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TEM images of fluorescent silica nanoparticles (scale bar = 100 nm) (a) without surface modification ? CuSO 4 and (b) with a Diamino functionalization ? CuSO 4
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Fluorescent silica nanoparticles are widely used for various applications from mechanical reinforcement to biology. In many
cases, their surface has to be tailored. Herein fluorescent silica nanoparticles are synthesized by a reverse micro-emulsion
process and functionalized by silane coupling agents owning amino and thiol groups. The functionaliza...
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Context 1
... nanoscale characterization of the functionalized silica nanoparticles is shown Fig. 6. The image on the right is obtained by adding a CuSO 4 to a Diamino- functionalized silica suspension. The copper ions are chelated by the Diamino functions present on the silica surface ( Zolezzi et al. 1999). The picture on the left illustrates the fact that there is no specific interaction between Cu 2? and Silica. Therefore, one ...
Citations
... This mixed synthetic route will be discussed later. Some properties of silica nanoparticle include [82][83][84][85] easy surface functionalization, [86][87][88][89] chemical inertness, low toxicity, light transparency, and good water solubility. These properties have promoted silica-based nanomaterials as potential candidates for engineering hybrid multifunctional nanostructures for biomedical applications [90]. ...
Carbon dots (CDs) are carbon nanoparticles with sizes below 10 nm and have attracted attention due to their relatively low toxicity, great biocompatibility, water solubility, facile synthesis, and exceptional photoluminescence properties. Accordingly, CDs have been widely exploited in different sensing and biomedical applications, for example, metal sensing, catalysis, biosensing, bioimaging, drug and gene delivery, and theragnostic applications. Similarly, the well-known properties of silica, such as facile surface functionalization, good biocompatibility, high surface area, and tunable pore volume, have allowed the loading of diverse inorganic and organic moieties and nanoparticles, creating complex hybrid nanostructures that exploit distinct properties (optical, magnetic, metallic, mesoporous, etc.) for sensing, biosensing, bioimaging, diagnosis, and gene and drug delivery. In this context, CDs have been successfully grafted into diverse silica nanostructures through various synthesis methods (e.g., solgel chemistry, inverse microemulsion, surfactant templating, and molecular imprinting technology (MIT)), imparting hybrid nanostructures with multimodal properties for distinct objectives. This review discusses the recently employed synthesis methods for CDs and silica nanoparticles and their typical applications. Then, we focus on combined synthesis techniques of CD–silica nanostructures and their promising biosensing operations. Finally, we overview the most recent potential applications of these materials as innovative smart hybrid nanocarriers and theragnostic agents for the nanomedical field.
Graphical abstract
... After EPD modification in neutral NS suspension, the bond strength of CF to the cementitious matrix was pronouncedly increased up to 2.6 MPa. This increase in interfacial adhesion can be explained that the nano-SiO 2 particles deposited on the CFs can not only tailor the fiber surface wettability due to their hydrophilic properties [72,73] but act as nucleating seeds and silica source to form calcium silicate hydrate (C-S-H) gel [74] and calcite [9]. This could generate a more compact and denser interfacial area neighboring CFs (see Fig. 15b.) and thereby enhance the bond performance resulting from some interlocking mechanisms, as reported in the previous investigation [9]. ...
... When CFs are electrophoretically treated in acidic NS suspension at pH 2.65, the pullout results showed the highest value of shear bond strength of 3.6 MPa. This bonding enhancement can be mainly traced back to two phenomena: A large amount of NS particles attached to fiber surface formed a homogeneous coating, as revealed in ESEM images, improving the surficial wettability owing to the silanol groups of nano-SiO 2 [72,73]. This coated nano-SiO 2 reacted with the Ca(OH) 2 to C-S-H gel due to a pozzolanic reaction, as described above; see Fig. 15c. ...
Electrophoretic deposition (EPD) of nano-silica (NS) onto carbon fiber (CF) surfaces may considerably improve the bond properties toward cementitious matrices. In the article at hand, varied pH conditions (neutral, acidic, and alkaline environments) are studied during EPD for a tailorable interfacial bond. Zeta potential measurements and cyclic voltammetry (CV) confirmed the importance of pH with regard to the EPD process. Scanning electron microscopy (SEM) and X- ray photoelectron spectroscopy (XPS) revealed that an acidic environment enables the most pronounced and homogeneous NS coating on the CF surfaces. X-ray diffraction (XRD) analysis delivered deeper insights into the microstructures of modified CFs, indicating a decreased graphite interlayer spacing and an increased crystallite size after treatment. This results in a changed temperature-stability as well as mechanical properties, as revealed by thermogravimetric analysis (TGA), single-fiber tensile tests, and Weibull analysis.
