Post-impregnation Method Research Articles

Fluconazole adsorption and release study using KIT-6 for targeted and controlled drug delivery system

ABSTRACT This study presents the development of a mesoporous silica, i.e. KIT-6 synthesised using the hydrothermal technique, followed by the loading of fluconazole as the model drug using the post-impregnation method. The results of drug entrapment studies exposed that 76% of the drug was entrapped in the silica matrix. The drug release rate was investigated in phosphate buffer with pH = 6.8. The fluconazole-loaded KIT-6 prolonged the drug’s release for 12 hours, ensuring Higuchi’s square root kinetics, with diffusion via the matrix as the releasing mechanism, which revealed that the release rate was under control. The MTT assay-based biocompatibility experiments on Vero cells show that the pure and drug-loaded composite systems have minimal cytotoxicity. Hence, drug delivery and adsorption may be facilitated, and repeated administration of drugs is reduced by a controlled drug release rate using the prepared silicious composite.

Design and synthesis of magnesium-modified copper oxide nanosheets as efficient electrocatalysts for CO2 reduction.

Electroreduction of carbon dioxide (CO2) to multiple carbon products plays a significant role in carbon neutrality and the production of valuable chemicals. Herein, we developed a magnesium-modified copper oxide nanosheet catalyst (Mg-CuO) using a post-impregnation method. Comprehensive elemental analysis demonstrated the effective incorporation of magnesium into CuO nanosheets, resulting in a noticeable alteration of the electron density of Cu atoms. Consequently, the Mg-CuO nanosheets exhibited an increased efficiency for CO2 electroreduction in comparison with the unmodified CuO nanosheets. The optimized Mg-CuO catalyst exhibited faradaic efficiencies of 46.33% for ethylene production and 62.64% for C2+ production at -1.3 V vs. reversible hydrogen electrode (RHE). DFT proved that the introduction of Mg species could increase the charge density of Cu and decrease the adsorption energy of *CO, which promoted C-C coupling and enhanced the selectivity of C2+ products. This study presents an effective way to adjust the electronic structure of common copper-based electrocatalysts and the corresponding interaction with *CO, resulting in an improved faradaic efficiency of C2+ products.

Cu-Zr/SiO2 catalysts featured by different Cu-Zr-Si coordinations for ethanol conversion to 1,3-butadiene

Catalytic upgrading of bio-ethanol to 1,3-butadiene (1,3-BD, ETB) is a renewable and low-carbon technology for the bulk chemical production. Exploring robust catalysts and getting in-depth understanding of the relationship between the structure of catalytic sites and reaction selectivity are of great significance for ETB process applications. In this study, we constructed a robust Cu-Zr/SiO2 catalyst by an ammonia evaporation and post-impregnation method. Over the optimal 2%Cu-8%Zr/SiO2 catalyst, superior performance of 69.6% 1,3-BD selectivity and 71.2% ethanol conversion were obtained. Systematic characterizations revealed that three types of Cu-Zr-Si active sites were probably constructed on the Cu-8%Zr/SiO2 catalysts as varying the Cu loadings from 0.5 to 20%, affording greatly different activity and selectivity in the ETB process. The 1,3-BD productivity over the (SiO)2(CuO)Zr-OH sites was 8.2 and 77.2 times higher than that of (CuO)2-Zr-(OSi)2 and Cu-(O)2-Zr-(OSi)2 sites, respectively, attributed to the high activities and good balance among the reactions of dehydrogenation, aldol condensation, and MPVO reduction.

Removal of antibiotics by adsorption and catalytic ozonation using magnetic activated carbons prepared from Sargassum sp.

