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Halloysite nanotubes (HNTs) are naturally occurring nanomaterials with a tubular shape and high aspect ratio, a promising functional additive for active food packaging applications. HNTs have been shown to possess unique properties such as high surface area, thermal stability, and biocompatibility, making them attractive for active food packaging materials. This review summarizes recent research on the use of HNTs as functional additives in active food packaging applications, including antimicrobial packaging, ethylene scavenging packaging, moisture, and gas barrier packaging. The potential benefits and challenges associated with the incorporation of HNTs into food packaging materials are discussed. The various modification methods, such as the physical, chemical, biological, and electrostatic methods, along with their impact on the properties of HNTs, are discussed. The advantages and challenges associated with each modification approach are also evaluated. Overall, the modification of HNTs has opened new possibilities for the development of advanced packaging materials with improved performance for various functional food packaging materials with enhanced properties and extended shelf life.

ZnFe 2 O 4 is a highly desirable catalyst due to its exceptional photo-response in the visible light region, but various drawbacks, such as rapid recombination of photo-generated electron–hole pairs and severe particle agglomeration, make it difficult to use. In this study, a co-precipitation approach was used to create ZnFe 2 O 4 /HNT (ZF/HNTs) composites. XRD, SEM, TEM, FTIR, BET, and DRS were used to characterize the ZF/HNT composites. Furthermore, the effectiveness of removing crystal violet under simulated visible light irradiation was used to assess photocatalytic activity. The results showed that ZnFe 2 O 4 with typical diameters of around 20 nm was significantly distributed on halloysite nanotubes. Because of the synergistic impact of the improved agglomeration phenomena of ZnFe 2 O 4 and the decreased recombination rate of photo-generated electrons and holes, all of the composites had superior photocatalytic performance than pure ZnFe 2 O 4 . The ZF/HNTs-11 composite exhibited the highest removal performance, removing 96.7% of the sample in less than 150 min. In addition, the composite was very stable and reusable. Consequently, ZF/HNTs-11 composite is an effective catalyst for treating pollutants found in wastewater.

The use of synthetic materials and the attention towards environmental hazards and toxicity impose the development of green composites with natural origins. Clay is one of the candidates for this approach. Halloysite is a natural clay mineral, a member of the Kaolin group, with characteristic tubular morphology, usually named halloysite nanotubes (HNTs). The different surface chemistry of halloysite allows the selective modification of both the external surface and the inner lumen by supramolecular or covalent interactions. An interesting aspect of HNTs is related to the possibility of introducing different species that can be released more slowly compared to the pristine compound. Due to their unique hollow morphology and large cavity, HNTs can be employed as an optimal natural nanocarrier. This review discusses the structure, properties, and application of HNTs in the biological field, highlighting their high biocompatibility, and analyse the opportunity to use new HNT hybrids as drug carriers and delivery systems.

Nine halloysite nanotubes (HNTs) have been examined using scanning electron microscopy (SEM), atomic force microscopy (AFM) and (cross-sectional) transmission electron microscopy (TEM) to evaluate details of their external and internal morphologies. The samples span morphologies within the cylindrical to prismatic-polygonal framework proposed by Hillier et al. (2016). The 'carpet roll' model assumed in the conceptualization of most technological applications of HNTs is shown to be far too simplistic. Both cylindrical and prismatic forms have abundant edge steps traversing their surfaces that, by analogy with plates of kaolinite, correspond to prism faces. The mean value for the diameter of the central lumen of the tubes is 12 nm. Numerous slit-like nanopores, with diameters up to 18 nm, also occur between packets of layers, particularly in prismatic forms at the junction between a central cylindrical core and outer packets of planar layers. These pores expose aluminol and siloxane surfaces, but unlike the lumen, which is assumed only to expose an aluminol surface, they do not extend along the entire length of the nanotube. Edge steps seen most clearly by AFM correspond in height to the packets of layers seen in TEM. TEM cross-sections suggest that tube growth occurs by accretion of a spiralled thickening wedge of layers evolving from cylindrical to polygonal form and reveal that planar sectors may be joined by either abrupt angular junctions or by short sections of curved layers. A more realistic model of the internal and external morphologies of HNTs is proposed to assist with understanding of the behaviour of HNTs in technological applications.

The development of novel materials and approaches for effective energy consumption and the employment of renewable energy sources is one of the current trends in modern material science. With this respect, the number of researches is focused on the effective harvesting and storage of solar energy for various applications. Phase change materials (PCMs) are known to be able to store thermal energy of the sunlight due to adsorption and release of latent heat through reversible phase transitions. Therefore, PCMs are promising as functional additives to construction materials and paints for advanced thermoregulation in building and industry. However, bare PCMs have limited practical applications. Organic PCMs like paraffins suffer from material leakage when undergoing in a liquid state while inorganic ones like salt hydrates lack long-term stability after multiple phase transitions. To avoid this, the loading of PCMs in porous matrices are intensively studied along with the thermal properties of the resulted composites. The loading of PCMs in microcontainers of natural porous or layered clay materials appears as a simple and cost-effective method of encapsulation significantly improving the shape and cyclic stability of PCMs. Additionally, the inclusion of functional clay containers into construction materials allows for improving their mechanical and flame-retardant properties. This article summarizes the recent progress in the preparation of composites based on PCM-loaded clay microcontainers along with their future perspectives as functional additives in thermo-regulating materials.

