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Silver nanoparticles enhanced luminescence of Er3+ ions in boro-tellurite glasses
Materials Letters 112 (2013) 136–138
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Silver nanoparticles enhanced luminescence of Er3 þ ions in boro-tellurite glasses Zahra Ashur Said Mahraz 1, M.R. Sahar n, S.K. Ghoshal, M.R. Dousti, R.J. Amjad Advanced Optical Materials Research Group, Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor, Malaysia
art ic l e i nf o
a b s t r a c t
Article history: Received 24 June 2013 Accepted 29 August 2013 Available online 6 September 2013
Improving the optical properties of rare earth doped glasses for diverse optical applications is the current challenge in materials science and technology. We report for the first time, the enhancement of the visible emissions of the Er3 þ -doped zinc boro-tellurite glasses containing silver nanoparticles with mean diameter 4.5 nm. The surface plasmon band is observed at 630 nm. The enhancement in the luminescence is attributed to the localized electric field in vicinity of nanoparticles, while the concentration quenching is ascribed to the energy transfer from Er3 þ ions to the surface of nanoparticles. Our results suggest that proposed glasses are potential for photonic devices. & 2013 Elsevier B.V. All rights reserved.
Keywords: Optical materials and properties Nanoparticles Luminescence
1. Introduction Optical properties of the rare earth (RE) doped glasses are considered as one of the most interesting research areas due to their various applications, e.g. lasers, sensors, telecommunication, display devices, etc. Phenomena related to the interaction of light with RE-doped glasses containing metallic nanoparticles (NPs) have attracted much attention since the presence of NPs strongly influences their luminescence and nonlinear optical properties [1– 10]. As a result of interaction between electromagnetic field of excitation light with metallic NPs, the local electric field in vicinity of the lanthanide ions extremely enhances. Therefore, the intensities and probabilities of transitions within the f electronic shell of lanthanides are altered [11]. The enhancement is further intensified when the wavelength of the excitation or the luminescence beams are near to the surface plasmon resonance (SPR) frequency of metallic NPs and greater than the optical band gap energy of semiconducting NPs [8]. The electromagnetic oscillation of surface electrons is known as the localized surface plasmon and its frequency varies by the type, size, and shape of the metal nanostructure [7]. Thus, the formation of metallic NPs with specific size distribution embedded in the glass matrix is a challenging issue. The effect of the silver NPs on the luminescence properties of the erbium doped zinc tellurite glasses has recently been reported by Dousti et al. [5,6]. Kassab et al. [4] have also studied the effect of silver NPs on the luminescence of Pr3 þ , ions in different glass compositions. Singh et al. [9] have observed the enhancement of
n
Corresponding author. Tel.: þ 60 755 34050. E-mail addresses: [email protected] (Z. Ashur Said Mahraz), [email protected] (M.R. Sahar). 1 Tel.: þ60 75534050; fax: þ 60 75566162. 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.08.131
up-conversion emission in Er3 þ doped tellurite glass containing silver NPs and found that the heat-treatment can enhance the upconversion fluorescence by about four times due to large local field induced by the silver NPs. On the other hand, to our knowledge, the influence of metallic NPs on the erbium doped boro-tellurite glass is not studied. As previously reported, the optimum concentration of Er3 þ ions in zinc boro-tellurite glass is 0.5 mol% [12]. Thus, the aim of this letter is to study the effect of silver NPs on the optical properties of the proposed boro-tellurite glass.
2. Experimental procedure Melt quenching technique was used to prepare the glass samples with nominal compositions 30B2O3–10ZnO–(59.5x) TeO2–0.5Er2O3 xAgCl (x¼0, 0.1, 0.3, 0.5, 0.7, 1.0 and 1.5 mol%). The proper amounts of analytical grades zinc oxide, boric acid, tellurium dioxide, erbium oxide and silver chloride were mixed homogenously and melted at 950 1C for about 20 min. In order to obtain transparent viscous melt, the batches were stirred frequently and poured between two preheated stainless steel molds. The glass samples were kept at 300 1C for about 3 h to reduce the thermal and mechanical strains. The glasses were labeled as listed in Table 1. The amorphous nature of samples was confirmed (not shown here) using the Bruker D8 Advance X-ray diffractometer (XRD, Kα¼ 1.54 Å) working at 40 kV and 100 mA. Transmission electron microscope (Philips CM12) working at 200 kV was used. The specimens were prepared by dispersing the powder in acetone using ultrasonic bath. Optical absorption spectra were recorded in the wavelength range 400–1800 nm using a Shimadzu UV-PC3101 spectrophotometer. Luminescence measurement was performed in the wavelength range 500–800 nm under the excitation of 476 nm using a Perkin-Elmer Luminescence Spectrometer (LS 55).
