Spy Must Be Spotted: A Multistimuli-Responsive Luminescent Material

Subscriber access provided by Kaohsiung Medical University

Functional Inorganic Materials and Devices

A spy must be spotted: a multi-stimuli-responsive luminescent material for dynamic multimodal anticounterfeiting and encryption Zhenyu Sun, Jiaxuan Yang, Linwei Huai, Wenxiang Wang, Zhidong Ma, Jika Sang, Jiachi Zhang, Huihui Li, Zhipeng Ci, and Yuhua Wang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b08977 • Publication Date (Web): 06 Jun 2018 Downloaded from http://pubs.acs.org on June 6, 2018

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 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 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.

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 23 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

A Spy Must be Spotted: A Multi-StimuliResponsive Luminescent Material for Dynamic Multimodal Anticounterfeiting and Encryption Zhenyu Sun a, Jiaxuan Yang a, Linwei Huai a, Wenxiang Wang a, Zhidong Ma a, Jika Sang a, Jiachi Zhang a *, Huihui Li a *, Zhipeng Ci a, Yuhua Wang a a. National & Local Joint Engineering Laboratory for Optical Conversion Materials and Technology, Lanzhou University, Lanzhou 730000, P. R. China. E-mail: [email protected]; E-mail: [email protected] KEYWORDS: luminescent image; photostimulated luminescence; upconversion luminescence; anticounterfeiting; information encryption

ABSTRACT: The development of luminescent materials for anticounterfeiting and encryption is of great importance. Herein, we develop a multi-stimuli-responsive luminescent material, Na2CaGe2O6:Pb2+/Er3+, and use it to print luminescent images. The photoluminescence (PL) and upconversion luminescence (UCL) of these images show different patterns and colors under different stimuli. The photostimulated luminescence (PSL) of the printed images causes dynamic changes in appearance and is accordingly applied for dynamic multimodal anticounterfeiting on banknotes. The PSL of these luminescent images is also applied in a virtual war scenario to demonstrate that the dynamic PSL-encrypted information in the fabricated image is sufficiently

ACS Paragon Plus Environment

1

ACS Applied Materials & Interfaces 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 2 of 23

safe even in extreme cases and that spies will be detected. These results can inspire us with more creative security designs based on this luminescent material.

1 Introduction Information security is a vitally important issue in the economic, social and military fields as well as our individual daily lives.1-4 During recent decades, a wide variety of technologies, such as markers5, plasmonic labels6-7, magnetic labels8, holograms9, and luminescence10-11, have been developed as security features. In particular, luminescence offers the advantages of visibility, high throughput and facile design and is therefore widely applied for anticounterfeiting and encryption.12-13 In recent years, a large number of luminescent materials based on carbon dots1415

, semiconductor dots16-17, MOFs18, rare earth nanoparticles19-20 and organic dyes21 have been

widely reported for security designs. Generally, luminescent materials are invisible under normal conditions but visible under multiple stimuli; thus, luminescent materials can be applied to protect confidential information.22-23 Unfortunately, the photoluminescence (PL) or upconversion luminescence (UCL) of existing materials is unchanged by reading; thus, the theft of information leaves no trace.24-25 Therefore, the development of a safer luminescent material is urgent. Clearly, if the luminescence of materials could change dynamically during reading, the theft of information would be much more easily discovered. Significantly, photostimulated luminescence (PSL) changes dynamically under thermal or near-infrared (NIR) stimulation and thus may meet the needs of dynamic anticounterfeiting and encryption.26 To date, PSL materials have seldom been reported for security designs.


2

Page 3 of 23 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


In this work, we have developed a multi-stimuli-responsive luminescent material, Na2CaGe2O6:Pb2+/Er3+ (NCG:Pb2+/Er3+), and printed luminescent images based on this material. The PL/PSL/UCL properties and mechanisms and the trap properties of the luminescent material were studied, and the stability of the luminescent images was tested experimentally. On the basis of the unique PL/PSL/UCL features, this luminescent image was applied to dynamic multimodal anticounterfeiting on banknotes and to encryption in a virtual war scenario. The results demonstrate that the dynamically PSL-encrypted information in the image is sufficiently safe even in extreme cases, and any spy must be detected, exactly as in quantum communication.27 Accordingly, this multi-stimuli-responsive luminescent material exhibits potential applications in the fields of anticounterfeiting and encryption.

