Hydrophilic Particles Research Articles

Enhancing the Cellular Uptake and Antibacterial Activity of Rifampicin through Encapsulation in Mesoporous Silica Nanoparticles.

An urgent demand exists for the development of novel delivery systems that efficiently transport antibacterial agents across cellular membranes for the eradication of intracellular pathogens. In this study, the clinically relevant poorly water-soluble antibiotic, rifampicin, was confined within mesoporous silica nanoparticles (MSN) to investigate their ability to serve as an efficacious nanocarrier system against small colony variants of Staphylococcus aureus (SCV S. aureus) hosted within Caco-2 cells. The surface chemistry and particle size of MSN were varied through modifications during synthesis, where 40 nm particles with high silanol group densities promoted enhanced cellular uptake. Extensive biophysical analysis was performed, using quartz crystal microbalance with dissipation (QCM-D) and total internal reflection fluorescence (TIRF) microscopy, to elucidate the mechanism of MSN adsorption onto semi-native supported lipid bilayers (snSLB) and, thus, uncover potential cellular uptake mechanisms of MSN into Caco-2 cells. Such studies revealed that MSN with reduced silanol group densities were prone to greater particle aggregation on snSLB, which was expected to restrict endocytosis. MSN adsorption and uptake into Caco-2 cells correlated well with antibacterial efficacy against SCV S. aureus, with 40 nm hydrophilic particles triggering a ~2.5-log greater reduction in colony forming units, compared to the pure rifampicin. Thus, this study provides evidence for the potential to design silica nanocarrier systems with controlled surface chemistries that can be used to re-sensitise intracellular bacteria to antibiotics by delivering them to the site of infection.

Pickering Emulsions of Hydrophilic Silica Particles and Symmetrical Organic Electrolytes.

At high pH, bare silica particles are not an effective Pickering emulsion stabilizer of nonpolar oils with water due to their high surface charge. One way to promote particle adsorption to the oil-water interface is to add salt to the aqueous phase, although particle flocculation normally ensues. In most cases, inorganic salts are added, while little attention has been paid to the use of organic salts. Here, we describe the effects of adding tetraalkylammonium salts (R4NX, X is an anion) to aqueous dispersions of silica nanoparticles at high pH and investigating the possibility of subsequently stabilizing octane-in-water (o/w) emulsions. The chain length of the R group is systematically increased from 1 (methyl) to 4 (butyl). Unlike inorganic electrolytes, the addition of these salts does not lead to particle flocculation in water, although the particle charge is reduced. No stable emulsion forms for the methyl analogue, but very stable o/w emulsions can be prepared with the other three members, with the minimum concentration of salt being required decreasing with R chain length to as low as 5 × 10-5 M. The three-phase oil-water-solid contact angle increases with salt concentration and R chain length, confirming the increase in particle hydrophobicity on addition of salt. We show that the butyl analogue behaves similarly to that of cetyltrimethylammonium bromide surfactant with respect to promoting silica particles to emulsion drop interfaces. Finally, we compare the arrangement of micrometer-sized silica particles at both curved droplet interfaces and at a planar oil-water interface at different concentrations of the most hydrophobic salt.

Robust, transparent, superhydrophobic coatings using novel hydrophobic/hydrophilic dual-sized silica particles

HypothesisThe superhydrophobic lotus leaf has dual-scale surface structures, that is, nano-bumps on micro-mountains. Large hydrophilic particles, due to its high surface energy and weight, have high affility to substrates and tend to precipitate at the bottom of coating films. Small hydrophobic particles, due to its low surface energy and weight, tends to sit on the top of coating films and form porous structures. To mimic the lotus leaf surface, it may be possible to develop dual-sized particle films, in which small particles are decorated on large particles. ExperimentsA one-step spin coating of a mixture of dual-sized silica particles (55/200 nm) was used. Epoxy resin was added to improve the adhesion of particle films. The single-sized and dual-sized particle films were compared. The mechanical robustness of particle films was tested by tape peeling and droplet impact. FindingsThe novel combination of hydrophobic silica (55 nm) and hydrophilic silica (200 nm) is essential in creating the hierarchical structures. By combining the strong adhesion of hydrophilic silica (bottom of coating film) to polymer substrates and porous structures of hydrophobic silica (top of coating film), we first time report a one-step and versatile approach to create uniform, transparent, robust, and superhydrophobic surface.

