Browsing by Author "Doong, Ruey-an"

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Aggregation and sedimentation of shattered graphene oxide nanoparticles in dynamic environments: a solid-body rotational approach
(2018-08-01)
Babakhani, Peyman
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Bridge, Jonathan
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Phenrat, Tanapon
;
Doong, Ruey-an
;
Whittle, Karl R.
Nanoparticle (NP) aggregation is typically investigated in either quiescent or turbulent mixing conditions; neither is fully representative of dynamic natural environments. In groundwater, complex interacting influences of advective-diffusive transport, pore tortuosity, and the arrival of aggregates from up-gradient pores impacts the aggregation behaviour of NPs, whereas in surface waters, continuous mixing of fresh particle and aged aggregate populations amends aggregation rates. To mimic such conditions, a cylinder reactor containing shattered graphene oxide NP (<100 nm) suspension was set to rotate with a Reynolds number (Re) close to one and with zero shear. Two main aggregation phases were then observed. Up to 250-350 min, NP remained near the rotational axis longer than in static conditions, giving rise to higher aggregation rates interpreted as an enhanced perikinetic aggregation and differential sedimentation due to mixing with resuspending aggregates. In this phase, a population-balance model estimated an attachment efficiency >5 times in the rotating system than in the static system. Later (5-13 h) aggregates collided with extensively each other, broke, and reformed on the rotating cylinder wall giving rise to larger, denser aggregates (>1 cm). These results thus shed new light on the differences in aggregation behaviour between porous media and other natural environmental systems compared to quiescent batch experiments.
Boron Doped Graphene Quantum Structure and MoS2 Nanohybrid as Anode Materials for Highly Reversible Lithium Storage
(2019-03-13)
Riyanto
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Sahroni, Imam
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Bindumadhavan, Kartick
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Chang, Pei-Yi
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Doong, Ruey-an
Herein, the boron-doped graphene quantum structure (BGQS), which contains both the advantages of 0-D graphene quantum dot and 2-D reduced graphene oxide, has been fabricated by top-down hydrothermal method and then mixed with molybdenum sulfide (MoS2) to serve as an active electrode material for the enhanced electrochemical performance of lithium ion battery. Results show that 30 wt% of BGQS/MoS2 nanohybrid delivers the superior electrochemical performance in comparison with other BGQS/MoS2 and bare components. A highly reversible capacity of 3,055 mAh g(-1) at a current density of 50mA g(-1) is achieved for the initial discharge and a high reversible capacity of 1,041 mAh g(-1) is obtained at 100mA g(-1) after 50 cycles. The improved electrochemical performance in BGQS/MoS2 nanohybrid is attributed to the well exfoliated MoS2 structures and the presence of BGQS, which can provide the vitally nano-dimensional contact for the enhanced electrochemical performance. Results obtained in this study clearly demonstrate that BGQS/MoS2 is a promising material for lithium ion battery and can open a pathway to fabricate novel 2-D nanosheeted nanocomposites for highly reversible Li storage application.
Boron-doped reduced graphene oxide-based bimetallic Ni/Fe nanohybrids for the rapid dechlorination of trichloroethylene
(2017-03-01)
Sahu, Rama Shanker
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Bindumadhavan, Kartick
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Doong, Ruey-an
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環境工程研究所
;
Institute of Environmental Engineering
In this study, a simple chemical reduction method for the synthesis of novel and efficient graphene-based bimetallic Fe/Ni nanoparticles was developed for the rapid and effective dechlorination of trichloroethylene (TCE). Boron-doped reduced graphene oxide (B-rGO) was used as a support for the homogenous dispersion of Fe/Ni nanoparticles between the B-rGO nanosheets. The surface morphological results showed that the particle sizes of the bimetallic Fe/Ni nanoparticles were in the range of 10-50 nm with a mean diameter of 20 nm and the elements, including B, Fe and Ni, were homogenously distributed in the graphitic matrix. The Raman, X-ray photoelectron and electrochemical impedance spectra clearly indicated that the doped boron as well as the immobilized Fe/Ni increased the disordered structure of B-rGO. Conjointly, the interaction between the graphitic backbone and bimetallic nanoparticles resulted in fast and low-resistant electron transport in B-rGO/Fe/Ni for the enhanced dechlorination efficiency and rate of TCE. A rapid and complete hydrodechlorination of TCE by B-rGO/Fe/Ni, which followed the Langmuir-Hinshelwood kinetics, was observed between pH 4 and 7. In addition, the B-rGO-immobilized Fe/Ni could retain the high reactivity after 7 cycles of repeated injection of TCE. The results obtained in this study clearly demonstrate the efficiency, longevity and recyclability of B-rGO-immobilized Fe/Ni nanoparticles, which could pave a new way to prepare novel bimetallic Fe/Ni nanoparticles with high reactivity and long stability for the removal of environmental contaminants in water purification and waste-water treatment.
