Stretchable and Thermally Stable Dual Emission Composite Films of

Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)

Article

Stretchable and Thermally Stable Dual Emission Composite Films of On-Purpose Aggregated Copper Nanoclusters in Carboxylated Polyurethane for Remote White Light-Emitting Devices Zhenguang Wang, Bingkun Chen, Minshen Zhu, Stephen V Kershaw, Chunyi Zhi, Haizheng Zhong, and Andrey L. Rogach ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b10828 • Publication Date (Web): 21 Nov 2016 Downloaded from http://pubs.acs.org on November 26, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Stretchable and Thermally Stable Dual Emission Composite Films of On-Purpose Aggregated Copper Nanoclusters in Carboxylated Polyurethane for Remote White Light-Emitting Devices Zhenguang Wang,†‡ Bingkun Chen,†‡ǁ Minshen Zhu,† Stephen V. Kershaw,†‡ Chunyi Zhi,† Haizheng Zhongǁ and Andrey L. Rogach†‡* †

Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City

University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR ‡ Centre for Functional Photonics (CFP), City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR ǁ Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing, 100081, China Keywords: copper nanoclusters, aggregation-induced emission enhancement, carboxylated polyurethane, thermal stability, remote light-emitting device, white LED

ABSTRACT: Stretchable, mechanically stable films with thermally stable dual emission peaked in the blue and orange spectral range are fabricated by condensation and aging of carboxylated polyurethane in the presence of on-purpose aggregated copper nanoclusters. The aggregation of copper clusters leads to the enhancement of their emission in the orange, while polyurethane matrix contributes with the blue emission band, with an overall photoluminescence quantum yield of the films as high as 18%. Composite Cu nanoclusters / polyurethane films are sufficiently transparent over the visible spectral range and are absorbing in the UV range; more than 90% of their emission intensity is preserved after 10 times of cycle of stretch and recovery, as well as aging of up to 10 hours at 95oC, making them useful for optoelectronic devices. Remote white light emitting devices have been fabricated by placing a down-conversion layer of

1 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

composite Cu nanoclusters / polyurethane film separated through a silicone resin spacer from the UV LED chip, with Commission Internationale de l’Eclairage color coordinates, color rendering index and correlated color temperature of (0.34, 0.29), 87, and 5426 K, respectively.

1. INTRODUCTION Metal nanoclusters (NCs) consisting of a few to few hundreds of atoms exhibit molecule-like optical properties, such as strong photoluminescence (PL).1-4 Due to their ultrafine size, large Stokes shifts and low environmental toxicity, noble metal NCs composed of Au and Ag are considered as useful fluorophores, and have been already applied in chemical sensing, biological imaging and, recently, optoelectronic devices.5-9 Compared with those expensive noble metals, Cu is an earth abundant and inexpensive element. Recent years have evidenced increasing efforts of the synthetic activities on Cu NCs,10-14 and their employment as active luminescent materials in light emitting devices (LEDs), in particular white LEDs (WLEDs).15,16 Yang group reported on WLEDs based on the combination of red emitting Au and green emitting Cu NCs,15 while our group fabricated WLEDs from a combination of blue emitting Cu NCs and two commercial green and red emitting rare-earth phosphors,16 or blue and orange emitting Cu NCs deposited on the UV-LED chip.17 Most of these approaches require dispersion of NC powders within a silicone or epoxy resins, which imposes several limitations, such as, poor compatibility of components leading to undesirable phase separation and re-absorption of light.18,19 This calls for alternative device architectures such as remote-type LEDs,20,21 with an added advantage being a reduced operation temperature due to minimizing the heating of the phosphor-containing active layer by the UV light from the LED chips.19,22 Liu and co-authors fabricated remote WLEDs employing Cu and Au sheets electrophoretically deposited onto ITO glass,23 thus separating 2 ACS Paragon Plus Environment

