Surface Of TiO2 Nanoparticles Research Articles

Potential-Resolved Multicolor Electrochemiluminescence of N-(4-Aminobutyl)-N-ethylisoluminol/tetra(4-carboxyphenyl)porphyrin/TiO2 Nanoluminophores.

Most electrochemiluminescence (ECL) studies involve single luminophore with a unique emission process, which severely limits its applications. Recently, multicolor ECL has attracted considerable interests. Herein, we report a novel nanoluminophore prepared by coating 5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin (TCPP) and N-(4-aminobutyl)-N-ethylisoluminol (ABEI) on the surface of TiO2 nanoparticles (TiO2-TCPP-ABEI), which exhibited unique potential-resolved multicolor ECL emissions using H2O2 and K2S2O8 as coreactants in an aqueous solution. Three ECL peaks, ECL-1 at 458 nm, ECL-2 at 686 nm, and ECL-3 at 529 nm, were obtained with peak potentials of 1.05, -1.65, and -1.85 V, which were attributed to the ECL emission of ABEI, TCPP, and TiO2 moiety of the nanoluminophores, respectively. Potential-resolved multicolor ECL from a nanoluminophore was observed for the first time in an aqueous solution. It opens a new research area of multicolor ECL of nanoluminophores, which is of great importance in ECL field from fundamental studies to practical applications.

Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties.

Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25) system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method). Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications.

Malachite Green Derivatives for Dye-Sensitized Solar Cells: Optoelectronic Characterizations and Persistence on TiO2

Abstract Derivatives of malachite green, a well-known triphenylmethine dye, have been adapted for third-generation photovoltaic applications as dye-sensitized solar cells (DSSC). The solar cells were developed based on a concentrated Br3−/Br− liquid electrolyte coupled to different trifluoroacetate (TFA−), triflate (TfO−), bromide (Br−) and tetrafluoroborate (BF4−) malachite green salts as dye sensitizers and mesoporous TiO2 anatase as electron collector, and their optoelectronic properties were characterized. The adsorption patterns of such salts at the TiO2 nanoparticle surface were studied by zeta (ζ) potential measurements on colloidal suspensions under neat conditions, and compared to the desorption rates of the dyes when exposed to the DSSC electrolyte. The different affinities of the ionic pairs for the oxide surface and the bulk were found crucial for the stability of the self-assembled monolayer of carboxylic acid-anchored chromophores at the surface, and for the photoconversion efficiency associated therewith. This study aimed at depicting the behavior of the ionic pairs at the surface and gave insights for their physical and chemical stabilization in the DSSC environment.

Photocatalytic Activity of Titanium Dioxide Nanoparticles Immobilized in the Polymer Network of Polyacrylamide Hydrogel

Composite hydrogels based on polyacrylamide immobilized nanoparticles of commercial (P25 brand) titanium dioxide and of titanium dioxide nanoparticles prepared by electric explosion of a wire were synthesized. The enthalpy of interaction at the polyacrylamide/TiO2 interface was determined by microcalorimetry using the thermochemical cycle method. Interaction of polyacrylamide polymer chains with the surface of TiO2 nanoparticles is energetically unfavorable. The absence of interactions between the hydrogel polymer network and surface of TiO2 nanoparticles favors manifestation of the UV-induced photocatalytic activity of TiO2 nanoparticles immobilized in the hydrogel. Immobilization in the polyacrylamide hydrogel matrix decreases the photocatalytic activity of P25 brand TiO2 nanoparticles, but does not affect the photocatalytic activity of titanium dioxide nanoparticles prepared by the electric explosion method. The photocatalytic activity of TiO2 nanoparticles immobilized in the bulk of polyacrylamide hydrogel evaluated by the decomposition of Methyl Orange dye is controlled by the diffusion rate of the dye molecules into the bulk of the hydrogel and depends also on the aggregation of TiO2 nanoparticles in the hydrogel matrix.

Luminescence from Erbium Doped Tellurite Glass: An Insight on Titania Nanoparticles Surface Plasmon Mediation

