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Supporting Information

Acacia nilotica(Babool) Leaf ExtractMediated Size Controlled Rapid Synthesis of Gold Nanoparticles and Study of its Catalytic Activity

Test for phenolic compounds (FeCl3 Test):


This test was performed to confirm the presence of phenolic compounds in the leaf extract of Acacia nilotica. A freshly prepared aqueous solution of FeCl3 was added to the aqueous plant extract contained in a test tube and shaken. Instant appearance of greenish color indicated the presence of phenolic compounds in the leaf extract of Acacia nilotica.

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Figure S1: Mass spectrum of Acacia nilotica leaf extract


Figure S2: High Resolution Transmission Electron Microscopy Images of AuNPs obtained with the leaf extract of Acacia nilotica at (a) 200 mgL-1 concentration, (b) 60 mgL-1.


Figure S3: Energy Disperse X-ray (EDX) Spectra of AuNP derived from Acacia nilotica leaf

extract (60 mgL-1)


Figure S4: X-Ray Diffraction Pattern of AuNPs synthesized from HAuCl4 solution (0.42 mM) by using leaf extract of Acacia nilotica.

Reduction of 4-nitrophenol to 4-aminophenol:

Catalytic reduction of 4-nitrophenol was carried out as follows: (a) Initially an aliquot of 4-nitrophenol (1 mM, 0.2 mL) wasdiluted to 4 mL with distilled water and UV-visible spetrum was recorded.(b)Then an aliquot of 4-nitrophenol (1 mM, 0.2 mL) was treated with freshly prepared sodium borohydride solution (15 mM, 3.6 mL/3.4 mL) and the volume was made upto 4mL with distilled water (0.2 mL / 0.4 mL respectively) andUV-visible spetrum was recorded. (c) An aliquot of 4-nitrophenol (1 mM, 0.2 mL) was treated with freshly prepared sodium borohydride solution (15 mM, 3.6 mL/3.4 mL) and freshly prepared gold nanoparticles (synthesized from Acacia nilotica leaf extract (60 mgL-1), 0.2 mL / 0.4 mL). After shaking the reaction mixture, the UV-visible spectra was recorded at room temperature. The progress of the reaction was monitored by recording the absorption intensity of 4- nitrophenolate ion with certain time intervals and the value of the apparent catalytic rate constant was calculated.

Calculation of Apparent Catalytic Rate Constant (k)


Figure S5: ln A vs time plot (A = absorbance of 4-nitrophenolate): (a) with 0.2 mL AuNP colloid (60 mgL-1 leaf extract), (b) with 0.4 mL AuNP colloid (60 mgL-1 leaf extract). From the slopes, the apparentcatalytic rate constants (k) were calculated to be 0.35 min-1 in (a) and 0.42 min-1 in (b).