This study was carried out to determine the best conditions for the preparation of magnetic activated carbons (mACs) from Sargassum sp. as both adsorbents and catalytic supports. Coupling of adsorption and catalytic ozonation for removal and degradation of antibiotics was implemented for several cycles of use in order to assess the efficiency and the stability of these mACs. The mAC prepared by the post-impregnation method (activated carbon with Sargassum sp. + FeCl2.4H2O pyrolyzed at 200 °C for 120 min) showed better adsorption capacity of a mixed solution of antibiotics (95.3, 48.3, 13.4 mg g−1 for tetracycline (Tc), penicillin (Pen) and erythromycin (Ery) respectively after 3 cycles of use) than the mAC prepared by the pre-impregnation method (Sargassum sp. + FeCl2.4H2O pyrolyzed at 664 °C for 65 min). Whereas the evaluation of the degradation under ozone after mAC saturation by adsorption showed a better degradation after 3 cycles of reuse higher than 96 % for Ery, and higher than 99 % for Tc and Pen for the mAC prepared by the pre-impregnation method. Their physicochemical properties were characterized by different techniques, in particular X ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), analysis of the surface acid-base groups by Boehm method, pore analysis and specific surface area measurement (using the Brunauer–Emmett–Teller method) by nitrogen adsorption, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The use of Sargassum sp. is therefore promising for the preparation of efficient bio-sourced mACs for the removal of organic pollutants from polluted waters.

Confinement effect and Hetero-interface enable High-Performing MnOx/CeO2 oxidation catalysts with exceptional sintering resistance:Morphology effect of ceria support

Combining both low-temperature activity and sintering resistance to meet practical requirements is still a great challenge for the most of effective catalysts. Herein, nano ceria with different morphologies (nanosphere, nanorod, nanocube) were applied to construct novel MnOx/CeO2 catalysts by post impregnation method for catalytic combustion of carcinogenic benzene. Detail structural/physio-chemical characterizations and activity measurements were conducted to investigate the structure-dependent behavior and interfacial effect on catalytic performance and sintering resistance properties. Compared to blank ceria supports, the low-temperature activities of all MnOx/CeO2 catalysts are significantly improved, and the T90 of best-performed MnOx/CeO2 nanorods composite is only 225 °C which is 197 °C lower than that of pure ceria nanorods. Experimental studies indicate low-temperature reducibility, oxygen mobility and surface defects could be greatly promoted by introducing hetero-interface with synergistic effects between ceria and MnOx nanocrystals. Moreover, the morphology-effect on sintering resistance is dramatically different, and the T90 of spherical MnOx/CeO2 increased to only 270 °C from 245 °C after thermal ageing at 750 °C for 100 h while this value raised to 507 °C from 256 °C on MnOx/CeO2 nanocube catalyst. This exceptional sintering resistance over spherical MnOx/CeO2 can be attributed to confinement effect of Ceria nanosphere where the supported MnOx nanoparticles is trapped in the nanopores so that it’s difficult for MnOx particles to aggregate through thermal ageing treatment. In addition, due to the small contact area between the spherical particles, there is no obvious sintering phenomenon such as growth, aggregation and collapse of the spherical particles after thermal ageing, further leading to enhancement of sintering resistance. This work provides a versatile strategy for designing highly active thermal combustion catalysts with good low-temperature activities and sintering resistance for industrial applications.

Synthesis of MgO-doped ordered mesoporous carbons by Mg2+-tannin coordination for efficient isomerization of glucose to fructose

In-situ MgO-doped ordered mesoporous carbon (OMC@MgO) was fabricated by formaldehyde-free self-assembly method, in which biomass-derived tannin was used as carbon precursor replacing fossil-based phenolics, Mg2+ as both cross-linker and precursor of catalytic sites. Up to ∼20 wt% MgO could be doped in the carbon skeleton with good dispersion retaining well-ordered mesoporous structures, while more MgO content (35 wt%) led to the failing in the formation of ordered mesoporous structure. The OMC@MgO possessed a high specific surface area (298.8 m2 g−1), uniform pore size distribution (4.8 nm) and small crystallite size of MgO (1.73 nm) due to the confinement effect of ordered mesoporous structure. Using OMC@MgO as the heterogeneous catalyst, a maximum fructose yield of 32.4% with a selectivity up to 81.1% was achieved from glucose in water (90 °C, 60 min), which is much higher than that obtained using the MgO doped active carbon via conventional post-impregnation method (26.5% yield with 58.3% selectivity). Higher reaction temperature (>90 °C) resulted in decrease of selectivity due to the formation of humins. The designed OMC@MgO displayed tolerant to high initial glucose concentrations (10 wt%) and could remain good recyclability without significant loss of activity for three cycles.

