Non-hydrolytic Sol-gel Method Research Articles

Photocatalytic Degradation of Paracetamol and Antibacterial Activity of La-Modified TiO2 Obtained by Non-Hydrolytic Sol–Gel Route

The current study aims to synthesize and analyze both pure and La-doped TiO2, and evaluate the photocatalytic and antibacterial activity of as-prepared samples. Doped and undoped samples were prepared by the non-hydrolytic sol–gel method from titanium(IV) chloride, benzyl alcohol, and lanthanum(III) nitrate followed by thermal treatment. Lanthanum content in synthesized samples was 0.4, 1, and 5 mol%. The resulting nanopowders’ structure and morphology were described using XRD, IR, and UV–Vis analysis. The average particle sizes of pure and doped TiO2 were about 6–15 nm and anatase was found to be a dominant crystalline phase in the samples. It was observed that particle sizes decreased on increasing La content. The photocatalytic activity of the pure and La-doped sol–gel powders was estimated in the decomposition of paracetamol in distilled water using ultraviolet light illumination. Doping with lanthanum ions has been shown to increase the photocatalytic properties on the degradation of paracetamol. Furthermore, the annealed catalysts (pure and La3+ doped) showed increased photocatalytic activity and degradation of the analgesic in comparison with non-annealed materials. In both cases, the highest photocatalytic efficiency is observed at the optimal La3+ (1 mol%) concentration. The antimicrobial activity of 1 mol% La/TiO2 was tested against a reference strain E. coli in the presence of ultraviolet light and in dark conditions. The number of viable bacterial cells was determined by a spread plate method, and kill curves were performed. The results showed that photoactivated 1 mol% La/TiO2 exhibited a strong bactericidal effect, and in concentration, 1 mg/mL efficiently killed bacteria at an initial cell density of about 105 colony forming units in 1 mL within 15 min.

Pressure field assisted non-hydrolytic sol-gel in-situ synthesis of novel seed-pulp-structured C@ZrSiO4 pigments

Novel pressure field assisted non-hydrolytic sol-gel method is developed for the in-situ synthesis of novel seed-pulp-structured C@ZrSiO4 pigments. The obtained pigments, which are composed of in-situ carbon derived from leaving organic groups as core and zircon as shell, were characterized via DSC-TG, XRD, FT-IR, Raman, XPS, SEM, TEM, UV–Vis, and automatic colorimeters. It was found that the pressure field promotes the non-hydrolytic sol-gel heterogeneous polycondensation reaction and the direct transformation of reaction groups into in-situ spherical carbon. Meanwhile, the in-situ spherical carbon was enclosed by heterogeneous condensation bonds wrap and formed a dense structure. The as-prepared pigments exhibited excellent color rendering performance (L* = 21.07, a* = 0.48, b* = 0.75) and thermal stability.

Copper, potassium promoted iron on metallosilicate and aluminum oxide supports synthesized via a non-hydrolytic sol-gel for Fischer-Tropsch

We developed a promoted iron based catalyst that converts 20% more CO to diesel than the unpromoted counterparts. The synthesis involves a non-hydrolytic sol-gel method (NHSG) and 0.04 g g−1 copper and 0.02 g g−1 potassium as promoters. The iron catalyst supports included cerium and zirconium metallosilicates and Catalox and Dispal commercial aluminum oxides from Sasol. At 325 ∘C and 20 bar, CO conversion over the Fe/Ce/SiO2-K,Cu, exceeded 85% while at the same conditions it was only 68% over the unpromoted catalyst. Fe/Zr/SiO2-K,Cu converted less CO than the cerium-silicate (75%) but the unpromoted zirconium-silicate only converted 43% of the CO. The conversion and selectivity of the Catalox was about the same as the cerium-silicate, while the Dispal performance was equivalent to the zirconium-silicate. This study also highlights the importance of support and promoters in FTS, demonstrates the potential of the NHSG method to synthesize promoted iron catalysts with various supports and lays the foundation for developing efficient and stable catalysts for converting syngas to hydrocarbons.

