Showing papers by "Nanjing Tech University published in 2013"

Enhancing solar cell efficiency: the search for luminescent materials as spectral converters

Abstract: Photovoltaic (PV) technologies for solar energy conversion represent promising routes to green and renewable energy generation. Despite relevant PV technologies being available for more than half a century, the production of solar energy remains costly, largely owing to low power conversion efficiencies of solar cells. The main difficulty in improving the efficiency of PV energy conversion lies in the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the bandgap of a semiconductor material. In recent years, luminescent materials, which are capable of converting a broad spectrum of light into photons of a particular wavelength, have been synthesized and used to minimize the losses in the solar-cell-based energy conversion process. In this review, we will survey recent progress in the development of spectral converters, with a particular emphasis on lanthanide-based upconversion, quantum-cutting and down-shifting materials, for PV applications. In addition, we will also present technical challenges that arise in developing cost-effective high-performance solar cells based on these luminescent materials.

Recent progress in luminescent and colorimetric chemosensors for detection of thiols

Abstract: In the past few decades, the development of optical probes for thiols has attracted great attention because of the biological importance of the thiol-containing molecules such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). This tutorial review focuses on various thiol detection methods based on luminescent or colorimetric spectrophotometry published during the period 2010–2012. The discussion covers a diversity of sensing mechanisms such as Michael addition, cyclization with aldehydes, conjugate addition–cyclization, cleavage of sulfonamide and sulfonate esters, thiol–halogen nucleophilic substitution, disulfide exchange, native chemical ligation (NCL), metal complex-displace coordination, and nanomaterial-related and DNA-based chemosensors.

Progress in solid oxide fuel cells with nickel-based anodes operating on methane and related fuels.

Abstract: Operating on Methane and Related Fuels Wei Wang,† Chao Su,‡ Yuzhou Wu, Ran Ran,† and Zongping Shao*,† †State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry & Chemical Engineering, Nanjing University of Technology, No. 5 Xin Mofan Road, Nanjing 210009, People’s Republic of China ‡Department of Chemical Engineering, Curtin University, Perth, WA 6845, Australia Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia

A flexible Eu(III)-based metal–organic framework: turn-off luminescent sensor for the detection of Fe(III) and picric acid

Abstract: A metal–organic framework (MOF) {[Eu2(MFDA)2(HCOO)2(H2O)6]·H2O}n (1) (H2MFDA = 9,9-dimethylfluorene-2,7-dicarboxylic acid) has been solvothermally synthesized and structurally characterized. 1 possesses the three-dimensional pcu type rod-packing structure with one-dimensional rhombic channels. The framework of 1 can reversibly shrink/swell along the c axis upon partial/full release of the water molecules. Correspondingly, the rhombic channels become narrow/large and 1 transforms to narrow-pore 1a/large-pore 1b. 1, 1a and 1b have almost the same excitation and emission spectra with the strong characteristic red-light-emission of Eu(III). A high photoluminescence quantum yield of 77% and long luminescence lifetime of around 1.1 ms was observed for 1. The potential of 1b for Fe3+ ions and PA sensing was studied in DMF through the luminescence quenching experiments, which show 1b is a potential turn-off luminescent sensory material for the selective detection of Fe3+ ions and PA with detection limits of around 10−7 M for both of them. The fluorescence quenching mechanism for Fe3+ ions and PA was also investigated.

Thermoelectric Ceramics for Energy Harvesting

Abstract: Metal oxides (Ca3Co4O9, CaMnO3, SrTiO3, In2O3), Ti sulfides, and Mn silicides are promising thermoelectric (TE) material candidates for cascade-type modules that are usable in a temperature range of 300–1200 K in air. In this paper, we review previous studies in the field of TE materials development and make recommendations for each material regarding future research. Furthermore, the R&D of TE modules composed of metal oxide materials and the prospect of their commercialization for energy harvesting is demonstrated.

Plant leaf-derived fluorescent carbon dots for sensing, patterning and coding

Abstract: We report a simple, low-cost and green route for fabrication of fluorescent carbon dots (CDs), and demonstrate their applications in sensing, patterning, and coding. Pyrolysis of various plant leaves yielded bright blue-emitting CDs, providing a one-step way for large-scale production of CDs without surface passivation treatment or the use of toxic/expensive solvents and starting materials. Also, further improvement in the fluorescence intensity of CDs was achieved after treatment using plasma and microwave-assisted techniques. The obtained CDs were applied as a fluorescent sensing platform for sensitive and selective detection of Fe3+ ions, and as fluorescent inks for printing luminescent patterns useful in anti-counterfeit and optoelectronic applications. Moreover, uniform fluorescent microbeads of polymer-encapsulated CDs, CD/QD nanocomposites, and CD/organic fluorescent dye nanocomposites were prepared via a microfluidic process, which may expand the potential applications of CDs in coding, bioimaging, and drug delivery.

