Design of Photobioreactors for Mass Cultivation of Photosynthetic Organisms

Photosynthetic microorganisms are important bioresources for producing desirable and environmentally benign products, and photobioreactors （PBRs） play important roles in these processes. Designing PBRs for photocatalysis is still challenging at present, and most reactors are designed and scaled up using semi- empirical approaches. No appropriate types of PBRs are available for mass cultivation due to the reactors＇ high capital and operating costs and short lifespan, which are mainly due to a current lack of deep understanding of the coupling of light, hydrodynamics, mass transfer, and cell growth in efficient reactor design. This review provides a critical overview of the key parameters that influence the performance of the PBRs, including light, mixing, mass transfer, temperature, pH, and capital and operating costs. The lifespan and the costs of cleaning and temperature control are also emphasized for commercial exploitation. Four types of PBRs-tubular, plastic bag, column airlift, and flat-panel airlift reactors are recommended for large- scale operations. In addition, this paper elaborates the modeling of PBRs using the tools of computational fluid dynamics for rational design. It also analyzes the difficulties in the numerical simulation, and presents the prospect for mechanism-based models.

Tantalum （Oxy）Nitride： Narrow Bandgap Photocatalysts for Solar Hydrogen Generation

Photocatalytic water splitting, which directly converts solar energy into hydrogen, is one of the most desirable solar-energy-conversion approaches. The ultimate target of photocatalysis is to explore efficient and stable photocatalysts for solar water splitting. Tantalum （oxy）nitride-based materials are a class of the most promising photocatalysts for solar water splitting because of their narrow bandgaps and sufficient band energy potentials for water splitting. Tantalum （oxy）nitride-based photocatalysts have experienced intensive exploration, and encouraging progress has been achieved over the past years. However, the solar- to-hydrogen （STH） conversion efficiency is still very far from its theoretical value. The question of how to better design these materials in order to further improve their water-splitting capability is of interest and importance. This review summarizes the development of tantalum （oxy）nitride-based photocatalysts for solar water spitting. Special interest is paid to important strategies for improving photocatalytic water- splitting efficiency. This paper also proposes future trends to explore in the research area of tantalum-based narrow bandgap photocatalysts for solar water splitting.

Approaches for enhancing the photocatalytic activities of barium titanate:A review

Barium titanate(Ba TiO_(3)),a dielectric/ferroelectric semiconductor with perovskite structures is the most widely used photocatalyst in the field of environmental applications due to its low-cost,chemical stability,and non-toxicity.Different types and forms of Ba TiO_(3)have shown their great potential toward the significant photocatalytic reactions owing to the several beneficial properties,including appropriate band positions,high oxygen vacancies,multiple crystal structures,the feasibility of size and morphology tailoring,spontaneous polarization,rapid migration of photogenerated charge carriers,and band bending.However,the large band gap and recombination of photogenerated charge carriers limit the overall photocatalytic efficiency of Ba TiO_(3).These difficulties can be further overcome by modifying the electronic band structure of Ba TiO_(3)to broaden its absorption to the visible region of the spectrum.Hence,this review encompasses various strategies,including modification of sizes and morphologies of particles by varying the reaction time and synthesis temperature,doping with non-metals/metals,loading with noble metals,and forming heterojunctions for enhancing the photocatalytic activities of Ba TiO_(3)-based photocatalysts possessing the effective capability of charge carrier separation,trapping and their transfer to the surface of photocatalyst.Also,this review highlights the photocatalytic applications of Ba TiO_(3)-based photocatalysts along with the proposed mechanism in dyes/drugs degradation,H_(2)production,and bacteria killing.

Fabrication of Aluminum/Single-Walled Carbon Nanotube Oxidation Films through CNT-Added Surface Treatment

CNT-added surface treatment (CAST) is a newly developed technology that incorporates single-walled carbon nanotubes (SWCNTs) into a metal surface through alternate current electrolysis using a dispersion of SWCNTs in an alkaline aqueous solution. We apply this method to Al-plates and characterize their surface morphology and components through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. After CAST processing, protrusion structures of Al-oxide containing SWCNTs are formed on the surface of the Al-plate, and the surface morphology differs significantly from that of the surface of Al films treated through conventional anodic oxidation. The height and spacing of the protrusion structures formed on the surface of the CAST-treated Al-plates are 100 - 200 nm and 50 - 100 nm, respectively. In addition, we investigate the formation mechanism of the protrusion structure by applying a DC voltage between the working electrode (Al-plate) and a counter electrode immersed in a dispersion of SWCNTs in an alkaline aqueous solution. Comparing the Al-plate surface after treatment under both current directions, we propose a model for the formation process of protrusion structures containing SWCNTs based on catalyst surface etching.