Modulating water mobility in comminuted meat protein gels using model hydrophilic filler particles

Glass microspheres (3–6 μm and 30–50 μm diameter) and diamond particulates (1–3 μm, 3–7 μm, and 30–50 μm diameter) were employed as model hydrophilic fillers in comminuted poultry meat protein gels to evaluate the contribution of surface characteristics. The irregular surface morphology and more mild hydrophilic nature of the diamonds contrasted with the high sphericity and strong hydrophilicity of the glass microspheres. For comminuted meat protein gels prepared with both low and high protein content (9.5% and 10.2%), substantial liquid expulsion was observed in the absence of filler. The 3–6 μm glass fillers enhanced the large deformation and recovery properties of the low protein gels, while both protein levels displayed a significant reduction in thermally-induced liquid expulsion. The diamond particles had no significant impact on liquid retention or gel strength at either protein level; however, the smaller particulates decreased the recoverable energy of the high protein composite gels. Light microscopy and T2 relaxometry support the hypothesis that the 3–6 μm glass microspheres reduce water mobility by supporting water-filled capillary channels within the gel network. In contrast, the diamond particles are unable to immobilize the aqueous phase by this mechanism due to their weaker hydrophilic nature and irregular surface morphology.

Encapsulation of alkenylsuccinic anhydride oil droplets in Laponite nanoparticles modified by carbon nitride quantum dots: Enhancement of emulsion stability and paper sizing performance

Alkenylsuccinic Anhydride (ASA) is commonly applied as oil-in-water emulsions in papermaking industry. Herein, a particle stabilized ASA emulsion was developed for avoiding the adverse effect of surfactant, further improving the sizing performance and reducing the hydrolysis of ASA Pickering emulsions, where Laponite nanoparticles were employed as a stabilizer of the ASA Pickering emulsions after being modified with carbon nitride quantum dots. It was found that the hydrophilic Laponite particles became partially hydrophobic after being modified with CNQDs in dosage of 20–40 wt%, and thus promoted the formation of emulsions with fine and uniform droplets that resisted creaming/coalescence formation. The adsorption of the Laponite/CNQDs particles on the ASA droplet surface improved the emulsion stability, which was verified by fluorescent confocal laser scanning microscopy. Meanwhile, by using Laponite/CNQDs nanoparticles, the storage stability of ASA Pickering emulsion and its sizing performance on paper was also improved.

Solid polymer desiccants based on poly(acrylic acid-co-acrylamide) and Laponite RD: Adsorption isotherm and kinetics studies

This study investigates the potential application of superporous hydrogels (SPHs) and their composites with Laponite-RD (Lap-RD) for the adsorption of water vapors from humid air. Super-hydrogel composites (SPHCs) wee synthesized via gas blowing and foaming technique. Synthesized adsorbents were characterized using different techniques such as fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermos-gravimetric analysis (TGA). The incorporation of Lap-RD within the polymer matrix increased its thermal stability. Further, P(AA-co-AM) SPHs as well as SPHCs were used to adsorb water vapors from humid air. The adsorption of water vapors in both of these materials exhibited type-III isotherm with a maximum adsorption capacity of 1.03 and 1.24 gw/gads for P(AA-co-AM) SPH and SPHC at 25 °C, respectively. Higher adsorption capacity of SPHC was due to the combined effects of capillary condensation and the presence of hydrophilic Lap-RD particles within the polymer matrix. Adsorption isotherm for both materials followed Guggenheim, Anderson and Boer (GAB) model which suggested that the main driving force for water vapors adsorption was capillary condensation. The adsorption capacity of both materials decreased with increasing temperature. Furthermore, the adsorption capacity for these materials was quite low in the relative humidity range of 20–50 % which increased abruptly with increasing the relative humidity above 50 %. The isosteric heat of water vapors adsorption for P(AA-co-AM) SPHs and SPHC were found to be in the range of 59−48 and 57−49 kJ/mol, respectively. Adsorption kinetics followed linear driving force model and the diffusion of water molecules followed non-Fickian type diffusion mechanism. Finally, the synthesized adsorbents showed very good reusable efficiency and used successfully for ten cycles of adsorption.

