Emad A. Elshehy

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.

Hierarchical inorganic–organic multi-shell nanospheres for intervention and treatment of lead-contaminated blood

The highly toxic properties, bioavailability, and adverse effects of Pb(2+) species on the environment and living organisms necessitate periodic monitoring and removal whenever possible of Pb(2+) concentrations in the environment. In this study, we designed a novel optical multi-shell nanosphere sensor that enables selective recognition, unrestrained accessibility, continuous monitoring, and efficient removal (on the order of minutes) of Pb(2+) ions from water and human blood, i.e., red blood cells (RBCs). The consequent decoration of the mesoporous core/double-shell silica nanospheres through a chemically responsive azo-chromophore with a long hydrophobic tail enabled us to create a unique hierarchical multi-shell sensor. We examined the efficiency of the multi-shell sensor in removing lead ions from the blood to ascertain the potential use of the sensor in medical applications. The lead-induced hemolysis of RBCs in the sensing/capture assay was inhibited by the ability of the hierarchical sensor to remove lead ions from blood. The results suggest the higher flux and diffusion of Pb(2+) ions into the mesopores of the core/multi-shell sensor than into the RBC membranes. These findings indicate that the sensor could be used in the prevention of health risks associated with elevated blood lead levels such as anemia.

Optical mesoscopic membrane sensor layouts for water-free and blood-free toxicants

Advances in fabrication of mesoscopic membrane sensors with unique structures and morphologies inside anodic alumina membrane (AAM) nanochannels have led to the development of various methods for detecting, visualizing, adsorbing, filtering, and recovering ultra-trace concentrations of toxic metal ions, such as Hg2+ and Pb2+, in water and blood. These often “one-pot” screening methods offer advantages over conventional methods in that they do not require sophisticated instruments or laborious sample preparation. In the present study, we fabricated two mesoscopic membrane sensors for naked-eye detection, recognition, filtration, and recovery of Hg2+ and Pb2+ in biological and environmental samples. These sensors were characterized by the dense immobilization of organic colorants on the mesopore surfaces of silica nanotubes that were constructed using the nanochannels of an AAM as a scaffold. We confirmed that the nanotubes were oriented along the long axis of the AAM nanochannels, open at both ends, and completely and uniformly filled with organic colorants; also, the dense immobilization of the organic colorants did not affect the speed of ion-to-ligand binding events. We used simple, desk-top, flow-through assays to assess the suitability of the developed membrane sensors for detection, removal, and filtration of Hg2+ and Pb2+ with respect to recyclability and continuous monitoring. Removal of the target ions from biological fluids was assessed by means of flow cytometric analysis. Our results demonstrate the potential of our membrane sensors to be used for preventing the health risks associated with exposure to toxic metal ions in the environment and blood.

Photo-induced recovery, optical detection, and separation of noxious SeO32− using a mesoporous nanotube hybrid membrane

A macroscopic-scale disc-like membrane capable of photo-induced recovery, optical detection, and separation of ultra-trace levels of SeO32− was fabricated using a mesoporous TiO2–SiO2 nanotube (TSN)–porous anodic alumina (PAA) hybrid. The synergistic pressure-assisted filling and condensed formation of TSN inside the entire PAA (200 nm channel neck size and 60 μm longitudinal length) were evident. This approach enabled fabrication of an optical, photo-induced macroscopic membrane sensor (MS) by direct embedding of an organic colorant onto the long and mesoporous TSN/PAA channels. The TSN-MS structure of uniformly aligned, long, interconnected, tubular and nano-sized channel-like pores integrated the control patterns of photo-induced SeO32− recovery/extraction through surface chelation. As a result, a stable and recyclable TSN-MS against long-term exposure to UV light (for several days) is produced. MS functionality in terms of optical detection and selective separation (i.e., rejection and permeation) of toxic SeO32− among a group of interferent ions was assessed using a simple desktop filtration technique. The developed TSN-MS holds promise for use in advanced indoor and outdoor recovery, detection, and separation of SeO32− from aquatic sources in a one-step process. Our findings expand efforts for the environmental approach for production of SeO32−-free water, photo-hazardous SeO32− collection and management, and volume reduction of solution or solid wastes after multi-cyclic remediation.

Nanomembrane Canister Architectures for the Visualization and Filtration of Oxyanion Toxins with One-Step Processing.

Nanomembrane canister-like architectures were fabricated by using hexagonal mesocylinder-shaped aluminosilica nanotubes (MNTs)-porous anodic alumina (PAA) hybrid nanochannels. The engineering pattern of the MNTs inside a 60 μm-long membrane channel enabled the creation of unique canister-like channel necks and cavities. The open-tubular canister architecture design provides controllable, reproducible, and one-step processing patterns of visual detection and rejection/permeation of oxyanion toxins such as selenite (SeO3(2-)) in aquatic environments (i.e., in ground and river water sources) in the Ibaraki Prefecture of Japan. The decoration of organic ligand moieties such as omega chrome black blue (OCG) into inorganic Al2O3@tubular SiO2/Al2O3 canister membrane channel cavities led to the fabrication of an optical nanomembrane sensor (ONS). The OCG ligand was not leached from the canister as observed in washing, sensing, and recovery assays of selenite anions in solution, which enabled its multiple reuse. The ONS makes a variety of alternate processing analyses of selective quantification, visual detection, rejection/permeation, and recovery of toxic selenite quick and simple without using complex instrumentation. Under optimal conditions, the ONS canister exhibited a high selectivity toward selenite anions relative to other ions and a low-level detection limit of 0.0093 μM. Real analytical data showed that approximately 96% of SeO3(2-) anions can be recovered from aquatic and wastewater samples. The ONS canister holds potential for field recovery applications of toxic selenite anions from water.

Detection and recovery of palladium, gold and cobalt metals from the urban mine using novel sensors/adsorbents designated with nanoscale wagon- wheel-shaped pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobaltmetals.