Ultrasonic assisted synthesis of TiO2–reduced graphene oxide nanocomposites with superior photovoltaic and photocatalytic activities

In this work, TiO₂–reduced graphene oxide (RGO) nanocomposites were successfully produced by an ultrasonication-assisted reduction process. The reduction of graphene oxide (GO) and the formation TiO₂ crystals occurred simultaneously. The synthesized nanocomposite was characterized by SEM, EDX, Raman spectroscopy, FTIR, XRD, XPS, UV–vis spectroscopy, photoluminescence spectrometer and electrochemical impedance spectroscopy. As a result of the introduction of RGO, the light absorption of octahedral TiO₂ was markedly improved. The photocatalytic results revealed that weight percent of RGO has substantial influence on degradation of Rhodamine B under visible light irradiation. The enhancement of the photocatalytic activity can be attributed to the enhancement of the visible-light irradiation harvesting and efficiently separation of the photogenerated charge carriers. Meanwhile, upon the RGO loading, the photoelectric conversion efficiency of TiO₂–RGO nanocomposite modified electrode was also highly improved.     

Metal–organic frameworks-derived TiO2 for photocatalytic degradation of tetracycline hydrochloride

This work will change the common understanding that C doping of MIL-125(Ti)-derived TiO₂ is a key factor in improving its photocatalytic performance, and it can also help to understand the internal relationship between the structure and performance of photocatalytic materials deeply. It provides a simple synthesis method for the wider application of TiO₂ in the field of photocatalysis. Compared with previous studies, this article uses the titanium-based metal-organic framework MIL-125(Ti) to prepare the semiconductor photocatalyst M-TiO₂ by calcination in the air at a lower temperature and shorter time. After analyzing the M-TiO₂ prepared in the experiment, the results can be received that there is no obvious agglomeration and the morphology is almost unchanged, as the frame structure does not collapse at the same time. As a result, the advantages of the large specific surface area and porousness of metal–organic frameworks (MOF) as precursor derivatives are preserved. As for the changes in the micro-morphology, pore structure, and specific surface area of M-TiO₂ compared with the precursor, they are investigated seriatim. The results show that, compared with commercial TiO₂-P25, the performance of M-TiO₂ photocatalytic degradation of tetracycline hydrochloride is 5.7 times that of the precursor metal-organic framework MIL-125(Ti) and 2.2 times that of P25, and has good cycle stability.     

Novel TiO₂-Pt@SiO₂ nanocomposites with high photocatalytic activity

This article reports a facile and controllable two-step method to construct TiO(2)-Pt@SiO(2) nanocomposites. TiO(2) nanoparticles (NPs), with small size and high surface energy, were synthesized by a solvothermal reaction process. The TiO(2)-Pt@SiO(2) nanocomposites were fabricated by a reverse micro-emulsion method. SiO(2) shell coated NPs were adopted for further photocatalytic reaction. Because of their small size and high surface energy, TiO(2)@SiO(2) and TiO(2)-Pt@SiO(2) nanocomposites show higher photocatalytic activity than commercial Degussa P25. Compared with TiO(2)@SiO(2), TiO(2)-Pt@SiO(2)nanocomposites have improved photocatalytic activity due to the Pt induced spatial separation of electrons and holes. The silica shells not only maintain the structure of the nanocomposites but also prevent their aggregation during the photocatalytic reactions, which is highly important for the good durability of the photocatalyst. This strategy is simple, albeit efficient, and can be extended to the synthesis of other composites of noble metals. It has opened a new window for the construction of hetero-nanocomposites with high activity and durability, which would serve as excellent models in catalytic systems of both theoretical and practical interest.     

