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Understanding the underlying physics of natural gas hydrate dissociation is necessary for efficient CH4 extraction and in the exploration of potential additives in the chemical injection method. Silica being "sand" is already present inside the reservoir, making the silica nanoparticle a potential green additive. Here, molecular dynamics (MD) simulations have been performed to investigate the dissociation of the CH4 hydrate in the presence and absence of ∼1, ∼2, and ∼3 nm diameter hydrophilic silica nanoparticles at 100 bar and 310 K. We find that the formation of a CH4 nanobubble has a strong influence on the dissociation rate. After the initial hydrate dissociation, the rate of dissociation slows down till the formation of a CH4 nanobubble. We find the critical concentration and size limit to form the CH4 nanobubble to be ∼0.04 mole fraction of CH4 and ∼40 to 50 CH4 molecules, respectively. The solubility of CH4 and the chemical potential of H2O and CH4 are determined via Gibbs ensemble Monte Carlo simulations. The liquid phase chemical potential of both H2O and CH4 in the presence and absence of the nanoparticle is nearly the same, indicating that the effect of this additive will not be significant. While the formation of the hydration shell around the nanoparticle via hydrogen bonding confirms the strength of interactions between the water molecules and the nanoparticle in our MD simulations, the contact of the nanoparticle with the interface is infrequent, leading to no explicit effect of the nanoparticle on the dynamics of methane hydrate dissociation. [ABSTRACT FROM AUTHOR]

Regarding the rheological properties of fluids, certain nanoparticles can markedly modify the rheological behavior of low surface tension solutions by interacting with surfactant molecules. In this work, a low surface tension fluid with cetyltrimethylammonium chloride was prepared, and the silica nanoparticles were uniformly dispersed into it by ultrasonic dispersion. By adjusting the size, shape, and concentration of nanoparticles, the fluid behavior can be changed from Newtonian to non-Newtonian with finely tuned viscosity and characterized by a shear-thinning rheological behavior. In addition, this work explored how variations in environmental temperature and solution pH affect the rheological responses of the low surface tension suspension system. The experimental findings revealed that increasing the temperature substantially decreases the system's viscosity and induces a shear-thickening behavior. It is particularly significant that, under extreme pH conditions (either strongly acidic or alkaline), the viscosity of the nanoparticle suspensions was markedly enhanced at a particle concentration of 10 000 ppm. This interesting result coincided with a notable reduction in the zeta potential and an increase in the average particle size, suggesting an intensified aggregation of particles within the suspension system. A mechanism detailing the interaction between silica nanoparticles and surfactant micelles was proposed. This work indicates that the incorporation of nanoparticles into surfactant solutions offers a powerful approach to modulating fluid rheology across various conditions. [ABSTRACT FROM AUTHOR]

The prevention of drying-induced cracking is crucial in maintaining the mechanical integrity and functionality of colloidal deposits and coatings. Despite exploring various approaches, controlling drying-induced cracking remains a subject of great scientific interest and practical importance. By introducing chain-like particles composed of the same material and with comparable size into commonly used colloidal suspensions of spherical silica nanoparticles, we can significantly reduce the cracks formed in dried particle deposits and achieve a fivefold increase in the critical cracking thickness of colloidal silica coatings. The mechanism underlying the crack suppression is attributed to the increased porosity and pore sizes in dried particle deposits containing chain-like particle, which essentially leads to reduction in internal stresses developed during the drying process. Meanwhile, the nanoindentation measurements reveal that colloidal deposits with chain-like particles exhibit a smaller reduction in hardness compared to those reported using other cracking suppression approaches. This work demonstrates a promising technique for preparing colloidal coatings with enhanced crack resistance while maintaining desirable mechanical properties. [ABSTRACT FROM AUTHOR]

A combination of experimental and numerical investigations on metallic silver and platinum nanoparticles deposited on silica substrates is presented, with a focus on metal–substrate interactions. Experimentally, the nanoparticles, obtained by ultra-high vacuum atom deposition, are characterized by grazing-incidence small-angle x-ray scattering and high resolution transmission electronic microscopy to determine their structure and morphology and, in particular, their aspect ratio (height/diameter), which quantifies the metal–substrate interaction, from the as-grown to equilibrium state. Numerically, the interactions between the metal and the silica species are modeled with the Lennard-Jones (12, 6) potential, with two parameters for each metal and silica species. The geometric parameters were found in the literature, while the energetic parameters were determined from our experimental measurements of the aspect ratio. The parameters are as follows: σAg–O = 0.278 nm, σAg–Si = 0.329 nm, ɛAg–O = 75 meV, and ɛAg–Si = 13 meV for Ag–silica and σPt–O = 0.273 nm, σPt–Si = 0.324 nm, ɛPt–O = 110 meV, and ɛPt–Si = 18 meV for Pt–silica. The proposed Ag–silica potential reproduces quantitatively the unexpected experimental observation of the variation of the aspect ratio for Ag nanoparticles larger than 5 nm, which has been interpreted as a consequence of the silica roughness. The nanoparticle orientation, structure, and disorder are also considered. This metal–silica potential for Ag and Pt should be helpful for further studies on pure metals as well as their alloys. [ABSTRACT FROM AUTHOR]

