Synthesis and characterization of photoswitchable fluorescent silica nanoparticles

We have designed and synthesized a new functional (amino reactive) highly efficient fluorescent molecular switch (FMS) with a photochromic diarylethene and a rhodamine fluorescent dye. The reactive group in this FMS -N-hydroxysuccinimide ester- allows selective labeling of amino containing molecules or other materials. In ethanolic solutions, the compound displays a large fluorescent quantum yield of 52 % and a large fluorescence modulation ratio (94 %) between two states that may be interconverted with red and near-UV light. Silica nanoparticles incorporating the new FMS were prepared and characterized, and their spectroscopic and switching properties were also studied. The dye retained its properties after the incorporation into the silica, thereby allowing light-induced reversible high modulation of the fluorescence signal of a single particle for up to 60 cycles, before undergoing irreversible photobleaching. Some applications of these particles in fluorescence microscopy are also demonstrated. In particular, subdiffraction images of nanoparticles were obtained, in the focal plane of a confocal microscope.     

Synthesis and characterization of functionalized rhodamine B-doped silica nanoparticles

In this paper, we have prepared the fluorescent silica nanoparticles (FSNPs) covalently doped with rhodamine B (RB) dye molecules via 3-aminopropyltriethoxysilane (APTES) in reverse microemulsion method. Then by the cohydrolysis and polymerization of tetraethoxysilane (TEOS) and APTES, the surface of the FSNPs formed another thin silica shell with the functionalized amino groups. The resulting nanoparticles were characterized by infrared (IR) spectrum, transmission electron microscopy (TEM), and spectrofluorimetry. TEM showed that the particles with diameters in the range of 70–500 nm were obtained, with core and shell sizes controlled by varying component content. At the same time, the effect of RB content on the fluorescent properties of the FSNPs was studied, and the results indicated that the fluorescence intensity of the FSNPs could be precisely tuned by varying the doping amount of RB dyes. Finally, the dye leakage was also tested, displaying that RB molecules would not leak out from the silica nanoparticles after dispersing in the aqueous solution.     

Synthesis of mesoporous silica with embedded nickel nanoparticles for catalyst applications

Here we describe a new route for the synthesis of nanometric Ni particles embedded in a mesoporous silica material with excellent potential for catalytic applications. Mesoporous silica with a surface area in the range of 202-280 m2/g, with narrow pore size distribution and Ni nanoparticles (particles in the range of 3-41 nm) were obtained in a direct process. A different approach was adopted to process such a nanocomposite. This new approach is based on the formation of a polymer with the silicon oxianion and nickel cation chelated to the macromolecule structure and on the control of the pyrolysis step. The CO/CO2 atmosphere resulting from the pyrolysis of the organic material promotes the reduction of the Ni citrate.     

Synthesis and physical characterization of magnetite nanoparticles for biomedical applications

Iron oxide nanoparticles for biomedical applications in the size range of 15–130 nm were prepared by either oxidative hydrolysis of ferrous sulfate with KOH or precipitation from ferrous/ferric chloride solutions. The magnetite particle size is controlled by variation of pH and temperature. The synthesized magnetite nanoparticles are partially oxidized as signaled by ferrous concentrations of below 24 wt% Fe²⁺ and lattice parameters of a₀ ≤ 8.39 Å which are smaller compared to 8.39 Å for stoichiometric magnetite. The extend of oxidation increases with decreasing particle size. Heating at 150–350 °C topotactically transforms the magnetite nanoparticles into stoichiometric tetragonal maghemite (ferrous ion concentration c_Fe²⁺=0 and a₀ = 8.34 Å) without significant particle growth. The magnetite–maghemite transformation is studied with thermal analysis, XRD and IR spectroscopy. The saturation magnetizations of the magnetite and maghemite particles decrease with decreasing particle size. The variation of M_s with particle size is interpreted using a magnetic core–shell particle model. Magnetite particles with d ≤ 16 nm show superparamagnetic behavior at room temperature whereas particles with diameter >16 nm display hysteresis behavior. These particles are candidates for biomedical applications, e.g. controlled drug release or hyperthermia.     

