Supporting information

Transcription

1 Supporting information Tunable color in 2, 6-Diaminopyridine functionalized graphene oxide Supriya Mondal,,$ Diptiman Dinda, Bikash kumar Shaw and Shyamal K. Saha,*,* Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata , India $ Present Address: Department of Physics, P.R. Thakur Govt.College, Thakurnagar,Gaighata, North 24 parganas , India of corresponding author: cnssks@iacs.res.in

2 General Characterizations of DAP-fGO material: The as synthesized DAP-fGO material has been charecterized using FTIR, Raman, XPS, TGA and SEM measurements. Detailed charecterization of this material is reported in our previous work. From Fig. S1(a), it is seen that the amine groups of 2, 6-Diaminopyridine attack besal epoxy groups of the GO surface through S N 2 mechanism resulting DAP-fGO material. The absance of epoxy peak (1070 cm -1 ) and appearance of N-H peaks (3388 and 3336 cm -1 for 1 0 and 2 0 amines) confirm the functionalization of graphene oxide. From XPS measurements, we can see that the intensity of C-O peak is decreased compared to GO as shown in Fig. S1(b). Two new peaks of C-N and C=N (285.6 and ev) are also noticed in the deconvoluted C 1S spectra of DAP-fGO material confirming the functionalization of GO by amine groupsof DAP. The raman spectra in Fig. S1(c) shows that the D band of DAP-fGO is red shifted to 1581cm - 1 compared to GO (1601 cm -1 ) indicating the presence of localized sp 3 defects within the sp 2 carbon network during surface functionalization process. From TGA analysis, a sharper weight loss is occurred between 130 to C shown in Fig. S1(d). 34% residual weight at C compared to GO confirms the conversion of GO to more stable DAP-fGO during functionalization technique. To check the change in morphology during functionalization process, we have carried out SEM analysis. The smooth and compact surface of GO is converted to rough and porous as a result of functionalization by amine groups of DAP molecules as shown in Fig. S2.

3 We have also carried out AFM measurments for DAP-fGO and GO films. All the results are given in Fig. S3 (a and b). The observed thickness for GO is ~2 nm suggesting the presence of two layers of graphene sheets. Whereas, this is ~2.6 nm for DAP-fGO. The increament in thickness for DAP-fGO is associated with the attachment of DAP molecules on the graphene surfaces during the functionalization of graphene oxide. Figure S1: (a) FTIR, (b) XPS, (c) Raman and (d) TGA spectra of DAP-fGO.

4 Figure S2: SEM images of GO and DAP-fGO Figure S3: AFM images and corresponding height profile of (a) GO and (b) DAP-fGO.

5 UV-Vis absorption study: Figure S4: UV-Vis absorption spectra of DAP-fGO in solution phase. DFT model calculations and optimized structures : Density functional theory (DFT) calculations are carried out with B3LYP/6-31G**basis sets using the standard Gaussian 09 software package.

6 Fig. S5: DFT model calculations,energy levels and optimizing structure containing (a) two benzene rings and one DAP molecule, (b) five benzene rings and two DAP molecules, (c) five benzene rings and three DAP molecules and (d) seven benzene rings and six DAP molecules Quantum Yield (QY) measurement: We have calculated the relative fluorescence QY of DAP-fGO aqueous solution taking quinine sulfate (0.1M H 2 SO 4 ) as referancefollowing the expression mentioned below; Фs = (Is/Ir) (Ar/As) (ηs2/ηr2) Фr Where the subscripts r and s refer to the reference and the measured sample respectively, Φ is the fluorescence quantum yield, I is the measured integrated fluorescence emission intensity, A is the optical density and η is the refractive index of water. Here, QY of quinine sulfate is taken as The obtained QY of DAP-fGO is18.4 % for the blue region peak. Grafting density calculation: The grafting density has been calculated from TGA of DAP-fGO and GO using following Equation. Grafting density δ = w C ( ) 100 w 100 [ C ] M S100 w G O Here, W C (= 66%) is the weight loss in percentage of DAP-fGO, W GO (=91%) is the weight loss in percentage for graphene oxide, M is molar mass of DAP molecules and S is the surface area of DAP-fGO as measured using BET adsorption isotherms method. The surface

7 area of DAP fgo composite is m 2 /g. So the calculated grafting density of DAP on GO is equal to 0.21 chains/nm 2. Figure S6: TGA spectra of Graphene Oxide