Search

[Display omitted] • Unique strategy to produce tunable FRET emission as a function of medium pH. • Maximum sensing efficiency of the biosensor at a particular pH. • Drastic FRET ON-and-OFF behavior in aqueous media. • Conformational change of the drug molecules at elevated pH resulting stable fluorescent exciplex switching off the FRET emission. • Proficient cell permeability of the sensor will help in the controlled drug delivery to tumor cell lines. The present contribution depicts a unique approach to generate tunable Förster resonance energy transfer (FRET) emission with variation of pH of the medium. The pH sensitive absorption of Doxorubicin leads to modification of spectral overlap between emission spectra of donor (Pyrazoline) and absorption spectra of acceptor (Doxorubicin) thereby sensing maximum FRET efficiency in an optimum pH (near pK a of Doxorubicin). This drug molecule exhibits an instantaneous conformation change at a particular pH, which consequences on abrupt ON-and-OFF FRET efficiency. At elevated pH, both the drug molecules exhibit conformational change and form stable fluorescent exciplex, switching off the FRET emission. Confocal fluorescence images of live HepG2 cells imply that the sensor can proficiently go through the cell membrane and can be applied in the controlled delivery of drug to the tumor cell lines. [ABSTRACT FROM AUTHOR]

The aim of this research was the analysis of heat and mass transfer in vacuum membrane distillation (VMD), specifically for a dead-end feed set-up. The influence of support material on the supported membranes VMD performance was identified. A mathematical model was proposed to evaluate the membrane/feed interface temperature, membrane tortuosity, membrane mass transfer coefficient, and temperature polarization coefficient (TPC). The model was solved by an excel solver based on experimental results of feed temperature, system pressure and the evaporative fluxes. The SEM images showed that the thickness of unsupported membrane was reduced by 42% after the VMD test. Pore shrinkage and tortuosity increase were also expected during this pore collapsing process. On the other hand, the cross-sectional views of the supported membranes did not show significant changes. These results show that the support material can help prevent the membrane pore channel structure from collapsing during the VMD experiment. TPC is close to unity at low feed temperatures. However, it decreases with an increase in evaporation flux as the feed temperature increases, or when a high flux supported membrane is applied. [ABSTRACT FROM AUTHOR]

Separation using selective polymeric membranes has been well-established as an energy-efficient and cost-effective technology in water treatment and many other applications involving aqueous solutions. However, limited chemical, thermal, and mechanical resistances besides their tendency to fouling and inadequate pure water flux may often restrict their applications. To this end, inorganic materials as additives have been demonstrated to be able to enhance chemical, thermal, and fouling membrane resistances, which demonstrate their great potential for developing novel membranes by using them as additives in polymer matrices. Considering the excellent characteristics of the nanosized particles, this study reviews the effects of inorganic nano-additives on properties and performance of polymer/nanoparticle composite membranes. It has been demonstrated that using nanomaterials in a polymer matrix could enhance the mechanical strength and stiffness, wettability, selectivity, water permeability, and antifouling characteristics of the host polymer. [ABSTRACT FROM PUBLISHER]

