The role of particle size of particulate nano-zinc oxide wood preservatives on termite mortality and leach resistance

Wood Surface Modification with Hybrid Materials Based on Multi-Walled Carbon Nanotubes

In this work, new treatments based on multi-walled carbon nanotubes (MWCNTs), MWCNTs decorated with zinc oxide (ZnO), MWCNTs decorated with hydroxyapatite (HAp) and MWCNTs decorated with silver (Ag) nanoparticles dispersed in PHBHV solution are proposed for improving sound oak wood properties. We hypothesize that the solutions containing decorated MWCNTs will be more efficient as wood consolidants, not only because of the improved mechanical properties of the treated wood but also because of the hydrophobic layer created on the wood surface. In order to test these hypotheses, the treatments' potential was investigated by a number of complex methods, such as colorimetric parameter measurements, water absorption tests, mechanical tests, artificial aging and antifungal tests. The data confirm that the treated wood materials have moderate stability, and the color differences are not perceived with the naked eye. A significant improvement of the treated samples was observed by water absorption, humidity and mechanical tests compared to untreated wood. The best results were obtained for samples treated by brushing with solutions based on decorated CNTs, which confirms that a uniform and thicker layer is needed on the surface to ensure better protection. The wood behavior with accelerated aging revealed that the control sample degraded faster compared to the other treated samples. Antifungal tests showed that higher growth inhibition was obtained for samples treated with 0.2% MWCNTs_ZnO + PHBHV. Considering all of the obtained results, it can be concluded that the most effective treatment was MWCNTs_ZnO + PHBHV at a nanocomposite concentration of 0.2%, applied by brushing. Thus, wood protection against mold and fungi will be achieved, simultaneously ensuring improved mechanical strength and water barrier properties and therefore maintaining the structural integrity of sound oak wood over time.

Nano-AgCu Alloy on Wood Surface for Mold Resistance

The mold infection of wood reduces the quality of its surface and potentially endangers human health. One category of the most popular mold inhibitors on the market is water-soluble fungicides. However, easy leaching due to ionic forms is a problem, which reduces the effectiveness of their antimicrobial action, as well as causing environmental pollution. Interestingly, nanometer-sized sterilizing agents present strong permeability and highly fungicidal behavior, and they are not easily leached, due to the unique nanoscale effect, and they have become alternative candidates as marketable anti-mold agents for wood protection. In this study, we first designed and explored a nanoscale alloy (nano silver–copper alloy, nano-AgCu) to treat wood surfaces for mold growth resistance. The results showed that three molds, i.e., Aspergillus niger, Penicillium citrinum and Trichoderma viride, mainly grew on the surface of wood within a depth of 100 μm; and that the nano-AgCu alloy with a particle size of ~15 nm presented improved retention and anti-mold efficiency at a nanomaterial concentration on the wood surface. Its leaching rate increased non-linearly with the increase in nano-AgCu retention and then it showed a gradually decreasing trend. When the concentration reached 1000 mg/L, the nano-AgCu alloy uniformly distributed on the wood surface in a monodispersed state and exhibited a lower retention of 0.342 g/m², with an anti-mold efficiency of more than 75% and a leaching rate of only 7.678%. Such results positioned 1000 mg/L as the toxic threshold concentration of nano-AgCu against the three molds. This study can provide a scientific basis for the analysis of the anti-mold mechanisms of nano-AgCu alloy on wood surfaces and guide the application of nano-metal alloy materials in the field of wood antimicrobials.

Nanomaterials Used in Conservation and Restoration of Cultural Heritage: An Up-to-Date Overview

In the last few years, the preservation of cultural heritage has become an important issue globally, due to the fact that artifacts and monuments are continually threatened by degradation. It is thus very important to find adequate consolidators that are capable of saving and maintaining the natural aspect of these objects. This study aims to provide an updated survey of the main nanomaterials used for the conservation and restoration of cultural heritage. In the last few years, besides the classic nanomaterials used in this field, such as metal nanoparticles (copper and silver) and metal oxides (zinc and aluminum), hydroxyapatite and carbonated derivatives, tubular nanomaterials (such as carbon nanotubes) have been used as a potential consolidate material of cultural heritage. Tubular nanomaterials have attracted attention for use in different fields due to their structures, as well as their ability to present multiple walls. These nanotubes have the necessary properties in preserving cultural heritage, such as superior mechanical and elastic strength (even higher than steel), high hydrophobicity (with a contact angle up to 140°), optical properties (high photodegradation protection), large specific surface area (from 50 to 1315 m2/g, depending on the number of walls) for absorption of other nanomaterials and relatively good biocompatibility.

Overview of biochar production from preservative-treated wood with detailed analysis of biochar characteristics, heavy metals behaviors, and their ecotoxicity

Concerns over the disposal of preservative-treated wood waste and its related environmental problems are the main driving forces of research into the recycling of preservative-treated wood. Preservative-treated wood waste composed of cellulose, hemicellulose, and lignin with several types of heavy metals can be recycled in various ways, such as wood-based composites, heavy metal extraction, energy recovery, etc. In particular, thermochemical conversion has attracted considerable attention recently because energy can be recovered from biomass as liquid fuel and bio-oil, as well as produce bio-char with a high carbon content, which can be applied to valuable products, such as soil amendment, adsorbents, solid fuels, and catalyst supports. On the other hand, environmental issues, such as heavy metal volatilization and heavy metal leaching, are still a challenge. This review reports the state-of-the-art knowledge of biochar production from preservative-treated wood with the main focus on the feedstock, process technology, biochar characteristics, application, and environmental issues. This review provides important information for future studies into the recycling of preservative-treated woods into biochar.

