Chemical Properties Of Nanoparticles Research Articles

Evaluation of Potential Occupational Exposure and Release of Nanoparticles in Semiconductor-Manufacturing Environments

Occupational exposure to airborne nanoparticles in semiconductor-manufacturing facilities is of growing concern. Currently, comprehensive information regarding atmospheric concentrations, potential origins, and the physical and chemical properties of nanoparticles in these industrial settings is lacking. This study investigated the occurrence of airborne nanoparticles within a semiconductor-research and -manufacturing facility, during both routine operation and maintenance activities. A Scanning Mobility Particle Sizer was used to monitor size-resolved airborne-nanoparticle number concentrations spanning the range of 6 to 220 nm. Breathing zone filter samples were also collected during maintenance processes and underwent subsequent analyses via Transmission Electron Microscopy and Inductively Coupled Plasma Mass Spectrometry, to discover the size, morphology, and chemical composition of the observed nanoparticles. The findings reveal low levels of airborne nanoparticles during routine operations, but maintenance tasks resulted in substantial concentration surges particularly for plasma-enhanced chemical vapor deposition tools with concentrations up to 11,800 particles/cm3. More than 80% of observed particles were smaller than 30 nm. These smallest particles were predominately composed of metals such as iron, nickel, and copper. Moreover, larger particles above 100 nm were also identified, comprising process-related materials such as silicon and indium. Comparative assessment against established mass-based exposure limits did not yield any exceedances. Current exposure limits do not typically consider size though, and the preponderance of small nanoparticles (<30 nm) would warrant a more size-differentiated exposure-risk assessment.

Structure-dependent oxidation behavior of Au-Cu nanoparticles

Thermal oxidation is an easily controlled method to change the physical and chemical properties of nanoparticles, thus optimizing and expanding their applications. Unfortunately, less attention has been paid to the role of the crystal structure whose atomic arrangements can be critical for oxidation. Au-Cu nanoparticles showing a fast order-disorder transformation are oxidized at two temperatures of ordered (L10) and disordered (A1) phase regions. The oxidation rates between the two phases are compared by the Arrhenius equation, and a lower oxidation rate is determined in the L10 lattice than in the A1 lattice based on the time required for the complete oxidation. One possible reason is attributed to the longer diffusion length in the L10 lattice compared to the A1 lattice due to the anisotropic diffusion path of the former while isotropic diffusion of the latter, resulting in longer oxidation time and then slower oxidation for the ordered sample. The crystalline phase of Au-Cu nanoparticles can be straightforwardly tuned and the resulting atomic disposition is a powerful tool to control oxidation evolution.

Optimization of metal dopant effect on ZnO nanoparticles for enhanced visible LED photocatalytic degradation of citalopram: comparative study and application to pharmaceutical cleaning validation

AbstractMetal doping is an effective method to tune the optical and chemical properties of nanoparticles. Herein, a comparative study was conducted to assess the effect of metal dopant (Mg, Cu and Sn) on ZnO nanoparticles for visible LED photocatalysis. The photocatalysts were synthesized via a facile co-precipitation method. Doped ZnO nanoparticles were employed for photodegradation of citalopram; a commonly used antidepressant drug. The structural, morphological and optical properties of the nanoparticles were analyzed using high resolution transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller measurements and diffuse reflectance spectroscopy. A decrease in band gap energy was obtained for Mg (3.21 eV), Cu (3.15 eV) and Sn (3.05 eV) compared to undoped ZnO (3.34 eV). Results showed that the photocatalytic activity of ZnO nanoparticles towards citalopram degradation under visible light was enhanced by doping with Sn which showed superior photocatalytic performance compared to Cu. Whereas, Mg doped ZnO demonstrated the lowest photocatalytic activity. Full factorial design (24) was conducted to investigate the effect of dopant, pH, catalyst loading and initial citalopram concentration on the efficiency of the treatment process. The interaction between the metal dopant and pH had significant impact on photodegradation efficiency. At optimum conditions, 80% degradation of 25 µg mL−1 citalopram was obtained in 2 h using commercially available LED light using 0.5 mg mL−1 Sn doped ZnO. Kinetics of citalopram degradation was also investigated and was found to follow pseudo-first order kinetics. The optimized photocatalytic protocol was successfully applied for treatment of water samples obtained from production lines during the cleaning validation cycles of citalopram. Sn and Cu doped ZnO nanoparticles had great sustainability for wastewater treatment as it kept its catalytic behavior up to three cycles without significant decrease in photocatalytic activity. The integration of such an approach into the currently employed cleaning validation protocols would offer an economical advantage for pharmaceutical wastewater treatment. Graphical Abstract

