Nagabhushana, K.N Narasimhamurthy, Photoluminescence and photocatalytic properties of novel Bi2O3:Sm3+ nanophosphor, Journal of Science: Advanced Materials and Devices, https://doi.org/1
Trang 1To appear in: Journal of Science: Advanced Materials and Devices
Received Date: 2 May 2019
Revised Date: 18 August 2019
Accepted Date: 6 September 2019
Please cite this article as: S Ashwini, S.C Prashantha, R Naik, Y.V Naik, H Nagabhushana,
K.N Narasimhamurthy, Photoluminescence and photocatalytic properties of novel Bi2O3:Sm3+
nanophosphor, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/
j.jsamd.2019.09.001
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Trang 2Photoluminescence and photocatalytic properties of novel Bi 2 O 3 :Sm 3+ nanophosphor
S Ashwini a,b , S.C Prashantha b *, Ramachandra Naik c* , Yashwanth V Naik d , H
Department of Physics, New Horizon College of Engineering, Bengaluru-560103, India
Trang 3Photoluminescence and Photocatalytic properties of novel
Bi2O3:Sm3+nanophosphor
Abstract
The current work involves studies of the synthesis, characterization and photoluminescence for Sm3+ (1-11 mol %) doped Bi2O3 nanophosphors (NPs) by a solution combustion method The average particle size was determined using powder X-ray diffraction (PXRD) and found
to be in the range of 13- 30 nm The Kubelka-Munk (K-M) function was used to assess the energy gap of Sm3+ doped Bi2O3 nanophosphors which was found to be 2.92- 2.96 eV From the Emission spectra, the Judd–Ofelt parameters (Ω2 and Ω4), the transition probabilities (AT), the quantum efficiency (η), the luminescence lifetime (τr), the colour chromaticity coordinates (CIE) and the correlated colour temperature (CCT) values were estimated and discussed in detail The CIE chromaticity co-ordinates were close to the NTSC (National Television Standard Committee) standard value of Orange emission Using the Langmuir-Hinshelwood model and Acid Red-88, the photocatalytic activity results showed that Bi2O3:
Sm3+ NPs are potential materials for the development of an efficient photocatalyst for environmental remediation The obtained results prove that the Bi2O3:Sm3+ nanophosphors synthesised by this method can potentially be used for Solid State display and Photocatalyst
Keywords: Bi2O3:Sm3+, Photoluminescence, Judd- Ofelt, CIE and CCT
* Corresponding authors
E-mail: scphysics@gmail.com (Prashantha S.C), Tel.: +91 9886021344,
email: rcnaikphysics@gmail.com (Ramachandra Naik), Tel.:+91 7204408041
Trang 41 Introduction
Lanthanide ions doped (Ln3+) nanophosphors (NPs) have gained massive attention owing to their potential applications in various fields ranging from display [1], solar cells [2], bio- imaging [3], solid state lasers [4], remote photo activation [5], temperature sensors [6] and drug release [7]
Furthermore, NPs should possess superior physicochemical characteristics, such as long lifetimes, large anti- Stokes shifts, high penetration depth, low toxicity, as well as high resistance to photo bleaching [8] Bismuth is the only nontoxic heavy metal that can easily be purified in large quantities [9]
The semiconductors such as Bi2MoO6 , BiOX (X=Cl, Br, I), BiVO4 and Bi2O3 have a high refractive index and excellent properties for visible light absorb ion, photoluminescence, dielectric permittivity, photoconductivity, large oxygen ion conductivity, and, noteworthy, for photocatalytic activity [10-12]
