Organic-inorganic Hybrid Particles Research Articles

Constructing flame retardant silica nanoparticles through styrene maleic anhydride copolymer grafting for PC/ABS composites

Organic-inorganic hybrid particles have been prepared by grafting styrene maleic anhydride copolymer (SMA) onto reactive amino-modified silica nanoparticles. The SMA modified SiO2 (SMA-SiO2) was incorporated into polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) composites (4:1, wt%/wt%) with bisphenol A bis (diphenyl phosphate) (BDP) to simultaneously improve the mechanical properties and flame retardancy. The mechanical properties of the sample containing SMA-SiO2 are apparently improved compared with that of samples containing unmodified SiO2. It is found that SMA-SiO2 tends to distribute at the phase interface of PC/ABS, and therefore improves the compatibility between PC and ABS. Besides, the peak of heat release rate (PHRR) and the total smoke production (TSP) of the PC/ABS composites are decreased by the presence of SMA-SiO2. It is suggested that SMA-SiO2 can form a flame retarding shell at the phase interface to protect ABS. In summary, both the mechanical properties and flame retardancy of PC/ABS composites are significantly improved due to the selective distribution of SMA-SiO2.

Controlling Superhydrophobicity and Oleophobicity of Polydimethylsiloxane-Coated Silica Hybrid Particles

Hierarchical functional organic-inorganic hybrid particles for versatile control of surface wettability have attracted much attention in a wide range of applications from makeup cosmetics to anti-smudging optoelectronic devices. In this study, superhydrophobic and oleophobic organic-inorganic hybrid particles were prepared by a simple and systematic fabrication strategy using the synergistic combination of commonly available silica particles and polydimethylsiloxanes (PDMSs) with hydrophobic chain ends. Various types of PDMSs with different chain lengths and chemical structures were surface-grafted to silica microparticles through facile physical dispersion and subsequent thermal treatment to form hydrogen bonds or covalent bonds between the inorganic silica and organic PDMS polymers and thus induce a core-shell structure for the hybrid particles, which imparts superhydrophobicity and oleophobicity to the surface of silica particles. The prepared PDMS-coated silica hybrid particles with long PDMS chains exhibited a water contact angle of 151.2° and an oil contact angle of 15.2° due to the rough surface morphology and hydrophobic long-chain effects. Furthermore, the resulting organic-inorganic hybrid particles were thermally stable up to 420 °C. This controlled approach endowed the organic-inorganic hybrid particles with both superhydrophobic and oleophobic surfaces and, therefore, these particles were proven to be suitable for waterproof applications.

Hydrophilic PAA-g-MWCNT/TiO2@PES nano-matrix composite membranes: Anti-fouling, antibacterial and photocatalytic

The synthesis of composite nano-matrix membranes from a variety of nanoscale materials will impair the comprehensive properties of the materials. Therefore, it is not easy to prepare multifunctional nano-matrix membranes with excellent performance. Carbon nanotubes (CNTs) have superiority in absorption of impurities and contaminants in aqueous solution. Therefore, Polyethersulfone (PES) ultrafiltration membrane modified by CNTs and PAA-g-MWCNT/TiO2 (AMT) organic-inorganic hybrid particles is synthesized. And a new nano-matrix composite membrane PAA-g-MWCNT/TiO2@PES (AMTP) is prepared after the combination of the two particles, which endows the new composite membrane with three major effects of fouling resistance, photocatalysis and antibacterial properties. When the amount of AMT was 1 wt%, AMTP had the highest anti-pollution rate (31.21%); the best flux recovery rate (85.76%) and the degradation efficiency of MB and MO reached 90.03%, 62.36% within 2 h; the antibacterial rate was 98.12 %. When the dosage was 2 wt%, the antibacterial rate of AMTP reached 100 %. AMTP nano-matrix composite membranes have considerable adaptability and practicability of a wide application in the wastewater recovery and recycling.