Page 2 of 22

Page 3 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


these phosphors from the UV chip, but the PL quantum yield (QY) of the samples was rather low, 4.6% for Cu NCs and 1.1% for Au NCs, respectively. Surface ligands, such as, polymers,6 proteins,24 DNA25 and thiol-containing molecules,26-28 play an important role on the PL of Cu NCs29,30. Among them, thiolated aminoacids such as glutathione (GSH) have been reported to cause the aggregation-induced emission (AIE) enhancement for Cu NCs,17,27,31 which could improve their PL QY to as high as 24%.17 In this work, we made use of the AIE phenomenon to produce strongly luminescent composite films of the on-purpose aggregated Cu NCs embedded in carboxylated polyurethane (PU) matrix. The resulting films show strong (PL QY of 18%) dual emission with blue and orange PL bands originating from PU and aggregated Cu NCs, respectively. The composite Cu NC/PU films were free-standing, stretchable and showed a thermally stable emission as demonstrated by tensile measurements, thermal gravimetric analysis (TGA) and PL intensity measurements performed under different curing temperatures and heating times. These films were employed as color converters placed at a certain distance onto a UV-LED chips to demonstrate remote WLEDs with Commission Internationale de l’Eclairage (CIE) color coordinates, color rendering index (CRI) and correlated color temperature (CCT) of (0.34, 0.29), 87 and 5426 K, respectively. Such remote LEDs avoid issues of phase separation upon mixing Cu NC luminophores with packaging silicone resin, and at the same time reduce the operating temperature for phosphors placed under distance to the excitation UV source. In addition, they do not use any rare-earth elements or noble metals, which is promising for their large scale industrial applications.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2. EXPERIMENTAL SECTION 2.1. Materials. Cu(NO3)2, reduced L-glutathione (GSH), and ethanol (analytical grade) were obtained from Sigma-Aldrich, U.S.A. Carboxylated polyurethane (PU) has been purchased from Shenzhen Jinxiu Waterproof Material Co., Ltd. Components of silicone resin OE-6551A and OE-6551B were purchased from Dow Corning Co. GaN UV LED chips, with the peak emission wavelength centered at 370 nm, were obtained from EPILED Co., Ltd. 2.2. Synthesis of Cu NCs. GSH capped Cu NCs were synthesized according to our previous report.17 Briefly, 0.5 mL aqueous solution of Cu(NO3)2 (50 mM) and 2.5 mL aqueous solution of GSH (50 mM) were mixed with 2.0 mL of water, followed by adjusting the pH to 5.0 using 2 M NaOH. 2.3. Fabrication of Cu NC/PU films. Carboxylated PU (0.5 mL) was mixed with 9.0 mL of ethanol, under sonication for 20 min. 0.5 mL of as-prepared aqueous solution of Cu NCs was injected under vigorous stirring, and the resulting mixture was poured into cylindrical molds and allowed to dry for 48 h at room temperature under vacuum to produce luminescent Cu NC/PU films. Bare PU films fabricated for reference purpose were prepared in a same way using 0.5 mL of H2O instead of the aqueous solution of Cu NCs. 2.4. Fabrication of remote WLEDs. 0.1 g of thermal-curable silicone resin OE-6551A was mixed with 0.2 g of the hardener OE-6551B, and a drop of this mixture was placed onto the surface of the GaN UV LED chip to serve as a spacer between the Cu NC/PU film. Cu NC/PU film was cut into pieces (3 mm × 5 mm), placed on top of the silicone layer and the structure was dried at 50 oC for 1 h.