Zirconium–Cerium Oxides Supported on SBA-15 as Catalyst for Shape-Selective Synthesis of Lactic Acid from Glycerol

The conversion of an oleochemical waste i.e. glycerol into lactic acid (LA) using bifunctional catalyst is receiving intensive research attention. The major concern is to achieve a suitable combination of the non-precious active metals with specific roles to achieve a fast and selective reaction. Catalyst with a Ce-to-Zr ratio of 1:2 and supported on SBA-15 at total active metal loadings between 10 and 40 wt% were prepared via a two-sequential-step post-impregnation method. The catalysts were then characterized using nitrogen adsorption–desorption and SEM analyses to elucidate their properties. They were then employed in selective glycerol oxidation reaction carried out at between 240 and 280 °C for up to 3 h to yield LA. The catalytic performance in terms of glycerol conversion and lactic acid yield was successfully correlated with the physicochemical properties of the catalysts. The highest glycerol conversion of 91.2% of glycerol was obtained using 10 wt% of CeZr/SBA-15 at a catalyst loading of 25 wt% with almost 51.4% of corresponding LA yield. It was attributed to the desired shape selectivity effect in the benzylic rearrangement (Cannizzaro reaction) of pyruvaldehyde to suppress by-product formations.

In situ one-pot fabrication of MoO3−x clusters modified polymer carbon nitride for enhanced photocatalytic hydrogen evolution

Developing low-cost and high-efficient noble-metal-free cocatalysts has been a challenge to achieve economic hydrogen production. In this work, molybdenum oxides (MoO3−x) were in situ loaded on polymer carbon nitride (PCN) via a simple one-pot impregnation-calcination approach. Different from post-impregnation method, intimate coupling interface between high-dispersed ultra-small MoO3−x nanocrystal and PCN was successfully formed during the in situ growth process. The MoO3−x-PCN-X (X=1, 2, 3, 4) photocatalyst without noble platinum (Pt) finally exhibited enhanced photocatalytic hydrogen performance under visible light irradiation (λ>420 nm), with the highest hydrogen evolution rate of 15.6 µmol/h, which was more than 3 times that of bulk PCN. Detailed structure-performance revealed that such improvement in visible-light hydrogen production activity originated from the intimate interfacial interaction between high-dispersed ultra-small MoO3−x nanocrystal and polymer carbon nitride as well as efficient charge carriers transfer brought by Schottky junction formed.

Enhanced Performance for Selective Catalytic Reduction of NOx with NH3 over Nanosized Cu/SAPO‐34 Catalysts

AbstractA series of nanosized Cu/SAPO‐34 catalysts with different silicon contents were successfully synthesized by in situ hydrothermal method by using tetraethylammonium hydroxide and copper‐tetraethylenepentamine as co‐templates. The in situ prepared nanosized Cu/SAPO‐34 catalysts possess strong Brønsted acidity and well‐dispersed Cu species, showing enhanced performance for selective catalytic reduction of NOx with NH3 compared with micronsized and nanosized counterparts prepared by post impregnation method. Significantly, Cu/SAPO‐34 nanocatalysts prepared by in situ method maintain the catalytic activity after the hydrothermal aging treatment, suggesting their excellent hydrothermal stability. This work will provide some guidance for the design of highly efficient catalysts for NH3−SCR reactions.