Synthesis and characterization of sol-gel silica films doped with size-selected gold nanoparticles

Homogeneous nanocomposite silica films uniformly doped with size-selected gold nanoparticles (AuNPs) have been prepared by a combined use of colloidal chemistry and the sol-gel process. For this purpose, stable thiol-functionalized AuNPs (DDT-AuNPs) were first synthesized by a two-phase aqueous/organic system and, subsequently, dispersed in an acid-catalysed sol-gel silica solution. The microstructural morphology of the samples was investigated by x-ray diffraction and field emission scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) and UV-vis optical spectrophotometry were instead employed to investigate the elemental chemical behaviour and the evolution of the surface plasmon resonance (SPR) band of the AuNPs from their synthesis up to the formation of the Au-doped silica films. The results show that the size, shape and crystalline domains of the AuNPs remain unchanged during the entire preparation process, indicating that their aggregation or decomposition was prevented. XPS results show that the DDT-AuNPs lose the capping shells and oxidize themselves when dispersed in acid-catalysed sol-gel solutions, and that bare AuNPs are embedded in the SiO(2) films. A large broadening of the SPR band, observed for systems with DDT-AuNPs, suggests the presence of interface effects which cause a surface electron density lowering. Thiol chain detachment from the AuNPs determines an increase of the SPR peak intensity while the oxidation of the Au surfaces causes a red shift of its position. The latter is no longer observed in doped films, suggesting that no interfacial effects between bare AuNPs and the host medium are present.     

Synthesis and characterization of magnetic nanoparticles coated with a uniform silica shell

Magnetic nanoparticles with a proper surface coating are of outstanding interest for several applications, especially in the biomedical field. In this paper we present the synthesis of CoFe₂O₄ magnetic nanoparticles covered by a uniform silica shell. These particles were characterized by means of Transmission Electron Microscopy (TEM) and Small Angle Scattering of Polarized Neutrons (SANSPOL). This newly developed technique, taking advantage from the variation of magnetic contrast, allowed us to verify that the thickness of the silica shell can be accurately tailored through a very simple synthetic approach.     

Bioconjugated silica nanoparticles: Development and applications

Advanced bioanalysis, including accurate quantitation, has driven the need to understand biology and medicine at the molecular level. Bioconjugated silica nanoparticles have the potential to address this emerging challenge. Particularly intriguing diagnostic and therapeutic applications in cancer and infectious disease as well as uses in gene and drug delivery, have also been found for silica nanoparticles. In this review, we describe the synthesis, bioconjugation, and applications of silica nanoparticles in different bioanalysis formats, such as selective tagging, barcoding, and separation of a wide range of biomedically important targets. Overall, we envisage that further development of these nanoparticles will provide a variety of advanced tools for molecular biology, genomics, proteomics and medicine. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Mesoporous silica nanoparticles in nanomedicine applications

In the last few years mesoporous silica nanoparticles (MSNs) have gained the attention of the nanomedicine research community, especially for the potential treatment of cancer. Although this topic has been reviewed before, periodic updates on such a hot topic are necessary due to the dynamic character of this field. The reasons that make MSNs so attractive for designing controlled drug delivery systems lie beneath their physico-chemical stability, easy functionalisation, low toxicity and their great loading capacity of many different types of therapeutic agents. The present brief overview tries to cover some of the recent findings on stimuli-responsive mesoporous silica nanocarriers together with the efforts to design targeted nanosystems using that platform. The versatility of those smart nanocarriers has promoted them as very promising candidates to be used in the clinic in the near future to overcome some of the pitfalls of conventional medicine.