Antibacterial and photocatalytic active transparent TiO2 crystallized CaO–BaO–B2O3–Al2O3–TiO2–ZnO glass nanocomposites

Transparent TiO₂ crystallized 5CaO–10BaO–65B₂O₃–Al₂O₃–20TiO₂–10ZnO (CBBATZ) glass nanocomposites were fabricated using melt-quenching technique followed by specific heat treatments. As-quenched glass samples were provided three different heat treatments at 630°C for 3, 5, and 10 hours in order to obtain different amounts of TiO₂ nanocrystals in the glass. The presence of rutile phase of TiO₂ nanocrystals in glass was confirmed by X-ray diffraction. The glass nanocomposite heat treated for 10 hours showed a hydrophobic nature with contact angle of 90.90°. Contact angle decreased from 90.90 to 22.20°, when irradiated under ultraviolet (UV) radiation for 45 minutes. This photoinduced hydrophilicity showed a photocatalytic and self-cleaning properties of glass nanocomposite. During photocatalytic ink test, the maximum change in color of Resurin (Rz) ink and 60% degradation in absorbance of ink within 150 minutes under UV radiation were found for glass nanocomposite heat treated at 10 hours. Also, 78% degradation in absorbance of methylene blue dye (pollutant) within 180 minutes under UV irradiation was found for glass naocomposite heat-treated at 10 hours. Antibacterial performance of transparent glass nanocomposite against Escherichia coli was evaluated as well. More than 95% of the bacterial cells were degraded with glass nanocomposite heat-treated at 10 hours. CBBATZ glass nanocomposite found to impart the antibacterial effect through generation of reactive oxygen species (ROS) in aqueous medium. ROS species which was confirmed in the bacterial cell through intracellular ROS generation kit. During evaluation of mechanical properties using nanoindentation technique, the values of hardness and reduced modulus increased by ~26% and 10%, respectively, for glass nanocomposite heat-treated at 10 hours as compared to as-quenched glass.     

Unique photocatalytic oxidation reactivity and selectivity of TiO₂-graphene nanocomposites

Mesoporous TiO(2)-graphene nanocomposites are fabricated in high yield via two successive steps: (1) hydrothermal hydrolysis of Ti(SO(4))(2) in an acidic suspension of graphene oxide to gain TiO(2)-graphene oxide nanocomposites; (2) UV-assisted photocatalytic reduction of graphene oxide to get the TiO(2)-graphene nanocomposites. The anatase TiO(2) nanocrystals with a crystallite size of 10-20 nm are densely packed and supported on meshy graphene sheets with close interfacial contacts, which is confirmed by transmission electron microscopy (TEM) together with Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Although a low graphene loading (0-2 wt%) slightly influences the textural properties (including the crystallite size, specific surface areas, and pore volume etc.), the incorporation of graphene in TiO(2)-graphene nanocomposites greatly increases the adsorption capacity towards azo dyes such as MO and MB, which is possibly associated with their unique surface properties. Significantly, the incorporated graphene exerts combined effects on the adsorption and charge transfer dynamics in TiO(2)-graphene nanocomposites, which together endow them with good photocatalytic reactivity and tunable photocatalytic selectivity in decomposing MO and MB in aqueous solution.     

Sol-gel derived TiO2–carbon composites with adsorption-enhanced photocatalytic activity and gas sensing performance

We report the in-situ sol-gel synthesis of TiO₂–carbon composites (black TiO₂) by carbonization of the gel. With ultra-fine anatase TiO₂ nanoparticles dispersed homogeneously on amorphous carbon, the as-prepared black TiO₂ possesses a BET surface area as high as 145.4 m²/g. Due to the synergy effect of adsorption and photocatalysis, the as-synthesized black TiO₂ is demonstrated to exhibit enhanced photocatalytic activity. The gas sensing properties of black TiO₂ have been rigorously investigated with and without UV illumination at room temperature. It is found that increased adsorption of gas molecules can effectively improve the sensor response. The mechanism of the adsorption-enhanced gas sensing performance of black TiO₂ has been detailedly discussed.     

Synthesis and characterization of novel PbS–graphene/TiO2 composite with enhanced photocatalytic activity

In this study novel material PbS–graphene/TiO₂ composites were prepared by sol–gel method. The “as-prepared” composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS) and Raman spectroscopic analysis. The photocatalytic activities were investigated by the degradation of methylene blue (MB) as a standard dye. We observed that coupling of PbS with TiO₂ extends the photoresponse to visible region. This revealed that the excellent photoinduced charge separation abilities and transport properties of graphene make these hybrids as potential candidates for developing high-performance next-generation devices.     

