Sherif A. El-Safty

Synthesis of Mesoporous NiO Nanosheets for the Detection of Toxic NO2 Gas

one of the most highly toxic gases. Humans inhale low-level concentrations of NO2 ( � 50 ppm), which can cause damage to the lungs, cardiovascular system, and upper respiratory tract. Therefore, the Occupational Safety and Health Administration (US) announced that the permissible exposure for general industries is 5 ppm, and 1 ppm for short-term exposure (15 min). The development of gas sensors for monitoring NO2 is highly important and necessary to protect people from over exposure to such dangerous gases and improve environmental quality. Resistive-type gas sensors have been developed for the detection of toxic gases and explosive gases because of their simple design and fabrication, easy read-out signal, on-line monitoring, and high compatibility with microelectronic processing. [2] Recently, research is focused on the development of sensing materials with new structures or morphologies to improve sensitivity, selectivity, and stability of sensors. [3] The two-dimensional nanostructure materials, such as graphene, ZnO, and SnO2 nanosheets, have been developed for gas sensor applications because they have excellent properties, such as high crystallinity and high specific surface areas; these attributes enhance the sensitivity and stability of sensing devices. [4] On the other hand, the success in the synthesis of ordered mesoporous materials using a liquid-crystal template has opened a new strategy in their development, especially in gas-sensing applications, in which the high specific surface area of materials is required to improve the sensitivity of

A weak-base fibrous anion exchanger effective for rapid phosphate removal from water.

This work investigated that weak-base anion exchange fibers named FVA-c and FVA-f were selectively and rapidly taken up phosphate from water. The chemical structure of both FVA-c and FVA-f was the same; i.e., poly(vinylamine) chains grafted onto polyethylene coated polypropylene fibers. Batch study using FVA-c clarified that this preferred phosphate to chloride, nitrate and sulfate in neutral pH region and an equilibrium capacity of FVA-c for phosphate was from 2.45 to 6.87 mmol/g. Column study using FVA-f made it clear that breakthrough capacities of FVA-f were not strongly affected by flow rates from 150 to 2000 h(-1) as well as phosphate feed concentration from 0.072 to 1.6mM. Under these conditions, breakthrough capacities were from 0.84 to 1.43 mmol/g indicating high kinetic performances. Trace concentration of phosphate was also removed from feeds containing 0.021 and 0.035 mM of phosphate at high feed flow rate of 2500 h(-1), breakthrough capacities were 0.676 and 0.741 mmol/g, respectively. The column study also clarified that chloride and sulfate did not strongly interfere with phosphate uptake even in their presence of equimolar and fivefold molar levels. Adsorbed phosphate on FVA-f was quantitatively eluted with 1M HCl acid and regenerated into hydrochloride form simultaneously for next phosphate adsorption operation. Therefore, FVA-f is able to use long time even under rigorous chemical treatment of multiple regeneration/reuse cycles without any noticeable deterioration.

Efficient adsorbents of nanoporous aluminosilicate monoliths for organic dyes from aqueous solution

Growing public awareness on the potential risk to humans of toxic chemicals in the environment has generated demand for new and improved methods for toxicity assessment and removal, rational means for health risk estimation. With the aim of controlling nanoscale adsorbents for functionality in molecular sieving of organic pollutants, we fabricated cubic Im3m mesocages with uniform entrance and large cavity pores of aluminosilicates as highly promising candidates for the colorimetric monitoring of organic dyes in an aqueous solution. However, a feasible control over engineering of three-dimensional (3D) mesopore cage structures with uniform entrance (~5 nm) and large cavity (~10 nm) allowed the development of nanoadsorbent membranes as a powerful tool for large-quantity and high-speed (in minutes) adsorption/removal of bulk molecules such as organic dyes. Incorporation of high aluminum contents (Si/Al=1) into 3D cubic Im3m cage mesoporous silica monoliths resulted in small, easy-to-use optical adsorbent strips. In such adsorption systems, natural surfaces of active acid sites of aluminosilicate strips strongly induced both physical adsorption of chemically responsive dyes and intraparticle diffusion into cubic Im3m mesocage monoliths. Results likewise indicated that although aluminosilicate strips with low Si/Al ratios exhibit distortion in pore ordering and decrease in surface area and pore volume, enhancement of both molecular converges and intraparticle diffusion onto the network surfaces and into the pore architectures of adsorbent membranes was achieved. Moreover, 3D mesopore cage adsorbents are reversible, offering potential for multiple adsorption assays.

