Supporting Information

Synthesis of Diverse Ag2O Crystals and Their Facet-Dependent Photocatalytic

Activity Examination

Ying-Jui Chen, Yun-Wei Chiang, and Michael H. Huang*

Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan

E-mail: hyhuang@mx.nthu.edu.tw

S-1

Catalytic Amount Calculations

For best comparison of the catalytic effects of different faces, the total surface

area of Ag2O particles used should be kept the same. From average particle sizes,

surface area and volume of a single cube, octahedron, and rhombic dodecahedron can

be calculated. Knowing particle volume, the weight of a single particle can be

determined from the density of Ag2O (7.14 g/cm3). The ratio of surface area per unit

mass (surface/mass or surface/(volume × density)) is then calculated, giving a ratio of

1 : 2.74 : 4.79 for rhombic dodecahedron : octahedron : cube (see Figure S1 for

surface area and volume of each particle shape). The corresponding amounts of

Ag2O rhombic dodecahedra, octahedra, and cubes having the same total particle

surface area for the photocatalytic activity experiment are 8.2, 3.0, and 1.7 mg,

respectively.

Cube:a = 454 nm

A = 6a2 = 1236696 nm2

V = a3 = 93576664 nm3

Octahedron:a = h/√2 = 974.4 nm

A = 3289010 nm2

V = 436119564nm3

Edge length (a)= 454 nm

Opposite corner length

=1378 nm

h(√2)

a (1)

Edge size (L) = 2174 nm

a (√3)Rhombic dodecahedron

L= 2174 nm

a = L(√6)/4 = 1331.3 nm

A = 8√2 a2 = 20051960 nm2

V = (16√3)/9 a3 = 7265506516 nm3

L(2√2)

S (2)

Figure S1. Calculations of surface area and volume of a single Ag2O cube,

octahedron, and rhombic dodecahedron.

S-2

Figure S2. Size distribution histograms for Ag2O (a) cubes, (b) great

rhombicuboctahedra, (c) cuboctahedra, (d) corner-truncated octahedra, (e) octahedra,

and (f) rhombic dodecahedra. Average particle sizes are also given.

Table S1. Average particle sizes and their standard deviations.

Shape average particle size

(nm)

standard

deviation (%)

cubes 454 ± 72 15

great rhombicuboctahedra 1317 ± 128 9

cuboctahedra 848 ± 96 11

corner-truncated octahedra 1262 ± 91 7

octahedra 1378 ± 115 8

rhombic dodecahedra 2174 ± 255 11

S-3

Figure S3. Photographs showing the changes in the solution color in the growth of

Ag2O cubes, octahedra, and rhombic dodecahedra at various time points. After 2

min, the solution color remains fixed and can be considered as the final solution color.

Table S2. Experimental conditions used in the synthesis of various Ag2O crystals by

adding additional NH4NO3 solution relative to that of AgNO3 solution introduced.

shape H2O

(mL)

0.4 M

NH4NO3

(µL)

2 M

NaOH

(µL)

Extra

NH3

(µmol)

0.1 M

AgNO3

(µL)

0.2 M

NaOH

(mL)

edge- and

corner-truncated cubes 3.20 250 50 0 500 1

great rhombicuboctahedra 3.11 325 65 30 500 1

small

rhombicuboctahedra 3.05 375 75 50 500 1

edge-truncated octahedra 2.98 437.5 87.5 75 500 1

S-4

900 1000 1100 1200 1300 1400 1500 16000

5

10

15

20

25

30

35

40

%

Particle size (nm)

450 500 550 600 650 700 750 8000

5

10

15

20

25

30

35

Particle size (nm)

%

b

Opposite {100} face distance= 1317 nm

Opposite {100} face distance

= 627 nm

a

1700 1800 1900 2000 2100 2200 2300 24000

5

10

15

20

25

30

35

Particle size (nm)

%

Opposite {100} face distance= 2122 nm

3650 3800 3950 4100 4250 4400 4550 47000

5

10

15

20

25

30

35

40

Particle size (nm)

%

Opposite corner distance

= 4136 nm

c d

Figure S4. Size distribution histograms for Ag2O (a) edge- and corner-truncated

cubes, (b) great rhombicuboctahedra, (c) small rhombicuboctahedra, and (d)

edge-truncated octahedra.

Table S3. Average particle sizes of additional Ag2O crystals shapes and their

standard deviations.

