|Our current work
Modeling and Simulation:
In the past, PI and his research group have published models (Fig. 3b) and simulation of spherical,36 core-shell 37,38 and anisotropic nanoparticles,39 of different semiconductor materials (CdS, CdS-ZnS, PbS-ZnS, ZnO, ZnS) and validated these with experimental data of both their own and others’. Thus the PI has a theoretical framework, elucidating the simultaneous interplay of species-transport, chemical reaction, nucleation, particle growth and coagulation, leading to a nanoparticle dispersion in a liquid phase. This will be further generalized to tackle the special issues of intermediate metal cluster formation, finally translating to metal nanoparticle formation.
On the application front, we have successfully made Ag particle embedded AC for the first time in the recent past (Figs. 1c and 1d), to assess its ability in inhibiting the growth of E. coli.40 Ag-AC was made by impregnating AC with AgNO3 and then reducing it to metallic Ag. Plate assay showed slight inhibition of E. coli, even with Ag-AC prepared from 0.005 M AgNO3, but this and shake flask tests showed a conspicuous effect only for higher concentrations of 0.1 M – 1 M AgNO3 (Fig. 4) . Flow tests further indicated that Ag-AC made from 1.0 M AgNO3 caused a desirable 3 orders of reduction in E. coli number concentration in less than 30 seconds. Based on these preliminary results one can conclude that, about 9 - 10.5 wt.% of embedded Ag in the final Ag-AC product is necessary for the requisite complete inhibition of E. coli, killing bacteria in the contact-mode for up to 350 liters of flowing water. These results have shown us that Ag-AC possesses antibacterial property and can be used for disinfection to produce potable quality water. We have started Ag nanoparticle synthesis by citrate reduction too (Fig. 5).
Our results, therefore, establishes the role of Ag used directly in solid AC granules, facilitating potential adoption of already used AC,41 as a value added Ag-AC product for potable water production. This is in contrast to the previous work in the literature focusing only on the role of colloidal solutions of metallic Ag particles,42,43 or Ag ions in some cases,44 in mitigating bacterial growth.
Next we want to study surface modification of AC and other methods of Ag synthesis and impregnation (discussed in detail in the section on “Methodology”) for their disinfection capabilities. So these are the directions (emanating from recent work in our group) in which further investigation will be carried out in the proposed research project.
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