Bimodal Pore Size Distribution Research Articles

Effects of pore size on the photocatalytic activity of mesoporous TiO2 prepared by a sol–gel process

Highly crystalline mesoporous TiO2 was prepared by a facile sol–gel process in the presence of poly(oxyethylene-23) lauryl ether (Brij-35) surfactant. The pore size distribution of the samples became wider as the amount of Brij-35 increased. When the sample was prepared with moderate concentration of Brij-35, the sample had a bimodal pore size distribution with the small pores at 7 nm and the large pores at 20 nm. The photocatalytic activity was evaluated by the degradation of methylene blue under UV irradiation. The sample with large pore size and wide pore size distribution showed higher photocatalytic activity. The crystalline mesoporous TiO2 with large pore size and wide pore size distribution showed higher photocatalytic activity.

Preparation of spiral porous stainless steel hollow fiber membranes by a modified phase inversion–sintering technique

The practical use of inorganic hollow fibre membranes has been limited by their brittleness. When assembled inside a membrane module for high temperature applications, the unavoidable thermal expansion or shrinkage would break the membrane. To overcome this problem, in this paper, spiral-shaped porous stainless steel (PSS) hollow fiber membranes have been developed via a modified phase inversion–sintering technique using 316L stainless steel powder as the membrane material, polysulfone as the polymeric binder and N-methylpyrrolidone as the solvent, respectively. The effects of sintering conditions on the hollow fiber properties have been investigated extensively to optimize the preparation. In order to obtain the desired porous structure, high performance and appropriate mechanical strength, the PSS hollow fiber precursors should be calcined in O2-free sintering atmosphere between 1050°C and 1100°C. Under the optimal sintering conditions, the resultant PSS hollow fibre membranes have a bimodal pore size distribution of 0.1–3μm diameter, high mechanical strength of 290–600MPa, and the nitrogen permeances ranged between 2.23×10−4 and 2.84×10−5molm−2s−1Pa−1. When two sides are fixed by sealant, such spiral hollow fiber membranes are able to flexibly expand by 20% and shrink by at most 57% of its original length, thus suitable for variable high-temperature operations as they can offset the thermal expansion and contraction caused by the temperature change.

Porous alumina, zirconia and alumina/zirconia for bone repair: fabrication, mechanical and in vitro biological response

Zirconia (ZrO2) and alumina (Al2O3) based ceramics are widely used for load-bearing applications in bone repair due to their excellent mechanical properties and biocompatibility. They are often regarded as bioinert since no direct bone–material interface is created unless a porous structure intercedes, leading to better bone bonding. In this regard, investigating interactions between cells and porous ceramics is of great interest. In the present study, we report on the successful fabrication of sintered alumina A-61, zirconia Z-50 and zirconia/alumina composite ZA-60 ceramics with medium porosities of 61, 50 and 60%, respectively, indicating a bimodal pore size distribution and good interconnectivity. They exhibit elastic moduli of 3–10 GPa and compressive strength values of 60–240 MPa, similar to those of human cortical bone.We performed in vitro cell–material investigations comparing the adhesion, proliferation and differentiation of mouse pre-osteoblasts MC3T3-E1 on the three porous materials. While all three ceramics demonstrate a strong cell attachment, better cell spreading is observed on zirconia-containing substrates. Significantly higher cell growth was quantified on the latter ceramics, revealing an increased alkaline phosphatase activity, higher collagen production and increased calcium biomineralization compared to A-61. Hence, these porous zirconia-containing ceramics elicit superior biological responses over porous alumina of similar porosity, promoting enhanced biological interaction, with potential use as non-degradable bone grafts or as implant coatings.

Sintering of bi-porous titanium dioxide scaffolds: Experimentation, modeling and simulation

Highly bimodal pore size distributions are found in ceramic scaffolds prepared by freeze casting (ice templating). The scaffolds, with preferred orientation in the ice crystal growth direction, have large interlamellar pores between the scaffold walls and small intergranular pores within the walls. The constitutive equations based on a continuum theory of sintering are used in a finite element analysis of the sintered scaffolds. The calculations employed a model of large isolated pores surrounded by a shell containing small pores. During sintering at 1173 to 1773K the scaffold walls densified first, followed by wall closure at higher temperatures. Excellent agreement is found between the predicted and measured porosity. The compressive strength and elastic modulus depend on the fraction of interlamellar porosity, not the total porosity, indicating that the scaffold wall strength does not affect these properties.

