The Capture and Catalytic Conversion of CO_(2) by Dendritic Mesoporous Silica-Based Nanoparticles

Dendritic mesoporous silica nanoparticles own three-dimensional center-radial channels and hierarchical pores,which endows themselves with super-high specific surface area,extremely large pore volumes,especially accessible internal spaces,and so forth.Dissimilar guest species(such as organic groups or metal nanoparticles)could be readily decorated onto the interfaces of the channels and pores,realizing the functionalization of dendritic mesoporous silica nanoparticles for targeted applications.As adsorbents and catalysts,dendritic mesoporous silica nanoparticles-based materials have experienced nonignorable development in CO_(2)capture and catalytic conversion.This comprehensive review provides a critical survey on this pregnant subject,summarizing the designed construction of novel dendritic mesoporous silica nanoparticles-based materials,the involved chemical reactions(such as CO_(2)methanation,dry reforming of CH_(4)),the value-added chemicals from CO_(2)(such as cyclic carbonates,2-oxazolidinones,quinazoline-2,4(1H,3H)-diones),and so on.The adsorptive and catalytic performances have been compared with traditional silica mesoporous materials(such as SBA-15 or MCM-41),and the corresponding reaction mechanisms have been thoroughly revealed.It is sincerely expected that the in-depth discussion could give materials scientists certain inspiration to design brand-new dendritic mesoporous silica nanoparticles-based materials with superior capabilities towards CO_(2)capture,utilization,and storage.

Effects of silica nanoparticles on growth and photosynthetic pigment contents of Scenedesmus obliquus

To assess the aquatic ecosystem safety for silica （SiO2） nanoparticles （NPs）, the growth inhibition and photosynthetic pigment contents of Scenedesmus obliquus in logarithm growth phase exposed to SiO2 NPs and SiO2 bulk particles （BPs） suspensions were measured. SiO2 NPs with 10-20 nm diameters were found to be toxic. The 20% effective concentration （EC20） values for 72 and 96 hr were 388.1 and 216.5 mg/L, respectively. The contents of chlorophyll decreased significantly under moderate and high concentration （50, 100, and 200 mg/L） of SiO2 NPs after 96-hr exposure, but the carotenoids did not. SiO2 BPs were found to be nontoxic up to 200 mg/L. The toxicity of SiO2 NPs probablely due to their sorption to algal cells surface. The results imply that there is potential harm to aquatic environment by using SiO2 NPs, and it should deserve special concern.

Application of Modified Silica Coated Magnetite Nanoparticles for Removal of Iodine from Water Samples

The adsorption of iodine onto silica coated magnetite nanoparticles(im-SCMNPs) that modified with imidazole was investigated for removal of high concentrations of iodine from wastewater. Modified silica magnetite nanoparticles showed high efficiency in removing iodine from wastewater samples. The optimum pH for iodine removal was 7.0-8.0. The adsorption capacity was evaluated using both the Langmuir and Freundlich adsorption isotherm models. The size of the produced magnetite nanoparticles was determined by X-ray diffraction analysis and scanning electron microscopy. Synthesized magnetite nanoparticles showed the high adsorption capacity and would be a good method to increase adsorption efficiency for the removal of iodine in a wastewater treatment process. The Langmuir adsorption capacity(qmax) was found to be 140.84 mg/g of the adsorbent.

Effect of silica nanoparticles/poly(vinylidene fluoride-hexafluoropropylene) coated layers on the performance of polypropylene separator for lithium-ion batteries

In an effort to reduce thermal shrinkage and improve electrochemical performance of porous polypropylene （PP） separators for lithium-ion batteries, a new composite separator is developed by introducing ceramic coated layers on both sides of PP separator through a dip-coating process. The coated layers are comprised of heat-resistant and hydrophilic silica nanoparticles and polyvinylidene fluoride-hexafluoropropylene （PVDF-HFP） binders. Highly porous honeycomb structure is formed and the thickness of the layer is only about 700 nm. In comparison to the pristine PP separator, the composite separator shows significant reduction in thermal shrinkage and improvement in liquid electrolyte uptake and ionic conduction, which play an important role in improving cell performance such as discharge capacity, C-rate capability, cycle performance and coulombic efficiency.

