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Journal of Nanoscience and Nanotechnology Vol. 11, 9693–9696, 2011
Study on NIR Optical Rewritable Film Based on Dithienylethene and Upconversion Nanocrystals Xuesong Zhai, Feng Shi, Huan Chen, Dan Zhao, Daisheng Zhang, and Weiping Qin∗ State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China Tm3+ and Yb3+ codoped NaYF4 upconversion (UC) nanoparticles (NPs) with intense ultraviolet (UV) fluorescence were synthesized using a solvothermal approach. NIR optical rewritable film incorporated with the UCNPs and dithienylethene (DTE) were performed for optical storage based on the photochromic reaction of DTE induced by the intense UV from themultiphoton UC fluorescence of NaYF4 NPs. The photochromic DTE did not exhibit obvious fatigue after repetitious write/erase cycles using NIR/green irradiation.
Keywords: NIR Optical Film, UV Upconversion, Nanocrystals, NaYF4 , DTE.
1. INTRODUCTION
∗
Author to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2011, Vol. 11, No.11
2. EXPERIMENTAL DETAILS NaYF4 :0.5 mol% Tm3+ , 20 mol% Yb3+ (NaYF4 :Tm, Yb) NPs were synthesized using a simple hydrothermal method.10 Ln2 O3 (Ln = 795%Y, 20%Yb, and 0.5%Tm) were dissolved in dilute HNO3 under heating to prepare the stock solution of Ln(NO3 3 . Then, rare-earth stearate precursors (precipitates) were prepared by adding 0.6 g of NaOH aqueous solution dropwise into a transparent solution containing 5 mmol of Ln(NO3 3 and 4.2672 g of stearate acid. Subsequently, a homogeneous solution containing 5 mL of water, 15 mL of ethanol, and 5 mL of oleic acid, 0.95 g of the precursor and 0.2099 g of NaF was prepared under stirring and sonication. Lastly, the solution was transferred to an autoclave, sealed, and solvothermally treated at 150 C for 24 h. A mixture of 5 mg 1,2-bis(2,4-dimethyl-5-phenyl-3thienyl)-3,3,4,4,5,5-heafluoro-1-cyclopentene (DTE derivative), 40 mg NaYF4 :Tm, Yb UCNPs and chloroform (∼10 drops) was sonicated until being homogenous.
1533-4880/2011/11/001/004
doi:10.1166/jnn.2011.5260
9693
RESEARCH ARTICLE
The optical data storage on photochromic reactions has received significant attentions in recent years.1–3 Most of them are focused on how to achieve 3D data storage, increase memory density, and fulfill nondestructive readout and high sensitivity.1–5 Many attempts to achieve these properties have been reported. For example, Yan et al. reported on a rewritable 2D optical storage medium with high-density recording capacity and nondestructive readout that were functionalized by the luminescence modulation of ordered upconversion nano patterns via a photochromicdithienylethene (DTE).4 They also wanted to fulfill 3D optical storage using the UCNP-photochrome strategy. Song et al. demonstrated an amplification of fluorescent contrast by applying photonic crystals to theoptical storage system and provided much better resolution and sensitivity.5 However, in these versatile photoresponsive systems based on DTE, UV light was needed for the ring-closing reaction of DTE. Using UV light as the irradiation source may bring detrimental effects such as unwanted side reactions6–7 and low penetration depth into materials.7–8 These disadvantages can be avoided if low energy photons are used as the irradiation source in photoresponsive systems. Upconversion nanocrystals (UCNPs) can efficiently convert NIR light (980 nm) to visible or UV light.9–13 Especially, Tm3+ and Yb3+ codoped NaYF4 NPs have been proved to be excellent UC materials for intense UV
fluorescence.10 13 Therefore, they might be good candidates for inducing the ring-closing reaction of DTE under NIR irradiation. In this paper, we present a study on a NIR optical rewritable film incorporated with UCNPs and DTE. Data can be written in the film by NIR (980 nm) and erased by green light (532 nm). Many cycles of writing/erasing experiments suggested that the film might be a candidate of nondestructive optical storage working in the NIR region.
