Carrier Based Metal Nanoparticles:Synthesis, Characterization, And Applications

Synthesis of nanoparticles (NPs) has gained rising attention due to their high specific surface area and higher catalytic reactivity than bulk. On the other hand, nanotechnology for environmental specially wastewater remediation is a highly foreseen frontier, as the growing demand for a limited supply of clean water places an vital need on technologies that can bring cleaner, faster, and more affordable water treatment measures. Two kinds of carrier (graphene, spherical polyelectrolyte brushes) and metal NPs (Fe, Ag, and Cu) were used for nanocomposite synthesis, which are used for the removal of contaminants like chlorinated compounds, bacteria, and organic dyes.Graphene oxide (GO) and nano-sized zero valent iron-reduced graphene oxide (nZVI-rGO) composite were prepared by in situ method. The GO and nZVI-rGO composite were characterized by transmission electron microscopy (TEM), FTIR, EDS and Raman spectroscopy. The size of nZVI was about 6 nm as observed by TEM. The system of nZVI-rGO and persulfate (PS) was used for the degradation of trichloroethylene (TCE) in water, and showed 26.5% more efficiency as compared to nZVI/PS system. The different parameters were studied to determine the efficiency of nZVI-rGO to activate the PS system for the TCE degradation. By increasing the PS amount, TCE removal was also improved while no obvious effect was observed by varying the catalyst loading. Degradation was decreased as the TCE initial concentration was increased from 20 to 100 mg/L. Moreover, when initial solution pH was increased, efficiency deteriorated to 80%. Bicarbonate showed more negative effect on TCE removal among the solution matrix. To better understand the effects of radical species in the system the scavenger tests were performed. The·SO4- and ·O2-were predominant species responsible for TCE removal. The nZVI-rGO activated PS process shows potential applications in remediation of highly toxic organic contaminants such as TCE present in the groundwater.nZVI-rGO activated PS was used to investigate the generation of reactive oxygen species (ROS) for the degradation of TCE in the aqueous solution. More than 98% of TCE was degraded within 2 minutes under experimental conditions. The generation of·OH increased when the pH was shifted towards basic region while·SO4- radicals’ intensity increased in the acidic pH. Different effects have been observed in ·O2- generation in the neutral and strong basic pH and decreased in acidic or slightly basic pH. In addition, The intensity of·OH was increased with the addition of HCO3- (10 mM) and NO3- (100 mM) while decreased in the presence of Cl- (10 and 100 mM), HCO3 (100 mM), and NO3- (10 mM). The degradation of anisole, probe for both ·OH and ·SO4-, was slightly enhanced by 10 mM NO3- anions but decreased in 100 mM anions solution. ·O2- intensity was increased while HCO3- (10 and 100 mM) and NO3- (100 mM) anions were used. nZVI-rGO activated persulfate process could remove TCE in aqueous effectively, and the ROS generation and intensity were influenced by solution pH values and anions.Simple one pot synthesis of different composition of iron-silver bimetallic nanoparticles on graphene support has been demonstrated. The nanoparticles are well dispersed on the graphene sheet as revealed by the TEM. The XRD and Raman spectra show that graphene supported FeAg nanocomposites (NC) were successfully synthesized. The antibacterial activity of graphene-FeAg NC towards Bacillus subtilis, Escherichia coli, and Staphylococcus aureus was investigated by colony counting method. Graphene-FeAg NC demonstrates excellent antibacterial activity as compared to FeAg bimetallic without graphene. To understand the antibacterial activity of the NC, a mechanism study was conducted. Oxidative stress caused by ROS was investigated in the system. It has been observed that ROS production is concentration dependent while the enhancement of silver content generally increases the ROS production. The oxidation capability towards the glutathione (GSH) oxidation also shows concentration dependent tendency. Graphene loaded FeAg NCs demonstrate higher GSH oxidation capacity than bare FeAg bimetallic nanocomposite. The mechanism study suggests that the antibacterial activity is probably due to membrane and oxidative stress produced by the nanocomposites. The possible antibacterial pathway includes the non-ROS oxidative stress and metals NC contact with the bacteria or ions mediated ROS within the bacterial cells.Magnetic bimetallic FeCu nanoparticles supported on the reduced graphene oxide (rGOFeCu) is synthesized which exhibit enhanced antibacterial, as well as shows high efficiency in the removal of 1,1,1-trichloroethnae (TCA). The nanocomposite is characterized by TEM and XRD. Nano-sized FeCu on the graphene are successfully synthesized as confirm by TEM. Iron has strong bactericidal effect toward bacteria. To better understand antibacterial activity of rGOFeCu, we conducted the antibacterial activity of different composition of nanocomposite toward the E. coli. In the same concentration and incubation time conditions, rGOFeCu shows the highest antibacterial activity, as compare to the rGO supported iron. Results show that antibacterial activity is time and concentration dependent. rGOFeCu with 5% copper loading exhibits excellent removal efficiency. This rGOFeCu represent a highly potential material for antibacterial activity and remediation of other contaminants in the wastewater.In addition, Ag2O nanoparticles were synthesized using colloidal solution of spherical polyelectrolyte brushes (SPB) as nano-reactors. In this work, the average diameter of Ag2O nano-particles was around 10 nm as determined by TEM. The composite nano-particles of Ag2O immobilized in SPB (Ag2O-SPB) showed significant absorption in the visible light region as confirmed by UV-Vis diffuse reflectance spectra (DRS), and their photoluminescence (PL) exhibited emission peak in the visible range. Ag2O-SPB has shown outstanding photo-catalytic activity during degradation of methyl blue (MB) in the visible light, which opened up a new way to prepare ideal Ag2O nano-catalyst for the remediation of wastewater using visible light.