Photoluminescence and photocatalytic properties of novel Bi2O3:Sm3+ nanophosphor

Lanthanide ions doped (Ln 3 þ ) nanophosphors (NPs) have gained massive attention owing to their potential applications in various ﬁelds ranging from display [1] , solar cells [2] , bio-[r]

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Original Article

Photoluminescence and photocatalytic properties of novel Bi2O3:Sm3ỵ

nanophosphor

S Ashwinia,b, S.C Prashanthab,*, Ramachandra Naikc,**, Yashwanth V Naikd,

H Nagabhushanad, K.N Narasimhamurthye

aDepartment of Physics, Channabasaveshwara Institute of Technology, Gubbi 572216, India

bResearch Center, Department of Science, East West Institute of Technology, VTU, Bengaluru 560091, India cDepartment of Physics, New Horizon College of Engineering, Bengaluru 560103, India

dProf CNR Rao Center for Advanced Materials, Tumkur University, Tumkur 572103, India eDepartment of Physics, Government First Grade College, Tumkur 572102, India

a r t i c l e i n f o Article history:

Received May 2019 Received in revised form 18 August 2019

Accepted September 2019 Available online 14 September 2019 Keywords:

Bi2O3:Sm3ỵ

Photoluminescence JuddeOfelt CIE CCT

a b s t r a c t

The current work involves studies of the synthesis, characterization and photoluminescence for Sm3ỵ(1 e11 mol%) doped Bi2O3nanophosphors (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 13e30 nm The KubelkaeMunk (KeM) function was used to assess the energy gap of Sm3ỵdoped Bi

2O3nanophosphors

which was found to be 2.92e2.96 eV From the Emission spectra, the JuddeOfelt parameters (U2andU4),

the transition probabilities (AT), the quantum efﬁciency (h), the luminescence lifetime (tr), 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 LangmuireHinshelwood model and Acid Red-88, the photocatalytic activity results showed that Bi2O3:Sm3ỵNPs are potential materials for the development

of an efﬁcient photocatalyst for environmental remediation The obtained results prove that the Bi2O3

:-Sm3ỵnanophosphors synthesised by this method can potentially be used in solid state displays and as a photocatalyst

© 2019 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1 Introduction

Lanthanide ions doped (Ln3ỵ) 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 (X¼ Cl, Br, I), BiVO4

and Bi2O3have 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[10e12]

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 pu-riﬁcation, organic waste degradation[15], CO2reduction[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, ZrO2and other semiconductors with a wide band

gap[17], theﬁnding out of new photocatalysts with sturdy degra-dation abilities has become additionally important Thus, we can consider Bi2O3as 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 * Corresponding author

** Corresponding author

E-mail addresses:scphysics@gmail.com(S.C Prashantha),rcnaikphysics@gmail com(R Naik)

Peer review under responsibility of Vietnam National University, Hanoi

Contents lists available atScienceDirect

Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2019.09.001

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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 Bi2O3is its

polymorphism, which results in polymorphic forms (a,b,g,dand

u) with different structures and properties [22], among them monoclinicawhich is stable at room temperature and face-centered cubicdthat is stable at high temperature There are various methods available for the synthesis of Bi2O3 nanophosphors viz.,

sono-chemical, microwave irradiation, hydrothermal, chemical vapour deposition, micro-emulsion, surfactant thermal strategy, solegel approach, solution combustion and electro-spinning[23,24]

In this work we report the synthesis of Bi2xO3:Smx(x¼ 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 Sm3ỵdoping on the photoluminescence properties were studied in detail for their possible usage in display applications

2 Experimental

2.1 Synthesis of Bi2xO3:Smx(x¼ 0.01 to 0.11)

The synthesis of Bi2xO3:Smx (x ¼ 0.01 to 0.11) via solution

combustion method was made using analytical grade Bismuth ni-trate (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 con-taining a stoichiometric quantity of reactants were taken such that Oxidizer (Bi (NO3)3$5H2O) to Fuel (Urea) ratio is (O/F¼ 1)[25]and

introduced into a pre heated mufﬂe furnace at temperature of 400± 10C 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 C for h The theoretical equation, assuming complete combustion of the redox mixture used for the synthesis of Bi2O3, can be written as:

