Broadening microwave absorption via a multi-domain structure

Materials with a high saturation magnetization have gained increasing attention in the field of microwave absorption; therefore, the magnetization value depends on the magnetic configuration inside them. However, the broad-band absorption in the range of microwave frequency (2-18 GHz) is a great challenge. Herein, the three-dimensional (3D) Fe/C hollow microspheres are constructed by iron nanocrystals permeating inside carbon matrix with a saturation magnetization of 340 emu/g, which is 1.55 times as that of bulk Fe, unexpectedly. Electron tomography, electron holography, and Lorentz transmission electron microscopy imaging provide the powerful testimony about Fe/C interpenetration and multi-domain state constructed by vortex and stripe domains. Benefiting from the unique chemical and magnetic microstructures, the microwave minimum absorption is as strong as -55 dB and the bandwidth (<-10 dB) spans 12.5 GHz ranging from 5.5 to 18 GHz. Morphology and distribution of magnetic nano-domains can be facilely regulated by a controllable reduction sintering under H2/Ar gas and an optimized temperature over 450-850 C. The findings might shed new light on the synthesis strategies of the materials with the broad-band frequency and understanding the association between multi-domain coupling and microwave absorption performance.This work was supported by the Ministry of Science and Technology of China (973 Project Nos. 2013CB932901 and 2016YFE0105700) and the National Natural Science Foundation of China (Nos. 51672050 and 51172047) and NSAF-U1330118. The authors extend their appreciation to the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP# 0018.Scopu

Facile Synthesis of Uniform Virus-like Mesoporous Silica Nanoparticles for Enhanced Cellular Internalization

The low-efficiency cellular uptake property of current nanoparticles greatly restricts their application in the biomedical field. Herein, we demonstrate that novel virus-like mesoporous silica nanoparticles can easily be synthesized, showing greatly superior cellular uptake property. The unique virus-like mesoporous silica nanoparticles with a spiky tubular rough surface have been successfully synthesized via a novel single-micelle epitaxial growth approach in a low-concentration-surfactant oil/water biphase system. The virus-like nanoparticles' rough surface morphology results mainly from the mesoporous silica nanotubes spontaneously grown via an epitaxial growth process. The obtained nanoparticles show uniform particle size and excellent monodispersity. The structural parameters of the nanoparticles can be well tuned with controllable core diameter (60-160 nm), tubular length (6-70 nm), and outer diameter (6-10 nm). Thanks to the biomimetic morphology, the virus-like nanoparticles show greatly superior cellular uptake property (invading living cells in large quantities within few minutes, <5 min), unique internalization pathways, and extended blood circulation duration (t1/2 = 2.16 h), which is much longer than that of conventional mesoporous silica nanoparticles (0.45 h). Furthermore, our epitaxial growth strategy can be applied to fabricate various virus-like mesoporous core-shell structures, paving the way toward designed synthesis of virus-like nanocomposites for biomedicine applications. 2017 American Chemical Society.The work was supported by China National Key Basic Research Program (973 Project) (Nos. 2013CB934100 and 2012CB224805), NSFC (Grant Nos. 21322508 and 21210004), Shanghai Shuguang Program, China Postdoctoral Science Foundation (2015M570327). The authors extend their appreciation to the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP# 0018.Scopu

A template-catalyzed: In situ polymerization and co-assembly strategy for rich nitrogen-doped mesoporous carbon

N-doped mesoporous carbon materials are greatly useful in adsorption, catalysis and energy storage. Controlled synthesis of such materials with both high nitrogen content and desired pore structures remains a great challenge. Herein, we report a new template-catalyzed in situ polymerization and co-assembly approach to synthesize rich N-doped and uniform mesoporous carbons by using urea-formaldehyde (UF) as a carbon precursor and nitrogen source, and the acidic block copolymer polystyrene-block-poly(acrylic acid) (PS-b-PAA) as both a structure-directing agent and a catalyst for UF resin. In this synthesis, UF precursors can selectively interact with partially ionized PAA segments via hydrogen bonding and electrostatic interaction, and subsequently in situ polymerize to form bulk UF resin/PS-b-PAA composites by the catalysis of acidic PAA segments. After pyrolysis at 600 °C in nitrogen, the resulting N-doped mesoporous carbons possess high N content (up to ∼19 wt%), high ratio of basic species (∼49% pyridinic nitrogen and ∼28% pyrrolic nitrogen), uniform and large pore size (9.5–17.2 nm) and high surface area (458–476 m2 g−1). Owing to such unique features, the N-doped mesoporous carbons show high normalized CO2 adsorption capacity (4.71–5.15 μmol m−2) and excellent selectivity (60 : 1–67 : 1) to CO2 compared to N2 at 298 K and 1.0 bar, and exhibit excellent performance as a supercapacitor electrode with a high specific capacitance (239–252 F g−1).Scopu

A versatile in situ etching-growth strategy for synthesis of yolk–shell structured periodic mesoporous organosilica nanocomposites

