Surface Of TiO2 Nanoparticles Research Articles

Nanoscale Probing of Bandgap States on Oxide Particles Using Electron Energy-Loss Spectroscopy

Surface and near-surface electronic states were probed with nanometer spatial resolution in MgO and TiO2 anatase nanoparticles using ultra-high energy resolution electron energy-loss spectroscopy (EELS) coupled to a scanning transmission electron microscope (STEM). This combination allows the surface electronic structure determined with spectroscopy to be correlated with nanoparticle size, morphology, facet etc. By acquiring the spectra in aloof beam mode, radiation damage to the surface can be significantly reduced while maintaining the nanometer spatial resolution. MgO and TiO2 showed very different bandgap features associated with the surface/sub-surface layer of the nanoparticles. Spectral simulations based on dielectric theory and density of states models showed that a plateau feature found in the pre-bandgap region in the spectra from (100) surfaces of 60nm MgO nanocubes is consistent with a thin hydroxide surface layer. The spectroscopy shows that this hydroxide species gives rise to a broad filled surface state at 1.1eV above the MgO valence band. At the surfaces of TiO2 nanoparticles, pronounced peaks were observed in the bandgap region, which could not be well fitted to defect states. In this case, the high refractive index and large particle size may make Cherenkov or guided light modes the likely causes of the peaks.

Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy

Surface and near-surface electronic states were probed with nanometer spatial resolution in MgO and TiO2 anatase nanoparticles using ultra-high energy resolution electron energy-loss spectroscopy (EELS) coupled to a scanning transmission electron microscope (STEM). This combination allows the surface electronic structure determined with spectroscopy to be correlated with nanoparticle size, morphology, facet etc. By acquiring the spectra in aloof beam mode, radiation damage to the surface can be significantly reduced while maintaining the nanometer spatial resolution. MgO and TiO2 showed very different bandgap features associated with the surface/sub-surface layer of the nanoparticles. Spectral simulations based on dielectric theory and density of states models showed that a plateau feature found in the pre-bandgap region in the spectra from (100) surfaces of 60nm MgO nanocubes is consistent with a thin hydroxide surface layer. The spectroscopy shows that this hydroxide species gives rise to a broad filled surface state at 1.1eV above the MgO valence band. At the surfaces of TiO2 nanoparticles, pronounced peaks were observed in the bandgap region, which could not be well fitted to defect states. In this case, the high refractive index and large particle size may make Cherenkov or guided light modes the likely causes of the peaks.

Synthesis of conductive PSt-g-PANi/TiO2 nanocomposites by metal catalyzed and chemical oxidative polymerization

Well-defined polymer-TiO2 nanocomposites of core–shell structure were prepared by two-steps, surface-initiated atom transfer radical polymerization (ATRP) of styrene and in situ chemical oxidative polymerization of aniline monomers from the surfaces of the TiO2 nanoparticles. The methods used include the following: initially, the ATRP initiator was covalently attached to the surface of TiO2 nanoparticles by esterification of 2-bromo-2-methyl propionic acid with hydroxyl group. The metal-catalyzed radical polymerization of styrene with modified TiO2 nanoparticles was performed using a copper catalyst system to give the TiO2-based core hybrids linking PSt segments (TiO2-PSt hybrids). Next, the TiO2-PSt reacted with HNO3/H2SO4 to produce a nitro group containing polystyrene to form TiO2-PSt-NO2, and obtained TiO2-PSt-NO2 was treated with hydrochloric acid/SnCl2, and converted to an amine group containing polystyrene (TiO2–PSt-NH2). Finally, surface oxidative graft copolymerization of aniline, using the –NH2 moieties of TiO2/PSt-NH2 as the anchoring sites. Characterization of these well-defined nanocomposites included FTIR, thermogravimetric analysis, transmission electron microscopy, and X-ray diffraction.