Inhomogeneous oxidation behaviors of FeCoNiTiCu high-entropy alloy nanoparticles confined within graphite shells

The oxidation of magnetic high-entropy alloy nanoparticles (HEA-NPs) is an inevitable process in service environments, which can induce unexpected properties and result in the failure of devices. Graphite shells coating is an effective approach to prevent the oxidation of nanoparticles, and the defects on graphite shells can also have a significant impact on the physical and chemical properties of nanoparticles. Thus, it is significant to uncover the oxidation process and understand the change of magnetic properties of HEA-NPs encapsulated in graphite shells (HEA@C-NPs). Herein, we demonstrate the microstructure evolution of HEA@C-NPs under different annealing temperatures. With the increase of annealing temperatures, the graphite shell is broken gradually and then oxygen atoms enter into the HEA core across the defects in graphite shell. An inhomogeneous partial-empty structure is observed at 300 ℃, which can result from the heterogeneous diffusion of different elements across graphite shell with ununiform defects. Accompanied with the formation of the oxide, the saturation magnetization decreases linearly and the exchange bias effect increases gradually. Our results give some understanding for the oxidation process and thus provide a guidance for designing HEA-NPs on complex service environments.

Antibacterial Activity of Green Synthesized Silver Nanoparticle using Banana Flower Extract

In recent years, due to unique physical and chemical properties of nanoparticles, its uses to disrupt biofilm of bacteria are revolutionary steps in antimicrobial research. To use in bioprocess the silver nanoparticles should be biocompatible and free from toxic chemicals. In the present study we report a cost effective and environment friendly route for green synthesis of silver nanoparticles using banana flower extract (BFE) as reducing as well as capping agent. This plant has been opted for the present study for its known medicinal properties and it is easily available. The biosynthesized silver nanoparticles are characterized by UV–Vis spectroscopy which showed a broad peak at around 450 nm, indicated the stability of synthesized silver nanoparticles. Antimicrobial potential of silver nanoparticles synthesized were tested against both Gram positive and Gram-negative bacteria. It was found to be effective against both of them and it showed maximum activity against Gram positive bacteria S. aureus. Silver nanoparticles (AgNPs) have been imposed as an excellent antimicrobial agent being able to combat bacteria in vitro and in vivo causing infections. The results show green synthesized silver nanoparticles, using BFE extract, have a potential to inhibit the growth of bacteria.

Recent Progress of Preparation Strategies in Organic Nanoparticles for Cancer Phototherapeutics.

Phototherapy has the advantages of being a highly targeted, less toxic, less invasive, and repeatable treatment, compared with conventional treatment methods such as surgery, chemotherapy, and radiotherapy. The preparation strategies are significant in order to determine the physical and chemical properties of nanoparticles. However, choosing appropriate preparation strategies to meet applications is still challenging. This review summarizes the recent progress of preparation strategies in organic nanoparticles, mainly focusing on the principles, methods, and advantages of nanopreparation strategies. In addition, typical examples of cancer phototherapeutics are introduced in detail to inform the choice of appropriate preparation strategies. The relative future trend and outlook are preliminarily proposed.

Characterization Nanoparticles via Newtonian Heating for Fractionalized Hybrid Nanofluid in a Channel Flow

The characterization or measurement of the physical and chemical properties of nanoparticles usually lies in the field of nanometrology based on the different characterization techniques. In order to boost the rate of heat transmission, in this regard, an unsteady and convection flow of a fractionalized hybrid nanofluid in a vertical microchannel consisting of two parallel plates apart is studied through Newtonian heating. The governing equations are fractionalized based on the Caputo–Fabrizio derivative of the non-singular and as an exponential kernel. The fractionalized governing equations are solved by utilizing the Laplace approach. For the Laplace inversions, the Zakian algorithm is utilized to acquire the semi-analytical solution. The obtained solutions are also compared with Stehfest and Tzou numerical algorithms to check the validity. For understanding the physics of the under-considered problem, Mathcad software is used for numerical results and graphical representations. The impacts of different physical parameters are deliberated and exhibited in figures. The Prandtl number Pr always shows a decreasing trend for the temperature and velocity profile. Velocity decreases by growing φ due to increasing the viscosity of nanofluid with φ. The thermal conductivity is improved by increasing φ, so that temperature distribution is increased. This study has numerous applications in thermal engineering.