Catalytic Nanoreactors of Au@Fe3O4 Yolk-Shell Nanostructures with Various Au Sizes for Efficient Nitroarene Reduction
(2017-04-13)
Lin, Fang-hsin
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Doong, Ruey-an
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環境工程研究所
;
Institute of Environmental Engineering
Au@Fe3O4 yolk shell nanocatalysts based on the thermal decomposition of iron pentacarbonyl in the presence of 2.5-10-nm Au core nanoparticles were successfully fabricated for the catalytic reduction of nitroarenes. The particle sizes of the Au@Fe3O4 nanostructures were in the range 8-15 nm, with Fe3O4 shell layer thicknesses of 2.0-2.4 nm. The Fe3O4 layer not only can form a magnetic shell for recovery but also enables the protection of the catalytic activity of the Au core nanoparticles toward the reduction of nitrobenzene derivatives including 2-nitrophenol, 4-nitrophenol, 4-nitrotoluene, and 1-chloro-4-nitrobenzene in the presence of NaBH4. The catalytic performance of Au@Fe3O4 is highly dependent on the particle size of the Au core materials and the substituent groups of the nitroarenes. The reduction rates of nitroarenes with electron-withdrawing groups were found to be 2.3-2.6 times higher than those of nitroarenes with electron-donating groups. In addition, the reduction of nitroarenes by the Au@Fe3O4 yolk shell nanocatalysts was found to be a surface-mediated reaction, and the relationship rate and the initial NaBH4 concentration was found to follow Langmuir Hinshelwood kinetics. Moreover, the yolk shell nanoparticles showed good separation ability and reusability, as they could be repeatedly applied for the nearly complete reductions of 4-nitrophenol and 1-chloro-4-nitrobenzene for at least five successive cycles. These unique properties make Au@Fe3O4 nanocatalysts an ideal platform for tailoring yolk shell nanoreactors with various active materials and also for studying various heterogeneous catalytic processes.
Characterization of Zr-doped TiO2 nanocrystals prepared by a nonhydrolytic sol-gel method at high temperatures
(2006-10-26)
Chang, Sue-min
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
Highly crystalline and surface-modified Zr-doped TiO2 nanorods were successfully prepared using a nonhydrolytic sol-gel method that involves the condensation of metal halides with alkoxides in anhydrous trioctylphosphine oxide (TOPO) at either 320 or 400 degrees C. In addition, the interaction of the cross-condensation between the Ti and Zr species was studied by characterizing the morphologies, crystalline structures, chemical compositions, surface properties, and band gaps of the nanocrystals obtained at different reaction temperatures and Zr-to-Ti stoichiometric ratios. Increases in the concentration of Zr4+ and in the reaction temperature led to large nanorods and regular shapes, respectively. In addition, only the anatase form was observed in the Zr-doped TiO2 nanorods. The Zr-to-Ti ratios obtained ranged from 0.01 to 2.05, all of which were far below the stoichiometric ratios used during the preparation of the samples (0.25-4). Moreover, the Zr4+ units accumulated mainly at the surface of the TiO2 nanocrystals. The band gaps of the Zr-doped TiO2 nanorods ranged from 2.8 to 3.8 eV, which are smaller than those of pure TiO2 (3.7 eV) or ZrO2 (5.2 eV). The Zr-doped anatase TiO2 nanorods prepared at 400 degrees C at an initial stoichiometric Zr-to-Ti ratio of 2: 3 exhibited the highest photoactivities for the decomposition of rhodamine B because of the presence of trace amounts of Zr4+ (Zr/Ti = 0.03) in the TiO2 and the regular shapes of these particles. DSC analysis indicated that the temperatures for forming nanocrystalline TiO2 and ZrO2 were 207 and 340 degrees C, respectively. Moreover, the reactivities of condensation between the Ti species were reduced when Zr species were involved in the NHSG reactions. The results obtained in this study clearly demonstrate that the faster kinetics for the generation of TiO2 controls the material properties as well as the photoactivities of the nonhydrolytic sol-gel-derived nanocrystals.
