Synthesis and Characterization of Highly Crystalline Bi-Functional Mn-Doped Zn2SiO4 Nanostructures by Low-Cost Sol–Gel Process

Herein, we demonstrate a process for the synthesis of a highly crystalline bi-functional manganese (Mn)-doped zinc silicate (Zn2SiO4) nanostructures using a low-cost sol–gel route followed by solid state reaction method. Structural and morphological characterizations of Mn-doped Zn2SiO4 with variable doping concentration of 0.03, 0.05, 0.1, 0.2, 0.5, 1.0, and 2.0 wt% were investigated by using X-ray diffraction and high-resolution transmission electron microscopy (HR-TEM) techniques. HR-TEM-assisted elemental mapping of the as-grown sample was conducted to confirm the presence of Mn in Zn2SiO4. Photoluminescence (PL) spectra indicated that the Mn-doped Zn2SiO4 nanostructures exhibited strong green emission at 521 nm under 259 nm excitation wavelengths. It was observed that PL intensity increased with the increase of Mn-doping concentration in Zn2SiO4 nanostructures, with no change in emission peak position. Furthermore, magnetism in doped Zn2SiO4 nanostructures was probed by static DC magnetization measurement. The observed photoluminescence and magnetic properties in Mn-doped Zn2SiO4 nanostructures are discussed in terms of structural defect/lattice strain caused by Mn doping and the Jahn–Teller effect. These bi-functional properties of as-synthesized Zn2SiO4 nanostructures provide a new platform for their potential applications towards magneto-optical and spintronic and devices areas.


Introduction
Multifunctional nanomaterials play an important role in different fields of applied sciences including semiconductor electronics, solar energy, memory devices, and optoelectronics devices for development of efficient nanosensors and nanosystems [1][2][3][4][5][6]. Therefore, tailoring of these nanomaterials for their desired properties is extremely important, especially for applications in advanced portable devices [7][8][9][10][11][12]. There are several nanomaterials which show tunability with size, shape, and properties with variation of doping concentration [9,[13][14][15][16]. Zinc silicate especially (Zn 2 SiO 4 ) is a promising candidate for applications in flat panel optical displays, UV detectors, gas sensors, adsorption of toxic ions from water, and thin film electro-luminescence devices applications [17][18][19]. Furthermore, Zn 2 SiO 4 structures have received significant attention due to their unique wide range of multiple color luminescent properties, wide band gap (5.5 eV), and excellent chemical stability [20]. The willemite Zn 2 SiO 4 host material is heavily used for applications in the field of phosphors for light emitting devices [21].The Zn 2 SiO 4 is a natural orthosilicate with a phenacite-like structure in which Zn-O tetrahedral and Si-O tetrahedral share corners to form hollow 'tubes' parallel to [0001] planes; and it is a well-known host material for potential applications in the area of phosphors for optoelectronics and blue, green, and red color light emitting devices [1,3,20]. The incorporation of transition metal centers and rare earth ions (luminescence centers) in a Zn 2 SiO 4 host lattice results in a various interesting luminescent property. Various methods such as vapor phase synthesis, high temperature solid-state reaction, and ball milling have been previously reported for synthesis of the Zn 2 SiO 4 nanostructures. However, these reported methods require complicated procedure, huge thermal energy, high reaction temperature and time, and the synthesized materials exhibit irregular micro structure morphologies which is unsuitable for applications in devices where precise control over shapes and properties is required.
Recently, several new methods have been reported for the synthesis of Zn 2 SiO 4 including sol-gel, polymer precursor, spray pyrolysis, and hydrothermal to get different luminescence emissions for various potential application [21][22][23][24]. R. Krsmanovic et al. prepared Sm-and Tb-doped Zn 2 SiO 4 particle by sol-gel method to get reddish orange and pseudo white emissions [25]. H. Wang et al. and R. Pozas et al. prepared the Zn 2 SiO 4 with Co dopant using hydrothermal method to obtain the blue pigments [26,27]. K Omri et al. reported the yellow phosphor of Mn-doped Zn 2 SiO 4 using sol-gel method [28]. G. Gao et al. reported the Eu-doped Zn 2 SiO 4 nanoparticles prepared by using solid state method to get red color emission [29]. Moreover, K. Omri [30][31][32].
In the present investigations, we synthesized Mn-doped Zn 2 SiO 4 nanostructures phosphors with various doping concentration using the cost effective and facile sol-gel method. Crystal structure, morphology, and photo luminescence properties of Mn-doped Zn 2 SiO 4 nanostructures were studied. Effect of doping concentration of Mn in Zn 2 SiO 4 on its structural, morphological, luminescence, and magnetic properties was also studied. Based on this, a correlation of lattice strain with observed magnetic properties and luminescence behavior is presented.