Study of submicrocapsules structure stabilized by modified silica dioxide nanoparticles

In this research the structures of Miglyol 812 submicrocapsules, stabilized by silica dioxide nanoparticles, modified by oleic acid, were studied. It was found that the size distribution of silica particles modified with oleic acid depends on the amount of oleic acid. There is a limit to the ratio of oleic acid to silica at modification of silica particles with oleic acid. Experimental results have shown that the optimal ratio of oleic acid to silica is in the range from 110−2 to 5 10−1. The use of silica particles modified with oleic acid allows to obtain an emulsion with a 30 % of oil phase, with an average size from 80-300 nm. Thus, modification of hydrophilic silica particles with surfactants such as oleic acid in order to make them more hydrophilic and able to be adsorbed at the oil / water interface can be used to prepare a stable Pickering emulsion. As a result the stable Pickering emulsions which can be used for encapsulation of various substances were obtained, and the use of microcapsules allows one to decrease their impact on environment and increase efficiency of usage.

Change in interfacial behavior by variation of amphiphilic nanosheets/anionic surfactant ratio using dynamic tensiometry

Nanoparticles/surfactant interplays can robustly manipulate interfacial properties, while it is still unclear how their interactions affect interface behavior. This research recap unprecedented research for determination of dynamics of adsorption and dynamic surface properties of amphiphilic sheet-like nanoparticles in anionic surfactant mixtures and generalizing their characteristics in industrial and macroscopic applications by controlling microscopic active mechanism, particularly tuning foam properties and controlling its behavior. Amphiphilic nanosheets are surface-active particles which tend to self-assemble at the air-water interface. In this study, a system of an anionic surfactant (sodium dodecylsulfate (SDS)) and an amphiphilic nanoparticle (Graphene oxide (GO)) is studied at different ratios. It appears that there is a critical value for the minimum number of surfactants per nanosheets (> 160) to make the amphiphilic nanoparticle more hydrophilic. The results set out that below this critical ratio, the amphiphilic nanoparticles are partially hydrophobic and they are surface-active enough to be adsorbed considerably at the air-water interface. The nanoparticle adsorption causes an increase in surface elasticity and a decrease in surface tension (ST). As SDS/GO ratio increases, GO particles are heavily surrounded by SDS molecules rendering them hydrophilic particles. The hydrophilic GO particles start traveling back into the bulk, drastically decreasing elasticity and increasing the ST. When SDS concentration approaches the pure SDS critical micelle concentration (CMC), there appears that some of GO/SDS complexes are still on the air-water interface to slow down the dynamics of ST. The presence of GO/SDS complexes at the interface also decreases ST to lower values compared to the pure SDS near the CMC. The hydrophilic transition of GO nanoparticles is also confirmed by ζ potential and DLS measurements. This suggests a simple way to tune foam properties and behavior by selecting proper nanoparticle/surfactant ratio.

Surface Modification of Nano-Hydroxyapatite by Coating Stearic Acid

Todays, researchers are challenging with manufacturing polymeric nanocomposites reinforced with ceramic particles due to two inherent properties of ceramic reinforcement particles, particle agglomeration and incompatibility between hydrophilic ceramic particles and hydrophobic polymeric matrix. So in this study, we used nano-Hydroxyapatite (n-HA) as ceramic material and Stearic acid as amphiphilic material for coating n-HA, hydroxysteric acid (SA) surfactant was used for surface coating particles between the hydrophilic HA powders and the hydrophobic polymers. The surface modification and effect of this method were evaluated by by Fourier transformation infrared (FTIR), x-ray diffractometer (XRD), thermal gravimetric analysis (TGA) and Scanning electron microscopy (SEM). The result of FTIR showed that n-HA surfaces were modified successfully and the modification method had the proper grafting amount according to TGA due to this method of modification will be proper for coating reinforcement particles in polymeric matrix.

Molecular Dynamics Study of Binary Nanodroplet Evaporation on a Heated Homogeneous Substrate.