Z. Ashur Said Mahraz et al. / Materials Letters 112 (2013) 136–138
Emission bands are enhanced owning to the presence of silver NPs up to 1.0 mol%. However, further increase in the concentration of NPs diminishes the emission intensities in entire visible range. Although, the primary reason for enhancement in the fluorescence of Er3 þ ions is the local field enhancement (LFE) induced by SPR of metal NPs, it cannot explain the reduction of the emission band of Er3 þ in S7 glass sample. The local field persistently grows with concentration of the Ag NPs until it saturates at concentration 1 mol%; this behavior was also reported by Le et al. [16].
3. Results and discussion
Optical Density (a.u.)
Fig. 1(a) shows the TEM image of Ag NPs in S2 glass sample. The TEM image clearly reveals homogeneously dispersion of spherical Ag NPs. Fig. 1(b) shows the Gaussian size distribution of Ag NPs in the corresponding TEM (glass S2). The diameter of the NPs varies from 3 to 10 nm with an average size 4.5 nm. The room temperature absorption spectra of the glass sample S2 is presented in Fig. 2. Seven transitions from the ground state 4 I15/2 to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2, 4F7/2 and 4F3/2 excited states were observed corresponding to the bands centered at 6553, 10,224, 12,484, 15,267, 19,230, 20,661 and 22,522 cm 1. Due to small concentration of Ag NPs and the overlap of the SPR band by Er3 þ absorption bands, no plasmon band is observed for S2–S7 glasses. Therefore, an Er3 þ -free sample doped with 1 mol% AgCl was prepared (labeled as S8) to display the plasmon peak of silver NPs. The UV–vis–IR absorption spectrum remarkably confirms the formation of noble metallic NPs. The inset of Fig. 2 presents the UV–vis absorption spectrum of latest sample (S8) with an absorption peak at around 630 nm. By and large, the plasmon peak position depends on the refractive index of the surrounding dielectric; the higher refractive index causes a red-shift in the wavelength of plasmon peak [13]. For example, the SPR for Ag NPs in sodalime silicate glasses with a refractive index around 1.5 appear around 410 nm [14], while our ZBT glasses have a relatively higher refractive index ( 2), thus the plasmon peak is generally red-shifted to 630 nm. The interactions between the closely spaced metallic NPs shift the plasmon peak to lower energies [15]. Thus, the red-shift of the SPR band can be attributed to Ag–Ag inter-particle distance. Fig. 3 shows the luminescence spectra of the glasses in the range of 500–800 nm under 476 nm excitation. Three bands are observed at 536, 550 and 632 nm and are attributed to transitions from 2H11/2, 4S3/2 and 4F9/2 levels to ground state, respectively.
400
TeO2
ZnO
Er2O3
AgCl
S1 S2 S3 S4 S5 S6 S7 S8
30 30 30 30 30 30 30 30
59.5 59.4 59.2 59.0 58.8 58.5 58.0 59.0
10 10 10 10 10 10 10 10
0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.0
0 0.1 0.3 0.5 0.7 1.0 1.5 1.0
1200
1600
Fig. 2. Absorption spectra of zinc boro-tellurite glasses with NPs (S2). Inset shows the surface plasmon band of silver NPs in glass S8 centered at 630 nm.
800
Intensity (a.u)
B2O3
800
Wavelength (nm)
Table 1 Proposed Er3 þ :Ag co-doped boro-tellurite glass composition (mol%) and their labels. Glass
137
S1 S2 S3 S4 S5 S6 S7
600
400
200
0 550
600
650
700
750
800
Wavelength (nm) Fig. 3. Emission spectra of Er3 þ :Ag co-doped zinc boro-tellurite glass.
