Salem S. Al-Deyab

A review of one-dimensional TiO2 nanostructured materials for environmental and energy applications

One-dimensional TiO2 (1D TiO2) nanomaterials with unique structural and functional properties have been extensively used in various fields including photocatalytic degradation of pollutants, photocatalytic CO2 reduction into energy fuels, water splitting, solar cells, supercapacitors and lithium-ion batteries. In the past few decades, 1D TiO2 nanostructured materials with a well-controlled size and morphology have been designed and synthesized. Compared to 0D and 2D nanostructures, more attention has been paid to 1D TiO2 nanostructures due to their high aspect ratio, large specific surface area, and excellent electronic or ionic charge transport properties. In this review, we present the crystal structure of TiO2 and the latest development on the fabrication of 1D TiO2 nanostructured materials. Besides, we will look into some critical engineering strategies that give rise to the excellent properties of 1D TiO2 nanostructures such as improved enlargement of the surface area, light absorption and efficient separation of electrons/holes that benefit their potential applications. Moreover, their corresponding environmental and energy applications are described and discussed. With the fast development of the current economy and technology, more and more effort will be put into endowing TiO2-based materials with advanced functionalities and other promising applications.

Robust superhydrophobic TiO2@fabrics for UV shielding, self-cleaning and oil–water separation

Inspired by the surface geometry and composition of the lotus leaf with its self-cleaning behavior, in this work, a TiO2@fabric composite was prepared via a facile strategy for preparing marigold flower-like hierarchical TiO2 particles through a one-pot hydrothermal reaction on a cotton fabric surface. In addition, a robust superhydrophobic TiO2@fabric was further constructed by fluoroalkylsilane modification as a versatile platform for UV shielding, self-cleaning and oil–water separation. The results showed TiO2 particles were uniformly distributed on the fibre surface with a high coating density. In comparison with hydrophobic cotton fabric, the TiO2@fabric exhibited a high superhydrophobic activity with a contact angle of ∼160° and a sliding angle lower than 10°. The robust superhydrophobic fabric had high stability against repeated abrasion without an apparent reduction in contact angle. The as-prepared composite TiO2@fabric demonstrated good anti-UV ability. Moreover, the composite fabric demonstrated highly efficient oil–water separation due to its extreme wettability contrast (superhydrophobicity/superoleophilicity). We expect that this facile process can be readily and widely adopted for the design of multifunctional fabrics for excellent anti-UV, effective self-cleaning, efficient oil–water separation, and microfluidic management applications.

Controlled release of bone morphogenetic protein 2 and dexamethasone loaded in core-shell PLLACL-collagen fibers for use in bone tissue engineering.

Electrospun nanofibers mimic the native extracellular matrix of bone and have generated considerable interest in bone tissue regeneration. The aim of this study was to fabricate novel poly(l-lactide-co-caprolactone) (PLLACL), PLLACL/collagen nanofibers blended with bone morphogenetic protein 2 (BMP2) and dexamethasone (DEX) for controlled release during bone tissue engineering (BTE). The morphology, surface hydrophilicity, and mechanical properties of the PLLACL/collagen nanofibrous mats were analyzed by scanning electron microscopy and water contact angle and mechanical stability determination. The performance of the scaffolds was investigated in terms of the viability and morphology of human mesenchymal stromal cells (hMSC) on the nanofibrous mats. BMP2 and DEX were successfully incorporated into PLLACL/collagen nanofibers by means of blending or coaxial electrospinning and the PLLACL/collagen blended fibers proved useful for hMSC culture. Release of the two growth factors from PLLACL/collagen nanofibrous mats in vitro was investigated by UV spectrophotometry. The release profiles for core-shell nanofibers showed more controlled release of the growth factors compared with the blended electrospun fibers. The experimental results show that controlled release of BMP2 and DEX can induce hMSC to differentiate into osteogenic cells for bone tissue engineering. The results imply that PLLACL/collagen nanofibers encapsulating two drugs and/or proteins have great potential in bone tissue engineering.