Shape average particle

size (nm)

standard

deviation (%)

edge- and corner-truncated

cubes 627 ± 67 10

great rhombicuboctahedra 1317 ± 128 10

small rhombicuboctahedra 2122 ± 137 6

edge-truncated octahedra 4136 ± 232 6

S-5

364 366 368 370 372 374 376 378

Inte

nsi

ty (

a. u

.)

367.9 eV

367.9 eV

373.9 eV

373.9 eV

373.9 eV

Binding Energy (eV)

367.9 eV

526 527 528 529 530 531 532 533 534 535

530.7 eV

530.8 eV

531.0 eV529.3 eV

529.2 eV

O 1s

Binding Energy (eV)

529.3 eV

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

B in d in g E n e r g y ( e V )

Inte

nsity

(a.

u.)

O K

LL

Ag

3s

Ag

3p1

Ag

3p3

O 1

s1

C 1

s

Ag

4s

Ag

4pA

g 4d A

g 3d

a

b cAg 3d5/2

Ag 3d3/2

Figure S5. (a) Full XPS spectra of Ag2O cubes, octahedra, and rhombic

dodecahedra. (b) Expanded XPS spectra showing the Ag 3d peak region. (c)

Expanded XPS spectra showing the O 1s peak region.

S-6

-30 -20 -10 0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

80

90

100

Time (min)

C/C

0 (

%)

Figure S6. MO photodegradation extent versus reaction time. Three experiments

have been carried out for each particle shape, giving highly consistent results.

Average standard deviations of data points for Ag2O cubes, octahedra, and rhombic

dodecahedra are 1.5%, 2.6% and 0.8%, respectively.

Figure S7. Analysis of EPR spectrum obtained. The radicals generated consist of

50% OH radicals, 35% O2– radicals, and 15% unidentified radicals.

S-7

a b c

d e f

Figure S8. SEM images of Ag2O (a, d) cubes, (b, e) octahedra, and (c, f) rhombic

dodecahedra before (a‒c) and after (d‒f) photocatalysis. Scale bars are all equal to 1

µm. All particle shapes show etching with formation of Ag2O flakelike structures.

Quantum Yield Calculations

The quantum yield (QY) is defined as

QY = number of decomposed molecules / number of incident photons

where N0 is the initial number of molecules, N is the number of remained molecules,

D is the fraction of photodegradation (between 0 and 1), and Nphoton is the number of

incident photons. Specifically,

where the Ephoton is the energy of one photon with wavelength λm, Preal is the power of

incident light in [Watt], which was measured using a power meter in our experiment, t

is the physical time in [s], ρs is the density of solution (assume about 1000 kg/cm3), C0

is the initial concentration of pollutant molecules in [ppm], V0 is the volume of

pollutant molecule in [L], M0 is the molecular mass of pollutant, NA is Avogadro’s

number (about 6.022 × 1023

), h is Planck’s constant, c is the speed of light, and λm is

the wavelength for monochrome light or average wavelength for light spectrum in

[cm].1

S-8

Table S4. Values of relevant parameters needed for the determination of quantum

yield in the photodegradation of methyl orange using Ag2O cubes, octahedra, and

rhombic dodecahedra as the catalysts. Shapes of

Ag2OAverage

hc/(Preal*λm)ρs

(Density of solution,kg/cm3)

NA D(Fraction of

photodegradation)

Co

(Concentrationof methyl

orange, ppm)

Vo

(Volume, L)t

(Time, s)Mo

(Molecularweight of methyl orange)

Quantumyield

Cubes 1.07E-20 1000 6.022E+23 0.85 15 0.006 5400 327.33 0.278

Octahedra 1.07E-20 1000 6.022E+23 0.35 15 0.006 5400 327.33 0.114

Rhombicdodecahedra

1.07E-20 1000 6.022E+23 0.15 15 0.006 5400 327.33 0.049

Average hc / (Preal × λm) was determined by recording the power of the Xe lamp

reaching to the cuvette (varying from 0.172 W to 0.746 W) over the wavelength range

of 400–1050 nm. After finding (Preal × λm) for each wavelength, the obtained (Preal ×

λm) values were averaged.

References

(1) Shidpour, R.; Vossoughi, M.; Simchi, A. R.; Micklich, M. Extended Quantum

Yield: A Dimensionless Factor Including Characteristics of Light Source,

Photocatalyst Surface, and Reaction Kinetics in Photocatalytic Systems. Ind. Eng.

Chem. Res. 2014, 53, 11973−11978.

S-9