Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries

Diatom Frustules Decorated with Co Nanoparticles for the Advanced Anode of Li-Ion Batteries

Silica is regarded as a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, large volume variation and poor electrical conductivity are limiting factors for the development of SiO₂ anode materials. To solve this problem, combining SiO₂ with a conductive phase and designing hollow porous structures are effective ways. In this work, The Co(II)-EDTA chelate on the surface of diatom biosilica (DBS) frustules and obtained DBS@C-Co composites decorated with Co nanoparticles by calcination without a reducing atmosphere is first precipitated. The unique three-dimensional structure of diatom frustules provides enough space for the volume change of silica during lithiation/delithiation. Co nanoparticles effectively improve the electrical conductivity and electrochemical activity of silica. Through the synergistic effect of the hollow porous structure, carbon layer and Co nanoparticles, the DBS@C-Co-60 composite delivers a high reversible capacity of >620 mAh g^-1 at 100 mA g^-1 after 270 cycles. This study provides a new method for the synthesis of metal/silica composites and an opportunity for the development of natural resources as advanced active materials for LIBs.

Synthesis of Monodispersed Hollow Mesoporous Organosilica and Silica Nanoparticles with Controllable Shell Thickness Using Soft and Hard Templates

Hollow mesoporous nanoparticles with controllable size (less than 100 nm) are desired as drug-delivery carriers. Herein, we report the synthesis of monodispersed hollow mesoporous organosilica (HMOS) and hollow mesoporous silica (HMS) nanoparticles using soft and hard templating methods. HMOS shells, with 1,2-bis(triethoxysilyl)ethane (BTEE) as the precursor and hexadecyltrimethylammonium bromide and sodium dodecyl sulfate (SDS) as the soft templates, were formed on monodispersed silica nanoparticles (SNPs), which were used as the hard templates. HMOS and HMS nanoparticles were obtained by removing the SNPs after three rounds of ammonia dialysis. The hollow size of HMOS can be tuned by changing the size of the SNPs. By using SNPs with a size of 36.5 nm, hollow spaces of approximately 20 nm connected the surface through narrow pores (<5 nm). Mesopores of approximately 12 nm were formed by the surfactant micelles. Additionally, the interparticle space in HMOS and HMS was approximately 12 nm. The shell thicknesses of HMOS and HMS could be tuned in the range of 5-9 nm by changing the BTEE amount. Moreover, the amount of surfactant used varied the porous structure. The HMOS with a thickness of 5 nm exhibited a Brunauer-Emmett-Teller (BET) surface area of 268 m²/g and a total pore volume of 1.14 cm³/g. Meanwhile, HMS demonstrated a BET surface area of 553 m²/g and a total pore volume of 1.82 cm³/g while maintaining a hollow structure. HMOS displayed a high loading capacity for ibuprofen (3009 mg/g), and its drug release system showed a sustained-release property. Therefore, the HMOS preparation using hard and soft templates proposed herein can control the hollow size and shell thickness for drug-delivery applications.

Highly Active Ruthenium Catalyst Supported on Magnetically Separable Mesoporous Organosilica Nanoparticles

A facile and direct method for synthesizing magnetic periodic mesoporous organosilica nanoparticles from pure organosilane precursors is described. Magnetic ethylene- and phenylene-bridged periodic mesoporous organosilica nanoparticles (PMO NPs) were prepared by nanoemulsification techniques. For fabricating magnetic ethylene- or phenylene-bridged PMO NPs, hydrophobic magnetic nanoparticles in an oil-in-water (o/w) emulsion were prepared, followed by a sol–gel condensation of the incorporated bridged organosilane precursor (1,2 bis(triethoxysilyl)ethane or 1,4 bis(triethoxysilyl)benzene), respectively. The resulting materials were characterized using high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (XRD), solid-state NMR analysis, and nitrogen sorption analysis (N2-BET). The magnetic ethylene-bridged PMO NPs were successfully loaded using a ruthenium oxide catalyst by means of sonication and evaporation under mild conditions. The obtained catalytic system, termed Ru@M-Ethylene-PMO NPS, was applied in a reduction reaction of aromatic compounds. It exhibited very high catalytic behavior with easy separation from the reaction medium by applying an external magnetic field.

Advances in PEG-based ABC terpolymers and their applications

ABC terpolymers are a class of very important polymers because of their expansive molecular topologies and extensive architectures. As block A, poly(ethylene glycol) (PEG) is one of the most principal categories owing to good biocompatibility and wide commercial availability. More importantly, the synthetic approaches of ABC terpolymers using PEG as a macroinitiator are facile and varied. PEG-based ABC terpolymers from design and synthesis to applications are highlighted in this review. Linear, 3-miktoarm, and cyclic polymers as the architecture are separated. The synthetic approaches of PEG-based ABC terpolymers mainly include the sequential polymerization or coupling of polymers. PEG-based ABC terpolymers have wide applications in the fields of drug carriers, gene vectors, templates for the fabrication of inorganic hollow nanospheres, and stabilizers of metal nanoparticles.