Adsorptive Removal of Methyl Orange and Methylene Blue from Aqueous Solution with Finger-Citron-Residue-Based Activated Carbon

Abstract: Activated carbon derived from finger citron residue (FAC) was tested as a new type of adsorbent for the removal of harmful dyes, namely, the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB), from contaminated water. Liquid-phase adsorption experiments were conducted, and the maximum adsorption capacity was determined. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and to calculate the isotherm constants. It was found that the adsorption capacity of FAC is much higher than those of other types of activated carbons. Maximum equilibrium adsorption capacities of 934.58 and 581.40 mg/g for MO and MB, respectively, were achieved. Three simplified kinetic models, namely, pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations, were used to investigate the adsorption process. The pseudo-seco...

Fabrication of Flexible, All‐Reduced Graphene Oxide Non‐Volatile Memory Devices

Abstract: A flexible, all reduced graphene oxide non-volatile memory device, with lightly reduced GO as an active layer and highly reduced GO as both top and bottom electrodes, is fabricated by a full-solution process and its performance is characterized. It provides a convenient method to construct other all-carbon devices.

Bioinspired Graphene Nanopores with Voltage-Tunable Ion Selectivity for Na+ and K+

Abstract: Biological protein channels have many remarkable properties such as gating, high permeability, and selectivity, which have motivated researchers to mimic their functions for practical applications Herein, using molecular dynamics simulations, we design bioinspired nanopores in graphene sheets that can discriminate between Na+ and K+, two ions with very similar properties The simulation results show that, under transmembrane voltage bias, a nanopore containing four carbonyl groups to mimic the selectivity filter of the KcsA K+ channel preferentially conducts K+ over Na+ A nanopore functionalized by four negatively charged carboxylate groups to mimic the selectivity filter of the NavAb Na+ channel selectively binds Na+ but transports K+ over Na+ Surprisingly, the ion selectivity of the smaller diameter pore containing three carboxylate groups can be tuned by changing the magnitude of the applied voltage bias Under lower voltage bias, it transports ions in a single-file manner and exhibits Na+ selectivi

Membranes with highly ordered straight nanopores by selective swelling of fast perpendicularly aligned block copolymers.

Abstract: Membranes with uniform, straight nanopores have important applications in diverse fields, but their application is limited by the lack of efficient producing methods with high controllability. In t...

Binder-free α-MoO3 nanobelt electrode for lithium-ion batteries utilizing van der Waals forces for film formation and connection with current collector

Abstract: We demonstrate a facile and effective way for the fabrication of a flexible, homogeneous and neat α-MoO3 thin-film electrode for lithium-ion batteries with high performance without using any binder and conductive additives. Single-crystalline α-MoO3 nanobelts with uniform width of around 200 nm and length at the micrometer level are first synthesized by a simple water-based hydrothermal route. The as-obtained α-MoO3 slurry is then directly deposited onto a copper foil current collector by the doctor blade method. The formation of the α-MoO3 film and its good adhesion to the current collector is realized via van der Waals attraction forces through a drying process. The structure and morphology of the α-MoO3 nanobelt particles and thin-film electrode are systematically characterized by XRD, Raman spectra, TEM, SEM and XPS techniques, and the electrochemical properties are investigated by CV and constant current discharge–charge test techniques. The α-MoO3 film electrode exhibits a reversible specific capacity of ∼1000 mA h g−1 at 50 mA g−1 and a stable capacity retention of 387–443 mA h g−1 at 2000 mA g−1, indicating its high Li storage capacity, superior rate performance and good cycling stability. The electrode material, as well as the fabrication technique, is highly promising for practical use in high energy and power density lithium-ion batteries.

Facile and green synthesis of mesoporous Co3O4 nanocubes and their applications for supercapacitors

Abstract: Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs) In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer

Accelerated carbonation – A potential approach to sequester CO2 in cement paste containing slag and reactive MgO

Abstract: The cement industry and concrete producers are under pressure to reduce the carbon footprint and energy demands of cement-based construction materials. This study investigates the CO2 uptake of paste mixtures designed with general use (GU) Portland cement, ground granulated blast furnace slag (GGBFS) and reactive MgO as cement replacement due to exposure to an accelerated carbonation curing regime with 99.9% concentration of CO2. The CO2 uptake, carbonation mechanism, microstructure and microhardness of cement pastes are examined. Key outcomes revealed that: (i) samples exposed to accelerated carbonation curing exhibit a denser microstructure and higher microhardness in comparison to non-carbonated samples, (ii) irrespective of the presence of reactive MgO, CO2 uptake increases with age from 7 to 56 d, (iii) by 56 d, pastes containing 10% and 20% reactive MgO uptake similar amounts of CO2 in comparison to mixtures without reactive MgO, and (iv) pastes containing 40% reactive MgO uptake the least amount of CO2 however, exhibit the greatest microhardness and the lowest porosity.