Innovative Wood Surface Treatments Based on Nanotechnology

This work reviewed innovative wood surface treatments based on nanotechnology. It is well documented in the literature that the cell walls of wood present significant porosity; this porosity is on a molecular scale. The main reason for the use of nanotechnology in wood science and technology is the unique characteristic of nano-based materials to effectively penetrate deeply into wood substrates, which, in turns, results in the alteration of their surface chemistry. This subsequently causes an improvement in wood properties. Any potential change in the wood properties due to treatment with nanomaterials is based on the higher interfacial area which is developed due to the treatment. This occurs because the number of particles is significantly reduced to the nanoscale. The nanomaterials improve the properties of wood as a raw material and alter its original features to a limited extent. However, their potential impact on both health and the environment should be addressed by applying tools such as life-cycle assessments. This will avoid mistakes being made in which new technologies are released on the market prior to an impact assessment having been carried out.

Nanomaterials and Chemical Modifications for Enhanced Key Wood Properties: A Review

This work briefly reviews the research milestones in the area of wood chemical modification, focusing on acetylated and furfurylated wood which have been scaled up, and exploits the solutions that nanotechnology can offer to wood protection as an alternative green innovative approach in improving key wood properties, namely the dimensional stability when subjected to a fluctuating moisture content and a susceptibility to biodegradability by microorganisms. Recently, nanomaterials were found to be able applicable in wood science. The target is to improve some special physicochemical characteristics of wood in order to resist extreme conditions (climate, bacteria, etc.), giving an enhanced potentiality. It is well-established that the wood cell wall shows a porosity of molecular scale dimensions; this is caused by the partial filling of spaces between the microfibrils of the cellulose mainly by polyoses and lignin. The small-sized nanoparticles can deeply and effectively penetrate into the wood, altering its surface chemistry, improving its properties, and therefore, resulting in a hyper-performance product.

Zinc oxide nanoparticles: Synthesis, antiseptic activity and toxicity mechanism

Zinc oxide (ZnO), as a material with attractive properties, has attracted great interest worldwide, particularly owing to the implementation of the synthesis of nano-sized particles. High luminescent efficiency, a wide band gap (3.36eV), and a large exciton binding energy (60meV) has triggered intense research on the production of nanoparticles using different synthesis methods and on their future applications. ZnO nanomaterials can be used in industry as nano-optical and nano-electrical devices, in food packaging and in medicine as antimicrobial and antitumor agents. The increasing focus on nano zinc oxide resulted in the invention and development of methods of nanoparticles synthesis. Recently, various approaches including physical, chemical and biological ("green chemistry") have been used to prepare ZnO nanocomposites with different morphologies. The obtained nanoparticles can be characterized with a broad range of analytical methods including dynamic light scattering (DLS), electron microscopy (TEM, SEM), UV-VIS spectroscopy, X-ray diffraction (XRD) or inductively coupled plasma with mass spectrometry (ICP-MS). With these it is possible to obtain information concerning the size, shape and optical properties of nanoparticles. ZnO NPs exhibit attractive antimicrobial properties against bacteria (Gram-positive and Gram-negative) and fungi. Zinc oxide nanocomposites show also selective toxicity toward normal and cancerous cells, which is explained by reactive oxygen formation (ROS). Yet despite the potentially interesting antitumor activity of ZnO nanoparticles, it has been proven that they can be also cytotoxic and genotoxic for multiple types of human cells (i.e. neuronal or epithelial cells). This paper reviews the methods of synthesizing zinc oxide nanocomposites as well as their characteristics, antimicrobial activity and cytotoxicity against normal and tumor cells.

Limonia acidissima L. leaf mediated synthesis of zinc oxide nanoparticles: A potent tool against Mycobacterium tuberculosis

OBJECTIVE/BACKGROUND

The present investigation was undertaken to synthesize zinc oxide nanoparticles using Limonia acidissima L. and to test their efficacy against the growth of Mycobacterium tuberculosis.

METHODS

The formation of zinc oxide nanoparticles was confirmed with UV-visible spectrophotometry. Fourier transform infrared spectroscopy shows the presence of bio-molecules involved in the stabilization of zinc oxide nanoparticles. The shape and size was confirmed with atomic force microscope, X-ray diffraction, and high resolution transmission electron microscope. These nanoparticles were tested for their effect on the growth of M. tuberculosis through the microplate alamar blue assay technique.

RESULTS

The UV-visible data reveal that an absorbance peak at 374nm confirms formation of zinc oxide nanoparticles and they are spherical in shape with sizes between 12nm and 53nm. These nanoparticles control the growth of M. tuberculosis at 12.5μg/mL.

CONCLUSION

Phytosynthesis of zinc oxide nanoparticles is a green, eco-friendly technology because it is inexpensive and pollution free. In the present investigation, based on our results we conclude that the aqueous extract of leaves of L. acidissima can be used for the synthesis of zinc oxide nanoparticles. These nanoparticles control the growth of M. tuberculosis and this was confirmed with the microplate alamar blue method. The potential of biogenic zinc oxide nanoparticles may be harnessed as a novel medicine ingredient to combat tuberculosis disease.