Page 4 of 22

Page 5 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.5. Material Characterization. Absorption spectra of solutions and transmission spectra of films were recorded on a Varian Cary 50. PL spectra were measured by a Cary Eclipse fluorescence spectrometer. Transmission electron microscopy (TEM) images were recorded on a Philips CM 20 microscope operated at 200 kV. The surface morphology of films was studied on an environmental scanning electron microscope (SEM, FEI/Philips XL30). Time-correlated single-photon counting set-up equipped with a 320 nm laser as the excitation light source was employed to measure the time-resolved PL decay curves. PL decays were fitted with multiexponential functions, and PL lifetimes were calculated by taking a weighted average. For the absolute PL QY measurements, spectrofluorimeter FLS920P equipped with an integrating sphere (Edinburgh Instruments) with its inner surface coated with BENFLEC was used. Excitation wavelength for PL QY measurements was 375 nm. The stress-strain curves were measured on a Zwick Z030 tester (tensile rate = 50 mm min-1). Thermogravimeric analysis (TGA) was performed on a SDT-Q600 instrument (TA Instruments, USA) in the nitrogen gas atmosphere, with a heating rate of 10 °C/min. 3. RESULTS AND DISCUSSION 3.1. Design of the dual-emitting Cu NC/PU films. Scheme 1 shows a schematic illustration of the design and fabrication process of the dual-emitting Cu NC/PU films. Onpurpose aggregated Cu NCs showing AIE enhancement are combined with PU chosen as a matrix, not only because it is a mechanically strong, self-healing polymer widely used in the textile industry,32-34 but also due to its strong blue emission occurring under UV excitation. After injection of aqueous solution of as-synthesized Cu NCs into ethanol with dissolved carboxylated PU, the aggregation of NCs happens and it is accompanied by the PL enhancement in the orange spectral range, while dual (blue and orange) emissive Cu NC/PU free-standing films can be conveniently obtained as a result of polycondensation and aging of the mixture, as will be demonstrated below.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

3.2. Preparation and optical properties of a mixed Cu NC/PU solution. The mixed Cu NC/PU solution has been prepared through an injection of aqueous solution of as-synthesized Cu NCs into an ethanol solution of carboxylated PU. According to the previous report,35 the hydration shell of Cu NCs is disrupted by ethanol, leading to controlled aggregation of clusters resulting in an AIE enhancement. TEM image in Figure 1a evidences on the formation of quasispherical agglomerates with sizes ranging from 50 to 100 nm, consisting of small (90% of the initial PL intensity recovered. 3.5. Thermal stability of Cu NC/PU films. TGA curves taken in nitrogen atmosphere (Figure 4a) evidence on just 2.3%, 3.2% and 4.5% weight loss for the Cu NC/PU films heated to 100oC, 150oC and 200oC, respectively, which demonstrates their high thermal stability in the range of 30 to 200oC. With the temperature increasing over 200oC, a significant loss of weight is observed down to only 2% residual weight, which is caused by the decomposition of PU, as confirmed by the same trend for the TGA curve of the bare PU film shown in the same Figure 4a. The latter shows 4.5%, 6.1% and 6.9% weight loss at 100oC, 150oC and 200oC, respectively, pointing out on the improved thermal stability of the Cu NC/PU films in this temperature range. This can again be attributed to the interactions of amine groups from the GSH ligands on Cu NCs with carboxylate group of PU, where additional amide bonds formed contribute to the higher thermal stability of the composite film. We further studied the PL intensity changes of the Cu NC/PU films curied in air at different temperatures and for a different period of time. As


