Nano-interfacial decoration of Halloysite Nanotubes for the development of antimicrobial nanocomposites

DOI: 10.1002/aenm.202000768 conveniences have raised serious concerns over global warming.[1] In this regard, harnessing solar energy for the electricity would be an immediate and effective remedy to the menacing global warming issues. Solar energy is an endless green energy source that offers 1000 times of power that the entire planet requires, while photovoltaic technology provides an ideal and clean route to be pursued.[2] An electronic device that converts solar energy into electricity is known as a photovoltaic cell.[3] With power conversion efficiencies (PCEs) reaching steadily beyond 25.2%, just marginally smaller than those of Si solar cells, perovskite solar cells (PSCs) have grabbed intensive attractions in the field of photovoltaic research.[4] However, the commercial scaling of PSCs will greatly rely on paths to reduced fabrication cost, enhanced PCE, and improved stability.[5] In addition to the great success of PSCs, halide perovskites are also promising materials for various high-performance optoelectronic devices such as lightemitting diodes (LEDs),[6] scintillators,[7] and photo detectors[8] due to their excellent photoluminescence quantum yield (PLQY), tunable bandgap, solution processability, and charge transport properties.[9] The halide perovskites have a general formula ABX3, where “A” corresponds to monovalent organic or inorganic cations such as methylammonium (CH3NH3, MA+), formamidinium (NH2 = CHNH2, FA+) or Cs+, “B” can be divalent metal cations such as Pb2+ and Sn2+, and “X” can be anions of the VII A group (halides) of the periodic table, namely I, Br, or Cl.[10] These halide perovskites are salts that can easily take up moisture if packed improperly. Light exposure can easily break the fragile bonds in perovskites, create halogen vacancies or interstitial pairs allowing them to migrate, and convert any oxygen present inside the crystals into highly active superoxide.[11] Even under moderate temperature and light/heat exposure, the perovskites can react with most of the metals, with heat causing organic species to volatilize, whereas light promotes mobility of ions inside the crystal.[12] Furthermore, the fracture energy of the perovskites is extremely low in the order[13] <1 J m−2. On the contrary, the perovskites possess an extremely high thermal expansion coefficient of the order of nearly ten times in magnitude to that of glass. Eventually, thermal stresses Moisture, heat, and light instabilities of halide perovskites (HPs) represent a serious Achilles’ heel that must be overcome, to enable future advancements in perovskite-based optoelectronic devices such as solar cells and light-emitting diodes. The instabilities are attributed to the unavoidable fragile ionic bonding between cationic and anionic parts of HPs during their formation. Surface passivation of HPs by various surface-passivating materials has proven to be an attractive approach to stabilize perovskites against moisture, heat, and light, keeping intact their structural integrity and ionic bonding. Herein, the experimental and theoretical background for degradation mechanisms of HPs is reviewed along with various surface passivating materials to stabilize HPs. Finally, the existing challenges associated with thin-film and device fabrication and an outlook for improving the stability of perovskites in optoelectronics are presented

Interface Engineering Driven Stabilization of Halide Perovskites against Moisture, Heat, and Light for Optoelectronic Applications

Recent advances in drug delivery and controlled release had a great impact on bioscience, medicine and tissue engineering. Consequently, a variety of advanced drug delivery vehicles either have already reached the market or are approaching the phase of commercial production. Progressive growth of the drug delivery market has led to the necessity to earnestly concern about economically viable, up-scalable and sustainable technologies for a large-scale production of drug delivery carriers. We have identified three attractive natural sources of drug carriers: aluminosilicate clays, minerals of calcium carbonate, and cellulose. Three classes of drug delivery carriers derived from these natural materials are halloysite nanotubes, vaterite crystals and nanocellulose. These carriers can be produced using “green” technologies from some of the most abundant sources on the Earth and have extremely high potential to meet all criteria applied for the manufacture of modern delivery carriers. We provide an up-to-date snapshot of these drug delivery vehicles towards their use for bioapplications, in particular for drug delivery and tissue engineering. The following research topics are addressed: (i) the availability, sources and methodologies used for production of these drug delivery vehicles, (ii) the drug loading and release mechanisms of these delivery vehicles, (iii) in vitro, in vivo, and clinical studies on these vehicles, and (iv) employment of these vehicles for tissue engineering. Finally, the prospects for vehicles’ further development and industrialisation are critically assessed, highlighting most attractive future research directions such as the design of third generation active biomaterials.

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Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

Halloysite nanotubes loaded with nano silver for the sustained-release of antibacterial polymer nanocomposite scaffolds

Emerging role of nanoclays in cancer research, diagnosis, and therapy

Halloysite nanotubes with different outer surface/inner lumen chemistry (SiO2/Al2O3) are natural objects with a 50 nm diameter hollow cylindrical structure, which are able to carry functional compounds both inside and outside. They are promising for biological applications where their drug loading capacity combined with a low toxicity ensures the safe interaction of these nanomaterials with living cells. In this paper, the antimicrobial properties of the clay nanotube-based composites are reviewed, including applications in microbe-resistant biocidal textile, paints, filters, and medical formulations (wound dressings, drug delivery systems, antiseptic sprays, and tissue engineering scaffolds). Though halloysite-based antimicrobial materials have been widely investigated, their application in medicine needs clinical studies. This review suggests the scalable antimicrobial nano/micro composites based on natural tubule clays and outlines research and development perspectives in the field.

Vadim Sangarov

Papers

Antimicrobial Applications of Clay Nanotube-Based Composites.