Ala’a F. Eftaiha

Recent advances of non-fullerene, small molecular acceptors for solution processed bulk heterojunction solar cells

Organic, planar, and electron deficient small molecules were utilized as acceptors in the first reported bilayer heterojunction solar cells, however, current state-of-the-art organic photovoltaic (OPV) cells utilize fullerene derivatives as acceptor molecules. Recently, intensive efforts have been directed towards the development and understanding of soluble, non-fullerene, organic small molecules to fabricate bulk heterojunction (BHJ) solar cells. These efforts have been aimed at overcoming the inherent limitations of fullerene compounds such as the limited spectral breadth, air instability, and the typically higher production costs of fullerenes. In this focused review, we have highlighted the most recent progress over the last couple of years towards developing n-type organic small molecules utilized in BHJ devices in order to provide insight towards improving the overall performance of OPVs.

A Novel Superdisintegrating Agent Made from Physically Modified Chitosan with Silicon Dioxide

Disintegrants and fillers represent important excipients for immediate-release solid dosage forms in many pharmaceutical applications. A new excipient based on the coprecipitation of chitosan and silica has been achieved. The “intimate” physical association between chitosan and silica creates an insoluble, hydrophilic, highly absorbent material, consequently, resulting in superiority in water uptake, water saturation for gelling formation, and compactability among other superdisintegrants. The new excipient has an outstanding functionality that does not primarily depend on water wicking and swelling properties. In fact, it translates it into superior disintegration characteristics with improved powder flow and compaction properties. Thus, the new excipient could act as a superdisintegrant and pharmaceutical filler at the same time. Studies have shown that chitosan–silica delivers superior performance in wet granulation formulations and is the only disintegrant that is effective at all concentrations in tablet formulation.

Phthalimide–thiophene-based conjugated organic small molecules with high electron mobility

A series of low-cost phthalimide end-capped oligothiophene small molecules with variations to the terminal alkyl chain and number of thiophene units in the conjugated core have been synthesized and investigated. All molecules exhibit H-aggregation in the solid-state but different crystal structures and electronic properties, showing that subtle chemical modifications can result in dramatic changes to molecular self-assembly. Field-effect transistors display high electron mobilities of up to 0.2 cm2 V−1 s−1.

Bioadhesive Controlled Metronidazole Release Matrix Based on Chitosan and Xanthan Gum

Metronidazole, a common antibacterial drug, was incorporated into a hydrophilic polymer matrix composed of chitosan xanthan gum mixture. Hydrogel formation of this binary chitosan-xanthan gum combination was tested for its ability to control the release of metronidazole as a drug model. This preparation (MZ-CR) was characterized by in vitro, ex vivo bioadhesion and in vivo bioavailability study. For comparison purposes a commercial extended release formulation of metronidazole (CMZ) was used as a reference. The in vitro drug-release profiles of metronidazole preparation and CMZ were similar in 0.1 M HCl and phosphate buffer pH 6.8. Moreover, metronidazole preparation and CMZ showed a similar detachment force to sheep stomach mucosa, while the bioadhesion of the metronidazole preparation was higher three times than CMZ to sheep duodenum. The results of in vivo study indicated that the absorption of metronidazole from the preparation was faster than that of CMZ. Also, MZ-CR leads to higher metronidazole Cmax and AUC relative to that of the CMZ. This increase in bioavailability might be explained by the bioadhesion of the preparation at the upper part of the small intestine that could result in an increase in the overall intestinal transit time. As a conclusion, formulating chitosan-xanthan gum mixture as a hydrophilic polymer matrix resulted in a superior pharmacokinetic parameters translated by better rate and extent of absorption of metronidazole.

The influence of salinity on surfactant miscibility in mixed dipalmitoylphosphatidylcholine-perfluorooctadecanoic acid monolayer films.

The miscibility, mechanical and morphological properties of mixed Langmuir and Langmuir-Blodgett monolayers prepared from the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and the perfluorinated fatty acid perfluorooctadecanoic acid have been studied as a function of film composition and subphase salinity. It was demonstrated here, for the first time, that the extent of surfactant miscibility in mixed phospholipid-perfluoroacid monolayers, and hence the resulting mechanical properties of the monolayer film, can be controlled by altering the concentration of sodium ions in the underlying subphase. Elevated Na(+) concentrations resulted in lower net attractive interactions between film components, likely through specific ion adsorption to the negatively-charged perfluoroacid, along with decreased film elasticities. These results differ significantly from conventional fatty-acid-carboxylate monolayer systems in which film cohesion is typically enhanced through adsorption of cations to surfactant headgroups. Atomic force microscope images of films deposited onto solid mica substrates revealed that the films deposited from pure water formed multimolecular aggregates of surfactant, which could be attributed to the highly cohesive nature of the films, but the use of salt in the subphase diminished aggregate formation and resulted in the production of homogeneous monolayer films.