Palygorskite–TiO2 nanocomposites: Part 1. Synthesis and characterization

In this paper we describe the synthesis and characterization of small-sized TiO₂ particles supported on palygorskite (Pal) with Pal to TiO₂ mass ratios of 10:90, 20:80, 30:70, 40:60 and 50:50. The above Pal–TiO₂ nanocomposites were prepared by deposition of anatase form of TiO₂ on the Pal surfaces using a sol-gel method with titanium isopropoxide as a precursor under hydrothermal treatment at 180 °C. Phase composition, particle morphology and physical properties of these samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflection using Fourier transform infrared spectroscopy (ATR-FTIR) and N₂ surface area analysis by BET. In order to investigate the absorption properties of the catalysts, UV–vis reflection spectra were measured. Preparation of Pal–TiO₂ nanocomposites led to good dispersion of TiO₂ on Pal surfaces. By increasing the amount of TiO₂, the deposited 3–10 nm TiO₂ particles were found to be aggregated on the surfaces of the Pal particles. However, by decreasing the amount of TiO₂, the Pal particles were found to be aggregated. After treating with TiO₂, Pal samples largely showed interparticle mesopores of about 5.8 nm. It was observed that the commercial titania P25 showed no absorption in visible light region. In contrast, the prepared Pal–TiO₂ samples showed gray color and absorption in visible light region.     

Synthesis,characterization and photocatalytic activity of CdS–montmorillonite nanocomposites

Nanocomposites based on cadmium sulfide (CdS) and Na-montmorillonite (Na⁺-Mt) were prepared by a hydrothermal method using Cd[NH₂CSNH₂]SO₄ complex as precursor of CdS which was derived from cadmium sulfate and thiourea. These nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and X-fluorescence (XF). The nanocomposites consist of nanosized CdS pillars, which tend to increase in size as the amount of complex precursor increases. The CdS crystals have a hexagonal symmetry. The photocatalytic activity of the obtained CdS–Mt nanocomposites is improved significantly compared to that of the Mt and pure CdS. The resulting CdS–Mt nanocomposites could degrade methylene blue and rhodamine 6G under near UV–visible irradiation.     

Spectrophotometric evaluation of the photocatalytic degradation of formaldehyde by Fe2O3–TiO2 nano hybrid

Photocatalytic capabilities of sol–gel synthesized Fe₂O₃–TiO₂ nano hybrid was investigated in degradation of formaldehyde in presence of ultra violet and visible irradiation. The reaction stream was evaluated by UV–vis spectrophotometry at 330–500 nm spectral region, using Fluoral-P (4-amino-3-penten-2-one) as a complexing agent. Obtained results confirmed the effective role of Fe₂O₃ phase in nano hybrid for degradation of formaldehyde according to Baeyer–Villiger reaction. On the other hand TiO₂ would play the role of photocatalyst in presence of UV ray. Nano hybrid assisted process was monitored by spectrophotometry, utilizing multivariate curve resolution chemometric technique.     

Fabrication of superhydrophilic self-cleaning SiO2–TiO2 coating and its photocatalytic performance

Generally, superhydrophilic self-cleaning coatings are prepared from semiconductors with photocatalytic properties. Organic pollutants attached to the coating surface can be degraded by its photocatalytic performance realizing a self-cleaning goal. Herein, SiO₂–TiO₂ composite particles were fabricated by the hydrolysis and precipitation of TiOSO₄, and SiO₂ microspheres were chosen as carriers, which are inexpensive and environmentally friendly. Then, superhydrophilic self-cleaning SiO₂–TiO₂ coatings were fabricated by spraying the composites on the surfaces of substrates. The morphology, structure and self-cleaning performance of the SiO₂–TiO₂ coating were characterized and tested. The results revealed that nano-TiO₂ was loaded on the surfaces of SiO₂ microspheres uniformly forming a hierarchical micro/nanostructure. The SiO₂–TiO₂ composite particles exhibited excellent photocatalytic degradation performance, and the degradation rate of methyl orange (10 ppm) was more than 98% under UV irradiation for 40 min. Furthermore, the coating prepared with the SiO₂–TiO₂ composite particles exhibited superhydrophilicity. A water droplet spreads completely on the coating surface in 0.35 s, and the contact angle reaches 0°. In addition, rhodamine B (RhB) and methylene blue (MB) on the coating surface can be degraded efficiently under sunlight irradiation. The SiO₂–TiO₂ composite particles can be sprayed directly on the surfaces of concrete, brick, wood, and glass slides. Therefore, the particles showed good adaptability to different substrates. The superhydrophilic property was due to the hydrophilicity of SiO₂ and TiO₂, the hierarchical micro/nanostructure of the SiO₂–TiO₂ composites, and the photoinduced superhydrophilicity of TiO₂. The above experimental results show that the as-prepared superhydrophilic self-cleaning SiO₂–TiO₂ coating has a large application potential.     

