Silica Nanoparticles In Solution Research Articles

A Nanofluorescent Probe for Evaluating the Fluctuation of Aminopeptidase N in Nonalcoholic Fatty Liver Disease and Hepatic Fibrosis.

Aminopeptidase N (APN/CD13) is a widely expressed transmembrane ectoenzyme that is crucial for maintaining normal physiological activities. It exhibits abnormal activity closely associated with hepatic fibrosis and nonalcoholic fatty liver disease (NAFLD). Therefore, there is a high demand for noninvasive detection of aminopeptidase N (APN) in the diagnosis and research of related diseases. Here, we developed a small molecule fluorescent probe, Hcy-APN, which is a fluorescent probe with high sensitivity and selectivity for the detection of APN. Furthermore, we synthesized the fluorescent nanoprobe Hcy-APN@MSN by self-assembling Hcy-APN and mesoporous silica nanoparticles in solution using a combination of molecular probe design and nanofunctionalization strategies. The detection limit of this probe was 1.5 ng/mL. Hcy-APN@MSN exhibits more stable spectral characteristics compared to Hcy-APN and is suitable for detecting APN activity in live cells and mice. Hcy-APN@MSN was utilized for in vivo and intracellular imaging of NAFLD and hepatic fibrosis at different stages, as well as for a systematic assessment of APN levels in the liver. The results confirm an elevation in the expression levels of APN in NAFLD and hepatic fibrosis models. Furthermore, we investigated the inhibitory effect of the APN inhibitor bestatin in nonalcoholic fatty liver and hepatic fibrosis disease models, confirming its regulatory effect on APN levels in cells and in vivo in both disease models. Therefore, this study may offer diagnostic possibilities for detecting NAFLD and hepatic fibrosis.

Efficient end-to-end simulation of time-dependent coherent X-ray scattering experiments.

Physical optics simulations for beamlines and experiments allow users to test experiment feasibility and optimize beamline settings ahead of beam time in order to optimize valuable beam time at synchrotron light sources like NSLS-II. Further, such simulations also help to develop and test experimental data processing methods and software in advance. The Synchrotron Radiation Workshop (SRW) software package supports such complex simulations. We demonstrate how recent developments in SRW significantly improve the efficiency of physical optics simulations, such as end-to-end simulations of time-dependent X-ray photon correlation spectroscopy experiments with partially coherent undulator radiation (UR). The molecular dynamics simulation code LAMMPS was chosen to model the sample: a solution of silica nanoparticles in water at room temperature. Real-space distributions of nanoparticles produced by LAMMPS were imported into SRW and used to simulate scattering patterns of partially coherent hard X-ray UR from such a sample at the detector. The partially coherent UR illuminating the sample can be represented by a set of orthogonal coherent modes obtained by simulation of emission and propagation of this radiation through the coherent hard X-ray (CHX) scattering beamline followed by a coherent-mode decomposition. GPU acceleration is added for several key functions of SRW used in propagation from sample to detector, further improving the speed of the calculations. The accuracy of this simulation is benchmarked by comparison with experimental data.

Multivariate Analysis of Protein-Nanoparticle Binding Data Reveals a Selective Effect of Nanoparticle Material on the Formation of Soft Corona.

When nanoparticles are introduced into the bloodstream, plasma proteins accumulate at their surface, forming a protein corona. This corona affects the properties of intravenously administered nanomedicines. The firmly bound layer of plasma proteins in direct contact with the nanomaterial is called the "hard corona". There is also a "soft corona" of loosely associated proteins. While the hard corona has been extensively studied, the soft corona is less understood due to its inaccessibility to analytical techniques. Our study used dynamic light scattering to determine the dissociation constant and thickness of the protein corona formed in solutions of silica or gold nanoparticles mixed with serum albumin, transferrin or prothrombin. Multivariate analysis showed that the nanoparticle material had a greater impact on binding properties than the protein type. Serum albumin had a distinct binding pattern compared to the other proteins tested. This pilot study provides a blueprint for future investigations into the complexity of the soft protein corona, which is key to developing nanomedicines.

