Browsing by Issue Date, starting with "2019-10-02"

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Algogenic organic matter derived DBPs: Precursor characterization, formation, and future perspectives - A review
(2019-10-02)
Hua, Lap-Cuong
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Lai, Chun-Hsi
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Wang, Gen-Shuh
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Lin, Tsair-Fuh
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Huang, Chihpin
Algogenic organic matter (AOM) in water is a critical issue for sustainable treatment of drinking water, especially when algal eutrophication occurs because it is not amenable to removal by traditional coagulation/sedimentation/filtration processes. AOM is thus proved as a major precursor of disinfection by-products (DBPs). Its occurrence in water is undesirable and impacts the safety of drinking water. This review paper aims to broaden our current knowledge on the formation of AOM-derived DBPs and its precursor characterization. The future perspectives of research needs on AOM-DBP precursor characterization for an effective prediction are also given by this review. AOMs from various algal species have high-yielding potentials to produce both carbonaceous and nitrogenous DBPs upon chlorination, especially for the intracellular OM (IOM) from the algal cell. The practical treatment of eutrophic water with preoxidation thus should be used in caution to avoid the release of IOM from ruptured cells. Characterization of the physiochemical properties, such as basic parameters, optical properties, molecular weight distribution, and chemical functional groups, of AOM can give advantages for the better understanding of AOM-derived DBPs. Among the characterization tools, the fluorescent technique is highly recommended for the application of AOM-DBP prediction.
Highly durable and flexible gallium-based oxide conductive-bridging random access memory
(2019-10-02)
Gan, Kai-Jhih
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Liu, Po-Tsun
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Chien, Ta-Chun
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Ruan, Dun-Bao
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Sze, Simon M.
The flexible conductive-bridging random access memory (CBRAM) device using a Cu/TiW/Ga2O3/Pt stack is fabricated on polyimide substrate with low thermal budget process. The CBRAM devices exhibit good memory-resistance characteristics, such as good memory window (>10(5)), low operation voltage, high endurance (>1.4 x 10(2) cycles), and large retention memory window (>10(5)). The temperature coefficient of resistance in the filament confirms that the conduction mechanism observed in the Ga2O3 layer is similar with the phenomenon of electrochemical metallization (ECM). Moreover, the performance of CBRAM device will not be impacted during the flexibility test. Considering the excellent performance of the CBRAM device fabricated by low-temperature process, it may provide a promising potential for the applications of flexible integrated electronic circuits.
Computational Study on the Mechanisms and Rate Constants for the O(P-3,D-1) + OCS Reactions
(2019-10-03)
Chen, Hsin-Tsung
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Pham, Tien, V
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Lin, M. C.
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交大名義發表
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應用化學系
The mechanisms and kinetics of O(P-3,D-1) + OCS(X-1 Sigma(+)) reactions have been studied by the high-level G2M(CC2) and CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) methods in conjunction with the transition-state theory and variational Rice-Ramsperger-Kassel-Marcus theory calculations. The result shows that the triplet surface proceeds directly by abstraction and substitution channels to produce SO(P-3) + CO(X-1 Sigma(+)) and S(P-3) + CO2(X-1 Sigma(+)(g)) bypassing the barriers of 7.6 and 9.1 kcal.mol(-1) at the G2M(CC2)//B3LYP/6-311+G(3df) level, respectively, while two stable intermediates, LM1 (OSCO1) and LM2 (SC(O)O-1), are formed barrierlessly from O(D-1 ) + OCS(X-1 Sigma(+)) in the singlet surface, which lie at -40.5 and -50.1 kcal.mol(-1) relative to O(P-3) + OCS(X-1 Sigma(+)) reactants and decompose to CO (X-1 Sigma(+)) + SO (a(1)Delta) and S(D-1) + CO2(X-1 Sigma g(+)). LM1 and LM2 may also be produced by singlet-triplet surface crossings via MSX1 and MSX2; the predicted total rate constant for the O(P-3) + OCS(X-1 Sigma(+)) reaction including the crossings, 9.2 X 10(-11) exp(-5.18 kcal-mol(-1)/RT) cm(3) molecule(-1) s(-1), is in good agreement with available experimental data. The branching ratio of the CO2 product channel, 0.22-0.32, between 1200 and 1600 K, is also in excellent agreement with the value of 0.2-0.3 measured by Isshiki et al. (J. Phys. Chem. A. 2003, 107, 2464).
