Supporting Information Activating Room Temperature Long Afterglow of Carbon Dots via Covalent Fixation Kai Jiang,, Yuhui Wang, Congzhong Cai, and Hengwei Lin*, Key Laboratory of Graphene Technologies and Applications of Zhejiang Province, Ningbo Institute of Materials Technology & Engineering (NIMTE), Chinese Academy of Sciences, Ningbo 31521, China. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Department of Applied Physics, Chongqing University, Chongqing 444, China. *Correspondence and requests for materials should be addressed to H.L. (email: linhengwei@nimte.ac.cn). Experimental section Materials Reagent grade of m-phenylenediamines (mpd) was purchased from Aldrich. Colloidal nanosilica (i.e. nsio 2 ) (LUDOX TMA colloidal silica, 34 wt% suspension in H 2 O, ph=4~7) was provided from Sigma-Aldrich. Ethanol, methanol, methylene chloride, polyethylene glycol (PEG) (Mw=1) and poly(vinyl alcohol) (PVA) (Mw=175±5) were provided by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). All chemicals were used as received without further purification unless otherwise specified. Deionized (DI) water was used throughout this study. 1 / 9
Equipments and characterization Transmission electron microscopy (TEM) observations were performed on a Tecnai F2 microscope. Fourier transform infrared (FT-IR) spectra were obtained on a Nicolet 67 FT-IR spectrometer. XPS were carried out with ESCALAB 25Xi (Thermo Scientific). Photoluminescence, afterglow emission and excitation spectra (phosphorescence mode) were measured on a Hitachi F-46 spectrophotometer at ambient conditions. For the temperature-dependent experiment, the sample was placed in a high temperature fluorescence attachment (Orient KOJI, TAP-2) with temperatures controlled between 298.15 and 473.15 K. The UV-vis absorption spectra were recorded on a PERSEE T1CS UV-Vis spectrophotometer. PL and afterglow lifetimes were measured using Fluorolog 3-11 (HORIBA Jobin Yvon). Photographs of PL, RTP and RTDF were taken using a Canon camera (EOS 55) under excitation by a hand-hold UV lamp (365 nm). Preparation of m-cds, m-cds@nsio 2 and corresponding inks Synthesis of m-cds: mpd (.9 g) was dissolved in 9 ml of ethanol, and then these solution was transferred into poly(tetrafluoroethylene)-lined autoclaves. After heating at 18 ºC in oven for 12 h and cooling down to room temperature naturally, gray suspension was obtained. The crude product was followed purification with a silica column chromatography using mixtures of methylene chloride and methanol as eluents. After removing solvents and further drying under vacuum, the purified m-cds could be finally obtained in 8-15 wt% yields. Preparation of m-cds@nsio 2 :.15 g (or.6,.3,.75, and 1.5 g) nsio 2 solution were firstly diluted with 9 ml DI water and mixed with 1. ml of m-cds solution (1. mg/ml in ethanol). The mixture was then transferred into poly(tetrafluoroethylene)-lined autoclaves. After heating at 18 ºC in oven for 12 h and cooling down to room temperature naturally, the resulting bluish green suspension was centrifuging at 2 rpm for 3 min to remove the solvent. The final products were collected after twice washing with ethanol to remove unreacted m-cds, and the precipitates were re-dissolved in water for further use. The m-cds@nsio 2 powders can be simply obtained through drying the ethanol-washed precipitates. Phosphorescence ink (a typical formulation): 2 µl of m-cds solution (5. mg/ml in ethanol) were firstly diluted with 3 µl DI water, and then mixed with 1.5 ml of PVA (Mw=175±5) 2 / 9
solution (1. g in 15 ml water). Such obtained PVA solutions are employed as luminescent inks to prepare PVA films or write on filter paper directly. Delayed fluorescence ink: 2 µl of m-cds@nsio 2 solution (5 mg/ml in ethanol) were firstly diluted with 3 µl DI water, and the following process was the same as the preparation of phosphorescence emissive inks. Fluorescence ink: 2 µl of m-cds solution (5. mg/ml in ethanol) were firstly diluted with 3 µl DI water, and then mixed with 1.5 ml of PEG (Mw=3) solution (1. g in 5 ml water). Such obtained PEG solutions are employed as PL inks to write on filter paper directly. Supporting Figures and Tables a) PL PHs 4 3 2 1 14 12 1 8 6 4 2 m-cds@nsio 2-1:2 m-cds@nsio 2-1:5 m-cds@nsio 2-1:1 m-cds@nsio 2-1:25 m-cds@nsio 2-1:5 4 45 5 55 6 65 m-cds@nsio 2-1:2 m-cds@nsio 2-1:5 m-cds@nsio 2-1:1 m-cds@nsio 2-1:25 m-cds@nsio 2-1:5 4 45 5 55 6 65 Figure S1. The PL a) and afterglow emission spectra of m-cds@nsio 2 prepared with different ratios of m-cds to nsio 2 by weight (i.e. 1:2, 1:5, 1:1, 1:25, 1:5, respectively) with the excitation of 365 nm. 3 / 9
