## 1 Introduction  
Nanotechnology is predominantly concerned with synthesis of nanoparticles of variable sizes, shapes, and chemical compositions, along with their potential use in human welfare [1]. The metal and semiconductor nanoparticles synthesis is an extending research area for the potential applications of nanoparticles and for the advancement of novel technologies [2; 3]. The nanoparticles can be synthesized by different methods (physical, chemical, and biological) and by using different substrates (pure compounds, microorganism, and plant extract) [4; 5]. The chemical approach is robustly scaled for the large-scale production of nanoparticles of tunable shape and size by using different synthesis conditions. However, the chemical method uses toxic solvents, which are hazardous and makes them unsuitable for biomedical applications [6]. The physical methods for nanoparticles synthesis are expensive and not appropriate for large-scale production [7; 8]. Therefore, there is an increasing demand to develop environmentally feasible, low-cost, energy-efficient, and high-yield procedures for their synthesis. So, the biological approaches (bacteria, fungi, yeasts, and plant/plant extract) for synthesizing nanoparticles become imperative to an ecofriendly synthesis procedure [9; 10; 11].  
Silver as well as gold nanoparticles are of great medicinal importance. Gold nanoparticles (GNPs) possess unique physicochemical properties, which attract the interest and demand of nanoparticles researchers [12; 13; 14]. Gold nanoparticles find applications in sensor devices, catalysis, optoelectronics [15], and in medicine [16].  
The unique and unexpected catalytic properties of GNPs [16; 17] make them suitable for the small-sized nanoparticle synthesis [15; 18; 19]. GNPs have additionally been utilized for different applications, such as immunoassay [20; 21], protein analysis assay [22], mass spectrometry [6], capillary electrophoresis [23], and identification of cancer cells [24]. Nanoparticles can act as antimicrobial agents, due to their ability to interact with microorganisms [25; 26; 27]. The interaction of nanoparticles with the cell wall of a microorganism disturbs the cell's functions by altering permeability, damaging the respiratory chain enzymes by depressing its activity, and, ultimately, causing cell death [28]. Plant-mediated nanoparticles have also been screened for antibacterial activity [29]. Silver nanoparticles are good antimicrobial agent and, in some studies, silver-based antimicrobial material was used to achieve a wide spectrum of functionalities [30]. Despite silver nanoparticles, gold nanoparticles were also screened for antibacterial potential. In one study, the author mixed gold nanoparticles with antibiotics, and enhancement in antibacterial activity was observed [31]. Another author's experimental finding showed that the observed activity was actually attributed to the antibiotic, not GNPs [32]. These results contradict the concept of the antibacterial activity possessed by GNPs. The present study, based on green chemistry synthesis of nanoparticles, proposes synthesis of nanoparticles using _Quercus incana_. The added advantage of using _Quercus incana_ is that it simultaneously acts as a reducing, capping, and stabilizing agent. This study also compared the results of antimicrobial activities with standard and leaves extract of _Quercus incana_. To confirm the presence and support the synthesis of bioactive compounds, physiochemical, Gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared (FT-IR) analyses were conducted.