Synthesis of Zn 2 SiO 4 Nanoparticles
A flow chart for the preparation of Mn-doped Zn 2 SiO 4 nanoparticles is shown in Figure 1. Mn-doped Zn 2 SiO 4 nanoparticles were synthesized by sol-gel method under ambient atmosphere followed by thermal annealing. In the first step, 2.0433 mg of ZnCl 2 aqueous solution was prepared using 16 mL H 2 O and 64 mL EtOH. Then, "x" amount (x = 0.03, 0.05, 0.1, 0.2, 0.5, 1.0, 2.0 wt%) of Mn(CH 3 COO) 2 was dissolved into main solution. The prepared solution was mixed in a magnetic stirrer at 400 rpm at room temperature for 1 hr. Further, 2 mL of TEOS was slowly added drop by drop using micropipette while stirring after 1 h. Then, the solution was heated at 70 0 C resulting, initially in the formation of a white gel and then into a powder when the gel was left overnight. This white powder was then calcined at 1000 • C in box furnace under natural atmospheric pressure for 6 h. Finally, the resultant white Zn 2 SiO 4 nanoparticles was washed with distilled water and collected for characterization. stirring after 1 h. Then, the solution was heated at 70 0 C resulting, initially in the formation of a white gel and then into a powder when the gel was left overnight. This white powder was then calcined at 1000 °C in box furnace under natural atmospheric pressure for 6 h. Finally, the resultant white Zn2SiO4 nanoparticles was washed with distilled water and collected for characterization.

Measurement and Characterizations
The structural properties of the prepared samples were measured by X-ray diffraction (XRD) technique using a Rigaku (ultima IV model, Japan) benchtop X-ray diffractometer equipped with a monochromatic Cu-Kα radiation (λ = 1.541 Å) X-ray source. The morphology of the samples was analyzed by high resolution transmission electron microscopy (HR-TEM) JEM 2100F operating at 200 keV and the attached GATAN (Version: GMS 2.32) digital-micrograph software. Elemental mapping was performed using Oxford attachment in HRTEM. The room temperature photoluminescence (PL) investigation was performed using a Perkin Elmer LS-55 fluorescence spectrophotometer with a Xenon (Xe) lamp as the source of excitation. The magnetic properties at room temperature were examined by a SQUID magnetometer (MPMS7 Tesla, Quantum Design, San Diego, CA, USA) in the field range + 2T with a step size of 400 Oe and a field scan rate of 100 Oe per minute.

Formation of α-Phase Zn2SiO4
The chemical reaction process and crystal growth mechanism for formation of αphase Zn2SiO4 nanostructures can be explained by the following chemical reaction steps:

Measurement and Characterizations
The structural properties of the prepared samples were measured by X-ray diffraction (XRD) technique using a Rigaku (ultima IV model, Japan) benchtop X-ray diffractometer equipped with a monochromatic Cu-Kα radiation (λ = 1.541 Å) X-ray source. The morphology of the samples was analyzed by high resolution transmission electron microscopy (HR-TEM) JEM 2100F operating at 200 keV and the attached GATAN (Version: GMS 2.32) digital-micrograph software. Elemental mapping was performed using Oxford attachment in HRTEM. The room temperature photoluminescence (PL) investigation was performed using a Perkin Elmer LS-55 fluorescence spectrophotometer with a Xenon (Xe) lamp as the source of excitation. The magnetic properties at room temperature were examined by a SQUID magnetometer (MPMS7 Tesla, Quantum Design, San Diego, CA, USA) in the field range ± 2T with a step size of 400 Oe and a field scan rate of 100 Oe per minute.