Characterization of a highly stable zwitterionic hydrophilic interaction chromatography stationary phase based on hybrid organic-inorganic particles.

We have characterized a sulfobetaine stationary phase based on 1.7 μm ethylene‐bridged hybrid organic–inorganic particles, which is intended for use in hydrophilic interaction chromatography. The efficiency of a column packed with this material was determined as a function of flow rate, demonstrating a minimum reduced plate height of 2.4. The batch‐to‐batch reproducibility was assessed using the separation of a mixture of acids, bases, and neutrals. We compared the retention and selectivity of the hybrid sulfobetaine stationary phase to that of several benchmark materials. The hybrid sulfobetaine material gave strong retention for polar neutrals and high selectivity for methyl groups, hydroxy groups, and configurational isomers. Large differences in cation and anion retention were observed among the columns. We characterized the acid and base stability of the hybrid sulfobetaine stationary phase, using accelerated tests at pH 1.3 and 11.0, both at 70°C. The results support a recommended pH range of 2–10. We also investigated the performance of columns packed with this material for metal‐sensitive analytes, comparing conventional stainless steel column hardware to hardware that incorporates hybrid surface technology to mitigate interactions with metal surfaces. Compared to the conventional columns, the hybrid surface technology columns showed a greatly improved peak shape.

Porous Mixed-Metal Oxide Li-Ion Battery Electrodes by Shear-Induced Co-assembly of Precursors and Tailored Polymer Particles.

Due to their various applications, metal oxides are of high interest for fundamental research and commercial usage. Per applications as catalysts or electrochemical devices, the tailored design of metal oxides featuring a high specific surface area and additional functionalities is of the utmost importance for the performance of the resulting materials. We report a new method for preparing free-standing films consisting of hierarchically porous metal oxides (titanium and niobium based) by combining emulsion polymerization and shear-induced monodisperse particle self-assembly in the presence of sol-gel precursors. After thermal treatment, the resulting porous materials can be used as electrodes in Li-ion batteries. The titanium and niobium sol-gel precursors were partially immobilized to the surface of organic core-interlayer particles featuring hydroxyl groups to obtain hybrid organic-inorganic particles through the melt-shear organization process. Free-standing particle-based films, in analogy to elastomeric opal films and colloidal crystals, can be prepared in a convenient one-step preparation process. After thermal treatment, ordered pores are obtained, while the pristine metal oxide precursor shell can be converted to the (mixed) metal oxide matrix. Heat treatment under CO2 leads to mixed-TiNb oxide/carbon hybrid materials. The highly porous derivative structure enhances electrolyte permeation. When tested as Li-ion battery electrodes, it shows a specific capacity of 335 mAh·g-1 at a rate of 10 mA·g-1. After 1000 cycles at 250 mA·g-1, the electrodes still provided a specific capacity of 191 mAh·g-1.

Highly Scattering Hierarchical Porous Polymer Microspheres with a High-Refractive Index Inorganic Surface for a Soft-Focus Effect.

Functional light scattering materials have received considerable attention in various fields including cosmetics and optics. However, a conventional approach based on optically active inorganic materials requires considerable synthetic effort and complicated dispersion processes for special refractive materials. Here, we report a simple and effective fabrication strategy for highly scattering hierarchical porous polymer microspheres with a high-refractive index inorganic surface that mitigates the disadvantages of inorganic materials, producing organic-inorganic hybrid particles with an excellent soft-focus effect. Hierarchical organic-inorganic hybrid particles were synthesized using the simple physical mixing of porous poly (methyl methacrylate) (PMMA) microparticles with different pore sizes and regularities as the organic core and titanium dioxide (TiO2) nanoparticles with different particle sizes as the inorganic shell. The polar noncovalent interactions between polar PMMA microspheres and the polar surface of TiO2 nanoparticles could induce the hierarchical core-shell structure of hybrid particles. The synthesized hybrid particles had increased diffuse reflectance properties of up to 160% compared with single inorganic particles. In addition, the light scattering efficiency and soft-focus effect could be increased further, depending on the size of the TiO2 nanoparticles and the pore characteristics of the PMMA microspheres. The proposed study can provide a facile and versatile way to improve the light scattering performance for potential cosmetics.