Photocatalytic self-cleaning cotton fabrics with platinum (IV) chloride modified TiO2 and N-TiO2 coatings

To enable photocatalytic self-cleaning cotton fabrics working under visible light irradiation, platinum (IV) chloride modified TiO2 (Pt-TiO2) and N-TiO2 (Pt-N-TiO2) nanosols are synthesized through a low temperature precipitation-peptization method. According to the characterizations of XRD, DRS and TEM, all nanoparticles are anatase nanocrystallites in the sizes of less than 10nm, while N-TiO2 nanoparticles have better crystallization and smaller sizes. However, the cotton fabrics functionalized with Pt-TiO2 display significantly enhanced photocatalytic activity for methyl orange degradation and coffee stain removal under both solar simulator and visible light irradiation, while the performance of that coatings of Pt-N-TiO2 is poor. Further XRF and XPS results indicate that surface species on N-TiO2 block the adsorption of PtCl62− anions, whereas these anions strongly attach on the surface of TiO2 nanoparticles, and accordingly enable functionalized cotton fabrics efficient visible light driven activities based on a mechanism of charge transfer from ligand to metal (CTLM) excitation.

Preparation and properties of short oil alkyd resin/TiO2 nanocomposites based on surface modified TiO2 nanoparticles

Alkyd resin/TiO2 nanocomposites (NC) were prepared from short oil alkyd resin and TiO2 nanoparticles (NPs) surface modified with in situ formed imine ligand, based on 3,4‐dihydroxybenzaldehyde and oleylamine, or with three gallic acid esters. The short oil alkyd resin was synthesized from sunflower oil, phthalic anhydride, and trimethylolpropane. Unmodified and surface modified TiO2 NPs were examined by transmission electron microscopy. Rheological investigation revealed that prepared dispersions have higher dynamic viscosity than pure alkyd resin. Using different characterization methods it was obtained that NCs have similar thermooxidative stability as alkyd resin, lower glass transition temperature, better barrier properties, enhanced hardness, better chemical resistance, and lower adhesion to the metal, except in the case of NC prepared using TiO2 NPs surface modified with imine, which exhibited better adhesion to the metal than pure alkyd resin. POLYM. COMPOS., 39:1488–1499, 2018. © 2016 Society of Plastics Engineers

Three horizontal anchor porphyrins for dye-sensitized solar cells: An optical, electrochemical and photovoltaic investigation

Porphyrins are promising DSSC sensitizers focused on novel anchoring. Herein, three horizontal anchor zinc porphyrins have been designed, synthesized, and well-characterized. Their optical, photovoltaic, theory calculation and electrochemical performances in dye-sensitized solar cells were investigated. Absorption spectra indicated the stronger H-aggregation in ortho carboxylic acid anchor porphyrin (o-ZnPA) than that in meta carboxylic acid anchor porphyrin (m-ZnPA) on the surface of TiO2 nanoparticles. The photoelectric conversion efficiency studies showed a significantly enhanced photovoltaic behavior for meta carboxylic acid anchor porphyrin (m-ZnPA) compared to meta tetrazolium anchor porphyrin (m-ZnPTz). The infrared spectroscopies, theory calculations and the electrochemical impedance spectroscopies revealed that carboxylic acid anchoring binding modes could increase the efficiency of electron injection.

Selecting the optimal process for the removal of reactive red 198 dye from textile wastewater using analytical hierarchy process (AHP)

In this study, the application of adsorption processes on the surface of TiO2 nanoparticles and oxidation by O3, UV, O3/TiO2, and the UV/TiO2 in the removal of reactive red 198 dye form textile wastewater was examined. Then, Analytical Hierarchy Process (AHP) was used to choose the best removal method. The studied criteria for decision-making in selecting the best choice included the rate of dye removal in different situations, with the sub-criteria of studied variables, cost, with the sub-criteria of initial operation and maintenance cost, and the required expertise to use each method. Grading and preference of each method were calculated based on the efficiency of removal in different conditions, the price of each tool in the market, and the consumed energy of each method. The UV/TiO2 process was considered as the best-known method based on AHP model. Results indicated that this model can be a useful and suitable tool for policy-makers and decision-makers to choose the best treatment process in different conditions.

