Conjugated Polymer Modifying TiO2 Performance for Visible-Light Photodegradation of Organics

Up to now, the use of TiO₂ has been considered a promising advanced technology for organic pollutants removal from air or water, since it has high biological and chemical stability, high photoactivity, low toxicity, and low-cost production. However, there are issues to be addressed in enhancing TiO₂ performance, and one of the current key issues is redesigning UV-active photocatalysts and making them active in the visible region of the electromagnetic spectrum. This way, solar light absorption will be insured, and thus, a more efficient photocatalyst could be obtained. For this reason, conjugated polymers and their derivatives are considered to act as photosensitizers, being able to shift the TiO₂ activity from the UV to the visible region. Therefore, this study focuses on the synthesis of TiO₂/conjugated polymer systems, which was accomplished by the deposition of poly-3,4-ethylene-dioxy-thiophene (PEDOT [-C₆H₄O₂S-]_n), a low-band semiconductor with an excellent stability due to its extending π-conjugated electron system, on titania nanoarchitecture. First of all, a TiO₂ nanoarchitecture was synthesized by an ultrasound-assisted sol-gel method. Then, TiO₂/PEDOT systems were obtained and characterized by using different techniques such as X-ray diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, UV-Vis diffuse reflectance, and N₂ sorption measurements. The synthesized composites confirmed their mesoporosity and lower band gap values compared to bare titania, which clearly shows the ability to work as photocatalysts under visible-light activity. Further, we demonstrated that an organic pollutant, Congo Red dye, used as a model molecule could be photodegraded with the synthesized TiO₂/PEDOT systems, with efficiencies of up to 95% in the case of T_convPEDOT under UV light and up to 99% for T_convPEDOT under visible-light irradiation, accomplishing in this way a successful synthesis of visible-light-activated titania photocatalyst.

Composites of Montmorillonite and Titania Nanoparticles Prepared by Inverse Microemulsion Method: Physico-Chemical Characterization

TiO₂/montmorillonite composites were synthesized using inverse micellar route for the preparation of titania nanoparticles (4-6 nm diameter) in 1-hexanol and for the dispersion of one of the clay components. Two series of composites were obtained: one derived from cetyltrimethylammonium organomontmorillonite (CTA-Mt), exfoliated in 1-hexanol, and the other from sodium form of montmorillonite (Na-Mt) dispersed by formation of an inverse microemulsion in 1-hexanol. The TiO₂ content ranged from 16 to 64 wt.%. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, thermal analysis, and N₂ adsorption-desorption isotherms. The Na-Mt-derived component was shown to undergo transformation to CTA-Mt, as indicated by basal spacing of 17.5 nm, due to the interaction with the CTABr surfactant in inverse microemulsion. It was also better dispersed and intermixed with TiO₂ nanoparticles. As a result, the TiO₂/Na-Mt series displayed superior textural properties, with specific surface area up to 256 m²g^-1 and pore volume up to 0.247 cm³g^-1 compared with 208 m²g^-1 and 0.231 cm³g^-1, respectively, for the TiO₂/CTA-Mt counterpart. Members of both series were uniformly mesoporous, with the dominant pore size around 5 nm, i.e., comparable with the dimensions of titania nanoparticles. The advantage of the adopted synthesis method is discussed in the context of other preparative procedures used for manufacturing of titania-clay composites.

Synthesis and Characterization of Hierarchical Zeolites Modified with Polysaccharides and Its Potential Role as a Platform for Drug Delivery

Hierarchical zeolites are aluminosilicates with a crystal structure, which next to the micropores possess secondary porosity in the range of mesopores and/or small macropores. Due to their ordered structure and additional secondary porosity, they have aroused great interest among scientists in recent years. Therefore, the present work concerns the synthesis and characterization of hierarchical zeolites with secondary mesoporosity, based on commercial zeolites such as MFI (ZSM-5), BEA (β) and FAU (Y), and modified with polysaccharides such as inulin, hyaluronic acid, and heparin. All materials were characterized by various analytical techniques and applied as a platform for delivery of selected drug molecules. On the basis of X-ray diffraction (presence of reflections in the 2θ angle range of 1.5-2.5°) and low-temperature nitrogen sorption isotherms (mixture of isotherms of I and IV type) additional secondary porosity was found in the mesopore range. Additional tests were also conducted to determine the possibility of loading selected molecules with biological activity into the aforementioned materials and then releasing them in the therapeutic process. Molecules with different therapeutic options were selected for testing, namely ibuprofen, curcumin, and ferulic acid with anti-inflammatory, potentially anticancer, antioxidant, and skin discoloration activities, respectively. Preliminary studies have confirmed the possibility of using hierarchical zeolites as potential carriers for bioactive molecules, as the loading percentage of active substances ranged from 39-79% and cumulative release for ibuprofen reached almost 100% after 8 h of testing.

Tailoring of Textural Properties of 3D Reduced Graphene Oxide Composite Monoliths by Using Highly Crosslinked Polymer Particles toward Improved CO2 Sorption

The main constraint on developing a full potential for CO₂ adsorption of 3D composite monoliths made of reduced graphene oxide (rGO) and polymer materials is the lack of control of their textural properties, along with the diffusional limitation to the CO₂ adsorption due to the pronounced polymers' microporosity. In this work, the textural properties of the composites were altered by employing highly crosslinked polymer particles, synthesized by emulsion polymerization in aqueous media. For that aim, waterborne methyl methacrylate (MMA) particles were prepared, in which the crosslinking was induced by using different quantities of divinyl benzene (DVB). Afterward, these particles were combined with rGO platelets and subjected to the reduction-induced self-assembly process. The resulting 3D monolithic porous materials certainly presented improved textural properties, in which the porosity and BET surface area were increased up to 100% with respect to noncrosslinked composites. The crosslinked density of MMA polymer particles was a key parameter controlling the porous properties of the composites. Consequently, higher CO₂ uptake than that of neat GO structures and composites made of noncrosslinked MMA polymer particles was attained. This work demonstrates that a proper control of the microstructure of the polymer particles and their facile introduction within rGO self-assembly 3D structures is a powerful tool to tailor the textural properties of the composites toward improved CO₂ capture performance.