Understanding polymer transport in nanopores is crucial for optimizing heterogeneously catalyzed processes in polymer upcycling and fabricating high-performance nanocomposite films and membranes. Although confined polymer dynamics have been extensively studied, the behavior of polyethylene (PE)—the most widely used commodity polymer—in pores smaller than 20 nm remains largely unexplored. We investigate the effects of extreme nanoconfinement on PE transport using capillary rise infiltration in silica nanoparticle packings with average pore radii ranging from ∼1 to ∼9 nm. Using in situ ellipsometry and the Lucas–Washburn model, we discover a previously unknown inverse relationship between effective viscosity (ηeff) and average pore radius (Rpore). Additonally, we determine that PE transport under these extreme conditions is primarily governed by physical confinement, rather than pore surface chemistry. We refine an existing theory to provide a generalized formalism to describe the polymer transport dynamics over a wide range of pore radii (from 1 nm and larger). Our results offer valuable insights for optimizing catalyst supports in polymer upcycling and improving infiltration processes for nanocomposite fabrication. [ABSTRACT FROM AUTHOR]

In this study, glutathione (GSH)-responsive magnetic mesoporous silica nanoparticles grafted by disulfide organosilicon (SMNPs) were synthesized, characterized, and evaluated as controlled drug carriers. The nanoparticles exhibited consistent dispersion, considerable drug-loading capacity, and high saturation magnetization. Importantly, they demonstrated the ability to release doxorubicin (DOX) by up to 43% in a reducing tumor microenvironment, highlighting their potential for targeted therapy. In addition, the SMNPs displayed favorable biocompatibility, making them suitable for biomedical applications. Most notably, the SMNPs loaded with DOX effectively killed both HepG2 and HeLa cancer cells, while also showing efficient cellular uptake in HeLa cells. These findings suggest that SMNPs are a promising platform for magnetic-targeted and GSH-responsive delivery of therapeutic agents. [ABSTRACT FROM AUTHOR]

In this work, we show that the use of silica nanoparticles improves the imaging and 3D-morphological measurement down to nanometer thicknesses of fixed cells in solution with picosecond ultrasonics (PU). Synchronized ultrafast fs-laser pulses are used to generate coherent acoustic phonons (CAPs) that evoke the Brillouin light scattering and enable the recording of the time-resolved Brillouin oscillations along with the propagation of the acoustic nanopulses through a thin transparent cell in solution. Silica nanoparticles, whose size matches the phonon wavelength at the frequency of the Brillouin scattering in the solution, are used to strongly scatter the CAPs in the solution. Suppressing the Brillouin signature of the surrounding liquid, this protocol improves significantly the PU imaging and makes it possible to measure the mechanical properties of a transparent cell, including the thin peripheral region where the thickness is less than the Brillouin wavelength, equal to half the probe light wavelength in the cell, and where crucial interaction of the cell with its surroundings occurs. We present experimental evidence of the considerable improvement in the cartography of the entire cell using nanoparticles. The intricate frequency dependence of Brillouin scattering and of resonances for a very thin cell is analyzed using a semi-analytical model leading to the challenging measurement of the 3D-morphology of the immersed cell at thicknesses down to 1 / 9 of the optical wavelength. [ABSTRACT FROM AUTHOR]

