Effect of free oxygen radical anions and free electrons in a Ca12Al14O33 cement structure on its optical, electronic and antibacterial properties
Chaiwat Phrompet,
Chaval Sriwong,
Pornjuk Srepusharawoot,
Santi Maensiri,
Prinya Chindaprasirt,
Chesta Ruttanapun
Affiliations
Chaiwat Phrompet
Smart Materials Research and Innovation Unit (SMRIU), Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang, Bangkok 10520, Thailand; Department of Physics, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang, Bangkok 10520, Thailand
Chaval Sriwong
Smart Materials Research and Innovation Unit (SMRIU), Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang, Bangkok 10520, Thailand; Department of Chemistry, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang, Bangkok 10520, Thailand; Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400, Thailand
Pornjuk Srepusharawoot
Institute of Nanomaterials Research and Innovation for Energy (IN-RIE), Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand; Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400, Thailand
Santi Maensiri
School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400, Thailand
Prinya Chindaprasirt
Sustainable Infrastructure Research and Development Center, Department of Civil Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand; Academy of Science, The Royal Society of Thailand, Dusit, Bangkok 10300, Thailand
Chesta Ruttanapun
Smart Materials Research and Innovation Unit (SMRIU), Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang, Bangkok 10520, Thailand; Department of Physics, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang, Bangkok 10520, Thailand; Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400, Thailand; Corresponding author.
The aim of this work was to investigate the effect of free oxygen radicals and free electrons in a Ca12Al14O33 (C12A7) cement structure on the optical, electronic and antibacterial activity of this material. Ca12Al14O33 was successfully fabricated via rapid heating to high temperatures by high frequency electromagnetic induction. Ca12Al14O33 cement samples were characterized using XRD and UV-Vis-DRS spectroscopy. The morphology and chemical composition of the samples were also investigated using SEM and EDS techniques. The presence of free oxygen radicals (O2−ions) in the insulating structure of Ca12Al14O33 was confirmed using Raman spectroscopy showing a spectrum peak at 1067 cm−1. The excitation of free electrons in the Ca12Al14O33 cement was indicated by UV-Vis absorption spectra at 2.8 eV and an optical energy gap of 3.5 eV, which is consistent with the first-principles calculations for the band energy level. The effects of free oxygen radicals and free electrons in the Ca12Al14O33 structure as antibacterial agents against Escherichia Coli (E. coli) and Staphylococcus Aureus (S. aureus) were investigated using an agar disk-diffusion method. The presence of O2− anions as a reactive oxygen species (ROS) at the surface of Ca12Al14O33 caused inhibition of E. coli and S. aureus cells. The free electrons in the conducting C12A7 reacted with O2 gas to produce ROS, specifically super oxides (O2−), superoxide radicals (O2•-), hydroxyl radicals (OH•) and hydrogen peroxide (H2O2), which exhibited antibacterial properties. Both mechanisms were active against bacteria without effects from nano-particle sized materials and photocatalytic activity. The experimental results showed that the production of ROS from free electrons was greater than that of the free O2− anions in the structure of Ca12Al14O33. The antibacterial actions for insulating and conducting Ca12Al14O33 were different for E. coli and S. aureus. Thus, Ca12Al14O33 cement has antibacterial properties that do not require the presence of nano-particle sizes materials or photocatalysis.
