Hybrid Metal (Gold)-Inorganic (Silica) Nanoparticles: Synthesis,Characterization, and Spin-Labeling

Water-soluble gold nanoparticles, capped with captopril, have been synthesized and characterized. Their average size is 2.3 nm, with a spherical shape. These gold nanoparticles can be easily labeled with stable free radicals (4-amino-tempo) by a coupling reaction performed in the presence of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ). Both synthesized and spin-labeled gold nanoparticles can be incorporated into much bigger (100 nm) silica nanoparticles using the Stober method, thus forming hybrid metal (gold)-inorganic (silica) nanoparticles. These hybrid silica nanoparticles (containing or not spin-labeled gold nanoparticles) can be easily spin-labeled with another stable free radical (4-isocyanato-tempo), leading to the formation of a double spin-labeled material. In this way, some stable free radicals are attached on the gold surface while others are attached on the silica surface. Three types of EPR spectra were recorded and discussed for the hybrid gold-silica nanoparticles: (1) where the spin labels are attached to the embedded gold nanoparticles, (2) where the spin labels are attached to the silica nanoparticles, and (3) in the case of the double spin labeled material where both gold and silica nanoparticles are spin-labeled. Influence of different solvents on the EPR spectra is also discussed.     

Synthesis and Microstructural Investigations of Organometallic Pd(II) Thiol-Gold Nanoparticles Hybrids

In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II) centers is presented. Pd(II) thiol, trans, trans-[dithiolate-dibis(tributylphosphine)dipalladium(II)-4,4′-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II) thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II) and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2–10 nm) was achieved by choosing the suitable AuCl₄ ⁻/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NO _x with the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid –gas interaction.     

Grafting of amphiphilic polymers containing quaternary ammonium group on SiO2 surface via surface-initiated ATRP

This article reports the fabrication of hybrid silica nanoparticles using surface-initiated atom transfer radical polymerization (SI-ATRP) technique. The surface of silica nanoparticles were densely grafted with 2-(dimethylamino) ethyl methacrylate (DMAEMA) and then quaternized with 1-bromohexane via two methods. FTIR, ¹H NMR, XPS, SEM, TGA, and GPC were used to determine the chemical structure, morphology, and other properties of the products. SEM images of nanocomposites showed spherical shaped morphology with an average diameter of ∼50 nm and they were direct evidences that the hybrid silica nanoparticles had uniform core-shell morphology. Evolution of GPC traces of grafted polyDMAEMA showed that the SI-ATRP could be conducted in a well-controlled manner.     

Microgel/SiO2 hybrid colloids prepared using a water soluble silica precursor

In the present work we demonstrate that functional polymer microgels may act as smart self-catalyzing system inducing controlled formation of silica nanoparticles inside the polymer network and formation of hybrid colloids. We synthesized a water soluble silica precursor PEG-PEOS via post-modification of hyperbranched poly(ethoxysiloxane) (PEOS) with poly(ethylene glycol) monomethyl ether. We used poly(N-vinylcaprolactam)-based microgel functionalized with imidazole and β-diketone groups as a matrix for biomimetic deposition of silica. Composite microgel particles containing silica nanoparticles (up to 20 wt.-%) have been prepared by simultaneous PEG-PEOS conversion and silica deposition in the microgels. TEM studies indicate the infiltration of silica nanoparticles (～10 nm) inside the corona region of the microgels due to the strong acid–base interaction between the acidic silica and basic imidazole groups. The resulting composite particles were found to be colloidally stable and no aggregation was observed even after months of storage. The incorporation of silica nanoparticles increased the rigidity of the microgel particles and reduced their thermal sensitivity.     

Poly(ionic liquid) nanoparticles as novel colloidal template for silica nanocasting

Spherical poly(ionic liquid) (PIL) nanoparticles of different size (25–70 nm) were synthesized and applied as a novel colloidal soft template for the preparation of meso- and macroporous inorganics, here exemplified with silica and its metal nanoparticle doping via nanocasting. Pore size and pore architecture can be adjusted by appropriate choice of the template and the reaction conditions. Unexpectedly, it was found that the in situ generated methanol plays a very important role during the casting process. It enlarged the overall surface area by introducing a significant fraction of micropores and small mesopores. The largest specific surface area was obtained at an optimized ratio of tetramethyl orthosilicate (TMOS) to PIL nanoparticle. In addition, PIL nanoparticles pre-functionalized with Pt metal nanoparticles were used in the same manner as hybrid templates for nanocasting. The pyrolysis conditions were optimized to synthesize mesoporous silica functionalized with uniformly distributed metal nanoparticles of very small size in a one-pot process.     

