Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 27
Filtrar
Más filtros













Base de datos
Intervalo de año de publicación
1.
J Colloid Interface Sci ; 669: 402-418, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-38723530

RESUMEN

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core-shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

2.
J Colloid Interface Sci ; 662: 263-275, 2024 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-38354554

RESUMEN

Defect-engineered metal-organic frameworks (DEMOFs) are emerging advanced materials. The construction of DEMOFs is of great significance; however, DEMOF-based catalysis remains unexplored. (E)-vinylboronates, an important building block for asymmetric synthesis, can be synthesized via the hydroboration of alkynes. However, the lack of high-performance catalysts considerably hinders their synthesis. Herein, a series of DEHKUST-1 (HKUST = Hong Kong University of Science and Technology) (Da-f) catalysts with missing occupation of linkers at Cu nodes were designed by partially replacing benzene-1,3,5-tricarboxylate (H3BTC) with defective connectors of pyridine-3,5-dicarboxylate (PYDC) to efficiently promote the hydroboration of alkynes. Results showed that the Dd containing 0.8 doping ratio of PYDC exhibited remarkable catalytic activity than the defect-free HKUST-1. This originated from the improved accessibility for reactants towards the Lewis acid active Cu sites of DEHKUST-1 due to the presence of plenty of rooms next to the Cu sites and enhanced coordination ability in such 'defective' HKUST-1. Dd had high selectivity (>99 %) and yield (>96 %) for (E)-vinylboronates and extensive functional group compatibility for terminal alkynes. Density functional theory (DFT) calculations were performed to elucidate the mechanism of hydroboration. Compared with that of defect-free HKUST-1, the low energy barrier of DEHKUST-1 can be attributed to the lower coordination number of Cu sites and enhanced accessibility of Cu active sites towards reagents.

3.
Chemosphere ; 352: 141296, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38296214

RESUMEN

It is feasible to improve the photodegradation efficiency of organic pollutants by metal-organic frameworks (MOF)-based semiconductors via ligand engineering. In this work, three (Fe/Co)-XBDC-based MOFs were synthesized by introducing different ortho-functional groups X (X = -H, -NO2, -NH2) next to the carboxyl group of the organic ligand (i.e., terephthalic acid). The analysis focused on the influence mechanism of the adjacent functional group effect of the ligand on the physicochemical properties of the material and the actual photodegradation activity of TC. Multiple pieces of evidences suggested that the differences in electron-induced and photocharge-transfer mechanisms of the above ortho functional groups affect the crystal morphology and photocatalytic activity of FeCo-MOF during pyrolysis. Interestingly, (Fe/Co)-NH2BDC exhibited the highest photocatalytic activity under neutral conditions. The results of density functional theory show that the introduction of a strong donor-NH2 group can enhance light absorption and act as an "electron pump" to supply electrons to the iron center, accelerating the separation and efficient transport of photogenerated carriers on the ligand-metal bridge. In conclusion, this study is a proposal for a strategy of structural regulation for the enhancement of the catalytic activity of (Fe/Co)-MOFs in the photodegradation of TC.


Asunto(s)
Compuestos Heterocíclicos , Estructuras Metalorgánicas , Ligandos , Tetraciclina , Antibacterianos , Electrones
4.
J Colloid Interface Sci ; 652(Pt A): 737-748, 2023 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-37500314