Preparation of Micro‐/Mesoporous SiOC Bulk Ceramics

Micro‐/mesoporous SiOC bulk ceramics with high surface area and bimodal pore size distribution were prepared by pyrolysis of polysiloxane in argon atmosphere at 1100°C–1400°C followed by etching in hydrofluoric acid solution. Their thermal behaviors, phase compositions, and microstructures at different nano‐SiO2 filler contents and pyrolysis temperatures were investigated by XRD, SEM, DSC, and BET. The SiO2 fillers and SiO2‐rich clusters in the SiOC matrix act as pore‐forming sites and can be etched away by HF. At the same time, the SiO2 filler promotes SiOC phase separation during the pyrolysis. The filler content and pyrolysis temperature have important effects on phase compositions and microstructures of porous SiOC ceramics. The resulting porous SiOC bulk ceramic has a maximum specific surface area of 822.7 m2/g and an average pore size of 2.61 nm, and consists of free carbon, silicon carbide, and silicon oxycarbide phases.

Unfolding and aggregation of monoclonal antibodies on cation exchange columns: Effects of resin type, load buffer, and protein stability

The chromatographic behavior of a monoclonal antibody (mAb) that exhibits a pronounced two-peak elution behavior is studied for a range of strong cation exchange resins and with varying load buffer pH and composition. Six stationary phases are considered, including two tentacle-type resins (Fractogel EMD SO3-(M) and Eshmuno S), a resin with grafted polymeric surface extenders (Nuvia S), a resin with a bimodal pore size distribution (POROS HS 50), and two macroporous resins without polymer grafts (Source 30S and UNOsphere Rapid S). The two-peak elution behavior is very pronounced for the tentacle and polymer-grafted resins and for POROS HS 50, but is essentially absent for the two macroporous resins. The extent of this behavior decreases as the buffer pH and concentration increase and, consequently, mAb binding becomes weaker. Replacing sodium with arginine as the buffer counterion, which is expected to decrease the mAb binding strength, nearly completely eliminates the two-peak behavior, while replacing sodium with tetra-n-butylammonium hydroxide, which is expected to increase the mAb binding strength, dramatically exacerbate the effect. As shown by hydrogen–deuterium exchange mass spectrometry (HX-MS), the two-peak elution behavior is related to conformational changes that occur when the mAb binds. These changes result in increased solvent exposure of specific peptides in the Fc-region for either the Fractogel or the Nuvia resin. No significant conformational changes were seen by HX-MS when the mAb was bound to the UNOsphere resin or on the Fractogel resin when arginine was used in lieu of sodium as the load buffer counterion. Experiments with two additional mAbs on the Fractogel resin show that the two-peak elution behavior is dependent on the particular antibody. Circular dichroism suggests that the propensity of different mAbs to either precipitate directly or to form stabilizing intermolecular structures upon exposure to thermal stress can be related to their chromatographic behaviors.

Selective Adsorption of Naphthalene in Aqueous Solution on Mesoporous Carbon Functionalized by Task-specific Ionic Liquid

As a large group of persistent organic pollutants, polycyclic aromatic hydrocarbons (PAHs) commonly coexist with chlorinated organic compounds in industrial wastewater. Preferential adsorption of PAHs from wastewater and final effluent is essential in pretreatment processes. In this study, a novel nitrogen-doped mesoporous carbon (NMC) with high surface area (2130 m2/g) and bimodal pore size distribution (∼2 and ∼9.4 nm) was synthesized via a solvent evaporation induced self-assembly process using task-specific ionic liquid (TSIL) as the nitrogen source. The selective adsorption of naphthalene (NAP) with pentachlorophenol (PCP) on NMC in aqueous solution was investigated compared with conventional ordered mesoporous carbon (OMC). Kinetic studies revealed that the NAP adsorption process achieved equilibrium within 5 min and followed a pseudo-second-order rate equation. The adsorption capacity of NMC for NAP was 3.2 mmol/g, which was about 13 times that for PCP at pH 10 in a bi-solute system. The equilibriu...