Creating Tunable Mesoporosity by Temperature-Driven Localized Crystallite Agglomeration

A new synthetic approach for tunable mesoporous metal-organic frameworks (MeMs) is developed. In this approach, mesopores are created in the process of heat conversion of highly mosaic metal-organic framework (MOF) crystals with non-interpenetrated low-density nanocrystallites into MOF crystals with two-fold interpenetrated high-density nanocrystallites. The two-fold interpenetration reduces the volume of the nanocrystallites in the mosaic crystal, and the accompanying localized agglomeration of the nanocrystallites results in the formation of mesopores among the localized crystallite agglomerates. The pore size can be easily modulated from 7 to 90 nm by controlling the heat treatment conditions, that is, the aging temperature and aging time. Various proteins can be encapsulated in the MeM, and immobilized enzymes show catalyst activity comparable to that of the free native enzymes. Immobilized β-galactosidase is recyclable and the enzyme activity of the immobilized catalase is maintained after exposure to high temperatures and various organic solvents.

Engineering Oversaturated Fe-N5 Multifunctional Catalytic Sites for Durable Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are regarded as a promising next-generation system for advanced energy storage owing to a high theoretical energy density of 2600 Wh kg^-1 . However, the practical implementation of Li-S batteries has been thwarted by the detrimental shuttling behavior of polysulfides, and the sluggish kinetics in electrochemical processes. Herein, a novel single atom (SA) catalyst with oversaturated Fe-N₅ coordination structure (Fe-N₅ -C) is precisely synthesized by an absorption-pyrolysis strategy and introduced as an effective sulfur host material. The experimental characterizations and theoretical calculations reveal synergism between atomically dispersed Fe-N₅ active sites and the unique carbon support. The results exhibit that the sulfur composite cathode built on the Fe-N₅ -C can not only adsorb polysulfides via chemical interaction, but also boost the redox reaction kinetics, thus mitigating the shuttle effect. Meanwhile, the robust three-dimensional nitrogen doped carbon nanofiber with large surface area, and high porosity enables strong physical confinement and fast electron/ion transfer process. Attributed to such unique features, Li-S batteries with S/Fe-N₅ -C composite cathode realize outstanding cyclability and rate capability, as well as high areal capacities under raised sulfur loading, which demonstrates great potential in developing advanced Li-S batteries.

Microporous Carbon Nitride (C3 N5.4 ) with Tetrazine based Molecular Structure for Efficient Adsorption of CO2 and Water

Mesoporous carbon nitrides with C₃ N₅ and C₃ N₆ stoichiometries created a new momentum in the field of organic metal-free semiconductors owing to their unique band structures and high basicity. Here, we report on the preparation of a novel graphitic microporous carbon nitride with a tetrazine based chemical structure and the composition of C₃ N_5.4 using ultra-stable Y zeolite as the template and aminoguanidine hydrochloride, a high nitrogen-containing molecule, as the CN precursor. Spectroscopic characterization and density functional theory calculations reveal that the prepared material exhibits a new molecular structure, which comprises two tetrazines and one triazine rings in the unit cell and is thermodynamically stable. The resultant carbon nitride shows an outstanding surface area of 130.4 m²  g^-1 and demonstrates excellent CO₂ adsorption per unit surface area of 47.54 μmol m^-2 , which is due to the existence of abundant free NH₂ groups, basic sites and microporosity. The material also exhibits highly selective sensing over water molecules (151.1 mmol g^-1 ) and aliphatic hydrocarbons due to its unique microporous structure with a high amount of hydrophilic nitrogen moieties and recognizing ability towards small molecules.

Enhancing Lithium and Sodium Storage Properties of TiO2(B) Nanobelts by Doping with Nickel and Zinc

Nickel- and zinc-doped TiO2(B) nanobelts were synthesized using a hydrothermal technique. It was found that the incorporation of 5 at.% Ni into bronze TiO2 expanded the unit cell by 4%. Furthermore, Ni dopant induced the 3d energy levels within TiO2(B) band structure and oxygen defects, narrowing the band gap from 3.28 eV (undoped) to 2.70 eV. Oppositely, Zn entered restrictedly into TiO2(B), but nonetheless, improves its electronic properties (Eg is narrowed to 3.21 eV). The conductivity of nickel- (2.24 × 10-8 S·cm-1) and zinc-containing (3.29 × 10-9 S·cm-1) TiO2(B) exceeds that of unmodified TiO2(B) (1.05 × 10-10 S·cm-1). When tested for electrochemical storage, nickel-doped mesoporous TiO2(B) nanobelts exhibited improved electrochemical performance. For lithium batteries, a reversible capacity of 173 mAh·g-1 was reached after 100 cycles at the current load of 50 mA·g-1, whereas, for unmodified and Zn-doped samples, around 140 and 151 mAh·g-1 was obtained. Moreover, Ni doping enhanced the rate capability of TiO2(B) nanobelts (104 mAh·g-1 at a current density of 1.8 A·g-1). In terms of sodium storage, nickel-doped TiO2(B) nanobelts exhibited improved cycling with a stabilized reversible capacity of 97 mAh·g-1 over 50 cycles at the current load of 35 mA·g-1.

A New Approach for Controlling Mesoporosity in Activated Carbon by the Consecutive Process of Air Oxidation, Thermal Destruction of Surface Functional Groups, and Carbon Activation (the OTA Method)

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO2 gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm3/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m2/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm3/g (33.0% of total pore volume) and surface area of 1499 m2/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.

