Hollow Silica Nanoparticles Research Articles

Encapsulation of an Anionic Surfactant into Hollow Spherical Nanosized Capsules: Size Control, Slow Release, and Potential Use for Enhanced Oil Recovery Applications and Environmental Remediation.

A new platform that allows encapsulation of anionic surfactants into nanosized capsules and subsequent release upon deployment is described. The system is based on DOWFAX surfactant molecules incorporated into sub-100 nm hollow silica nanoparticles composed of a mesoporous shell. The particles released 40 wt % of the encapsulated surfactant at 70 °C compared to 24 wt % at 25 °C after 21 and 18 days, respectively. The use of the particles for subsurface applications is assessed by studying the effectiveness of the particles to alter the wettability of hydrophobic surfaces and reduction of the interfacial tension. The release of the surfactant molecules in the suspension reduces the contact angle of a substrate from 105 to 25° over 55 min. A sustained release profile is demonstrated by a continuous reduction of the interfacial tension of an oil suspension, where the interfacial tension is reduced from 62 to 2 mN m–1 over a period of 3 days.

Polystyrene nanoparticles prepared by nanoprecipitation: A recyclable template for fabricating hollow silica

Polystyrene was synthesized and applied as a template for fabricating hollow silica nanoparticles. Organic solvent and water were used as a solvent and an anti-solvent, respectively, to produce the polystyrene nanoparticles via. nanoprecipitation technique. The influence of precipitation method (one-shot or drop), solvent for dissolution of polystyrene, and concentration of polystyrene or CTAB linker on the diameter of polystyrene nanoparticles was investigated. The hollow silica nanoparticles were fabricated using the as-made polystyrene nanoparticles as a template with the help of CTAB linker. Polystyrene was recovered by the extraction of polystyrene@SiO2 composite with the tetrahydrofuran solvent, and the recovered polystyrene was re-used to make the polystyrene nanoparticles as a template for fabricating hollow silica nanoparticles. Our study can be applied for other types of polymeric materials as long as those polymeric materials form nanoparticles via. nanoprecipitation technique. In comparison with the polystyrene hard template prepared by emulsion polymerization, the size of polystyrene nanoparticles produced by the nanoprecipitation technique can be well-tuned by changing the polystyrene and linker concentrations.

Downshifting and antireflective thin films for solar module power enhancement

Efforts to enhance the solar conversion efficiency have prevailed for decades. There is a growing interest in improving the spectral response of solar modules, especially in harvesting UV photons, which offer intense energy in a narrow wavelength range. To harvest UV photons and reduce reflection without interfering with the formulas and manufacturing process of solar cells, in this work, thin films that possess downshifting and antireflection capabilities were fabricated on the cover glass of multicrystalline Si solar cells. The thin films were composed of graded index layers of europium-doped yttrium orthovanadate (YVO4:Eu) and hollow silica nanoparticles (HSNPs). The design of the composite thin films was assisted by the FDTD mathematical model that simulated the refractive index and thickness of each layer to obtain the optimum transmittance. The cover glass with multifunctional thin films harvested more than 30% of UV photons and enhanced the solar conversion efficiency by 4.12% at normal incidence compared to the uncoated cover glass.

Colorimetry-based System for Gaseous Carbon Dioxide Detection

The study of sensing materials to the detection of carbon dioxide (CO2) was achieved using p-nitrophenol (pNPh) as a colorimetric indicator. The sensing material was polymerized (NPLn), functionalized with 3-triethoxysilyl propyl isocyanate (IPTES) which sensitivity was tested in the form of a membrane as is and encapsulated in hollow silica nanoparticles. The sensing membranes were tested in a closed gas system comprising very precise flow controllers to deliver different concentrations of CO2 (vs. N2). The combination of the sensing membranes with multimode optical fibers and a dual-wavelength diode (LED) allows the measurement of the CO2 through the analysis of the induced absorbance changes with a self-referenced ratiometric scheme. The analysis of the sensing materials have shown significant changes in their chemical and physical properties and the results attest these materials with a strong potential for assessing CO2 dynamics in environmental, medical, and industrial applications.

Self-Assembled Surfactant-Templated Synthesis of Porous Hollow Silica Nanoparticles: Mechanism of Formation and Feasibility of Post-Synthesis Nanoencapsulation.

