evaluation of shape and size effects on optical properties of zno pigment

Applied

Surface

Science

270 (2013) 33–

38
Contents

lists

available

at

SciVerse

ScienceDirect
Applied

Surface

Science
j

our

nal

ho

me

p

age:

www.elsevier.com/loc

ate/apsusc
Evaluation

of

shape

and

size

effects

on

optical

properties

of

ZnO

pigment
Narges

Kiomarsipour
a,∗
, Reza

Shoja

Razavi
a
, Kamal

Ghani
b
,

Marjan

Kioumarsipour
c
a
Department

of

Materials

Engineering,

Malek

Ashtar

University

of

Technology,

Shahin

Shahr

P.O.

Box

83145/115,

Isfahan,

Iran
b
Department

of

Chemistry,

Malek

Ashtar

University

of

Technology,

Shahin

Shahr

P.O.

Box

83145/115,

Isfahan,

Iran
c
Department

of

Physics,

University

of

Kashan,

Kashan,

Iran
a

r

t

i

c

l

e

i

n

f

o
Article

history:
Received

16

July

2012
Received

in

revised

form
30

November

2012
Accepted

30

November

2012
Available online 10 December 2012
Keywords:
Zinc

oxide

pigment
Light

scattering

efficiency
Optical

property
Hydrothermal

method
a

b

s

t

r

a

c

t
The

pigment

with

optimized

morphology

would

attain

maximum

diffuse

solar

reflectance

at

a

lower
film

thickness

and

reduce

the

pigment

volume

concentration

required.

This

factor

would

contribute

to

a
reduction

in

overall

weight

and

possibly

extend

the

durability

of

the

system

to

longer

time

scales,

specially
in

space

assets.

In

the

present

work,

five

different

morphologies

of

ZnO

pigment

were

synthesized

by
hydrothermal

method.

The

ZnO

pigments

were

characterized

by

X-ray

diffraction

(XRD),

field-emission
scanning

electron

microscopy

(FE-SEM),

atomic

force

microscopy

(AFM)

and

N
2
adsorption

(BET).

The
optical

property

of

the

ZnO

pigments

was

investigated

by

UV/VIS/NIR

spectrophotometer.

The

results
indicated

that

the

optical

properties

of

ZnO

powders

were

strongly

affected

by

the

particle

size

and
morphology.

The

nanorods

and

microrods

ZnO

structures

showed

the

minimum

spectral

reflectance

in
visible

and

near

infrared

regions,

whereas

the

novel

nanoparticle-decorated

ZnO

pigment

revealed

the
maximum

spectral

reflectance

in

the

same

regions.

The

reflectance

spectra

of

scale-like

and

submicro-
rods

ZnO

were

in

the

middle

of

the

others.

The

higher

surface

roughness

led

to

higher

light

scattering

in
nanoparticle-decorated

ZnO

pigment

and

multiple-scattering

in

them.

These

results

proved

that

a

signif-
icant

improvement

in

the

scattering

efficiency

of

ZnO

pigment

can

be

realized

by

utilizing

an

optimized
nanoparticle-decorated

pigment.
© 2012 Elsevier B.V. All rights reserved.
1.

Introduction
Zinc

oxide

is

used

in

the

manufacture

of

paints,

rubber

prod-
ucts,

cosmetics,

pharmaceuticals,

floor

coverings,

plastics,

printing
inks,

soap,

storage

batteries,

textiles

and

electrical

equipment.
Addition

of

pigments

to

coatings

is

a

common

industrial

practice.
Pigments

not

only

provide

esthetics

to

the

coatings

but

also

help

in
improving

many

properties

of

the

coatings

such

as

UV

resistance,
corrosion

resistance

and

mechanical

properties

like

scratch

and
abrasion

[1].

Direct

fabrication

of

special

structures

with

controlled
crystalline

morphology

represents

significant

challenge

in

various
fields,

because

it

can

provide

a

better

model

for

investigating

the
dependence

of

electronic

and

optical

properties

on

the

size

confine-
ment

and

dimensionality

[2–5].

Various

ZnO

structures

including
nanobrushs

[6],

nanowires

[7],

nanobowls

[8]

and

nanopellets

[9]
have

been

produced.

