Search query: Fabrication of Monodispersed Au@SiO2 Nanoparticles with Highly Stable Silica Layers by Ultrasound{Assisted Stober Method

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abstract: Metal@dielectric composite nanostructures are of high demand for their vast technological applications. The Stober method, either in its original form or by modification, has been utilized for the fabrication of silica shells over metal, semiconductor, or even dielectric nanostructures, with the aim to protect them from degradation, enhance their biocompatibility, or use them for molecular anchoring. However, the stability of silica shells and the dispersion of core shell nanostructures remain the main limitations for their efficient applications. Here we demonstrate that utilization of ultrasound during hydrolysis and condensation of the metal organic silicon precursor in Stober process can produce stable and uniform silica shell layers around gold nanoparticles, enhancing both their stability and dispersion. Through transmission electron microscopy and infrared spectroscopy techniques, we demonstrate that the Au@SiO2 nanoparticles fabricated with ultrasound treatment during silica shell growth contain a.
author_names: Jose Luis Montano-Priede

Joao Paulo Coelho

Andres Guerrero-Martinez

Ovidio Pena-Rodriguez

Umapada Pal
title: Fabrication of Monodispersed Au@SiO2 Nanoparticles with Highly Stable Silica Layers by Ultrasound Assisted Stober Method
year: 2017

abstract: Abstract A system of chemical reactions has been developed which permits the controlled growth of spherical silica particles of uniform size by means of hydrolysis of alkyl silicates and subsequent condensation of silicic acid in alcoholic solutions. Ammonia is used as a morphological catalyst. Particle sizes obtained in suspension range from less than 0.05 m to 2 m in diameter.
author_names: Werner Stober

Arthur I Fink

Ernst Bohn
title: Controlled growth of monodisperse silica spheres in the micron size range
year: 1968

abstract: Colloidal hollow mesoporous silica nanoparticles (HMSNs) are aspecial type of silica based nanomaterials with penetrating mesopore channels on their shells. HMSNs exhibit unique structural characteristics useful for diverse applications: Firstly, the hollow interiors can function as reservoirs for enhanced loading of guest molecules, or as nanoreactors for the growth of nanocrystals or for catalysis in confined spaces. Secondly, the mesoporous silica shell enables the free diffusion of guest molecules through the intact shell. Thirdly, the outer silica surface is ready for chemical modifications, typically via its abundant Si OH bonds. As early as 2003, researchers developed a soft templating methodto prepare hollow aluminosilicate spheres with penetrating mesopores in a cubic symmetry pattern on the shells. However, adapting this method for applications on the nanoscale, especially for biomedicine, has proved difficult because the soft templating micelles are very sensitive to liquid environments, making it difficult to tune key parameters such as dispersity, morphology and structure. In this Account, we present the most recent developments in the tailored construction of highly dispersive and monosized HMSNs using simple silica etching chemistry, and we discuss these particles' excellent performance in diverse applications. We first introduce general principles of silica etching chemistry for controlling the chemical composition and the structural parameters (particle size, pore size, etching modalities, yolk shell nanostructures, etc. of HMSNs. Secondly, we include recent progress in constructing heterogeneous, multifunctional, hollow mesoporous silica nanorattles via several methods for diverse applications. These elaborately designed HMSNs could be topologically transformed to prepare hollow mesoporous carbon nanoparticles or functionalized to produce HMSN based composite nanomaterials. Especially in biomedicine, HMSNs are excellent as carriers to deliver either hydrophilic or hydrophobic anti cancer drugs, to tumor cells, offering enhanced chemotherapeutic efficacy and diminished toxic side effects. Most recently, research has shown that loading one or more anticancer drugs into HMSNs can inhibit metastasis or reverse multidrug resistance of cancer cells. HMSNs could also deliver hydrophobic perfluorohexane (PFH) molecules to improve high intensity focused ultrasound (HIFU) cancer surgery by changing the tissue acoustic environment; and HMSNs could act as nanoreactors for enhanced catalytic activity and/or durability. The versatility of silica etching chemistry, a simple but scalable synthetic methodology, offers great potential for the creation of new types of HMSN based nanostructures in a range of applications.
author_names: Yu Chen

Hang Chen

Jian Lin Shi
title: Construction of homogenous/heterogeneous hollow mesoporous silica nanostructures by silica etching chemistry: principles, synthesis, and applications.
venue: Accounts of chemical research
year: 2014

abstract: We investigate the dependence of the center of mass tomogram of a system with many degrees of freedom $N$ on the Planck constant \hbar It is shown that to use the central limit theorem under taking the limit $N\to \infty one should keep the energy of the system to be constant. In the case, the resulting distribution is Gaussian if the initial distribution is a product of independent excited states of a quantum oscillator or even and odd coherent states either. Then, if one turns the Planck constant \hbar \to 0$ we get \delta function associated with the distribution concentrated in zero with the probability equal to one.
author_names: Grigori G Amosov