Poly(NIPAM-co-MPS)-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system

Hybrid drug delivery systems(DDS) have been prepared by grafting poly(NIPAM-co-MPS) chains on multimodal porous silica nanoparticles having an inner mesoporous structure and an outer thin layer of micropores. The hybrid thermoresponsive DDS were fully characterized and loaded with a model drug. The in vitro drug release tests are carried out at below and above the lower critical solution temperature(LCST) of the copolymer. The results have revealed that due to the presence of small diameter(~1.3 nm) micropores at the periphery of the particles, the collapsed globules of the thermoresponsive copolymer above its LCST hinders the complete release of the drug which resulted in a reverse thermoresponsive drug release profile by the hybrid DDS.

How much would silica nanoparticles enhance the performance of low-salinity water flooding?

Nanofluids and low-salinity water(LSW)flooding are two novel techniques for enhanced oil recovery.Despite some efforts on investigating benefits of each method,the pros and cons of their combined application need to be evaluated.This work sheds light on performance of LSW augmented with nanoparticles through examining wettability alteration and the amount of incremental oil recovery during the displacement process.To this end,nanofluids were prepared by dispersing silica nanoparticles(0.1 wt%,0.25 wt%,0.5 wt% and 0.75 wt%)in 2,10,20 and 100 times diluted samples of Persian Gulf seawater.Contact angle measurements revealed a crucial role of temperature,where no wettability alteration occurred up to 80 ℃.Also,an optimum wettability state(with contact angle 22°)was detected with a 20 times diluted sample of seawater augmented with 0.25 wt% silica nanoparticles.Also,extreme dilution(herein 100 times)will be of no significance.Throughout micromodel flooding,it was found that in an oil-wet condition,a combination of silica nanoparticles dispersed in 20 times diluted brine had the highest displacement efficiency compared to silica nanofluids prepared with deionized water.Finally,by comparing oil recoveries in both water-and oil-wet micromodels,it was concluded that nanoparticles could enhance applicability of LSW via strengthening wettability alteration toward a favorable state and improving the sweep efficiency.

Synthesis and Characterization of Carboxyl-terminated Polyethylene Glycol Functionalized Mesoporous Silica Nanoparticles

Colloidal mesoporous silica nanoparticles functionalized with carboxy-terminated polyethylene glycol(CMS-PEG-COOH) were successfully synthesized by covalently grafting dicarboxy-terminated polyethylene glycol(HOOC-PEG-COOH) on the surface of the amino functionalized CMS nanoparticles with amide bond as a cross linker. Moreover, the structural and particle properties of CMS-PEG-COOH were characterized by nuclear magnetic resonance spectroscopy(1 H-NMR), transmission electron microscopy(TEM), dynamic light scattering(DLS), nitrogen adsorption-desorption measurements, X-ray diffraction(XRD), and Fourier transform infrared spectroscopy(FT-IR). The nanomaterials presented a relatively uniform spherical shape morphology with diameters of about 120 nm,and favorable dispersibility in weak acid solution. The CMSPEG-COOH exhibited no changes in the state of amorphous, while the mesopores sizes of 5.25 nm might provide the nanomaterials with large capacity for the loading and releasing of drugs. So the results indicated that CMSPEG-COOH might be a critical nanomaterial for drug delivery system in the future.

pH-responsive mesoporous silica nanoparticles employed in controlled drug delivery systems for cancer treatment

In the fight against cancer, controlled drug delivery systems have emerged to enhance the therapeutic efficacy and safety of anti-cancer drugs. Among these systems, mesoporous silica nanoparticles （MSNs） with a functional surface possess obvious advantages and were thus rapidly developed for cancer treatment. Many stimuli-responsive materials, such as nanopartides, polymers, and inorganic materials, have been applied as caps and gatekeepers to control drug release from MSNs. This review presents an overview of the recent progress in the production of pH-responsive MSNs based on the pH gradient between normal tissues and the tumor microenvironment. Four main categories of gatekeepers can respond to acidic conditions. These categories will be described in detail.