At present, the photocatalysis technology has been anticipated to be a perfect “green” technology by the usage of solar energy in many fields such as, water-splitting [13], solar cell [14], water and air purification, organic waste degradation [15], CO2 reduction [16] etc The decomposition of dye contaminants in contaminated water, as a branch of photocatalysis, has attracted great attention To date, with the exception of intensive research on conventional photocatalysts such as TiO2, ZnO, ZrO2 and other semiconductors with a wide band gap [17], the finding out of new photocatalysts with sturdy degradation abilities has become additionally important Thus, we can consider Bi2O3 as a suitable host material, which is having all these features
Bismuth oxide (Bi2O3) is a semiconductor with attractive optical and electronic properties Because of these properties, Bi2O3 has become an important material for several applications such as fuel cells [18], photocatalysts [19], gas sensors [20], and electronic components [21] Another significant characteristic of Bi2O3 is its polymorphism, which results in 5 polymorphic forms (α, β, γ, δ and ω) with different structures and properties [22], among them monoclinic α which is stable at room temperature and face-centered cubic δ that
is stable at high temperature There are various methods available for the synthesis of Bi2O3nanophosphors viz., sonochemical, microwave irradiation, hydrothermal, chemical vapour
Trang 5deposition, micro-emulsion, surfactant thermal strategy, sol-gel approach, solution combustion and electro-spinning [23, 24]
In this work we report the synthesis of Bi2-xO3: Smx (x= 0.01 to 0.11) NPs via a simple low temperature solution combustion method Compared with the conventional methods adopted for synthesis, the solution combustion method is advantageous in view of its low temperature and reduced time consumption which result in a high degree of crystallinity and homogeneity The synthesised nanophosphor is characterized by PXRD and DRS The effect of Sm3+ doping on the photoluminescence properties were studied in detail for their possible usage in display applications
2 Experimental
Synthesis of Bi2-xO3: Smx (x= 0.01 to 0.11)
The synthesis of Bi2-xO3: Smx (x= 0.01 to 0.11) via solution combustion method was made using analytical grade Bismuth nitrate (Bi(NO3)3.5H2O: 99.99%, Sigma Aldrich Ltd.), Samarium nitrate ( Sm(NO3)3.6H2O: 99.99%, Sigma Aldrich Ltd) as dopant and Urea as fuel
In a cylindrical Petri dish (300 ml), the aqueous solution containing stoichiometric quantity of reactants were taken such that Oxidizer (Bi (NO3)3.5H2O) to Fuel (Urea) ratio is 1 (O/F=1) [25] and introduced into a pre heated muffle furnace at temperature of 400 ±10 oC Thermal dehydration of the reaction mixture takes place and auto-ignites with liberation of gaseous products resulting in the nano powders Finally, the so-prepared powders were calcined at
600 oC for 3 h The theoretical equation, assuming complete combustion of the redox mixture used for the synthesis of Bi2O3, can be written as:
Photocatalytic Activity of Bi 2 O 3 :Sm 3+
At room temperature, the experiment was conducted in a reactor by utilizing a 125 W
mercury vapour lamp as the UV light source (λ=254nm) Using Acid red dye 88 (AR-88) as a
model dye, the UV light photocatalytic activities of Bi2O3:Sm3+ NPs were evaluated In this experiment, 30 mg of synthesized Bi2O3:Sm3+ NPs was dissolved completely into 10 ppm of AR-88 dye solution and stirred continuously to form a uniform solution At each 15 min, 5
ml of the dye solution was inhibited and tested by a UV-Vis spectrophotometer by means of the typical adsorption band at 510 nm after centrifugation for the computation of the disintegration of dye [26]
Trang 6Characterization