Study on NIR Optical Rewritable Film Based on DTE and Upconversion Nanocrystals
Then, poly(ethylene glycol) dimethacrylate (PEGDMA) (∼30 drops) and Darocur 4265 (∼1 drop) were added to the mixture under sonication until being homogenous. The solution was placed between two microscope slides spaced apart by 1 mm thick glass and cured for approximately 30 min to produce flexible polymeric composites using 355 nm light. The film was subsequently irradiated with 532 nm light for 10 min to yield a slightly yellow film. The phase identification was performed by X-ray diffraction (XRD) (Model Rigaku Ru-200b), using a nickel-filtered Cu K radiation ( = 014518 nm) in the range of 10 ≤ 2 ≤ 70 . Morphologies were characterized by a Hitachi S-4800 scanning electron microscope (SEM). Under 980 nm excitation, UC spectra were recorded by a Hitachi F-4500 fluorescence spectrometer (1.0 nm for slit width and 400 V for PMT voltage). UV-vis absorbance spectra were measured by a UV-vis spectrophotometer (Shimadzu Pharmaspce UV-1700) at room temperature.
RESEARCH ARTICLE
3. RESULTS AND DISCUSSION The crystal structures and the phase purity of as-prepared NaYF4 :Tm, Yb UCNPs were examined by XRD. Typical XRD patterns of as-prepared UCNPs are presented in Figure 1. The diffraction peaks of NPs are well-defined, and the X-ray diffraction pattern of NaYF4 :Tm, Yb samples can be indexed as a mixture of the cubic (JCPDS file number 6-342) and hexagonal (JCPDS file number 16-334) phases of NaYF4 . Figure 2 shows the morphology of NaYF4 :Tm, Yb NPs characterized by SEM. The UCNPs are uniform nanospheres with an average diameter of about 35 nm. Photoluminescence (PL) spectra show the UC luminescence of NaYF4 :Tm, Yb nanocrystals under 980 nm excitation, as shown in Figure 3. The UV, blue, and red emissions were observed as previously described in the literature.12 These spectral peaks correspond to the following transitions: 1 I6 → 3 H6 ∼291 nm), 1 I6 → 3 F4 ∼346 nm), 1 D2 → 3 H6 (∼362 nm), 1 D2 → 3 F4 ∼457 nm),
Fig. 1. XRD patterns of the NaYF4 :Yb, Tm NPs.
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Fig. 2. SEM images of NaYF4 :Yb, Tm NPs.
G4 →3 H6 ∼474 nm), 1 G4 → 3 F4 ∼642 nm). Obviously, the UV emissions were stronger than the visible ones. Therefore, the intense UV upconversion fluorescent NaYF4 :Tm, Yb UCNPs were selected to prepare the composite Film. Upon NIR excitation ( = 980 nm), they exhibit extensive UV luminescence bands with three peaks at ca. ∼291 nm, 346 nm and 362 nm (Fig. 3). For the organic photochromic materials, we selected a DTE derivative 1 2-bis(2, 4-dimethyl-5-phenyl-3-thienyl)3 3 4 4 5 5-heafluoro-1-cyclopentene which exhibits reversible ring-opening and ring-closing reactions under appropriate UV (355 nm) and green (532 nm) irradiations (Scheme 1), respectively. Figure 3 shows the changed absorption spectra of DTE in CH3 CN solution after ∼355 nm irradiation from UV light. Upon the irradiation with 355 nm light, a colorless hexane solution turned to blue–violet, in which the absorption maximum was observed at 571 nm.6 The blue–violet color disappeared upon 532 nm irradiation. Notably, 1O displays a broad absorption band from 250 to 369 nm, which ideally overlaps with the narrow emission band at around 291 nm, 1
Fig. 3. Absorption spectra of opening-ring and closed-ring forms of DTE in CH3 CN, and upconversion emission spectrum of NaYF4 :Tm, Yb UCNPs under 980 nm (280 W/cm2 .
J. Nanosci. Nanotechnol. 11, 9693–9696, J. Nanosci. Nanotechnol. 11, 1–4, 2011
Zhai et al.
Study on NIR Optical Rewritable Film Based on DTE and Upconversion Nanocrystals
Scheme 1. Molecular structures of the open-ring and closed-ring isomers of the DTE 1 and the corresponding photo isomerization IN reactions.