They

are

widely

used

in

many

important

areas,
such

as

solar

cells

[10],

gas

sensors

[11],

electronics

[12]

and

photo-
catalysts

[13].

One

of

the

most

important

applications

of

ZnO

is

in
∗
Corresponding

author.

Tel.:

+98

312

5225041;

fax:

+98

312

5228530.

E-mail

address:

(N.

Kiomarsipour).
the

paint

industry

as

pigment.

The

ZnO

is

a

white

powder

that

usu-
ally

used

as

pigment

and

by

volume

is

the

second

most

significant
white

pigment

[14].

There

are

several

potential

benefits

to

optimize

the

scatter-
ing

efficiency

of

the

ZnO

pigment

through

control

of

particle

size.
An

ideal

coating

design

would

obtain

the

theoretical

maximum
reflectance

(i.e.

opacity)

with

the

lowest

pigment

volume

concen-
tration

(PVC)

and

dry

film

thickness

(DFT).

Any

additional

pigment
does

not

contribute

to

scattering

and

is

detrimental

to

the

physi-
cal

properties

of

the

film

[15].

The

surface

texture

of

a

scattering
particle,

in

addition

to

the

overall

particle

geometric

shape,

is
also

an

important

morphological

factor

in

determining

the

opti-
cal

properties

of

the

scatter.

In

the

past

two

decades,

the

effect

of
asphericity

of

a

particle

on

its

single-scattering

parameters

(e.g.,
phase

function

and

cross

section)

has

been

extensively

investi-
gated.

However,

only

a

handful

of

studies

have

investigated

the
effect

of

surface

texture

or

roughness

on

particle

optical

properties
[16,17].
The

present

paper

is

focused

on

the

development

of

a

novel
morphology

of

ZnO

pigment

that

can

potentially

raise

the

scatter-
ing

efficiency

of

ZnO

pigment.

In

the

present

work,

five

different

morphologies

of

ZnO

were

synthesized

by

hydrothermal

method
and

then

the

morphology

effects

on

the

spectral

reflectance

were
studied.
0169-4332/$

–

see

front

matter ©

2012 Elsevier B.V. All rights reserved.
/>34 N.

Kiomarsipour

et

al.

/

Applied

Surface

Science

270 (2013) 33–

38
Table

1
Synthesis

conditions

of

hydrothermally

synthesized

ZnO

pigments.
Morphology

[Zinc

solution]
a
[Hydroxide

solution]

a
pH

of

final

solution

Temprature

(
◦
C)

Time

(h)
Scale-like

1.5

2.0

11

160

18
Submicrorods

0.5

1.5

12

150

20
Microrods 0.5

1.5

12

180

20
nanorods

0.5

1.5

12

120

20

Decorated-nanoparticles 1.0

4.0

12.5

170

14
a
The

concentration

of

zinc

nitrate

and

potassium

hydroxide

solutions

(Molar).
2.

Experimental
2.1.

Preparation

of

pigments
ZnO

samples

were

prepared

by

hydrothermal

method

and

used
for

the

evaluation

of

morphology

effects

of

ZnO

pigments

on

their
optical

properties.

The

synthesis

conditions

were

according

to

our
previous

works

[18,19].

Typical

synthesis

conditions

of

ZnO

pow-
ders

synthesized

in

this

work,

were

summarized

in

Table

1.

All

of
the

samples

were

prepared

as

follows:
The

zinc

nitrate

aqueous

solution

was

prepared

by

adding
appropriate

amount

of

Zn(NO
3
)
2
·6H
2
O

(Reagent

Grade,

98%
Sigma–Aldrich)

to

distilled

water.

The

pH

of

solution

increased

by
adding

dropwise

a

solution

of

KOH

(appropriate

amount

of

KOH
added

in

distilled

water)

and

stirring

vigorously

for

10

min

at

room
temperature.

Then

the

resulting

slurry

mixture

was

transferred

into
a

100

mL

Teflon-lined

stainless

steel

autoclave

up

to

80%

of

the

total
volume.

Hydrothermal

reaction

was

conducted

in

an

oven.