Silicon oxides: a promising family of anode materials for lithium-ion batteries

Silicon oxides have been recognized as a promising family of anode materials for high-energy lithium-ion batteries (LIBs) owing to their abundant reserve, low cost, environmental friendliness, easy synthesis, and high theoretical capacity. However, the extended application of silicon oxides is severely hampered by the intrinsically low conductivity, large volume change, and low initial coulombic efficiency. Significant efforts have been dedicated to tackling these challenges towards practical applications. This Review focuses on the recent advances in the synthesis and lithium storage properties of silicon oxide-based anode materials. To present the progress in a systematic manner, this review is categorized as follows: (i) SiO-based anode materials, (ii) SiO2-based anode materials, (iii) non-stoichiometric SiOx-based anode materials, and (iv) Si-O-C-based anode materials. Finally, future outlook and our personal perspectives on silicon oxide-based anode materials are presented.

Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

Cellular Internalization and Biocompatibility of Periodic Mesoporous Organosilica Nanoparticles with Tunable Morphologies: From Nanospheres to Nanowires

This work describes the sol-gel syntheses of para-substituted phenylene-bridged periodic mesoporous organosilica (PMO) nanoparticles (NPs) with tunable morphologies ranging from nanowires to nanospheres. The findings show the key role of the addition of organic co-solvents in the aqueous templates on the final morphologies of PMO NPs. Other factors such as the temperature, the stirring speed, and the amount of organic solvents also influence the shape of PMO NPs. The tuning of the shape of the PMO nanomaterials made it possible to study the influence of the particle morphology on the cellular internalization and biocompatibility.

Mn-N-C Nanoreactor Prepared through Heating Metalloporphyrin Supported in Mesoporous Hollow Silica Spheres

Mesoporous hollow silica spheres have been drawing tremendous interest due to their special structure and properties and potential applications. Here we synthesized a nanoreactor via ship-in-bottle method, encapsulated with Mn-N-C by heating manganese porphyrin in nanocages of mesoporous hollow silica spheres. And manganese porphyrin is first encapsulated and confined in the hollow spheres. The nanoreactors are investigated through transmission electron microscopy (TEM) and high angle annular dark field scanning TEM (HAADF-STEM) as well as nitrogen adsorption-desorption isotherms. The results demonstrate that the mesoporous hollow spheres with well-defined morphology hold large pore volumes (0.29-0.46 cm³ g^-1), high specific surface areas (428-600 m² g^-1) and uniform pore sizes (4.0 nm). In addition, the ethylbenzene oxidation is conducted in order to explore the catalytic performance of the nanoreactors. And the nanoreactors are observed to possess remarkable catalytic activity and attractive stability for ethylbenzene oxidation, which should be ascribed to the special architectures and confined effect.

One-pot synthesis of mesoporous silica hollow spheres with Mn-N-C integrated into the framework for ethylbenzene oxidation

Mesoporous silica spheres with Mn-N-C materials integrated into the framework are synthesized via the surfactant (CTAB) template-assisted one-pot approach. A manganese porphyrin is used as the precursor of the Mn-N-C structure. The as-prepared catalyst exhibits remarkable activity and stability in heterogeneous catalytic systems for ethylbenzene oxidation.

Micelle-templated synthesis of Pt hollow nanospheres for catalytic hydrogen evolution

We report an efficient, mild and simple strategy for the fabrication of colloidal hollow platinum nanospheres with the ability to tune wall-thickness and void-space over several nanometers, for application in hydrogen evolution from ammonia–borane.

Surfactant-free synthesis of hollow mesoporous organosilica nanoparticles with controllable particle sizes and diversified organic moieties

The versatility of the surfactant-free synthesis of hollow organosilica nanoparticles was shown in terms of particle diameters and organic moieties. The porous structures were investigated precisely by advanced adsorption–desorption measurements.

A composite with SiOx nanoparticles confined in carbon framework as an anode material for lithium ion battery

A composite with ultrafine SiO_x (x = 1.57, around 2 nm) nanoparticles confined in a carbon framework is synthesized by a simple thermopolymerization process and subsequent heat treatment.

Syntheses and applications of periodic mesoporous organosilica nanoparticles

Periodic Mesoporous Organosilica (PMO) nanomaterials are envisioned to be one of the most prolific subjects of research in the next decade. Similar to mesoporous silica nanoparticles (MSN), PMO nanoparticles (NPs) prepared from organo-bridged alkoxysilanes have tunable mesopores that could be utilized for many applications such as gas and molecule adsorption, catalysis, drug and gene delivery, electronics, and sensing; but unlike MSN, the diversity in chemical nature of the pore walls of such nanomaterials is theoretically unlimited. Thus, we expect that PMO NPs will attract considerable interest over the next decade. In this review, we will present a comprehensive overview of the synthetic strategies for the preparation of nanoscaled PMO materials, and then describe their applications in catalysis and nanomedicine. The remarkable assets of the PMO structure are also detailed, and insights are provided for the preparation of more complex PMO nanoplatforms.

