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The hard agglomeration of bismuth silicate prepared by sol–gel method is the main reason to hinder its modification, photocatalytic performance and application. In order to better improve the photocatalytic performance of photocatalysts, polystyrene (PS) spheres modified Bi12SiO20–Bi2O2SiO3 composites (PBSO) and silver-loaded PS spheres modified BSO composites (Ag-PBSO) are prepared by PS spheres and photoreduction method. The crystal phase, morphology and optical properties of the catalysts were characterized by XRD, SEM and UV–Vis DRS, respectively. The visible light degradation activity of the photocatalysts is analyzed via ultraviolet-visible spectrophotometer. The results show that the Ag-PBSO photocatalyst can degrade more than 97% of the pollutants within 75 min. This is attributed to the synergy of heterojunction, specific surface area and SPR effect. Among them, after the introduction of PS template, the structure becomes loose and the specific surface area increases. This greatly increases the contact area of the catalyst with pollutants, providing a more robust loading environment for the subsequent Ag. In addition, the SPR effect possessed by Ag can synergize with the large specific surface area to accelerate electron transfer between heterojunctions. This method provides a new idea for the degradation of organic pollutants in the environment. [ABSTRACT FROM AUTHOR]

A TiO2-based ternary oxide was synthesized as a visible-light photocatalyst (TiO2/ZrTiO4/SiO2, SZT) by introducing SiO2–ZrO2 into TiO2 through sol–gel method. The related material compositions and microstructures were characterized, and the optical and photochemical performances were evaluated and compared with pure anatase TiO2. By introducing SiO2–ZrO2, the grain size of TiO2 was reduced from 29.9 nm in the pure anatase phase to 11.5 nm in SZT, accompanied by the formation of ZrTiO4. Moreover, the synthesized SZT demonstrated greatly lowered photoluminescence intensity and electrochemical impedance, and significantly increased photocurrent. The new photocatalyst also exhibited superior adsorption and photocatalytic ability for RhB, and higher catalytic stability. The improved photodegradation performance was attributed to the enhanced charge transfer and charge carrier separation as a result of the refined grains, the formation of TiO2/ZrTiO4 heterojunction, and a higher amount of built-in oxygen vacancies. [ABSTRACT FROM AUTHOR]

Novel Bi12SiO20–Bi2SiO5 heterostructure photocatalysts were prepared by controlling the molar ratio of Bi/Si in the reactants via Pechini method. With the increasement of the molar ratio of Bi/Si, the samples tend to be well-crystallized Bi12SiO20 and the content of Bi2SiO5 decreases in composites. Experiments reveal that the heterojunction shows higher visible light photocatalytic activity than pure Bi12SiO20 and Bi2SiO5 due to an increase in light harvesting efficiency and an efficient electron–hole separation. And the heterostructure photocatalyst is stable in the photocatalytic reaction process. The influence of some trapping agents on the photodegradation of Rhodamine B was investigated, and h+ and ·O2− were verified to play more important roles than ·OH−. [ABSTRACT FROM AUTHOR]

BiSiO is a metastable phase compound and one of the important Bi-based Aurivillius phase oxide semiconductors. Pure BiSiO powders were synthesized successfully by Pechini sol-gel method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, thermal analyzer, FTIR spectrometer, Raman spectrometer, fluorescence spectrophotometer and UV/Vis/NIR spectrophotometer. The mechanism of the reaction process was studied. The structure, the optical and photocatalytic properties of pure samples were investigated. The results show that citric acid, polyethylene glycol, solvents and calcination temperature have important effects on the reaction, and pure BiSiO can be obtained at 650 °C for 1 h. The as-prepared BiSiO has a typical Aurivillius-like structure and its bang gap energy is 3.5 eV. The results of degradation of Rhodamine B reveal that pure BiSiO powders prepared by Pechini sol-gel method possess a synergistic effect of adsorption and photocatalysis, which indicates that the BiSiO powders can be used as an efficient material for wastewater treatment. [ABSTRACT FROM AUTHOR]