SiO2 is bioinert and highly functionalizable, thus making it a very attractive material for nanotechnology applications such as drug delivery and nanoencapsulation of pesticides. Herein, we synthesized porous hollow SiO2 nanoparticles (PHSNs) by using cetyltrimethylammonium bromide (CTAB) and Pluronic P123 as the structure-directing agents. The porosity and hollowness of the SiO2 structure allow for the protective and high-density loading of molecules of interest inside the nanoshell. We demonstrate here that loading can be achieved post-synthesis through the pores of the PHSNs. The PHSNs are monodisperse with a mean diameter of 258 nm and a specific surface area of 287 m2 g-1. The mechanism of formation of the PHSNs was investigated using 1-D and 2-D solid-state nuclear magnetic resonance (SS-NMR) and Fourier-transform infrared spectroscopy (FTIR). The data suggest that CTAB and Pluronic P123 interact, forming a hydrophobic spherical hollow cage that serves as a template for the porous hollow structure. After synthesis, the surfactants were removed by calcination at 550 °C and the PHSNs were added to an Fe3+ solution followed by addition of the reductant NaBH4 to the suspension, which led to the formation of Fe(0) NPs both on the PHSNs and inside the hollow shell, as confirmed by transmission electron microscopy imaging. The imaging of the formation of Fe(0) NPs inside the hollow shell provides direct evidence of transport of solute molecules across the shell and their reactions within the PHSNs, making it a versatile nanocarrier and nanoreactor.

Hollow silica reinforced magnesium nanocomposites with enhanced mechanical and biological properties with computational modeling analysis for mandibular reconstruction

The present study investigates Mg-SiO2 nanocomposites as biodegradable implants for orthopedic and maxillofacial applications. The effect of presence and progressive addition of hollow silica nanoparticles (0.5, 1, and 1.5) vol.% on the microstructural, mechanical, degradation, and biocompatibility response of pure Mg were investigated. Results suggest that the increased addition of hollow silica nanoparticles resulted in a progressive increase in yield strength and ultimate compressive strength with Mg-1.5 vol.% SiO2 exhibiting superior enhancement. The response of Mg-SiO2 nanocomposites under the influence of Hanks’ balanced salt solution revealed that the synthesized composites revealed lower corrosion rates, indicating rapid dynamic passivation when compared with pure Mg. Furthermore, cell adhesion and proliferation of osteoblast cells were noticeably higher than pure Mg with the addition of 1 vol.% SiO2 nanoparticle. The biocompatibility and the in vitro biodegradation of the Mg-SiO2 nanocomposites were influenced by the SiO2 content in pure Mg with Mg-0.5 vol.% SiO2 nanocomposite exhibiting the best corrosion resistance and biocompatibility when compared with other nanocomposites. Enhancement in mechanical, corrosion, and biocompatibility characteristics of Mg-SiO2 nanocomposites developed in this study are also compared with properties of other metallic biomaterials used in alloplastic mandibular reconstruction in a computational model.

Development and Characterization of a Glimepiride-Loaded Gelatin-Coated Mesoporous Hollow Silica Nanoparticle Formulation and Evaluation of Its Hypoglycemic Effect on Type-2 Diabetes Model Rats.

In this study, we prepared gelatin-coated mesoporous hollow silica nanospheres (GSN) as a drug carrier to improve the water solubility and regulate the release rate of glimepiride (GLM). GLM was loaded into GSN by an absorption method, and drug-loaded samples (GLM-GSN) were characterized by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). Cellular uptake and in vivo intestinal uptake experiments were performed in rats. In addition, the studies of in-vitro drug dissolution, pharmacokinetics, and pharmacodynamic experiments also were performed. GLM-GSN showed excellent drug loading (39.7% ± 0.7%) and sustained GLM release. The state of GLM in GSN was amorphous according to DSC and XRD results. Cellular uptake and in vivo intestinal uptake experiments indicated that GSN could be effectively absorbed, and an MTT experiment demonstrated that GSN had good biocompatibility. Furthermore, the GLM-GSN had a higher bioavailability in pharmacokinetics experiments and a prominent hypoglycemic effect on type-2 diabetes model rats in pharmacodynamic experiments. This study clearly shows that GSN is a promising platform for delivering GLM for the treatment of type-2 diabetes.

