Search

There are ever increasing concerns about environmental and health hazards of conventional synthetic polymers. These polymers are not sustainable because their production process relies on fossil-based feedstocks and energy sources. Economic benefits and beneficial physicochemical and mechanical properties have made synthetic polymers to be used in wide range of applications from packaging to biomedicine. On the other hand, modern chemistry has provided us with invaluable tools to make well-defined polymers with tailored properties which can be used in biomedical filed such as designing advanced drug delivery systems (DDSs). In fact, polymers are indispensable constituents of most of novel DDSs. However, sustainability concerns about raw materials and polymeric building blocks of such DDSs, remains unsolved. In addition, efficient and proper degradability of sustainable building blocks of DDSs is important for their clearance from human body. Accordingly, development of sustainable and biodegradable polymeric materials is highly demanding in development of sustainable DDSs. This perspective provides a general overview on sustainable polymers and highlights their potential applications in designing novel DDSs. Unsolved challenges and future prospects are discussed accompanied by offering potential solutions.

3D printing gave biomedical engineering great potential to mimic native tissues, accelerated regenerative medicine, and enlarged capacity of drug delivery systems; thus, advanced biomimetic functional biomaterial developed by 3D-printing for tissue engineering demands.

Polysaccharides (PSA) have taken specific position among biomaterials for advanced applications in medicine. Nevertheless, poor mechanical properties are known as the main drawback of PSA, which highlights the need for PSA modification. Nanocomposites PSA (NPSA) are a class of biomaterials widely used as biomedical platforms, but despite their importance and worldwide use, they have not been reviewed. Herein, we critically reviewed the application of NPSA by categorizing them into generic and advanced application realms. First, the application of NPSA as drug and gene delivery systems, along with their role in the field as an antibacterial platform and hemostasis agent is discussed. Then, applications of NPSA for skin, bone, nerve, and cartilage tissue engineering are highlighted, followed by cell encapsulation and more critically cancer diagnosis and treatment potentials. In particular, three features of investigations are devoted to cancer therapy

Tissue engineering intends to create functionalized tissues/organs for regenerating the injured parts of the body using cells and scaffolds. A scaffold as a supporting substrate affects the cells' fate and behavior, including growth, proliferation, migration, and differentiation. Hydrogel as a biomimetic scaffold plays an important role in cellular behaviors and tissue repair, providing a microenvironment close to the extracellular matrix with adjustable mechanical and chemical features that can provide sufficient nutrients and oxygen. To enhance the hydrogel performance and compatibility with native niche, the cell-laden hydrogel is an attractive choice to mimic the function of the targeted tissue. Injectable hydrogels, due to the injectability, are ideal options for in vivo minimally invasive treatment. Cell-laden injectable hydrogels can be utilized for tissue regeneration in a noninvasive way. This article reviews the recent advances and future opportunities of cell-laden injectable hydrogels and their functions in tissue engineering. It is expected that this strategy allows medical scientists to develop a minimally invasive method for tissue regeneration in clinical settings. Impact statement Cell-laden hydrogels have been vastly utilized in biomedical application, especially tissue engineering. It is expected that this upcoming review article will be a motivation for the community. Although this strategy is still in its early stages, this concept is so alluring that it has attracted all scientists in the community and specialists at academic health centers. Certainly, this approach requires more development, and a bunch of crucial challenges have yet to be solved. In this review, we discuss this various aspects of this approach, the questions that must be answered, the expectations associated with it, and rational restrictions to develop injectable cell-laden hydrogels.