Mesoporous Carbons from Polysaccharides and Their Use in Li-O2 Batteries

Previous studies have demonstrated that the mesoporosity of carbon material obtained by the Starbon^® process from starch-formed by amylose and amylopectin can be tuned by controlling this ratio (the higher the amylose, the higher the mesoporosity). This study shows that starch type can also be an important parameter to control this mesoporosity. Carbons with controlled mesoporosity (V_meso from 0.1–0.7 cm³/g) have been produced by the pre-mixing of different starches using an ionic liquid (IL) followed by a modified Starbon^® process. The results show that the use of starch from corn and maize (commercially available Hylon VII with maize, respectively) is the better combination to increase the mesopore volume. Moreover, “low-cost” mesoporous carbons have been obtained by the direct carbonization of the pre-treated starch mixtures with the IL. In all cases, the IL can be recovered and reused, as demonstrated by its recycling up to three times. Furthermore, and as a comparison, chitosan has been also used as a precursor to obtain N-doped mesoporous carbons (5.5 wt% N) with moderate mesoporosity (V_meso = 0.43 cm³/g). The different mesoporous carbons have been tested as cathode components in Li-O₂ batteries and it is shown that a higher carbon mesoporosity, produced from starch precursor, or the N-doping, produced from chitosan precursor, increase the final battery cell performance (specific capacity and cycling).

Correction: An advanced structural characterization of templated meso-macroporous carbon monoliths by small- and wide-angle scattering techniques

[This corrects the article DOI: 10.3762/bjnano.11.23.].

Tunable Periodically Ordered Mesoporosity in Palladium Membranes Enables Exceptional Enhancement of Intrinsic Electrocatalytic Activity for Formic Acid Oxidation

Developing superior electrocatalysts for formic acid oxidation (FAO) is the most crucial step in commercializing direct formic acid fuel cells. Herein, we electrodeposited palladium membranes with periodically ordered mesoporosity obtained by asymmetrically replicating the bicontinuous cubic phase structure of a lyotropic liquid-crystal template. The Pd membrane with the largest periodicity and highest degree of order delivered up to 90.5 m²  g^-1 of electrochemical active surface area and 3.34 A mg^-1 electrocatalysis capability towards FAO, 3.8 and 7.8 times the values of the commercial Pd/C catalyst, respectively. By controlling the temperature and potential of the electrodeposition procedure, the periodicity area and order degree of the mesoporosity are highly tunable. These Pd membranes gave prototype formic acid fueled cells with 4.3 and 2.4 times the maximum current and power density of the commercial Pd/C catalyst.

An advanced structural characterization of templated meso-macroporous carbon monoliths by small- and wide-angle scattering techniques

This study is dedicated to link the nanoscale pore space of carbon materials, prepared by hard-templating of meso-macroporous SiO2 monoliths, to the corresponding nanoscale polyaromatic microstructure using two different carbon precursors wthat generally exhibit markedly different carbonization properties, i.e., a graphitizable pitch and a non-graphitizable resin. The micro- and mesoporosity of these monolithic carbon materials was studied by the sorption behavior of a relatively large organic molecule (p-xylene) in comparison to typical gas adsorbates (Ar). In addition, to obtain a detailed view on the nanopore space small-angle neutron scattering (SANS) combined with in situ physisorption was applied, using deuterated p-xylene (DPX) as a contrast-matching agent in the neutron scattering process. The impact of the carbon precursor on the structural order on an atomic scale in terms of size and disorder of the carbon microstructure, on the nanopore structure, and on the template process is analyzed by special evaluation approaches for SANS and wide-angle X-ray scattering (WAXS). The WAXS analysis shows that the pitch-based monolithic material exhibits a more ordered microstructure consisting of larger graphene stacks and similar graphene layer sizes compared to the monolithic resin. Another major finding is the discrepancy in the accessible micro/mesoporosity between Ar and deuterated p-xylene that found for the two different carbon precursors, pitch and resin, which can be regarded as representative carbon precursors in general. These differences essentially indicate that physisorption using probe gases such as Ar or N2 can provide misleading parameters if to be used to appraise the accessibility of the nanoscale pore space.

Carbon Black as Conductive Additive and Structural Director of Porous Carbon Gels

This work investigates the impact of carbon black (CB) as a porogenic agent and conductive additive in the preparation of electrically conductive nanoporous carbon gels. For this, a series of materials were prepared by the polycondensation of resorcinol/formaldehyde mixtures in the presence of increasing amounts of carbon black. The conductivity of the carbon gel/CB composites increased considerably with the amount of CB, indicating a good dispersion of the additive within the carbon matrix. A percolation threshold of ca. 8 wt.% of conductive additive was found to achieve an adequate "point to point" conductive network. This value is higher than that reported for other additives, owing to the synthetic route chosen, as the additive was incorporated in the reactant's mixture (pre-synthesis) rather than in the formulation of the electrodes ink (post-synthesis). The CB strongly influenced the development of the porous architecture of the gels that exhibited a multimodal mesopore structure comprised of two distinct pore networks. The microporosity and the primary mesopore structure remained rather unchanged. On the contrary, a secondary network of mesopores was formed in the presence of the additive. Furthermore, the average mesopore size and the volume of the secondary network increased with the amount of CB.

