Photoactive Earth‐Abundant Iron Pyrite Catalysts for Electrocatalytic Nitrogen Reduction Reaction

The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO₂ emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth‐abundant iron pyrite (FeS₂) nanocrystals grown on carbon fiber paper (FeS₂/CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS₂/CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH₃ yield rate of ≈0.096 µg min^?1 at ?0.6 V versus RHE electrode in 0.25 m LiClO₄. During the electrochemical catalytic reaction, the crystal structure of FeS₂/CFP remains in the cubic pyrite phase, as analyzed by in situ X‐ray diffraction measurements. With near‐infrared laser irradiation (808 nm), the NH₃ yield rate of the FeS₂/CFP catalyst can be slightly improved to 0.1 µg min^?1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N₂ molecule has strong chemical adsorption energy on the iron atom of FeS₂. Overall, iron pyrite‐based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.     

Semiconductive Behavior of Polymer‐Derived SiCN Ceramics for Hydrogen Sensing

A low‐cost sensing mechanism of hydrogen gas is developed using polymer‐derived ceramic, a liquid organic precursor, polysilazane with the addition of 5 wt% of photoinitiator, 2,2 Dimethoxy‐2‐phenyl acephenone. UV photopolymerization is utilized to partially cross‐link the H‐shaped free standing specimen, and then pyrolyzed at 1400°C in hot isostatic press under nitrogen gas to convert the partially cross‐linked polymer into conducting and amorphous ceramic, silicon carbonitride. This work presents the preparation of free standing silicon carbonitride specimens as the sensor body for sensing hydrogen gas, depending on the semiconductive behavior of polymer‐derived ceramics in high‐temperature environments. The band gap of silicon carbonitride would be varied from adsorbing hydrogen molecules on the surface of the H‐shaped free standing specimen with two different thicknesses. An amenable specimen‐geometry for the four‐point test of measuring resistance is developed in a furnace filled with pure hydrogen and vacuumed environments.     

Biomimetic Engineering of a Scavenger‐Free Nitric Oxide‐Generating/Delivering System to Enhance Radiation Therapy

Nitric oxide (NO) is a potent tumor‐cell radiosensitizer but it can be readily scavenged by hemoglobin (Hb) in vivo. A biomimetic incubator that can generate and deliver NO in a scavenger (Hb)‐free environment to enhance its radiosensitizing effect to maximize its efficacy in radiotherapy is proposed. This NO incubator comprises a poly(lactic‐co‐glycolic acid) (PLGA) hollow microsphere (HM) that contains an NO donor (NONOate) and a surfactant molecule (sodium caprate, SC) in its aqueous core. In acidic tumorous environments, the PLGA shell of the HM allows the penetration of protons from the outside, activating the hydrolytic cleavage of NONOate, spontaneously generating NO bubbles, which are immediately trapped/stabilized by SC. The SC‐stabilized NO bubbles in the HM are then squeezed through the spaces of its PLGA matrices by the elevated internal pressure. Upon leaving the HM, the entrapped NO molecules may passively diffuse through their SC‐stabilized/protected layer gradually to the tumor site, having a long‐lasting radiosensitizing effect and inhibiting tumor growth. The entire process of NO generation and delivery is conducted in a scavenger (Hb)‐free environment, mimicking the development of young ovoviviparous fish inside their mothers' bodies in the absence of predators before birth.     

Modeling sediment impact on the transport of fecal bacteria

Sediment storage of fecal bacteria has been observed for a long time. However, limited modeling efforts have been conducted to dynamically and explicitly study the impact of sediment on the transport of fecal bacteria. In this paper, a modeling framework based on the Environmental Fluid Dynamics Code (EFDC) model has been proposed. Free and particle-associated fecal bacteria can be modeled explicitly using the developed model. A linear adsorption relationship is incorporated into the model to obtain a sediment concentration dependent attachment ratio. The deposition and resuspension fluxes of fecal bacteria across the sediment bed–water interface are calculated coupled with the sediment deposition and resuspension flux. The model was applied to hypothetical scenarios to evaluate the sediment impacts under ideal settling and resuspension conditions. A case study was provided to test the resuspension calculation of fecal bacteria under an artificial flooding condition. Using this model, the contributions of fecal bacteria from sediment bed and from the watershed can be modeled separately and explicitly.     

Nanostructured alignment layer for liquid crystals

A new type of nanostructured alignment surface is proposed and demonstrated. As in previous nanostructured alignment surfaces, a large pretilt angle of near 45° can be produced reliably. Moreover, this new structure is fabricated with a mask, and there is no randomness involved. The uniformity and anchoring properties of this new surface have been measured to be of excellent quality.     

Nonlinear system identification using BBO-based multilayer perceptron network method

Microsystem Technologies - Recently, nonlinear system identification has received increasingly more attention due to its promising applications in engineering fields. It has become a challenging...     

Ink drop filling by a slot coating die for an electrowetting display panel

Ink drops have to be filled into the square cells for an electrowetting display panel. Several ink solutions such as dodecane, tetradecane, and hexadecane were used as test liquids. These fluids have viscosities less than 4 mPas and surface tensions between 23.3 and 26 mN/m and contact angles less than 50°. A slot coating die was employed to deliver these liquids to fill up the square cells. The effects of several parameters such as coating thickness and coating speed were examined. Operating windows inside which the stable filling is possible could be found for these liquids. Several defects were observed outside the operating windows. A flow visualization technique was applied to observe the fluid motion in the coating bead region, particularly the movements of upstream and downstream menisci, the mechanism of liquid filling was discussed.