2 Experimental section 2.1 Synthesis of the multi-stimuli-responsive luminescent material Typical NCG:Pb2+/Er3+ materials were prepared by the solid-state method. Stoichiometric raw materials, Na2CO3 (99.9%), CaCO3 (99.9%), GeO2 (99.99%), PbO (99.9%) and Er2O3 (99.99%), were homogeneously mixed and sintered at 950 °C in the air for 6 h. Then, the samples were obtained by careful grinding in an agate mortar after natural cooling to room temperature. 2.2 Preparation of the luminescent images The luminescent materials were mixed with polydimethylsiloxane (PDMS, with a curing agent in a 10:1 ratio) in a weight ratio of 1:1 to form viscous phosphor slurries. The multi-stimuliresponsive luminescent images were fabricated by two methods: the stamp method and the mask


3


Page 4 of 23

method. (1) In the stamp method, the material slurry was coated onto the raised surface of a stamp by dipping and then impressed on common copy paper or a real banknote. (2) In the mask method, a 1×2 cm matrix was directly printed on a piece of clean glass with the slurry, and then the patterns were loaded through a mask irradiated by an ultraviolet (254 nm) lamp. All the stamps and masks in our experiment were simply obtained with a commercial 3D printer (Raise3D N2). 2.3 Structural and optical characterizations The powder X-ray diffraction (XRD) patterns of the materials were recorded by an X-ray diffractometer (Rigaku D/Max-2400) with Ni-filtered Cu Kα radiation. High-resolution transmission electron microscopy (HRTEM) was performed with a transmission electron microscope (TEM) operated at 300 kV (FEI Tecnai F30). The diffuse reflection (DR) and absorption spectra were obtained by a UV-vis spectrophotometer (Perkin-Elmer Lambda 950) using BaSO4 as a reference. The PL and PLE spectra were measured with a fluorescence spectrophotometer (Edinburgh Instrument Ltd., FLS-920T). The PSL and UCL spectra were measured with the above spectrophotometer equipped with an external 980 nm semiconductor laser (Changchun New Industries Optoelectronics Tech. Co., Ltd.) as the excitation source. The TL experiments were performed with a TL detector (Beijing Nuclear Instrument Factory, FJ427A) with a heating rate of 1 K/s in the temperature range from 20 to 400 °C. Before a typical TL measurement, the sample was preheated at 200 °C for 5 min and then cooled before irradiation by an ultraviolet (254 nm) lamp for 10 min. All photographs in Figure 5 were taken with an iPhone 6 smartphone, and the other photographs were taken with a digital camera (Canon EOS 800D) with an NIR filter.


4

Page 5 of 23 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 Results and discussion Figure 1 presents the phase characterization and crystal analysis of the materials. The results indicate that the material has a trigonal structure, and the space group is R-3m according to XRD refinement, as shown in Figure 1a and Table S1.28 There are four types of cation sites in NCG (Figure 1b, Table S2-S4), and both Na and Ca atoms occupy the polyhedral sites coordinated by eight or twelve oxygens (Figure 1c). The Ge atoms are located at the other dodecahedral sites. According to the XRD patterns in Figure S1, S2, all NCG:xPb2+ and NCG:xEr3+ solid solutions are formed. However, owing to the larger ion radii of Pb2+ and Er3+, the XRD peaks are shifted slightly to lower angles, according to Bragg’s law (Figure S1, S2).29 Figure 1d shows the X-ray photoelectron spectrum (XPS) of a typical NCG:Pb2+/Er3+ sample, which displays the characteristic peaks of Na, Ca and Ge. Additionally, the peaks of Pb and Er can be identified in the high-resolution XPS spectra in Figure 1e. Figure 1f shows an HRTEM image, in which the measured interplanar spacing is 4.393 Å, which matches the (021) interplanar distance of 4.413 Å. Moreover, a typical SEM image of this material is shown in Figure S3.


