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Article Cite This: ACS Omega 2018, 3, 9505−9512
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Enhanced Efficiency of Functional Smart Window with Solar Wavelength Conversion Phosphor−Photochromic Hybrid Film Myung Jong Kang, Edgardo Gabriel Santoro, and Young Soo Kang* Korea Center for Artificial Photosynthesis, Department of Chemistry, Sogang University, 35, Baekbeom-ro, Mapo-gu, 04107 Seoul, Republic of Korea
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S Supporting Information *
ABSTRACT: Here, the high sensitivity and enhanced photochromic efficiency of the hybrid film of solar wavelength conversion phosphor and photochromic film for functional smart window have been achieved by fabricating a doublelayered hybrid structure of wavelength conversion phosphor and photochromic film. Y2SiO5:Pr3+ phosphor nanoparticles, which upconvert visible light to UV light, were synthesized by simple hydrothermal method. The synthesized Y2SiO5:Pr3+ nanoparticle was coated as layered structured film on photochromic H 3 PW 1 2 O 40 film. The Y 2 SiO 5 :Pr 3 + / H3PW12O40 hybrid film showed an enhanced sensitivity and efficiency of photochromic process with solar light irradiation due to the increased UV portion of solar light through upconversion process of visible light by wavelength conversion phosphor layer. The increased UV portion by upconversion process of Y2SiO5:Pr3+ layer through excited-state absorption and energy transfer upconversion process, contributed to an enhancement of coloration rate of photochromic H3PW12O40 film by 7 times with 50 min of 1 sun irradiation due to fast conversion of W6+ state to W5+ state in H3PW12O40 film with 5 times enhanced photochromic sensitivity compared with pristine photochromic film.
1. INTRODUCTION For energy saving, smart windows, which change optical transmittance according to the light intensity of external environments, have attracted much attention because of their ability to control the transmission intensity of IR light.1 This technology can reduce the energy consumption of buildings by maintaining inside temperature in a homeostatic state. The switchable smart windows can be operated by external parameters such as the electricity, light irradiation, or heat through the electrochromic,2−4 photochromic,5−7 or thermochromic processes, respectively.8 Several previous researches on smart window have been focused on the electrochromic smart window for its durability. However, electrochromic smart window has limitation because the additional electric system is needed to operate it, leading to the high installation cost. In case of thermochromic windows, it is hard to be utilized because high-temperature (∼70 °C) condition is required.9−11 Among those kinds of smart window systems, photochromic windows are cost effective because they do not need additional device or heating system for the photochromic process. Photochromism, the essential concept for photochromic windows, is based on the ability of visible and IR light transmittance control derived from the color change due to the molecular structure or oxidation state change between two different states with different thermodynamic energy levels. Generally, the photochromic phosphotungstic acid (H3PW12O40, HPW) film has been changed to colored one © 2018 American Chemical Society
by exposing to UV light and turned back to colorless one under visible-light irradiation.5,7,12,13 HPW, one of the polyoxometalate compound, has the photochromic properties due to reduction of tungsten metal ion from W6+ to W5+ through charge transfer from oxygen to metal under UV light irradiation.14 The advantage of smart window of HPW film is that it can absorb the UV light and be colored, controlling the visible-light intensity by coloration density of the HPW film.6,15−18 However, the small portion of the UV region in solar light (∼5%) limits the efficiency of photochromic smart windows because most of the photochromic films of HPW are active under the UV light absorption. Hence, increasing the UV light intensity of the incident solar light could be a promising key technology to improve the efficiency of the photochromic HPW smart windows. The ways to breakthrough those limitations of HPW are to increase the portion of the UV light in the irradiated solar light spectrum by upconverting visible or IR range of the solar light with phosphor material. For the efficient solar light upconversion and downconversion, lanthanide metal ions such as Pr3+, Tm3+, Eu3+, and Er3+ are widely used, which are doped into the host materials. Because those ions have the 4fn electronic configurations and exhibit f−f transitions, which allow the Received: May 22, 2018 Accepted: August 8, 2018 Published: August 20, 2018 9505
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Figure 1. SEM images of Y2SiO5 particles with (a) YSO, (b) YSO:Pr 1, (c) YSO:Pr 5, (d) YSO:Pr 10, and (e) YSO:Pr 15 and (f) XRD patterns of YSO and YSO:Pr (all scale bars are 100 nm).
