Antibacterial effects of carbon quantum dots@hematite nanostructures deposited on titanium against Gram-positive and Gram-negative bacteria

Abstract

Thin films of nanostructured hematite (α-Fe2O3) and carbon quantum dots-incorporated hematite (CQDs@α-Fe2O3) were uniformly grown on titanium substrate and their antibacterial properties against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria were studied under dark and illumination conditions. The surface morphology of the samples was investigated with FE-SEM and HRTEM. The antimicrobial investigations demonstrate that α-Fe2O3 and CQDs@α-Fe2O3 are toxic to the selected microorganisms and the samples exhibit sustainable antibacterial activity against Gram-positive bacterial strains compared to Gram-negative bacteria mainly due to the presence of extra outer membrane layer in Gram negative bacteria. Based on the results of the antibacterial activity of α-Fe2O3 and CQDs@α-Fe2O3 under dark and the light irradiation conditions, it was concluded that the preferred mechanism of bactericidal activity of hematitebased thin films is both the penetration of iron cations into the bacteria cell via their membrane and the generation of reactive oxygen species. These results indicate that CQDs@α-Fe2O3 nanoparticulates provide insight into the development of visible-light antimicrobial materials for their potential bactericidal applications.

Quaternized carbon quantum dots with broad-spectrum antibacterial activity for the treatment of wounds infected with mixed bacteria

“…Nevertheless, the proton peaks of C=C (6. 21 due to the effect that the qCQDs contained more quaternary ammonium groups and formed more conjugated systems, which weakened the electronegativity in their structures and generated shielding effect, causing the proton peaks to shift toward high eld 35 .…”

“…Carbon quantum dots (CQDs), especially hetero-element doped CQDs with particle size of less than 10 nm, stand out in the eld of antibacterial research due to their advantageous properties including nontoxic nature, photostability, versatility in surface functionality for desired microbial adhesion and interactions, and their production from abundant and inexpensive precursors for extremely broad and low to ultralow cost applications [11][12][13][14][15][16] . At present, the mechanism of action of CQDs against bacteria mainly focuses on the three aspects of directly producing reactive oxygen species (ROS), such as superoxide (•O 2 − ) and hydroxyl radical (•OH) 17,18 , producing ROS assisted by photoactivation or other compound 6, [19][20][21] and damaging the cell membrane caused by the insertion of surface controlled CQDs through electrostatic interaction and/or hydrophobic interaction [22][23][24] . However, the above mechanism cannot further explain the signaling pathway of antibacterial CQDs against bacteria at the molecular level and there has been a lack of in-depth understanding of the interaction between such CQDs and bacteria.…”

Antibacterial properties of Ag/TiO2/PDA nanofilm on anodized 316L stainless steel substrate under illumination by a normal flashlight

“…It is based on the photochemical properties of semiconductor photocatalyst to generate reactive oxygen species (ROS), superoxide anion (O À 2 ) radicals under external energy such as the natural energy of sunlight [20][21][22]. TiO 2 , a wide band gap semiconductor (3.2 eV), is generally used as a photocatalyst in the presence of ultraviolet (UV) radiation [23,24]. However, it is still restricted by the large band gap structure and very high recombination rate of photogenerated electron-hole pairs [25].…”

Renewable Carbon Nanomaterials: Novel Resources for Dental Tissue Engineering

“…The introduction of graphene quantum dots (GQD) has, to some extent, overcome the shortcomings of graphene in biomedical applications. Besides lowering the cytotoxic effects of graphene, graphene quantum dots have shown sustainable antibacterial properties against Gram-negative and Gram-positive dental pathogens [6].…”