Communication pubs.acs.org/IC
Nonlinear-Optical Response of Prussian Blue: Strong Three-Photon Absorption in the IR Region Jan K. Zaręba,*,† Janusz Szeremeta,‡ Magdalena Waszkielewicz,† Marcin Nyk,† and Marek Samoć† †
Advanced Materials Engineering and Modelling Group and ‡Department of Organic and Pharmaceutical Technology, Faculty of Chemistry, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland S Supporting Information *
From a structural point of view, PB is a 3D inorganic CP crystallizing in the centrosymmetric cubic space group Fm3m. For our study, we have assumed the chemical formula Fe4[Fe(CN)6]3·15H2O.15 Nanoparticles were synthesized using a modification of previously known protocol (Supporting Information, SI).16 A powder X-ray diffraction study of bulk PB nanoparticle powders yielded several sets of peaks that match calculated theoretical pattern, confirming the presence of a single phase (Figure 1). An average particle diameter of 15.5 nm was calculated from the broadening of the (220) diffraction peak by means of Scherrer’s formula.17
ABSTRACT: The nonlinear-optical properties of Prussian Blue nanoparticles have been evaluated with the use of femtosecond Z-scan measurements in the 1350−1750 nm range. This well-known inorganic pigment having interesting magnetic and electrochemical properties was found to be an efficient near-IR three-photon absorber. The maximum of the effective three-photon cross section is as high as 4.5 × 10−78 cm6 s2 at 1375 nm. By a comparison of the three-photon molar-mass-normalized merit factors, σ3/M, we show that this material is a competitive multiphoton absorber, especially in comparison to semiconductor quantum dots.
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n the search for new materials with large nonlinear-optical (NLO) response, attention is being turned to systems exhibiting aggregation phenomena, such as protein fibrils1 and coordination polymers (CPs).2 In the latter case, a noteworthy factor is that variation of metal ions and ligands that are strongly bound as elements of the structure may offer much opportunity for tuning of the optical properties of such systems. However, NLO studies of materials available in microcrystalline powder form, as most CPs are, pose problems. Some authors used the strategy of dissolving a CP in a strongly coordinating solvent, such as N,N-dimethylformamide or dimethyl sulfoxide, and studying the NLO properties of the solution,3 but this raises questions concerning the chemical form of the species present in the samples. Upon solvation, the networks of CPs may decompose to the metal−organic oligomers or even to a simple mixture of ligand(s) and metal ions. Keeping this reservation in mind, we decided to study the NLO properties of certain CPs in the form of nanoparticles, which form a clear colloidal dispersion suitable for femtosecond Z-scan studies. Herein, we present the results for Prussian Blue (PB), a well-recognized pigment possessing interesting magnetic4 and electrochemical properties5 and known for applications in catalysis,6 sensing,7 energy storage,8 and the removal of cesium from nuclear waste.9 Owing to its low-solubility product in water, PB has also been applied in a variety of bioapplications,10 e.g., such as biofriendly magnetic resonance imaging11 and a photoacoustic imaging agent.12 To the best of our knowledge, the multiphoton absorption properties of PB have not been studied to date. A survey of literature indicates that so far NLO studies of PB analogues were concentrated on second-order properties such as second harmonic generation (SHG)13 and magnetizationinduced SHG.14 © XXXX American Chemical Society
Figure 1. (a) Comparison of the experimental and calculated diffraction patterns. (b) Transmission electron microscopy image of PB nanoparticles.