Preparation of Ionic Liquid Functionalized Silica Nanoparticles for Oral Drug Delivery

The objective of this study is to utilize the pH sensitivity of modified silica nanoparticles (SNIL) by imidazole-based ionic liquid for oral delivery of insulin. In the first time, the imidazole was covalently attached to the 3-trimethoxysily-lpropyl chloride with replacement of all the chlorine atoms. Then, a silica nanoparticle was modified by N-(3-trimeth-oxysilylpropyl) imidazole. The nanocapsule (NCIL) was achieved after the etching of the modified silica nanoparticle template with hydrofluoric acid. The nanoparticles connected through an ionic liquid-like network were characterized by FTIR and SEM. Insulin was entrapped in these carriers and the in vitro release profiles were established separately in both enzyme-free simulated gastric and intestinal fluids (SGF, pH 1) and (SIF, pH 7.4), respectively. When these drug-loaded nanoparticles was placed in physiological buffer solution (pH 7.4), a partial negative surface charge on the modified silica nanoparticle was generated due to the deprotonation of silanol groups, and the strong electrostatic repulsion triggered a sustained release of the loaded molecules.

Preparation and Characterization of Carboxyl Functionalized Fluorescent Mesoporous Silica Nanoparticles Containing 8-Hydroxyquinolinate Zinc Complexes

Fluorescent mesoporous silica nanoparticles functionalized with carboxyl group(Znq-CMSCOOH) were successfully synthesized by in situ formation route of 8-hydroxyquinolinate zinc complexes in channels of mesoporous silica nanoparticles and post-grafting of carboxyl group on the surface. Moreover,the particle size and structural properties of Znq-CMS-COOH were characterized by transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FT-IR),UV-vis spectrometer, fluorescence spectrometer and nitrogen adsorption-desorption measurements. The obtained results suggest that the Znq-CMS-COOH presents the uniform spherical shape with the mean diameter of about 85 nm and the obvious wormhole arrangement mesoporous. In addition, the Znq-CMS-COOH possesses green fluorescence with the emission peaks at 495 nm. So the Znq-CMS-COOH, which is beneficial to further modification and tracing, might be a great potential carrier for applying in drug delivery system in the future.

Subchronic Oral Toxicity of Silica Nanoparticles and Silica Microparticles in Rats

Objective To investigate the subchronic oral toxicity of silica nanoparticles（NPs） and silica microparticles（MPs） in rats and to compare the difference in toxicity between two particle sizes.Methods Sprague-Dawley rats were randomly divided into seven groups： the control group; the silica NPs low-, middle-, and high-dose groups; and the silica MPs low-, middle-, and high-dose groups [166.7,500, and 1,500 mg/（kg·bw·day）]. All rats were gavaged daily for 90 days, and deionized water was administered to the control group. Clinical observations were made daily, and body weights and food consumption were determined weekly. Blood samples were collected on day 91 for measurement of hematology and clinical biochemistry. Animals were euthanized for necropsy, and selected organs were weighed and fixed for histological examination. The tissue distribution of silicon in the blood, liver,kidneys, and testis were determined.Results There were no toxicologically significant changes in mortality, clinical signs, body weight,food consumption, necropsy findings, and organ weights. Differences between the silica groups and the control group in some hematological and clinical biochemical values and histopathological findings were not considered treatment related. The tissue distribution of silicon was comparable across all groups.Conclusion Our study demonstrated that neither silica NPs nor silica MPs induced toxicological effects after subchronic oral exposure in rats.