5


Page 6 of 23

Figure 1. Structural characterizations and crystal analysis of the NCG host and NCG:Pb2+/Er3+ materials. a) Rietveld refinement of the powder XRD profile of NCG host. b) Unit-cell crystal structure representation of NCG. c) Coordination environment of the Na+/Ca2+ and Ge4+ sites; illustration of the four different cation sites of Na+/Ca2+ in NCG. d) XPS spectrum of NCG:Pb2+/Er3+ samples. e) High-resolution XPS spectra of Pb 4f and Er 4d/Auger. f) HRTEM image of the (021) crystal face. Figure

2

shows

the

unique

multi-stimuli-responsive

luminescence

properties

of

NCG:Pb2+/Er3+. NCG:Pb2+ exhibits bright white-blue PL when excited at 254 nm due to the 3P11

S0 transition of Pb2+ (Figure 2a)30-31 and deep blue PSL (λNIR = 980 nm) after charging by an

ultraviolet (254 nm) lamp, as shown in Figure 2b. Interestingly, although no PL can be observed for NCG:Er3+ excited at 254 nm (Figure 2a), the strong green UCL of Er3+ can be observed. Figure 2c shows the 980 nm NIR laser-stimulated UCL spectrum and a photograph of the green UCL. The laser power dependence of UCL under 980 nm NIR laser stimulation is presented in the inset of Figure 2c and demonstrates that the UCL of NCG:Er3+ is a two-photon process.32


6

Page 7 of 23 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


The PL, PSL and UCL mechanisms of typical NCG:Pb2+/Er3+ are depicted in Figure 2d,e,f, respectively. Importantly, the PL excitation band of NCG:Pb2+ is assigned to the 6s2-6s16p2 interconfigurational transition (240-330 nm) of Pb2+, and the PSL of NCG:Pb2+ can be charged at 200-310 nm according to the PSL excitation spectrum in Figure 2b. The optimal charging wavelength is determined to be 255 nm, which is very close to the emission wavelength of a common ultraviolet (254 nm) lamp. Figure 2a also depicts the diffuse reflectance spectrum of the NCG host, and the absorption band in the range 200-270 nm can be ascribed to the band-to-band host absorption. Based on the theory presented by Mott and Davis, the optical band gap (Eg) of NCG was determined to be approximately 4.9 eV (Figure S4).33 The host absorption is consistent with the PSL excitation band, which indicates that the PSL is charged via the band-to-band pathway (Figure 2e). After charging, the carriers are trapped below the bottom of the conduction band (CB). Finally, the linear dependence of I-1 versus t in Figure S5 reveals that the tunneling process is the only return path for carriers when stimulated by an NIR laser.34-37


7


Page 8 of 23

Figure 2. Luminescence properties and mechanisms of the multi-stimuli-responsive material NCG:Pb2+/Er3+. a) DR spectrum of NCG host; PL (λex = 254 nm) and PLE (λem = 405 nm) spectra of NCG:0.9%Pb2+ sample; PL spectrum of NCG:8%Er3+ sample (Inset: PL photographs of Pb2+- and Er3+-doped samples). b) PSL excitation and emission spectra (λex = 980 nm) of NCG:0.9%Pb2+ sample (Inset: photographs of PSL). c) 980 nm laser-stimulated UCL spectrum of NCG:8%Er3+ (Inset: laser power dependence of UCL and photograph of UCL). Mechanisms of the d) PL and e) PSL of NCG:Pb2+ and of the f) UCL of NCG:Er3+. One of the useful features for multimodal anticounterfeiting designs is that, as shown in the photographs in Figure 2, the PL color of the NCG:Pb2+ sample is somewhat different from the PSL color. Figure 3b shows the PL and PSL emission spectra fitted by multiple Gaussian components. The PL spectrum can be divided into four components, while the PSL corresponds only to P2 and P3. As a result, the PL and PSL show different colors when viewed. Additionally, the CIE coordinates of the PL, PSL and UCL spectra were calculated and are labeled in Figure S6. As the Pb2+ content increases, the PSL (Figure 3a, Figure S7) spectra gradually shift to higher wavelengths (redshift). According to Figure 3c, the redshift may be attributed to the variations in the P2 and P3 components. As summarized in Figure 3d, the P2 intensity decreases as the Pb2+ content increases, and the P3 peak increases. As a consequence, the PSL peak gradually shifts from 370 to 430 nm. Considering the color sensitivity of the human eye, the NCG:0.9%Pb2+ sample with a maximum emission peak at 425 nm was selected for subsequent security designs. Meanwhile, the optimal Er3+ content for UCL was determined to be 8%, according to the results in Figure S8.