activation process of the excited electron transitions.19 The representative photo-upconversion and photo-downconversion materials are La2O2S:Er3+ or Yb3+,20 NaYF4:Yb3+/Er3+,21 NaYF4:Yb3+/Tm3+,22 and Y2SiO5:Pr3+.23 Among those materials, a praseodymium-doped yttrium silicate (Y2SiO5:Pr3+, YSO:Pr3+) is the best phosphor material that can emit UV light by absorbing visible light of solar light via wavelength conversion. The YSO:Pr3+ is excited by absorbing the visible light (∼505 nm) and emits UV light (270−380 nm) through the wavelength-upconversion process. This upconverting phosphor emits a photon with a higher energy than that of absorbed photons through the excited-state absorption (ESA) and energy-transfer upconversion (ETU).24,25 Previous studies on the application of the downconversion and upconversion materials for increasing visible light portion of the solar light have been reported an enhanced performance of dye-sensitized solar cell or energy storage system.26−29 Herein, we report the first application for smart window film by getting Y2SiO5:Pr3+/H3PW12O40 double-layer hybrid film of phosphor layer for solar wavelength upconversion and photochromic layer. The YSO:Pr3+ upconverting thin layer (UCM layer) on the surface of photochromic HPW film (PCM film). The upconverting properties of UCM layer were measured by photoluminescence spectroscopy and light absorption properties and coloration rate of PCM film and UCM−PCM double-layer hybrid film were measured by UV− vis spectroscopy. The upconversion from visible light to UV light by nanosized YSO:Pr3+ particle layer (UCM layer) resulted in a dramatic enhancement in efficiency and kinetics
of photochromic process with solar light irradiation of PCM film by supplying a higher intensity of UV light toward the PCM film through the upconversion of incident solar light.
2. RESULTS AND DISCUSSION The Y2SiO5 nanoparticles (YSO) with 1, 5, 10, and 15 mol% Pr3+ (YSO:Pr 1, YSO:Pr 5, YSO:Pr 10, and YSO:Pr 15, respectively) were successfully synthesized via hydrothermal method and confirmed with scanning electron microscopy (SEM) (Figure 1a−e). The shape of the synthesized YSO and YSO:Pr particles was spherical and they aggregated easily. The X-ray diffraction (XRD) patterns of the synthesized YSO were matched with representative standard YSO patterns within 29.71, 31.02, 32.52, and 33.64°, which corresponded to the plane of (−202), (211), (−212), and (−221) (PDF#52-1810, C2/c space group with monoclinic), respectively.30 As the Pr3+ ions were doped into YSO, there was little low 2θ angle shifting, indicating the change in d-spacing distance of the crystal structure due to Pr3+ doping into the YSO crystal. The electrons in ground state of Pr3+ ion in YSO are excited by absorbing visible light of 505 nm and transferred higher energy to the other Pr3+ ions in YSO during the decay through the double excitation procedure. The double-excited electrons reached the intermediate state of 4f5d band of the Pr3+ ion, emitting UVC light during the decay to ground state (Figure S1).31,32 The detailed size and morphology of YSO and YSO:Pr3+ clusters were investigated by high resolution transmission electron microscopy (HR-TEM) image. The size of YSO and YSO:Pr3+ clusters was determined as around 9506
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Figure 2. TEM images of Y2SiO5 particles with (a) YSO, (b) YSO:Pr 1, (c) YSO:Pr 5, (d) YSO:Pr 10, and (e) YSO:Pr 15 and (f) TEM-energydispersive system (EDS) analysis data for Pr atomic ratio in each sample (all scale bars are 10 nm).