To assess the interaction of the modified CFs with cementitious matrices, single-fiber pullout tests were performed, showing the highest bond strength and total pullout work of CFs treated in an acidic environment. This is mainly explained by a reaction of the high number of NS particles with calcium hydroxide to form calcium silicate hydrate (C-S-H) gel and, thus, intensifying the interfacial transition zone, subsequently increasing the bond properties of CF to a matrix. As well, abundant oxygen-related functional groups were introduced on the CF surfaces from anodic oxidation, leading to an enhanced bond by promoting precipitation of cement hydration products onto the CF surfaces.
... On the whole, the pullout forces for CF treated with 1 V are higher than those for CF treated with 3 V, indicating better interaction between fiber and matrix. The increase in bond strength between CF and the cementitious matrix is mainly attributable to two phenomena: NS particles deposited onto the CF surface are hydrophilic due to the presence of silanol groups [52,69], providing better wettability of the CF surface. The improvement in hydrophilicity of fiber surface leads consequently to a denser fiber/matrix interphase and higher bond strength [14,21]. ...
Nano-silica (NS) is deposited onto Carbon fibers (CFs) using electrophoretic deposition (EPD) to improve their bond to cementitious matrices. Two different voltage ranges and two deposition times were applied. The mobility of the negatively charged NS-colloids in deionized water in a controlled electric field was proven by zeta potential measurements and cyclic voltammetry (CV). Scanning electron microscopy and energy dispersive X-ray analysis (EDX) showed homogeneously distributed nano-silica particles on the surfaces of the CF. Thermo-gravimetric analysis (TGA) and single-fiber tensile tests were conducted to assess the impact of the parameters under investigation on the CF properties. Single-fiber pullout tests from a cement-based matrix showed markedly enhanced bond strength of the modified filaments, indicating improved reinforcing action of CF in cementitious composites. Storing the modified fibers in a cement pore solution showed that nano-silica deposits act as nucleating seeds for building calcium silicate hydrate (C–S–H) and calcite. This explains the enhanced bond properties.
... PVP-and APTES-functionalization led to a pronounced change in surface charge comparable to previous studies on bare and amino-functionalized SiO 2 nanoparticles. 46 To explore further biofunctionalization, the primary amine groups from APTES were conjugated to folic acid (FA). FA can be used to selectively target FA-receptor overexpressing tumor cells. ...
High-Z metal oxide nanoparticles hold promise as imaging probes and radio-enhancers. Hafnium dioxide nanoparticles have recently entered clinical evaluation. Despite promising early clinical findings, the potential of HfO2 as a matrix for multimodal theranostics is yet to be developed. Here, we investigate the physicochemical properties and the potential of HfO2-based nanoparticles for multimodal theranostic imaging. Undoped and lanthanide (Eu3+, Tb3+, and Gd3+)-doped HfO2 nanoparticles were synthesized and functionalized with various moieties, including poly(vinylpyrrolidone) (PVP), (3-aminopropyl)triethoxysilane (APTES) and folic acid (FA). We show that different synthesis routes, including direct precipitation, microwave-assisted synthesis, and sol-gel chemistry allow preparation of hafnium dioxide particles with distinct physicochemical properties. Sol-gel based synthesis allows preparation of uniform nanoparticles with dopant incorporation efficiencies superior to the other two methods. Both luminescence and contrast properties can be tweaked by lanthanide doping. We show that MRI contrast can be unified with radio-enhancement by incorporating lanthanide dopants in the HfO2 matrix. Importantly, ion leaching from the HfO2 host matrix in lysosomal-like conditions was minimal. For Gd:HfO2 nanoparticles, leaching was reduced >10× compared to Gd2O3 and no relevant cytotoxic effects have been observed in monocyte-derived macrophages for nanoparticle concentrations up to 250 µg/mL. Chemical surface modification allows further tailoring of the cyto- and hemocompatibility and enables functionalization with molecular targeting entities, which lead to enhanced cellular uptake. Taken together, the present study illustrates the manifold properties of HfO2-based nanomaterials with prospective clinical utility beyond radio-enhancement.