Dopant concentration dependent magnetism of Cu-doped TiO2 nanocrystals

Undoped and Cu-doped nanocrystals of TiO2 having the size range of 8–11 nm were synthesized by peroxide gel method. XRD analysis using Rietveld refinement confirmed anatase phase with a small percentage of rutile content for undoped TiO2 nanocrystals while a pure anatase phase with preferential growth along [004] direction was observed for nanocrystals of Cu-doped TiO2. Variation in the intensity ratios of the XRD peaks of the doped samples compared to that of the undoped sample offered an evidence for the substitutional incorporation of Cu ions in the TiO2 lattice. The preferential growth of the nanocrystals along the [004] direction was verified using HRTEM analysis. Cu doping extended the optical absorption edge of TiO2 nanocrystals to the visible spectral region and caused a blue shift and broadening of the E g (1) Raman active mode of anatase TiO2. Undoped TiO2 sample showed a weak ferromagnetism superimposed on a diamagnetic background while Cu-doped TiO2 samples exhibited a weak ferromagnetism in the low-field region with a paramagnetic component in the high-field region. The magnetic moment exhibited by the doped samples is interpreted as the resultant of a weak ferromagnetic moment in the low-field region arising from the presence of defects near the surface of TiO2 nanoparticles or from the interaction of the substituted Cu ions with the oxygen vacancies, and the paramagnetic contribution from the increased Cu dopant concentration near the surface of the particles arising from self-purification mechanism.

Titania-on-gold nanoarchitectures for visible-light-driven hydrogen evolution from water splitting

Titania-on-gold “inverse” nanocomposites were formed by loading smaller TiO2 nanoparticles onto bigger gold nanospheres by combining seed-mediated method with solvothermal method. This new nanoarchitecture exhibits excellent properties in hydrogen evolution from water splitting under visible-light irradiation. The enhanced performance was attributive to the synergistic effect between ultrafine TiO2 nanoparticle and localized surface plasmon resonance effect of gold nanoparticles, which induce the faster separation of photo-generated electrons from Au nanospheres to TiO2 nanoparticle. Besides, the nanocomposites have a strong absorption at around 550 nm, corresponding to the maximum irradiation intensity of solar spectrum. Owing to these outstanding properties, the as-obtained titania-on-gold nanoarchitectures showed promising and great potential for practical applications in photocatalytic field.