Nanoporous polystyrene fibers for oil spill cleanup

The development of oil sorbents with high sorption capacity, low cost, scalable fabrication, and high selectivity is of great significance for water environmental protection, especially for oil spillage on seawater. In this work, we report nanoporous polystyrene (PS) fibers prepared via a one-step electrospinning process used as oil sorbents for oil spill cleanup. The oleophilic-hydrophobic PS oil sorbent with highly porous structures shows a motor oil sorption capacity of 113.87 g/g, approximately 3-4 times that of natural sorbents and nonwoven polypropylene fibrous mats. Additionally, the sorbents also exhibit a relatively high sorption capacity for edible oils, such as bean oil (111.80 g/g) and sunflower seed oil (96.89 g/g). The oil sorption mechanism of the PS sorbent and the sorption kinetics were investigated. Our nanoporous material has great potential for use in wastewater treatment, oil accident remediation and environmental protection.

A review of extractive desulfurization of fuel oils using ionic liquids

Hydrodesulfurization (HDS), a widely employed method in industries for the desulfurization of fuel oils, such as gasoline and diesel fuel is faced with the challenge of producing lower-sulfur or sulfur-free fuel oils, which are required by more and more countries. However, HDS is not very effective for the removal of thiophenic sulfur compounds due to sterically-hindered adsorption on the catalyst surface, unless operated under harsh conditions, such as high temperature, high pressure, and requirement of a noble catalyst and hydrogen. Extractive desulfurization (EDS) of fuel oils using ionic liquids (ILs) has been intensively studied in recent decades and has a good future as an alternative or complementary method to HDS. In this review, we reviewed the research results of EDS using ILs and provided comprehensive discussions on diverse factors, which influence desulfurization, such as the IL species, IL–oil mass ratio, initial sulfur content, temperature, time, mutual solubility, multiple extractions and regeneration. Potential problems or shortcomings were also stated. Some other desulfurization methods currently under study, such as extraction, oxidation, adsorption and biodesulfurization were also briefly outlined. It can be inferred that ILs remain a class of ideal solvents to realize clean fuel oil in the near future because of their desirable physiochemical properties, which are lacking in molecular organic solvents, while there are possible challenges, such as relatively high viscosity and low efficiency.

Robust fluorine-free superhydrophobic PDMS–ormosil@fabrics for highly effective self-cleaning and efficient oil–water separation

Superhydrophobic cotton fabrics were prepared via a facile and environmentally friendly strategy to deposit an organically modified silica aerogel (ormosil) thin film onto the fabrics first, followed by polydimethylsiloxane (PDMS) topcoating. The PDMS–ormosil coating displayed a uniform 3D fractal-like structure with numerous loose micro-scale pores, while the PDMS layer increased the binding strength of the hierarchical ormosil film to form a highly robust porous network on the fibers. In comparison with hydrophilic cotton fabrics, the modified cotton fabric exhibited a highly superhydrophobic activity with a water contact angle higher than 160° and a sliding angle lower than 10°. The as-constructed PDMS–ormosil@fabrics are able to withstand 100 cycles of abrasion and 5 cycles of accelerated machine wash without an apparent decrease of superhydrophobicity. In addition, the superhydrophobic cotton fabrics are very stable in strongly acidic and alkaline solutions. Furthermore, the superhydrophobic coating has no or negligible adverse effect on the important textile physical properties of the cotton fabric, such as the strength, air permeability, and flexibility. The composite super-antiwetting fabrics have demonstrated excellent anti-fouling, self-cleaning ability and are highly efficient in oil–water separation for various oil–water mixtures. This facile synthesis technique has the advantages of scalable fabrication of multifunctional fabrics for potential applications in self-cleaning and versatile water–oil separation.

