Effects of Additives on Electrochromic Properties of Nanocrystalline Tungsten Oxide Films Prepared by Complexation-Assisted Sol-Gel Method.

To improve the electrochromic (EC) properties of sol-gel-derived WO3 films, a series of organic small molecules, such as dopamine (DA), catechol, tyramine, phenol and 2-phenylethylamine, were added into peroxotungstic acid precursor sols as structure-directing additives, and five modified WO3 films were prepared by a simple and low-cost complexation-assisted sol-gel method. The effects of the above additives on the EC properties of the modified WO3 films have been studied in detail. Compared with the pure WO3 polycrystalline film, all the modified films combine the advantages of nanocrystalline and amorphous phases and show higher EC properties attributed to the unique nanocrystal-embedded amorphous structure. The results indicate that different additives with different numbers and types of functional groups (hydroxyl and amino groups) can change the microstructure, morphology, and thus electrochemical and EC properties of the films in various degrees. The additives, in order of their strong interactions with the sols, are DA, catechol, tyramine, phenol and 2-phenylethylamine, primarily depending on the number of hydroxyl groups. Of all the additives, DA with both catechol hydroxyl and amino groups shows the most positive effect; that is, the WO3 film modified with DA exhibits the best EC properties in terms of contrast, switching speed, stability, and coloration efficiency.

Response of different benthic biotic indices to eutrophication and sediment heavy metal pollution, in fujian coastal water, East China sea.

The types and intensity of anthropogenic pressure in the same sea area may differ spatially and may change as time passes, but response of benthic biotic indices to different pressure is different, which makes it unreasonable to use the same benthic biotic indices in a large sea area. We provided a new way of thinking as to selecting benthic biotic indices according to pressure type. The study took six bays under eutrophication and sediment heavy metal pollution to different levels in Fujian coastal water, East China sea, as examples, analysed the response of five benthic biotic indices, namely AZTI marine biotic index (AMBI), multivariate AMBI (M-AMBI), Shannon-Wiener diversity index (H'), benthic opportunistic polychaetes amphipods (BOPA) and benthic polychaetes amphipods (BPA), to eutrophication factors and sediment heavy metal pollution factors firstly. The result indicated that AMBI well responded to dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP); M-AMBI responded soundly in the range of DIN >0.131 mg L-1 and DIP >0.022 mg L-1 and responded universally to heavy metals; H' responded to only Hg and Cd; BOPA has response to eutrophication condition of DIN >0.242 mg L-1; BPA had response to DIN, Cu and As. Then, suitable indices were selected based on the four pressure scenarios in the study area. AMBI was selected in no pressure scenario; M-AMBI was chosen under only eutrophication pressure and under dual pressure; H' was preferred in only heavy metal pressure scenario (mainly Hg pollution). At last, the density plot of the distribution of the selected indices in the evaluation grades under different pressure scenarios proved the proposal of selecting benthic biotic indices according to pressure types feasible. This study can offer some new insights into rapidly choosing indices to evaluate the coastal benthic ecological quality status.

Dysprosium(III) Metal-Organic Framework Demonstrating Ratiometric Luminescent Detection of pH, Magnetism, and Proton Conduction.

A multifunctional metal-organic framework, (Hdmbpy)[Dy(H2dobdc)2(H2O)]·3H2O (Dy-MOF, H4dobdc = 2,5-dihydroxyterephthalic acid, dmbpy = 4,4'-dimethyl-2,2'-bipyridine), was synthesized and structurally characterized. The metal center DyIII is connected by four carboxyl groups to form the [Dy2(CO2)4] binuclear nodes, which are further interconnected by eight separate H2dobdc2- ligands to form a three-dimensional (3D) framework including hydrophilic triangular channels and abundant hydrogen-bonding networks. Dy-MOF has good stability in aqueous solution as well as in harsh acidic or alkaline solutions (pH range: 2.0-12.0). Furthermore, the luminescence signal of Dy-MOF undergoes a visualized color change as the acidity of the solution alters, which is the typical behavior of pH ratiometric probe. At a 100% relative humidity, Dy-MOF exhibits a high proton conductivity σ (1.70 × 10-4 S cm-1 at 303 K; 1.20 × 10-3 S cm-1 at 343 K) based on the proton hopping mechanism, which can be classified as a superionic conductor with σ exceeding 10-4 S cm-1. Additionally, the ferromagnetic interaction and magnetic relaxation behavior are simultaneously achieved in Dy-MOF. Herein, the combination of luminescence sensing, magnetism, and proton conduction in a single-phase 3D MOF may offer great potential applications in smart multitasking devices.

