Synthesis, characterization, DNA binding and photocleavage studies of a di-ruthenated porphyrin
Metal-decorated carbon substrates such as carbon nanotubes, graphene oxide (GO), and carbon nanoparticles have been of great interest to the scientific community for the last three decades due to numerous potential applications. Graphene oxide is an oxidized derivative of graphene and is obtained from the severe oxidation of graphite powder. This process introduces oxygen-containing functional groups to the surface of GO. Chemical species both organic and inorganic molecules can be attached to the surface of graphene oxide via these functional groups. Also, functional groups on its surface can serve as nucleation and growth sites for metalnanoparticles. Metal nanoparticles especially Ag, have exhibited remarkable optical, antibacterial, and imaging properties just to name a few, at the nanometer level. However, during synthesis, these nanoparticles tend to agglomerate resulting in loss of their nanoscale properties. Since GO high surface area can serve as nucleation sites for metal nanoparticles, it can be used as a substrate to deposit metal nanoparticles. This will reduce agglomeration of Ag nanoparticles, thus allowing the properties that Ag exhibit at the nano-level to be accessed. In addition, recent results show that Ag-GO has very good antibacterial results. GO traps bacteria while Ag kills bacteria. Therefore, we intend to obtain the optimum ratio of Ag to GO which can be used in future studies in antibacterial filters. In this work, synthesis and characterization of Ag-decorated GO was investigated using sonochemistry. The initial approach to control the loading of Ag nanoparticle on the surface of GO involved changing the weight ratio between silver acetate and GO. However, it failed to achieve the desired control of Ag loading on GO surface and has led to the second approach, in which 26 wt% Ag-GO sample (26 wt% Ag) was mixed with GO. TEM analysis showed the second approach offers a better control of silver loading on GO surface. 26 wt% Ag-GO sample was prepared by mixing GO with silver acetate in DMF and sonicated for 20 minutes. By varying the weight ratio between 26 wt% Ag-GO and GO, a series of Ag-GO samples with different Ag loadings (15 to 6 wt% Ag) were synthesized and studied using TEM, XRD, TGA and DSC. Resulting Ag nanoparticles were spherical in shape with an average size of ̃6-7 nm, a size distribution of 1-22 nm, and were evenly distributed on the surface of GO sheets. In XRD, all the Ag-decorated GO samples exhibited the characteristic peaks of GO and fcc Ag. Thermal analysis performed for all Ag-GO samples using simultaneous TGA/DSC measurement revealed that the peak related to the combustion of graphitic carbon shifted to lower temperatures after GO was decorated with Ag nanoparticles. The analysis of Ag-GO samples with different Ag loadings, especially TEM analysis revealed that the newly added GO is also homogeneously decorated with Ag nanoparticles. This means Ag nanoparticles should migrate from 26 wt% Ag-GO to newly-added GO without any coalescence of Ag nanoparticles. Since the newly added GO has the same morphology as GO of 26 wt% Ag-GO, it is difficult to confirm the migration of Ag nanoparticles from Ag-GO to newly-added GO. For this purpose, multi-walled carbon nanotube (MWNTs) was mixed in DMF with 26 wt% Ag-GO instead of GO because MWNTs have very different morphology from GO. Resulting Ag-GO-MWNTs product consistently demonstrated that MWNTs were evenly decorated with Ag nanoparticles and XRD analysis confirmed the presence of fcc silver nanoparticles in the sample. This control experiment confirmed that Ag nanoparticles are migrating from GO to newly-added MWNTs without any coalescence. In addition, little or no migration of Ag nanoparticles was observed in other solvents, including water and hexane. In addition, our further experiments showed that Ag nanoparticles did not migrate from Ag-GO to neither carbon nanoparticles nor cotton wool even though these materials possess similar functional groups.