Designing biomaterials capable of biomimicking wound healing and skin regeneration has been receiving increasing attention recently. Some biopolymers behave similarly to the extracellular matrix (ECM), supporting biointerfacial adhesion and intrinsic cellular interactions. Polydopamine (PDA) is a natural bioadhesive and bioactive polymer that endows high chemical versatility, making it an exciting candidate for a wide range of biomedical applications. Moreover, biomaterials based on PDA and its derivatives have near-infrared (NIR) absorption, excellent biocompatibility, intrinsic antioxidative activity, antibacterial activity, and cell affinity. PDA can regulate cell behavior by controlling signal transduction pathways. It governs the focal adhesion behavior of cells at the biomaterials interface. These features make melanin-like PDA a fascinating biomaterial for wound healing and skin regeneration. This paper overviews PDA-based biomaterials' synthesis, properties, and interactions with biological entities. Furthermore, the utilization of PDA nano- and microstructures as a constituent of wound-dressing formulations is highlighted.

Zeolite, as an intricate microporous material with redox sites, has been widely examined in many chemical industries. However, zeolite is not available everywhere, and it is expensive considering the price of raw materials from which it can be synthesized. In this study, ZSM-5 zeolite, as a local silica source with the high crystallinity, was synthesized, based on diatomite exploited from a mine in the north-west of Iran. The diatomite was employed as the only source of silica, and underwent hydrothermal transformation in a Teflon-lined autoclave operating at 170 °C without any alkaline post-treatment. The effects of the reaction pH and the reaction time on the properties of the synthesized MFI-type zeolite were monitored. The hydrothermal reaction time was optimized and hierarchical ZSM-5 hexagonal crystals were obtained. Furthermore, the effect of Si/Al ratio on the crystallinity of the resulting zeolite was investigated. The XRD, SEM, TEM, BET, FTIR, TPD, TGA, and DSC analyses were carried out to characterize the synthesized zeolites. The results confirmed the creation of MFI-type zeolites from diatomite applying hydrothermal process at an optimized pH and reaction time. In addition, the synthesized ZSM-5 zeolites exhibited a narrow pore size distribution resembling the mesoporous structure of standard ZSM-5 zeolites. Plenty of regularly arranged pores with diameters of 300–500 nm were observed inside the round circle-like sections of diatomite. For zeolites in which Si/Al ratio was higher (55 compared to 37), a relatively narrower pore size distribution similar to that of the standard ZSM-5 zeolite was detected. Comparably, the synthesized zeolites also contained stronger acid sites, rendering it as an excellent catalyst for the conversion of methanol to gasoline.

Agarose is a prominent marine polysaccharide representing reversible thermogelling behavior, outstanding mechanical properties, high bioactivity, and switchable chemical reactivity for functionalization. As a result, agarose has received particular attention in the fabrication of advanced delivery systems as sophisticated carriers for therapeutic agents. The ever-growing use of agarose-based biomaterials for drug delivery systems resulted in rapid growth in the number of related publications, however still, a long way should be paved to achieve FDA approval for most of the proposed products. This review aims at a classification of agarose-based biomaterials and their derivatives applicable for controlled/targeted drug delivery purposes. Moreover, it attempts to deal with opportunities and challenges associated with the future developments ahead of agarose-based biomaterials in the realm of advanced drug delivery. Undoubtedly, this class of biomaterials needs further advancement, and a lot of critical questions have yet to be answered.

Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). Some chemical characteristics of poloxamers such as temperature-dependent self-assembly and thermo-reversible behavior along with biocompatibility and physiochemical properties make poloxamer-based biomaterials promising candidates for biomedical application such as tissue engineering and drug delivery. The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. Poloxamers are also used for the modification of hydrophobic tissue-engineered constructs. This article collects the recent advances in design and application of poloxamer-based biomaterials in tissue engineering, drug/gene delivery, theranostic devices, and bioinks for 3D printing. STATEMENT OF SIGNIFICANCE: Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. However, no reports have systematically reviewed the critical role of poloxamer for biomedical applications. Research on poloxamers is growing today opening new scenarios that expand the potential of these biomaterials from "traditional" treatments to a new era of tissue engineering. To the best of our knowledge, this is the first review article in which such issue is systematically reviewed and critically discussed in the light of the existing literature.