Using Bi(NO)·5HO and Si(OCH) as the starting materials, citric acid and polyethylene glycol (PEG)-6000 as the complexing agents, pure BiSiO powders with good photocatalytic activity were first prepared at low temperature via Pechini sol-gel method. The effect of calcination temperature on the preparation of pure phase as well as the photocatalytic properties was investigated. The thermal analysis and X-ray diffraction results showed that the crystallization temperature of BiSiO is about 400 °C and pure sample can be obtained at 550 °C. The infrared spectra indicated the pure BiSiO samples have an Aurivillius-like structure. Furthermore, the as-prepared BiSiO exhibited efficient photocatalytic activity in the decomposition of Rhodamine B due to a synergistic effect of adsorption and photocatalysis. [ABSTRACT FROM AUTHOR]

Metastable Bi2SiO5phase powders were synthesized successfully by Pechini sol-gel method using a simple starting hydro-alcoholic solution consisting of Bi(NO3)3 · 5H2O, TEOS, citric acid, and PEG-6000. The effects of Bi/Si molar ratio, citric acid, and PEG-6000 on the properties of pure Bi2SiO5powders were investigated. The crystalline phase and fluorescence properties were characterized. The process of Pechini sol-gel method and the effect of purity on fluorescence properties were studied in this paper. X-ray diffraction results illustrate that single phase of Bi2SiO5can be obtained at 650°C for 1 h. Furthermore, the maximum fluorescence emission wavelength of the powders is located at 355 nm, which represents the band gap of Bi2SiO5powders is 3.49 eV. [ABSTRACT FROM PUBLISHER]

• The homogeneous double-layer TZS powders with multi-heterojunction structure was prepared by Pechini sol–gel method. • The inner and outer TZS layers form a homogenous junction with excellent compatibility. • The structure of multiple heterojunctions between two layers makes the transfer between electrons and holes more efficient. Traditional heterojunctions are usually constructed with different material systems, resulting in weaker interfacial effects in the catalytic system. In order to solve this problem, we use a simple sol–gel method to construct a homogeneous double-layer TiO 2 -ZrO 2 -SiO 2 photocatalyst with multi-heterojunction (d -TZS), which can effectively improve the photocatalytic property. By investigating the influence of various factors on the photocatalytic performance, the degradation rate of Rh B by d -TZS can reach about 99.6 % within 40 min of photoreaction, and Rh B almost completely degraded within 60 min. This is attributed to three aspects of homogeneity, multiple heterojunctions and oxygen vacancies. Firstly, the inner and outer layers are homogeneous with excellent compatibility, and the outer layer has strong adsorption. Secondly, the multi-heterostructure which forms between the inner-layer multi-heterojunction and the outer layer can separate the photogenerated electrons in each layer to a certain extent. Finally, the oxygen vacancies formed after the bonding of the outer and inner layers can further enhance the mobility of photogenerated carriers. This idea provides new methods for the study of homogenous multiple heterojunctions with high visible light degradation rate. [ABSTRACT FROM AUTHOR]

In this work, barium titanate (BaTiO3) powders were synthesized via two Pechini sol-gel processes using citric acid and polyethylene glycol-6000 as chelating agents. Attempts had been made to understand the thermal behavior of the polymeric intermediates with the help of thermogravimetry-differential scanning calorimetry (TG-DTG-DSC) thermograms. The structural coordination of as-prepared polymeric intermediates was investigated by Fourier transform infrared (FTIR) analysis. The phase and structure of the powders calcined at different temperatures were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Preparation of the polymeric precursors can influence the mechanism of the BaTiO3 synthesis. The formed intermediate phase BaCO3 appears in gel-2 system, and BaCO3 phase does not disappear at 720°C. The formed intermediate phases of gel-1 differ from that of gel-2. The intermediate phases of gel-1 are anatase TiO2 and rutile TiO2, and the intermediate phase BaCO3 doesn't appear in gel-1system. When the powders are calcined at 720°C, the particles of gel-1 system are agglomerated spheres with about 25 nm, but the particles of gel-2 system have varied shapes. [ABSTRACT FROM AUTHOR]

