Supporting Information
Real-time quality monitoring and organic pollutants degradation of water using atomically thin Magnesiochromite
Preeti Lata Mahapatraa, Partha Kumbhakarb*, Basudev Lahiric, Shyam Kanta Sinhad, Chandra Sekhar Tiwaryb*
aSchool of Nano Science and Technology, Indian Institute of Technology, Kharagpur, West Bengal-721302 India
bMetallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
cDepartment of Electronics and Electrical Communication Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
dDepartment of Materials Engineering, Indian Institute of Science, Bangalore 560012, India
*Corresponding Author E-mail address: [email protected] (C.S. Tiwary), [email protected] (P. Kumbhakar)
Supporting Figures & Tables
1. SEM images of bulk and Exfoliated MgCr2O4
Figure S1: SEM images of bulk and exfoliated MgCr2O4.
Figure S1.1: AFM images of exfoliated MgCr2O4 with the respective thickness of the particle in the inset.
2. Elemental analysis by EDS
Figure S2: EDS elemental image mapping of (a-c) bulk, (d-f) exfoliated MgCr2O4, (g-h) bulk MgCr2O4 and Exfoliated MgCr2O4 with combined elemental colors and respective atomic percentages of elements present.
3. Optical images of MgCr2O4
Figure S3: Optical images of bulk and exfoliated MgCr2O4.
4. Laser light irradiation and dispersion effect
5. Colorimetric measurement set up
Figure S4: Laser light irradiation on exfoliated sample.
Figure S5: Stepwise dye degradation test and colorimetric analysis by smartphone-based application.
a. Comparative degradation efficiency of 2D with bulk MgCr2O4
Figure S6: (a) Performance comparison graph of Bulk and 2D catalyst in terms of colorimetric absorbance in dye degradation (inset shows digital image of degraded dye) and (b) comparative degradation efficiency bar graph of bulk and 2D catalysts.
b. Catalyst performance for different dye concentrations
Figure S7: Upper panel showing digital images of different dye concentration with 1mL catalyst application, and bottom graph shows pseudo-first order rate kinetics for Methylene blue dye degradation by 2D MgCr2O4.
Kinetic Analysis: Figure S7 (upper panel) shows the digital photographs of the solution as a function of dye concentration and time.
The dye degradation rate of reaction is determined by pseudo-first-order kinetics from the Langmuir Hinshelwood model [S7.1] given by:
Ct=Coe−kt
Where Ct is the concentration at time t and Co is the initial concentration of dye, k is the reaction rate constant for pseudo-first-order kinetics and t is the sonication time.
This equation can also be written as:
Ct Co
¿e−kt
lnCt Co
=−kt
lnCo Ct=kt
We have plotted the rate of reaction constant (k) against the sonication time of methylene blue dye shown in Figure S7 (graph). The graph shows a plot of ln (Co/Ct) versus time which has linear behavior where the slope is equal to the first-order rate constant (k). We have observed the rate constant is maximum for a dye concentration of 0.2 mg/mL and it decreases again for 0.3 mg/mL.
c. Catalyst performance under UV irradiation
Figure S8: Ultra-Violet (UV) light irradiation effect on dye containing 2mL exfoliated spinel oxide and daylight showing (a) digital image and (b) degradation efficiency bar graph, and (c) bar graph representation of absorbance difference in different wavelength of light.
d. Catalysis test at different pH
Figure S9: pH change effect on dye containing 2mL exfoliated spinel oxide in in conc. 1 (20mg MB/100mL H2O) showing (a) digital image, (b) Bar graph of degradation efficiency, e. Spectrophotometric results
Figure S10: UV-Vis spectrophotometer results of (a) Methylene blue dye at 0 min and 20 min of catalytic dye degradation, (b) Methyl orange dye at 0 min and 20 min of catalytic dye degradation, (c) Methylene blue dye at 0 min and 20 min of catalytic dye degradation, (d) Degradation efficiency bar graph from spectrophotometer data, and (e) comparative analysis of both detection methods of degradation efficiency mapping.
f. Our experimental parameters
Parameters Experimental inputs
pH Neutral (6)
Light UV and sunlight
Concentration of dye 20mg/100mL
Catalyst type Exfoliated Spinel oxide
Heat 35°C
Time of sonication 1 - 20 minutes
Table S1: Colorimetric calculations for initial dye degradation from 0 to 20 mins of sonocatalysis by 2D MgCr2O4
DYE Time (min)
R G B I(RGB) Ac D% Ibackgr
ound
MB 0 8 154 229 130.33 0.5829 0 255
5 145 209 221 191.66 0.248 57.45 255
10 196 220 222 212.66 0.1577 72.94 255
20 239 243 246 242.66 0.0430 92.62 255
MO 0 193 107 8 102.66 0.662 0 220
10 210 168 130 169.33 0.2273 65.66 220
20 231 207 179 205.66 0.0585 91.1 220
RhB 0 205 50 152 135.66 0.385 0 211.33
10 214 154 190 186 0.1108 71.22 211.33
20 231 187 212 210 0.0054 98.59 211.33
Table S2: Colorimetric calculations for dye degradation from 1 to 5 months of 2D MgCr2O4
exposed dyes
Table S3: Literature overview and comparison of different spinel oxides in dye degradation
DYE Months R G B I(RGB
)
Ac D% Ibackgroun
d
MB 1 138 155 162 151.66 0.1678 0 184
2 162 162 164 162.66 0.1070 36.23 184
4 169 167 168 168 0.0790 52.92 184
5 177 173 174 174.66 0.0452 73.06 184
MO 1 194 120 25 113 0.5257 0 207
4 193 153 101 149 0.2855 45.69 207
5 203 185 161 183 0.1070 79.64 207
RhB 1 172 88 150 136.66 0.1584 0 164
4 151 131 143 141.66 0.1271 19.76 164
5 154 150 151 151.66 0.0679 57.13 164
Material Properti es
Struct ure
Ligh t
Time of activi ty
Degradatio n method
Degrada tion efficienc y
Deg eff./
min
Ref
ZnFe2O4 Narrow band gap (1.9 eV) and high Stability
3D/Bul k
Visi ble
60 mins
Photodegrad ation using catalyst/H2 O2
86.6%
(Orange dye)
1.44 1
Co0.5Zn0.5Fe
2O4
High permeabi lity, high saturatio n
magnetic flux density, high electrical resistivit y
3D/Bul k
Visi ble
60 mins
Photocatalyt ic
degradation
77%
(MB dye)
1.28 2
ZnCr2O4- ZnS
ZnS has light absorbin g
propertie s
3D/Bul k
Visi ble
105 min
Photodegrad ation
Azo dye (96.88%)
0.922 3
MgCr2O4/A
g Resistanc
e to attack against thermal shock, high thermal stability
3D/Bul k
UV 60
mins
Photo degradation
70%
(rhodami ne B) 42%
(MO dye) 58%
(MB dye)
1.16 4
MgCr2O4 sheets
Highly crystalli ne, stable, enormou s defect
2D Visi
ble
20 mins
Sonocatalys is
94%
(MB dye) 74%
(MO dye)
4.7 Thi s wo rk
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