Wettability alteration and retention of mixed polymer-grafted silica nanoparticles onto oil-wet porous medium

Enhanced oil recovery(EOR)processes are applied to recover trapped or residual oil in the reservoir rocks after primary and secondary recovery methods.Changing the wettability of the rock from oil-wet to water-wet is named wettability alteration.It is an important factor for EOR.Due to their unique properties,nanoparticles have gained great attention for improving oil recovery.Despite the promising results,the main challenges of applying nanoparticles are related to the colloidal stability of the nanofuids in the harsh conditions of the reservoirs.In recent years,polymer-grafted nanoparticles have been considered as novel promising materials for EOR.The obtained results showed that adding a hydrophobic agent trimethoxy(propyl)silane on the surface of modifed silica nanoparticles with polyethylene glycol methyl ether has an efective role in improving retention and wettability alteration,especially in the oil-wet substrate due to hydrophobic interaction.The modifed silica nanoparticle by mixed polyethylene glycol methyl ether(Mn~5000)and trimethoxy(propyl)silane showed a proper performance at a concentration of 1000 ppm and a salinity range of 2000-40,000 ppm.The obtained fndings can help for a better understanding of the silica nanofuid modifcation with both hydrophilic and hydrophobic agents for the EOR application of near-wellbore.

Silica nanoparticle design for colorectal cancer treatment:Recent progress and clinical potential

Colorectal cancer(CRC)is the third most common cancer worldwide and the second most common cause of cancer death.Nanotherapies are able to selectively target the delivery of cancer therapeutics,thus improving overall antitumor eff-iciency and reducing conventional chemotherapy side effects.Mesoporous silica nanoparticles(MSNs)have attracted the attention of many researchers due to their remarkable advantages and biosafety.We offer insights into the recent advances of MSNs in CRC treatment and their potential clinical application value.

Determination of Sulfadimidine in Royal Jelly by C_(18)-functionalized Magnetic Silica Nanoparticles Solid Phase Extraction-High Performance Liquid Chromatography-Tandem Mass Spectrometry

[Objective] This study aimed to develop a method of C_18-functionalized magnetic silica nanoparticles solid phase extraction-high performance liquid chro- matography-tandem mass spectrometry for the determination of sulfadimidine in royal jelly. [Method] The royal jelly samples were pretreated by MCX SPE column and C_18-functionalized magnetic silica nanoparticles, and the purified samples were de- tected by HPLC-MS/MS. [Result] The detection method showed a good linear rela- tionship in the range of 5-80 ugkg （r=0.993 1）. The recovery ranges were between 93%- 104% with the relative standard deviations （RSD） below 11.3%. [Conclusion] Combined with automation equipment, the method is simple, fast, time-saving, and easy to real- ize the automation of sulfadimidine in the royal jelly samples before determination.

Evaluating the potential of surface-modified silica nanoparticles using internal olefin sulfonate for enhanced oil recovery

