DOI 10.1007/s10717-017-9960-x Glass and Ceramics, Vol. 74, Nos. 5 – 6, September, 2017 (Russian Original, Nos. 5 – 6, May – June, 2017)
UDC 666.113.654’82’27:546’621:666.11.01:539.213.1
PARTICULARS OF THE FORMATION OF LUMINESCENT AND PLASMON NANOPARTICLES OF GOLD IN PHOSPHATE GLASS G. Yu. Shakhgil’dyan,1, 3 A. A. Stepko,1 V. N. Sigaev,1 and G. E. Malashkevich2 Translated from Steklo i Keramika, No. 6, pp. 6 – 9, June, 2017.
It is shown that gold nanoclusters and nanoparticles, possessing luminescence and plasmon properties depending on size, can form in potassium-aluminum-phosphate glass as a result of heat-treatment at temperatures below Tg . Key words: gold nanoclusters, gold nanoparticles, phosphate glass, luminescence, surface plasmon resonance.
Class containing gold nanoparticles has been known now for more than 2000 years. For a long time such glass was used for coloring articles — art objects, decorations, stained-glass windows — in saturated shades of red color. The nature of this coloring was first understood only in the 20th century, when the structure and properties of metal nanoparticles were studied and localized plasmon resonance effect (LPR), consisting of collective oscillations of the electron gas in a nanoparticles and manifested as an increase of the extinction of incident radiation at the resonance wavelength, was described. For gold nanoparticles the resonance wavelength lies in the visible range of the spectrum, and depending on their size and shape they can absorb in the green and red regions [1]. The increasing interest in glassy materials, activated by nanoparticles of gold and other metals, is due to the possibility of using their unique optical and nonlinearly optical properties in photonics: creation of ultrafast optical switches, increasing the efficiency of lazing, production of plasmon waveguide structures for information transmission, and so on [2]. The application of the indirect effect of gold nanoparticles on the increase in the can efficiency of conversion of short wavelength UV light into the visible range of the spectrum by Au–Ln containing glassy materials also opens up interesting possibilities [3]. However, together with nanoparticles manifesting LPR, so-called plasmon nanoparticles with sizes 5 – 100 nm, there 1 2 3
also exists a class of objects with reduced size — nano clusters, whose structural particularity is the presence of discrete energy levels. This feature is largely responsible for the properties of nanoclusters — extinction due to LPR practically does not appear in them, but appreciable recombination luminescence is possible [1]. Luminescent gold and silver nanoparticles are being actively studied for applications as molecular sensors and fluorophores for cellular bioimaging [4]. The work on the formation and study of nanoclusters in glass has largely been devoted to silver nanoclusters [5 – 7], while at the same time there are virtually no data on the formation of gold nanoclusters in glass. An understanding of the processes resulting in the formation of gold nanoclusters and nanoparticles in glass is important for developing the fundamental ideas about nanoscale transformations in the structure of glass and for practical applications — the possibility of controlled formation of luminescence and plasmon nanoparticles opens up ways for super dense writing of information and the development of integrated nonlinearly optical devices. In the present work we have shown the possibility of formation of gold nanoclusters and nanoparticles possessing luminescence and plasmon properties depending on size in potassium-aluminum-phosphate glass upon heat treatment at temperatures below Tg . The investigations were performed on a sample of class with the following molar composition (%): five dots with 0.01 wt.% Au above 100%. This glass composition is called R60-A. The method for synthesizing the class is described in detail in [8]. The glass samples after synthesis were transparent, uniform, and completely x-ray amorphous. Differen-
D. I. Mendeleev Russian University of Chemical Technology, Moscow, Russia. B. I. Stepanov Institute of Physics, National Academy of Science of Belarus, Minsk, Belarus. E-mail:
[email protected].