Extraordinary Destabilization of Silica Nanocolloids by Filtration

After silica nanoparticles in solutions were filtered by a syringe filter with a much larger pore size than the particle diameter Dp, the filtrated effects on the rapid coagulation rate in 1 M KCl solution, the dynamic light scattering diameter, and the zeta potential at pH ∼ 6 were investigated by employing the particles of two different sizes: S particles (Dp ∼ 50 nm) of silica and latex and L particles (Dp ∼ 300 nm) of silica. It was found that the hydrodynamic diameters of silica particles became a little smaller and the absolute values of their zeta potentials decreased significantly by filtration, but that is not the case for latex particles. As for the rapid coagulation rate, the value of silica S particles increased more than 2 orders of magnitude by filtration, but no significant difference was found in the case of silica L and latex S particles. From these data, it was postulated that the gel-like layer was removed from the surface of silica S particles by filtration and the existence of the gel-like layer resulted into about 2 orders of magnitude reduction of the rapid coagulation rate. The extraordinary reduction of rapid coagulation of silica particles at Dp < 150 nm was successfully estimated by the revised Smoluchowski theory, which we call the Higashitani-Mori (HM) model. It was also found that the rapid coagulation rate of filtrated particles decreased slowly with a decreasing particle size at Dp < ca. 250 nm, which was also estimated properly by the HM model, neglecting the contribution of the redispersion of coagulated particles. Another finding in this study was that the gel-like layers were recovered with time even if they were removed by filtration, although the detailed mechanism of this recovering is not known at present and left as a future problem.

A Simple and Convenient Method for Preparing Fluorine-Free Durable Superhydrophobic Coatings Suitable for Multiple Substrates.

Superhydrophobic coatings have attracted a lot of attention due to their excellent self-cleaning and anti-fouling capabilities. However, the preparation processes for several superhydrophobic coatings are intricate and expensive, which restricts their usefulness. In this work, we present a straightforward technique for creating durable superhydrophobic coatings that can be applied to a variety of substrates. The addition of C9 petroleum resin to a styrene-butadiene-styrene (SBS) solution lengthens the SBS backbone and undergoes a cross-linking reaction to form a dense spatial cross-linked structure, improving the storage stability, viscosity, and aging resistance of the SBS. The combined solution functions as a more stable and effective adhesive. Using a two-step spraying technique, the hydrophobic silica (SiO2) nanoparticles solution was applied to the surface to create durable nano-superhydrophobic coatings. Additionally, the coatings have excellent mechanical, chemical, and self-cleaning stability. Furthermore, the coatings have wide application prospects in the fields of water-oil separation and corrosion prevention.

Interplay of interactions in nanoparticle–surfactant complexes in aqueous salt solution

The evolution of phase behavior and interactions in anionic silica nanoparticles (Ludox HS40), surfactants [non-ionic decaethylene glycol mono-dodecyl ether (C12E10) and anionic sodium dodecyl sulfate (SDS)], and nanoparticle–surfactant solutions in the presence of salt (NaCl) has been studied using small-angle neutron scattering and dynamic light scattering. In an anionic silica nanoparticle solution (1 wt. %), the phase behavior is controlled by salt concentrations (0–1 M) through screening electrostatic interactions. In the case of 1 wt. % surfactant solutions, the anionic SDS surfactant micelles show significant growth upon adding salt, whereas non-ionic surfactant C12E10 micelles remain spherical until a high salt concentration (1 M). In the mixed system of HS40–C12E10, a transition from a highly stable transparent phase to a two-phase turbid system is observed with a small amount of salt addition CS* (∼0.06 M). The single transparent phase of this system corresponds to sterically stabilized micelles-decorated nanoparticles. For the turbid phase, the results are understood in terms of depletion attraction induced by non-adsorption of C12E10 micelles, which explains the appearance of turbidity at a much lower concentration of salt. In the mixed system of similarly charged nanoparticles and micelles (HS40-SDS), the phase behavior is governed by no physical interaction between the components, and salt screens the repulsive interaction among nanoparticles. These results are further utilized to tune multicomponent interactions and phase behavior of nanoparticles with a mixed C12E10-SDS surfactant system in the presence of salt. The mixed surfactants provide tuning of nanoparticle–micelle as well as micelle–micelle interactions to dictate the phase behavior of a nanoparticle–surfactant solution. In these systems, the effective potential can be described by double-Yukawa potential taking account of attractive and repulsive parts at low and intermediate salt concentrations (&amp;lt;CS*). At high salt concentrations (&amp;gt;CS*), the aggregation of nanoparticles is characterized by fractal aggregates.

