Efficacy Evaluation of Cu- and Ag-Based Antibacterial Treatments on Polypropylene Fabric and Comparison with Commercial Products

Filter masks are disposable devices intended to be worn in order to reduce exposure to potentially harmful foreign agents of 0.1–10.0 microns. However, to perform their function correctly, these devices should be replaced after a few hours of use. Because of this, billions of non-biodegradable face masks are globally discarded every month (3 million/minute). The frequent renewal of masks, together with the strong environmental impact of non-biodegradable plastic-based mask materials, highlights the need to find a solution to this emerging ecological problem. One way to reduce the environmental impact of masks, decrease their turnover, and, at the same time, increase their safety level is to make them able to inhibit pathogen proliferation and vitality by adding antibacterial materials such as silver, copper, zinc, and graphene. Among these, silver and copper are the most widely used. In this study, with the aim of improving commercial devices’ efficacy and eco-sustainability, Ag-based and Cu-based antibacterial treatments were performed and characterized from morphological, compositional, chemical–physical, and microbiological points of view over time and compared with the antibacterial treatments of selected commercial products. The results demonstrated the good distribution of silver and copper particles onto the surface of the masks, along with almost 100% antibacterial capabilities of the coatings against both Gram-positive and Gram-negative bacteria, which were still confirmed even after several washing cycles, thus indicating the good potential of the developed prototypes for mask application

Block Copolymer and Cellulose Templated Mesoporous TiO2-SiO2 Nanocomposite as Superior Photocatalyst

A dual soft-templating method was developed to produce highly crystalline and mesoporous TiO2-SiO2 nanocomposites. Pluronic F127 as the structure-directing agent and pure cellulose as the surface area modifier were used as the templating media. While Pluronic F127 served as the sacrificing media for generating a mesoporous structure in an acidic pH, cellulose templating helped to increase the specific surface area without affecting the mesoporosity of the TiO2-SiO2 nanostructures. Calcination at elevated temperature removed all the organics and formed pure inorganic TiO2-SiO2 composites as revealed by TGA and FTIR analyses. An optimum amount of SiO2 insertion in the TiO2 matrix increased the thermal stability of the crystalline anatase phase. BET surface area measurement along with low angle XRD revealed the formation of a mesoporous structure in the composites. The photocatalytic activity was evaluated by the degradation of Rhodamine B, Methylene Blue, and 4-Nitrophenol as the model pollutants under solar light irradiation, where the superior photo-degradation activity of Pluronic F127/cellulose templated TiO2-SiO2 was observed compared to pure Pluronic templated composite and commercial Evonik P25 TiO2. The higher photocatalytic activity was achieved due to the higher thermal stability of the nanocrystalline anatase phase, the mesoporosity, and the higher specific surface area

Synthesis of Au-Ag alloy nanoparticles with Au/Ag compositional control in SiO(2) film matrix

Au-Ag alloy nanoparticles with tunable atomic ratios have been generated in SiO(2) film matrix using a new two layer (TL) approach. Two successive overlapping coating layers of similar thickness were deposited on silica glass substrates using Au- and Ag-incorporated inorganic-organic hybrid silica sots, respectively. The Au and Ag concentrations in the individual layers were varied to obtain the desired Au-Ag alloys of different compositions. Four sets of such TL coating assemblies were prepared from the following pair of sots: (i) 4 equivalent mol.% Au-96% SiO(2) and 2 equivalent mol.% Ag-98% SiO(2), (ii) 3 equivalent mol.% Au-97% SiO(2) and 2 equivalent mol.% Ag-98% SiO(2), (iii) 3 equivalent mol.% Au-97% SiO(2) and 3 equivalent mol.% Ag-97% SiO(2), and (iv) 2 equivalent mol.% Au-98% SiO(2) and 3 equivalent mol.% Ag-97% SiO(2) and subjected to UV (2.75 J/cm(2)) and heat-treatments (450-550 degrees C) in air and H(2)-N(2) atmospheres for the generation of Au-Ag alloy nanoparticles of approximate compositions Au(0.66)Ag(0.33), Au(0.6)Ag(0.4), Au(0.5)Ag(0.5), and Au(0.4)Ag(0.6), respectively. After UV-treatment, individual Au and Ag nanoparticles were formed in the respective layers. The heat-treatment (450-550 degrees C) induces interlayer diffusion of Au and Ag to each other with the generation of Au-Ag alloy nanoparticles, and as a result, Au-Ag alloy surface plasmon resonance (SPR) absorptions were observed in between the Ag- and Au-SPR absorption positions in the visible spectra. The expected alloy compositions are formed through several intermediate alloy nanoparticles, which can also be arrested by controlling the annealing parameters. The alloy formations were monitored by UV-VIS, FTIR, XRD, EDAX, and TEM studies