Design of a digit-serial multiplier over GF(2(m)) using a karatsuba algorithm
(2019-10-03)
Lee, Trong-Yen
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Liu, Min-Jea
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Huang, Chia-Han
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Fan, Chia-Chen
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Tsai, Chia-Chun
A Karatsuba algorithm (KA) is used for highly accurate multiplication using a divide and conquer approach. A new approach to a polynomial digit-serial multiplier that uses an optimal digit size (d) for KA decomposition has recently been proposed. In this study, the proposed architecture uses three small multipliers to derive an optimal digit size (d) for the case of trinomial based fields. Using the proposed KA decomposition, this study establishes five types of sub-quadratic multipliers, which are, the recombined m-bit exponentiation multipliers using a KA. The theoretical results show that the proposed polynomial exponentiation multipliers that use a KA have a value of (d x m)/2 and involve significantly less time and area complexity than existing digit-serial multipliers. The simulation results for the proposed method demonstrate a respective 68.20%, 77.37%, 72%, 83.18%, 36.66% decrease in area x time over GF(2(36)), GF(2(84)), GF(2(126)), GF(2(204)) and GF(2(340)).
Pharmacokinetics and pharmacodynamics of pegylated interferon for the treatment of hepatitis B
(2019-10-03)
Yeh, Ming-Lun
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Huang, Jee-Fu
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Dai, Chia-Yen
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Yu, Ming-Lung
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Chuang, Wan-Long
Introduction: Interferon (IFN) had both antiviral and immunomodulatory effects, and was one of the approved treatments for hepatitis B virus (HBV). Herein, we reviewed the pharmacokinetics and pharmacodynamics of pegylated IFN-? (PegIFN-?) for the treatment of HBV. Areas covered: The steady-state serum levels of PegIFN-? were reached within 5 to 8?weeks, and the week 48 mean trough concentrations were approximately 2-fold higher than week 1. There was also no difference of the pharmacokinetics in male or female, healthy volunteers or patients with hepatitis B or C infection. PegIFN-? did not affect the metabolism of the cytochrome P450 (CYP) isozymes, except inhibition of CYP1A2. There was also no pharmacokinetic interaction between PegIFN-? and HBV nucleot(s)ide analogues (NUCs). Forty-eight weeks of PegIFN-? achieved 32% of HBeAg seroconversion, 32-43% of HBV DNA suppression, 41-59% of ALT normalization, and 3% of HBsAg seroconversion rate with a post-treatment durable response up to 80% in the initial responders. Expert opinion: On-treatment HBsAg titer guided the treatment of HBV with PegIFN-?. The recommendation of PegIFN-? and NUC combination or switch remained controversial. New immunotherapeutic agents are now in development. Although, PegIFN-? should continue to play a role in the treatment of HBV.
Schur method for robust pole assignment of descriptor systems via proportional plus derivative state feedback
(2019-10-03)
Guo, Zhen-Chen
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丘成桐中心
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Shing-Tung Yau Center
The pole assignment problem for descriptor systems is a classical inverse algebraic eigenvalue problem, which has attracted attention for decades. In this paper, we propose a direct method to solve the problem with the application of the proportional plus derivative state feedback, intending to obtain a robust closed-loop system. Theorems on the feasibility of our method will be presented. Numerical examples show that our method yields poles of high relative accuracy.
Synthesis and mesomorphic behaviors of a series of heterocyclic pyridine-imine-ester based liquid crystals
(2019-10-03)
Foo, K. -L.
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Ha, S. -T.
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Yeap, G. -Y.
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Lin, H. -C.