Fig. 5. Pictures of different patterns written into photochromic memory using a 980 nm (1000 W/cm2 , 30 s) laser diode.
between two isomers.1–3 Therefore, it is possible to prepare NIR rewritable optical films that can be written by NIR and erased by green light based on a reversible photochromic DTE for the optical storage. In the data recording experiments, the NIR composite film sample was placed under several different masks, illuminated or written by the NIR laser beam ( = 980 nm) and erased by green laser beam. During the whole photoswitching process, the high/low absorption intensity centered at 571 nm is named to be the “1”/“0” state. Many attempts to read the data have been reported, including confocal microscope reading,14 polarization reading,15 reflection confocal reading16 and fluorescent reading.4–5 Here in, some photographs of the NIR optical film were shown, on which different patterns were written into photochromic memory using a 980 nm laser diode. Seven cycles of alternating NIR/green light irradiations were performed (Fig. 6), and the absorption spectra were found to be well repeatable, implying no obvious degradation of the recording material. This is ascribed to the excellent fatigue resistance of all the species employed.1–3
4. CONCLUSIONS Fig. 4. Changes in the UV-vis absorption spectra of the NIR optical film containing (a) DTE 1O with 980 nm light (1000 W/cm2 and (b) 1C with 532 nm light (100 W/cm2 .
J. Nanosci. Nanosci. Nanotechnol. Nanotechnol. 11, 11,9693–9696, 1–4, 2011 2011 J.
A NIR rewritable optical film incorporated with NaYF4 :Tm, Yb UCNPs and DTE has been successfully constructed. With intense UV upconversion of UCNPs, we can quickly record the data using NIR laser beam.
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RESEARCH ARTICLE
347 nm and 362 nm of UCNPs, suggesting that the PL intensity of UCNPs can be modulated by the controllable energy transfer between inorganic and organic species. Though 1O have a strong absorption band centered at 271 nm, DTE can efficiently show an isomeric reaction form 1O to 1C. Accordingly, the UCNPs are ideal for the NIR data recording of optical film. It is essential for us to demonstrate the rewritable process in a compatibility system. Both UCNPs modified by oleic acid and DTE are hydrophobic and soluble in oilsoluble (non-polar?) solvent. We can reduce the distance between UCNPs and DTE to promote DTE to absorb the light emitted from UCNPs by casting both components into a cross-linked PEGDMA. Figure 4(a) shows the change of absorption spectra of this NIR composite film. It shows that DTE’s ring-closing reactions have been achieved using 980 nm light in the presence of UCNPs that emit UV light. More importantly, the photo stationary state will be almost achieved in 45 s because of the intense UV upconversion emitted from UCNPs. DTE’s ring-opening reactions can be achieved using 532 nm light, as shown in Figure 4(b). Then, compounds constructed from DTE cannot undergo thermally irreversible photochemical ring-closing and ring-opening reactions, but the reversible photo-induced transformation of a molecule
Study on NIR Optical Rewritable Film Based on DTE and Upconversion Nanocrystals
Zhai et al.
National Natural Science Foundation of China (NNSFC) (grants 10874058, 51072065, and 60908031).
References and Notes 1. 2. 3. 4.
5. 6. 7. Fig. 6. Normalized absorbance in 7 cycles of alternating 980/532 nm irradiation.
8. 9. 10.
Furthermore, we also demonstrated excellent fatigue resistance of the film after several write/erase cycles. This inorganic/organic binary system can be extended to other UCNPs and photochromes whose spectra show considerable overlap, which will offer new opportunities in the nondestructive readout and 3D data storage.
11. 12.
13.
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14.
Acknowledgment: This work was supported by the National High Technology Research and Development Program of China (863 Program: 2009AA03Z309) and the
15. 16.
