Fabrication of alumina nanofibers by precipitation reaction combined with heterogeneous azeotropic distillation process

γ-Alumina nanofibers have been prepared from a precipitation reaction between aluminum ammonium sulfate and Baker's salt solutions followed by a heterogeneous azeotropic distillation process with N-butanol and calcination at 1173 K. Experimental results indicate that the terminal pH value of the reaction mixture should be kept at 7.00-8.00 in order to obtain γ-Al₂O₃ nanofibers. The resulting spherical aluminum hydrate precipitates are evolved into two-dimensional crystallized pseudoboehmite lamellae after the heterogeneous azeotropic distillation and then transformed into γ-Al₂O₃ nanofibers with ca. 3-5 nm thick and 50-150 nm long after further calcination at 1173 K. The formation of γ-Al₂O₃ nanofibers can attribute to the preferential growth along the longitudinal axis due to the inherent instability of the planar structure of the pseudoboehmite during the calcination process.     

Stacked-lamellar structure of electrospun poly(heptamethylene terephthalate) nanofibers

Poly(heptamethylene terephthalate) (poly(7GT)), which is an aromatic polyesters was synthesized, and nanofibers of poly(7GT) were prepared via electrospinning from its solution in 1,1,1,3,3,3-hexafluoro-2-propanol. Uniaxially oriented thin films were also prepared by applying shear strain to molten poly(7GT). Morphology of as-spun and annealed nanofibers and that of uniaxially oriented thin films were investigated by transmission electron microscopy. Selected-area electron diffraction (SAED) of bundles of the annealed nanofibers gave a highly oriented fiber pattern. In addition, dark-field images of the poly(7GT) nanofibers, which had been annealed at 85 °C for 48 h, were taken by using some of the reflections on/near the equator. The images showed a stacked-lamellar structure, in which crystalline lamellae appearing as bright striations oriented perpendicularly to the fiber axis were stacked in the direction of the fiber axis, and the corresponding average long period was estimated at about 19 nm. As for the uniaxially oriented thin films, SAED also gave an oriented fiber pattern. When the annealing of the films was performed similar to nanofibers, crystallization occurred and a stacked-lamellar structure was constructed parallel to the shearing direction. The corresponding average long period was estimated at about 27 nm. By comparing the fiber patterns between annealed nanofibers and thin films, it seems that electrospinning is more effective than uniaxial stretching in enhancing the molecular orientation in the case of poly(7GT).     

Super‐Strong,Super‐Stiff Macrofibers with Aligned,Long Bacterial Cellulose Nanofibers

With their impressive properties such as remarkable unit tensile strength, modulus, and resistance to heat, flame, and chemical agents that normally degrade conventional macrofibers, high‐performance macrofibers are now widely used in various fields including aerospace, biomedical, civil engineering, construction, protective apparel, geotextile, and electronic areas. Those macrofibers with a diameter of tens to hundreds of micrometers are typically derived from polymers, gel spun fibers, modified carbon fibers, carbon‐nanotube fibers, ceramic fibers, and synthetic vitreous fibers. Cellulose nanofibers are promising building blocks for future high‐performance biomaterials and textiles due to their high ultimate strength and stiffness resulting from a highly ordered orientation along the fiber axis. For the first time, an effective fabrication method is successfully applied for high‐performance macrofibers involving a wet‐drawing and wet‐twisting process of ultralong bacterial cellulose nanofibers. The resulting bacterial cellulose macrofibers yield record high tensile strength (826 MPa) and Young's modulus (65.7 GPa) owing to the large length and the alignment of nanofibers along fiber axis. When normalized by weight, the specific tensile strength of the macrofiber is as high as 598 MPa g^?1 cm³, which is even substantially stronger than the novel lightweight steel (227 MPa g^?1 cm³).     

Atomic force microscopy visualization of hard segment alignment in stretched polyurethane nanofibers prepared by electrospinning

Molecular-level orientation within nanofibers has been attracting attention as a tool for controlling and designing highly functional nanofibers. In this study, we used atomic force microscopy to visualize the phase separation between soft and hard segments on a polyurethane (PU) nanofiber surface prepared by electrospinning. Furthermore, the stretched nanofibers prepared with a high-speed rotating collector were found to have a different phase distribution in the phase-separated structure, with the hard segment domains aligned to the fiber axis. In contrast, unstretched PU nanofibers prepared without rotation were observed to have nonuniformly distributed segments. These results indicate that the application of an intense elongation force along the nanofiber axis with a rotating mandrel collector changed the distribution of segment alignments.     