Caesium Salt of Tungstophosphoric Acid Supported on Mesoporous SBA-15 Catalyst for Selective Esterification of Lauric Acid with Glycerol to Monolaurin

$$\hbox {Cs}_{2.5}\hbox {H}_{0.5}\hbox {PW}_{12}\hbox {O}_{40}$$ supported on SBA-15 catalysts were prepared via two-sequential-step post-impregnation method with different ratios of cesium salt. The synthesized catalysts were then characterized using nitrogen adsorption–desorption, FTIR, EDX, SEM, BET and TGA analyses in order to determine the physicochemical properties of the catalysts. The activity of the catalysts in the esterification of glycerol to monolaurin was investigated under various reaction parameters including catalyst loadings, reaction temperatures and glycerol-to-lauric acid molar ratio. The highest lauric acid conversion (71.8%) with 44.9% of monolaurin yield was obtained using 20 wt%Cs-HPW/SBA-15 catalyst in 4 h at 170 $${^{\circ }}\hbox {C}$$ using 4:1 of glycerol-to-lauric acid molar ratio and 2.5 wt% of catalyst loading. This catalyst was stable and reusable for up to three cycles in the esterification reaction without significant loss in catalytic activity.

Influence of functionalized mesoporous silica in controlling azathioprine drug release and cytotoxicity properties

The present study is focused on functionalisation of mesoporous silica (or SBA-15) to control azathioprine drug release rate and its toxic effect. The mesoporous silica was functionalised by (γ-chloropropyl)triethoxysilicane and (3-aminopropyl)triethoxysilane (APTES) via hydrothermal process. The azathioprine was loaded into SBA-15 via post impregnation method. Azathioprine-loaded pristine and functionalised SBA-15 samples were characterised using UV–visible spectrophotometry and thermogravimetric analysis to measure the drug loading efficiency. The samples were also characterised by small and wide-angle powder X-ray diffraction, scanning electron microscope, transmission electron microscope, infrared spectroscopy and nitrogen adsorption/desorption analysis to study the structure, morphology, functionalisation and drug loading in detail. The maximum drug loading efficiency of 65(±1)% was achieved. In vitro azathioprine release profiles were studied in phosphate buffered saline (pH 7.4) and results suggested that the drug release amount could be controlled by functionalisation of carrier matrix SBA-15. Azathioprine-loaded APTES-functionalised material revealed lowest release amount of ~64.5% in 60 h. The toxicity of azathioprine was significantly reduced by loading the drug into the mesoporous pristine and functionalised silica. The controlled azathioprine release reduced its repeated administration and can reduce its toxicity and side effects. These outcomes recommend that the functionalised SBA-15 is an advantageous drug carrier for achieving extended release time.

A comparative study of the incorporation of TiO2 into MCM-41 nanostructure via different approaches and its effect on the photocatalytic degradation of methylene blue and CO oxidation

Two sets of titania incorporated within mesoporous MCM-41 were successfully fabricated through two fundamental approaches to look for better dispersion of titania and robust catalysts for the photocatalytic degradation of methylene blue and carbon monoxide oxidation. The first involves the incorporation of titania via a one-pot synthesis method to produce Ti-MCM-41. The second approach carried out uses the post-impregnation method to deliver TiO2/MCM-41 with various titania contents. The synthesized materials were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, nitrogen physisorption, high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The results demonstrate that, as compared with the post-impregnation approach, the one-pot synthesis of titanium into MCM-41 assists the incorporation and the good dispersion of titanium ions into the mesochannel of MCM-41 frameworks. It also hinders the growth of large TiO2 crystallites, which are beneficial to produce outstanding catalysts for the photocatalytic degradation of methylene blue and carbon monoxide oxidation. It is conceivable to propose that the strategy of preparation did pronouncedly contribute to the overall activity.

Improved antimicrobial property and controlled drug release kinetics of silver sulfadiazine loaded ordered mesoporous silica

The present study deals with the loading of silver sulfadiazine into ordered mesoporous silica material by post-impregnation method and its effect on the in vitro release kinetics and antimicrobial property of the drug. The formulated SBA-15 silica material with rope-like morphology and SBA-15-silver sulfadiazine (SBA-AgSD) were characterized by UV–visible spectrophotometer, small and wide-angle powder X-ray diffraction (PXRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). Thermo-gravimetric analysis of SBA-AgSD revealed a high loading amount of 52.87%. Nitrogen adsorption–desorption analysis confirmed the drug entrapment into host material by revealing a reduced surface area (214 m2/g) and pore diameter (6.7 nm) of the SBA-AgSD. The controlled release of silver sulfadiazine drug from the mesoporous silica to simulated gastric, intestinal and body fluids was evaluated. The Korsmeyer–Peppas model fits the drug release data with the non-Fickian diffusion model and zero order kinetics of SBA-AgSD. The antibacterial performance of the SBA-AgSD was evaluated with respect to Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa. The controlled drug delivery of the SBA-AgSD revealed improved antibacterial activity, thus endorsing its applicability in effective wound dressing.