A facile and controllable one-pot synthesis approach to amino-functionalized hollow silica nanoparticles with accessible ordered mesoporous shells

The development of a practical synthetic method to functionalize hollow mesoporous silica with organic groups is of current interest for selective adsorption and energy storage applications. Herein, a facile and controllable one-pot approach for the synthesis of monodisperse amino-functionalized hollow mesoporous silica nanoparticles is presented. A novel solid-to-hollow structural transformation procedure of the silica nanoparticles is presented. The structural transformation is easily designed, as observed through transmission electron microscopy, by tailoring the HCl and N-lauroylsarcosine sodium molar ratio and the water content in the sol-gel. Ordered and radially oriented in situ amino-functionalized mesochannels were successfully introduced into the shells of the hollow silica nanoparticles. A formation mechanism for the hollow mesoporous silica materials is discussed.

Sacrificial sulphonated polystyrene template-assisted synthesis of mesoporous hollow core-shell silica nanoparticles for drug-delivery application

Spherical mesoporous hollow core-shell silica nanoparticles (HCSNs) of size 200 ± 50 nm with tunable thickness from 20 to 60 nm are synthesized using a sacrificial sulphonated polystyrene (PS, particle size 160 nm) template. A facile method is adopted for the sulphonation of PS using sulphuric acid, which enhanced the negative charge on the surface of PS as confirmed by zeta potential analysis and Fourier transform infrared radiation analysis. The thickness of the silica shell is tuned by altering the concentration of the silica precursor and is found to increase due to the use of the sulphonated PS template. N2 adsorption/desorption studies reported the variation of specific surface area of HCSNs from 644.1 to 197.8 m2 g−1 and average pore size from 1.55 to 3.4 nm. The drug release behaviour of HCSNs with different shell thicknesses is investigated using doxorubicin as the model drug. A delay in the drug release for ~300 min is successfully achieved by employing HCSNs with enhanced thickness of 60 nm. Application of HCSNs in targeted drug delivery was further supported by the in-vitro cytotoxicity studies carried out on lung adenocarcinoma cells.

The role of electro-sprayed silica-coated zinc oxide nanoparticles to hollow silica nanoparticles for optical devices material and their characterization

Studies of the synthesis of composite zinc oxide-silica (ZnO@SiO2) particles remain a great challenge in terms of obtaining a more precise design and suppress the agglomeration of pure ZnO. However, recent methods encounter problems in production, such as time consumption, multistep processes, and agglomeration of the final product. To this end, a one-step process for the production of composite ZnO@SiO2 particles which has good potential as UV-attenuating materials was proposed via the electrospray method for the first time. The results from this study offer, for the first time, new insights into the design of ZnO@SiO2 as a core-shell particles morphology in which ZnO was coated with SiO2 by using the electrospray method with good control of particle agglomeration. A possible core-shell formation mechanism is proposed to offer an in-depth understanding. When tested as ultraviolet (UV) attenuation materials, the obtained core-shell particles exhibited an activation transmission near 30 % in the wavelength range of 280−400 nm under UV A and B light. This activation transmission is better than that of the same composite without a core-shell structure. Another particle with different characteristics (e.g., hollow SiO2) was obtained after the removal of ZnO from the core-shell composite structure. The activation transmission of hollow silica reached approximately 80 % under UV–vis light, indicating that hollow SiO2 has potential applications in future transparent devices.

Embedding hollow silica nanoparticles of varying shapes and dimensions in nanofiltration membranes for optimal performance

Spherical, cubic, or rodlike hollow silica nanoparticles were embedded in nanofiltration polyamide membranes. Each nanoparticle was separately added to an n-hexane solution of trimesoyl chloride, which was reacted with piperazine through interfacial polymerization. The modified membranes exhibited higher hydrophilicity. Field emission scanning electron microscopy depicted less aggregation in the case of the embedded spherical silica nanoparticles, on account of the smallest dimensions. Moreover, the corresponding modified membrane delivered the greatest water flux. The weight ratio of the spherical nanoparticles to trimesoyl chloride was established to be optimum at 0.5, at which the membrane yielded a pure water flux of 90 ± 3 L/m2 h (6 bar), and the rejection of different salts followed this trend: Na2SO4 (92%) > MgSO4 (70%) > MgCl2 (14%) > NaCl (11%). Therefore, the shape of hollow silica nanoparticles exerts an influence on the separation efficiency of the modified nanofiltration membranes.