... The disadvantage of using silicon particles is their aggregation, but this can be avoided by modifications of their surfaces [35]. In the preparation of the hybrid silica materials, functionalization of the surfaces of silica particles and functionalization of other type of particles with silica are therefore often the first step in their various applications [36,37]. The SiO 2 particles can be functionalized by introducing chemical groups, such as amino [33,36], thiol [32,38], vinyl [33], epoxy [39], carboxy [40], azido [34] or alkyne groups [34]. ...
In this study, we report on the fluorimetric method for the determination of biogenic amine agmatine based on hybrid SiO2 particles functionalized with thiol groups of 3-mercaptopropyltrimethoxysilane (MPTMS, SiO2–SH) and further conjugated with indicator dye o-phthaldialdehyde (OPA, SiO2–SH–OPA). Under optimal conditions, OPA reacted with agmatine and formed a fluorescent product in the alkaline media (pH 13). The fluorescence excitation and emission wavelengths were located at 340 and 430 nm. The relative fluorescence intensity was linear in the concentration range between 1.0 × 10−7 and 1.0 × 10−2 mol/L. Obtained SiO2–SH particles were characterized using infrared spectroscopy (FTIR), transmission electron microscopy, zeta potential and potentiometric titration.
Graphical Abstract
... Silicon oxide nanoparticles (SiO 2 NPs) were synthesized by reverse microemulsion method, in order to allow the grafting of chosen functional groups onto the NPs surface [28][29][30]. An organic dye, rhodamine 6G, was introduced within the structure to provide luminescent properties to the NPs. ...
This publication presents one of the first uses of silicon oxide nanoparticles to detect fingermarks. The study is not confined to showing successful detection of fingermarks, but is focused on understanding the mechanisms involved in the fingermark detection process. To gain such an understanding, various chemical groups are grafted onto the nanoparticle surface, and parameters such as the pH of the solutions or zeta potential are varied to study their influence on the detection. An electrostatic interaction has been the generally accepted hypothesis of interaction between nanoparticles and fingermarks, but the results of this research challenge that hypothesis, showing that the interaction is chemically driven. Carboxyl groups grafted onto the nanoparticle surfaces react with amine groups of the fingermark secretion. This formation of amide linkage between carboxyl and amine groups has further been favoured by catalyzing the reaction with a compound of diimide type. The research strategy adopted here ought to be applicable to all detection techniques using nanoparticles. For most of them the nature of the interaction remains poorly understood.
... The fluorescent dye is covalently bound to a coupling agent which participates in the synthesis of monodisperse silica spheres (Verhaegh and Vanblaaderen, 1994). These particles can also be easily modified through the addition of organic functions that control on demand the surface properties of the particles ( Samuel et al., 2010).The fluorescence intensity of these dye-doped silica nanoparticles might be not sufficient for environmental applications, for which low detection limits in complex matrices are required. Radio ( 14 C)-and fluorescent-doubly labeled silica nanoparticles was recently synthesized for biological and environmental toxicity assessment ( Geranio et al., 2010). ...
... Volumes of 0.1 mol L À1 HCl and 0.1 mol L À1 NaOH solutions were automatically added by the titrator (Autotitrator mpt-2, Malvern Instruments) in the cell measurement to adjust the solution pH. Zeta potential values were compared to zeta potential measurements of commercial silver nanoparticles (658804, Sigma Aldrich) and silica nanoparticles ( Samuel et al., 2010). ...
... The fluorescent dye is covalently bound to a coupling agent which participates in the synthesis of monodisperse silica spheres (Verhaegh and Vanblaaderen, 1994). These particles can also be easily modified through the addition of organic functions that control on demand the surface properties of the particles ( Samuel et al., 2010).The fluorescence intensity of these dye-doped silica nanoparticles might be not sufficient for environmental applications, for which low detection limits in complex matrices are required. Radio ( 14 C)-and fluorescent-doubly labeled silica nanoparticles was recently synthesized for biological and envi- ronmental toxicity assessment ( Geranio et al., 2010). ...
... Volumes of 0.1 mol L À1 HCl and 0.1 mol L À1 NaOH solutions were automatically added by the titrator (Autotitrator mpt-2, Malvern Instruments) in the cell measurement to adjust the solution pH. Zeta potential values were compared to zeta potential measurements of commercial silver nanoparticles (658804, Sigma Aldrich) and silica nanoparticles ( Samuel et al., 2010). ...
