Preparation of hollow iron/halloysite nanocomposites with enhanced electromagnetic performances

Natural Nano-Minerals (NNMs): Conception, Classification and Their Biomedical Composites

Natural nano-minerals (NNMs) are minerals that are derived from nature with a size of less than 100 nm in at least one dimension in size. NNMs have a number of excellent properties due to their unique nanostructure and have been applied in various fields in recent years. They are rising stars in various disciplines, such as materials, biomedicine, and chemistry, taking advantage of their huge surface area, multiple active sites, excellent adsorption capacity, large quantity, low cost, and nontoxicity, etc. To provide a more comprehensive overview of NNMs and the biomedical applications of NNMs-based nanocomposites, this review classifies NNMs into three types by dimension, lists the structure and properties of typical NNMs, and illustrates their biomedical applications. Furthermore, a novel concept of natural nanomineral medical materials (NNMMs) is proposed, focusing on the medical value of NNMs. In addition, this review attempts to address the current challenges and delineate future directions for the advancement of NNMs. With the deepening of biomedical applications, it is believed that NNMMMs will inevitably play an important role in the field of human health and contribute to its promotion.

Effective Solid Phase Extraction of Toxic Pyrrolizidine Alkaloids from Honey with Reusable Organosilyl-Sulfonated Halloysite Nanotubes

Pyrrolizidine alkaloids are plant secondary metabolites that have recently attracted attention as toxic contaminants in various foods and feeds as they are often harvested by accident. Furthermore, they prove themselves as hard to analyze due to their wide structural range and low concentration levels. However, even low concentrations show toxic behavior in the form of chronic liver diseases and possible carcinogenicity. Since sample preparation for this compound group is in need of more green and sustainable alternatives, modified halloysite nanotubes present an interesting approach. Based on the successful use of sulfonated halloysite nanotubes as inexpensive, easy-to-produce cation exchangers for solid phase extraction in our last work, this study deals with the further modification of the raw nanotubes and their performance in the solid phase extraction of pyrrolizidine alkaloids. Conducting already published syntheses of two organosilyl-sulfonated halloysite nanotubes, namely HNT-PhSO3H and HNT-MPTMS-SO3H, both materials were used as novel materials in solid phase extraction. After the optimization of the extraction protocol, extractions of aqueous pyrrolizidine alkaloid mixtures showed promising results with recoveries ranging from 78.3% to 101.3%. Therefore, spiked honey samples were extracted with an adjusted protocol. The mercaptopropyl-sulfonated halloysite nanotubes revealed satisfying loading efficiencies and recoveries. Validation was then performed, which displayed acceptable performance for the presented method. In addition, reusability studies using HNT-MPTMS-SO3H for solid phase extraction of an aqueous pyrrolizidine alkaloid mixture demonstrated excellent results over six cycles with no trend of recovery reduction or material depletion. Therefore, organosilyl-sulfonated halloysite nanotubes display a green, efficient and low-cost alternative to polymeric support in solid phase extraction of toxic pyrrolizidine alkaloids from complex honey matrix.

PANI/BaFe12O19@Halloysite ternary composites as novel microwave absorbent

A three-phase PANI/BaFe₁₂O₁₉@Hal heterostructure was designed and fabricated in this paper as efficient lightweight electromagnetic wave absorbing material through the combination of citrate assisted sol-gel self-propagating combustion and in-situ oxidative polymerization of aniline. In addition, the effects of the weight ratio of different PANI to BF@Hal on the microwave absorption properties of the materials were studied. The results show that when the weight ratio of PANI is 40%, the material has the best microwave absorption performance. The frequency bandwidth below -5 dB reached 9.60 GHz and the minimum absorption peak at 11.92 GHz was -14.77 dB. The combination of the PANI and BF@Hal nanosheets take advantage of the interfacial polarization, natural resonance, dielectric polarization and trapping of EM waves by internal reflection in PANI/BaFe₁₂O₁₉@Hal. Taking advantage of the unique microscopic morphology and interface characteristics, halloysite was introduced to improve the microwave absorption performance and enrich the absorbing mechanism of the composite materials. This work may provide a reliable candidate for the synthesis of electromagnetic attenuation materials with fairly good performances.