Figure 3. (a) Emission spectra for YSO:Pr3+ particles with different molar ratios of Pr3+ ions (1, 5, 10, and 15 mol%). (b) Emission intensity of YSO:Pr3+ particles with different molar ratios of Pr3+ ions (1, 5, 10, and 15 mol%).
values were increased after Pr3+ doping into YSO. The binding energy and chemical oxidation state of YSO:Pr3+ were revealed by the X-ray photoelectron spectroscopy (XPS) analysis. The O 1s spectra of YSO:Pr3+ showed a peak at the binding energy of 527.5 eV, which is typical O 1s peak position in YSO (Figure S5a). The Si 2p spectra of YSO:Pr3+ showed a peak at the binding energy of 98 eV and Y 3d spectra of YSO:Pr3+ showed two peaks at the binding energy of 154 eV for Y 3d6/2 and 156 eV for Y 3d8/2, which is well matched with the typical binding energy of Si and Y in YSO (Figure S5b,c).33 In the XPS spectra of Pr3+ 3d, peaks of Pr3+ 3d6/2 and Pr3+ 3d8/2 appeared at the binding energy of 930 and 950 eV, respectively, whereas the peak intensity was increased with
40 nm with undesignated morphologies (Figures 2a−e and S2). In the selected area electron diffraction (SAED) pattern of each YSO particle (Figure S3), the d-spacing value of (−212) plane also showed an increase from 0.271 to 0.276 nm after doping Pr3+ into YSO due to larger radius of Pr3+ ion compared with Y3+ ion. The atomic ratios of Pr3+ in YSO:Pr3+ were determined as 0, 0.56 at%, 2.68 at%, 6.45 at%, and 8.5 at% for YSO, YSO:Pr 1, YSO:Pr 5, YSO:Pr 10, and YSO:Pr 15, respectively, with TEMEDS (Figure 2f) and detailed EDS spectra for YSO and YSO:Pr3+ (Figure S4). These are consistent with lattice dspacing values of SAED patterns. These results were well matched with XRD data in Figure 1f, and the lattice d-spacing 9507
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Figure 4. (a) Scheme for fabricating UCM−PCM film, SEM cross-sectional images of Y2SiO5 particle with (b) 0 mol% of Pr3+, (c) 1 mol% of Pr3+, (d) 5 mol% of Pr3+, (e) 10 mol% of Pr3+, and (f) 15 mol% of Pr3+, and (g) cross-sectional SEM image of PCM film (all scale bars are 100 μm).
increasing atom % of Pr3+ in YSO:Pr3+ (Figure S5d). The photoluminescence spectra of YSO:Pr 1, YSO:Pr 5, YSO:Pr 10, and YSO:Pr 15 are shown in Figure 3a. According to the photoluminescence measurement of YSO:Pr3+, YSO:Pr 1 showed the highest photoluminescence intensity, which decreased as doped Pr3+ ratio was increased. This tendency was also shown in the calculated area under emission spectra in Figure 3b. YSO:Pr 1 showed an enhanced emission intensity over 200% compared with that of YSO:Pr 5. It is believed that the concentration of doped Pr3+ ions higher than 5 mol% leads to high luminescent quenching, thus inhibiting the double-excitation process in YSO:Pr3+.34,35 Phosphotungstic acid (H3PW12O40, HPW) changes the color due to the oxidation state change of W ions by absorbing UVA light. In the XPS spectra, when HPW was bleached, the dominant oxidation state of W ion is W6+ state with 37 eV binding energy, whereas the dominant state of W6+ ion was changed to W5+ state with 34 eV binding energy during colored state through photochromic reaction by UV-light irradiation (Figure S6). The mechanism of this coloration process was revealed based on the reduction from W6+ state to W5+ state by electron transfer from O 2p orbital in HPW to W d0 orbital.36,37 The transferred electron from O 2p to W d0 results in the oxygen vacancies, and those oxygen vacancies suppress the electron−hole recombination by trapping the photogenerated oxygen radicals, thus enhancing the photochromic efficiency.16,38 The double-layered hybrid structure of the UCM layer and the PCM film (UCM−PCM hybrid film) were fabricated by doctor blading method. The upconverting particles (YSO, YSO:Pr3+) were spread on the oxygen plasma treated PCM film on poly(ethylene terephthalate) (PET) film (Figure 4a). The thickness of each UCM layer was investigated