S. Kawata and Y. Kawata, Chem. Rev. 100, 1777 (2000). M. Irie, Chem. Rev. 100, 1685 (2000). H. Tian and S. J. Yang, Chem. Soc. Rev. 33, 85 (2004). C. Zhang, H. P. Zhou, L. Y. Liao, W. Feng, W. Sun, Z. X. Li, C. H. Xu, C. J. Fang, L. D. Sun, Y. W. Zhang, and C. H. Yan, Adv. Mater. 22, 633 (2010). H. Li, J. X. Wang, H. Lin, L. Xu, W. Xu, R. M. Wang, Y. L. Song, and D. B. Zhu, Adv. Mater. 22, 1237 (2010). M. Irie, K. Sakemura, M. Okinaka, and K. Uchida, J. Org. Chem. 60, 8305 (1995). C. J. Carling, J. C. Boyer, and N. R. Branda, J. Am. Chem. Soc. 131, 10838 (2009). Z. Q. Li, Y. Zhang, and S. Jiang, Adv. Mater. 20, 4765 (2008). J. S. Zhang, W. P. Qin, Y. Wang, C. Y. Cao, Y. Jin, G. D. Wei, G. F. Wang, and L. L. Wang, J. Nanosci. Nanotechnol. 8, 1388 (2008). M. Wang, C. C. Mi, W. X. Wang, C. H. Liu, Y. F. Wu, Z. R. Xu, C. B. Mao, and S. K. Xu, ACS Nano 3, 1580 (2009). C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, Y. Jin, G. D. Wei, G. F. Wang, and L. Wang, J. Nanosci. Nanotechnol. 8, 1384 (2008). C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, P. F. Zhu, G. F. Wang, G. D. Wei, L. L. Wang, and L. Z. Jin, J. Fluorine Chem. 129, 204 (2008). C. J. Carling, F. Nourmohammadian, J. C. Boyer, and N. R. Branda, Angew. Chem. Int. Edit. 49, 3782 (2010). Y. Kawata, R. Juskaitis, T. Tanaka, T. Wilson, and S. Kawata, Appl. Opt. 35, 2466 (1996). T. Wilson, Y. Kawata, and S. Kawata, Opt. Lett. 21, 1003 (1996). Z. Sekkat, P. Pretre, A. Knoesen, W. Volksen, V. Y. Lee, R. D. Miller, J. Wood, and W. Knoll, J. Opt. Soc. Am. B 15, 408 (1998).
Received: 24 October 2010. Accepted: 21 March 2011.
9696
J. Nanosci. Nanotechnol. 11, 1–4, 2011 J. Nanosci. Nanotechnol. 11, 9693–9696,
Journal of Nanoscience and Nanotechnology Vol. 11, 9693–9696, 2011
Study on NIR Optical Rewritable Film Based on Dithienylethene and Upconversion Nanocrystals Xuesong Zhai, Feng Shi, Huan Chen, Dan Zhao, Daisheng Zhang, and Weiping Qin∗ State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China Tm3+ and Yb3+ codoped NaYF4 upconversion (UC) nanoparticles (NPs) with intense ultraviolet (UV) fluorescence were synthesized using a solvothermal approach. NIR optical rewritable film incorporated with the UCNPs and dithienylethene (DTE) were performed for optical storage based on the photochromic reaction of DTE induced by the intense UV from themultiphoton UC fluorescence of NaYF4 NPs. The photochromic DTE did not exhibit obvious fatigue after repetitious write/erase cycles using NIR/green irradiation.
Keywords: NIR Optical Film, UV Upconversion, Nanocrystals, NaYF4 , DTE.
1. INTRODUCTION
∗
Author to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2011, Vol. 11, No.11
2. EXPERIMENTAL DETAILS NaYF4 :0.5 mol% Tm3+ , 20 mol% Yb3+ (NaYF4 :Tm, Yb) NPs were synthesized using a simple hydrothermal method.10 Ln2 O3 (Ln = 795%Y, 20%Yb, and 0.5%Tm) were dissolved in dilute HNO3 under heating to prepare the stock solution of Ln(NO3 3 . Then, rare-earth stearate precursors (precipitates) were prepared by adding 0.6 g of NaOH aqueous solution dropwise into a transparent solution containing 5 mmol of Ln(NO3 3 and 4.2672 g of stearate acid. Subsequently, a homogeneous solution containing 5 mL of water, 15 mL of ethanol, and 5 mL of oleic acid, 0.95 g of the precursor and 0.2099 g of NaF was prepared under stirring and sonication. Lastly, the solution was transferred to an autoclave, sealed, and solvothermally treated at 150 C for 24 h. A mixture of 5 mg 1,2-bis(2,4-dimethyl-5-phenyl-3thienyl)-3,3,4,4,5,5-heafluoro-1-cyclopentene (DTE derivative), 40 mg NaYF4 :Tm, Yb UCNPs and chloroform (∼10 drops) was sonicated until being homogenous.