The evaporation mechanism of miscible binary nanodroplets from heated homogeneous surfaces was studied by molecular dynamics simulations, which has never been studied before. The binary droplets contain a hydrophilic component (type-2 particles) and a hydrophobic component (type-3 particles). It is shown that liquid-liquid interaction strength (ε23) and hydrophilic particle number fraction (φ) have great influence on the surface tension, wetting characteristics, evaporation patterns, evaporation rate, and local mass flux. It is observed that when ε23 ≥ 1, or φ ≈ 0.5, the evaporation mode is the constant-contact-angle mode. Otherwise, it is the mixed mode. We found that the evaporation rate becomes faster when φ and ε23 increase. The droplets become more hydrophilic when φ increases, which promotes heat transfer efficiency between the liquid-solid interface. Besides, a larger ε23 promotes the heat transfer inside the droplet. The mass transfer to the vapor phase occurs preferentially in the vicinity of TPCL (three phase contact line) in the hydrophilic systems (θ < θc), where θc is the critical contact angle, while in most hydrophobic systems (θ > θc), the mass flux close to the TPCL is suppressed. We found that θc ∈ (102°-106°), which is different from the theoretical one, θc = 90°. The discrepancy is attributed to the existence of the adsorption layer near the TPCL.

Effect of hydrophobicity degree of polymer particles on lipase immobilization and on biocatalyst performance

Many studies describe the advantages of using hydrophobic particles on lipase immobilisation. However, many of these works neglect the effect of other variables of the supports, such as specific area and porosity, on the biocatalyst performance, and do not evaluate the influence of the hydrophobicity level of the particles on the biocatalysts’ activity as a single variable. Thus, the focus of the present work was to evaluate the effect of the hydrophobicity degree of polymeric particles on the biocatalysts’ activities, mitigating the influence of other variables. The study was divided into two steps. Firstly, distinct particles, exhibiting different composition and hydrophobicity levels, were used for the immobilization of a commercial lipase B from Candida antarctica (CAL-B). Then, distinct core-shell polymeric particles presenting different functional compounds on the surface were produced, using as comonomers styrene, divinylbenzene, 1-octene, vinylbenzoate and cardanol. Such particles were subsequently used for CAL-B immobilisation and the performance of the biocatalysts was evaluated on hydrolysis (using p-nitrophenyl laurate, as substrate) and esterification (using ethanol and oleic acid, as substrate) reactions. Based on the screening step, it was observed that for non-porous particles the correlation coefficients between the hydrophobicity level of the supports and the biocatalysts performance, for both hydrolysis and esterification reactions, were very low (0.32 and 0.45, respectively). It highlights that there was no significant correlation between these variables and that, probably, the chemical composition of the polymeric chains affects more significantly the biocatalyst performance. Then, analysing the subsequent stage, it was observed that small changes in the surface composition of the core-shell particles result in significant changes on the textural properties of the supports (specific area ranging from 1.2 m2.g−1 to 18.3 m2.g−1; and contact angles ranging from 71° (hydrophilic particles) to 92° (hydrophobic supports) when polymer films were put in contact with water). Such particles were also employed on CAL-B immobilization and it was noticed that higher correlation coefficients were achieved for hydrolysis (ρ = 0.53) and esterification (ρ = 0.74) reactions. Therefore, it is shown that the hydrophobicity degree of such supports starts to affect more effectively the biocatalysts performance when other textural features of the supports become more significant, such as specific area and porosity.

Morphology and chemical composition of composite electrochemical coatings Zn-Al2O3 and Zn-PTFE

The effect is studied of addition of hydrophilic aluminum oxide and hydrophobic polytetrafluoroethylene on the morphology and chemical composition of zinc coatings from acidic electrolytes. Inclusion of hydrophobic polytetrafluoroethylene particles into zinc coatings from acidic zinc electrolytes in the absence of any surfactants is more facilitated than that of hydrophilic aluminum oxide particles of various dispersion and phase composition. The formation of composite electrochemical Zn-Al2O3 and Zn-polytetrafluoroethylene coatings is determined by the state of the surface of the growing zinc deposit (its comparative hydrophobicity) that facilitates the adhesion of hydrophobic polytetrafluoroethylene particles. Addition of aluminum oxide particles into the electrolyte causes no fundamental changes in the overall surface morphology of the zinc deposits. However, a relatively large number of inclusions of aggregates of nanosized aluminum oxide particles are observed over the entire coating surface. The concentration of aluminum oxide inclusions in Zn-Al2O3 composite coatings reaches 5...7 wt.%. The surface of Zn-polytetrafluoroethylene deposit is represented by globules. The total polytetrafluoroethylene content in the obtained composite coatings reaches 30 wt.%. An increased oxygen content is found in such coatings. It is probably explained by formation of a relatively larger amount of surface zinc oxide due to the significant development of the surface morphology of the deposits.