Non-hydrolytic sol-gel synthesis of BaTiO3 nano-powder: Effect of calcination temperature and modified titanium source on particles

In this study, BaTiO3 nanopowders were prepared by non-hydrolytic sol-gel (NHSG) method using barium acetate and tetrabutyl titanate (TBT) as precursors and acetylacetone (Hacac) as additive. The effects of acetylacetone modification and calcination temperature on nanoparticle size and crystalline phase were evaluated. The products were analysed by SEM, TEM, DSC/TG, FTIR, XRD, Raman. FTIR analysis showed the formation of Ba-O-Ti bond at the sol stage of the NHSG method. DSC/TG and XRD analyses showed that BaTiO3 was produced at 500 ℃. According to SEM/TEM, the particle size of the powder becomes larger as the temperature increases, meanwhile the addition of acetylacetone can make the final product particle size decrease. Raman analysis showed that BaTiO3 has the presence of tetragonal phase, so the crystalline phases of the product and impurities were analysed by XRD refinement, and the results showed that the relative content of tetragonal phase of BaTiO3 was linearly correlated with the calcination temperature.

Plasmonic effect on the emission intensity of Ce3+ ions doped zirconia-silicate glass

Ce3+:SiO2-ZrO2 samples doped with and without plasmonic nanoparticles of copper were prepared by the easy and economic non-hydrolytic sol–gel method. Structural, morphological, and optical studies were done on the samples after being dried at room temperature and annealed at 800 °C. Fourier transform infrared (FTIR) spectra confirms the formation of the host glass SiO2-ZrO2 from the asymmetric stretching of Si-O-Zr bond. Tetragonal ZrO2 and plasmonic copper nanoparticles formation was affirmed from the X-ray diffraction (XRD) spectra. Transmission electron microscopy (TEM) confirms the formation of plasmonic nanoparticles of copper. UV/Visible spectra show an absorption around 330 nm. The photoluminescence (PL) spectra show emission centered around 469 nm; an enhancement in the PL intensity occurred due to the localized surface plasmon resonance (LSPR) effect of the plasmonic nanoparticles of copper.

Color tunability studies of samarium ions/silver nanoparticles doped titanosilicate glass matrix

The current study aims at synthesizing a titanosilicate glass composite doped with rare earth/plasmonic nanoparticles using a cost effective and easier method of non-hydrolytic sol gel method. The rare earth employed is samarium ions while the plasmonic nanoparticle used is Silver. For densification samples were annealed at 800 0C and further characterized by FTIR, XRD, TEM. Matrix confirmation is done by FTIR spectroscopic studies which confirm the presence of Si-O-Si, Si-O, and Ti-O-Ti bonds. Both XRD and TEM analysis affirm the presence and morphology of Ag and TiO2 nanoparticles respectively. In the photoluminescence analysis the trivalent samarium ions show strong reddish-orange luminescence in the 550–670 nm range. The major peaks are obtained at 581 nm, 662 nm, 605 nm. Each of the spectra obtained show three prominent characteristic emission bands correlated to the transitions 4G5/2 to 6H5/2, corresponding to 581 nm, 4G5/2 to 6H7/2 corresponding to 605 nm, and 4G5/2 to 6H9/2 corresponding to 662 nm. We successfully plotted the CIE colorimetry diagram and it is observed that the effect of plasmonic nanoparticles can tune the relative emission intensity of rare earth ions in CIE colorimetry. Our study highlights the significance of incorporating the rare earth ions doping with plasmonic nanoparticles in the color tunability studies, exhibiting their broad applications in LED devices.