Crystal morphology of the synthesised NPs was determined by PXRD using X-ray diffractometer (Shimadzu) (V-50 kV, I-20 mA, λ-1.541Å, scan rate of 2o min-1) Photoluminescence studies are made using Horiba, (model fluorolog-3, xenon-450 W) Spectroflourimeter at Room Temperature Fluor Essence™ software is used for spectral analysis DRS studies of the samples were performed using Shimadzu UV- 2600 in the range 200–800 nm
3 Results and Discussion
3.1 PXRD studies
Fig 1 shows the Powder X-ray diffraction (PXRD) pattern of undoped and Sm3+ (1-11 mol
%) doped Bi2O3 NPs All the recorded peaks were indexed to the Cubic phase of Bi2O3 (JCPDS card No.52-1007, Space Group: Fm-3m (no.225)), suggesting high purity and crystallinity of the synthesized powders As the acceptable percentage difference Dr (ionic radii) [27] is less than 15% between Bi3+ and Sm3+ ions, Sm3+ ions substitute the Bi3+ ions in the Bi2O3 host
Bi2O3:Sm3+ (1-11 mol %) samples These are in the range of13-30 nm which indicates that,
as doping concentration increases, crystallite sizes decrease
3.2 Diffuse Reflectance Spectroscopy studies
To evaluate the energy band gap, the diffuse reflectance spectra (DRS) of Bi2O3: Sm3+NPs were carried out and shown in Fig 2 The spectra mainly exhibit absorption at ~410 nm which
Trang 7is the characteristic for the absorption of Sm3+ ions [30] The Kubelka- Munk relation was adopted to calculate the band gap of the NPs [31],
$ ∞ h& = C h& − () *− − − 4
where$ ∞ is the Kubelka-Munk function, ℎ& the photon energy, C a constant, () the
optical energy band gap, n an exponent which value depends on the nature of the inter band electronic transition, viz., n = ½ ( direct allowed transition), n = 2 (indirect allowed transition), n = 3/2 (direct forbidden transition) and n = 3 (indirect forbidden transition) [24]
Direct or indirect transitions are ''allowed'' transitions, if the momentum matrix element characterizing the transition is different from zero This means that the transition can hold for sure if sufficient energy is given to the particle (e.g electron) involved in the process
Direct or indirect transitions are ''forbidden'' transitions, if the momentum matrix element characterizing the transition is equal to zero The transition cannot hold even if sufficient energy is given However, a forbidden transition can sometimes become allowed Sometimes a transition can be forbidden in first order (first order perturbation theory) but it becomes allowed in second order (second order perturbation theory) [32]
As Bi2O3 is a direct band gap material, from the extrapolation of the line [$ ∞ ℎ&]
to zero (Fig 3), the ()of the synthesised NPs was found to be in the range of 2.92–2.96 eV, indicating that the present material can be a promising photocatalyst since it can absorb UV
as well as the visible region of solar light
3.3 Photoluminescence studies
Fig 4 shows the excitation spectra of Bi2O3: Sm3+NPs for 3, 5 and 7mol% The spectra were taken in the range of 360 nm to 500 nm and exhibit bands at 365 nm (6H5/2→4D3/2, 5/2), at 395
nm (6H5/2→4F7/2), at 418 nm(6H5/2→4M19/2), at 448 nm(6H5/2→4G9/2), at 465 nm(6H5/2→4I13/2) and at 488 nm(6H5/2→4I11/2) attributed to the 4f-4f transition of Sm3+ [33] Among these, the prominent transition at 465 nm (6H5/2→4I13/2) was taken to explicate the emission spectra of the NPs
Fig 5 shows the emission spectra of Bi2-xO3: Smx (x= 0.01 to 0.11) calcined at 600 oC excited under 465 nm The spectra consist of four typical transition emission bands centered
Trang 8at 565 nm(yellow), 616 nm(orange), 653 nm(orange red) and 713 nm(red) which are due to 4