Page 8 of 22

Page 9 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


shown in Figure 4b, 1 h thermal treatment of Cu NC/PU films in the temperature range from 20oC to 90oC only results in a minor PL intensity loss. An 11% loss was recorded after the treatment at 100oC, and 15% loss was observed at 120oC. In yet another thermal stability test, Cu NC/PU films were kept in air at an elevated temperature of 90oC, and their PL intensity at different time intervals has been recorded as a function of time. As shown in Figure 4c, there are no major changes of the relative PL intensity of Cu NC/PU films even after 10 h of treatment, with >90% of the PL intensity preserved. These results are encouraging for the use of Cu NC/PU composite films in solid-state lighting applications.45 3.6. Application of Cu NC/PU films in remote WLEDs. Previously discussed data show that the emission of Cu NC/PU films is thermally stable and peaks in the blue and orange regions, thus covering the whole visible spectral region under UV excitation. Combined with favorable mechanical properties of the films, this favors their use as color down-converters deposited at UV LED chips to demonstrate the remote WLEDs. Figure 5a demonstrates the process for fabricating remote white LEDs, by simply attaching the Cu NCs film onto UV LED chip, employing silicone resin as a sticky spacer. Unlike for the previously reported Cu NC based WLEDs which required the mixing of the powdered phosphors with silicone or epoxy resin,15,17,23 such remote WLEDs benefit from avoiding the issues of phase segregation and compatibility between Cu NCs and packaging material, and at the same time reduce the operating temperature of the phosphor active layer remotely placed on the UV chip. The emission spectrum of WLEDs shown in Figure 5b is similar to the PL spectrum of Cu NCs film from Figure 2c, with two peaks centered at 430 and 600 nm, belonging to PU and aggregated Cu NCs, respectively. The combination of blue and orange emission bands results in the white light emission with CIE 1931 chromaticity coordinate of (0.34, 0.29), which is rather close to the ideal



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 22

coordinate of the pure white light (0.33, 0.33). The CRI of 87 was calculated by averaging color rendering of each Munsell code presented in Fig. 5d, which exceeds the typical CRI values (6580) of currently available commercial WLEDs.46,47 4. CONCLUSIONS Mechanically stable and stretchable (with more than 900% strain and tensile stress of 1.1 MPa) composite films comprising aggregated Cu NCs in PU matrix have been fabricated and used as an active down-converting layer in the remote WLEDs. The films showed thermally stable (with 90% intensity preserved after curing for 10 h at 90oC) emission with two PL peaks in the blue and orange regions originating from PU and aggregated Cu NCs, with overall absolute PL QY as high as 18%. Applying the luminescent Cu NC/PU films for fabrication of the remote WLEDs (deposited at a distance on the commercial UV-LED chips), avoids the compatibility issues of powdered Cu NC phosphors with silicone resin packaging materials. The resulting Cu NC/PU based WLEDs showed CIE coordinates of (0.34, 0.29) and high CRI of 87. The overall procedure of fabrication of such remote WLEDs is simple and low in cost, showing potential of luminescent Cu NC/PU films for flexible solid-state lighting, displays and other optoelectronic devices. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] Notes The authors declare no competing financial interests.


Page 11 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ACKNOWLEDGMENTS This work was supported by the Research Grant Council of Hong Kong S.A.R. (project T23713/11) and the Hong Kong Scholar Program (XJ2014046).

REFERENCES (1) Jin, R. Quantum Sized, Thiolate-Protected Gold Nanoclusters. Nanoscale 2010, 2, 343-362. (2) Goswami, N.; Yao, Q.; Luo, Z.; Li, J.; Chen, T.; Xie, J. Luminescent Metal Nanoclusters with Aggregation-Induced Emission. J. Phys. Chem. Lett. 2016, 7, 962-975. (3) Wilcoxon, J. P.; Abrams, B. L. Synthesis, Structure and Properties of Metal Nanoclusters. Chem. Soc. Rev. 2006, 35, 1162-1194. (4) Tao, Y.; Li, M.; Ren, J.; Qu, X. Metal Nanoclusters: Novel Probes for Diagnostic and Therapeutic Applications. Chem. Soc. Rev. 2015, 44, 8636-8663. (5) Song, X.-R.; Goswami, N.; Yang, H.-H.; Xie, J. Functionalization of Metal Nanoclusters for Biomedical Applications. Analyst 2016, 141, 3126-3140. (6) Susha, A. S.; Ringler, M.; Ohlinger, A.; Paderi, M.; LiPira, N.; Carotenuto, G.; Rogach, A. L.; Feldmann, J. Strongly Luminescent Films Fabricated by Thermolysis of Gold−Thiolate Complexes in a Polymer Matrix. Chem. Mater. 2008, 20, 6169-6175. (7) Niesen, B.; Rand, B. P. Thin Film Metal Nanocluster Light-Emitting Devices. Adv. Mater. 2014, 26, 1446-1449.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 22