2BiNO3ị3$5H2O

ỵ 5CH4N2O/Bi2O3ỵ 8N2ỵ 5CO2ỵ 20H2O (1)

2.2 Photocatalytic activity of Bi2O3:Sm3ỵ

At room temperature, the experiment was conducted in a reactor by utilizing a 125 W mercury vapour lamp as the UV light source (l¼ 254 nm) Using Acid red dye 88 (AR-88) as a model dye, the UV light photocatalytic activities of Bi2O3:Sm3ỵNPs were evaluated In

this experiment, 30 mg of synthesized Bi2O3:Sm3ỵNPs was

dis-solved completely into 10 ppm of AR-88 dye solution and stirred continuously to form a uniform solution At each 15 min, ml of the dye solution was inhibited and tested by a UVeVis spectropho-tometer by means of the typical adsorption band at 510 nm after centrifugation for the computation of the disintegration of dye[26]

2.3 Characterization

Crystal morphology of the synthesised NPs was determined by PXRD using X-ray diffractometer (Shimadzu) (V-50 kV, I-20 mA,l -1.541 Å, scan rate of 2 min1) Photoluminescence studies are

made using Horiba (model ﬂuorolog-3, xenon-450 W) Spectro-ﬂourimeter 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 200e800 nm

3 Results and discussion

3.1 PXRD studies

Fig 1shows the Powder X-ray diffraction (PXRD) pattern of undoped and Sm3ỵ(1e11 mol%) doped Bi2O3NPs 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 per-centage difference Dr(ionic radii)[27]is less than 15% between Bi3ỵ

and Sm3ỵions, Sm3ỵions substitute the Bi3ỵions in the Bi2O3host

DrẳRhCNị RR dðCNÞ hðCNÞ

(2)

For Coordination number CN equal to 6, the radius of the host cation Rh(CN) is 1.03 Å, and the radius of the doped ion Rd(CN) is

0.958 Å The calculated Dris found to be 6.99%[28]

The average crystallite size (D) was calculated by using Scherer's formula[29]

D¼b0:9l

cosq (3)

wherelrepresents the wavelength of X-rays (1.54Å),q; the inci-dent angle, andb; the full width at half maximum (FWHM) of the XRD peaks.Table gives the crystallite sizes of the Bi2O3:Sm3ỵ

(1e11 mol%) samples These are in the range of 13e30 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:Sm3ỵNPs were carried out and shown inFig The

spectra mainly exhibit absorption at ~410 nm which is

Fig PXRD patterns of undoped and Sm3ỵ(1e11 mol%) doped Bi2O3NPs

Table

Crystallite size of Bi2O3:Sm3ỵ

Sl no Compound Crystallite size (nm)

1 Bi2O3:Sm3ỵ: mol% 23.535

2 Bi2O3:Sm3ỵ: mol% 22.553

3 Bi2O3:Sm3ỵ: mol% 19.426

4 Bi2O3:Sm3ỵ: mol% 16.640

5 Bi2O3:Sm3ỵ: mol% 13.243

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characteristic for the absorption of Sm3ỵ ions [30] The Kubel-kaeMunk relation was adopted to calculate the band gap of the NPs[31],

FRịhnẳ Chn Eg

n (4)

where FðR∞Þ is the KubelkaeMunk function, hn; the photon energy,

C; a constant, Eg ; the optical energy band gap, n; an exponent

which value depends on the nature of the inter band electronic transition, viz., nẳ ẵ (direct allowed transition), n ¼ (indirect allowed transition), n¼ 3/2 (direct forbidden transition) and n ¼ (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 infirst order (first order perturbation theory) but it becomes allowed in second order (second order perturbation theory)[32]

As Bi2O3is a direct band gap material, from the extrapolation of

the lineẵFRịhn2to zero (Fig 3), the Egof the synthesised NPs was

found to be in the range of 2.92e2.96 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 4shows the excitation spectra of Bi2O3:Sm3ỵNPs for 3, and

7 mol% The spectra were taken in the range of 360 nme500 nm and

200 300 400 500 600 700 800

0 20 40 60

80 Bi2O3:Sm3+(1-11 mol %)

)

