Europium Complex Covalently Grafted on Si(100) Surfaces

Article pubs.acs.org/JPCC

Europium Complex Covalently Grafted on Si(100) Surfaces, Engineered with Covalent Polystyrene Nanostructures Domenico A. Cristaldi,† Salvatrice Millesi,† Placido Mineo,†,‡ and Antonino Gulino*,† †

Dipartimento di Scienze Chimiche, Università di Catania and I.N.S.T.M. UdR of Catania, Viale Andrea Doria 6, 95125 Catania, Italy Istituto per i Processi Chimico Fisici- CNR, Viale Ferdinando Stagno D’Alcontres, 37 - 98158 Messina, Italy

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S Supporting Information *

ABSTRACT: Light-emitting devices are important materials for photonic applications, and lanthanide complexes have been incorporated into polymers to produce luminescent flexible composite materials for large-area optoelectronic devices. To optimize the synthetic strategy of core−shell luminescent nanostructures, in the present study, we report on a bottom-up approach to synthesize a monolayer of the tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) complex covalent-assembled on top of a film composed of polystyrene chains that, in turn, were covalently grown perpendicular to the Si(100) surface by an atomtransfer radical-polymerization reaction. The electronic characterization of the final monolayer was performed by X-ray photoelectron spectroscopy, IR, UV−visible, and luminescence measurements. The surface morphology was imaged by atomic force microscopy. Emission measurements revealed the luminescent behavior of the Eu monolayer.

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INTRODUCTION The synthesis of hybrid organic/inorganic nanostructures on appropriate substrates represents an advanced method for the production of magnetic, electronic, and photonic devices.1−4 Lanthanide complexes display exceptional luminescence characteristics such as high luminous intensity, long fluorescence lifetime, large Stokes shifts, and sharp emission profiles from the f−f electron transitions, which make them useful in fluorescence, DNA hybridization, cell activity, bioimaging assays, and so on.5−20 However, pure lanthanide complexes usually have poor thermal and mechanical stabilities, which restrict their practical applications.21 For these reasons, lanthanide complexes have been incorporated into polymers, sol−gel precursors, and so on to obtain composite materials.22−26 In addition, lanthanide complexes conjugated to polymers may combine their luminescence properties for improved photonic applications.27−29 In fact, lanthanide complexes embedded in polymeric matrices have been reported to have unique luminescent properties,30,31 and polymers are regarded as appropriate hosts for flexible, large-area displays and light-emitting diodes.32 The polymers typically used are: polymethylmetacrylate (PMMA), polyvinylalcohol (PVA), polyethylene (PE), polystyrene (PS), and fluorinated polymers (for IR luminescence). In this context, it has been reported that the intensity of the Eu(III) photoluminescence (PL) is dependent on the chemical nature of the complexing groups, the monomer constituents (in a polymer), and spacers.33 Therefore, polymer matrices (photoactive and photoinert) play different roles in PL.33 For example, the presence of benzene substituents in the polymer chains influences the PL intensity © 2013 American Chemical Society

of lanthanides, and values three times larger than those observed for lanthanides embedded in polymer matrices with no benzene groups have been observed.33 Thus, the polystyrene seems to be one of the better polymer to conjugate lanthanides. For a facile integration of the luminescent systems within electronic devices, it is important to implement the luminescent lanthanides on Si substrates. Moreover, covalent-assembled polymeric films, grown perpendicular to the silicon surface by a bottom-up approach, offer significant advantages to control both chain length and concentration of functional groups.34−48 Recently, we reported on an approach for fabricating nanoscale polystyrene structures on silicon surfaces by a covalent-assembly procedure, combined with an atom transfer radical polymerization reaction (ATRP) mediated by a copper complex.49,50 Using this approach, we observed a linear dependence of the thickness of the polystyrene structures with the increasing of the reaction time. Therefore, this thickness control corresponds to a control of the styrene monomers (functional groups) in the polystyrene chains. Now, we reacted the surface polystyrene functionalities with the tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) complex (Eu(dbm)3-phen) to produce a monolayer of this europium complex covalently bound to the polystyrene nanostructures, in turn, covalently assembled on Received: March 28, 2013 Revised: June 11, 2013 Published: July 16, 2013 16213

dx.doi.org/10.1021/jp403070y | J. Phys. Chem. C 2013, 117, 16213−16220

The Journal of Physical Chemistry C

Article

Scheme 1. Reaction Pathway for the Europium β-Diketonate Complex, Covalently Bound to Nanoscale, Surface-Confined Polystyrene Assemblies

theoretical profile. The R factor (residual or agreement factor), R = [Σ(Fo − Fc)2/Σ(Fo)2]1/2, after minimization of the function Σ(Fo − Fc)2 converged to R values ≤0.036.52 UV−vis measurements were carried out on a UV−vis V-650 Jasco spectrometer, and the spectra were recorded with a 0.2 nm resolution at room temperature using quartz-based monolayers. Luminescence measurements were carried out using a Varian Cary eclipse fluorescence spectrophotometer with different λexc in the 220−380 nm range (step 10 nm) and at 1 nm resolution at room temperature. The emission was recorded at 90° with respect to the exciting line beam using 10:10 slit-widths. Infrared attenuated reflectance spectra of the monolayers were recorded using a Jasco FT/IR-430 spectrometer equipped with a Harrick GATR germanium single-reflection ATR (attenuated total reflectance) accessory, in the 4000−400 cm−1 range, with a resolution of 4 cm−1. One hundred scans per spectrum were collected. Surface morphology studies were performed by atomic force microscopy (AFM), and the images were obtained by an instrument manufactured by the NT-MTD. The noise level before and after each measurement was 0.01 nm. AFM characterizations were performed in a high-amplitude mode (tapping mode) with a tip whose nominal curvature radius is 10 nm.

the silicon surface. This hybrid system demonstrated unique luminescence characteristics.