This study investigated the non-linear rheological behaviors of silver nanowire (AgNW) suspensions containing silica nanoparticles (SiNPs) dispersed in aqueous polyvinyl alcohol (PVA) solutions under large amplitude oscillatory shear (LAOS) flows with various methods including LAOS moduli, Fourier-transform (FT) rheology, and the sequence of physical processes (SPP). The microstructures of the suspensions depended on the ratio of SiNP and AgNW concentrations (φSi/φAg). Lower φSi/φAg ratios yielded entangled AgNWs, whereas high φSi/φAg ratios induced AgNW–SiNP bundle formation due to strong attraction between SiNPs and AgNWs. Non-linear rheological behaviors were classified into three new LAOS types (A, B, and C) based on distinct microstructures including entangled networks of individual AgNWs, stiff AgNW–SiNP bundles, and a combination of both. Type A, with dominant entangled AgNWs, displayed two-step strain thinning attributed to flocculated network formation. Network disruption aggravated the non-linearities due to strain-induced structure formations, followed by the appearance of minima in FT intensities due to disentangled and aligned AgNWs. Type B, comprising AgNW entangled networks and AgNW–SiNP bundles owing to higher SiNP contents, exhibited broad one-step strain thinning. Type C, with dominant stiff bundles, presented the simplest network structures, resulting in one-step strain thinning. Furthermore, intracycle structural changes during LAOS flows were examined using two SPP parameters: instantaneously recoverable elasticity G t , max ′ and internal area of SPP moduli. The SPP analysis also exhibited different behaviors depending on the LAOS types. Thus, employing FT rheology and SPP methods, complex microstructures containing PVA, AgNWs, and SiNPs and their structural changes during LAOS flows were investigated. [ABSTRACT FROM AUTHOR]

Localized surface plasmon resonance from metallic nanoparticles (NPs) under optical excitation brings out intriguing applications in photonics. We realize plasmon-enhanced Raman scattering of two-dimensional (2D) materials (up to 19 times of magnitude for SnSe2 and 12 times for MoS2) via embedded silver nanoparticles in fused silica glass (hereby Ag NPs:glass), suggesting that the fabricated ion-modified multifunctional substrate shows a good compatibility that couple with 2D nanosheets. Moreover, the existence of insulating layers of SiO2 blocks the direct electron transfer and protects the intrinsic properties of surface materials, the Ag NPs:glass substrate exhibits excellent environmental stability and reusability, maintaining higher enhancement ability after a number of repeated uses. Our work opens up a novel route to develop reusable functional substrates for practical applications toward the weak-signal detection and label-free enhanced Raman scattering. [ABSTRACT FROM AUTHOR]

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 (CS*), the aggregation of nanoparticles is characterized by fractal aggregates. [ABSTRACT FROM AUTHOR]

Amorphous silicon dioxide (hereafter SiO2) samples were implanted with 380 keV Fe ions at room temperature. After the implantation, some samples were irradiated with 16 MeV Au ions. The magnetic property was investigated by using a SQUID magnetometer, and the morphology of Fe-implanted SiO2 samples was examined by using a transmission electron microscope and x-ray absorption spectroscopy (extended x-ray absorption fine structure and x-ray absorption near edge structure). The size of Fe nanoparticles increases with an increase in the amount of Fe implantation. A part of Fe nanoparticles consists of Fe oxides, and with an increase in the amount of Fe implantation, the valence state of Fe atoms and the structure of Fe nanoparticles gets close to those of metallic α-Fe. The room temperature magnetism was observed in Fe-implanted SiO2 samples. The magnetization–magnetic field curves for samples implanted with a small amount of Fe are reproduced by the Langevin equation, implying that Fe nanoparticles present the superparamagnetic behavior. For a large amount of Fe implantation, the magnetization–magnetic field curve shows the ferromagnetic state. Such a result of magnetic property is consistent with the results of the x-ray absorption. By the subsequent 16 MeV Au irradiation, the Fe nanoparticles were fragmentated, resulting in the decrease in magnetization. The optical absorption property of the SiO2 samples is briefly discussed. [ABSTRACT FROM AUTHOR]

The micelle structure of surfactant is easy to be destroyed in the flow process resulting in a decrease in its drag reduction (DR) efficiency; therefore, how to strengthen the stability of the micelle structure during the flow process and thus improve the drag reduction efficiency deserves intensive research. In this work, by comparing a variety of nanoparticles, hydrophobic silica nanoparticles were selected as the best additive to enhance the turbulence drag reduction efficiency of surfactant solution with spherical micelle structure. The experimental results also demonstrated that the hydrophobic silica nanoparticles had a reinforcing effect on anionic, cationic, nonionic, and zwitterionic surfactant solutions with the same concentration (dominated by spherical micelles), and the optimal nanoparticle addition concentration and maximum drag reduction rate were obtained. Meanwhile, the effect of silica nanoparticles on the turbulence drag reduction efficiency of surfactant solutions with different micelle structures was evaluated by inducing the surfactant micelle structure change. It was shown that the hydrophobic silica nanoparticles had a strengthening effect on the turbulence drag reduction performance of surfactant solutions with spherical micelle structure, while they had an inhibiting effect on the turbulence drag reduction performance of surfactant solutions with worm-like micelle structure. The change in solution viscoelasticity indicated that the decrease in viscoelasticity was the main reason for the decrease in drag reduction efficiency of surfactant solution with worm-like micelle structure when silica nanoparticles were added. A mechanism for the interaction of hydrophilic/hydrophobic silica nanoparticles with spherical micelles and wormlike micelle structures was finally discussed and proposed. [ABSTRACT FROM AUTHOR]

