The optical memristive switches are electrically activated optical switches that can memorize the current state. They can be used as optical latching switches in which the switching state is changed only by applying an electrical Write/Erase pulse and maintained without external power supply.We demonstrate an optical memristive switch based on a silicon MMI structure covered with nanoscale-size Ge2Sb2Te5 (GST) material on top. The phase change of GST is triggered by resistive heating of the silicon layer beneath GST with an electrical pulse. Experimental results reveal that the optical transmissivity can be tuned in a controllable and repeatable manner with the maximum transmission contrast exceeding 20 dB. Partial crystallization of GST is obtained by controlling the width and amplitude of the electric pulses. Crucially, we also demonstrate that both Erase and Write operations, to and from any intermediate level, are possible with accurate control of the electrical pulses. Our work marks a significant step forward towards realizing photonic memristive switches without static power consumption, which are highly demanded in highdensity large-scale integrated photonics.

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Low-power reconfigurable optical circuits are highly demanded to satisfy a variety of different applications. Conventional electro-optic and thermo-optic refractive index tuning methods in silicon photonics are not suitable for reconfiguration of optical circuits due to their high static power consumption and volatility. We propose and demonstrate a nonvolatile tuning method by utilizing the reversible phase change property of GST integrated on top of the silicon waveguide. The phase change is enabled by applying electrical pulses to the lm-sized GST active region in a sandwich structure. The experimental results show that the optical transmission of the silicon waveguide can be tuned by controlling the phase state of GST.

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This research deals with the modeling and experimental verification of polychlorinated biphenyl (PCB) dechlorination using a porous membrane reactor embedded with Fe/Pd nanoparticles. We synthesized core/shell Fe/Pd nanoparticles in polyvinylidene fluoride (PVDF) microfiltration membranes functionalized with poly(acrylic acid) (PAA). PAA functionalization was achieved by in situ free radical polymerization of acrylic acid in microfiltration membrane pores. Target ferrous ions were then introduced into the membranes by the ion exchange process. Subsequent reduction resulted in the in situ formation of 20-40 nm Fe nanoparticles. Bimetallic nanoparticles can be formed by post-deposition of Pd. The membranes and Fe/Pd nanoparticles were characterized by thermogravimetric analyzer (TGA), FTIR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). 2,2′-Dichlorobiphenyl (PCB4) and 3,3′,4,4′-tertrachlorobiphenyl (PCB77) were chosen as the model compounds to investigate the catalytic properties of bimetallic nanoparticles, the reaction mechanism, and the intrinsic kinetics. A two-dimensional steady-state model was developed to correlate and simulate mass transfer and reaction in the membrane pores under pressure-driven convective flow conditions. The 2D model equations were solved by a finite element technique. The influence of changing parameters such as reactor geometry (i.e., membrane pore size) and Pd coating composition were evaluated by the model and compared well with the experimental data.

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Palladium-based nanoparticles immobilized in polymeric matrices were applied to the reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) at room temperature. Two different dechlorination platforms were evaluated using (1) Pd nanoparticles within conductive polypyrrole films; or (2) immobilized Fe/Pd nanoparticles within polyvinylidene fluoride microfiltration membranes. For the first approach, the polypyrrole film was electrochemically formed in the presence of perchlorate ions that were incorporated into the film to counter-balance the positive charges of the polypyrrole chain. The film was then incubated in a solution containing tetrachloropalladate ions, which were exchanged with the perchlorate ions within the film. During this exchange, reduction of tetrachloropalladate by polypyrrole occurred, which led to the formation of palladium nanoparticles within the film. For the second approach, the membrane-supported Fe/Pd nanoparticles were prepared in three steps: polymerization of acrylic acid in polyvinylidene fluoride microfiltration membrane pores was followed by ion exchange of Fe(2+), and then chemical reduction of the ferrous ions bound to the carboxylate groups. The membrane-supported iron nanoparticles were then soaked in a solution of tetrachloropalladate resulting in the deposition of Pd on the Fe surface. The nanoparticles prepared by both approaches were employed in the dechlorination of PCB77. The presence of hydrogen was required when the monometallic Pd nanoparticles were employed. The results indicate the removal of chlorine atoms from PCB77, which led to the formation of lower chlorinated intermediates and ultimately biphenyl. Toxicity associated with vascular dysfunction by PCB77 and biphenyl was compared using cultured endothelial cells. The data strongly suggest that the dechlorination system used in this study markedly reduced the proinflammatory activity of PCB77, a persistent organic pollutant.