New fluorinated hybrid organic/inorganic water soluble polymeric network

This work presents the elaboration of nanoparticle networks from HASE (hydrophobically alkali-soluble emulsion) thickeners grafted with silica nanoparticles. Three HASE were realized by copolymerization in emulsion of methacrylic acid and ethyl acrylate or trifluoroethyl methacrylate and a hydrocarbon or fluorocarbon macromonomer. The macromonomer contains a hydrophobic pendant group separated from the backbone by a polyethylene glycol spacer chain. The free acid functions of the copolymer were coupled with amine functionalized silica nanoparticles. In basic aqueous solutions, the suspensions containing 1 wt.% of this polymer/SiO₂ nanocomposite characterized by DLS (size analysis) and Cryo-SEM are stable, translucent, and gel-like at pH = 7.5. Rheological measurements demonstrated that the grafting of silica nanoparticles did not affect the thickening effect of precursor co-polymers. Coating of glass plates was realized with these hybrid networks and characterized by AFM, indicating that the silica nanoparticles were more homogeneously dispersed when a fluorocarbon co-polymer was used.     

Bi-Functional Silica Nanoparticles Doped with Iron Oxide and CdTe Prepared by a Facile Method

Cadmium telluride (CdTe) and iron oxide nanoparticles doped silica nanospheres were prepared by a multistep method. Iron oxide nanoparticles were first coated with silica and then modified with amino group. Thereafter, CdTe nanoparticles were assembled on the particle surfaces by their strong interaction with amino group. Finally, an outer silica shell was deposited. The final products were characterized by X-ray powder diffraction, transmission electron microscopy, vibration sample magnetometer, photoluminescence spectra, Fourier transform infrared spectra (FT-IR), and fluorescent microscopy. The characterization results showed that the final nanomaterial possessed a saturation magnetization of about 5.8 emu g⁻¹ and an emission peak at 588 nm when the excitation wavelength fixed at 380 nm.     

Facile Preparation of Crosslinked Polymeric Nanocapsules via Combination of Surface-Initiated Atom Transfer Radical Polymerization and Ultraviolet Irradiated Crosslinking Techniques

A facile approach for the preparation of crosslinked polymeric nanocapsules was developed by the combination of the surface-initiated atom transfer radical polymerization and ultraviolet irradiation crosslinking techniques. The well-defined polystyrene grafted silica nanoparticles were prepared via the SI-ATRP of styrene from functionalized silica nanoparticles. Then the grafted polystyrene chains were crosslinked with ultraviolet irradiation. The cross-linked polystyrene nanocapsules with diameter of 20–50 nm were achieved after the etching of the silica nanoparticle templates with hydrofluoric acid. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy.     

Synthesis of hybrid materials via photopolymerization of benzoin functionalized silica nanoparticles

Photopolymerization of methyl methacrylate (MMA) was achieved on the surface of silica nanoparticles by “Grafting from” method. Well defined spherical silica nanoparticles prepared by Stöber method was functionalized with isocyanate groups of toluene di-isocyanate in order to achieve both improved dispersion of nanoparticles in organic solvents and further attachment of benzoin photoinitiator moieties onto the surface of silica nanoparticles. FTIR spectroscopy analysis confirmed the covalent bonding of the functional moieties and grafting of polymethylmethacrylate (PMMA) onto the surface of silica nanoparticles. Thermogravimetric analysis indicated the ratios of attached functionalities and PMMA grafting with a good agreement of SEM observations.     

Combining confinement and NO calcination to arrive at highly dispersed supported nickel and cobalt oxide catalysts with a tunable particle size

Control over the size and size distribution of supported nanoparticles is key to their efficient use in catalysis. In the preparation of nanoparticles by impregnation using nitrate precursors, the support pore diameter can be used to influence the average crystallite size. However, the particle size distributions obtained via this method are generally broad and the dispersions relatively low. Higher dispersions and narrow particle size distributions are obtained via thermal decomposition of the metal nitrate precursor in 1% (v/v) NO in Ar instead of air. Here we will show that by combining the confinement effect of ordered mesoporous silica with a decomposition step of metal nitrates in NO, silica supported nickel and cobalt oxides with a tunable particle size (2–4 nm) can be obtained at high loadings (10–20 wt%).     

