Photocatalytic Activity Of TiO2 Nanoparticles Research Articles

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.

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.

Effect of porphyrin on photocatalytic activity of TiO2 nanoparticles toward Rhodamine B photodegradation

As known, porphyrins have central role in photosynthesis, biological oxidation and reduction and oxygen transport beside to their intensive color which qualify them to be good photosensitizers. Herein, tetra (4-carboxyphenyl) porphyrin (TCPP) was prepared by a simple one-pot synthesis to use as a visible antenna for TiO2 nanoparticles that were prepared via a simple template-free sol-gel method. Various loading percentages of TCPP (0.05–1%) were incorporated on the surface of TiO2 as photosensitizer for photocatalytic degradation of Rhodamine B (Rh B) dye as a primary cationic pollutant model. Among them, 0.1% TCPP-TiO2 was the most reactive sample. It was found that the photoactivity of 0.1% TCPP-TiO2 sample (0.5g/L) was approximately 1.5 times greater than that of pure TiO2 (0.5g/L) toward the degradation of Rh B (1×10−5M) under UV-A irradiation. Transient fluorescence decay measurements showed that the life time of TiO2 excited state has doubled after anchoring TCPP, thus the probability of electron-hole recombination has decreased. The samples were characterized by XRD, HR-TEM, DRS and N2 adsorption-desorption isotherms. The XRD patterns confirmed the successful preparation of TiO2 nanoparticles with average crystalline size of 25.7nm. Also, XRD patterns suggested the presence of mixed phase TiO2 nanoparticles of 77% anatase and 23% rutile. DRS showed that the characteristic peaks of TCPP covered the whole visible range 400–700nm. HR-TEM images showed the spheroids shape of TiO2 nanoparticles and confirmed the presence of anatase and rutile phases as suggested from XRD data. The different parameters affecting the photodegradation of Rh B dye such as catalyst dose, dye concentration and pH were studied to obtain the optimum conditions. Almost complete degradation of Rh B was obtained which confirmed by HPLC and TOC measurements. The effect of scavengers was studied to indicate the most active species. TCPP-TiO2 gave a good response toward the photodegradation of Rh B under visible irradiation. Finally, the mechanism of photocatalytic degradation process was suggested.

Effects of bulk and surface defects on the photocatalytic performance of size-controlled TiO2 nanoparticles

Defects are one of the crucial factors influencing the photocatalytic activities of TiO2 nanoparticles (NPs), as they directly affect the charge separation efficiencies. However, we found that the effect of bulk or surface defects on the photocatalytic performance of TiO2 is totally different. Here, we controllably synthesized four kinds of uniform TiO2 NPs, which were used to investigate how the bulk and surface defects influenced the photoactivities of samples with different particle sizes. Through XPS and EPR analysis, bulk and surface defects were observed in all the TiO2 samples and their amounts had been reduced after the calcination process. The reduction of bulk and surface defects enhanced the photoactivities of TiO2 NPs with diameters >10 nm, but the situation was inverse for those samples with diameters <10 nm. Therefore, we demonstrated that bulk defects play a dominate role in the change in photoactivity in particles larger than 10 nm, while surface defects are more important than bulk defects for particles less than 10 nm.

Influence of agglomeration and aggregation on the photocatalytic activity of TiO2 nanoparticles

Particle aggregation and agglomeration influence the optical properties of materials and therefore their ability to absorb and scatter the incoming radiation, also affecting their photocatalytic activity [1–7]. We have studied the correlation between aggregation and photocatalytic activity for titanium dioxide by means of experimental measurements of extinction and photocatalytic activity and calculations of their optical properties (extinction, absorption and scattering cross-sections). This approach can be adopted to quantitatively assess the quantum yields of the heterogeneous photocatalytic systems. The study was performed on TiO2 PC105 Cristal ACTiV™, made of aggregated (and agglomerated) primary particles of anatase. The size of the aggregates has been reduced with ultra-sonication. Aqueous suspensions of the obtained materials were characterized by measuring the optical properties (UV–vis extinction), the sizing properties (DLS) and the photocatalytic activity (degradation of phenol under standard conditions). The extinction and absorption spectra of the suspensions were derived from the calculated coefficients, considering also the size distributions measured with DLS, and revealed that light absorption is maximized when particle aggregation and agglomeration are avoided, while diffusion of the incoming radiation dominates when large aggregates and agglomerates are present. The present paper represents a valuable approach to the accurate and reproducible measurement of the photocatalytic activity of TiO2 nanoparticles suspensions, thus allowing a more reliable comparison of the properties of different materials.