High-Yield Production of Lignin-Derived Functional Carbon Nanosheet for Dye Adsorption.

In this article, we report the preparation of lignin-derived carbon nanosheet (L-CNS) by direct thermal treatment of lignin without activation operation and the functions of the L-CNS as an adsorbent for rhodamine dye. The L-CNSs are fabricated by freeze-drying (FD) methods of lignin followed by high-temperature carbonization. It is found that lower frozen temperature in FD or lower concentration of lignin aqueous solution renders L-CNSs' more porous morphology and higher specific surface area (SSA), allowing a promising application of the L-CNSs as an efficient adsorbent for organic pollutants. In particular, the alkaline hydroxide catalyst helps to increase the SSA of carbon products, leading to a further improved adsorption capacity. On the other hand, p-toluenesulfonic acid (TsOH) catalyzed pyrolysis, which dramatically increased the L-CNS product yield, and provided a high-yield approach for the production of pollutant absorbent.

Bifunctional oxygen evolution and supercapacitor electrode with integrated architecture of NiFe-layered double hydroxides and hierarchical carbon framework.

Layered double hydroxide with exchangeable interlayer anions are considered promising electro-active materials for renewable energy technologies. However, the limited exposure of active sites and poor electrical conductivity of hydroxide powder restrict its application. Herein, bifunctional integrated electrode with a 3D hierarchical carbon framework decorated by nickel iron-layered double hydroxides (NiFe-LDH) is developed. A conductive carbon nanowire array is introduced not only to provide enough anchoring sites for the hydroxide, but also affords a continuous pathway for electron transport throughout the entire electrode. The 3D integrated architecture of NiFe-hydroxide and hierarchical carbon framework possesses several beneficial effects including large electrochemical active surfaces, fast electron/mass transport, and enhanced mechanical stability. The as-prepared electrode affords a current density of 10 mA cm-2 at a low overpotential of 269 mV for oxygen evolution reaction (OER) in 1 M of KOH. It also offers excellent stability with negligible current decline even after 2000 cycles. Besides, density functional theory calculations revealed that the (110) surface of NiFe-LDH is more active than the (003) surface for OER. Furthermore, the electrode possesses promising application prospects in alkaline battery-supercapacitor hybrid devices with a capacity of 178.8 mAh g-1 (capacitance of 1609.6 F g-1) at a current density of 0.2 A g-1. The viability of the as-prepared bifunctional electrode will provide a potential solution for wearable electronics in the near future.

Contributed Review: Instruments for measuring Seebeck coefficient of thin film thermoelectric materials: A mini-review.

Thin film thermoelectric materials (TF TEMs) based on organic semiconductors or organic/inorganic composites exhibit unique properties such as low-temperature processability, mechanical flexibility, great freedom of material design, etc. Thus they have attracted a growing research interest. Similar to inorganic bulk thermoelectric materials (IB TEMs), the Seebeck coefficient combined with electrical conductivity and thermal conductivity is a fundamental property to influence the performance of TF TEMs. However, due to the differences in material and sample geometries, the well-established characterization devices for IB TEMs are no longer applicable to TF TEMs. And until now, a universal standard of measuring the Seebeck coefficient of TF TEMs is still lacking. This mini-review presents the development of instruments designed for measuring the Seebeck coefficient of TF TEMs in the last decade. Primary measurement methods and typical apparatus designs will be reviewed, followed by an error analysis induced by instrumentation. Hopefully this mini-review will facilitate better designs for a more accurate characterization of the Seebeck coefficient of thin film thermoelectric materials.