8

Page 9 of 23 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. PSL optimization of the NCG:Pb2+ material. a) Normalized PSL spectra with different Pb2+ contents (Inset: PSL intensity dependence on Pb2+ content). b) PL and PSL spectra of a typical NCG:0.5%Pb2+ sample fitted by multiple Gaussian components. c) Spectral variations in the P2 and P3 components. d) Quantitative variations in the P2 and P3 components. The PSL properties depend strongly on the trap properties of phosphors, and accordingly, Figure 4 exhibits the investigation of the traps. Figure 4a presents the thermoluminescence (TL) curve of a typical NCG:0.9%Pb2+ sample, and by using a classical multipeak fitting method, it can be divided into two TL peaks corresponding to two kinds of traps.38-40 Excitation temperature-dependent TL experiments (Figure 4b) based on the initial rising method (Figure 4c) were performed to reveal the trap distribution, as shown in Figure 4d.41 The results indicate that shallow traps are distributed in the broad range of 0.40-0.65 eV, and narrowly distributed deep traps are located at approximately 0.72 eV. In addition, the ET versus Texc plot (Figure 4e) can be


9


Page 10 of 23

fitted by two linear equation functions, which also correspond to the two types of traps.42 To reveal the roles of traps in the PSL, Figure 4f exhibits the results of a time-fading TL experiment. These results indicate that the PSL intensity always decreases even without NIR stimulation, and the PSL decay effect can be demonstrated in Figure 4g. Subsequently, after fading for 6 h, the samples were stimulated with a 980 nm NIR laser. As shown in the photographs in Figure 4h, in the NIR laser-fading TL experiment, the blue PSL is no longer visible after 4 s of irradiation with the 980 nm NIR laser, which illustrates that the deep traps have been completely emptied in 4 s. Clearly, the PSL feature of this luminescent material can be utilized to realize the dynamic multimodal anticounterfeiting and encryption.

Figure 4. Trap properties of the NCG:Pb2+ material. a) TL curve of the optimal NCG:0.9%Pb2+ sample and the result of multipeak fitting. b) Results of the excitation temperature-dependent TL experiment. c) TL curves analyzed by the initial rising method for trap depth evaluation. d) Estimated trap distribution according to the method introduced in ref. [41]. e) Trap depth dependence on the excitation temperature and the linear fitting. f) Results of the time-fading TL


10

Page 11 of 23 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


experiment. g) PSL decay effect: the PSL intensity dependence on placement time. h) NIR laserfading TL experiment on the NCG:0.9%Pb2+ sample faded for 6 h (Inset: photographs of PSL at different stimulation times 0 s, 2 s and 4 s). On the basis of the unique features of the NCG:Pb2+/Er3+ materials, the dynamic multimodal luminescent images were designed for anticounterfeiting. Figure 5 illustrates the fabrication of the luminescent images by the stamp method and some simple examples. Under indoor conditions, the images printed on common copy paper are not visible (Figure 5b) but can be clearly felt by touch. Interestingly, the luminescent images are able to show different patterns and colors under different stimulations, as if by magic. For example, in Figure 5b, we can see the blue PL of the letters “LZ”, the number “4”, and a smiling face under excitation at 254 nm, but they change to the green letters “LZU”, the number “9” and a sad face (UCL) when stimulated by the NIR laser. Schematic diagrams of these changing images are depicted in Figure 5c. This variability of the luminescent images can clearly inspire more creative anticounterfeiting designs. Moreover, luminescent images can also be obtained by the filling method. For a typical example, as shown in Figure 5d, a two-dimensional code is embedded into the PMMA plate through laser ablation, and then the NCG:Pb2+,Er3+@PDMS slurry is filled into the code pattern.