This study explores the effects of nanoparticles on the dynamics of drop spreading under external vibration, presenting an advance in the understanding of nanofluid behavior on vibrating substrates. This work introduces insights into nanoparticle-mediated drop spreading, offering implications for improving particulate coatings, mini-mixers, and particle segregation technologies. By employing a twofold approach that combines oscillating drop dynamics with internal flow pattern analysis, we find how even small concentrations of hydrophilic or hydrophobized silica nanoparticles inside water sessile droplets significantly alter the spreading process on silanized glass surfaces. Our study allows distinct drop spreading regimes to be identified based on nanoparticle concentration and vibration amplitude, for both hydrophilic and hydrophobized nanoparticles. Through a comprehensive analysis, we demonstrate that the vibration-triggered spreading of nanofluids can lead to a stable and controlled manipulation of complex liquids. [ABSTRACT FROM AUTHOR]

Interaction of different-sized anionic silica nanoparticles with non-spherical micelles and bilayers of non-ionic surfactant C12E10 has been studied by small-angle neutron scattering (SANS). The non-ionic surfactant C12E10 in aqueous solution self-assembles to form core–shell spherical micelles. Different means (temperature, salts, and alcohols) have been examined to induce the structural transition of micelles from spherical to non-spherical and bilayer formation. The dehydration from micellar shell leads to such transition in the cases of increasing temperature and selective salt (e.g., KF). On the other hand, for alcohols, spherical to non-spherical micellar transition or bilayer formation arises for long-chain length alcohols CnOH (n > 5) because of the mixed micelles formation of alcohol with surfactant. From the different ways to alter the micellar morphology, transitions obtained by alcohols were found to be the best suited for nanoparticle–surfactant solution as they do not influence the interactions between nanoparticle and surfactant and among nanoparticles. It is found that the shorter chain length alcohols (CnOH, n ≤ 5) interact with nanoparticles via the adsorption of individual micelles while the non-spherical micelles and bilayers of surfactant formed in the presence of long-chain length alcohols rearrange themselves to attach onto the nanoparticles. SANS with an advantage of contrast variation (contrast matching silica nanoparticles with solvent) provides the evidence of bilayer formation around nanoparticles. The concentration effect of long-chain length alcohol on micelle morphology and subsequently on the nanoparticle–surfactant system is also examined. It is found that the adsorption of surfactant bilayer structures is prominent in the case of larger particle size due to flattened curvature. [ABSTRACT FROM AUTHOR]

The key parameter controlling the glass transition of colloidal suspensions is φ, the fraction of the sample volume occupied by the particles. Unfortunately, changing φ by varying an external parameter, e.g., temperature T as in molecular glass formers, is not possible, unless one uses thermosensitive colloidal particles, such as the popular poly(N-isopropylacrylamide) (PNiPAM) microgels. These, however, have several drawbacks, including high deformability, osmotic deswelling, and interpenetration, which complicate their use as a model system to study the colloidal glass transition. Here, we propose a new system consisting of a colloidal suspension of non-deformable spherical silica nanoparticles, in which PNiPAM hydrogel spheres of ∼ 100 − 200 μ m size are suspended. These non-colloidal "mesogels" allow for controlling the sample volume effectively available to the silica nanoparticles and hence their φ, thanks to the T-induced change in mesogels' volume. Using optical microscopy, we first show that the mesogels retain their ability to change size with T when suspended in Ludox suspensions, similarly as in water. We then show that their size is independent of the sample thermal history such that a well-defined, reversible relationship between T and φ may be established. Finally, we use space-resolved dynamic light scattering to demonstrate that, upon varying T, our system exhibits a broad range of dynamical behaviors across the glass transition and beyond, comparable with those exhibited by a series of distinct silica nanoparticle suspensions of various φ. [ABSTRACT FROM AUTHOR]