Preparation of HfSiO4 via Non-Hydrolytic Sol-Gel method at low temperatures

Hafnon (HfSiO4) can be applied in electronics, dielectric films, refractory materials, and many other critical application areas. To explore an efficient preparation process of HfSiO4, a novel non-hydrolytic sol-gel (NHSG) method was used to synthesize high-purity HfSiO4 in this study. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), thermogravimetric differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FT-IR), and infrared thermal imaging (ITI) were used to investigate the synthesis temperature and mechanism of HfSiO4 and the effects of process parameters on its synthesis efficiency. The results show that the prepared sols undergo a highly reactive non-hydrolytic polycondensation reaction at room temperature. High temperature reflux or long time aging step is not necessary to form the strong Hf-O-Si bonds. Furthermore, with the introduction of the mineralizer agent LiF, the synthesis temperature of HfSiO4 can be drastically reduced, and the HfSiO4 with high purity can be synthesized at low temperatures. A moderate molar ratio of silicon to hafnium (Si:Hf) and molar concentration of the solution contribute to improve the synthesis efficiency of HfSiO4, and the purity of HfSiO4 products can reach up to 98.12 %.

Low-temperature synthesis of ultrafine Cr,Mg-codoped Al2TiO5 nanocrystals as high-temperature green ceramic pigment

Tialite (Al2TiO5) is attracting as a high-temperature ceramic host matrix, but the decomposition of Al2TiO5 at 780–1280 °C is a serious obstacle for practical application. Herein we prepared successfully ultrafine Cr,Mg-codoped Al2TiO5 green ceramic pigment with the nanocrystal sizes less than 50 nm and high-temperature stability of up to 1200 °C via nonhydrolytic sol-gel (NHSG) method followed by heating treatment of 750 °C. The effects of Cr and Mg content on phase composition, crystal structure, thermal stability and color property were well investigated. The optimum Cr,Mg-codoped Al2TiO5 pigment with 20 mol% Mg and 6 mol% Cr exhibited an excellent green color (L* = 76.94, a* = −9.62, b* = 14.17), which can be reasonably maintained in exposed air by a heating treatment at 1200 °C for 10 h or in transparent ceramic glaze at 1200 °C for 30 min. These enhanced performances were mainly attributed to synergistic effect of Cr and Mg doping, which hindered the tendency of Al2TiO5 toward decomposition, indicative of its potential application in high-temperature ceramic decoration.

Preparation of Magnesium Aluminate Spinel Nanofibers with High Temperature Resistance by Electrospinning Process Based on Non-Hydrolytic Sol-Gel Method

Preparation of Magnesium Aluminate Spinel Nanofibers with High Temperature Resistance by Electrospinning Process Based on Non-Hydrolytic Sol-Gel Method

Photodegradation of Fipronil by Zn-AlPO4 Materials Synthesized by Non-Hydrolytic Sol–Gel Method

In recent decades, the increasing use of pesticides to improve food productivity has led to the release of effluents that contaminate the environment. To prepare a material that may help to treat effluents generated during agricultural practice, we used a new method based on the non-hydrolytic sol-gel route to obtain zinc photocatalysts in aluminophosphate matrixes. IR spectroscopy, X-ray diffraction, thermal analysis, differential scanning electron microscopy, energy dispersion spectroscopy, and specific surface area and pore volume determined from the nitrogen adsorbed were used to characterize materials treated at different temperatures. X-ray analysis showed how heat-treatment affected the structure of the material: Zn-AlPO4 in the trigonal and orthorhombic phase was obtained at 750 and 1000 °C, respectively. These phases directly influenced the ability of the material to generate OH radicals. The capacity of the materials to treat effluents was tested in the photodegradation of the pesticide Fipronil. The photocatalytic reactions were monitored by ultraviolet-visible spectroscopy and gas chromatography-mass spectrometry analyses. Zn-AlPO4 treated at 750 °C showed better photodegradation results--it removed 80% of the pesticide in 2 h when higher mass (150 mg) was tested. Long-time treatment of the effluent with Zn-AlPO4 treated at 750 °C completely photodegraded Fipronil. GC-MS analysis confirmed the photodegration profile, and only traces of Fipronil were observed after photocatalytic reaction for 120 min in the presence of Zn-AlPO4 treated at 750 °C under UV radiation.