Electrical properties of polyaniline and multi-walled carbon nanotube hybrid fibers

We have fabricated for the first time one-dimensional multiwalled carbon nanotube (MWNT) nanocomposite fibers with improved electrical properties using electrospinning. Polyaniline (PANi) and poly(ethylene oxide) (PEO) were used as a conducting and a nonconducting matrix, respectively, for hybrid nanofibers including MWNTs. The hybrid nanofibers fabricated by electrospinning had a length of several centimeters and a diameter ranging from approximately 100 nm to approximately 1 microm. Transmission electron microscopic analysis confirmed that the MWNTs were successfully oriented along the fiber axis without any severe aggregation during electrospinning. The hybrid nanofibers showed an enhanced electrical conductance with increasing MWNT content up to 0.5 wt%, and compared to PANi/PEO fibers, they also showed a stable linear ohmic behavior. These hybrid conducting nanofibers can be applied to chemical and biosensors that require a high sensitivity.     

Electrocatalysts for methanol oxidation based on platinum/carbon nanofibers nanocomposite

New carbon nanomaterials, i.e., carbon nanotubes and nanofibers, with special physico-chemical properties, are recently studied as support for methanol oxidation reaction electrocatalysts replacing the most widely used carbon black. Particularly, carbon fibrous structures with high surface area and available open edges are thought to be promising. Platelet type carbon nanofibers, which have the graphene layers oriented perpendicularly to the fiber axis, exhibit a high ratio of edge to basal atoms. Different types of carbon nanofibers (tubular and platelet) were grown by plasma enhanced chemical vapour deposition on carbon paper substrates. The process was controlled and optimised in term of growth pressure and temperature. Carbon nanofibers were characterised by high resolution scanning electron microscopy and X-ray photoelectron spectroscopy to assess the morphological properties. Then carbon nanofibers of both morphologies were used as substrates for Pt electrodeposition. High resolution scanning electron microscopy images showed that the Pt nanoparticles distribution was well controlled and the particles size went down to few nanometers. Pt/carbon nanofibers nanocomposites were tested as electrocatalysts for methanol oxidation reaction. Cyclic voltammetry in H2SO4 revealed a catalyst with a high surface area. Cyclic voltammetry in presence of methanol indicated a high electrochemical activity for methanol oxidation reaction and a good long time stability compared to a carbon black supported Pt catalyst.     

Nanofibers Comprising Yolk–Shell Sn@void@SnO/SnO2 and Hollow SnO/SnO2 and SnO2 Nanospheres via the Kirkendall Diffusion Effect and Their Electrochemical Properties

Nanofibers with a unique structure comprising Sn@void@SnO/SnO₂ yolk–shell nanospheres and hollow SnO/SnO₂ and SnO₂ nanospheres are prepared by applying the nanoscale Kirkendall diffusion process in conventional electrospinning process. Under a reducing atmosphere, post‐treatment of tin 2‐ethylhexanoate‐polyvinylpyrrolidone electrospun nanofibers produce carbon nanofibers with embedded spherical Sn nanopowders. The Sn nanopowders are linearly aligned along the carbon nanofiber axis without aggregation of the nanopowders. Under an air atmosphere, oxidation of the Sn–C composite nanofibers produce nanofibers comprising Sn@void@SnO/SnO₂ yolk–shell nanospheres and hollow SnO/SnO₂ and SnO₂ nanospheres, depending on the post‐treatment temperature. The mean sizes of the hollow nanospheres embedded within tin oxide nanofibers post‐treated at 500 °C and 600 °C are 146 and 117 nm, respectively. For the 250th cycle, the discharge capacities of the nanofibers prepared by the nanoscale Kirkendall diffusion process post‐treated at 400 °C, 500 °C, and 600 °C at a high current density of 2 A g^?1 are 663, 630, and 567 mA h g^?1, respectively. The corresponding capacity retentions are 77%, 84%, and 78%, as calculated from the second cycle. The nanofibers prepared by applying the nanoscale Kirkendall diffusion process exhibit superior electrochemical properties compared with those of the porous‐structured SnO₂ nanofibers prepared by the conventional post‐treatment process.     