Developing Superhydrophobic Surface Using Multi Jet 3D Printing Durability Analysis

Superhydrophobicity is a surface property used in several sectors, including self-cleaning, drag reduction, improved buoyancy, and antibacterial behavior of the surfaces. The majority of available approaches for creating superhydrophobic surfaces (SHS) are complex and time-consuming. Goal: This article aims to fabricate the SHS by using Multi jet printer three-dimensional (3D) printing. Methods: The texture of cylindrical protrusions (diameter 300 Micro Meter (µm), pitch 400 and 500 µm) and pyramidical (side 200 µm, side by side distance 200 µm, and height 800 µm) micro-pattern were created using Three-Dimensional Printing (3DP) to achieve the SHS. Results: The fabricated geometries yielded a water contact angle of 145 and 148°, respectively. In order to enhance the durability and Water Contact Angle (WCA), 3D printed geometry was treated with an aqueous solution of silica nanoparticles and Hexafor 644-D, which increased the contact angles to 161 and 160° for cylindrical and pyramid patterns, respectively. The reported geometries are durable against peeling tape tests. Hence MJP, based on 3DP, can be used to fabricate the SHS having the geometries height in micron (µm).

Structural Characterization of Silica and Amino-Silica Nanoparticles by Fourier Transform Infrared (FTIR) and Raman Spectroscopy

Mesoporous silica nanoparticles were synthesized via the sol-gel method using hexadecyltrimethylammonium bromide (CTAB) micelles as a template and a similar method was used for amino-silica nanoparticle synthesis. Compositional and structural analysis of materials involved Fourier transform infrared (FTIR) and Raman spectroscopies. A comparative study of the two spectra revealed the distinctive pattern for the samples, such as a strong peak from 1030 to 1050 cm−1 in the FTIR spectra, characteristic of Si–O–Si stretching vibration and the specific pattern of silica between 90 and 500 cm−1 and 2880 and 2980 cm−1 in the Raman spectra. A point of interest in this study was the control of CTAB removal during the second stage of synthesis that was highlighted in the FTIR spectra by decreasing intensity or disappearance of the peaks 2850 and 2930 cm−1 for - CH2 absorption. The presence of – NH2 groups in the amino-silica was evidenced by the changes from 1000 to 1500 cm−1 and the sharp band at 2900 cm−1 in the Raman spectra. The peaks at 1050, 1230, 1421, and 1464 cm−1 are present only in the spectra of the amino-silica as well as the higher and sharp band around 2900 cm−1, unlike the pattern in the spectra of silica without amino groups. The two spectroscopic methods offer valuable information concerning the structure of silica and amino-silica. Moreover, thermogravimetric analyses were confirmed these findings and the stability of silica nanoparticles in solution was investigated.

Stabilization of clay-rich interburdens using silica nanoparticles

Detachment of clay particles from clay-rich interburdens is the main source of solid production in coal seam gas wells (CSG), costing the Australian operators millions of dollars every year. Several techniques have been proposed to reduce the solid production and consequent pump failure in already constructed open hole/slotted liner wells. Amongst all remedial techniques for these existing problematic wells, chemical stabilization seems to be the most practical method. The high cost of chemical additives, their environmental issues, potential low effectiveness and technical difficulties for their placement downhole have, however, hindered their wide application. In particular, the long-term effect of current chemical additives on interburden stability and their influence on coal seam matrix gas diffusion need further investigation. In this study, the application of colloidal silica nanoparticle solution (silica SOL) as a long-term chemical stabilization method for clay-rich interburden in CSG wells was investigated. A series of comprehensive experiments were performed to investigate the effect of the silica SOL on stability of pure compacted dry smectite clays and clay-rich sandstone samples in stationary and turbulent conditions (resembling the wellbore condition during gas production) using a uniquely designed experimental setup. Additionally the effect of silica SOL on coal and its gas adsorption was analyzed. The results of this study demonstrated that the silica SOL is a suitable candidate for long-term chemical stabilization of clay minerals as a cost-efficient and environmentally friendly additive. Its non-reactivity with coal and its inert response on gas sorption is another significant benefit of the proposed chemical solution.