Theranostic platforms bring about a revolution in disease management. During recent years, theranostic nanoparticles have been utilized for imaging and therapy simultaneously. Zeolites, because of their porous structure and tunable properties, which can be modified with various materials, can be used as a delivery agent. The porous structure of a zeolite enables it to be loaded and unloaded with various molecules such as therapeutic agents, photosensitizers, biological macromolecules, MRI contrast agents, radiopharmaceuticals, near-infrared (NIR) fluorophores, and microbubbles. Furthermore, theranostic zeolite nanocarriers can be further modified with targeting ligands, which is highly interesting for targeted cancer therapies.

There have been several attempts to find promising biomaterials for skin regeneration, among which polylysine (a homopolypeptide) has shown benefits in the regeneration and treatment of skin disorders. This class of biomaterials has shown exceptional abilities due to their macromolecular structure. Polylysine-based biomaterials can not only be used as tissue engineering scaffolds for skin regeneration, but also as drug carriers or even gene delivery vectors for the treatment of skin diseases. In addition, polylysine can play a preservative role in extending the lifetime of skin tissue by minimizing the appearance of photodamaged skin. Research on Polylysine is growing today, opening new scenarios that expand the potential of these biomaterials from traditional treatments to a new era of tissue regeneration. This review aims to address the basic concepts, recent trends, and prospects of polylysine-based biomaterials for skin regeneration. Undoubtedly, this class of biomaterials needs further evaluations and explorations, and many critical questions have yet to be answered.

The biodegradability and mechanical properties of polysaccharides are dependent on their architecture (linear or branched) as well as their crystallinity (size of crystals and crystallinity percent). The amount of crystalline zones in the polysaccharide significantly governs their ultimate properties and applications (from packaging to biomedicine). Although synthesis, characterization, and properties of polysaccharides have been the subject of several review papers, the effects of crystallization kinetics and crystalline domains on the properties and application have not been comprehensively addressed. This review places focus on different aspects of crystallization of polysaccharides as well as applications of crystalline polysaccharides. Crystallization of cellulose, chitin, chitosan, and starch, as the main members of this family, were discussed. Then, application of the aforementioned crystalline polysaccharides and nano-polysaccharides as well as their physical and chemical interactions were overviewed. This review attempts to provide a complete picture of crystallization-property relationship in polysaccharides.

New emerging technologies, remarkably miniaturized 3D organ models and microfluidics, enable simulation of the real in vitro microenvironment ex vivo more closely. There are many fascinating features of innovative organ-on-a-chip (OOC) technology, including the possibility of integrating semipermeable and/or stretchable membranes, creating continuous perfusion of fluids into microchannels and chambers (while maintaining laminar flow regime), embedding microdevices like microsensors, microstimulators, micro heaters, or different cell lines, along with other 3D cell culture technologies. OOC systems are designed to imitate the structure and function of human organs, ranging from breathing lungs to beating hearts. This technology is expected to be able to revolutionize cell biology studies, personalized precision medicine, drug development process, and cancer diagnosis/treatment. OOC systems can significantly reduce the cost associated with tedious drug development processes and the risk of adverse drug reactions in the body, which makes drug screening more effective. The review mainly focus on presenting an overview of the several previously developed OOC systems accompanied by subjects relevant to pharmacy-, cancer-, and placenta-on-a-chip. The challenging issues and opportunities related to these systems are discussed, along with a future perspective for this technology.

The necessity of research on flame retardancy has directed attentions toward development of advanced coating systems in order to meet requirements of competitive markets. As a result, a wide range of organic coating materials were developed in the quest of higher flame retardancy performance. Polyaniline (PANI) as a promising conductive polymer has been widely considered for various applications, and it quite frequently took credit for the success. This article deals with the benefits expecting from PANI in advanced flame retardant systems in view of its extraordinary fire retardancy performance. The necessity of study on potentially high thermal stability and flame retardancy of advanced coating systems containing PANI was also discussed. There is a belief that identifying the worth of PANI as the most famous member of conductive polymers may help determine the locus of PANI in an inevitable shift from general-purpose to advanced flame retardant (FR) systems in which PANI plays a dual role. Harmoniously, ongoing progress in the knowledge and technology of FR coating systems would enliven emerging technologies for utilizing organic materials in response to increasing demand for PANI-based systems with an additional flame retardancy mission in the near future.