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EXPERIMENTAL DETAILS

Si(100) and fused silica (quartz) substrates were cleaned and functionalized with a monolayer of trichloro[4-(chloromethyl)phenyl]silane and then with polystyrene nanostructures (SA_PSS), as already reported.49−51 Then, the SA_PSS substrates were washed and sonicated with n-methylpyrrolidone and THF to remove any residual physisorbed material, loaded into glass pressure vessels under N2, immersed in a fresh prepared 1.5 × 10−3 M toluene solutions of the Eu(dbm)3-phen (Aldrich), and heated to 90 °C for 72 h. Finally, the functionalized substrates bearing the covalently self-assembled Eu(dbm)3-phen molecules, SA_PSS_Eu, were left to cool to room temperature and repeatedly washed and sonicated with toluene and dichloromethane to remove any residual physisorbed metal complex. The films strongly adhere to the substrates because they cannot be removed by abrasion with toluene-wetted wipes and were stable for more than 6 months, as evidenced by X-ray photoelectron spectra. X-ray photoelectron spectra (XPS) were measured at 45°, relative to the surface plane with a PHI 5600 multi technique system, which gives a good control of the electron takeoff angle (base pressure of the main chamber 3 × 10−10 Torr).52−56 Spectra were excited with monochromatized Al−Kα radiation (pass energy 11.75 eV). XPS peak intensities were obtained after Shirley background removal. Spectra calibration was achieved by fixing the main C 1s peak at 285.0 eV.52,53 Experimental uncertainties in binding energy (B.E.) lie within ±0.4 eV. Spectra deconvolution was carried out by fitting the experimental profiles with symmetrical Gaussian peaks after subtraction of the background. This process involves data refinement based on the method of the least-squares fitting, carried out until there was the highest possible correlation between the experimental spectrum and the

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RESULTS AND DISCUSSION The Eu(dbm)3-phen complex was covalently grafted on Si(100) substrates, engineered with covalent polystyrene nanostructures. In particular, Si(100) substrates were functionalized with a covalent 4-ClCH2C6H4SiCl3 monolayer. Next, self-assembled polystyrene structures were obtained by an optimized redox reaction between the benzyl chloride functionality of the silane and the Cu+ catalyst49,50 to produce Cu2+, reduction of the Cl· radical to Cl− anion (due to homolytic fragmentation of the C−Cl bond) and formation of 16214



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the surface-bound benzyl radical.49,50 Afterward, the benzyl radical reacted with the styrene monomer to form the surfacebound styrene radical that, in turn, reacted with the Cu2+ to return the starting Cu+ catalyst and the surface-bound styrene chloride.49 The cycling of this reaction pathway allowed the growth of polystyrene structures covalently bound to the Si(100) surface.49 After 2 h, the substrates were removed from this reaction mixture, sonicated in n-methylpyrrolidone and in THF, and reacted with the toluene solution of the europium complex. The surface-bound styrene chloride reacted with the amine substituent of the phenanthroline ligand and allowed additional functionalization with the Eu complex to give an Eu(dbm)3-phen monolayer covalently bound to surfaceconfined polystyrene assemblies, in turn, covalently bound to the silicon (Scheme 1). Figure 1 shows the UV−vis spectra of the Eu(dbm)3-phen 1.6 × 10−5 M CH2Cl2 solution (black line) and of the

Figure 2. Monochromatized Al Ka excited XPS for the SA_PSS_Eu on Si(100) in the Eu 3d binding energy region at 45° takeoff angle.

orbit doublet at 1134.8−1164.5 eV, with a 29.7 eV spin−orbit separation, is consistent with Eu(III) states.65 The N 1s spectrum of the present SA_PSS_Eu shows a symmetric peak at 399.6 eV (Figure 3). This signal accounts for

Figure 1. UV−vis spectra of the: Eu(dbm)3-phen 1.6 × 10−5 M CH2Cl2 solution (black line) whose absorbance values have been divided by 30; SA_PSS_Eu on quartz (red line). Figure 3. Monochromatized Al Ka excited XPS for the SA_PSS_Eu on Si(100) in the N 1s binding energy region at 45° takeoff angle.

SA_PSS_Eu (red line). These spectra show a close correspondence. In fact, in both cases two bands are apparent whose positions for the Eu solution are at 287.5 and 348.6 nm and for the SA_PSS_Eu are at 290.8 and 358.6 nm. The surface coverage of the SA_PSS_Eu with europium molecules (number of Eu(dbm)3-phen/cm2) was calculated using the Beer−Lambert law, dsurf = Aε−1 (A = εlc, where A is the absorbance and ε, l, and c are the extinction coefficient, the thickness of the monolayer, and the concentration of the Eu(dbm)3-phen molecules in the monolayer, respectively).57−64 Taking into account the ε value of 63 000 M−1cm−1 for the band at 358.6 nm of Eu(dbm)3-phen in CH2Cl2, the calculated density value is 3.59 × 1013 molecules/cm2 with a footprint of 278 Å2 per molecule. This value is in agreement with a full surface coverage once the Eu molecule’s cross-sectional area (201 Å2 estimated with the Gaussian 03 code) has been taken into account.65 FTIR-ATR measurements of the SA_PSS_Eu gave the expected νa(CH2) and νs(CH2) stretching modes at 2920 and 2854 cm−1, respectively.49 Furthermore, modes at 1536 and 1504 cm−1 are due to the CO and CC stretching, respectively, for β diketonate complexes. Finally, at 1648 and 1632 cm−1 there is evidence of the C−N group (Figure S1 in the Supporting Information). The structural characterization of the SA_PSS_Eu was performed with X-ray photoelectron spectroscopy. Figure 2 shows the XPS spectrum of the SA_PSS_Eu in the Eu 3d energy region. The spectral resolution is good, and the spin−