RESUMEN

The chemical conversion of carbon dioxide (CO2) into highly value-added products not only alleviates the environmental issues caused by global warming but also makes an impact on economic benefits in the world. The synthesis of cyclic carbonates by the cycloaddition of CO2 with epoxides is one of the most attractive methods for CO2 conversion. However, the development of green and highly efficient heterogeneous catalysts is considered to be a great challenge in catalysis. In this work, alkenyl-modified melamine-based porous organic polymer (MPOP-4A) was firstly synthesized by a one-pot polycondensation method, and it was again modified with imidazolium-based ionic liquids to obtain final modified catalyst (MPOP-4A-IL). Various analytical techniques were used to confirm structure and chemical composition of the prepared materials. The MPOP-4A-IL catalyst synthesized by the post-modification strategy with imidazolium-based ionic liquids exhibited enhanced catalytic activity for CO2 cycloaddition reaction. The enhanced catalytic performance could be attributed to the presence of abundant active sites in their structure such as hydrogen bond donors (HBD), nitrogen (N) sites, and nucleophilic groups for an effective chemical reaction. The MPOP-4A-IL catalyst was found to be metal-free, easy to recycle and reuse, and has good versatility for a series of different epoxides. The interaction of MPOP-4A-IL catalyst with epoxide and CO2 was further verified by density functional theory (DFT) calculations, and the possible mechanism of the CO2 cycloaddition reaction was proposed.

5.
Environ Sci Pollut Res Int ; 30(25): 67290-67302, 2023 May.
Artículo en Inglés | MEDLINE | ID: mdl-37103698

RESUMEN

Nitrogen-rich organic polymer poly(chloride triazole) (PCTs) was synthesized by a one-step method as metal-halogen-free heterogeneous catalyst for the solvent-free CO2 cycloaddition. PCTs had abundant nitrogen sites and hydrogen bond donors, exhibited great activity for the cycloaddition of CO2 and epichlorohydrin, and achieved 99.6% yield of chloropropene carbonate under the conditions of 110 ℃, 6 h, and 0.5 MPa CO2. The activation of epoxides and CO2 by hydrogen bond donor and nitrogen sites was further explained by density functional theory (DFT) calculations. In summary, this study showed that nitrogen-rich organic polymer is a versatile platform for CO2 cycloaddition, and this paper provides a reference for the design of CO2 cycloaddition catalysts.


Asunto(s)
Dióxido de Carbono , Nitrógeno , Polímeros , Dióxido de Carbono/química , Catálisis , Reacción de Cicloadición , Compuestos Epoxi/química , Polímeros/química
6.
Environ Technol ; 44(5): 631-646, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34516358

RESUMEN

The adsorption of chlorinated aromatic compounds (CACs) on pristine biochar was often limited. Surface modification can greatly improve the adsorption capacity of biochar. In this work, by pyrolysis activation of rubber-seed shell wastes, nitrogen auto-doped biochar (RSS-NBC) was synthesized and used for purifying CACs-containing wastewater. Systematic characterization results showed that after proper treatment, the as-prepared RSS-NBC had high specific surface area, abundant surface oxygen- and nitrogen-containing functional groups, and nano-scale pore structure. Batch adsorption experiments were conducted with using three typical CACs probing pollutants, i.e. 1,2-dichlorobenzene (1,2-DCB), 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorobenzoic acid (2,4-DCBA). The adsorption experiments results showed that the maximum adsorption amounts of 1, 2-DCB, 2,4-DCP, and 2,4-DCBA could reach 2284, 1921, and 1142 mg/g at 298.15 K. Moreover, 90% of the equilibrium adsorption amount can be reached within 0.5 h. The adsorption kinetic results showed that the adsorption processes of the three CACs followed the pseudo-second-order rate model and were dominated by chemisorption. Also, the adsorption isotherms of 1, 2-DCB and 2, 4-DCP belonged to the Freundlich model and were valid for multilayer adsorption, while the adsorption of 2,4-DCBA followed Langmuir model and single-layer adsorption. The thermodynamics data indicated that the spontaneous adsorption process of 1, 2-DCB and 2, 4-DCP was endothermic while that of 2,4-DCBA was exothermic. After 5 cycles of adsorption-regeneration, the removal efficiency of RSS-NBC particles still remained more than 80% for the three typical CACs, indicating that it could be reused as an effective and retrievable adsorbent in the treatment of CACs-containing effluents.


