Shima Taheri

Transformation of four silver/silver chloride nanoparticles during anaerobic treatment of wastewater and post-processing of sewage sludge

The increasing use of silver (Ag) nanoparticles [containing either elemental Ag (Ag-NPs) or AgCl (AgCl-NPs)] in commercial products such as textiles will most likely result in these materials reaching wastewater treatment plants. Previous studies indicate that a conversion of Ag-NPs to Ag2S is to be expected during wastewater transport/treatment. However, the influence of surface functionality, the nature of the core structure and the effect of post-processing on Ag speciation in sewage sludge/biosolids has not been investigated. This study aims at closing these knowledge gaps using bench scale anaerobic digesters spiked with Ag nitrate, three different types of Ag-NPs, and AgCl-NPs at environmentally realistic concentrations. The results indicate that neither surface functionality nor the different compositions of the NP prevented the formation of Ag2S. Silver sulfides, unlike the sulfides of other metals present in sewage sludge, were stable over a six month period simulating composting/stockpiling.

KHSO4: a catalyst for the chemo-selective preparation of 1,1-diacetates from aldehydes under solvent-free conditions

A simple, mild, effective and green method to form acylals from aliphatic and aromatic aldehydes in good to excellent yields in the presence of potassium hydrogen sulfate, KHSO4, as catalyst under solvent-free conditions is described. Ketones are not affected under the reaction conditions.

Silver nanoparticle based coatings enhance adipogenesis compared to osteogenesis in human mesenchymal stem cells through oxidative stress

Silver nanoparticle (AgNP) based antibacterial surfaces were fabricated using plasma polymerization technology and their effects on differentiation of human bone-marrow derived mesenchymal stem cells (hMSCs) were investigated in this study. The results showed that AgNP coated surfaces do not affect the initial adhesion, spreading and proliferation of hMSCs. Furthermore, the silver coated surface promoted adipogenic differentiation of hMSCs as demonstrated by more accumulation of lipid droplets and upregulation of adipogenesis-related genes such as peroxisome proliferator activated receptor gamma (PPARγ), adipocyte determination and differentiation factor (ADD1) and CCAAT/enhancer binding protein alpha (C/EBPα). In addition, silver incorporation activated the expression of antioxidant enzymes as a consequence of the accumulation of intracellular reactive oxygen species (ROS) in adipogenic induced cells, which was correlated with the enhanced adipogenic capacity of hMSCs. ROS generation was enhanced due to silver ion release and consequently reduced osteogenesis at the early stage after 7 days of osteogenic induction as a result of reducing alkaline phosphatase (ALP) activity. However, the differentiation and mineralization capacity of osteoblasts were restored after 14 days of osteogenic induction, which indicated that adipogenesis favors intracellular ROS accumulation mediated by silver coatings compared to osteogenesis. None of the osteogenic related genes was affected by ROS mediated by AgNP dissolution. The findings in this work are instructive for the use of silver as an antibacterial agent in the areas of tissue engineering, stem cell therapies and implantable biomedical devices.

Synthesis and surface immobilization of antibacterial hybrid silver-poly(l-lactide) nanoparticles

Infections associated with medical devices are a substantial healthcare problem. Consequently, there has been increasing research and technological efforts directed toward the development of coatings that are capable of preventing bacterial colonization of the device surface. Herein, we report on novel hybrid silver loaded poly(L-lactic acid) nanoparticles (PLLA-AgNPs) with narrowly distributed sizes (17 ± 3 nm) prepared using a combination of solvent evaporation and mini-emulsion technology. These particles were then immobilized onto solid surfaces premodified with a thin layer of allylamine plasma polymer (AApp). The antibacterial efficacy of the PLLA-AgNPs nanoparticles was studied in vitro against both gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria. The minimal inhibitory concentration values against Staphylococcus epidermidis and Escherichia coli were 0.610 and 1.156 μg · mL(-1), respectively. The capacity of the prepared coatings to prevent bacterial surface colonization was assessed in the presence of Staphylococcus epidermidis, which is a strong biofilm former that causes substantial problems with medical device associated infections. The level of inhibition of bacterial growth was 98%. The substrate independent nature and the high antibacterial efficacy of coatings presented in this study may offer new alternatives for antibacterial coatings for medical devices.