Nanoceria-curcumin conjugate: Synthesis and selective cytotoxicity against cancer cells under oxidative stress conditions

A water- and alcohol-soluble cerium oxide-curcumin conjugate was obtained by co-evaporation with poly(N-vinylpyrrolidone) (PVP). A nanocomposite consisting of hybrid organic-inorganic particles was stable in a wide range of pH values. Its properties were evaluated using nine cell lines: normal (MDBK, ST, Vero) and malignant (L929, T98G, HEp-2, A549, RIN-m5F, Hep G2). PVP-stabilised nanoceria was shown to inhibit autoxidation of curcumin, to enhance curcumin photostability, to promote bioaccumulation and to affect curcumin cytotoxicity and photocytotoxicity, depending on cell type, being more toxic to cancer cells in a selective manner. Under the conditions of UVA/UVC or H2O2-induced oxidative stress, the nanoceria-PVP-curcumin (NPC) conjugate was found to possess a selective cytotoxicity: it caused drastic inhibition of metabolic activity or a decrease in the total number of tumour cells, while in non-transformed cultures under the same conditions, the nanoceria-PVP-curcumin conjugate protected cells from these damaging factors. The NPC-conjugate, unlike curcumin itself, demonstrated a photosensitising effect in tumour cell cultures, while protecting non-transformed cultures from the damaging effects of UV radiation or oxidative stress. Based on the results obtained, we strongly believe that this novel hybrid material has enhanced characteristics compared to other curcumin formulations, and can be considered as a potent drug for biomedical applications, including cancer therapy.

Silica/poly(styrene‐alt‐maleic anhydride) hybrid particles as a reactive toughener for epoxy resin

AbstractAmino‐modified silica nanoparticles (SiO2─NH2) were first prepared by hydrolytic condensation of tetraethyl orthosilicate and 3‐aminopropylmethyldiethoxysilane. Then, organic–inorganic hybrid particles (SiO2─SMA) were prepared by the amidation reaction between SiO2─NH2 and poly(styrene‐alt‐maleic anhydride) (SMA). Subsequently, SiO2─SMA particles were employed for modifying bisphenol‐A epoxy/anhydride thermoset. Compared with pure cured epoxy, the modified epoxy thermosets with only 1 wt % of SiO2─SMA particles could achieve a simultaneous toughening and reinforcing performance. The tensile strength, impact strength, and fracture toughness of epoxy thermoset were increased by 14.1, 44.3, and 114.4%, respectively. Moreover, the modification also improved the thermal stability of epoxy thermosets, and the modulus and glass transition temperature of cured resin were not sacrificed. It can be attributed to the rigid structure of SiO2, as well as the anhydride and carboxyl groups onto the surface of SiO2─SMA particles participating in the epoxy curing reaction and effectively enhancing the crosslinking density of epoxy thermoset.

Reversed-phase liquid chromatography system constant database over an extended mobile phase composition range for 25 siloxane-bonded silica-based columns

The solvation parameter model is used to characterize the retention properties of 25 siloxane-bonded type-B silica columns under typical reversed-phase liquid chromatography conditions with binary aqueous mobile phases containing 10–70% (v/v) methanol and acetonitrile. To further explore the affect of solvent type on column selectivity complementary information is presented for aqueous phases containing 10–70% (v/v) tetrahydrofuran for two columns. Columns were selected to include examples of all common column packing morphologies for small molecule separations (totally porous particles, superficially porous particles, organic–inorganic hybrid particles, and a monolith) and common topologies octadecylsiloxane-bonded (including phases with a polar-embedded group, mixed-mode phases with a short-chain siloxane-bonded polar functional group, sterically crowded, positive shield, and fluorine-containing phases); octylsiloxane-bonded; and various phenyl-containing stationary phases with different linker arms, pentafluorophenylalkyl and biphenyl groups. The column properties are reported as a system constant database and as system maps for the full range of mobile phase compositions. Selectivity differences are evaluated using principal component factor analysis to classify the columns into selectivity groups and correlation plots of the system constants for compared columns at all mobile phase compositions. The later is shown to be a suitable technique to identify (near) selectivity equivalent columns and varied columns suitable for method development. Contributions to retention from steric resistance and cation-exchange interactions not parameterized in the solvation parameter model are identified for columns and conditions where they may be important. It is shown that the interaction parameters employed in the hydrophobic-subtraction model have little overlap with those of the solvation parameter model and a quantitative comparison of column properties delineated by both models is not possible.