Formation of α-Phase Zn 2 SiO 4
The chemical reaction process and crystal growth mechanism for formation of α-phase Zn 2 SiO 4 nanostructures can be explained by the following chemical reaction steps: The reaction mechanism leading to the formation of zinc silicate can be summarized in the following steps. In the first step, ZnCl 2 reacts with H 2 O and C 2 H 5 OH at 70 • C and is transformed into Zn (OH)Cl. Then, this Zn(OH)Cl reacts with TEOS, and hydrated hemimorphite leading to formation of Zn 4 (OH) 2 Si 2 O 7 .H 2 O powder. This powder, when annealed at~550 • C forms dehydrated hemimorphite Zn 4 (OH) 2 Si 2 O 7 . Dehydrated hemimorphite Zn 4 (OH) 2 Si 2 O 7 is transformed into β-phase ZnSi 2 O 7 by annealing at~750 • C and into α-phase Zn 2 SiO 4 by annealing at 1000 • C.

Structural Analysis
The X-ray diffraction (XRD) pattern of the annealed Zn 2 SiO 4 nanostructures collected at room temperature is shown in Figure 2. All diffraction peaks in the pattern can be indexed to the crystalline willemite (α-Zn 2 SiO 4 , JCPDS card 37-1485) structure of rhombohedral system with lattice parameters a = b = 13.938 Å and c = 9.31 Å, α = β = 90 • , γ = 120 • revealing the crystallinity of the samples [33].
The reaction mechanism leading to the formation of zinc silicate can be summarized in the following steps. In the first step, ZnCl2 reacts with H2O and C2H5OH at 70 °C and is transformed into Zn (OH)Cl. Then, this Zn(OH)Cl reacts with TEOS, and hydrated hemimorphite leading to formation of Zn4(OH)2Si2O7.H2O powder. This powder, when annealed at ~550 °C forms dehydrated hemimorphite Zn4(OH)2Si2O7. Dehydrated hemimorphite Zn4(OH)2Si2O7 is transformed into β-phase ZnSi2O7 by annealing at ~750 °C and into α-phase Zn2SiO4 by annealing at 1000 °C.

Structural Analysis
The X-ray diffraction (XRD) pattern of the annealed Zn2SiO4 nanostructures collected at room temperature is shown in Figure 2. All diffraction peaks in the pattern can be indexed to the crystalline willemite (α-Zn2SiO4, JCPDS card 37-1485) structure of rhombohedral system with lattice parameters a = b = 13.938 Å and c = 9.31 Å , α = β = 90°, γ = 120° revealing the crystallinity of the samples [33].  The average crystallite size of the as grown samples was calculated using the Williamson and Hall method which is a combination of the Scherrer's equation for size broadening and the Stokes and Wilson expression for strain broadening [34][35][36][37].
where β is the full width at half maximum of diffraction peak, η is the strain in the crystallites, and D is the crystallites size [38][39][40]. The constant k is typically close to unity and ranges from 0.8 to 1.39. To calculate the strain and crystallite size, a graph was plotted in between β cos θ B and sin θ B . The strain (η) was then extracted from the slope and the crystallite size was determined from the y-intercept. The average crystallite size of the undoped Zn 2 SiO 4 nanostructures was found to be 28 nm. in the lattice which results in slight angle shifts in XRD spectra as shown in Figure 3a. Moreover, depending on different θ positions, the separation of size and strain broadening analysis is done using Williamson and Hall method. Crystal imperfections and distortion of strain-induced peak broadening can be related by the well-known Williamson and Hall method shown in Figure S1. ranges from 0.8 to 1.39. To calculate the strain and crystallite size, a graph was plotted in between β cos and sin . The strain (η) was then extracted from the slope and the crystallite size was determined from the y-intercept. The average crystallite size of the undoped Zn2SiO4 nanostructures was found to be 28 nm.
The XRD patterns of Zn2SiO4 samples doped with various doping concentration of Mn are shown in Figure 3a. The result shows that the diffraction peaks of nanostructures shifted towards lower angle with an increase in Mn concentration. This shift in the diffraction peak can be attributed to lattice expansion as a result of induced strain from Mn doping. The likely position of Mn substitution in Zn2SiO4 lattice is shown in the Figure 3b and it is proposed that Mn 2+ occupies the Zn 2+ position. Furthermore, a close view of unit cell can be easily seen from right inset (top and bottom) of Figure 3b.  Figure S1. Figure 4 shows the calculated strain and crystalline size of Zn2SiO4 as a function of % of Mn doping. It is clearly observed that the strain increases with an increase in Mn doping in the host lattice. The obtained results also indicate that crystallite size increases due to