Asunto(s)
Goma , Contaminantes Químicos del Agua , Adsorción , Pirólisis , Carbón Orgánico/química , Agua , Cinética
7.
Int J Biol Macromol ; 228: 548-558, 2023 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-36423811

RESUMEN

High-speed shear system is usually used for the dispersion improvement of slurry, nanomaterials preparation, and even two-dimensional materials production. However, there is barely study that focused on the regenerated cellulose (RC) which was coagulated with shear induced. In this work, a new type of all-cellulose air filter was fabricated through high-speed shear in aqueous regeneration system using parenchyma cellulose from corn stalk. The obtained RC were aggregated by ribbon-like fine cellulose and nanocellulose sheets. The study exhibited the micro-structure of RC displayed excellent unidirectional alignment and a relatively high crystallinity. All-cellulose air filter which was produced via RC presented excellent filtration efficiency (PM2.5 97.3 %, PM10.0 97.7 %) with slightly pressure drop (19 Pa). Therefore, this work provides a facile method to obtain a novel RC with nanocellulose particles used for air filtration, which gives an effective strategy application in the conversion of all-cellulose materials from agricultural waste.


Asunto(s)
Filtros de Aire , Nanoestructuras , Celulosa/química , Nanoestructuras/química , Agua/química , Zea mays/química
8.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 39(5): 1022-1032, 2022 Oct 25.
Artículo en Chino | MEDLINE | ID: mdl-36310492

RESUMEN

Polymer micelles formed by self-assembly of amphiphilic polymers are widely used in drug delivery, gene delivery and biosensors, due to their special hydrophobic core/hydrophilic shell structure and nanoscale. However, the structural stability of polymer micelles can be affected strongly by environmental factors, such as temperature, pH, shear force in the blood and interaction with non-target cells, leading to degradations and drug leakage as drug carriers. Therefore, researches on the structural integrity and in vivo distribution of micelle-based carriers are very important for evaluating their therapeutic effect and clinical feasibility. At present, fluorescence resonance energy transfer (FRET) technology has been widely used in real-time monitoring of aggregation, dissociation and distribution of polymer micelles ( in vitro and in vivo). In this review, the polymer micelles, characteristics of FRET technology, structure and properties of the FRET-polymer micelles are briefly introduced. Then, methods and mechanism for combinations of several commonly used fluorescent probes into polymer micelles structures, and progresses on the stability and distribution studies of FRET-polymer micelles ( in vitro and in vivo) as drug carriers are reviewed, and current challenges of FRET technology and future directions are discussed.


Asunto(s)
Portadores de Fármacos , Micelas , Portadores de Fármacos/química , Polímeros/química , Transferencia Resonante de Energía de Fluorescencia , Polietilenglicoles/química
9.
ACS Appl Mater Interfaces ; 14(34): 39004-39013, 2022 Aug 31.
Artículo en Inglés | MEDLINE | ID: mdl-35980817

RESUMEN

Chemical looping reforming of CH4 coupled with CO2 reduction is a novel technology for the utilization of CH4 and CO2. Here, we report a durable and outstanding LaFe0.8Co0.15Cu0.05O3/S-1 oxygen carrier at lower operating temperature to efficiently convert CH4 and utilize CO2. LaFe0.8Co0.15Cu0.05O3 showed a high CH4 reaction rate (7.0 × 10-7 mol·(g·s)-1), CO selectivity (84.2%), and CO yield (0.045 mol·g-1) at 800 °C. However, the reactivity of LaFe0.8Co0.15Cu0.05O3 reduced quickly with the redox cycles. The introduction of Silicalite-1 promoted the performance of the LaFe0.8Co0.15Cu0.05O3 perovskite oxygen carrier during the redox cycles. It can be attributed to the fact that under heat treatment, the LaFe0.8Co0.15Cu0.05O3 particles grew along the edge of Silicalite-1 and the LaFe0.8Co0.15Cu0.05O3 nanoparticles were homogeneously dispersed on the Silicalite-1 surface, which improved the thermal stability and reactivity of the oxygen carrier. In addition, the interface between Silicalite-1 and LaFe0.8Co0.15Cu0.05O3 nanoparticles also played important roles because the porous structure of Silicalite-1 could reduce the mass transfer restriction of the interface. In addition, Silicalite-1 also possessed high CH4 and CO2 adsorption selectivity, leading to higher reactivity.