An experimental study of the combination of smart water and silica nanoparticles to improve the recovery of asphaltenic oil from carbonate reservoirs

Within recent decades, smart water (SW) injection has become an attractive approach to improve oil recovery from conventional oil reservoirs. However, less attention has been devoted to the application of this method to asphaltenic oil reservoirs. This study aims to evaluate the performance of the injection of SW + silica nanoparticles (SNPs) in improving oil recovery from such reservoirs. To this end, an extended series of measurements were conducted, including of oil-water interfacial tension (IFT), wettability, emulsion formation/stability, and core flooding tests. After the introduction of SNPs to formation brine (FB) and SW solutions, oil-water IFT was reduced by 17.5% and 52.5% respectively compared to their corresponding initial values. In addition, the SW + SNP solution could improve the wettability of the rock surface compared to FB + SNPs. Interestingly, we found that, due to its high asphaltene content, the crude oil used forms sludge in contact with FB, which will impose serious operational problems and production costs associated with the system. However, we observe that the presence of SNPs restrains sludge formation by breaking down asphaltene molecules as well as destabilizing oil-water emulsions. This is demonstrated by several centrifuge tests conducted to evaluate emulsion stability in the presence of FB + SNP and SW + SNP solutions. SARA analyses were also performed on the oil produced from core plugs after the injection of SW and SW + SNPs to better understand the role of SNPs in the deposition of complex structures like asphaltenes and resins groups in crude oil. • The performance of smart water + silica nanoparticles in IFT reduction and wettability alteration. • Crude oil-water emulsion stability in the presence of silica nanoparticles. • Application of SARA analyses to study asphaltene precipitation during core flooding tests. • Micrograph studies for emulsion stability in the presence of various aqueous solutions.

Evaluation of the evaporation route of a liquid droplet on Au coated and non-coated glass surfaces

The contact angle was used to estimate the rate of evaporation of liquid droplets on bare glass or gold (Au) sputtered glass surfaces. The rate of evaporation of water (a pure liquid) was higher than non-pure liquid composed of a 3 wt% solution of silica nanoparticles (SNP) on these two solid supports. Despite using the same initial drop volume (1 µL) throughout the experiment, the base diameter of the liquid droplet after evaporation on the different surfaces interestingly showed variations. While the liquid–solid interface displayed slip-length and contact angle variations throughout the evaporation time, the slip-length variations were more pronounced with colloidal SNP on Au-sputtered glass surfaces than pure liquid on bare glass surface. Potential application of this study was also investigated in the surface control of uniform silica microwires from colloidal SNP on Au-sputtered glass surface under low temperature conditions.

Evaluating a transparent coating on a face shield for repelling airborne respiratory droplets.

A face shield is an important personal protective equipment to avoid the airborne transmission of COVID-19. We assess a transparent coating on a face shield that repels airborne respiratory droplets to mitigate the spread of COVID-19. The surface of the available face shield is hydrophilic and exhibits high contact angle hysteresis. The impacting droplets stick on it, resulting in an enhanced risk of fomite transmission of the disease. Further, it may get wetted in the rain, and moisture may condense on it in the presence of large humidity, which may blur the user's vision. Therefore, the present study aims to improve the effectiveness of a face shield. Our measurements demonstrate that the face shield, coated by silica nanoparticles solution, becomes superhydrophobic and results in a nominal hysteresis to the underlying surface. We employ high-speed visualization to record the impact dynamics of microliter droplets with a varying impact velocity and angle of attack on coated and non-coated surfaces. While the droplet on non-coated surface sticks to it, in the coated surface the droplets bounce off and roll down the surface, for a wide range of Weber number. We develop an analytical model and present a regime map of the bouncing and non-bouncing events, parametrized with respect to the wettability, hysteresis of the surface, and the Weber number. The present measurements provide the fundamental insights of the bouncing droplet impact dynamics and show that the coated face shield is potentially more effective in suppressing the airborne and fomite transmission.

