References of "Aqil, Abdelhafid"
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See detailNitroaldol condensation catalyzed by topologically modulable cooperative acid–base chitosan–TiO2 hybrid materials
Aqil, Abdelhafid ULg; El Kadib, Abdelkrim; Aqil, Mohamed ULg et al

in RSC Advances (2014), 4(63), 33360-33363

Chitosan–TiO2 shaped as macroporous aerogels, lamellar cryogels or electrospun films act synergistically as acid–base bifunctional catalysts. Depending on the topology of the material, a marked difference ... [more ▼]

Chitosan–TiO2 shaped as macroporous aerogels, lamellar cryogels or electrospun films act synergistically as acid–base bifunctional catalysts. Depending on the topology of the material, a marked difference in the selectivity for nitroaldol condensation is observed. [less ▲]

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See detailHigh-quality thin graphene films from fast electrochemical exfoliation
Aqil, Abdelhafid ULg; Ouhib, Farid ULg; Detrembleur, Christophe ULg et al

Poster (2013, November)

Many methods have been developed in the last few decades to obtain high-quality graphene thin sheets. They are based on very different physicochemical processes. Here we demonstrate a novel one step and ... [more ▼]

Many methods have been developed in the last few decades to obtain high-quality graphene thin sheets. They are based on very different physicochemical processes. Here we demonstrate a novel one step and simple electrografting acrylate monomer method to exfoliate highly oriented pyrolytic graphite (HOPG) into thin nanoplatelets and even down to the single graphene sheet level. Among the high research activity in the area of surface modification, electrografting is a very powerful method which has received comparatively little attention. This is surprising because this technique has many attractive features for modification of conducting or semi-conducting surfaces. The main interest of the electrografting process is to solve the recurrent problem of the organic/substrates interface weakness. The electrografting warranties a robust polymer/substrates interface and offers the possibility to tailor the functionality of the grafted polymer film opening the door to a wide range of demanding technological applications. The graphene sheets obtained through electrografting process give a stable suspension in dimethyl formamide (DMF), and they can self-precipitate on the surface of substrates after adding water as an antisolvent due to their strong surface hydrophobicity. Interestingly, the continuous films obtained exhibit ultratransparency (∼98% transmittance), and the lateral size of the exfoliated graphene sheets observed by AFM ~1nm. Raman and TEM characterizations corroborate that the graphene sheets exfoliated by our electrochemical method preserve the intrinsic structure of grapheme and give preferentially monolayered graphene sheets. The electrochemical behaviour of the acrylate monomer grafted graphene sheets was evaluated in lithium-half cells with no addition of conductive additive or binder. The PAN grafted graphene dispersed in DMF was coated on Cu foil and dried in a vacuum oven at 55°C for 12h. After 200 cycles, the reversible capacity was still kept at 300mAh/g at the current density of 50mA/g. These results indicate that the prepared high quality graphene sheets possess good electrochemical performances for lithium storage. This work provides an efficient approach to obtain high-quality, cost-effective, and scalable production of “graphene ink”, which may pave a way toward future applications in lithium- ion batteries. [less ▲]

Detailed reference viewed: 292 (5 ULg)
See detailNovel and simple electrografting monomer method to exfoliate HOPG for lithium-ion batteries
Aqil, Abdelhafid ULg; Ouhib, Farid ULg; Jérôme, Christine ULg et al

Conference (2013, October 28)

Many methods have been developed in the last few decades to obtain high-quality graphene thin sheets. They are based on very different physicochemical processes. Here we demonstrate a novel one step and ... [more ▼]