Comparison of a new mass-concentration, chain-reaction model with the population-balance model for early- and late-stage aggregation of shattered graphene oxide nanoparticles
(2019-12-05)
Babakhani, Peyman
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Bridge, Jonathan
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Phenrat, Tanapon
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Fagerlund, Fritjof
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Doong, Ruey-an
Aggregation as an essential mechanism impacting nanoparticle (NP) functionality, fate, and transport in the environment is currently modelled using population-balance equation (PBE) models which are computationally expensive when combined with other continuum-scale reactive transport models. We propose a new simple mass-concentration-based, chain-reaction modelling (CRM) framework to alleviate computational expenses of PBE and potentially to facilitate combination with other fate, transport, and reaction models. Model performance is compared with analytical PBE solution and a standard numerical PBE technique (fixed pivot, FP) by fitting against experimental data (i.e., hydrodynamic diameter and derived count rate of dynamic light scattering used as a representative of mass concentration) for early- and late-stage, aggregation of shattered graphene oxide (SGO) NP across a broad range of solution chemistries. In general, the CRM approach demonstrates a better match with the experimental data with a mean Nash-Sutcliffe model efficiency (NSE) coefficient of 0.345 than the FP model with a mean NSE of 0.29. Comparing model parameters (aggregation rate constant and fractal dimension) obtained from fitting CRM and FP to the experimental data, similar trends or ranges are obtained between the two approaches. Computationally, the modified CRM is an order-of-magnitude faster than the FP technique, suggesting that it can be a promising modelling framework for efficient and accurate modelling of NP aggregation. However, in the scope of this study, reaction rate coefficients of the CRM have been linked to collision frequencies based on simplified and empirical relationships which need improvement in future studies.
Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review
(2017-08-01)
Babakhani, Peyman
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Bridge, Jonathan
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Doong, Ruey-an
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Phenrat, Tanapon
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環境工程研究所
Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operative transport mechanisms of physicochemical filtration, blocking, and physical retention. The second regime is characterized by the domination of particle-particle attachment tendency over particle-surface affinity. In this regime although physicochemical filtration as well as straining may still be operative, ripening is predominant together with agglomeration and further subsequent retention. In both regimes careful assessment of NP fate and transport is necessary since certain combinations of concurrent transport phenomena leading to large migration distances are possible in either case.