Facile Preparative Access to Bioactive Silicon Oxycarbides with Tunable Porosity

In the present work, Ca-containing silicon oxycarbides (SiCaOC) with varying Ca content have been synthesized via sol-gel processing and thermal treatment in inert gas atmosphere (pyrolysis). It has been shown that the as-prepared SiCaOC materials with low Ca loadings (Ca/Si molar ratios = 0.05 or 0.12) were X-ray amorphous; their glassy network contains Q3 sites, indicating the presence of Ca2+ at non-bridging-oxygen sites. SiCaOC with high Ca content (i.e., Ca/Si molar ratio = 0.50) exhibits the presence of crystalline calcium silicate (mainly pseudowollastonite). Furthermore, it has been shown that the incorporation of Ca into the SiOC glassy network has a significant effect on its porosity and specific surface area. Thus, the as-prepared Ca-free SiOC material is shown to be non-porous and having a specific surface area (SSA) of 22.5 m2/g; whereas SiCaOC with Ca/Si molar ratio of 0.05 exhibits mesoporosity and a SSA value of 123.4 m2/g. The further increase of Ca content leads to a decrease of the SSA and the generation of macroporosity in SiCaOC; thus, SiCaOC with Ca/Si molar ratio of 0.12 is macroporous and exhibits a SSA value of 39.5 m2/g. Bioactivity assessment in simulated body fluid (SBF) confirms the hydroxyapatite formation on all SiCaOC samples after seven days soaking, unlike the relatively inert ternary silicon oxycarbide reference. In particular, SiCaOC with a Ca/Si molar ratio of 0.05 shows an increased apatite forming ability compared to that of SiCaOC with Ca/Si molar ratio of 0.12; this difference is considered to be a direct consequence of the significantly higher SSA of the sample with the Ca/Si ratio of 0.05. The present work indicates two effects of Ca incorporation into the silicon oxycarbide glassy network on its bioactivity: Firstly, Ca2+ is shown to contribute to the slight depolymerization of the network, which clearly triggers the hydroxyapatite formation (compare the bioactive behavior of SiOC to that of SiCaOC with Ca/Si molar ratio 0.12 upon SBF exposure); secondly, the Ca2+ incorporation seems to strongly affect the porosity and SSA in the prepared SiCaOC materials. There is an optimum of Ca loading into the silicon oxycarbide glassy network (at a Ca/Si molar ration of 0.05), which provides mesoporosity and reaches maximum SSA, both highly beneficial for the bioactive behavior of the materials. An increase of the Ca loading leads, in addition to the crystallization of calcium silicates, to a coarsening of the pores (i.e., macroporosity) and a significant decrease of the SSA, both negatively affecting the bioactivity.

Sorption of Heavy Metal Cations on Mesoporous ZSM-5 and Mordenite Zeolites

Desilication and dealumination techniques were used to obtain mesoporous ZSM-5 and mordenite zeolites. The study provides insight into specific structural, textural, and sorption properties of obtained materials with different Si/Al ratios. Subsequent dealumination and desilication procedures were found to be efficient methods of generating a secondary system of mesopores in mordenite and ZSM-5 crystals while preserving their microporous character. The investigated materials were evaluated in terms of their sorption properties of selected heavy metal cations (Cd²⁺, Cr³⁺, and Pb²⁺). Particular emphasis was placed on the structural examination of the materials via infrared spectroscopy (FT-IR). Other research methods included X-ray diffraction (XRD), X-ray fluorescence (XRF), nuclear magnetic resonance (NMR) and atomic absorption spectrometry (AAS).

Carbon Xerogels Hydrothermally Doped with Bimetal Oxides for Oxygen Reduction Reaction

A total of two carbon xerogels doped with cobalt and nickel were prepared by the sol-gel method. The obtained carbon xerogels underwent further surface modification with three binary metal oxides namely: nickel cobaltite, nickel ferrite, and cobalt ferrite through the hydrothermal method. The mesopore volumes of these materials ranged between 0.24 and 0.40 cm3/g. Moreover, there was a morphology transformation for the carbon xerogels doped with nickel cobaltite, which is in the form of nano-needles after the hydrothermal process. Whereas the carbon xerogels doped with nickel ferrite and cobalt ferrite maintained the normal carbon xerogel structure after the hydrothermal process. The prepared materials were tested as electrocatalysts for oxygen reduction reaction using 0.1 M KOH. Among the prepared carbon xerogels cobalt-doped carbon xerogel had better electrocatalytic performance than the nickel-doped ones. Moreover, the carbon xerogels doped with nickel cobaltite showed excellent activity for oxygen reduction reaction due to mesoporosity development. NiCo2O4/Co-CX showed to be the best electrocatalyst of all the prepared electrocatalysts for oxygen reduction reaction application, exhibiting the highest electrocatalytic activity, lowest onset potential Eonset of -0.06 V, and the lowest equivalent series resistance (ESR) of 2.74 Ω.

[Phosphate Removal Using Rice Husk Biochars Modified with Lanthanum Hydroxide]

La-modified RHBCs (La-RHBCs) were fabricated by immobilizing La(OH)₃ nanoparticles on mesoporous rice husk biochars (RHBCs) using a co-precipitation method. Specifically, the effects of the pore structure of the RHBCs, solution pH, and coexisting substances on phosphate adsorption by the La-RHBCs were studied. The results showed that the La loading of the La-RHBCs was positively correlated with the mesoporosity of the RHBCs. La-modified RHBCs with higher mesoporosity hosts showed faster adsorption rates and lower leaching of La during phosphate adsorption. The adsorption process could be described by a pseudo second-order kinetic model, and the reaction rate was controlled by intraparticle diffusion. The Langmuir isotherm model fitted the adsorption process better, and the theoretical maximum adsorption capacities were 41.22, 43.26, and 45.62 mg·g^-1, respectively. The high P/La molar ratios of more than 1.5 indicated the high utilization efficiencies of the La in the La-immobilized RHBCs. Moreover, phosphate could be effectively removed by the La-modified RHBCs over a wide pH range of 3-9. The La-modified RHBCs also exhibited good adsorption selectivity towards phosphate in the presence of coexisting anions and humic acids. Phosphate adsorption by the La-RHBCs was enhanced in the presence of Ca²⁺, while it was inhibited in the presence of Mg²⁺.

Extended Nitric Oxide-Releasing Polyurethanes via S-Nitrosothiol-Modified Mesoporous Silica Nanoparticles

S-Nitrosothiol (RSNO)-modified mesoporous silica nanoparticles (MSNs) were doped into polyurethane (PU) to achieve extended NO-releasing coatings. Parameters influencing the synthesis of RSNO-functionalized nitric oxide (NO)-releasing MSNs were evaluated to elucidate the impact of pore structure on NO release characteristics. The porous particles were characterized as having larger NO payloads and longer NO release durations than those of nonporous particles, a feature attributed to the recombination of the NO radical in confined intraporous microenvironments. NO release kinetics, particle leaching, and thermal stability of the RSNO-modified MSNs dispersed in PU were evaluated as a function of PU structure to determine the feasibility of preparing a range of NO-releasing polymers for biomedical device-coating applications. The NO release kinetics from the PUs proved to be highly extended (>30 d) and consistent over a range of PU properties. Furthermore, RSNO-modified MSN leaching was not observed from the PUs. The NO release payloads were also maintained for 4 days for polymers stored at 0 °C.