Characterization of carbon fiber reinforced polymer strengthened concrete and gap detection with a piezoelectric-based sensory technique

In this article, a piezoelectric-based sensory technique is proposed for detection of the gap between surfaces of a carbon fiber reinforced polymer plate and a concrete specimen and characterization of shrinkage of early-age concrete. The proposed technique uses the propagation properties of the guided waves in the carbon fiber reinforced polymer plate excited and received by piezoelectric transducers attached to an external surface of the carbon fiber reinforced polymer–strengthened concrete specimen. Measurements are conducted with fresh and hardened early-age concrete specimens and two carbon fiber reinforced polymer plates at different gaps. A piezoelectric actuator is excited using a sine burst signal, and the generated wave is received by a sensor after propagation along the specimen. The received signal at different gap values is used to detect a gap. To quantify the gap, damage indices, including correlation coefficient, peak-to-peak amplitude of resultant signal, and root-mean-square deviation, are used. The shrinkage of concrete is detected and predicted by comparing the damage indices at different gaps with the indices at different stages of early-age concrete. The proposed technique is relatively simple method using small transducers. It is one-sided, non-destructive, and cost-effective solution for gap detection and concrete characterization.

A substrate independent approach for fabrication of biocompatible nano-silver/polymer antibacterial coatings

N including quantum dots, fullerenes, nanoparticles (zero dimension), nanotubes, nanowires, nanofibrils (one dimension), and graphene (two dimension) possess intriguing physical, chemical and biological properties. As a consequence, these materials form the basis of many interdisciplinary studies, where scientists have been inspired by self-assembly processes occurring in nature to construct advanced nanomaterials with applications in many fields. Self-assembly involves the organization of molecules into highly ordered structures through specific, local interactions among the components, without any external direction. Weak interactions, such as Van der Waals, electrostatic, and π-π interactions, as well as hydrogen bonding, and halogen bonding can lead to all kinds of challenging self-assembled nanostructures. The hierarchical structures of many peptides are attributed to self-assembly, therefore, could potentially act as building blocks for new materials with significant functionalities and a range of biological functions. In our recent work, non-covalent interactions including hydrogen bonding, hydrophobic interaction and electrostatic interaction were employed to modulate the peptide assembled nanostructures. We could successfully realize the peptide assembly transition from nanospheres to nanofiber by tuning hydrogen bond and hydrophobic interaction; furthermore, two dimension peptide nanopatch could be constructed instead of nanofiber by introducing the terminus intermolecular hydrogen bonding between the peptide and small molecules. The electrostatic interaction was proved to play an important role in peptide self-assembly and disassembly. Furthermore, it is significant to be addressed that the mechanical properties of peptide assemblies do changing after the nanostructure transition of peptide occurred. These peptide-based nanostructures could potentially be applied to be a candidate of biomaterials with potential importance in a wide range of technological applications.Z oxide (ZnO) nanoparticles (grown in the template of folic acid) are biologically useful, luminescent material. It can be used for multifunctional purposes, such as biosensor, bioimaging, targeted drug delivery and as growth promoting medicine. Though, ZnO is categorized as: “generally recognized as safe” (GRAS) but ZnO nanoparticle system may be cytotoxic. ZnO nanosystem could be of important relevance in the context of nanomedicine, where targeted treatment of biological systems at molecular level is a necessity. ZnO quantum dots with their surface modification and bio-conjugation for selective destruction of tumor cells and their potential use for drug delivery applications is the cardinal issue of this presentation..Nano-sized particle incorporation into metal matrix for fabrication of advance surface coatings find variety of applications