A facile and green synthetic approach toward fabrication of alcea- and thyme-stabilized tio2 nanoparticles for photocatalytic applications

A facile and green synthetic approach was considered for the synthesis of stabilized titanium dioxide (TiO2) nanoparticles. Extracts of Alcea and Thyme plants were used to synthesis TiO2 nanoparticles for photocatalytic applications. Evaluation of the structural and phase formation via X-ray diffraction (XRD) indicated the formation of the anatase phase of TiO2 along with the rutile phase. A desired single phase of anatase was obtained upon heating the as-synthesized samples at 500 °C for 3 h. Using the information provided by the XRD analyzer and the Debye Scherer relationship, the average crystallite size was found to be around 6 and 10 nm for the samples synthesized using Alcea and Thyme plants, respectively. To determine the elemental analysis and chemical structure, the energy dispersive X-ray (EDX) analyzer and Fourier Transform Infrared (FTIR) spectroscopy were employed. Field emission scanning electron microscopy (FESEM) indicated batches of ultrafine agglomerated particles for both samples, which their sizes grew by the heating process. The UV–visible analysis of photocatalytic properties confirmed the priority of TiO2 nanoparticles prepared with Thyme extracts

Phosphoric acid functionalized graphene oxide: a highly dispersible carbon-based nanocatalyst for the green synthesis of bio-active pyrazoles

Carbon-based catalysts are gained significant interest for improving a number of catalytic processes due to their unique set of benefits. However, a few of such catalysts are proper for synthesis of organic compounds in water. Therefore, there is a strong need for developing water-tolerant and dispersible catalysts. Here, we demonstrate a simple and efficient method for the preparation of highly dispersible phosphonic acid functionalized carbocatalyst. The applied functionalization method was flexible in controlling the functionalization level. The prepared nanocatalyst exhibited superior catalytic performance toward multicomponent synthesis of pyrano[2,3-c]pyrazole, with 80-90% yield within 15 min in water. Moreover, this water-tolerant solid acid. catalyst could be simply retrieved and after 6 successive cycles of reactions, the reaction time and yield still keeps within the same level

Sandwich structure polymer electrolyte membranes containing phosphotungstic acid immobilized electospun nanofibers

The advances in proton exchange membranes (PEM)s is critical for improving the performance of fuel cells [1]. Membranes compromising perfluorosulfonic acid polymers such as Nafion have been used extensively due to their desired conductivity and stability. However, these materials need to be saturated with water to obtain practical level of proton conductivity. There is a strong demand for the PEMs to work at lower relative humidity or under anhydrous conditions because the electrochemical reactions will be accelerated and water management of fuel cell will be simpler. Various designing strategies and advanced materials have been developed to mitigate for this issue without causing serious loss in proton conductivity or stability [2]. Among all, the introducing of inorganic proton conductors such as heteropoly acids have been considered widely. Generally, HPAs (such as phosphotungstic acid H3PW12O40, PWA) have a very strong Brønsted acidity approaching the superacid region (more acidic than Nafion) [3]. In this work, high level of PWA was self-anchored onto nylon electrospun nanofiberous sheet (Figure 1b). Sandwich structured proton conducting membranes were fabricate by assembling nanofibrous central layer with outer Nafion layers (Figure 1b). Since the PWA is attached to the polymer backbones, the risk of leaching out is minimized. Moreover, the significant synthetic versatility of the method helps to increase PWA immobilization level. As shown in the Figure 1c, proton conductivity of as high as 60 mS cm-1 at 30 °C was achieved which is comparable with Nafion 115. The durability of the proton conductivity of sandwiched membrane

Phosphonated polyimides: enhancement of proton conductivity at high temperatures and low humidity

A new class of highly conductive and durable polymer electrolyte membranes have been developed for fuel cell applications under elevated temperature and/or low relative humidity (RH). Highly phosphonated and fully aromatic diamine monomer was prepared via three-step high-yielding procedure from previously synthesized phosphonated bisphenol: halogen displacement of 1-fluoro-4-nitrobenzene, reducing of nitro groups, and hydrolysis of phosphonate ester groups. A series of phosphonated copolyimide ionomers with ion exchange capacity (IEC) of 2.4–4.6 mequiv g−1 were obtained by a typical polycondensation reaction followed by solution casting to form transparent and flexible membranes. Proton conductivity of the phosphonated membranes was comparable to that of the commercial perfluorinated ionomer at 100% RH. Typically, the conductivity value of up to 125 mS cm−1 was obtained for the membrane with IEC of 3.5 mequiv g−1 at 100 °C. However, by reducing the relative humidity the merits of phosphonated polyimides became more evidence and their dry state conductivity was 1–3 order of magnitudes higher than Nafion 115 and substantially higher than the values reported for phosphonated membranes. Thermogravimetric analysis and long-term proton conductivity study of phosphonated copolyimides at high temperatures (up to 160 °C) and low humidity confirmed small amount of undesired self-condensation of phosphonic acid groups compared with other phosphonated membranes