Silica‐Supported Phosphotungstic Acid for Gas Phase Dehydration of Glycerol

AbstractPhosphotungstic acid (H3PW12O40 6H2O) was immobilized within a hierarchically structured silica matrix by sol–gel inclusion using polyethylene oxide as a phase separation initiator (one‐pot synthesis). The macropore size of the SiO2‐HPW composites was controlled by the polymer content. The hierarchically structured catalysts with different HPW loadings were tested against their counterparts with monomodal pore size distribution, applying the dehydration of glycerol as a test reaction. The catalysts with bimodal pore size distribution showed a significantly better long‐term stability. The improved performance was attributed to their balanced acidity, excellent leaching stability, and enhanced mass transfer within the hierarchically structured pore system.

Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> Materials with Bimodal Pore Size Distribution as Support for Heterogeneous Catalysts

The Al2O3/SiO2 materials prepared by impregnation of mesoporous silica with water solution of Al(NO3)3·9H2O were suggested to be used as supports for catalyst of high-temperature catalytic reactions. It was shown that the distribution of Al2O3 component inside wide pores of silica (10-50 nm) occurs with the formation of Al2O3 layer in case of low loading and porous layer or particles, if Al2O3 loading increases. Thus, materials with bimodal pore size distribution were obtained. The Cr-containing catalysts were prepared on the basis of these supports and tested in the process of isobutane dehydrogenation at 540 °C. It was observed that the activity of the obtained Cr/Al2O3/SiO2 materials was comparable with the one for Cr/Al2O3 catalyst. Thus, the suggested Al2O3/SiO2 materials with unique porous structure are promising to be used as supports for catalysts for high-temperature reactions.

Hierarchical polymeric scaffolds support the growth of MC3T3-E1 cells.

Tissue engineering makes use of the principles of biology and engineering to sustain 3D cell growth and promote tissue repair and/or regeneration. In this study, macro/microporous scaffold architectures have been developed using a hybrid solid freeform fabrication/thermally induced phase separation (TIPS) technique. Poly(lactic-co-glycolic acid) (PLGA) dissolved in 1,4-dioxane was used to generate a microporous matrix by the TIPS method. The 3D-bioplotting technique was used to fabricate 3D macroporous constructs made of polyethylene glycol (PEG). Embedding the PEG constructs inside the PLGA solution prior to the TIPS process and subsequent extraction of PEG following solvent removal (1,4-dioaxane) resulted in a macro/microporous structure. These hierarchical scaffolds with a bimodal pore size distribution (<50 and >300μm) contained orthogonally interconnected macro-channels generated by the extracted PEG. The diameter of the macro-channels was varied by tuning the dispensing parameters of the 3D bioplotter. The in vitro cell culture using murine MC3T3-E1 cell line for 21days demonstrated that these scaffolds could provide a favorable environment to support cell adhesion and growth.

A stochastic permeability model for the shale-gas systems

The pore network in shale reservoirs consists of pores associated with both organic matter and inorganic matrix. The range of pore sizes within the organic matter is usually an order of magnitude smaller than pore sizes within the inorganic matrix, causing a bimodal pore-size distribution for the total system revealed in nitrogen adsorption tests. We use a stochastic classification method based on a mixture of Gaussian assumption to separate two distributions of pores in organic matter and inorganic matrix. We construct an ensemble-based stochastic model conditioned to total organic content (TOC) and the characteristics of pore-size distributions in organic and inorganic media. This treatment of different pore sizes in organic and inorganic enables us to assign sorption process only in organic matter. The model can be used to calculate the apparent gas permeability (AP) in shale from a combination of nitrogen-adsorption and SEM-image data. We validate the model with data from the literature, and use it to determine permeability and tortuosity from pulse-decay experimental data. The model results show that AP is more sensitive to the mean of pores within inorganic matrix than within organic matter. These results suggest that pore sizes corresponding to each compartment; organic and inorganic should be considered to estimate permeability. The model results also confirm permeability enhancement owing to the sorption process in organic matter below critical sorption pressure.