196 0361-7610/17/0506-0196 © 2017 Springer Science+Business Media New York
Particulars of the Formation of Luminescent and Plasmon Nanoparticles of Gold in Phosphate Glass
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Optical density
Luminescence intensity, arb. units
Wavelength, nm
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Fig. 1. Optical density spectrum (dashed line, curves 1 – 4 ) and luminescence spectra (solid lines, curves 5 – 8 ) of the sample R60-A heat-treated at the temperatures: 2, 8 ) 340°C; 3, 7 ) 390°C; 4, 6 ) 440°C; 1, 5 ) no heat treatment.
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tial-scanning calorimetry showed that the temperature Tg of the glass was 516°C. To study the influence of temperature on the possibility of formation of gold nanoparticles in the glass on a 60 ´ 10 ´ 2 mm plane-parallel class sample he treatment was performed in a gradient furnace in the temperature range 340 – 440°C. A Shimadzu UV-3600 spectrophotometer was used to obtain the optical density spectra; an SDL-2 spectrofluorimeter was used to obtain the luminescence spectrum at temperature T = 298 K. The average diameter of the gold nanoparticles formed in the glass was determined by analyzing the LPR band according to the relation
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. . Photon energy, eV
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440°C are displayed in Fig. 1. The optical density spectra show that as a result of the treatment of the glass a band, whose intensity increases with increasing temperature, appears at 2.3 eV. The appearance of this band is due to the LPR effect, characteristic for gold nanoparticles larger than 5 nm [9]. The dynamics of the change in the optical density spectrum of a sample with increasing treatment temperature graphically demonstrates the formation of gold nanoparticles in glass — gold atoms and nano clusters, dispersed in the glass matrix and not manifesting the LPR effect, gradually aggregate under the action of temperature into nanoparticles with sizes sufficient for the appearance of LPR. According to calculations the size of the nanoparticles with he treatment increases from about 3 up to 6.5 nm (Fig. 2). It is worth noting that the computational method used makes it possible to determine only the size of the nanoparticles possessing LPR; the pre-plasmon gold nanoparticles and nanoclusters are much smaller, 0.5 – 2.0 nm. It is evident in the luminescence spectra upon excitation wavelength 280 nm (see Fig. 1) that before he treatment lu-
D = 2vF (Dw) – 1, where D is the diameter of the particles; vF is the velocity of the electrons at the Fermi level in gold nanoparticles, 1.4 ´ 1015 nm/sec; and, Dw is the total width at half height of the LPR band of the gold nanoparticles [9]. The optical density and luminescence spectra of the sample R60-A before and after heat treatment in the range 340 –
Fig. 2. Optical density in the band lmax = 530 nm (p), intensity of the luminescence band with lmax = 550 nm (lexc = 280 nm) (;), and the sizes of the gold nanoparticles ()) of the sample R60-A versus heat treatment temperature.
, ,
Treatment temperature, °C
Particle diameter, nm
,
Optical density
Luminescence intensity, arb. units
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minescence is practically absent in the glass, while heat treatment at 340°C results in the appearance of a wide luminescence band peaking at 2.25 eV, whose intensity is more than in order of magnitude greater than that of the luminescence of the sample before he treatment. Subsequent heat treatment of the samples at temperatures up to 440°C results in gradual reduction of luminescence intensity. The studied luminescence peaking at 2.2 – 2.4 eV is characteristic for gold nano clusters [10, 11] and is a result of recombination of electrons formed under exultation in the UV range in the sp conduction band and holes in the d valence band of gold nano clusters. As was shown, the radical difference of the properties of nano clusters and nanoparticles is associated with their electronic structure. The electron levels of plasmon nanoparticles are discrete, but they are arranged so densely that the distance between the upper free and lower occupied levels remain minimal, creating a density of states for which the electrons can directly occupy overlying levels and participate in conduction. As a result of such a structure of the electronic levels there is no luminescence in the nanoparticles. In nano clusters, instead of a continuous density of electronic states, there is a discrete set of electronic levels with quite wide energy gap and rated to recombination processes (luminescence) are possible [12]. The describes results of the analysis of the optical spectra of a sample of R60-A agree with the structure and properties of gold nanoparticles and nano clusters and demonstrate the possibility of the formation of plasmon as well as luminescence particles in the glass. Figure 2 displays the optical density in the LPR band of gold nanoparticles and the intensity of the luminescence band of gold nano clusters as functions of the treatment temperature. It is evident that as temperature increases from 340 up to four and 40°C, the intensity of luminescence drops, while the intensity of the LPR band increases, as does the size of the gold nanoparticles. The obtained results agree with the data of [7], where upon he treatment of a sample of sink-phosphate glass the luminescence intensity of the formed silver nano clusters dropped at the same time as the optical density increased as a result of LPR of the formed silver nanoparticles. The demonstrated possibility of separate formation of gold nano clusters and nanoparticles will be realized in the future using the approaches of femtosecond laser modification and will make it possible to create in the interior volume of glass masses of luminescence and plasmon microstruc-