Elastomeric materials are among the important classes of versatile polymers and provide exceptional advantages such as softness, stability, elasticity, and extensibility. Plastomers as a polymeric material combine characteristics and features of plastics and elastomers including rubber-like features with the handling capability of plastic materials. The word “plastomer” is a portmanteau of “plastic” and “elastomer”. Thanks to their unique features, elastomers and plastomers have been widely employed, individually and in combination with identical or non-identical families, in various applications. In this chapter, several types of elastomeric and plastomeric materials have been outlined with a particular emphasis on naturally occurring and bottlebrush elastomer/plastomer materials. Different types of smart elastomeric materials have also been covered in this chapter. It was attempted to discuss how and to what extent the novel elastomeric materials have functioned in tires, electric and electronic devices, actuators, soft robotics, microfluidics, tissues and other products.

The ability of mesenchymal stem cells (MSCs) to enhance cutaneous wound healing has been well established. Extensive expansion of cells to reach sufficient cell numbers for regenerating tissues has always limited cell-based therapies. An ingenious solution to address this challenge is to develop a strategy to increase the immunomodulatory effects of MSCs without expanding them. In this study, we employed a simple characteristic of cells. It was observed that an optimized three-dimensional (3D) MSC culture in spheroid forms significantly improved their paracrine effects. An electrospray (ES) encapsulation apparatus was used to encapsulate individual or 3D spheroid MSCs into microscale alginate beads (microbeads). Furthermore, alginate microbeads were embedded in an injectable thermosensitive hydrogel matrix, which gels at skin temperature. The hydrogel fills and seals the wounds cavities, maintains high humidity at the wound area, absorbs exudate, and fixes microbeads, protecting them from direct contact with the harsh wound environment. In vitro investigations revealed that secretion of interleukin 10 (IL-0) and transforming growth factor β1 (TGF-β1) gene was gradually enhanced, providing a delivery platform for prolonged release of bioactive molecules. In vivo study on full-thickness wounds showed granulation and re-epithelialization, only after 7 days. Moreover, increased expression of α-smooth muscle actin (α-SMA) in the first 14 days after treatment ensured wound contraction. Besides, a gradual decrease in α-SMA secretion resulted in reduced scar formation. Well-organized collagen fibrils and high expression of the angiogenesis biomarker CD31 confirmed the promoting effect of the hydrogel on the wound-healing process. The proposed wound-dressing system would potentially be used in scalable and effective cell-based wound therapies.

Magnetic nanoparticles (MNPs) are a very interesting class of metal oxides, which can be magnetized by an external field. The magnetic properties of MNPs give them potential for heat generation and actuation, which are highly appealing for in vivo applications. MNPs can be served as contrast agents for magnetic resonance imaging in cancer screening and diagnosis. Furthermore, they can be loaded with various therapeutics agent or photosensitizers as delivery systems for cancer therapy. Moreover, they can be easily hybridized (functionalized, coated, or combined) with various chemicals which endows them tumor-targeting capability, enhanced biocompatibility, nonimmunogenic properties, enhanced drug-loading capacity, and multimodal imaging capability. This chapter summarizes the current status of MNPs usage in cancer therapy with an emphasis on recent works. Moreover, a brief overview is presented on the importance of mathematical modeling and computer simulation for cancer therapy using MNPs.