Recent progress in the synthesis of inorganic particulate materials using microfluidics

Abstract Microfluidic systems have unique advantages originating from the miniaturization of real chemical processes. On this basis, the synthesis of inorganic materials, including micro- and nanomaterials, can be used to develop useful features, such as a uniform particle size distribution, morphology control, online monitoring, etc. In this review, we introduce and discuss the recent progress in the preparation of inorganic materials, mainly microfluidics systems. Furthermore, utilizing microfluidic devices, we present the basic principles and representative shape of microfluidic systems. In addition, the synthesis of various inorganic material particles using microfluidic systems, such as metal nanoparticles, metal oxide nanoparticles, semiconductor nanoparticles, organic-inorganic hybrid particles, surface functionalized particles, core-shell particles, and traditional porous materials, is introduced. Finally, we propose the future prospects of microfluidics in the synthesis of noble inorganic materials.

Microfluidic preparation of monodisperse polymeric microspheres coated with silica nanoparticles

The synthesis of organic-inorganic hybrid particles with highly controlled particle sizes in the micrometer range is a major challenge in many areas of research. Conventional methods are limited for nanometer-scale fabrication because of the difficulty in controlling the size. In this study, we present a microfluidic method for the preparation of organic-inorganic hybrid microparticles with poly (1,10-decanediol dimethacrylate-co-trimethoxysillyl propyl methacrylate) (P (DDMA-co-TPM)) as the core and silica nanoparticles as the shell. In this approach, the droplet-based microfluidic method combined with in situ photopolymerization produces highly monodisperse organic microparticles of P (DDMA-co-TPM) in a simple manner, and the silica nanoparticles gradually grow on the surface of the microparticles prepared via hydrolysis and condensation of tetraethoxysilane (TEOS) in a basic ammonium hydroxide medium without additional surface treatment. This approach leads to a reduction in the number of processes and allows drastically improved size uniformity compared to conventional methods. The morphology, composition, and structure of the hybrid microparticles are analyzed by SEM, TEM, FT-IR, EDS, and XPS, respectively. The results indicate the inorganic shell of the hybrid particles consists of SiO2 nanoparticles of approximately 60 nm. Finally, we experimentally describe the formation mechanism of a silica-coating layer on the organic surface of polymeric core particles.

Effect of different contents of organic-inorganic hybrid particles poly(methyl methacrylate)[sbnd]ZrO2 on the properties of poly(vinylidene fluoride-hexafluoroprolene)-based composite gel polymer electrolytes