When introducing a nanoparticle into an optical trap, its mass and shape are not immediately apparent. We combine a charge-based mass measurement with a shape determination method based on light scattering and an analysis of the damping rate anisotropy, all on the same set of silica nanoparticles, trapped using optical tweezers in vacuum. These methods have previously only been used separately, and the mass determination method has not been applied to asymmetric particles before. We demonstrate that the combination of these classification techniques is required to distinguish particles with similar mass but different shape, and vice versa. The ability to identify these parameters is a key step for a range of experiments on precision measurements and sensing using optically levitated nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, molecular dynamics simulations are used to examine the self-assembly of anisotropically coated "patchy" nanoparticles. Specifically, we use a coarse-grained model to examine silica nanoparticles coated with alkane chains, where the poles of the grafted nanoparticle are bare, resulting in strongly attractive patches. Through a systematic screening process, the patchy nanoparticles are found to form dispersed, string-like, and aggregated phases, dependent on the combination of alkane chain length, coating chain density, and the fractional coated surface area. Correlation analysis is used to identify the ability of various particle descriptors to predict bulk phase behavior from more computationally efficient single grafted nanoparticle simulations and demonstrates that the solvent-accessible surface area of the nanoparticle core is a key predictor of bulk phase behavior. The results of this work enhance our knowledge of the phase space of patchy nanoparticles and provide a powerful approach for future screening of these materials. [ABSTRACT FROM AUTHOR]

Amorphous photonic structures (APSs) with non-iridescent, non-fading, vivid structural colors have attracted great attention in several fields. Tremendous efforts have been dedicated to developing the effective and low-cost approaches for APSs with full-color displays. Resulting from the isotropic photonic pseudogap, APSs have non-iridescent structural colors. We demonstrate that incorporating F e 3 O 4 @ Si O 2 black nanoparticles into the interspace of the periodically arranged Si O 2 white nanospheres can synthesize APSs with different colors. The addition of F e 3 O 4 @ Si O 2 black nanoparticles can enhance the saturation of the non-iridescent structural colors of the APSs by reducing the incoherent scattering in the visible spectrum. In this case, different non-iridescent colors originate from the different diameters of the Si O 2 white nanospheres, and we obtained red, orange, yellow, green, and purple APSs with high reflective index successfully. The APSs with different colors may have potential applications in coatings, cosmetics, textiles, and displays. Moreover, as we use F e 3 O 4 @ Si O 2 as the additive, APSs can be recycled through its magnetic property. [ABSTRACT FROM AUTHOR]

We report the reaction of muonium (Mu = [μ+e−]), a light isotopic analog of hydrogen, with uncapped gold nanoparticles embedded in mesoporous silica. Using the radio-frequency muon spin rotation (RF-μSR) technique, we directly observe and characterize the resulting final state on the nanoparticle surface, showing conclusively its diamagnetic nature. The magnetic environment experienced by the reacted muons is only weakly perturbed compared to that of muons in a silica reference, consistent with the surface of the gold nanoparticles being metallic and non-magnetic. We demonstrate the potential of RF-μSR for the investigation of the surface properties of nanoparticles and show the feasibility of Knight shift measurements of muons on metal surfaces. [ABSTRACT FROM AUTHOR]

Perfluorosulfonic acid (PFSA) ionomer nanocomposites are a promising solution to address the poor ion selectivity of current membranes utilized in vanadium redox flow batteries. Herein, we investigate the impact of a casting substrate on the nanostructure and vanadium ion transport in bulk ionomer and ionomer nanocomposite membranes (i.e., films with thicknesses of ∼100 μm). Specifically, solution-cast ionomer nanocomposite membranes, containing either unfunctionalized (hydroxyl groups), amine-functionalized, or sulfonic acid-functionalized silica nanoparticles (SiNPs), were fabricated by casting on either a polished quartz or polytetrafluoroethylene (PTFE) substrates. Surprisingly, the choice of the casting substrate was seen to affect the bulk morphology of the PFSA ionomers, resulting in substrate-specific vanadium ion transport, where suppressed ion transport was observed for membranes cast on the polished quartz, when compared to their PTFE-cast counterparts. Additionally, the chemical composition of the substrate-adjacent surface was a function of both the substrate and the surface functionality of the SiNPs. Moreover, it was observed that both the chemical composition of the membrane surface and the substrate-induced changes to the bulk ionomer morphology governed vanadyl ion transport through the PFSA ionomers. Results from this work have direct implications for the design of next-generation ionomer nanocomposites, as the casting substrate used to fabricate these materials, and the orientation of these membranes inside the operating flow battery, can significantly influence transport of vanadium ions. [ABSTRACT FROM AUTHOR]

