Polyvinyl pyrrolidone (PVP)-stabilized polymer spheres synthesized at elevated temperature by Stober-like method are carbonized to obtain carbon spheres. Their size is tunable in the range from 875 nm to 60 nm by adjusting the amount of PVP during synthesis at elevated temperature. These spheres are obtained by using resorcinol and formaldehyde as carbon precursors, ethylene diamine (EDA) as nitrogen source and basic catalyst, and PVP as stabilizer and an additional source of nitrogen dopant. A synergistic effect is shown between (i) elevated temperature that facilitates the formation of a large number of small polymeric nuclei and (ii) varying amount of PVP that controls the growth of formed nuclei by hindering polymerization of resorcinol and formaldehyde. The elevated temperature synthesis not only produces monodispersed carbon spheres but also eliminates the need for hydrothermal treatment that generally requires high-pressure autoclave vessel. The nitrogen content increases from 3.0 wt% to 5.0% with increasing PVP amount. Besides nitrogen originating from ethylene diamine, an additional amount of doped nitrogen in carbon spheres is supplied by PVP during its decomposition. The resulting carbon spheres were subjected to the post-synthesis CO2 activation in order to improve their structural properties. The surface area of activated carbon spheres increased almost twice from (516 m(2)/g-581 m(2)/g) to (1010 m(2)/g-1060 m(2)/g). A significant enhancement of microporosity as well as presence of nitrogen species in activated carbon spheres resulted in high CO2 uptake at ambient temperatures. The tunable size, high microporosity, nitrogen doping and cost-effective synthesis make these carbon spheres attractive for a variety of uses ranging from adsorption, catalysis, electrode materials to biomedical applications. (C) 2019 Elsevier Inc. All rights reserved.

One-pot synthesis of nitrogen doped mesoporous graphitic carbon spheres with dispersed metal oxide nanoparticles using a single temperature treatment step serves as one of the big challenges in materials research.

It is shown that the pore size and pore volume of carbon spheres (CSs) can be effectively tuned by varying the amount of tetraethyl orthosilicate (TEOS) during the one-pot modified Stober synthesis that involves polymerization of resorcinol and formaldehyde in the presence of ethylenediamine used as a basic catalyst and nitrogen source. Namely, an increase in the amount of added TEOS caused a considerable reduction in the micropore volume accompanied by a three-fold increase in the total pore volume. This substantial increase in porosity was achieved after dissolution of the TEOS-generated silica and additional activation. Importantly, the controlled addition of TEOS was effectively used to tune the structure of the composite carbon-silica spheres to obtain, for instance, the composite spheres with uniformly distributed carbon and silica, and core-shell structures with single shells (silica core/mixed silica-carbon shell), and double shells (silica core/mixed silica-carbon shell/silica shell), which upon suitable post-synthesis treatment can be respectively converted to mesoporous CSs, hollow mesoporous CSs, and yolk-shell silica spheres. Beside the well-developed porosity and interesting morphology, the resulting CSs were N-doped and featured high surface area in the range of 1000e1439 m2/g. (C) 2017 Elsevier Ltd. All rights reserved.

Carbonization of the composite materials obtained by co-condensation of phenol-formaldehyde resin and tetraethyl orthosilicate (TEOS) in a basic aqueous solution in the presence of Pluronic F127 block copolymer template yields mesoporous carbon/silica composite materials (CSX). These materials have mesopore volumes of about 0.4 cm(3)/g and pore sizes between 6 and 8 nm (at the maximum of the pore size distribution) that are larger than those of the ordered mesoporous carbons (OMC) synthesized by the same procedure but without TEOS. Calcination of CSX in air yields mesoporous silicas (SX) with pore sizes around 11 nm and pore volumes of about 1 cm(3)/g. Dissolution of the silica domains in CSX yields carbons (CX) with pore volumes and surface areas as high as 1.84 cm(3)/g and 1500 m(2)/g, respectively. These carbons feature bimodal structures with larger mesopores of about 7-8 nm (porosity of CSX) and smaller mesopores with sizes closer to 5 nm, which are created by silica dissolution. The mesopore volume of CX after silica dissolution can be tuned by varying carbonization temperature (between 500 and 850 degrees C) to modify the concentration of silica nanodomains in CSX without significant change in the size of mesopores in CSX. Regardless of the phenol/TEOS ratio used (between 2 and 7) all the materials have similar composition, pore size distribution and pore volumes; however, the synthesis yield decreases with decreasing amount of TEOS. The final SiO2 content in CSX does not increase with the amount of TEOS added like in the synthesis of OMC by evaporation induced self-assembly or self-assembly in acidic solutions. (C) 2016 Elsevier Inc. All rights reserved.

