Xiaoming Fang

Enhanced Performance of the Dye-Sensitized Solar Cells with Phenothiazine-Based Dyes Containing Double D−A Branches

Double donor-acceptor (D-A) branched dyes (DBD) with a phenothiazine unit as electron donor and a 2-cyanoacrylic acid unit as electron acceptor were synthesized and used as sensitizers for solar cells (DSSCs). The conversion efficiency of the DSSCs amounts up to 4.22% (2.91% for the single D-A branched dye) under AM 1.5 G irradiation. The results show that the performance of DSSCs can be effectively enhanced by the cooperation of two donor-acceptor containing branches in one molecule of the dyes.

Novel Z-scheme visible-light-driven Ag3PO4/Ag/SiC photocatalysts with enhanced photocatalytic activity

Visible-light-driven Ag3PO4/Ag/SiC photocatalysts with different weight fractions of SiC were synthesized via an in situ precipitation method and characterized by X-ray diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (DRS). Under visible light irradiation (>420 nm), the Ag3PO4/Ag/SiC photocatalysts degraded methyl orange (MO) and phenol efficiently and displayed much higher photocatalytic activity than that of pure Ag3PO4/Ag or SiC/Ag, and the Ag3PO4/Ag/SiC hybrid photocatalyst with 10% of SiC exhibited the highest photocatalytic activity. The quenching effects of different scavengers demonstrated that reactive h+ and O2˙− played the major role in the MO degradation. It was elucidated that the excellent photocatalytic activity of Ag3PO4/Ag/SiC for the degradation of MO under visible light (λ > 420 nm) can be ascribed to the efficient separation of photogenerated electrons and holes through the Z-scheme system composed of Ag3PO4, Ag and SiC, in which the Ag nanoparticles acted as the charge transmission-bridge. The Ag3PO4/Ag/SiC hybrid maintained good photocatalytic activity after 10 times of cycle experiments.

Surfactant-free ionic liquid-based nanofluids with remarkable thermal conductivity enhancement at very low loading of graphene

We report for the first time the preparation of highly stable graphene (GE)-based nanofluids with ionic liquid as base fluids (ionic liquid-based nanofluids (Ionanofluids)) without any surfactant and the subsequent investigations on their thermal conductivity, specific heat, and viscosity. The microstructure of the GE and MWCNTs are observed by transmission electron microscope. Thermal conductivity (TC), specific heat, and viscosity of these Ionanofluids were measured for different weight fractions and at varying temperatures, demonstrating that the Ionanofluids exhibit considerably higher TC and lower viscosity than that of their base fluids without significant specific heat decrease. An enhancement in TC by about 15.5% and 18.6% has been achieved at 25 °C and 65 °C respectively for the GE-based nanofluid at mass fraction of as low as 0.06%, which is larger than that of the MWCNT-dispersed nanofluid at the same loading. When the temperature rises, the TC and specific heat of the Ionanofluid increase clearly, while the viscosity decreases sharply. Moreover, the viscosity of the prepared Ionanofluids is lower than that of the base fluid. All these advantages of this new kind of Ionanofluid make it an ideal fluid for heat transfer and thermal storage.

Comparison of Heat Transfer and Pressure Drop for the Helically Baffled Heat Exchanger Combined with Three-Dimensional and Two-Dimensional Finned Tubes

Experiments were performed to compare the shell-side heat transfer coefficient and pressure drop of a helically baffled heat exchanger with petal-shaped finned tubes to those of low-finned tubes for oil cooling using water as a coolant. The experimental results showed that for the heat exchanger with petal-shaped finned tubes, the shell-side heat transfer coefficients were augmented by 28–48%, yet the shell-side pressure drops were reduced by 35–75% at the same volumetric flow rates of oil. The possible mechanisms responsible for this heat transfer enhancement were analyzed for helically baffled heat exchanger combined with petal-shaped finned tubes.

Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior

Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%–35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings.

Rheological Property and Thermal Conductivity of Multi-walled Carbon Nano-tubes-dispersed Non-Newtonian Nano-fluids Based on an Aqueous Solution of Carboxymethyl Cellulose

The non-Newtonian nano-fluids with 0.1, 0.5, 1, and 2 wt% of multi-walled carbon nano-tubes have been prepared by dispersing different amounts of multi-walled carbon nano-tubes into an aqueous solution of carboxymethyl cellulose at a weight fraction of 3 wt%, respectively. The nano-fluids exhibit the shear-thinning rheological behavior. The viscosity of the nano-fluid increases with the weight fraction of multi-walled carbon nano-tubes and decreases with the increase in temperature. The thermal conductivity of all the nano-fluids is higher than that of the base liquid. The thermal conductivity enhancement is as high as 14.6% for the nano-fluid containing 2 wt% of multi-walled carbon nano-tubes.