Poly(vinylidene fluoride-hexafluoroprolene) (P(VDF-HFP))-based composite polymer electrolyte (CPE) membranes doped with organic-inorganic hybrid particles poly(methyl methacrylate)ZrO2 (PMMA-ZrO2) are fabricated by phase inversion, in which PMMA is firstly successfully grafted onto the surface of the homemade nano-ZrO2 particles via in situ polymerization confirmed by FT-IR. XRD and DSC patterns show that adding PMMA-ZrO2 into the polymer matrix can decrease the crystallinity of the CPE membranes and TG curves indicate the CPE membranes possess desirable thermal stability. It can be found that the CPE membrane presents a uniform surface with abundant interconnected micro-pores when the added amount of PMMA-ZrO2 increases to 5 wt % vs. polymer matrix, in which the ionic conductivity at room temperature and tensile strength can be up to 3.595 mS cm−1 and 26.18 MPa, respectively. In particular, the CPE membrane shows the minimum deformation of about 8% after being exposed at 160 °C for 1 h, and the electrochemical working window of the assembled Li/CPE/SS cell can be stable at 5.1 V (vs Li/Li+) at room temperature. Moreover, the LiCoO2/CPE/Li coin cell can deliver a specific capacity of 114.5 mAh g−1 with 79.13% capacity retention at 2.0 C after 110 cycles. The results suggest that the as-fabricated P(VDF-HFP)-based CPE doped with 5 wt % organic-inorganic hybrid particles PMMA-ZrO2 can be a promising polymer electrolyte for lithium ion batteries.

A novel ultra low-k nanocomposites of benzoxazinyl modified polyhedral oligomeric silsesquioxane and cyanate ester

Benzoxazinyl modified polyhedral oligomeric silsesquioxane (BZPOSS) is successfully synthesized and used to prepare nanocomposites with bisphenol A cyanate ester (BADCy). The DSC results showed that the curing peak temperature of BZPOSS/BADCy blend decrease significantly from 317.1 °C to 160.3 °C, suggesting the high catalytic activity of BZPOSS to the polymerization of cyanate ester. The SEM micrographs of poly(BZPOSS/BADCy) and Silicon element distribution maps given by EDS both indicated that BZPOSS disperses evenly in BADCy. Dielectric properties tests showed that the dielectric constant can be reduced by the introduction of BZPOSS, which is attributed to the nano-pores from the cage structure of POSS. When 15 wt% BZPOSS was added, the dielectric constant decreased to 2.01 and the dielectric loss was also only 0.0070 at 1 MHz. Meanwhile, DMA and TGA result showed that the thermal stability and heat resistance of poly(BZPOSS/BADCy) at high temperature decreased with increasing BZPOSS, which is due to the change of crosslinking structure of the copolymers. The influences of the crosslinking structure and the nano-porous organic-inorganic hybrid particles on the dielectric and thermal property of poly(BZPOSS/BADCy) were also discussed.

Enhanced performance of P(VDF-HFP)-based composite polymer electrolytes doped with organic-inorganic hybrid particles PMMA-ZrO2 for lithium ion batteries

To improve the ionic conductivity as well as enhance the mechanical strength of the gel polymer electrolyte, poly(vinylidene fluoride-hexafluoroprolene) (P(VDF-HFP))-based composite polymer electrolyte (CPE) membranes doped with the organic-inorganic hybrid particles poly(methyl methacrylate) -ZrO2 (PMMA-ZrO2) are prepared by phase inversion method, in which PMMA is successfully grafted onto the surface of the homemade nano-ZrO2 particles via in situ polymerization confirmed by FT-IR. XRD and DSC patterns show adding PMMA-ZrO2 particles into P(VDF-HFP) can significantly decrease the crystallinity of the CPE membrane. The CPE membrane doped with 5 wt % PMMA-ZrO2 particles can not only present a homogeneous surface with abundant interconnected micro-pores, but maintain its initial shape after thermal exposure at 160 °C for 1 h, in which the ionic conductivity and lithium ion transference number at room temperature can reach to 3.59 × 10−3 S cm−1 and 0.41, respectively. The fitting results of the EIS plots indicate the doped PMMA-ZrO2 particles can significantly lower the interface resistance and promote lithium ions diffusion rate. The Li/CPE-sPZ/LiCoO2 and Li/CPE-sPZ/Graphite coin cells can deliver excellent rate and cycling performance. Those results suggest the P(VDF-HFP)-based CPE doped with 5 wt % PMMA-ZrO2 particles can become an exciting potential candidate as polymer electrolyte for the lithium ion battery.