Interpenetrating polymer networks (IPNs) are a special type of polymer blends benefiting from combination of properties of two or more homo-/copolymers. Polysaccharide-based IPNs are promising materials for designing and manufacturing drug delivery and/or theranostic platforms. Ionically crosslinked polysaccharide-based IPNs in which polymer chains are crosslinked using non-toxic metal ions or low-molecular weight organic ions can be utilized to develop advanced delivery systems, which can disassemble in response to specific exogenous or endogenous stimuli such as pH, temperature, ion concentration, and redox species. Accordingly, such smart and stable delivery platforms are very interesting biomaterials to be loaded with various therapeutic agents. This chapter summarizes the application of these fascinating composite biomaterials in fabrication of delivery platforms.

Polysaccharides are building blocks of many drug delivery systems with outstanding performance. Carboxymethyl derivatives obtained from polysaccharides improve solubility and physiochemical properties making them good alternatives for various applications. Carboxymethyl polysaccharides bearing cationic charges can be physically crosslinked via electrostatic and ionic interaction with polycationic species, small molecules, and metal ions to induce integrity. In this chapter, drug delivery platforms based on carboxymethyl polysaccharides in which ionic species are used as crosslinking agents which are outlined. We highlight that ionically crosslinked carboxymethyl polysaccharides carriers are promising candidates for delivery of various drugs such as chemotherapeutics, anti-inflammatory drugs, and protein-based therapeutic agents.

Polysaccharides are the most abundant naturally available carbohydrate polymers; composed of monosaccharide units covalently connected together. Chitosan is the most widely used polysaccharides because of its exceptional biocompatibility, mucoadhesion, and chemical versatility. However, it suffers from a few drawbacks, e.g. poor mechanical properties and antibacterial activity for biomedical applications. Blending chitosan with natural or synthetic polymers may not merely improve its physicochemical and mechanical properties, but may also improve its bioactivity-induced properties. This review paper summarizes progress in chitosan blends with biodegradable polymers and polysaccharides and their biomedical applications. Blends of chitosan with alginate, starch, cellulose, pectin and dextran and their applications were particularly addressed. The critical and challenging aspects as well as the future ahead of the use of chitosan-based blends were eventually enlightened.

Architecting an appropriate platform for biomedical applications requires setting a balance between simplicity and complexity. Polysaccharides (PSAs) play essential roles in our life in food resources, structural materials, and energy storage capacitors. Moreover, the diversity and abundance of PSAs have made them an indispensable part of food ingredients and cosmetics. PSA-based hydrogels have been extensively reviewed in biomedical applications. These hydrogels can be designed in different forms to show optimum performance. For instance, electroactive PSA-based hydrogels respond under an electric stimulus. Such performance can be served in stimulus drug release and determining cell fate. This review classifies and discusses the structure, properties, and applications of the most important polysaccharide-based electroactive hydrogels (agarose, alginate, chitosan, cellulose, and dextran) in medicine, focusing on their usage in tissue engineering, flexible electronics, and drug delivery applications.

Hydrogel membranes (HMs) are defined and applied as hydrated porous media constructed of hydrophilic polymers for a broad range of applications. Fascinating physiochemical properties, unique porous architecture, water-swollen features, biocompatibility, and special water content dependent transport phenomena in semi-permeable HMs make them appealing constructs for various applications from wastewater treatment to biomedical fields. Water absorption, mechanical properties, and viscoelastic features of three-dimensional (3D) HM networks evoke the extracellular matrix (ECM). On the other hand, the porous structure with controlled/uniform pore-size distribution, permeability/selectivity features, and structural/chemical tunability of HMs recall membrane separation processes such as desalination, wastewater treatment, and gas separation. Furthermore, supreme physiochemical stability and high ion conductivity make them promising to be utilised in the structure of accumulators such as batteries and supercapacitors. In this review, after summarising the general concepts and production processes for HMs, a comprehensive overview of their applications in medicine, environmental engineering, sensing usage, and energy storage/conservation is well-featured. The present review concludes with existing restrictions, possible potentials, and future directions of HMs.

