Electrochemical sensor and photocatalytic studies of ferrite nanoparticle using different fuels via green approach

Figures & data

Table 1. List of chemicals, specifications and suppliers used.

Name	Molecular formula	Molar mass and density	Suppliers
Nickel nitrate	Ni (NO3)2.6H2O	Molar mass: 290.79 Density: 2.05 g/cm^3	Merck
Ferric nitrate	Fe (NO3)3⋅9H2O	Molar mass: 404 g/mol 1.68 g/cm^3	Merck
Aloe vera	C16H13NO3	Molar mass: 267.279 g/mol Density: 1.2 ± 0.1 g/cm^3	Karnataka, India
Licorice plant root extract	C42H62O16Zn	Molar mass: 888.3 g/mol	Natural plant

Figure 1. Schematic representation for the preparation of NiFe₂O₄ by combustion method.

Figure 2. XRD pattern of (a) NiFe₂O₄-aloe vera; (b) NiFe₂O₄-root extract.

Table 2. Crystalline size and structural constraints of NiFe₂O₄ nanoparticles.

Sample	Crystalline size (nm)	Strain (ε) $x{10}^{-3}$	Stacking fault (SF)	Dislocation density (δ) (${10}^5 \mathit{\text{lin}} m^{-2})$
NiFe2O4-aloe vera	21.7	1.70	0.379	2.1
NiFe2O4-root extract	23.6	1.52	0.381	1.7

Figure 3. FE-SEM images of (a) NiFe₂O₄-aloe vera and (b) NiFe₂O₄-root extract.

Figure 4. EDAX spectrum of (a) NiFe₂O₄-aloe vera; (b) NiFe₂O₄-root extract.

Figure 5. CV of NiFe₂O₄-alovera electrode.

Figure 6. CV of NiFe₂O₄-root extract electrode.

Figure 7. Proton deficient coefficient and linear fitting of (a) NiFe₂O₄-aloe vera and (b) NiFe₂O₄-root extract electrode.

Table 3. Reversibility and proton deficient coefficient of NiFe₂O₄-aloe vera nanoparticle.

Scan rate (mV)	${\mathit{\text{ip}}}_c\times {10}^{-4}$	${\mathit{\text{ip}}}_a\times {10}^{-4}$	Reversibility (ER) $\times {10}^{-4}$	Diffusion co-efficient (D)
10	−1.12	1.36	2.48	7.05 X 10^−6
20	−1.39	1.96	3.35
30	−1.54	2.93	4.47
40	−1.65	3.56	5.21
50	−1.76	3.99	5.75

Table 4. Reversibility and proton deficient coefficient of NiFe₂O₄ root extract nanoparticle.

Scan rate (mV)	${\mathit{\text{ip}}}_c\times {10}^{-5}$	${\mathit{\text{ip}}}_a\times {10}^{-5}$	Reversibility (ER) $\times {10}^{-5}$	Diffusion co-efficient (D)
10	−0.09	0.45	0.54	1.533 X 10^−^5
20	−1.85	1.71	3.56
30	−2.46	3.18	6.04
40	−2.86	4.84	7.70
50	−3.39	6.44	9.83

Figure 8. Nyquist plots of NiFe₂O₄-aloe vera electrode vs. Ag/AgCl electrode.

Figure 9. Nyquist plots of NiFe₂O₄-root extract electrode vs. Ag/AgCl electrode.

Figure 10. CV response for the NiFe₂O₄ root extract electrode at 0.1 M HCl of sensor arsenic trioxide.

Figure 11. CV response for the NiFe₂O₄ extract electrode at 0.1 M HCl of sensor mercuric acetate.

Table 5. Redox reaction values of NiFe₂O₄ extract using arsenic trioxide sensor.

Concentration	${\mathit{\text{ip}}}_c\times {10}^{-4}$	${\mathit{\text{ip}}}_a\times {10}^{-4}$	Reversibility $\times {10}^{-4}$	Potential (V)
Without sensor	−0.98	0.45	1.43	0.32 to 0.51
0.001	−2.93	1.24	4.17
0.002	−4.58	2.34	6.92
0.003	−5.98	3.50	9.48

Table 6. Redox reaction values of NiFe₂O₄ extract using mercuric acetate sensor.

Concentration	${\mathit{\text{ip}}}_c$	${\mathit{\text{ip}}}_a$	Reversibility (ER)	Potential (V)
Without sensor	−0.0369	0.0265	0.0634	Anodic = −0.381 to −0.153 Cathodic = −0.081 to 0.105
0.001	−0.0335	0.0244	0.0579
0.002	−0.0316	0.0239	0.0555
0.003	−0.0313	0.0238	0.0551
0.004	−0.0309	0.0230	0.0539

Figure 12. Diffuse reflectance spectra of the synthesised NiFe₂O₄ from aloe vera and root extract methods.

Figure 13. Kubelka-Munk plot transformed reflectance spectra of the synthesised NiFe₂O₄ from aloe vera and Root extract methods.

Figure 14. Absorbance of AR-88 (30 ppm) in presence of NiFe₂O₄ NPs by (a) aloe vera method; and (b) plant root mediated combustion method under UV-light. (c) Plot of % degradation vs time indicating the AR-88 dye photo-degradation capability (d) plot of % degradation vs no. of cycles of AR-88 dye.

Figure 15. (a) Half time analysis of AR-88 (30 ppm) in presence of NiFe₂O₄ NPs prepared by a aloe vera method; (b) plant root mediated combustion method under UV-light and (c) the kinetics studies of NiFe₂O₄ NPs.

Figure 16. The probable photo-catalytic mechanism for degradation of AR-88 dye for NiFe₂O₄ NPs under UV-light irradiation.