Tuning Texture and Morphology of Mesoporous TiO₂ by Non-Hydrolytic Sol-Gel Syntheses

The development of powerful synthetic methodologies is paramount in the design of advanced nanostructured materials. Owing to its remarkable properties and low cost, nanostructured TiO₂ is widely investigated for applications such as photocatalysis, energy conversion or energy storage. In this article we report the synthesis of mesoporous TiO₂ by three different non-hydrolytic sol-gel routes, and we investigate the influence of the synthetic route and of the presence and nature of the solvent on the structure, texture and morphology of the materials. The first route is the well-known ether route, based on the reaction of TiCl₄ with ⁱPr₂O. The second and third routes, which have not been previously described for the synthesis of mesoporous TiO₂, involve the reaction of Ti(OⁱPr)₄ with stoichiometric amounts of acetophenone and benzoic anhydride, respectively. All materials are characterized by XRD, N₂ physisorption and SEM. By playing with the non-hydrolytic route used and the reaction conditions (presence of a solvent, nature of the solvent, calcination), it is possible to tune the morphology and texture of the TiO₂. Depending on the reaction conditions, a large variety of mesoporous TiO₂ nanostructures could be obtained, resulting from the spontaneous aggregation of TiO₂ nanoparticles, either rounded nanoparticles, platelets or nanorods. These nanoparticle networks exhibited a specific surface area up to 250 m² g⁻¹ before calcination, or up to 110 m² g⁻¹ after calcination.

Catalytic Fast Pyrolysis of Kraft Lignin With Conventional, Mesoporous and Nanosized ZSM-5 Zeolite for the Production of Alkyl-Phenols and Aromatics

The valorization of lignin that derives as by product in various biomass conversion processes has become a major research and technological objective. The potential of the production of valuable mono-aromatics (BTX and others) and (alkyl)phenols by catalytic fast pyrolysis of lignin is investigated in this work by the use of ZSM-5 zeolites with different acidic and porosity characteristics. More specifically, conventional microporous ZSM-5 (Si/Al = 11.5, 25, 40), nano-sized (≤20 nm, by direct synthesis) and mesoporous (9 nm, by mild alkaline treatment) ZSM-5 zeolites were tested in the fast pyrolysis of a softwood kraft lignin at 400-600°C on a Py/GC-MS system and a fixed-bed reactor unit. The composition of lignin (FT-IR, 2D HSQC NMR) was correlated with the composition of the thermal (non-catalytic) pyrolysis oil, while the effect of pyrolysis temperature and catalyst-to-lignin (C/L) ratio, as well as of the Si/Al ratio, acidity, micro/mesoporosity and nano-size of ZSM-5, on bio-oil composition was thoroughly investigated. It was shown that the conventional microporous ZSM-5 zeolites are more selective toward mono-aromatics while the nano-sized and mesoporous ZSM-5 exhibited also high selectivity for (alkyl)phenols. However, the nano-sized ZSM-5 zeolite exhibited the lowest yield of organic bio-oil and highest production of water, coke and non-condensable gases compared to the conventional microporous and mesoporous ZSM-5 zeolites.

Cobalt Nanoparticles Chemically Bonded to Porous Carbon Nanosheets: A Stable High-Capacity Anode for Fast-Charging Lithium-Ion Batteries

A two-dimensional electrode architecture of ∼25 nm sized Co nanoparticles chemically bonded to ∼100 nm thick amorphous porous carbon nanosheets (Co@PCNS) through interfacial Co-C bonds is reported for the first time. This unique 2D hybrid architecture incorporating multiple Li-ion storage mechanisms exhibited outstanding specific capacity, rate performance, and cycling stabilities compared to nanostructured Co₃O₄ electrodes and Co-based composites reported earlier. A high discharge capacity of 900 mAh/g is achieved at a charge-discharge rate of 0.1C (50 mA/g). Even at high rates of 8C (4 A/g) and 16C (8 A/g), Co@PCNS demonstrated specific capacities of 620 and 510 mAh/g, respectively. Integrity of interfacial Co-C bonds, Co nanoparticles, and 90% of the initial capacity are preserved after 1000 charge-discharge cycles. Implementation of Co nanoparticles instead of Co₃O₄ restricted Li₂O formation during the charge-discharge process. In situ formed Co-C bonds during the pyrolysis steps improve interfacial charge transfer, and eliminate particle agglomeration, identified as the key factors responsible for the exceptional electrochemical performance of Co@PCNS. Moreover, the nanoporous microstructure and 2D morphology of carbon nanosheets facilitate superior contact with the electrolyte solution and improved strain relaxation. This study summarizes design principles for fabricating high-performance transition-metal-based Li-ion battery hybrid anodes.

Visual Sensor for Sterilization of Polymer Fixtures Using Embedded Mesoporous Silicon Photonic Crystals

A porous photonic crystal is integrated with a plastic medical fixture (IV connector hub) to provide a visual colorimetric sensor to indicate the presence or absence of alcohol used to sterilize the fixture. The photonic crystal is prepared in porous silicon (pSi) by electrochemical anodization of single crystal silicon, and the porosity and the stop band of the material is engineered such that the integrated device visibly changes color (green to red or blue to green) when infiltrated with alcohol. Two types of self-reporting devices are prepared and their performance compared: the first type involves heat-assisted fusion of a freestanding pSi photonic crystal to the connector end of a preformed polycarbonate hub, forming a composite where the unfilled portion of the pSi film acts as the sensor; the second involves generation of an all-polymer replica of the pSi photonic crystal by complete thermal infiltration of the pSi film and subsequent chemical dissolution of the pSi portion. Both types of sensors visibly change color when wetted with alcohol, and the color reverts to the original upon evaporation of the liquid. The sensor performance is verified using E. coli-infected samples.

Photocatalytic and adsorption properties of TiO2-pillared montmorillonite obtained by hydrothermally activated intercalation of titanium polyhydroxo complexes

We report on a new approach for the synthesis of TiO₂-pillared montmorillonite, where the pillars exhibit a high degree of crystallinity (nanocrystals) representing a mixture of anatase and rutile phases. The structures exhibit improved adsorption and photocatalytic activity as a result of hydrothermally activated intercalation of titanium polyhydroxo complexes (i.e., TiCl₄ hydrolysis products) in a solution with a concentration close to the sol formation limit. The materials, produced at various annealing temperatures from the intercalated samples, were characterized by infrared spectroscopy, differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA), X-ray diffraction, dynamic light scattering (DLS) measurements, and liquefied nitrogen adsorption/desorption. The photocatalytic activity of the TiO₂-pillared materials was studied using the degradation of anionic (methyl orange, MO) and cationic (rhodamine B, RhB) dyes in water under UV irradiation. The combined effect of adsorption and photocatalysis resulted in removal of 100% MO and 97.5% RhB (with an initial concentration of 40 mg/L and a photocatalyst-sorbent concentration of 1 g/L) in about 100 minutes. The produced TiO₂-pillared montmorillonite showed increased photocatalytic activity as compared to the commercially available photocatalyst Degussa P25.

A "Nanopore Lithography" Strategy for Synthesizing Hierarchically Micro/Mesoporous Carbons from ZIF-8/Graphene Oxide Hybrids for Electrochemical Energy Storage

Porous carbons derived from metal-organic frameworks (MOFs) are promising materials for a number of energy- and environment-related applications, but their almost exclusively microporous texture can be an obstacle to their performance in practical uses. Here, we introduce a novel strategy for the generation of very uniform mesoporosity in a prototypical MOF, namely, zeolitic imidazolate framework-8 (ZIF-8). The process, referred to as "nanopore lithography", makes use of graphene oxide (GO) nanosheets enclosing ZIF-8 particles as masks or templates for the transfer of mesoporous texture to the latter. Upon controlled carbonization and activation, nanopores created in the GO envelope serve as selective entry points for localized etching of carbonized ZIF-8, so that such nanopores are replicated in the MOF-derived carbonaceous structure. The resulting porous carbons are dominated by uniform mesopores ∼3-4 nm in width and possess specific surface areas of ∼1300-1400 m² g^-1. Furthermore, we investigate and discuss the specific experimental conditions that afford the mesopore-templating action of the GO nanosheets. Electrochemical characterization revealed an improved capacitance as well as a faster, more reversible charge/discharge kinetics for the ZIF-8-derived porous carbons obtained through nanopore lithography, relative to those for their counterparts with standard activation (no GO templating), thus indicating the potential practical advantage of the present approach in capacitive energy storage applications.

Facile Synthesis of a Novel Hierarchical ZSM-5 Zeolite: A Stable Acid Catalyst for Dehydrating Glycerol to Acrolein

Catalytic biomass conversion is often hindered by coking. Carbon compounds cover active surface and plug pores, causing catalyst deactivation. Material design at the nanoscale allows tailoring of the catalytic activity and stability. Here, we report a simple synthesis of nanosized ZSM‐5 materials by using a silicalite‐1 seeding suspension. ZSM‐5 crystals were grown from a deionized silica source in the presence of ammonia. By using silicalite‐1 seeds, crystalline ZSM‐5 is synthesized without any structure‐directing agent. This method allows parallel preparation of a range of ZSM‐5 samples, eliminating time‐consuming ion‐exchange steps. Mesoporosity is introduced by formation of intercrystallite voids, owing to nanocrystal agglomeration. The effects of crystal sizes and morphologies are then evaluated in the catalytic dehydration of glycerol to acrolein, with results compared against commercial ZSM‐5. The most active nanosized ZSM‐5 catalysts were five times more stable compared with commercial ZSM‐5, giving quantitative conversion and twice the acrolein yield compared with the commercial catalyst. The influence of the catalyst structure on the chemical diffusion and the resistance to coking are discussed.

Enhanced Visible-Light-Driven Photocatalytic Disinfection Performance and Organic Pollutant Degradation Activity of Porous g-C3N4 Nanosheets

Porous g-C₃N₄ nanosheet (PCNS) photocatalyst with a thickness of 2.0 nm, pore volume of 0.61 cm³ g^-1, and surface area of 190.1 m² g^-1 was prepared by a simple two-step template-free approach without the addition of extra reagents. Compared with the bulk g-C₃N₄ (BCN), PCNS possesses a greater number of surface reactive sites, improved efficiency of charge transfer, and accelerated separation of photogenerated electron-hole pairs. Accordingly, the visible-light-driven photocatalytic disinfection performance and organic pollutant degradation activity of PCNS are significantly enhanced. Escherichia coli (E. coli) cells can be killed completely by PCNS within 4 h, whereas only 77.1% of E. coli cells can be killed by BCN. The photodegradation rates of PCNS on methylene blue, Acid Red 27, and bisphenol A are almost 6.4, 4.0, and 1.9 times as fast as that of BCN, respectively. The photocurrent intensity of PCNS is about 3.7 times in comparison with that of BCN. Considering the easy preparation and excellent performance, PCNS could be a promising and competitive visible-light-driven photocatalyst in the field of environment remediation.

Applying Capacitive Energy Storage for In Situ Manipulation of Magnetization in Ordered Mesoporous Perovskite-Type LSMO Thin Films

Mesostructured nonsilicate materials, particularly mixed-metal oxides, are receiving much attention in recent years because of their potential for numerous applications. Via the polymer-templating method, perovskite-type lanthanum strontium manganese oxide (La_1-xSr_xMnO₃, LSMO, with x ≈ 0.15 to 0.30) with a continuous 3D cubic network of 23 nm pores is prepared in thin-film form for the first time. Characterization results from grazing incidence X-ray scattering, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and electron microscopy and tomography show that the dip-coated sol-gel-derived films are of high quality in terms of both composition and morphology and that they are stable to over 700 °C. Magnetic and magnetotransport measurements demonstrate that the material with the highest strontium concentration is ferromagnetic at room temperature and exhibits metallic resistivity behavior below 270 K. Besides, it behaves differently from epitaxial layers (e.g., enhanced low-field magnetoresistance effect). It is also shown that carriers (electrons and holes) can be induced into the polymer-templated mesostructured LSMO films via capacitive double-layer charging. This kind of electrostatic doping utilizing ionic liquid gating causes large relative changes in magnetic susceptibility at room temperature and is a viable technique to tune the magnetic phase diagram in situ.