Enhanced photocatalytic activity of TiO2 nanoparticles using WS2/g-C3N4 hybrid as co-catalyst

TiO2/WS2/g-C3N4 composite photocatalysts were synthesized by a liquid-exfoliation-solvothermal method. In this process, the WS2/g-C3N4 nano-sheets were prepared by liquid-exfoliation method from the bulk WS2 and C3N4 in the alcohol system, and then the TiO2 nanoparticles (NPs) grew on the WS2/g-C3N4 nano-sheets by in-situ synthesized technique. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic degradation of methyl orange (MO). The results showed that the as-prepared samples exhibited higher photocatalytic activities as compared to the pure TiO2, g-C3N4 and TiO2/g-C3N4 composite. The enhanced photocatalytic activities of TiO2/WS2/g-C3N4 photocatalysts could be attributed to the synergistic effect of heterostructure between TiO2 NPs and WS2/g-C3N4 nano-sheets, which could efficiently improve the separation of photogenerated electron/hole pairs and utilization efficiency of photons. The quenching tests of radicals indicated that ·O−2 had crucial effect on degradation of MO, which demonstrated that ·O−2 was the main active radical in photocatalytic reaction process.

Enhancing the photocatalytic activity of TiO2 nano-particles using novel tridentate N2O Schiff base complexes

Two novel tridentate N2O Schiff base ligands, H2L1 ((E)-3-((2-amino-5-nitrophenylimino)methyl)benzene-1,2-diol) and H2L2 ((E)-4-((2-amino-5-nitrophenylimino)methyl)benzene-1,3-diol) and metal complexes [ML(DMF)] (where M = Ni2+, Cu2+ and VO2+) were synthesized. All new materials were studied by spectroscopic methods. The Schiff base complexes were loaded over TiO2 nano-particles and calcined at 450 °C. The MOX/TiO2 structure and morphology were characterized by IR, UV, TEM, SEM and XRD techniques. The effect of the photocatalytic activity of MOX/TiO2 semiconductor nano-particles on the degradation of methylene blue was investigated via visible light in the aqueous solution. Based on the results, incorporation of metal Schiff base complexes was found to improve the activation of mixed oxide nano particles with visible light.

Iridium, carbon and nitrogen multiple-doped TiO2 Nanoparticles with enhanced photocatalytic activity

The aim of this research is to enhance the photocatalytic activity of TiO2 nanoparticles for the UV–visible light by multiple-doping with Iridium, carbon and nitrogen. The tridoped TiO2 photocatalyst were prepared by wet chemical method, and characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible light diffuse reflection spectroscopy and room temperature photoluminescence spectroscopy. Besides, the photocatalytic H2 evolution performance of Ir-C-N tridoped TiO2 under UV–visible light irradiation was evaluated. It was found that Ir existed as Ir4+ by substituting Ti in the lattice of TiO2; meanwhile, C and N were also incorporated into the surface of TiO2 nanoparticles in interstitial mode. Meanwhile, Ir-C-N tridoping extended the absorption of TiO2 into the visible light region and narrowed its band gap to ~3.0eV, resulting in enhanced photocatalytic H2 evolution under UV–visible light irradiation. This could be attributed to narrow band gap and proper electronic structure of TiO2 after Ir-C-N tridoping.

Cu and Zr surface sites in the photocatalytic activity of TiO2 nanoparticles.