One-pot synthesis of highly ordered SBA-15 type silica-tethered phosphonic acid at weakly acidic pH (3.75) allows for higher loading of phosphonic functionality (up to 33%) without significant deterioration of the mesostructure. In this synthesis sodium metasilicate was used instead of tetraethylorthosilicate. The resulting samples featured high specific surface areas (362-533 m(2)/g) and well-developed mesoporosity. The hexagonal structure and high concentration of phosphonic acid groups (1.0-3.0 mmol/g) in the synthesized samples were established by XRD, TEM, EDS and elemental analysis methods. Since inexpensive sodium metasilicate was used as a source of silica, these materials can be of interest for large-scale applications. Experimental studies of the synthesized materials showed that they are effective for extraction of trace uranium species under weak basic conditions (pH 8.3), which are relevant for practical use such as uranium extraction from seawater. (C) 2015 Elsevier B.V. All rights reserved.

A 3D N-doped graphene foam with a 6.8 at% nitrogen content is prepared by annealing a freeze-dried graphene oxide foam in ammonia. It is used as an anode in sodium ion batteries to deliver a high initial reversible capacity of 852.6 mA h g(-1) at 1 C between 0.02 and 3 V with a long-term retention of 69.7% after 150 cycles.

A series of ordered mesoporous titania–carbon composites was synthesized by self-assembly of carbon and titania precursors in the presence of Pluronic F127 block copolymer as a template under acidic conditions. Resorcinol and formaldehyde were used as carbon precursors and titanium isopropoxide was employed as titania precursor. Pluronic F127 [poly(ethylene oxide) – poly(propylene oxide) – poly(ethylene oxide) triblock copolymer] was employed as a soft template. The controlled polymerization of phenolic resin precursors and condensation of titania precursor in hydrophilic domains of the block copolymer template followed by carbonization resulted in ordered mesoporous titania–carbon composites. These composites possessed uniform ordered cylindrical mesopores (7–8nm) created by thermal decomposition of the soft template, crystalline titania particles (anatase phase, 7–8nm) embedded in the carbon matrix, and high percentage of titania (up to 48%). N2 adsorption analysis showed that the aforementioned composites exhibited large surface area (close to reaching 600m2/g) and enhanced photocatalytic activity toward photodegradation of rhodomine B due to the presence of titania nanoparticles uniformly dispersed in the carbon mesostructure.

Major strategies for the preparation and rational design of nanoporous carbon spheres as well as the investigation of their properties for energy conversion and storage, catalysis and biomedical applications are now critically reviewed.

Metal nanoparticle-decorated carbon spheres (mn-CSs) are prepared by combining one-pot hydrothermal synthesis and post-synthesis modification. The former sol-gel type process is employed to obtain heteroatom-containing polymer spheres (PSs), which easily attract metal species that, during thermal treatment, are initially converted to nanoparticle-decorated PSs and finally to mn-CSs.

Biocompatible ZnMoS4 NPs can selectively remove intracellular copper ions via ion-exchange rather than chelation. This strategy represents a paradigm shift in designing new-generation intracellular metal detoxifying drugs.

