Plant-mediated synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. In the present study, we synthesized silver (Ag) nanoparticles using aqueous extracts of fresh leaves of Impatiens balsamina and Lantana camara medicinal plants as bioreducing agents. This method allowed the synthesis of nanoparticles, which was confirmed by ultraviolet-visible (UV-Vis) spectrophotometry and transmission electron microscopy (TEM). UV-Vis spectra and visual observation showed that the color of the fresh leaf extracts of L. camara and I. balsamina turned into grayish brown and brownish yellow, respectively, after treatment with Ag precursors. In addition, TEM analysis confirmed that AgNO3 solutions for all concentrations produced Ag nanoparticles and their average size was less than 24 nm. Moreover, aqueous leaf extracts of I. balsamina and L. camara were separately tested for their antimicrobial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. The results showed that the bacterial growth was inhibited by the extracts containing Ag nanoparticles. Statistical calculation performed using the Tukey test showed that zones of inhibition for the two bacteria produced by the aqueous leaf extracts of L. camara containing 3 mM and 5 mM Ag precursors were not significantly different from that by ciprofloxacin as positive control. On the contrary, there was significant difference between the zone of inhibition for E. coli by ciprofloxacin and that by the extracts of I. balsamina leaves containing 3 mM and 5 mM Ag precursors. A similar result was observed on the zone of inhibition for S. aureus by the extracts of I. balsamina leaves containing 3 mM Ag precursor. It was shown that the aqueous extracts of fresh L. camara leaves containing Ag nanoparticles were comparable to ciprofloxacin in inhibiting bacterial growth.

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Platinum (Pt) nanoparticles have been synthesized from a precursor solution of potassium tetrachloroplatinate (K2PtCl4) using a matrix of bacterial cellulose (BC). The formation of Pt nanoparticles occurs at the surface and the inside of the BC membrane by reducing the precursor solution with a hydrogen gas reductant. The Pt nanoparticles obtained from the variations of precursor concentration, between 3 mM and 30 mM, and the formation of Pt nanoparticles have been studied using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and thermogravimetry analysis (TGA). Based on X-ray diffraction patterns, Pt particles have sizes between 6.3 nm and 9.3 nm, and the Pt particle size increases with an increase in precursor concentration. The morphology of the Pt nanoparticles was observed by SEM-EDS and the content of Pt particles inside the membrane is higher than that on the surface of BC membranes. This analysis corresponds to the TGA analysis, but the TGA analysis is more representative in how it describes the content of Pt particles in the BC membrane.

Summary The Pt nanoparticles have been synthesized in situ using bacterial cellulose (BC) membranes as the matrix. The BC was immersed in a solution of PtCl4 and H2PtCl6 as Pt(IV) precursors also in surfactant stabilized Multiwall Carbon Nanotubes (MWCNT) as carbon source. Then, the Pt(IV) was reduced by hydrogen gas. Two routes have been applied for the insertion Pt particles; in the first route the Pt particles were inserted before the insertion of MWCNT and in the second route the other way around was applied. The products of these two insertion routes for each precursor are designated as BC‐PtPtCl4‐MWCNT, BC‐PtnormalH2PtCl6‐MWCNT for the first route and BC‐MWCNT‐PtPtCl4, BC‐MWCNT‐PtnormalH2PtCl6 for the second route, respectively. Both routes revealed that the Pt particles insertion in BC depends on the type of precursors and insertion routes, as seen from the morphology and Pt particles content. The first route produces Pt diameter of 26 nm while the second one 42 nm. The use of PtCl4 in the first route resulted in higher content of Pt particles (50%) compared to H2PtCl6 (39%). On the other hand, the type of precursor did not give any significant effect to the content of Pt inserted; both gave 29% of Pt to the second route. The high Pt content observed on the BC‐PtPtCl4‐MWCNT membrane surface is possible because PtCl4 precursor forms H2[PtCl4(OH)2] that initially can be bound via hydrogen bonding to the BC backbone. It is concluded that smaller size and high content of Pt particles have been obtained from PtCl4 precursor, the distribution of Pt particles and MWCNT are almost homogenous in the BC‐PtPtCl4‐MWCNT membrane derived from precursor PtCl4.