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Microfluidic fuel cells are a group of miniaturized fuel cells without membranes for operation. Their unique flow of the steams in a microchannel allows a parallel laminar flow without mixing with each other. We investigated the cell performance with different iron-based soluble salts as oxidants. The best performance was achieved by FeCl3 as the oxidant, achieving the highest power density of 192.71 mW cm-3 and the largest limiting current density of 883.33 mA cm-3 (normalized to the active electrode volume). And we optimized the performance of the FeCl3-based microfluidic fuel cell by adjusting the flow rates, HCl concentrations, and FeCl3 concentrations. The optimal flow rate was 20 mL h-1. Although the maximum power density of the cell with 4 M HCl and 0.5 M FeCl3 solution reached high values of 212.21 mW cm-3 and 250.42 mW cm-3, respectively, both cell performances were under mass transfer control at high current densities. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have been widely used in various applications, such as high-voltage sources, actuators, sensors, motors, frequency standard, vibration reducer, and so on. In the past decades, lead zirconate titanate (PZT) binary ferroelectric ceramics have dominated the commercial piezoelectric market due to their excellent properties near the morphotropic phase boundary (MPB), although they contain more than 60% toxic lead element. Here, we report a lead-free and one-composition molecular ferroelectric trimethylbromo-methylammonium tribromomanganese(II) (TMBM-MnBr3) with a large piezoelectric coefficient d33 of 112 pC/N along polar axis, comparable with those of typically one-composition piezoceramics such as BaTiO3 along polar axis [001] (∼90 pC/N) and much greater than those of most known molecular ferroelectrics (almost below 40 pC/N). More significantly, the effective local piezoelectric coefficient of TMBM-MnBr3 films is comparable to that of its bulk crystals. In terms of ferroelectric performance, it is the low coercive voltages, combined with the multiaxial characteristic, that ensure the feasibility of piezo film applications. Based on these, along with the common superiorities of molecular ferroelectrics like light weight, flexibility, low acoustical impedance, easy and environmentally friendly processing, it will open a new avenue for the exploration of nextgeneration piezoelectric devices in industrial and medical applications. [ABSTRACT FROM AUTHOR]

Following our recent finding of interesting dielectric and ferroelectric properties in semiconducting organic-inorganic layered perovskites (benzylammonium)2PbCl4 and (cyclohexylammonium)2PbBr4-4xI4x (x = 0-1), we designed a new layered perovskite-type crystal (cyclohexylmethylammonium)2CdCl4. By systematic characterizations, including differential scanning calorimetry measurements, dielectric measurements, and variable-temperature structural analysis, this crystal was found to undergo a reversible first-order phase transition at around Tc = 342 K. The origin of the phase transition is associated with the order-disorder change of the organic cation as expected. The phase transition is accompanied by the anticipated large dielectric constant change and remarkable dielectric anisotropy. These dielectric performances reveal potential application of the crystal as a high-temperature dielectric material. More interesting dielectric crystals are expected to be tailored in the future by taking advantage of the richness of layered perovskites. [ABSTRACT FROM AUTHOR]

Luminescence of ferroelectric materials is one important property for technological applications, such as low-energy electron excitation. However, the vast majority of doped inorganic ferroelectric materials have low luminescent efficiency. The past decade has envisaged much progress in the design of both ferroelectric and luminescent organic-inorganic hybrid complexes for optoelectronic applications. The combination of ferroelectricity and luminescence within organic-inorganic hybrids would lead to a new type of luminescent ferroelectric multifunctional materials. We herein report a hybrid molecular ferroelectric, (pyrrolidinium)MnCl3, which exhibits excellent ferroelectricity with a saturation polarization of 5.5 µC/cm² as well as intense red luminescence with high quantum yield of 56% under a UV excitation. This finding may extend the application of organic-inorganic hybrid compounds to the field of ferroelectric luminescence and/or multifunctional devices. [ABSTRACT FROM AUTHOR]

The one-dimensional organic-inorganic hybrid compound bis(cyclohexylammonium) tetrachlorocadmate(II) (1), in which the adjacent infinite [CdCl4]n- chains are connected to each other though Cd--Cl weak interactions to form perovskite-type layers of corner-sharing CdCl6 octahedra separated by cyclohexylammonium cation bilayers, was synthesized. It undergoes two successive structural phase transitions, at 215 and 367 K, which were confirmed by systematic characterizations including differential scanning calorimetry (DSC) measurements, variable-temperature structural analyses, and dielectric and second harmonic generation (SHG) measurements. A precise structural analysis discloses that the phase transition at 215 K is induced by the disorder-order transition of cyclohexylammonium cations, while the phase transition at 367 K derives from changes in the relative location of Cd atoms. Emphatically, both the dielectric constant and SHG intensity of 1 show a striking change between low and high states at around 367 K, which reveals that 1 might be considered as a potential dielectric and nonlinear optical (NLO) switch with high-temperature response characterization, excellent reversibility, and obvious change of states. [ABSTRACT FROM AUTHOR]