The synthesis and the characterization of three kinds of labeled silica nanoparticles were performed. Three different labeling strategies were investigated: fluorescent organic molecule (FITC) embedded in silica matrix, heavy metal core (Ag(0)) and radioactive core ((110m)Ag) surrounded by a silica shell. The main properties and the suitability of each kind of labeled nanoparticle in terms of size, surface properties, stability, detection limits, and cost were determined and compared regarding its use for transport studies. Fluorescent labeling was found the most convenient and the cheapest, but the best detection limits were reached with chemical (Ag(0)) and radio-labeled ((110m)Ag) nanoparticles, which also allowed nondestructive quantifications. This work showed that the choice of labeled nanoparticles as surrogates of natural colloids or manufactured nanoparticles strongly depends on the experimental conditions, especially the concentration and amount required, the composition of the effluent, and the timescale of the experiment.
... Table 3 shows that the zeta potential of pure gadolinium oxide nanoparticles is around 23 mV whereas the zeta potential values of hybrid nanoparticles are lower (16 and -4 mV). This trend can be explained by considering the zeta potential values of pure silica nanoparticles (-40 mV) and amino functionalized silica nanoparticles (?10 mV) (Samuel et al. 2010). Therefore, the surface of the as-prepared nanoparticles has been clearly modified by this silane treatment. ...
... Primary gadolinium oxide nanoparticles having been recovered by a silica shell, the next step is to perform their surface functionalization. This surface functionalization is well known and has already been described many times (Samuel et al. 2010). Especially, the surface functionalization of silica nanoparticles with hexadecyltrimethoxysilane has already been shown (Iijima et al. 2007). ...
Gadolinium oxide nanoparticles are more and more used. They can notably provide interesting fluorescence properties. Herein
they are incorporated into a non-aqueous-based polymer, the poly(methyl methacrylate). Their dispersion within the polymer
matrix is the key to improve the composite properties. As-received gadolinium oxide nanopowders cannot be homogeneously dispersed
in such a polymer matrix. Two surface treatments are, therefore, detailed and compared to achieve a good stability of the
nanoparticles in a non-aqueous solvent such as the 2-butanone. Then, once the liquid suspensions have been stabilized, they
are used to prepare nanocomposites with homogeneous particles dispersion. The two approaches proposed are an hybrid approach
based on the growth of a silica shell around the gadolinium oxide nanoparticles, and followed by a suitable silane functionalization;
and a non-hybrid approach based on the use of surfactants. The surface treatments and formulations involved in both methods
are detailed, adjusted and compared. Thanks to optical methods and in particular to the use of a ‘home made’ confocal microscope,
the dispersion homogeneity within the polymer can be assessed. Both methods provide promising and conclusive results.
KeywordsDispersion–Nanomaterials–Rare earth oxides–Composites–Surface treatments–Nanohybrids–Synthesis rare metals
... The dyes selected for the study were: PABI, PPC, IR 806, NBA, HITC and ICG (Figure 1). We also reproduced the encapsulation of fluorescein and rhodamine with the standard microemulsion sol-gel process as the successful encapsulation of those two dyes has been investigated and optimised in our labora- tories [50]. It is important to mention that all dyes and fluorophores selected for this study are commercially available and their hydrophilic structural character confer them good to excellent water solubility. ...
Numerous luminophores may be encapsulated into silica nanoparticles (< 100 nm) using the reverse microemulsion process. Nevertheless, the behaviour and effect of such luminescent molecules appear to have been much less studied and may possibly prevent the encapsulation process from occurring. Such nanospheres represent attractive nanoplatforms for the development of biotargeted biocompatible luminescent tracers. Physical and chemical properties of the encapsulated molecules may be affected by the nanomatrix. This study examines the synthesis of different types of dispersed silica nanoparticles, the ability of the selected luminophores towards incorporation into the silica matrix of those nanoobjects as well as the photophysical properties of the produced dye-doped silica nanoparticles. The nanoparticles present mean diameters between 40 and 60 nm as shown by TEM analysis. Mainly, the photophysical characteristics of the dyes are retained upon their encapsulation into the silica matrix, leading to fluorescent silica nanoparticles. This feature article surveys recent research progress on the fabrication strategies of these dye-doped silica nanoparticles.