1533-4880/2011/11/001/004
doi:10.1166/jnn.2011.5260
9693
RESEARCH ARTICLE
The optical data storage on photochromic reactions has received significant attentions in recent years.1–3 Most of them are focused on how to achieve 3D data storage, increase memory density, and fulfill nondestructive readout and high sensitivity.1–5 Many attempts to achieve these properties have been reported. For example, Yan et al. reported on a rewritable 2D optical storage medium with high-density recording capacity and nondestructive readout that were functionalized by the luminescence modulation of ordered upconversion nano patterns via a photochromicdithienylethene (DTE).4 They also wanted to fulfill 3D optical storage using the UCNP-photochrome strategy. Song et al. demonstrated an amplification of fluorescent contrast by applying photonic crystals to theoptical storage system and provided much better resolution and sensitivity.5 However, in these versatile photoresponsive systems based on DTE, UV light was needed for the ring-closing reaction of DTE. Using UV light as the irradiation source may bring detrimental effects such as unwanted side reactions6–7 and low penetration depth into materials.7–8 These disadvantages can be avoided if low energy photons are used as the irradiation source in photoresponsive systems. Upconversion nanocrystals (UCNPs) can efficiently convert NIR light (980 nm) to visible or UV light.9–13 Especially, Tm3+ and Yb3+ codoped NaYF4 NPs have been proved to be excellent UC materials for intense UV
fluorescence.10 13 Therefore, they might be good candidates for inducing the ring-closing reaction of DTE under NIR irradiation. In this paper, we present a study on a NIR optical rewritable film incorporated with UCNPs and DTE. Data can be written in the film by NIR (980 nm) and erased by green light (532 nm). Many cycles of writing/erasing experiments suggested that the film might be a candidate of nondestructive optical storage working in the NIR region.
Study on NIR Optical Rewritable Film Based on DTE and Upconversion Nanocrystals
Then, poly(ethylene glycol) dimethacrylate (PEGDMA) (∼30 drops) and Darocur 4265 (∼1 drop) were added to the mixture under sonication until being homogenous. The solution was placed between two microscope slides spaced apart by 1 mm thick glass and cured for approximately 30 min to produce flexible polymeric composites using 355 nm light. The film was subsequently irradiated with 532 nm light for 10 min to yield a slightly yellow film. The phase identification was performed by X-ray diffraction (XRD) (Model Rigaku Ru-200b), using a nickel-filtered Cu K radiation ( = 014518 nm) in the range of 10 ≤ 2 ≤ 70 . Morphologies were characterized by a Hitachi S-4800 scanning electron microscope (SEM). Under 980 nm excitation, UC spectra were recorded by a Hitachi F-4500 fluorescence spectrometer (1.0 nm for slit width and 400 V for PMT voltage). UV-vis absorbance spectra were measured by a UV-vis spectrophotometer (Shimadzu Pharmaspce UV-1700) at room temperature.
RESEARCH ARTICLE
3. RESULTS AND DISCUSSION The crystal structures and the phase purity of as-prepared NaYF4 :Tm, Yb UCNPs were examined by XRD. Typical XRD patterns of as-prepared UCNPs are presented in Figure 1. The diffraction peaks of NPs are well-defined, and the X-ray diffraction pattern of NaYF4 :Tm, Yb samples can be indexed as a mixture of the cubic (JCPDS file number 6-342) and hexagonal (JCPDS file number 16-334) phases of NaYF4 . Figure 2 shows the morphology of NaYF4 :Tm, Yb NPs characterized by SEM. The UCNPs are uniform nanospheres with an average diameter of about 35 nm. Photoluminescence (PL) spectra show the UC luminescence of NaYF4 :Tm, Yb nanocrystals under 980 nm excitation, as shown in Figure 3. The UV, blue, and red emissions were observed as previously described in the literature.12 These spectral peaks correspond to the following transitions: 1 I6 → 3 H6 ∼291 nm), 1 I6 → 3 F4 ∼346 nm), 1 D2 → 3 H6 (∼362 nm), 1 D2 → 3 F4 ∼457 nm),
Fig. 1. XRD patterns of the NaYF4 :Yb, Tm NPs.
