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Modulation of Si–O bonds under mild conditions has been a challenging issue in the field of material science, which is critical to manufacture high‐performance silica‐based optical and photonic devices. Herein, we introduce a nondestructive technique to achieve Si–O bond rearrangement, leading to plastic deformation and photoluminescence enhancement of amorphous silica nanoparticles using supercritical carbon dioxides in EtOH/H2O solution under mild temperature. Specifically, plastic deformation is achieved by treating hollow mesoporous silica nanospheres using supercritical CO2 at 40 °C under 20 MPa. Experimental and theoretical studies revealed the critical role of supercritical CO2 in the plastic deformation process, which can be intercalated into the hollow mesoporous silica nanospheres with anisotropic stresses and induces the rearrangement of Si–O bonds and transformation of ring structures. This work suggests a novel approach to engineer high‐performance nano‐silica glass components for numerous optical and photonic devices under mild condition. [ABSTRACT FROM AUTHOR]

The multi-scale characterization of building materials is necessary to understand complex mechanical processes, with the goal of developing new more sustainable materials. To that end, imaging methods are often used in materials science to characterize the microscale. However, these methods compromise the volume of interest to achieve a higher resolution. Dark-field (DF) contrast imaging is being investigated to characterize building materials in length scales smaller than the resolution of the imaging system, allowing a direct comparison of features in the nano-scale range and overcoming the scale limitations of the established characterization methods. This work extends the implementation of a dual-phase X-ray grating interferometer (DP-XGI) for DF imaging in a lab-based setup. The interferometer was developed to operate at two different design energies of 22.0 keV and 40.8 keV and was designed to characterize nanoscale-size features in millimeter-sized material samples. The good performance of the interferometer in the low energy range (LER) is demonstrated by the DF retrieval of natural wood samples. In addition, a high energy range (HER) configuration is proposed, resulting in higher mean visibility and good sensitivity over a wider range of correlation lengths in the nanoscale range. Its potential for the characterization of mineral building materials is illustrated by the DF imaging of a Ketton limestone. Additionally, the capability of the DP-XGI to differentiate features in the nanoscale range is proven with the dark-field of Silica nanoparticles at different correlation lengths of calibrated sizes of 106 nm, 261 nm, and 507 nm. [ABSTRACT FROM AUTHOR]

This research delves into the comprehensive exploration of silica nanoparticles (SiO2-NPs) synthesis via ultrasonic spray pyrolysis. Essential factors investigated encompassed varying concentrations of tetraethyl orthosilicate (TEOS) (0.51 M, 0.25 M, and 0.12 M), furnace temperatures (200°C, 300°C, and 400°C), carrier gases (Ar, N2, O2), residence times of reactants in the furnace (0.5 sec, 1.5 sec, 5 sec), and solvents (acetone, ethyl acetate, and ethanol). The influence of incorporating F127 in the synthesis process was scrutinized for its role in producing mesoporous silica nanoparticles. Results indicated that an escalation in TEOS concentration from 0.12M to 0.51M at 400°C resulted in a proportional increase in the average particle diameter of SiO2 nanoparticles from 7 nm to 40 nm and the specific surface area decreased from 147 to 97 m²/g, revealing a narrow size distribution. Manipulating the nitrogen flow rate during the furnace process from 100 to 300 ml/min exhibited the capability to yield SiO2 nanoparticles by increasing their particle size to 61nm. Additionally, an extension of the residence time of precursors, achieved through careful regulation of the carrier gas flow rate, yielded a noticeable augmentation in the average particle diameter. Notably, the choice of solvent emerged as a discernible factor, leading to the fabrication of SiO2-NPs with various morphologies. This multifaceted investigation provides valuable insights into the intricacies of silica nanoparticle synthesis, contributing to the understanding of the nuanced interplay of parameters in achieving desired particle characteristics for diverse applications in nanotechnology and materials science. [ABSTRACT FROM AUTHOR]