(8) Venkatesh, V.; Shukla, A.; Sivakumar, S.; Verma, S. Purine-Stabilized Green Fluorescent Gold Nanoclusters for Cell Nuclei Imaging Applications. ACS Appl. Mater. Interfaces 2014, 6, 2185-2191. (9) Chang, H.-C.; Chang, Y.-F.; Fan, N.-C.; Ho, J.-a. A. Facile Preparation of High-QuantumYield Gold Nanoclusters: Application to Probing Mercuric Ions and Biothiols. ACS Appl. Mater. Interfaces 2014, 6, 18824-18831. (10) Guo, Y.; Cao, F.; Lei, X.; Mang, L.; Cheng, S.; Song, J. Fluorescent Copper Nanoparticles: Recent Advances in Synthesis and Applications for Sensing Metal Ions. Nanoscale 2016, 8, 4852-4863. (11) Wang, C.; Yao, Y.; Song, Q. Interfacial Synthesis of Polyethyleneimine-Protected Copper Nanoclusters: Size-Dependent Tunable Photoluminescence, PH Sensor and Bioimaging. Colloids Surf. B 2016, 140, 373-381. (12) Balogh, L.; Tomalia, D. A. Poly(Amidoamine) Dendrimer-Templated Nanocomposites. 1. Synthesis of Zerovalent Copper Nanoclusters. J. Am. Chem. Soc. 1998, 120, 7355-7356. (13) Wei, W.; Lu, Y.; Chen, W.; Chen, S. One-Pot Synthesis, Photoluminescence, and Electrocatalytic Properties of Subnanometer-Sized Copper Clusters. J. Am. Chem. Soc. 2011, 133, 2060-2063. (14) Chen, H.; Lin, L.; Li, H.; Li, J.; Lin, J.-M. Aggregation-Induced Structure Transition of Protein-Stabilized Zinc/Copper Nanoclusters for Amplified Chemiluminescence. ACS Nano 2015, 9, 2173-2183. (15) Wu, Z.; Liu, J.; Gao, Y.; Liu, H.; Li, T.; Zou, H.; Wang, Z.; Zhang, K.; Wang, Y.; Zhang, H.; Yang, B. Assembly-Induced Enhancement

of Cu Nanoclusters

Mechanochromic Property. J. Am. Chem. Soc. 2015, 137, 12906-12913.


