The use of noble metal loading such as Ag to improve the photocatalytic performance of TiO2 has been well studied. Though different synthesis methods have been used to synthesize Ag-TiO2 nano-composite, the effect of the different synthesis routes on the photocatalytic performance has not been studied and compared. This study focusses not only on the enhancement of photocatalytic performance by the addition of Ag, but also on the influence of the synthesis process on photocatalytic performance. Two different routes: photodeposition (PD) and formaldehyde assisted microwave (MW) synthesis of Ag-TiO2 nano-composite and their photocatalytic performance were evaluated using model pollutants. The Ag-TiO2 were synthesized using different wt.% (0.5, 1.0, 1.5 and 2.0 wt.%) of Ag. The synthesized Ag-TiO2 were characterized with x-ray diffractometer, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and UV-vis spectrophotometry. The Ag-TiO2 photocatalyst showed superior photocatalytic performance towards rhodamine b dye as compared to raw TiO2. 0.5 wt.% Ag-TiO2-PD recorded the highest rate constant and degradation percent among the composites synthesized using photodeposition (PD) method. On the other hand, 1.0 wt.% Ag-TiO2-MW performed better among the composites synthesized using microwave and formaldehyde assisted synthesis. The potential of these best performing composites; 0.5 wt.% Ag-TiO2 and 1.0 wt.% Ag-TiO2 to photocatalytically degrade pharmaceutical (Naproxen Sodium and Flurbiprofen) and pesticide (Atrazine and Pyrimethanil) pollutants were examined. These composites degraded the pollutants exceptionally well with 0.5 wt.% Ag-TiO2-PD outperforming the 1.0 wt.% Ag-TiO2-MW. 1H NMR and 13C NMR analysis revealed that the synthesized Ag-TiO2 were effective in degrading the model pollutants.
Silver nanoparticles (AgNPs) have been synthesized from the more chemically rich and diverse cocoa pod; the synthesis of silver nanoparticles from cocoa leaves, which are less rich and have low diversity in bioactive molecules, is yet to be achieved. In this work, AgNPs produced using the extracts of the cocoa leaf (CL) and cocoa pods (CP) have been investigated and their antimicrobial activity against E. coli was evaluated. UV-visible absorption spectroscopy was used to examine the reduction of silver ions in solution and the surface plasmon resonance of AgNPs. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to further characterize the nanoparticles. The crystalline nature of AgNPs was confirmed by XRD, and the purity and presence of elemental silver were determined by EDX. CL-AgNPs were observed to have a surface plasmon resonance of 425 nm, while CP-AgNPs had a surface plasmon resonance of 440 nm. CL-AgNPs had a significantly higher purity than CP-AgNPs. With a shorter nucleation time, the intensity of the UV-Vis spectrum was always higher in the case of CL-AgNPs, indicating a larger population of bioactive molecules available for CL-AgNPs synthesis. FTIR confirmed the presence of phenolic compounds in the leaf and pod extract, implying that water-soluble polyphenolic and flavonoid chemicals are responsible for nanoparticle reduction, capping, and stability. AgNPs generated from CL and CP extracts are polydispersed, with particle sizes of 10–110 nm and 20–680 nm, respectively, according to DLS. The corresponding zeta potentials measured are −2.7 mV for CL-AgNPs and −0.93 mV for CP-AgNPs. The zeta potential values suggest that the particles have long-term stability. Furthermore, CL-AgNPs outperformed CP-AgNPs in terms of antibacterial activity against Escherichia coli. CL-AgNPs were found to have a maximal inhibitory zone of 21 mm.
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