Zwitterionic brush grafting is considered a serious strategy for surface modification on mesoporous silica nanoparticles (MSN) and a prominent alternative to polyethylene glycol films for antifouling applications. In this study, the solution behavior of poly(sulfobetaine methacrylate) (pSBMA) polymer brushes grafted on MSN (95 ± 15 nm particle diameter, 2.8 nm pore size) was evaluated. The layers increased their hydrodynamic diameter (dH) with increasing temperature, indicating a conformational change from a surface-collapsed state to a fully solvated brush. This development was marked by a transition temperature, related to the molecular weight and the theoretical length of the polymer chains. Variation of dH with pH values was studied and a zwitterionic range of 5–9 was established where the electric charges in the molecule were balanced. Zeta potential (ZP) values for all pSBMA-MSN products were also measured. A decreasing trend of ZP with pH and an isoelectric point around 5.5–6.5 was obtained for all dispersions. Furthermore, the influence of temperature was analyzed on ZP and a directly proportional correlation was found, with increasing rates of 0.50–0.87%/°C. Finally, ZP variation with electrolyte concentration was determined and a range of 40–60mM of NaCl concentration was established to reach an almost zero-charge point for all nanoparticles. It was demonstrated that the solution response of pSBMA-MSN can be modulated by temperature, pH, and ionic concentration of the media. These behaviors could be used as controlled release mechanisms for the application of pSBMA-MSN as carriers in biomedicine and nanophamaceutical fields in the future. [ABSTRACT FROM AUTHOR]

Preparation of supported metal nanoparticles for catalytic applications often relies on an assumption that the initially prepared wet-impregnated support material is covered with approximately a monolayer of adsorbed species that are shaped into the target nanoparticulate material with a desired size distribution by utilizing appropriate post-treatments that often include calcination and reduction schemes. Here, the formation and evolution of surface nanoparticles were investigated for wet-chemistry deposition of platinum from trimethyl(methylcyclopentadienyl)platinum (IV) precursor onto flat silica supports to interrogate the factors influencing the initial stages of nanoparticle formation. The deposition was performed on silicon-based substrates, including hydroxylated silica (SiO2) and boron-impregnated hydroxylated silica (B/SiO2) surfaces. The deposition resulted in the immediate formation of Pt-containing nanoparticles, as confirmed by atomic force microscopy and x-ray photoelectron spectroscopy. The prepared substrates were later reduced at 550 °C under H2 gas environment. This reduction procedure resulted in the formation of metallic Pt particles. The reactivity of the precursor and dispersion of Pt nanoparticles on the OH-terminated silica surface were compared to those on the B-impregnated surface. The size distribution of the resulting nanoparticles as a function of surface preparation was evaluated, and density functional theory calculations were used to explain the differences between the two types of surfaces investigated. [ABSTRACT FROM AUTHOR]

Mesoporous silica nanoparticles/polymer hybrid materials were prepared via metal-free surface-initiated atom-transfer radical polymerization (SI-ATRP). Self-synthesized mesoporous SBA-15 with surface hydroxyl groups was modified with (3-aminopropyl)-triethoxysilane, followed by anchoring of the ATRP initiator α-bromoisobutyryl bromide onto the surface via amide reaction. The SI-ATRP of methyl methacrylate was then carried out with fluorescein (FL) as a photocatalyst and trimethylamine (TEA) as an electron donor under irradiation with blue light. Thus, polymer chains grew directly from mesoporous walls. The hybrid materials were characterized by gel permeation chromatography, N2 adsorption/desorption measurements, and thermogravimetric analysis. The effects of the ligand/photocatalyst molar ratios, solvent, and the monomer/initiator molar ratios on grafting density, molecular weight, and molecular-weight distribution were investigated. The results show that a higher TEA/FL ratio led to a higher reaction rate and better controllability of the polymerization but also to a lower grafting density. These properties were also affected by the solvent. With an increasing monomer/initiator molar ratio, the grafting rate, molecular weight, and grafting density exhibited increasing trends. [ABSTRACT FROM AUTHOR]