5 nm Figure S2. TEM image of the nsio 2. a) m-cds C1s Raw data Fitted line Background 284.7 ev C-C/C=C 285.5 ev C-N/C=N 286.3 ev C-O m-cds N1s Raw data Fitted line Background 398.4 ev pyridinic N 399. ev amino N 4.2 ev pyrrolic N c) 29 285 28 275 Binding Energy (ev) m-cds@nsio 2 C1s Raw data Peak Background 283.9 ev C-Si 284.6 ev C-C/C=C 285.4 ev C-N/C=N 286.6 ev C-O d) 45 4 395 39 385 m-cds@nsio 2 N1s Binding Energy (ev) Raw data Peak Background 397.8 ev N-Si 398.5 ev pyridinic N 399.3 ev amino N 4.8 ev pyrrolic N 29 285 28 275 Binding Energy (ev) 45 4 395 39 385 Binding Energy (ev) Figure S3. The high resolution XPS spectra of C1s and N1s of m-cds (a, and m-cds@nsio 2 (c,d), respectively. 4 / 9
PL 3 25 2 15 1 5 35 4 45 5 55 6 65 Figure S4. PL emission spectra of m-cds@nsio 2 in water dispersions under air (black line) and argon (red line) conditions (excitation of 365 nm). Air Ar PL 1 1 1 1 1 IRF m-cds@nsio 2 Fitted Line 4 6 8 1 12 14 Time (ns) τ avg = 7.56 ns Figure S5. PL decay spectrum and fitting curves of the m-cds@nsio 2 in water dispersion. 5 / 9
1 298.15 K 323.15 K 348.15 K 373.15 K 1 398.15 K 423.15 K 448.15 K 473.15 K 1 1 1 2 3 4 5 Time (s) Figure S6. Afterglow decay profiles of the m-cds@nsio 2 (powder) at 298.15-473.15 K. Table S1. Afterglow lifetimes of the m-cds@nsio 2 (powder) at different temperatures. T [K] τ 1 [ms] B 1 [%] τ 2 [ms] B 2 [%] τ 3 [ms] B 3 [%] τ avg [ms] ϕ 298.15 2.91 1.74 224.54 18.86 858.22 79.4 82.74 1.18274 323.15 7.99.66 115.46 14.69 468.23 84.65 453.7 1.23865 348.15 12.7 1.95 134.51 36.55 297.36 61.5 262.59 1.2264 373.15 3.12 1.68 64.17 38.46 139.1 59.86 121.91 1.2431 398.15 1.9 1.41 3.41 37.95 66.64 6.65 58.56 1.3513 423.15 2.28 2.85 18.73 52.27 36.46 44.88 29.76 1.22847 448.15 1.18 2.52 1.43 56.87 19.48 4.61 15.57 1.1982 473.15 1.5 1.8 6.17 62.13 11.17 33.79 8.56 1.22256 Nor. Em Intensity 1..8.6.4.2 454 nm 58 nm Phos (77K) FL (77K) 4 45 5 55 6 65 7 Figure S7. The low temperature (77K) fluorescence (red curve) and phosphorescence (black curve) spectra of m-cds@nsio 2 under excitation at 365 nm. 6 / 9
a) 12 TADF-298.15 K 1 8 6 4 2 25 2 15 1 5 462 nm 519 nm 4 45 5 55 6 65 35 TADF-348.15 K 3 461 nm 515 nm 4 45 5 55 6 65 c) d) e) g) 6 TADF-423.15 K 5 4 3 2 1 463 nm 518 nm 4 45 5 55 6 65 6 TADF-448.15 K 5 4 3 2 1 463 nm 519 nm 4 45 5 55 6 65 f) 2 TADF-323.15 K 462 nm 514 nm 15 1 5 3 2 1 4 45 5 55 6 65 TADF-373.15 K 4 4 3 2 1 461 nm 516 nm 4 45 5 55 6 65 TADF-398.15 K 5 463 nm 518 nm 4 45 5 55 6 65 Figure S8. The afterglow emission spectra of m-cds@nsio 2 (powder) at different temperatures and the Gaussian fitted by two emission peaks. Table S2. The relative contents of the two peaks for the m-cds@nsio 2. T [K] λ em [nm] B 1 [%] λ' em [nm] B 2 [%] 298.15 462 59. 519 41. 323.15 462 63.4 514 36.96 348.15 461 64.69 515 35.31 373.15 461 66.48 516 33.52 398.15 463 69.46 518 3.54 423.15 463 69.58 518 3.42 448.15 463 68.93 519 31.7 7 / 9
a) 1 1 1 Decay Fit 1 1 1 Decay Fit 1 2 3 4 5 Time (s) 1 2 3 4 5 Time (s) Figure S9. The afterglow emission decay spectra and fitting curves of m-cds@sio 2 at 461 nm (a) and 518 nm ( under excitation at 365 nm. Table S3. Fitting results of the afterglow lifetimes of the m-cds@nsio 2 at 461 nm and 518 nm under 365 nm excitation. Emission (nm) τ 1 (ms) B 1 (%) τ 2 (ms) B 2 (%) τ 3 (ms) B 3 (%) τ avg (ms) ϕ 461 6.9 1.3 128.2 19.15 713.88 79.55 689.55 1.21812 518 14.65 4.28 179.98 27.92 788.19 67.77 728.9 1.2597 Abs (a.u) 1..8.6.4.2. Abs of m-cds Abs of m-cds@nsio 2 RTDF Ex 3 4 5 6 7 8 2 15 1 5 Figure S1. Absorption spectra of m-cds (black line), m-cds@nsio 2 (red line) dispersed in ethanol, and RTDF excitation spectrum of m-cds@nsio 2 (blue line) dispersed in ethanol. 8 / 9
Absorbtion 342 292 322 285 337318 292 285 173 163 162 152 152 138 128 m-cds-t m-cds 11 829 4 35 3 25 2 15 1 5 Wavenumber (cm -1 ) Figure S11. FT-IR spectra of m-cds, and m-cds after a treatment with light irradiation (365 nm) during air bubbling for 6 hours (named m-cds-t). a) 5 4 3 2 1 25 2 15 1 5 Dry wet 4 45 5 55 6 65 7 Dry wet 4 45 5 55 6 65 7 Figure S12. RTP and RTDF spectra of (a) m-cds-pva and ( m-cds@sio 2 -PVA films before and after damped by water vapours; all measurement was carried out on phosphorescence mode. 9 / 9