Development of ZnO/selenium nanoparticles embedded chitosan-based anti-bacterial wound dressing for potential healing ability and nursing care after paediatric fracture surgery.

The current study was aimed at the assessment of the effect of chitosan-ZnO/Selenium nanoparticles scaffold on infected wound healing and care of paediatric surgery treatment. The nanoparticle scaffolds were developed from sources such as chitosan (CS), different concentrations of zinc oxide (ZnO), and Selenium (SeNPs) nanoparticles by freeze-drying method. The structural and chemical properties of nanoparticles were investigated by UV-Vis, fourier transform infrared spectroscopy (FTIR), and phase identification by x-ray diffraction analysis. The surface morphology of CS, chitosan-ZnO (CS-ZnO) and chitosan-ZnO/SeNPs was analysed using a scanning electron microscope. The incorporation of ZnO and SeNPs along with CS polymer induces antioxidant and antimicrobial functions. The bacterial susceptibility to nanoparticle scaffolds against Escherichia coli and Staphylococcus aureus showed the excellent antibacterial effects of ZnO and SeNPs. In-vitro studies of fibroblast of NIH 3T3 and HaCaT cell lines revealed the biocompatibility, cell adhesion, cell viability, and proliferation of scaffold in the wound site. Also, results of in-vivo studies strongly enhanced collagen synthesis, re-epithelialization, and rapid wound closure. Thus, the synthesised chitosan-ZnO/SeNPs nanoparticle scaffold resulted in significant improvement in histopathological indices in the full thickness of wound healing after nursing care of paediatric fracture surgery.

Synthesis and Evaluation of Gold Nanoparticles/Nanorods to Use in Plasmonic Photothermal Therapy

Introduction: Photothermal therapy is a method of cancer treatment that plasmonic nanoparticles are used to convert infrared light into local heat. Due to the plasmonic properties of gold nanoparticles, this compound was used as a contrast agent. The aim of this study was to synthesize gold nanoparticles with different conjugations for photothermal therapy.
 Methods: This research was an experimental study. The method used for the synthesis of spherical and rod gold nanoparticles in this research was the Seeding Method. The nanoparticles were then conjugated with various compounds such as rifampicin, quercetin and RGD. Then, the physical and chemical properties of nanoparticles were determined by DLS, UV-Vis and TEM methods. Cytotoxicity test was also performed on MCF-7 ((Michigan Cancer Foundation-7)) cell line. Cell viability was calculated using prism software. Differences were compared by analysis of variance (ANOVA) using SPSS version 16 software.
 Results: In the UV test, two-peaked rod nanoparticles were observed in the range of 523 and 738 nm, and in the case of spherical nanoparticles at 535 wavelengths, which indicates the correct synthesis without impurities and with the appropriate size .In the cell test, a decrease in cell viability was observed compared to the control group. In the first 24 hours, spherical nanoparticles had the highest lethality to the point that at a concentration of 20 μg / ml, it had almost 50% lethality. In addition, after 48 hours at low concentrations, rod nanoparticles showed better results, so they were more suitable. By targeting these nanoparticles to specific cancer cells, in addition to being used to kill cancer cells, the effect of these nanoparticles on healthy cells can be prevented. By conjugating different compounds on the surface of these nanoparticles, cell uptake can also be increased and cancer cells can be killed using photothermal therapy.
 Conclusion: According to the results obtained in this study, it seems that low-concentration of gold nano-rods are more suitable for photothermal therapy.

Nanoparticles for Coronavirus Control.

More than 2 years have passed since the SARS-CoV-2 outbreak began, and many challenges that existed at the beginning of this pandemic have been solved. Some countries have been able to overcome this global challenge by relying on vaccines against the virus, and vaccination has begun in many countries. Many of the proposed vaccines have nanoparticles as carriers, and there are different nano-based diagnostic approaches for rapid detection of the virus. In this review article, we briefly examine the biology of SARS-CoV-2, including the structure of the virus and what makes it pathogenic, as well as describe biotechnological methods of vaccine production, and types of the available and published nano-based ideas for overcoming the virus pandemic. Among these issues, various physical and chemical properties of nanoparticles are discussed to evaluate the optimal conditions for the production of the nano-mediated vaccines. At the end, challenges facing the international community and biotechnological answers for future viral attacks are reviewed.