Transparent silica aerogel slabs synthesized from nanoparticle colloidal suspensions at near ambient conditions on omniphobic liquid substrates

This paper presents a novel sol-gel method to synthesize large and thick silica aerogel monoliths at near ambient conditions using a commercial aqueous solution of colloidal silica nanoparticles as building blocks. To achieve slabs with high visible transmittance and low thermal conductivity, the method combines the strategies of (i) synthesizing gels on an omniphobic perfluorocarbon liquid substrate, (ii) aging at temperatures above room temperature, and (iii) performing solvent exchange with a low-surface-tension organic solvent prior to ambient drying. The omniphobic liquid substrates were used to prevent cracking and ensure an optically-smooth surface, while nanoparticle building blocks were small (<10 nm) to limit volumetric light scattering. Gels were aged at temperatures between 25 and 80 °C for up to 21 days to make them stronger and stiffer and to reduce shrinkage and cracking during ambient drying. Ambient drying was achieved by first exchanging water in the gel pores for octane, followed by drying in an octane-rich atmosphere to decrease capillary forces. The synthesized nanoparticle-based silica aerogel monoliths had thicknesses up to 5 mm, diameters up to 10 cm, porosities exceeding 80%, and thermal conductivities as low as 0.08 W m−1 K−1. Notably, the slabs featured visible transmittance exceeding 75% even for slabs as thick as 5 mm. The as-synthesized aerogel monoliths were exposed to TMCS vapor to induce hydrophobic properties resulting in a water contact angle of 140° that prevented water infiltration into the pores and protected the aerogels from water damage. This simple synthesis route conducted at near ambient conditions produces hydrophobic aerogel monoliths with promising optically transparent and thermally insulating properties that can be adhered to glass panes for window insulation and solar-thermal energy conversion applications.

Optimizing carbon coating parameters for obtaining SiO2/C anodes with improved electrochemical performance

In this work, we present a comprehensive and systematic study on the use of low-cost and highly abundant carbon precursors to obtain SiO2/C anodes with superior electrochemical performance towards Li-ions. Different SiO2/C composites are prepared by soaking silica nanoparticles in solutions containing 20 wt%, 40 wt%, or 60 wt% of glucose, sucrose, or cornstarch, followed by thermal decomposition of the carbohydrates at 850 °C or 1200 °C. Structural, microstructural, and textural differences on the composites derived from the different carbon coating treatments are related to the electrochemical performance of the anodes. Composites containing final carbon contents close to 15 wt% show a complete coverage of the SiO2 particles with a nanometric carbon layer and exhibit the best electrochemical results. The increase in the annealing temperature from 850 to 1200 °C reduces the porosity of the carbon layer and increases its level of ordering, both having positive effects on the overall electrochemical performance of the electrodes. SiO2/C composites coated with 40 wt% sucrose and heat treated at 1200 °C display the best electrochemical performance, delivering a reversible specific capacity of 723 mAhg−1 at 50 mAg−1 after 100 cycles, which is considerably higher than the reversible capacity of 233 mAhg−1 obtained with the uncoated material cycled under the same conditions.

Preparation, Characterization and Adsorption into Aqueous Solutions of Polyethyleneimine-Coated Silica Nanoparticles

