Supporting Information

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1 Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, Supporting Information for Adv. Mater., DOI: /adma Quantum-Dot-Doped Polymer Nanofibers for Optical Sensing Chao Meng, Yao Xiao, Pan Wang, Lei Zhang, Yanxin Liu, and Limin Tong *

2 DOI: /adma Submitted to Quantum-Dot-Doped Polymer Nanofibers for Optical Sensing By Chao Meng, Yao Xiao, Pan Wang, Lei Zhang, Yanxin Liu and Limin Tong* [*] Prof. L. M. Tong, C. Meng, Y. Xiao, P. Wang, Dr. L. Zhang, Yanxin Liu State Key Laboratory of Modern Optical Instrumentation Department of Optical Engineering Zhejiang University Hangzhou, , China 1

3 Supporting Information Submitted to 1. Evanescent coupling method Here we employ an evanescent coupling method for high-efficiency in/out-coupling of light from a single NF. As shown in Figure S1, we place a fiber taper with tip diameter down to 400 nm in parallel contact with the NF for optical launching and signal collecting. The fiber taper is flame-heated drawn from a standard optical fiber (SMF-28e; Corning). Figure S1. Optical microscope images of (a) evanescent coupling between a fiber taper and a NF and (b) coupling region between the fiber taper and the NF. 2. Experimental setup for optical sensing The sensor element is sealed in a glass chamber with a vapor inlet/outlet for gas flowing and a hygrometer for monitoring humidity. The mass flow rates and the mixing ratio of the moisture gases and carrier gases are controlled by mass flow 2

4 Submitted to controllers (MFCs). The output of the NF is measured using an optical spectrum analyzer or photodetector. Figure S2. Schematic diagram of the experimental setup for humidity sensing. 3. TEM of CdSe/ZnS core-shell QDs Figure S3. Typical TEM images of core-shell CdSe/ZnS QDs (left: λem 605 nm, right: λem 637 nm) used in this work. The insets are HRTEM images of single QDs. Scale bar, 2 nm. 3

5 Submitted to 4. Absorption and PL spectra of Rhodamine 6G and CdSe/ZnS QDs Figure S4. Absorption and PL spectra of (a) Rhodamine 6G (λ em 585 nm, 0.1 µm, diluted in chloroform) and (b,c) typical CdSe/ZnS QDs (0.1 µm diluted in chloroform) with λ em of 605 nm and 637 nm, respectively. 5. Estimated quantum efficiencies of CdSe/ZnS QDs in PS NFs To estimate the quantum efficiencies of CdSe/ZnS QDs in PS NFs, we compare PL intensities of QD/PS NFs with R6G/PS NFs under same excitation conditions. As shown in Figure S5, PL microscope images of a 420-nm-diameter R6G/PS NF (λ em 585 nm, C R6G 0.5 wt %), a 460-nm-diameter QD/PS NF (λ em 542 nm, C QD 0.5 wt %), a 450-nm-diameter QD/PS NF (λ em 605 nm, C QD 0.5 wt %), and a 420-nm-diameter QD/PS NF (λ em 637 nm, C QD 0.5 wt %), are excited by a 532-nm-wavelength continuous-wave light and captured by a calibrated CCD camera (DS-Fi1c; Nikon) without saturation in dark-field mode of the optical microscope (eclipse 50i, Nikon). All the four NFs are supported on the same substrate (glass slide). By transforming the images from RGB mode to grey level using Adobe Photoshop, and then summing up the gray values to obtain corresponding intensities, [S1] we obtained the relative PL 4

6 Submitted to intensities of the QD/PS NFs to be 40% (Figure S5(b)), 43% (Figure S5(c)) and 44% (Figure S5(d)) of the R6G/PS NFs (Figure S5(a)), respectively. Considering that quantum efficiency of R6G dye is about 0.9 under a 532-nm-wavelength excitation, [S2,S3] the quantum efficiencies of the QD/PS NFs are estimated to be 36% (Figure S5(b)), 39% (Figure S5(c)) and 40% (Figure S5(d)), respectively. Figure S5. Optical microscope images of (a) R6G/PS NFs and (b-d) QD-doped polymer NFs with λ em of 542 nm, 605 nm and 637 nm, respectively. All the images are obtained under same excitation condition and exposure time. Scale bar, 5 µm. 6. SEM of a typical tungsten probe Figure S6. SEM of a typical tungsten probe (i.e., a scanning tunneling microscope (STM) probe fabricated by electrochemical etching) used for direct drawing of QD-doped solvated PS. 5

7 Submitted to References [S1]A. L. Pyayt, B. Wiley, Y. N. Xia, A. Chen, L. Dalton, Nat. Nanotechnol. 2008, 3, 660. [S2]L. S. Rohwer, J. E. Martin, J. Lumin. 2005, 115,77. [S3]M. Grabolle, M. Spieles, V. Lesnyak, N. Gaponik, A. Eychmuller, U. Resch-Genger, Anal. Chem. 2009, 81,