Table 1 CA-AuNPs and cf-CA-AuNPs synthesized using various concentrations of caffeic acid
From: Catalytic reduction of 4-nitrophenol with gold nanoparticles synthesized by caffeic acid
Caffeic acid final concentrations | 0.08 mM | 0.12 mM | 0.16 mM | 0.20 mM | 0.24 mM | 0.28 mM | 0.32 mM | 0.36 mM | 0.40 mM | |
|---|---|---|---|---|---|---|---|---|---|---|
CA-AuNPs | Absorbance | 0.541 | 0.823 | 1.012 | 1.101 | 1.130 | 1.045 | 1.056 | 1.066 | 1.059 |
Wavelength (nm) | 537.5 | 549.0 | 545.0 | 535.0a | 544.0 | 550.5 | 561.5 | 576.5 | 587.0 | |
Particle size (nm) from HR-TEM images | 32.61 ± 6.13 | 31.37 ± 6.06 | 29.33 ± 5.41 | 29.99 ± 7.43b | 23.73 ± 3.20 | 25.79 ± 4.73 | 26.51 ± 5.27 | 27.46 ± 5.82 | 29.55 ± 7.43 | |
Number of particles in HR-TEM taken for size measurement | 132 | 88 | 137 | 123c | 148 | 128 | 125 | 104 | 105 | |
Hydrodynamic size (nm)d | 619.6 | 423.1 | 153.4 | 109.6 | 95.4 | 89.4 | - | - | 222.6 | |
pH | 4.36 | 4.29 | 4.23 | 4.09 | 4.07 | 4.15 | 4.11 | 3.92 | 3.87 | |
cf-CA-AuNPs | Absorbance | 0.455 | 0.677 | 0.724 | 0.812 | 0.896 | 0.680 | 0.705 | 0.769 | 0.722 |
Wavelength (nm) | 538.0 | 554.0 | 550.50 | 548.5 | 547.0 | 555.5 | 568.0 | 584.0 | 592.5 | |
Hydrodynamic size (nm) | 155.3 | 134.0 | 104.4 | 80.6 | 72.0 | 75.4 | 88.6 | 96.2 | 122.6 | |
pH | 5.18 | 5.47 | 5.41 | 5.22 | 5.17 | 5.20 | 5.04 | 5.30 | 5.18 | |
Absorbance ratio [cf-CA-AuNPs/CA-AuNPs] × 100 (%) | 84.1 | 82.3 | 71.5 | 73.8 | 79.3 | 65.1 | 66.8 | 72.1 | 68.2 | |