in surface protection techniques. Al 2 O 3 , Cr 2 O 3 and SiO 2 nanoparticles have been codeposited with Zn using electrodeposition process to produce Zn nanocomposite coatings. The fabricated coatings were characterized using Scanning Electron Microscope affixed with Energy Dispersive Spectroscopy and X-ray diffractometer. The mechanical and tribological properties of the coatings were investigated using diamond microhardness indenter and dry abrasive wear tester. Zn-10g/L Cr 2 O 3 nanocomposite exhibited the highest microhardness of 228 HV and Zn-5g/L Al 2 O 3 nanocomposite possessed the highest corrosion resistance and lowest wear loss. Zn-5g/L SiO 2 nanocomposite showed good stability as compared to other composite coatings. The incorporation of the nanoparticles of Al 2 O 3 , Cr 2 O 3 and SiO 2 induce grain refinement and modify crystallographic orientation of Zn matrix. Zn-5g/L Al 2 O 3 and Zn-5g/L SiO 2 proved to be better coatings which can find variety of industrial applications where both mechanical and electrochemical properties are required.The existence of vibrations in undesired parts of mechanical machinery, civil structures, aerospace and automotive components,will cause overall setback and efficiency reductions in processes when the above parts are used. Hence is advising to completely get rid of the unnecessary vibrations or reduce them to a minimum possible value. This experiment is an effort to reduce these vibrations using Magneto Rheological fluids. A Magneto Rheological fluid provides viscous damping. The damping factor increases when a magnetic field is applied and is multiplied as the strength of the magnetic field is more, also the natural frequency of the body under test changes from to a value which is different from the initial value. This technique was utilized and a three layered MR fluid sandwich beam was fabricated. This beam was subjected to testing and analysis under both undamped and damped conditions. The controllability of variations in the various dynamic parameters like natural frequencies, vibration amplitudes and damping factors were observed. A reduction is natural frequency of beam was obtained in the presence of MR fluid under magnetic field, from 550 Hz to 300 Hz. Keywords: Magnetorheological fluid, MRFluid sandwich Beam, Natural frequency, Damping factor, Damping coefficient.A perovskite-like phase, K3B6O10Cl exhibits a large second harmonic response about four times that of KH2PO4 (KDP) and is transparent from the deep UV (180 nm) to middle-IR region. A high quality single crystal of K3B6O10Cl with dimensions up to 30 × 15 × 7 mm3 was successfully grown by the top-seeded solution growth method. Crystal morphologies and growth habits of K3B6O10Cl grown with seeds oriented along [101] and [211] were studied, and the best growth direction was obtained., The refractive indices of the crystal were measured by the minimum deviation technique and fitted to the Sellmeier equations. The nonlinear optical coefficients have been determined by the method of Maker fringes at λ=1064 nm. The suitable nonlinear optical coefficients as well as comparatively easy crystal growth make the K3B6O10Cl crystal a promising candidate for NLO materials.A carbon and fiberglass are the two mostly studied materials in air filtration industry due to their good performance with associated low cost. The advancement in the field of nanoscience and nanotechnology produced materials with improved properties than conventional materials. Nanofibers are one of the nanotechnology products, which have been explored for applications such as healthcare, water, energy, electronics, catalysis, environmental, air filtration, bioengineering and biotechnology. Pores and pore size distribution of nanofibers can be easily tunable. Recently, they have been explored in various air filtration products such as high efficiency particulate absorption (HEPA) filters and so on. In this talk, various nanofibers that are electrospun and deposited on HEPA filters, process variation, additives addition, and their performances, challenges faced and their potential application in air filtration industry will be presented.O (OA) and meniscus injury are often met from injury and aging. In the USA alone, approximately 50 million people are affected by OA, and over 50% among them require replacing total joints, which cost approximately

Synthesis of 2,4,5-triaryl-imidazoles catalyzed by NiCl2·6H2O under heterogeneous system