Many methods have been developed in the last few decades to obtain high-quality graphene thin sheets. They are based on very different physicochemical processes. Here we demonstrate a novel one step and simple electrografting acrylate monomer method to exfoliate highly oriented pyrolytic graphite (HOPG) into thin nanoplatelets and even down to the single graphene sheet level. Among the high research activity in the area of surface modification, electrografting is a very powerful method which has received comparatively little attention. This is surprising because this technique has many attractive features for modification of conducting or semi-conducting surfaces. The main interest of the electrografting process is to solve the recurrent problem of the organic/substrates interface weakness. The electrografting warranties a robust polymer/substrates interface and offers the possibility to tailor the functionality of the grafted polymer film opening the door to a wide range of demanding technological applications. The graphene sheets obtained through electrografting process give a stable suspension in dimethyl formamide (DMF), and they can self-precipitate on the surface of substrates after adding water as an antisolvent due to their strong surface hydrophobicity. Interestingly, the continuous films obtained exhibit ultratransparency (∼98% transmittance), and the lateral size of the exfoliated graphene sheets observed by AFM ~1nm. Raman and TEM characterizations corroborate that the graphene sheets exfoliated by our electrochemical method preserve the intrinsic structure of grapheme and give preferentially monolayered graphene sheets. The electrochemical behaviour of the acrylate monomer grafted graphene sheets was evaluated in lithium-half cells with no addition of conductive additive or binder. The PAN grafted graphene dispersed in DMF was coated on Cu foil and dried in a vacuum oven at 55°C for 12h. After 200 cycles, the reversible capacity was still kept at 300mAh/g at the current density of 50mA/g. These results indicate that the prepared high quality graphene sheets possess good electrochemical performances for lithium storage. This work provides an efficient approach to obtain high-quality, cost-effective, and scalable production of “graphene ink”, which may pave a way toward future applications in lithium- ion batteries. [less ▲]

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See detailElectrospinning for tissue engineering
Aqil, Abdelhafid ULg; Jérôme, Christine ULg

Conference (2013, May 22)

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See detailPhysicochemical properties of pH-controlled polyion complex (PIC) micelles of poly(acrylic acid)-based double hydrophilic block copolymers and various polyamines
Warnant, Jérôme; Marcotte, N.; Reboul, J. et al

in Analytical and Bioanalytical Chemistry (2012), 403

The physicochemical properties of polyion complex (PIC) micelles were investigated in order to characterize the cores constituted of electrostatic complexes of two oppositely charged polyelectrolytes. The ... [more ▼]

The physicochemical properties of polyion complex (PIC) micelles were investigated in order to characterize the cores constituted of electrostatic complexes of two oppositely charged polyelectrolytes. The pH-sensitive micelles were obtained with double hydrophilic block copolymers containing a poly(acrylic acid) block linked to a modified poly(ethylene oxide) block and various polyamines (polylysine, linear and branched polyethyleneimine, polyvinylpyridine, and polyallylamine). The pH range of micellization in which both components are ionized was determined for each polyamine. The resulting PIC micelles were characterized using dynamic light scattering and smallangle X-ray scattering experiments (SAXS). The PIC micelles presented a core–corona nanostructure with variable polymer density contrasts between the core and the corona, as revealed by the analysis of the SAXS curves. It was shown that PIC micelle cores constituted by polyacrylate chains and polyamines were more or less dense depending on the nature of the polyamine. It was also determined that the density of the cores of the PIC micelles depended strongly on the nature of the polyamine. These homogeneous cores were surrounded by a large hairy corona of hydrated polyethylene oxide block chains. Auramine O (AO) was successfully entrapped in the PIC micelles, and its fluorescence properties were used to get more insight on the core properties. Fluorescence data confirmed that the cores of such micelles are quite compact and that their microviscosity depended on the nature of the polyamine. The results obtained on these core–shell micelles allow contemplating a wide range of applications in which the AO probe would be replaced by various cationic drugs or other similarly charged species to form drug nanocarriers or new functional nanodevices. [less ▲]

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See detailChitosan-based biomimetic scaffolds and methods for preparing the same
Filée, Patrick; Freichels, Astrid ULg; Jérôme, Christine ULg et al

Patent (2011)

The invention concerns chitosan-based biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and ... [more ▼]