AgBr@Ag/TiO2 core–shell composite with excellent visible light photocatalytic activity and hydrothermal stability

AgBr@Ag/TiO₂ core–shell photocatalysts were fabricated by a facile green route. TiO₂ was uniformly coated on the surface of cubic AgBr, making AgBr@Ag/TiO₂ core–shell photocatalyst show excellent hydrothermal stability. Beneficial from that Ag nanoparticles and AgBr can respond to visible light and core–shell structure can effectively separate the photogenerated electrons and holes, AgBr@Ag/TiO₂ core–shell composites exhibited outstanding visible light photocatalytic activity for the degradation of acid orange 7. The activity of AgBr@Ag/TiO₂ is related to the thickness of TiO₂ shell, and the optimal shell thickness for obtaining the highest activity is 10 nm.     

Preparation of novel Ni/Co co-doping Fe3O4/TiO2 core–shell nanocomposites and their use in effective photocatalytic degradation of Amlodipine drug.

Ni/Co co-doping Fe₃O₄/TiO₂ magnetic core–shell nanocomposites (wt% varied amount of dopants) have been prepared by sol-gel method at low temperature. X-ray diffraction, Fourier transform infrared, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma optical emission spectroscopy and vibrating sample magnetometry studies have been made to investigate the crystalline structure, morphology and magnetic properties of these composites. The prepared Ni/Co co-doping Fe₃O₄/TiO₂ nanocomposites exhibit high degree of crystallinity and suitable magnetic properties at room temperature. Their use has been made in effective photocatalytic degradation of Amlodipine a pharmaceutical contaminant under UV light irradiation at 365 nm. The results have shown that wt% amount of dopants, calcination time, calcination temperature and pH of the Amlodipine aqueous solution are important factors in degradation efficiency of Amlodipine. The optimal weight ratios of Ni and Co to Ti were 0.015%. The nanocomposites can be recovered from the aqueous system easily by using a magnet. Their photocatalytic degradation activity for Amlodipine drug remained 94.43% after five times of repetitive use.     

Synthesis and characterization of TiO2–Montmorillonite/Polythiophene-SDS nanocomposites: Application in the sonophotocatalytic degradation of rhodamine 6G

Titanium dioxide–montmorillonite/Polythiophene–sodium dodecyl sulphate (TiO₂–Mt/PTP–SDS) nanocomposites were synthesized via the in situ intercalative oxidative polymerization of thiophene (TP) in TiO₂–Mt clay and CHCl₃ solvent using anhydrous ferric chloride (FeCl₃) at ambient temperature for 24 h in the presence of anionic surfactant SDS at a ratio by mass of 20% of TP/TiO₂–Mt. The TiO₂–Mt was obtained by the modification of sodium montmorillonite (Na-Mt) with titanium isopropoxide (Ti (OPrⁱ) ₄) at 50 °C for 3 h. The products obtained were characterized using different techniques, such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray Fluorescence Analysis (XRF), X-ray diffraction (XRD), and Environmental Scanning Electron Microscopy (ESEM), which proved the successful intercalation of polythiophene in the TiO₂–MT in the presence of anionic surfactants. The degradation of rhodamine 6G (R6G) in aqueous solutions was investigated kinetically in the presence of catalysts under Sun-test simulator at 400 W/m², sonocatalysis at 500 kHz (30 W), and sonophotocatalysis. The findings revealed that the TiO₂–Mt/PTP20%-SDS catalyst exhibited good levels of photocatalytic, sonocatalytic, and sonophotocatalytic degradability for R6G. The synergistic effect between the two techniques was observed using TiO₂–Mt/PTP20%-SDS (w %) as a catalyst, and the kinetic results indicated that enhanced degradation rate constants were achieved particularly with sonophotocatalytic processes.     