Silica nanoparticles have become an important tool in material sciences, nanomedicine, biotechnology, and pharmaceutics, with recent suggested applications also in environmental sciences. In life and environmental sciences, the application field is usually aqueous media; however, the crucial issue of silica nanoparticle dissolution behavior and rate in the target medium is often neglected, overlooked, or taken for granted. Silica nanoparticles are not stable in aqueous solutions until equilibrium silica concentrations are reached. While for life science applications, the degradability of silica nanoparticles is prerequisite for biocompatibility, this characteristic impedes the successful application of silica nanoparticles as environmental tracer, where long-term stability is needed. In this study, the impact of external (temperature, pH values, salinity, availability of silica) and internal (degree of condensation, size, porosity) parameters on the stability of ~ 45-nm-sized silica nanoparticles is characterized. Results show that external factors such as elevated temperature and alkaline pH-values accelerate the dissolution, acidic pH, high salinities, and high initial silica concentrations exhibit a contrary effect. Consequently, in applications, where external parameters cannot be controlled (e.g., in vivo, subsurface reservoirs), dissolution control and stability improvement of silica nanoparticles can be achieved by various means, such as adding a protective layer or by condensation of the silanol bonds through calcination. [ABSTRACT FROM AUTHOR]

Background: Ultrasound-triggered sonodynamic therapy (SDT), as a noninvasive approach, has attracted considerable attention in a wide variety of malignant tumors and other diseases. Over the past 2 decades, the number of scientific publications on SDT has increased rapidly. However, there is still a lack of one comprehensive report that summarizes the global research trends and knowledge landscapes in the field of SDT in detail. Thus, we performed a bibliometric analysis on SDT from 2000 to 2021 to track the current hotspots and highlight future directions. Methods: We collected publications on SDT research from the Web of Science Core Collection database. The annual number of publications and citations, major contributors, popular journals, international collaborations, co-cited references and co-occurrence keywords were analyzed and visualized with CiteSpace, VOSviewer, and R-bibliometrix. Results: A total of 701 publications were included. The annual publication output increased from 5 in 2000 to 175 in 2021, and the average growth rate was 18.4%. China was the most productive country with 463 documents (66.05%), and Harbin Medical University was the most prolific institution (N = 73). Ultrasound in Medicine and Biology published the most papers related to SDT. Materials Science, and Chemistry were the research areas receiving the most interest. All the keywords were divided into four different clusters including studies on mechanisms, studies on drug delivery and nanoparticles, studies on cancer therapy, as well as studies on ultrasound and sonosensitizers. In addition to nanomaterials-related studies including nanoparticles, mesoporous silica nanoparticles, nanosheets, liposomes, microbubble and TiO2 nanoparticle, the following research directions such as immunogenic cell death, metal-organic framework, photothermal therapy, hypoxia, tumor microenvironment, chemodynamic therapy, combination therapy, tumor resistance, intensity focused ultrasound, drug delivery, and Staphylococcus aureus also deserve further attention and may continue to explode in the future. Conclusion: SDT has a bright future in the field of cancer treatment, and nanomaterials have increasingly influenced the SDT field with the development of nano-technology. Overall, this comprehensive bibliometric study was the first attempt to analyze the field of SDT, which could provide valuable references for later researchers to better understand the global research trends, hotspots and frontiers in this domain. [ABSTRACT FROM AUTHOR]

Silica has drawn the attention of many researchers from all over the world owing to its excellent biological, mechanical, and physiochemical properties. Different synthetic routes, reagents, characterization techniques, and applications of silica nanoparticles (SiO2 NPs) are discussed in this review article. A detailed discussion on sol-gel, ultrasonication, chemical precipitation, and hydrothermal route is presented. Biological synthesis of SiO2 NPs from bamboo leaves, rice husk, and sugarcane bagasse is also focused. Different characterization techniques including X-ray diffraction, dynamic light scattering, transmission electron microscopy, and Fourier transform infrared spectroscopy are discussed in detail. A study on SiO2 NPs conjugated with metallic oxides and polymers is also discussed. Being important materials with a wide variety and novel applications, these conjugates are used in agriculture, mechanical engineering, material science, electronics, and biomedical engineering. However, greater emphasis has been laid on biomedical aspects, including antibacterial applications and drug delivery along with its cytotoxic properties. The review article reflects that SiO2 NPs are potential candidates for several biomedical applications due to their biocompatibility and appreciable biological activity. [ABSTRACT FROM AUTHOR]