10.
Carbohydr Res ; 520: 108632, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-35839641

RESUMEN

Hydrogels loaded with magnetic nanoparticles have been widely researched recently as biomaterials, due to their good biocompatibility and unique magnetic characteristics. In this study, water-soluble superparamagnetic iron oxide nanoparticles (Fe3O4) prepared by coprecipitation were physically doped into the dextran hydrogels which were formed via Schiff base reactions between ethylenediamine and oxidized dextran. The combination of magnetic nanoparticles and chemical cross-linked hydrogels leads to magnetic/pH dual-sensitive hydrogels which can be used as stimuli-responsive carrier. Magnetic properties, swelling, and rheology behaviors of the resulted magnetic hydrogels were strongly affected by the Fe3O4 nanoparticle content. Moreover, doxorubicin (DOX⋅HCl) was embedded into the magnetic hydrogels and pH/magnetic sensitive release profiles were identified. The release mechanism analysis indicated that the release behaviors of DOX⋅HCl were controlled by the diffusion, swelling, and erosion processes simultaneously. The prepared hydrogel/Fe3O4 composites with dual magnetic/pH stimuli-responsiveness hold the promise to be used in various applications such as drug release.


Asunto(s)
Portadores de Fármacos , Hidrogeles , Dextranos/química , Portadores de Fármacos/química , Liberación de Fármacos , Hidrogeles/química , Concentración de Iones de Hidrógeno , Fenómenos Magnéticos
11.
Int J Biol Macromol ; 203: 1-9, 2022 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-35063490

RESUMEN

Wound healing is a challenged and complicated process due to the bacterial infections and frequent replacement in healing process. Hydrogels with properties of visibility and biocompatibility provided convenient and effective treatment during the wound healing process. Bamboo parenchyma cells have a great potential utilized on cellulosic materials fabrication for their high specific surface area and accessibility of chemical reagents. Herein, we present a simple and facile manufacture of transparent wound dressing from bamboo parenchymal cellulose via dissolution in DMAc/LiCl system. Rifampicin (RIF) was loaded on the hydrogel through immersion method. The result exhibited that the maximum drug loading efficiency of cellulose hydrogels was 82.13%. Hydrogel loaded RIF (HLR) showed that the inhibition zones against Gram-negative and Gram-positive bacteria were 19.11 mm and 36.93 mm, respectively. It was observed that the wound was healed more than 60% at 11th day in murine wound models. Meanwhile, RIF provided an exceptionally antibacterial property to hydrogels and promoted proliferation of epidermis cells in wound. As a result of observations, HLR demonstrating potential application in visual wound dressing materials for their excellent transparency, antibacterial effect, wound healing, and biocompatibility.


Asunto(s)
Antiinfecciosos , Hidrogeles , Animales , Antibacterianos/química , Antibacterianos/farmacología , Antiinfecciosos/farmacología , Celulosa/farmacología , Hidrogeles/química , Hidrogeles/farmacología , Ratones , Rifampin/farmacología , Cicatrización de Heridas
12.
Carbohydr Polym ; 275: 118741, 2022 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-34742444

RESUMEN

In recent years, smart-responsive nanocellulose composite hydrogels have attracted extensive attention due to their unique porous substrate, hydrophilic properties, biocompatibility and stimulus responsiveness. At present, the research on smart response nanocellulose composite hydrogel mainly focuses on the selection of composite materials and the construction of internal chemical bonds. The common composite materials and connection methods used for preparation of smart response nanocellulose composite hydrogels are compared according to the different types of response sources such as temperature, pH and so on. The response mechanisms and the application prospects of different response types of nanocellulose composite hydrogels are summarized, and the transformation of internal ions, functional groups and chemical bonds, as well as the changes in mechanical properties such as modulus and strength are discussed. Finally, the shortcomings and application prospects of nanocellulose smart response composite hydrogels are summarized and prospected.