In-vitro drug release kinetics studies of mesoporous SBA-15-azathioprine composite

The mesoporous silica (or SBA-15) was loaded with azathioprine drug. Azathioprine drug was incorporated into mesoporous silica by post impregnation method to reduce its toxic effects by controlling the drug release property. The synthesized pure SBA-15 and SBA-15-azathioprine composite were characterized by UV–visible spectrophotometry, thermo-gravimetric analysis, small and large angle powder X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption–desorption analysis. The successful inclusion of azathioprine drug in host material SBA-15 was confirmed by the reduced surface area (114 m2/g) and pore diameter (6.5 nm) of the organic–inorganic composite material. The drug entrapment efficiency of 90.67 % and loading efficiency of 72.67 % was achieved. The azathioprine drug release process from the mesoporous silica to simulated gastric, intestinal and body fluid were examined and the controlled release effect of the azathioprine drug in all fluids were studied. The Korsmeyer–Peppas model fits well the drug release data with the non-Fickian diffusion model and zero order kinetics for produced mesoporous silica. The controlled drug release enhanced the bioavailability and reduces its repeated administration. Hence, the composite drug can reduce the toxicity and side effects of the azathioprine.

A novel cotton fabric with anti-bacterial and drug delivery properties using SBA-15-NH2/polysiloxane hybrid containing tetracycline

Here, mesoporous silica particles containing tetracycline were loaded on cotton fabric for possible application on the infected human skin. Amino functionalized mesoporous silica, SBA-15-NH2, was chosen as a safe drug carrier loaded with tetracycline via post impregnation method. Diverse content of the drug loaded silica particles were then attached on the cotton fabric surface using polysiloxane reactive softener as a soft and safe fixing agent. UV–Vis spectroscopy was used to study the drug delivery properties of the mesoporous silica on the treated cotton fabrics. The treated fabric with long drug release properties was selected as the optimized sample. Further analysis was carried out on this sample including anti-bacterial, water contact angle, bending length, mineral content and washing durability. Also, SEM images, EDX patterns, X-Ray spectra and thermal behavior of the optimum sample were studied. The optimized treated sample indicated the gradual release profile of tetracycline in PBS buffer media within 48h along with excellent anti-bacterial efficiency as a good feature for biological application.

Synthesis of Cr,N-codoped titania nanotubes and their visible-light-driven photocatalytic properties

Cr and N-codoped TiO2 nanotubes with larger specific surface area and smaller band gap energy compared with pure TiO2 nanotubes were prepared via a two-step process of hydrothermal and post-impregnation method. The obtained catalysts were characterized by TEM, XRD, XPS, BET, FT-IR and UV–Vis DRS measurements for investigating nanostructure, crystal phase, specific surface area, bonding state and light-harvesting properties of these samples, respectively. Additionally, the effects of doping amount of Cr ions on the morphology, crystal structure, optical adsorption and photocatalytic activity of codoped TiO2 nanotubes were investigated. The photocatalytic activity was evaluated by degradation of methyl orange (MO) under visible light for 100min. It was found that the highest photocatalytic activity could be realized when the concentration of Cr was 1.06%, and the degradation rate was up to 97.16%, far higher than that of undoped TiO2 nanotubes (10.56%). In addition, photocatalytic degradation of MO on codoped TiO2 nanotubes surface was proven to be in accordance with the first-order kinetics.