Morphology Analysis
The morphology and microstructure of the as-synthesized Zn2SiO4 nanostructure was analyzed by high-resolution transmission electron microscope (HR-TEM). Figure 5a shows the nanorod-like morphology of 0.2 wt% Mn-doped Zn2SiO4. The estimation of the dimension of individual nanorods is presented in the inset of Figure 5a. Figure 5b shows the magnified view of nanorod-like morphology of the individual rod with 620 nm length and 300 nm width. Its selected area electron diffraction (SAED) pattern recorded without sample tilting is shown in the inset of Figure 5b. The SAED result reveals that the nanorod is crystalline in nature. The HR-TEM image of the nanorod in Figure 5c shows regular lattice fringes with d-spacing of 0.26 nm, which is in agreement with the inter planar spacing of (300) plane in XRD pattern. Figure 5d shows the magnified view of nanoflake-like morphology of individual rod with length of 970 nm and width of 370 nm. The inset in

Morphology Analysis
The morphology and microstructure of the as-synthesized Zn 2 SiO 4 nanostructure was analyzed by high-resolution transmission electron microscope (HR-TEM). Figure 5a shows the nanorod-like morphology of 0.  shows the magnified view of nanorod-like morphology of the individual rod with 620 nm length and 300 nm width. Its selected area electron diffraction (SAED) pattern recorded without sample tilting is shown in the inset of Figure 5b. The SAED result reveals that the nanorod is crystalline in nature. The HR-TEM image of the nanorod in Figure 5c shows regular lattice fringes with d-spacing of 0.26 nm, which is in agreement with the inter planar spacing of (300) plane in XRD pattern. Figure 5d shows the magnified view of nanoflake-like morphology of individual rod with length of 970 nm and width of 370 nm. The inset in Figure 5d shows the clear lattice fringe of nanorods which corresponds to 113 plane.   Figure 7a shows the photoluminescence (PL) spectra of Mn-doped Zn2SiO4 measured with an excitation wavelength of 259 nm at room temperature (Figure 7b). The emission spectra of the samples show broad green emission centered at 521 nm which arises due to Mn 2+ ion transitions. The green emission from the sample can be understood in terms of various transition states of Mn element. The green PL emission results transition from the 4 T1( 4 G) excited state to the 6 A1 ( 6 S) ground state in 3D orbital electrons of the Mn 2+ ion [45]. The variation in the PL intensity is due to the size variation and defect level introduced from the doping. It is noted that the nanostructure has large surface area, which significantly impairs the PL intensity by introducing a correspondingly large number of defects. The transition of free electrons in the conduction band by the charge transfer transition of Mn is as described below Mn 2+ (3d 5 ) → Mn 3+ + (3d 4 ) + Eg CB (8) Figure 6. (b-i) show the spectra obtained from the EDS mapping of (a) which confirmed the Mn doping in Zn 2 SiO 4 lattice. (j) shows the quantitative analysis was also carried out to estimate the weight and atomic percentage of samples and EDS spectra. Figure 7a shows the photoluminescence (PL) spectra of Mn-doped Zn 2 SiO 4 measured with an excitation wavelength of 259 nm at room temperature (Figure 7b). The emission spectra of the samples show broad green emission centered at 521 nm which arises due to Mn 2+ ion transitions. The green emission from the sample can be understood in terms of various transition states of Mn element. The green PL emission results transition from the 4 T 1 ( 4 G) excited state to the 6 A 1 ( 6 S) ground state in 3D orbital electrons of the Mn 2+ ion [45]. The variation in the PL intensity is due to the size variation and defect level introduced from the doping. It is noted that the nanostructure has large surface area, which significantly impairs the PL intensity by introducing a correspondingly large number of defects. The transition of free electrons in the conduction band by the charge transfer transition of Mn is as described below Mn 2+ (3d 5 ) → Mn 3+ + (3d 4 ) + Eg CB (8) These excited free electrons further relax from the conduction band to the 4 T 1 ( 4 G) lowest excitation energy level of the Mn 2+ ion via non-radiative transitions, followed by a radiative transition from the 4 T 1 ( 4 G) level to the 6 A 1 ( 6 S) ground state or valance state which results in the green PL emission peak centered at 521 nm. A schematic image of the corresponding transition is shown in the Figure 7b. Changing the doping % of Mn 2+ resulted in only a very small shift in peak position. However, the PL intensity shows nonlinear trend with doping concentration. For better understanding, the PL peak intensity as a function of x at 521 nm was also plotted along with the FWHM as a function of x and is shown in Figure S2. It is clearly observed that the PL intensity first increases with doping concentration with a maxima at 0.2 wt% and then decreases with a further increase in doping. As Mn concentration increases from 0.03 wt % to 0.2 wt%, stress in the crystal lattice also increases as discussed in the XRD section and also shown in Table  S1. The decrease of intensity with higher concentration of Mn doping is due to activator concentration quenching and the decrease in the inter-ionic distance between two adjacent Mn 2+ ion pairs. This reduction of inter-ionic distance between the Mn 2+ ion pairs leads to exchange of excited free electron migration from one Mn 2+ ion to another, which causes non-radiative transitions and reduces the emission efficiency and the demonstration at 0.4 wt% Mn doped Zn 2 SiO 4 is shown in Video V1 [46].