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材料科學與工程學系
A series of new calamitic liquid crystals, 4-{[(5-methylpyridin-2-yl)imino]methyl}phenyl 4-alkoxybenzoates were synthesized. This series consists of nine members wherein they are differed by the length of alkoxy chain. Spectral analysis results were in accordance with the expected structure. Their thermotropic behaviors were analyzed with Differential Scanning Calorimetry (DSC), Polarizing Optical Microscopy (POM) and powder X-ray diffraction techniques. First member with the shortest alkoxy chain (n = 2) is a non-mesogen. As the alkoxy chain increased to n = 4, the monotropic nematic phase appeared. An enantiotropic mesophase (nematic) was observed for the following three members (n = 6, 8, 10). As the alkoxy chain increased to n = 12, enantiotropic nematic phase exhibited together with monotropic smectic A (SmA) phase. As the alkoxy chain continuously increased to n = 14 and 16, enantiotropic phases were observed for both N and SmA. When moving to n = 18, the nematic phase disappeared and this compound only exhibited a single mesophase (SmA).
Ge nanodot-mediated densification and crystallization of low-pressure chemical vapor deposited Si3N4 for advanced complementary metal-oxide-semiconductor photonics and electronics applications
(2019-10-04)
Peng, Kang-Ping
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Huang, Tsung Lin
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George, Tom
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Lin, Horng-Chih
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Li, Pei-Wen
A new phenomenon of highly localized, nanoscale densification and crystallization of silicon-nitride (Si3N4) layers has been observed. A drastic reduction in the thermal budget (temperature and processing time) for local densification and even nanocrystallization of low-pressure chemical vapor deposited amorphous Si3N4 layers is mediated by the presence of Ge, Si, and O interstitials in close proximity to the Si3N4. The enhancement of localized densification and nanocrystallization observed in Si3N4 layers appears to be catalyzed by proximal Ge quantum dots (QDs) 'migrating' through the Si3N4/Si layers and are influenced by the oxidation time and Ge QD size. Implications of the highly localized, nanoscale densification and crystallization of silicon-nitride (Si3N4) layers for photonic and electronic device applications are discussed.
Different spreading speeds in a weak competition model with two free boundaries
(2019-10-05)
Wu, Chang-Hong
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應用數學系
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Department of Applied Mathematics
In this paper, we focus on the spreading behavior of a two-species weak competition system with two free boundaries in a spherically symmetric setting. This model may describe how two weakly competing species spread into the right empty space. When both two species spread successfully and one species cannot keep pace with the other one, it can be expected that two species spread asymptotically in a linear fashion but spread with different speeds. By the help of a semi-wave system and a construction of supersolution and subsolution, we establish the precise spreading speeds and population distribution of two weakly competing species, which provides a new spreading behavior. (C) 2019 Elsevier Inc. All rights reserved.
Vertical GaN-on-GaN PIN diodes fabricated on free-standing GaN wafer using an ammonothermal method
(2019-10-05)
Chen, Sung-Wen Huang
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Wang, Hao-Yu
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Hu, Cong
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Chen, Yong
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Wang, Hao
We report vertical GaN-on-GaN PIN diodes with a record high figure-of-merit (V-BR(2)/R-on) of 29.7 GW/cm(2) on free-standing GaN wafer using a complementary metal-oxide-semiconductor (CMOS) compatible contact materials. Due to the low substrate resistivity, low contact resistance, and high quality of GaN drift layer, a low on-state resistance R(on )of 0.31 m Omega cm(2) is obtained. With integrating of the metal filed plate structure in the vertical device, the peak electrical field along the GaN mesa edge can be significantly reduced, thus leading to a high breakdown voltage V-BR of 3.04 kV. The vertical GaN-on-GaN PIN diodes in this work show turn-on voltage V-on of similar to 3.4 V, on/off current ratio of similar to 1.3 x 10(7), and ideal factor n of similar to 2.2. According to the reverse switching measurement, the reverse recovery time T-rr. (reverse recovery charge Q(rr)) is 22.8 ns (4.8 nC) and 24.0 ns (5.4 nC), respectively, under a testing temperature of 300 K and 500 K. (C) 2019 Elsevier B.V. All rights reserved.
