Majid Hosseini

Phosphinite-functionalized silica and hexagonal mesoporous silica containing palladium nanoparticles in Heck coupling reaction: synthesis, characterization, and catalytic activity

A series of mono, di and tri phosphinite ligands functionalized on modified silica and modified hexagonal mesoporous silica (HMS) were synthesized and characterized. The complexation of these ligands with PdCl2 was carried out to obtain palladium supported on phosphinite functionalized silica. TEM images of the catalysts showed that Pd dispersed in nanoparticle size on these heterogeneous catalytic systems. Hexagonal and mesoporous structures with high surface area of HMS were examined by SEM, TEM and BET techniques. In a typical Heck coupling reaction (HCR), catalytic activity of the Pd catalysts was compared. It was shown that di-functionalized phosphinite ligands react better for both silica and HMS. Aryl halides (also known as haloarenes or halogenoarenes) of different varieties with olefinic substrates in the HCR exhibited high efficiency and stability for the selected catalyst. Repeating Heck reaction cycles illustrated that the catalyst could be recycled.

Smart Stimuli-Responsive Nano-sized Hosts for Drug Delivery

The evolution in the synthesis of smart polymers broadens new horizons for their potent application in medicine, especially in drug delivery. Many synthetic polymers that exhibit environmentally responsive behavior are potential smart carrier candidates that allow for controlled therapeutic delivery. These materials can be loaded with specific drugs for therapeutic applications, releasing treatment in response to a stimulus. This stimuli-responsive capability has enabled smart polymeric materials to distribute drugs in response to commonly known exogenous and/or endogenous stimuli. Examples of these various stimuli include pH, enzyme concentration, temperature, ultrasound intensity, as well as light, magnetic field, redox gradients and a multitude of other potential stimuli. This chapter provides a detailed critical discussion and an overview of the stimuli-responsive polymers which have found applications in targeted drug delivery. Furthermore, multiresponsive systems and their forthcoming development as well as challenges associated with some stimuli-responsive systems are discussed. Finally, the most recent and emerging trends along with a look toward expected future breakthroughs using these types of nanocarriers are discussed.

Thin chitosan films containing super-paramagnetic nanoparticles with contrasting capability in magnetic resonance imaging

Magnetic nanoparticles have found application as MRI contrasting agents. Herein, chitosan thin films containing super-paramagnetic iron oxide nanoparticles (SPIONs) are evaluated in magnetic resonance imaging (MRI). To determine their contrasting capability, super-paramagnetic nanoparticles coated with citrate (SPIONs-cit) were synthesized. Then, chitosan thin films with different concentrations of SPIONs-cit were prepared and their MRI data (i.e., r2 and r2*) was evaluated in an aqueous medium. The synthesized SPIONs-cit and chitosan/SPIONs-cit films were characterized by FTIR, EDX, XRD as well as VSM with the morphology evaluated by SEM and AFM. The nanoparticle sizes and distribution confirmed well-defined nanoparticles and thin films formation along with high contrasting capability in MRI. Images revealed well-dispersed uniform nanoparticles, averaging 10 nm in size. SPIONs-cit’s hydrodynamic size averaged 23 nm in diameter. The crystallinity obeyed a chitosan and SPIONs pattern. The in vitro cellular assay of thin films with a novel route was performed within Hek293 cell lines showing that thin films can be biocompatible.Graphical Abstract

Superhydrophobic Coatings for the Protection of Natural Stone

Superhydrophobic and water-repellent coatings can have numerous applications including the protection of monuments and other stone objects of the cultural heritage. In this study, the fundamental observations, concepts, and equations provided by T. Young, R.N. Wenzel, A.B.D. Cassie, S. Baxter, and other researchers on the wettability of solid surfaces are briefly described. Moreover, some interesting methods which were devised to induce enhanced hydrophobicity and water repellency to natural stone are briefly reviewed. Finally, a case study is described in detail: siloxane-nanoparticle dispersions are sprayed on sandstone and marble specimens. Using nanoparticles (NPs) in appropriate concentration, the deposited polysiloxane-nanoparticle composite coatings exhibit superhydrophobic and water-repellent properties. It is demonstrated that superhydrophobicity and water repellency can be (1) achieved using exclusively aqueous products, (2) achieved using inherent hydrophilic materials, and (3) accompanied by superoleophobicity and oil repellency. The effects of the coatings on the color, vapor permeability, and water absorption by capillarity of the treated sandstone and marble are discussed.

Smart Polymeric-Based Microencapsulation: A Promising Synergic Combination

Microencapsulation technology can be used to provide protection, control the release of the loaded material, negate compatibility issues, and avoid toxicity of the encapsulated materials. Microencapsulation provides the possibility of combining different types of smart polymers, thus achieving specific properties that are difficult to get using other techniques. This chapter describes the combination of microencapsulation technology using smart polymers for industrial applications, such as coatings and paints (encapsulation of self-healing agents), construction (encapsulation of phase-change materials), textile industry (encapsulation of thermal or moisture-sensitive polymers and light-responsive polymers), food and beverage industry (encapsulation of a vitamin, flavor, or aromatic substance), pharmaceutical formulations (encapsulation of a drug for its protection or controlled drug delivery), biomedical applications (encapsulation of a specific anticancer drug for target therapy, cell-based systems, and DNA or RNA encapsulation), and aerospace and automobiles applications (encapsulation of self-healing materials, flame retardant, plasticizers, and catalysts).

Technical challenges of fermentative bio-hydrogen production from biomass

F the last few years, the production of butanol has been the focus of researchers’ attention when looking for alternatives to biofuels’ production. Interesting results have already been achieved with heterologous organisms such as Escherichia coli. However, native producers from clostridia group still presents the best alternative to succeed; as they possess all the machinery required and evolutionarily were optimized to produce butanol. However, there are several limitations that need to be assessed in order to control the production of other unwanted end-products such as ethanol, acetone, lactate or succinate that may deviate the fluxes away from butanol. Strategies of metabolic engineering have been on the table for over the last 15 years. However, the targets that seemed obvious at first, have proven not to increment significantly butanol titers showing that C. acetobutylicum metabolism is not as straightforward as it seemed. Going deep into understanding the solventogenic metabolism became therefore a key step into overcoming the difficulties to channel the metabolism towards butanol production. In this work, we apply deep in silico analysis in order to learn and understand the peculiarities of this microorganism metabolism. Our study suggests a new in silico strategy to maximize butanol production.