G5/2→6H5/2, 4G5/2→6H7/2, 4G5/2→6H9/2 and 4G5/2→6H11/2 respectively Actually at excitation, the doped ions are excited to the higher energy state 4H9/2 from which they relax non-radiatively to the metastable state 4G5/2 through the4F7/2, 4G7/2, and 4F3/2 levels But 4H9/2 and 4
G5/2 correspond to very close and fast non-radiative relaxations So the spectra will have the four transition bands from 4G5/2 Among all the emitted transitions, 4G5/2→6H7/2 (616 nm) is the most prominent one with strong orange emission which is partly magnetic dipole and partly electric dipole.4G5/2→6H9/2 (653 nm) is purely electric dipole and in this study the intensity of the electric dipole transition is less compared to that of the magnetic dipole one, indicating the symmetry behaviour of Sm3+ ions in the host Bi2O3 [34, 35] The variation of the PL intensity with respect to the Sm3+ dopant concentration is shown in Fig 6 The PL intensity at 616 nm emission increases up to 5mol% with the increase of Sm3+ content and, subsequently, it decreases owing to concentration quenching The energy of the phosphor is lost due to non-radiative (or also multi phonon-assisted non-radiative) transitions by the incorporation of Sm3+ in the host or Sm3+-Sm3+ interaction when excited through vacancies
3.4 Judd Ofelt (J-O) analysis
Quantum efficiency is an important parameter which determines the efficiency of nanophosphors for the applications of display devices The electric-dipole (ED) and magnetic-dipole (MD) transitions are generally used in the investigation of rare earth ions doped luminescent materials However, it is challenging to calculate the J-O intensity Ωt (t =
2, 4, 6) parameters for powder materials because the absorption spectra of powder materials can hardly be recorded
The radiative transition probabilities (/0) from an excited state 2343 to the final state
24 are related to forced electric dipole transitions and they may be written as a function of the
J–O intensity parameters:
/0 2343− 24 =3ℎ 24 + 1 9646 7̅ : : + 29 ;< + : ;= > − − − − 5
Where, ;< and ;= are the electric and magnetic dipole strengths, respectively, 7J is the wavenumber of the respective electronic transition, h is Planck’s constant, n is the effective refractive index of the nanophosphor [36]
Trang 9The total radiative transition probability (/?) for an excited state 2343 is transition
The luminescence quantum efficiency (E) can be calculated by the relation [39] and was
found to be ~ 75 % for the present phosphor:
E = / /0
0+ /F0 = //0?− − − − − − − − − − − − 8
Table 2 gives the results of J-O intensity parameters (Ω2 and Ω4) and radiative properties of
Bi2O3:Sm3+ nanophosphors that are calculated from the emission spectra From the results it
is clear that the Ω2 and Ω4values are comparatively high due to the fact that the samples generally possess higher fractions of the rare earth ions on the surface of the nano crystals compared to the bulk counterparts [40] The parameter Ω2 is related to the short range impact
in the vicinity of the rare earth Sm3+ ion and Ω4 is related to the long range impact AR and τrwere calculated from the emission spectra The quantum efficiency (η) is calculated with equation (8) and found to be equal to 74.8% as shown in Table 2 An increase in quantum efficiency indicates a better applicability for display devices It was observed that 4
G5/2→6H7/2transition of Sm3+ doped Bi2O3 NPs dominates the intensity emitted by the NPs in the emission spectra The results infer that the current NPs can be utilized for display devices [38]
3.5 CIE and CCT analysis
“Commission International de i’Eclairage (CIE) 1931 standards” were used to calculate the colour coordinates of Bi2-xO3: Smx (x= 1-11 mol %) from the emission spectra In the colour space, coordinates (x, y) are used to specify the colour quality and to evaluate the phosphors performance these coordinates are the most prominent parameters Fig 7(a) shows the CIE