Anisotropic Particle Fabrication Using Thermal Scanning Probe Lithography

Size, shape, and chemical properties of nanoparticles are powerful tools to modulate the optical and physicochemical properties of a particle suspension. Despite having many methods to synthesize anisotropic nanoparticles, often there are challenges in terms of controlling the polydispersity, shape, size, or composition of anisotropic nanoparticles. This work has been inspired by the potential for developing a unique pathway to make different shaped monodispersed anisotropic nano- and microparticles with large flexibility in material choice. Compared to existing methods, this state-of-the-art nanolithographic method is fast, easy to prototype, and much simple in terms of its mechanical requirement. We show that this technique has been efficiently used to make a variety of anisotropic nano- and microparticles of different shapes, such as triangular prisms, ovals, disks, flowers, and stairs following the same pathway, at the same time showing the potential of being flexible with respect to the composition of the particles. The thermal scanning probe lithographic method in combination with dry reactive ion etching was used to make two-dimensional and three-dimensional templates for the fabrication of anisotropic nano- and microparticles. Deposition of different metal/metal oxides by the electron-beam evaporation method onto these templates allowed us to fabricate a range of nanomaterials according to the required functionality in potential applications. The particles were characterized by atomic force microscopy, He-ion microscopy, scanning electron microscopy, and dynamic light scattering to ensure that the developed method is reproducible, flexible, and robust in choosing the shapes for making monodispersed anisotropic nanoparticles with great control over shape and size.

Crossing the Blood-Brain Barrier: Advances in Nanoparticle Technology for Drug Delivery in Neuro-Oncology.

The blood-brain barrier (BBB) constitutes a microvascular network responsible for excluding most drugs from the brain. Treatment of brain tumors is limited by the impermeability of the BBB and, consequently, survival outcomes for malignant brain tumors remain poor. Nanoparticles (NPs) represent a potential solution to improve drug transport to brain tumors, given their small size and capacity to target tumor cells. Here, we review the unique physical and chemical properties of NPs that aid in BBB transport and discuss mechanisms of NP transport across the BBB, including paracellular transport, carrier-mediated transport, and adsorptive- and receptor-mediated transcytosis. The major types of NPs investigated for treatment of brain tumors are detailed, including polymeric NPs, liposomes, solid lipid NPs, dendrimers, metals, quantum dots, and nanogels. In addition to their role in drug delivery, NPs can be used as imaging contrast agents and can be conjugated with imaging probes to assist in visualizing tumors, demarcating lesion boundaries and margins, and monitoring drug delivery and treatment response. Multifunctional NPs can be designed that are capable of targeting tumors for both imaging and therapeutic purposes. Finally, limitations of NPs for brain tumor treatment are discussed.

Dynamic nanosurface reconfiguration by host-guest supramolecular interactions.

The dynamic functionalization of the nanoparticle surface with biocompatible coatings is a critical step towards the development of functional nano-sized systems. While covalent approaches have been broadly exploited in the stabilization of nanoparticle colloidal systems, these strategies hinder the dynamic nanosurface chemical reconfiguration. Supramolecular strategies based on specific host-guest interactions hold promise due to their intrinsic reversibility, self-healing capabilities and modularity. Host/guest couples have recently been implemented in nanoparticle platforms for the exchange and release of effector molecules. However, the direct exchange of biocompatible hydrophilic oligomers (e.g. peptides) for the modulation of the surface charge and chemical properties of nanoparticles still remains a challenge. Here, we show the intracellular reconfiguration of nanoparticles by a host/guest mechanism with biocompatible oligomeric competitors. The surface of gold nanoparticles was functionalized with cyclodextrin hosts and the guest exchange was studied with biocompatible mono and divalent adamantyl competitors. The systematic characterization of the size and surface potential of the host/guest nanoparticles allowed the optimization of the binding and the stabilization properties of these supramolecular systems. The in cellulo host/guest-mediated direct reconfiguration of the peptide layer at the surface of nanoparticles is achieved by controlling the valence of adamantane-equipped peptides. This work demonstrates that host/guest supramolecular systems can be exploited for the direct exchange of pendants at the surface of nanoparticles and the intracellular dynamic chemical reconfiguration of biocompatible colloidal systems.