Asunto(s)
Materiales Biocompatibles/química , Celulosa/química , Hidrogeles/química , Nanoestructuras/química , Concentración de Iones de Hidrógeno , Pruebas Mecánicas , Temperatura
13.
Biomass Convers Biorefin ; : 1-13, 2021 Sep 16.
Artículo en Inglés | MEDLINE | ID: mdl-34549016

RESUMEN

Numerous studies have shown that patients with COVID-19 have a high incidence of renal dysfunction. However, the dialysis supplies, including dialysates, are also severely inadequate in hospitals at the pandemic centers. Therefore, there is an urgent need to develop materials that can efficiently and rapidly remove toxins and thus regenerate dialysate to make this vital resource remains readily available. In this work, by simple carbonization and activation treatment, the porous activated carbon from waste rubber seed shell (RAC) was prepared. The adsorption results showed that the maximum adsorption capacities of the obtained RAC for creatinine and uric acid were 430 mg/g and 504 mg/g, respectively. Significantly, the adsorption process can be close to the equilibrium state within 0.5 h, which proved the ultra-fast adsorption response capacity of RAC. Further, the thermodynamics analysis results showed that both the creatinine and uric acid adsorption processes were monolayer, exothermic, and spontaneous. The adsorption kinetics results indicated that the adsorption process of the two uremic toxins followed the pseudo-second-order rate model and was dominated by chemisorption. The instrument analysis results reflected the efficient adsorption of the RAC for the above uremic toxins which might be due to the dipole-dipole interaction between the dipolar oxygen-containing groups of the surface of RAC and the dipoles of the toxins. Moreover, the formed hydrogen bonds between the oxygen groups and the toxins also played an important role. In all, the as-prepared RAC has the potential to efficiently remove major toxins from the dialysate and can be used in in vitro dialysis of numerous patients during the current COVID-19 pandemic.

14.
J Hazard Mater ; 416: 126046, 2021 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-34492891

RESUMEN

Efficient removal of antibiotics from aqueous solution is of fundamental importance due to the increasingly severe antibiotic-related pollution. Herein, a high-performance Fe-ZIF-8-500 adsorbent was synthesized by Fe-doping strategy and subsequent activation with high-temperature. In order to evaluate the feasibility of Fe-ZIF-8-500 as an adsorbent for tetracycline (TC) removal, the adsorption properties of Fe-ZIF-8-500 were systematically explored. The results showed that the Fe-ZIF-8-500 exhibited ultrahigh adsorption capacity for TC with a record-high value of 867 mg g-1. Additionally, the adsorption kinetics and isotherms for TC onto the Fe-ZIF-8-500 can be well-fitted by the pseudo-second-order kinetics model and the Freundlich model, respectively. The ultrahigh adsorption capacity of Fe-ZIF-8-500 can be explained by the synergistic effect of multi-affinities, i.e., surface complexation, electrostatic attraction, π-π interaction and hydrogen bonding. After being used for four cycles the adsorption capacity of Fe-ZIF-8-500 remains a high level, demonstrating its outstanding reusability. The ultrahigh adsorption capacity, excellent reusability, satisfactory water stability and easy-preparation nature of Fe-ZIF-8-500 highlight its bright prospect for removing tetracycline pollutant from wastewater.


Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Adsorción , Antibacterianos , Cinética , Tetraciclina , Agua , Contaminantes Químicos del Agua/análisis
15.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 38(3): 609-620, 2021 Jun 25.
Artículo en Chino | MEDLINE | ID: mdl-34180208