%(

ec

na

tc

elf

e

R

es

uff

i

D

Wavelength (nm) mol %

mol % mol % mol % mol % 11 mol %

Fig DRS of Sm3ỵ(1e11 mol%) doped Bi2O3NPs

Fig Energy gap of Bi2O3:Sm3ỵNPs

Fig Emission spectra of Bi2O3:Sm3ỵ(1e11 mol%) (lexcẳ 465 nm)

1 3 5 7 9 11

4x105

6x105

8x105

1x106

).

u.

a(

yti

s

ne

t

nI

L

P

Sm3+ Concentration (mol%)

(4)

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) which are attributed

to the 4f-4f transition of Sm3ỵ[33] Among these, the prominent transition at 465 nm (6H5/2/4I13/2) was taken to explicate the

emission spectra of the NPs

Fig 5shows the emission spectra of Bi2xO3:Smx(x¼ 0.01 to 0.11)

calcined at 600C excited under 465 nm The spectra consist of four typical transition emission bands centered at 565 nm (yellow), 616 nm (orange), 653 nm (orange red) and 713 nm (red) which are due to4G5/2/6H5/2,4G5/2/6H7/2,4G5/2/6H9/2and4G5/2/6H11/2

respectively Actually at excitation, the doped ions are excited to the higher energy state4H9/2from which they relax non-radiatively to the

metastable state4G5/2through the4F7/2,4G7/2, and4F3/2levels But4H9/ and 4G5/2 correspond to very close and fast non-radiative

re-laxations So the spectra will have the four transition bands from4G5/2

Among all the emitted transitions,4G

5/2/6H7/2(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, indi-cating the symmetry behaviour of Sm3ỵions in the host Bi2O3[34,35]

The variation of the PL intensity with respect to the Sm3ỵdopant concentration is shown inFig The PL intensity at 616 nm emission increases up to mol% with the increase of Sm3ỵcontent and, sub-sequently, 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 Sm3ỵin the host or Sm3ỵ-Sm3ỵinteraction when excited through vacancies

3.4 Judd Ofelt (JeO) analysis

Quantum efﬁciency is an important parameter which de-termines 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 calcu-late the JeO intensityUt(t¼ 2, 4, 6) parameters for powder

ma-terials because the absorption spectra of powder mama-terials can hardly be recorded

The radiative transition probabilities (AR) from an excited state j0J0to theﬁnal statejJ are related to forced electric dipole

transi-tions and they may be written as a function of the JeO intensity parameters:

AR

j0J0jJẳ 64p4w3 3h2J ỵ 1ị

nn2ỵ 22

9 Sedỵ n

3S md

!

(5)

where, Sedand Smdare the electric and magnetic dipole strengths,

respectively, wJ is the wavenumber of the respective electronic

transition, h is Planck's constant, n is the effective refractive index of the nanophosphor[36]

The total radiative transition probability (AT) for an excited state j0J0is transition[37]given by formula:

ATjJị ẳ X

jJ AR

j0J0jJ (6)

The radiative lifetimeðtrÞ of the excited statej0J0 can be

ob-tained by[38]

trj0J0ẳ ARjJị

(7)

The luminescence quantum efﬁciency (h) can be calculated by the relation [39] and was found to be ~75% for the present phosphor:

Table

JeO intensity parameters and radiative properties of Sm3ỵdoped Bi 2O3NPs

Phosphor Bi2O3:Sm3ỵ JeO intensity parameters

(1020cm2)

Transitions AR(s1) ANR(s1) AT(s1) tr(ms) h(%)