Core-shell-corona polymeric micelles as a versatile template for synthesis of inorganic hollow nanospheres

Hollow, inorganic nanoscale capsules have many applications, from the delivery of encapsulated products for cosmetic and medicinal purposes to use as lightweight composite materials. Early methods for producing inorganic hollow nanospheres using hard templates suffered from low product yield and shell weakness upon template removal. In the past decade, researchers have turned to amphiphilic copolymers to synthesize hollow nanostructures and ordered mesoporous materials. Amphiphilic molecules self-assemble into well-defined nanostructures including spherical micelles. Micelles formed from simple, two-component AB diblock and ABA triblock copolymers, however, have been difficult to work with to construct inorganic hollow nanoparticles, because the corona of the micelle, which serves as the template for the shell, becomes unstable as it absorbs inorganic shell precursors, causing aggregates to form. Newly developed, three-component ABC triblock copolymers may solve this problem. They provide nanoassemblies with more diverse morphological and functional features than AB diblock and ABA triblock copolymers. Micelles formed from ABC triblock copolymers in selective solvents that dissolve only one or two of the blocks provide templates for these improved nanoassemblies. By manipulating individual polymer blocks, one can "encode" additional features at the molecular level. For instance, modifying the functional groups or substitution patterns of the blocks allows better morphological and size control. Insights into polymer self-assembly gained over years of work in our group have set the stage to systematically engineer inorganic spherical hollow nanoparticles using ABC triblock copolymers. In this Account, we report our recent progress in producing diverse, inorganic hollow spherical nanospheres from asymmetric triblock copolymeric micelles with core-shell-corona architecture as templates. We discuss three classes of polymeric micelles-with neutral, cationic, and anionic shell structures-that allow fabrication of a variety of hollow nanoparticles. Importantly, we synthesized all of these particles in water, avoiding use of hazardous organic solvents. We have designed the precursor of the inorganic material to be selectively sorbed into the shell domain, leaving the corona free from the inorganic precursors that would destabilize the micelle. The core, meanwhile, is the template for the formation of the hollow void. By rationally tailoring experimental parameters, we readily and selectively obtained a variety of hollow nanoparticles including silica, hybrid silicas, metal-oxides, metal-carbonates, metal-sulfates, metal-borates, and metal-phosphates. Finally, we highlight the state-of-the-art techniques we used to characterize these nanoparticles, and describe experiments that demonstrate the potential of these hollow particles in drug delivery, and as anode and cathode materials for lithium-ion batteries.

Access to ultralarge-pore ordered mesoporous materials through selection of surfactant/swelling-agent micellar templates

The surfactant-micelle-templating method has revolutionized the synthesis of high-surface-area materials with mesopores (diameter 2-50 nm) that have well-defined shapes and sizes. One of the major benefits of this method is the ability to tailor the pore size by manipulating the size of the templating micelles. The uniform pores typically form ordered arrays. Although the choice of surfactant can tune the size of the micelles, it is more convenient to use a single surfactant and tailor the micelle size by adding a swelling agent. Unfortunately, the swelling agent tends to induce disorder or heterogeneity in the resulting structures, which can make this approach difficult to implement. We hypothesized that the swelling agents that are moderately solubilized within the micelles of a particular surfactant could generate well-defined micelle-templated structures with significantly enlarged pores. Using this idea, we could judiciously select candidate swelling agents from families of compounds whose extent of solubilization in the surfactant micelles systematically changes with variations in the compound structure. Alkyl-substituted benzenes proved very useful as swelling agents, because their extent of solubilization in micelles of common Pluronic surfactants (EO(m)PO(n)EO(m); EO = ethylene oxide, PO = propylene oxide) significantly increases as the number or size of alkyl substituents decreases. On the basis of these principles, we identified 1,3,5-triisopropylbenzene and cyclohexane as swelling agents for the synthesis of ultralarge-pore SBA-15 silica (pore diameter up to 26 nm) and organosilicas with 2-D hexagonal structures of cylindrical mesopores. Moreover, we used xylene, ethylbenzene, and toluene as swelling agents for the synthesis of large-pore (pore diameter up to 37 nm) face-centered cubic silicas and organosilicas with spherical mesopores. During the early stages of the synthesis, the entrances to large cylindrical and spherical mesopores of these materials were much smaller than the inner pore diameter. Therefore we can often use calcination at sufficiently high temperatures (400-950 °C) to produce closed-pore silicas. Using hydrothermal treatments, we can obtain materials with large pore entrance sizes. In Pluronic-templated synthesis, we observed the propensity for formation of single-micelle-templated nanoparticles as the ratio of the framework precursor to surfactant decreased, and this process afforded organosilica nanotubes and uniform hollow spheres with inner diameters up to ∼21 nm. Consequently, the adjustment of variables in the micelle-templated synthesis allows researchers to tailor the pore size and connectivity and to form either periodic pore arrays or individual nanoparticles.