Noureddine Abidi

Wettability and Surface Free Energy of Graphene Films

Graphene sheets were produced through chemical exfoliation of natural graphite flake and hydrazine conversion. Subsequently, graphene sheets were assembled into a thin film, and microscale liquid droplets were placed onto the film surface for measurement of wettability and contact angle. It is found that a graphene oxide sheet is hydrophilic and a graphene sheet is hydrophobic. Isolated graphene layers seem more difficult to wet in comparison to graphite, and low adhesion work was found in the graphene-liquid interface. Approximation of solid-liquid interfacial energy with the equation of state theory was applied to determine the graphene surface energy. The results indicate that surface energy of graphene and graphene oxide is 46.7 and 62.1 mJ/m2, respectively, while natural graphite flake shows a surface free energy of 54.8 mJ/m2 at room temperature. These results will provide valuable guidance for the design and manufacturing of graphene-based biomaterials, medical instruments, structural composites, electronics, and renewable energy devices.

Changes in the cell wall and cellulose content of developing cotton fibers investigated by FTIR spectroscopy.

Fourier transform infrared (FTIR) spectra of cotton fibers harvested at different stages of development were acquired using Universal Attenuated Total Reflectance FTIR (UATR-FTIR). The main goal of the study was to monitor cell wall changes occurring during different phases of cotton fiber development. Two cultivars of Gossypium hirsutum L. were planted in a greenhouse (Texas Marker-1 and TX55). On the day of flowering, individual flowers were tagged and bolls were harvested. From fibers harvested on numerous days between 10 and 56 dpa, the FTIR spectra were acquired using UATR (ZnSe-Diamond crystal) with no special sample preparation. The changes in the FTIR spectra were used to document the timing of the transition between primary and secondary cell wall synthesis. Changes in cellulose during cotton fiber growth and development were identified through changes in numerous vibrations within the spectra. The intensity of the vibration bands at 667 and 897 cm(-1) correlated with percentage of cellulose analyzed chemically.

Functionalization of a cotton fabric surface with titania nanosols: applications for self-cleaning and UV-protection properties.

In this study, cotton fabric was successfully modified by titania nanosols prepared by means of the sol-gel process with tetrabutyl orthotitanate [Ti(OC(4)H(9))(4)] as the active ingredient. The cotton fabric was padded with the nanosol solution, dried at 60 degrees C, and cured at 150 degrees C. Scanning electron microscopy showed the presence of a titania film on the fiber surface. The photocatalytic properties of titania-nanosol-treated cotton fabric were investigated. The results showed that stains of coffee and red wine were successfully decomposed by exposure of the stained fabric to UV radiation. Furthermore, titania-nanosol treatment imparted to the cotton fabric a very good protection against UV radiation. The durability of the treatment was investigated by performing repeated home laundering, and the results showed no effect of laundering on the UV-protection efficiency.

Creation of a Set of Reference Material for Cotton Fiber Maturity Measurements

It was the goal of the authors to create a set of reference cottons for maturity measurements. To achieve this they selected 104 cotton bales representing the two principal cultivated species. The vast majority of the bales originated in the USA, but some foreign-grown cotton bales were also selected (Egypt, Uzbekistan, Pakistan, Cameroon, Syria, Benin, and Australia). A representative sample of approximately 30 kg (70 pounds) was taken from each bale. Each sample was homogenized according to the protocol used by the International Cotton Calibration Standard Committee (ICCSC) to produce reference cottons. Eight sub-samples per bale were taken and a minimum of 500 cross-sections per sub-sample were analyzed. A broad range of average values of fiber perimeter and fiber maturity for the 104 bales were obtained. Evaluation of the mathematical and statistical relationships pertinent to maturity and fineness revealed that four critical criteria for adequate calibration standards were met. Therefore, this population of bales constitutes a good base for the calibration of the indirect measurement instruments for maturity and fineness.

Chemical cationization of cotton fabric for improved dye uptake

Cotton fabric is usually dyed with reactive dyes. During the dyeing process, a large amount of salt is required to achieve higher exhaustion of the dye from the dyebath onto the fiber. Dyeing of cotton with reactive dyes has a substantial environmental impact due to the discharge of a large volume of highly colored and saline effluents. Chemical cationization allows cotton fibers to be dyed without salt by chemically modifying cellulosic macromolecules to introduce positively charged sites. In this study, cotton fabric was cationized using (3-chloro-2-hydroxylpropyl) trimethyl-ammonium chloride (CHPTAC). Dye uptake was assessed using two reactive dyes, CI Reactive Blue 235 and CI Reactive Blue 19. Dye exhaustion kinetics were determined using a Datacolor-HueMetrix Monitor system. Analysis of variance demonstrated significant effects of CHPTAC concentration and exhaustion time on the percent exhaustion. Color strength at the end of the dyeing cycle was significantly higher for cationized fabrics compared to the control fabric. This work shows that treatment of cotton with CHPTAC enhanced dye uptake properties due to the introduction of cationic sites and resulted in superior dyeing without the addition of salt.