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Zhai et al.
Fig. 2. SEM images of NaYF4 :Yb, Tm NPs.
G4 →3 H6 ∼474 nm), 1 G4 → 3 F4 ∼642 nm). Obviously, the UV emissions were stronger than the visible ones. Therefore, the intense UV upconversion fluorescent NaYF4 :Tm, Yb UCNPs were selected to prepare the composite Film. Upon NIR excitation ( = 980 nm), they exhibit extensive UV luminescence bands with three peaks at ca. ∼291 nm, 346 nm and 362 nm (Fig. 3). For the organic photochromic materials, we selected a DTE derivative 1 2-bis(2, 4-dimethyl-5-phenyl-3-thienyl)3 3 4 4 5 5-heafluoro-1-cyclopentene which exhibits reversible ring-opening and ring-closing reactions under appropriate UV (355 nm) and green (532 nm) irradiations (Scheme 1), respectively. Figure 3 shows the changed absorption spectra of DTE in CH3 CN solution after ∼355 nm irradiation from UV light. Upon the irradiation with 355 nm light, a colorless hexane solution turned to blue–violet, in which the absorption maximum was observed at 571 nm.6 The blue–violet color disappeared upon 532 nm irradiation. Notably, 1O displays a broad absorption band from 250 to 369 nm, which ideally overlaps with the narrow emission band at around 291 nm, 1
Fig. 3. Absorption spectra of opening-ring and closed-ring forms of DTE in CH3 CN, and upconversion emission spectrum of NaYF4 :Tm, Yb UCNPs under 980 nm (280 W/cm2 .
J. Nanosci. Nanotechnol. 11, 9693–9696, J. Nanosci. Nanotechnol. 11, 1–4, 2011
Zhai et al.
Study on NIR Optical Rewritable Film Based on DTE and Upconversion Nanocrystals
Scheme 1. Molecular structures of the open-ring and closed-ring isomers of the DTE 1 and the corresponding photo isomerization IN reactions.
Fig. 5. Pictures of different patterns written into photochromic memory using a 980 nm (1000 W/cm2 , 30 s) laser diode.
between two isomers.1–3 Therefore, it is possible to prepare NIR rewritable optical films that can be written by NIR and erased by green light based on a reversible photochromic DTE for the optical storage. In the data recording experiments, the NIR composite film sample was placed under several different masks, illuminated or written by the NIR laser beam ( = 980 nm) and erased by green laser beam. During the whole photoswitching process, the high/low absorption intensity centered at 571 nm is named to be the “1”/“0” state. Many attempts to read the data have been reported, including confocal microscope reading,14 polarization reading,15 reflection confocal reading16 and fluorescent reading.4–5 Here in, some photographs of the NIR optical film were shown, on which different patterns were written into photochromic memory using a 980 nm laser diode. Seven cycles of alternating NIR/green light irradiations were performed (Fig. 6), and the absorption spectra were found to be well repeatable, implying no obvious degradation of the recording material. This is ascribed to the excellent fatigue resistance of all the species employed.1–3
4. CONCLUSIONS Fig. 4. Changes in the UV-vis absorption spectra of the NIR optical film containing (a) DTE 1O with 980 nm light (1000 W/cm2 and (b) 1C with 532 nm light (100 W/cm2 .
J. Nanosci. Nanosci. Nanotechnol. Nanotechnol. 11, 11,9693–9696, 1–4, 2011 2011 J.
A NIR rewritable optical film incorporated with NaYF4 :Tm, Yb UCNPs and DTE has been successfully constructed. With intense UV upconversion of UCNPs, we can quickly record the data using NIR laser beam.