Luminescence with

Page 13 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(16) Wang, Z.; Susha, A. S.; Chen, B.; Reckmeier, C.; Tomanec, O.; Zboril, R.; Zhong, H.; Rogach, A. L. Poly(vinylpyrrolidone) Supported Copper Nanoclusters: Glutathione Enhanced Blue Photoluminescence for Application in Phosphor Converted Light Emitting Devices. Nanoscale 2016, 8, 7197-7202. (17) Wang, Z.; Chen, B.; Susha, A. S.; Wang, W.; Reckmeier, C. J.; Chen, R.; Zhong, H.; Rogach, A. L. All-Copper Nanocluster Based Down-Conversion White Light-Emitting Devices. Adv. Sci. 2016, 3, 1600182. (18) Wang, Y.; Yin, Z.; Xie, Z.; Zhao, X.; Zhou, C.; Zhou, S.; Chen, P. Polysiloxane Functionalized Carbon Dots and Their Cross-Linked Flexible Silicone Rubbers for Color Conversion and Encapsulation of White LEDs. ACS Appl. Mater. Interfaces 2016, 8, 9961-9968. (19) Song, Y.-H.; Ji, E. K.; Bak, S.-H.; Kim, Y. N.; Lee, D. B.; Jung, M. K.; Jeong, B. W.; Yoon, D.-H. New Design of Hybrid Remote Phosphor with Single-Layer Graphene for Application in High-power LEDs. Chem. Eng. J. 2016, 287, 511-515. (20) Lin, H.; Wang, B.; Xu, J.; Zhang, R.; Chen, H.; Yu, Y.; Wang, Y. Phosphor-in-Glass for High-Powered Remote-Type White AC-LED. ACS Appl. Mater. Interfaces 2014, 6, 2126421269. (21) Zhang, X.; Wang, J.; Huang, L.; Pan, F.; Chen, Y.; Lei, B.; Peng, M.; Wu, M. Tunable Luminescent Properties and Concentration-Dependent, Site-Preferable Distribution of Eu2+ Ions in Silicate Glass for White LEDs Applications. ACS Appl. Mater. Interfaces 2015, 7, 1004410054. (22) Kim, J. S.; Kwon, O. H.; Jang, J. W.; Lee, S. H.; Han, S. J.; Lee, J. H.; Cho, Y. S. LongTerm Stable, Low-Temperature Remote Silicate Phosphor Thick Films Printed on a Glass Substrate. ACS Comb. Sci. 2015, 17, 234-238.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 22

(23) Liu, J.; Wu, Z.; Li, T.; Zhou, D.; Zhang, K.; Sheng, Y.; Cui, J.; Zhang, H.; Yang, B. Electrophoretic Deposition of Fluorescent Cu and Au Sheets for Light-Emitting Diodes. Nanoscale 2016, 8, 395-402. (24) Wang, C.; Wang, C.; Xu, L.; Cheng, H.; Lin, Q.; Zhang, C. Protein-Directed Synthesis of pH-Responsive Red Fluorescent Copper Nanoclusters and Their Applications in Cellular Imaging and Catalysis. Nanoscale 2014, 6, 1775-1781. (25) Jia, X.; Li, J.; Han, L.; Ren, J.; Yang, X.; Wang, E. DNA-Hosted Copper Nanoclusters for Fluorescent Identification of Single Nucleotide Polymorphisms. ACS Nano 2012, 6, 3311-3317. (26) Chen, P.-C.; Li, Y.-C.; Ma, J.-Y.; Huang, J.-Y.; Chen, C.-F.; Chang, H.-T. Size-Tunable Copper Nanocluster Aggregates and Their Application in Hydrogen Sulfide Sensing on Paperbased Devices. Sci. Rep. 2016, 6, 24882. (27) Jia, X.; Li, J.; Wang, E. Cu Nanoclusters with Aggregation Induced Emission Enhancement. Small 2013, 9, 3873-3879. (28) Cao, H.; Chen, Z.; Zheng, H.; Huang, Y. Copper Nanoclusters as a Highly Sensitive and Selective Fluorescence Sensor for Ferric Ions in Serum and Living Cells by Imaging. Biosens. Bioelectron. 2014, 62, 189-195. (29) Ghosh, R.; Sahoo, A. K.; Ghosh, S. S.; Paul, A.; Chattopadhyay, A. Blue-Emitting Copper Nanoclusters Synthesized in the Presence of Lysozyme as Candidates for Cell Labeling. ACS Appl. Mater. Interfaces 2014, 6, 3822-3828. (30) Barthel, M. J.; Angeloni, I.; Petrelli, A.; Avellini, T.; Scarpellini, A.; Bertoni, G.; Armirotti, A.; Moreels, I.; Pellegrino, T. Synthesis of Highly Fluorescent Copper Clusters Using Living Polymer Chains as Combined Reducing Agents and Ligands. ACS Nano 2015, 9, 11886-11897.