Electrospun carbon-tin oxide composite nanofibers for use as lithium ion battery anodes

Composite carbon-tin oxide (C-SnO(2)) nanofibers are prepared by two methods and evaluated as anodes in lithium-ion battery half cells. Such an approach complements the long cycle life of carbon with the high lithium storage capacity of tin oxide. In addition, the high surface-to-volume ratio of the nanofibers improves the accessibility for lithium intercalation as compared to graphite-based anodes, while eliminating the need for binders or conductive additives. The composite nanofibrous anodes have first discharge capacities of 788 mAh g(-1) at 50 mA g(-1) current density, which are greater than pure carbon nanofiber anodes, as well as the theoretical capacity of graphite (372 mAh g(-1)), the traditional anode material. In the first protocol to fabricate the C-SnO(2) composites, tin sulfate is directly incorporated within polyacrylonitrile (PAN) nanofibers by electrospinning. During a thermal treatment the tin salt is converted to tin oxide and the polymer is carbonized, yielding carbon-SnO(2) nanofibers. In the second approach, we soak the nanofiber mats in tin sulfate solutions prior to the final thermal treatment, thereby loading the outer surfaces with SnO(2) nanoparticles and raising the tin content from 1.9 to 8.6 wt %. Energy-dispersive spectroscopy and X-ray diffraction analyses confirm the formation of conversion of tin sulfate to tin oxide. Furthermore, analysis with Raman spectroscopy reveals that the additional salt soak treatment from the second fabrication approach increases in the disorder of the carbon structure, as compared to the first approach. We also discuss the performance of our C-SnO(2) compared with its theoretical capacity and other nanofiber electrode composites previously reported in the literature.     

Optical and mechanical anisotropies of aligned electrospun nanofibers reinforced transparent PMMA nanocomposites

This study aims to assess the nanofiber directionality effects on optomechanical properties of a widely used transparent thermoplastic poly(methyl methacrylate) (PMMA). Aligned fiber-hybrid mats consisted of nylon-6 (PA-6) nanofibers and PMMA microfibers are prepared using a self-blending co-electrospinning method, followed by hot press molding to fabricate into transparent nanocomposites. Effects of nanofiber orientation degree in two orthogonal directions and loading fraction on the optomechanical behavior of the nanocomposites are examined. Optical transmittance differences parallel and perpendicular to the nanofibers’ orientation are found to vary in a range of 3.9–5.4% at 589 nm, and strong mechanical anisotropy is observed with the 1% PA-6/PMMA nanocomposites. A maximal of 3% PA-6 nanofiber loading maintains the nanocomposite high transmittance (>75%) with improved strength and toughness along the nanofiber axis. This study reveals evident anisotropic optomechanical properties of transparent nanocomposites, and highlights the great designability of transparent nanocomposites by using aligned nanofibers as the designing elements.     

High performance polyimide composite films prepared by homogeneity reinforcement of electrospun nanofibers

Highly aligned polyimide (PI) and PI nanocomposite fibers containing carbon nanotubes (CNTs) were produced by electrospinning. Scanning electron microscopy showed the electrospun nanofibers were uniform and almost free of defects. Transmission electron microscopy indicated that the CNTs were finely dispersed and highly oriented along the CNT/PI nanofiber axis at a relatively low concentration. The as-prepared well-aligned electrospun nanofibers were then directly used as homogeneity reinforcement to enhance the tensile strength and toughness of PI films. The neat PI nanofiber reinforced PI films showed good transparency, decreased bulk density and significantly improved mechanical properties. Compared with neat PI film prepared by solution casting, the tensile strength and elongation at break for the PI film reinforced with 2 wt.% CNT/PI nanofibers were remarkably increased by 138% and 104%, respectively. The significant increases in the overall mechanical properties of the nanofibers reinforced polyimide films can be ascribed to good compatibility between the electrospun nanofibers and the matrix as well as high nanofiber orientation in the matrix. Our study demonstrates a good example for fabricating high performance and high toughness polyimide nanocomposites by using this facile homogeneity self-reinforcement method.     