Delivery systems play a vital role in disease treatment, especially cancer therapy. Typically, simple delivery systems and free drugs cannot tolerate the harsh condition of the biological systems. Therefore designing more sophisticated and smart platforms is a necessity for proper disease diagnosis and treatment. Amphiphilic block copolymers, which combine hydrophilic and hydrophobic segments at nanoscale, can interact with a variety of hydrophilic and hydrophobic drugs. Their microstructure depends on self-assembly at nanoscale, which itself depends on the chemical structure and surrounding environment. Block copolymers can form polymeric micelles in dilute solutions, which can serve as carriers for therapeutic and diagnostic agents. Moreover, such platforms can be engineered to enter the cell and deliver the payload to cytoplasm or cell nucleus. Block copolymer containing cationic residue can condense DNA or RNA via electrostatic interactions to carry them into the cells while preserving them from extracellular environment. Furthermore, such platforms can be tailored to respond to various endogenous/exogenous stimuli such as temperature and pH, which is highly desired for cancer therapy. In this section, various types of block copolymer for manufacturing nanostructured delivery systems will be discussed to pave a way for scientist to choose a best platform as a delivery agent.

Nanotechnology-driven strategies have enabled scientists and engineers to fabricate diverse drug delivery and (bio)sensor platforms. It is now possible to develop nanoscale drug carriers for delivery of different payloads to target locations and even into cells. Furthermore, stimuli-responsive and self-propelled nanocarriers can be developed for achieving a better performance. On the other hand, biosensors are more complicated platforms, which include recognition, transduction, and signal processing elements such that they are usually fabricated through miniaturization techniques, frequent in electronic industries. Accordingly, it has been near-to-impossible to make fully functional scale biosensors so far. This chapter discusses these biosensing platforms along with wearable delivery and biosensor platforms that can be integrated into intelligent biosensing-delivery platforms.

Limited therapeutic efficacy of biomolecular drugs has resulted in the development of various drug delivery systems to protect them from degradation and renal clearance. Protein and peptide-based materials are very promising to develop drug delivery systems. In this chapter, the importance of self-assembly in creation of protein- and peptide-based nanostructures is discussed. Then, various delivery systems based on different peptides and proteins are outlined. It is expected that nanoengineered protein and peptide-based delivery systems play a critical role in the development of the next generation of advanced delivery systems.

Nanotechnology is growing fast, effectively and innovatively to rely on the requirements of human. The nanotechnology has significantly enlarged the potential and promising features of materials science in medicine. Designing novel nanostructured carriers with the ability to release the diagnostic and/or therapeutic agents at predetermined, zone in a controlled manner has been one of the most appealing features of nanotechnology in biomedicine. This chapter discusses the importance of nanomaterials of different dimensions, shapes, architectures, size, and chemistry in delivery of different payloads. Moreover, nanocarriers targeted as responding to the endogenous/exogenous stimuli and new emerging elaborate self-propelling carriers are outlined.

In-out surface modification of halloysite nanotubes (HNTs) has been successfully performed by taking advantage of 8-hydroxyquinolines in the lumen of HNTs and precisely synthesized aniline oligomers (AO) of different lengths (tri- and pentamer) anchored on the external surface of the HNTs. Several analyses, including FTIR, H-NMR, TGA, UV-visible spectroscopy, and SEM, were used to establish the nature of the HNTs’ surface engineering. Nanoparticles were incorporated into epoxy resin at 0.1 wt.% loading for investigation of the contribution of surface chemistry to epoxy cure behavior and kinetics. Nonisothermal differential scanning calorimetry (DSC) data were fed into home-written MATLAB codes, and isoconversional approaches were used to determine the apparent activation energy (Eα) as a function of the extent of cure reaction (α). Compared to pristine HNTs, AO-HNTs facilitated the densification of an epoxy network. Pentamer AO-HNTs with longer arms promoted an Excellent cure, with an Eα value that was 14% lower in the presence of this additive than for neat epoxy, demonstrating an enhanced cross-linking. The model also predicted a triplet of cure (m, n, and ln A) for autocatalytic reaction order, non-catalytic reaction order, and pre-exponential factor, respectively, by the Arrhenius equation. The enhanced autocatalytic reaction in AO-HNTs/epoxy was reflected in a significant rise in the value of m, from 0.11 to 0.28. Kinetic models reliably predict the cure footprint suggested by DSC measurements.