1931 chromaticity diagram for Bi2-xO3:Smx (x= 1- 11 mol%) NPs excited at 365 nm and 465
nm
Trang 10The CIE colour coordinates so calculated for Bi2-xO3: Smx (x= 1-11 mol%) are summarized
in Fig 7(a) It is clear that all the samples fall into the scope of orange red light emission Fig 7(b) show CCT of Bi2-xO3:Smx (x= 1-11 mol%) and the average value was found to be 1758
K [41] Hence, it is obvious that the NPs can be used as an Orange red light source to meet the needs of the illustrated applications
3.6 Photocatalytic Activity of AR-88 Dye
Acid Red-88(AR-88) is an azo dye Due to its intense colour, Ar-88 was used to dye cotton textiles red and used for Photocatalytic studies The PCA of Bi2-xO3: Smx (x= 1- 11 mol %) were analysed for the decolourization of AR-88 in aqueous solution under UV light irradiation for a time duration of 60min The UV visible absorption spectra of the dye for various concentrations of Bi2-xO3: Smx (x= 1- 11 mol %) are shown in Fig 8(a-f) To know about the response kinetics of AR-88 Dye decolourization, the Langmuir-Hinshelwood model was adopted which follows the equation, ln(C/C0) = kt + a, where, k is the reaction rate constant, C0 the preliminary attention of AR-88, C the attention of AR-88 on the response time t [22, 42] Fig9 shows the plot of ln(C/C0) photo decolourization of all catalysts
Bi2O3:Sm3+ under UV light irradiation As the doping concentration increases, the photo decolourization efficiency decreases and after 60 min irradiation it was found that the photo decolourization efficiency was 98.57% which is the maximum for 7 mol% (Fig 10) This might be due to the fact that at 7 mol%, Sm3+ ions on the host Bi2O3 behave as electron trapper to detach the electron-hole pairs which is much needed for PCA At other molar concentrations, the catalyst may behave as recombination centres and this leads to less PCA
efficiency
3.7 Conclusions
The present Bi2O3:Sm3+ nanophosphors were prepared by a solution combustion method The crystallite size was found to be in the range 13-30 nm The phosphors upon exciting at comparably low energy of 465 nm, emit orange colour with all characteristic transitions of
Sm3+ ions CCT of 1758 K shows that the phosphors are potential materials for warm white light emitting display devices Further, it shows an excellent photocatalytic activity which proofs the multi functionality of the prepared nanophosphors
Trang 11References
[1] R Deng, F Qin, R Chen, W Huang, M Hong, X Liu, “Temporal full-colour tuning
through non-steady-state upconversion”, Nat Nanotechnol., 10 (2015) 237
[2] J de Wild, A Meijerink, J K Rath, W G J H M van Sark and R E I Schropp,
“Upconverter solar cells: materials and applications”, Energy Environ Sci., 4 (2011)
[6] Fischer LH, Harms GS, Wolfbeis OS, “Upconverting nanoparticles for nanoscale thermometry”, Angew Chem Int Ed Engl 50 (2011) 4546-51
[7] Shen J, Zhao L, Han G, “Lanthanide-doped upconverting luminescent nanoparticle
platforms for optical imaging-guided drug delivery and therapy”, Adv Drug Deliv
Rev., 65 (2013)744-55
[8] Huang P, Zheng W, Zhou S, Tu D, Chen Z, Zhu H, Li R, Ma E, Huang M, Chen X,
“Lanthanide-doped LiLuF(4) upconversion nanoprobes for the detection of disease biomarkers”, Angew Chem Int Ed Engl., 53 (2014)1252-7
[9] P Lei, X Liu, L Dong, Z Wang, S Song, X Xu, Y Su, J Feng and H Zhang,
“Lanthanide doped Bi2O3 upconversion luminescence nanospheres for temperature
sensing and optical imaging”, Dalton Trans 45 (2016) 2686
[10] Buagun Samran,Sumneang lunput, Siriporn Tonnonchiang,Saranyoo Chaiwichian,
“BiFeO3/BiVO4 nanocomposite photocatalysts with highly enhanced photocatalytic activity for rhodamine B degradation under visible light irradiation”, Physica B, 561, ( 2019) 23-28
[11] J.Yesuraj, S.Austin Suthanthiraraj, O.Padmaraj, “Synthesis, characterization and electrochemical performance of DNA-templated Bi2MoO6 nanoplates for supercapacitor applications”, Mater Sci Semicond Process., 90 (2019) 225-235 [12] Aleksandra Bielicka Giełdoń, Patrycja Wilczewska, Anna Malankowska et al.,
“Morphology, surface properties and photocatalytic activity of the bismuth oxyhalides semiconductors prepared by ionic liquid assisted solvothermal method”, Sep Purif Technol., 217 (2019) 164-173
[13] S.U.M Khan, M Al-Shahry, W.B Ingler Jr., “Efficient Photochemical Water Splitting
by a Chemically Modified n-TiO2”, Science, 297 (2002) 2243-2245
Trang 12[14] O K Varghese, M Paulose, C.A Grimes, “Long vertically aligned titania nanotubes
on transparent conducting oxide for highly efficient solar cells”, Nature Nanotech, 4, (2009) 592 - 597
[15] N.N.Rao, V.Chaturvedi, G.L Puma, “Novel pebble bed photocatalytic reactor for solar treatment of textile wastewater”, Chem Engg J, 184 (2012) 90–97
[16] A Dhakshinamoorthy, S Navalon, A.Corma, H Garcia, “Photocatalytic
CO2 reduction by TiO2 and related titanium containing solids”, Energy Envi Scie, 5 (2012) 9217-9233
[17] L Renuka, K.S Anantharaju, S.C Sharma, H Nagabhushana, Y.S Vidya, H.P.Nagaswarupa, S.C Prashantha, “A comparative study on the structural, optical, electrochemical and photocatalytic properties of ZrO2nanooxide synthesized by different routes”, J Alloys Compd, 695 (2017) 382-395
[18] W zuo, W Zhu, D Zhao, Y Sun, Y Li, J Liu and X W D Lou, “Bismuth oxide: a versatile high-capacity electrode material for rechargeable aqueous metal-ion batteries”, Energy Environ Sci., 9 (2016) 2881
[19] Hassan Najafiana, Faranak Manteghia, Farshad Beshkarb, Masoud Salavati-Niasaric,
“Enhanced photocatalytic activity of a novel NiO/Bi2O3/Bi3ClO4 nanocomposite for the degradation of azo dye pollutants under visible light irradiation”, Sep Purif Technol,
209 (2019) 6–17
[20] H Takeda, T Ueda, K Kamada, K Matsuo, T Hyodo, Y Shimizu, “CO-sensing properties of a NASICON-based gas sensor attached with Pt mixed with Bi2O3 as a sensing electrode”, Electrochim Acta, 155(2015) 8-15
[21] L Li, X Zhang, Z Zhang, M Zhang, L Cong, Y Pan, S Lin, J Mater Chem A, 4 (2016) 16635
[22] Yanlin Huang , Jie Qin, Xuanxuan Liu , Donglei Wei, Hyo Jin Seo, “Hydrothermal synthesis of flower-like Na-doped α-Bi2O3 and improved photocatalytic activity via the induced oxygen vacancies”, J Taiwan Inst Chem Eng., 96 (2019) 353-360
[23] Ashwini S, Prashantha SC, Naik R, Nagabhushana H, “Enhancement of luminescence intensity and spectroscopic analysis of Eu3+ activated and Li+ charge-compensated Bi2O3 nanophosphors for solid-state lighting”, J Rare Earths, 37 (2019) 356-364 [24] S Ashwini, S.C Prashantha, Ramachandra Naik, Yashwanth V Naik, H Nagabhushana, D.M Jnaneshwara, “Photoluminescence of a novel green emitting
Bi2O3:Tb3+ nanophosphors for display, thermal sensor and visualisation of latent fingerprints”, Optik, 192 (2019) 162956
[25] K.C Patil, M.S Hegde, T Rattan, S.T Aruna, Chemistry of Nanocrystalline Oxide materials, World Scientific Press, Singapore, 2008
[26] QingheQue, Yonglei Xing, Zuoli He, Yawei Yang, Xingtian Yin, WenxiuQue,
“Bi2O3/Carbon quantum dots heterostructured photocatalysts with enhanced photocatalytic activity”, Mater Lett,209 (2017) 220-223
[27] B.D Cullity, Elements of X-ray Diffraction, Addison-Wesley, 1956