Study on morphology and characterization of poly(mphenylene isophtalamide)/multi-walled carbon nanotubes composite nanofibers by electrospinning

Electrospinning technique is the main method of preparing polymer nanofiber simply, directly and continuously at present. In this work, electrospinning blend solution was prepared by in-situ polymerization using acid-modified multi-walled carbon nanotubes (MWNTs), m-phenylenediamine (MPD) and isophthaloyl chloride (IPC). And then composite nanofibers were prepared by electrospinning. MWNTs played an important role in nanofiber's properties. The effects of MWNTs on the morphology and characterization of the MWNTs/PMIA composite nanofibers were investigated. Scanning electron microscopy (SEM), thermal gravimetric analyzer (TGA), and X-ray diffraction (XRD) were utilized to characterize the MWNTs/PMIA nanofibers morphology and properties. The experimental results indicated that the nanofibers diameter decreased and solution dynamic viscosity increased with increasing MWNTs contents. XRD data demonstrated that PMIA composite nanofibers had the same crystal type as the pure PMIA nanofiber, and crystallinity was improved with increasing MWNTs loading. Transmission electron microscopy (TEM) was used to confirm MWNTs aligned along the axis of composite nanofibers.     

Manganese oxyhydroxide and oxide nanofibers for high efficiency degradation of organic pollutants

Ultrathin MnOOH nanofibers were synthesized on a large scale from diluted Mn(NO(3))(2) aqueous solution at room temperature. These MnOOH nanofibers were shape-reservedly converted into Mn(3)O(4) and MnO(2) nanofibers by post-heat treatment in air at 400?°C and 600?°C for 1 h, respectively. The morphology and crystalline structures of the nanofibers were characterized by electronic microscopes and x-ray diffraction. These nanofibers had good crystalline structures. These nanofibers were in bundles with a diameter of 25 nm composed of 3-5 nm fine crystalline nanofibers. The Mn(3)O(4) nanofibers had a specific surface area of 71 m(2) g(-1) and demonstrated highly catalytic degradation of the organic pollutant methylene blue with the assistance of H(2)O(2) at room temperature.     

Development of photocatalytic TiO2 nanofibers by electrospinning and its application to degradation of dye pollutants

We have developed photocatalytic TiO2 nanofibers for the treatment of organic pollutants by using electrospinning method. We found that the optimized electrospinning conditions (electric field and flow rate) were 0.9 kV cm(-1) and 50 microL min(-1). After annealing at 550 degrees C for 30 min, we fabricated TiO2 nanofibers (average 236 nm thick) with anatase crystalline phase. To increase photocatalytic activity and effective surface area, we coated photocatalytic TiO2 particles on the TiO2 nanofibers by using sol-gel method. The degradation rate (k'=85.4x10(-4) min(-1)) of composite TiO2 was significantly higher than that (15.7x10(-4) min(-1)) of TiO2 nanofibers and that (14.3x10(-4) min(-1)) of TiO2 nanoparticles by the sol-gel method. Therefore, we suggested that the composite TiO2 of nanofibers and nanoparticles be suitable for the degradation of organic pollutants.     

Structures,thermal stability,and crystalline properties of polyamide6/organic-modified Fe-montmorillonite composite nanofibers by electrospinning

In the present work, Fe-montmorillonite (Fe-MMT) was synthesized by hydrothermal method, and then was modified by cetyltrimethyl ammonium bromide (CTAB). The polyamide6 (PA6)/organic-modified Fe-montmorillonite (Fe-OMT) composite nanofibers were prepared by facile compounding and electrospinning. Fe-OMT was first dispersed in N, N-dimethyl formamide and then compounded with PA6 which was dissolved in formic acid. The composite solutions were electrospun to form PA6/Fe-OMT composite nanofibers. The structure, morphology, thermal stability, and crystalline properties of the composite nanofibers were characterized by Fourier transfer infrared (FTIR) spectra, Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), High-resolution electron microscopy (HREM), Scanning electron microscopy (SEM), and Thermogravimetric analyses (TGA), respectively. It was found that the silicate clay layers were well exfoliated within the composite nanofibers and were oriented along the fiber axis. The SEM images indicated that the loading of Fe-OMT decreased the diameters of composite nanofibers. TGA analyses revealed that the thermal stability was notably improved in the presence of silicate clay. It was also observed from wide-angle XRD analyses that the presence of nanoclays improved the γ-form crystals and induced the formations of α-form crystals of the PA6, attributed to effective nucleating effects of silicate clay platelets.     