11


Page 12 of 23

Figure 5. Printing of the luminescent images and some simple design cases. a) Schematic illustration of the stamp method and the multimodal responsive effect. b) Three different luminescent patterns under natural light, 254 nm light and 980 nm NIR laser, respectively. Scale bar: 4 mm. c) Revelation of the transformation based on multi-stimuli-responsive images. d) A two-dimensional code pattern on the PMMA plate printed by the filling method and its optical responses to natural light, 254 nm light and 980 nm NIR laser. The QR code is linked to the three characters “LZU”. Scale bar: 6 mm. Figure 6 presents typical examples of anticounterfeiting design on real banknotes. The currency values “100”, “50” and “1” have been printed by the stamp method on the top left of Chinese, Canadian and American banknotes, respectively. The applied slurry was NCG:Pb2+,Er3+@PDMS. Figure 6a,b shows that the images printed on the banknotes are flexible and completely invisible in daylight. However, when excited by an ultraviolet (254 nm) lamp, the blue number “100” (PL) can be clearly seen (Figure 6c). The banknote can be encrypted


12

Page 13 of 23 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


based on the PSL feature of this image. In a typical example, the printed image is first charged by an ultraviolet (254 nm) lamp for 10 min and then placed in the dark for 6 h. Subsequently, a 980 nm NIR laser is used to illuminate the image, and we can then observe the blue number “100” due to PSL. In addition, the blue PSL vanishes rapidly in 4 s and leaves only the green number “100” due to UCL, as shown in Figure 6d. However, if the luminescent image has not been previously encrypted, we can observe only the green UCL of the number “100” upon stimulation by the NIR laser.

Figure 6. Typical examples of anticounterfeiting design on real banknotes. a) The images “100”, “50” and “1” on the top left of Chinese, Canadian and American banknotes. b) Photographs of the Chinese banknote to show the flexibility of the printed images. c) Photographs of the PL excited at 254 nm. d) Photographs of the UCL and the PSL-encrypted UCL at 1-4 s stimulated by a 980 nm laser. The stability of the luminescent image is important, and accordingly, we conducted a series of stability tests on the images in Figure 7. First, the printed image was placed in the dark for different times, and the PL/UCL intensities were recorded at room temperature, as shown in


13


Page 14 of 23

Figure 7a. The results indicate that, even after 1 month, the printed image was still stable, and approximately 90% of the initial PL/UCL remained. Second, the wear and water resistances of the luminescent images printed on banknotes were investigated. The results indicate that even after being rubbed by hands 1000 times or placed in tap water for 10 h, the image remained whole, and the PL/UCL intensities were not clearly decreased, as summarized in Figure 7b,c.

Figure 7. Stability tests of the luminescent images printed on banknotes. a) Lifetime test: the PL/UCL intensities of the printed image after different placed times. b) Wear and c) water resistance of the printed image after being rubbed by hands 1000 times or placed in tap water for 10 h. Based on the PSL features, this type of luminescent image can be utilized for military applications. As shown in Figure 8a, the command “CAL” is loaded in the luminescent image by


14

Page 15 of 23 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


the mask method, and then the fading of the PSL “CAL” can be observed in 4 s under 980 nm NIR laser stimulation. In a virtual war scenario, a command must be sent to the ports in 6 h, as shown in Figure 8b. If the image is irradiated by an ultraviolet lamp (spy A) or stimulated by an NIR laser (spy B), the PSL command in the image will be damaged, as shown in Figure 8c. According to this clue, spies A and B will be detected by the commander. In an extreme case, the PSL command in the luminescent image is replicated by spy C using the same mask. Spy C intends the commander to see the expected fast-fading blue PSL “CAL” and therefore thinks he will not be discovered. However, because of the PSL decay effect (Figure 4g), the PSL intensity of the replicated command is always different from that of the initial command, as shown in Figure 8c. Moreover, as shown in Figure S9, it demonstrates that the replication of a PSLencrypted image is very difficult. Because of the PSL difference, spy C will also be detected. Owing to the discovery of the espionage, the commander decisively changes the scheduled landing site (CAL) to avoid the coming tanks and then makes a successful landing in NMD, as shown in Figure 8b.