Well-dispersed palladium supported on ordered mesoporous Co3O4 for catalytic oxidation of o-xylene

Ordered mesoporous Co3O4(3D) and Pd/Co3O4(3D) were prepared by a nanocasting route using mesoporous silica (KIT-6) as a hard template. In addition, Pd/Co3O4(3DL) was prepared as a reference by post-impregnation of Pd in Co3O4(3D). All catalysts were tested for the total oxidation of o-xylene in the temperature range of 150–300°C. The mesoporous Co3O4(3D) showed better activity than bulk Co3O4 (B) for o-xylene oxidation. As for Pd-loaded samples, Pd/Co3O4(3D) had much higher activity than Pd/Co3O4(3DL). These catalysts were characterized by BET, XRD, TEM, XPS, H2-TPR and XAFS methods. The characterization results show that the Pd/Co3O4(3D) synthesized by in situ nanocasting presented a more ordered mesostructure and more well-dispersed PdO species than the Pd/Co3O4(3DL) prepared with the post-impregnation method, which account for its excellent activity for o-xylene oxidation. In addition, it was demonstrated that Pd in the oxidized state is the active site for o-xylene oxidation.

Nickel‐Promoted Tungsten Carbide Catalysts for Cellulose Conversion: Effect of Preparation Methods

A series of Ni-promoted W(2) C catalysts was prepared by means of a post-impregnation method and evaluated for the catalytic conversion of cellulose into ethylene glycol (EG). Quite different from our previously reported Ni-W(2) C/AC catalysts, which were prepared by using the co-impregnation method, the introduction of Ni by the post-impregnation method did not cause catalyst sintering, but resulted in redispersion of the W component, which was identified and characterized by means of XRD, TEM, and CO chemisorption. The highly dispersed Ni-promoted W(2) C catalyst was very active and selective in cellulose conversion into EG, with a 100% conversion of cellulose and a 73.0% yield in EG. The underlying reason for the enhanced catalytic performance was most probably the significantly higher dispersion of active sites on the catalyst.

Visible light driven photocatalytic evolution of hydrogen from water over CdS encapsulated MCM-48 materials

CdS encapsulated cubic MCM-48 mesoporous photocatalysts were prepared by a post-impregnation method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption isotherm, UV-visible diffuse reflectance spectroscopy (DRS), FT-IR spectrometry, X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and photoluminescence (PL) spectroscopy were employed for the characterization of the CdS incorporated MCM-48 siliceous materials. MCM-48 was loaded with different amounts of CdS. In the current study, all the samples showed photocatalytic activity under visible light (λ > 400 nm) irradiation for production of hydrogen from splitting of water in the absence of Pt, which is usually used in photocatalytic splitting of water. The photocatalytic activity of the CdS incorporated MCM-48 mesoporous photocatalysts was found to be dependent on the CdS loading and the pore size of MCM-48 siliceous support. The highest solar hydrogen evolution rate by visible light irradiation from the splitting of water was determined to be 1.81 mmol h−1 gCdS−1 and the apparent quantum yield was estimated to be 16.6%.

A Comparative Study of Variously Prepared Carbon-Supported Pt / MoOx Anode Catalysts for a Polymer Electrolyte Fuel Cell

Carbon-supported anode catalysts were prepared by the preimpregnation, postimpregnation, and chemical reduction methods. The physicochemical characteristics of all catalysts were determined by X-ray diffraction, scanning transmission electron microscopy, and CO pulse titration. The electrochemical oxidation of CO verified from CO-stripping voltammetry shows that most of the were oxidized on the Pt sites. The catalyst prepared by the chemical reduction method showed superior hydrogen electrochemical oxidation in pure , apparently due to the much smaller Pt particle size than those of the other catalysts. However, the anode performances in the presence of 500 ppm mixture showed that a catalyst with high CO tolerance was derived from the catalyst prepared by postimpregnation method. The oxidation of CO by the water–gas shift (WGS) reaction is shown by the formation of even under an open-circuit condition. With an increase in current, active sites for the WGS reaction is regenerated by electrochemical oxidation of hydrogen.