Nanostructured thin lignin-derived carbon sheets as excellent reinforcement fillers in polypropylene.

In this article, natural alkali lignin was freeze-dried and then annealed at different temperatures to achieve lignin-derived carbons (LCs) with mesh-shape or sheet-like morphology, which were incorporated into polypropylene (PP) matrix by melt compounding. Owing to the significantly increased interfacial area and improved dispersion of the carbons in the polymer matrices, with the addition of only 2 wt% relatively low temperature annealed freeze-dried lignin-derived carbon (FD-LC), the obtained PP/LC composites show notably enhanced tensile mechanical properties, including markedly improved Young's modulus and remarkably increased elongation at break compared with those of neat PP. The enhancements brought by the nano-structured thin FD-LC sheets are far more impressive than that with the same loading of particulate as-received lignin-derived carbon (AR-LC). The FD-LC filled PP composites also have rough fractured surfaces with fiber pull-out near the interface, revealing the non-negligible toughening effect of the LC. In addition, the higher temperature annealed FD-LC filler induces the further reinforcement of the composites. For the FD-LC annealed at 900 °C, the corresponding composite possesses the highest Young's modulus of 668 MPa.

Formation of multilayers by star polyelectrolytes: effect of number of arms on chain interpenetration.

We have investigated the influence of number of arms on chain interpenetration in the growth of star poly[2-(dimethylamino)ethyl methacrylate] (PDEM)/star poly(acrylic acid) (PAA) multilayers using a quartz crystal microbalance with dissipation (QCM-D). The oscillations in the changes of dissipation and frequency reflect the chain interpenetration and the variation of the mass of multilayer, respectively. The QCM-D results demonstrate that the growth of multilayers has two different mechanisms in terms of chain interpenetration. That is, the arm chains of star PDEM insert into a predeposited PAA layer to form a swollen multilayer, but the complex of star PAA with predeposited star PDEM is an "octopus-like" structure forming a dense multilayer. The transition between these two penetration modes is controlled by the number of arms in the star polyelectrolytes. As the number of arms of either PAA or PDEM increases, it becomes more difficult for star PDEM to penetrate into the PAA layer, but star PAA can more easily penetrate into the PDEM layer. According to atomic force microscopy and water contact angle measurements, all eight-bilayer multilayer surfaces have similar roughness values, and the surface wettability of the multilayers is dominated by the outermost PDEM layer.

Effect of dehydration on the interfacial water structure at a charged polymer surface: negligible χ(3) contribution to sum frequency generation signal.

Interfacial water structure at charged surfaces plays a key role in many physical, chemical, biological, environmental, and industrial processes. Understanding the release of interfacial water from the charged solid surfaces during dehydration process may provide insights into the mechanism of protein folding and the nature of weak molecular interactions. In this work, sum frequency generation vibrational spectroscopy (SFG-VS), supplemented by quartz crystal microbalance (QCM) measurements, has been applied to study the interfacial water structure at polyelectrolyte covered surfaces. Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) chains are grafted on solid surfaces to investigate the change of interfacial water structure with varying surface charge density induced by tuning the solution pH. At pH ≤ 7.1, SFG-VS intensity is linear to the loss of mass of interfacial water caused by the dehydration of PDMAEMA chains, and no reorientation of the strongly bonded water molecules is observed in the light of χ(ppp)/χ(ssp) ratio. χ((3)) contribution to SFG signal is deduced based on the combination of SFG and QCM results. It is the first direct experimental evidence to reveal that the χ((3)) has a negligible contribution to SFG signal of the interfacial water at a charged polymer surface.