the three nitrogen atoms of the amino-phenanthroline ligand.66−68 The N/Eu XPS atomic concentration ratio of 2.8 is largely compatible with the expected theoretical value of 3. Figure 4 shows the C 1s peak for the SA_PSS_Eu. The accurate deconvolution of the experimental profile reveals three components. The first at 285.0 eV is due to the aliphatic and aromatic carbon atoms. The second component at 286.8 eV is due to the not-reacted C−Cl functionalities of the SA_PSS_Eu (Scheme 1) and to the C−N groups of the amino-phenanthroline; and that at 288.2 is consistent with the CO groups of the β diketonate anions.69 The intensity ratio between the 286.8 and 288.2 eV components is 2.66:1. In the Eu complex there are 6 C−N and 6 CO groups. Therefore, the expected C−N/CO intensity ratio is 1. The extra intensity of the 286.8 component is due to the C−Cl functionalities. It emerges that the 2.66:1 intensity ratio is consistent with 10 not-reacted C−Cl plus 6 CN and 6 CO groups in the 16:6 ratio. This result is in total agreement with the UV−vis footprint of 278 Å2 per Eu molecule that corresponds to the footprint of 11 silane moieties, each of which has a 24 Å2 footprint.46 Moreover, because the average height of the SA_PSS_Eu nanostructures is 6.7 nm (vide infra), XPS is able to probe the whole present thickness (Figure S2 in the Supporting Information).52 Quantum mechanical calculations indicate a ∼100 Å2 footprint for each polystyrene chain (Figure S3 in the Supporting 16215



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undergoes the electric-dipole 5D0 → 7F2 strong transition with emissions in the 610−620 nm range.19,20,65 The SA_PSS_Eu exhibits PL with a strong, sharp, and wellresolved emission at 616 nm (Figure 6a) that can be ascribed to

Figure 4. Monochromatized Al Ka excited XPS for the SA_PSS_Eu on Si(100) in the C 1s binding energy region at 45° takeoff angle. The black empty dots refer to the experimental profile; the cyan and magenta lines refer to the Gaussian at 286.8 and 288.2, respectively; the red line superimposed to the experimental profile refers to the sum of the Gaussian components.

Figure 6. (a) Luminescence spectra of the SA_PSS_Eu on Si(100) at different excitation wavelengths: 340 (black line), 350 (blue line), and 360 nm (red line). (b) Behavior of the PL intensity of the SA_PSS_Eu on Si(100) at different excitation wavelengths: 593 nm emission (black histograms) and 616 nm emission (red histograms); the two blue lines represent arbitrary thresholds.

Information) that corresponds to the footprint of four silane moieties. Therefore, each Eu complex substitutes for 1 to 3 polystyrene C−Cl groups, and this corresponds to 1 Eu complex by 11 to 12 silane benzyl chloride functionalities. From these considerations, it appears that the coupling of UV− vis and XPS techniques is very useful to study monolayers because it provides unique information. Figure 5 shows the AFM micrograph for the SA_PSS_Eu on Si(100). A uniform distribution of polystyrene nanostructures on the substrate surface is evident. The average height of these features is 6.7 nm (Figure 5, right), in total agreement with the thickness of ∼6.5 nm, expected on the basis of previously reported data related to the increase in the polystyrene thickness versus the reaction time.49 Because of the effective intramolecular energy transfer from the coordinated ligands to the luminescent central lanthanide ion, emission of Eu(III) is strongly influenced by the metal environment.19,20,65 In fact, Eu(III) has five narrow emission bands corresponding to the 5D0 → 7Fj transitions, where j = 0, 1, 2, 3, 4 and the cross section for the 5D0 (lowest excited state) → 7F0−6 (ground states) transitions depends on the Eu site symmetry.19,20,65 Eu(III) in sites with inversion symmetry mainly shows the magnetic-dipole 5D0 → 7F1 transition at ∼590 nm while, Eu(III) in sites with no inversion symmetry

the electric-dipole 5D0 → 7F2 transition of the Eu3+ ions located at the sites without inversion symmetry.19,20,65,70−73 A less intense emission peak for the 5D0 → 7F1 is also evident at 593 nm.19,20,65,70−73 Other very weak PL signals are present at higher wavelength, out of the range of Figure 6a.19,20,65,70−73 Therefore, even though they have different intensities, both electric- and magnetic-dipole transitions are evident in the present Eu(III)-monolayer.65 In fact, 4f levels in lanthanide compounds have been generally considered essentially atomic in nature and simple spectators with respect to the chemical bond because filled 5s2 and 5p6 levels shield 4f orbitals from ligand field effects. This certainly holds for ionic oxides and halogenated lanthanides.74−76 In contrast, quantum-mechanical calculation combined with photoelectron spectroscopic studies highlighted some lanthanide−ligand covalency in discrete organometallic molecules.77−79 In practice, the various states arising from fn configurations are split by external fields only to a small extent (∼100 cm−1).19,20,65 Therefore, even though they have different intensities, both electric- and magnetic-dipole transitions are expected and evident in Eu(III)-containing materials.

Figure 5. AFM of SA_PSS_ Eu on Si(100) (left); average height (right). 16216



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CONCLUSIONS We synthesized a monolayer of the tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) complex covalent-assembled on a polystyrene film grown on both Si(100) and quartz substrates. The structural, optical, and morphological characterization was performed by XPS, UV− vis, IR, luminescence, and AFM measurements. In particular, XPS gave information on the bonding states of the grafted molecules. PL spectra showed both the magnetic-dipole 5D0 → 7 F1 and electric-dipole 5D0 → 7F2 transitions. The intensity of the related emission bands can be tuned by changing the excitation wavelength. Therefore, the SA_PSS_Eu represents a new designed chemical platform that responds to light inputs by luminescence intensity variations and may be used in optoelectronic devices. These measurements have been performed many times with different monolayers and outputs proved to be highly reproducible. The read-out procedure is fast and highly reliable, and the system can be used as a tunable luminescent device. In addition, the monolayer is stable at room temperature in air for at least 6 months, thus excluding any photobleaching. Finally, this study also shows a method to implement lanthanide complexes on flexible polystyrene films for large-area optic devices, and this is an important issue nowadays.