Grafting of water‐soluble sulfonated monomers onto functionalized fumed silica nanoparticles via surface‐initiated redox polymerization in aqueous medium

Sulfonated polymer/fumed silica hybrid nanoparticles were prepared via surface‐initiated free radical polymerization of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (PAMPS‐g‐FSN), styrene sulfonic acid sodium salt (PSSA‐g‐FSN) and vinyl sulfonic acid sodium salt (PVSA‐g‐FSN) from the surface of aminopropyl‐functionalized fumed silica nanoparticles (AFSNs) dispersed in aqueous medium. Cerium(IV) ammonium nitrate/nitric acid and sodium dodecyl sulfate were used as redox initiator and stabilizer respectively. AFSNs were prepared by covalently attaching 3‐aminopropyltriethoxysilane onto the surface of fumed silica nanoparticles. Sulfonated monomers (AMPS, SSA or VSA) were then grafted onto the AFSNs ultrasonically dispersed in water via redox initiation at 40 °C. Structure, thermal properties, particle size and morphology of the AFSNs and PAMPS‐g‐FSN, PSSA‐g‐FSN and PVSA‐g‐FSN hybrid nanoparticles were characterized by Fourier transform infrared spectroscopy, TGA, SEM, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The results indicated that the sulfonated monomers were successfully grafted onto the fumed silica nanoparticles. Grafting amounts of the sulfonated polymers onto the fumed silica nanoparticle surface were estimated from TGA thermograms to be 59%, 13% and 29% for the PAMPS, PSSA and PVSA, respectively. From SEM, TEM and DLS analysis, polymer‐grafted fumed silica nanoparticles with an average diameter smaller than 70 nm and a (semi‐) spherical shape were observed. A significant bimodal particle size distribution was observed only for the PAMPS‐g‐FSN with average diameters of 39.6 nm (84.1% per number) and 106 nm (15.9% per number). The hydrophilic sulfonated polymer/grafted fumed silica obtained from the redox graft polymerization gave a stable colloidal dispersion in acidic aqueous medium. Copyright © 2012 Society of Chemical Industry     

Effect of addition of surface modified nanosilica into silica–zirconia hybrid sol–gel matrix

An organic–inorganic hybrid sol (MZ) comprising a methacrylate functionalized silane matrix (M) and zirconium-n-propoxide (Z) was prepared using sol–gel technique. Two methodologies were adopted to modify the hybrid sol for generating nanocomposite coatings viz., (a) addition of acrylic surface modified silica nanoparticles (N) of diameter ～20 nm to the sol to enhance their compatibility with the hybrid sol–gel matrix and (b) in-situ formation of a three dimensional silica network by addition of tetraethoxy silane (T) to the sol MZ. In the first methodology, the sols were prepared with six different weight ratios of the nanoparticles to the sol, i.e. 0, 0.01, 0.05, 0.1, 0.25 and 1 which were labelled as MZ+Nx where x=0, 1, 2, 3, 4 and 5 respectively. The prepared sols were dip coated on 100 mm×100 mm polycarbonate substrates followed by thermal curing at 130 °C. The coatings were characterized for their mechanical properties like pencil scratch hardness, scratch resistance using scratch tester, nanoindentation hardness, and abrasion resistance as well as visible light transmittance. FT-IR studies were also carried out on heat-treated gels derived from the sols. A maximum pencil scratch hardness of 3H was obtained for the MZ+T coatings and these coatings withstood a critical load of 4.3±0.7 N before failure during scratch test. The maximum nanoindentation hardness of 3.8±0.01 GPa was obtained for the MZ+N5 coatings. The abrasion resistance of MZ+T coatings was higher when compared to MZ+N0 and MZ+N5 coatings. The scratch and nanoindentation hardness were seen to be better for an in-situ formed –Si–O–Si– network in the hybrid sol when compared to those obtained from coatings generated by external addition of acrylic surface modified silica nanoparticles. The difference in properties was attributed to the level of interaction between the nanoparticles and hybrid sol–gel matrix.     

Aunps and Agμps-functionalized zirconia surfaces by hybrid laser technology for dental implants