Mesoporous NiO nanoarchitectures for electrochemical energy storage: influence of size, porosity, and morphology

The development of flexible, sustainable, and efficient energy storage has recently attracted considerable attention to satisfy the demand for huge energy and power density and meet future societal and environmental needs. Consequently, numerous studies have focused on the design/development of nanomaterials based on mesoporous architectures to improve energy and power densities. We explored how nanoarchitectures in term of morphology, particle size, surface area, and pore size/distribution define energy and power performance. The large-scale production, low-cost manufacturing, and high-performance of supercapacitors based on the microwave-assisted synthesis of mesoporous nickel oxide nanocrystals (NCs) were presented. Mesoporous NiO in various morphologies including nanoslices (NSs) and nanoplatelets (NPLs), were synthesized. The superior electrochemical performance of mesoporous NiO NPLs is related to their unique morphology, size, and pore size distribution, which enhance the diffusion of hydroxide ions through mesoporous networks, i.e. “superhighways”. These characteristics induce the high capacitance and excellent recyclability of NiO NPLs more than NiO NSs. Moreover, the microwave-assisted synthesis enhanced charge storage and stability compared with those prepared through the hydrothermal approach. This approach demonstrates the potential of free-standing NiO NPL electrodes for developing high-performance pseudocapacitors.

Removal of trace arsenic(V) and phosphate from water by a highly selective ligand exchange adsorbent

A highly selective ligand exchange type adsorbent was developed for the removal of trace arsenic(V) (As(V)) and phosphate from water. This adsorbent was prepared by loading zirconium(IV) on monophosphonic acid resin. This adsorbent was able to remove toxic anions efficiently at wide pH ranges. However, low pH was preferable for maximum breakthrough capacity in an adsorption operation. The effect of a large amount of competing anions such as chloride, bicarbonate, and sulfate on the adsorption systems of As(V) and phosphate anions was investigated. The experimental findings revealed that the As(V) and phosphate uptakes were not affected by these competing anions despite the enhancement of the breakthrough points and total adsorption. Phosphate anion was slightly preferable than As(V) in their competitive adsorption by the adsorbent. The adsorbed As(V) and phosphate on the Zr(IV)-loaded resin were quantitatively eluted with 0.1 mol/L sodium hydroxide solution, and the adsorbent was regenerated by 0.5 mol/L sulfuric acid. During several cycles of adsorption-elution-regeneration operations, no Zr(IV) was detected in the column effluents. Therefore, the Zr(IV)-loaded monophosphonic acid resin is an effective ligand exchange adsorbent for removing trace concentrations of As(V) and phosphate from water.

Large three-dimensional mesocage pores tailoring silica nanotubes as membrane filters: nanofiltration and permeation flux of proteins

Large three-dimensional (3D) mesocage structures that have multidirectional pore networks and uniform openings perpendicular to the longitudinal axis of NTs are of particular interest in terms of their potential. This paper reports on the feasibility of direct control of 3D mesopore cage structures throughout silica nanotubes (NTs) vertically aligned inside Anodic Alumina Membrane (AAM) nanochannels without the use of any organic stabilizing modifiers. This is the first reported study which uses direct synthesis of ordered cubic Im3m mesocage structures inside well-aligned silica-NTs that have open surfaces of top-bottom ends, and multidirectional (3D) mesopore connectivity. These 3D mesocage silica-NT arrays hybrid AAM channels function as nanofilters that can rapidly (in seconds) separate large quantities of proteins. In this nanofiltration assay, three proteins that differ in molecular weight and size such as cytochrome c (CytC), myoglobin (Mb), and hemoglobin (Hb) were used. The prominent factors affecting nanofiltration and permeation flux performance of nanoscale cage membranes are: (i) the concentration of the feed solution of protein (retentate), (ii) molecular sizes and weights of proteins, and (iii) stability of the hierarchical mesocage structures during the filtration and permeation processes. Although the protein nanofiltration efficiency decreased during the reuse cycles of the nanofilter membranes, the proposed nanofilters still exhibited well-controlled molecular-size cut-off after a number of cycles. These mesocage silica-NT-supported membranes are expected to be promising for the development of new generation high-precision, uniform-porosity, and bio-compatible nanofilters with molecular-size cut-off systems.