In Situ Synthesis of Cuprous Oxide/Cellulose Nanofibers Gel and Antibacterial Properties

Cellulose nanofibers were synthesized by acetobacter xylinum (xylinum 1.1812). The cellulose nanofibers with 30-90 nm width constructed three-dimension network gel, which could be used as a wound dressing since it can provide moist environment to a wound. However, cellulose nanofibers have no antimicrobial activity to prevent wound infection. To achieve antimicrobial activity, the cellulose nanofibers can load cuprous oxide (Cu₂O) particles on the surface. The cuprous oxide is a kind of safe antibacterial material. The copper ions can be reduced into cuprous oxides by reducing agents such as glucose, N₂H₄ and sodium hypophosphite. The cellulose nanofibers network gel was soaked in CuSO₄ solution and filled with copper ions. The cuprous oxide nanoparticles were in situ synthesized by glucose and embedded in cellulose nanofibers network. The morphologies and structure of the composite gel were analyzed by FESEM, FTIR, WAXRD and inductively coupled plasma (ICP). The sizes of Cu₂O embedded in cellulose nanofibers network are 200-500 nm wide. The peak at 605 cm⁻¹ attributed to Cu(I)-O vibration of Cu₂O shits to 611 cm⁻¹ in the Cu₂O/ cellulose composite. The Cu₂O/ cellulose nanofibers composite reveals the obvious characteristic XRD pattern of Cu₂O and the results of ICP show that the content of Cu₂O in the composite is 13.1%. The antibacterial tests prove that the Cu₂O/ cellulose nanofibers composite has the high antibacterial activities which is higher against S. aureus than against E. coli.     

Gas flow-assisted alignment of super long electrospun nanofibers

Electrospinning provides a simple and versatile method for generating ultra thin fibers with diameters ranging from nanometer to micron out of various materials. However, there are still challenges in the alignment of electrospun nanofibers, which is an important step toward the exploitation of these fibers in applications. In this letter, we report a method using the gas flow to assist the alignment of electrospun nanofibers, which can form well-aligned super long polymeric nanofibers over large areas with the length of more than 20 cm. The improved collector is built by coupling a "T"-shaped electrode and a rectangle electrode, and it can make the electrospun nanofiber form a fixed site at the "T"-shaped electrode under the electric field and make it possible to use an assisting gas flow (AGF) to draw the other part of the nanofiber to fly toward the upside of the rectangle electrode and obtain well-aligned long nanofibers. These well-aligned long nanofibers can be further applied easily without disturbing the aligned structure, which is convenient for the measurement and device fabrications.     

Morphological studies on single crystals and nanofibers of poly(heptamethylene terephthalate)

Poly(heptamethylene terephthalate) (poly(7GT)) was synthesized, and its lamellar single-crystals were grown isothermally at 70 °C from a dilute solution in 1-octanol. Poly(7GT) nanofibers were prepared via electrospinning of its solution in 1,1,1,3,3,3-hexafluoro-2-propanol. Morphology of the single crystals and that of as-spun and annealed nanofibers were investigated by transmission electron microscopy. Selected-area electron diffraction (SAED) of the crystals gave a well-defined N-pattern consisting of spot-like hk0 reflections, and that of bundles of the annealed nanofibers indicated a highly oriented fiber pattern. From the analysis of SAED diagrams for single crystals and nanofibers, it can be assumed that poly(7GT) takes an orthorhombic crystal system and its unit cell parameters estimated are as follows: a = 1.409 nm, b = 1.480 nm, c (chain axis) = 3.392 nm, and α = β = γ = 90°.     

Ultrafast Zn2+ Intercalation and Deintercalation in Vanadium Dioxide

Although rechargeable aqueous zinc‐ion batteries have attracted extensive interest due to their environmental friendliness and low cost, they still lack suitable cathodes with high rate capabilities, which are hampered by the intense charge repulsion of bivalent Zn²⁺. Here, a novel intercalation pseudocapacitance behavior and ultrafast kinetics of Zn²⁺ into the unique tunnels of VO₂ (B) nanofibers in aqueous electrolyte are demonstrated via in situ X‐ray diffraction and various electrochemical measurements. Because VO₂ (B) nanofibers possess unique tunnel transport pathways with big sizes (0.82 and 0.5 nm² along the b‐ and c‐axes) and little structural change on Zn²⁺ intercalation, the limitation from solid‐state diffusion in the vanadium dioxide electrode is eliminated. Thus, VO₂ (B) nanofibers exhibit a high reversible capacity of 357 mAh g^?1, excellent rate capability (171 mAh g^?1 at 300 C), and high energy and power densities as applied for zinc‐ion storage.     