Recently,nanoparticles have proven to enhance oil recovery on the core-flood scale in challenging high-pressure high-temperature reservoirs.Nanomaterials generally appear to improve oil production through wettability alteration and reduction in interfacial tension between oil and water phases.Besides,they are environmentally friendly and cost-effective enhanced oil recovery techniques.Studying the rheological properties of nanoparticles is critical for field applications.The instability of nanoparticle dispersion due to aggregation is considered as an unfavorable phenomenon in nanofluid flooding while conducting an EOR process.In this study,wettability behavior and rheological properties of surface-treated silica nanoparticles using internal olefins sulfonates(IOS20–24 and IOS19–23),anionic surfactants were investigated.Surface modification effect on the stability of the colloidal solution in porous media and oil recovery was inspected.The rheology of pure and surfacetreated silica nanoparticles was investigated using a HPHT rheometer.Morphology and particle size distributions of pure and coated silica nanoparticles were studied using a field emission scanning electron microscope.A series of core-flood runs was conducted to evaluate the oil recovery factor.The coated silica nanoparticles were found to alter rheological properties and exhibited a shear-thinning behavior as the stability of the coated silica nanoparticles could be improved considerably.At low shear rates,the viscosity slightly increases,and the opposite happens at higher shear rates.Furthermore,the surfacemodified silica nanoparticles were found to alter the wettability of the aqueous phase into strongly water-wet by changing the contact angle from 80°to 3°measured against glass slides representing sandstone rocks.Oil–water IFT results showed that the surface treatment by surfactant lowered the oil–water IFT by 30%.Also,the viscosity of brine increased from 0.001 to 0.008 Pa s by introducing SiO2 nanoparticles to the aqueous phase for better displacement efficiency during chemicalassisted EOR.The core-flood experiments revealed that the ultimate oil recovery is increased by approximately 13%with a surfactant-coated silica nanofluid flood after the conventional waterflooding that proves the potential of smart nanofluids for enhancing oil recovery.The experimental results imply that the use of surfactant-coated nanoparticles in tertiary oil recovery could facilitate the displacement efficiency,alter the wettability toward more water-wet and avoid viscous fingering for stable flood front and additional oil recovery.

Experimental investigation of the effects of oil asphaltene content on CO_(2) foam stability in the presence of nanoparticles and sodium dodecyl sulfate

Foam stability tests were performed using sodium dodecyl sulfate(SDS)surfactant and SiO2 nanoparticles as foaming system at different asphaltene concentrations,and the half-life of CO_(2) foam was measured.The mechanism of foam stability reduction in the presence of asphaltene was analyzed by scanning electron microscope(SEM),UV adsorption spectrophotometric concentration measurement and Zeta potential measurement.When the mass ratio of synthetic oil to foam-formation suspension was 1:9 and the asphaltene mass fraction increased from 0 to 15%,the half-life of SDS-stabilized foams decreased from 751 s to 239 s,and the half-life of SDS/silica-stabilized foams decreased from 912 s to 298 s.When the mass ratio of synthetic oil to foam-formation suspension was 2:8 and the asphaltene mass fraction increased from 0 to 15%,the half-life of SDS-stabilized foams decreased from 526 s to 171 s,and the half-life of SDS/silica-stabilized foams decreased from 660 s to 205 s.In addition,due to asphaltene-SDS/silica interaction in the aqueous phase,the absolute value of Zeta potential decreases,and the surface charges of particles reduce,leading to the reduction of repulsive forces between two interfaces of thin liquid film,which in turn,damages the foam stability.

Co-adsorption behavior of aggregated asphaltenes and silica nanoparticles at oil/water interface and its effect on emulsion stability

In petroleum industry, crude oil emulsions are commonly formed in oilfields. The asphaltenes and fine particles in crude oil may affect the stability of the emulsions by adsorbing at the water/oil interface. In this research, the effect of silica nanoparticles and asphaltenes on emulsion stability is explored first. The asphaltenes are proved to benefit emulsion stability. Unlike the asphaltenes, however, the modified silica nanoparticles may have positive or negative effect on emulsion stability, depending on the asphaltene concentration and aggregation degree in the emulsions. Further, it is confirmed by conducting interfacial experiment that the asphaltenes and particles can adsorb at the interface simultaneously and determine the properties of the interfacial layer. More in-depth experiments concerning contact angle and asphaltene adsorption amount on the particles indicate that the asphaltenes can modify the wettability of the particles. Higher concentration and lower aggregation degree of the asphaltenes can increase their adsorption amount on the surface of particles and then improve the modification effectiveness of the particles. Resultantly, the particles with good modification effectiveness can enhance the emulsion stability while the particles with poor modification effectiveness will weaken the emulsion stability.