Optical mesosensors for monitoring and removal of ultra-trace concentration of Zn(II) and Cu(II) ions from water

Optical captor design is necessary for the controlled development of a technique for detecting and removing heavy and toxic metals from drinking water with high flexibility and low capital cost. We designed chemical mesocaptors for optical separation/extraction and monitoring/detection of Cu(II) and Zn(II) ions from water even at trace concentration levels without a preconcentration process. The mesoporous aluminosilica carriers with three-dimensional (3D) structures, high aluminum content, natural surfaces, and active acid sites strongly induced H-bonding and dispersive interactions with organic moieties, thereby leading to the formation of stable captors without chromophore leaching during the removal assays of Cu(II) and Zn(II) ions. Using such a tailored mesocaptor design, the direct immobilization of these hydrophobic ligands (4,5-diamino-6-hydroxy-2-mercaptopyrimidine and diphenylthiocarbazone) into ordered pore-based aluminasilica monoliths enabled the easy generation and transduction of optical colour signals as a response to metal-to-ligand binding events, even at ultra-trace concentrations (~10(-9) mol dm(-3)) of Cu(II) and Zn(II) ions in drinking water, without the need for sophisticated instruments. Theoretical models have been developed to provide insights into the effect of active site surfaces on the enhancement of the optical removal process in terms of long-term stability, reversibility, and selectivity, hence allowing us to understand the role of mesoscopic geometry and nanoscale pore orientation of mesocaptors better. Generally, this ion-capture model enables the development of a simple and effective technique for effective wastewater treatment and management.

Architecture of optical sensor for recognition of multiple toxic metal ions from water.

Here, we designed novel optical sensor based on the wormhole hexagonal mesoporous core/multi-shell silica nanoparticles that enabled the selective recognition and removal of these extremely toxic metals from drinking water. The surface-coating process of a mesoporous core/double-shell silica platforms by several consequence decorations using a cationic surfactant with double alkyl tails (CS-DAT) and then a synthesized dicarboxylate 1,5-diphenyl-3-thiocarbazone (III) signaling probe enabled us to create a unique hierarchical multi-shell sensor. In this design, the high loading capacity and wrapping of the CS-DAT and III organic moieties could be achieved, leading to the formation of silica core with multi-shells that formed from double-silica, CS-DAT, and III dressing layers. In this sensing system, notable changes in color and reflectance intensity of the multi-shelled sensor for Cu(2+), Co(2+), Cd(2+), and Hg(2+) ions, were observed at pH 2, 8, 9.5 and 11.5, respectively. The multi-shelled sensor is added to enable accessibility for continuous monitoring of several different toxic metal ions and efficient multi-ion sensing and removal capabilities with respect to reversibility, selectivity, and signal stability.

Tailor‐Made Micro‐Object Optical Sensor Based on Mesoporous Pellets for Visual Monitoring and Removal of Toxic Metal Ions from Aqueous Media

Methods for the continuous monitoring and removal of ultra-trace levels of toxic inorganic species (e.g., mercury, copper, and cadmium ions) from aqueous media such as drinking water and biological fluids are essential. In this paper, the design and engineering of a simple, pH-dependent, micro-object optical sensor is described based on mesoporous aluminosilica pellets with an adsorbed dressing receptor (a porphyrinic chelating ligand). This tailor-made optical sensor permits ultra-fast (≤ 60 s), specific, pH-dependent visualization and removal of Cu(2+) , Cd(2+) , and Hg(2+) at sub-picomolar concentrations (∼10(-11) mol dm(-3) ) from aqueous media, including drinking water and a suspension of red blood cells. The acidic active acid sites of the pellets consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures densely coated with the chelating ligand. The sensor can be used in batch mode, as well as in a flow-through system in which sampling, target ion recognition and removal, and analysis are integrated in a highly automated and efficient manner. Because the pellets exhibit long-term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be expected to be useful for the fabrication of inexpensive sensor devices for naked-eye detection of toxic pollutants.

Optical Nanosphere Sensor Based on Shell‐By‐Shell Fabrication for Removal of Toxic Metals from Human Blood

Because toxic heavy metals tend to bioaccumulate, they represent a substantial human health hazard. Various methods are used to identify and quantify toxic metals in biological tissues and environment fluids, but a simple, rapid, and inexpensive system has yet to be developed. To reduce the necessity for instrument-dependent analysis, we developed a single, pH-dependent, nanosphere (NS) sensor for naked-eye detection and removal of toxic metal ions from drinking water and physiological systems (i.e., blood). The design platform for the optical NS sensor is composed of double mesoporous core-shell silica NSs fabricated by one-pot, template-guided synthesis with anionic surfactant. The dense shell-by-shell NS construction generated a unique hierarchical NS sensor with a hollow cage interior to enable accessibility for continuous monitoring of several different toxic metal ions and efficient multi-ion sensing and removal capabilities with respect to reversibility, longevity, selectivity, and signal stability. Here, we examined the application of the NS sensor for the removal of toxic metals (e.g., lead ions from a physiological system, such as human blood). The findings show that this sensor design has potential for the rapid screening of blood lead levels so that the effects of lead toxicity can be avoided.