Both carbon nanotubes (CNTs) and polyaniline (PANI), because of their unique structures and properties, have been used individually in diverse applications. On the other hand, PANI-CNT nanocomposites, which inherit fascinating properties of both PANI and CNTs, have gained increasing attention for advanced particular uses. Some of these applications, including sensors, energy storage devices, solar cells, electromagnetic interference (EMI) shields, anticorrosive coatings, biomedical uses, heavy metal removal, and catalysis, are summarized in this chapter. In each application, an overview of the technology and related parameters is presented first; then, the usage and benefits of CNTs, PANI, and PANI/CNTs are summarized and discussed. Generally speaking, PANI/CNT nanocomposites have superior properties with respect to pure CNT or PANI, which results in a more successful/specific performance.

Many advanced materials and systems are designed in nanoscale to act as efficiently as possible. An enormous amount of investigation has been done to exert control over the nanostructure of advanced materials and also to manipulate their specific structures. Nanostructures, because of the high surface area that can be imparted to the system, can boost the performance of materials. Emerging conductive polymers have revolutionized the polymer industry and indeed widened the polymer usage realm. Polyaniline (PANI), as a well-known conductive polymer, has been utilized in various applications such as electronics, anticorrosive coatings, and biomedical devices. Because of the adjustable properties of PANI, this material can be used in a wide range of applications; hence, its nanostructure can be optimized to achieve the highest possible level of performance. In this chapter, we illuminate PANI nanostructure formation and application to provide rational strategies for the selection of proper structures for specific applications.

Functionalized graphene oxide (FGO)/epoxy nanocomposite coatings were prepared through a cathodic electrophoretic deposition (C-EPD) process for anti-corrosion applications. The C-EPD process was carried out at different voltages, for 5 min to create uniform coatings of different thicknesses (i.e., 5−10 μm). Electrochemical impedance spectroscopy (EIS) and salt spray tests showed that nanocomposite coatings containing 0.1 wt. % FGO possess outstanding corrosion resistance properties. It was concluded that the incorporation of FGO act equivalent to thickness increase in terms of retarding corrosive agents to diffuse into the coating. However, at higher loadings, FGO aggregates may adversely affect anti-corrosion properties.

Since drinkable water resources are not infinite, the most plausible solution to address the forthcoming water scarcity is to treat the polluted water streams. This state-of-the-art review highlights the prime role of conductive polymers (CPs), widely known as intrinsically conductive polymers (ICPs), in wastewater treatment through reviewing very recent studies conducted on the elimination of noxious contaminations. Herein, after a brief introduction to the characteristics of conductive polymers, we tried to give a more comprehensive overview of the decontamination of polluted water based on different prevailing water treatment processes. The first section belonged to the adsorptive removal of pollutants is well-featured on various heavy-metal ions capture along with a comprehensive discussion on the governing uptake mechanism. After that, diversified types of CP-based composites applied for sorptive elimination of other types of pollutants, especially organic dyes, and their possible adsorption mechanism was also reviewed in detail. Next, recent publications related to CP-based photocatalysts utilized for the degradation of aquatic contamination were adequately summarized. The applicability and efficiency of the CP-based membrane for water purification through different membrane filtration techniques were underscored. Moreover, In the last section of the current study, a conclusion and perspective are provided, in which we discussed what one could discern from the remaining distinctive challenges, limitations, and, more importantly, the envisaged future directions of CP-based materials toward water treatment.