Graphene and its related materials are important areas of research in recent years owing to their unique properties. The wide-range industrial application of graphene-related compounds has led to the development of novel and simple methods for the synthesis of graphene. In this paper, an environmentally friendly green synthesis for the partial reduction of graphene oxide (GO) to reduced GO (RGO) in a cost-effective single-step mechanism was reported. The method completely avoids the use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain RGO. The reduction of GO was carried out using aqueous leaf extracts of Paederia foetide L. The prepared GO and green RGO were characterized by ultraviolet-visible, Raman and Fourier transform infra-red spectroscopic analysis which showed a clear indication of the partial removal of oxygen-containing groups from the GO and the formation of RGO. The morphology of the green RGO was characterized by transmission electron and scanning electron microscopy. Dynamic light scattering was used for zeta potential measurement and correlated with the morphology of the sheets. Electrical conductivity was also measured to check the extent of reduction of GO to RGO. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a promising separation technique capable of being used in the desalination of marine and brackish water. Poly(vinylidene fluoride) (PVDF) flat sheet nano-composite membranes were surface modified by coating with electro-spun PVDF nano-fibres to increase the surface hydrophobicity. For this purpose, the nano-composite membrane containing 7 wt.% superhydrophobic SiO 2 nano-particles, which showed the highest flux in our previous work, was first subjected to pore size augmentation by increasing the concentration of the pore forming agent (Di-ionized water). Then, the prepared flat sheet membranes were subjected to nanofibres coating by electro-spinning. The uncoated and coated composite fabricated membranes were characterized using contact angle, liquid entry pressure of water, and scanning electron microscopy. The membranes were further tested for 6 h desalination by direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD), with a 3.5 wt.% synthetic NaCl aq as the feed. In DCMD the feed liquid and permeate side temperature were maintained at 27.5 °C and 15 °C, respectively. For VMD, the feed liquid temperature was 27 °C and a vacuum of 94.8 kPa was applied on the permeate side. The maximum permeate flux achieved was 3.2 kg/m 2 .h for VMD and 6.5 kg/m 2 .h for DCMD. The salt rejection obtained was higher than 99.98%. The coated membranes showed a more stable flux than the uncoated membranes indicating that the double layered membranes have great potential in solving the pore wetting problem in MD. [ABSTRACT FROM AUTHOR]

Effects of hydrophilic silica nanoparticles and Non-Woven Fabric (NWF) backing material on the properties and performance of the Polyvinylidene Fluoride (PVDF) membrane have been studied in this work. The nanocomposite membranes were prepared by the phase inversion method and characterized in terms of surface pore size, cross-sectional morphology, thickness, porosity, surface roughness and hydrophobicity. The fabricated membranes were subjected to Vacuum Membrane Distillation (VMD) experiments and their performance was evaluated through measuring the pure water flux and salt rejection. According to the results, effects of the hydrophilic nano-additives and NWF polyester enabled much higher VMD flux than the neat PVDF membrane when an appropriate amount of the nano-filler was added, possibly due to increase in the surface pore size and the reduction of the sponge-like layer thickness. The supported nanocomposite membranes possessed appropriate Liquid Entry Pressure (LEP w ) and mechanical strength, which make the membrane applicable in VMD process. When 7.0 wt.% of the silica nanoparticles was incorporated in a NWF supported membrane, the pure water flux became 12749.6 g/m 2 h at feed temperature of 27.5 °C and permeate side pressure of 1.2 kPa, representing a 2456% increase from the neat PVDF membrane. Almost complete NaCl rejection was also achieved when tested with 35 g/L NaCl aqueous solution. [ABSTRACT FROM AUTHOR]

ABSTRACT This work focuses on utilizing the dual role of sulfonated polyphenyl sulfone (SPPSU) as both an anchoring agent and an interlayer modifying agent in the preparation of nano MgO/SPPSU/PPSU membranes for oil removal from water. These asymmetric membranes were prepared using the phase inversion technique. The dispersed nano MgO was observed in the membrane matrix as seen by scanning electron microscope and energy dispersive X-ray analysis. The reduction in contact angle value establishes the increases in hydrophilicity. An increase in SPPSU (wt %) loosens the nano MgO/SPPSU/PPSU membrane packing as exhibited by the increase of d-spacing by X-ray diffraction analysis. The antifouling properties were tested using humic acid, as a model foulant. Further, in castor oil/water emulsion separation, it was found that the membrane with 25 wt % anchored moiety SPPSU/nano MgO produced a greater flux recovery ratio of 94.9% (±0.3) without compromising the oil rejection of 99% (±0.4) and better oleophobic surfaces for oil. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42848. [ABSTRACT FROM AUTHOR]