RESUMEN

Polymeric hydrogels have been widely researched as drug delivery systems, wound dressings and tissue engineering scaffolds due to their unique properties such as good biocompatibility, shaping ability and similar properties to extracellular matrix. However, further development of conventional hydrogels for biomedical applications is still limited by their poor mechanical properties and self-healing properties. Currently, nanocomposite hydrogels with excellent properties and customized functions can be obtained by introducing nanoparticles into their network, and different types of nanoparticles, including carbon-based, polymer-based, inorganic-based and metal-based nanoparticle, are commonly used. Nanocomposite hydrogels incorporated with polymeric micelles can not only enhance the mechanical properties, self-healing properties and chemical properties of hydrogels, but also improve the in vivo stability of micelles. Therefore, micelle-hydrogel nanocomposites have been recently considered as promising biomaterials. In this paper, the structure, properties and methods for preparation of the micelle-hydrogel nanocomposite systems are introduced, and their applications in drug delivery, wound treatment and tissue engineering are reviewed, aiming to provide reference for further development and application of the nanocomposites.


Asunto(s)
Hidrogeles , Nanocompuestos , Materiales Biocompatibles , Micelas , Polímeros
16.
Carbohydr Polym ; 265: 118085, 2021 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-33966849

RESUMEN

Dextran hydrogels (Dex-SS) containing both disulfide and Schiff base bonds were developed via facile method based on the dextran oxidation and subsequent formation of Schiff base linkages between polyaldehyde dextran and cystamine, denoted as the disulfide-containing Schiff base reactions. Results of rheology, swelling and 13C CP/MAS NMR study indicated that cross-linking degree of Dex-SS hydrogels depended strongly on the molar ratio of -CHO/-NH2. Acidic and reductive (GSH) environment sensitive degradation behaviors of Dex-SS hydrogels were then evidenced by SEM, rheology study and Ellman's assay. Moreover, doxorubicin (DOX) was loaded into the hydrogel matrix and pH/GSH-responsive release behaviors were demonstrated. Cytocompatibility of Dex-SS hydrogel and effective cell uptake of released DOX was finally proved by transwell assay with HepG2 cells. Take advantages of the abundance of vicinal hydroxyl on a variety of polysaccharides, the disulfide-containing Schiff base reactions is considered as versatile method to develop stimuli-sensitive hydrogels for local drug delivery.

17.
Carbohydr Polym ; 236: 116079, 2020 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-32172892

RESUMEN

Old corrugated containers-based cellulose and fly ash-based fresh wet silica gel were used as raw materials for in situ synthesis of a series of silica/cellulose aerogels in NaOH/urea solution. At a silicon to cellulose ratio of less than 2.5:1, the skeleton structure of the synthesized composite material was dominated by fibrils decorated with spherical silica nanoparticles. At a silicon to cellulose ratio of higher than 2.5:1, the skeleton structure of the composite material was dominated by spherical silica particles interspersed with cellulose. The synthesized composite material was applied to capture CO2 at ambient temperature and pressure. We observed that with increasing silicon content, the CO2 adsorption capacity of the composite material decreased (regardless of its dominant structure), while its selectivity for CO2/N2 increased. This work presents a facile method for the synthesis of adsorption material that has high capacity and selectivity for CO2.

18.
Carbohydr Polym ; 227: 115380, 2020 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-31590848

RESUMEN

Old corrugated containers with low recyclability were used as raw materials to synthesize a series of aerogels with varying cellulose concentrations in NaOH/urea solution via a freeze-drying process. The resulting aerogels had a rich porous structure with specific surface areas in the range of 132.72-245.19 m2.g-1 and mesopore volumes in the range of 0.73-1.53 cm3.g-1, and were tested for CO2 sorption at ambient temperature and pressure, displaying excellent CO2 adsorption capacities in the range of 1.96-11.78 mmol.g-1. Furthermore, the CO2/N2 selectivity of aerogels decreased with decreasing specific surface area, which was mainly caused by the decrease in CO2 capture. In addition, the CO2 sorption capacity of the sample with 2% cellulose content, CA-2, exceeded the values reported so far for many other sorbents with higher specific surface areas, and showed reasonable cyclic stability for CO2 capture. Therefore, this adsorbent represents an attractive prospect for CO2 uptake at room temperature.