with cross-sectional SEM images (Figure 4b−f). The average thickness both PCM film and UCM layer was determined as ∼50 μm. The scheme of the photochromic process of UCM− PCM hybrid film is shown in Figure 5a. The role of UCM layer is to convert visible range of incident solar light into UV light through the ESA and ETU upconversion process. The UV abundant solar light by upconversion process of UCM layer was irradiated on the PCM film, enhancing the efficiency and kinetics of the photochromic reaction of the PCM film. Because the emission intensity trends of the YSO:Pr3+ particle were the same as that with the UCM layer with different amounts of doped Pr3+ ion, the emission spectrum of the UCM−PCM hybrid film fabricated by 1 mol% of YSO:Pr particle showed the highest emission intensity (Figure 5b). The emission intensity of the UCM−PCM hybrid film can be determined by measuring the relative areas under curves and the results are shown in Figure 5c. The emission intensity of the UCM−PCM double-layered hybrid film fabricated with YSO:Pr 1 shows an enhanced intensity by approximately 30% compared with the UCM− PCM hybrid film fabricated with YSO:Pr 5. The emission intensity difference between YSO:Pr 1 and other YSO:Pr was increased in the order YSO:Pr 5 > YSO:Pr 10 > YSO:Pr 15 after UCM layer coating on the surface of PCM film. This is caused by the higher absorption of visible light and the quenching effect of the increased at% of Pr3+ ions doped into YSO host matrices, which decreases the emission intensity of the UCM layer on the PCM film during photoluminescence spectra measurement (Figure S7a). By attaching the UCM− PCM hybrid film on the glass, the transmission light intensity in the 450−550 nm range passing through the window was 9508
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Figure 5. (a) Scheme on the photochromic process of UCM−PCM films. (b) The emission spectra for UCM−PCM films with different molar ratios of Pr3+ ions (1, 5, 10, and 15 mol%). (c) Emission intensity of UCM−PCM films with different molar ratios of Pr3+ ions (1, 5, 10, and 15 mol%).
decreased by absorption with UCM layer. The PCM film has faster kinetics of photochromism from colorless to dark green by absorbing higher intensity of incident UV light by changing visible light of 505 nm to UV light through the doubleexcitation upconversion process of the UCM layer. The increased UV light intensity reduces W6+ state to W5+ state of the PCM film, leading to an enhanced photochromism of light absorption by the PCM film (Figure S7a). As the solar light was illuminated on both PCM and UCM−PCM hybrid films in the same conditions to compare, the total light absorption intensity of the UCM−PCM hybrid film was higher than that of the PCM film, which was contrastingly appeared on by the different degree of color change to dark green between two kinds of films (Figure S7b−e). According to the UV−vis spectra, the light absorption ability of the PCM film depending on the solar light illumination time was much lower than that of the UCM−PCM hybrid film (Figure S8). The amount of the total light absorption intensity of bare PCM film and UCM−PCM hybrid film at 400−800 nm versus irradiation time is shown in Figure 6a. The coloration rate of PCM film is calculated by linear fitting of coloration curves with the equation like below
coloration rate =
Δarea under UV − vis curve Δt
where Δt is the irradiation time of the solar light. Only the PCM films showed coloration rate of 0.07436, whereas the UCM−PCM hybrid film showed the coloration rate of 0.5694, being enhanced by 7 times. It indicates that, in the same irradiation intensity, the UCM−PCM hybrid film shows an enhanced photochromic kinetics by solar light absorption by 7 times compared with only PCM film on the window. The kinetic constants during the photochromic reaction (k) from W6+ to W5+ in PCM by electron transfer were calculated by the following equation39 ij A − A∞ yz zz = kt lnjjj 0 j A t − A∞ zz k {