Photoluminescence Analysis
These excited free electrons further relax from the conduction band to the 4 T1( 4 G) lowest excitation energy level of the Mn 2+ ion via non-radiative transitions, followed by a radiative transition from the 4 T 1 ( 4 G) level to the 6 A1( 6 S) ground state or valance state which results in the green PL emission peak centered at 521 nm. A schematic image of the corresponding transition is shown in the Figure 7(b). Changing the doping % of Mn 2+ resulted in only a very small shift in peak position. However, the PL intensity shows nonlinear trend with doping concentration. For better understanding, the PL peak intensity as a function of x at 521 nm was also plotted along with the FWHM as a function of x and is shown in Figure S2. It is clearly observed that the PL intensity first increases with doping concentration with a maxima at 0.2 wt% and then decreases with a further increase in doping. As Mn concentration increases from 0.03 wt % to 0.2 wt%, stress in the crystal lattice also increases as discussed in the XRD section and also shown in Table S1. The decrease of intensity with higher concentration of Mn doping is due to activator concentration quenching and the decrease in the inter-ionic distance between two adjacent Mn 2+ ion pairs. This reduction of inter-ionic distance between the Mn 2+ ion pairs leads to exchange of excited free electron migration from one Mn 2+ ion to another, which causes nonradiative transitions and reduces the emission efficiency and the demonstration at 0.4 wt% Mn doped Zn2SiO4 is shown in Video V1 [46].

Magnetic Analysis
The M-H plot of Mn-doped Zn2SiO4 nanorods at room temperature is shown in Figure 8a. It is observed that the value of magnetization increased with increase in the Mn doping concentration, which may be due to the increased amount of impurity in the host lattice of Zn2SiO4 [47,48]. It was observed in the present study that pristine Zn2SiO4 exhibits only diamagnetic behavior at room temperature. Further, observed remanence and coercivity for higher Mn content indicates nucleation of ferromagnetic characteristic, whereas diamagnetic behavior was found to be still prevailing for lower Mn 2+ content. The M-H loops of all the samples were plotted after substituting the diamagnetic contribution of each of the sample [36,37,49]. Magnetization of Zn2SiO4 with increased Mn doping can be explained in terms of the Jahn-Teller effect which relates the suppressing the spiral spin structure of Zn2SiO4 by the incorporation of Mn at Zinc sites [30,31]. It is also proposed that Mn cations presented in the Zn2SiO4 are in mixed valence states of 2+, 3+, and 4+ which could support ferromagnetic coupling through Zener double exchange interaction. In low concentration, the Jahn-Teller effect would be expected to cause a shows a schematic image of shows the green PL emission peak centered at 521 nm transition from the 4 T 1n ( 4 G) excited state to the 6 A 1 ( 6 S) ground state.