U2 U4

1 mol% 0.41059 0.361985 4G

5/2/6H5/2 4G

5/2/6H7/2 4G

5/2/6H9/2

71.316 24.025 95.341 10.489 74.8

3 mol% 0.401301 0.495693 69.703 23.482 93.185 10.731 74.8

5 mol% 0.351343 0.323457 61.025 20.558 81.584 12.257 74.8

7 mol% 0.386104 0.347901 67.063 22.592 89.656 11.154 74.8

9 mol% 0.354646 0.347472 61.599 20.752 82.351 12.143 74.8

11 mol% 0.392754 0.417446 68.218 22.982 91.199 10.965 74.8

Fig (a) CIE chromaticity diagram of Bi2O3:Sm3ỵ NPs (b) CCT diagram of

(5)

h¼ AR ARỵ ANRẳ

AR AT

(8) Table 2gives the results of JeO intensity parameters (U2andU4)

and radiative properties of Bi2O3:Sm3ỵ nanophosphors that are

calculated from the emission spectra From the results it is clear that theU2andU4values 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 parameterU2is related to the short range

impact in the vicinity of the rare earth Sm3ỵion andU4is related to

the long range impact ARandtrwere calculated from the emission

spectra The quantum efﬁciency (h) is calculated with equation(8)

and found to be equal to 74.8% as shown inTable An increase in quantum efﬁciency indicates a better applicability for display de-vices It was observed that4G5/2/6H7/2transition of Sm3ỵdoped

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 Bi2xO3:Smx

(x ¼ 1e11 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 chro-maticity diagram for Bi2xO3:Smx(x¼ 1e11 mol%) NPs excited at

365 nm and 465 nm

The CIE colour coordinates so calculated for Bi2xO3:Smx

(x¼ 1e11 mol%) are summarized inFig 7(a) It is clear that all the

350 400 450 500 550 600 650

0.00 0.02 0.04 0.06 0.08 0.10

(a) Bi2O3: Sm1mol% 0 Min

15 Min 30 Min 45 Min 60 Min

Absorbance

Wavelength(nm)

350 400 450 500 550 600 650

0.00 0.02 0.04 0.06 0.08

0.10 (b) Bi2O3: Sm3 mol% 0 Min

15 Min 30 Min 45 Min 60 Min

Absorbance

Wavelength(nm)

350 400 450 500 550 600 650

0.00 0.02 0.04 0.06 0.08

0.10 (c) Bi2O3: Sm5mol% 0 Min

15 Min 30 Min 45 Min 60 Min

Absorbance

Wavelength(nm)

350 400 450 500 550 600 650

0.00 0.02 0.04 0.06 0.08 0.10

(d) Bi2O3: Sm7mol% 0 Min

15 Min 30 Min 45 Min 60 Min

Absorbance

Wavelength(nm)

350 400 450 500 550 600 650

0.00 0.05 0.10 0.15

Wavelength(nm)

Absorbance

(e) Bi2O3: Sm9 mol% Min

15 Min 30 Min 45 Min 60 Min

350 400 450 500 550 600 650

0.00 0.05 0.10 0.15

(f) Bi2O3: Sm11 mol% 0 Min

15 Min 30 Min 45 Min 60 Min

Absorbance

Wavelength(nm)

(6)

samples fall into the scope of orange red light emission.Fig 7(b) shows CCT of Bi2xO3:Smx(x¼ 1e11 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 illus-trated 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 Bi2xO3:Smx(x¼ 1e11 mol%) were analysed for

the decolourization of AR-88 in aqueous solution under UV light irradiation for a time duration of 60 The UV visible absorption spectra of the dye for various concentrations of Bi2xO3:Smx

(x ¼ 1e11 mol%) are shown in Fig 8(aef) To know about the response kinetics of AR-88 Dye decolourization, the LangmuireHinshelwood model was adopted which follows the equation, ln (C/C0)ẳ kt ỵ a, where, k is the reaction rate constant,

C0the preliminary attention of AR-88, C the attention of AR-88 on

the response time t[22,42].Fig 9shows the plot of ln (C/C0) photo

decolourization of all catalysts Bi2O3:Sm3ỵunder UV light

irradia-tion As the doping concentration increases, the photo decolouri-zation efﬁciency decreases and after 60 irradiation it was found that the photo decolourization efﬁciency was 98.57% which is the

maximum for mol% (Fig 10) This might be due to the fact that at mol%, Sm3ỵions on the host Bi2O3behave as electron trapper to

detach the electronehole pairs which is much needed for PCA At other molar concentrations, the catalyst may behave as recombi-nation centres and this leads to less PCA efﬁciency