15


Page 16 of 23

Figure 8. Military application of the luminescent image. a) Fabrication of a PSL-encrypted command on the NCG:Pb2+ printing by the mask method. b) Military map of the virtual scenario. c) Different operations and observations by three spies (A, B, C) and the commander.

4 Conclusion A multi-stimuli-responsive luminescent material NCG:Pb2+/Er3+ and luminescent image printing based on the material are developed. The images exhibit PL, UCL and PSL under different stimuli, and the results demonstrate that these printed images are applicable in dynamic multimodal anticounterfeiting on banknotes. In addition, applying these luminescent images in a virtual war scenario demonstrates that the PSL-encrypted information in the image is safe and provides a vivid example of how spies can be detected in extreme cases. Therefore, this unique luminescent material is highly useful for both societal and military applications.

Supporting Information: the XRD patterns of the NCG host, NCG:Pb2+ and NCG:Er3+, the typical SEM image, the UV-vis absorption spectrum of the NCG host, the results of PSL decay curves for the Pb2+ doped sample, the CIE coordinates of the PL, PSL and UCL spectra, the PSL spectra with different Pb2+ contents, the UCL spectra with different Er3+ contents, and etc. are provided in supporting information. Corresponding Author * [email protected] * [email protected]


16

Page 17 of 23 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


Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the Hui-Chun Chin and Tsung-Dao Lee Chinese Undergraduate Research Endowment (No. LZU-JZH1928), and the Fundamental Research Funds for Central Universities (No. lzujbky-2017-sp22). The authors would like to thank the technical supports of the Changchun new industries optoelectronics technology Co., Ltd. REFERENCES 1 Zhou, L.; Zhao, A.; Wang, Z.; Chen, Z.; Ren, J.; Qu, X. Ionic liquid-assisted synthesis of multicolor luminescent silica nanodots and their use as anti-counterfeiting ink. ACS Appl. Mater. Interfaces 2015, 7, 2905-2911. 2 Singh, V. K.; Chitumalla, R. K.; Ravi, S. K.; Zhang, Y.; Xi, Y.; Sanjairaj, V.; Zhang, C., Jang, J.; Tan, S. C. Inkjet-printable hydrochromic paper for encryption information and anticounterfeiting. ACS Appl. Mater. Interfaces 2017, 9, 33071-33079. 3 Kumar, P.; Singh, S.; Gupta, B. K. Future prospects of luminescent nanomaterial based security inks: from synthesis to anti-counterfeiting applications. Nanoscale 2016, 8, 1429714340. 4 Yoon, B.; Lee, J.; Park I. S.; Jeon, S.; Lee, J.; Kim, J.-M. Recent functional material based approaches to prevent and detect counterfeiting. J. Mater. Chem. C 2013, 1, 2388-2403.


17


Page 18 of 23

5 Si, K. J.; Sikdar, D.; Yap, L. W.; Foo, J. K. K.; Guo, P.; Shi, Q.; Premaratne, M.; Cheng, W. Dual-coded plasmene nanosheets as next-generation anticounterfeit security labels. Adv. Opt. Mater. 2015, 3, 1710-1717. 6 Smith, A. F.; Patton, P.; Skrabalak, S. E. Plasmonic nanoparticles as a physically unclonable function for responsive anti-counterfeit nanofingerprints. Adv. Funct. Mater. 2016, 26, 13151321. 7 Park, K.; Jung, K.; Kwon, S. J.; Jang, H. S.; Byun, D.; Han, I. K.; Ko, H. Plasmonic nanowireenhanced upconversion luminescence for anticounterfeit devices. Adv. Funct. Mater. 2016, 26, 7836-7846. 8 Li, R.; Zhang, Y.; Tan, J.; Wan, J.; Guo, J.; Wang, C. Dual-mode encoded magnetic composite microsphere based on fluorescence reporters and raman probes as covert tag for anticounterfeiting applications. ACS Appl. Mater. Interfaces 2016, 8, 9384-9394. 9 Wan, W.; Gao, J.; Yang, X. Metasurface holograms for holographic imaging. Adv. Opt. Mater. 2017, 1700541. 10 Kumar, P.; Nagpal, K.; Gupta, B. K. Unclonable security codes designed from multicolor luminescent lanthanide-doped Y2O3 nanorods for anticounterfeiting. ACS Appl. Mater. Interfaces 2017, 9, 14301-14308. 11 Kumar, P.; Singh, S.; Gupta, B. K. A novel approach to synthesis a dual mode luminescent composite pigment for unclonable high security codes to combat counterfeiting. Chem. Eur. J. 2017, 23, 17144 – 17151.


