Silica Coating of Nanoparticles by the Sonogel Process

Chen, Quan; Boothroyd, Chris; Tan, G. H.; Sutanto, Nelvi; Soutar, Andrew M.; Zeng, Xiaofei

doi:10.1021/la703872k

Cited by 28 publications

(11 citation statements)

References 30 publications

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“…Extensive studies have been conducted to establish the consequences of the so‐called sono–gel process regarding their kinetics and structural characteristics. For example, Chen et al reported the silica coating of nanoparticles using the sono–gel process 41. Compared to traditional energy sources, ultrasonic irradiation provides rather unusual reaction conditions that cannot be realized by other methods.…”

Section: Resultsmentioning

confidence: 99%

Biosilicification Templated by Amphiphilic Block Copolypeptide Assemblies

Xia

Liu

2010

Macromolecular Bioscience

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An amphiphilic poly(L-lysine·HBr)-block-poly(L-leucine) (KL) diblock copolypeptide and its supramolecular assembly are used as a template to direct silica formation, which proceeds by a cooperative process involving biomimetic mineralization and copolypeptide reassembly under ambient conditions. Various silica structures can be obtained by using different counterions, changing the chain length of the KL diblocks, and applying a sol-gel mineralization method. We find that the chain length of the KL diblock is an important factor in terms of controlling biosilica morphologies. We also find that the nature of the counterions strongly affects the resulting silica structures. For the same KL diblock, variation of anions from phosphate to sulfate and to carbonate can produce hexagonal silica platelets, silica rods, and fused silica platelets, respectively. In contrast, application of a sol-gel method can replicate the copolypeptide fibril network morphology in water, while employment of ultrasonication to the sol-gel medium transforms the silica fibrils to rigid silica rods. The resulting silica morphology has been systematically characterized using SEM and TEM, and the polypeptide conformation is explored using FT-IR and CD spectroscopy.

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Section: Resultsmentioning

confidence: 99%

Biosilicification Templated by Amphiphilic Block Copolypeptide Assemblies

Xia

Liu

2010

Macromolecular Bioscience

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“…[109,110] Very recently, Chen and coworkers synthesized silica coating over indium tin oxide (ITO) nanoparticles via a sonochemical route. [111] Sonochemical deposition of metal sulfides over metal oxides provides an alternative way to produce hetero-structured core/shell composites. Gao and coworkers sonochemically synthesized core/shell hetero-structures of SnO 2 / CdS and ZnO/CdS.…”

Section: Nanostructured Materials Via Sonochemical Depositionmentioning

confidence: 99%

Applications of Ultrasound to the Synthesis of Nanostructured Materials

2010

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Recent advances in nanostructured materials have been led by the development of new synthetic methods that provide control over size, morphology, and nano/microstructure. The utilization of high intensity ultrasound offers a facile, versatile synthetic tool for nanostructured materials that are often unavailable by conventional methods. The primary physical phenomena associated with ultrasound that are relevant to materials synthesis are cavitation and nebulization. Acoustic cavitation (the formation, growth, and implosive collapse of bubbles in a liquid) creates extreme conditions inside the collapsing bubble and serves as the origin of most sonochemical phenomena in liquids or liquid-solid slurries. Nebulization (the creation of mist from ultrasound passing through a liquid and impinging on a liquid-gas interface) is the basis for ultrasonic spray pyrolysis (USP) with subsequent reactions occurring in the heated droplets of the mist. In both cases, we have examples of phase-separated attoliter microreactors: for sonochemistry, it is a hot gas inside bubbles isolated from one another in a liquid, while for USP it is hot droplets isolated from one another in a gas. Cavitation-induced sonochemistry provides a unique interaction between energy and matter, with hot spots inside the bubbles of approximately 5000 K, pressures of approximately 1000 bar, heating and cooling rates of >10(10) K s(-1); these extraordinary conditions permit access to a range of chemical reaction space normally not accessible, which allows for the synthesis of a wide variety of unusual nanostructured materials. Complementary to cavitational chemistry, the microdroplet reactors created by USP facilitate the formation of a wide range of nanocomposites. In this review, we summarize the fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis.

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“…Coating core materials with various functional polymer shells by in situ polymerization to form an encapsulated or core − shell structure has roused much attention over many years . Among these functional polymer shell materials, melamine − formaldehyde (MF) resin has been extensively applied in flame‐retardant, self‐healing materials and even in phase change materials such as for the encapsulation of red phosphorus, ammonium polyphosphate, epoxy, polythiol, styrene etc.…”

Section: Introductionmentioning

confidence: 99%

Core-shell structure design of pulverized expandable graphite particles and their application in flame-retardant rigid polyurethane foams

et al. 2013

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Pulverized expandable graphite (pEG) and melamine − formaldehyde (MF) resin core − shell structure particles (pEG@MF) as specific flame retardants for rigid polyurethane foam (RPUF) were synthesized by encapsulating pEG particles with a layer of MF resin via in situ polycondensation. The initial feed weight ratio of pEG and MF prepolymer was found to be the key factor affecting the shell forming process, and the shell growth can be regarded as a combination of 'raspberry-like' and conventional 'core-shell' formation mechanisms. With the encapsulation of a well formed MF shell, the expandability of pEG particles was significantly enhanced from 42 mL g -1 to 76 mL g -1 and thus the pEG@MF particles showed good flame-retardant performance in RPUF. The RPUF/pEG@MF composites passed the V-0 rate and the limiting oxygen index was remarkably increased from 21 to 28 vol% by adding only 10 wt% pEG@MF particles; both the expandability and available expandable graphite content played an important role in controlling the flame-retardant performance of pEG@MF particles. With a loading of fine sized pEG@MF particles, desirable mechanical and thermal insulation properties of RPUF/pEG@MF composites were achieved by preserving the complete cell structure of RPUF and screening the high thermal conductivity of the pEG particles with the thermally inert MF resin shell. The exciting application of the novel pEG@MF particles indicates that the core-shell structure design of expandable graphite can serve as promising solution for fabricating halogen-free flame-retardant RPUF composites with high performance.

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Silica Coating of Nanoparticles by the Sonogel Process

Cited by 28 publications

References 30 publications

Biosilicification Templated by Amphiphilic Block Copolypeptide Assemblies

Biosilicification Templated by Amphiphilic Block Copolypeptide Assemblies

Applications of Ultrasound to the Synthesis of Nanostructured Materials

Core-shell structure design of pulverized expandable graphite particles and their application in flame-retardant rigid polyurethane foams

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