4 Conclusion

The present Bi2O3:Sm3ỵ nanophosphors were prepared by a

solution combustion method The crystallite size was found to be in the range 13e30 nm The phosphors upon exciting at comparably low energy of 465 nm, emit orange colour with all characteristic transitions of Sm3ỵions CCT of 1758 K shows that the phosphors are potential materials for warm white light emitting display de-vices Further, it shows an excellent photocatalytic activity which proofs the multi functionality of the prepared nanophosphors

References

[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, R.E.I Schropp,

Upconverter solar cells: materials and applications, Energy Environ Sci (2011) 4835

[3] Jing Zhou, Zhuang Liu, Fuyou Li, Upconversion nanophosphors for small-animal imaging, Chem Soc Rev 41 (2012) 1323e1349

[4] G Rumbles, Synthesis and upconversion luminescence of BaY2F8:Yb3ỵ/Er3ỵ nanobelts, Nature 409 (2001) 572e573

[5] M.K Jayakumar, N.M Idris, Y Zhang, Remote activation of biomolecules in deep tissues using near-infrared-to-UV upconversion nanotransducers, Proc Natl Acad Sci U S A 109 (2012) 8483e8488

[6] L.H Fischer, G.S Harms, O.S Wolfbeis, Upconverting nanoparticles for nano-scale thermometry, Angew Chem Int Ed Engl 50 (2011) 4546e4551 [7] J Shen, L Zhao, G Han, Lanthanide-doped upconverting luminescent

nano-particle platforms for optical imaging-guided drug delivery and therapy, Adv Drug Deliv Rev 65 (2013) 744e755

[8] P Huang, W Zheng, S Zhou, D Tu, Z Chen, H Zhu, R Li, E Ma, M Huang, X Chen, Lanthanide-doped LiLuF(4) upconversion nanoprobes for the detec-tion of disease biomarkers, Angew Chem Int Ed Engl 53 (2014) 1252e1257 [9] P Lei, X Liu, L Dong, Z Wang, S Song, X Xu, Y Su, J Feng, H Zhang, Lanthanide doped Bi2O3upconversion luminescence nanospheres for tem-perature 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) 23e28

[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) 225e235 [12] Aleksandra Bielicka Giełdon, 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) 164e173

[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) 2243e2245

[14] O.K Varghese, M Paulose, C.A Grimes, Long vertically aligned titania nano-tubes on transparent conducting oxide for highly efﬁcient solar cells, Nat Nanotechnol (2009) 592e597

[15] N.N Rao, V Chaturvedi, G.L Puma, Novel pebble bed photocatalytic reactor for solar treatment of textile wastewater, Chem Eng J 184 (2012) 90e97 [16] A Dhakshinamoorthy, S Navalon, A Corma, H Garcia, Photocatalytic CO2

reduction by TiO2and related titanium containing solids, Energy Environ Sci (2012) 9217e9233

[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 ZrO2 nanooxide synthesized by different routes, J Alloys Compd 695 (2017) 382e395 [18] W zuo, W Zhu, D Zhao, Y Sun, Y Li, J Liu, X.W.D Lou, Bismuth oxide: a

versatile high-capacity electrode material for rechargeable aqueous metal-ion batteries, Energy Environ Sci (2016) 2881

[19] Najaﬁana Hassan, 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) 6e17

[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) 8e15

[21] L Li, X Zhang, Z Zhang, M Zhang, L Cong, Y Pan, S Lin, J Mater Chem A (2016) 16635

0 15 30 45 60

-1.5 -1.0 -0.5 0.0

ln

(

c/c

0

)

Time(min)

Bi2O3: Sm1 mol %

Bi2O3: Sm11 mol %

Fig Plots of ln (C/Co) photo decolourization of all catalysts Bi2O3:Sm3ỵNPs under

UV light irradiation

0 10 20 30 40 50 60

0 20 40 60 80 100

Bi2O3: Sm3+

Time(min)

)

%(

noi

tis

o

p

mo

ce

D

mol% mol% mol% mol% mol% 11 mol%

(7)