70
Number (a.u.)
60 50 40 30 20 10 0 1
2
3
4
5
6
7
8
9
10
Cluster diameter (nm) Fig. 1. (a) TEM image of S2 glass sample. Black spots show the silver NPs. (b) The size distribution of Ag nanoparticles in S2 glass sample with a Gaussian distribution.
138
Z. Ashur Said Mahraz et al. / Materials Letters 112 (2013) 136–138
while further introduction of silver NPs resulted in luminescence quenching by ET from Er3 þ ions to Ag NPs. The results suggest that boro-tellurite glass could be a favorable host for the development of optoelectronic devices.
Acknowledgments Financial supports by Ministry of Higher Education of Malaysia (MOHE) and Research Management Center (RMC, UTM) through vote nos. 4L032 and 07J80 are highly acknowledged.
References
Fig. 4. Schematic energy level diagram of Er3 þ :Ag NPs co-doped boro-tellurite glass. Ground state absorption (GSA) under 576 nm excites the ion, which terminated to populate the lower-lying levels through non-raditaive (NR) decays. Cooperative energy transfer between erbium ions (CET) and energy transfer (ET) between erbium and NP are also shown.
The energy transfer (ET) from the metal to RE ions is mainly proposed to be an inefficient factor for luminescence enhancements, since the lifetime of metal is extremely shorter than the excited states of RE ions [3]. On the other hand, the quench can be described by ET from Er3 þ ions to Ag NPs (Er3 þ -Ag) and reabsorption by SPR of Ag NPs which is in resonance with the emissions from Er3 þ ions [3]. Fig. 4 illustrates the schematic energy level diagram of the Er3 þ ions in vicinity of a silver NP doped boro-tellurite glass. The excitation under 476 nm stimulates the ion from 4I15/2 to 4F7/2 level, where the multi-phonon non-radiative decays populate both (2H11/2 þ 4S3/2) and 4F9/2 excited states, and the green and red lines are generated, respectively. The presence of the B–O–B and O–B–O groups with relatively high phonon energies favors the multiphonon decays and results in strong red emission of the Er3 þ ions in our glass system. Moreover, 4F9/2 excited state can be populated by the cooperative energy transfers (CET) between two neighboring erbium ions in the present system. 4. Conclusion The influence of silver NPs concentration on the luminescence of erbium doped boro-tellurite glasses is reported. Maximum enhancement in visible fluorescence is obtained for 1 mol% of AgCl. The presence of intensified local electric field by silver NPs with mean diameter4.5 nm and the plasmon frequency around 630 nm is attributed as the major mechanism for luminescence enhancement,
[1] De Almeida R, Da Silva DM, Kassab LRP, de Araujo CB. Eu3 þ luminescence in tellurite glasses with gold nanoparticles. Optics Communications 2008;281:108–12. [2] Rivera VGA, Osorio SPA, Manzani D, Messaddeq Y, Nunes LAO, Margera Jr E. Growth of silver nano-particle embedded in tellurite glass: interaction between localized surface plasmon resonance and Er3 þ ions. Optical Materials 2011;33:888–92. [3] Malta OL, dos Santos MAC. Theoretical analysis of the fllourescence yield of rare earth ions in glasses containing small metallic particles. Chemical Physics Letters 1990;174:13–8. [4] Kassab LRP, de Araújo CB, Kobayashi RA, de Almeida Pinto R, da Silva DM. Influence of silver nanoparticles in the luminescence efficiency of Pr3 þ-doped tellurite glass. Journal of Applied Physics 