Preliminary studies of effects of surface morphology and chemistry of silica-based antireflection coatings on anti-soiling performance under Ningbo’s climate

Silica-based antireflection coatings (ARCs) used in photovoltaic (PV) modules often encounter soiling problems, which has been recognized as one of the most serious problems degrading the power output of PV modules. In this work, four kinds of silica-based ARCs were prepared to investigate the effects of surface morphology and chemistry on their anti-soiling properties under Ningbo’s climate. To reveal the influences of surface morphology, hollow silica nanoparticle (HSN)- and solid silica nanoparticle (SSN)-based ARCs were prepared and compared. To understand the surface chemical effects, we comparatively studied the soiling behavior of hydrophilic and hydrophobic HSN ARCs postmodified with methyl and fluorinated groups (named CH3-HSN and F-HSN, respectively). After half-year field tests, we found that the HSN ARCs with a rougher surface exhibited better anti-soiling performance than the SSN ARCs. On the other hand, the hydrophilic ARCs showed better soiling resistance than the hydrophobic controls because of the role of rain cleaning in the soiling mitigation of the hydrophilic samples installed at a moderate tilt angle under a typical coastal climate. Comparing the hydrophobic samples modified with methyl and fluorinated groups, the former was superior to the latter in both laboratory and outdoor tests because of the larger adhesion force between contaminants and the surface in the fluorinated-HSN ARCs. These findings provide constructive guidance for the applications of silica-based ARCs in PV modules installed in coastal areas, which is the key to maximizing the power output of PV modules in practice.

Silica Encapsulated-Gold Nanoparticles as a Nano-reactor for Aerobic Oxidation of Benzyl alcohols and Tandem Oxidative A3 coupling Reactions in Water

In this work, the encapsulated-Au nanoparticles (NPs) into the silica hollow NPs were synthesized by microwave-assisted preparation of PEG-coated Au NPs, coating them with a layer of organically modified silica and removing the PEG around the Au NPs. The structure of these encapsulated NPs was characterized by TEM, SEM, XRD, FTIR, EDX, TGA, and ICP-OES. These NPs have shown excellent activities in the aerobic oxidation of benzyl alcohol derivatives and tandem oxidative A3 coupling reactions as a catalyst and reactor in the water at room temperature. Synthesis of a new silica/gold nanoparticles as catalytic nano-reactor for carrying out A3-coupling reaction in the water at ambient temperature

Preparation of hollow silica nanoparticles using cationic spherical polyelectrolyte brushes as catalytic template

This paper presents a facile procedure to fabricate uniform-sized hollow silica nanoparticles (SNP) under a mild condition by using cationic spherical polyelectrolyte brushes (SPB) with a polystyrene (PS) core and densely grafted poly(2-aminoethyl methacrylate hydrochloride) (PAEMH) brush shell as a catalytic template. By changing the brush layer thickness of SPB, hollow SNP with different silica shell thickness could be easily obtained. This method provides a new way for the preparation of hollow SNP without additional catalyst. The obtained hollow SNP exhibited a high-drug encapsulation efficiency (80%) for doxorubicin hydrochloride (DOX), should be of significance in the fields of drug delivery, cancer therapy, and bioimaging.

Effects of cations on the size and silica shell microstructure of hollow silica nanoparticles prepared using PAA/cation/NH4OH template

This paper describes the effect of cations on the size and silica shell microstructure of hollow silica nanoparticles (HSNPs) using polyacrylic acid/cation/ammonium templates in ethanol. The influence of the cations was investigated using four kinds of cations such as sodium, potassium, magnesium, and calcium. The smaller hydrated radius cation could prepare the smaller HSNPs, because the smaller hydrated radius cations could easily interact with the PAAs due to the lower steric hindrance. Moreover, the divalent cations could prepare the smaller HSNPs with the denser silica shell, because the divalent cations could be used as the cross-linker for the PAAs. These results show that the multivalent cation, which has the smaller hydrated radius, can prepare the small HSNPs and the dense silica shell. Therefore, the 10 nm HSNPs with dense silica shell could be prepared using the calcium ion which is a divalent ion with a smaller hydrated radius.