Particle-induced nanobubble generation for material-selective nanoparticle flotation

The presented work investigates particle-induced nanobubble generation in order to extend the applicability of material-selective pressure flotation towards nanoscale materials. During a gas treatment procedure, filtered compressed air in the range of 0 bar–2 bar overpressure was introduced into colloidal suspensions in ultra-purified water until saturation was obtained. Nanobubble formation in the suspension occurred after slow depressurization with a gas vent. Suspensions of platinum nanoparticles and polystyrene beads were used to examine the effects of particle hydrophobicity and roughness. Using nanoparticle-tracking-analysis (NTA), the evaluation of particle size and scattered light intensity showed the occurrence of nanobubbles, both, as a separate phase (bulk nanobubbles) and attached to the particles’ surface. The sharply separated nanobubble peak was observed in number density NTA plots of gas treated platinum nanoparticles. The size of the hydrophilic platinum particles remained unchanged. In contrast, for hydrophobic polystyrene particles, the hydrodynamic diameter increased during a gas treatment procedure. The experimental results are understood, on the one hand, as the nucleation of bulk nanobubbles in the cavities of hydrophilic platinum particles and, on the other, as surface-growth of nanobubbles attached to the hydrophobic polymer particles.

Regimes of drainage instability caused by wash water

Wash water is widely used in flotation to increase the gravity-driven drainage rate of water within the froth phase and the efficiency of removing entrained (hydrophilic) particles. At a high rate, it can disturb the froth. Here, we investigate the drainage instability caused by wash water using the forced drainage experiments. We quantitatively confirm that foam suffers from convective instability when a sufficiently high flow rate of wash water is employed. A comparison between the theoretical onset predictions of convective instability and experimental results shows that some available drainage experiments might have suffered from convective instability. Our new experimental results show three drainage regimes and structures associated with increased flow rate of wash water: (1) stable foam structure, (2) relative motion of bubbles and (3) convective roll. Our study presents both theoretical analysis and experimental results for quantifying convective instability, which can be eliminated to improve flotation.

Effect of particle size distribution on rheological properties of chocolate.

This study focused on the influence of the particle size distribution (PSD) of ingredients used for chocolate preparation (cocoa powder and sugar) on viscosity of model chocolates with different fat contents. Model chocolates with varying PSDs and two particle size ratios (cocoa particles : sugar of 1 : 4 and 1 : 6) were prepared by mixing highly defatted cocoa powder as a fine fraction and sugar as coarse fraction in several proportions. Samples containing spherical quartz beads were included as a reference to gain insight into the role of particle properties. Comparing chocolate samples with the same composition, but different particle size ratio, the largest difference in viscosity was found at a proportion of coarse fraction of 0.6. This shows that at this proportion of coarse particles, the highest maximum packing fraction was reached, which is in accordance with theoretical predictions. However, for the investigated chocolate samples, the lowest viscosity values were obtained at a proportion of the coarse fraction of 0.8 or 1. This could be attributed to parameters other than PSD, such as a decrease in surface area with an increasing amount of coarse particles. Also the morphology and surface properties were shown to influence viscosity. Compared to cocoa and sugar particles, spherical and smooth quartz beads led to an improved particle packing, and therefore a lower viscosity. The addition of lecithin led to a decrease in viscosity due to a decrease in particle-particle interactions, particularly for hydrophilic sugar particles. The knowledge obtained in this study provides possible approaches on how to reduce fat content of chocolates.

Correlation of the entrainment factor with frother types and their mixtures in the column flotation

In flotation, entrainment is a mechanical mass transfer process and it is based on the changes depending on the establishment of linear relationship between water and solid recovery. The present paper presents results obtained in investigating the effect of frother mixture concentrations on the entrainment of fine particles’ during the column flotation. The aim of the present study was to investigate more specifically the relationship between the recovery via entrainment of a range of different hydrophilic calcite particles. For this, to determine entrainment factor of fine particle was used a mixture of artificial ore (celestite/calcite; 1:1). The results showed that the frother mixtures had important effect on the grade and recovery, superficial air rate, gas hold-up and entrainment of fine gangue particles. Entrainment factors for frother mixtures were compared in flotation column. Kirjaveinen (1989) model was used for explaining the specific entrainment factor (Pi) of hydrophilic particles and it has been observed that this model supports the results of this study. This, together with the increased recovery, resulted in higher celestite grades of valuable mineral recovered to the concentrate when using the frother mixtures (Pine Oil+MIBC).

