Zhaoyang Liu

Fluorescent Aptasensor Based on Aggregation-Induced Emission Probe and Graphene Oxide

Recently, a great variety of aggregation-induced emission (AIE)-active molecules has been utilized to design bioprobes for label-free fluorescent turn-on aptasensing with high sensitivity. However, due to nonspecific binding interaction between aptamer and AIE probe, these AIE-based aptasensors have nearly no selectivity, thereby significantly limiting the development. In this work, a 9,10-distyrylanthracene with two ammonium groups (DSAI) is synthesized as a novel AIE probe, and the fluorescent aptasensor based on DSAI and graphene oxide (GO) is developed for selective and sensitive sensing of targeted DNA and thrombin protein. Given its AIE property and high selectivity and sensitivity, this aptasensor can be also exploited to detect other targets.

One-step solution synthesis of bismuth sulfide (Bi2S3) with various hierarchical architectures and their photoresponse properties

In this paper, we introduce a facile and phosphine-free one-step solution method to synthesize size- and shape-controlled bismuth sulfide (Bi2S3) with hierarchical architectures. Changing variables, such as the reaction temperature, the ratio of precursors, and the concentration of oleic acid were observed to influence the resultant shape of Bi2S3 microstructures. For the formation of Bi2S3 hierarchical architectures, the crystal splitting growth mechanism played the dominant role. The absorption spectra were recorded at room temperature, which revealed that the obtained Bi2S3 product was a direct band gap semiconductor and the band gap Eg was estimated to be about 1.9 eV. Furthermore, the I–V characteristics of the Bi2S3-based device show a significant increase by ca. 1 order of magnitude compared with the dark state, indicating an enhanced conductivity and high sensitivity. The response and decay times are estimated to be about 0.5 and 0.8 s, respectively, which are short enough for it to be an excellent candidate for high-speed and high-sensitivity photodetectors or optical switches. Thus the Bi2S3 hierarchies as building blocks may offer the potential for monolithic, low-cost and large-scale integration with CMOS electronics.

Solution synthesis of copper selenide nanocrystals and their electrical transport properties

In this paper, we developed a one-pot solution strategy to synthesize copper selenide NCs with controllable shape and structure. By changing the precursors in the reaction, copper selenide NCs (Cu2−xSe nanoparticles, nanorods and CuSe nanoplates) with various morphologies could be achieved. We proposed a possible mechanism to explain the influence of precursors on the shape of copper selenide NCs and we found that the chemical activities of precursors played key roles in the morphologies and crystal structures of the final products. Moreover, the electrical transport properties of as-prepared products were investigated. The morphologies of copper selenide NCs have a great influence on the electrical transport properties. The copper selenide NCs with nanorods display the best electrochemical performance compared with the other two types. We believe that copper selenide NCs would be promising candidates for electrical transport materials.

A low band gap donor–acceptor copolymer containing fluorene and benzothiadiazole units: synthesis and photovoltaic properties

A new low band gap copolymer containing dialkylfluorene and 4,7-dithienyl-2,1,3-benzothiadiazole (TBT), poly(fluorenevinylene-alt-4,7-dithienyl-2,1,3-benzothiadiazole) (PF-TBT) was synthesized by Heck cross-coupling polymerization. The copolymer is soluble in common organic solvents such as chloroform, tetrahydrofuran and chlorobenzene. The TGA result indicated that the copolymer possesses good thermal stability. The absorption, electrochemical and photovoltaic properties of PF-TBT were investigated and compared with those of poly(fluorenevinylene-alt-4,7-diphenyl-2,1,3-benzothiadiazole) (PF-DBT) whose structure is similar to PF-TBT. The copolymer exhibited a broad absorption band with an absorption edge close to 700 nm and an optical band gap of 1.82 eV. Cyclic voltammetry studies indicated that the relatively low HOMO energy level assured a higher open circuit voltage (Voc) when PF-TBT is used as the donor material in a photovoltaic cell. The bulk heterojunction (BHJ) solar cell using PF-TBT as the donor and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as the acceptor with the structure of ITO/PEDOT : PSS/copolymer : PCBM/LiF/Al, exhibited a Voc of 0.86 V, short-circuit current density (Jsc) of 3.97 mA cm−2, fill factor (FF) of 0.35, and a power conversion efficiency (PCE) of 1.18% under one sun of AM 1.5 solar simulator illumination (100 mW cm−2).

Solution-Processed Organic Photovoltaics Based on Indoline Dye Molecules Developed in Dye-Sensitized Solar Cells

A donor-acceptor (D-A) type indoline dye, D149, was used as an electron donor in solution-processed organic solar cells (OSCs). For bulk-heterojunction (BHJ) type OSCs with PC70BM as electron acceptor, the power conversion efficiency (PCE) is sensitive to the amount of D149 in the D149/PC70BM blend film. When the concentration of D149 in the blend film was as low as 5%, the highest PCE of up to 1.29%, together with a short-circuit current density (Jsc) of 4.58 mA·cm−2, an open-circuit voltage (Voc) of 0.90 V and a fill factor (FF) of 0.31, was achieved. In order to improve the PCE of D149-based OSCs, a bilayer-heterojunction configuration with C70 as electron acceptor has been employed. By optimizing the thickness of the D149 layer and varying the electron- and hole-transport layers, a highest PCE of up to 2.28% with a Jsc of 4.38 mA·cm−2, a Voc of 0.77 V, and an FF of 0.62 was achieved under AM 1.5G solar illumination (100 mW·cm−2).

Prediction of a new layered phase of nitrogen from first-principles simulations

A new phase of nonmolecular nitrogen has been suggested by first-principles density functional theory simulations at high pressures. The phase has zigzag chains similar to the BP, A7 and LB phases, but the zigzag chains in the PP phase are connected by two atoms with double bonds with Pmna symmetry, which we designated as the PP phase. Properties of PP are presented in comparison with other polymeric phases of nitrogen discussed previously. The calculated enthalpy versus pressure reveals a similarity between the PP and CH phases. The equation of state of nitrogen in the PP, CG and e phases shows that an e transition to the PP phase happens at 90 GPa. The band structure and bulk modulus of PP phase are also calculated.

Synthesis and photovoltaic properties of non-fullerene solution processable small molecule acceptors

Two non-fullerene small molecules, BT-C6 and BT-C12, based on the vinylene-linked benzothiadiazole-thiophene(BT) moiety flanked with 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile have been synthesized and characterized by solution/thin film UV-Vis absorption, photoluminescence(PL), and cyclic voltammetry(CV) measurements. The two molecules show intense absorption bands in a wide range from 300 nm to 700 nm and low optical bandgaps for BT-C6(1.60 eV) and for BT-C12(1.67 eV). The lowest unoccupied molecular orbital(LUMO) levels of both the molecules are relatively higher than that of [6,6]-phenyl C61 butyric acid methyl ester(PCBM), promising high open circuit voltage(Voc) for photovoltaic application. Bulk heterojunction(BHJ) solar cells with poly(3-hexylthiophene) (P3HT) as the electron donor and the two molecules as the acceptors were fabricated. Under 100 mW/cm2 AM 1.5 G illumination, the devices based on P3HT:BT-C6(1:1, mass ratio) show a power conversion efficiency(PCE) of 0.67%, a short-circuit current(Jsc) of 1.63 mA/cm2, an open circuit voltage(Voc) of 0.74 V, and a fill factor(FF) of 0.56.