Electrically conducting graphene-based polyurethane nanocomposites for microwave shielding applications in the Ku band
(2017-02)
Bansala, Taruna
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Joshi, Mangala
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Mukhopadhyay, Samrat
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Doong, Ruey-an
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Chaudhary, Manchal
Electrically conducting, thermally reduced graphene nanosheets (TRG) were synthesized through thermal exfoliation and subsequent annealing of graphene oxide at 800 A degrees C. Thermoplastic polyurethane (TPU)-based nanocomposites with different concentrations (ranging between 0 and 5.5 vol%) of TRG nanosheets were prepared by the solution blending method. Morphology, phase purity, and conducting properties of TPU and TPU/TRG nanocomposites were investigated through scanning electron microscopy, X-ray diffraction, conductive atomic force microscopy (C-AFM) and Raman spectroscopy. C-AFM images show the presence of electrically conducting TRG nanosheets embedded in the TPU matrix. Electromagnetic interference (EMI) shielding measurements were also undertaken on 2-mm-thick rectangular pellets. Shielding parameters such as shielding effectiveness, DC electrical conductivity, and dielectric properties, i.e., real and imaginary parts of permittivity were investigated. Our results show that the TPU/TRG nanocomposite at 5.5 vol% loading exhibits an enhanced electrical conductivity of the order of 3.1 x 10(-2) S/m and shows a superior EMI SE of similar to-26 to -32 dB in the Ku band frequency region. EMI shielding values were found to be dominated by the material\'s absorption behavior. The dielectric properties of TPU/TRG nanocomposites were also analyzed, and they demonstrate a good correlation with EMI shielding.
Enhanced catalytic reduction of nitrophenols by sodium borohydride over highly recyclable Au@graphitic carbon nitride nanocomposites
(2019-01-01)
Thanh Binh Nguyen
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Huang, C. P.
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
In this study, a photochemical green synthesis using thermal exfoliation process is developed to fabricate Au@graphitic carbon nitride (g-C3N4) nanocomposite, highly recyclable and reusable, for the catalytic reduction of nitrophenols by NaBH4. Au nanoparticles (Au NPs) in the diameter of 5-15 nm are deposited onto the surface of g-C3N4 in 3-6 layers of structure. The synthesized Au@g-C3N4 nanocomposites exhibit excellent catalytic activity and stability in the reduction of nitrophenols including 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-nitrophenol, and 2,4,6-nitriophenol. The catalytic performance of Au@g-C3N4 is highly dependent on the initial nitrophenol concentration, Au loading, inorganic anions, and pH. The rate constant of 4-nitrophenol reduction over Au@g-C3N4 (2 wt%) is 26.4 times that of pure Au NP in the presence of 7 mM of NaBH4 at pH 5. Moreover, Au@g-C3N4 can be reused for at least 10 consecutive cycles without considerable loss of catalytic activity. The presence of anions (0.1 M) such as H2PO4-, SO42-, HCO3-, and NO3- decreases the rate of 4-nitrophenol reduction by a factor of 1.2-8.8; whereas there is a 1.2-time increase in rate constant upon the addition of Cl- ion. The detection of H-center dot radical adducts indicates that Au NPs adsorbs BH4- ions and forms Au-H species. The porous and conductive g-C3N4 provides large surface area for nitroarene adsorption and subsequent electron transfer from the Au-H species to 4-nitrophenol, which results in accelerating the reduction of 4-nitrophenol. Results clearly demonstrate that Au@g-C3N4 is a promising green catalyst of enormous potential for nitroaromatic reduction, which provides a new venue for tailoring Au-based nanomaterials in elucidation of a wide variety of heterogeneous catalytic reactions.
Enhanced photoactivity of Cu-deposited titanate nanotubes for removal of bisphenol A
(2013-01-17)
Doong, Ruey-an
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Chang, Sue-min
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Tsai, Chia-wei
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環境工程研究所
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Institute of Environmental Engineering
One-dimensional nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the Cu-deposited titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method at 150 degrees C and then 0.5-2 wt% Cu(II) ions were photodeposited onto the calcined TNTs at 500 degrees C for enhanced photodegradation of bisphenol A (BPA) under illumination of 365 nm UV light. The as-synthesized TNTs showed tubular structures with the outer diameter and inter-layer spacing of 7-10 and 0.8 nm, respectively. The X-ray absorption near-edge spectral results provided a strong support on the partially structural change from layered trititanate to anatase TiO2 through the distortion of octahedral TiO6 unit at 500 degrees C and the production of mixture of CuO and Cu2O after photodeposition of Cu ions, resulting in the formation of Cu-deposited TiO2/TNT nanocomposites to enhance the photocatalytic activity. A nearly complete removal of BPA by the Cu-deposited TiO2/TNTs was observed, and the pseudo-first-order rate constants (k(obs)) for BPA photodegradation by Cu-deposited TiO2/TNTs at pH 7.0 were 1.8-5.2 and 4.3-12.7 times higher than those of pure Degussa P25 and ST01 TiO2, respectively. In addition, the k(obs) for BPA photodegradation reached the maximum value of 0.253 +/- 0.032 min(-1) at 1 wt% Cu(II). The X-ray photoelectron spectra showed that the ratio of Cu2O to total Cu increased from 3.2% in the dark to 35.2% after illumination of 365 nm UV light for 5 min. In addition, electron paramagnetic resonance results indicated that the copper ions could serve as the electron mediators to prolong the retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by Cu-deposited TiO2/TNTs. (C) 2012 Elsevier B.V. All rights reserved.