A multi-controlled drug delivery system based on magnetic mesoporous Fe3O4 nanopaticles and a phase change material for cancer thermo-chemotherapy

Herein a novel multi-controlled drug release system for doxorubicin (DOX) was developed, in which monodisperse mesoporous Fe3O4 nanoparticles were combined with a phase change material (PCM) and polyethylene glycol 2000 (PEG2000). It is found that the PCM/PEG/DOX mixture containing 20% PEG could be dissolved into water at 42 °C. The mesoporous Fe3O4 nanoparticles prepared by the solvothermal method had sizes of around 25 nm and exhibited a mesoporous microstructure. A simple solvent evaporation process was employed to load the PCM/PEG/DOX mixture on the mesoporous Fe3O4 nanoparticles completely. In the Fe3O4@PCM/PEG/DOX system, the pores of the Fe3O4 nanoparticles were observed to be filled with the mixture of PCM/PEG/DOX. The Fe3O4@PCM/PEG/DOX system showed a saturation magnetization value of 50.0 emu g-1, lower than 71.1 emu g-1 of the mesoporous Fe3O4 nanoparticles, but it was still high enough for magnetic targeting and hyperthermia application. The evaluation on drug release performance indicated that the Fe3O4@PCM/PEG/DOX system achieved nearly zero release of DOX in vitro in body temperature, while around 80% of DOX could be released within 1.5 h at the therapeutic threshold of 42 °C or under the NIR laser irradiation for about 4 h. And a very rapid release of DOX was achieved by this system when applying an alternating magnetic field. By comparing the systems with and without PEG2000, it is revealed that the presence of PEG2000 makes DOX easy to be released from 1-tetradecanol to water, owing to its functions of increasing the solubility of DOX in 1-tetradecanol as well as decreasing the surface tension between water and 1-tetradecanol. The novel drug release system shows great potential for the development of thermo-chemotherapy of cancer treatment.

Two-Step Precise Determination of the Parameters of the Single-Diode Equivalent Circuit Model for Dye-Sensitized Solar Cells

In this work, a two-step method to determine all the five parameters of the single-diode equivalent circuit model for dye-sensitized solar cells with high accuracy is demonstrated. With the five parameters extracted by the graphic method as the initial values, the accurate values of the five parameters are obtained by nonlinear least squares fitting. The accuracy of the two-step method is validated by fitting several I-V characteristics of dye-sensitized solar cells both from our experimental results and from other research groups. The root mean square errors of all the fitting results by the two-step method are less than 1%.

Novel facile self-assembly approach to construct graphene oxide-decorated phase-change microcapsules with enhanced photo-to-thermal conversion performance

In this study, self-assembled and graphene oxide (GO) modified microcapsules of paraffin@mixed cellulose were prepared. The microstructure and morphology of the as-prepared phase-change composites were characterized by a polarizing microscope, SEM, FT-IR, XRD, and Raman spectrum. The results indicated that the paraffin@ethylcellulose (EC)/methylcellulose (MC)/GO composite consists of spherical particles that have core@shell structure, which indicates the absence of chemical reactions between the core (i.e., paraffin) and shell (i.e., EC/MC/GO) materials. The melting temperature (i.e., 49.7 °C) and latent heat (i.e., 152.2 J g−1) of the paraffin@EC/MC/GO composite were determined through DSC. The encapsulation rate of paraffin in the composite can be as high as 85.4% based on the results of the DSC measurement. The as-prepared paraffin@EC/MC/GO composites had no leakage, which was observed by SEM, and possess perfect phase-change capability after experiencing 100 melting–freezing cycles. Furthermore, the microencapsulation was dispersed into the base fluid (i.e., water) to form a stable suspension, which shows enhanced photo-thermal conversion performance with temperature range from 30 to 80 °C. The efficiency of paraffin@EC/MC/GO-based phase-change slurry is maintained at 80% in a wide temperature range compared with that of paraffin@EC/MC-based phase-change slurry. The paraffin@EC/MC/GO composite with high thermal storage capacity, good thermal reliability and enhanced photothermal performance exhibits a good potential for using as a solar thermal storage material in practical applications.

A one-step process for preparing a phenyl-modified g-C3N4 green phosphor with a high quantum yield

Herein a simple one-step process for preparing a g-C3N4-based green phosphor was presented, which just involved thermal polymerization of a single precursor, 2,4-diamino-6-phenyl-1,3,5-triazine, under an atmosphere of argon, to prepare phenyl-modified g-C3N4. The effects of the annealing temperature and time on the crystalline structure, chemical composition, morphology, optical absorption properties, and photoluminescence emission behavior of the obtained samples were investigated systematically. It was found that the phenyl-modified g-C3N4 prepared at 400 °C for 40 min exhibits strong green emission with a quantum yield of as high as 38.08%, comparable to those of the g-C3N4 nanoparticles and quantum dots obtained from the multi-step preparation and post-treatment processes. The emission spectrum of the phenyl-modified g-C3N4 sample can be fitted into four peaks centered at around 465, 490, 520 and 545 nm, suggesting that the phenyl-modified g-C3N4 phosphor possesses multi-fluorophores or luminescent species. The introduction of the phenyl groups leads to the decrease in band gap and thus the red shift in emission as compared with pristine g-C3N4. The simple preparation process along with high quantum yield make this phenyl-modified g-C3N4 green phosphor show great potential in practical applications.