To use the SA_PSS_Eu as a tunable luminescent device, PL measurements have been carried out using different excitation wavelengths (Figure 6b).71,80−86 It turned out that the highest PL intensity values for both emission bands (at 593 and 616 nm) were observed using a λexc = 340 nm, while the lowest values were observed using λexc = 360, thus showing that the luminescence intensity is strongly dependent on the excitation radiation. From these results it emerges that the cross sections of the two magnetic-dipole and electric-dipole mechanisms are significantly and differently affected by the excitation radiations, and it is the emission at 593 nm that suffers the stronger variation.65 In fact, the PL intensity ratio of the two bands (at 616 nm/593 nm) seems rather constant (1.4 to 1.3) on passing from λexc = 340 to 350 nm, while it strongly increases to 3.1 using λexc = 360 nm. Recently, we reported on the luminescence properties of a monolayer of the same Eu complex covalently assembled on a quartz substrate (Eu-SAM). A comparison of the present with previously reported data indicates some relevant differences. In fact, at λexc = 340 nm, the relative intensities of the two observed (593 and 616 nm) emissions are significantly different in the two systems. Indeed, the intensity ratio of the 614/593 emissions is 8.8 for the Eu-SAM, while it is only 1.4 for the present SA_PSS_Eu on Si(100). At λexc = 360 nm, this ratio decreases from 8.8 to 1.7 for the Eu-SAM, while it increases from 1.4 to 3.1 for the SA_PSS_Eu on Si(100). High ratios correspond to the predominance of the electric-dipole 5D0 → 7 F2 transition of the Eu3+ ions located at the sites without inversion symmetry. As a consequence, the low-intensity ratio value (1.4) observed for the Eu-complex in the present SA_PSS_Eu on Si(100) during the transition at λexc = 340 nm suggests that the Eu3+ ions reach a symmetry higher than that in their ground state if compared with the Eu-SAM. Conversely, at λexc = 360 nm, the larger intensity ratio value (3.1) suggests that the excited Eu3+ ions experience a symmetry lower than that in their ground state (with some inversion symmetry) because magnetic-dipole 5D0 → 7F1 transition intensity at ∼593 nm increases. As a consequence, this strong luminescence variation, upon the excitation wavelength, can be used as on/off controls. Concerning the emission at 616 nm, it is possible to choose an arbitrary high-intensity threshold (Figure 6b) to get it ON (above the threshold) only at λexc = 340 nm and OFF (below the threshold) at λexc = 350 and 360 nm, where the emission at 593 is always OFF. Alternatively, one can choose a lower intensity threshold (Figure 6b) to get both emissions ON at λexc = 340 or 350 nm. The emission at 593 nm can now be OFF and that at 616 nm ON at λexc = 360 nm. Therefore, the obtained emission values can be triggered at will simply by choosing one or more arbitrary thresholds. These measurements have been performed many times, and outputs proved to be highly repeatable. The emission intensity can be alternated between different low- and high-intensity values. Therefore, this SA_PSS_Eu represents a new system that responds to excitation inputs by luminescence emission intensity variations (output). The read-out procedure is fast and highly reliable, and the system can be used as a tunable light-emitting device for photonic applications. We are aware that our system does not represent a switch because the different luminescence intensities of any of the two emission bands at any of the excitation wavelengths are not due to different and stable physical states of the europium complex.

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ASSOCIATED CONTENT

S Supporting Information *

ATR-FTIR measurements of the SA_PSS_Eu on Si(100) (Figure S1); Al Ka excited XPS for the SA_PSS_Eu in the Si 2p binding energy region at 45° takeoff angle (Figure S2); and polystyrene chain area obtained by quantum mechanical calculations (Figure S3). This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +39-095-7385067. Fax: +39095-580138. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS A.G. thanks the MIUR, the FIRB projects ITALNANONET (RBPR05JH2P) and RINAME (RBAP114AMK), and University of Catania.

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REFERENCES

(1) Mannini, M.; Pineider, F.; Danieli, C.; Totti, F.; Sorace, L.; Sainctavit, P.; Arrio, M. A.; Otero, E.; Joly, L.; Cezar, J. C.; Cornia, A.; Sessoli, R. Quantum Tunnelling of the Magnetization in a Monolayer of Oriented Single-Molecule Magnets. Nature 2010, 468, 417−421. (2) Yang, W. L.; Fabbri, J. D.; Willey, T. M.; Lee, J. R. I.; Dahl, J. E.; Carlson, R. M. K.; Schreiner, P. R.; Fokin, A. A.; Tkachenko, B. A.; Fokina, N. A.; et al. Monochromatic Electron Photoemission from Diamondoid Monolayers. Science 2007, 316, 1460−1462. (3) Wachowiak, A.; Yamachika, R.; Khoo, K. H.; Wang, Y.; Grobis, M.; Lee, D.-H.; Louie, S. G.; Crommie, M. F. Visualization of the Molecular Jahn-Teller Effect in an Insulating K4C60 Monolayer. Science 2005, 310, 468−470. (4) Lin, T.; Shang, X. S.; Adisoejoso, J.; Liu, P. N.; Lin, N. Steering On-Surface Polymerization with Metal-Directed Template. J. Am. Chem. Soc. 2013, 135, 3576−3582. 16217