G. Yu. Shakhgil’dyan et al.
tures and waveguides, which will find application for super dance writing and transmission of information. This work was supported by the Ministry of Education and Science of the Russian Federation (contract 14.Z50.31.0009). REFERENCES 1. K. L. Kelly, E. Coronado, L. L. Zhao, and G. C. Schatz, “The optical properties of metal nanoparticles: the influence of size, shape, and dielectric environment,” J. Phys. Chem. B, 107(3), 668 – 677 (2002). 2. P. Chakraborty, “Metal nanoclusters in glasses as nonlinear photonic materials,” J. Mater. Sci., 33, 2235 – 2249 (1998). 3. G. E. Malashkevich, O. V. Chukova, S. G. Nedilko, et al., “Influence of gold nanoparticles on luminescence of Eu3+ ions sensitized by structural defects in germanate films,” J. Phys. Chem. C, 120(28), 15369 – 15377 (2016). 4. S. Choi and R. M. Dickson, “Developing luminescent silver nanodots for biological applications,” Chem. Soc. Rev., 41(5), 1867 – 1891 (2012). 5. V. P. Afanas’ev, E. V. Kolobkova, N. V. Nikonorov, et al., “New luminescent glasses and glass ceramics and their prospects in thin-film solar energetics,” Opt. Zh., 80(10), 69 – 79. 6. I. Belharouak, C. Parent, B. Tanguy, et al., “Silver aggregates in photoluminescent phosphate glasses of the Ag2O–ZnO–P2O5 system,” J. Non-Cryst. Solids, 244(2), 238 – 249 (1999). 7. N. Marquestaut, Y. Petit, A. Royon, et al., “Three-dimensional silver nanoparticle formation using femtosecond laser irradiation in phosphate glasses: analogy with photography,” Adv. Funct. Mater., 24, 5824 – 5832 (2014). 8. V. I. Savinkov, G. Yu. Shakhgil’dyan, A. Paleari, and V. N. Sigaev, “Synthesis of optically uniform glasses containing gold nanoparticles: Spectral and nonlinear optical properties,” Steklo Keram., No. 4, 35 – 40 (2013); V. I. Savinkov, G. Yu. Shakhgil’dyan, A. Paleari, and V. N. Sigaev, “Synthesis of optically uniform glasses containing gold nanoparticles: Spectral and nonlinear optical properties,” Glass Ceram., 70(3 – 4), 143 – 148 (2013). 9. V. N. Sigaev, V. I. Savinkov, G. Y. Shakhgildyan, A. Paleari, et al., “Spatially selective Au nanoparticle growth in laser-quality glass controlled by UV-induced phosphate-chain cross-linkage,” Nanotechnology, 24, 225 – 302 (2013). 10. J. Wilcoxon, J. Martin, F. Parsapour, et al., “Photoluminescence from nanosize gold clusters,” J. Chem. Phys., 108, 9137 – 9143 (1998). 11. E. Dulkeith, T. Niedereichholz, T. A. Klar, et al., “Plasmon emission in photoexcited gold nanoparticles,” Phys. Rev. B, 70, 205424 – 205427 (2004). 12. R. L. Johnston, Atomic and Molecular Clusters, Masters Series in Physics and Astronomy, Taylor & Francis, London – New York (2002).