[22] Yanlin Huang, Jie Qin, Xuanxuan Liu, Donglei Wei, Hyo Jin Seo, Hydrothermal synthesis ofﬂower-like Na-dopeda-Bi2O3and improved photocatalytic activity via the induced oxygen vacancies, J Taiwan Inst Chem Eng 96 (2019) 353e360 [23] S Ashwini, S.C Prashantha, R Naik, H Nagabhushana, Enhancement of luminescence intensity and spectroscopic analysis of Eu3ỵactivated and Liỵ charge-compensated Bi2O3 nanophosphors for solid-state lighting, J Rare Earths 37 (2019) 356e364

[24] S Ashwini, S.C Prashantha, Ramachandra Naik, Yashwanth V Naik, H Nagabhushana, D.M Jnaneshwara, Photoluminescence of a novel green emitting Bi2O3:Tb3ỵnanophosphors for display, thermal sensor and visual-isation of latentﬁngerprints, 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] Qinghe Que, Yonglei Xing, Zuoli He, Yawei Yang, Xingtian Yin, Wenxiu Que, Bi2O3/carbon quantum dots heterostructured photocatalysts with enhanced photocatalytic activity, Mater Lett 209 (2017) 220e223

[27] B.D Cullity, Elements of X-Ray Diffraction, Addison-Wesley, 1956 [28] http://abulaﬁa.mt.ic.ac.uk/shannon/

[29] P Klug, L.E Alexander, X-Ray Diffraction Procedure, Wiley, New York, 1954 [30] A.K Bedyal, Vinay Kumar, H.C Swart, A potential green emitting citrate gel synthesized NaSrBO3:Tb3ỵphosphor for display application, Physica B 535 (2018) 189e193

[31] P Kubelka, F Munk, Ein Beitrag Zur Optik der Farbanstriche, Z Tech Phys 12 (1931) 593e601

[32] http://web.mit.edu/course/6/6.732/OldFiles/www/6.732-pt2.pdf

[33] W.T Carnall, P.R Fields, K Rajanak, Electronic energy levels in the trivalent lanthanide aquo ions I Pr3ỵ, Nd3ỵ, Pm3ỵ, Sm3ỵ, Dy3ỵ, Ho3ỵ, Er3ỵ, and Tm3ỵ, J Chem Phys 49 (1968) 4424e4442

[34] G.H Dieke, Spectra and Energy Levels of Rare Earth Ions in Crystals, Wiley, New York, 1968

[35] C.P Reddy, V Naresh, B.C Babu, S Buddhudu, Photoluminescence and energy transfer process in Bi3ỵ/Sm3ỵCo-doped phosphate zinc lithium glasses, Adv Mater Phys Chem (2014) 165e171

[36] C.K Jorgensen, R Reisfeld, Judd-Ofelt parameters and chemical bonding, J Less Common Met 93 (1983) 107e112

[37] S Som, Subrata Das, S Dutta, Hendrik G Visser, et al., Synthesis of strong red emitting Y2O3:Eu3ỵ phosphor by potential chemical routes: comparative investigations on the structural evolutions, photometric properties and JuddeOfelt analysis, RSC Adv (2015) 70887e70898

[38] G.P Darshan, H.B Premkumar, H Nagabhushana, S.C Sharma, B Daruka Prasad, S.C Prashantha, Neodymium doped yttrium aluminate synthesis and optical properties e a blue light emitting nanophosphor and its use in advanced forensic analysis, Dyes Pigments 134 (2016) 227e233

[39] V Venkataramu, P Babu, C.K Jayasankar, Th Troster, W Sievers, G Wortmann, Optical spectroscopy of Sm3ỵions in phosphate and ﬂuo-rophosphate glasses, Opt Mater 29 (2007) 1429e1439

[40] Ramachandra Naik, S.C Prashantha, H Nagabhushana, Effect of Liỵcodoping on structural and luminescent properties of Mg2SiO4:RE3ỵ(RE ẳ Eu, Tb) nanophosphors for displays and eccrine latentﬁngerprint detection, Opt Mater 72 (2017) 295e304

[41] D.L Monika, H Nagabhushana, R Hari Krishna, B.M Nagabhushana, S.C Sharma, T Thomas, Synthesis and photoluminescence properties of a novel Sr2CeO4:Dy3ỵnanophosphor with enhanced brightness by Liỵ co-doping, RSC Adv (2014) 38655e38662