The invention concerns chitosan-based biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the present invention relates to a layered chitosan-based scaffold wherein said layered scaffold comprises at least two fused layers, wherein at least one layer consists of a chitosan nanofiber scaffold membrane and at least one of the other layers of a porous chitosan scaffold support layer. Moreover, the present invention provides a layered chitosan-based scaffold characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water or other solvents and a process for the preparation of such layered chitosan-based scaffold.Finally, the present invention provides the use of the layered electrospun chitosan-based scaffold of the invention or the layered electrospun chitosan-based scaffold produced by the process of the invention as a wound dressing, in tissue engineering or for biomedical applications. [less ▲]

Detailed reference viewed: 74 (13 ULg)
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See detailChitosan-based biomimetic scaffolds and methods for preparing the same
Filée, Patrice; Freichels, Astrid ULg; Jérôme, Christine ULg et al

Patent (2011)

The invention concerns chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and ... [more ▼]

The invention concerns chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the present invention relates to a layered chitosan scaffold wherein said layered scaffold comprises at least two fused layers, wherein at least one of the fused layers comprises a chitosan nanofiber membrane and the other fused layer comprises a porous chitosan support layer. Moreover, the present invention provides a layered chitosan scaffold characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water or other solvents and a process for the preparation of such layered chitosan scaffold. Finally, the present invention provides the use of the layered electrospun chitosan scaffold of the invention or the layered electrospun chitosan scaffold produced by the process of the invention as a wound dressing, in tissue engineering or for biomedical applications. [less ▲]

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See detailCharged poly(D,L-lactide) nanofibers: towards customized surface properties
Croisier, Florence ULg; Aqil, Abdelhafid ULg; Malherbe, Cédric ULg et al

in Macromolecular Symposia (2011), 309/310(1), 20-27

Surface-charged nanofibers were prepared by electrospinning technique (ESP). For this purpose, a copolymer bearing carboxylic acid functions was added to a poly(D,L-lactide) solution just before ESP ... [more ▼]

Surface-charged nanofibers were prepared by electrospinning technique (ESP). For this purpose, a copolymer bearing carboxylic acid functions was added to a poly(D,L-lactide) solution just before ESP process. In a basic medium, negative charges were therefore revealed on fiber surface. By deposition of positively charged particles or polyelectrolytes, surface properties of the fibers could be tailor-made for a specific application. This versatile method can, for example, be applied to the preparation of new biomedical scaffolds. [less ▲]

Detailed reference viewed: 90 (20 ULg)
See detailDevelopment of electrospun chitosan scaffold for wound dressing application
Aqil, Abdelhafid ULg; Tchemtchoua, Victor; Colige, Alain ULg et al

Poster (2011, November 28)

Wound dressing is one of the most promising medical applications for chitosan, due to its adhesive nature, together with some biological properties including bacteriostatic and fungistatic properties that ... [more ▼]

Wound dressing is one of the most promising medical applications for chitosan, due to its adhesive nature, together with some biological properties including bacteriostatic and fungistatic properties that help in faster wound healing. In this work we propose a chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the chitosan scaffold comprising at least two fused layers, wherein the advantage of a first fused layer composed of a chitosan electrospun nanofiber membrane are oxygen-permeability, high porosity, variable pore-size distribution, high surface to volume ratio, and most importantly, morphological similarity to natural extracellular matrix in skin, which promote cell adhesion migration and proliferation. The advantages of a second fused layer comprising a porous chitosan support layer are improving mechanical property, good absorption capacities to remove excess exudates and good water and gas exchange. Moreover, the scaffold was characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water. Finally, the scaffolds have shown tremendous promise as a wound dressing, in tissue engineering. The three main human cell types fibroblasts, endothelial cells and keratinocytes was cultured in vitro on electrospun nanofibers scaffold. Properties of electrospun chitosan scaffold and chitosan sponges obtained by lyophilization were also compared in vivo, in order to evaluate importance of the 3D-architecture of the biomaterial. [less ▲]