Enhanced photocatalytic activity of Cu-deposited N-TiO2/titanate nanotubes under UV and visible light irradiations
(2017-05-31)
Doong, Ruey-an
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Liao, Chun-Yi
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環境工程研究所
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Institute of Environmental Engineering
A rapid and green synthesis of Cu-deposited N-doped TiO2/titanate nanotubes (TNTs) by the aid of microwave-assisted hydrothermal method was developed for the enhanced photocatalytic activity toward bisphenol A (BPA) degradation under UV and visible light irradiations. The TNTs are first synthesized at 150 degrees C for 3 h by microwave-assisted method followed by the calcination at 450 degrees C under NH3/N-2 atmosphere after the adsorption of 2-10 wt% Cu(II) ions to produce metallic Cu-deposited N-TiO2/TNTs nanocomposites. The microstructural analyses show that the Cu(II) ions are converted to Cu-0 in NH3/ N-2 with mean particle sizes of 39-42 nm and N atoms are incorporated into the lattices of TiO2/TNTs. The Cu-deposited N-TiO2/TNT nanocomposites show the superior photoactivity toward BPA degradation under both UV and visible light irradiations. The photodegradation efficiency and rate of BPA increases upon increasing Cu amount and the optimal mass loadings of 8-10 wt% are obtained. In addition, the pseudo-first-order rate constants for BPA degradation increase 5.3-6.8 and 2.1-3.0 times under UV and visible light irradiations, respectively, when compare with those of Degussa P25 TiO2. The Schottky barrier between Cu-0 and N-TiO2 promotes the electron transfer from N-doped TiO2 to metallic Cu nanoparticles under UV and visible light irradiations, resulting in the efficient generation of prolonged oxygen-containing radicals for enhanced photodegradation of BPA. Results obtained in this study clearly open a new pave for the green synthesis of 1-dimensional metal-metal oxide nanophotocatalysts which can be potentially used in the fields of purification, green chemistry and photocatalysis. (C) 2017 Elsevier B.V. All rights reserved.
Enhanced photocatalytic degradation of sulfamethoxazole by visible-light-sensitive TiO2 with low Cu addition
(2015-12-17)
Chiang, Li-Fen
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
In this study, the one-pot microwave-assisted impregnation method was developed to prepare the visible-light-sensitive Cu-TiO2 at low mass ratios of 0.006-0.063 wt% for the enhanced photocatalytic degradation of sulfamethoxazole (SMX) under visible light irradiation. The electron probe microanalysis and X-ray absorbance near-edge spectroscopic results indicated that the distribution of copper ions was even on TiO2 nanoparticles and the dominant species of copper element was CuO. The photodegradation efficiency and rate of SMX by Cu-TiO2 increased positively upon increasing Cu loading from 0.006 to 0.045 wt% Cu and then decreased when further increasing the Cu mass loading to 0.063 wt%. The pseudo-first-order rate constants for SMX photodegradation by Cu-TiO2 were in the range 0.0103-0.0506 min-1, which were 1.9-13.1 times higher than that of pure Degussa P25 TiO2. The photodegradation efficiency and rate of SMX can be maintained in the pH range of 5-9, and the release of Cu ions in the solution was only few 1.1.g/L, which indicates the stability of Cu-TiO2 during the photocatalytic reaction in aqueous solutions. In addition, the Cu-TiO2 could be recycled for at least 4 cycles and maintained the highly stable photoactivity toward SMX degradation under visible light irradiation. Results obtained in this study clearly demonstrate that low mass loading of Cu(II) onto TiO2 can effectively shorten the route of electron transfer and can serve as the efficient visible-light-driven photocatalysts for photodegradation of SMX and other pharmaceutical products. (C) 2015 Elsevier B.V. All rights reserved.