2007;102:103515. [5] Dousti MR, Sahar MR, Ghoshal SK, Amjad RJ, Samavati AR. Effect of AgCl on spectroscopic properties of erbium doped zinc tellurite glass. Journal of Molecular Structure 2013;1035:6–12. [6] Dousti MR, Sahar MR, Amjad RJ, Ghoshal SK, Khorramnazari A, Dordizadeh Basirabad A, et al. Enhanced frequency upconversion in Er3 þ -doped sodium lead tellurite glass containing silver nanoparticles. The European Physical Journal D 2012;66:237. [7] Som T, Karmakar B. Nanosilver enhanced upconversion fluorescence of erbium ions in Er3 þ :Ag-antimony glass nanocomposites. Journal of Applied Physics 2009;105:013102. [8] Malta OL, Santa-Cruz PA, de Sa GF, Auzel F. Fluorescent enhancement induced by the presence of small silver particles in Eu3 þ doped materials. Journal of Luminescence 1985;33:261–72. [9] Xu S, Yang Z, Dai S, Wang G, Hu L, Jiang Z. Upconversion fluorescence spectroscopy of Er3 þ -doped lead oxyflouride germanate glass. Materials Letters 2004;58:1026–9. [10] Amjad RJ, Sahar MR, Dousti MR, Ghoshal SK, Jamaludin MNA. Surface enhance Raman scattering and plasmon enhanced fluorescence in zinc-tellurite glass. Optics Express 2013;21(12):14282. [11] Mertens H, Koenderink AF, Polman A. Plasmon-enhanced luminescence near noble-metal nanospheres: comparison of exact theory and an improved Gersten and Nitzan model. Physical Review B 2007;76:115123. [12] Ashur Said Mahraz Z, Sahar MR, Ghoshal SK, Dousti MR. Concentration dependent luminescence quenching of Er3 þ -doped zinc boro-tellurite glass. Journal of Luminescence 2013;144:139–45. [13] Mulvaney P. Surface plasmon spectroscopy of nanosized metal particles. Langmuir 1996;12:788–800. [14] Gonella F, Mazzoldi P. In: Nalwa HS, editor. Handbook of nanostructured materials and nanotechnology. San Diego: Academic; 2000. [15] Su KH, Wei QH, Zhang X, Mock JJ, Smith DR, Schultz S. Interparticle coupling effects on plasmon resonances of nanogold particles. Nano Lett 2003;3 (8):1087–90. [16] Le F, Brandl DW, Urzhumov YA, Wang H, Kundu J, Halas NJ, et al. Metallic nanoparticles arrays: a common suitable for both surface-enhanced Raman scattering and surface-enhanced infrared absorption. ACS Nano 2008;2:707–18.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Silver nanoparticles enhanced luminescence of Er3 þ ions in boro-tellurite glasses Zahra Ashur Said Mahraz 1, M.R. Sahar n, S.K. Ghoshal, M.R. Dousti, R.J. Amjad Advanced Optical Materials Research Group, Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor, Malaysia
art ic l e i nf o
a b s t r a c t
Article history: Received 24 June 2013 Accepted 29 August 2013 Available online 6 September 2013
Improving the optical properties of rare earth doped glasses for diverse optical applications is the current challenge in materials science and technology. We report for the first time, the enhancement of the visible emissions of the Er3 þ -doped zinc boro-tellurite glasses containing silver nanoparticles with mean diameter 4.5 nm. The surface plasmon band is observed at 630 nm. The enhancement in the luminescence is attributed to the localized electric field in vicinity of nanoparticles, while the concentration quenching is ascribed to the energy transfer from Er3 þ ions to the surface of nanoparticles. Our results suggest that proposed glasses are potential for photonic devices. & 2013 Elsevier B.V. All rights reserved.