Weak stimulated emission cross-section of rare earth ions (REIs) as dopants inside various glass hosts are disadvantageous for practical applications and needs improvement. We determine the mechanism of Titania (TiO2) nanoparticles (TNPs) mediated Surface Plasmon Resonance (SPR) assisted modification in the spectral properties of tellurite glass doped with Erbium (Er3+) ions. Transparent and thermally stable glass samples with varying TNPs contents are synthesized using melt-quenching technique. TEM images revealed the existence of TNPs with average size ranged from 16 to 26 nm. Glass containing 0.4 mol% of TNPs displayed an enhancement in the Raman signal by a factor of 2.25, 1.83, 1.98, 1.56 and 3.58 for the bands centered at 388, 495, 673, 758, and 845 cm-1, which is attributed to the SPR assisted effects. Absorption spectra of TNPs embedded glass (devoid of erbium ions) manifested two surface plasmon (SP) bands at 552 and 580 nm. Up-conversion (UC) PL spectra showed three prominent bands centered at 525, 545, and 660 nm due to the Er3+ ion transition from the excited states to the ground state. Furthermore, glass containing 0.4 mol% of TiNPs exhibited an intensity enhancement by a factor of 30, and 28.57 (green bands) and 19.60 (red band), which are ascribed to the generation of strong local electric field mediated by SPR effect of TNPs situated in the vicinity of Er3+ ion. The presence of TNPs surface plasmon is asserted to be responsible for the alteration of the Er3+ ions absorbance and modification of the UC emission intensity. A correlation between SPR and Surface Enhance Raman Scattering (SERS) is established.

Ultrasonic-promoted rapid preparation of PVC/TiO2-BSA nanocomposites: Characterization and photocatalytic degradation of methylene blue

In the present project in order to prevent agglomeration and better dispersion of TiO2 nanoparticles (NPs) in the poly(vinyl chloride) (PVC) matrix, initially, the surface of TiO2 NPs was covered by bovine serum albumin protein (BSA) via sonication method. Then, the TiO2-BSA powders were embedded into the PVC matrix using ultrasonic irradiations. With mechanical and magnetic stirring homogenous mixture was not obtained. So sonication process was very essential and vital. Physical, chemical and structural properties of the samples were investigated with various tools. Morphology studies showed the well distribution of spherical TiO2 NPs in the PVC matrix. TGA analysis showed that nanocomposites (NCs) have higher thermal stability than the pristine polymer. The photocatalytic activity tests by destroying the methylene blue dye on the pristine TiO2 NPs, TiO2-BSA NPs and PVC/TiO2-BSA NC 6 wt% were examined. The results showed that the photocatalytic activity of TiO2 NPs was reduced in the presence of BSA and PVC. It can be concluded that the TiO2-BSA NPs and PVC/TiO2-BSA NC 6 wt% have UV shielding properties and can protect film from degradation by UV.

Kinetics of Photoinduced Wettability Switching on Nanoporous Titania Surfaces under Oil

AbstractTitanium dioxide (titania or TiO2) is well known for its photocatalytic properties and its ability to remove organic contaminants under UV light illumination. It is also known to switch its surface wetting characteristics from being hydrophilic to superhydrophilic under exposure to UV light in air. However, less is known about the switching of the hydrophilicity of TiO2 surfaces immersed in an oil medium. In this work, self‐assembled TiO2 nanoparticle surfaces are immersed in an oil environment, and the kinetics of contamination‐induced hydrophobicity and photoinduced hydrophilicity are studied using in situ contact angle measurements. A simple model is developed to relate the evolution in the measured contact angle to photocatalytically induced changes on the surface of nanoporous titania by integrating the Langmuir–Hinshelwood adsorption isotherm with the Cassie–Baxter analysis of the effective contact angle of a drop sitting on a composite surface. The resulting model can be used to predict and control wetting kinetics in drop coalescence applications. Moreover, it is shown that immersed oil–water separation membranes which have been fouled by low surface tension contaminants can be rapidly recovered in situ using this underwater photocatalytic reaction without the need for backwashing or harsh chemical reagents.

Ionic and electronic transport in PSF/NiO and PSF/TiO2 polymer nanocomposites: A positron lifetime study

Polymer nanocomposites of PSF/NiO and PSF/TiO2 with different wt% of nanofiller have been prepared and subjected to SEM, FTIR, X-ray diffraction, DSC, PALS and electrical conductivity measurements. The relationship between crystallinity, surface morphology, glass transition temperature, free volume and the electrical conductivity of these polymer nanocomposites was systematically investigated. The increased AC and DC electrical conductivity at the lower concentration of NiO suggests the increased number of mobile ions and electrical charge carriers due to the increased crystallinity of PSF/NiO composites. The decreased conductivity at higher concentration of NiO indicates the reduced conducting pathways for the mobility of ions and the electrical charge carriers due to the decreased crystallinity by the nanoparticles aggregations. The increased AC and DC electrical conductivity with increasing the concentration of TiO2 indicates more and more positive charges in front of the cathode, resulting proper polymer-nanofiller interface due to the conductivity chain formation through the nanoparticles aggregation. The surface morphology of PSF/NiO and PSF/TiO2 nanocomposites show dispersion of nanoparticles over the surface of PSF matrix and the formation of filler aggregates at higher wt% of nanofiller incorporation. The increased glass transition temperature (Tg) and decreased o-Ps lifetime (τ3) at the lower concentration of NiO and TiO2 indicates the improved interfacial interaction between the surface of NiO and TiO2 nanoparticles with the side chains of PSF polymer matrix. This is evident from Fourier Transform Infrared Spectroscopy (FTIR) studies. The increased o-Ps lifetime (τ3) at higher concentration of NiO and TiO2 suggests the increased interfacial space for o-Ps to annihilate at the interface of PSF and NiO and TiO2 nanoclusters.

