The use of TiO2 nanoparticles for photoprotection comprise a side effect due to the photocatalysis of the nanoparticles under UV radiation. In this work we studied how the suppression of TiO2 photocatalytic activity may affect the production of phenoxy radicals and the color of wood surfaces exposed to UV radiation. The experimental work considered the modification of TiO2 nanoparticles to reduce its photoactivity and the use electron paramagnetic resonance to test free radical production. Wood samples were treated with the different TiO2 nanoparticles and the radical production and color changes were evaluated after UV exposure. Experimental results showed that in wood samples exposed to UV radiation the use of TiO2 with suppressed photoactivity yielded increased amounts of phenoxy radicals, in comparison to samples treated with photoactive TiO2. Similar results were obtained in terms of color change, where samples treated with suppressed photoactivity TiO2 showed significantly higher color changes values, after 2000 h of UV exposure, than samples treated with photoactive TiO2. These results suggest that in wood surfaces, the photocatalytic effect of TiO2 may be crucial on the performance of the nanoparticles as photoprotective treatment.

Fungal isolates obtained from rotten wood samples were identified and selected by their ability to produce fungal dyes in liquid media. Fungal isolates produced natural extracellular dyes with colors ranging from red to orange, yellow and purple. Dyes from two of these fungi, Talaromyces australis (red) and Penicillium murcianum (yellow), were extracted and used to dye wool samples in a Data Color Ahiba IR Pro-Trade (model Top Speed II) machine. The protein nature of wool interacted well with the fungal dyes producing colors suitable for textile applications when used to a concentration of 0.1 g•L −1. Results on color fastness when washing confirmed the affinity of the dyes with wool as the dyed samples kept their color in acceptable ranges after washing, without the implementation of mordanting pretreatments or the use of fixing agents.

Mold growth is a continuing issue when it comes to human health, as well as a growing concern in localized wood decay, as numerous ‘traditional’ molds have been found to have soft rotting capabilities. Mold inhibitors on the market are often synthetic; however, the fungal kingdom has a wide range of more ‘natural’ options. Pigments produced by many fungi have been found to be toxic to other fungi, especially soft rotting fungi. This study looked at the pigments produced by Talaromyces australis (red) and Penicillium murcianum (yellow) and their effect upon the growth and pigment production of two species of Trichoderma and two species of Penicillium. Penicillium murcianum pigment inhibited growth and pigment production of all tested species at 3 mg/mL and higher. Results from this study indicate that P. murcianum colorants have the potential to inhibit growth and pigment production against other select ‘mold’ fungi. This holds potential not only for the wood preservation industry, but for the greater natural dye industry, especially in the area of antimicrobial textiles.

In this work, TiO2 and ZnO nanoparticles of different sizes and crystallographic configuration were used to protect wood surfaces against UV radiation. The sizes and levels of photoactivity of the nanoparticles were measured in vitro by transmittance electron microscopy and electron paramagnetic resonance spectroscopy, and then they were impregnated into radiata pine samples. The production of aromatic radicals, absorbance of UV and visible light, and chemical and color changes of treated and untreated wood surfaces were assessed after UV irradiation. Results show that nanoparticles that were less photoactive were better at reducing the production of organic radicals and the chemical and color changes on wood surfaces subjected to UV. Similarly, smaller nanoparticles (40 nm) were better at reducing photochemical reactions than larger (100 nm) nanoparticles. In terms of the crystallographic configuration of nanoparticles, differences in the production of phenoxy radicals were verified only for short-term exposure. Previous research revealed that certain levels of photoactivity in TiO2 nanoparticles may contribute to decreases in the photodegradation of wood surfaces possibly by an electron sink mechanism. Our observations indicate that this is unlikely to occur in the presence of highly photoactive nanoparticles.

PurposeThe study aims to test the color fastness of wool and linen fabrics dyed by simple immersion in ethanol dissolutions of fungal dyes.Design/methodology/approachEthanol dissolutions of Talaromyces australis and Penicillium murcianum dyes were prepared to a concentration of 0.3% and used to dye wool and linen samples by immersion. Color fastness to washing, dry cleaning, wet and dry rubbing, perspiration and light, were tested according to AATCC standards.FindingsColor fastness reached acceptable results at dry cleaning and wet and dry rubbing by crocking but did not performed well at laundering, perspiration and light exposure. Results indicate that ethanol dissolutions of tested dyes had better affinity for wool fabrics than linen, but the dyeing method requires further improvements to be considered attractive for full scale applications.Originality/valueIn this work sustainability of fabrics dyeing is improved by using natural pigments produced by filamentous fungi and a method to dye that requires no increment of temperature and mordants.

Photoactive nanoparticles are used to reduce microbial colonization and self-clean surfaces of materials such as glass and ceramics. To test whether such an approach is feasible for wood surfaces, we treated radiata pine samples with TiO2 (rutile and anatase) or ZnO nanoparticles and then coated the samples with different finishes. Coated samples and uncoated controls were exposed outdoors for six months. After exposure, fungi colonizing wood surfaces were identified using molecular techniques and microscopy, and colour changes in the wood samples were also measured. Treatment of uncoated surfaces with nanoparticles reduced the discolouration of wood during weathering but had little effect on colonization of wood by black mould fungi. In contrast, pretreatment of samples with titanium dioxide nanoparticles increased the number and diversity of fungi including basidiomycetes colonizing coated samples, whereas zinc oxide nanoparticles had the opposite effect. Zinc oxide nanoparticles, however, were less effective than rutile titanium dioxide nanoparticles at reducing the discolouration of coated samples exposed to natural weathering. We conclude that none of the photoactive nanoparticles on their own are able to reduce microbial colonization and discoloration of samples. This suggests that it may be difficult to create self-cleaning wood surfaces using photoactive nanoparticles.