Magnetic Analysis
The M-H plot of Mn-doped Zn 2 SiO 4 nanorods at room temperature is shown in Figure 8a. It is observed that the value of magnetization increased with increase in the Mn doping concentration, which may be due to the increased amount of impurity in the host lattice of Zn 2 SiO 4 [47,48]. It was observed in the present study that pristine Zn 2 SiO 4 exhibits only diamagnetic behavior at room temperature. Further, observed remanence and coercivity for higher Mn content indicates nucleation of ferromagnetic characteristic, whereas diamagnetic behavior was found to be still prevailing for lower Mn 2+ content. The M-H loops of all the samples were plotted after substituting the diamagnetic contribution of each of the sample [36,37,49]. Magnetization of Zn 2 SiO 4 with increased Mn doping can be explained in terms of the Jahn-Teller effect which relates the suppressing the spiral spin structure of Zn 2 SiO 4 by the incorporation of Mn at Zinc sites [30,31]. It is also proposed that Mn cations presented in the Zn 2 SiO 4 are in mixed valence states of 2+, 3+, and 4+ which could support ferromagnetic coupling through Zener double exchange interaction. In low concentration, the Jahn-Teller effect would be expected to cause a reduction in the tendency toward ferromagnetism since it leads to a splitting of the states. The splitting will reduce the interactions between Mn pairs since hopping requires an extra energy [9,14,34,35,50]. On the other hand, the interaction between Mn-Mn pairs at realistic distances is sufficiently large that it dominates over the Jahn-Teller effect. The interactions between Mn atoms is not greatly affected by lattice relaxations and there is always a clear tendency for ferromagnetic alignment of Mn pairs as evidenced in the present study for higher Mn concentrations. reduction in the tendency toward ferromagnetism since it leads to a splitting of the states. The splitting will reduce the interactions between Mn pairs since hopping requires an extra energy [9,14,34,35,50]. On the other hand, the interaction between Mn-Mn pairs at realistic distances is sufficiently large that it dominates over the Jahn-Teller effect. The interactions between Mn atoms is not greatly affected by lattice relaxations and there is always a clear tendency for ferromagnetic alignment of Mn pairs as evidenced in the present study for higher Mn concentrations. Figure 8b shows value of magnetization with increase in Mn doping wt% concentration into Zn2SiO4 host lattice.

Conclusions
We successfully synthesized highly crystalline bi-functional Mn-doped Zn2SiO4 nanostructures with various doping concentration using a low-cost sol-gel process. The X-ray diffraction results confirmed the rhombohedral phase of Mn-doped Zn2SiO4 nanostructure. The HR-TEM results confirm the nanorod-like morphology. The PL results show the strong green emission peak centered at 521 nm under 259 nm excitation wavelength. The optimization for highest photoluminescence intensity was achieved by varying different concentrations of Mn-doping in Zn2SiO4 lattice. We observed that 0.2 wt% Mn doping in Zn2SiO4 nanostructure showed the highest PL intensity. Magnetic studies confirmed the magnetic nature of Mn-doped Zn2SiO4 nanostructures and magnetization increased with increase of Mn concentration. Thus, the bi-functional behavior of Mndoped Zn2SiO4 nanostructures offers a new avenue to further exploit its potential application in magneto-optical devices.
Supplementary Materials: The following supporting information can be downloaded at: www.mdpi.com/xxx/s1, Figure S1: (a-g) shows the graphs between β cos θ B and sin θ B ; Figure S2: Comparative strain and crystallite size of Zn2SiO4 as a function of Mn doping in Zn2SiO4 host lattice; Table S1: Effect of Mn doping on the FWHM, strain and crystallites size of Zn2SiO4 nanostructure; Video S1: The demonstration at 0.4 wt% Mn doped Zn2SiO4 is shown in Video V1.

Conclusions
We successfully synthesized highly crystalline bi-functional Mn-doped Zn 2 SiO 4 nanostructures with various doping concentration using a low-cost sol-gel process. The X-ray diffraction results confirmed the rhombohedral phase of Mn-doped Zn 2 SiO 4 nanostructure. The HR-TEM results confirm the nanorod-like morphology. The PL results show the strong green emission peak centered at 521 nm under 259 nm excitation wavelength. The optimization for highest photoluminescence intensity was achieved by varying different concentrations of Mn-doping in Zn 2 SiO 4 lattice. We observed that 0.2 wt% Mn doping in Zn 2 SiO 4 nanostructure showed the highest PL intensity. Magnetic studies confirmed the magnetic nature of Mn-doped Zn 2 SiO 4 nanostructures and magnetization increased with increase of Mn concentration. Thus, the bi-functional behavior of Mn-doped Zn 2 SiO 4 nanostructures offers a new avenue to further exploit its potential application in magnetooptical devices.
Supplementary Materials: The following supporting information can be downloaded at: https://www. mdpi.com/article/10.3390/nano13030538/s1, Figure S1: (a-g) shows the graphs between β cos θ B and sin θ B ; Figure S2: Comparative strain and crystallite size of Zn2SiO4 as a function of Mn doping in Zn2SiO4 host lattice; Table S1: Effect of Mn doping on the FWHM, strain and crystallites size of Zn 2 SiO 4 nanostructure; Video S1: The demonstration at 0.4 wt% Mn doped Zn 2 SiO 4 is shown in Video V1.

Data Availability Statement:
The data presented in this study are available in the article.