Effect on mass transference phenomena by textural change inside monolithic carbon aerogels

The effects on mass transference phenomena due textural changes of monolithic carbon aerogels were studied by hexane adsorption. The monolithic carbon aerogels were prepared after carbonization of the organic aerogels obtained by resorcinol–formaldehyde polymerization, using p-toluenesulfonic acid (acid-catalyst) and sodium carbonate catalysts (basic-catalyst). Internal texture was modified by CO2 activation. The characterization by gas adsorption showed that the monolithic carbon aerogels presents a bi-modal pore size distribution with presence of both microporous and mesoporous. It was shown that the activation process of monolithic carbon aerogels increases their micropore volume bigger than the other one acid-catalyst aerogel. The mesopores volume in the carbon aerogels plays an important role on mass transport mechanism. The samples with presence of significant mesopore volume present a lower height of mass transfer zone than others less mesopore volume; therefore better efficiency of adsorption in mass transfer zone in dynamic adsorption. The breakthrough curve methodology proposed in this work has allowed finding a relationship between the structural parameters and dynamic adsorption variables, which opens new approaches for measuring textural parameters of material.

Cordierite/steatite/CeO2 porous materials – Preparation, structural characterization and their photocatalytic activity

The study is focused on structural characterization of new cordierite/steatite/CeO2 ceramic catalysts sintered from the mixtures containing vermiculite/CeO2 (Ver/CeO2) ceria precursor and testing their photocatalytic ability to decompose nitrous oxide (N2O). Two preceramic mixtures named A and B contained the amount of kaolinite (47 wt% and 50 wt%, respectively), different quantity of talc (40 wt% and 20 wt%, respectively) and vermiculite (13 and 30 wt%, respectively). Their counterpart mixtures A/CeO2 and B/CeO2 contained vermiculite/CeO2 instead of pure vermiculite. Ceramic cordierite/steatite (A and B) and cordierite/steatite/CeO2 (A/CeO2 and B/CeO2) sintered at 1300 °C were composed of indialite, hexagonal form of cordierite, orthorhombic protoenstatite and orthoenstatite, and CeO2 (3 wt% at A/CeO2 and 10 wt% at B/CeO2). The cordierite/steatite ceramic samples A and B showed the porosity 34 and 21%, respectively, a unimodal pore size distribution and the median pore diameter 22 and 15 μm, respectively. The cordierite/steatite/CeO2 samples A/CeO2 and B/CeO2 showed bimodal pore size distribution and porosity of 54 and 58%, respectively, and the median pore diameter 8 and 7 μm, respectively. A mean crystallite size D(220) of CeO2 was found for Ver/CeO2 = 8.5 ± 0.5 nm, A/CeO2 = 27.1 ± 2.8 nm and for B/CeO2 = 31.1 ± 3.0 nm. Photocatalytic decomposition of N2O over the ceramic samples A/CeO2 and B/CeO2 was performed during 20 h in annular batch reactor illuminated with 8 W Hg lamp (254 nm wavelength). Reaction kinetic corresponds to first-order reaction rate which is in agreement with plausible reaction mechanisms. The highest N2O conversion of 91% was achieved over the sample B/CeO2.

Lipid-bilayer coated nanosized bimodal mesoporous carbon spheres for controlled release applications.

Highly mesoporous nanosized carbon spheres (MCS) equipped with an active lipid bilayer demonstrate pronounced molecular release behavior, and excellent potential for drug delivery applications. We report a facile synthesis route for the creation of colloidal MCS with a bimodal pore size distribution, featuring a high BET surface area combined with high pore volume. Bimodal mesoporosity was achieved by a simultaneous co-assembly of a polymer resin (resol), tetraethyl orthosilicate (TEOS) and a block copolymer (Pluronic F127). The spherical geometry originates from casting the precursor mixture into a macroporous silica hard template, having a mean pore size of 60 nm, followed by thermopolymerization and final carbonization at 900 °C in nitrogen atmosphere. The final bimodal mesoporous MCS were obtained after removal of inorganic compounds by etching with hydrofluoric acid. Colloidal suspensions of MCS were prepared by oxidation with ammonium persulfate. MCS were loaded with calcein as a model drug. Efficient sealing of the MCS was achieved with a supported lipid bilayer (SLB). The SLB acts as a diffusion barrier against the uncontrolled release of encapsulated dye molecules until the release is triggered via the addition of a surface active agent. The high surface area and pore volume and the excellent release characteristics make the SLB-coated MCS a promising release-on-demand system.

Si/Ag composite with bimodal micro-nano porous structure as a high-performance anode for Li-ion batteries.