In this study, polyethyleneimine-coated silica nanoparticles (PEI-SiNP) were used to prepare a polymeric material that can effectively and selectively adsorb Au (III) from aqueous solutions. For this purpose, silica nanoparticles were firstly reacted with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) to achieve epoxy functionality. The structures of the silica nanoparticles (SiNP), silica nanoparticles with epoxy functionality (E-SiNP) and polyethyleneimine-coated silica nanoparticles were determined using ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared) and XPS (X-Ray Photoelectron Spectroscopy), while their thermal properties were characterized using thermogravimetric analyses (TGA). The Au (III) ion-binding capacity of the PEI-SiNP adsorbent nanocomposite that contain high levels of imine was investigated. The effects of the interactions between pH, contact time and foreign metal ions on adsorption were tested to determine the optimum conditions. The optimum contact time was 3 hours at pH 2. The adsorption capacity of the adsorbent nanocomposite prepared for Au (III) was found to be 116.27 mg/g. The Langmuir and Freundlich isotherms were used to determine the adsorption behaviors and the Langmuir isotherm model was selected as the best fit model (R2: 0.997). The prepared PEI-SiNP adsorbent nanocomposite showed a high selectivity for the Au (III) metal even when different metal cations such as Cu (II), Cd (II) and Pb (II) were present.

Understanding the stability mechanism of silica nanoparticles: The effect of cations and EOR chemicals

We have investigated the conditions of colloidal stability of silica nanoparticles smaller than 100 nm for their applications in enhanced oil recovery (EOR), especially pertaining to chemical flooding processes. Using zeta sizer and dynamic light scattering techniques, the stability of silica nanoparticle (SNP) dispersions has been investigated by variation of the pH, composition of salt solutions, addition of surfactants and polyelectrolytes. Such conditions can be encountered in oil reservoirs. It was found that changing pH from 5 to 10 had a negligible effect on the size of SNPs, whereas its zeta potential increased with increasing pH. Aggregation of SNPs is a partially reversible process for low degrees of aggregation in 500 mM NaCl, whereas observed strong aggregation in 1000 mM NaCl was irreversible. A critical aggregation concentration (CAC) was defined for the different salts investigated, above which the SNP dispersion became unstable at a fixed pH of 9.5. The CAC for NaCl was approximately 200 times higher than for CaCl2 and MgCl2. Our observations could not be explained completely by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Therefore, we have included non-DLVO interactions such as cation bridging, hydration forces, and steric effects. The additional presence of anionic alcohol alkoxy sulfate (AAS) surfactant slightly destabilized the SNP solution, but by the addition of polyacrylate (PA) was effectively stabilized. With increasing PA concentration, the CAC for both CaCl2 and MgCl2 increased. Upon addition of 100 ppm PA, the CAC increased by a factor of five compared to the situation in the absence of PA. Reducing the solution pH below 8.5, SNP can be stabilized in higher salinity in the presence of PA. The obtained results contribute to a better fundamental understanding of the SNP stability mechanism and a guide to optimize the SNP injection process with EOR chemicals.

Exploring the organic\u2013inorganic interface in biosilica: atomistic modeling of polyamine and silica precursors aggregation behavior

Diatoms are a significant group of algae displaying a sizeable morphological diversity, whose underlying structure arises from nanopatterned silica. Extensive experimental evidence suggests that a delicate interplay between various organic components and polysilicic acid plays a crucial role in biosilica mineralization. Thus, gaining insight into the properties of this organic–inorganic interface is of great interest in understanding the mechanisms controlling biosilica formation over different length scales. In this work, we use all-atom Molecular Dynamics simulations to investigate the aggregation behavior of polysilicic acid and silica nanoparticles in solution in the presence of protonated long-chain polyamines with a focus on the nature of the driving forces mediating the organic–inorganic aggregation process. Our results show that electrostatic forces between organic and inorganic species are the dominant interaction responsible for largely preserving the structural integrity of the organic–inorganic aggregates in solution. Thus, aggregates involving electrically neutral polysilicic acid are fully dissolved in an aqueous environment, since hydrogen bonding and van der Waals interactions turn out to be not strong enough to keep the aggregates together. Our main simulation results are in qualitative agreement with in vitro experiments, so that we expect they can contribute to shedding light on the initial stages of biosilica mineralization in diatoms.