Surface modification of TiO2 nanoparticles by magnetic ions: Synthesis and application in enhancement of photocatalytic performance

The surface of TiO2 nanoparticles was modified by Samarium (Sm) and Gadolinium (Gd) doping to enhance their adsorption and photocatalytic performance. The undoped TiO2 and different (Sm or Gd)/Ti molar ratios of 0.9, 1.8 and 3.6at.%, were prepared through a combined sol-gel milling method and sintered in two different temperatures of 550 and 700°C. Scanning electron microscope (SEM) images of composite samples revealed a clear reduction in particle size compared to the undoped samples of the same temperature. Excellent adsorption and photodegradation of Congo red dye solution under ultraviolet (UV) irradiation were attained for Sm-TiO2 and Gd-TiO2 nanoparticles compared to the undoped samples sintered at the same temperature. The photocatalytic performance of composites was improved up to 1.8at.% of Sm or Gd content. The results showed that the Gd-TiO2 composite nanoparticles had much better performance compared to the Sm-TiO2 composite nanoparticles with the same molar ratio and the same sintering temperature.

Preparation of TiO2/Ag binary nanocomposite as high-activity visible-light-driven photocatalyst via graft polymerization

We report the synthesis of a TiO2/Ag binary nanocomposite with high activity for visible-light-driven photocatalysts using graft copolymerization: (1) conversion of terminal OH groups on the surface of TiO2 nanoparticles to Cl groups, (2) graft polymerization from TiO2–Cl via ATRP with ionically charged poly(styrene sulfonic acid), (3) ion exchange process with an AgNO3 solution following sintering. TiO2/Ag binary nanocomposite showed enhanced photocatalytic performance for the degradation of methyl orange under visible light illumination. The improved photocatalytic performance of the TiO2/Ag binary nanocomposite was due to the plasmonic effect, recombination rate of electron–hole pairs that was suppressed by Ag nanoparticles.

High performance surface-modified TiO2/silicone nanocomposite

The mismatch of refractive index (RI) between light emitting diode (LED) chips and packaging resins severely lowers the lighting emitting efficacy of LED. The RI can be enhanced by the introduction of high RI nanoparticles but meanwhile it is a great challenge to maintain the high transparency for resins due to the agglomeration of nanoparticles. In this work, a facile strategy is proposed to fabricate silicone nanocomposites with a high transparency (>88%, less than 2% decrease relative to pure silicone resin), largely enhanced RI (an increase from 1.42 to 1.60) and improved thermal stability (73 °C increase in weight loss of 50%). Specifically, the ultra-fine monodispersed TiO2/silicone composites are prepared by direct solvent mixing of 1 wt% surface modified TiO2 nanoparticles (S-TiO2) into the silicone resin, in which S-TiO2 are prepared by direct introduction of titanate coupling agent in the process of TiO2 growth to induce the formation of protective layer on the surfaces of TiO2 nanoparticles. This methodology demonstrated is simple, cost-effective and versatile for the massive fabrication of highly transparent LED packaging materials with greatly enhanced refractive index and meanwhile enhanced thermal stability.

Super-hydrophilic and fouling resistant PVDF ultrafiltration membranes based on a facile prefabricated surface

The hydrophilicity of PVDF membrane is playing an enormously important role in its widespread water treatment fields considering the excellent intrinsic properties of PVDF raw materials. Rather than the conventional surface modification or hybridization, herein, we report a novel approach to prepare super-hydrophilic PVDF ultrafiltration (UF) membrane by creating a prefabricated super-hydrophilic surface of inorganic TiO2 nanoparticles (NPs). The resultant membrane [prepared by prefabrication surface adhesion of TiO2 NPs on PVDF-PEG-TiO2 hybrid membrane (SaT-PPT)] has a uniform distribution of TiO2 NPs not only on the membrane surface but also within membrane matrix, this will maximize the super-hydrophilic feature throughout the membrane: from inner porous structures to outer surfaces, and will avoid “dead-corner” to block fast water pass through. The performances of SaT-PPT membrane as compared with the control membranes (PVDF-PEG, and PVDF-PEG with TiO2 anchored only at surface) were investigated in terms of humic acid (HA) rejection, flux and flux decline in lab-made cross flow UF experiments with and without UV irradiation. It indicated that SaT-PPT membrane exhibited the highest hydrophilicity and flux, lowest flux decline and total resistance, but still with the highest HA rejection rate. In addition, SaT-PPT membrane showed the highest flux recovery after simple physical cleaning to extend the longer life span of membrane. It is reasonable to believe that our developed SaT-PPT membranes will provide insightful engineering practices to benefit the broad water treatment applications.