Constructing bridged multifunctional calixarenes by intramolecular indole coupling
(2019-10-07)
Bolshchikov, Boris
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Volkov, Sergey
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Sokolova, Dania
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Gorbunov, Alexander
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Serebryannikova, Alina
2,2 '-Bisindole units are suggested as new bridging motifs which can be easily created at calixarene cores. In TFA solutions, calix[4]arenes having pairs of indole groups originating from tryptamine or tryptophan residues are converted selectively into macrocycles bridged by indolylindoline moieties. The latter are easily transformed into fluorescent 2,2 '-bisindole bridges upon oxidation. The coupling/oxidation sequence works fine at bridging the cavities of the cone and 1,3-alternate (thia)calix[4]arenes in their distal positions. Ester groups, triazole units and crown ether loops, which are practically important functionalities in calixarene chemistry, are compatible with the bridging strategy thus making available diverse calixarene-based hosts comprising novel features provided by the 2,2 '-bisindole bridges. Of them the abilities to self-assembly and to bind anions through multiple hydrogen bonds were observed by X-ray crystallography, fluorescence measurements, and NMR experiments. When combined with a cation-binding site, the 2,2 '-bisindole units can turn the calixarene molecules into heteroditopic receptors being able to stabilize the anionic parts of the ion pairs. This feature was assessed by using the 1,3-alternate calix[4]arene having the 2,2 '-bisindole bridge and the crown-5-ether loop which was found to form neutral complexes with potassium acetate or potassium benzoate.
Insight into the Catalytic Effects of Open Metal Sites in Metal - Organic Frameworks on Hydride Dehydrogenation via Nanoconfinement
(2019-10-07)
Wu, Yi-Ju
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Wang, Cheng-Yu
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材料科學與工程學系
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Department of Materials Science and Engineering
Chemical hydride ammonia borane (AB, NH3BH3) draws attentions as a hydrogen storage medium for its high hydrogen capacity (19.6 wt %) and good thermal stability at ambient environments. However, high hydrogen generation temperatures and slow kinetics limit AB practical applications. One way to overcome the obstacles is the nanoconfinement effect: AB incorporated with porous materials has facilitated dehydrogenation process. However, the mechanism is still under debate, and several factors have been proposed, like hydride nanosize or catalytic environments controlled/provided by microporous supports. In this research, metal organic frameworks (MOFs) of Cu-BDC (BDC = benzenedicarboxylate) with/without manipulated active open metal sites by solvent removal/capping are applied for AB thermolysis via nanoconfinement. Both AB@MOFs show the same dehydrogenation peaked temperature regardless of catalytic environments, strengthening the theory that high surface tension from hydride nanosize controlled by MOF microporosity results in reduced dehydrogenation temperature. In addition, compared to solvent-capped MOFs, Cu-BDC with copper open metal sites eliminates byproduct emission and hence increases hydrogen yield from AB and also decreases dehydrogenation activation energy considerably. However, short cycle life due to copper reduction is observed in desolvated Cu-BDC, while lowered dehydrogenation temperature can be kept in solvated MOFs. In general, we clarify possible mechanisms and factors to hydride nanoconfinement and catalysis that improve AB dehydrogenation temperature and kinetics and provide new strategies for future hydride composite materials design.
Long-term Prognostic Value of Estimated Plasma Volume in Heart Failure with Preserved Ejection Fraction
(2019-10-07)
Huang, Chen-Yu
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Lin, Ting-Tse
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Wu, Yi-Fan
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Chiang, Fu-Tien
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Wu, Cho-Kai
Plasma volume, estimated by several indirect methods, has been viewed as a biological surrogate for intravascular fluid status. The clinical implication of estimated plasma volume status (ePVS) for long term outcomes in heart failure with preserved ejection fraction (HFpEF) remains unclear. We investigate the prognostic value of ePVS calculated by Strauss formula and its association with cardiovascular events and mortality in a prospective HFpEF cohort. There were 449 individuals met the inclusion criteria of our cohort. Estimated plasma volume variation (Delta ePVS) and its instantaneous derivatives were calculated by the Strauss formula. Our study endpoints were events of heart failure hospitalization and mortality. Kaplan-Meier estimates and Cox regression analysis were applied to determine the power of Delta ePVS and baseline ePVS in predicting long term cardiovascular outcomes. Both baseline ePVS and Delta ePVS were independent predictors of heart failure hospitalization and mortality. Kaplan-Meier estimates of these outcomes stratified by optimal cut-off value showed that HFpEF individuals with higher baseline ePVS and Delta ePVS were associated with elevated risk of composite endpoint of heart failure hospitalization and mortality. This study demonstrated the prognostic value of a novel biological surrogate, instantaneous derivatives ePVS, in predicting long term cardiovascular outcomes in HFpEF population. Monitoring instantaneous plasma volume may assist in identifying patients at high risk for future cardiovascular events. Further prospective studies validating the role of ePVS in predicting long-term prognosis in patients with HFpEF are warranted.