This work presents innovative zirconia surfaces functionalized with gold nanoparticles (Aunps) and silver microparticles (Agμps) through versatile laser technology where laser parameters and subtractive/additive strategies were combined to apply in dental implant surfaces regarding antibacterial potentialities. Au_nps-functionalized zirconia surfaces were produced by a hybrid process starting with nanoparticles production by Nd:YAG laser ablation, followed by its deposition through spray system and its adhesion to the zirconia surface by the laser CO₂ action, varying laser power and scan speed parameters. Ag_μps-functionalized zirconia surfaces were obtained through a hybrid laser process starting by laser texturing of the compacted zirconia surface, followed by allocation of Ag powder into the texture and its subsequent laser sintering, varying laser power. The functionalized zirconia surfaces were analyzed through SEM/EDS. In order to mimic the implant screwing effect, the samples were subjected to reciprocating friction tests against bone. It allows to evaluate the adhesion of the zirconia surface to the bone and the resistance to surface detachment. A purple colloidal solution of spherical gold nanoparticles with an average size of 5 ± 3 nm was successfully produced by laser. The friction tests revealed a good behavior of both functionalized zirconia surfaces indicating that their integrity is not affected during implant screwing insertion. A good dispersion of nanoparticles on the zirconia surface was observed indicating that the spray system is an effective way to deposit nanoparticles on the surface. A high amount of agglomerates was found for samples where low laser power (P = 11W) and scan speed (v = 1000 mm/s) were applied, probably due to the high density of energy (E). A decrease of defects on the sintered Ag layer with increasing laser power from 3 to 6 W was found, mainly related with the amount of laser energy density. The ion release showed to be strongly dependent on particle size.     

Polymeric Nanocapsule from Silica Nanoparticle@Cross-linked Polymer Nanoparticles via One-Pot Approach

A facile strategy was developed here to prepare cross-linked polymeric nanocapsules (CP nanocapsules) with silica nanoparticles as templates. The silica nanoparticle@cross-linked polymer nanoparticles were prepared by the encapsulation of the silica nanoparticles by the one-pot approach via surface-initiated atom transfer radical polymerization of hydroxyethyl acrylate in the presence of N,N′-methylenebisacrylamide as a cross-linker from the initiator-modified silica nanoparticles. After the silica nanoparticle templates were etched with hydrofluoric acid, the CP nanocapsules with particle size of about 100 nm were obtained. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis and transmission electron microscopy.     

Homogeneous dispersion of SiO2 nanoparticles in an hydrosoluble polymeric network

The main difficulty still encountered in the elaboration of polymer/silica nanocomposites is the control of the nanoparticles dispersion homogeneity and the stability of the nanoparticle dispersion in the surrounding substance. The innovative point of this work is the elaboration of hybrid networks in aqueous solution performed with ASE (alkali swellable emulsion) thickeners grafted with silica nanoparticles. The thickening ability of the polymer should favour silica nanoparticles dispersion in fluid matrices. Two ASE copolymers were realised by copolymerisation in emulsion of MA (methacrylic acid) and EA (ethyl acrylate) and/or TFEM (trifluoroethyl methacrylate). The substitution of a part of EA by TFEM gave fluorinated ASE copolymers. Their free acid functions were then coupled with different ratio of amine functionalized silica nanoparticles to afford nanocomposites. The amounts of silica nanoparticles in the copolymers were determined by thermogravimetric experiments. Depending on the silica nanoparticles/copolymer ratio in basic aqueous solutions we achieved stable translucent gel like aqueous suspensions of silica nanoparticles containing 1 wt.% of the polymer/SiO₂ nanocomposite.     

Synthesis and characterization of hybrid organic–inorganic materials based on sulphonated polyamideimide and silica

The preparation of hybrid organic–inorganic membrane materials based on a sulphonated polyamideimide resin and silica filler has been studied. The method allows the sol–gel process to proceed in the presence of a high molecular weight polyamideimide, resulting in well dispersed silica nanoparticles (<50 nm) within the polymer matrix with chemical bonding between the organic and inorganic phases. Tetraethoxysilane (TEOS) was used as the silica precursor and the organosilicate networks were bonded to the polymer matrix via a coupling agent aminopropyltriethoxysilane (APTrEOS). The structure and properties of these hybrid materials were characterized via a range of techniques including FTIR, TGA, DSC, SEM and contact angle analysis. It was found that the compatibility between organic and inorganic phases has been greatly enhanced by the incorporation of APTrEOS. The thermal stability and hydrophilic properties of hybrid materials have also been significantly improved.     

