Sherif El-Safty | Waseda University (original) (raw)

Papers by Sherif El-Safty

Journal of Energy Chemistry, 2015

ABSTRACT Immobilizing biocomponents on solid surfaces is a critical step in the development of ne... more ABSTRACT Immobilizing biocomponents on solid surfaces is a critical step in the development of new devices for future biological, medical, and electronic applications. Therefore, numerous integrated films were recently developed by immobilizing different proteins or enzymes on electrode surfaces. In this work, hemeproteins were safely immobilized onto macroporous nickel-based electrodes while maintaining their functionality. Such modified electrodes showed interesting pseudo-capacitive behavior. Among hemeproteins, hemoglobin (Hb) film has a higher electrochemical performance and greater charge/discharge cycling stability than myoglobin (Mb) and cytochrome C (CytC). The heme group in an alkaline medium could induce the formation of superoxides on the electrode surface. These capacitive features of hemeprotein-Ni electrode were related to strong binding sites between hemeproteins and porous Ni electrode, the accumulation of superoxide or radicals on the Ni surface, and facile electron transfer and electrolyte diffusion through the three-dimensional macroporous network. Thus, these new protein-based supercapacitors have potential use in free-standing platform technology for the development of implantable energy-storage devices.

Chemical Communications, 2010

S1.1. Synthesis of organic-inorganic mesoporous hybrid AAM In typical conditions, anhydrous tolue... more S1.1. Synthesis of organic-inorganic mesoporous hybrid AAM In typical conditions, anhydrous toluene (10 ml) solutions containing (3 ml) trymethylchlorosilane (TMCS) and the calcined silica NSs hybrid AAM were refluxed at 80-100 o C for 24 h, under N 2 atmosphere. A 5 ml of dehydrated pyridine was added to the refluxed mixture to remove the resultant Clanions. The total mixture was then refluxed 60 o C for 24 h. The reaction mixture was washed thoroughly with cyclohexane and acetone to remove the unreacted TMCS. Of these grafting techniques, layered surface chemistry was achieved inside the pore channel by means of a series of dense silanization cycles used to graft TMS to the silica NSs grown in the AAM membranes. 29 Si nuclear magnetic resonance (NMR) spectra (Fig. S1 ESI †) of silica and TMS-silica strands show two main

Advanced …, Jan 1, 2008

General design of optical chemical nanosensors is needed to develop efficient sensing systems wit... more General design of optical chemical nanosensors is needed to develop efficient sensing systems with high flexibility, and low capital cost for control recognition of toxic analytes. Here, we designed optical chemical nanosensors for simple, high-speed detection of multiple toxic metal ions. The systematic design of the nanosensors was based on densely patterned chromophores with intrinsic mobility, namely, ''building-blocks'' onto three-dimensional (3D) nanoscale structures. The ability to precisely modify the nanoscale pore surfaces by using a broad range of chromophores that have different molecular sizes and characteristics enables detection of multiple toxic ions. A key feature of this building-blocks design strategy is that the surface functionality and good adsorption characteristics of the fabricated nanosensor arrays enabled the development of ''pool-on-surface'' sensing systems in which high flux of the metal analytes across the probe molecules was achieved without significant kinetic hindrance. Such a sensing design enabled sensitive recognition of metal ions up to sub-picomolar detection limits ($10 À11 mol dm À3 ), for first time, with rapid response time within few seconds. Moreover, because these sensing pools exhibited long-term stability, reversibility and selectivity in detecting most pollutant cations, for example, Cr(VI), Pb(II), Co(II), and Pd(II) ions, they are practical and inexpensive. The key result in our study is that the pool-on-surface design for optical nanosensors exhibited significant ion-selective ability of these target ions from environmental samples and waste disposals.

Chemistry of …, Jan 1, 2008

Large-scale cubic Pm3n silica monoliths (HOM) were fabricated in wormhole and ordered mesostructu... more Large-scale cubic Pm3n silica monoliths (HOM) were fabricated in wormhole and ordered mesostructures and in shape-and size-controlled cage pores by using a simple and fast strategy. The functional use of these 3D HOM monoliths as probe anchoring templates enabled the efficient designs of optical nanosensors. In this regard, the synthesized chromoionophore was physisorbed into the 3D HOM pore surface carriers without potential leaching. Results revealed that the structural features of the HOM monoliths such as ordered and worm-like cage pores substantially influenced the ion-sensing functionality in terms of their probe inclusion capacities, ion-transport diffusion, optical responsive profile, and visual color transition series during the detection of ultratraces of toxic Pb(II) ions. The nanosensors were selective in discriminating trace Pb(II) ions over multicomponent matrix species, with reliable and reproducible detection and quantification limits. A comparative study on the ion-sensing efficiency of the chromoionophore in both solution and solid phases indicated that the solid HOM monoliths show promise as probe templates to design-made nanosensors for the detection of ultratraces Pb(II) ions. Considering the environmental factors, nanosensors were solvent-free systems and had the capacity to serve as ion preconcentrators with complete reversibility and reusability. The significant features of the probe-design nanosensors led to overcoming the disposal problems, which were normally associated with the liquid probe systems.