Article

(5) Yuan, J.; Wang, G. Lanthanide Complex-Based Fluorescence Label for Time-Resolved Fluorescence Bioassay. J. Fluoresc. 2005, 15, 559−568. (6) Ida, S.; Ogata, C.; Shiga, D.; Izawa, K.; Ikeue, K.; Matsumoto, Y. Dynamic Control of Photoluminescence for Self-Assembled Nanosheet Films Intercalated with Lanthanide Ions by Using a Photoelectrochemical Reaction. Angew. Chem., Int. Ed. 2008, 47, 2480−2483. (7) Deiters, E.; Song, B.; Chauvin, A.-S.; Vandevyver, C. D. B.; Bünzli, J.-C. G. Effect of the Length of Polyoxyethylene Substituents on Luminescent Bimetallic Lanthanide Bioprobes. New J. Chem. 2008, 32, 1140−1152. (8) Su, Y.; Li, L.; Li, G. Self-Assembly and Multicolor Emission of Core/Shell Structured CaWO4:Na+/Ln3+ Spheres. Chem. Commun. 2008, 34, 4004−4006. (9) Arrachart, G.; Karatchevtseva, I.; Cassidy, D. J.; Triani, G.; Bartlett, J. R.; Man, M. W. C. Synthesis and Characterisation of Carboxylate-Terminated Silica Nanohybrid Powders and Thin Films. J. Mater. Chem. 2008, 18, 3643−3649. (10) Quach, A.; Escax, V.; Nicole, L.; Goldner, P.; Guillot-Noel, O.; Aschehoug, P.; Hesemann, P.; Moreau, J.; Gourier, D.; Sanchez, C. Rare Earth Doped Mesoporous Hybrid Thin Films with Tunable Optical Responses. J. Mater. Chem. 2007, 17, 2552−2560. (11) Liu, J.; Li, Y. General Synthesis of Colloidal Rare Earth Orthovanadate Nanocrystals. J. Mater. Chem. 2007, 17, 1797−1803. (12) Zhang, R.-J.; Cui, J.-W.; Lu, D.-M.; Hou, W.-G. Study on HighEfficiency Fluorescent Microcapsules Doped with Europium βDiketone Complex by LbL Self-Assembly. Chem. Commun. 2007, 1547−1549. (13) Leonard, J. P.; Nolan, C. B.; Stomeo, F.; Gunnlaugsson, T. Photochemistry and Photophysics of Coordination Compounds: Lanthanides. Top. Curr. Chem. 2007, 281, 1−43. (14) Plush, S. E.; Gunnlaugsson, T. Luminescent Sensing of Dicarboxylates in Water by a Bismacrocyclic Dinuclear Eu(III) Conjugate. Org. Lett. 2007, 9, 1919−1922. (15) Hanaoka, K.; Kikuchi, K.; Kobayashi, S.; Nagano, T. TimeResolved Long-Lived Luminescence Imaging Method Employing Luminescent Lanthanide Probes with a New Microscopy System. J. Am. Chem. Soc. 2007, 129, 13502−13509. (16) Zhang, N.; Bu, W.; Xu, Y.; Jiang, D.; Sh, J. Self-Assembled Flowerlike Europium-Doped Lanthanide Molybdate Microarchitectures and Their Photoluminescence Properties. J. Phys. Chem. C 2007, 111, 5014−5019. (17) Liu, L.; Xu, Z.; Lou, Z.; Zhang, F.; Sun, B.; Pei, J. Photoluminescence and Electroluminescence Mechanism on a Novel Complex Eu(o-BBA)3(phen). J. Lumin. 2007, 122−123, 961−963. (18) Bünzli, J.-C. G. Benefiting from the Unique Properties of Lanthanide Ions. Acc. Chem. Res. 2006, 39, 53−61. (19) Fujihara, S.; Tokumo, K. Multiband Orange-Red Luminescence of Eu3+ Ions Based on the Pyrochlore-Structured Host Crystal. Chem. Mater. 2005, 17, 5587−5593. (20) Li, Y.; Yan, B.; Yang, H. Construction, Characterization, and Photoluminescence of Mesoporous Hybrids Containing Europium(III) Complexes Covalently Bonded to SBA-15 Directly Functionalized by Modified β-Diketone. J. Phys. Chem. C 2008, 112, 3959− 3968. (21) Sun, Z.; Bai, F.; Wu, H.; Boye, D. M.; Fan, H. Monodisperse Fluorescent Organic/Inorganic Composite Nanoparticles: Tuning Full Color Spectrum. Chem. Mater. 2012, 24, 3415−3419. (22) Wang, L.-H.; Wang, W.; Zhang, W.-G.; Kang, E.-T.; Huang, W. Synthesis and Luminescence Properties of Novel Eu-Containing Copolymers Consisting of Eu(III)-Acrylate-β-Diketonate Complex Monomers and Methyl Methacrylate. Chem. Mater. 2000, 12, 2212− 2218. (23) McGehee, M. D.; Bergstedt, T.; Zhang, C.; Saab, A. P.; O’Regan, M. B.; Bazan, G. C.; Srdanov, V. I.; Heeger, A. J. Narrow Bandwidth Luminescence from Blends with Energy Transfer from Semiconducting Conjugated Polymers to Europium Complexes. Adv. Mater. 1999, 11, 1349−1354.