N掺杂TiO2纳米纤维高可见光催化CO2合成甲醇

采用气相生长法在介孔SiO₂球的表面上制备了ϕ 8~10 nm的TiO₂纳米纤维, 采用相同的方法, 还成功地制备了氮掺杂的TiO₂(N-TiO₂) 纳米纤维, 它具有更高的可见光催化活性。采用X射线光电子能谱(XPS)、紫外光电子能谱(UPS)、X射线衍射(XRD)、扫描电镜(SEM)、透射电子显微镜(TEM)、紫外–可见分光光度计(UV-Vis)、荧光分光光度计(PL)等对样品进行了测试分析。TiO₂纳米纤维具有高结晶度的锐钛矿晶型, 掺氮后的TiO₂纳米纤维带隙变窄, 在可见光波段有明显的吸收, 同时, 光生电子还原能力更强, 大大提高了可见光下催化还原CO₂合成甲醇的产率。在300 W氙灯光照2 h后, 用纯TiO₂纤维催化CO₂合成甲醇, 产率为493.4 μmol•g^-1∙h^-1, 转换频率(TOF) 为0.089 h^-1; 以N-TiO₂为催化剂合成甲醇产率提高了40.1%, 达695.1 μmol∙g^-1∙h^-1, 转换频率(TOF) 提高了40.4%, 为0.125 h^-1。     

An approach for evaluating nanomaterials for use as packed bed adsorber media: a case study of arsenate removal by titanate nanofibers

The primary goal of this paper is to propose a series of logical testing steps to determine whether a new adsorbent media is suitable for application in packed bed configurations for treating drinking water pollutants. Although the focus of the study is placed on titanate nanofibers, as a never before tested media for arsenate removal, the set of testing processes that encompasses nanomaterial characterization, equilibrium and kinetics tests, and modeling, can be used on any material to quickly determine whether these materials are suitable for water treatment applications in a packed bed configurations. Bundle-like titanate nanofibers were produced by an alkaline synthesis method with Degussa P25 TiO(2). The synthesized nanofibers have a rectangular ribbon-like shape and exhibited large surface area (126 m(2) g(-1)) and high adsorbent porosity (epsilon(P) approximately 0.51). Equilibrium batch experiments conducted in 10 mM NaHCO(3) buffered ultrapure water at three pH values (6.6, 7.6 and 8.3) with 125 microg L(-1) As(V) were fit with the Freundlich isotherm equation (q=KxC(E)(1/n)). The Freundlich adsorption intensity parameter (1/n) ranged from 0.51 to 0.66, while the capacity parameters (K) ranged from 5 to 26 microg g(-1). The pore diffusion coefficient and tortuosity were estimated to be D(P) approximately 1.04 x 10(-6) cm(2) s(-1), and tau approximately 4.4. For a packed bed adsorbent operated at a realistic loading rate of 11.6 m(3) m(-2) h(-1) with particles obtained by sieving the media through US mesh 80 x 120, the external mass transport coefficient was estimated to be k(f) approximately 8.84 x 10(-3) cm s(-1). In this study, surface diffusion was ignored because the adsorbent has high porosity. Pore surface diffusion model (PSDM) was used to predict the arsenate breakthrough curve, and a short bed adsorbent (SBA) test was conducted under the same conditions to verify validity of the estimated values. There was no titanium release in the treated effluent during the SBA test. The pore Biot number (Bi(P)>100) implied that pore intraparticle resistance controls the overall mass transport. The PSDM was used to predict arsenate breakthrough in a simulated full-scale system. The overall combined use of modeling, material characterization, equilibrium, and kinetics tests was easier, cheaper and faster than a long duration pilot tests. While the conclusion regarding the titanate nanofibers is that they are less suitable for arsenate removal from water than commercially available media, there may be other applications where this novel nanomaterial may be suitable because of unique surface chemistry and porosity.