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Synthesis, properties, and applications of iron nanoparticles

Iron, the most ubiquitous of the transition metals and the fourth most plentiful element in the Earth's crust, is the structural backbone of our modern infrastructure. It is therefore ironic that as a nanoparticle, iron has been somewhat neglected in favor of its own oxides, as well as other metals such as cobalt, nickel, gold, and platinum. This is unfortunate, but understandable. Iron's reactivity is important in macroscopic applications (particularly rusting), but is a dominant concern at the nanoscale. Finely divided iron has long been known to be pyrophoric, which is a major reason that iron nanoparticles have not been more fully studied to date. This extreme reactivity has traditionally made iron nanoparticles difficult to study and inconvenient for practical applications. Iron however has a great deal to offer at the nanoscale, including very potent magnetic and catalytic properties. Recent work has begun to take advantage of iron's potential, and work in this field appears to be blossoming.     

Synthesis and properties of hollow silica nanoparticles

Hollow nanoparticles of silicon dioxide (SiO₂) have been obtained using Cu/SiO₂ core-shell nanoparticles as precursors. An original technique based on heating the precursor nanoparticles to T = 400°C followed by a nanochemical reaction of copper oxide separation from hollow silica particles has been proposed and implemented for the first time. The obtained hollow SiO₂ nanoparticles have been studied by transmission electron microscopy. Mechanisms involved in the formation of hollow silica nanoparticles are discussed.     

氨丙基功能化二氧化硅的制备及结构表征

分别采用液相法和溶胶-凝胶法制备了氨基功能化的二氧化硅(APS),利用FTIR,BET,元素分析和TG等技术对制备的APS进行了结构表征.在液相法制备APS的过程中,为使SiO2表面有更多的羟基与氨丙基三乙氧基硅烷(APTES)发生反应,采用4种方法对SiO2表面进行了预处理.结果表明,微波辐射效果最好,可使SiO2表面羟基数由1.08(个/nm2)增加到1.29(个/nm2).采用液相法制备的APS中氨丙基负载量为8.59%(质量分数),活性位(氨丙基)浓度为1.49mmol/g.采用溶胶一凝胶法制备的APS中氨丙基负载量为6.88%(质量分数),活性位(氨丙基)浓度为1.19mmol/g,均较液相法制备的APS低.     

Synthesis and characterization of manganese containing mesoporous bioactive glass nanoparticles for biomedical applications

Mesoporous bioactive glass (BG) nanoparticles based in the system: SiO₂–P₂O₅–CaO–MnO were synthesized via a modified Stöber process at various concentrations of Mn (0–7 mol %). The synthesized manganese-doped BG nanoparticles were characterized in terms of morphology, composition, in vitro bioactivity and antibacterial activity. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis confirmed that the particles had spherical morphology (mean particle size: 110?nm) with disordered mesoporous structure. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn, Ca, Si and P in the synthesized Mn-doped BG particles. Moreover, X-ray diffraction (XRD) analysis showed that Mn has been incorporated in the amorphous silica network (bioactive glass). Moreover, it was found that manganese-doped BG particles form apatite crystals upon immersion in simulated body fluid (SBF). Inductively coupled plasma atomic emission spectroscopy (ICP-OES) measurements confirmed that Mn is released in a sustained manner, which provided antibacterial effect against Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. The results indicate that the incorporation of Mn in the bioactive glass network is an effective strategy to develop novel multifunctional BG nanoparticles for bone tissue engineering.     

超顺磁性Fe3O4纳米颗粒的合成及应用

总结了超顺磁性Fe3O4纳米颗粒的常用制备方法:沉淀法、水热法、微乳液法、模板合成法及生物矿化合成法,并综述了其研究现状,同时比较了它们各自的优缺点及所面临的问题.此外,还概述了超顺磁性Fe3O4纳米颗粒在靶向药物、癌症治疗、磁共振成像(MR I)及生物活性物质的检测和分离等生物医学方面的应用,并对前景进行了展望.     

Synthesis and characterization of CdS nanoparticles

In the present work a chemical reduction method is followed to grow CdS nanoparticles at room temperature with varying the amount of reducing agent sodiumborohydride. The dispersed samples in ethanol are characterized using electron diffraction techniques. Simultaneously optical absorption, photoluminescence and longtime photorelaxation of these samples are studied at room temperature. An increase in band gap is observed in each case as compared to bulk CdS. Also particle size decreases with increased amount of reducing agent. Simultaneously long time relaxation increases with decrease of stoichiometric ratio of reducing agent. An attempt is made to correlate the structural, optical, electrical and opto-electrical properties.     