In situ synthesis of silica/polyacrylate nanocomposite particles simultaneously bearing carboxylate and sulfonate functionalities via soap-free seeded emulsion polymerization

Organic-inorganic hybrid particles of nanosilica encapsulated by Poly (methyl methacrylate-co-butyl acrylate) were synthesized by a soap-free seeded emulsion polymerization. The nanosilica was initially treated by a silane coupling agent bearing unsaturated carbon double bond to increase its hydrophobicity and enhance its ability to take part in free radical polymerization. Two ionic comonomers including sodium salt of styrene sulfonic acid (NaSS) and potassium methacrylate (KMAA) were used simultaneously to stabilize the nanoparticles and create ionic charge groups on their surface. The prepared samples were characterized by different methods. The X-ray photoelectron spectroscopy (XPS) and energy dispersive X-Ray analysis (EDX) results confirmed the simultaneous presence of both ionic comonomers on the surface of the nanoparticles; however, their population on the surface was not proportional to their concentrations in the feed. The burial of the KMAA was more significant than that of NaSS and the NaSS reduced the average particle size more sharply than KMAA. Thermogravimetric analysis (TGA) showed that the efficiency of encapsulation was around 100% and no free polyelectrolyte chains were synthesized during the course of the polymerization. Transmission electron microscopy (TEM) showed an organic/inorganic hybrid structure for the prepared encapsulated nanosilica.

Aerosol processing: a wind of innovation in the field of advanced heterogeneous catalysts.

Aerosol processing is long known and implemented industrially to obtain various types of divided materials and nanomaterials. The atomisation of a liquid solution or suspension produces a mist of aerosol droplets which can then be transformed via a diversity of processes including spray-drying, spray pyrolysis, flame spray pyrolysis, thermal decomposition, micronisation, gas atomisation, etc. The attractive technical features of these aerosol processes make them highly interesting for the continuous, large scale, and tailored production of heterogeneous catalysts. Indeed, during aerosol processing, each liquid droplet undergoes well-controlled physical and chemical transformations, allowing for example to dry and aggregate pre-existing solid particles or to synthesise new micro- or nanoparticles from mixtures of molecular or colloidal precursors. In the last two decades, more advanced reactive aerosol processes have emerged as innovative means to synthesise tailored-made nanomaterials with tunable surface properties, textures, compositions, etc. In particular, the "aerosol-assisted sol-gel" process (AASG) has demonstrated tremendous potential for the preparation of high-performance heterogeneous catalysts. The method is mainly based on the low-cost, scalable, and environmentally benign sol-gel chemistry process, often coupled with the evaporation-induced self-assembly (EISA) concept. It allows producing micronic or submicronic, inorganic or hybrid organic-inorganic particles bearing tuneable and calibrated porous structures at different scales. In addition, pre-formed nanoparticles can be easily incorporated or formed in a "one-pot" bottom-up approach within the porous inorganic or hybrid spheres produced by such spray drying method. Thus, multifunctional catalysts with tailored catalytic activities can be prepared in a relatively simple way. This account is an overview of aerosol processed heterogeneous catalysts which demonstrated interesting performance in various relevant chemical reactions like isomerisation, hydrogenation, olefin metathesis, pollutant total oxidation, selective oxidation, CO2 methanation, etc. A short survey of patents and industrial applications is also presented. Our objective is to demonstrate the tremendous possibilities offered by the coupling between bottom up synthesis routes and these aerosol processing technologies which will most probably represent a major route of innovation in the mushrooming field of catalyst preparation research.