The rate of methylene blue and terephthalic acid degradation assisted with double metal-modified catalyst (0.1mol% Cu and 1.0mol% Zr) was enhanced as compared with single metal-modified catalysts (0.1, 0.5mol% Cu and 1.0mol% Zr). The wet impregnation method was used for copper and zirconium modification of the surface of Aeroxide P25 TiO2 particles. Simultaneous loading of both metals on the surface of P25 leads to an increased specific surface area of the obtained material despite negative Cu influence. The tendency of stabilization and agglomerate size rising with the time for Cu and Zr-modified catalysts were traced by dynamic light scattering (DLS) measurements. The observed optical characteristics suggest that Cu compensated the broadening of band gap caused by Zr loading. Crystal structure of obtained photocatalysts was explored by XRD; morphological data and particle size were obtained by SEM. EDX was used for Zr and Cu content determination. Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analytical techniques were used to investigate the local Cu neighbourhood in the samples and to identify copper coordination and valence state of copper species in the synthesized nanocomposites.

Enhancement of TiO₂ NPs Activity by Fe₃O₄ Nano-Seeds for Removal of Organic Pollutants in Water.

The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses, the crystallinity of TiO2 nanoparticles (NPs) seems to be affected by Fe3O4, acting as nano-seeds to improve the tetragonal TiO2 anatase structure with respect to the amorphous one. Photocatalytic activity data, i.e., the degradation of methylene blue and the Ofloxacin fluoroquinolone emerging pollutant, give evidence that the increased crystalline structure of the NPs, even if correlated to a reduced surface to mass ratio (with respect to commercial TiO2 NPs), enhances the performance of this type of catalyst. The achievement of a relatively well-defined crystal structure at low temperatures (Tmax = 150 °C), preventing the sintering of the TiO2 NPs and, thus, preserving the high density of active sites, seems to be the keystone to understand the obtained results.

Enhanced photocatalytic activity of TiO2 nanoparticles using SnS2/RGO hybrid as co-catalyst: DFT study and photocatalytic mechanism

Graphene-semiconductor nanocomposites, considered as one of the most promising noblemetal-free photocatalysts, have shown remarkable performance and drawn significant attention in the field of photocatalytic reaction using solar energy, due to the excellent physicochemical properties of graphene. Here, a facile and novel method called liquid-exfoliation and solvethermal method was used for preparing TiO2/SnS2/RGO nanocomposite with intimate hetero-interface. Under visible-light irradiation, the TiO2/SnS2/RGO nanocomposite showed high photoactivity for the degradation of Rhodamine B (RhB). The positive synergistic effect is emerged between these layered SnS2 and RGO components, which contributes to the enhanced photoactivity of TiO2 nano-particles through reducing the recombination of photogenerated electron/hole pairs, enhancing the rate of electron-transfer and providing more reaction active sites for the degradation of dye molecules. The coupling formation of TiO2, SnS2 and RGO at the interface of composite photocatalyst was investigated by density functional theory (DFT) method in a molecular cluster level and the calculations results showed that the firm structures could be formed at the interfaces of TiO2 nanoparticles and SnS2/RGO. and Active component analysis showed that the synergy of various components containing ·O2−, e−, OH was predicted to determine the degradation process. The photocatalytic mechanism was also discussed and Z-scheme electron-transfer was predicted as the charge-transfer type of TiO2/SnS2 on RGO.

Does photocatalytic activity of TiO2 nanoparticles correspond to photo-cytotoxicity? Cellular uptake of TiO2 nanoparticles is important in their photo-cytotoxicity

Titanium dioxide (TiO2) nanoparticles are important industrial nano-objects with wide applications, including as photocatalysts and sunscreen components. Recently, the phototoxicity of TiO2 nanoparticles has been a concern. However, phototoxicity caused by photocatalytic activity may differ between anatase and rutile nanoparticles. In the present study, we compared the phototoxicity of anatase and rutile nanoparticles. Human keratinocyte HaCaT cells were treated with stable TiO2 nanoparticle suspensions. Without UVA irradiation, TiO2 nanoparticles did not affect mitochondrial activity or cell membranes. However, exposure to rutile nanoparticle suspensions inhibited cell growth and induced HO-1 gene expression without UVA irradiation. These effects may be explained by the hydrophobic surface of rutile nanoparticles. Next, TiO2-exposed cells were irradiated with UVA for 4 h and effects of TiO2 nanoparticles on cells were examined. The rutile nanoparticles did not show any cellular effects after UVA irradiation. However, the anatase nanoparticles caused strong phototoxicity. Decreased mitochondrial activity, cell membrane damage and the induction of oxidative stress were observed in the cells exposed to anatase nanoparticles with UVA irradiation. Cellular uptake of the nanoparticles was observed in both anatase- and rutile-exposed cells. These results suggest that internalized anatase nanoparticles are important for phototoxicity. Additionally, the exposure of a 3D skin model to TiO2 nanoparticles did not result in significant toxicity. In conclusion, rutile nanoparticles used in sunscreen did not exhibit phototoxic activity. Despite the strong phototoxic activity of anatase nanoparticles in cell cultures, they demonstrated no phototoxicity using a 3D skin model.