Due to population growth and subsequent growing energy demand, clean energy generation is one of the major challenges today and in the future. Dye-sensitized solar cells (DSSCs) is one of the new approaches to producing clean, endless energy. In this review, the primary function, structure, performance parameters, and key elements of DSSCs are analyzed first, with a focus on the photosensitizer as the crucial part due to electron production. Photosensitizers based on natural resources recently attracted attention because of their economic and environmental advantages, but there are substantial challenges such as low conversion efficiency and long term stability. Also, diverse and, in some cases, contradictory results presented in the literature make conclusions difficult. Here, different challenges about DSSCs based on natural dyes are categorized and discussed according to the published papers, and possible solutions are presented, which could shed light on future investigations. Furthermore, according to different factors, such as average solar radiation and economic/technological aspects, DSSCs based on natural dyes are proposed to be the most promising renewable energy technology for arid to semi-arid, sunny countries like Iran in the future. Accordingly, the performance of DSSCs based on natural dyes manufactured using dye extract of different plants grow in Iranian is summarized then. In recent years, many DSSCs based on natural dyes have been manufactured using different plants grown in different parts of the country. Interestingly, it is possible to extract many natural dyes for DSSCs based on natural dyes from agricultural wastes such as saffron petals and walnut shells, of which thousand tons them are disposed every year.

In this paper, chemical polymerization of aniline and aniline/multi-walled carbon nanotubes (MWCNTs) is investigated, and a modified polymerization model is proposed based on the obtained experimental results. In the experimental section, the variation in temperature of the reaction mixture was measured during the polymerization reaction. According to the obtained thermographs, it was concluded that the polymerization of aniline or aniline/MWCNTs takes place in three different steps. In the first step, some nuclei of phenazine-type trimers are formed for pure aniline while for aniline/MWCNTs, aniline molecules are adsorbed on the nanotubes surfaces. In the second step, cation-radical polymerization occurs at a high speed where there are a significant number of monomers around the growing chains. It is proposed that in the third step a new polymerization reaction begins on the pre-synthesized polymers. For pure PANI, it seems that only oligomers are created in this step while for PANI/MWCNTs, long chain polymers can also grow. Experimental results show that the enthalpy of polymerization reduces while polymerization yield increases with the weight percent of MWCNTs, which can be explained by the new observed polymerization model.

In this paper, we investigate the CO emission from an oil refinery gas incinerator both theoretically and experimentally. At the beginning of this research, our collected data from this incinerator showed that the CO contamination would be far exceeding the permissible environmental standards at the stack exhaust. Therefore, we decided to perform a combined theoretical-experimental study to find a reasonable solution to reduce the CO pollution suitably. Our theoretical study showed that a reliable solution would be to increase the incinerator operating temperature. However, we needed to collect some data from this incinerator to examine if our achieved analytical solution would work correctly. In data collection procedure, we were faced with one major difficulty due to the limits of automatic system of incinerator control, which did not let us increase the incinerator temperature readily in real work conditions. As a general remedy, our suggestion was to interfere in this automatic control system and to increase its maximum possible limit of temperature. Evidently, this needed a number of considerations, which could not be performed in a short length period. As a short length remedy, we designed a number of manual control procedures, which let us examine different temporary working conditions for the incinerator. Trying different operating condition, we eventually found a suitable one with minimum CO emission from the incinerator. Although this choice resulted in an increase in the incinerator temperature and a remedy to reduce the high CO emission, it was inversely increased the incinerator fuel consumption, which is rather a negative point. Our further data collection indicated that the excess air of primary incinerator was relatively high. Therefore, we designed an automatic system of inlet air damper to adjust the inlet air, which resulted in avoiding high excess air and consequently suitable saving in the fuel consumption. The details are provided in the rest of paper.Copyright © 2014 by ASME