A microstructured fiber Bragg grating (MSFBG) was created to accurately and simultaneously monitor the cell growth of photosynthetic bacteria (PSB) Rhodopseudomonas palustris CQK 01 and the temperature in, a photobioreactor. The proposed sensor was made from an FBG unit that was separated into three regions, an unperturbed region, and two etched regions with smooth surfaces. The unperturbed grating region was employed to monitor the temperature. To eliminate the effects of the liquid concentration and temperature on the biomass, a polyimide-silica hybrid membrane was created and coated on an etched grating region to separate the liquids from the PSB; that is, this thinned region was developed to analyze the liquid concentration and temperature. Another etched grating region with a smaller diameter was used to determine the response to the temperature, biomass, and liquid concentration. In addition, two models were also presented to demonstrate accurate simultaneous measurement of the biomass and temperature. We discovered that the MSFBG sensor can rapidly and accurately determine the difference in the Bragg wavelength shifts caused by changes in the temperature, biomass, and liquid-phase concentration. The measured biomass is highly correlated with the real cell growth, with a correlation of 0.9438; the hydrogen production rate and temperature difference from metabolic heat production reached 1.97 mmol/L/h and 2.8 °C, respectively, in the PSB culture. [ABSTRACT FROM AUTHOR]

A layered organic-inorganic hybrid compound, tetra(cyclopentylammonium) decachlorotricadmate(II) (1), in which the two-dimensional [Cd3Cl10]4-n networks built up from three face-sharing CdCl6 octahedra are separated by cyclopentylammonium cation bilayers, has been discovered as a new phase transition material. It undergoes two successive structural phase transitions, at 197.3 and 321.6 K, which were confirmed by differential scanning calorimetry measurements, variable-temperature structural analyses, and dielectric measurements. The crystal structures of 1 determined at 93, 298, and 343 K are solved in P212121, Pbca, and Cmca, respectively. A precise analysis of the structural differences between these three structures reveals that the origin of the phase transition at 197.3 K is ascribed to the order-disorder transition of the cyclopentylammonium cations, while the phase transition at 321.6 K originates from the distortion of the two-dimensional [Cd3Cl10]4-n network. [ABSTRACT FROM AUTHOR]

A new simple fiber-optic evanescent wave sensor was created to accurately monitor the growth and hydrogen production performance of biofilms. The proposed sensor consists of two probes (i.e., a sensor and reference probe), using the etched fibers with an appropriate surface roughness to improve its sensitivity. The sensor probe measures the biofilm growth and change of liquid-phase concentration inside the biofilm. The reference probe is coated with a hydrophilic polytetrafluoroethylene membrane to separate the liquids from photosynthetic bacteria Rhodopseudomonas palustris CQK 01 and to measure the liquid concentration. We also developed a model to demonstrate the accuracy of the measurement. The biofilm measurement was calibrated using an Olympus microscope. A linear relationship was obtained for the biofilm thickness range from 0 to 120 μm with a synthetic medium under continuous supply to the bioreactor. The highest level of hydrogen production rate occurred at a thickness of 115 μm. [ABSTRACT FROM AUTHOR]

A new one-dimensional organic-inorganic material, 1,5-pentanediammonium pentabromoantimonate (III) (1), exhibits a centrosymmetric-to-non-centrosymmetric symmetry breaking phase transition at 366.5 K, showing a prominent second harmonic generation (SHG) response and dielectric anomalies. The differential scanning calorimetry results indicate the phase transition is a second-order one. The variable-temperature structural analyses reveal that the space group changes from Pnma at 393 K in the high-temperature phase to P212121 at 293 K in the low-temperature phase, accompanied by the loss of a symmetry plane and inversion center. The crystal structure is composed of one-dimensional zigzag chains of corner-sharing SbBr6 octahedra and 1,5-pentanediammonium cations. The origin of the phase transition can be attributed to both the deformation of the zigzag chains and the order-disorder transition of the 1,5-pentanediammonium cations. The compound is SHG-active below the transition temperature, demonstrating its second-order nonlinear optical properties. It is also SHG-inactive above the transition temperature, which further confirms the symmetry breaking phenomenon. These findings will pave a new way to explore organic-inorganic multifunctional phase transition material. [ABSTRACT FROM AUTHOR]

Coupling of ferroelectricity and optical properties has become an interesting aspect of material research. The switchable spontaneous polarization in ferroelectrics provides an alternative way to manipulate the light-matter interaction. The recent observation of strong photoluminescence emission in ferroelectric hybrid organic-inorganic compounds, (pyrrolidinium)MnX3 (X = Cl or Br), is an attractive approach to high efficiency luminescence with the advantages of ferroelectricity. However, (pyrrolidinium)MnX3 only displays ferroelectricity near or below room temperature, which limits its future applications in optoelectronics and multifunctional devices. Here, we rationally designed and synthesized high-temperature luminescent ferroelectric materials. The new hybrid compound (3-pyrrolinium)MnCl3 has a very high Curie temperature, Tc = 376 K, large spontaneous electronic polarization of 6.2 μC/cm², and high fatigue resistance, as well as high emission efficiency of 28%. This finding is a further step to the practical use of ferroelectric luminescence based on organic-inorganic compounds. [ABSTRACT FROM AUTHOR]