Membranes for Aqueous All Vanadium Redox Flow Battery

Redox Flow Battery (RFBs) are electrochemical devices that store electrical energy in soluble electro-active species dissolved in a liquid electrolyte. All Vanadium Redox Flow Batteries (VRFB) is one of the most promising and suitable technologies for large-scale energy storage for a wide range of renewable power sources. The RFB system separates capacity from power density: the capacity of the battery being determined by the size of the electrolyte tanks (the larger the volume of the electrolyte solutions, the higher the capacity of the battery), the system power is determined by the size of cell stacks. The flexible design, showed by this system, allows an easy scale up, but it is necessary to develop stable and high energy density redox electrolytes and efficient and low cost membranes or separators.[1] The membrane is a critical component that to a great extent determines the performance of RFB systems for practical applications The membrane is responsible for electronically insulating the negative and positive compartments while allowing the transport of charge balancing ions to complete the circuit. A membrane that exhibits excellent ionic conductivity, low permeability of the active species, and high chemical stability, is thus critically important for the development of RFB technologies. Perfluorosulfonic polymers such as Nafion are commonly used in different electrochemical devices, like Polymeric Fuel Cell (PEM), electrolyzers or RFB, due to their high proton conductivity, good chemical and thermal stability. However, when used in VRFBs, Nafion membranes suffer from the crossover of vanadium ions which results in decreased energy efficiency. So far studies are concentrated on the development of novel composite membranes leading to a low self-discharge rate and low costs. In this work, several cation exchange membranes (CEM) to be used in aqueous electrolyte VRFBs were investigated. Our approach to reduce costs and vanadium-ion crossover was based on the use of sulfonated poly ether ether ketone (SPEEK) due to its low permeability of diffusing specie and high ionic conductivity. Moreover, to further block vanadium-ion permeability through the membrane, we also evaluated the effect of adding a filler in the polymer matrix. In particular, an organically-modified ceramic material (TiO2-RSO3H) was synthesized by covalently grafting propylsulfonic acid groups on the surface of TiO2 nanoparticles [2] and added into the ion exchange polymer. To obtained homogeneous composite membranes two different deposition techniques were evaluated: solution casting and air spraying method. Filled and unfilled Nafion membranes were prepared and used as reference. Permeability measurements were carried out using a static H-type glass cell and the vanadium concentration were evaluated by UV-Vis spectrophotometry. The ionic conductivities of cation exchanged membranes was evaluated by electrochemical impedance spectroscopy. Coulombic and energy efficiencies of the system were studied by galvanostatic charge-discharge cycles using a lab-scale RFB cells. The overall performance of the RFB system was further analyzed by polarization curve at different state of charge (SOC) and Electrochemical Impedance Spectroscopy (EIS). Changes in the electrolyte composition were studied with cyclic voltammetry (CV) and UV-vis spectroscopy. Early insights on the understanding of battery capacity loss in long-term cycling tests is also reported in this work. Reference [1] Aishwarya Parasuramana, Tuti Mariana Lima, Chris Menictasc, Maria Skyllas-Kazacos, Electrochimica Acta, 101, 2013 , 27-40 [2] D. Cozzi, C. de Bonis, A. D’Epifanio, B. Mecheri, A. C. Tavares, S. Licoccia Journal of Power Sources 248, (2014) 1127-1132

Enhanced photoelectrochemical detection of l-cysteine based on the ultrathin polythiophene layer sensitized anatase TiO2 on F-doped tin oxide substrates

An effective photoelectrochemical (PEC) detection methodology was established and used to determine l-cysteine based on the ultrathin polythiophene layer sensitized anatase TiO2 on F-doped tin oxide substrates (PTh/TiO2/FTO). The PTh/TiO2 core-shell composites were synthesized by in situ polymerization of thiophene on TiO2 nanoparticle surfaces, resulting in a 1-nm-thick PTh layer decorated TiO2. The ultrathin layer could improve the electronic conductivity and enhance the light absorption, indicating that the PTh/TiO2/FTO electrode might strengthen a weak electrical signal response in detecting the low concentration of l-cysteine. Under Xe light of 25mWcm−2, the PEC detection limit of l-cysteine was 12.8μM from the transient photocurrent response method (linear range: 0.1–0.8mM) and 12.6μM the amperometric response method (linear range: 0.06–0.5mM), respectively. Moreover, the results also indicated an acceptable accuracy and excellent anti-interference in practical application, providing a rapid and sensitive PEC detection.

Excited-state dynamics of size-dependent colloidal TiO2-Au nanocomposites.

The ultrafast excited-state dynamics of size-dependent TiO2-Au nanocomposites synthesized by reducing gold nanoclusters to the surface of colloidal TiO2 nanoparticles are studied using pump-probe transient absorption spectroscopy with 400 nm excitation pulses. The results show that the relaxation processes of the plasmon depletion band, which are described by electron-phonon and phonon-phonon scattering lifetimes, are independent of the gold nanocluster shell size surrounding the TiO2 nanoparticle core. The dynamics corresponding to interfacial electron transfer between the gold nanoclusters and the TiO2 bandgap are observed to spectrally overlap with the gold interband transition signal, and the electron transfer lifetimes are shown to significantly decrease as the nanocluster shell size increases. Additionally, size-dependent periodic oscillations are observed and are attributed to acoustic phonons of a porous shell composed of aggregated gold nanoclusters around the TiO2 core, with frequencies that decrease and damping times that remain constant as the nanocluster shell size increases. These results are important for the development of improved catalytic nanomaterial applications.

Preparation of titanium dioxide nanoparticles supported on hexagonal mesoporous silicate (HMS) modified by oak gall tannin and its photocatalytic performance in degradation of azo dye

In this study, a new type of photocatalyst, TiO2 based on hexagonal mesoporous silicate (HMS) loaded by different concentrations of natural polyphenol oak gall tannin,OGT, (TiO2–OGTx-HMS, x=0.3, 0.6, 1wt.%) was synthesized and used in batch photocatalytic experiments. The synthesized catalysts were characterized using XRD, SEM, EDX and TEM analysis. The analysis showed that tannin was immobilized on the surface of HMS and TiO2 nanoparticles were distributed well and uniform on the surface of OGT-HMS without aggregation, while TiO2 nanoprticles aggregated on the surface of tannin free HMS. The performance of TiO2–OGTx-HMS phtocatalysts for degredation of anionic dye (i.e., Direct yellow 86) in aqueous solution were also compared with the performance of TiO2 (P-25) and TiO2–HMS. TiO2–OGT0.6%-HMS Photocatalyst exhibited higher performance than that of other photocatalysts with the adsorption and degradation efficiencies of 36.7% and 92.2%, respectively. The relative high value of activation energy, 24.8kJ/mol, confirms the effect of temperature to accelerate the photocatalytic reaction. It was also shown that photocatalytic reaction follows first order kinetic and up to 120mg/l of dye solution, Langmuir–Hinshelwood (L–H) kinetic model is acceptable.

TiO2 Nanotubes with Open Channels as Deactivation-Resistant Photocatalyst for the Degradation of Volatile Organic Compounds.

We synthesized ordered TiO2 nanotubes (TNT) and compared their photocatalytic activity with that of TiO2 nanoparticles (TNP) film during the repeated cycles of photocatalytic degradation of gaseous toluene and acetaldehyde to test the durability of TNT as an air-purifying photocatalyst. The photocatalytic activity of TNT showed only moderate reduction after the five cycles of toluene degradation, whereas TNP underwent rapid deactivation as the photocatalysis cycles were repeated. Dynamic SIMS analysis showed that carbonaceous deposits were formed on the surface of TNP during the photocatalytic degradation of toluene, which implies that the photocatalyst deactivation should be ascribed to the accumulation of recalcitrant degradation intermediates (carbonaceous residues). In more oxidizing atmosphere (100% O2 under which less carbonaceous residues should form), the photocatalytic activity of TNP still decreased with repeating cycles of toluene degradation, whereas TNT showed no sign of deactivation. Because TNT has a highly ordered open channel structure, O2 molecules can be more easily supplied to the active sites with less mass transfer limitation, which subsequently hinders the accumulation of carbonaceous residues on TNT surface. Contrary to the case of toluene degradation, both TNT and TNP did not exhibit any significant deactivation during the photocatalytic degradation of acetaldehyde, because the generation of recalcitrant intermediates from acetaldehyde degradation is insignificant. The structural characteristics of TNT is highly advantageous in preventing the catalyst deactivation during the photocatalytic degradation of aromatic compounds.

Continuum and atomistic description of excess electrons in TiO2

The modelling of an excess electron in a semiconductor in a prototypical dye sensitised solar cell is carried out using two complementary approaches: atomistic simulation of the TiO2 nanoparticle surface is complemented by a dielectric continuum model of the solvent–semiconductor interface. The two methods are employed to characterise the bound (excitonic) states formed by the interaction of the electron in the semiconductor with a positive charge opposite the interface. Density-functional theory (DFT) calculations show that the excess electron in TiO2 in the presence of a counterion is not fully localised but extends laterally over a large region, larger than system sizes accessible to DFT calculations. The numerical description of the excess electron at the semiconductor–electrolyte interface based on the continuum model shows that the exciton is also delocalised over a large area: the exciton radius can have values from tens to hundreds of Ångströms, depending on the nature of the semiconductor (characterised by the dielectric constant and the electron effective mass in our model).