Page 15 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(31) Huang, Y.; Liu, W.; Feng, H.; Ye, Y.; Tang, C.; Ao, H.; Zhao, M.; Chen, G.; Chen, J.; Qian, Z. Luminescent Nanoswitch based on Organic-Phase Copper Nanoclusters for Sensitive Detection of Trace Amount of Water in Organic Solvents. Anal. Chem. 2016, 88, 7429-7434. (32) Xu, W.; Ma, C.; Ma, J.; Gan, T.; Zhang, G. Marine Biofouling Resistance of Polyurethane with Biodegradation and Hydrolyzation. ACS Appl. Mater. Interfaces 2014, 6, 4017-4024. (33) Huang, Y.; Huang, Y.; Zhu, M.; Meng, W.; Pei, Z.; Liu, C.; Hu, H.; Zhi, C. MagneticAssisted, Self-Healable, Yarn-Based Supercapacitor. ACS Nano 2015, 9, 6242-6251. (34) Tan, J.; Zou, R.; Zhang, J.; Li, W.; Zhang, L.; Yue, D. Large-Scale Synthesis of N-doped Carbon Quantum Dots and Their Phosphorescence Properties in a Polyurethane Matrix. Nanoscale 2016, 8, 4742-4747. (35) Luo, Z.; Yuan, X.; Yu, Y.; Zhang, Q.; Leong, D. T.; Lee, J. Y.; Xie, J. From AggregationInduced Emission of Au(I)–Thiolate Complexes to Ultrabright Au(0)@Au(I)–Thiolate Core– Shell Nanoclusters. J. Am. Chem. Soc. 2012, 134, 16662-16670. (36) Ghosh, S.; Das, N. K.; Anand, U.; Mukherjee, S. Photostable Copper Nanoclusters: Compatible Förster Resonance Energy-Transfer Assays and a Nanothermometer. J. Phys. Chem. Lett. 2015, 6, 1293-1298. (37) Ghosh, R.; Goswami, U.; Ghosh, S. S.; Paul, A.; Chattopadhyay, A. Synergistic Anticancer Activity of Fluorescent Copper Nanoclusters and Cisplatin Delivered through a Hydrogel Nanocarrier. ACS Appl. Mater. Interfaces 2015, 7, 209-222. (38) Hu, X.; Liu, T.; Zhuang, Y.; Wang, W.; Li, Y.; Fan, W.; Huang, Y. Recent Advances in the Analytical Applications of Copper Nanoclusters. Trends Anal. Chem. 2016, 77, 66-75. (39) Mutlugun, E.; Hernandez-Martinez, P. L.; Eroglu, C.; Coskun, Y.; Erdem, T.; Sharma, V. K.; Unal, E.; Panda, S. K.; Hickey, S. G.; Gaponik, N.; Eychmüller, A.; Demir, H. V. Large-Area