Oriented Au-Cu nanoalloy particle incorporated SiO(2) films using a new layer by layer deposition technique

Oriented Au-Cu nanoalloys have been generated in SiO(2) films using a new two-layer (TL) coating approach. Two successive overlapping coating layers were deposited on silica glass substrate using Au- and Cu-incorporated inorganic-organic hybrid silica sols. The concentrations of the Au and Cu (3 equivalent mol% metal-97% SiO(2) in each case) in the respective layers and their individual coating thicknesses were kept similar for the generation of Au-Cu alloys of an approximate atomic ratio 1 : 1. The UV-visible and X-ray diffraction (XRD) spectra of the TL films show the formation of nanoalloys with a gradual increase of Cu content with increasing heat-treatment temperature up to 750 degrees C in 10% H(2)-90% Ar. The XRD patterns reveal that the Au and Cu gradually formed Au-Cu nanoalloys of different ratios with a orientation. Estimation shows that the final nanoalloy composition reaches Au(0.58)Cu(0.42). The transmission electron microscope (TEM) image obtained from an Au(0.58)Cu(0.42) nanoalloy containing film shows the presence of mainly oriented plate-like circular nanoalloys of diameter 9-14 nm. XRD and TEM confirm that the alloy formation took place mainly through the diffusion and gradual dissolution of Cu atoms onto the planes of Au and intermediate Au-Cu nanoalloy crystals

Formation of Au-Pt bimetallic nanoparticles in a two-layer SiO(2) films doped with Au and Pt, respectively, through interlayer diffusion

Bimetallic Au-Pt nanoparticles have been generated inside a relatively porous SiO(2) film matrix by a two-layer (2L) coating methodology. Two overlapping coating layers were deposited on glass substrates from Au- and Pt-doped inorganic-organic hybrid silica sols and air dried at 60 degrees C. The 2L coating assembly was then UV- and followed by heat-treated at 450 and 550 degrees C in air. UV-treatment decomposes AuCl(4)(-) and PtCl(6)(2-) ions in the respective layers and the subsequent heat treatment in air influences the diffusion of Au- and Pt nanometals to each other to form bimetallic Au-Pt nanoparticles inside the silica matrix. A UV-visible study showed damping of Au-plasmon after heat treatments. GIXRD and TEM analyses reveal the formation of a partial Au/Pt solid solution with a small fraction of Pt (similar to 16%), while the major fraction of Pt remains fused with the Au(Pt) solid solution

A new approach for the synthesis of Au-Ag alloy nanoparticle incorporated SiO(2) films

A new synthesis procedure has been developed to prepare Au-Ag alloy nanoparticles inside glassy SiO(2) film matrix. Two successive overlapping coating layers were prepared on glass substrate using Au-and Ag-incorporated inorganic-organic hybrid silica sols, respectively. The concentrations of the An and Ag (3 equivalent mol % metal - 97% silica in each case) in the respective layers and their individual coating thicknesses were kept similar for the generation of 1:1 Au-Ag (AU(0.5)Ag(0.5)) alloy. The dried two-layer (TL) coating assembly after UV (2.75 J/cm(2)) and followed by thermal treatments (450-550 degrees C) yielded Au-Ag alloy nanoparticles of controllable molar ratios in a glassy SiO(2) matrix. Thus, the UV-treated TL film when heated at 450 degrees C yielded spherical Au-Ag alloy nanoparticles (An mol fraction;approximate to 0.8) of average diameter ((D)) 2.5 nm whereas the 550 degrees C heated film sample showed relatively larger alloy nanoparticles of 4.5 nm having An mol fraction of approximate to 0.5. The alloy nanoparticles were formed through the interlayer diffusion of Ag and Au during the thermal annealing in the solid state