Chia Yun Chen

The chemically crosslinked metal-complexed chitosans for comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in aqueous medium

The chemically crosslinked metal-complexed chitosans were synthesized by using the ion-imprinting method from a chitosan with four metals (Cu(II), Zn(II), Ni(II) and Pb(II)) as templates and glutaraldehyde as a crosslinker. The influences of adsorption conditions, including molar ratios of crosslinker/chitosan and pH changes, were studied. They were used to investigate for comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in an aqueous medium. They were demonstrated the comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in the orders of the adsorbed amounts with templates: Cu(II) approximately Pb(II)>Zn(II) approximately Ni(II), Zn(II)>Cu(II) approximately Pb(II)>Ni(II), Ni(II)>Pb(II)>Zn(II)>Cu(II) and Pb(II) approximately Cu(II)>Zn(II)>Ni(II), respectively. In addition, the dynamical study showed to be well followed the second-order kinetic equation in the adsorption process. At the same time, the equilibrium adsorption data were fitted in three adsorption isotherm models, namely, Langmuir, Freundlich, and Dubinin-Radushkevich to show very good fits in the Langmuir isotherm equation for the monolayer adsorption process. The most important aspect of the chemically crosslinked metal-complexed chitosans with glutaraldehyde demonstrated to afford a higher adsorption capacity, and a more efficient adsorption toward metals in an aqueous medium.

Asymmetric coupling between subradiant and superradiant plasmonic resonances and its enhanced sensing performance

We present symmetric and asymmetric couplings within a pair of split-ring resonators (SRRs). The former shows a single transmittance dip, following the equivalent circuit model; yet, the latter introduces an additional transmittance peak, stemming from an asymmetrically coupled resonance (ACR) between the subradiant and superradiant modes. The mechanism of such induced transparency is elucidated well by the suppression of induced currents within the SRR element with a lower quality factor. Finally, the excitation of ACR is further associated with remarkable confinement of electromagnetic field, providing a compelling sensing performance based on its excellent sensitivity and figure of merit.

Biosorption of Cu(II), Zn(II), Ni(II) and Pb(II) ions by cross-linked metal-imprinted chitosans with epichlorohydrin

Cross-linked metal-imprinted chitosan microparticles were prepared from chitosan, using four metals (Cu(II), Zn(II), Ni(II), and Pb(II)) as templates, and epichlorohydrin as the cross-linker. The microparticles were characterized by Fourier transform infrared spectroscopy, solid state (13)C nuclear magnetic resonance spectroscopy, and energy-dispersive X-ray spectroscopy. They were used for comparative biosorption of Cu(II), Zn(II), Ni(II) and Pb(II) ions in an aqueous solution. The results showed that the sorption capacities of Cu(II), Zn(II), Ni(II), and Pb(II) on the templated microparticles increased from 25 to 74%, 13 to 46%, 41 to 57%, and 12 to 43%, respectively, as compared to the microparticles without metal ion templates. The dynamic study showed that the sorption process followed the second-order kinetic equation. Three sorption models, Langmuir, Freundlich, and Dubinin-Radushkevich, were applied to the equilibrium isotherm data. The result showed that the Langmuir isotherm equation best fitted for monolayer sorption processes. Furthermore, the microparticles can be regenerated and reused for the metal removal.

Competitive biosorption of azo dyes from aqueous solution on the templated crosslinked-chitosan nanoparticles.

The nanoparticles of templated crosslinked chitosan, ECH-RB5 and ECH-3R, were prepared through the imprinting process using Remazol Black 5 (RB5) and Remazol Brilliant Orange 3R (3R) dyes, respectively, as templates and ECH as a crosslinker. The nanoparticles exhibited significantly higher adsorption capacities of the dyes than other nanoparticles formed without a dye template and with three crosslinkers (ECH, GLA, and EGDE). The adsorption of the dyes on the nanoparticles was affected by the initial pH, dye concentration, and temperature. The results were in accordance with the second-order and the Langmuir adsorption models. Meanwhile, the E values of the dyes calculated using the Dubinnin-Radushkevich model revealed that the adsorption process may be due to the dual nature of the process, physisorption and chemisorption, and that adsorption was predominant in the chemisorption process. The adsorption processes in the nanoparticles were spontaneous and exothermic. Moreover, competition adsorption through analysis of the intraparticle diffusion model apparently favored the 3R dye more than the RB5 dye on the nanoparticles in mixture solution B. The nanoparticles for the adsorption of the dyes were regenerated efficiently through the alkaline solution and were then reused for dye removal.