Separation and Purification of Kudinoside D and Its Nanoparticle Preparation and Characterization

Objective: To improve the water solubility of Kudinoside D. Methods: Using atmospheric column chromatography, semi-preparative high performance liquid chromatography and other means to separate and purify saponins from Ilex kudingcha C.J.Tseng, the compound Kudinoside D was obtained. Using polyglutamic acid (γ-PGA) and L-phenylalanine ethyl ester (L-PAE) as raw materials, Kudinoside D nanoparticles were prepared by precipitation method and dialysis method respectively. The physical and chemical properties of nanoparticles were characterized by transmission electron microscopy and dynamic nanoparticle size analyzer, and their in vitro drug release characteristics were investigated by dialysis. Results: Compared with the precipitation method, the encapsulation efficiency and drug loading of Kudinoside D nanoparticles prepared by the dialysis method were increased by 1.5 and 4.5 times, respectively, the encapsulation rate reached 65.46%, and the drug loading reached 13.24%. Kudinoside D nanoparticles had a regular spherical shape with an average particle size of (75±25) nm and a Zeta potential of 33.7. Conclusion: In vitro drug release experiments show that Kudinoside D nanoparticles can significantly improve the water solubility of the drug and have a good sustained release effect in vitro.

Hybrid Nanoparticles as an Efficient Porphyrin Delivery System for Cancer Cells to Enhance Photodynamic Therapy.

Photodynamic therapy (PDT) is a potential non-invasive approach for application in oncological diseases, based on the activation of a photosensitizer (PS) by light at a specific wavelength in the presence of molecular oxygen to produce reactive oxygen species (ROS) that trigger the death tumor cells. In this context, porphyrins are interesting PS because they are robust, have high chemical, photo, thermal, and oxidative stability, and can generate singlet oxygen (1O2). However, porphyrins exhibit low solubility and a strong tendency to aggregate in a biological environment which limits their clinical application. To overcome these challenges, we developed hybrid nanostructures to immobilize 5,10,15,20-tetrakis[(4-carboxyphenyl) thio-2,3,5,6-tetrafluorophenyl] (P), a new third-generation PS. The biological effect of this system was evaluated against bladder cancer (BC) cells with or without light exposition. The nanostructure composed of lipid carriers coated by porphyrin-chitosan (P-HNP), presented a size of ca. 130 nm and low polydispersity (ca. 0.25). The presence of the porphyrin-chitosan (P-chitosan) on lipid nanoparticle surfaces increased the nanoparticle size, changed the zeta potential to positive, decreased the recrystallization index, and increased the thermal stability of nanoparticles. Furthermore, P-chitosan incorporation on nanoparticles increased the stability and enhanced the self-organization of the system and the formation of spherical structures, as observed by small-angle X-ray scattering (SAXS) analysis. Furthermore, the immobilization process maintained the P photoactivity and improved the photophysical properties of PS, minimizing its aggregation in the cell culture medium. In the photoinduction assays, the P-HNP displayed high phototoxicity with IC50 3.2-folds lower than free porphyrin. This higher cytotoxic effect can be correlated to the high cellular uptake of porphyrin immobilized, as observed by confocal images. Moreover, the coated nanoparticles showed mucoadhesive properties interesting to its application in vivo. Therefore, the physical and chemical properties of nanoparticles may be relevant to improve the porphyrin photodynamic activity in BC cells.

Protein-Mimicking Nanoparticles for a Cellular Regulation of Homeostasis

The distinct physical and chemical properties of nanoparticles (NPs) offer great opportunities to develop new strategies for diagnostic and therapeutic purposes. Whereas NPs often serve as inert nanocarriers, their inherent "biological" activities have recently been extensively unveiled and explored. These protein-mimicking NPs (dubbed protmins) have been reported to modulate a cellular homeostasis without displaying a general toxicity, which may act as potential nanomedicines to provide a monotherapy or combination therapy in a disease treatment. In the meanwhile, the unexpected behaviors of protmins in complex biological systems also raise new concerns on the biosafety issue. Herein, we summarize several categories of the protmin-based regulation of cellular homeostasis and discuss their broad effects on cell functions and behaviors.

Mechanisms underlying the strength enhancement of UHPC modified with nano-SiO2 and nano-CaCO3