Hydrogen plasma-treated MoSe2 nanosheets enhance the efficiency and stability of organic photovoltaics
(2019-10-07)
Wang, Hao-Cheng
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Lin, Yu-Che
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Chen, Chung-Hao
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Huang, Chi-Hsien
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Chang, Bin
In this paper we report the effect on the power conversion efficiency (PCE) and stability of photovoltaic devices after incorporating hydrogenated two-dimensional (2D) MoSe2 nanosheets into the active layer of bulk heterojunction (BHJ) organic photovoltaics (OPV). The surface properties of 2D MoSe2 nanosheets largely affect their dispersion in the active layer blend and, thus, influence the carrier mobility, PCE, and stability of corresponding devices. We treated MoSe2 nanosheets with hydrogen plasma and investigated their influence on the polymer packing and fullerene domain size of the active layer. For the optimized devices incorporating 37.5 wt% of untreated MoSe2, we obtained a champion PCE of 9.82%, compared with the champion reference PCE of approximately 9%. After incorporating the hydrogen plasma-treated MoSe2 nanosheets, we achieved a champion PCE of 10.44%-a relative increase of 16% over that of the reference device prepared without MoSe2 nanosheets. This PCE is the one of the highest ever reported for OPVs incorporating 2D materials. We attribute this large enhancement to the enhanced exciton generation and dissociation at the MoSe2-fullerene interface and, consequently, the balanced charge carrier mobility. The device incorporating the MoSe2 nanosheets maintained 70% of its initial PCE after heat-treatment at 100 degrees C for 1 h; in contrast, the PCE of the reference device decreased to 60% of its initial value-a relative increase in stability of 17% after incorporating these nanosheets. We also incorporated MoSe2 nanosheets (both with and without treatment) into a polymer donor (PBDTTBO)/small molecule (IT-4F) acceptor system. The champion PCEs reached 7.85 and 8.13% for the devices incorporating the MoSe2 nanosheets with and without plasma treatment, respectively-relative increases of 8 and 12%, respectively, over that of the reference. These results should encourage a push toward the implementation of transition metal dichalcogenides to enhance the performances of BHJ OPVs.
Ionic Liquids with Various Constituent Ions To Optimize Non-Enzymatic Electrochemical Detection Properties of Graphene Electrodes
(2019-10-07)
Xie, Jian-De
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Wang, Chueh-Han
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Patra, Jagabandhu
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Rath, Purna Chandra
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Gandomi, Yasser Ashraf
Palladium (Pd) nanoparticles, ionic liquids (ILs), or both are integrated with graphene sheets to serve as an electrochemical sensor for detecting various bio-species. Ascorbic acid (AA), uric acid (UA), and dopamine (DA) are used as the model analytes. To assess the effects of the constituent ions of ILs on sensing properties, various ILs, namely, EMI-SCN, EMI-DCA, BMP-DCA, BMI-PF6, EMI-NTF2, and BMP-NTF2, are investigated. The results demonstrate that the graphene/IL electrode shows superior detection sensitivity compared to those of the graphene/Pd and graphene/Pd/IL electrodes. Interestingly, the IL anions are found to play a crucial role in sensing performance. Angle-resolved X-ray photoelectron spectroscopy reveals that graphene can create an aligned cation/anion orientation in the adsorbed IL film, with the anions preferentially occupying the topmost surface, thus dominating the interaction with analytes. The graphene/EMI-SCN electrode shows the highest sensitivity among the electrodes, 1.49 mu A mu M-1 cm(-2), and a detection limit of 0.11 mu M toward DA. Even with large excesses of AA and UA, the concentration of DA can be effectively detected.