Testing the photo-sensitive nanocomposite system for potential controlled metallo-drug delivery

Photo-responsive drug release systems are promising for drug delivery applications due to many benefits compared to conventional chemotherapy such as targeted, controlled release of a drug and reduced toxicity to healthy tissues. In this work, we report synthesis of the nanocomposite system based on carrier TiO2 nanoparticles and potential anticancer ruthenium complex, with light controllable release properties. Nanocomposite system showed biological activity and induced the generation of free radicals, which are implied in the efficient cell killing. The drug release tests demonstrated sustained release of the transition metal complex from the surface implying the potency for the controlled drug delivery system. Taking into account photoactivity of the Ru-complex, in the next step we have investigated the influence of green light on the rate of the complex release, and the results showed dependence of the Ru-complex release from the surface of TiO2 nanoparticles on the applied laser energy. Therefore, these characteristics make this nanocomposite system promising for the photo-responsive chemotherapy.

Immobilization of nanomaterials in PMMA composites for photocatalytic removal of dyes, phenols and bacteria from water

Nanomaterials represent a possible solution to solve many of the current issues involving water quality, but several limitations exist for efficient applications, primarily concerning the dispersion of such nanomaterials in water, their recovery after water treatment and the resulting impact on human health and ecosystems. We present an approach based on the incorporation of several nanomaterials into polymeric composites as a valid solution to overcome these problems. We embedded active TiO2 nanostructures in poly (methyl methacrylate) (PMMA), with the advantage of no need of recovery of the nanoparticles after water treatment. Furthermore, we combined titanium dioxide nanoparticles with single walled carbon nanotubes, as acceptor of electrons, and obtained a significantly higher photocatalytic efficiency under UV irradiation, compared to the systems with TiO2 only. Photoactive materials even under visible light were synthesized thanks to the functionalization of the TiO2 nanoparticle surface with meso-tetraphenylporphyrin-4,4′,4′′,4′′′-tetracarboxylic acid (TCPP) as dye sensitizer. We realized these polymeric nanocomposites by low-cost solution casting and evaluated their photocatalytic activity by degradation of some dyes and phenol in an aqueous medium. A significant antibacterial activity, measured through CFU (colony forming units) count using Escherichia coli as a model organism, is also reported.

Paramagnetic defects in KH2PO4 crystals with high concentration of embedded TiO2 nanoparticles

Qualitative transformations of spectra of Electron Paramagnetic Resonance, EPR, were found in KH2PO4 crystals grown from liquor with 10−5–10−1 wt. % of anatase TiO2 nanoparticles in comparison with nominally pure KH2PO4. The nanoparticles have larger segregation coefficient for prismatic parts of the crystals than for pyramidal ones. Significant decrease in resonance absorption, complete disappearance of EPR lines of Fe3+ and Cr3+ centers, and appearance of four weak lines of equal intensities together with broad asymmetric lines with g-factors about 2.07–2.5 was observed in pyramidal parts grown with concentration of TiO2 nanoparticles larger than the threshold value 10−2 wt. %. The four lines were attributed to non-controlled impurity As substituted for P. In the presence of TiO2 nanoparticles, non-paramagnetic AsO43− clusters trap electrons becoming AsO44−. Disappearance of Fe3+ and Cr3+ centers was explained by their recharge to “EPR-silent” states and/or pairing at the surface of TiO2 nanoparticles.

Dexamethasone-loaded TiO2 nanoparticles to locally target wear-debris induced inflammation

