Yong-Chien Ling

Preparation and characterization of ZnO nanoparticles coated paper and its antibacterial activity study

Coating of ZnO nanoparticles on paper surface has potential technological applications. With this motivation, a simple approach of ultrasound assisted coating of paper with ZnO nanoparticles (∼20 nm) without the aid of binder is reported for the first time in this work. The ultrasound assisted coating approach concurs with “green” chemistry as it is simple and environmentally friendly. Scanning electron microscope is used to characterize the surface morphology showing ZnO nanoparticles bound to cellulose fibers. Further characterization of coated surface is performed by attenuated total reflectance-Fourier transform infrared, X-ray diffraction, and time-of-flight secondary ion mass spectrometry in positive ion detection mode along with its imaging capability. The effect of ultrasound irradiation time on ZnO nanoparticles loading is estimated by thermogravimetric analysis. A plausible coating mechanism is proposed. The ZnO nanoparticles coated paper is found to possess antibacterial activity against Escherichia coli 11634.

Graphene-based photothermal agent for rapid and effective killing of bacteria.

Conventional antibiotic therapies are becoming less efficient due to the emergence of antibiotic-resistant bacterial strains. Development of novel antibacterial material to effectively inhibit or kill bacteria is crucial. A graphene-based photothermal agent, magnetic reduced graphene oxide functionalized with glutaraldehyde (MRGOGA), was synthesized for efficient capture and effective killing of both gram-positive Staphylococcus aureus ( S. aureus ) and gram-negative Escherichia coli ( E. coli ) bacteria upon near-infrared (NIR) laser irradiation. In the present work, we took advantage of the excellent photothermal properties of reduced graphene oxide upon NIR laser irradiation and glutaraldehyde as an efficient capturing agent toward both bacteria. Its magnetic characteristic allows bacteria to be readily trapped in a small volume by the external magnet. The synergetic effects increase the heating extent by MRGOGA upon NIR laser irradiation and the killing of the captured bacteria. The survival rate and membrane integrity assay demonstrate that 80 ppm MRGOGA solution provided rapid and effective killing of up to 99% of both gram-positive and gram-negative bacteria in 10 min upon NIR laser irradiation under batch operation mode. Graphene demonstrated better photothermal antibacterial efficiency than carbon nanotubes. Furthermore, a microfluidic chip system under continuous operation mode demonstrates the reusability of MRGOGA and offers a biocompatible platform for online phothothermal sterilization.

Oriented assembly of Au nanorods using biorecognition system

The design and formation of a linear assembly of gold nanorods using a biomolecular recognition system are described. Anti-mouse IgG was immobilized on the {111} end faces of gold nanorods through a thioctic acid containing a terminal carboxyl group. The biofunctionalized nanorods can be assembled with the desired length using mouse IgG for biorecognition and binding. The gold nanorods can be assembled to extended nanorod chains, which can be as long as 3 microm. These assembled nanostructures may be used as the precursors for future nanodevices.

Levels of PCDD/FS in ambient air and soil in the vicinity of a municipal solid waste incinerator in Hsinchu

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in twenty-one ambient air samples, eight soil samples and two stack gas samples, collected near or in a municipal solid waste incinerator (MSWI) in Hsinchu, Taiwan. A systematic decrease of PCDD/Fs in the ambient air from the northeastern area was observed. PCDD/Fs levels measured in the ambient air range from 0.058 to 0.127 pg-TEQ/m3. Higher PCDD/Fs levels in the ambient air were found during winter. In addition, PCDD/Fs levels measured in the soil range from 0.524 to 5.02 pg-TEQ/g d.m. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) did not provide sufficient evidence that the environmental PCDD/Fs contamination was caused by emissions from the Hsinchu MSWI. An unknown PCDD/Fs source was proposed using congener profile analysis and supported by both PCA and HCA.

Graphene-Based Nanomaterials as Heterogeneous Acid Catalysts: A Comprehensive Perspective

Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, “graphene”, a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative and eco-friendly solid carbocatalyst for a variety of acid-catalyzed reactions. Owing to their exceptional physical, chemical, and mechanical properties, graphene-based nanomaterials (G-NMs) offer highly stable Brønsted acidic sites, high mass transfer, relatively large surface areas, water tolerant character, and convenient recoverability as well as recyclability, whilst retaining high activity in acid-catalyzed chemical reactions. This comprehensive review focuses on the chemistry of G-NMs, including their synthesis, characterization, properties, functionalization, and up-to-date applications in heterogeneous acid catalysis. In line with this, in certain instances readers may find herein some criticisms that should be taken as constructive and would be of value in understanding the scope and limitations of current approaches utilizing graphene and its derivatives for the same.

Application of paramagnetic graphene quantum dots as a platform for simultaneous dual-modality bioimaging and tumor-targeted drug delivery