Vladimir I Man'ko
title: A use of the central limit theorem to obtain a classical limit for the center of mass tomogram
year: 2009

abstract: Although humans have been exposed to airborne nanosized particles (NSPs; 100 nm) throughout their evolutionary stages, such exposure has increased dramatically over the last century due to anthropogenic sources. The rapidly developing field of nanotechnology is likely to become yet another source through inhalation, ingestion, skin uptake, and injection of engineered nanomaterials. Information about safety and potential hazards is urgently needed. Results of older bio kinetic studies with NSPs and newer epidemiologic and toxicologic studies with airborne ultrafine particles can be viewed as the basis for the expanding field of nanotoxicology, which can be defined as safety evaluation of engineered nanostructures and nanodevices. Collectively, some emerging concepts of nanotoxicology can be identified from the results of these studies. When inhaled, specific sizes of NSPs are efficiently deposited by diffusional mechanisms in all regions of the respiratory tract. The small size facilitates uptake into cells and transcytosis across epithelial and endothelial cells into the blood and lymph circulation to reach potentially sensitive target sites such as bone marrow, lymph nodes, spleen, and heart. Access to the central nervous system and ganglia via translocation along axons and dendrites of neurons has also been observed. NSPs penetrating the skin distribute via uptake into lymphatic channels. Endocytosis and biokinetics are largely dependent on NSP surface chemistry (coating) and in vivo surface modifications. The greater surface area per mass compared with larger sized particles of the same chemistry renders NSPs more active biologically. This activity includes a potential for inflammatory and pro oxidant, but also antioxidant, activity, which can explain early findings showing mixed results in terms of toxicity of NSPs to environmentally relevant species. Evidence of mitochondrial distribution and oxidative stress response after NSP endocytosis points to a need for basic research on their interactions with subcellular structures. Additional considerations for assessing safety of engineered NSPs include careful selections of appropriate and relevant doses/concentrations, the likelihood of increased effects in a compromised organism, and also the benefits of possible desirable effects. An interdisciplinary team approach (e.g. toxicology, materials science, medicine, molecular biology, and bioinformatics, to name a few) is mandatory for nanotoxicology research to arrive at an appropriate risk assessment.
author_names: Gunter Oberdorster

Eva Oberdorster

Jan Oberdorster
title: Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles
venue: Environmental health perspectives
year: 2005

abstract: Colloidal nanoparticles composed out of a 4 nm monodisperse, radioactively labelled gold core (198Au) and a radioactively labelled polymer shell (111In) were administered via intravenous injection to rats. These nanoparticles have excellent colloidal stability in vitro. Independent biodistribution data obtained from the 198Au and 111In labels indicate that in vivo the polymer shell comes at least partially off the nanoparticle core. This demonstrates that even high quality nanoparticles with well defined colloidal properties in vitro, can radically change their physicochemical properties in in vivo scenarios. Additional "in test tube" and in vitro data suggest that degradation of the polymer shell may be caused by proteolytic enzymes. Thus physicochemical characterization as performed of the nanoparticles in media outside cells has to be considered to apply only partly for internalized nanoparticles.
author_names: Abuelmagd M Abdelmonem
title: Nanoparticles: Synthesis, Surface Modification and Functionalization for Biological and Environmental Applications
year: 2014

abstract: In order to selectively target malignant cells and eliminate severe side effects of conventional chemotherapy, biocompatible and redox responsive hollow nanocontainers with tumor specificity were fabricated. The mechanized nanocontainers were achieved by anchoring mechanically interlocked molecules, i.e. [2]rotaxanes, onto the orifices of hollow mesoporous silica nanoparticles via disulfide bonds as intermediate linkers for intracellular glutathione triggered drug release. The [2]rotaxane employed was mainly composed of U.S. Food and Drug Administration approved tetraethylene glycol chains, a cyclodextrin, and folic acid. In this study, folate groups on the mechanized hollow nanocontainers act as both the tumor targeting agents and stoppers of the [2]rotaxanes. Detailed investigations showed that anticancer drug doxorubicin loaded mechanized nanocontainers could selectively induce the apoptosis and death of tumor cells. The drug loaded nanocontainers enhanced the targeting capability to tumor tissues in vitro and inhibited the tumor growth with minimal side effects in vivo. The present controlled and targeted drug delivery system paves the way for developing the next generation of nanotherapeutics toward efficient cancer treatment.
author_names: Zhong Luo

Xingwei Ding

Yan Hu

Shaojue Wu

Yang Xiang

Yongfei Zeng

Beilu Zhang

Hong Yan

Huacheng Zhang

Liangliang Zhu

Junjie Liu

Jinghua Li

Kaiyong Cai

Yanli Zhao
title: Engineering a hollow nanocontainer platform with multifunctional molecular machines for tumor targeted therapy in vitro and in vivo.
venue: ACS nano
year: 2013

abstract: Semiconducting quantum dots, whose particle sizes are in the nanometer range, have very unusual properties. The quantum dots have band gaps that depend in a complicated fashion upon a number of factors, described in the article. Processing structure properties performance relationships are reviewed for compound semiconducting quantum dots. Various methods for synthesizing these quantum dots are discussed, as well as their resulting properties. Quantum states and confinement of their excitons may shift their optical absorption and emission energies. Such effects are important for tuning their luminescence stimulated by photons (photoluminescence) or electric field (electroluminescence) In this article, decoupling of quantum effects on excitation and emission are described, along with the use of quantum dots as sensitizers in phosphors. In addition, we reviewed the multimodal applications of quantum dots, including in electroluminescence device, solar cell and biological imaging.
author_names: Debasis Bera

Lei Qian

Teng-Kuan Tseng

Paul H Holloway
title: Quantum Dots and Their Multimodal Applications: A Review
venue: Materials
year: 2010

abstract: Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004 2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930 2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed. Copyright (c) 2014 John Wiley Sons, Ltd.
author_names: Michael J Whitcombe

Nicole Kirsch

Ian A Nicholls
title: Molecular imprinting science and technology: a survey of the literature for the years 2004 2011
venue: Journal of molecular recognition JMR
year: 2014

abstract: We gratefully acknowledge funding and support from King Abdullah University of Science and Technology (KAUST) Thanks are also due to the KAUST communication department for designing several images for this Review.
author_names: Vivek Polshettiwar

Rafael Luque

Aziz Fihri

Haibo Zhu

Mohamed Bouhrara

Jean-Marie Basset
title: Magnetically recoverable nanocatalysts.
venue: Chemical reviews
year: 2011