Keywords: Optical materials and properties Nanoparticles Luminescence
1. Introduction Optical properties of the rare earth (RE) doped glasses are considered as one of the most interesting research areas due to their various applications, e.g. lasers, sensors, telecommunication, display devices, etc. Phenomena related to the interaction of light with RE-doped glasses containing metallic nanoparticles (NPs) have attracted much attention since the presence of NPs strongly influences their luminescence and nonlinear optical properties [1– 10]. As a result of interaction between electromagnetic field of excitation light with metallic NPs, the local electric field in vicinity of the lanthanide ions extremely enhances. Therefore, the intensities and probabilities of transitions within the f electronic shell of lanthanides are altered [11]. The enhancement is further intensified when the wavelength of the excitation or the luminescence beams are near to the surface plasmon resonance (SPR) frequency of metallic NPs and greater than the optical band gap energy of semiconducting NPs [8]. The electromagnetic oscillation of surface electrons is known as the localized surface plasmon and its frequency varies by the type, size, and shape of the metal nanostructure [7]. Thus, the formation of metallic NPs with specific size distribution embedded in the glass matrix is a challenging issue. The effect of the silver NPs on the luminescence properties of the erbium doped zinc tellurite glasses has recently been reported by Dousti et al. [5,6]. Kassab et al. [4] have also studied the effect of silver NPs on the luminescence of Pr3 þ , ions in different glass compositions. Singh et al. [9] have observed the enhancement of
n
Corresponding author. Tel.: þ 60 755 34050. E-mail addresses: [email protected] (Z. Ashur Said Mahraz), [email protected] (M.R. Sahar). 1 Tel.: þ60 75534050; fax: þ 60 75566162. 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.08.131
up-conversion emission in Er3 þ doped tellurite glass containing silver NPs and found that the heat-treatment can enhance the upconversion fluorescence by about four times due to large local field induced by the silver NPs. On the other hand, to our knowledge, the influence of metallic NPs on the erbium doped boro-tellurite glass is not studied. As previously reported, the optimum concentration of Er3 þ ions in zinc boro-tellurite glass is 0.5 mol% [12]. Thus, the aim of this letter is to study the effect of silver NPs on the optical properties of the proposed boro-tellurite glass.
2. Experimental procedure Melt quenching technique was used to prepare the glass samples with nominal compositions 30B2O3–10ZnO–(59.5x) TeO2–0.5Er2O3 xAgCl (x¼0, 0.1, 0.3, 0.5, 0.7, 1.0 and 1.5 mol%). The proper amounts of analytical grades zinc oxide, boric acid, tellurium dioxide, erbium oxide and silver chloride were mixed homogenously and melted at 950 1C for about 20 min. In order to obtain transparent viscous melt, the batches were stirred frequently and poured between two preheated stainless steel molds. The glass samples were kept at 300 1C for about 3 h to reduce the thermal and mechanical strains. The glasses were labeled as listed in Table 1. The amorphous nature of samples was confirmed (not shown here) using the Bruker D8 Advance X-ray diffractometer (XRD, Kα¼ 1.54 Å) working at 40 kV and 100 mA. Transmission electron microscope (Philips CM12) working at 200 kV was used. The specimens were prepared by dispersing the powder in acetone using ultrasonic bath. Optical absorption spectra were recorded in the wavelength range 400–1800 nm using a Shimadzu UV-PC3101 spectrophotometer. Luminescence measurement was performed in the wavelength range 500–800 nm under the excitation of 476 nm using a Perkin-Elmer Luminescence Spectrometer (LS 55).
Z. Ashur Said Mahraz et al. / Materials Letters 112 (2013) 136–138
Emission bands are enhanced owning to the presence of silver NPs up to 1.0 mol%. However, further increase in the concentration of NPs diminishes the emission intensities in entire visible range. Although, the primary reason for enhancement in the fluorescence of Er3 þ ions is the local field enhancement (LFE) induced by SPR of metal NPs, it cannot explain the reduction of the emission band of Er3 þ in S7 glass sample. The local field persistently grows with concentration of the Ag NPs until it saturates at concentration 1 mol%; this behavior was also reported by Le et al. [16].
3. Results and discussion
Optical Density (a.u.)