The pH at silica-water interfaces (pHint) was measured by grafting a dual emission fluorescent probe (SNARF) onto the surface of mesoporous silica nanoparticles (MSN). The values of pHint of SNARF-MSN suspended in water were different from the pH of the bulk solution (pHbulk). The addition of acid or base to aqueous suspensions of SNARF-MSN induced much larger changes in pHbulk than pHint, indicating that the interface has buffering capacity. Grafting additional organic functional groups onto the surface of SNARF-MSN controls the pHint of its buffering region. The responses of pHint to variations in pHbulk are consistent with the acid/base properties of the surface groups as determined by their pKa and are affected by electrostatic interactions between charged interfacial species as evidenced by the dependence of ζ-potential on pHbulk. Finally, as a proof of principle, we demonstrate that the hydrolysis rate of an acid-sensitive acetal can be controlled by adjusting pHint via suitable functionalization of the MSN surface. Our findings can lead to the development of nanoreactors that protect sensitive species from adverse conditions and tune their chemical reactivity. [ABSTRACT FROM AUTHOR]

Polyhedral Oligomeric Silsesquioxanes (POSS) molecules have emerged as promising alternatives to traditional silica nanoparticles and organosilicon molecules due to their ability to attach a variety of substituents to their central siloxane cages. The electronic features of POSS are dependent on the structures of substituents and cages, making them attractive for applications, such as drug nanocarriers, chemosensors, Janus particles, and inorganic–organic nanocomposites. However, the lack of detailed geometric data poses a difficulty in extending POSS studies using the force field method or beyond the quantum mechanical level. To lay a foundation for future experimental and computational studies, we present new theoretical insights into the influence of substituent and cage on the cage geometries (Si–O bond length, pore width, cage volume, etc.) of 16 substituted POSS molecules with various substituents and cages (T7, T8, T10, T12). Our results show that the mean Si–O bond length of the POSS cage can be in the range of 1.619–1.670 Å depending on the substituent and cage. Moreover, we show that the expansion or shrinkage of POSS depends on the types of substituents, rather than the inductive effect of substituents. Our results demonstrate that the conformational stability, dipole moment, and polarizability of POSS depend on the substituents' size, substituents' shape, type of functional moieties of substituents, and cage size. In addition, the HOMO-LUMO bandgap of POSS can be tuned by changing the hydrocarbon chain length, number of aromatic rings, and types of functional groups on the substituents. Finally, we report several sets of geometric data that are transferable to the existing parametrization methods of force field models. [ABSTRACT FROM AUTHOR]

We report a novel template method for synthesizing silica nanoparticles that are mesoporous as well as biocompatible. The mesoporous silica nanoparticles were synthesized using the Stober process and peptization method. We have used surface-modified deoxyribonucleic acid (DNA) with cetyl trimethyl ammonium bromide as a capping agent. The obtained silica particles were analyzed using x-ray diffraction, UV–vis spectroscopy, the Brunauer–Emmet–Teller method, scanning electron microscopy, and the open aperture Z-scan technique. The characterization results indicated that the DNA polymer's presence influenced the formation of the silica particles. The silica particles are mesoporous, nanosized, and good adsorbent and also show enhanced non-linear optical properties when compared with existing silica nanoparticles. The solubility of the silica nanoparticles was also verified in dimethyl sulfoxide (DMSO). We have verified that the enhanced mesoporous surface area and reduced porous size of the silica nanoparticles influenced the photoluminescence of Rhodamine 6G dye in DMSO. This can be applied to lower the lasing threshold of the gain medium in lasing applications. Hence, the obtained silica nanoparticles have a variety of applications such that they can be used as adsorbents of nanosized particles, which is applicable for drug delivery purposes, bioimaging, catalytic activities, doping surface for thin film making, biosensing applications, and improvement of material quality for solar devices. The non-linear optical property of the mesoporous silica nanoparticles can be used for optical limiting applications in photonic devices. [ABSTRACT FROM AUTHOR]

Protein coronas, formed by proteins and nanomaterials, have various applications in the biomedical field. Here, large-scale simulations of protein coronas have been carried out by an efficient mesoscopic coarse-grained method with the BMW-MARTINI force field. The effects of protein concentration, size of silica nanoparticles (SNPs), and ionic strength on the formation of lysozyme-SNP coronas are investigated at the microsecond time scale. Simulations results indicate that (i) an increase in the amount of lysozyme is favorable for the conformation stability of adsorbed lysozyme on SNPs. Moreover, the formation of ringlike and dumbbell-like aggregations of lysozyme can further reduce the conformational loss of lysozyme; (ii) for a smaller SNP, the increase of protein concentration exhibits a greater effect on the adsorption orientation of lysozyme. The dumbbell-like lysozyme aggregation is unfavorable for the stability of lysozyme's adsorption orientation; however, the ringlike lysozyme aggregation can enhance the orientation stability; (iii) the increase of ionic strength can reduce the conformation change of lysozyme and accelerate the aggregation of lysozyme during their adsorption process on SNPs. This work provides some insights into the formation of protein coronas and some valuable guidelines for the development of novel biomolecule-NP conjugates. [ABSTRACT FROM AUTHOR]