Tailoring of the electrochemical stability and dielectric behaviour of inorganic matrix-based ionogels

Silicon dioxide (SiO2), lithium salt (lithium perchlorate, LiClO4), ionic liquid (IL; 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIMTFSI]), and succinonitrile (SCN)- based ionogels (IGs) are synthesized using cost-effective non-hydrolytic sol-gel (NHSG) method. The electrochemical stability and electrical properties are associated with their molecular structures. The electrochemical stability of the IGs (I1, I2, and I3) was studied using the highest occupied molecular orbital (HOMO) & lowest unoccupied molecular orbital (LUMO) methods. AC impedance spectroscopy was used to illustrate the electronic properties of the prepared IGs. The dielectric characteristics of the synthesized IGs were studied at various temperatures and frequencies. The dielectric constant (ε′), dielectric loss or dissipation factor (ε″), tangent loss (tanδ), electric modulus (M′ and M″), and AC conductivity (σ ac) of SiO2/IL based IGs (I1, I2, and I3) were investigated.

Preparation, characterisation, and growth mechanism of mesoporous petal-like MgAl2O4 spinel

Petal-like MgAl2O4 spinel was successfully prepared using a novel inorganic salt-assisted nonhydrolytic sol-gel method without a template and was employed as absorbent in the removal of the Congo red (CR). The effects of the inorganic salt type, heat-treatment temperature, and dwelling time on the morphology and phase composition of the petal-like MgAl2O4 spinel were investigated systematically. Results indicated that when Na2MoO4 was employed as the salt and the heat-treatment temperature and dwelling time were 600 °C and 5 h, respectively, the as-obtained petal-like MgAl2O4 spinel exhibited a highly uniform morphology with a thickness of 19–23 nm and a length of 240–280 nm. The N2 adsorption-desorption results revealed that the petal-like MgAl2O4 exhibited a large BET specific surface area of 161 m2g-1 with a pore volume of 0.24 cm3g-1. The growth mechanism of the petal-like MgAl2O4 is believed to be the formation of a two-dimensional layered network structure by the coordination between the condensation product of the magnesium aluminium bimetallic alkoxides and the ions in the salt. The as-prepared MgAl2O4 petal exhibited an effective adsorption capacity toward anionic dyes CR. The maximum adsorption capacity of CR onto the mesoporous MgAl2O4 petal was found to be 572.01 mg/g, it is showed the petal-like MgAl2O4 exhibit huge potential of application in the field of environmental remediation.

Effect of iron source on nonhydrolytic sol-gel synthesis of Fe2TiO5

Fe2TiO5 was synthesized via nonhydrolytic sol-gel method at 600?C. The effects of iron sources on the synthesis of Fe2TiO5 were investigated. It was demonstrated that Fe-O-Ti bonds will not be formed in the xerogels prepared by taking FeCl3 as iron source because it is strong Lewis acid and induces homocondensation. Fe-O-Ti bonds were formed in the xerogels prepared by using Fe(OC2H5)3 and FeOH(CH3COO)2 as iron sources. However, the hydroxyl group in FeOH(CH3COO)2 easily leads to homocondensation and particles agglomeration. Thus, Fe(OC2H5)3 is optimal iron source with both excellent synthesis and particle dispersion effects.

