Synthesis of hybrid carbon nanotube structures coated with Sophora flavescens nanoparticles and their application to antimicrobial air filtration

Abstract

a b s t r a c tControlling airborne microorganisms has become increasingly important with increase in human indoor activities, epidemic disease outbreaks, and airborne pathogen transmission. Treatments using antimicrobial nanoparticles have shown promise because of the high surface-to-volume ratio of nanoparticles compared to their bulk counterparts, and their unique physical and chemical properties. In this study, hybrid nanostructures of multiwalled carbon nanotubes (MWCNTs) coated with antimicrobial, natural product (NP) nanoparticles were synthesized using a twin-head electrospray system (THES). The coated nanoparticles were then used in antimicrobial air filters to increase their antimicrobial efficiency. Electrosprayed droplets were converted to NP nanoparticles and MWCNTs through ethanol evaporation. Oppositely charged NP nanoparticles and MWCNTs were coagulated via Coulombic collisions to form hybrid nanoparticles that were deposited continuously onto an air filter medium. The size distribution and composition of the hybrid NP/MWCNT particles were characterized using a wide-range particle spectrometer (WPS) and transmission electron microscope (TEM). The concentration of hybrid NP/MWCNT nanoparticles was lower than that of NP nanoparticles but higher than that of MWCNTs and showed a bimodal size distribution with peak diameters of 21.1 and 49 nm. TEM analyses confirmed that the NP nanoparticles were attached to the MWCNT surface with a density of $ 4-9 particles/MWCNT. When deposited onto the filter medium, NP/MWCNT particles formed dendrites on the filter's fiber surface. The filtration efficiency and pressure drop of the NP/MWCNT-coated filters were higher than those of pristine, NP nanoparticles-coated or MWCNTs-coated filters. The hybrid filter also exhibited stronger antimicrobial activity than those of NP or MWCNT-coated filters at identical deposited volumes (1.1 Â 10 -2 cm 3 / cm 2 filter ). Ninety-five percent of the tested bacterial aerosols were inactivated on the NP/ MWCNTs filter while only o70% were inactivated on NP-or MWCNT-coated filters.

Electrospun Nanofibers Membranes for Effective Air Filtration

“…Copyright 2008, Springer. b) Experimental setup for antimicrobial, filtration efficiency, and pressure drop test . Reproduced with permission .…”

“…There is another testing apparatus to determination antimicrobial efficiency, as shown in Figure b). In detail, dispersed bacterial aerosols passed through a diffusion dryer to remove moisture and are then introduced to a filter holder where the fabricated antimicrobial filter is installed.…”

“…The size distribution and concentration of the bacterial aerosol are measured using an aerodynamic particle size. The bacterial inactivation rate is reported using the Equation where CFU antimicrobial is the number of Colony‐Forming Units (CFUs) counted in the filter medium after filtration and CFU pristine is the number of CFU counted in the filter medium after filtration using a pristine filter.…”

Antimicrobial Air Filter Fabrication Using a Continuous High-Throughput Aerosol-Based Process

“…To monitor the stable spray mode of the system, transparent viewing ports were inserted on opposite sides of the mixing chamber. One was to allow the introduction of light into the chamber (MLC-150; Motic Instruments Inc., Richmond, BC, Canada), and the other was for observing the shape of the electrospray liquid meniscus using a CCD digital camera (MARIN F-145C2; Allied Vision Technologies Inc., Stadtroda, Germany) (Jung et al, 2009a, b;Hwang et al, 2015b). We carefully checked the stability of the electrospray mode in all experiments.…”

Antimicrobial nanoparticle-coated electrostatic air filter with high filtration efficiency and low pressure drop

“…Recently, extracts of natural products with antimicrobial activity have been considered as novel, efficient, and cost-effective materials for the development of antimicrobial filter media (Dixon, 2001). Plant extracts, such as Melaleuca alternifolia (tea tree), Eucalyptus, and Sophora flavescens, in particular, can be used as a coating for filters to inactivate fungal spores, bacteria, and influenza viruses (Huang et al, 2010;Hwang et al, 2015aHwang et al, , 2015bPyankov et al, 2008;Pyankov et al, 2012). The treatment of filter surfaces with nanosized particles of a natural product is an effective method for enhancing their antimicrobial activity, because the nanosized natural products provide the maximum possible specific surface area to contact surrounding agents.…”