One‐dimensional TiO2 Nanotube Photocatalysts for Solar Water Splitting

Hydrogen production from water splitting by photo/photoelectron‐catalytic process is a promising route to solve both fossil fuel depletion and environmental pollution at the same time. Titanium dioxide (TiO2) nanotubes have attracted much interest due to their large specific surface area and highly ordered structure, which has led to promising potential applications in photocatalytic degradation, photoreduction of CO2, water splitting, supercapacitors, dye‐sensitized solar cells, lithium‐ion batteries and biomedical devices. Nanotubes can be fabricated via facile hydrothermal method, solvothermal method, template technique and electrochemical anodic oxidation. In this report, we provide a comprehensive review on recent progress of the synthesis and modification of TiO2 nanotubes to be used for photo/photoelectro‐catalytic water splitting. The future development of TiO2 nanotubes is also discussed.

In situ cross-linked superwetting nanofibrous membranes for ultrafast oil–water separation

Creating a practical and energy-efficient method with high efficacy to separate oil–water mixtures, especially those stabilized by surfactants, has proven to be extremely challenging. To overcome this challenge, a novel and scalable strategy was developed for the synthesis of superhydrophilic and prewetted oleophobic nanofibrous membranes by the facile combination of in situ cross-linked polyethylene glycol diacrylate nanofibers supported on polyacrylonitrile/polyethylene glycol nanofibrous (x-PEGDA@PG NF) membranes. The as-prepared x-PEGDA@PG NF membranes have shown superhydrophilicity with ultralow time of wetting and promising oleophobicity to achieve effective separation for both immiscible oil–water mixtures and oil-in-water microemulsions solely driven by gravity. These new membranes having a good mechanical strength of 14 MPa and mean pore sizes between 1.5 and 2.6 μm have shown a very high flux rate of 10 975 L m−2 h−1 with extremely high separation efficiency (the residual oil content in filtrate is 26 ppm). More importantly, the membranes exhibit high separation capacity, which can separate 10 L of an oil–water mixture continuously without a decline in flux, and excellent antifouling properties for long term use, thus making them important candidates for treating wastewater produced in industry and daily life. Such membranes are also ideal for high viscosity oil purification such as purification of crude oil.

Antimicrobial activity of carboxymethyl chitosan/polyethylene oxide nanofibers embedded silver nanoparticles

A facile method to synthesize silver nanoparticles (AgNPs) using carboxymethyl chitosan (CMCTS), which act as reducing agent for silver ions as well as protecting agent for the formed AgNPs, is reported. CMCTS embedded AgNPs are mixed with polyethylene oxide (PEO). The blend polymers containing AgNPs are electrospun resulting in blend nano-fiber mats. The formation of AgNPs has been confirmed using UV-vis and TEM. The diameter range of 12-18 nm of well-dispersed AgNPs with a concentration of 100 ppm was obtained. The electrospun mats are characterized using SEM, EDX as well as TGA. Antimicrobial activity against different species of pathogenic/nonpathogenic; Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922 in addition to the fungus Candida albicans ATCC 10231 was studied. The results show excellent antimicrobial activity compared with nanofibers without AgNPs and AgNPs alone.

Sandwich-structured PVdF/PMIA/PVdF nanofibrous separators with robust mechanical strength and thermal stability for lithium ion batteries

Novel, sandwich-structured PVdF/PMIA/PVdF nanofibrous battery separators with robust mechanical strength and thermal stability are fabricated via a sequential electrospinning technique. The nanofibers of the PVdF and the PMIA layers are bonded and interconnected on the interface boundary without any polymer binder or post-treatment. Benefiting from the high porosity of the as-prepared membranes and the introduction of PMIA, the PVdF/PMIA/PVdF composite membranes exhibit high ionic conductivity (2.3 times higher than that of the Celgard membrane), robust tensile strength (13.96 MPa), and excellent thermal stability, sustaining insulation after closing the pores in the PVdF layer. Hot oven testing reveals that the composite membranes exhibit no dimension shrinkage after being exposed to 180 °C for 1 h. Furthermore, the as-prepared-membrane-based Li/LiCoO2 cell shows a higher capacity retention of 93.10% after 100 cycles and better rate performance compared with the cell using the Celgard membrane, providing new insight into the design and development of high-performance rechargeable lithium ion batteries.