Tuning of Na+ Concentration in an Ionic Liquid Electrolyte to Optimize Solid-Electrolyte Interphase at Microplasma-Synthesized Graphene Anode for Na-Ion Batteries
(2019-10-07)
Luo, Xu-Feng
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Chiang, Wei-Hung
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Su, Ching-Yuan
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Wu, Tzi-Yi
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Majumder, S. B.
Two-dimensional (2D) materials are promising anodes for Na-ion batteries owing to their unique architectures and tunable physiochemical properties. However, their high surface area requires sophisticated electrolyte/electrode interface control to improve the charge-discharge efficiency and reversibility. This study uses microplasma-synthesized graphene nanosheets (MPGNSs) as a model 2D material. The effects of NaFSI concentration in an N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ionic liquid (IL) electrolyte are systematically investigated. It is found that the chemical composition of the solid-electrolyte interphase depends on the electrolyte formulation, leading to distinct Coulombic efficiency, discharge capacity, rate capability, and cyclability of the MPGNS electrodes. The thermal reactivity of the sodiated MPGNSs (in terms of exothermic onset temperature and total heat released) upon heating is studied using differential scanning calorimetry. The IL electrolyte with a proper Na+ fraction is superior to a conventional organic carbonate electrolyte for practical NIB applications.
The impact of employees' perceptions of HR practices on identification with the company and citizenship behavior A moderated mediation model
(2019-10-07)
Chih, Charles
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Lin, Chieh-Peng
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經營管理研究所
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Institute of Business and Management
Purpose The purpose of this paper is to review two work groups' (local vs foreign) perceptions, attitudes and behavior and propose a moderated mediation model to examine perceived HR practices' impact on identification with the company and organizational citizenship behavior (OCB). Design/methodology/approach This paper selects 320 local and foreign production operators at high-tech firms in Taiwan. The hypotheses are tested using SEM-AMOS, and the mediation effects are analyzed by Sobel test with bootstrapping. Findings Results show that: first, the relationship influence between identification with the company and OCB is stronger for foreign workers than for local workers; and, second, the moderated mediation of work status exists in perceived practice of rewards for the whole worker model. Originality/value This paper studies employees' perception on HR practices, compares a three-variable model between local and foreign workers, and proposes a moderated mediation model to handle HR practices' effects on identification with the company and OCB.
High Effectiveness in Actions of Carfilzomib on Delayed-Rectifier K+ Current and on Spontaneous Action Potentials
(2019-10-07)
So, Edmund Cheung
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Liu, Ping-Yen
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Lee, Chien-Ching
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Wu, Sheng-Nan
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影像與生醫光電研究所
Carfilzomib (CFZ, Kyprolis (R)) is widely recognized as an irreversible inhibitor of proteasome activity; however, its actions on ion currents in electrically excitable cells are largely unresolved. The possible actions of CFZ on ionic currents and membrane potential in pituitary GH(3), A7r5 vascular smooth muscle, and heart-derived H9c2 cells were extensively investigated in this study. The presence of CFZ suppressed the amplitude of delayed-rectifier K+ current (I-K(DR)) in a time-, state-, and concentration-dependent manner in pituitary GH(3) cells. Based on minimal reaction scheme, the value of dissociation constant for CFZ-induced open-channel block of I-K(DR) in these cells was 0.33 mu M, which is similar to the IC50 value (0.32 mu M) used for its efficacy on inhibition of I-K(DR) amplitude. Recovery from I-K(DR) block by CFZ (0.3 mu M and 1 mu M) could be well fitted by single exponential with 447 and 645 ms, respectively. The M-type K+ current, another type of K+ current elicited by low-threshold potential, was slightly suppressed by CFZ (1 mu M). Under current-clamp condition, addition of CFZ depolarized GH(3) cells, broadened the duration of action potentials as well as raised the firing frequency. In A7r5 vascular smooth muscle cells or H9c2 cardiac cells, the CFZ-induced inhibition of I-K(DR) remained efficacious. Therefore, our study led us to reflect that CFZ or other structurally similar compounds should somehow act on the activity of membrane K-V channels through which they influence the functional activities in different types of electrically excitable cells such as endocrine, neuroendocrine cells, smooth muscle cells, or heart cells, if similar in vivo findings occur.
