence. The pitches of the helical fibers are non-uniform, and both left- and right-handed helical fibers are observed in equal quantities. Intermolecular π-π interactions between aromatic segments have been demonstrated to be the driving force for aggregate formation. This helical structure of BOXD-T8 is dependent on the solvent, concentration, and the layer-structured intermediate liquid-crystalline state.

Self-assembly of highly luminescent bi-1,3,4-oxadiazole derivatives through electron donor–acceptor interactions in three-dimensional crystals, two-dimensional layers and mesophases

We report on the synthesis and self-assembly of a new series of highly luminescent bi-1,3,4-oxadiazole derivatives [2,2′-bis(4-alkoyphenyl)-bi-1,3,4-oxadiazole, BOXD-n, n = 1, 3, 4, 5, 6, 7, 10, 16]. Fully conjugated conformations were demonstrated either by computer simulation or in a single-crystal state. Well-defined 3D donor–acceptor (DA) architectures with strong face-to-face and edge-to-edge donor–acceptor interactions were observed in the single-crystal structure of BOXD-1. Highly oriented face-on two-dimensional DA layered structures due to edge-to-edge donor–acceptor interactions were observed on highly oriented pyrolytic graphite (HOPG) in BOXD-7 and BOXD-16. Nematic phase, smectic C phase with large tilted angle (θ ≈ 50°) and relatively large transition enthalpic values and a highly ordered smectic X phase were demonstrated in BOXD-n (n = 5, 6, 7, 8, 10, 16) through tailing the terminal chains and relatively large scale monodomains were prepared in the smectic X phase of BOXD-5 even without any surface treatment. Strong blue fluorescent emissions were observed in BOXD-6 either in cyclohexane (ФF ≈ 92%) or in solid state (ФF ≈ 57%). The donor–acceptor interactions between alkyoxyphenylene rings and 1,3,4-oxadiazole rings were thought to be the driving force for the molecules to self-assemble into a large angle tilted layered structure.

Nanoparticles, Helical Fibers, and Nanoribbons of an Achiral Twin-Tapered Bi-1,3,4-oxadiazole Derivative with Strong Fluorescence

A twin-tapered bi-1,3,4-oxadiazole derivative (BOXD-T8) showed a monomeric feature and intramolecular charge transition at concentrations lower than 10(-5) mol/L. BOXD-T8 molecules self-assembled to nanoparticles and further to helical nanofibers with blue fluorescence emission in DMSO, while nanoribbons resulted in an emission-enhanced gel in ethanol. The strong fluorescent emissions of BOXD-T8 in an isolated state in apolar solvents were attributed to the coplanar conformation of the rigid backbone and the strong fluorescent emissions of BOXD-T8 in the aggregation states were attributed to the coplanar conformation of the rigid backbone and J aggregation.

Efficient Quantum Dot Light-Emitting Diodes by Controlling the Carrier Accumulation and Exciton Formation

The performances and spectroscopic properties of CdSe/ZnS quantum dot light-emitting diodes (QD-LEDs) with inserting a thickness-varied 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) layer between the QD emission layer and 4,4-N,N-dicarbazole-biphenyl (CBP) hole transport layer (HTL) are studied. The significant enhancement in device peak efficiency is demonstrated for the device with a 3.5 nm TPBi interlayer. The photoluminescence lifetimes of excitons formed within QDs in different devices are also measured to understand the influence of electric field on the QD emission dynamics process and device efficiency. All the excitons on QDs at different devices have nearly the same lifetime even though at different bias. The improvement of device performance is attributed to the separation of charge carrier accumulation interface from the exciton formation zone, which suppresses exciton quenching caused by accumulated carriers.