Synthesis and characterization of Fe doped CeO2 nanoparticles for pigmented ultraviolet filter applications

Iron doped CeO2 nanoparticles with doping concentrations between 0 and 30 mol% were synthesized by the co-precipitation method for potential application as a pigmented ultraviolet filtration material. Each sample was calcined in air and in argon. The iron solubility limit in the CeO2 lattice was found to be between 10 and 20 mol%. Raman spectroscopy results revealed that both iron doping and argon calcination increase the concentration of oxygen vacancies in the CeO2 lattice. Iron doping causes a blue-shift of the absorbance spectrum, which can be linked to the decreased crystallite size, as obtained by XRD peak broadening using the Scherrer formula. The undoped samples showed weak ferromagnetic behaviour whereas the doped samples were all paramagnetic.     

Synthesis and characterization of copper nanoparticles

Reduction of copper salt by sodium citrate/SFS and myristic acid/SFS leads to phase pure Cu nanoparticles. However, a similar reaction with hydrazine hydrate (HH) and sodium formaldehyde sulfoxylate (SFS) in polymer afforded only a mixture of Cu₂O and Cu. Copper nanoparticles so-prepared were characterized by UV-Visible spectroscopy, X-ray diffraction measurements (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Freshly prepared solutions showed an absorption band at about 600 nm due to surface plasmon resonance (SPR). XRD analysis revealed all relevant Bragg's reflection for fcc crystal structure of copper metal. The particle size by use of Scherrer's equation is calculated to be about 30 nm. TEM showed nearly uniform distribution of the particles in PVA.     

Biotemplated silica and titania nanowires: synthesis, characterization and potential applications

A simple biotemplating method for the synthesis of silica (SiO2) and titania (TiO2) nanowires was designed on a fibrillar protein (alpha-synuclein) template. The diameter of SiO2 and TiO2 nanowires could be varied, between 20-100 nm, by varying the processing conditions. The nanowires were characterized by energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Due to their high surface area and porosity, the nanowires were tested for potential applications in enzymatic biosensor design.     

Synthesis, characterization, and antibacterial activity of silver-doped silica nanocomposite particles

Silver nanoparticles were adsorbed preferentially on silica surface to form composite particles using a reverse micelle process that stabilizes the silver particles by an anionic sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant in isooctane solvent together with the silica particles in which their surface being mediated by a cationic poly(allylamine hydrochloride) (PAH) polyelectrolyte. The heterogeneous adsorption was rendered by both electrostatic attraction and hydrophilic/hydrophobic interaction, and was carried out in multiple deposition cycles. The resulting nanocomposite particles were characterized by zeta-potential measurement, electron microscopy, X-ray diffractometry, field-emission electron spectroscopy for chemical analysis (ESCA), and inductively coupled plasma analysis, respectively. In addition, antibacterial activity of the composite particles was examined against Escherichia coli (E. coli) in aqueous environment.     

Synthesis of mesoporous silica monoliths with embedded nanoparticles

Mesostructured silica-nanoparticle monolithic composites have been synthesized by dispersing prefabricated nanoparticles of gold or zeolite (silicalite) in ethanolic reaction mixtures containing SiCl4 and a Pluronic triblock copolymer template. Whereas silicalite nanoparticles were used directly, surface functionalization of the gold nanoparticles with either primed silicate ions or a discrete 3-5-nm-thick silica shell was required to increase the interfacial compatibility with the hydrophilic poly(ethylene oxide) blocks. Under these conditions, the resulting monoliths consisted of distributed nanoparticles within an ordered mesostructured silica matrix. Removal of the polymer template by calcination produced corresponding mesoporous silica-nanoparticle replicas. The combination of the structure and the porosity of the silica framework with the crystal chemical properties of the embedded nanoparticles suggests that such composites should be useful as multifunctional materials.