Over the past researches, the formulation of nanoparticles is considered to be a most time-consuming process. Accordingly, it is a relevant process to attempt the synthesis of the silica nanoparticle with a reasonable series of time. Therefore, shock wave as a source of energy has contributed an effective role in the field of material science. The research is motivated to reduce the processing time, and the alternative source of energy in the form of shock waves is intruded over the precursor and initiates the reaction in the precursor and also it is used to sustain and control the reactions of nanoparticles. In this research, an attempt has been made to use shock wave as a source of energy to synthesis silica nanoparticles. Henceforth, the processing time taken for the synthesis of silica is comparatively very high in the existing manufacturing schemes. Initially, the synthesis is initiated from the phase of material selection that is capable of the composition. Henceforth, tetraethyl orthosilicate, ethanol, water, ammonium hydroxide and shock tubes are the material participates in the composition. Accordingly, a disparate solution has been formed after the fusion of the relative materials. The prepared solution is treated with the consecutive shock pulses for the formation of the ammonium acetate and further treated in the centrifuge tube. Concurrently, on the basis of Fourier transform infrared spectroscopy (FTIR) the formation of silica nanoparticles is confirmed. Using field emission scanning electron microscope, the growth in the polymerization of silica nanoparticles is analyzed with a relative progress by inserting the shocks. Extensively, by acquiring the specified shock wave energy as an alternative solution the processing time attained for the synthesis will be more effectively performed when compared to the existing techniques as such that the existing practices will require 3 h to fulfill the synthesis as the proposed energy will attain only 15 min to formulate the nanoparticle. Ultimately, the FTIR analysis upon the research exhibits from the allotted region of the asymmetric vibration over basic intense band of silica is rectified as Si–O–Si over 1100–1120 cm−1 and also deliberates a bending vibration with vibration of the corresponding Si–O–Si at 1670–1677 cm−1, respectively. Conclusively, the research rectifies an immense of evolution in the processing time to synthesis silica nanoparticle from the existing practices followed in real-time scenario, respectively. [ABSTRACT FROM AUTHOR]

In this study, a series of hydrogels based on the physical adsorption between hydroxyethyl cellulose (HEC) and colloidal silica nanoparticles (SNPs) were developed, and the effects of SNPs addition on the prepared gels were also investigated. The addition of SNPs into the HEC solution (1.0 wt%) induced gelation, and the gel strength was enhanced by increasing the SNPs concentration from 5 to 20 wt%, which was due to the formation of a denser gel network, as evidenced by SEM observations. Rheological tests suggested that the gelation temperature (T g) was decreased with the increasing SNPs addition, and the gels exhibited slightly thermal hysteresis, with a temperature lag of 6–7 °C. However, when the SNPs concentration was above 21 wt%, a phase separation was observed. Furthermore, it was found that the addition of SNPs led to the intensified hydrogen bonds between the HEC molecules and the added SNPs, which may be the predominant factor governing the adsorption process. Overall, a facile method for hydrogel preparation was proposed in this study, and the gel properties were also systematically investigated. These results may provide useful information to the field of material science. • The addition of SNPs induced the gelation of HEC solution. • Physical adsorption between HEC and SNPs is the predominant factor governing the gelation process. • The prepared gels exhibited slight thermal hysteresis. • An increase in SNPs concentration led to the decreased T g. [ABSTRACT FROM AUTHOR]

The interdisciplinary integration among material science, nanotechnology and biology has been promoting the emergences of a large number of feasible nanoplatforms for diverse biomedical applications. Thanks to the unique mesoporous structure, large specific surface area, abundant surface chemistry and tunable framework composition, mesoporous silica nanoparticles (MSNs) and mesoporous organosilica nanoparticles (MONs) have been extensively applied for diverse therapeutic, or diagnostic applications. The past two decades have witnessed the blooming growth of researches on the elaborate design and fabrication of multifunctional MSNs/MONs-based nanosystems, which have greatly pushed forward the development of next-generation theranostic biomaterials. These mesoporous silica-based nanomaterials feature varied structural, compositional and morphological characteristics, leading to the great diversity in their downstream physicochemical properties and theranostic performances, which further catalyzes the emergence of advanced therapeutic strategies for optimized treatment efficacies and mitigated side effects. In this review, we will comprehensively elucidate very-recent advances on the construction of MSNs/MONs-based theranostic nanoplatforms for various therapeutic and diagnostic applications, and discuss the underlying material chemistry of these exquisite nanosystems that confers varied theranostic functionalities. Especially, the interdependent relationship among the synthesis, biological effects and biomedical applications of MSNs and MONs will be discussed in depth, and their further clinical-translation potential/challenge will be clarified and outlooked. It is highly expected that we will witness a second leap-forward development of the biomedical applications of MSNs and MONs in the next one or two decades, especially for the further clinical translation. [ABSTRACT FROM AUTHOR]