Advanced Functional …, Jan 1, 2008

The integration of actively-functional receptors into nanoscale networks outperformed competent d... more The integration of actively-functional receptors into nanoscale networks outperformed competent detection devices and other ion-sensing designs. Synthesis of azo chromophores with long hydrophobic tails showed an ecofriendly sensing and an extreme selectivity for divalent mercury analytes. In order to tailor the tip to Hg II ion-sensing functionality, we manipulated the chromophores into nanoscale membrane discs, which led to small, easy-to-use optical sensor strips. The design of these hydrophobic probes into ordered pore-based membranes transformed the ion-sensing systems into smart, stable assemblies and portable laboratory assays. The nanosensor membrane strips with chemical and mechanical stability allowed for reversible, stable and reusable detectors without any structural damage, even under rigorous chemical treatment for several numbers of repeated cycles. The optical membrane strips provided Hg II ion-sensing recognition for both cost-and energy-saving systems. Indeed, the synthetic strips proved to have an efficient ability for various analytical applications, targeting especially for on-site and in situ chemical analyses, and for continuous monitoring of toxic Hg II ions. On the proximity-sensing front, these miniaturized nanomembrane strips can revolutionize the consumer and industrial market with the introduction of the probe surface-mount naked-eye ion-sensor strips.

The Journal of …, Jan 1, 2008

With recent advances in materials science and nanotechnology, development of optical chemosensors... more With recent advances in materials science and nanotechnology, development of optical chemosensors with uniformly shaped three-dimensional (3D) nanostructures applicable for large-scale sensing systems of toxic pollutants can forge new frontiers in materials. Here, highly ordered cubic Fd3m silica monoliths that had nanopore-like cages were fabricated, for the first time, by direct templating of cationic surfactant phases. This simple strategy offered significant control over the pore connectivity and structural regularity of the cubic Fd3m geometry. The potential functionalities of these uniformly sized cage cubic Fd3m materials show promise as the primary component in efficient sensing systems that can satisfy analytical needs as well, such as simplicity in fabrication design and sensing functionality in terms of selectivity and sensitivity with a fast response time of the recognition of pollutant cations. However, successful immobilization of chromophore probe molecules into the 3D network matrixes enabled manipulation of optically defined chemosensors into new shapes and functionality for visual detection of toxic analytes. Here, 3D cubic Fd3m chemosensors were developed and fabricated and successfully enabled highly revisable, selective and sensitive detection of Bi-(III) target ions down to nanomolar concentrations (∼10 -10 mol/dm 3 ) with rapid response assessment (e25 s). Significantly, the HOM nanosensors not only worked under standardized conditions but also could be used for reliable sensing of the Bi(III) ion in a real-life sample such as wastewater.

The Journal of Physical …, Jan 1, 2005

Highly ordered cage and cylindrical mesoporeous silica monoliths (HOM) with 2-and 3-dimensional (... more Highly ordered cage and cylindrical mesoporeous silica monoliths (HOM) with 2-and 3-dimensional (2D and 3D, respectively) structures, mesopore/micropore volumes, and thick-walled frameworks were successfully fabricated by instant direct templating of lyotropic phases of copolymer (EO m -PO n -EO m ) surfactants. Large cage-like pores with uniform constriction sizes up to 10 nm and open cylindrical channel-like mesopores can be easily achieved by this simple and efficient synthesis design. Our results show that the cage-like pores could be fabricated at relatively lower copolymer concentrations used in the lyotropic phase domains at copolymer/TMOS ratios of 35 wt %. These ordered cage pore architectures underwent transition to opencylindrical pores by increasing the copolymer concentration. High EO/PO block copolymers, in general, were crucially affected on the increase of the interior cavity sizes and on the stability of the cage mesopore characters. However, for F108 (EO 141 PO 44 EO 141 ) systems, the fabrication of ordered and stable cage pore monoliths was achieved with significantly higher copolymer concentrations up to 90 wt %. Interestingly, the effective copolymer molecular nature was also observed in the ability to design various ordered mesophase geometries in large domain sizes. Our findings here show evidence that the synthetic strategy provides realistic control over a wide range of mesostructured phase geometries and their extended long-range ordering in the final replicas of the silica monolith frameworks. In addition, the HOM silica monoliths exhibited considerable structural stability against higher thermal temperature (up to 1000°C) and longer hydrothermal treatment times under boiling water and steam. The remarkable structural findings of 3D frameworks, transparent monoliths, and micropores combined with large cage-and cylindrical-like mesopores are expected to find promising uses in materials chemistry.