Proton Conduction in Sulfonated Organic-Inorganic Hybrid Monoliths with Hierarchical Pore Structure

Porous organic-inorganic hybrid monoliths with hierarchical porosity exhibiting macro- and mesopores are prepared via sol-gel process under variation of the mesopore size. Organic moieties in the pore walls are incorporated by substituting up to 10% of the silicon precursor tetramethylorthosilicate with bisilylated benzene molecules. After functionalization with sulfonic acid groups, the resulting sulfonated hybrid monoliths featuring a bimodal pore structure are investigated regarding proton conduction depending on temperature and relative humidity. The hierarchical pore system and controlled mesopore design turn out to be crucial for sulfonation and proton conduction. These sulfonated hybrid hierarchical monoliths containing only 10% organic precursor exhibit higher proton conduction at different relative humidities than sulfonated periodic mesoporous organosilica made of 100% bisilylated precursors exhibiting solely mesopores, even with a lower concentration of sulfonic acid groups.

Hollow Mesoporous Plasmonic Nanoshells for Enhanced Solar Vapor Generation

In the past decade, nanomaterials have made their way into a variety of technologies in solar energy, enhancing the performance by taking advantage of the phenomena inherent to the nanoscale. Recent examples exploit plasmonic core/shell nanoparticles to achieve efficient direct steam generation, showing great promise of such nanoparticles as a useful material for solar applications. In this paper, we demonstrate a novel technique for fabricating bimetallic hollow mesoporous plasmonic nanoshells that yield a higher solar vapor generation rate compared with their solid-core counterparts. On the basis of a combination of nanomasking and incomplete galvanic replacement, the hollow plasmonic nanoshells can be fabricated with tunable absorption and minimized scattering. When exposed to sun light, each hollow nanoshell generates vapor bubbles simultaneously from the interior and exterior. The vapor nucleating from the interior expands and diffuses through the pores and combines with the bubbles formed on the outer wall. The lack of a solid core significantly accelerates the initial vapor nucleation and the overall steam generation dynamics. More importantly, because the density of the hollow porous nanoshells is essentially equal to the surrounding host medium these particles are much less prone to sedimentation, a problem that greatly limits the performance and implementation of standard nanoparticle dispersions.

MnO Conversion in Li-Ion Batteries: In Situ Studies and the Role of Mesostructuring

Complex manganese oxides have been extensively studied as intercalation Li-ion battery electrodes. The simple oxide MnO has been proposed as a conversion anode material with a theoretical capacity of 756 mAh g(-1) for full reduction to the metal. We report the reaction of MnO with Li using in situ X-ray diffraction and find no sign of crystalline products upon either discharge or charge. However, the absence of reflections, paired with electrochemical impedance spectroscopy, suggests disordered discharge products. We also examine composite electrodes with porous particles of MnO as the active component, with pores generated through the reductive heating of Mn3O4. We compare the behavior of these with more dense MnO powders, including studies of the electrode morphologies pre- and postcyling. We find differences in the first discharge relevant to the utility of such mesostructuring in conversion reaction materials. Specifically, we find this type of mesostructure, which gives advantage in intercalation and pseudocapacitive storage, does not yield the same benefits for conversion reaction systems.

Mesoporous Few-Layer Graphene Platform for Affinity Biosensing Application

A label-free, highly reproducible, sensitive, and selective biosensor is proposed using antiapolipoprotein B 100 (AAB) functionalized mesoporous few-layer reduced graphene oxide and nickel oxide (rGO-NiO) nanocomposite for detection of low density lipoprotein (LDL) molecules. The formation of mesoporous rGO-NiO composite on indium tin oxide conductive electrode has been accomplished via electrophoretic technique using colloidal suspension of rGO sheets and NiO nanoparticles. This biosensor shows good stability obtained by surface conjugation of antibody AAB molecules with rGO-NiO matrix by EDC-NHS coupling chemistry. The defect-less few layer rGO sheets, NiO nanoparticles (nNiO) and formation of nanocomposite has been confirmed by Raman mapping, electron microscopic studies, X-ray diffraction, and electrochemical techniques. The synthesized rGO-NiO composite is mesoporous dominated with a small percentage of micro and macroporous structure as is evident by the results of Brunauer-Emmett-Teller experiment. Further, the bioconjugation of AAB with rGO-NiO has been investigated by Fourier transform-infrared spectroscopy studies. The kinetic studies for binding of antigen-antibody (LDL-AAB) and analytical performance of this biosensor have been evaluated by the impedance spectroscopic method. This biosensor exhibits an excellent sensitivity of 510 Ω (mg/dL)(-1) cm(-2) for detection of LDL molecules and is sensitive to 5 mg/dL concentration of LDL in a wide range of 0-130 mg/dL. Thus, this fabricated biosensor is an efficient and highly sensitive platform for the analysis of other antigen-antibody interactions and biomolecules detection.

Mesoporous Phosphorus-Doped g-C3N4 Nanostructured Flowers with Superior Photocatalytic Hydrogen Evolution Performance

Graphitic carbon nitride (g-C3N4) has been deemed a promising heterogeneous metal-free catalyst for a wide range of applications, such as solar energy utilization toward water splitting, and its photocatalytic performance is reasonably adjustable through tailoring its texture and its electronic and optical properties. Here phosphorus-doped graphitic carbon nitride nanostructured flowers of in-plane mesopores are synthesized by a co-condensation method in the absence of any templates. The interesting structures, together with the phosphorus doping, can promote light trapping, mass transfer, and charge separation, enabling it to perform as a more impressive catalyst than its pristine carbon nitride counterpart for catalytic hydrogen evolution under visible light irradiation. The catalyst has low cost, is environmentally friendly, and represents a potential candidate in photoelectrochemistry.