Improving Flow Property of Nifedipine Loaded Solid-Lipid Nanoparticles by Means of Silica for Oral Solid Dosage Form

In this study, a new formulation of silica nanocomposite containing nifedipine (NI) loaded freeze-dried solid-lipid nanoparticles (NI-SLNs) and silica have been developed with improved flowability of powders, which can lead to the formulation of a widely acceptable oral dosage form. The stable NI-SLNs were prepared using two phospholipids, hydrogenated soybean phosphatidylcholine and dipalmitoylphosphatidylglycerol mixed with 2.5% w/v trehalose as a cryoprotectant followed by lyophilization. We employed various grades of two types of silica, such as fumed and precipitated. Silica improved the poor flow property of NI-SLNs to good category as per USP-29. In addition, most of the silica nanocomposites showed the satisfactory results in their physicochemical properties such as particle size, polydispersity index, zeta potential, and recovered potency by around 100 nm, 0.3, -50 mV, and 80%, respectively. Furthermore, it was found that NI-SLNs were easily released form nanocomposites within 30 min, therefore, suggesting an improvement of drug dissolutions. Among them, precipitated silica cooperated fairly in improving the powder characteristics as well as the physicochemical, morphological, and pharmaceutical properties.

Characterization of modified mesoporous silica nanoparticles as vectors for siRNA delivery

Gene therapy using siRNA molecules is nowadays considered as a promising approach. For successful therapy, development of a stable and reliable vector for siRNA is crucial. Non-viral and non-organic vectors like mesoporous silica nanoparticles(MSN) are associated with lack of most viral vector drawbacks, such as toxicity, immunogenicity, but also generally a low nucleic acid carrying capacity. To overcome this hurdle, we here modified the pore walls of MSNs with surface-hyperbranching polymerized poly(ethyleneimine)(hbPEI), which provides an abundance of amino-groups for loading of a larger amount of siRNA molecules via electrostatic adsorption. After loading, the particles were covered with a second layer of pre-polymerized PEI to provide better protection of siRNA inside the pores, more effective cellular uptake and endosomal escape. To test the transfection efficiency of PEI covered si RNA/MSNs, MDA-MB 231 breast cancer cells stably expressing GFP were used. We demonstrate that PEI-coated si RNA/MSN complexes provide more effective delivery of si RNAs compared to unmodified MSNs. Thus, it can be concluded that appropriately surface-modified MSNs can be considered as prospective vectors for therapeutic siRNA delivery.

Investigation into the effect of silica nanoparticles on the rheological characteristics of water-in-heavy oil emulsions

The effect of silica nanoparticles on the rheological characteristics of water-in-heavy oil emulsions has been investigated.Enhanced oil recovery methods for heavy oil production(most especially,thermal fluid injection)usually result in the formation of water-in-oil(W/O)emulsion.In reality,the emulsion produced also contains some fine solid mineral particles such as silica,which,depending on its quantity,may alter the viscosity and/or rheological properties of the fluid.A series of binary-component emulsions were separately prepared by dispersing silica nanoparticles[phase fraction,βs,=0.5%–5.75%(wt/v)]in heavy oil(S/O suspension)and by dispersing water[water cut,θw=10%–53%(v/v)]in heavy oil(W/O emulsion).Ternary-component emulsions comprising heavy oil,water droplets and suspended silica nanoparticles(S/W/O)were also prepared with similar ranges ofθw andβs.The viscosity was measured at different shear rates(5.1–1021.4 s-1)and temperatures(30–70°C).Both binary-component and ternary-component emulsion systems were observed to exhibit nonNewtonian shear thinning behaviour.The viscosity of the heavy oil and W/O emulsions increased in the presence of silica nanoparticles.The effect was,however,less signifi cant belowβs=2%(wt/v).Moreover,a generalized correlation has been proposed to predict the viscosity of both binary-component and ternary-component emulsions.