Ruey-an Doong

Highly Sensitive and Selective Detection of Nanomolar Ferric Ions Using Dopamine Functionalized Graphene Quantum Dots

The good stability, low cytotoxicity, and excellent photoluminescence property of graphene quantum dots (GQDs) make them an emerging class of promising materials in various application fields ranging from sensor to drug delivery. In the present work, the dopamine-functionalized GQDs (DA-GQDs) with stably bright blue fluorescence were successfully synthesized for low level Fe(3+) ions detection. The as-synthesized GQDs are uniform in size with narrow-distributed particle size of 4.5 ± 0.6 nm and high quantum yield of 10.2%. The amide linkage of GQDs with dopamine, confirmed by using XPS and FTIR spectra, results in the specific interaction between Fe(3+) and catechol moiety of dopamine at the interfaces for highly sensitive and selective detection of Fe(3+). A linear range of 20 nM to 2 μM with a detection limit of 7.6 nM is obtained for Fe(3+) detection by DA-GQDs. The selectivity of DA-GQDs sensing probe is significantly excellent in the presence of other interfering metal ions. In addition, the reaction mechanism for Fe(3+) detection based on the complexation and oxidation of dopamine has been proposed and validated. Results obtained in this study clearly demonstrate the superiority of surface functionalized GQDs to Fe(3+) detection, which can pave an avenue for the development of high performance and robust sensing probes for detection of metal ions and other organic metabolites in environmental and biomedical applications.

Enhanced visible-light-responsive photodegradation of bisphenol A by Cu, N-codoped titanate nanotubes prepared by microwave-assisted hydrothermal method.

In this study, a rapid and effective microwave-assisted hydrothermal method was developed for the synthesis of Cu, N-codoped titanate nanotubes (Cu, N-TNTs) to enhance the photocatalytic degradation efficiency and rate of bisphenol A (BPA) under UV and visible light irradiations. The TNTs were first synthesized at 150°C for 3h under microwave heating conditions followed by the calcination at 450°C in the presence of 6wt% Cu ions and N2/NH3 to fabricate Cu, N-TNTs composites. The Cu, N-TNTs exhibited excellent photocatalytic activity toward BPA degradation under UV and visible light irradiations. The X-ray photoelectron spectra indicated that Cu species in Cu, N-TNTs were mainly in zerovalent form and could serve as the electron donors as well as shuttling species to accelerate the photodegradation of BPA. In addition, the nitrogen atoms were incorporated into the anatase lattices to increase the visible-light-responsive capability. The surface normalized reaction rate constants for BPA degradation were 4.3 and 1.5 times higher than those of Degussa P25 TiO2 under UV and visible light irradiations, respectively. The electron spin resonance spectra showed that Cu, N-codoped TNTs prolonged the generation of oxygen-containing radicals for at least 5min, resulting in the significant enhancement of photodegradation efficiency and rate of BPA. Results obtained in this study open a new avenue by using simple and effective microwave-assisted hydrothermal method to fabricate low dimensional codoped TNTs which can be potentially applied in a wide variety of fields of purification, green chemistry and photocatalysis.

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

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.

Fabrication of highly visible-light-responsive ZnFe2O4/TiO2 heterostructures for the enhanced photocatalytic degradation of organic dyes

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.

Boron-doped reduced graphene oxide-based bimetallic Ni/Fe nanohybrids for the rapid dechlorination of trichloroethylene

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.

Parameterization and prediction of nanoparticle transport in porous media: A reanalysis using artificial neural network

The continuing rapid expansion of industrial and consumer processes based on nanoparticles (NP) necessitates a robust model for delineating their fate and transport in groundwater. An ability to reliably specify the full parameter set for prediction of NP transport using continuum models is crucial. In this paper we report the reanalysis of a data set of 493 published column experiment outcomes together with their continuum modeling results. Experimental properties were parameterized into 20 factors which are commonly available. They were then used to predict five key continuum model parameters as well as the effluent concentration via artificial neural network (ANN)-based correlations. The Partial Derivatives (PaD) technique and Monte Carlo method were used for the analysis of sensitivities and model-produced uncertainties, respectively. The outcomes shed light on several controversial relationships between the parameters, e.g., it was revealed that the trend of math formula with average pore water velocity was positive. The resulting correlations, despite being developed based on a “black-box” technique (ANN), were able to explain the effects of theoretical parameters such as critical deposition concentration (CDC), even though these parameters were not explicitly considered in the model. Porous media heterogeneity was considered as a parameter for the first time and showed sensitivities higher than those of dispersivity. The model performance was validated well against subsets of the experimental data and was compared with current models. The robustness of the correlation matrices was not completely satisfactory, since they failed to predict the experimental breakthrough curves (BTCs) at extreme values of ionic strengths.

Heterostructured ZnFe2O4/TiO2 nanocomposites with a highly recyclable visible-light-response for bisphenol A degradation

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 ZnFe2O4–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.

Significance of Early and Late Stages of Coupled Aggregation and Sedimentation in the Fate of Nanoparticles: Measurement and Modeling

Despite aggregations crucial role in controlling the environmental fate of nanoparticles (NP), the extent to which current models can describe the progressive stages of NP aggregation/sedimentation is still unclear. In this paper, 24 model combinations of two population-balance models and various collision frequency and settling velocity models are used to analyze spatiotemporal variations in the size and concentration of hydroxyapatite (HAp) NP. The impact of initial conditions and variability in attachment efficiency, α, with aggregate size are investigated. Although permeability models perform well in calculating collision frequencies, they are not appropriate for describing settling velocity because of their negative correlation or insensitivity in respect to fractal dimension. Considering both early and late stages of aggregation, both experimental and model data indicate overall mass removal peaks at an intermediate ionic strength (5 mM CaCl2) even though the mean aggregate size continued to increase through higher ionic strengths (to 10 mM CaCl2). This trend was consistent when different approaches to the initial particle size distribution were used and when a variable or constant α was used. These results point to the importance of accurately considering different stages of aggregation in modeling NP fate within various environmental conditions.

Photocatalytic degradation of bisphenol A over a ZnFe2O4/TiO2 nanocomposite under visible light

A ZnFe2O4-TiO2 nanocomposite combining p-type ZnFe2O4 and n-type TiO2 was successfully fabricated. The ZnFe2O4-TiO2 nanocomposite greatly enhanced the bisphenol A (BPA) photodegradation under visible light irradiation at 465 ± 40 nm. Loading TiO2 with 1 wt% of ZnFe2O4 produced high photocurrent and low charge transfer resistance. The photodegradation rate of BPA by ZnFe2O4-TiO2, which was highly dependent on the water chemistry including pH, anions, and humic acid, was 20.8-21.4 times higher than that of commercial TiO2 photocatalysts. Chloride and sulfate ions enhanced BPA photodegradation mostly due to the production of more radical species; whereas nitrate, dihydrogen phosphate, and bicarbonate ions decreased the photodegradation rate of BPA due to the scavenge of hydroxyl radicals. The photoactivity and recyclability of ZnFe2O4-TiO2 in lake water was also assessed. A near complete BPA removal from lake water was observed under visible light irradiation. Furthermore, >90% of photocatalytic activity toward BPA degradation was achieved in 5 cycles of continuous addition of BPA to the lake water. The BPA degradation intermediates were identified by HPLC/MS/MS and possible reaction pathways were proposed. Results clearly demonstrate the excellent visible-light-sensitive photocatalytic degradation of BPA over ZnFe2O4-TiO2 composite which has a great application potential for the decomposition of emerging contaminants in impaired waters.

A rapid and sensitive detection of glutathione using nanostructured V2O5 mimicking the oxidase activity as inorganic nanozyme

A polyesters are commonly applied in bio-medical engineering for drug delivery devices and tissue engineering products because of their biodegradable and biocompatible properties. Unsaturated aliphatic polyesters, such as poly(αmethylene-γ-butyrolactone) (PMBL), are of scientific and technological interest for producing tailor-made functionalized biodegradable shape memory materials due to their exocyclic alkene functionality. Cross-linking in biodegradable polymers, like hydrogels, usually produces shape memory polymers that are sensitive to their environment. Due to unfavourable thermodynamics involved in the ring-opening polymerization (ROP) of MBL, which is from its low strain energy of the fivemembered lactone ring that brings about too small negative change of enthalpy (ΔH) to offset a large negative entropy change (ΔS) of its ROP, MBL prefers vinyl addition polymerization to ROP. Therefore, ring-opening homo polymerization of MBL and developing an effective cross-linking strategy will provide a gateway into a smart biodegradable polymeric material for shape-memory applications.G detection has been one of the important and critical line of investigations for biotechnologists in recent years. Herein, we introduce vanadium pentoxide nanosheets (V2O5 NS) as a novel nanozyme mimicking peroxidase reaction as a fast selective colorimetric assay for the detection and quantification of glutathione (GSH). The V2O5 NS have been prepared by ultrasonication assisted exfoliation of bulk V2O5 and characterised. The present process involves catalysis by V2O5 in the oxidation of pale yellow 3,3ʹ,5,5ʹ,-tetramethylbenzidine (TMB) to blue color with an absorption peak centered at 650 nm. On introduction of GSH, a fading in deep blue color of oxidized TMB occurs with a simultaneous decrease in absorbance intensity at 650 nm, indicating the sensitivity of V2O5 catalysed reaction. Also, GSH selectively inhibits this reaction with a detection limit of 10 nM. The high specificity of inhibition by GSH allows this system to be used for determination of GSH concentration in human serum samples. This method is simple, fast and cost effective and can evolve as a potential method in discriminatively detecting GSH.U molecular weight polyethylene is a kind of resin with excellent physical, chemical, mechanical properties and low price.With high mechanical strength and gel-like structure when melting,UHMWPE lithium ion battery separators show better safety properties than traditional separators. In this work, UHMWPE separators were prepared by thermally induced phase separation (TIPS), using liquid paraffin (LP) as diluent. Specified UHMWPE resin for LiB separators with 1.2 million viscosity molecular weight in average was produced by Shanghai Research Institute of Chemical Industry and used as raw material.The UHMWPE resin was dissolved by LP under heat and shear of a twin-screw extruder, then processed to be film. Raw films were cooled through a series of casting rolls and followed with solid-liquid phase separation, where paraffin was extracted from the film by dichloromethane. The film was then drawn to ideal thickness and tested.The preparation process was optimized by Uniform Design, where permeability, tensile strength, puncture intensity and heat shrinkage was considered as key characteristic for the separators.The results were analyzed via DPS (Data Processing System) software by quadratic polynomial regression method. The simulation result show that ideal experiment condition is the extrusion temperature at 225oc, twin-screw speed at 36rpm, solution concentration at 24% and cooling temperature at 55oc. Verification test was then taken place and the results showed that the air permeability of the separator increased by 53% to 820 s/100ml ,the tensile strength increased by 21% to 173 Mpa,puncture intensity increased by 11% to 515 g/20μm, the heat shrinkage decreased by 57% to 1.2%.