(24) Lenaerts, P.; Driesen, K.; Van Deun, R.; Binnemans, K. Covalent Coupling of Luminescent Tris(2-thenoyltrifluoroacetonato)lanthanide(III) Complexes on a Merrifield Resin. Chem. Mater. 2005, 17, 2148−2154. (25) Li, H.; Inouem, S.; Machida, K. I.; Adachi, G. Y. Preparation and Luminescence Properties of Organically Modified Silicate Composite Phosphors Doped with an Europium(III) β-Diketonate Complex. Chem. Mater. 1999, 11, 3171−3176. (26) Gai, S.; Yang, P.; Li, C.; Wang, W.; Dai, Y.; Niu, N.; Lin, J. Synthesis of Magnetic, Up-Conversion Luminescent, and Mesoporous Core-Shell-Structured Nanocomposites as Drug Carriers. Adv. Funct. Mater. 2010, 20, 1166−1172. (27) Dillon, A. C.; Gennett, T.; Jones, K. M.; Alleman, J. L.; Parilla, P. A.; Heben, M. J. A Simple and Complete Purification of Single-Walled Carbon Manitoba Materials. Adv. Mater. 1999, 11, 1354−1358. (28) Vancaeyzeele, C.; Ornatsky, O.; Baranov, V.; Shen, L.; Abdelrahman, A.; Winnik, M. A. Lanthanide-Containing Polymer Nanoparticles for Biological Tagging Applications: Nonspecific Endocytosis and Cell Adhesion. J. Am. Chem. Soc. 2007, 129, 13653−13660. (29) Kuriki, K.; Koike, Y. Plastic Optical Fiber Lasers and Amplifiers Containing Lanthanide Complexes. Chem. Rev. 2002, 102, 2347− 2356. (30) Ishizaka, T.; Kasai, H.; Nakanishi, H. Fabrication and Luminescence Properties of Eu-Complex/Polyimide Composite Nanoparticles. J. Mater. Sci. 2009, 44, 166−169. (31) Ishizaka, T.; Kasai, H.; Oikawa, H.; Nakanishi, H. Unique Luminescence Properties of Eu3+-Doped Polyimide. J. Photochem. Photobiol., A. 2006, 183, 280−284. (32) de Souza, J. M.; Alves, S., Jr.; De Sá, G. F.; de Azevedo, W. M. Doped Polymers with Ln(III) Complexes: Simulation and Control of Light Colors. J. Alloys Compd. 2002, 344, 320−322. (33) Yakimanskii, A. V.; Goikhman, M. Ya.; Podeshvo, I. V.; Anan’eva, T. D.; Nekrasova, T. N.; Smyslov, R. Yu. Luminescence of Ln3+ Lanthanide Complexes in Polymer Matrices. Polym. Sci., Ser. A 2012, 54, 921−941. (34) Matyjaszewski, K.; Dong, H.; Jakubowski, W.; Pietrasik, J.; Kusumo, A. Grafting from Surfaces for “Everyone”: ARGET ATRP in the Presence of Air. Langmuir 2007, 23, 4528−4531. (35) LeMieux, M. C.; McConney, M. E.; Lin, Y.-H.; Singamaneni, S.; Jiang, H.; Bunning, T. J.; Tsukruk, V. V. Polymeric Nanolayers as Actuators for Ultrasensitive Thermal Bimorphs. Nano Lett. 2006, 6, 730−734. (36) Xu, F. J.; Xu, D.; Kang, E. T.; Neoh, K. G. Self-Doped Conductive Polymer-Silicon Hybrids from Atom Transfer Radical Graft Copolymerization of Sodium Styrenesulfonate with Polyaniline Covalently Tethered on the Si(100) Surface. J. Mater. Chem. 2004, 14, 2674−2682. (37) Xu, F. J.; Cai, Q. J.; Kang, E. T.; Neoh, K. G. Surface-Initiated Atom Transfer Radical Polymerization from Halogen-Terminated Si(111) (Si-X, X = Cl, Br) Surfaces for the Preparation of WellDefined Polymer-Si Hybrids. Langmuir 2005, 21, 3221−3225. (38) Juang, A.; Scherman, O. A.; Grubbs, R. H.; Lewis, N. S. Formation of Covalently Attached Polymer Overlayers on Si(111) Surfaces Using Ring-Opening Metathesis Polymerization Methods. Langmuir 2001, 17, 1321−1323. (39) Orski, S. V.; Poloukhtine, A. A.; Arumugam, S.; Mao, L.; Popik, V. V.; Locklin, J. High Density Orthogonal Surface Immobilization via Photoactivated Copper-Free Click Chemistry. J. Am. Chem. Soc. 2010, 132, 11024−11026. (40) Palomaki, P. K. B.; Dinolfo, P. H. A Versatile Molecular Layerby-Layer Thin Film Fabrication Technique Utilizing Copper(I)Catalyzed Azide-Alkyne Cycloaddition. Langmuir 2010, 26, 9677− 9685. (41) Chen, R.; Zhu, S.; Maclaughlin, S. Grafting Acrylic Polymers from Flat Nickel and Copper Surfaces by Surface-Initiated Atom Transfer Radical Polymerization. Langmuir 2008, 24, 6889−6896. (42) Senkovskyy, V.; Khanduyeva, N.; Komber, H.; Oertel, U.; Stamm, M.; Kuckling, D.; Kiriy, A. Conductive Polymer Brushes of 16218