Stable dispersion of nanoparticles in water was subjected to dynamic light scattering analysis (Figure S1 in the SI). The biggest share of nanoparticles has a hydrodynamic diameter of 15.6 nm, while the mean size is equal to 18.2 nm (PdI = 0.191). The dominant optical transition in PB is charge transfer from FeII to FeIII over the cyanide bridge, which appears in the visibleto near-IR portion of the electromagnetic spectrum, peaking at 690 nm. The multiphoton absorption properties were investigated in the range of the optical transparency of the sample (1350−1750 nm) using the Z-scan technique in D2O dispersion. The lower range of measurements is dictated by the presence of the tail of one-photon absorption in PB, which expands up to 1300 nm (Figure S2 in the SI). The upper limit results from significant one-photon absorption of heavy water, which starts to steeply increase above 1750 nm. Experimental details of the Z-scan procedure are given in the SI. The transmittance traces corresponding to closed- and open-aperture (OA) Z-scan signals were fitted using appropriate expressions.18 Received: June 29, 2016
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DOI: 10.1021/acs.inorgchem.6b01556 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry
centrosymmetric, the local environments of FeIII ions may contain variable amounts of coordination water (on average, the coordination sphere has the composition FeN4.5O1.5),15b whose presence introduces the local noncentrosymmetry. For this reason, one cannot exclude overlap of the maximum of 2PA with twice the wavelength of 1PA; i.e., a 2PA maximum at 1400 nm would not be entirely unexpected. The direct 3PA should peak at about 2000 nm. Thus, one can suspect that the observed 3PA at the wavelength of possible 2PA can be explained in terms of 2PA followed by fast excited-state absorption of the third photon; it is an overall cubic process, and thus it is the origin of the observed narrowing of the Z-scan traces. This assumption has been corroborated by a degenerate pump−probe experiment performed at 1350 nm (Figure S3 in the SI). Experimental traces show a long decay tail with a time constant of 0.26 ps, which is apparent by a comparison with the SHG autocorrelation signal obtained from a β-barium borate crystal, while direct 3PA, as an instantaneous process, would show only a fast autocorrelation component. We argued in the past that absolute cross sections are not the proper way to compare the efficiency of third-order NLO phenomena, especially if materials of different chemical nature are considered. For this reason, a molar-mass-normalized merit factor (σ2/M) has been introduced.19 Quite recently, analogous merit factors (σ3/M, σ4/M, etc.), scaling the strength of higherorder nonlinear processes, have been also used.20 For PB, at 1375 nm the molar mass merit factor σ3/M = 0.41 × 10−80 cm6 s2 g−1 mol may be calculated, assuming the formula Fe4[Fe(CN)6]3· 15H2O. To put this value in context, we have compared these factors with selected materials of different types investigated to date (Table 1) and also with the use of a femtosecond Z-scan technique.
In the whole spectral range, the material was found to exhibit strong nonlinear absorption having distinctly three-photon absorption (3PA) character. Indeed, inspection of the OA traces throughout the measurement region (Figure 2) reveals that experimental data are systematically much better fitted using expressions for a 3PA than for a two-photon absorption (2PA) process.
Figure 2. OA Z-scan data for dispersion of PB in D2O at 1375, 1475, 1600, and 1725 nm. The theoretical curves assuming 2PA (red lines) or 3PA (black lines) are overlaid on the Z-scan data.
Figure 3 presents values of the three-photon cross sections afforded from OA Z-scans. Considering the scatter of the results,
Table 1. Comparison of Molecular-Weight-Scaled ThreePhoton Cross Sections for Various Materials material PB 4.4 nm CdSe QDs 3.7 × 10.7 nm CdSe nanorods 5 nm CdS QDs MEH−PPV solutiona rr-P3HT thin filmb dendrimer “Ru3” dendrimer “Ru9” Ru dendrimer α-synuclein amyloid fibrils insulin amyloid fibrils fluorenyl oligomer sulfonyl Y-shaped molecule
Figure 3. Plot of σ3 for PB in D2O (black squares) and plots of the 1PA spectrum as a function of twice (light gray) and three times (gray) the wavelength. The black line is drawn to guide the eyes.
one is led to conclude that the spectrum has the main peak around 1400 nm with a value of about 4.5 × 10−78 cm6 s2. For longer wavelengths, the three-photon cross sections become gradually smaller, with possibly a local maximum at 1600 nm (1.74 × 10−78 cm6 s2). The presence of 3PA in the spectral region where 2PA might be expected requires a comment. Quite often plotting of the onephoton absorption (1PA) spectrum as a function of twice and three times the wavelength (as is done in Figure 3) can provide an idea where 2PA and 3PA may take place. This, however, fails for centrosymmetric systems, where 1PA-allowed states are 2PAforbidden and the reverse. On the other hand, 1PA-allowed states should be also 3PA-allowed. Although the lattice of PB is
a
λ (nm)
σ3/M (cm6 s2 g−1 mol × 10−80)
ref
1375 1500 1400 1525
0.41 0.14 1.4 × 10−3 0.026
this work this work 21 22
1200 1200 1500 1150 1200 1150 750 725 1300 1400
1.7 × 10−3 0.76 1.34 0.57 0.86 0.14 0.97 0.57 0.95 1.54
23 24 25 20 20 26 1 1 27 28
Poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]. gioregular poly(3-hexylthiophene-2,5-diyl).