The dielectric and structural properties of an amorphous SiO2 nanopowder have been characterized in the framework of Bergman's spectral representation. The methodology used in this paper is based on the acquisition of reflectivity spectra from a set of nanopowder pellets with different levels of porosity and the measurement of the transmittance spectra of KBr pellets containing low levels of silica nanoparticles. The fit of the spectra was performed with a dielectric function model through the solution of a nonlinear optimization problem including all the experimental data. In addition to the optical properties, the complete analysis also provided an accurate estimate of the total porosity of pellets and evaluated the percolation of the silica agglomerates in the porous matrix. A comparison with the predictions obtained by other mixing formulas clearly demonstrates that Bergman's theory is the most appropriate for treating this type of powder. [ABSTRACT FROM AUTHOR]

We study the enhancement of the stiffness of two families of hydrogels (polyacrylamide, PAAm, and polydimethylacrylamide, PDMA) due to the additions of very small amounts of silica nanofillers. It is well established that high concentrations of silica nanoparticles enhance the toughness of both hydrogel types, but significantly more for the PDMA based gels that adsorb readily to silica surfaces. In order to decouple the structural changes in the gels that stem either from polymerization kinetics or from the interactions between nanofillers and polymers, we use a photoinitiator for the polymerization of the composite gels that promotes the structural homogeneity of the hydrogels. We characterize both the mechanical and structural properties of the composite hydrogels as a function of nanofiller concentration, by calculating the single particle diffusion of inert polystyrene tracer particles of three different sizes. In agreement with previous experiments, we find that silica nanoparticles increase the stiffness of PAAm gels more than expected for passive fillers. Surprisingly, we find that a small addition of silica nanoparticles during gel polymerization to PDMA based hydrogels softens them. We attribute this effect to an increase of the average mesh size of the gel, allowing particles of 0.49 μm in diameter to diffuse normally through the gel, but restricting the motion of larger particles. A further increase in silica nanoparticle concentration results in the expected stiffening of the gel. PDMA based composites with a large mean pore size, as reported here, may find applications in particle separation and gentle fixation of microorganisms and cells. [ABSTRACT FROM AUTHOR]

Clean loading of silica nanoparticles with a radius as small as ∼ 50 nm is required for experiments in levitated optomechanics that operate in ultra-high vacuum. We present a cheap and simple experimental method for dry launching of silica nanoparticles by shaking from a polytetrafluoroethylene surface (PTFE). We report on the successful launching of single silica nanoparticles with a minimum radius of 43 nm, which is enabled by the low stiction to the launching surface. Nanoparticles with radii of 43 and 71.5 nm are launched with a high flux and small spread. The measured velocities are significantly smaller than 1 m/s. The demonstrated launching method allows for controlled loading of dry nanoparticles with radii as small as 43 nm into optical traps in (ultra-)high vacuum, although we anticipate that loading of smaller sizes is equally feasible. [ABSTRACT FROM AUTHOR]

Nanoparticle-based materials are of interest because of their unique thermal properties. Possessing the lowest thermal conductivities of any solid materials known, they have been widely used as insulating materials. However, the presence of water vapor has been shown to have a large influence on those properties. In this work, we investigate the effect of water vapor on the heat transfer between nanoparticles using non-equilibrium molecular dynamics simulations. We calculate the absolute thermal resistance and Kapitza resistance between adjacent amorphous spherical silica nanoparticles, when water molecules are allowed to diffuse as vapor into the interstitial pores between particles. The thermal resistance between nanoparticles is shown to decrease rapidly when water vapor is introduced into the pores between particles. The largest decrease in interparticle resistance occurs as a result of the silanization of the silica particle surfaces. A secondary decrease is attributable to the liquid bridge that forms as water molecules condense around the contact point between nanoparticles. Most of the decrease in resistance between nanoparticles occurs when water vapor is first introduced at relative humidities (rh) of less than 1%. As the relative humidity increases above 1%, the interparticle thermal resistance decreases more slowly, approaching a constant value near 50% rh. Numerical results are compared to experimental measurements of heat transfer across packed beds of 20 nm silica nanoparticles exposed to water vapor. The simulation results are shown to be consistent with the experimental measurements for relative humidities below 15% rh, while underpredicting the experimental measurements above 15% rh. [ABSTRACT FROM AUTHOR]