The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications.

Experimental verification of standing-wave plasmonic resonances in split-ring resonators

We experimentally demonstrate multiple resonances in split-ring resonators (SRRs) from direct electric excitations in midinfrared and near infrared regions. The ratio of the entire length of SRRs to the resonance modes and wavelengths presents a clear linear relationship. Such expression validates in both cases of electric and magnetic responses in SRRs excited by electric field and is further confirmed by examining the SRRs with different lengths. Therefore, our quantitative observations indicate that the multiple resonances can be interpreted by the standing-wave plasmonic resonances and further facilitate to design the desired operation frequencies and responses of SRRs for practical applications.

Recognition of molecularly imprinted polymers for a quaternary alkaloid of berberine

Selective and affinitive imprinted polymers incorporating a quaternary alkaloid of berberine (BER) were prepared using a non-covalent imprinting method. The results showed that, compared to other imprinted polymers, the polymer AD-10 had not only a higher of the ratio of Q(MIP)/Q(BP) for BER adsorption, and but also a larger of the ratio of Q(MIP,B)/Q(MIP,P) for BER and palmatine (PAL) adsorptions. Spectrophotometric analysis demonstrated that a 1:1 cooperative hydrogen-bonding complex might be predominating in the pre-polymerization between the BER template and AA monomer. Adsorption experiments of BER on the polymer AD-10 were in accordance with the second-order and Langmuir adsorption models. The E value (5.70 kJ/mol) calculated from the Dubinin-Radushkevich model indicated that the adsorption followed a physisorption process. In addition, a Scatchard plot showed a single straight line with an equilibrium dissociation constant (K(D)) of 65.80 μmol/L. SPE analyses of a mixture of BER and PAL and the methanol extract from the cortices of Phellodendron wilsonii showed that AD-10 had more efficiency, and higher specificity and selectivity for SPE in the concentration and determination of BER and its extraction from natural products.

Inducing transparency with large magnetic response and group indices by hybrid dielectric metamaterials

We present metamaterial-induced transparency (MIT) phenomena with enhanced magnetic fields in hybrid dielectric metamaterials. Using two hybrid structures of identical-dielectric-constant resonators (IDRs) and distinct-dielectric-constant resonators (DDRs), we demonstrate a larger group index (ng~354), better bandwidth-delay product (BDP~0.9) than metallic-type metamaterials. The keys to enable these properties are to excite either the trapped mode or the suppressed mode resonances, which can be managed by controlling the contrast of dielectric constants between the dielectric resonators in the hybrid metamaterials.

Tailoring Broadband Antireflection on a Silicon Surface through Two-Step Silver-Assisted Chemical Etching

Combined nanostructure arrays with tailored structural profiles are presented (see picture, GN: graded nanostructure). These arrays exhibit a sharp decrease in reflectivity when submitted to strong sunlight irradiation, showing great potential for diverse applications, such as optical and electro-optical devices and other antireflection designs.

PHOTOCATALYTIC DECOLORIZATION OF REMAZOL BLACK 5 AND REMAZOL BRILLIANT ORANGE 3R BY MESOPOROUS TIO2

Mesoporous TiO2 microparticles (TiO2-11) were prepared through the micelle hydrothermal method using a 1:1 M ratio of 1-tetradecylamine:Ti(OiPr)4. TiO2-11 microparticles exhibited significantly higher decolorization percentage of Remazol Black 5 (RB5) and Remazol Brilliant Orange (3R) dyes than other TiO2 microparticles formed with different molar ratios of 1-tetradecylamine:Ti(OiPr)4, and P25 and anatase TiO2. The results showed that the decolorization of the dyes by the microparticles was affected by the different irradiation wavelengths, catalyst dosages, dye concentrations, initial pH values, as well as electron acceptors. The kinetic experiments with varying initial pH values were in accordance with the second-order model. In addition, the adsorption study of the dyes in the dark fitted well with the Langmuir isotherm model. With the addition of 20 mmol/mL of three electron acceptors, H2O2, KBrO3, and (NH4)2S2O8, the decolorization of the RB5 and 3R dyes increased by 54% and 35%, 59% and 41%, and 36% and 33%, respectively. Hence, this technique for the preparation of the mesoporous TiO2 microparticles can facilitate more efficient decolorization of dyes in an aqueous solution.