Fabrication of highly visible-light-responsive ZnFe2O4/TiO2 heterostructures for the enhanced photocatalytic degradation of organic dyes
(2016-01-01)
Thanh Binh Nguyen
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Doong, Ruey-an
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, a novel visible-light-sensitive ZnFe2O4-TiO2 photocatalyst has been fabricated by coupling 0.2-2 wt% p-type ZnFe2O4 narrow bandgap material with n-type anatase TiO2 for the enhanced photocatalytic degradation of organic dyes under 465 nm visible light irradiation. Transmission electron microscopy (TEM) and high resolution TEM confirm that ZnFe2O4 and TiO2 are strongly linked with an average particle size of 8-9 nm, leading to a decrease in hole-electron recombination rate as well as the enhanced photocatalytic activity of the ZnFe2O4-TiO2 heterostructures under visible light irradiation. The optimized 1 wt% ZnFe2O4 not only significantly extends the absorption edge of TiO2-based heterostructures to the visible light region but can also retain a stable photodegradation efficiency of >99% for at least 5 cycles. In addition, the photocatalytic activity of ZnFe2O4-TiO2 toward dye decomposition follows the order cationic rhodamine B > neutral methyl red > anionic methyl orange. Our results clearly demonstrate that the coupling of a low loading mass of ZnFe2O4 with anatase TiO2 is a reliable green technology approach to prepare visible-light-responsive heterostructure photocatalysts with great potential for application in the decomposition of organic dyes and other emerging pollutants in the treatment of water and wastewater.
Femtomolar Detection of Dengue Virus DNA with Serotype Identification Ability
(2018-11-06)
Chowdhury, Ankan Dutta
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Ganganboina, Akhilesh Babu
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Nasrin, Fahmida
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Takemura, Kenshin
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Doong, Ruey-an
Dengue surveillance trusts only on reverse transcription-polymerase chain reaction (RT-PCR) type methodologies for confirmation of dengue virus serotypes; however, its real time application is restricted due to the expensive, complicated, and time-consuming process. In search of a new sensing system, here, we have reported a two-way-detection method for Dengue virus (DENV) serotype identification along with DNA quantification by using a new class of nanocomposite of gold nanoparticles (AuNP) and nitrogen, sulfur codoped graphene quantum dots (N,S-GQDs). The N,S-GQDs@AuNP has been used for serotype detection via a simple fluorescence technique using four dyecombined probe DNAs which is further validated by confocal microscopy. The quantification of the DNA has been measured by the differential pulse voltammetric (DPV) technique using methyelene blue as a redox indicator. Results obtained in this study, clearly demonstrate that the N,S-GQDs@AuNP can efficiently detect the four serotypes of DENV individually in the concentration range of 10(-14 )to 10(-6 )M with the LOD of 9.4 fM. In addition, to confirm its applicability in long chained complex DNA system, the sensor was also applied to the clinically isolated DENV DNA and showed satisfactory performances for serotype identification as well as quantification. We hope this simple and reliable method can pave an avenue for the development of sensitive and robust sensing probes in biomedical applications.