Rapid Prototyping of an Open-Surface Microfluidic Platform Using Wettability-Patterned Surfaces Prepared by an Atmospheric-Pressure Plasma Jet
(2019-10-08)
Wu, She-Ting
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Huang, Chen-Yu
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Weng, Chih-Chiang
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Chang, Chia-Chih
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Li, Bor-Ran
Open-surface microfluidics is promising in terms of enabling economical and rapid biochemical analysis for addressing challenges associated with medical diagnosis and food safety. To this end, we present a simple and economical approach to develop an open-surface microfluidic platform suitable for facile liquid transport and mixing. Customizable patterns with tailored wettability are deposited using a plasma-assisted deposition technique under atmospheric pressure. The flow of the dispensed liquid is driven by gravity, and the tilting angle of the device determines the extent of mixing. First, a hexamethyldisiloxane film was deposited to create hydrophobic patterns on glass, and then, hydrophilic acrylic acid was deposited by a patterned cardboard mask to construct a channel suitable for forming channels to transport aqueous liquids without the need of an external energy input; the liquid can be confined to designated pathways. Several designs including Y-junctions, serpentine-shaped patterns, splitting channels, and concentration gradient generation patterns are presented. The proposed method can spatially pattern a surface with a hydrophobic/hydrophilic area, which can function as a microfluidic channel, and the surface can be applied in microfluidic devices with other types of substrates.
Nanocatalyst-Assisted Fine Tailoring of Pore Structure in Holey-Graphene for Enhanced Performance in Energy Storage
(2019-10-09)
Dutta, Dipak
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Jiang, Jian-Yong
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Jamaluddin, Anif
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He, Shih-Ming
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Hung, Yu-Han
Nanoporous holey-graphene (HG) shows potential versatility in several technological fields, especially in biomedical, water filtration, and energy storage applications. Particularly, for ultrahigh electrochemical energy storage applications, HG has shown promise in addressing the issue of low gravimetric and volumetric energy densities by boosting of the ion-transport efficiency in a high-mass-loaded graphene electrode. However, there are no studies showing complete control over the entire pore architecture and density of HG and their effect on high-rate energy storage. Here, we report a unique and cost-effective method for obtaining well-controlled HG, where a copper nanocatalyst assists the predefined porosity tailoring of the HG and leads to an extraordinary high pore density that exceeds 1 x 10(3) mu m(-2). The pore architectures of the hierarchical and homogenous pores of HG were realized through a rationally designed nanocatalyst and the annealing procedure in this method. The HG electrode with a high mass loading results in improved supercapacitor performance that is at least 1 order of magnitude higher than conventional graphene flakes (reduced electrochemically exfoliated graphene (rECG)) in areal capacitance (similar to 100% retention of capacitance until 15 000 cycles), energy density, and power density. The diffusion coefficient of the HG electrode is 1.5-fold higher than that of rECG at a mass loading of 15 mg cm(-2), indicating excellent ion-transport efficiency. The excellent ion-transport efficiency of HG is further proved by nearly 4-fold magnitude lowering of its R-ion (the ionic resistance in the electrolyte-filled pores) value as compared with rECG when estimated for equivalent high-mass loaded electrodes. Furthermore, the HG exhibits a packing density that is 2 orders of magnitude higher than rECG, revealing the utility of the maximum electrode mass and possessing higher volumetric capacitance. The perfect tailoring of HG with optimized porosity allows the achievement of high areal capacitance and excellent cycling stability due to the facile ion-and charge-transport at high-mass-loaded electrodes, which could open a new avenue for addressing the long-existing issue of practical application of graphene-based energy storage devices.