Browsing by Subject "Pore size"

Now showing 1 - 3 of 3

Open Access
Poly-cyclodextrin cryogels with aligned porous structure for removal of polycyclic aromatic hydrocarbons (PAHs) from water
(Elsevier, 2017-08) Topuz, F.; Uyar, Tamer
Cyclodextrins (CDs) are sugar-based cyclic oligosaccharides, which form inclusion complexes with small guest molecules through their hydrophobic cavity. Here we successfully synthesized highly porous poly-cyclodextrin (poly-CD) cryogels, which were produced under cryogenic conditions by the cross-linking of amine-functional CDs with PEG-based diepoxide cross-linker. The poly-CD cryogels showed aligned porous network structures owing to the directional freezing of the matrix, of which the pore size and architecture exposed variations depending on the composition of the reactants. The cryogels were employed for the removal of genotoxic polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. They reached PAH sorption capacities as high as 1.25 mg PAH per gram cryogel. This high sorption performance is due to interactions between PAHs and the complete swollen network, and thus, is not restricted by interfacial adsorption. Given that the hydrophilic nature of the components, the sorption performance could only be attributed to the inclusion complex formation of CDs with PAH molecules. The poly-CD cryogels could be recycled with an exposure to ethanol and reused without any significant loss in the sorption capacity of PAHs.
Open Access
Rapid and alternative fabrication method for microfluidic paper based analytical devices
(Elsevier B.V., 2016) Malekghasemi, S.; Kahveci, E.; Duman, M.
A major application of microfluidic paper-based analytical devices (µPADs) includes the field of point-of-care (POC) diagnostics. It is important for POC diagnostics to possess properties such as ease-of-use and low cost. However, µPADs need multiple instruments and fabrication steps. In this study, two different chemicals (Hexamethyldisilazane and Tetra-ethylorthosilicate) were used, and three different methods (heating, plasma treatment, and microwave irradiation) were compared to develop µPADs. Additionally, an inkjet-printing technique was used for generating a hydrophilic channel and printing certain chemical agents on different regions of a modified filter paper. A rapid and effective fabrication method to develop µPADs within 10 min was introduced using an inkjet-printing technique in conjunction with a microwave irradiation method. Environmental scanning electron microscope (ESEM) and x-ray photoelectron spectroscopy (XPS) were used for morphology characterization and determining the surface chemical compositions of the modified filter paper, respectively. Contact angle measurements were used to fulfill the hydrophobicity of the treated filter paper. The highest contact angle value (141°±1) was obtained using the microwave irradiation method over a period of 7 min, when the filter paper was modified by TEOS. Furthermore, by using this method, the XPS results of TEOS-modified filter paper revealed Si2p (23%) and Si-O bounds (81.55%) indicating the presence of Si–O–Si bridges and Si(OEt) groups, respectively. The ESEM results revealed changes in the porous structures of the papers and decreases in the pore sizes. Washburn assay measurements tested the efficiency of the generated hydrophilic channels in which similar water penetration rates were observed in the TEOS-modified filter paper and unmodified (plain) filter paper. The validation of the developed µPADs was performed by utilizing the rapid urease test as a model test system. The detection limit of the developed µPADs was measured as 1 unit ml−1 urease enzyme in detection zones within a period of 3 min. The study findings suggested that a combination of microwave irradiation with inkjet-printing technique could improve the fabrication method of µPADs, enabling faster production of µPADs that are easy to use and cost-effective with long shelf lives.
Open Access
Role of organic and inorganic additives on the assembly of CTAB-P123 and the morphology of mesoporous silica particles
(2009) Poyraz, A. S.; Dag, Ö.
Mesoporous silica particles with various morphologies and structures have been synthesized by controlling the solubility, micellization, and assembly of a charged surfactant (cethyltrimethylammonium bromide, CTAB) and a pluronic (PEO20PPO70PEO20, P123) couple using an organic (benzene) or an inorganic (SO4 2-, NO3 -, or Cl-) additive. The effect of CTAB, with or without one of the Hofmeister ions or benzene in various concentrations, on the morphology, pore-size, pore-structure and the nature of the silica particles has been investigated. Increasing the lyotropic anion (SO4 2-) or benzene concentration of the synthesis media creates wormlike particles with enlarged pores and reduced wall thickness. However, the hydrotropic anion (NO3 -) influenced the solubility of the charged surfactant and increased the CTAB concentration in the CTAB-P123 micelles, and as a result, in the mesoporous silica particles. The surface area, unit cell, and pore size of the silica particles are diminished by increasing the nitrate ion centration. The effects of the Cl- ion are between the SO4 2- and NO3 -ions. It influenced the P123 at low and CTAB at high concentrations. At low CTAB/ P123 mol ratios, the Cl- ion affects mainly the P123, but at high CTAB/P123 it affects both the CTAB and P123. By carefully adjusting these ingredients (CTAB, SO4 2-, Cl-, NO3 - and benzene), not only the morphology of the particles, but also the pore-size and pore-structure of the mesoporous silica particles could be adjusted. The investigations were carried out by preparing a series of powder samples and, by varying the CTAB/P123 mol ratio (between 3.0 and 6.0) and the concentration of the organic (0.17 to 0.90 M) or inorganic (at 0.25, 0.50, or 1.00 M) additive in the synthesis media. The powder samples were analyzed using microscopy (SEM, TEM, and POM), diffraction (PXRD), and spectroscopy (FTIR, Raman, UV-vis, and EDS) techniques toward above goals. © 2009 American Chemical Society.