Performance and Characterization of Resistance to Ultraviolet Radiation of Vi-POSS-TiO<sub>2</sub>/EP Nanocomposites

Improving the mechanical properties and ultraviolet resistant properties of epoxy resin (EP) is attracting the scientists’ increasing interest in engineering industries at present. For this reason, novel Vi-POSS-TiO2/EPnanocomposites were prepared by incorporating nanotitanium dioxide (TiO2) and PSS-Octavinyl substituted (Vi-POSS) organic-inorganic hybridparticles into the epoxy resin. Filling up with TiO2 and Vi-POSS may create an inherent ultraviolet (UV) absorption property and mechanical property, respectively. The obtained composites were characterized by some standard analytical techniques such as UV-vis spectroscopy, Scanning electron microscope (SEM), and Thermal gravity analysis (TGA). When the content of TiO2was 1.5wt%, UV-vis absorption spectra showed that the excellent absorption properties of EP composites can be achieved. When the content of Vi-POSS was 6wt%, the values of bend strength and impact strength were improved 14.75%and37.94%, respectively. The TGA result showed that the thermal stability of EP composites varied in a small range before and after adding 6wt% Vi-POSS.

Stabilization of water-in-oil emulsions with complex of silica particles and hexylamine

The properties of emulsions stabilized by complexes of silica particles with hexylamine are analyzed. It is shown that water-in-oil emulsions were obtained only if the hexylamine volume fraction was greater than that of the silica (Aerosil) volume fraction in the aqueous phase. So, in the case of water-in-oil emulsions, hexylamine is a completely equivalent co-stabilizer together with silica, rather than just a solid surface modifier. It is assumed that at high concentrations this short-chain surfactant, together with silica, forms hybrid organic-inorganic particles that are attached at the oil/water interface and promotes the formation of oil droplets in the water.

Luminescent Terbium Doped Aluminate Particles: Properties and Surface Modification with Asparagine

New luminescent organic-inorganic hybrid particles based on Tb-doped aluminates and asparagine (Asn) surface modifiers were investigated. The Tb3+ doped inorganic core was obtained by spray pyrolysis, at 200 °C γ-AlOOH (BOE:Tbx%) or at 700 °C γ-Al2O3 (?TA:Tbx%). The reaction of Asn with boehmite in water disaggregated the sub-micronic boehmite particles to give stable dispersion of surface modified nanoparticles Asn:BOE:Tbx% (x = 1 or 5). Concerning the Asn:γTA:Tbx% system, an Asn film wrapping alumina particles was observed. Photoluminescence spectra exhibited the bands assigned to Tb3+ 5D4 → 7FJ = 6-3 transitions. A broad absorption band (240 nm) was assigned to the host (aluminate) to ion (Tb3+) energy transfer. Efficient energy transfer was observed when active ions are incorporated in the defect-spinel structure of γTA, whereas it was relatively weak for BOE:Tb where Tb3+ are bonded to the hydroxyls groups at nanocrystals surface. It is noticeable that Asn strengthens the linkage of Tb3+ with the aluminate matrix, enhancing the host to dopant energy transfer.

The formation of polyethyleneimine–trimethoxymethylsilane organic–inorganic hybrid particles

Polyethyleneimine–silica (PEI–silica) organic–inorganic hybrid particles were formed in the presence of multivalent anions, using trimethoxymethylsilane as the silica source. Here we present new understanding on the difference in particle formation when multi- and monovalent anions were used as well as providing clear evidence that anions other than phosphate may be used to produce PEI–silica particles, unlike the phosphorylated peptides involved in silication in nature. We also show that PEI–silica particle size increases with ionic strength when monovalent anions were used, but that the diameter is not ionic strength dependent with the use of multivalent anions. Furthermore, our results suggest that PEI–silica particle production involves the formation of polyethyleneimine aggregates with multivalent anions due to electrostatic interactions, producing sites from which silica particles can grow. In addition, for the first time zeta potential measurement data show the surface charge of the PEI–silica particles, giving evidence of the presence of the polyethyleneimine at the surface of the particles, without the need of an additional surface modification step. The superior understanding of silica particle growth in order to control the parameters needed to refine and improve the production of silica particles made using less toxic reagents is of great significance in silica particle fabrication and processing. In addition, the potential application of the polyethyleneimine on the silica particle surface is of great benefit since hybrid organic–inorganic silica particles have several applications from carbon dioxide capture to drug delivery in many fields of science, engineering and medicine.