The agglomeration of silica nanoparticles in aqueous solution is investigated from molecular simulations. Mimicking destabilization of colloidal solutions by full removal of protective moieties or surface charge, association of SiO2/Si(OH)4 core/shell particles leads to rapid proton transfer reactions that account for local silanole → silica ripening reactions. Yet, such virtually barrier-less binding is only observed within a limited contact zone. Agglomeration hence leads to the formation of oligomers of nanoparticles, whilst full merging into a compact precipitate is hampered by the need for extended structural reorganisation. Implementing sufficiently fast supply from colloidal solution, our simulations show the development of silica networks comprised of covalently bound, yet not fully merged nanoparticles. Within the oligomerized nanoparticle network, coordination numbers range from 2 to 5 –which is far below closest packing. Our simulations hence rationalize the formation of covalently bound network structures hosting extended pores. The resulting interfaces to the solvent show water immobilization only for the immediate contact layers, whilst the inner pores exhibit solvent mobility akin to bulk water. [ABSTRACT FROM AUTHOR]

For polymer-particle composites, limited thermodynamic compatibility of polymers and particles often leads to poor dispersal and agglomeration of the particles in the matrix, which negatively impacts the mechanics of composites. To study the impact of particle compatibility in polymer matrices on the mechanical properties of composites, we here study composite silica- protein based hydrogels. The polymer used is a previously studied telechelic protein-based polymer with end groups that form triple helices, and the particles are silica nanoparticles that only weakly associate with the polymer matrix. At 1mM protein polymer, up to 7% of silica nanoparticles can be embedded in the hydrogel. At higher concentrations the system phase separates. Oscillatory rheology shows that at high frequencies the particles strengthen the gels by acting as short-lived multivalent cross-links, while at low frequencies, the particles reduce the gel strength, presumably by sequestering part of the protein polymers in such a way that they can no longer contribute to the network strength. As is generally observed for polymer/particle composites, shear-induced polymer desorption from the particles leads to a viscous dissipation that strongly increases with increasing particle concentration. While linear rheological properties as function of particle concentration provide no signals for an approaching phase separation, this is very different for the non-linear rheology, especially fracture. Strain-at-break decreases rapidly with increasing particle concentration and vanishes as the phase boundary is approached, suggesting that the interfaces between regions of high and low particle densities in composites close to phase separation provide easy fracture planes. [ABSTRACT FROM AUTHOR]

Introduction: Antibiotic-loaded poly(methyl methacrylate) bone cements (ALBCs) are widely used in total joint replacement (TJR), for local delivery of antibiotics to provide prophylaxis against prosthetic joint infections (PJI). One of the shortcomings of the current generation of ALBCs is that the antibiotic release profile is characterized by a burst over the first few hours followed by a sharp decrease in rate for the following several days (often below minimum inhibitory concentration (MIC)), and, finally, exhaustion (after, typically, ~ 20 d). This profile means that the ALBCs provide only short-term antimicrobial action against bacterial strains involved PJI. Rationale: The purpose of the present study was to develop an improved antibiotic delivery system for an ALBC. This system involved using a layer-by-layer technique to load the antibiotic (gentamicin sulphate) (GEN) on silica nanoparticles, which are then blended with the powder of the cement. Then, the powder was mixed with the liquid of the cement (NP-GEN cement). For controls, two GEN-loaded brands were used (Cemex Genta and Palacos R+G). Gentamicin release and a host of other relevant properties were determined for all the cements studied. Results: Compared to control cement specimens, improved GEN release, longer antimicrobial activity (against clinically-relevant bacterial strains), and comparable setting time, cytocompatibility, compressive strength (both prior to and after aging in PBS at 37 oC for 30 d), 4-point bend strength and modulus, fracture toughness, and PBS uptake. Conclusions: NP-GEN cement may have a role in preventing or treating PJI. [ABSTRACT FROM AUTHOR]

