1. Engineering of Interfacial Electron Transfer from Donor-Acceptor Type Organic Semiconductor to ZnO Nanorod for Visible-Light Detection

        Organic solar cells have received extensive attention of scientists in recent years. Usually, the bulk phase of heterojunction solar cells with small organic molecules, polymers and fullerene derivatives act as the working medium. Receptors inorganic materials (e.g., ZnO, and CdS, etc.) has the advantages of good stability, high carrier mobility, therefore, the use of inorganic materials alternative to expensive fullerenes be a feasible scheme. Instead of using p - type small organic molecules or polymers to modify inorganic semiconductor, we prepared hybrid ZnO nanorods by grafting n-type perylene bisimide (PBI) derivatives bearing carboxylic acid groups at nitrogen positions. Through modulating the compound PBI with electron-rich moiety of oligothiophene, strong quenching of the fl uorescence of PBI moiety was observed after the grafting of nT-PBI (n = 1, 2) on the surface of ZnO nanorods, suggesting an e ffi cient cascade IET process from oligothiophene to PBI chromophore and then to ZnO nanorods. The time-resolved fl uorescence spectrum in the case of 1T-PBI/ZnO hybrid composite shows that the fl uorescence time pro fi les can be well fi tted with a dual-exponential function, where a minor longer decay (4.60 ± 0.04 ns, 12%) and a major short decay. The high visible-light response of the as-prepared hybrid devices nT-PBI/ZnO (n = 1, 2) makes it a promising candidate for applications in photo-to-electrical energy conversion.

2. Water-miscible organic J-aggregate nanoparticles as efficient two-photon fluorescent nano-probes for bio-imaging

        Two-photon fluorescence (TPF) microscopy has provided a powerful tool for biological imaging and sensing applications, where the use of near-IR laser light not only avoids auto-fluorescence from the biological background, but also reduces undesired tissue photo-damage due to the near-transparency of many tissues in this spectral range. For strong two-photon excited fluorescence (TPEF), a large TPF action cross-section and a high dye density (c) are usually required. Oligo-phenylene vinylene (OPV) molecules are typical D– p –A molecules with a large two-photon action cross-section (d). Unfortunately, a strong intermolecular π- π stacking interaction usually leads to H-aggregation of OPVs in thin films and crystals which show blue-shifted absorption and subradiance, Here, we report the preparation of water-soluble ONPs based on a oligo-phenylene vinylene (OPV) TPA dye, namely 1,4-dimethoxy-2,5-di[4′- (cyano)styryl]benzene (COPV). Based on single crystal data, we found that the synergistic effect between p – p stacking and hydrogen-bonding interactions causes a brickwork arrangement of COPV into J-aggregates, yielding a high solid-state fluorescence quantum yield of F > 0.4. Probably due to the exciton-vibration coupling and thus the coherent excitations involved in J-aggregates, the TPA cross-section of the J-aggregate COPV NPs is almost 20 times larger than that of the monomers, which results in a 10 times stronger two-photon fluorescence compared to that of the monomers. We suggest that these ONPs, having strong two-photon fluorescence, good water solubility, high photostability and low cytotoxicity, are promising as efficient two-photon fluorescent nano-probes for bio-imaging.

3.  Low-Threshold Nanolasers Based on Slab-Nanocrystals of H-Aggregated Organic Semiconductors

        Organic  semiconductors  are  of  current  interest  in  photonic  applications,   because  of  their  chemically  tuneable  optoelec tronic properties and their ability to self-assemble for bottom-up  fabrication. Optically pumped organic lasers have been demonstrated in a variety of resonator geometries, such as micro-cavity, micro-ring, distributed feedback (DFB), and photonic bandgap structures.  As a matter of fact, electrically driven organic lasers remain a great challenge, partially due to the high lasing-threshold observed so far. Therefore, the development of organic gain materials with optimized energy levels that help decrease the lasing threshold is of crucial importance. Here, we prepared rectangular slab-nanocrystals  (SNCs)  of  1,4-dimethoxy-2,5-di[4′-(methylthio) styryl]benzene  (TDSB), Due to the exciton–vibration coupling,  the  optically  allowed   | 10⟩ → | 0 n ⟩  ( n ≥ 1)  transitions  in  which  H-aggregation  is  advocated by tight co-facial molecular packing make  H-aggregated SNCs of TDSB highly emissive with a solid-state quantum yield of 0.81; meanwhile, the optically forbidden  | 10⟩↔ | 00⟩ transitions not only reduce the self-absorption effect but also minimize the direct radiative loss of the exciton reservoir to the  | 00⟩ state. The two lateral-faces of SNCs constitute a high quality built-in Fabry–Pérot (FP) cavity at the wavelength scale, in which a lasing threshold as low as 100 nJ cm− 2 was achieved. Moreover, the laser light generated in the ultra-small radial cavity of SNCs can propagate along its length up to hundreds of micrometers, making them attractive building blocks for miniaturized photonic circuits.

4. Intermolecular electron transfer promoted by directional donor-acceptor attractions in self-assembled diketopyrrolopyrrole-thiophene films

         π-Conjugated organic semiconductor materials have experienced remarkable development and are currently attracting considerable research efforts in various fields, such as organic light emitting diodes, organic field effect transistors (OFETs) and organic photovoltaic cells (OPVs). However, the microcosmic elementary processes lying underneath organic device operation have not been fully explored. In order to explore the inherent photophysical processes and to investigate the exciton dynamics and charge photogeneration processes within organic materials, a diketopyrrolopyrrole-bithiophene (DPP-BT) small molecule was used as a model compound to systematically investigate the photophysics, both in dichloromethane and in the thin film. The low-energy charge-transfer (CT) transition band was red-shifted by over 40 nm in the film compared to that in CH 2 Cl 2 , which is indicative of efficient p–p interactions between the adjacent molecules in the solid-state phase. The severe fluorescence quenching in the DPP-BT film is responsible for the intermolecular electron transfer, as evidenced by the accelerated fluorescence emission decay kinetics monitored using time-resolved fluorescence spectroscopy and femtosecond transient absorption spectroscopy. The GIXRD and SAED patterns of the DPP-BT nanobelts reveal that DPP-BT may be self-assembled into a slipped face-to-face configuration in the film, providing compact D–A interactions layer-by-layer. As a result, this special packing arrangement facilitates efficient intermolecular electron transfer between the adjacent molecules and also provides a moderate channel for charge transportation.

5. Construction and Conductance Measurement of Single Molecule Junctions

       

   PDI has received attractive attention for its excellent properties and its potential application in the field of organic field-effect transistor (OFET)、organic light-emitting diode (OLED)、organic photovoltaic (OPV). We fabricated PDI crystalline 2D microstructures via facile solution-exchange method. Further we fabricated electro-optical devices, which show excellent properties. (Chem. Commun., 2012, 48, 6402-6404)。

6. Fullerene Hollow Microspheres Prepared by Bubble-Templates as Sensitive and Selective Electrocatalytic Sensor for Biomolecules

             

      In the past several decades, Fullerene attracts extensive attention due to its novel structure and perfect symmetry. We fabricated C₆₀ porous membrane, and modified the Au electrode. Further, we successfully reached the detection of 0.1 nM DPA with the existence of ascorbic acid.（ACS Appl. Mater. Interface 2012,4, 1594-1600）。