Influence of Film Composition on the Morphology, Mechanical Properties, and Surfactant Recovery of Phase-Separated Phospholipid-Perfluorinated Fatty Acid Mixed Monolayers

Monolayer surfactant films composed of a mixture of phospholipids and perfluorinated (or partially fluorinated) surfactants are of potential utility for applications in pulmonary lung surfactant-based therapies. As a simple, minimal model of such a lung surfactant system, binary mixed monolayer films composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and perfluorooctadecanoic acid (C18F) prepared on a simplified lung fluid mimic subphase (pH 7.4, 150 mM NaCl) have been characterized in terms of mixing thermodynamics and compressibility (measured through π–A compression isotherms), film morphology (via atomic force, fluorescence, and Brewster angle microscopy), as well as spreading rate and hysteresis response to repeated expansion–contraction cycles for a variety of compositions of mixed films. Under all mixing conditions, films and their components were found to be completely immiscible and phase-separated, though there were significant changes in the aforementioned film properties as a function of composition. Of particular note was the existence of a maximum in the extent of immiscibility (characterized by ΔG(ex)(π) values) and enhanced surfactant recovery during hysteresis experiments at χ(C18F) ≥ 0.30. The latter was attributed to the relatively rapid respreading rate of the perfluorinated amphiphile in comparison with DPPC alone at the air–water interface, which enhances the performance of this mixture as a potential pulmonary lung surfactant. Further, monolayer film structure could be tracked dynamically as a function of compression at the air–water interface via Brewster angle microscopy, with the C18F component being preferentially squeezed out of the film with compression, but returning rapidly upon re-expansion. In general, addition of C18F to DPPC monolayers resulted in improvements to mechanical, structural, and respreading properties of the film, indicating the potential value of these compounds as additives to pulmonary lung surfactant formulations.

Chitin-acetate/DMSO as a supramolecular green CO2-phile

The supramolecular chemisorption of CO2 by the oligomeric chitin-acetate (CA) in DMSO as a green solvent offers a novel eco-friendly approach for CO2 capture. Since the amino groups in the sorbent material are blocked either by protonation or acetylation, the multi-armed hydroxyl based oligosaccharide captures CO2 through the formation of an organic carbonate species as confirmed by 13C NMR, in situ ATR-FTIR spectroscopy and conductivity. DFT calculations verified the formation of the CA-CO2 adduct, in which the organic carbonate group is stabilized through supramolecular ionic interaction and hydrogen bonding with the neighboring ammonium ion and hydroxyl functional group along the oligomer backbone. The use of other polar aprotic solvents (N,N-dimethylformamide (DMF), acetonitrile, and acetone) was not successful due to solubility issues.

Factors Involved in Formulation of Oily Delivery System for Proteins Based on PEG-8 Caprylic/Capric Glycerides and Polyglyceryl-6 Dioleate in a Mixture of Oleic Acid with Chitosan

Systematic experimental work is required to improve knowledge related to the use of oily delivery systems. This work aimed to examine the influence of different molecular weights chitosan on formation and solubilization ability of w/o system of Labrasol, Plurol Oleique, water and oleic acid. Phase diagrams were constructed. Size measurements were performed for each surfactant in oleic acid. Interfacial tension of chitosan was measured between oleic acid and water at pH 1.5 and 6.25. Effect of chitosan on microemulsion size was studied. When used to deliver rh-insulin to diabetic rats, the mixture showed reduction in blood glucose compared to control.

Phase-separated surfactant monolayers: Exploiting immiscibility of fluorocarbons and hydrocarbons to pattern interfaces

The mutual immiscibility of hydrogenated and fluorinated surfactants at interfaces frequently leads to phase-separation, which provides a useful and flexible method for patterning air-water and solid-air interfaces. In this article, we review recent advances in the use of hydrogenated-fluorinated surfactant mixtures to achieve interfacial patterning. For even relatively simple systems comprised of binary mixed monolayers of hydrogenated and perfluorinated fatty acids, a diverse range of film morphologies can be generated at the air-water interface and successfully transferred onto solid substrates. Systematic investigations reported over the past several years have allowed for correlation between the chemical structure of the film constituents with the gross film morphology and underlying crystalline structure of the films. Early thermodynamic models based on the interplay between dipole-dipole repulsion forces between charged headgroups balanced by line tension between phases that were formulated to describe phase-behavior in simple phospholipid monolayer systems have proven highly useful to describe morphologies for the immiscible surfactant blends. Beyond simple binary fatty acid mixtures, highly-structured films have also been reported in mixed phospholipid systems, which have found important application in controlling the physical, compositional and performance properties of lung surfactant mixtures, as well as in semifluorinated alkane monolayers which form unique, hemimicellar structures at both liquid and solid interfaces. We also describe advances in using these approaches to pattern photopolymerizable, luminescent surfactants, which have found extensive use in colorimetric and fluorometric sensing devices. The long-term outlook for this field, with an emphasis on potential applications and future research directions are discussed.

Bis-tris propane in DMSO as a wet scrubbing agent: carbamic acid as a sequestered CO2 species

CO2 capture is a hot topic that needs to be addressed by several disciplines, to integrate the structure–activity relationships of sorbents with industrial processes and to augment individual developments into an international collaborative effort. Herein, we suggest a new model compound 1,3-bis[tris(hydroxymethyl)-methylamino]propane (BTP) dissolved in DMSO as a new wet scrubbing agent. The sequestered species was found to be a carbamic acid dimer, as verified using ex situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy with the emergence of a peak at 1722 cm−1, together with nuclear magnetic resonance (NMR) spectroscopy with a 13C NMR chemical shift at 157.2 ppm. The formation of carbamic acid rather than carbamate was further elucidated using 1H/13C NMR correlation spectra, with coupled cross-peaks at 3.70 ppm together with peaks at 60.3 and 157.2 ppm. Furthermore, the sorbent reusability was proven by bubbling N2 gas with a molar CO2 loading capacity of 0.91 as measured by using an in situ ATR-FTIR autoclave. 13C NMR measurements indicated that the formation of the product was kinetically, rather than thermodynamically, controlled. Tris(hydroxymethyl)aminomethane (TRIS) and 1,3-diaminopropane (DAP) were also investigated as sub-structural model units for BTP. The proposed mechanisms were studied theoretically using density functional theory (DFT).