Nitrogen-doped carbon materials have attracted enormous interest in catalysis owing to their outstanding catalytic performance. In this work, nitrogen-doped carbonaceous catalysts (NCC) supported on inexpensive and naturally abundant halloysite nanotubes were successfully synthesized via precipitation polymerization, calcination, and sulfonation processes. The physical and chemical properties of the obtained catalysts were systematically characterized by different methods. The results indicated that NCC catalysts had mesoporous structures, excellent thermostability and acid-base bi-functional active sites. One-pot synthesis of 5-hydroxymethylfurfural (HMF) from glucose was performed to investigate the synthesized NCC catalysts. Benefiting from the synergistic effects of the acid-base bi-functional active sites, the highest HMF yield (62.8%) was achieved in an isopropanol-mediated DMSO system under optimal conditions. Moderate to excellent yields of HMF were also obtained from one-pot conversions of other carbohydrates, including inulin, sucrose, cellobiose, maltose and starch, with our developed catalytic system. The one-pot production of HMF from cellulose was also smoothly processed by the NCC bi-functional catalyst in an IL-based system. This work has developed a versatile strategy for designing nitrogen-doped carbonaceous catalysts that can be employed for the direct transformation of renewable carbohydrates to platform chemicals.

The increased demands of our rapidly developing way of life lead to the broadening of the ceramic market among other effects. Due to the advanced ceramic properties of halloysite and its abundance, combined with its good synergistic effect with other materials, it has been investigated for multifarious possible applications to produce traditional and advanced ceramics as well as ceramic composites. In this review, a substantial number of studies by several investigators into halloysite-based ceramics were are summarized. The possibilities and limitations of different halloysite-based ceramic materials for future applications are also discussed in this manuscript and new fields of research are proposed. The summarization of published results indicates a constant scientific interest in halloysite-based traditional ceramics and new potential uses in the future. Additionally, investigations on different novel ceramic composites with low cost halloysite nanotubes (HNTS) have rapidly increased, covering different scientific and technological areas. On the other hand, research into advanced ceramics (SiAlONS) has been pursued due to its highly cost effective technology treatments on a large scale.

The aim of this review was to analyze/investigate the synthesis, properties, and applications of polyvinyl alcohol–halloysite nanotubes (PVA–HNT), and their nanocomposites. Different polymers with versatile properties are attractive because of their introduction and potential uses in many fields. Synthetic polymers, such as PVA, natural polymers like alginate, starch, chitosan, or any material with these components have prominent status as important and degradable materials with biocompatibility properties. These materials have been developed in the 1980s and are remarkable because of their recyclability and consideration of the natural continuation of their physical and chemical properties. The fabrication of PVA–HNT nanocomposites can be a potential way to address some of PVA’s limitations. Such nanocomposites have excellent mechanical properties and thermal stability. PVA–HNT nanocomposites have been reported earlier, but without proper HNT individualization and PVA modifications. The properties of PVA–HNT for medicinal and biomedical use are attracting an increasing amount of attention for medical applications, such as wound dressings, drug delivery, targeted-tissue transportation systems, and soft biomaterial implants. The demand for alternative polymeric medical devices has also increased substantially around the world. This paper reviews individualized HNT addition along with crosslinking of PVA for various biomedical applications that have been previously reported in literature, thereby showing the attainability, modification of characteristics, and goals underlying the blending process with PVA.

Nano clays, such as halloysite nanotubes (HNT), has recently become a popular additive for improving the physicochemical properties of polymeric scaffolds used in tissue engineering. This study investigates the effect of HNT on the physical, mechanical, and biological properties of polyhydroxy butyrate (PHB)-based scaffolds for cartilage regeneration. Fibrous scaffolds made of PHB/HNT were prepared via electrospinning using 1–7 wt% HNT, and their properties were analyzed. Our results indicate that the scaffold containing 5 wt% HNT (P-5H) represents superior properties compared to PHB. Morphological studies showed that HNT incorporation decreased fiber diameter from 1017 ± 295.95 nm to 878.66 ± 128 nm. Also, HNT improved the scaffold’s mechanical properties in terms of ultimate strength and strain by 92% and 46% respectively. Moreover, differential scanning calorimetry and X-Ray Diffraction evaluations confirmed that HNT had increased crystallinity from 42.9 to 48.2%. Furthermore, the analysis of atomic force microscopy revealed that HNT has significantly increased surface roughness. According to our findings, HNT enhanced the structure’s resistance to degradation, which would benefit cartilage regeneration as a slow-healing tissue. Additionally, MTT analysis revealed that chondrocytes proliferated and grew with an increasing trend on the P-5H scaffold over seven days, which indicates HNT biocompatibility. Overall, the results of this study suggest that the incorporation of 5 wt% HNT positively enhance the properties of PHB-based electrospun scaffolds for cartilage tissue engineering.

Composite nanofiber membranes comprising bacterial cellulose (BC) and halloysite nanotubes (HNTs) were prepared by vacuum filtration. The tensile strength and ionic conductivity of the nanofiber membranes were improved by the blending of HNTs. The BC/HNTs nanofiber membrane with m(BC): m(HNTs) = 150: 1 (denoted as BC/HNTs-150) exhibited superior tensile strength (84.4 MPa), high porosity (83.0%), outstanding thermal stability as well as good electrolyte retention (369% electrolyte uptake). In addition, the BC/HNTs-150 membrane delivered a higher ionic conductivity (5.13 mS cm −1 ) than that of the BC (2.88 mS cm −1 ) and commercial PP–PE–PP (2.05 mS cm −1 ) separators. The battery containing the BC/HNTs-150 separator also showed better capacity (162 mAh g −1 ) and cycling property (95% after 100 cycles) than the battery using the BC separator, demonstrating the BC/HNTs composite membranes to be hopeful candidates used in high-performance lithium-ion batteries. Graphic abstract