<p> Supporting Information</p><p>Abroma augusta Linn bark extract-mediated green synthesis of gold nanoparticles and its application in catalytic reduction </p><p>Subhajit Das,a Braja Gopal Bag*,a and Ranadhir Basub a Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721102, West Bengal, India, Fax: 00913222275297, Email: [email protected] b Central Research Facility, Indian Institute of Technology, Kharagpur 721302, West Bengal, India</p><p>Figure S1: Mass spectrum of Abroma augusta L. bark extract. FTIR Study:</p><p>Figure S2: FTIR (KBr) spectra of (a) Abroma augusta L. bark extract, (b) stabilized AuNPs Kinetic study for the determination of catalytic rate constant (k):</p><p>Reduction of 4-nitrophenol to 4-aminophenol:</p><p>Catalytic reduction of 4-nitrophenol to 4- aminophenol was carried out as follows: (a)</p><p>Initially an aliquot of 4-nitrophenol (1 mM, 0.2 mL) was diluted with distilled water (3.8 mL) to make up the volume 4 mL 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, 3.7 mL/3.6 mL) and the volume was made upto 4 mL with distilled water (0.1 mL / 0.2 mL respectively) and UV-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, 3.7 mL/3.6 mL) and freshly prepared AuNPs (synthesized from Abroma augusta L. bark extract (200 mgL-1), 0.1 mL / 0.2 mL). The UV-visible spectrum was recorded at room temperature after shaking the reaction mixture. 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</p><p> catalytic rate constant was calculated by plotting the ln At/A0 values as a function of time.</p><p>Table TS1: Absorbance of 4-nitrophenolate at various time intervals during reduction with 0.1 mL AuNPs (synthesized with 200 mgL-1 concentration of green Abroma augusta L. bark extract): </p><p>Entry Time (second) Absorbance(A) lnAt/A0</p><p>1 26 0.874 -0.024 2 90 0.753 -0.173 3 180 0.438 -0.715 4 270 0.209 -1.454 5 360 0.065 -2.622 6 450 0 infinite 0.0</p><p>-0.5</p><p>-1.0 ) 0 A / t -1.5 A ( n l -2.0</p><p>-2.5</p><p>-3.0 0 50 100 150 200 250 300 350 400 t(sec)</p><p>Figure S3: Plot of ln(At/A0) vs time (sec) where At is the absorbance at time ‘t’ and A0 is the absorbance initially of 4-nitrophenolate. From the above plot, the slope was calculated to be -7.73 × 10-3. Thus the catalytic rate constant was calculated to be 7×10-3 sec-1.</p>