# Silver Nanoparticles-Loaded Exfoliated Graphite and Its Anti-Bacterial Performance
## 1 Introduction  
Microbial pollution caused by microorganisms has produced various problems in daily life (wound infection) and industry (wastewater discharge). Silver metal and compounds exhibit robust wide-spectrum bactericidal activity compared to other metal materials [1; 2; 3; 4]. Ag nanoparticles (AgNPs) are used in antimicrobial applications due to the antimicrobial effect of Ag ions. Nevertheless, practical applications of AgNPs may lose antibacterial activity owing to aggregation among particles [5; 6]. An effective way to prevent AgNPs from aggregation is to deposit AgNPs on some supports to fabricate AgNPs-loaded materials. Silica nanowires [7; 8; 9; 10], zeolite clay [6], titanium dioxide nanoparticles [11], and montmorillonite have been investigated for antibacterial support materials. However, unfavorable biocompatibility, large size, and low dispersity of these composites limit their practical applications.  
With huge specific surface area, proper micropores and excellent adsorption capacity, porous carbon materials have been widely used in wastewater treatments [12] and antibacterial support materials. Silver-loaded activated carbons, silver-loaded activated carbon fibers (Ag-ACFs) [13; 14; 15], and silver-loaded carbon aerogels [16] not only keep the excellent adsorption capacity of porouscarbon materials, but also endow them with antibacterial activity. Nanocarbon materials such as carbon nanotubes (CNT) [17; 18] and graphene [19; 20; 21; 22] have also been investigated as silver-carrying antibacterial agents. Especially graphene, for AgNPs loading, is a favorable matrix because of their abundant functional groups and large surface areas. A work provides the first direct evidence that Ag-loaded graphene oxide (Ag-GO) nanocomposites can inhibit the growth of microbial adhered cells, thus preventing the process of biofilm formation [23]. [PERSON] et al. [24] and [PERSON] et al. [25] demonstrated antibacterial activity for Ag-GO nanocomposites against Gram-negative _Escherichia coli_. The preparation of graphene is very complex and expensive; material availability and process-ability will encumber the performance and putative applications of graphene [26].  
Exfoliated graphite (EG) has layered structures, possessing in-plane electrical conductivity similar to that of natural flake graphite, but has larger layer spacing and higher volume. EG can be mass-produced and used in many applications such as gaskets, seals, etc. EG has abundant pore structure and excellent adsorption performance, and thus can be potentially used in depollution. For example, EGs have been studied for usage in dyeing wastewater treatment [27; 28]. EG has oxygen-containing functionalities such as hydroxyl, carboxylic, carbonyl, epoxide groups and can provide nucleation sites for Ag nanoparticles, therefore, Ag nanoparticles can strongly attach to the EG surface to obtain AgNPs-loaded EG. Compared to general polymer-based Ag composites [3], this material would have higher thermal and chemical stability. Ag-EG composite material keeps the electrical/thermal conductivity of EG, and its antibacterial effect gives it more extensive applications in industrial applications. Recently, metal nanoparticles-supported carbon materials have been effectively used for biomedical applications including wound healing [29; 30]. EGs possess excellent adsorption ability for protein [31], thus Ag-EG composites could be used as surgical dressing.  
In this study, we designed EG as the AgNPs' support, and prepared a new anti-bacterial composite. Firstly, graphite was chemically oxidized, and then was reduced by NaBH\({}_{4}\) together with AgNO\({}_{3}\) at normal atmospheric conditions. Finally, the antibacterial activities of Ag-EG composite materials were evaluated by using the zone of inhibition method.