Effect of Cu doping on TiO2 nanoparticles and its photocatalytic activity under visible light

This work studies the effect of Cu doping on structural, morphological, optical, dielectric and photocatalytic activity of TiO2 nanoparticles. Pure and Cu doped TiO2 nanoparticles were synthesized using sol–gel technique. The powder XRD pattern confirmed that all the samples were polycrystalline of anatase phase and increasing doping concentration reduces average crystallite size. The morphology and particle size were identified using FESEM images. The band gap energy was found to be decreased for increasing concentration of Cu in the reflectance spectrum. The rate of recombination and transition of photo excited electron–hole pairs in the synthesized nanoparticles were recognized by photoluminescence spectrum. A strong frequency dependence of dielectric constants (e′ and e″), dielectric loss (tan δ) and ac conductivity (σac) were observed for different dopant levels in the frequency range 10–10 MHz at room temperature. The photocatalytic activity of pure and Cu doped TiO2 nanoparticles were investigated against degradation of reactive red-198 under visible light and the results were compared with commercial TiO2.

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.

Effects of titanium dioxide nanoparticles on intestinal commensal bacteria

Nanomaterials and nanotechnology have great potential in the biological and biomedical field. Recent studies reveal that many nanomaterials possess antibacterial activities. While most of these studies focus on the ability of nanomaterials to inhibit the growth of pathogenic bacteria in vitro, few of them test the effects of nanomaterials on intestinal commensal bacteria. Here, we report that TiO2 nanoparticles (10, 50 and 100 nm in size) can inhibit the growth of Drosophila intestinal commensal bacteria in vitro. This activity depends on the dosage or size, but is independent of the photocatalytic activity of TiO2 nanoparticles. Surprisingly, dietary TiO2 nanoparticles of the same dosage fail to display similar effects in Drosophila larvae or adults. These flies show a normal amount of intestinal commensal bacteria, as well as a normal developmental cycle, energy store, and locomotor activity. These results imply that the antibacterial effect of TiO2 nanoparticles differs in vitro and in vivo.

Synthesis and photocatalytic activity of TiO2 nanoparticles prepared by sol–gel method

TiO2 nanoparticles were synthesized via sol–gel method by using TiCl4 ethanol solution as precursor. The effects of gelatinization time and calcination temperature were determined. X-ray diffraction measurements showed that TiO2 nanoparticles were polycrystalline with anatase phase and transform to rutile phase at high temperatures. The effects of gelatinization time and calcination temperature were examined using atomic force microscopy, field emission scanning electron microscopy, and photoluminescence spectra. Particle size increased from 58 to 89 nm when gelatinization time was increased from 1 to 5 days. Moreover, particle size increased from 58 to 111 nm when calcination temperature was increased from 500 to 900 °C. Photoluminescence intensity decreased when gelatinization time and calcination temperature increased. Photocatalytic properties of TiO2 nanoparticles were evaluated by photocatalytic degradation of methylene blue (MB) in water under UV light irradiation. The outcomes indicated that TiO2 nanoparticles exhibited efficient photocatalytic activity of up to 68 % after 180 min as shown by the degradation of MB aqueous solution.