Morphological,magnetic and EPR studies of ZnO nanostructures doped and co-doped with Ni and Sr

Herein, were analyzed the effects of Sr and Ni addition on the morphological, electronic and magnetic properties of ZnO nanoparticles synthesized by the sol gel route. Morphological analysis showed agglomerated particles with nonuniform shapes (polyhedral, hexagonal and spherical) and the average size distributions were calculated counting more than 100 nanoparticles (sizes between 43 and 75 nm). For pure ZnO sample, the selected area electron diffraction (SAED) showed bright and concentric discontinuous diffraction rings, while the co-doped samples, presented patterns well-organized concentric circular rings, typical of reflection of regularly arranged atoms. The electron paramagnetic resonance (EPR) was employed to analyze the intrinsic defects due to the dopant inclusion. In addition, the EPR spectra were simulated using the spin quantum number (S = 1) for Ni²⁺ to understand the experimental results. Ni ions were used as a local probe in the comparative study by EPR, capturing subtle modifications in the zero-field interactions due to induced strain in the lattice. Microscopically the changes observed, through the EPR study, result from the reduction of the axial distortion of the ligand field and increasing in the distortion perpendicular to the principal axis. Magnetic study showed a typical significant diamagnetism at 300 K, while a paramagnetic contribution was more evident at 4 K. The work contributes to clarify the complex magnetic response in ZnO nanoparticles doped and co-doped with Sr and Ni.     

Synthesis and properties of new polyimide-silica hybrid films through both intrachain and interchain bonding

In this study, the new polymer-silica hybrid materials were prepared based on the organo-soluble polyimides of 4,4′-hexafluoroisopropylidenediphthalic anhydride (6FDA) and four diamines. 3-Aminopropyl trimethoxysilane (APrTEOS) and γ-glycidyloxypropyltrimethoxysilanes (GOTMS) were used to increase the intrachain chemical bonding and interchain hydrogen bonding between the polyimide and silica moieties, respectively. The chemical interaction would significantly affect the morphologies and properties of the prepared films. Highly homogeneous hybrid thin films were obtained according to the studies of atomic force microscopy and TEM. The silica size observed by the TEM picture was smaller than 5 nm. The thermal properties of the organo-soluble polyimides were significantly enhanced by hybridizing only 6.30-7.99 wt% of silica. The intrachain chemical bonding could effectively enhance the coefficient of thermal expansion in comparison with the interchain interaction. Low dielectric constants in the range of 2.85-3.73 were obtained for the prepared hybrid films. The refractive indices of the prepared materials could be tuned through the polyimide structure or the silica content. The optical losses of the planar waveguides based on the prepared polyimides and their hybrids at 1310 nm were in the range of 0.5-2.7 dB/cm, which were mostly due to the higher harmonics of the aromatic C-H vibration and the extrinsic loss. The prepared polyimide-silica hybrid materials could have potential applications for microelectronics or optical communications.     

Synthesis and photochromic property of nanoparticles with spiropyran moieties via one-step miniemulsion polymerization

Summary  Photochromic nanoparticles with spiropyran moieties were prepared by a facile one-step miniemulsion polymerization. The nanoparticle dispersion was obtained by mixing the monomers, spiropyran-containing molecules and hydrophobe, dispersing them into an aqueous solution with surfactant, subjecting the dispersion to ultrasonification and polymerizing the monomers by using a water soluble initiator. The shape and size of the nanoparticles was determined with the atomic force microscope (AFM) and dynamic light scattering (DLS), and the determined average diameter of the nanoparticles ranges from 30 nm to 60 nm. The absorption and fluorescence spectra for the nanoparticles dispersions reveal that the spiropyran molecules were successfully incorporated in the polymer nanoparticles. Moreover, the nanoparticle dispersions were found to exhibit enhanced photo-reversibility, photo-stability and relatively fast photo-responsive property compare to the same species in aqueous solution.     

Size-controlled synthesis of mesoporous silica nanoparticles using rice husk by microwave-assisted sol–gel method

Mesoporous silica nanoparticles with distinct characteristics like particle size, tunable pores, and high surface area have received much interest for environmental remediation, energy conversion, and biological applications. In this work, we synthesized spherical silica nanoparticles with tunable particle size and mesoporous properties using a low-cost silica source (rice husk) and polyethylene glycol (PEG) via microwave-assisted sol–gel synthesis. The formation of an amorphous silica structure was found using XRD and FTIR analysis. FESEM analysis showed that altering the PEG concentration from .01 to .005 M produced spherical silica nanoparticles with 100–500 nm in size. Nitrogen adsorption–desorption demonstrated that silica nanoparticles obtained with .005, .007, and .01 M of PEG had unique pore sizes and distributions, with specific surface areas of 51.475, 62.367, and 84.251 m²/g, respectively. These results might be due to PEG molecules’ capping effect, which acts as a soft template to regulate particle size, pore size, and dispersion by interacting with sodium silicate precursor. Hence, this approach can be a facile and cost-effective method to prepare mesoporous silica nanoparticles with controllable nanoscale characteristics for suitable applications.