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 22

(over 50 cm × 50 cm) Freestanding Films of Colloidal InP/ZnS Quantum Dots. Nano Lett. 2012, 12, 3986-3993. (40) Liu, Z.; Xu, J.; Chen, D.; Shen, G. Flexible Electronics Based on Inorganic Nanowires. Chem. Soc. Rev. 2015, 44, 161-192. (41) Yoon, H. C.; Kang, H.; Lee, S.; Oh, J. H.; Yang, H.; Do, Y. R. Study of Perovskite QD Down-Converted LEDs and Six-Color White LEDs for Future Displays with Excellent Color Performance. ACS Appl. Mater. Interfaces 2016, 8, 18189-18200. (42) Dai, X.; Messanvi, A.; Zhang, H.; Durand, C.; Eymery, J.; Bougerol, C.; Julien, F. H.; Tchernycheva, M. Flexible Light-Emitting Diodes Based on Vertical Nitride Nanowires. Nano Lett. 2015, 15, 6958-6964. (43) Guan, N.; Dai, X.; Messanvi, A.; Zhang, H.; Yan, J.; Gautier, E.; Bougerol, C.; Julien, F. H.; Durand, C.; Eymery, J.; Tchernycheva, M. Flexible White Light Emitting Diodes Based on Nitride Nanowires and Nanophosphors. ACS Photonics 2016, 3, 597-603. (44) Tetsuka, H.; Ebina, T.; Mizukami, F. Highly Luminescent Flexible Quantum Dot–Clay Films. Adv. Mater. 2008, 20, 3039-3043. (45) Soran-Erdem, Z.; Erdem, T.; Gungor, K.; Pennakalathil, J.; Tuncel, D.; Demir, H. V. HighStability, High-Efficiency Organic Monoliths Made of Oligomer Nanoparticles Wrapped in Organic Matrix. ACS Nano 2016, 10, 5333-5339. (46) Demir, H. V.; Nizamoglu, S.; Erdem, T.; Mutlugun, E.; Gaponik, N.; Eychmüller, A. Quantum Dot Integrated LEDs using Photonic and Excitonic Color Conversion. Nano Today 2011, 6, 632-647. (47) Guzelturk, B.; Martinez, P. L. H.; Zhang, Q.; Xiong, Q.; Sun, H.; Sun, X. W.; Govorov, A. O.; Demir, H. V. Excitonics of Semiconductor Quantum Dots and Wires for Lighting and Displays. Laser Photonics Rev. 2014, 8, 73-93.


Page 17 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figures

Scheme 1. Schematics of the fabrication of dual emitting free-standing Cu NC/PU films with the on-purpose aggregated Cu NCs leading to AIE effect.

Figure 1. (a) TEM image of Cu NCs aggregated in the PU/ethanol mixture; inset shows an enlarged view of a single agglomerate; (b) Absorption spectrum (black line), PLE spectra (blue and orange lines) at the detection wavelengths of 423 nm and 600 nm, respectively, and PL spectrum (red line) at the excitation wavelength of 365 nm of the Cu NC/PU mixture in ethanol solution. Dotted blue and red lines show PLE (detection wavelength 423 nm) and PL (excitation wavelength 365 nm) spectra of PU in ethanol.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 22

Figure 2. (a) Transmission spectrum of the Cu NC/PU film with a thickness of 0.15 mm. Inset shows photographs of the film taken under day light (left) and UV excitation (right). (b) SEM image of the surface of the Cu NC/PU film. (c) PLE spectra (blue and orange lines) at the detection wavelengths of 423 nm and 600 nm, respectively, and PL spectrum (red line) at the excitation wavelength of 365 nm of the Cu NC/PU film. (d) PL decays (excitation wavelength 320 nm; recorded at 600 nm) of the Cu NC/PU mixture in ethanol solution (black dots) and of the Cu NC/PU film (red dots); solid lines are multi-exponential fits.


Page 19 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. (a) Tensile measurements of the Cu NC/PU film (black line) and bare PU film (red line). (b) Relative PL intensity (at 600 nm) of Cu NC/PU films subjected to a number of stretch and recovery cycles indicated on the X axis. Insets are respective photographs of the stretched and recovered samples taken under UV light.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 22

Figure 4. (a) TGA curves of the Cu NC/PU film (black line) and of the bare PU film (red line). (b) Relative PL intensity (at 600 nm) of Cu NC/PU films kept for 1 h under different temperatures indicated. (c) Relative PL intensity (at 600 nm) of Cu NC/PU films kept for up to 10 h at 90oC.


Page 21 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. (a) Schematics of a remote WLED with a Cu NC/PU film placed on top of a silicone resin layer at a distance from a UV chip. (b) Emission spectrum of the Cu NC/PU remote WLED; inset shows photographs of the operating device; (c) The CIE chromaticity coordinate and (d) CRIs at various Munsell codes of the Cu NC/PU remote WLED.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table of Contents Graphic


Page 22 of 22

Stretchable and Thermally Stable Dual Emission Composite Films of

Recommend Documents