Intensifying radiation induced grafting of 4-vinylpyridine/glycidyl methacrylate mixtures onto poly(ethylene-co-tetrafluoroethylene) films using ultrasound

A new ultrasound-aided method was used to enhance grafting of 4-vinylpyridine (4-VP) and glycidyl methacrylate (GMA) monomers mixtures onto electron beam (EB) irradiated poly(ethylene-co-tetrafluoroethylene) (ETFE) film for the first time. The effects of reaction parameters such as absorbed dose, monomer concentration, reaction time on both of degree of grafting (DG) and grafting efficiency (GE) were investigated under sonication and conventional grafting at similar temperatures. Fourier transform infrared (FTIR) and atomic force microscopy (AFM) were used to monitor the impact of the applied ultrasound on composition and surfaces of the grafted films whereas 1H-NMR was used to investigate composition of the grafting residues. The ultrasound-aided grafting of 4-VP/GMA was found to enhance both of DG% and GE remarkably. Moreover, it produced grafted ETFE films having smoother surfaces without homopolymer contamination compared to grafted films obtained from conventional grafting. The results of this study suggest that the use of ultrasound is a promising way for intensifying grafting process and improving its economy

Polyvinylamine-containing adsorbent by radiation-induced grafting of n-vinylformamide onto ultrahigh molecular weight polyethylene films and hydrolysis for CO2 capture

A facile method involving radiation induced grafting of N-vinylformamide (NVF) into the microporous structure of ultrahigh molecular weight polyethylene (UHMWPE) film followed by hydrolysis was used to prepare polyvinylamine (PVAm) containing adsorbent for CO2 capturing. The grafting parameters such as solvent type, monomer concentration, absorbed dose, and reaction time were varied to control the grafting yield (GY, %). The degree of hydrolysis of the grafted poly(N-vinylformamide) and density of the formed amine groups were evaluated. The chemical composition and morphology of PVAm modified films were studied using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. The distribution of amine groups across the films was monitored by energy dispersive X-ray spectroscopy (EDX). The static CO2 adsorption characteristic of PVAm modified film (from pure CO2) with a GY of 108% was found to be promising and reached a value of 48.6 mg/g at 25 °C and 1 bar. The breakthrough measurements of PVAm modified film showed an effective CO2 adsorption from binary mixtures with N2 without any significant loss in the performance after six adsorption/desorption cycles

Aerogel-based materials for adsorbent applications in material domains

Aerogels are considered to be promising materials in various applications due to their exclusive properties. Over the last decades, the potential of organic, inorganic, or hybrid aerogels has been practically exploited in different fields of use. Some aerogel compositions have been patented recently but their application in the area of adsorption remains limited. This review intends to discuss the potential of aerogels as adsorbents, which is summarised from the more recent progressive research and their capabilities. Furthermore, the potential of aerogels as viable absorbents for environmental remediation is also discussed. After a short introduction covering the aerogel properties, preparation procedures, and their possible classification options, the review is structured based on their possible use as adsorbents

Enhanced magnetorheology of soft magnetic carbonyl iron suspension with binary mixture of Ni-Zn ferrite and Fe3O4 nanoparticle additive

Fe3O4 and Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized via precipitation and mechanical alloying, respectively, and assessed as a potential magnetorheogical (MR) additive. X-ray diffraction and transmission electron microscopy were employed to evaluate the phase formation and structural and morphological changes. Vibrating sample magnetometer (VSM) was used to measure magnetic characteristics of the samples. The MR characteristics of carbonyl iron (CI)-based and 1 wt.% (Ni0.5Zn0.5Fe2O4 + Fe3O4) CI-based suspensions were measured from a steady and rotational rheometry by applying magnetic field strengths ranging from 0 to 558.39 kA/m with 79.77-kA/m increments. The results indicated that the MR effect of the micron-sized, CI-based MR fluid significantly improved in the presence of nanoparticle additives, e.g., having higher-yield characteristics. Chain-like structure formed in the presence of nanoscale additives improved the MR performance and sedimentation stability of the CI particles

Composite membranes based on heteropolyacids and their applications in fuel cells

Heteropolyacids (HPAs) are a class of inorganic materials that have been widely used as additives to enhance the performance of fuel cell membranes, recently. This chapter covers the use of HPAs in the preparation of proton exchange membranes (PEM) for polymer electrolyte membrane fuel cells (PEMFCs). The fundamental aspects of HPAs and their corresponding salts in addition to various structural configurations such as Keggin, Wells-Dawson, and Lacunar are discussed. The use of HPAs for preparation of membranes for high-temperature PEMFC and direct methanol fuel cell (DMFC) based on the immobilization on various substrates including perfluorinated sulfonic acids (PFSAs), aromatic hydrocarbons, poly(vinyl alcohol) (PVA), and polybenzimidazole (PBI) are reviewed. The research challenges that need to be addressed to bring the new composite membranes to practical application are also discussed