A one-step dealloying method is employed to conveniently fabricate a bimodal porous (BP) Si/Ag composite in high throughput under mild conditions. Upon dealloying the carefully designed SiAgAl ternary alloy in HCl solution at room temperature, the obtained Si/Ag composite has a uniform bicontinuous porous structure in three dimensions with micro-nano bimodal pore size distribution. Compared with the traditional preparation methods for porous Si and Si-based composites, this dealloying route is easily operated and environmentally benign. More importantly, it is convenient to realize the controllable components and uniform distribution of Si and Ag in the product. Owing to the rich porosity of the unique BP structure and the incorporation of highly conductive Ag, the as-made Si/Ag composite possesses the improved conductivity and alleviated volume changes of the Si network during repeated charging and discharging. As expected, the BP Si/Ag anode exhibits high capacity, excellent cycling reversibility, long cycling life and good rate capability for lithium storage. When the current rate is up to 1 A g(-1), BP Si/Ag can deliver a stable reversible capacity above 1000 mA h g(-1), and exhibits a capacity retention of up to 89.2% against the highest capacity after 200 cycles. With the advantages of unique performance and easy preparation, the BP Si/Ag composite holds great application potential as an advanced anode material for Li-ion batteries.

Characterizing the pore structure in the Silurian and Permian shales of the Sichuan Basin, China

Nitrogen sorption and mercury intrusion methods were applied to characterize the pore structure of the Lower Silurian shales of the Long-ma-xi Formation and Upper Permian shales of the Da-long Formation in the Sichuan Basin. The results indicate that the specific surface areas and porosities of the Silurian shales are in the range of 17.83–29.49 m2/g and 3.65–18.26%, respectively. The Silurian shales show a bimodal pore-size distribution, and consist of both micropores and nanopores, ranging from 30 to 60 μm and 1.7–20 nm, respectively. A strong positive linear correlation between the surface areas and total organic carbon content (TOC) suggests that the organic matter contributes mostly to the amount of specific surface area of the Silurian shales, whereas the contribution of clay minerals appears to be negligible. The organic matter also accounts for 50–70% of the porosity in the Silurian shales. Soluble organic matter in the form of bitumen, however has a negative impact on the surface area and porosity of the Silurian shales and reduce the amount of surface area and porosity in these shales. For the Permian shales, their surface area and porosity are lower than those of the Silurian shales, and are in the ranges of 2.20–3.52 m2/g and of 1.30–4.15%, respectively. The pore-size distribution of the Permian shales shows a unimodal pattern of micropores in a size range of 30–60 μm. Their TOC and clay mineral contents display poor correlation with the surface areas and suggest that both the organic matter and clay minerals have very low surface areas. A clear negative correlation between the porosity and TOC in the Permian shales indicates that organic matter contributes little or insignificantly to the porosity due to poorly developed organic pores in kerogen because the Permian shales are much lower in thermal maturity than the Silurian shales. Furthermore, there is a consistent negative linear correlations between the bitumen content and the porosity for both the Permian shales and Silurian shales and indicate that the bitumen may significantly reduce the porosity of the shales by occupying the pore spaces in the mineral and organic matrix. Finally, it is clear that the Lower Silurian shales have a greater shale gas potential than the Upper Permian shales do based on their surface area and porosity.

Macroporous cryogel based spin column with immobilized concanavalin A for isolation of glycoproteins.

In this work we have developed a hydrophilic poly(hydroxyethyl methacrylate-co-poly(ethylene glycol) diacrylate) cryogel placed in the centrifugal filter device. The composition of the polymerization mixture as well as the polymerization conditions were optimized in order to prepare a material with bimodal pore size distribution with 20-50μm flow through macropores and submicrometer pores in the polymer walls. The optimized, mechanically stable, highly porous, material was used for spin column lectin chromatography. The surface of the monolithic scaffold was activated by epichlorohydrin and used for immobilization of concanavalin A to provide the affinity supports for selective isolation of glycoproteins containing high mannose glycan structures. The performance of the developed lectin modified cryogels was evaluated by analyses of glycoprotein mixtures. The efficiency and selectivity of the affinity supports were confirmed by MALDI-MS analysis.

Semiconducting polymer encapsulated mesoporous silica particles with conjugated Europium complexes: toward enhanced luminescence under aqueous conditions.