Tunable luminescence of Tb3+ doped SiO2-TiO2-PDMS hybrid ORMOSILs

A new class of SiO2-TiO2-PDMS hybrid ORMOSILs doped with Tb3+ ions were synthesized by non-hydrolytic sol-gel method. The host matrix was developed from both organic and inorganic constituents and when doped with Tb3+ making it suitable for a wide range of optical applications. The X-ray Diffraction (XRD) analysis confirmed the amorphous nature of the samples. The Fourier Transform Infra-Red (FTIR) analysis confirmed the unaltered chemical structure of the samples while the Thermogravimetric (TG) analysis established its thermal stability. The photoluminescence (PL) analysis demonstrated that the Tb3+ doped samples emit blue light along with the characteristic Tb3+ emission when excited at 276 nm. This confirms the existence of a host to Tb3+ energy transfer pathway in the doped sample. These samples were also excited at 352, 369, 378 and 487 nm wavelengths which give similar emission spectra, but with increasing emission intensity. The Judd-Ofelt (JO) intensity parameters and the radiative properties of 5D4→7F3, 4, 5 transitions were also evaluated from the emission spectra. High values obtained for branching ratio and stimulated emission cross-section for the 5D4→7F5 transition make the material suitable for optical amplification. Furthermore, the CIE co-ordinates were calculated and found that color tuning is possible from blue to green region with Tb3+ doped SiO2-TiO2-PDMS ORMOSILs when excited at different wavelengths.

Non-hydrolytic sol-gel synthesis of mesoporous iron-aluminum oxide and their properties in the oxidation of hydrocarbons by hydrogen peroxide

Iron-containing alumina materials were prepared by the non-hydrolytic sol-gel method in the presence of surfactants and their use as catalysts in the oxidation of hydrocarbons was studied. The solids were mesoporous, with large specific surface areas, > 250 m 2 /g for the solids treated at 500 °C, depending on the surfactant used (cetyltrimethylammonium bromide, sodium dodecyl sulfate or hexadecylamine), and the calcination treatment applied (500 or 1000 °C). Iron was well distributed on the alumina surface, as confirmed by the EPR signals at 4.3 and 2.0 G and SEM imaging. The catalytic activity in the oxidation of cyclooctene, cyclohexane, and n -hexane was evaluated. After reaction for 48 h, the solid prepared with cetyltrimethylammonium bromide and calcined at 1000 °C showed a 25% conversion of cyclohexane with 51% selectivity to cyclohexanone. These were promising results, considering the mild reaction conditions, using a non-polluting oxidant at room temperature or 50–55 °C. • Iron-containing alumina catalysts were prepared by a non-hydrolytic sol-gel method. • Surfactants played a fundamental role in pore structuring in situ. • Iron-aluminas were effective oxidation catalysts, using H 2 O 2 as oxidant. • Cyclooctene, cyclohexane, and n-hexane were successfully oxidized. • Oxidation was effective under mild, environmentally friendly conditions.

Synthesis and characterization of Mn-doped C@ZrSiO4 black pigment via non-hydrolytic sol-gel method

With the increasing popularity of the black decorative ceramics, the development of black pigment with good properties has become significant for the ceramic industry. A Mn-doped zirconium silicate encapsulated carbon (C@ZrSiO4) black pigment was successfully prepared via non-hydrolytic sol-gel (NHSG) method at 800 °C, while MnCl2 and carbon-containing precursors (tetraethoxysilane, TEOS) were used as Mn and in-situ carbon sources, respectively. The results demonstrated that the L* value of black pigment first decreased and increased with the increase of MnCl2 content. The as-prepared pigment with the MnCl2 content of 10 mol% showed a deep dark hue (L* = 27.64, a* = 0.67, b* = 0.68), while the pigment without Mn doping exhibited poor chromatic properties (L* = 51.18). Moreover, XPS and EPR results indicated that the Mn(II) and Mn(IV) replaced the Zr(IV) in ZrSiO4, resulting in the formation of oxygen vacancies. In-situ carbon provided by TEOS incorporated into these oxygen vacancies, which can protect carbon from being oxidized. In addition, the prepared pigment exhibited higher chemical stability in acid/alkali solutions, favorable tinting strength and thermal stability in base transparent glaze, which displayed wide application prospect in the field of ceramic decoration.

Preparation of mesoporous petal-like MgAl2O4 via molten-salt assisted nonhydrolytic sol–gel method

Mesoporous petal-like MgAl2O4 spinel has been prepared by molten salt assisted nonhydrolytic sol–gel method. The influence of Mg/Al molar ratio (0.45, 0.50, 0.55, 0.60, 0.70 and 0.80) on the morphology and surface area of MgAl2O4 was investigated. The results reveal that Mg/Al molar ratio has a significant influence on the morphology. At Mg/Al molar ratio of 0.7, the achieved petal-like MgAl2O4 is highly uniformed in morphology, the surface area and pore volume reached maximum values of 141 m2g−1 and 0.24 cm3g−1, respectively. These properties make it have promising applications in the catalyst support field.