Formation of Cu2O/Titanate/Titania Heterojunctions from Hydrothermally Induced Dual Phase Transitions
(2016-09-29)
Chaudhary, Manchal
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Chang, Sue-min
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Doong, Ruey-an
;
Tsai, Hsin-mu
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環境工程研究所
A microwave-assisted hydrothermal method has been developed as an efficient approach to readily induce phase transition of titanate assemblies in conjunction with decoration of Cu2O dusters on the surface. The influence of Cu2+ ions on the hydrothermally induced structural evolution was examined, and the roles of heterojunctions in the resulting composites in charge separation for improved photocatalytic activity were clarified. Hierarchical titanate assemblies with high adsorption capacity for Cu2+-ions (95.7 meg) were prepared from a low alkaline condition, Microwave-assisted hydrothermal treatment was then used to transform the adsorbents into Cu2O/titanate/titania photocatalysts in 20 min via inducing titanate-to-titania and Cu2+-to-Cu2O dual transitions. While tubular architecture was maintained in, the composites, the Cu2O dusters highly dispersed on the surface. Adsorbed Cu2+ ions have been found to retard the titanate-to-titania transformation locally, thus leading to Cu2O/titanate/titania heterojanctions. The multiheterojunctions enabled the composites to exhibit 1.7-5.1 times higher activity than the commercial product P25 (k(obs), 0.06 min(-1)) for decomposition of bisphenol A due to charge separation. EPR results dearly reveal that the type II band alignment effectively drove electrons and holes to migrate toward the titania and the Cu2O moieties, respectively, and the titanate moiety positioning in between prevented back recombination. The optimal C(u)2O loading to the highest activity (k(obs),0.306 min(-1)) Was -3.7 wt %. Over the optimal amount, the rower reduction potential in the valence band of the Cu2O dusters compensated for the positive effect from charge separation, thus causing the activity to decline in turn.
Functionalized N-doped graphene quantum dots for electrochemical determination of cholesterol through host-guest inclusion
(2018-11-01)
Ganganboina, Akhilesh Babu
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
Functionalized nitrogen-doped graphene quantum dots (N-GQD) with mean particle size of 8.50.5nm were covalently linked to -cyclodextrin (-CD) to form a -CD@N-GQD nanoprobe. The probe is shown to enable voltammetric determination of cholesterol via selective host-guest recognition and by using ferrocene (FC) as the redox indicator.FC is first included in-cyclodextrin. Cholesterol has ahigher affinity for -CD (in comparison to FC). It forms a strong inclusion complex with -CD and can replace FC from its cavities. The quantity of released FC is proportional to the concentration of cholesterol. The differential pulse voltammetric signal for FC (with a peak at typically 0.22V vs Ag/AgCl) increases linearly in the 0.5-100M cholesterol concentration range, with a limit of detection as low as 80nM. The assay is found to be highly selective over 15 potentially interfering species. The method was successfully applied to the detection of cholesterol in spiked serum samples which gave recoveries between 96 and 101%. The probe can be stored for at least 28days after which the activity still is 87%.
Green synthesis of multifunctional mesoporous composites from display panel glasses for selective adsorption of metal ions
(2016-08-20)
Tsai, Cheng Kuo
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Doong, Ruey-an
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Hung, Huan-Yi
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環境工程研究所
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Institute of Environmental Engineering
Heterostructured ZnFe2O4/TiO2 nanocomposites with a highly recyclable visible-light-response for bisphenol A degradation
(2017-01-01)
Thanh Binh Nguyen
;
Doong, Ruey-an
;
環境工程研究所
;
Institute of Environmental Engineering
Novel visible-light-sensitive ZnFe2O4-TiO2 heterojunction photocatalysts are successfully fabricated by a facile solvothermal method for the enhanced photocatalytic degradation of bisphenol A (BPA) under different light sources. The photocatalytic degradation efficiency and rate of BPA by ZnFe2O4-TiO2 under the irradiation of different light sources follow the order 465 nm visible light > solar simulator > 365 nm UV light. The reaction rate of BPA by ZnFe(2)O(4-)TiO2 in the presence of 465 nm visible light is 42 times higher than that under 365 nm UV light irradiation. In addition, the ZnFe2O4-TiO2 nanocomposites exhibit excellent recycling and reusability and can retain their stable photocatalytic activity toward BPA photodegradation for at least 10 cycles of reaction with rate constants of 0.191-0.218 min(-1) under visible light irradiation. The photogenerated holes as well as oxygen-containing radicals are identified to be the predominant reactive species responsible for the photodegradation of BPA in the ZnFe2O4-TiO2 system. The possible reaction mechanisms for BPA photodegradation by p-n heterojunction ZnFe2O4-TiO2 are also proposed. Results obtained in this study clearly demonstrate the superior visible-light-driven photoactivity of ZnFe2O4-TiO2 toward BPA photodegradation and can open an avenue to fabrication of p-n heterojunctions of photocatalysts with a wide variety of potential applications in the fields of photocatalysis, water splitting and energy conversion.