Immobilization of lanthanide organic complexes in meso-organized hybrid materials for luminescence applications have attracted immense interest due to the possibility of controlled segregation at the nanoscopic level for novel optical properties. Aimed at enhancing the luminescence intensity and stability of the hybrid materials in aqueous media, we developed polyvinylpyrrolidone (PVP) stabilized, semiconducting polymer (poly(9-vinylcarbazole), PVK) encapsulated mesoporous silica hybrid particles grafted with Europium(III) complexes. Monosilylated β-diketonate ligands (1-(2-naphthoyl)-3,3,3-trifluoroacetonate, NTA) were first co-condensed in the mesoporous silica particles as pendent groups for bridging and anchoring the lanthanide complexes, resulting in particles with an mean diameter of ∼ 450 nm and a bimodal pore size distribution centered at 3.5 and 5.3 nm. PVK was encapsulated on the resulted particles by a solvent-induced surface precipitation process, in order to seal the mesopores and protect Europium ions from luminescence quenching by producing a hydrophobic environment. The obtained polymer encapsulated MSN-EuLC@PVK-PVP particles exhibit significantly higher intrinsic quantum yield (Φ(Ln) = 39%) and longer lifetime (τ(obs) = 0.51 ms), as compared with those without polymer encapsulation. Most importantly, a high luminescence stability was realized when MSN-EuLC@PVK-PVP particles were dispersed in various aqueous media, showing no noticeable quenching effect. The beneficial features and positive attributes of both mesoporous silica and semiconducting polymers as lanthanide-complex host were merged in a single hybrid carrier, opening up the possibility of using these hybrid luminescent materials under complex aqueous conditions such as biological/physiological environments.

Mineralogy and pore space characteristics of traprocks from Central Siberia, Russia: Prerequisite of weathering trends and soil formation

Pore space issues and mineral paragenesis of traprocks from the central part of the basaltic province (Central Siberia, Russia) were studied, as was the fine size fraction (<1μm) of well-drained soils from two groups — “shallow with hard rock” and “deeper and mature with saprolite.” The explanation of coexisting of these two groups was given via rocks' characteristics.The methods used included mercury intrusion porosimetry (MIP), impregnation of connective pores with a molten alloy (Wood's metal) combined with subsequent electron microscopy, optical microscopy, X-ray diffraction, and IR spectroscopy.Rock from the lithic contact is represented by slightly weathered dolerite and shows a tendency to bimodal pore size distribution with a second maximum in pore size at 10nm, which is due to the occurrence of phyllosilicates. Coarse pore systems are mainly due to cracks, which allow an easy exchange of water. Higher total porosity in the rock in one of two pits (~12vol.% compared with 4vol.%) appears to be a prerequisite for the formation of a deeper and more mature profile.Secondary products of dolerite weathering are smectites determining the association of clay minerals in both soil profiles and Fe-oxides. Most likely, desegregation and weathering of the rock fragments from soil horizons are fast enough to keep sufficient amounts of smectite only in the fine size fraction of the shallow profile. In the mature profile, pedogenesis leads to acidification of upper soil horizons and to a pronounced decrease in the smectite proportion, not only in the soil but also in the rock fragments from soil horizons. Thus, smectite(s) that was stable in early stages of rock weathering and soil formation and became unstable due to soil acidification illustrates the metastable nature of clay mineralogy in the well-drained soils from basic rock.

High‐Temperature Synthesis of Ordered Hexagonal Mesoporous Silica Materials (SBA‐15) with Adjustable Large Mesopores for Selective Adsorption of Biomolecules

AbstractAL‐SBA‐15 materials with additional large‐mesopore networks have been successfully synthesized at high‐temperature (200 °C) in the presence of inorganic salts. Compared with conventional SBA‐15 which has monomesopores, the samples synthesized by using cations and assisted by high‐temperature show a bimodal pore size distribution. Interestingly, the large mesopores in the samples can be tuned by a simple adjustment in the preparation time and temperature. In addition, this route also results in the formation of a high degree of silica condensation which is favorable for improvement of sample hydrothermal stability. More importantly, the adsorption and separation of biomolecules over AL‐SBA‐15 materials and conventional SBA‐15100 or SBA‐15200 samples shows that AL‐SBA‐15 samples exhibit superior selective adsorption and separation capabilities compared with conventional samples and this is potentially important for their applications in adsorption and separation of bulky biomolecules.