Asunto(s)
Dióxido de Carbono/química , Secuestro de Carbono , Celulosa/química , Adsorción , Geles , Papel , Porosidad , Reciclaje , Hidróxido de Sodio/química , Urea/química
19.
Int J Biol Macromol ; 128: 768-774, 2019 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-30716377

RESUMEN

Magnetic hybrid nanogels composed of magnetic nanoparticles and polymer hydrogel matrix have drawn much attention because of their unique superparamagnetic properties and biocompatibility as biomaterials. In this study, a facile method was developed for the preparation of iron oxide nanoparticle-loaded magnetic dextran nanogel as magnetic resonance imaging (MRI) probe. Water soluble superparamagnetic iron oxide nanocrystals (Fe3O4) was pre-synthesized and physically doped into a Schiff base-containing dextran nanogel formed using W/O microemulsion as nanoreactor. Magnetic dextran nanogel (Fe3O4@Dex) with particle size of 300-1000 nm was obtained with multiple Fe3O4 nanoparticles randomly encapsulated in the hydrogel networks. Magnetization and T2 relaxivity study shows that the resulted magnetic nanogel has similar superparamagneitc behaviors with single Fe3O4 nanocrystals, and relatively higher T2 relaxivity (277.2 mMFe-1·s-1) as MRI probe. Notably, Schiff base linkages and aldehyde groups on the dextran hydrogel matrix endow the magnetic nanogel with pH-sensitiveness and reactive groups for further modifications, which make the magnetic dextran nanogel a promising nanoplatform as MRI-guided drug delivery system with acid environment-responsiveness.


Asunto(s)
Dextranos/química , Dextranos/síntesis química , Imagen por Resonancia Magnética/métodos , Nanopartículas de Magnetita/química , Técnicas de Química Sintética , Geles , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Bases de Schiff/química
20.
RSC Adv ; 9(56): 32517-32534, 2019 Oct 10.
Artículo en Inglés | MEDLINE | ID: mdl-35529707

RESUMEN

A series of magnetically separable rGO/Fe3O4 nanocomposites with various amounts of graphene oxide were successfully prepared by a simple ultrasonication assisted precipitation combined with a solvothermal method and their catalytic activity was evaluated for the selective liquid phase oxidation of cyclohexene using hydrogen peroxide as a green oxidant. The prepared materials were characterized using XRD, FTIR, FESEM, TEM, HRTEM, BET/BJH, XPS and VSM analysis. The presence of well crystallized Fe3O4 as the active iron species was seen in the crystal studies of the nanocomposites. The electron microscopy analysis indicated the fine surface dispersion of spherical Fe3O4 nanoparticles on the thin surface layers of partially-reduced graphene oxide (rGO) nanosheets. The decoration of Fe3O4 nanospheres on thin rGO layers was clearly observable in all of the nanocomposites. The XPS analysis was performed to evaluate the chemical states of the elements present in the samples. The surface area of the nanocomposites was increased significantly by increasing the amount of GO and the pore structures were effectively tuned by the amount of rGO in the nanocomposites. The magnetic saturation values of the nanocomposites were found to be sufficient for their efficient magnetic separation. The catalytic activity results show that the cyclohexene conversion reached 75.3% with a highest 1,2-cyclohexane diol selectivity of 81% over 5% rGO incorporated nanocomposite using H2O2 as the oxidant and acetonitrile as the solvent at 70 °C for 6 h. The reaction conditions were further optimized by changing the variables and a possible reaction mechanism was proposed. The enhanced catalytic activity of the nanocomposites for cyclohexene oxidation could be attributed to the fast accomplishment of the Fe2+/Fe3+ redox cycle in the composites due the sacrificial role of rGO and its synergistic effect with Fe3O4, originating from the conjugated network of π-electrons in its surface structure. The rapid and easy separation of the magnetic nanocomposites from the reaction mixture using an external magnet makes the present catalysts highly efficient for the reaction. Moreover, the catalyst retained its activity for five repeated runs without any drastic drop in the reactant conversion and product selectivity.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA