Functionalized TiO2 Nanoparticles Research Articles

Graftfast<sup>©</sup>: Towards the Control of Surface Properties of any Type of Materials by the Grafting of Polymers

This document aims at presenting and explaining the mechanism of a simple green process, called Graftfast©, recently developed in order to graft polymer films onto any type of materials. This process is of great interest as it works in a short one step reaction at room temperature, atmospheric pressure in water. Particularly since this method is a redoxinduced process consisting in the reduction of diazonium salts into aryl radicals in presence of vinylic monomer, the involvement of such radicals was investigated. Moreover, this work demonstrates the efficiency of such process for the preparation of functionalized TiO2 nanoparticles. The composition and the grafted polymer quantities were investigated showing the successful grafting of the polymer onto the nanoparticles while conserving their morphology.

Effect of TiO2 nanoparticle surface functionalization on protein adsorption, cellular uptake and cytotoxicity: the attachment of PEG comb polymers using catalytic chain transfer and thiol–ene chemistry

A successful modification of titanium dioxide (TiO2) nanoparticles surfaces by a grafting-to polymer technique combining catalytic chain transfer and thiol–ene click chemistry is reported. Vinylic end functional polymers were first prepared by catalytic chain transfer polymerization (CCTP) using oligo(ethylene glycol) methacrylate as a monomer. The presence of vinylic end groups was then exploited to attach the polymers to thiol functionalized TiO2 nanoparticles via thiol–ene Michael nucleophilic reactions. X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-infrared (ATR-IR), dynamic light scattering (DLS), and thermogravimetric analyses (TGA) were used to verify the successful modification of the TiO2 surface. The modified TiO2 nanoparticles were stable in cell culture media and formed smaller aggregates when compared to non-surface modified nanoparticles. Cellular toxicity of the hybrid TiO2–polymer particles towards human lung cell lines A549 and H1299 in vitro was evaluated. Results from one-dimensional gel electrophoresis show the presence of polymer layers around the particles affects the adsorption of protein onto the TiO2 surface. The reduction in particle aggregate size and changes to the particle surface chemistry, following polymer grafting, was found to reduce cellular uptake and diminish cytotoxicity for both human lung cell lines tested.

Simultaneous amination of TiO2 nanoparticles in the gas phase synthesis for bio-medical applications

A simultaneous synthesis and surface amination method to effectively modify the surface of inorganic nanoparticles is discussed in this study. As a target material system and surface functional group, TiO2 nanoparticles and amine were selected. APTES (3-aminopropyltriethoxysilane), the source of amine group, was mixed with TTIP (titanium tetraisopropoxide) and used for the synthesis of aminated TiO2 nanoparticles. XRD (X-ray diffractometry) results showed TiO2 nanoparticles of pure anatase phase, 15 nm in crystallite size, were successfully synthesized at 700°C and 50 mbar. Fourier transformation infrared (FT-IR) spectroscopy measurement and confocal microscopy study using fluoresceine isothiocyanate (FITC) confirmed that amine groups were successfully deposited and activated on the surface of TiO2 nanoparticles.

UV/Vis photocatalytic functionalization of TiO2 nanoparticle surfaces toward water repellent properties

Surface modification reactions on inorganic nanoparticles have become a significant tool in attempts to manipulate their physical and chemical properties according to the application’s aim. However, overcoming their extensive aggregation and difficulties in their homogeneous dispersion in a number of organic media is critical to their exploitation. In this context, an alteration in the surface chemistry of nanoparticles has become an indispensable step in their further utilization. This work is devoted to the application of light (UV and visible) and sonication for the initiation of surface reactions on TiO2 nanoparticles with (3-chloropropyl)triethoxysilane, making them highly reactive species, and preparing them for further utilization. It was shown that all three methods were successful for TiO2 nanoparticle functionalization, and that light-initiated reactions are more effective than the sonication process under the same reaction conditions. Chloropropyl functionalities were introduced onto the nanoparticle surfaces, followed by intensive silylation, leading to the superhydrophobic and water repellent properties of the functionalized TiO2 nanoparticles.

Synthesis and characterisation of nanocomposite materials prepared by dispersion of functional TiO2 nanoparticles in PMMA matrix

Composite powders and thin films composed of poly(methyl methacrylate) (PMMA) and functionalised titania nanoparticles are successfully prepared by in situ bulk co-polymerisation using benzoyl peroxide (BPO) as the initiator. The functionalised titania nanoparticles are synthesised by an arrested hydrolysis of Ti(OiPr)4 with either undecylenic (UA) or undecenylphosphonic (UPA) acids used as the organic templates with the long hydrocarbon chains and functional (terminal double bond) groups. Surface-modified TiO2 nanoparticles could be easily dispersed in organic solvent due to the long hydrocarbon chain surrounding the titanium core, and engaged as a co-monomer in polymerisation with the MMA due to the presence of a terminal double bond. TEM and small angle X-ray scattering (SAXS) data presented support the homogeneous and consistent distribution of inorganic phase within the PMMA matrix, with the larger titania nanoparticles detected when the UPA was employed to modify a TiO2 nanoparticle. This is attributed to the UPA greater binding affinity towards the TiO2 surfaces and therefore particles aggregation to some extent.

