3-dimensional characterization of membrane with nanoporous structure using TEM tomography and image analysis

The nanoporous structure of membrane varies in 3-dimensional (3-D) space and has remarkable influences on the filtration or desalination achieved, fouling potentials and therefore, the quality of yielded water. Knowledge of the 3-D nanoporous structure is thus vital to understanding and predicting its performance. A novel method by incorporating transmission electronic microtomography, image processing and 3-D reconstruction is introduced to characterize membranes with nano structures. The reconstruction algorithm allows for the visualization of 3-D nanoporous structure in a non-destructive way from any directions. This novel technique Ieads to in-depth understanding and accurate prediction of filtration performance.

Preparation of cross-linked nanoporous poly(ethylene glycol) diacrylate membrane in hexagonal lyotropic liquid crystal phases

Cross-linked poly(ethylene glycol) diacrylate (PEGDA) membranes were prepared by polymerization in periodic nanostructured lyotropic liquid crystals (LLC) hexagonal phases under UV light. A series of membranes were prepared under different purification treatment conditions. Polarized light microscope was employed to determine the LLC phase texture of LLC system before and after polymerization. It is found that the LLC hexagonal structure retained to some degree after polymerization. The interior structures of final membranes were investigated with scanning electron microscope (SEM). The results suggested that purification process affect the structure retention.

3-dimensional characterization of membrane with nanoporous structure using TEM tomography and image analysis

The nanoporous structure of a membrane varies in a 3-dimensional (3-D) space and has remarkable influences on the filtration or desalination achieved, fouling potentials and therefore, the quality of yielded water. Knowledge of the 3-D nanoporous structure is thus vital to understanding and predicting its performance. A novel method by incorporating transmission electronic microtomography, image processing and 3-D reconstruction is introduced to characterize membranes with nano structures. The reconstruction algorithm allows for the visualization of 3-D nanoporous structure in a non-destructive way from any directions. This novel technique leads to in-depth understanding and accurate prediction of filtration performance.

Enhancement of the antifouling properties and filtration performance of poly(ethersulfone) ultrafiltration membranes by incorporation of nanoporous titania nanoparticles

Nanoporous titania nanoparticles (NTNs) were synthesized and used as an additive at a low concentration of 0.1-1 wt % in the fabrication of poly(ethersulfone) (PES) ultrafiltration membranes via non-solvent-induced phase separation. The structure and properties of nanoparticles were characterized using nitrogen sorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The NTNs have a size distribution with a particle size of mainly <100 nm and have a Brunauer, Emmett, and Teller surface area of ∼100 m2 g-1. The modified membranes were fabricated and investigated in terms of their pure water flux, solute rejection, and fouling resistance. The water permeability and molecular weight cutoffs (MWCOs) of membranes were determined under constant-pressure filtration in dead-end mode at 100 kPa. The membrane fouling resistance was characterized under constant flux operation using bovine serum albumin as a model foulant. The membranes were characterized in terms of morphology, porosity, pore size distribution, energy-dispersive X-ray spectroscopy, contact angle goniometry, surface free energy, and viscosity of the dope solution. Overall, the modified membrane showed increased wettability and reduced surface free energy and pore size. The modified UF membrane with 0.5 wt % NTN loading exhibited improved fouling resistance (fouling rate of 0.58 kPa/min compared to a rate of 0.70 kPa/min for the control membrane) with ∼80% water flux recovery. The same membrane showed an ∼20% increase in water flux, an improvement in MWCO, and a narrower pore size distribution.

Well-controlled preparation of evenly distributed nanoporous HOPG surface via diazonium salt assisted electrochemical etching process

Evenly distributed nanoporous highly oriented pyrolytic graphite (HOPG) surfaces with controllable pore size were successfully prepared via diazonium salt assisted electrochemical etching method. The porous HOPG was investigated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) Raman spectroscopy and X-ray diffraction. The size of these pores can be tuned by manipulating the electrochemical etching time. These porous HOPG substrates also demonstrated the enhanced electrocatalytical behaviour and were employed as benign arena for the immobilization of Ru(bpy)32+ for electrochemiluminescence (ECL) sensing applications.

Enhanced degradation efficiency of toluene using titania/silica photocatalysis as a regeneration process

Three kinds of titania/silica pellets were prepared using the sol-gel method with surface areas of 50.4m² g-1, 421.1m².g^-1 and 89.1m².g^-1. An annular reactor was designed and built to determine the degradation efficiency of toluene and to investigate the relationship between the adsorption and desorption-photocatalytic processes. Surface area is an important factor influencing the adsorption-photocatalytic efficiency. Higher surface areas of pellets contribute to high rates of conversion of toluene. Un-reacted toluene and reaction intermediates accumulating on their surface deactivated the titania/silica catalyst. To overcome this problem, the adsorption and regeneration process were alternated in a dual reactor system. Connecting or disconnecting the toluene feed gas enabled one reactor to adsorb toluene, while the second reactor was regenerated by photocatalysis. Using UV irradiation and titania/silica pellets with high BET surface area (421.1 m².g^-1), the alternating adsorption/regeneration processes kept the degradation efficiency of toluene at 90% after 8 hours operation. By improving the adsorption-photocatalysis efficiency, and minimising the generation and accumulation of intermediate on the surface of pellets, the method extended catalyst life and maintained a high degradation efficiency of toluene.

In vitro bioactivity evaluation of titanium and niobium metals with different surface morphologies

Current orthopaedic biomaterials research mainly focuses on designing implants that could induce controlled, guided and rapid healing. In the present study, the surface morphologies of titanium (Ti) and niobium (Nb) metals were tailored to form nanoporous, nanoplate and nanofibre-like structures through adjustment of the temperature in the alkali-heat treatment. The in vitro bioactivity of these structures was then evaluated by soaking the treated samples in simulated body fluid (SBF). It was found that the morphology of the modified surface significantly influenced the apatite-inducing ability. The Ti surface with a nanofibre-like structure showed better apatite-inducing ability than the nanoporous or nanoplate surface structures. A thick dense apatite layer formed on the Ti surface with nanofibre-like structure after 1 week of soaking in SBF. It is expected that the nanofibre-like surface could achieve good apatite formation in vivo and subsequently enhance osteoblast cell adhesion and bone formation.

Nanostructures and nanoporosity in thermoset epoxy blends with an amphiphilic polyisoprene-block-poly(4-vinyl pyridine) reactive diblock copolymer

Nanostructured thermoset blends were prepared based on a bisphenol A-type epoxy resin and an amphiphilic reactive diblock copolymer, namely polyisoprene-block-poly(4-vinyl pyridine) (PI-P4VP). Infrared spectra revealed that the P4VP block of the diblock copolymer reacted with the epoxy monomer. However, the non-reactive hydrophobic PI block of the diblock copolymer formed a separate microphase on the nanoscale. Ozone treatment was used to create nanoporosity in nanostructured epoxy/PI-P4VP blends via selective removal of the PI microphase and lead to nanoporous epoxy thermosets; disordered nanopores with the average diameter of about 60 nm were uniformly distributed in the blend with 50 wt% PI-P4VP. Multi-scale phase separation with a distinctly different morphology was observed at the air/sample interface due to the interfacial effects, whereas only uniform microphase separated morphology at the nanoscale was found in the bulk of the blend.