A series of nitrogen-containing polymer and carbon spheres were obtained by the sol-gel method. In particular, the nitrogen-rich carbon spheres were prepared by one-pot hydrothermal synthesis in the presence of resorcinol/formaldehyde as carbon precursors and ethylenediamine (EDA) as both a base catalyst and nitrogen precursor, followed by carbonization in nitrogen and activation with CO2. The introduction of EDA to the sol gel system resulted in structurally bonded nitrogen-containing carbon spheres. The nitrogen doping level and the particle size can be tuned by varying the EDA amount in the reaction mixture. The maximum nitrogen doping level of 7.2 wt % in carbon spheres could be achieved without sacrificing the spherical morphology. The diameter of these carbon spheres (CS) can be tuned in the rage of 50-1200 nm by varying the EDA amount. N-2 adsorption analysis showed that the aforementioned activated carbon spheres exhibited high surface area reaching up to 1224 m(2)/g. Ultra high CO2 adsorption capacities, 4.1 and 6.2 mmol/g, corresponding to an equilibrium pressure of I bar, were measured on nitrogen-containing activated carbon spheres at 25 and 0 degrees C, respectively. Electrochemical measurements performed on these carbon spheres for double layer capacitors showed very high capacitance up to similar to 388 F/g at 1.0 A/g, outstanding rate capability (60% capacitance retention at 100 A/g), and unprecedented cycling stability (similar to 98% capacitance retention even after 8000 cycles) in 1 M H2SO4 electrolyte solution.

A series of nitrogen-containing carbon spheres (CS) was prepared using the modified Stöber method. These CS were synthesized by using resorcinol and formaldehyde as carbon precursors, melamine as nitrogen precursor and ammonia as a polymerization reaction catalyst. Hydrothermal treatment followed by activation of these polymer spheres resulted in highly porous nitrogen-containing CS. Elemental analysis and N2 adsorption showed that the aforementioned CS exhibited high surface area (reaching 1,610 m2/g) with large fraction of fine micropores (volume of micropores smaller than 1 nm was estimated to be 0.40 cm3/g) and comparatively high nitrogen content (about 4.0 at.%). Interestingly, high CO2 adsorption capacities, 4.4 and 6.9 mmol/g, were obtained for these CS at 1 bar and two temperatures, 25 and 0 °C, respectively.

The evaporation-induced self assembly (EISA) strategy has been successfully employed to obtain ultra-large mesoporous carbons (UMC) by using Vorasurf 504 poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide), (PEO–PBO–PEO) triblock copolymer as a template. Resorcinol and formaldehyde were used as carbon precursors, whereas trimethyl benzene (TMB) was used as a pore expander. Nitrogen adsorption isotherms revealed that the resulting UMC materials possess ultra-large mesopores (about 27 nm) and relatively narrow pore size distribution. Mesoporous carbons synthesized without TMB show also fairly large mesopores (about 20 nm). These carbons were examined for adsorption of Lysozyme (Lz) from buffered solution at pH 10.8. All Lz adsorption isotherms were reasonably well fitted by Langmuir equation, giving high maximum adsorption capacity (31 μmol/g).

A series of cysteine-stabilized phenolic resin-based polymer and carbon spheres were prepared by the modified Stöber method. Cysteine plays a very important role in the proposed one-pot synthesis of the aforementioned spheres; namely, it acts as a particle stabilizer and a source of heteroatoms (nitrogen and sulfur) that can be introduced into these spheres. The diameter of these spheres can be tuned in the range of 70-610 nm by adjusting the cysteine amount and reaction temperature. Since polymer spheres obtained in the presence of cysteine contain sulfur and nitrogen heteroatoms, they were tested for adsorption of copper ions. It is shown that adsorption isotherms recorded for copper ions can be well fitted by Langmuir equation, giving unprecedented adsorption capacities up to ~65 mg/g.