Mechanistic study on silica nanoparticles-assisted guar gum polymer flooding for enhanced oil recovery in sandstone reservoirs

Nanoparticles-assisted polymer flooding has attracted the attention of researchers for its enhanced rheological properties and stability of the chemical slugs. The present work deals with the rheological properties of guar gum with and without silica nanoparticles in the temperature range from 25 °C to 75 °C. It is found that the viscosity of guar gum solution increases significantly with increasing concentration of silica nanoparticles. Imbibition experiments were performed with waxy crude oil-saturated sandstone cores using 2000 ppm brine, 4000 ppm guar gum solution, 0.2 wt% silica nanoparticles in distilled water, and 4000 ppm guar gum containing 0.2 wt% silica nanoparticles as test fluids for understanding the mechanism of wettability alteration in the presence of silica nanoparticles and guar gum. Mixture of 0.2 wt% silica nanoparticles and 4000 ppm guar gum shows higher oil recovery (∼36 % original oil-in-place) compared to other test solutions in imbibition experiments. Contact angles between crude oil and sandstone rock were measured in presence of 2000 ppm brine, 0.025 wt% silica nanoparticles in water, and guar gum (2000 ppm)-silica nanoparticles (0.025 wt%) mixture. Guar gum containing silica nanoparticles are effective in changing the contact angle towards water-wet state (Contact angle ∼115°) from oil-wet state (contact angle ∼72°). No significant phase change is observed during the phase behavior experiment except for light emulsion formation. Finally, core flooding experiments were conducted with guar gum, silica nanoparticles solution, and mixture of silica nanoparticles and guar gum for additional oil recovery to verify the effectiveness of the chemical slugs. Results showed that the addition of silica nanoparticles to guar gum solution improves the effectiveness of guar gum polymer by recovering 44.3 % of original oil-in-place. A comparative study was also conducted to show the performance of silica nanoparticles-assisted guar gum solution for additional oil recovery. Most of the research works have focused on the application of silica nanoparticles-induced polyacrylamide and xanthan gum chemical slugs in enhanced oil recovery. However, laboratory study based on the application of silica nanoparticles-induced guar gum solution in additional oil recovery adds some interesting findings to the literature compared to the existing information.

Transparent and hydrophobic hexylene-bridged polymethylsiloxane/sio2 composite coating with tunable refractive index and its application for broadband antireflection

Regulating refractive index over a wide range plays a key role in the design and fabrication of broadband antireflective coating in many optical energy-related fields. In this paper, hydrophobic refractive-tunable coating was fabricated from an effective solution mixing method starting from a synthesis solution of silica (SiO2) nanoparticles which was developed for dispersing nanoparticles into dense hexylene-bridged polymethylsiloxane polymer. In the mixing process, the microstructure and chemical structure of hexylene-bridged polymethylsiloxane/SiO2 were analyzed by fourier transform-infrared spectrometer and transmission electron microscope. Specially, the relationship between the microstructure and optical properties was also well investigated. Silica nanoparticles were dispersed homogeneously in polymer matrix modulating the refractive index of composite coating ranging from 1.16 to 1.47. When the composite coating with refractive index of 1.36 was used as the bottom layer and hexamethyldisilazane modified SiO2 coating with refractive index of 1.16 was used as the top layer. Thus-obtained double-layer broadband antireflective coating was fabricated with excellent broadband antireflective performance. In addition, the double-layer broadband silica antireflective coating showed good environmental stability. This work provides an alternative way to prepare a broadband antireflective coating for some applications in energy harvesting and optical devices.

Understanding the roles of patterning and foulant chemistry on nanofiltration threshold flux

This paper reports findings from a systematic study to understand the roles of colloidal chemistry and membrane surface properties on membrane fouling using constant flux filtration. Commercial polyamide nanofiltration membranes were modified with a line-and-groove pattern using nanoimprint lithography. Threshold flux measurements were made for as-received and patterned membranes by the flux-stepping measurement method using solutions of silica nanoparticles with different surface chemistry as model foulants. A combined intermediate pore blocking and cake filtration model was applied to the experimental data to determine threshold flux values. Model fits were in excellent agreement with experimental data, indicating that it is an effective tool for determining threshold flux with a sparse data set. Patterned membranes generally exhibited 20–25% higher threshold flux than as-received membranes. Differences in Coulombic interactions and hydrophilicity between the foulants and membrane surface influenced fouling rates. Nevertheless, patterning influenced the threshold flux more significantly than differences in the surface chemistry of foulant particles.