Pore size and surface charge control in mesoporous TiO2 using post-grafted SAMs

2010 ◽  
Vol 12 (7) ◽  
pp. 1473 ◽  
Author(s):  
Dereje Hailu Taffa ◽  
Murugavel Kathiresan ◽  
Lorenz Walder ◽  
Britta Seelandt ◽  
Michael Wark
Keyword(s):  
Surface Charge ◽  
Pore Size ◽  
Mesoporous Tio2 ◽  
Charge Control

scholarly journals Advancement of Measurement Techniques for Tunable Resistive Pulse Sensing

2021 ◽  
Author(s):  
◽  
Eva Weatherall
Keyword(s):  
Surface Charge ◽  
Pore Size ◽  
Applied Voltage ◽  
Particle Surface ◽  
Streaming Potential ◽  
Pore Surface ◽  
Size Distributions ◽  
Ζ Potential ◽  
Resistive Pulse ◽  
Tunable Resistive Pulse Sensing

<p>Tunable resistive pulse sensing (TRPS) is a particle-by-particle analysis technique combining the Coulter principle with size-tunable pores. TRPS can be used to characterize biological and synthetic particles 50 nm - 20 µm in diameter. Information is obtained from the resistive pulse signal, a transient change in ionic current observed when a particle passes through the pore. TRPS has been shown to provide excellent resolution and accuracy for measuring particle size and concentration as well as providing information about particle charge. TRPS is therefore applicable to many industrial and fundamental research areas involving aptamers, drug delivery particles, extracellular vesicles and other biological particle types. Advancement of this technology requires a better understanding of the technique, particularly in the area of particle surface charge measurement and this Thesis helps to provide that understanding.  In this work, firstly particle ζ-potential measurement using TRPS was investigated. A number of different measurement methods are presented and the uncertainties associated with each method are outlined. The ζ-potential for a variety of particles with different surface charges were measured in a range of electrolytes.  Particle ζ-potential measurements were then improved upon with the addition of streaming potential measurements to measure the pore surface charge. The ζ-potential of the pore surface, which makes a significant contribution to particle ζ-potential calculations, was measured using a set up which works alongside the qNano. Streaming potential measurements were also used to investigate changes in the pore surface charge following application of number of different chemical coatings. The volume of data collected and detail of analysis in this work (including uncertainties) is unprecedented in TRPS ζ potential measurements.  Biphasic pulses arising from the charge on the particles were investigated. The pulse is conventionally resistive, but biphasic pulses which include both resistive and conductive components are significant for less than 50 mM salt concentrations when measuring 200 nm particles. The experimental variables investigated include the concentration of the electrolyte, particle charge, pore size, applied voltage, and the direction of particlemotion. Conductive pulse size was seen to decrease with increasing electrolyte concentration and pore size and increase with applied voltage. A linear relationship was found between conductive pulse magnitude and particle surface group density. The influence of direction of motion on conductive pulses was consistent with concentration polarization of an ion selective pore. Biphasic pulses were also seen to affect conventional TRPS particle size measurements.  Finally, size distribution broadening due to varying particle trajectories was investigated. Pulse size distributions for monodisperse particles became broader when the pore size was increased and featured two distinct peaks. Relatively large pulses are produced by particles with trajectories passing near to the edge of the pore. Other experiments determined that pulse size distributions are independent of applied voltage but broaden with increasing pressure applied across the membrane.</p>

Combined Effects of Surface Charge and Pore Size on Co-Enhanced Permeability and Ion Selectivity through RGO-OCNT Nanofiltration Membranes

2018 ◽  
Vol 52 (8) ◽  
pp. 4827-4834 ◽  
Author(s):  
Haiguang Zhang ◽  
Xie Quan ◽  
Shuo Chen ◽  
Xinfei Fan ◽  
Gaoliang Wei ◽  
...  
Keyword(s):  
Surface Charge ◽  
Pore Size ◽  
Ion Selectivity ◽  
Combined Effects ◽  
Nanofiltration Membranes

scholarly journals Advancement of Measurement Techniques for Tunable Resistive Pulse Sensing

2021 ◽  
Author(s):  
◽  
Eva Weatherall
Keyword(s):  
Surface Charge ◽  
Pore Size ◽  
Applied Voltage ◽  
Particle Surface ◽  
Streaming Potential ◽  
Pore Surface ◽  
Size Distributions ◽  
Ζ Potential ◽  
Resistive Pulse ◽  
Tunable Resistive Pulse Sensing