Article

Assembled on a Molecularly Engineered Silica Surface. Chem. Mater. 2005, 17, 4043−4045. (62) Gulino, A.; Bazzano, S.; Condorelli, G. G.; Giuffrida, S.; Mineo, P.; Satriano, C.; Scamporrino, E.; Ventimiglia, G.; Vitalini, D.; Fragalà, I. Engineered Silica Surfaces with an Assembled C60 Fullerene Monolayer. Chem. Mater. 2005, 17, 1079−1084. (63) Gulino, A.; Bazzano, S.; Mineo, P.; Scamporrino, E.; Vitalini, D.; Fragalà, I. Characterization, Optical Recognition Behavior, Sensitivity, and Selectivity of Silica Surfaces Functionalized with a Porphyrin Monolayer. Chem. Mater. 2005, 17, 521−526. (64) Gulino, A.; Mineo, P.; Scamporrino, E.; Vitalini, D.; Fragalà, I. Molecularly Engineered Silica Surfaces with an Assembled Porphyrin Monolayer as Optical NO2 Molecular Recognizers. Chem. Mater. 2004, 16, 1838−1840. (65) Gulino, A.; Lupo, F.; Condorelli, G. G.; Motta, A.; Fragalà, I. Tunable Luminescent Properties of a Europium Complex Monolayer. J. Mater. Chem. 2009, 19, 3507−3511. (66) Kaminker, R.; Motiei, L.; Gulino, A.; Fragalà, I.; Shimon, L. J. W.; Evmenenko, G.; Dutta, P.; Iron, M. A.; van der Boom, M. E. Stepwise Assembly of Coordination-Based Metal-Organic Networks. J. Am. Chem. Soc. 2010, 132, 14554−14561. (67) Choudhury, J.; Kaminker, R.; Motiei, L.; de Ruiter, G.; Morozov, M.; Lupo, F.; Gulino, A.; van der Boom, M. E. Linear vs. Exponential Formation of Molecular-Based Assemblies. J. Am. Chem. Soc. 2010, 132, 9295−9297. (68) Motiei, L.; Altman, M.; Gupta, T.; Lupo, F.; Gulino, A.; Evmenenko, G.; Dutta, P.; van der Boom, M. E. Self-Propagating Assembly of a Molecular-Based Multilayer. J. Am. Chem. Soc. 2008, 130, 8913−8915. (69) Gulino, A.; Lupo, F.; Condorelli, G. G.; Mineo, P.; Fragalà, I. Viable Synthetic Route for a Luminescent Porphyrin Monolayer Covalently Assembled on a Molecularly Engineered Si(100) Surface. Chem. Mater. 2007, 19, 5102−5109. (70) Chang, C. H.; Yun, M. H.; Choi, W. J. Synthesis and Photoluminescence Properties of Eu(pzc) 3 (phen) and Eu(mpzc)3(phen). Synth. Met. 2004, 145, 1−6. (71) Bünzli, J.-C. C. Lanthanide Luminescent Bioprobes (LLBs). Chem. Lett. 2009, 38, 104−109. (72) Carlos, L. D.; Donega, C. D. M.; Albuquerque, R. Q.; Alves, J. R. S.; Menezes, J. F. S.; Malta, O. L. Highly Luminescent Europium(III) Complexes with Naphtoiltrifluoroacetone and Dimethyl Sulphoxide. Mol. Phys. 2003, 101, 1037−1045. (73) Robinson, M. R.; O’Regan, M. B.; Bazan, G. C. Synthesis, Morphology and Optoelectronic Properties of Tris[(Nethylcarbazolyl)(3′,5′-hexyloxybenzoyl)methane](phenanthroline) Europium. Chem. Commun. 2000, 1645−1646. (74) Roos, B. O.; Lindh, R.; Malmqvist, P.; Veryazov, V.; Widmark, P.-O.; Borin, A. C. New Relativistic Atomic Natural Orbital Basis Sets for Lanthanide Atoms with Applications to the Ce Diatom and LuF3. J. Phys. Chem. A 2008, 112, 11431−11435. (75) Adamo, C.; Maldivi, P. A Theoretical Study of Bonding in Lanthanide Trihalides by Density Functional Methods. J. Phys. Chem. A 1998, 102, 6812−6820. (76) Di Bella, S.; Gulino, A.; Lanza, G.; Fragala, I.; Stern, D.; Marks, T. J. Photoelectron Spectroscopy of f-Element Organometallic Complexes. 12. A Comparative Investigation of the Electronic Structure of Lanthanide Bis(polymethylcyclopentadienyl)hydrocarbyl Complexes by Relativistic ab Initio and DV-Xα Calculations and GasPhase UV Photoelectron Spectroscopy. Organometallics 1994, 13, 3810−3815. (77) Gulino, A.; Di Bella, S.; Fragalà, I.; Casarin, M.; Seyam, A. M.; Marks, T. J. Photoelectron Spectroscopy of f-Element Organometallic Complexes. 9. A Comparative Fully Relativistic/Nonrelativistic FirstPrinciples Xα-DVM and Photoelectron Spectroscopic Investigation of Electronic Structure in Homologous 4f and 5f tris(η5cyclopentadienyl)metal(IV) Alkoxide Complexes. Inorg. Chem. 1993, 32, 3873−3879. (78) Gulino, A.; Casarin, M.; Conticello, V. P.; Gaudiello, J. G.; Mauermann, H.; Fragalà, I.; Marks, T. J. Efficient Synthesis, Redox