Tuning photo-catalytic activities of TiO2 nanoparticles using dimethacrylate resins

ObjectiveThe unique photo-catalytic activities (PCAs) of titanium dioxide nanoparticles (TiO2 NPs) made them attractive in many potential applications in medical devices. The objective of this study is to optimize the benefits of PCAs of TiO2 NPs through varying chemical structures of dimethacrylate resins. MethodsTiO2 NPs were functionalized to improve the PCAs and bonding to the resins. The PCAs of TiO2 NPs were evaluated using electron paramagnetic resonance (EPR) and UV–vis spectroscopy to determine the amount of the radicals generated and the energy required for their production, respectively. The beneficial effects of the radicals were assessed through: (1) the improvement of degree of vinyl conversion (DC) and (2) modification of resin hydrophilicity. One-way ANOVA with a 95% confidence interval was used to indicate the significant differences between the experimental groups. ResultsEPR and UV–vis results clearly showed that the functionalization of TiO2 NPs enhanced PCAs in terms of generating radicals under visible light irradiation. The presence of hydroxyl and carboxylic acid functionalities played an important role in DC enhancement and hydrophilicity modification. The DC could be increased up to 22% by adding only 0.1wt% TiO2 NPs. Viscosity of the resins had minimal or no role in DC improvement through TiO2 NPs. In resins with abundant hydroxyl groups, radicals were more effective in making the resin more hydrophilic. SignificanceKnowledge learned from this study will help formulating nano-composites with optimized use of TiO2 PCAs as co-initiators for photo-polymerization, additives for making super-hydrophilic materials and/or antibacterial agents.

Improved Photodegradation of Organic Contaminants Using Nano-TiO2 and TiO2 -SiO2 Deposited on Portland Cement Concrete Blocks.

The photocatalytic activity of TiO2 nanoparticles (nano-TiO2 ) and its hybrid with SiO2 (nano-TiO2 -SiO2 ) for degradation of some organic dyes on cementitious materials was studied in this work. Nanohybrid photocatalysts were prepared using an inorganic sol-gel precursor and then characterized using XRD, SEM and UV-Vis. The grain sizes were estimated by Scherrer's equationto be around 10nm. Then, a thin layer was applied to Portland cement concrete (PCC) blocks by dipping them into nano-TiO2 and nano-TiO2 -SiO2 solution. The efficiency of coated PCC blocks for the photocatalytic decomposition of two dyes, Malachite Green oxalate (MG) and Methylene Blue (MB), was examined under UV and visible irradiation and then monitored by the chemical oxygen demand tests. The results showed that more than 80% and 92% of MG and MB were decomposed under UV-Vis irradiation using blocks coated with nano-TiO2 -SiO2 . TiO2 /PCC and TiO2 -SiO2 /PCC blocks showed a significant ability to oxidize dyes under visible and UV lights and TiO2 -SiO2 /PCC blocks require less time for dye degradation. Based on these results, coated blocks have increased photocatalytic activity which can make them commercially accessible photocatalysts.

Enhanced charge carrier efficiency and solar light-induced photocatalytic activity of TiO2 nanoparticles through doping of silver nanoclusters and C–N–S nonmetals

C–N–S-tridoped TiO2 nanoparticles is synthesized via sol–gel method using cysteine as nonmetals source. Moreover, to suppress recombination of photogenerated charge carriers, silver nanoclusters are deposited over C–N–S-tridoped TiO2 via photodeposition technique and the catalyst Ag@C,N,S–TiO2 is developed. The prepared catalysts are characterized by XRD, SEM-EDAX, TEM, XPS, IR, Raman, UV–vis DRS, and N2 adsorption–desorption isotherms. Our findings show that Ag@C,N,S–TiO2 catalyst has an excellent and outstanding photocatalytic performance compared to that of pure TiO2 and commercial TiO2 P25 which the reason is attributed to improved visible-light harvesting, enhanced organic pollutant adsorption and increased photo-efficiency in separation of the charge carriers.

Photocatalytical activity of amorphous hydrogenated TiO2 obtained by pulsed laser ablation in liquid

This work focuses on the photo-catalytic activity of TiO2 nanoparticles produced by an alternative, industrially compatible and environmentally friendly technique such as laser ablation in liquids. Amorphous and highly hydroxylated TiO2 nanoparticles were synthesized by using the first harmonic of a Nd:Yag laser. Despite their amorphous phase, the nanoparticles showed a photocatalytic activity comparable to that of crystalline TiO2 in the degradation of Methylene Blue dye. This unexpected high rate is discussed taking into account the amount of hydroxyl groups and the presence of amorphous phase. Furthermore, a possible mechanism to achieve this high activity is pointed out.