Here, we report the development of a multifunctional nanocarrier consisting of paramagnetic graphene quantum dots (GQDs), folate, and doxorubicin (Dox), used as delivery vehicles, a targeting ligand, and a chemotherapeutic drug, respectively. The paramagnetic GQDs, named folate-GdGQDs, were successfully prepared by covalently conjugating diethylenetriaminepentaacetic acid gadolinium and folic acid onto the surface of GQDs. The resultant folate-GdGQDs, which showed a longitudinal relaxivity r1 of 11.49 mM-1 s-1, greatly enhanced the brightness of the T1-weighted magnetic resonance (MR) images, indicating their potential for use as positive contrast agents for MR imaging (MRI). The feasibility of utilizing the folate-GdGQDs with strong luminescence emissions for targeted imaging of HeLa cells was also evaluated. An in vitro cell (HeLa and HepG2 cells) viability assay and in vivo evaluation of toxicity to the embryonic development of zebrafish showed that these folate-GdGQDs exhibited negligible cytotoxicity and excellent biocompatibility within the given range of concentrations. More importantly, strong therapeutic activity was achieved by loading Dox onto the surfaces of folate-GdGQDs through π-π stacking and hydrophobic interactions, leading to the formation of folate-GdGQD/Dox multifunctional nanocarriers. Approximately 80% of the loaded Dox was released from the folate-GdGQD/Dox nanocarriers under mild acidic conditions (pH 5.0), whereas only 20% of Dox was released at pH 7.0 after 48 h. Furthermore, these multifunctional nanocarriers could efficiently induce an inhibitory effect on HeLa cells, as confirmed by an in vitro cytotoxicity assay. The combined flow cytometry analysis and confocal laser scanning microscopic observation showed that these nanocarriers were efficiently taken up by the cancer cells overexpressing folate receptors. Taken together, these results suggested that the multifunctional nanocarriers could be used as promising targeted drug delivery vehicles for the diagnosis and image-guided chemotherapy of various cancers.

Multi-residue matrix solid-phase dispersion method for the determination of six synthetic pyrethroids in vegetables followed by gas chromatography with electron capture detection.

An effective multi-residue matrix solid-phase dispersion (MSPD) extraction and gas chromatographic-electron-capture detection method for the determination of six synthetic pyrethroids (fenpropathrin, cyhalothrin, permethrin, cypermethrin, fenvalerate and deltamethrin) in 5 g of vegetables (West Indian gherkin, eggplant, pak-choi, cabbage and garden peas) is described. The method uses a Florisil-based MSPD column for direct in-line clean-up with n-hexane-acetone (9:1). Recoveries calculated at 0.1 and 0.5 micrograms/g fortification levels were between 92 and 113%. The method detection limits were between 5.1 and 91.5 ng/g. The method compared favourably with the traditional method in terms of the sample size, analysis time and overall cost. The method may serve as a screening protocol for the determination of pyrethroids in vegetables.

CuxAgyInzZnkSm solid solutions customized with RuO2 or Rh1.32Cr0.66O3 co-catalyst display visible light-driven catalytic activity for CO2 reduction to CH3OH

CuxAgyInzZnkSm solid solutions, customized with RuO2 or Rh1.32Cr0.66O3 co-catalyst with a small energy band gap <2 eV were studied for photocatalytic CO2 reduction to CH3OH under visible light. Significantly, 118.5 µmol g−1 h−1CH3OH yield was obtained with RuO2/Cu0.30Ag0.07In0.34Zn1.31S2 under hydrogen effect.

Magnetic nano-adsorbent integrated with lab-on-valve system for trace analysis of multiple heavy metals

A novel system for trace analysis of multiple heavy metals was developed wherein we have integrated a magnetic nano-adsorbent with a lab-on-valve system and coupled this to an inductively coupled plasma mass spectrometer. The magnetic nano-adsorbent was prepared by surface modification of iron-based magnetic nanoparticles with polyacrylic acid (MNPs-PAA). The MNPs-PAA possessing the superparamagnetic nature of MNPs could be controllably immobilized in PTFE tubing by an external magnetic force. The high surface density of PAA (3.30 × 1011 molecules cm−2) on MNPs-PAA significantly reduced the amounts of adsorbent needed for adsorption of heavy metals (Mn2+, Co2+, Cu2+, Zn2+, and Pb2+). A detection limit of 0.04–0.06 µg L−1 (except 0.6 µg L−1 for Cu2+ and Zn2+), a precision smaller than 4% (RSD, n = 3), and a linear range of 0.5–50 µg L−1 were obtained by directly injecting an aliquot of 20 µL fortified standard solution analyzed at 5 min per sample. The accuracy was evaluated by analyzing certified reference materials of SRM 2670a (trace elements in urine, low level) and CASS-2 (nearshore seawater reference material for trace metals). Good agreement between the measured and certified values demonstrated that the system is useful for trace analysis of multiple heavy metals in environmental and biological aqueous samples. The potential of integrating functionalized nano-materials to improve the performance of existing analytical systems as an alternative approach to green analytical chemistry is foreseen.

Mechanism and kinetic modelling of PEEK pyrolysis by TG/MS

Abstract A new technique combining Py-GC/MS with TG/MS can be used in analyzing the mechanism and kinetic modelling of pyrolysis. The results of this study show that a combined approach of Py-GC/MS and TG/MS exhibited dynamic curves of 13 evolved gases from the pyrolysis of PEEK from room temperature to 900°C. In this study we also discovered that there are two stable pyrolysis reaction regions during the pyrolysis in helium atmosphere at a heating rate of 10°C/min from room temperature to 900°C. In the first pyrolysis region the ether group and ketone group from the main chain of PEEK decomposed to phenol and CO 2 , respectively. It also showed that the thermal stability of the ketone group was better than that of the ether group. Accompanied with the chain transfer in the first pyrolysis region, the fluorenone structure appeared in part of the carbonization scheme. Above 650°C it moved to the second reaction region. In this region the main decomposition products were CO 2 from the ketone group of fluorenone and from the carbonized structure described above. From the two flat regions of the activation energy curve of pyrolysis, we have proposed a kinetic model with two pyrolysis regions. Based on this model, we compared the theoretical pyrolysis curve with the experimental curve, the two curves being quite similar.