18

Page 19 of 23 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


12 Jiang, K.; Zhang, L.; Lu, J.; Xu, C.; Cai, C.; Lin, H. Triple-mode emission of carbon dots: applications for advanced anti-counterfeiting. Angew. Chem., Int. Ed. 2016, 55, 7231-7235. 13 Xu, L.; Chen, J.; Song, J.; Li, J.; Xue, J.; Dong, Y.; Cai, B.; Shan, Q.; Han, B.; Zeng, H. Double-protected all-inorganic perovskite nanocrystals by crystalline matrix and silica for triplemodal anti-counterfeiting codes. ACS Appl. Mater. Interfaces 2017, 9, 26556-26564. 14 Wang, J.; Wang, C.-F.; Chen, S. Amphiphilic egg-derived carbon dots: rapid plasma fabrication, pyrolysis process, and multicolor printing patterns. Angew. Chem., Int. Ed. 2012, 51, 9297-9301. 15 Liu, Y.; Zhou, L.; Li, Y.; Deng, R.; Zhang, H. Highly fluorescent nitrogen-doped carbon dots with excellent thermal and photo stability applied as invisible ink for loading important information and anti-counterfeiting. Nanoscale 2017, 9, 491-496. 16 Li, F.; Wang, X.; Xia, Z.; Pan, C.; Liu, Q. Photoluminescence tuning in stretchable PDMS film grafted doped core/multishell quantum dots for anticounterfeiting. Adv. Funct. Mater. 2017, 27, 1700051. 17 Chen, L.; Lai, C.; Marchewka, R.; Berry, R. M.; Tam, K. C. Use of CdS quantum dot functionalized cellulose nanocrystal films for anti-counterfeiting applications. Nanoscale 2016, 8, 13288-13296. 18 Zhang, C.; Wang, B.; Li, W.; Huang, S.; Kong, L.; Li, Z.; Li, L. Conversion of invisible metal-organic frameworks to luminescent perovskite nanocrystals for confidential information encryption and decryption. Nat. Commun. 2017, 8, 1138.


19


Page 20 of 23

19 Liu, Y.; Ai, K.; Lu, L. Designing lanthanide-doped nanocrystals with both up- and downconversion luminescence for anti-counterfeiting. Nanoscale 2011, 3, 4804-4810. 20 You, M.; Zhong, J.; Hong, Y.; Duan, Z.; Lin, M.; Xu, F. Inkjet printing of upconversion nanoparticles for anti-counterfeit applications. Nanoscale 2015, 7, 4423-4431. 21 Tian, W.; Zhang, J.; Yu, J.; Wu, J.; Zhang, J.; He, J.; Wang, F. Phototunable full-color emission of cellulose-based dynamic fluorescent materials. Adv. Funct. Mater. 2017, 1703548. 22 Andres, J.; Hersch, R. D.; Moser, J.-E.; Chauvin, A.-S. A new anti-counterfeiting feature relying on invisible luminescent full color images printed with lanthanide-based inks. Adv. Funct. Mater. 2014, 24, 5029-5036. 23 Hu, L.; Fan, Y.; Liu, L.; Li, X.; Zhao, B.; Wang, R.; Wang, P.; El-Toni, A. M.; Zhang, F. Orthogonal multiplexed luminescence encoding with near-infrared rechargeable upconverting persistent luminescence composites. Adv. Opt. Mater. 2017, 1700680. 24 Tran, C. D.; Cui, Y.; Smirnov, S. Simultaneous multispectral imaging in the visible and nearinfrared region: applications in document authentication and determination of chemical inhomogeneity of copolymers. Anal. Chem. 1998, 70, 4701-4708. 25 Li, M.; Yao, W.; Liu, J.; Tian, Q.; Liu, L.; Ding, J.; Xue, Q.; Lu, Q.; Wu, W. Facile synthesis and screen printing of dual-mode luminescent NaYF4:Er,Yb(Tm)/carbon dots for anticounterfeiting applications. J. Mater. Chem. C 2017, 5, 6512-6520. 26 Li, Y.; Gecevicius, M.; Qiu, J. Long persistent phosphors—from fundamentals to applications. Chem. Soc. Rev. 2016, 45, 2090-2136.