Fig. 1(a) shows the TEM image of Ag NPs in S2 glass sample. The TEM image clearly reveals homogeneously dispersion of spherical Ag NPs. Fig. 1(b) shows the Gaussian size distribution of Ag NPs in the corresponding TEM (glass S2). The diameter of the NPs varies from 3 to 10 nm with an average size 4.5 nm. The room temperature absorption spectra of the glass sample S2 is presented in Fig. 2. Seven transitions from the ground state 4 I15/2 to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2, 4F7/2 and 4F3/2 excited states were observed corresponding to the bands centered at 6553, 10,224, 12,484, 15,267, 19,230, 20,661 and 22,522 cm 1. Due to small concentration of Ag NPs and the overlap of the SPR band by Er3 þ absorption bands, no plasmon band is observed for S2–S7 glasses. Therefore, an Er3 þ -free sample doped with 1 mol% AgCl was prepared (labeled as S8) to display the plasmon peak of silver NPs. The UV–vis–IR absorption spectrum remarkably confirms the formation of noble metallic NPs. The inset of Fig. 2 presents the UV–vis absorption spectrum of latest sample (S8) with an absorption peak at around 630 nm. By and large, the plasmon peak position depends on the refractive index of the surrounding dielectric; the higher refractive index causes a red-shift in the wavelength of plasmon peak [13]. For example, the SPR for Ag NPs in sodalime silicate glasses with a refractive index around 1.5 appear around 410 nm [14], while our ZBT glasses have a relatively higher refractive index ( 2), thus the plasmon peak is generally red-shifted to 630 nm. The interactions between the closely spaced metallic NPs shift the plasmon peak to lower energies [15]. Thus, the red-shift of the SPR band can be attributed to Ag–Ag inter-particle distance. Fig. 3 shows the luminescence spectra of the glasses in the range of 500–800 nm under 476 nm excitation. Three bands are observed at 536, 550 and 632 nm and are attributed to transitions from 2H11/2, 4S3/2 and 4F9/2 levels to ground state, respectively.
400
TeO2
ZnO
Er2O3
AgCl
S1 S2 S3 S4 S5 S6 S7 S8
30 30 30 30 30 30 30 30
59.5 59.4 59.2 59.0 58.8 58.5 58.0 59.0
10 10 10 10 10 10 10 10
0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.0
0 0.1 0.3 0.5 0.7 1.0 1.5 1.0
1200
1600
Fig. 2. Absorption spectra of zinc boro-tellurite glasses with NPs (S2). Inset shows the surface plasmon band of silver NPs in glass S8 centered at 630 nm.
800
Intensity (a.u)
B2O3
800
Wavelength (nm)
Table 1 Proposed Er3 þ :Ag co-doped boro-tellurite glass composition (mol%) and their labels. Glass
137
S1 S2 S3 S4 S5 S6 S7
600
400
200
0 550
600
650
700
750
800
Wavelength (nm) Fig. 3. Emission spectra of Er3 þ :Ag co-doped zinc boro-tellurite glass.
70
Number (a.u.)
60 50 40 30 20 10 0 1
2
3
4
5
6
7
8
9
10
Cluster diameter (nm) Fig. 1. (a) TEM image of S2 glass sample. Black spots show the silver NPs. (b) The size distribution of Ag nanoparticles in S2 glass sample with a Gaussian distribution.
138
Z. Ashur Said Mahraz et al. / Materials Letters 112 (2013) 136–138
while further introduction of silver NPs resulted in luminescence quenching by ET from Er3 þ ions to Ag NPs. The results suggest that boro-tellurite glass could be a favorable host for the development of optoelectronic devices.
Acknowledgments Financial supports by Ministry of Higher Education of Malaysia (MOHE) and Research Management Center (RMC, UTM) through vote nos. 4L032 and 07J80 are highly acknowledged.
References
Fig. 4. Schematic energy level diagram of Er3 þ :Ag NPs co-doped boro-tellurite glass. Ground state absorption (GSA) under 576 nm excites the ion, which terminated to populate the lower-lying levels through non-raditaive (NR) decays. Cooperative energy transfer between erbium ions (CET) and energy transfer (ET) between erbium and NP are also shown.