Functionalization of Cotton Fabric with Vinyltrimethoxysilane

The surface of cotton fabric was successfully functionalized with vinyltrimethoxysilane in order to impart water repellency and wrinkle recovery and to introduce surface vinyl groups (—CH=CH2) to the fabric, which could then be initiated for copolymerization reactions with various monomers. The introduction of active groups onto the fabric surface was evidenced from the universal attenuated total reflectance Fourier transform infrared (UATR-FTIR) spectrum of the treated fabric. The spectrum shows two peaks located at 1410 and 1600 cm—1 (C=C stretch). An additional peak located at 756 cm—1 attributed to Si—O—Si symmetric stretch was also observed. Excellent water contact angle and wrinkle recovery angle values were obtained.

Polydopamine-Assisted Surface Modification for Bone Biosubstitutes

Polydopamine (PDA) prepared in the form of a layer of polymerized dopamine (DA) in a weak alkaline solution has been used as a versatile biomimetic surface modifier as well as a broadly used immobilizing macromolecule. This review mainly discusses the progress of biomaterial surface modification inspired by the participation of PDA in bone tissue engineering. A comparison between PDA-assisted coating techniques and traditional surface modification applied to bone tissue engineering is first presented. Secondly, the chemical composition and the underlying formation mechanism of PDA coating layer as a unique surface modifier are interpreted and discussed. Furthermore, several typical examples are provided to evidence the importance of PDA-assisted coating techniques in the construction of bone biosubstitutes and the improvement of material biocompatibility. Nowadays, the application of PDA as a superior surface modifier in multifunctional biomaterials is drawing tremendous interests in bone tissue scaffolds to promote the osteointegration for bone regeneration.

Using Fiber Elongation to Improve Genetic Screening in Cotton Breeding Programs

In this study, the bundle elongation and tenacity of cotton fibers were measured using a modified tensile testing instrument to which Pressley clamps (1/8” gage length) were adapted. 32 cotton genotypes with a range of bundle tenacity and elongation were carefully selected based on their distinct physical properties. The work of rupture was calculated from the load vs. elongation curves for each type of cotton. Results demonstrated the importance of fiber bundle elongation in the work of rupture of fiber bundles, which is critically important to processing performance. This study lays a foundation for future efforts to calibrate the high volume instrument elongation measurements and to breed new cultivars with improved work of rupture. This should result in lower fiber breakage when the cotton fibers are submitted to different mechanical stresses (ginning, carding, spinning, and weaving).

Distinct Chiral Nematic Self-Assembling Behavior Caused by Different Size-Unified Cellulose Nanocrystals via a Multistage Separation.

Cellulose nanocrystals (CNCs) are perfect rodlike nanofibers that can self-assemble and form a chiral nematic phase. We found that different self-assembling morphologies could be formed by different size-unified CNCs. This study reported a facile and new approach of fractionating raw (unseparated) CNCs in a wide particle size distribution (9-1700 nm) into a series of narrower size ranges to obtain size-unified CNCs via a well-designed multistage separation process composed of layered filter membranes with different pore size cutoffs followed by a fast pressurized filtration. The smaller size-unified CNCs readily self-assembled into polish chiral nematic phases with larger pitch value as compared to larger size-unified CNCs. Such a distinction among different chiral nematic phases and pitch values as functions of size was addressed by a mathematical evaluation, which suggested that the reduced volume fraction of the anisotropic phase as a function of both increased ionic strength and reduced crystallinity of rigid-rod-like CNCs is a critical factor. In addition, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction results revealed that different size-unified CNCs exhibited particular thermal stabilities and crystallinities even though their chemical and crystalline structures remained unchanged. The discrepancies in physicochemical characteristics and self-assembling chiral nematic behavior among different size-unified CNCs may benefit the specific functionalization of cellulose materials using size-unified fibers instead of raw CNCs containing mixed small and large fibers.

Porous poly(ε-caprolactone) scaffolds for load-bearing tissue regeneration: Solventless fabrication and characterization†

Three-dimensional interconnected porous poly(ε-caprolactone) scaffolds have been prepared by a novel solventless scaffold fabrication approach combining cryomilling and compression molding/porogen leaching techniques. This study investigated the effects of processing parameters on scaffold morphology and properties for tissue regeneration. Specifically, the effects of molding temperature, cryomilling time, and porogen mix were examined. Fifty percentage of porous scaffolds were fabricated with a range of properties: mean pore size from ∼40 to 125 μm, water uptake from ∼50 to 86%, compressive modulus from ∼45 to 84 MPa, and compressive strength at 10% strain from ∼3 to 4 MPa. Addition of 60 wt % NaCl salt resulted in a ∼50% increase in porosity in multimodal pore-size structures that depended on the method of NaCl addition. Water uptake ranged from ∼61 to 197%, compressive modulus from ∼4 to 8.6 MPa, and compressive strength at 10% strain from ∼0.36 to 0.40 MPa. Results suggest that this approach provides a controllable strategy for the design and fabrication of 3D interconnected porous biodegradable scaffolds for load-bearing tissue regeneration.