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See detailChitosan-based nanofibers for wound dressing
Aqil, Abdelhafid ULg; Tchemtchoua Tateu, Victor ULg; Colige, Alain ULg et al

Poster (2011, May 12)

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See detailEffect of non-ionic surfactant and acidity on chitosan nanofibers with different molecular weights
Ziani, Khalid; Henrist, Catherine ULg; Jerome, Christine et al

in Carbohydrate Polymers (2011), 83(2), 470-476

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See detailDevelopment of a Chitosan Nanofibrillar Scaffold for Skin Repair and Regeneration.
Tchemtchoua Tateu, Victor ULg; Atanasova, G.; Aqil, Abdelhafid ULg et al

in Biomacromolecules (2011), 12

The final goal of the present study was the development of a 3-D chitosan dressing that would shorten the healing time of skin wounds by stimulating migration, invasion, and proliferation of the relevant ... [more ▼]

The final goal of the present study was the development of a 3-D chitosan dressing that would shorten the healing time of skin wounds by stimulating migration, invasion, and proliferation of the relevant cutaneous resident cells. Three-dimensional chitosan nanofibrillar scaffolds produced by electrospinning were compared with evaporated films and freeze-dried sponges for their biological properties. The nanofibrillar structure strongly improved cell adhesion and proliferation in vitro. When implanted in mice, the nanofibrillar scaffold was colonized by mesenchymal cells and blood vessels. Accumulation of collagen fibrils was also observed. In contrast, sponges induced a foreign body granuloma. When used as a dressing covering full-thickness skin wounds in mice, chitosan nanofibrils induced a faster regeneration of both the epidermis and dermis compartments. Altogether our data illustrate the critical importance of the nanofibrillar structure of chitosan devices for their full biocompatibility and demonstrate the significant beneficial effect of chitosan as a wound-healing biomaterial. [less ▲]

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See detailNanostructured silica templated by double hydrophilic block copolymers with a comb-like architecture
Warnant, Jérôme ULg; Reboul, J.; Aqil, Abdelhafid ULg et al

in Powder Technology (2011), 208

An original way to synthesize nanostructured materials is the use of new structuring agents constituted of induced and reversible micelles of Double Hydrophilic Block Copolymers (DHBC). The present paper ... [more ▼]

An original way to synthesize nanostructured materials is the use of new structuring agents constituted of induced and reversible micelles of Double Hydrophilic Block Copolymers (DHBC). The present paper aims at showing that induced micelles can be obtained by complexation between a PAA-b-PAMPEO (DHBC) polymer containing a comb-type neutral block and a polyamine, that the micellization process is reversible as a function of the pH and finally, that the obtained polyion complex micelles can be successfully used in the preparation of well organized mesostructured silica materials. [less ▲]

Detailed reference viewed: 97 (20 ULg)
See detailElectrografting and LbL deposition for the elaboration of antimicrobial coatings
Aqil, Abdelhafid ULg; Cécius, Michaël; Jérôme, Christine ULg

Poster (2010, November 29)

Detailed reference viewed: 15 (2 ULg)
See detailChitosan nanofiber membranes for tissue engineering - synthesis, characterization and properties
Toncheva, Natalia ULg; Aqil, Abdelhafid ULg; Croisier, Florence ULg et al

Poster (2010, November 29)

This poster was presented by Natalia Toncheva

Detailed reference viewed: 57 (4 ULg)
See detailPreparation of cross-linked chitosan-based nanofibers as wound dressing
Aqil, Abdelhafid ULg; Ziani, K.; Tchemtchoua Tateu, Victor ULg et al

Poster (2009, November 18)

Detailed reference viewed: 56 (19 ULg)
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See detailDevelopment of multilayered chitosan-based nanofibers
Croisier, Florence ULg; Aqil, Abdelhafid ULg; Detrembleur, Christophe ULg et al

Poster (2009, June 14)