b
Re-
Examination of the σ3/M values reveals that a normalized nonlinear response of PB nanoparticles in the IR region is at least by 1 order of magnitude higher than that for semiconductor nanoparticles such as CdSe and CdS. It can also be seen that the normalized response σ3/M for PB is on the same order as that for ruthenium dendrimers as well as for amyloid fibrils, with the latter having a maximum at much shorter wavelength (around B
DOI: 10.1021/acs.inorgchem.6b01556 Inorg. Chem. XXXX, XXX, XXX−XXX
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structural characterization and optical properties. Dalton Trans. 2006, 838−845. (c) Hou, H.; Meng, X.; Song, Y.; Fan, Y.; Zhu, Y.; Lu, H.; Du, C.; Shao, W. Two-dimensional rhombohedral grid coordination polymers [M(bbbt)2(NCS)2]n (M = Co, Mn, or Cd; bbbt = 1,1′-(1,4butanediyl) bis-1H-benzotriazole): Synthesis, crystal structures, and third-order nonlinear optical properties. Inorg. Chem. 2002, 41, 4068− 4075. (d) Lian, Z.; Jiang, K.; Lou, T. Structures and third-order nonlinear optical properties of two three-dimensional Cd(ii) coordination polymers with trinodal (3, 4, 5) and dinodal (4, 5) connected network topologies. RSC Adv. 2015, 5, 82781−82788. (e) Zou, J. P.; Zhou, G. W.; Zhang, X.; Wang, M. S.; Lu, Y. B.; Zhou, W. W.; Zhang, Z. J.; Guo, G. C.; Huang, J. S. A novel heterometal-organic coordination polymer with chelidamic acid: Nonlinear optical and magnetic properties. CrystEngComm 2009, 11, 972−974. (f) Hou, H.; Song, Y.; Xu, H.; Wei, Y.; Fan, Y.; Zhu, Y.; Li, L.; Du, C. Polymeric complexes with ″piperazine-pyridine″ building blocks: Synthesis, network structures, and third-order nonlinear optical properties. Macromolecules 2003, 36, 999−1008. (4) Sato, O.; Iyoda, T.; Fujishima, A.; Hashimoto, K. Photoinduced magnetization of a cobalt-iron cyanide. Science 1996, 272, 704−705. (5) Karyakin, A. A. Prussian blue and its analogues: Electrochemistry and analytical applications. Electroanalysis 2001, 13, 813−819. (6) (a) Bu, F.-X.; Hu, M.; Xu, L.; Meng, Q.; Mao, G.-Y.; Jiang, D.-M.; Jiang, J.-S. Coordination polymers for catalysis: enhancement of catalytic activity through hierarchical structuring. Chem. Commun. 2014, 50, 8543−8546. (b) Bu, F. X.; Hu, M.; Zhang, W.; Meng, Q.; Xu, L.; Jiang, D. M.; Jiang, J. S. Three-dimensional hierarchical Prussian blue composed of ultrathin nanosheets: enhanced hetero-catalytic and adsorption properties. Chem. Commun. 2015, 51, 17568−17571. (7) (a) Ricci, F.; Palleschi, G. Sensor and biosensor preparation, optimization and applications of Prussian Blue modified electrodes. Biosens. Bioelectron. 2005, 21, 389−407. (b) Wang, T.; Fu, Y.; Chai, L.; Chao, L.; Bu, L.; Meng, Y.; Chen, C.; Ma, M.; Xie, Q.; Yao, S. Filling carbon nanotubes with prussian blue nanoparticles of high peroxidaselike catalytic activity for colorimetric chemo- and biosensing. Chem. Eur. J. 2014, 20, 2623−2630. (8) (a) Xiong, P.; Zeng, G.; Zeng, L.; Wei, M. Prussian blue analogues Mn[Fe(CN)6]0.6667·nH2O cubes as an anode material for lithium-ion batteries. Dalton Trans. 