20

Page 21 of 23 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


27 Duan, L.-M.; Lukin, M. D.; Cirac, J. I.; Zoller, P. Long-distance quantum communication with atomic ensembles and linear optics. Nature 2001, 414, 413-418. 28 Nishi, F.; Takéuchi, Y. Structure of sodium calcium germanate Na2CaGe2O6. Acta. Cryst. 1990, C46, 544-546. 29 Jauncey, G. E. M. The scattering of X-rays and Bragg’s law. Proc. Natl. Acad. Sci. 1924, 10, 57-60. 30 Folkerts, H. F.; Blasse, G. Luminescence of Pb2+ in SrTiO3. Chem. Mater. 1994, 6, 969-972. 31 Folkerts, H. F.; Blasse, G. Luminescence of Pb2+ in several calcium borates. J. Mater. Chem. 1995, 5, 273-276. 32 Pollnau, M.; Gamelin, D. R.; Lüthi, S. R.; Güdel, H. U.; Hehlen, M. P. Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems. Phys. Rev. B 2000, 61, 3337-3346. 33 Davis, E. A.; Mott, N. F. Conduction in non-crystalline systems V. Conductivity, optical absorption and photoconductivity in amorphous semiconductors. Philos. Mag. 1970, 22, 903922. 34 Avouris, P.; Morgan, T. N. A tunneling model for the decay of luminescence in inorganic phosphors: The case of Zn2SiO4:Mn. J. Chem. Phys. 1981, 74, 4347-4355. 35 Vedda, A.; Nikl, M.; Fasoli, M.; Mihokova, E.; Pejchal, J.; Dusek, M.; Ren, G.; Stanek, C. R.; McClellan, K. J.; Byler, D. D. Thermally stimulated tunneling in rare-earth-doped oxyorthosilicates. Phys. Rev. B 2008, 78, 195123.


21


Page 22 of 23

36 Trojan-Piegza, J.; Niittykoski, J.; Hölsä, J.; Zych, E. Thermoluminescence and kinetics of persistent luminescence of vacuum-sintered Tb3+-doped and Tb3+,Ca2+-codoped Lu2O3 materials. Chem. Mater. 2008, 20, 2252-2261. 37 Pan, Z.; Lu, Y.-Y.; Liu, F. Sunlight-activated long-persistent luminescence in the nearinfrared from Cr3+-doped zinc gallogermanates. Nat. Mater. 2011, 11, 58-63. 38 Chen, R. Glow curves with general order kinetics. J. Electrochem. Soc. 1969, 116, 12541257. 39 Nakazawa, E. A new method for the characterization of traps in luminescent materials. Jpn. J. Appl. Phys. 1984, 23, L755-L757. 40 Kitis, G.; Gomez-Ros, J. M.; Tuyn, J. W. N. Thermoluminescence glow-curve deconvolution functions for first, second and general orders of kinetics. J. Phys. D: Appl. Phys. 1998, 31, 26362641. 41 Van den Eeckhout, K.; J. J. Bos, A.; Poelman, D.; F. Smet, P. Revealing trap depth distributions in persistent phosphors. Phys. Rev. B 2013, 87, 045126. 42 Lin, H.; Xu, J.; Huang, Q.; Wang, B.; Chen, H.; Lin, Z.; Wang, Y. Bandgap tailoring via Si doping in inverse-garnet Mg3Y2Ge3O12:Ce3+ persistent phosphor potentially applicable in ACLED. ACS Appl. Mater. Interfaces 2015, 7, 21835-21843.


22

Page 23 of 23 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


Abstract Graphic


23

Spy Must Be Spotted: A Multistimuli-Responsive Luminescent Material

Recommend Documents