The unique physical and chemical properties of nano-particles can enhance the nature of cement-based materials at the micro-scale and nano-scale levels, leading to improved properties. To uncover the strengthening mechanism associated with various types of nano-particles, a laboratory investigation was undertaken to evaluate and compare the influence of nano-SiO2 and nano-CaCO3 on mechanical properties of ultra-high performance concrete (UHPC) made with 2% steel fibers. Each type of nano-particle was incorporated at four contents, and the mini-slump flow of the UHPC was maintained at 240–260 mm. The microstructure of the matrix and the fiber-matrix interface of UHPC, as well as the features of hydration products were characterized using advanced techniques, such as electron microscopy (SEM), X-ray diffraction (XRD), differential thermal gravimetric (DTG) analyses, 3D micro-tomography, and mercury intrusion porosimetry (MIP). Test results indicate that both the fiber-matrix strength and mechanical strength of UHPC increased with the increase of nano-SiO2 and nano-CaCO3 until threshold limits of 1% and 3.2%, respectively. The 28-d fiber-matrix bond, compressive, and flexural strengths of the optimal UHPC mixtures made with 3.2% nano-CaCO3 were approximately 40%, 10%, and 20%, respectively, greater than those of the reference mixture. These strength values were higher than those of UHPC made with 1% nano-SiO2. When used below these optimal nano-material contents, the filler and nucleation effects related of the nano-SiO2 and nano-CaCO3 promoted the strength development through improved density and homogeneity with optimized structure of hydration products, as indicated by SEM observation and DTG analysis. Beyond these limits, additional use of nano-materials resulted in increased volume of air voids and capillary pores and weak interfacial zones due to the agglomeration of nano-particles, which hindered strength development.

Green Synthesis of Metallic Nanoparticles and Their Prospective Biotechnological Applications: an Overview.

The green synthesis of nanoparticles (NPs) using living cells is a promising and novelty tool in bionanotechnology. Chemical and physical methods are used to synthesize NPs; however, biological methods are preferred due to its eco-friendly, clean, safe, cost-effective, easy, and effective sources for high productivity and purity. High pressure or temperature is not required for the green synthesis of NPs, and the use of toxic and hazardous substances and the addition of external reducing, stabilizing, or capping agents are avoided. Intra- or extracellular biosynthesis of NPs can be achieved by numerous biological entities including bacteria, fungi, yeast, algae, actinomycetes, and plant extracts. Recently, numerous methods are used to increase the productivity of nanoparticles with variable size, shape, and stability. The different mechanical, optical, magnetic, and chemical properties of NPs have been related to their shape, size, surface charge, and surface area. Detection and characterization of biosynthesized NPs are conducted using different techniques such as UV-vis spectroscopy, FT-IR, TEM, SEM, AFM, DLS, XRD, zeta potential analyses, etc. NPs synthesized by the green approach can be incorporated into different biotechnological fields as antimicrobial, antitumor, and antioxidant agents; as a control for phytopathogens; and as bioremediative factors, and they are also used in the food and textile industries, in smart agriculture, and in wastewater treatment. This review will address biological entities that can be used for the green synthesis of NPs and their prospects for biotechnological applications.

Highly Efficient AuPd Catalyst for Synthesizing Polybenzoxazole with Controlled Polymerization

Summary Using nanoparticles (NPs) to catalyze chemical reactions for the formation of functional polymers with controlled polymerization is an important field of chemical research. In this article, we report an AuPd NP system as an active and stable catalyst to catalyze one-pot reaction of formic acid, 1,5-diisopropoxy-2,4-dinitrobenzene, and terephthaldehyde, leading to the controlled polymerization and the formation of polybenzoxazole (PBO) (Mw = 3.6 kDa). The one-pot reaction is AuPd NP size and composition dependent, and 8-nm Au39Pd61 NPs are the best catalyst for the polymerization. The highly pure PBO shows excellent thermal stability up to 600°C and improved chemical and mechanical stability under challenging environmental conditions compared with commercial PBO (Zylon, Mw = 40 kDa). The reported NP-catalyzed one-pot reaction to polymerization is not limited to the formation of PBO but can be extended as a general approach to rigid polymers that are important for ballistic fiber, anti-flame, and smart-textile applications.

Durability of concrete with nano-particles under combined action of carbonation and alkali silica reaction

ABSTRACTSubway concrete is easy to be attacked by carbonation in the relatively closed space, and alkali silica reaction (ASR) is a serious durability problem of concrete, which is difficult to find and repair. The damage caused by carbonation and ASR seriously affects the durability of subway concrete. Two kinds of nano-particles (nano-SiO2 and nano-Fe2O3) are mixed into plain subway concrete in this paper, and their effects on the durability of concrete under the combined action of carbonation and ASR are studied experimentally. The test results show that, after mixing with nano-particles, the carbonation depth and expansion of subway concrete are decreased, as well as the sonic velocity of subway concrete is increased obviously, which demonstrate the durability of subway concrete with nano-particles is better than plain subway concrete. The enhancement of durability is due to the special physical and chemical properties of nanoparticles, which can improve the microstructure of concrete and the chemical composition of pore solution in concrete.