Preparation of hollow nanoparticles with controllable diameter by one-step controlled etching of microporous silica particles using an ammonia-based etchant

Hollow silica particles with spherical morphology and controllable diameter (100–250 nm) were successfully prepared by one-step etching process using an ammonia-based etchant under mild etching conditions. First, microporous silica particles with a low degree of condensation were synthesized by modified Stöber method using low concentration of ammonia solution. Then, the microporous silica particles were coated with polydimethyldiallylammonium chloride (PDDA). The PDDA-coated particles were treated with an aqueous ammonia solution to obtain hollow silica nanospheres. In this study, the condensation degree of silica particles, PDDA concentration, ammonia etchant concentration, and etching temperature were found to have significant impact on the morphology of hollow silica nanoparticles. Adsorption studies showed that the hollow silica particles could be efficiently used for the immobilization of bovine serum albumin.

Preparation of Hollow Silica Nanoparticles Using Ultrasonically Generated Microbubbles as a Template

Preparation of Hollow Silica Nanoparticles Using Ultrasonically Generated Microbubbles as a Template

Hollow silica nanoparticles: A tiny pore with big dreams

Hollow nanoparticles exhibit unique functions such as thermal insulation, low dielectricity, and abnormal light scattering, especially when the inner size reaches less than twice the mean free path of air molecules (mean free path of air is 68 nm). It is easy to imagine that a nano-sized pore improves the thermal insulation performance due to less air convection flow inside. However, not only the hollow interior but also the shell microstructure (size, thickness, and density) strongly affect the functionalities. For example, a lower apparent shell density induces a higher thermal insulation probably due to phonon scattering on the siloxane bond cleavages. The best performance for the thermal conductivity of the hollow particle/polymer composite was 0.019 W/m·K, which is superior to air. The structure design of the hollow nanoparticle is quite important to produce this effect. In this review, based on important parameters, how to design the structure and wide applications of hollow nanoparticles are reviewed and a bright outlook for the future is expected.

Preparation and characterization of hollow silica nanocomposite functionalized with UV absorbable molybdenum cluster

The nanoparticle-based material technology has recently opened a new heat shielding material generation for window applications such as aerogel, vacuum insulation panel or nanospace materials. Aiming to prepare a nanospace-based heat insulation material functionalized with an ultraviolet (UV) absorbent, the Mo6 cluster-deposited hollow silica nanoparticles (HSNs) were prepared by the vacuum impregnation process (VIP). The pore channels of the hollow silica wall filled with the Cs2[Mo6Ii8(OCOC2F5)a6] octahedral cluster (CMIF) were confirmed by an HR-TEM coupled EDX device, ICP-OES and BET analysis. The retention of the octahedral structure or the typical optical property of the Mo6 cluster in the pores of the HSNs was demonstrated by ultraviolet (UV) light absorption and photoluminescence spectroscopes even though the powders were heated to 200 °C. The multi-functional CMIF@HSNs nanocomposite could adsorb the UV rays under 400 nm and scatter the NIR light through the pores of the silica wall in order to reduce the heat passing a window. For this purpose, the film preparation based on the CMIF@HSNs nanocomposite was performed by dip coating in the commercially available top coat suspension (TCS) on soda lime glass. Excellent mechanical and optical properties of the CMIF@HSNs-based thin film were visibly obtained with a relative transmittance. This study suggests a potential insulation material prepared by a high efficiency and simple method for reducing the air temperature in buildings.

Redox-responsive hollow mesoporous silica nanoparticles constructed via host–guest interactions for controllable drug release

A novel redox-responsive hollow mesoporous silica (HMS) was constructed by host–guest interaction between β-cyclodextrin modified hollow mesoporus silica nanoparticles (HMS@β-CD) and the ferrocene-containing amphiphilic block copolymer PEG-b-PMAFc (PPFc), the prepared HMS@β-CD@PPFc system was used to control drug delivery in targeted cancer therapy through redox stimulus. The self-assembled morphology was investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Intracellular localization of DOX-loaded HMS@β-CD@PPFc in A549 cells was further investigated by confocal laser scanning microscopy (CLSM), and the results indicated that DOX-loaded HMS@β-CD@PPFc was ingested by A549 cells effectively. Furthermore, the redox agent H2O2 was used to trigger the release of DOX. The cytotoxicity evaluated by MTT method indicated that HMS@β-CD@PPFc had good biocompatibility and was promising as the drug carrier.