Lili Lv

A highly efficient (>6%) Cd1−xMnxSe quantum dot sensitized solar cell

Quantum dot sensitized solar cells (QDSCs) have attracted considerable attention recently and become promising candidates for realizing a cost-effective solar cell. The design and synthesis of quantum dots (QDs) for achieving high photoelectric performance is an urgent need imposed on scientists. Here, we have succeeded in designing a QDSC with a high efficiency η of 6.33% based on Cd0.8Mn0.2Se quantum dots by facile chemical bath deposition (CBD). The effects of Mn2+ ions on the physical, chemical, and photovoltaic properties of the QDSCs are investigated. The Mn2+ ions doped into QDs can increase the light harvesting to produce more excitons. In addition, the Mn2+ dopant also raises the conduction band of CdSe, accelerates the electron injection kinetics and reduces the charge recombination, improving the charge transfer and collection. The increase of the efficiencies of light-harvesting, charge-transfer and charge-collection results in the improvement of the quantum efficiency of the solar cells. The power conversion efficiency of the solar cell is increased to 6.33% (Voc = 0.58 V, Jsc = 19.15 mA cm−2, and FF = 0.57).

Rapid construction of TiO2 aggregates using microwave assisted synthesis and its application for dye-sensitized solar cells

Hierarchical TiO2 nanocrystallite aggregates, composed of ∼10 nm nanocrystallites, with a size of ∼500 nm have been synthesized by a microwave assisted method at 150 °C in a short time (∼10 minutes) as the photoanode of dye-sensitized solar cells (DSCs). Ethanol and TiCl4 are selected as the solvent and titanium precursor, respectively. The rapid heating rate and superheating/“hot spots” of the reaction system under microwave irradiation result in a large amount of nuclei instantly, which leads to the formation of a great deal of clusters. Moreover, the clusters that grow up rapidly are assembled into TiO2 nanocrystallite aggregates. The TiO2 aggregates show better light scattering property, larger specific surface area and higher dye-loading compared to the commercial P25 TiO2 nanoparticles. In comparison with DSC based P25 photoanode, the short current density (Jsc) and dye-loading of DSC based the as-synthesized TiO2 aggregates photoanode increase by 33% and 62%, respectively. As a result, the PCE of the DSC is up to 7.64%, and the TiO2 aggregates obtained by microwave assisted synthesis are a promising and potential candidate for DSCs.

Enhanced Performance of PbS-quantum-dot-sensitized Solar Cells via Optimizing Precursor Solution and Electrolytes.

This work reports a PbS-quantum-dot-sensitized solar cell (QDSC) with power conversion efficiency (PCE) of 4%. PbS quantum dots (QDs) were grown on mesoporous TiO2 film using a successive ion layer absorption and reaction (SILAR) method. The growth of QDs was found to be profoundly affected by the concentration of the precursor solution. At low concentrations, the rate-limiting factor of the crystal growth was the adsorption of the precursor ions, and the surface growth of the crystal became the limiting factor in the high concentration solution. The optimal concentration of precursor solution with respect to the quantity and size of synthesized QDs was 0.06 M. To further increase the performance of QDSCs, the 30% deionized water of polysulfide electrolyte was replaced with methanol to improve the wettability and permeability of electrolytes in the TiO2 film, which accelerated the redox couple diffusion in the electrolyte solution and improved charge transfer at the interfaces between photoanodes and electrolytes. The stability of PbS QDs in the electrolyte was also improved by methanol to reduce the charge recombination and prolong the electron lifetime. As a result, the PCE of QDSC was increased to 4.01%.

Dye-sensitized solar cells based on hierarchically structured porous TiO2 filled with nanoparticles

A new morphology of TiO2 photoanodes for N-719 dye-sensitized solar cells (DSCs) has been developed with enhanced power conversion performance. Strategies for the synthesis of hierarchically structured three-dimensionally ordered macroporous (HS-3DOM) TiO2 with controlled macropore sizes (ca. 85–155 nm) by using well-arrayed polymethyl methacrylate with different diameters as well as two kinds of photoanode films based on hierarchically structured porous TiO2 filled with nanoparticles have been demonstrated. DSCs based on a special TiO2 photoanode with a macropore size of 105 nm exhibited a current density (Jsc) of 20.6 mA cm−2 and a high photo-to-electrical energy conversion efficiency (η) of 9.7%. This high power conversion efficiency is ascribed to the special morphology of the TiO2 photoanode with high dye adsorption due to its ordered and open structures, and also its light scattering and charge collection efficiency.