J. Mater. Chem., Jan 1, 2005

Ordered cubic Fd3m mesoporous silica monoliths (HOM-11) were fabricated by using lyotropic and mi... more Ordered cubic Fd3m mesoporous silica monoliths (HOM-11) were fabricated by using lyotropic and microemulsion phases of block copolymers (EO m -PO n -EO m ) as templates. Aromatic and aliphatic hydrocarbon molecules were used in the formation of true microemulsion liquid crystal phases, in the expansion of pore sizes, and in the changes in the phase geometrical shape. Large cylinder-like pores in the range of 6-11 nm with uniform constrictions and bimodal mesopore sizes can be easily produced (within minutes) by adopting this simple and reproducible strategy. The degree of solubilization of the hydrocarbons crucially influenced the generation of the more open-pore systems with cylindrical cubic Fd3m channels. Our results also show that enlargement of pore sizes of cubic Fd3m monoliths was achieved with the use of a high concentration of copolymers in the composition phase domains, a high degree of swelling and a large size of PO-EO blocks (core-corona) of the copolymer templates. In addition, this synthetic approach is also efficient in designing cubic Fd3m silica monoliths with large-sized glass, thick-walled frameworks up to 30 nm thick and high mesopore/micropore volumes. Although XRD patterns show well-defined Bragg diffraction peaks indicative of highly ordered cubic Fd3m structures, TEM micrographs reveal that worm-like mesopore channels in large domains were observed with samples synthesized from copolymers with small EO-PO block ratios. This finding indicates that the molecular nature (i.e. the flexibility of the corona-and core-blocks) of the copolymer templates not only led to disordered pore channels but also reduced the ability to design more mesostructured phases.

Advanced Materials, Jan 1, 2005

Periodically mesoporous materials with two-and threedimensional (2D and 3D) structures are one of... more Periodically mesoporous materials with two-and threedimensional (2D and 3D) structures are one of the most exciting new developments in materials science and technology in the last decade. Features of these mesoscale architectures include controllable mesopore size (20±300 ) which enable these materials to be promising candidates in applications such as catalysis, separations, sensing, and optical and electronic systems. Since the discovery of the prominent class of the M41S mesoporous family, surfactant-templated synthesis approaches are commonly used to direct the design of materials. [2] The nature of these amphiphiles enable successful fabrication of highly ordered nanoscale structures. [2, The resultant 3D cubic mesoporous materials will find many industrial applications.

Advanced …, Jan 1, 2007

Scheme 1. Systematic design of nanosensors 1-4 by various synthesis protocols based on the immobi... more Scheme 1. Systematic design of nanosensors 1-4 by various synthesis protocols based on the immobilization of TMPyP, DPAP, DTAR, and DPC probes into the 3D cubic Fm3m cage monoliths (HOM-C10). The 3D TEM surface micrograph of cubic Fm3m carriers (HOM-C10) recorded along the [110] zone axis with 45°tilt.

… A European Journal, Jan 1, 2007

Advanced Materials, Jan 1, 2003

Mesoporous silica with large pores varying widely in size and with three-dimensional (3D) archite... more Mesoporous silica with large pores varying widely in size and with three-dimensional (3D) architectures are potential candidates for numerous applications. [1±5] Enlarging the pore size of mesoporous silica materials is an area that is actively researched. However, considerable attention has also been devoted to synthetic strategies for tailoring mesoporous silica dimensions in the 20±500 range through the use of various surfactant molecules, auxiliary chemicals, and synthetic conditions. [6±15] Furthermore, 3D mesoporous structures have been prepared through the phase transition of cylindrical phase assemblies by adding auxiliary molecules at ambient synthesis conditions. [7] The mesoporous silicates produced had an enlarged pore size; however, a loss of long-range order over the array was often observed, as revealed by the less well-resolved X-ray diffraction spectra and the broadening of the high-intensity peaks. In general, powdery mesoporous silica in micrometer-sized particles (1±2 lm) has been obtained; the formation of large, uniform monoliths was limited. [14±19] Furthermore, the utilization of a dilute surfactant in the synthesis of the mesoporous silica severely limited the ability to predict the mesophase topologies, because the primary phase of an amphiphile is affected by the interactions between the surfactant assemblies and the inorganic precursors. [5±7] Sol±gel synthesis of silica in a bulk lyotropic liquid-crystalline phase allows the inorganic precursors to precipitate in the synthesis solution during the solidification (i.e. rational precipitation), thereby allowing fabrication of large monoliths of the desired size and shape. [20±22] The use of a high template concentration (> 30 %) preserves the pre-existence of liquidcrystalline phases prior to solidification of the silica network, and thus allows a high degree of control over the amphiphilic phase domains and morphological organization of the mesopores. However, even in these syntheses, the pore size is limited to a maximum of 40 by the type and composition of the amphiphiles. [20±23] COMMUNICATIONS

Angewandte …, Jan 1, 2006

Chemical sensors are molecular receptors that transform their chemical information into analytica... more Chemical sensors are molecular receptors that transform their chemical information into analytically useful signals upon binding to specific guests. These sensors are attracting attention owing to their potential for easy detection and quantification of the pollutant species in many fields of application, such as waste management, environmental chemistry, clinical toxicology, and bioremediation of radionuclides. Among these, the sensitive detection of heavymetal ions, such as mercury and lead, is critical for monitoring the environment as they are highly toxic and common environmental pollutants. Although instrumental analyses such as atomic absorption or atomic emission spectroscopy are currently used in applications relevant to the detection of toxic metal ions, there is still a need to develop inexpensive and easy methods for the detection of these toxic ions. In view of these sophisticated experimental methods, emphasis is currently being placed on the development of sensor materials for the detection of toxic ions that offer high sensitivity,