Novel mold-resistant building materials impregnated with thermally reduced nano-silver

Functionalized electrospun nanofibers for high efficiency removal of particulate matter

In recent years, introducing electrospun airfilters to enhance the removal of PM_2.5 and PM_10–2.5 has received much interest. In this study, a novel poly-(vinyl) alcohol (PVA)/carbon nanoparticle (CNP)/tea leaf extract (TLE), functionalized nanofibrous air filter (FNA) was fabricated using an electrospinning method. Novelty of the unique work in the blending of CNP and TLE, first of its kind, for the preparation of FNA. Polysaccharide crosslinked FNA has a carbon complex with two monosaccharide units to produce the intrinsic properties of the PM_2.5 and PM_10–2.5 removal efficiency. The FNA had promising traits of UV protection. The prepared FNA was characterized using physicochemical, mechanical, antimicrobial activity, etc., in addition to its PM_2.5 and PM_10–2.5 removal efficiency. Pore size and distribution study using the capillary flow porometry method has proved the structure of FNA. FNA exhibited excellent low pressure drop (110 Pa), which are promising characteristics for air purification. FNA from PVA: CNP: TLE exhibited high PM_2.5 and PM_10–2.5 removal efficiencies of 99.25% and 99.29%, respectively. Hence, the study proved.

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.

Understanding building-occupant-microbiome interactions toward healthy built environments: A review

Built environments, occupants, and microbiomes constitute a system of ecosystems with extensive interactions that impact one another. Understanding the interactions between these systems is essential to develop strategies for effective management of the built environment and its inhabitants to enhance public health and well-being. Numerous studies have been conducted to characterize the microbiomes of the built environment. This review summarizes current progress in understanding the interactions between attributes of built environments and occupant behaviors that shape the structure and dynamics of indoor microbial communities. In addition, this review also discusses the challenges and future research needs in the field of microbiomes of the built environment that necessitate research beyond the basic characterization of microbiomes in order to gain an understanding of the causal mechanisms between the built environment, occupants, and microbiomes, which will provide a knowledge base for the development of transformative intervention strategies toward healthy built environments. The pressing need to control the transmission of SARS-CoV-2 in indoor environments highlights the urgency and significance of understanding the complex interactions between the built environment, occupants, and microbiomes, which is the focus of this review.

Moulds on cementitious building materials-problems, prevention and future perspectives

Materials rich in organic and inorganic compounds, such as building materials or paints, represent an excellent substrate for the development of moulds. Several conditions affect mould's growth on cementitious materials, such as nutrient and water availability, temperature, pH and moisture. Microorganisms, and especially moulds, attack these surfaces and contribute to their erosion, thereby reducing the life of the structure itself and negatively affecting human health through inhalation, ingestion and dermal contact with spores. Interventions are based on The European Communities Council Directive 89/106/EEC, that obliges the use of materials, products and building elements that are resistant to fungi and other forms of degradation, and that do not constitute a health risk for users and the environment. This mini-review summarises the current state of problems related to mould growth on cementitious building materials, emphasising new innovative approaches for limiting or contrasting their growth. In particular, the use of nanoparticles and the related nanomaterials as well as the potential use of new "biocides" from natural sources is discussed.

Effective disinfection of airborne microbial contamination in hospital wards using a zero-valent nano-silver/TiO2 -chitosan composite

A novel antimicrobial composite of zero-valent silver nanoparticles (AgNPs), titania (TiO₂ ), and chitosan (CS) was prepared via photochemical deposition of AgNPs on a CS-TiO₂ matrix (AgNPs@CS-TiO₂ ). Electron microscopy showed that the AgNPs were well dispersed on the CS-TiO₂ , with diameters of 6.69-8.84 nm. X-ray photoelectron spectra indicated that most of the AgNPs were reduced to metallic Ag. Fourier-transform infrared spectroscopy indicated that some AgNPs formed a chelate with CS through coordination of Ag⁺ with the CS amide II groups. The zones of inhibition of AgNPs@CS-TiO₂ for bacteria (Escherichia coli and Staphylococcus epidermidis) and fungi (Aspergillus niger and Penicillium spinulosum) were 6.72-11.08 and 5.45-5.77 mm, respectively, and the minimum (critical) concentrations of AgNPs required to inhibit the growth of bacteria and fungi were 7.57 and 16.51 µg-Ag/mm² , respectively. The removal efficiency of a AgNPs@TiO₂ -CS bed filter for bioaerosols (η) increased with the packing depth, and the optimal filter quality (qF) occurred for packing depths of 2-4 cm (qF = 0.0285-0.103 Pa^-1 ; η = 57.6%-98.2%). When AgNPs@TiO₂ -CS bed filters were installed in the ventilation systems of hospital wards, up to 88% of bacteria and 97% of fungi were removed within 30 minutes. Consequently, AgNPs@TiO₂ -CS has promising potentials in bioaerosol purification.