Amyloid-graphene oxide as immobilization platform of Au nanocatalysts and enzymes for improved glucose-sensing activity

Two-dimensional GO nanosheets and one-dimensional lysozyme nanofibrils were hybridized through electrostatic interaction to get a novel amyloid-GO composite, which promised a biocompatible immobilization platform for Au nanocatalysts as well as enzymes. The immobilization platform could load a large and tunable amount of Au NPs while maintaining their high catalytic activity. The immobilized catalysts showed high electrochemical behaviors, being ideal as glucose sensing systems. Furthermore, enzymes could also be immobilized on the residual bare surfaces of amyloid-GO, and served by a colorimetric method for a sensitive and selective analytical glucose-detecting platform. The introduction of amyloid fibrils with super large aspect ratios (>103) on GO nanosheets offers an unprecedented possibility of designing and developing novel biomimetic catalysts for broad applications in biotechnology.

Biomimetic Hybridization of Kevlar into Silk Fibroin: Nanofibrous Strategy for Improved Mechanic Properties of Flexible Composites and Filtration Membranes

Silk, one of the strongest natural biopolymers, was hybridized with Kevlar, one of the strongest synthetic polymers, through a biomimetic nanofibrous strategy. Regenerated silk materials have outstanding properties in transparency, biocompatibility, biodegradability and sustainability, and promising applications as diverse as in pharmaceutics, electronics, photonic devices and membranes. To compete with super mechanic properties of their natural counterpart, regenerated silk materials have been hybridized with inorganic fillers such as graphene and carbon nanotubes, but frequently lose essential mechanic flexibility. Inspired by the nanofibrous strategy of natural biomaterials (e.g., silk fibers, hemp and byssal threads of mussels) for fantastic mechanic properties, Kevlar was integrated in regenerated silk materials by combining nanometric fibrillation with proper hydrothermal treatments. The resultant hybrid films showed an ultimate stress and Youngs modulus two times as high as those of pure regenerated SF films. This is not only because of the reinforcing effect of Kevlar nanofibrils, but also because of the increasing content of silk β-sheets. When introducing Kevlar nanofibrils into the membranes of silk nanofibrils assembled by regenerated silk fibroin, the improved mechanic properties further enabled potential applications as pressure-driven nanofiltration membranes and flexible substrates of electronic devices.

Characterization of CDOM of river waters in China using fluorescence excitation‐emission matrix and regional integration techniques

The spatial characteristics of fluorescent-DOM (FDOM) components in river waters in China were firstly examined by excitation-emission matrix (EEM) spectra and fluorescence regional integration (FRI) with the data collected during September to November between 2013 and 2015. One tyrosine-like (R1), one tryptophan-like (R2), one fulvic-like (R3), one microbial protein-like (R4) and one humic-like (R5) components have been identified by FRI method. Principle components analysis (PCA) was conducted to assess variations in the five FDOM components (FRί (ί = 1, 2, 3, 4, 5)) and the humification index (HIX) for all 194 river water samples. The average fluorescence intensities of the five fluorescent components and the total fluorescence intensities FSUM differed under spatial variation among the seven major river basins (Songhua, Liao, Hai, Yellow and Huai, Yangtze, Pearl and Inflow Rivers) in China. When all the river water samples were pooled together, the fulvic-like FR3 and the humic-like FR5 showed a strong positive linear relationship (R2 = 0.90, n = 194), indicating that the two allochthonous FDOM components R3 and R5 may originate from similar sources. There is a moderate strong positive correlation between the tryptophan-like FR2 and the microbial protein-like FR4 (R2 = 0.71, n = 194), suggesting parts of two autochthonous FDOM components R2 and R4 are likely from some common sources. However, the total allochthonous substance FR(3+5) and the total autochthonous substances FR(1+2+4) exhibited a weak correlation (R2 = 0.40, n = 194). Significant positive linear relationships between FR3 (R2 = 0.69, n = 194), FR5 (R2 = 0.79, n = 194) and CDOM absorption coefficient a(254) were observed, respectively, which demonstrated the CDOM absorption were dominated by the allochthonous FDOM components R3 and R5.