where A0 indicates the solar light absorbance of the PCM film at 450 nm at 0 s, A∞ means absorbance of the PCM film under the irradiation of solar light for 30 min, and At means solar light absorbance at the irradiation time of t (s). The calculated kinetic constants during the photochromic reaction by electron transfer from W6+ to W5+ in the PCM film and the UCM− PCM hybrid film are shown in Figure 6b. The average kinetic 9509
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4. EXPERIMENTAL SECTION 4.1. Materials. Yttrium(II) nitrate tetrahydrate (Y(NO3)3· 4H2O, 99.99%, Aldrich), praseodymium(III) nitrate hexahydrate (Pr(NO3)3·6H2O, 99.9%, Aldrich), and sodium trisilicate solution (Na2O(SiO2)x·xH2O, Mw: 1.39 g mL−1, Aldrich) were used as yttrium, praseodymium, and silica precursors, respectively. To adjust the pH value of each solution, hydrochloric acid (HCl, 35%, PFP) and ammonium hydroxide solution (NH4OH, 28.0−30.0% NH3 basis, Junsei) were used. Poly(ethylene glycol) (PEG) methyl ether (CH3(OCH2CH2)nOH, Mn ∼ 5.000, Aldrich) was used as binder for the paste. Ethanol (C2H6O, ≥99.9%, Emsure) and deionized (DI) water (>18 MW, Millipore) were utilized in the reaction and washing process. All of the reagents were used without further purification. The photochromic film (PCM film, H3(PW12O40)·nH2O) coated on PET substrate (Mapro Ltd.) was used for checking the photochromic effect with or without an upconversion layer. 4.2. Synthesis of YSO:Pr3+ Nanoparticles for Fabrication of UCM Layer. Five kinds of Y2−xSiO5:xPr3+ (x = 0, 0.01, 0.05, 0.10, and 0.15) phosphor powders were synthesized using the hydrothermal method based on Chen’s report with some modifications.19 Y(NO3)3·4H2O (0.1 M) with Pr(NO3)3·6H2O (0, 0.02, 0.1, 0.20, and 0.30 M) were prepared using DI water, and the pH value of the solutions was adjusted to 10.2 by adding ammonia water. Following the same procedure, Na2O(SiO2)x·xH2O (0.1 M) solution with DI water was prepared with pH value of 1.1 by adding HCl solution (2.0 M). After adjustment of the pH value, 10 mL of Na2O (SiO2)x· xH2O (0.1 M) was added and mixed under vigorous stirring while 10 mL of Y(NO3)3·4H2O (0.1 M) with Pr(NO3)3·6H2O solution was added dropwise. The mixture was aged for 1 h. Then, it was transferred to a Teflon-lined autoclave (20 mL) and kept in an oven at 200 °C for 3 h. The collected particles were washed three times with water and ethanol successively using a centrifuge machine at 8000 rpm for 20 min. The particles were dried at 70 °C for 5 h and finely ground using an agar mortar. The powder was annealed at 1000 °C for 1 h and ground using a ball miller for 3 h. 4.3. Fabrication of the UCM Layer on PCM Film (UCM−PCM Hybrid Film). The paste was prepared by mixing 0.4 g Y2SiO5:Pr3+ powder, 0.5 g PEG, and 0.5 mL DI water followed by stirring for 30 min. The PCM film coated on PET substrate surface was treated with oxygen plasma for 90 s to increase surface hydrophilicity. The mixture was spread homogeneously over the treated PCM film surface and coated uniformly using doctor blading method. The film was dried at 80 °C during 5 min to improve binding of phosphor nanoparticles with the substrate. 4.4. Characterization. The crystal structure of the synthesized particles was investigated with X-ray diffraction (XRD, Rigaku MiniFlex-II desktop X-ray diffractometer, Cu Kα radiation, λ = 1.5406 Å). The morphology of the particles and the as-made films was observed by using scanning electron microscope (SEM, Hitachi S-4300) and transmission electron microscope (TEM, JEOL, JEM-2100F, operated at 200 keV). To obtain the emission spectra of YSO nanoparticle powder, UCM layer, and UCM−PCM hybrid film, fluorescence spectrophotometer (Hitachi F-700) was used under excitation wavelength of 505 nm. The function of the UCM film on the PCM film was investigated using solar simulated light source
Figure 6. (a) Total amount of absorbed visible light (400−800 nm) versus solar light irradiation time (red: UCM−PCM hybrid film; black: PCM film only). (b) Table of calculated kinetic constants obtained by emission intensity curves for the photochromism by electron transfer.
constant (k) of UCM−PCM is 0.000166 s−1, which is 5.5 times more sensitive than the PCM only film with 0.00003 s−1.