2015, 44, 16746−16751. (b) Nie, P.; Shen, L.; Luo, H.; Ding, B.; Xu, G.; Wang, J.; Zhang, X. Prussian blue analogues: A new class of anode materials for lithium ion batteries. J. Mater. Chem. A 2014, 2, 5852−5857. (c) Yue, Y.; Binder, A. J.; Guo, B.; Zhang, Z.; Qiao, Z. A.; Tian, C.; Dai, S. Mesoporous prussian blue analogues: Templatefree synthesis and sodium-ion battery applications. Angew. Chem., Int. Ed. 2014, 53, 3134−3137. (d) Pang, H.; Zhang, Y.; Cheng, T.; Lai, W. Y.; Huang, W. Uniform manganese hexacyanoferrate hydrate nanocubes featuring superior performance for low-cost supercapacitors and nonenzymatic electrochemical sensors. Nanoscale 2015, 7, 16012− 16019. (9) Ishizaki, M.; Akiba, S.; Ohtani, A.; Hoshi, Y.; Ono, K.; Matsuba, M.; Togashi, T.; Kananizuka, K.; Sakamoto, M.; Takahashi, A.; Kawamoto, T.; Tanaka, H.; Watanabe, M.; Arisaka, M.; Nankawa, T.; Kurihara, M. Proton-exchange mechanism of specific Cs+ adsorption via lattice defect sites of Prussian blue filled with coordination and crystallization water molecules. Dalton Trans. 2013, 42, 16049−16055. (10) Long, J.; Guari, Y.; Guerin, C.; Larionova, J. Prussian blue type nanoparticles for biomedical applications. Dalton Trans. 2016, DOI: 10.1039/C6DT01299J. (11) (a) Cai, X.; Gao, W.; Ma, M.; Wu, M.; Zhang, L.; Zheng, Y.; Chen, H.; Shi, J. A Prussian Blue-Based Core-Shell Hollow-Structured Mesoporous Nanoparticle as a Smart Theranostic Agent with Ultrahigh pH-Responsive Longitudinal Relaxivity. Adv. Mater. 2015, 27, 6382− 6389. (b) Fu, G.; Liu, W.; Li, Y.; Jin, Y.; Jiang, L.; Liang, X.; Feng, S.; Dai, Z. Magnetic Prussian Blue Nanoparticles for Targeted Photothermal Therapy under Magnetic Resonance Imaging Guidance. Bioconjugate Chem. 2014, 25, 1655−1663. (c) Dumont, M. F.; Hoffman, H. A.; Yoon, P. R. S.; Conklin, L. S.; Saha, S. R.; Paglione, J.; Sze, R. W.; Fernandes, R. Biofunctionalized gadolinium-containing Prussian blue nanoparticles as
750 nm). Only a few organic compounds and macromolecules like rr-P3HT offer a significantly better (up to 4-fold) σ3/M factor in this region. It should be, however, noted that the σ3/M values summarized in Table 1 are chosen for the best representatives in their own classes. It needs to be stressed that the facile one-step synthesis and possibility of obtaining of PB nanoparticles in large quantities make this material competitive with previously known multiphoton absorbers, especially in the second telecommunication band. In conclusion, our study has uncovered hitherto unknown NLO properties of PB, a compound known for over 3 centuries. Indeed, nanoparticles of PB are strong near-IR three-photon absorbers, reaching a maximum of the three-photon cross section of 4.5 × 10−78 cm6 s2 at around 1400 nm. The molar-mass-based merit factor, σ3/M, indicates that this material is an efficient multiphoton absorber in the IR range, superior to semiconductor quantum dots (QDs) investigated to date and comparable to the best organic and organometallic compounds. However, what sets PB apart from other NLO materials is its cost-efficient, one-step synthesis. The primary thrust of future work should be exploring the NLO properties in conjunction with other functionalities of PB.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01556. Experimental details (synthesis and descriptions of the Zscan setup and measurement and the degenerate pump− probe experiment) and additional figures (Figures S1−S3) (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Author Contributions
All authors have given approval to the final version of the manuscript. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We acknowledge financial support from the Polish National Science Centre Grant “Maestro” DEC-2013/10/A/ST4/00114 and the Faculty of Chemistry, Wrocław University of Science and Technology.
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REFERENCES
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DOI: 10.1021/acs.inorgchem.6b01556 Inorg. Chem. XXXX, XXX, XXX−XXX