Additional silica (silicon dioxide) nanoparticles were added in the tribo‐gap to prevent the severe abrasive wear. The method was a flat surface‐contact reciprocating sliding test between the sintered silicon carbide surfaces with water lubrication. Before testing, the silica nanoparticles were added in the tribo‐gap. These silica nanoparticles acted as a buffer layer during the initial running‐in, thus the abrasion risk was decreased. After running‐in, the silicon carbide surface was tribo‐chemically smoothened without severe abrasion. Comparing to the same tests without silica nanoparticles, the same ultra‐low friction state (friction coefficient was approx. 0.01) was built, and the running‐in period was shortened by 80 %. As has been well reported, the tribo‐chemical smoothening process for silicon carbide needs abundant water, e. g., in the point‐contact tests. However, in the surface‐contact case, water is locally insufficient, which induces severe wear. The preset silica nanoparticles can solve this wear problem. Therefore, it is not necessary to polish the silicon carbide surfaces as the seal faces in mechanical seals. Instead, a pair of rough silicon carbide surfaces can be pressed onto each other and then proceed to a running‐in with preset silica nanoparticles. After running‐in, a pair of precisely mated tribo‐chemically smoothened surfaces can be naturally obtained. [ABSTRACT FROM AUTHOR]

This work focuses on kinetic aspects of stability, mobility, and dissolution of bare Cu, Al and Mn, and SiO2 NPs in synthetic freshwater (FW) with and without the presence of natural organic matter (NOM). This includes elucidation of particle and surface interactions, metal dissolution kinetics, and speciation predictions of released metals in solution. Dihydroxy benzoic acid (DHBA) and humic acid adsorbed rapidly on all metal NPs (<1 min) via multiple surface coordinations, followed in general by rapid agglomeration and concomitant sedimentation for a large fraction of the particles. In contrast, NOM did not induce agglomeration of the SiO2 NPs during the test duration (21 days). DHBA in concentrations of 0.1 and 1 mM was unable to stabilize the metal NPs for time periods longer than 6 h, whereas humic acid, at certain concentrations (20 mg/L) was more efficient (>24 h). The presence of NOM increased the amount of released metals into solution, in particular for Al and Cu, whereas the effect for Mn was minor. At least 10% of the particle mass was dissolved within 24 h and remained in solution for the metal NPs in the presence of NOM. Speciation modeling revealed that released Al and Cu predominantly formed complexes with NOM, whereas less complexation was seen for Mn. The results imply that potentially dispersed NPs of Cu, Al and Mn readily dissolve or sediment close to the source in freshwater of low salinity, whereas SiO2 NPs are more stable and therefore more mobile in solution. [ABSTRACT FROM AUTHOR]

Surface modification of polymers and paints is a popular and effective way to enhance the properties of these materials. This can be achieved by introducing a thin coating that preserves the bulk properties of the material, while protecting it from environmental exposure. Suitable materials for such coating technologies are inorganic oxides, such as alumina, titania and silica; however, the fate of these materials during long-term environmental exposure is an open question. In this study, polymer coatings that had been enhanced with the addition of silica nanoparticles (SiO2NPs) and subsequently subjected to environmental exposure, were characterized both before and after the exposure to determine any structural changes resulting from the exposure. High-resolution synchrotron macro ATR-FTIR microspectroscopy and surface topographic techniques, including optical profilometry and atomic force microscopy (AFM), were used to determine the long-term effect of the environment on these dual protection layers after 3 years of exposure to tropical and sub-tropical climates in Singapore and Queensland (Australia). Principal component analysis (PCA) based on the synchrotron macro ATR-FTIR spectral data revealed that, for the 9% (w/w) SiO2NP/polymer coating, a clear discrimination was observed between the control group (no environmental exposure) and those samples subjected to three years of environmental exposure in both Singapore and Queensland. The PCA loading plots indicated that, over the three year exposure period, a major change occurred in the triazine ring vibration in the melamine resins. This can be attributed to the triazine ring being very sensitive to hydrolysis under the high humidity conditions in tropical/sub-tropical environments. This work provides the first direct molecular evidence, acquired using a high-resolution mapping technique, of the climate-induced chemical evolution of a polyester coating. The observed changes in the surface topography of the coating are consistent with the changes in chemical composition. [ABSTRACT FROM AUTHOR]