Preparation and Characterization of Nano-silver Loaded Montmorillonite with Strong Antibacterial Activity and Slow Release Property

Nano-silver loaded montmorillonite （Ag-MMT） was prepared by ion-exchange and then a UV-photoreduction two-step approach was applied. The silver content in Ag-MMT determined by Volhard method was about 6.4 wt%. The morphology and structure of as-synthesized Ag-MMT were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results showed that the Ag nanoparticles were spherical and their diameters were about 15-20 nm. Moreover, the structure of MMT did not change. The minimum inhibition concentration （MIC） of Ag-MMT was 100×10-6 and the sterilizing efficiency （SE） of Ag-MMT was approximately 100% against Escherichia coli ATCC 11229 （E. coli. In addition, the slow release property of silver in Ag-MMT was also demonstrated.

Covalent functionalization/polycarboxylation of tungsten disulfide inorganic nanotubes （INTs-WS2）

Inorganic nanotubes of tungsten disulfide （INTs-WS2） are insoluble in common solvents and practically inert, hindering their usefulness in both research and commercial applications. The covalent attachment of functional species onto the surface of INT-WS2 is a critical first step in realizing the potential that INT-WS2 offer for high-performance materials and products. Although a few attempts have been reported regarding preparing modified nanotubes, only a limited range of surface functionalities is possible with these methods. We have developed a versatile method, based on a modified, highly electrophilic acidic Vilsmeier- Haack reagent, to produce covalently bonded, polycarboxylated functional WS2 nanotubes that are dispersible in polar liquids, including water. The surface polycarboxylated shell provides a means for additional derivatization, enabling matching compatibility of derivatized nanotubes to both hydrophobic and hydrophilic materials. Nanocomposites incorporating derivatized INT-WS2 are expected to show improved properties as a result of enhanced interfacial compatibility, made possible by the large number of classes of functionalization available through the initial polycarboxylation step.

Optical and magnetic properties of perovskite materials:Ba_(0.3)La_(0.7)Ti_(0.3)Fe_(0.7)O_(3) and Ba_(0.1)La_(0.9)Ti_(0.1)Fe_(0.9)O_(3)

Structural,optical and magnetic properties are reported for new synthesized perovskite materials.Ba_(0.3)La_(0.7)Ti_(0.3)Fe_(0.7)O_(3) and Ba_(0.1)La_(0.9)Ti_(0.1)Fe_(0.9)O_(3) compositions were prepared via solid state reaction.X-ray analysis confirms that both compositions show feature of perovskite structure.Rietveld refinement method was used to confirm the phase formation and investigate the structure and space group.The study demonstrates the formation of orthorhombic structure with Pnma space group for Ba_(0.3)La_(0.7)Ti_(0.3)Fe_(0.7)O_(3) while the composition Ba_(0.1)La_(0.9)Ti_(0.1)Fe_(0.9)O_(3) structure adopts Pbnm symmetry.UV–vis spectroscopy measurements show very broad and intense UV–visible light absorption,the estimated band gap ranges between 2.07 and 2.15 eV.Magnetic measurements were carried out for the compositions Ba_(0.3)La_(0.7)Ti_(0.3)Fe_(0.7)O_(3) and Ba_(0.1)La_(0.9)Ti_(0.1)Fe_(0.9)O_(3).The hysteresis loops of both samples at 300 and 10 K show a strong ferromagnetic behavior.The temperature dependent magnetization at 0.05 T under field-cooled(FC)and zero field cooled(ZFC)modes shows magnetic frustration or spin glass-like behavior.

Gold Nanoparticle Enantiomers and Their Chiral-Morphology Dependence of Cellular Uptake

Chiral molecules are widely prevalent in nature and biological systems,and artificial chiral nanoparticles have drawn enormous interest owing to their unique optical and physical properties.However,nanoparticles with chiral morphologies and their potential role in biology have been rarely explored.Herein,we report a seed-mediated synthesis of enantiomorphic Au nanooctopods(NOPs)and their chiralmorphology dependence of cellular uptake.With a high yield(∼80%),the chiral NOPs possess eight uniform arms that bend from<111>to<100>directions,like a propeller structure.The chiral NOPs synthesized with L-or D-glutathione(GSH)have opposite handedness,resulting in opposite circular dichroism signals,which is consistent with finite-difference time-domain simulations.D-GSH NOPs demonstrate greater than 30%(ca.15%)enhanced cellular uptake in GL261 and bEnd.3 cells compared with L-GSH NOPs(racemic NOPs).Moreover,D-GSH NOPs modified with poly(ethylene glycol)or L-GSH are also preferred by the cells,proving the chiral-morphology dependence of cellular uptake.Our study develops the exploration of the chiral-specific interaction in biological systems,providing potential applications for drug delivery,biosensing,and tumor detection.