UV-curable polyurethane acrylate–Ag/TiO2 nanocomposites with superior UV light antibacterial activity

Polyurethane acrylate (PUA)–Ag/TiO₂ nanocomposites were synthesized through in situ polymerization. The well-dispersed Ag/TiO₂ nanorods serve as photoinitiator. Meanwhile, the PUA–Ag/TiO₂ nanocomposite films exhibit superior activity toward the photocatalytic degradation of Escherichia coli under UV light. The excellent UV curing and antibacterial activities can be ascribed to the synergistic effect of Ag and TiO₂, which promotes the effective electron/hole separation and thus generates various reactive species. Thin films with these nanoparticles are more hydrophilic after UV illumination. And the antibacterial mechanism of the UV-curable PUA–Ag/TiO₂ nanocomposites was proposed.     

Preparation of cobalt coated TiO2 and WO3–TiO2 nanotube films via photo-assisted deposition with enhanced photocatalytic activity under visible light illumination

Highly ordered TiO₂ and WO₃–TiO₂ nanotubes were prepared by one-step electrochemical anodizing method and cobalt has been successfully deposited on these nanotubes by photo-assisted deposition process. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show an appearance of red shift relative to the unloaded samples. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of these novel visible-light-responsive photocatalysts. Results showed that the photocatalytic activity of bare WO₃–TiO₂ samples is higher than that with undoped TiO₂ sample. Compared with unmodified TiO₂ and WO₃–TiO₂, the Co/TiO₂ and Co/WO₃–TiO₂ samples exhibited enhanced photocatalytic activity in the degradation of methylene blue. Kinetic research showed that the reaction rate constant of Co/WO₃–TiO₂ is approximately 2.26 times higher than the apparent reaction rate constant of bare WO₃–TiO₂. This work provides an insight into designing and synthesizing new TiO₂–WO₃ nanotubes-based hybrid materials for effective visible light-activated photocatalysis. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity.     

Sol–gel reverse micelle preparation and characterization of N-doped TiO2: Efficient photocatalytic degradation of methylene blue in water under visible light

A series of N-substituted titanium (IV) 2-ethyl-1,3-hexanediolate Ti(C₃₂H₆₈O₈) precursor were synthesized by the sol–gel reverse micelle (SGRM) method. The ethylene diaminetetraacetic acid (Na₂EDTA) has been used as a source of nitrogen n species. The obtained solids were calcined at 500 ?C for 1 h to obtain photoactive phases. The effect of nitrogen content (N/Ti = 0.025; 0.03; 0.05 atomic ratios) is examined. The materials were characterized by XRD, BET, TG/DTA and UV–vis reflectance spectroscopy (DRS). Photocatalytic decolourisation of methylen blue (MB) in aqueous solution was carried out using nano, doped TiO₂. Experimental results revealed that N/Ti = 0.05 atomic ratio N-doped TiO₂ required shorter irradiation time for complete decolourisation of MB than pure nano TiO₂ and commercial (Degussa P-25) TiO₂.     

Promoting role of transition metal oxide on ZnTiO3–TiO2 nanocomposites for the photocatalytic activity under solar light irradiation

Transition metal oxide (Fe₂O₃, Co₃O₄ and CuO) loaded ZnTiO₃–TiO₂ nanocomposites were successfully prepared by solid state dispersion method. The structural, morphological and optical properties of samples were characterized by TGA/DTA, XRD, BET, FT-IR, DRS, PL, XPS and SEM techniques. The photocatalytic activity of samples was investigated by degradation of 4-chlorophenol in water under sunlight. The Fe₂O₃ loaded sample was found to exhibit much higher photocatalytic activity than the other composite powders. 7Fe₂O₃/ZnTi sample has the highest percentage of 4-chlorophenol degradation (100%) and highest reaction rate (1.27 mg L⁻¹ min⁻¹) was obtained in 45 min. The enhancement of photocatalytic activity for ZnTiO₃–TiO₂ sample with Fe₂O₃ addition may be attributed to its small particle size, the presence of more surface OH groups, lower band gap energy than other samples in this paper and the presence of more hexagonal ZnTiO₃ phase in the morphology.