Compatibilizing effect of halloysite nanotubes in polar-nonpolar hybrid system

The Renaissance of Ferrocene-Based Electrocatalysts: Properties, Synthesis Strategies, and Applications

The fascinating electrochemical properties of the redox-active compound ferrocene have inspired researchers across the globe to develop ferrocene-based electrocatalysts for a wide variety of applications. Advantages including excellent chemical and thermal stability, solubility in organic solvents, a pair of stable redox states, rapid electron transfer, and nontoxic nature improve its utility in various electrochemical applications. The use of ferrocene-based electrocatalysts enables control over the intrinsic properties and electroactive sites at the surface of the electrode to achieve specific electrochemical activities. Ferrocene and its derivatives can function as a potential redox medium that promotes electron transfer rates, thereby enhancing the reaction kinetics and electrochemical responses of the device. The outstanding electrocatalytic activity of ferrocene-based compounds at lower operating potentials enhances the specificity and sensitivity of reactions and also amplifies the response signals. Owing to their versatile redox chemistry and catalytic activities, ferrocene-based electrocatalysts are widely employed in various energy-related systems, molecular machines, and agricultural, biological, medicinal, and sensing applications. This review highlights the importance of ferrocene-based electrocatalysts, with emphasis on their properties, synthesis strategies for obtaining different ferrocene-based compounds, and their electrochemical applications.

Combined Effect of Poly(lactic acid)-Grafted Maleic Anhydride Compatibilizer and Halloysite Nanotubes on Morphology and Properties of Polylactide/Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Blends

Given the global challenge of plastic pollution, the development of new bioplastics to replace conventional polymers has become a priority. It is therefore essential to achieve a balance in the performances of biopolymers in order to improve their commercial availability. In this topic, this study aims to investigate the morphology and properties of poly(lactic acid) (PLA)/ poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) (at a ratio of 75/25 (w/w)) blends reinforced with halloysite nanotubes (HNTs) and compatibilized with poly(lactic acid)-grafted maleic anhydride (PLA-g-MA). HNTs and PLA-g-MA were added to the polymer blend at 5 and 10 wt.%, respectively, and everything was processed via melt compounding. A scanning electron microscopy (SEM) analysis shows that HNTs are preferentially localized in PHBHHx nodules rather than in the PLA matrix due to its higher wettability. When HNTs are combined with PLA-g-MA, a finer and a more homogeneous morphology is observed, resulting in a reduction in the size of PHBHHx nodules. The presence of HNTs in the polymer blend improves the impact strength from 12.7 to 20.9 kJ/mm2. Further, with the addition of PLA-g-MA to PLA/PHBHHX/HNT nanocomposites, the tensile strength, elongation at break, and impact strength all improve significantly, rising from roughly 42 MPa, 14.5%, and 20.9 kJ/mm2 to nearly 46 MPa, 18.2%, and 31.2 kJ/mm2, respectively. This is consistent with the data obtained via dynamic mechanical analysis (DMA). The thermal stability of the compatibilized blend reinforced with HNTs is also improved compared to the non-compatibilized one. Overall, this study highlights the effectiveness of combining HNTs and PLA-g-AM for the properties enhancement of PLA/PHBHHx blends.

Impedimetric detection of 2,4,6-trinitrotoluene using surface-functionalized halloysite nanotubes

Herein, we report the application of amine-surface-functionalized halloysite nanotubes (HAs) as active materials for the quantitative detection of 2,4,6-trinitrotoluene (TNT). The findings indicated that HA could selectively capture TNT via a strong reaction between the amine groups on its surface and the TNT molecules. Plate electrodes were fabricated from HA to evaluate its TNT-sensing capacity by electrochemical impedance spectroscopy. Upon binding with TNT, the proton conductivity on the HA plate electrodes increased linearly with the TNT concentration from 1.0 × 10⁻¹¹ M to 1.0 × 10⁻⁴ M. The HA plate electrodes exhibited good sensitivity with a detection limit of 1.05 × 10⁻¹² M. Subsequently, the cycling measurements of the TNT binding/removal were performed on the HA plate electrode, and the material exhibited high stability, good regenerative ability, and good reversibility without a significant decrease in efficiency. The present work highlights the significant application potential of HAs for the electrochemical detection of TNT.

Amine-surface-functionalized halloysite nanotubes are used for electrochemical sensing TNT.

Antimicrobial Carvacrol-Containing Polypropylene Films: Composition, Structure and Function

Significant research has been directed toward the incorporation of bioactive plant extracts or essential oils (EOs) into polymers to endow the latter with antimicrobial functionality. EOs offer a unique combination of having broad antimicrobial activity from a natural source, generally recognized as safe (GRAS) recognition in the US, and a volatile nature. However, their volatility also presents a major challenge in their incorporation into polymers by conventional high-temperature-processing techniques. Herein, antimicrobial polypropylene (PP) cast films were produced by incorporating carvacrol (a model EO) or carvacrol, loaded into halloysite nanotubes (HNTs), via melt compounding. We studied the composition-structure-property relationships in these systems, focusing on the effect of carvacrol on the composition of the films, the PP crystalline phase and its morphology and the films’ mechanical and antimicrobial properties. For the first time, molecular dynamics simulations were applied to reveal the complex interactions between the components of these carvacrol-containing systems. We show that strong molecular interactions between PP and carvacrol minimize the loss of this highly-volatile EO during high-temperature polymer processing, enabling semi-industrial scale production. The resulting films exhibit outstanding antimicrobial properties against model microorganisms (Escherichia coli and Alternaria alternata). The PP/(HNTs-carvacrol) nanocomposite films, containing the carvacrol-loaded HNTs, display a higher level of crystalline order, superior mechanical properties and prolonged release of carvacrol, in comparison to PP/carvacrol blends. These properties are ascribed to the role of HNTs in these nanocomposites and their effect on the PP matrix and retained carvacrol content.

Influence of clay-nanofiller geometry on the structure and properties of poly(lactic acid)/thermoplastic polyurethane nanocomposites

The complex effect of platy and tubular nanofillers on the performance of a biodegradable multiphase polymer system is presented.