The Synthesis of Solvent-Free TiO<sub>2</sub> Nanofluids through Surface Modification

TiO2 nanoparticles with surface hydroxyl groups are treated by trimethoxysilane (CH3O)3Si(CH2)3O(CH2CH2O)6-9CH3 and a inorganic core/organic shell hybridmaterials, which shows itself a yellow viscous fluid, is obtained. We call it solvent-free TiO2 nanofliuds. Transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and rheometer are adopted to characterize the product. As a result, the content of TiO2 nanoparticles in the nanofliuds is about 5.5wt%, the functionalized TiO2 nanoparticles possess better dispersion, very low viscosity and an obvious liquid-like behavior at room temperature in absence of solvent.

Low-Potential Photoelectrochemical Biosensing Using Porphyrin-Functionalized TiO2 Nanoparticles

A novel photoelectrochemical biosensing platform for the detection of biomolecules at relatively low applied potentials was constructed using porphyrin-functionalized TiO₂ nanoparticles. The functional TiO₂ nanoparticles were prepared by dentate binding of TiO₂ with sulfonic groups of water-soluble [meso-tetrakis(4-sulfonatophenyl)porphyrin] iron(III) monochloride (FeTPPS) and characterized by transmission electron microscopy; contact angle measurement; and Raman, X-ray photoelectron, and ultraviolet-visible absorption spectroscopies. The functional nanoparticles showed good dispersion in water and on indium tin oxide (ITO) surface. The resulting FeTPPS-TiO₂-modified ITO electrode showed a photocurrent response at +0.2 V to a light excitation at 380 nm, which could be further sensitized through an oxidation process of biomolecules by the hole-injected FeTPPS. Using glutathione as a model, a methodology for sensitive photoelectrochemical biosensing at low potential was thus developed. Under optimal conditions, the proposed photoelectrochemical method could detect glutathione ranging from 0.05 to 2.4 mmol L⁻¹ with a detection limit of 0.03 mmol L⁻¹ at a signal-to-noise ratio of 3. The photoelectrochemical biosensor had an excellent specificity against anticancer drugs and could be successfully applied to the detection of reduced glutathione in gluthion injection, showing a promising application in photoelectrochemical biosensing.

Surface-Modified Titania Nanoparticles with Conjugated Polymer for Hybrid Photovoltaic Devices

A novel route is presented for preparation of poly(1-methoxy-4-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV)-functionalized TiO2 nanoparticles (NPs), resulting in a hybrid nanocomposite (MEH-PPV~TiO2 NPs). Thermogravimetric analysis (TGA) was used to evaluate the exact content of TiO2 nanoparticles in the MEH-PPV~TiO2 nanocomposites. Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and photophysical properties showed that the conjugated polymer chains intimately contact with the inorganic semiconductors. The performance of photovoltaic devices based on the MEH-PPV~TiO2 NPs nanocomposite was investigated by current–voltage (J–V) characteristics and intensity-modulated photovoltage spectroscopy (IMVS). Device performance was greatly improved by direct application of MEH-PPV~TiO2 NPs nanocomposites as the active layer as compared with devices with simply blended counterparts (MEH-PPV/TiO2 NPs). In addition, IMVS revealed that the longer electron lifetime was accompanied by higher open-circuit voltage in the MEH-PPV~TiO2 NPs devices.

Location of functionalized-TiO2 nanoparticle in an immiscible PP/PA6 blends and its effect on the compatibility of the components

Nanocomposites based on 70/30 (w/w) polypropylene (PP)/polyamide 6 (PA6) immiscible blends and functionalized-TiO2 nanoparticles were prepared via melt compounding. The influences of TiO2 on the morphology of nanocomposites were investigated. Scanning electron microscopy results revealed the domain size of the dispersed PA6 phase decreased in presence of functionalized-TiO2 and the TiO2 nanoparticles were preferentially located at the PA6 phase and at the interfacial region between PP and PA6, which were ascertained by differential scanning calorimetry. The functionalized-TiO2 nanoparticles played the compatibilizer for the immiscible PP/PA6 blends, increasing the interaction of the two phases in certain extent. Therefore, a clear compatibiliting effect was induced by the TiO2 in the immiscible PP/PA6 blends.

Planar photonic crystals infiltrated with nanoparticle/polymer composites

Infiltration of planar two-dimensional silicon photonic crystals with nanocomposites using a simple yet effective melt processing technique is presented. The nanocomposites that were developed by evenly dispersing functionalized TiO2 nanoparticles into a photoconducting polymer were completely filled into photonic crystals with hole sizes ranging from 90to500nm. The infiltrated devices show tuning of the photonic band gap that is controllable by the adjustment of the nanoparticle loading level. These results may be useful in the development of tunable photonic crystal based devices and hybrid light emitting diodes and solor cells.