Carbons with high surface area and large volume of ultramicropores were synthesized for CO2 adsorption. First, mesoporous carbons were produced by soft-templating method using triblock copolymer Pluronic F127 as a structure directing agent and formaldehyde and either phloroglucinol or resorcinol as carbon precursors. The resulting carbons were mainly mesoporous with well-developed surface area, large total pore volume, and only moderate CO2 uptake. To improve CO2 adsorption, these carbons were subjected to KOH activation to enhance their microporosity. Activated carbons showed 2–3-fold increase in the specific surface area, resulting from substantial development of microporosity (3–5-fold increase in the micropore volume). KOH activation resulted in enhanced CO2 adsorption at 760mmHg pressure: 4.4mmolg−1 at 25°C, and 7mmolg−1 at 0°C. This substantial increase in the CO2 uptake was achieved due to the development of ultramicroporosity, which was shown to be beneficial for CO2 physisorption at low pressures. The resulting materials were investigated using low-temperature nitrogen physisorption, CO2 sorption, and small-angle powder X-ray diffraction. High CO2 uptake and good cyclability (without noticeable loss in CO2 uptake after five runs) render ultramicroporous carbons as efficient CO2 adsorbents at ambient conditions.

A series of carbon spheres (CS) was prepared by carbonization of phenolic resin spheres obtained by the one-pot modified Stöber method. Activated CS (ACS), having diameters from 200 to 420 nm, high surface area (from 730 to 2930 m(2)/g), narrow micropores (<1 nm) and, importantly, high volume of these micropores (from 0.28 to 1.12 cm(3)/g), were obtained by CO2 activation of the aforementioned CS. The remarkably high CO2 adsorption capacities, 4.55 and 8.05 mmol/g, were measured on these AC spheres at 1 bar and two temperatures, 25 and 0 °C, respectively.

A series of highly graphitized mesoporous carbons was synthesized by self-assembly of polymeric carbon precursors and block copolymer template in the presence of poly(vinylpyrrolidone) (PVP)-coated Prussian blue (PB) nanoparticles used as a graphitization catalyst. Resorcinol and formaldehyde were used as carbon precursors, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic F127) was employed as a soft template. The carbon precursors were polymerized in hydrophilic domains of block copolymer along with PVP-coated PB nanoparticles, followed by carbonization. This recipe gave carbons with cylindrical mesopores created by thermal decomposition of the soft template, and with PB-derived iron oxide nanoparticles. In addition, the presence of iron species catalyzed graphitization at relatively low temperature. The XRD and TEM measurements revealed that the resulting carbons obtained with smaller amounts of PB exhibited ordered mesostructures with relatively high degree of graphitization; however, exceedingly graphitic carbons with disordered mesopores were obtained with higher amounts of PB. Furthermore, wide-angle XRD measurements and TGA analysis provided evidence that graphitization took place at 600 degrees C, which is considered to be a very low temperature for the graphitization process. N-2 adsorption and TGA analysis showed that the aforementioned carbons exhibited high surface area (reaching 621 m(2)/g) and an extremely high percentage of graphitic domains (approaching 87%). Interestingly, the carbon prepared with larger amount of PB showed magnetic properties. Electrochemical measurements performed on these carbons for double layer capacitors showed somewhat rectangular shape of cyclic voltammetry (CV) curves with a large capacitance of 211 F/g in 1 M H2SO4 electrolyte.

Phenolic resin-based carbon spheres obtained by a slightly modified Stober method are shown to be superior CO2 adsorbents. A direct KOH activation of polymeric spheres gave carbons with small micropores (<0.8 nm) and large specific surface area (2400 m2 g−1), which are able to adsorb an unprecedented amount of CO2 (up to 8.9 mmol g−1) at 0 °C and ambient pressure.

Boron-containing mesoporous carbon materials were prepared using resorcinol and formaldehyde as carbon precursors, boric acid as a boron precursor and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic F127) as a soft template. Another series of boron-containing samples was prepared by using the same chemicals in the presence of tetraethyl orthosilicate. Nitrogen adsorption, X-ray diffraction, NH3 temperature programmed desorption, X-ray photoelectron spectroscopy, and thermogravimetric analysis revealed that the resulting boron-carbon materials possessed acidic sites, high surface area ranging from 1047 to 1400 m2 g−1, large mesopores of about 10 nm, uniform pore size distribution, and high boron content (1.5–1.8%).