Regioregular Head-to-Tail Poly(3-alkylthiophenes) via Catalyst-Transfer Surface-Initiated Polycondensation. J. Am. Chem. Soc. 2007, 129, 6626−6632. (43) Malvadkar, N. A.; Hancock, M. J.; Sekeroglu, K.; Dressick, W. J.; Demirel, M. C. An Engineered Anisotropic Nanofilm with Unidirectional Wetting properties. Nat. Mater. 2010, 9, 1023−1028. (44) Malvadkar, N. A.; Demirel, G.; Poss, M.; Javed, A.; Dressick, W. J.; Demirel, M. C. Fabrication and Use of Electroless Plated Polymer Surface-Enhanced Raman Spectroscopy Substrates for Viral Gene Detection. J. Phys. Chem. C 2010, 114, 10730−10738. (45) Malvadkar, N. M.; Sekeroglu, K.; Dressick, W. J.; Demirel, M. C. Noncovalent Mechanism for the Conformal Metallization of Nanostructured Parylene Films. Langmuir 2010, 26, 4382−4391. (46) Brandow, S. L.; Chen, M.-S.; Dulcey, C. S.; Dressick, W. J. Formation of Aromatic Siloxane Self-Assembled Monolayers. Langmuir 2008, 24, 3888−3896. (47) Chen, M.-S.; Dulcey, C. S.; Chrisey, L. A.; Dressick, W. J. DeepUV Photochemistry and Patterning of (aminoethylaminomethyl)phenethylsiloxane Self-Assembled Monolayers. Adv. Funct. Mater. 2006, 16, 774−783. (48) Chen, M.-S.; Brandow, S. L.; Schull, T. L.; Chrisey, D. B.; Dressick, W. J. A Non-Covalent Approach for Depositing Spatially Selective Materials on Surfaces. Adv. Funct. Mater. 2005, 15, 1364− 1375. (49) Mineo, P.; Motta, A.; Lupo, F.; Renna, L.; Gulino, A. Si(111) Surface Engineered with Ordered Nanostructures by an Atom Transfer Radical Polymerization. J. Phys. Chem. C 2011, 115, 12293−12298. (50) Mineo, P. G.; Cristaldi, D. A.; Motta, A.; Gupta, T.; Gulino, A. Covalent Poly(methyl methacrylate) Nanostructures on Functionalized Si(100) Surfaces. RSC Adv. 2013, 3, 1137−1144. (51) Gulino, A.; Condorelli, G. G.; Mineo, P.; Fragalà, I. An X-Ray Photoelectron Spectra and Atomic Force Microscopy Characterization of Silica Substrates Engineered with a Covalently Assembled Siloxane Monolayer. Nanotechnology 2005, 16, 2170−2175. (52) Gulino, A. Structural and Electronic Characterization of SelfAssembled Molecular Nanoarchitectures by X-Ray Photoelectron Spectroscopy. Anal. Bioanal. Chem. 2013, 405, 1479−1495. (53) Briggs, D.; Grant, J. T. Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy; IMP: Chichester, U.K., 2003. (54) Gulino, A.; Egdell, R. G.; Fragalà, I. Low-Temperature Stabilization of Tetragonal Zirconia by Antimony. J. Mater. Chem. 1996, 11, 1805−1809. (55) Gulino, A.; Fiorito, G.; Fragalà, I. Deposition of Thin Films of Cobalt Oxides by MOCVD. J. Mater. Chem. 2003, 13, 861−865. (56) Gulino, A.; La Delfa, S.; Fragalà, I.; Egdell, R. G. LowTemperature Stabilization of Tetragonal Zirconia by Bismuth. Chem. Mater. 1996, 8, 1287−1291. (57) Gulino, A.; Gupta, T.; Altman, M.; Schiavo, S. L.; Mineo, P. G.; Fragalà, I. L.; Evmenenko, G.; Dutta, P.; van der Boom, M. E. Selective Monitoring of Parts per Million Levels of CO by Covalently Immobilized Metal Complexes on Glass. Chem. Commun. 2008, 2900−2902. (58) Gulino, A.; Fragalà, I.; Scamporrino, E.; Vitalini, D. Similarities and Differences among Monolayers of a Free Base Porphyrin and Its Copper Complex: Synthesis and Characterization of a Luminescent Copper(II) Porphyrin Monolayer. J. Phys. Chem. C 2007, 111, 14125− 14130. (59) Gulino, A.; Mineo, P.; Fragalà, I. Spectroscopic and Morphological Investigation of an Optical pH Meter Based on a Porphyrin Monolayer Covalently Assembled on a Engineered Silica Surface. J. Phys. Chem. C 2007, 111, 1373−1377. (60) Gulino, A.; Mineo, P.; Scamporrino, E.; Vitalini, D.; Fragalà, I. Spectroscopic and Microscopic Characterization and Behavior of an Optical pH Meter Based on a Functional Hybrid Monolayer Molecular System: Porphyrin Molecules Covalently Assembled on a Molecularly Engineered Silica Surface. Chem. Mater. 2006, 18, 2404−2410. (61) Gulino, A.; Mineo, P.; Bazzano, S.; Vitalini, D.; Fragalà, I. Optical pH Meter by Means of a Porphyrin Monolayer Covalently 16219



Article

Characteristics, and Electronic Structure of a Tetravalent Tris(cyclopentadienyl)cerium Alkoxide Complex. Organometallics 1988, 7, 2360−2364. (79) Fragalà, I. L.; Gulino, A. In Fundamental and Technological Aspects of Organo-f-Elements Chemistry: Photoelectron Spectroscopy of fElement Organometallic Complexes; Marks, T. J., Fragalà, I. L., Eds.; NATO ASI Series C 155; D. Reidel Pub. Co.: Boston, 1985; pp 327− 360. (80) Shi, F. N.; Cunha-Silva, L.; Sá Ferreira, R. A.; Mafra, L.; Trindade, T.; Carlos, L. D.; Almeida Paz, F. A.; Rocha, J. Interconvertable Modular Framework and Layered Lanthanide(III)Etidronic Acid Coordination Polymers. J. Am. Chem. Soc. 2008, 130, 150−167. (81) Massue, J.; Quinn, S. J.; Gunnlaugsson, T. Lanthanide Luminescent Displacement Assays: the Sensing of Phosphate Anions Using Eu(III)-Cyclen-Conjugated Gold Nanoparticles in Aqueous Solution. J. Am. Chem. Soc. 2008, 130, 6900−6901. (82) Li, Y.; Yan, B. J. Hybrid Materials of MCM-41 Functionalized by Lanthanide (Tb3+, Eu3+) Complexes of Modified meta-Methylbenzoic Acid: Covalently Bonded Assembly and Photoluminescence. Solid State Chem. 2008, 181, 1032−1039. (83) Yan, B.; Lu, H.-F. Lanthanide-Centered Covalently Bonded Hybrids through Sulfide Linkage: Molecular Assembly, Physical Characterization, and Photoluminescence. Inorg. Chem. 2008, 47, 5601−5611. (84) Qiao, X.; Yan, B. Assembly, Characterization, and Photoluminescence of Hybrids Containing Europium(III) Complexes Covalently Bonded to Inorganic Si-O Networks/Organic Polymers by Modified β-Diketone. J. Phys. Chem. B 2008, 112, 14742−14750. (85) Altman, M.; Zenkina, O.; Evmenenko, G.; Dutta, P.; van der Boom, M. E. Molecular Assembly of a 3D-Ordered Multilayer. J. Am. Chem. Soc. 2008, 130, 5040−5041. (86) Liu, J. L.; Yan, B. Lanthanide (Eu3+, Tb3+) Centered Hybrid Materials using Modified Functional Bridge Chemical Bonded with Silica: Molecular Design, Physical Characterization, and Photophysical Properties. J. Phys. Chem. B 2008, 112, 10898−10907.

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