<p>Tunable resistive pulse sensing (TRPS) is a particle-by-particle analysis technique combining the Coulter principle with size-tunable pores. TRPS can be used to characterize biological and synthetic particles 50 nm - 20 µm in diameter. Information is obtained from the resistive pulse signal, a transient change in ionic current observed when a particle passes through the pore. TRPS has been shown to provide excellent resolution and accuracy for measuring particle size and concentration as well as providing information about particle charge. TRPS is therefore applicable to many industrial and fundamental research areas involving aptamers, drug delivery particles, extracellular vesicles and other biological particle types. Advancement of this technology requires a better understanding of the technique, particularly in the area of particle surface charge measurement and this Thesis helps to provide that understanding.  In this work, firstly particle ζ-potential measurement using TRPS was investigated. A number of different measurement methods are presented and the uncertainties associated with each method are outlined. The ζ-potential for a variety of particles with different surface charges were measured in a range of electrolytes.  Particle ζ-potential measurements were then improved upon with the addition of streaming potential measurements to measure the pore surface charge. The ζ-potential of the pore surface, which makes a significant contribution to particle ζ-potential calculations, was measured using a set up which works alongside the qNano. Streaming potential measurements were also used to investigate changes in the pore surface charge following application of number of different chemical coatings. The volume of data collected and detail of analysis in this work (including uncertainties) is unprecedented in TRPS ζ potential measurements.  Biphasic pulses arising from the charge on the particles were investigated. The pulse is conventionally resistive, but biphasic pulses which include both resistive and conductive components are significant for less than 50 mM salt concentrations when measuring 200 nm particles. The experimental variables investigated include the concentration of the electrolyte, particle charge, pore size, applied voltage, and the direction of particlemotion. Conductive pulse size was seen to decrease with increasing electrolyte concentration and pore size and increase with applied voltage. A linear relationship was found between conductive pulse magnitude and particle surface group density. The influence of direction of motion on conductive pulses was consistent with concentration polarization of an ion selective pore. Biphasic pulses were also seen to affect conventional TRPS particle size measurements.  Finally, size distribution broadening due to varying particle trajectories was investigated. Pulse size distributions for monodisperse particles became broader when the pore size was increased and featured two distinct peaks. Relatively large pulses are produced by particles with trajectories passing near to the edge of the pore. Other experiments determined that pulse size distributions are independent of applied voltage but broaden with increasing pressure applied across the membrane.</p>

scholarly journals Enhanced Fouling Resistance and Antibacterial Properties of Novel Graphene Oxide-Arabic Gum Polyethersulfone Membranes

2019 ◽  
Vol 9 (3) ◽  
pp. 513 ◽  
Author(s):  
Ahmad Najjar ◽  
Souhir Sabri ◽  
Rashad Al-Gaashani ◽  
Viktor Kochkodan ◽  
Muataz Atieh
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Surface Charge ◽  
Pore Size ◽  
Bacterial Species ◽  
Inversion Method ◽  
Gram Positive ◽  
Arabic Gum ◽  
Gram Negative ◽  
Morphological Studies

Membrane biofouling has proved to be a major obstacle when it comes to membrane efficiency in membrane-based water treatment. Solutions to this problem remain elusive. This study presents novel polyethersulfone (PES) membranes that are fabricated using the phase inversion method at different loadings of graphene oxide (GO) and 1 wt. % arabic gum (AG) as nanofiller and pore forming agents. Synthesized GO was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for morphological studies and energy-dispersive X-ray spectroscopy (EDX) for elemental analysis. The prepared GO flakes showed a high content of oxygen-containing groups (~31%). The fabricated membranes were extensively characterized, including water contact angle analysis for hydrophilicity, zeta potential measurements for surface charge, SEM, total porosity and pore size measurements. The prepared membranes underwent fouling tests using bovine serum albumin (BSA) solutions and biofouling tests using model Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial suspensions as well as real treated sewage effluent (TSE). The results showed that the novel PES/GO membranes possessed strong hydrophilicity and negative surface charge with an increase in porosity, pore size and water flux. The PES/GO membranes exhibited superior antibacterial action against both Gram-positive and Gram-negative bacterial species, implicating PES membranes which incorporate GO and AG as novel membranes that are capable of high antibiofouling properties with high flux.

Effects of nanoconfinement and surface charge on iron adsorption on mesoporous silica

2021 ◽  
Author(s):  
Jeffery A. Greathouse ◽  
Tyler J. Duncan ◽  
Anastasia G. Ilgen ◽  
Jacob A. Harvey ◽  
Louise J. Criscenti ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Surface Charge ◽  
Pore Size ◽  
Molecular Simulation ◽  
Amorphous Silica ◽  
Surface Complexation ◽  
X Ray ◽  
Silica Surfaces

A combination of molecular simulation and X-ray adsorption spectroscopy reveal the effects of pore size and nanoconfinement on the adsorption and surface complexation of aqueous iron at amorphous silica surfaces.

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