3. CONCLUSIONS In conclusion, this work on the fabrication of double-layer structured UCM−PCM hybrid film showed 7 times enhanced photochromic kinetics by solar light absorption through the photochromic effect of the PCM film and 5.5 times faster sensitizing rate on solar light compared with the PCM singlelayer film. This is due to the upconversion of the incident solar light from vis to UV light through the UCM layer by ESA and ETU process of YSO:Pr3+ in UCM layer. Considering most of energy losses of buildings happen through the window, this research suggests the enhanced efficiency and kinetics of the photochromic film by applying UCM−PCM hybrid films on the smart window. The introduced method in this work can contribute to the enormous energy saving of buildings by absorption of solar energy through solar light upconverting and photochromism. 9510
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(Asahi HAL-320, 100 mW cm−2). The solar light was illuminated with solar simulator with different illumination times on the area of 1 cm2. The optical properties were studied with Varian Cary 5000 UV−vis−NIR Spectrophotometer (Agilent Technologies).
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(10) Dalavi, D. S.; Devan, R. S.; Patil, R. S.; Ma, Y.-R.; Kang, M.-G.; Kim, J.-H.; Patil, P. S. Electrochromic properties of dandelion flower like nickel oxide thin films. J. Mater. Chem. A 2013, 1, 1035−1039. (11) Ma, D.; Shi, G.; Wang, H.; Zhang, Q.; Li, Y. Morphologytailored synthesis of vertically aligned 1D WO3 nano-structure films for highly enhanced electrochromic performance. J. Mater. Chem. A 2013, 1, 684−691. (12) Ho, M.-L.; Chi, B.-J.; Hung, T.-Y.; Liao, H.-Y.; Wang, J.-C.; Wang, T.-Y.; Shyue, J.-J. Enhanced photochromism of chromen-based colorants near silver nanorods in sol-gel matrix. CrystEngComm 2013, 15, 5969−5979. (13) Tobaldi, D. M.; Leonardi, S. G.; Pullar, R. C.; Seabra, M. P.; Neri, G.; Labrincha, J. A. Sensing properties and photochromism of Ag-TiO2 nano-heterostructures. J. Mater. Chem. A 2016, 4, 9600− 9613. (14) Feng, W.; Zhang, T. R.; Liu, Y.; Lu, R.; Zhao, Y. Y.; Yao, J. N. Photochromic behavior of nanocomposite hybrid films of finely dispersed phosphotungstic acid particles into polyacrylamide. J. Mater. Sci. 2003, 38, 1045−1048. (15) Bechinger, C.; Burdis, M. S.; Zhang, J. G. Comparison between electrochromic and photochromic coloration efficiency of tungsten oxide thin films. Solid State Commun. 1997, 101, 753−756. (16) Yamase, T. Photo- and Electrochromism of Polyoxometalates and Related Materials. Chem. Rev. 1998, 98, 307−326. (17) de Oliveira, M.; de Souza, A. L.; Schneider, J.; Rodrigues-Filho, U. P. Local Structure and Photochromic Response in Ormosils Containing Dodecatungstophosphoric Acid. Chem. Mater. 2011, 23, 953−963. (18) Balaji, S.; Djaoued, Y.; Albert, A.