How Oxygen‐Containing Groups on Graphene Influence the Antibacterial Behaviors

Abstract

is time consuming and labor intensive and is not suitable for mass production. Epitaxial growth can produce good-quality graphene while it acquires rigorous conditions and expensive fabrication systems. CVD technique is an effective way to obtain graphene monolayers with large surface areas while it still cannot meet the needs of application. Presently, the reduction of GO stands out as an important strategy for production of graphene. [9] There mainly exist four kinds of oxygen-containing functional groups on GO including hydroxyl (CO), epoxide (COC), carbonyl (CO), and carboxyl (COOH). Hydroxyl and epoxide, located on the basal plane of GO, are the major components, while carbonyl and carboxyl are minor which are distributed at the edges of GO. [10] The nature of the reduction of GO is to remove the oxygen-containing groups from GO. Thermal annealing and chemical reduction are usually used for the reduction of GO. Carboxyl groups can be slowly reduced at 100-150 °C. [11] The high temperature process can remove most of the carbonyl and carboxyl groups by forming CO or CO 2 . [12] There are numerous chemical reducing agents that can be applied for the reduction of GO, for example, borohydrides, [13] hydrohalic acid, [14] nitrogen-containing reducing agents, [15] and so on. Reduction of GO by chemical reducing reagents is based on their chemical reactions. Therefore, we can selectively reduce oxygen-containing groups by choosing specific chemical reducing agents. To date, reduction methods with wellsupported mechanisms mainly include hydrazine hydrate and sodium borohydride. Hydrazine hydrate can open the ring of epoxy groups by forming hydroxyl groups generating dehydroxylation subsequently. [10] Sodium borohydride can turn carbonyl (CO) into hydroxyl (CO) while it does not reduce carboxyl groups, which results in the increasing CO ratio after being reduced. [16] Different reduction processes result in various types and quantities of oxygen-containing groups on the reduced graphene oxide (rGO) with assorted properties, which in turn influences the final performance of materials composed of rGO. Moreover, the biological responses certainly vary depending on the oxygen-containing groups and defects on rGO. Therefore, in this work, GO films were fabricated on the titanium surfaces by cathode electrophoretic deposition, followed by the reduction processes of thermal annealing, hydrazine hydrate, and sodium borohydride chemical reduction. The reduction degrees Graphene can be obtained with the reduction of graphene oxide (GO). Various reduction methods will result in different varieties and amounts of oxygen-containing groups on the reduced graphene oxide (rGO) with diverse properties. In this work, rGO is fabricated on the titanium surfaces by the reduction process of GO through three types of reduction methods, for example, vacuum thermal annealing, hydrazine hydrate, and sodium borohydride chemical reduction. Results show that thermal annealing can remove carboxyl entirely at 600 °C for 1 h, and hydrazine...

Combination types between graphene oxide and substrate affect the antibacterial activity

“…In our previous studies [ 27 ], we found that increasing the number of layers of GO on titanium surfaces could improve the antibacterial activity by increasing the reactive oxygen spices (ROS) levels which was opposite to the result as mentioned above. Moreover, we also found that GO on titanium surface presented stronger antibacterial activity than rGO which were reduced by vacuum heat treatment, hydrazine hydrate and sodium borohydride, respectively [ 28 ]. From above we can know that antibacterial activities of GDs vary with various factors, such as size, number of layers, oxygen-containing groups, experimental surroundings.…”

Graphene Materials in Antimicrobial Nanomedicine: Current Status and Future Perspectives

“…[57][58][59] In other words, the chemical nature of GMs presumably affects the oxidative stress generation capability and intermolecular interactions with microorganism surfaces. "nanoknife" mechanism), (ii) oxidative stress-induced damaging of cellular/membrane components, (iii) wrappingmediated blockage of membrane transport and/or restriction of growth, and (iv) membrane destabilization by insertion and destructive extraction of membrane components.…”

“…Among the critical experimental conditions that affect the interplay of the mechanisms explained above is the functional group profile of GMs. [57][58][59] In other words, the chemical nature of GMs presumably affects the oxidative stress generation capability and intermolecular interactions with microorganism surfaces. (Interested readers may find further insights regarding the structure-property-mechanism relationships of GMs' antimicrobial activity in ref.…”

Chemically Reduced Graphene Oxide-Reinforced Poly(Lactic Acid)/Poly(Ethylene Glycol) Nanocomposites: Preparation, Characterization, and Applications in Electromagnetic Interference Shielding

“…In this method, chemically reduced graphene oxide (RGO) (graphene), was prepared through oxidizing graphite in the presence of oxidants and strong acids, followed by graphene oxide (GO) reduction using one of the reduction chemical methods [31]. On its surface, the residual oxygen functional groups were retained by the resulting RGO, which will greatly influence its properties and that of its nanocomposites [32].…”