Shaking table test on the seismic failure characteristics of a subway station structure on liquefiable ground

Abstract: SUMMARY In order to investigate the seismic failure characteristics of a structure on the liquefiable ground, a series of shaking table tests were conducted based on a plaster model of a three-story and three-span subway station. The dynamic responses of the structure and ground soil under main shock and aftershock ground motions were studied. The sand boils and waterspouts phenomena, ground surface cracks, and earthquake-induced ground surface settlements were observed in the testing. For the structure, the upward movement, local damage and member cracking were obtained. Under the main shock, there appeared longer liquefaction duration for the ground soil while the pore pressure dissipated slowly. The acceleration amplification effect of the liquefied soil was weakened, and the soil showed a remarkable shock absorption and concentration effect with low frequency component of ground motion. However, under the aftershock, the dissipation of pore pressure in the ground soil became obvious. The peak acceleration of the structure reduced with the buried depth. Dynamic soil pressure on the side wall was smaller in the middle and larger at both ends. The interior column of the model structure was the weakest member. The peak strain and damage degree for both sides of the interior column exhibited an ‘S’ type distribution along the height. Moreover, the seismic response of both ground soil and subway station structure exhibited a remarkable spatial effect. The seismic damage development process and failure mechanism of the structure illustrated in this study can provide references for the engineers and researcher. Copyright © 2013 John Wiley & Sons, Ltd.

Synthesis and photoluminescence of Eu3+-activated double perovskite NaGdMg(W, Mo)O6 – a potential red phosphor for solid state lighting

Abstract: A novel high-efficiency double perovskite NaGdMg(W, Mo)O6:Eu phosphor is obtained by an improved citrate–EDTA complexing method. An emission intensity over twenty times that of a commercial red phosphor is observed. The host material has high-efficiency absorption, high doping concentration for many rare earth ions and intense emission with different colors.

A photoluminescent microporous metal organic anionic framework for nitroaromatic explosive sensing

Abstract: By using the octadentate ligand tetrakis[(3,5-dicarboxyphenoxy)methyl] methane (H8L), a rare (4,8)-scu type microporous coordination polymer, [In2L][NH2(CH3)2]2·(DMF)4(H2O)16, was synthesized and structurally characterized. The compound possesses an anionic three-dimensional open framework and exhibits permanent porosity with selective gas adsorption of CO2 over CH4. It exhibited strong fluorescence emission upon excitation at RT, and a selective, efficient emission quenching response towards nitroaromatic explosives.

BaNb0.05Fe0.95O3−δ as a new oxygen reduction electrocatalyst for intermediate temperature solid oxide fuel cells

Abstract: Cobalt-free perovskite BaNb0.05Fe0.95O3−δ (BNF) is synthesized and characterized towards application as a cathode material for intermediate temperature solid oxide fuel cells. In situ X-ray diffraction and transmission electron microscopy are applied to study the crystal structure and thermally induced phase transformation. BNF exists as a multiphase structure composed of a monoclinic phase and a cubic phase at room temperature, and then undergoes a phase transformation to a cubic structure starting at ∼400 °C, which is maintained at temperatures up to 900 °C during a thermal cycle between room temperature and 900 °C; while it retains the cubic perovskite lattice structure on cooling from 900 °C to room temperature. Oxygen temperature-programmed desorption, combined thermal expansion and thermo-gravimetric analysis are used to clarify the thermal reducibility of BNF. A relatively good stability of BNF is demonstrated by electrical conductivity and electrochemical impedance spectroscopy measurements. The activity of BNF for oxygen reduction reaction is probed by symmetrical cell and single fuel cell tests. Favorable electrochemical activities at intermediate temperature, e.g. very low interfacial resistance of only ∼0.016 Ω cm2 and maximum power density of 1162 mW cm−2 at 750 °C, are demonstrated, which could be attributed to the cubic lattice structure of BNF within the temperature range of cell operation.

Fabrication of Supported Cuprous Sites at Low Temperatures: An Efficient, Controllable Strategy Using Vapor-Induced Reduction

Abstract: Selective reduction of supported CuO to Cu2O was realized using the strategy of vapor-induced reduction, in which HCHO/H2O vapor diffuses into the pores of the support and interacts with predispersed CuO. This new strategy allows the fabrication of supported cuprous sites at much lower temperatures within a short time, avoids the formation of Cu(0) with a Cu(I) yield of nearly 100%, and results in materials with good adsorption performance, which is impossible to achieve by conventional methods.