Mesoporous carbon nitride-tungsten oxide composites for enhanced photocatalytic hydrogen evolution

Composites of mesoporous polymeric carbon nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk carbon nitrides and their composites and more notably even to the best reported mesoporous carbon nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the carbon nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

Mesoporous carbon nitride-tungsten oxide composites for enhanced photocatalytic hydrogen evolution

Composites of mesoporous polymeric carbon nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk carbon nitrides and their composites and more notably even to the best reported mesoporous carbon nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the carbon nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

Mesoporosity changes from cambium to mature tension wood: a new step toward the understanding of maturation stress generation in trees

In order to progress in the understanding of mechanical stress generation, the mesoporosity of the cell wall and its changes during maturation of poplar (Populus deltoides × P. nigra) tension wood (TW) and opposite wood (OW) were measured by nitrogen adsorption-desorption. Variations in the thickness of the gelatinous layer (G-layer) were also measured to clarify whether the mesoporosity change simultaneously with the deposition of the G-layer in TW. Results show that mesoporous structures of TW and OW were very similar in early development stages before the deposition of G-layers. With the formation of the S₂ layer in OW and the G-layer in TW, the mesopore volume decreased steeply before lignification. However, in TW only, the decrease in mesopore volume occurred together with the pore shape change and a progressive increase in pore size. The different patterns observed in TW revealed that pores from G-layers appear with a different shape compared to those of the compound middle lamella, and their size increases during the maturation process until stabilising in mature wood. This observation strongly supports the hypothesis of the swelling of the G-layer matrix during maturation as the origin of maturation stress in poplar tension wood.

Effects of adsorbed and templated nanosilver in mesoporous calcium-silicate nanoparticles on inhibition of bacteria colonization of dentin

Mesoporous calcium-silicate nanoparticles (MCSNs) are advanced biomaterials for controlled drug delivery and mineralization induction. Nanosilver-incorporated MCSNs (Ag-MCSNs) were prepared in the present study using both the adsorption and template methods. Both versions of Ag-MCSNs showed characteristic morphology of mesoporous materials and exhibited sustained release of ions over time. In antibacterial testing against planktonic Enterococcus faecalis, Ag-MCSNs showed significantly better antibacterial effects when compared with MCSNs (P<0.05). The Ag-MCSNs aggregated on the dentin surface of root canal walls and infiltrated into dentinal tubules after ultrasound activation, significantly inhibiting the adherence and colonization of E. faecalis on dentin (P<0.05). Despite this, Ag-MCSNs with templated nanosilver showed much lower cytotoxicity than Ag-MCSNs with adsorbed nanosilver (P<0.05). The results of the present study indicated that nanosilver could be incorporated into MCSNs using the template method. The templated nanosilver could release silver ions and inhibit the growth and colonization of E. faecalis both in the planktonic form and as biofilms on dentin surfaces as absorbed nanosilver. Templated Ag-MCSNs may be developed into a new intracanal disinfectant for root canal disinfection due to their antibacterial ability and low cytotoxicity, and as controlled release devices for other bioactive molecules to produce multifunctional biomaterials.

Mesoporous cerium phosphonate nanostructured hybrid spheres as label-free Hg²⁺ fluorescent probes

Porous phosphonate-based organic-inorganic hybrid materials have been shown to have novel and amazing physicochemical properties due to the integration of superiorities from both inorganic components and organic moieties. Herein, mesoporous cerium phosphonate nanostructured hybrid spheres are prepared with the assistance of cationic surfactant cetyltrimethylammonium bromide while using ethylene diamine tetra(methylene phosphonic acid) as the coupling molecule. The resulting hybrid is constructed from the cerium phosphonate nanoparticles, accompanied by high specific surface area of 455 m(2) g(-1). The uniform incorporation of rare-earth element cerium and organophosphonic functionalities endows mesoporous cerium phosphonate with excellent fluorescence properties for the development of an optical sensor for selective Hg(2+) detection on the basis of the fluorescence-quenching mechanism. The signal response of mesoporous cerium phosphonate against the Hg(2+) concentration is linear over the range from 0.05 to 1.5 μmol L(-1), giving a limit of detection of 16 nmol L(-1) (at a signal-to-noise ratio of 3). Most of the common physiologically relevant cations and anions did not interfere with the detection of Hg(2+). This label-free system provides a promising platform for further use in bioimaging and biomedical fields.

Oxidative nanopatterning of titanium generates mesoporous surfaces with antimicrobial properties

Mesoporous surfaces generated by oxidative nanopatterning have the capacity to selectively regulate cell behavior, but their impact on microorganisms has not yet been explored. The main objective of this study was to test the effects of such surfaces on the adherence of two common bacteria and one yeast strain that are responsible for nosocomial infections in clinical settings and biomedical applications. In addition, because surface characteristics are known to affect bacterial adhesion, we further characterized the physicochemical properties of the mesoporous surfaces. Focused ion beam (FIB) was used to generate ultrathin sections for elemental analysis by energy-dispersive X-ray spectroscopy (EDS), nanobeam electron diffraction (NBED), and high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) imaging. The adherence of Staphylococcus aureus, Escherichia coli and Candida albicans onto titanium disks with mesoporous and polished surfaces was compared. Disks with the two surfaces side-by-side were also used for direct visual comparison. Qualitative and quantitative results from this study indicate that bacterial adhesion is significantly hindered by the mesoporous surface. In addition, we provide evidence that it alters structural parameters of C. albicans that determine its invasiveness potential, suggesting that microorganisms can sense and respond to the mesoporous surface. Our findings demonstrate the efficiency of a simple chemical oxidative treatment in generating nanotextured surfaces with antimicrobial capacity with potential applications in the implant manufacturing industry and hospital setting.