Synergy is essential to maximize the photocatalytic performance of the catalyst, which makes the preparation of photocatalytic materials with the synergistic effect of adsorption and catalysis become an attractive research direction. Therefore, we have prepared TiO 2 –ZrO 2 –SiO 2 nano-powders by simple Pechini sol-gel method, which can effectively improve the synergistic effect of adsorption and degradation of photocatalytic materials. The results demonstrate that TiO 2 –ZrO 2 –SiO 2 possesses excellent photocatalytic performance and adsorption ability. And it can be deduced that in the TiO 2 –ZrO 2 –SiO 2 system, SiO 2 is as for adsorbent, and TiO 2 and ZrO 2 act synergistically as a photocatalyst. The enhanced photocatalytic ability of TiO 2 –ZrO 2 –SiO 2 is attributed to the acceleration of mass transfer by adsorption process, narrowed bandgap (Eg = 2.9 eV) and effective charge separation rate resulting from the formation of Ti–O–Zr. This work also studied the synergy effect between adsorption and photocatalytic properties in TiO 2 –ZrO 2 –SiO 2 , and synergy factor β is used to evaluate the synergistic effect. Moreover β > 1 in first 30 min of visible light irradiation demonstrates that the remarkable synergistic effect exists in TiO 2 –ZrO 2 –SiO 2 compound system. • TiO 2 –ZrO 2 –SiO 2 photocatalyst with both adsorption and photocatalytic properties was successfully prepared. • β (synergy factor) which explains the adsorption-photocatalytic synergistic effect of TiO 2 –ZrO 2 –SiO 2 system is remarkable. • The adsorption-photocatalytic performance can be regenerated. [ABSTRACT FROM AUTHOR]

ZrB 2 –ZrC–SiC nanopowders with uniform phase distribution were prepared from cost-effective ZrOCl 2 ·8H 2 O by a simple sol-gel method. The synthesis route, ceramization mechanism and morphology evolution of the nanopowders were investigated. ZrB 2 –ZrC–SiC ceramic precursor can be successfully obtained through hydrolysis and condensation reactions between the raw materials. Pyrolysis of the precursor was completed at 650 °C, and it produced ZrO 2 , SiO 2 , B 2 O 3 and amorphous carbon with a yield of 39% at 1300 °C. By heat-treated at 1500 °C for 2 h, highly crystallized ZrB 2 –ZrC–SiC ceramics with narrow size distribution were obtained. With the holding time of 2 h, both the crystal size and the particle size can be refined. Further prolonging the holding time can lead to serious particles coarsening. Studies on the microstructure evolution of the generated carbon during the ceramic conversion demonstrates the negative effect of the ceramic formation on the structure order improvement of the carbon, due to the large amount of defects generated in it by the boro/carbothermal reduction reactions. [ABSTRACT FROM AUTHOR]

• The BTO@TPU films were synthesized via electrospinning route. • The films are stretchable, flexible, waterproof and transparent. • The films can be used in the field of dynamic and multimodal anti-counterfeiting. [Display omitted] Developing novel and practical anti-counterfeiting materials has always been at the forefront of protecting information security. However, achieving the multimodal anti-counterfeiting remains a huge challenge. In this work, we synthesized a series of Bi 2 Ti 4 O 11 :xYb3+, 0.02Er3+ (x = 0.1, 0.2, 0.4) nanoparticles by a sol-gel method and realized the upconverting red, yellow and green luminescence under near infrared (NIR) excitation. To confirm the practicality of the materials, we designed the novel anti-counterfeiting flexible films based on thermoplastic polyurethane (TPU) via electrospinning route. The composite film (BTO@TPU) is transparent, elastic, stretchable, waterproof and environmentally friendly. In addition, no trace of light can be observed under daylight, indicating the films have excellent concealment. Nevertheless, any patterns you desired can be written by a 980 nm laser pointer and the patterns with red, yellow and green luminescence can be "read" by the streamer camera of smart phone. The proof-of-concept experiment provided the novel and flexible BTO@TPU films keen insights in the application of anti-counterfeiting. This work will supply an arena to boost the application of upconverting materials in the field of dynamic and multimodal anti-counterfeiting. [ABSTRACT FROM AUTHOR]