Synthesis of silver nanoparticles in montmorillonite and their antibacterial behavior

Figures & data

Table 1 Physical properties of Ag NPs in Ag/MMT NCs synthesized at different AgNO₃ concentrations: (S1) 0.5%, (S2) 1.0%, (S3) 1.5%, (S4) 2.0%, and (S5) 5.0%

Samples	Reaction volume (lit)	λmaxa	Absorbanceb	Approximated efficiency (%)	Ag NPs particle sizec (nm)
S1	0.50	396	0.91	98.04 ± 1.45	4.11 ± 1.67
S2	1.00	398	1.17	96.23 ± 1.39	4.19 ± 1.58
S3	1.50	400	1.91	95.40 ± 2.67	5.75 ± 1.93
S4	2.00	402	2.34	89.24 ± 2.14	6.74 ± 1.76
S5	5.00	406	3.72	85.57 ± 4.28	8.53 ± 1.81

Notes:

a The experiments were repeated three times and averaged to give the data in Table 1;

b The data were obtained by multiplying the absorbance of the corresponding diluted solutions by their dilution factors when diluted solutions were used for the data;

c The size of Ag NPs was determined by measuring diameters of about 100 nanoparticles in TEM image and by averaging them.

Table 2 Average inhibition zone and standard deviation for MMT, AgNO₃/MMT (S0), and Ag/MMT NCs at different AgNO₃ concentrations: (S2) 1.0%, (S4) 2.0%, and (S5) 5.0%

Bacteria	Inhibition zone (mm)				Control negative MMT (10 mg/mL)	Control positive (mm)
	S0	S2	S4	S5		CTX	C
E. coli	8.74 ± 0.23	8.30 ± 0.13	7.32 ± 0.14	8.07 ± 0.10	NA*	22.84	18.90
E. coli O157:H7	10.74 ± 0.32	9.80 ± 0.41	7.82 ± 0.10	7.36 ± 0.21	NA	30.01	20.84
K. pneumoniae	10.98 ± 0.17	10.38 ± 0.30	9.56 ± 0.30	9.72 ± 0.32	NA	31.04	24.69
S. aureus	10.02 ± 0.10	9.95 ± 0.10	9.52 ± 0.14	9.38 ± 0.21	NA	27.78	20.14
MRSA	8.97 ± 0.27	9.21 ± 0.13	8.98 ± 0.04	9.04 ± 0.17	NA	18.91	15.54

Abbreviations:

* NA, not appearing; MMT, montmorillonite; MRSA, methicillin-resistant Staphylococcus aureus; CTX, cefotaxime; C, chloramphenicol.

Figure 1 Schematic illustration of the synthesized Ag NPs in the interlayer space of MMT suspension by chemical reduction method.

Figure 2 Photograph and UV-visible absorption spectra of Ag/MMT suspension for different AgNO₃ concentrations; 0.5%, 1.0%, 1.5%, 2.0%, 5.0% (S1–S5), and (S0) AgNO₃/MMT suspension.

Figure 3 PXRD patterns of MMT and Ag/MMT NCs for determination of d-spacing at different AgNO₃ concentrations: (S2) 1.0%, (S4) 2.0%, and (S5) 5.0%.

Figure 4 PXRD patterns of MMT and Ag/MMT NCs for determination of silver crystals at different AgNO₃ concentrations: 0.5%, 1.0%, 1.5%, 2.0% and 5.0% (S1–S5).

Figure 5 TEM images and corresponding particle size distribution of Ag/MMT NCs at different AgNO₃ concentrations: 1.0% (A, B), 2.0% (C, D), and 5.0% (E, F).

Figure 6 SEM micrographs and EDXRF spectra respectively for the MMT (A, B), Ag/MMT NCs at different AgNO₃ concentrations: 1.0% (C), 2.0% (D), 5.0% (E), and (F).

Figure 7 FT-IR spectra for the MMT and Ag/MMT NCs at different AgNO₃ concentrations: (S2) 1.0%, (S4) 2.0%, (S5) 5.0%.

Figure 8 Comparison of the inhibition zone test between Gram-negative and Gram-positive bacteria (Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and methicillin-resistant S. aureus) form S0 (1), S2 (2), S4 (3), S5 (4), and MMT (5) respectively.