-S.; Bruning, R.; Beaudoin, N.; Robichaud, J. Porous orthorhombic tungsten oxide thin films: synthesis, characterization, and application in electrochromic and photochromic devices. J. Mater. Chem. 2011, 21, 3940−3948. (19) Hatanaka, M.; Yabushita, S. Theoretical Study on the f−f Transition Intensities of Lanthanide Trihalide Systems. J. Phys. Chem. A 2009, 113, 12615−12625. (20) Pokhrel, M.; Kumar, G. A.; Sardar, D. K. Highly efficient NIR to NIR and VIS upconversion in Er3+ and Yb3+ doped in M2O2S (M = Gd, La, Y). J. Mater. Chem. A 2013, 1, 11595−11606. (21) Tian, Q.; Yao, W.; Wu, Z.; Liu, J.; Liu, L.; Wu, W.; Jiang, C. Full-spectrum-activated Z-scheme photocatalysts based on NaYF4:Yb3+/Er3+, TiO2 and Ag6Si2O7. J. Mater. Chem. A 2017, 5, 23566−23576. (22) Ma, Y.; Liu, H.; Han, Z.; Yang, L.; Liu, J. Non-ultraviolet photocatalytic kinetics of NaYF4:Yb,Tm@TiO2/Ag core@comby shell nanostructures. J. Mater. Chem. A 2015, 3, 14642−14650. (23) Naccache, R.; Vetrone, F.; Speghini, A.; Bettinelli, M.; Capobianco, J. A. Cross-Relaxation and Upconversion Processes in Pr3+ Singly Doped and Pr3+/Yb3+ Codoped Nanocrystalline Gd3Ga5O12: The Sensitizer/Activator Relationship. J. Phys. Chem. C 2008, 112, 7750−7756. (24) Zhou, B.; Shi, B.; Jin, D.; Liu, X. Controlling upconversion nanocrystals for emerging applications. Nat. Nanotechnol. 2015, 10, 924−936. (25) Cates, S. L.; Cates, E. L.; Cho, M.; Kim, J.-H. Synthesis and Characterization of Visible-to-UVC Upconversion Antimicrobial Ceramics. Environ. Sci. Technol. 2014, 48, 2290−2297. (26) Kim, C. W.; Kim, D. K.; Shin, W. J.; Choi, M. J.; Kang, Y. S.; Kang, Y. S. Phosphor positioning for effective wavelength conversion in dye-sensitized solar cells. Nano Energy 2015, 13, 573−581. (27) Börjesson, K.; Dzebo, D.; Albinsson, B.; Moth-Poulsen, K. Photon upconversion facilitated molecular solar energy storage. J. Mater. Chem. A 2013, 1, 8521−8524. (28) Kakavelakis, G.; Petridis, K.; Kymakis, E. Recent advances in plasmonic metal and rare-earth-element upconversion nanoparticle doped perovskite solar cells. J. Mater. Chem. A 2017, 5, 21604−21624. (29) Zhou, D.; Liu, D.; Jin, J.; Chen, X.; Xu, W.; Yin, Z.; Pan, G.; Li, D.; Song, H. Semiconductor plasmon-sensitized broadband upconversion and its enhancement effect on the power conversion efficiency of perovskite solar cells. J. Mater. Chem. A 2017, 5, 16559−16567.
ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b01091.
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Energy diagram, TEM image, SAED patterns, EDS spectra, XPS spectra, optical image, UV−vis spectra (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Young Soo Kang: 0000-0001-5746-8171 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was financially supported by the Korea Center for Artificial Photosynthesis (KCAP) located at Sogang University (No. 2009-0093885), which is funded by the Ministry of Science and ICT (MSIT) through the National Research Foundation of Korea and the Brain Korea 21 Plus Project 2018.