Effect of Humidity on CO2/N2 and CO2/CH4 Separation Using Novel Robust Mixed Matrix Composite Hollow Fiber Membranes: Experimental and Model Evaluation.

In this work, the performance of new robust mixed matrix composite hollow fiber (MMCHF) membranes with a different selective layer composition is evaluated in the absence and presence of water vapor in CO2/N2 and CO2/CH4 separation. The selective layer of these membranes is made of highly permeable hydrophobic poly(trimethyl-1-silylpropine) (PTMSP) and hydrophilic chitosan-ionic liquid (IL-CS) hybrid matrices, respectively, filled with hydrophilic zeolite 4A particles in the first case and HKUST-1 nanoparticles in the second, coated over compatible supports. The effect of water vapor in the feed or using a commercial hydrophobic PDMSXA-10 HF membrane has also been studied for comparison. Mixed gas separation experiments were performed at values of 0 and 50% relative humidity (RH) in the feed and varying CO2 concentration in N2 and CH4, respectively. The performance has been validated by a simple mathematical model considering the effect of temperature and relative humidity on membrane permeability.

Role of randomly distributed nanoscale roughness for designing highly hydrophobic particle surface without using low surface energy coating

Surface texture and surface chemistry both are important to design the highly hydrophobic surfaces. Tuning surface chemistry with chemical coating can improve the hydrophobic nature of the surface to a limit. Further increase in hydrophobicity requires an alteration in surface roughness. The present work proposes the randomly distributed nanoscale roughness for designing highly hydrophobic surface engineered particle (SEP) from the hydrophilic particle. An alkali medium is used to engineer the surface of the original particle (OP) for the different time intervals. The surface is thoroughly characterized by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy, and contact angle (CA) measurement. Results reveal that the hydrophobic CA up to 147° can be tuned by nanoscale surface roughness even after Si-OH incorporation on the surface. Moreover, the silanization of the OP and SEP surface further identifies that a gradual increase in CA beyond 113° is due to the favorable nano-scale surface roughness and its distribution on the surface of SEP. The study is first of its kind to achieve highly hydrophobic micron-size particle surface (CA ~ 147°) without coating of any low surface energy material.

Selective aggregation by ultrasonic standing waves through gas nuclei on the particle surface.

Gas nuclei in water are usually too small to be directly observed. They will grow into bubbles under the negative pressure, which is called cavitation (heterogeneous cavitation). In this study, the gas nuclei in the hydrophilic and hydrophobic silica particle suspension were investigated using the transient cavitation threshold measured by a high-intensity focused ultrasound (HIFU). The transient cavitation bubbles were also observed by a high-speed camera. The results showed that the nuclei only exist on the surface of hydrophobic particles. Furthermore, the aggregation experiments revealed that the aggregates were only formed in the hydrophobic silica suspension by ultrasonic standing waves (USW) at 200kHz. This distinct difference was mainly due to the formation of gas nuclei on hydrophobic silica particles, which grew and coalesced into stable bubbles under the 200kHz USW. The aggregation process in suspension was observed by a CCD camera. Moreover, the cavitation thresholds and acoustic radiation forces were analyzed to explain the mechanism of the acoustic aggregation. This study showed a very promising acoustic method for the selective aggregation of hydrophobic particles, which might be efficiently used in the mineral separation industry.

Microscopic visualization of heterogeneous nucleation process on smooth spherical particle: Method and results

Heterogeneous nucleation is a very fundamental step in vapor condensation. However, it is scarcely possible to directly visualize the nucleation process because it is very quick and complicated. In present work, a method is proposed to create a mixed surface, where the hydrophilic SiO2 particle is dispersed on the super-hydrophobic substrate for a direct visualization of the nucleation process. The time-resolved images are recorded by Environmental Scanning Electron Microscopy (ESEM) system. The results indicate that only one embryo drop forms at a random point of a single particle surface and subsequently grows up and finally wraps the single particle. For multiple particles, the embryo drop occurs on the junction of particles and continues to enlarge to finally wrap all the particles. The numerical analysis shows that the nucleation ability of SiO2 is qualitatively consistent with the theoretical prediction, and quantitatively, the experimental Scr is much smaller than the predicted results.