Sonochemical Synthesis of Mg-TiO 2 nanoparticles for persistent Congo red dye degradation

Abstract In this article, modified TiO2 and Mg-TiO2 nanoparticles was prepared by the facile sonochemical method. The crystal structure evolution and elemental composition were analyzed by X-ray crystallography and X-ray photoelectron spectroscopy. The calculated band gap energy of Mg-TiO2 nanoparticles was lower than that of pure TiO2 −P25. The Fourier Transform Infrared (FT-IR) spectral study established the substitution of Mg2+ on the TiO2 surface. The Raman spectroscopy confirms that the Mg2+ ions were in situ doped on the surface of TiO2 nanoparticles. The photocatalytic efficiency of the synthesized Mg-TiO2-P25 nanoparticles was investigated by performing photocatalytic degradation of persistent Congo red dye under visible light irradiation. It has been found that the Mg-TiO2-P25 nanoparticles possess better catalytic activity than pure TiO2 −P25 and modified TiO2 nanoparticles.

Photoelectrochemical amperometric sensing of cyanide using a glassy carbon electrode modified with graphene oxide and titanium dioxide nanoparticles

The authors describe a modified glassy carbon electrode (GCE) for the amperometric determination of cyanide ions. First, the surface of TiO2 nanoparticles was modified with aminopropyltriethoxysilane (AS). These were then deposited, along with graphene oxide (GO) nanosheets, on the surface of the GCE. The modification steps were followed by reductive deposition of reduced 4-nitrophenol (rNPh). The GO/TiO2-AS-rNPh electrode was used to design a photoelectrochemical amperometric cyanide assay which works in pH 7 solution, best at 0.35 V (vs. Ag/AgCl). Characteristics of merit include a 0.1 μM detection limit, a 165.5 nA·nM−1·cm−2 sensitivity, and a dynamic linear range extending from 0.1 μM to 60 μM. The selectivity of the assay was tested by recording the response of the modified GCE to potentially interfering anions and was found to be very good. The inherent photocatalytic activity, good stability, wide linear analytical range, short response time, low detection limit and good selectivity make this assay highly advantageous

Synthesis, characterization, and electrophoretic concentration of titanium dioxide nanoparticles in AOT microemulsions.

Stable organosols of TiO2 nanoparticles were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in microemulsions of sodium bis(2-ethylhexyl)sulfoxynate (АОТ) in n-decane with increasing the content of aqueous pseudophase from 0.15 to 0.85vol.%. As the water content increased, the hydrodynamic diameter of nanoparticles grew from 10 to 225nm, and the ζ-potential, from -6 to 18mV (the surface of TiO2 nanoparticles was recharged when the water content was 0.45vol.%). Nonaqueous electrophoresis in a capacitor-type cell made it possible to concentrate nanoparticles with a diameter of 60 to 225nm (concentration factor was 10), separate 20nm and 225nm particles, and decrease the content of АОТ in organosol by an order of magnitude. Preparation of a concentrate of nanoparticles with a low content (0.015M) of AOT included the following stages: (i) electrophoresis after synthesis; (ii) sampling of the concentrate and its twenty-fold dilution with pure n-decane; and (iii) repeated electrophoresis. In situ laser and spectrophotometric scanning of the interelectrode space showed the formation of a sharp boundary between the raffinate and the layer of moving nanoparticles during electrophoresis.

Synthesis and optical properties investigation of highly dispersed TiO2 nanoparticles surface modified with a quinoline derivative

TiO2 nanoparticles were surface modified by (2-chloroquinoline-3-yl) methanol as the capping agent (QA) and p-toluene sulfonic acid (p-TsOH) as a strong catalyst, using a simple solvothermal treatment. As a result, highly dispersed TiO2 nanoparticles having particle size of approximately 10 nm and optical band gap of about 3.8 eV were synthesized which showed lower photoluminescence intensity due to lower amount of electron–hole recombination compared to pure TiO2. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the nanoparticles. Optical properties of the nanoparticles were investigated by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy.