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REFERENCES
(1) Baetens, R.; Jelle, B. P.; Gustavsen, A. Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review. Sol. Energy Mater. Sol. Cells 2010, 94, 87−105. (2) Jennings, J. R.; Lim, W. Y.; Zakeeruddin, S. M.; Grätzel, M.; Wang, Q. A Redox-Flow Electrochromic Window. ACS Appl. Mater. Interfaces 2015, 7, 2827−2832. (3) Yeh, M.-H.; Lin, L.; Yang, P.-K.; Wang, Z. L. Motion-Driven Electrochromic Reactions for Self-Powered Smart Window System. ACS Nano 2015, 9, 4757−4765. (4) de León, J. M. O.-R.; Acosta, D. R.; Pal, U.; Castañeda, L. Improving electrochromic behavior of spray pyrolised WO3 thin solid films by Mo doping. Electrochim. Acta 2011, 56, 2599−2605. (5) Pardo, R.; Zayat, M.; Levy, D. Photochromic organic-inorganic hybrid materials. Chem. Soc. Rev. 2011, 40, 672−687. (6) Zhang, G.; Chen, Z.; He, T.; Ke, H.; Ma, Y.; Shao, K.; Yang, W.; Yao, J. Construction of Self-Assembled Ultrathin Polyoxometalate/ 1,10-Decanediamine Photochromic Films. J. Phys. Chem. B 2004, 108, 6944−6948. (7) Ho, M.-L.; Yu, Y.-P.; Chen, Y.-T.; Lin, M.-H. Solid state photochromism of pyrano[3,2-c]chromen-5-one moiety with the assistance of localized surface plasmons. CrystEngComm 2012, 14, 4049−4059. (8) Kim, H.; Kim, Y.; Kim, K. S.; Jeong, H. Y.; Jang, A. R.; Han, S. H.; Yoon, D. H.; Suh, K. S.; Shin, H. S.; Kim, T.; Yang, W. S. Flexible Thermochromic Window Based on Hybridized VO2/Graphene. ACS Nano 2013, 7, 5769−5776. (9) Chen, Y.; Wang, Y.; Sun, P.; Yang, P.; Du, L.; Mai, W. Nickel oxide nanoflake-based bifunctional glass electrodes with superior cyclic stability for energy storage and electrochromic applications. J. Mater. Chem. A 2015, 3, 20614−20618. 9511
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(30) Kang, F.; Zhang, Y.; Peng, M. Controlling the Energy Transfer via Multi Luminescent Centers to Achieve White Light/Tunable Emissions in a Single-Phased X2-Type Y2SiO5:Eu3+,Bi3+ Phosphor For Ultraviolet Converted LEDs. Inorg. Chem. 2015, 54, 1462−1473. (31) Cates, E. L.; Wilkinson, A. P.; Kim, J.-H. Delineating Mechanisms of Upconversion Enhancement by Li+ Codoping in Y2SiO5:Pr3+. J. Phys. Chem. C 2012, 116, 12772−12778. (32) Cates, E. L.; Cho, M.; Kim, J.-H. Converting Visible Light into UVC: Microbial Inactivation by Pr3+-Activated Upconversion Materials. Environ. Sci. Technol. 2011, 45, 3680−3686. (33) Coetsee, E.; Terblans, J. J.; Swart, H. C. XPS analysis for degraded Y2SiO5:Ce phosphor thin films. Appl. Surf. Sci. 2010, 256, 6641−6648. (34) Yang, Y.; Liu, C.; Mao, P.; Wang, L.-J. Upconversion Luminescence and Photodegradation Performances of Pr Doped Y2SiO5 Nanomaterials. J. Nanomater. 2013, 2013, 1−6. (35) Jia, L.; Shao, Z.; Lü, Q.; Tian, Y.; Han, J. Optimum europium doped aluminoborates phosphors and their photoluminescence properties under VUV and UV excitation. Opt. Laser Technol. 2013, 54, 79−83. (36) Lee, S.-H.; Cheong, H. M.; Tracy, C. E.; Mascarenhas, A.; Czanderna, A. W.; Deb, S. K. Electrochromic coloration efficiency of a-WO3−y thin films as a function of oxygen deficiency. Appl. Phys. Lett. 1999, 75, 1541−1543. (37) Lee, S.-H.; Cheong, H. M.; Tracy, C. E.; Mascarenhas, A.; Benson, D. K.; Deb, S. K. Raman spectroscopic studies of electrochromic a-WO3. Electrochim. Acta 1999, 44, 3111−3115. (38) He, T.; Yao, J. Photochromic materials based on tungsten oxide. J. Mater. Chem. 2007, 17, 4547−4557. (39) Wang, J.; Li, S.-L.; Zhang, X.-M. Photochromic and Nonphotochromic Luminescent Supramolecular Isomers Based on Carboxylate-Functionalized Bipyridinium Ligand: (4,4)-Net versus Interpenetrated (6,3)-Net. ACS Appl. Mater. Interfaces 2016, 8, 24862−24869.
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DOI: 10.1021/acsomega.8b01091 ACS Omega 2018, 3, 9505−9512