The energy transfer (ET) from the metal to RE ions is mainly proposed to be an inefficient factor for luminescence enhancements, since the lifetime of metal is extremely shorter than the excited states of RE ions [3]. On the other hand, the quench can be described by ET from Er3 þ ions to Ag NPs (Er3 þ -Ag) and reabsorption by SPR of Ag NPs which is in resonance with the emissions from Er3 þ ions [3]. Fig. 4 illustrates the schematic energy level diagram of the Er3 þ ions in vicinity of a silver NP doped boro-tellurite glass. The excitation under 476 nm stimulates the ion from 4I15/2 to 4F7/2 level, where the multi-phonon non-radiative decays populate both (2H11/2 þ 4S3/2) and 4F9/2 excited states, and the green and red lines are generated, respectively. The presence of the B–O–B and O–B–O groups with relatively high phonon energies favors the multiphonon decays and results in strong red emission of the Er3 þ ions in our glass system. Moreover, 4F9/2 excited state can be populated by the cooperative energy transfers (CET) between two neighboring erbium ions in the present system. 4. Conclusion The influence of silver NPs concentration on the luminescence of erbium doped boro-tellurite glasses is reported. Maximum enhancement in visible fluorescence is obtained for 1 mol% of AgCl. The presence of intensified local electric field by silver NPs with mean diameter4.5 nm and the plasmon frequency around 630 nm is attributed as the major mechanism for luminescence enhancement,
[1] De Almeida R, Da Silva DM, Kassab LRP, de Araujo CB. Eu3 þ luminescence in tellurite glasses with gold nanoparticles. Optics Communications 2008;281:108–12. [2] Rivera VGA, Osorio SPA, Manzani D, Messaddeq Y, Nunes LAO, Margera Jr E. Growth of silver nano-particle embedded in tellurite glass: interaction between localized surface plasmon resonance and Er3 þ ions. Optical Materials 2011;33:888–92. [3] Malta OL, dos Santos MAC. Theoretical analysis of the fllourescence yield of rare earth ions in glasses containing small metallic particles. Chemical Physics Letters 1990;174:13–8. [4] Kassab LRP, de Araújo CB, Kobayashi RA, de Almeida Pinto R, da Silva DM. Influence of silver nanoparticles in the luminescence efficiency of Pr3 þ-doped tellurite glass. Journal of Applied Physics 2007;102:103515. [5] Dousti MR, Sahar MR, Ghoshal SK, Amjad RJ, Samavati AR. Effect of AgCl on spectroscopic properties of erbium doped zinc tellurite glass. Journal of Molecular Structure 2013;1035:6–12. [6] Dousti MR, Sahar MR, Amjad RJ, Ghoshal SK, Khorramnazari A, Dordizadeh Basirabad A, et al. Enhanced frequency upconversion in Er3 þ -doped sodium lead tellurite glass containing silver nanoparticles. The European Physical Journal D 2012;66:237. [7] Som T, Karmakar B. Nanosilver enhanced upconversion fluorescence of erbium ions in Er3 þ :Ag-antimony glass nanocomposites. Journal of Applied Physics 2009;105:013102. [8] Malta OL, Santa-Cruz PA, de Sa GF, Auzel F. Fluorescent enhancement induced by the presence of small silver particles in Eu3 þ doped materials. Journal of Luminescence 1985;33:261–72. [9] Xu S, Yang Z, Dai S, Wang G, Hu L, Jiang Z. Upconversion fluorescence spectroscopy of Er3 þ -doped lead oxyflouride germanate glass. Materials Letters 2004;58:1026–9. [10] Amjad RJ, Sahar MR, Dousti MR, Ghoshal SK, Jamaludin MNA. Surface enhance Raman scattering and plasmon enhanced fluorescence in zinc-tellurite glass. Optics Express 2013;21(12):14282. [11] Mertens H, Koenderink AF, Polman A. Plasmon-enhanced luminescence near noble-metal nanospheres: comparison of exact theory and an improved Gersten and Nitzan model. Physical Review B 2007;76:115123. [12] Ashur Said Mahraz Z, Sahar MR, Ghoshal SK, Dousti MR. Concentration dependent luminescence quenching of Er3 þ -doped zinc boro-tellurite glass. Journal of Luminescence 2013;144:139–45. [13] Mulvaney P. Surface plasmon spectroscopy of nanosized metal particles. Langmuir 1996;12:788–800. [14] Gonella F, Mazzoldi P. In: Nalwa HS, editor. Handbook of nanostructured materials and nanotechnology. San Diego: Academic; 2000. [15] Su KH, Wei QH, Zhang X, Mock JJ, Smith DR, Schultz S. Interparticle coupling effects on plasmon resonances of nanogold particles. Nano Lett 2003;3 (8):1087–90. [16] Le F, Brandl DW, Urzhumov YA, Wang H, Kundu J, Halas NJ, et al. Metallic nanoparticles arrays: a common suitable for both surface-enhanced Raman scattering and surface-enhanced infrared absorption. ACS Nano 2008;2:707–18.