Event Abstract Back to Event Dexamethasone-loaded TiO2 nanoparticles to locally target wear-debris induced inflammation Melissa Rodrigues1, Stefano D. Perni1, 2, Alastair Sloan3 and Polina D. Prokopovich1, 2 1 Cardiff University, Pharmacy, United Kingdom 2 Massachusetts Institute of Technology,, Department of Biological Engineering, United States 3 Cardiff University, Dentistry School, United Kingdom Introduction: Like other parts of the body, joints become damaged or weakened by age, accidents or disease; joint degenerative diseases such arthritis affect the quality of life of millions worldwide.One of the ways to help such people is to have artificial joint replacement, although considered a successful procedure, these implants generate a large number of particles as result of wear with time/age. Such released particles, wear-debris, can compromise survival of joint implants by triggering an adverse inflammatory-response, which can lead to periprosthetic bone-loss, so called osteolysis[5]. During last decades, aseptic loosening due to osteolysis has been considered one of the most common causes for revision surgery[6]. Therefore the present project aims to develop an anti-inflammatory drug-eluting implant model system to prevent aseptic loosening following wear-induced osteolysis. Materials and Methods: Dexamethasone-loaded functionalized TiO2 nanoparticles were synthesized by covalently conjugating dexamethasone to carboxylic acid-amino functionalized nanoparticles. The functionalization of TiO2 nanoparticles was assessed by means of zeta potential measurements and thermogravimetric-analysis (TGA). Whilst dexamethasone release from TiO2 nanoparticles was quantified as function of time and pH using high-performance-liquid chromatography. Results and Discussion: The zeta potential measurements (Figure 1) show a more positive surface charge after amino-functionalization of TiO2 particles when compared to bare-TiO2. In contrast a more negative charge is observed after carboxyl and dexamethasone functionalization. As previously indicated in other studies, this is an indirect evidence showing that amino[2], carboxyl-acid groups[1], and dexamethasone[4] were successfully conjugated to TiO2-nanoparticles. Furthermore, TGA profile (Figure 2) shows an increase weight-loss after each step of functionalization. These results are related to an increase of organic material after each step of functionalization, thus confirming the successful attachment of functional groups and dexamethasone on the surface of TiO2-nanoparticles. After 24h, dexamethasone release from the functionalized-nanoparticles was suppressed at pH 7.0, 6.0 and 5.0; whilst at pH 4.0, a constant daily release of dexamethasone (10µg/mL) was observed over a period of 6 days (Figure 3). The results suggest that functionalized nanoparticles may remain stable and release more dexamethasone under acidic inflammatory conditions (pH=4)[3],[7] . Conclusions: Despite being one the most common complication after total joint replacement, there is no approved therapy to avoid aseptic-loosening following wear-induced osteolysis. Our study indicated that dexamethasone was successfully attached to TiO2 nanoparticles, with the advantage that the chemistry utilized could be applicable to conjugate other anti-inflammatory drugs. Furthermore, being controlled and constant drug release one of the most important features to modulate inflammation, dexamethasone-loaded-nanoparticles appears to be a potential approach to overcome the several limitations of current anti-osteolytic therapies e.g. lack of efficacy, systemic side-effects. Therefore more studies i.e. in vitro assessment of the anti-inflammatory effect are currently being performed by our research group to confirm safety and efficacy of drug-eluting-implant model system developed. Arthritis Research UK

Synthesis and characterization of core/shell titanium dioxide nanoparticle/polyacrylate nanocomposite colloidal microspheres

Core/shell titanium dioxide (TiO2) nanoparticle/poly(methyl methacrylate-butyl acrylate-methacrylic acid) [P(MMA-BA-MAA)] nanocomposite colloidal microspheres have been successfully synthesized via in situ emulsion polymerization. TiO2 nanoparticles were firstly modified by silane coupling agent, vinyl triethoxysilane (A-151), to increase the dispersibility of TiO2 nanoparticles into the polyacrylate matrix. The A-151-modified TiO2 nanoparticles were characterized by Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques. The synthesized nanocomposite colloidal microspheres were characterized by TEM, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and differential scanning calorimetry analysis (DSC). The results showed that A-151 coupling molecules was chemically bonded on the TiO2 nanoparticles surface, and the amount of coated A-151 was 3.0 wt%. According to TEM micrographs and DLS results, the dispersibility of modified TiO2 nanoparticles was obviously improved. TEM analysis revealed that an obvious core/shell structure morphology was observed with the core TiO2 particles surrounded by a uniform 10∼15-nm thick polymer shell. SEM–EDS result showed that TiO2 nanoparticles were homogenously monodispersed in the polymer matrix. DSC measurements indicated a glass transition temperature (T g) enhancement of P(MMA-BA-MAA).