By combining electrospinning and layer-by-layer deposition techniques, new porous material scaffolds of multilayered, chitosan-based nanofibers were produced. Layer-by-layer (LBL) is a well-known method ... [more ▼]

By combining electrospinning and layer-by-layer deposition techniques, new porous material scaffolds of multilayered, chitosan-based nanofibers were produced. Layer-by-layer (LBL) is a well-known method for surface coating, based on electrostatic interactions. It enables the controllable deposition of a variety of polyelectrolytes including synthetic and natural materials, with designable layer structure, defined layer thickness and size. Electrospinning (ESP) allows the fabrication of polymer fibers ranging from nanometers to a few microns in diameter, depending on the polymer characteristics (a.o. molecular weight, solution viscosity and conductivity) and processing conditions (electric potential, distance between syringe-capillary and collection plate, concentration, flow rate). Mats of nanofibers produced by ESP display a very large surface area-to-volume ratio and high porosity with very small pore size. The nanometric scale of electrospun fibers also proves a positive effect on cellular growth, as fiber mats mimic extracellular matrix structure. The association of these two techniques with the use of biocompatible and biodegradable polymers such as chitosan, gives outstanding prospects in the field of biomedical applications, especially for the preparation of wound dressings, artificial skin or tissue engineering scaffolds. In the present study, a charged copolymer, poly(methylmethacrylate-block-methacrylic acid), was added to a poly(ε-caprolactone) or poly(D,L-lactide) solution before electrospinning in order to prepare surface charged nanofibers. Oppositely charged polyelectrolytes – chitosan and poly(styrene sulfonate) or hyaluronic acid – were then alternately deposited on these aliphatic polyester fiber “cores” using LBL method. The aliphatic polyester core was also removed selectively to confirm the growth of a multilayered shell, obtaining hollow fibers. [less ▲]

Detailed reference viewed: 164 (32 ULg)
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See detailDevelopment of multilayered chitosan-based nanofibers for tissue engineering
Croisier, Florence ULg; Aqil, Abdelhafid ULg; Detrembleur, Christophe ULg et al

Conference (2009, June 13)

By combining electrospinning and layer-by-layer deposition techniques, new porous material scaffolds of multilayered, chitosan-based nanofibers were produced. Layer-by-layer (LBL) is a well-known method ... [more ▼]

By combining electrospinning and layer-by-layer deposition techniques, new porous material scaffolds of multilayered, chitosan-based nanofibers were produced. Layer-by-layer (LBL) is a well-known method for surface coating, based on electrostatic interactions. It enables the controllable deposition of a variety of polyelectrolytes including synthetic and natural materials, with designable layer structure, defined layer thickness and size. Electrospinning (ESP) allows the fabrication of polymer fibers ranging from nanometers to a few microns in diameter, depending on the polymer characteristics (a.o. molecular weight, solution viscosity and conductivity) and processing conditions (electric potential, distance between syringe-capillary and collection plate, concentration, flow rate). Mats of nanofibers produced by ESP display a very large surface area-to-volume ratio and high porosity with very small pore size. The nanometric scale of electrospun fibers also proves a positive effect on cellular growth, as fiber mats mimic extracellular matrix structure. The association of these two techniques with the use of biocompatible and biodegradable polymers such as chitosan, gives outstanding prospects in the field of biomedical applications, especially for the preparation of wound dressings, artificial skin or tissue engineering scaffolds. In the present study, a charged copolymer, poly(methylmethacrylate-block-methacrylic acid), was added to a poly(ε-caprolactone) or poly(D,L-lactide) solution before electrospinning in order to prepare surface charged nanofibers. Oppositely charged polyelectrolytes – chitosan and poly(styrene sulfonate) or hyaluronic acid – were then alternately deposited on these aliphatic polyester fiber “cores” using LBL method. The aliphatic polyester core was also removed selectively to confirm the growth of a multilayered shell, obtaining hollow fibers. [less ▲]

Detailed reference viewed: 170 (22 ULg)