The enhanced structure stability and the reinforcement mechanism of 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating

The 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating was prepared on pure Mo substrate to improve its high-temperature oxidation resistance, of which the MoSi2 coating was prepared by a modified pack siliconizing process and subsequently the 0.1Al2O3-ZrO2 layer was generated on the as-prepared MoSi2 layer by a non-hydrolytic sol-gel method. The phase composition and microstructure of the as-prepared composite coating before and after oxidation exposure were investigated by XRD, SEM and EDS. Different from the loose structure of the single MoSi2 coating after oxidation exposure, the 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating exhibited a relatively compact internal structure with less through-thickness cracks. The introduction of 0.1Al2O3-ZrO2 layer effectively prevented the cracking and spalling of the glassy SiO2 scale formed on the surface of MoSi2 during the oxidation, and then the SiO2 scale could be well stabilized on the coating surface. The protective SiO2 glassy scale embedded with stable ZrO2 and ZrSiO4 phase was formed, contributing to the improvement in the structure stability of the composite coating. It was proposed that ZrO2, ZrSiO4 and SiO2 developed a special glass-ceramic skeleton structure, in which ZrO2 and ZrSiO4 played the role of “Zr nail” to the SiO2 scale. In addition, the reinforcement mechanism of 0.1Al2O3-ZrO2 layer to the MoSi2 coating was also discussed.

A process for fabrication of Li2TiO3 ceramic pebbles with high mechanical properties via non-hydrolytic sol-gel method

In this paper, the single-phase Li2TiO3 powder was successfully synthesized via non-hydrolytic sol-gel method (NHSG) using anhydrous lithium acetate (LiOAc) as lithium source and tetrabutyl titanate (TBOT) as titanium source. The effects of the temperature and the Li/Ti molar ratio on the synthesis of Li2TiO3 were investigated by XRD. FT-IR and XPS were used to characterize the synthesis mechanism and surface chemistry of Li2TiO3 powder heated at 650 °C for 2 h with 5 °C/min. Furthermore, the Li2TiO3 pebbles were successfully prepared using synthesized powder by indirect wet chemistry method. The results showed that the Li2TiO3 pebbles with diameter of 1.3mm–1.5 mm, crush load of 67 N, sphericity of 0.97, the relative density of 84.9%, the grain size of 2.85 μm and porosity of 19.84% were successfully fabricated when sintering temperature was 1050 °C for 2 h in air. Therefore，the NHSG method could provide a new efficient route for the production of Li2TiO3 ceramic pebbles.

Nonhydrolytic sol-gel in-situ synthesis of novel recoverable amorphous Fe2TiO5/C hollow spheres as visible-light driven photocatalysts

A novel recoverable visible-light photocatalyst, amorphous Fe2TiO5/C composite, was prepared via nonhydrolytic sol-gel method with carbon-containing precursors as in-situ carbon sources. It is demonstrated that the precursors, iron ethoxide and butyl titanate, react to form Fe-O-Ti bonds in gel through a ether elimination reaction and amorphous Fe2TiO5 at 300 °C, which finally crystallizes at 600 °C. The residual organic groups form uniform-doped C. Interestingly, the photocatalytic activity of amorphous Fe2TiO5/C is distinctly superior to those of its crystalline counterparts without C and P25 (43-fold increase and 12-fold increase, respectively), which is mainly attributed to the incorporation of C (8.17 wt%) and amorphous Fe2TiO5 with a hollow spherical structure and a high BET surface area of 195.5 m2/g. Importantly, the photocatalyst can be recovered with a recovery rate of 100% simply by an external magnetic field, making it have promising applications in the wastewater treatment field.