This paper describes a versatile in situ etching-growth strategy for the preparation of periodic mesoporous organosilica (PMO) composites with yolk-shell structure, which can generate the void space and construct the outer PMO shells at the same time. The superparamagnetic yolk-shell Fe3O4@PMO composites (YS-Fe3O4@PMO) with radical mesochannels were also synthesized with this unique in situ etching-growth strategy by using Fe3O4@nSiO2 nanoparticles as the initial core. This method provides a general route for the synthesis of yolk-shell structured nanomaterials with different sized void spaces, various chemical composition cores, as well as organic functional PMO shells with radical mesochannels. Moreover, we can also obtain asymmetric or asymmetric hollow Fe3O4@PMO materials with a cubic PMO shell. All the magnetic mesoporous composites possess very high surface areas and large pore volumes (586 m2 g-1 and 0.52 cm3 g-1 for YS-Fe3O4@PMO, 946 m2 g-1 and 0.86 cm3 g-1 for asymmetric hollow Fe3O4@PMO). Gold nanoparticles could be encapsulated and confined in the void space of YS-Fe3O4@PMO composites through an in situ salt impregnation. The resultant YS-Fe3O4@Au@PMO nanomaterials could be used to catalyze the reduction of 4-nitrophenol with an ultrahigh efficiency (k = 0.01197 s-1). The magnetic catalysts could be easily recovered by a magnet and reused for more than 10 cycles with efficiency retained as high as 95%. 2016 The Royal Society of Chemistry.This work was supported by the State Key Basic Research Program of the PRC (2012CB224805, 2013CB934104), the NSF of China (21210004 and U1463206), Shanghai Sci. & Tech. Committee (14JC1400700). We extended our appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the 530 research group Project No. RGP-227.Scopu

Ordered Mesoporous Alumina with Ultra-Large Pores as an Efficient Absorbent for Selective Bioenrichment

Alumina has recently turned out to be effective in enrichment of biomacrolecules like phosphopeptides due to its good affinity to phosphor groups. Ordered mesoporous alumina (OMA) materials with high surface areas, regular porous structures, and large pore size are an ideal absorbent for the enrichment of phosphopeptides. Herein, a ligand-assisted solvent evaporation induced coassembly route is developed to synthesize OMA materials with an ultralarge pore size (16.0-18.9 nm) using a high-molecular-weight poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a soft template, aluminum acetylacetonate as a precursor, and tetrahydrofuran as a solvent. The obtained ordered mesoporous alumina shows high surface area (114-197 m2/g), large pore volume (0.16-0.34 cm3/g), and high thermal stability (up to 900 �C). The OMA materials show crystalline ?-Al2O3 frameworks with crystal size of ?11 nm after calcination at 900 �C in air. Because of their high surface area, ultralarge pore size, and rich Lewis acid sites, the obtained OMA materials are demonstrated to be an excellent bioabsorbent in enriching phosphopeptides selectively from protein digestions with ultralow concentrations (2 ? 10-9 M), even from more complex samples from human serum.This work was supported by State Key Basic Research Program of PRC (2013CB934104), NSF of China (51372041, 51422202, 21673048, 51402049, 51432004, 21210004, and U1463206), the Shanghai Committee of Science and Technology, China (14ZR1400600, 14JC1400700, 15ZR1402000), Shanghai Leading Academic Discipline Project (B108), the ?Shu Guang? Project (13SG02) supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation, National Youth Topnotch Talent Support Program of China, Shanghai Pujiang Program, China (No. 16PJ1401100), the Innovation Program of Shanghai Municipal Education Commission (13ZZ004), Program for New Century Excellent Talents in University, "Young Talent Support Plan" of Xi?an Jiaotong University, and the Qatar University and Princess Nourah bint Abdulrahman University under GCC Co-Fund Program Grant GCC-2017-001. The authors extend their appreciation to the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP# 0018.Scopu

General Strategy to Synthesize Uniform Mesoporous TiO₂/Graphene/Mesoporous TiO₂ Sandwich-Like Nanosheets for Highly Reversible Lithium Storage

Uniform oxide deposition on graphene to form a sandwich-like configuration is a well-known challenge mainly due to their large lattice mismatches and poor affinities. Herein, we report a general strategy to synthesize uniform mesoporous TiO₂/graphene/mesoporous TiO₂ sandwich-like nanosheets (denoted as G@mTiO₂), which cannot be achieved by conventional one-pot synthetic methods. We show that by rational control of hydrolysis and condensation of Ti precursors in a slow way, GO sheets can be conformably coated by amorphous TiO₂ shells, which then can be facilely transformed into the well-defined G@mTiO₂ nanosheets by annealing. This amorphous-to-crystalline strategy conveniently allows bypassing strain fields that would inevitably arise if direct growth of mesoporous anatase shells on graphene. As distinct from the most common structures of graphene-based composites (mixed, wrapped, or anchored models), the resultant materials display a uniform sandwich-like configuration: few-layer graphene conformably encapsulated by mesoporous TiO₂ shells. This new G@mTiO₂ nanosheet exhibits ultrathin nature (∼34 nm), small size and high crystalline nanocrystals (∼6 nm), high surface areas (∼252 m²/g) and uniform mesopores (∼3.4 nm). We further show that the thickness of mesoporous TiO₂ shells can be facilely adjusted as desired by controlling the ammonia content, and this facile strategy can be easily extended to design other oxide/graphene/oxide sandwich-like materials. More importantly, we showcase the benefits of the resultant G@mTiO₂ nanosheets as anodes in lithium ion batteries: they deliver an extra high capacity, an excellent high-rate capability, and long cycle life