15 billion per year. Tissue engineering (TE) approach to cartilage regeneration has promises to repair damaged or diseased cartilage. Biodegradable scaffolds as one of key elements in TE are expected to offer a complex biological microenvironment mimicking with native tissue to promote cell ingrowth and tissue regeneration. However, current scaffolds cannot simulate the complex microenvironment of native cartilage. To the end, our group developed a biodegradable extracellular matrix (ECM) hydrogel derived from pig cartilages. The hydrogel contained complex components including collagen, glycosaminoglycan, growth factors and peptides, which were mimetic with biological components in the cartilage. This hydrogel solution was flowable at 4oC and formed a solid hydrogel at a body temperature, which is appropriate for non-invasive surgery. The mechanical properties of the hydrogels could be tuned by altering ECM concentration. The chondrocytes survived and proliferated inside the hydrogel with a round shape due to a good cellular microenvironment. The hydrogel solution was easily injected into a mouse subcutaneous model and formed a solidified hydrogel in vivo. No severe immunogenetic response was observed till to 7 day implantation, indicating a good biocompatibility. The attractive injectability and biomimetic complexity showed that the cartilage-derived hydrogel would be a good candidate to be applied for cartilage regeneration.T development of silver nanoparticle (AgNPs) as a potent alternative to conventional antibiotics has been extensively investigated over the last decades. However, due to the prominent cytotoxic effect of silver on mammalian cells, there is always strong motivation to develop alternative technology that can compact bacterial infection without affecting the mammalian cells. Capping AgNPs with appropriate functional groups and incorporating them into a polymeric matrix is a feasible alternative to overcome these limitations. AgNPs with different chemical structures (nanocapsules and nanoparticles) and functionalities (polymer, lipid, and starch) were synthesized. To demonstrate application as antibacterial coatings, the stabilized AgNPs were then immobilized onto model surfaces made of a thin layer of allylamine plasma polymerized film. This substrate-independent technique preserves the AgNPs functionalities for a longer period of application time. All fabricated surface coatings exhibited superior antibacterial activity against four important Gram-positive and Gram-negative pathogens. This study further aimed to focus on investigating the effects of AgNPs surface components on delivery of engineered AgNPs from the coatings into the human fibroblast cell as well as bone marrow derived macrophages (BMDM). Most of the surfaces did not affect BMDM function or viability and demonstrated no toxicity toward fibroblast cells, except for lipid coated nanosilvers. Therefore, the chemical structures of nanoparticles significantly affect the coatings’ antibacterial, biofilm prevention and biocompatibility capabilities. We believe that such biocompatible nanostructures are of potential interest for various biomedical applications such as smart drug carriers and antibacterial coatings for medical devices and wound dressings.I order to develop compliant seal systems for SOFCs operating in the temperature range of 800-950°C, this project has focused on iterations in materials systems. The materials consisting of composites of a base glass with appropriate ceramic components in order to identify a stable sealing system with adequate and acceptable thermal characteristics, such as, the viscosity and coefficient of thermal expansion. Appropriate viscosity was targeted to ensure good flow behavior of the glass at temperatures where fuel cells operate and sealing effects are required. Viscosity variation in the composites was brought about by the selection of ceramic additives; a large number of candidates ranging from phase pure alumina, magnesia, ceria and barium zirconate, to ceria doped with 10 mole % gadolinium oxide (GDC). SCN1 glass (trade name of sealing glass developed by SEM-COM) was used as the base component, whose composition was such as to provide a CTE match with the SOFC system (in the RT-Tg range), when composited with a second ceramic phase. Additives in both nanoand micro-scale dimensions (as fine powders or in the form of fibers) were introduced mainly to block the bubbles from moving but also to make the composite structure stronger. In addition, their role was also to inhibit the growth of air bubbles within the glass matrix and to or prevent their coalescence during long soak-time at 850°C, with the goal of eliminating or minimizing the CTE drift in the resultant glass composition. No reaction between SCN1 glass and the GDC additives was discerned. Moreover, the bubbles remained small and did not move or coalesce. The CTE of the GDC composites was very close to the targeted value and not change significantly when aged up to 232 h at 850°C in air.