9695
RESEARCH ARTICLE
347 nm and 362 nm of UCNPs, suggesting that the PL intensity of UCNPs can be modulated by the controllable energy transfer between inorganic and organic species. Though 1O have a strong absorption band centered at 271 nm, DTE can efficiently show an isomeric reaction form 1O to 1C. Accordingly, the UCNPs are ideal for the NIR data recording of optical film. It is essential for us to demonstrate the rewritable process in a compatibility system. Both UCNPs modified by oleic acid and DTE are hydrophobic and soluble in oilsoluble (non-polar?) solvent. We can reduce the distance between UCNPs and DTE to promote DTE to absorb the light emitted from UCNPs by casting both components into a cross-linked PEGDMA. Figure 4(a) shows the change of absorption spectra of this NIR composite film. It shows that DTE’s ring-closing reactions have been achieved using 980 nm light in the presence of UCNPs that emit UV light. More importantly, the photo stationary state will be almost achieved in 45 s because of the intense UV upconversion emitted from UCNPs. DTE’s ring-opening reactions can be achieved using 532 nm light, as shown in Figure 4(b). Then, compounds constructed from DTE cannot undergo thermally irreversible photochemical ring-closing and ring-opening reactions, but the reversible photo-induced transformation of a molecule
Study on NIR Optical Rewritable Film Based on DTE and Upconversion Nanocrystals
Zhai et al.
National Natural Science Foundation of China (NNSFC) (grants 10874058, 51072065, and 60908031).
References and Notes 1. 2. 3. 4.
5. 6. 7. Fig. 6. Normalized absorbance in 7 cycles of alternating 980/532 nm irradiation.
8. 9. 10.
Furthermore, we also demonstrated excellent fatigue resistance of the film after several write/erase cycles. This inorganic/organic binary system can be extended to other UCNPs and photochromes whose spectra show considerable overlap, which will offer new opportunities in the nondestructive readout and 3D data storage.
11. 12.
13.
RESEARCH ARTICLE
14.
Acknowledgment: This work was supported by the National High Technology Research and Development Program of China (863 Program: 2009AA03Z309) and the
15. 16.
S. Kawata and Y. Kawata, Chem. Rev. 100, 1777 (2000). M. Irie, Chem. Rev. 100, 1685 (2000). H. Tian and S. J. Yang, Chem. Soc. Rev. 33, 85 (2004). C. Zhang, H. P. Zhou, L. Y. Liao, W. Feng, W. Sun, Z. X. Li, C. H. Xu, C. J. Fang, L. D. Sun, Y. W. Zhang, and C. H. Yan, Adv. Mater. 22, 633 (2010). H. Li, J. X. Wang, H. Lin, L. Xu, W. Xu, R. M. Wang, Y. L. Song, and D. B. Zhu, Adv. Mater. 22, 1237 (2010). M. Irie, K. Sakemura, M. Okinaka, and K. Uchida, J. Org. Chem. 60, 8305 (1995). C. J. Carling, J. C. Boyer, and N. R. Branda, J. Am. Chem. Soc. 131, 10838 (2009). Z. Q. Li, Y. Zhang, and S. Jiang, Adv. Mater. 20, 4765 (2008). J. S. Zhang, W. P. Qin, Y. Wang, C. Y. Cao, Y. Jin, G. D. Wei, G. F. Wang, and L. L. Wang, J. Nanosci. Nanotechnol. 8, 1388 (2008). M. Wang, C. C. Mi, W. X. Wang, C. H. Liu, Y. F. Wu, Z. R. Xu, C. B. Mao, and S. K. Xu, ACS Nano 3, 1580 (2009). C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, Y. Jin, G. D. Wei, G. F. Wang, and L. Wang, J. Nanosci. Nanotechnol. 8, 1384 (2008). C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, P. F. Zhu, G. F. Wang, G. D. Wei, L. L. Wang, and L. Z. Jin, J. Fluorine Chem. 129, 204 (2008). C. J. Carling, F. Nourmohammadian, J. C. Boyer, and N. R. Branda, Angew. Chem. Int. Edit. 49, 3782 (2010). Y. Kawata, R. Juskaitis, T. Tanaka, T. Wilson, and S. Kawata, Appl. Opt. 35, 2466 (1996). T. Wilson, Y. Kawata, and S. Kawata, Opt. Lett. 21, 1003 (1996). Z. Sekkat, P. Pretre, A. Knoesen, W. Volksen, V. Y. Lee, R. D. Miller, J. Wood, and W. Knoll, J. Opt. Soc. Am. B 15, 408 (1998).
Received: 24 October 2010. Accepted: 21 March 2011.
9696
J. Nanosci. Nanotechnol. 11, 1–4, 2011 J. Nanosci. Nanotechnol. 11, 9693–9696,