Activation of Actuating Hydrogels with WS2 Nanosheets for Biomimetic Cellular Structures and Steerable Prompt Deformation

Macroscopic soft actuation is intrinsic to living organisms in nature, including slow deformation (e.g., contraction, bending, twisting, and curling) of plants motivated by microscopic swelling and shrinking of cells, and rapid motion of animals (e.g., deformation of jellyfish) motivated by cooperative nanoscale movement of motor proteins. These actuation behaviors, with an exceptional combination of tunable speed and programmable deformation direction, inspire us to design artificial soft actuators for broad applications in artificial muscles, nanofabrication, chemical valves, microlenses, soft robotics, etc. However, so far artificial soft actuators have been typically produced on the basis of poly(N-isopropylacrylamide) (PNiPAM), whose deformation is motived by volumetric shrinkage and swelling in analogue to plant cells, and exhibits sluggish actuation kinetics. In this study, alginate-exfoliated WS2 nanosheets were incorporated into ice-template-polymerized PNiPAM hydrogels with the cellular microstructures which mimic plant cells, yet the prompt steerable actuation of animals. Because of the nanosheet-reinforced pore walls formed in situ in freezing polymerization and reasonable hierarchical water channels, this cellular hybrid hydrogel achieves super deformation speed (on the order of magnitude of 10° s), controllable deformation direction, and high near-infrared light responsiveness, offering an unprecedented platform of artificial muscles for various soft robotics and devices (e.g., rotator, microvalve, aquatic swimmer, and water-lifting filter).

Supramolecular proteinaceous biofilms as trapping sponges for biologic water treatment and durable catalysis

Inspired by the bacterial biofilms and chorions of living organisms which are made by proteinaceous assemblies and functional for multi-applications, various artificial protein fibrils-based nanoporous films are developed, and show their potential applications in multiple fields. Here, a simple and environmental friendly method was identified to produce bovine serum albumin (BSA) nanofibrils based biofilms, through a combination of protein fibrillation and reverse dialysis. BSA nanofibrils formed biofilms through intermolecular interactions, the resultant biofilms showed tunable thickness by altering the initial protein amount, good stability in organic and salty solvents, transparency and fluorescence properties, hold high capacity of trapping different substances (e.g. nanomaterials, organic dyes, heavy-metal ions and enzymes), and further enabled applications in biologic water treatment and enzyme stabilization. Taken o-phenylenediamine as substrate, the trapped horseradish peroxidase showed a catalytic activity 9-38 folds higher than free ones in organic phase, together with enhanced stability. These protein nanofibrils-based films offered an attractive biologic platform to hybridize diverse materials for on-demand functions and applications.

Relationship changes between CDOM and DOC in the Songhua River affected by highly polluted tributary, Northeast China

In this study, the dissolved organic carbon (DOC) concentrations, chromophoric dissolved organic matter (CDOM) absorption coefficient a(254), and excitation-emission matrix fluorescence (EEM) were examined in the Songhua River (SHR) and its highly polluted tributary of Northeast China. Fluorescence regional integration (FRI) was used to identify five fluorescent regions: one tyrosine-like (R1), one tryptophan-like (R2), one fulvic-like (R3), one microbial by-product-like (R4), and one humic-like (R5) regions. The five EEM-FRI regions for all water samples have site-specific properties. Principle component analysis (PCA) was conducted to assess variations in the five FRI regions and the humification index (HIX) for all water samples. For the water samples from the mainstream of SHR, CDOM absorption coefficient a(254) was correlated with either DOC or FRI fluorescent regions (R3 and R5), respectively. FRI R3 region was also correlated with R5 region for the water samples in the mainstream of SHR. However, the determination coefficients (R2) and slopes of these relationships among CDOM absorption, fluorescent regions, and DOC all decreased when the SHR waters were influenced by the highly polluted tributary of Yinma River (YMR) and Yitong River (YTR), which has a negative effect on the estimation of DOC flux transported by the SHR to oceans.