Hierarchically ordered mesoporous carbons and silver nanoparticles as asymmetric electrodes for highly efficient capacitive deionization
(2016-11-15)
Tsai, Yuan-Cheng
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Doong, Ruey-an
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環境工程研究所
;
Institute of Environmental Engineering
In this study, a novel capacitive deionization (CDI) technology by using silver nanoparticles and hierarchically ordered mesoporous carbons (HOMCs) as the anode and cathode electrodes, respectively, was developed to enhance the desalination efficiency of sodium ions. The TEM images show that HOMCs are 2-D hexagonal mesostructures with highly ordered 1-D strip-like channels and Ag is spherical with mean diameter of 30 nm. The electrochemical performance of HOMCs and activated carbons (ACs) show rectangular voltammograms at 5-100 mV s(-1), while two peaks with Faradic reaction occur for Ag electrode. The specific capacitance of HOMC electrode is 104.2 F g(-1) at 5 mV s(-1), which is 2.84 times higher than that of ACs. In addition, the asymmetric Ag parallel to HOMC electrodes show excellent electrosorption capacity and high stability toward sodium ion removal and the specific electrosorption capacity (SEC) is 356.3 and 251.6 mu mol g(-1) at 1.2 V in batch and continuous flowing solutions, respectively, which is 1.4-2.7 and 2.2-2.7 times higher than those of symmetric carbon-based electrodes. Results obtained in this study clearly indicate that the asymmetric Ag HHOMC electrode is a promising alternative nanomaterial which can open an innovative CDI technology to treat grey and brown waters that need high desalination efficiency. (C) 2016 Elsevier B.V. All rights reserved.
Highly sensitive and selective detection of mercury ions using N, S-codoped graphene quantum dots and its paper strip based sensing application in wastewater
(2017-11-01)
Nguyen Thi Ngoc Anh
;
Chowdhury, Ankan Dutta
;
Doong, Ruey-an
;
環境工程研究所
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Institute of Environmental Engineering
The development of robust and low-cost sensing materials with superior selectivity and sensitivity for rapid detection of analytes in a wide variety of samples has attracted much attention. Herein, the N, S-codoped graphene quantum dots (N, S-GQDs) with high quantum yield were fabricated by one-pot hydrothermal method for highly sensitive and selective detection of nanomolar level of mercury ions (Hg2+) in water and wastewater. The as-prepared N, S-GQDs are uniform in size with mean particle size of 3.5 +/- 0.5 nm. The doping of nitrogen atoms increases the quantum yield to 41.9%, while the introduction of sulfur atoms enhances the selectivity of Hg2+ via strong coordination interaction. The fluorescence intensity of N, S-GQDs is quenched proportionally after adding Hg2+ and a dynamic range of 4 orders of magnitude with limit of detection of 0.14nM is obtained in deionized water. The N, S-GQDs nanosensing probes can be successfully applied to the sewage and dye wastewater samples and a linear range of 0.1-15 mu M with recovery of 96-116% is obtained. In addition, the coating of N, S-GQDs onto paper strip provides an excellently rapid screening and highly selective technique for Hg2+ detection in real wastewater. Results obtained in this study clearly indicate that the N, S-GQDs are promising nanomaterials which can open an new avenue to design the GQD based sensing probe for highly sensitive and selective detection of metal ions and other analytes in environmental and biological fluid samples. (C) 2017 Elsevier B.V. All rights reserved.