Physical Mechanisms of Exchange Coupling Effects in Nanoparticulate Diluted Magnetic Oxides Obtained by Laser Pyrolysis

TiO2 nanoparticles, undoped and doped with Fe, have been prepared by laser pyrolysis and further investigated with respect to morphological, structural and magnetic aspects by transmission electron microscopy, diffractometry, Mossbauer spectroscopy, and magnetometry. The obtained nanoparticles, consisting of mainly anatase phase, agglomerate in clusters of tenths of units and present a large size distribution in the range from 5 to 40 nm. The anatase to rutile weight ratio (about 9) and the morphology of particles is similar in all analyzed samples (doped by up to 12 at. % Fe). Only Fe3+ ions in high spin configuration were observed mainly at the surface of TiO2 nanoparticles, either distributed or forming fine clusters of Fe oxide. Both a paramagnetic phase and a superparamagnetic one with blocking temperature lower than 50 K are superposed over a long-range ferromagnetic phase specific to diluted magnetic oxide systems. The influence of doping Fe ions on the magnetic behavior of each phase is discussed ...

TiO2/polymeric supported silver nanoparticles applied as superior nanocatalyst in reduction reactions

A novel polymeric nanocomposites (TiO2/poly(acrylamide-co-methylenbisacrylamide)) decorated with silver nanoparticles (Ag NPs) denoted as (Ag–TiO2/poly(AM-co-MBAM)) was prepared and fully characterized. Initially, the surface of TiO2 nanoparticles was modified using methacryloxypropyltrimethoxysilan (MAPTMS), thus a CC bond for polymerization was generated, which polymerized wih acrylamide and methylenbisacrylamide monomers. Ag NPs then were immoblized on the surface of this obtained polymeric nanocomposites via reduction in the presence of AgNO3. The catalytic efficiency of Ag–TiO2/poly(AM-co-MBAM) nanocomposites was investigated for the reduction of nitroarenes and some carbonyl compounds in the presence of sodium borohydride (NaBH4) as reducing agent in aqueous media to give the corresponding anilines and alcohols with excellent yields and short reaction times, respectively. The nanocatalyst was easily recovered and reused for at least seven cycles without appreciable loss of its catalytic activity.

Magnetron-sputtering fabrication of noble metal nanodots coated TiO2 nanoparticles with enhanced photocatalytic performance

Magnetron-sputtering deposition of coatings onto a flat surface is well established, but coating metal on the curved surface of nanoparticles (NPs) is still challenging. Herein, by using a magnetron sputtering system in which a vibration generator with variable frequency is applied to the sample stage to maintain NPs' dispersity and movability, we successfully deposit noble metal (Au, Ag, Pt) nanodots onto the surface of TiO2 NPs. It is found that the metal nanodots are of a size of 1–6nm and they are firmly bonded to the TiO2 NPs' surface. The photocatalytic activity of Ag/TiO2 is demonstrated to be 2.7 times that of pure TiO2 under simulated sunlight irradiation. This study creates new opportunities for fabricating excellent NP composite catalysts by liquid-free methods.

Remarkable catalytic activity of Bi2O3/TiO2 nanocomposites prepared by hydrothermal method for the degradation of methyl orange

Visible light Bi2O3/TiO2 nanocomposites are successfully prepared with different dosages of Bi2O3 by hydrothermal process. All the as-prepared samples are characterized by X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM and TEM), Brunauer-Emmett-Teller analysis (BET), N2 adsorption-desorption measurement, and UV-Vis diffuse reflectance spectra (DRS). XRD and Raman spectra reveal the anatase phase of both TiO2 and Bi2O3/TiO2 nanocomposites. X-ray diffraction patterns demonstrate that the bismuth ions did not enter into the lattice of TiO2, and Bi2O3 is extremely dispersive on the surface of TiO2 nanoparticles. The incorporation of Bi2O3 in TiO2 leads to the spectral response of TiO2 in the visible light region and efficient separation of charge carriers. The enhanced visible light activity is tested by the photocatalytic degradation of methyl orange under light illumination, and the performance of Bi2O3/TiO2 nanocomposites are superior than that of pure TiO2 which is ascribed to the efficient charge separation and transfer across the Bi2O3/TiO2 junction. Bi2O3/TiO2 nanocomposite (20 mg) loaded with 0.25 of Bi2O3 dispersed in 50 ml of 5 ppm methyl orange solution exhibited the highest photocatalytic activity of 98.86% within 240 min of irradiation, which is attributed to the low band gap, high surface area, and the strong interaction between Bi2O3 and TiO2.