After

the
reaction

was

completed,

the

autoclave

was

cooled

very

slowly

to
room

temprature

and

the

final

product

was

collected

by

pressure
filtration.

Powdered

sample

was

thoroughly

washed

with

distilled
water

and

then

dried

in

air

at

120
◦
C

for

12

h.
2.2.

Characterization

of

pigments
Crystal

structure

of

as-prepared

products

was

characterized
by

powder

X-ray

diffraction

(XRD)

on

a

Bruker

D8

Advance
X-ray

diffractometer

using

Cu-K␣

radiation

(40

kV,

40

mA

and


=

0.1541

nm).

XRD

patterns

were

recorded

from

0
◦
to

90
◦
with
a

scanning

step

of

0.02
◦
/s.

Morphology

and

size

of

the

samples
were

analyzed

by

Hitachi

S-4160

Field

Emission

Scanning

Elec-
tron

Microscopy

(FE-SEM)

at

an

accelerating

voltage

of

15

kV.
The

diffuse

reflectance

spectra

of

prepared

powders

were

mea-
sured

by

JASCO

V-670

UV–vis

Spectrophotometer

(in

the

range
of

220–2200

nm).

The

specific

surface

areas

were

measured

by
Brunauer–Enmet–Teller

(BET)

method

employing

N
2
adsorption

at
77

K

after

treating

the

sample

at

170
◦
C

and

10
−4
Pa

for

2

h,

using
a

Tristar-3000

apparatus.

Atomic

force

microscopy

(AFM)

mea-
surements

for

ascertaining

the

surface

roughness

of

the

scale-like
and

nanoparticle-decorated

pigments

were

performed

by

atomic
force

spectroscope

(AFM;

DME

Dualscope

DS-95-200-E;

0.12

nN,
30

mm/s).
3.

Results

and

discussion
The

typical

XRD

patterns

of

the

products

are

shown

in

Fig.

1.
All

of

the

diffraction

peaks

can

be

indexed

as

hexagonal

wurtzite
ZnO

with

cell

constants

a

=

3.2490
˚
AÅ

and

c

=

5.2050
˚
AÅ

for

prod-
ucts,

in

good

agreement

with

the

reported

data

for

ZnO

(JCPDS

File,
00-005-0664).

The

very

sharp

diffraction

peaks

indicated

the

good
crystallinity

of

the

prepared

crystals

and

no

characteristic

peaks
were

detected

from

any

other

impurities

such

as

Zn(NO
3
)
2
·6H
2

O
and

Zn(OH)
2
.
Fig.

2(a–k)

shows

the

low-magnification

and

high-magnification
FE-SEM

images

of

the

five

corresponding

obtained

pigments:
scal-like,

submicrorods,

microrods,

nanorods

and

nanoparticle-
decorated

ZnO.

In

Fig.

2,

it

can

be

seen

that

the

morphology

of
ZnO

pigments

is

greatly

affected

by

the

hydrothermal

conditions.
Fig.

2(a)

and

(b),

shows

the

scale-like

ZnO,

which

all

of

the

scales
have

fairly

uniform

diameters

about

300

nm

and

thicknesses

of
50

nm.

In

Fig.

2(c)

and

(d),

FE-SEM

images

of

the

submicrorods
ZnO

is

shown.

The

diameters

of

ZnO

rods

are

about

100

nm

and
their

lenghts

are

up

to

2

␮m.

The

FE-SEM

images

of

the

microrods
ZnO

pigment

are

shown

in

Fig.

2(e)

and

(f).

The

lower

magnifica-
tion

Image

2(e)

indicates

that

the

highly

dispersed

microrod

ZnO
structures

have

diameters

of

about

200

nm

and

lengths

of

3

␮m.
The

FE-SEM

images

of

nanorod

ZnO

pigment

are

shown

in

Fig.

2(g)
and

(h).

It

is

found

that

the

product

is

composed

of

well-dispersed
Fig.

1.

XRD

patterns

of

the

as-synthesized

ZnO

pigments.
N.

Kiomarsipour

et

al.

/

Applied

Surface

Science

270 (2013) 33–

38 35
crystals

on

a

large

scale,

and

all

of

the

nanorods

have

diameters
of

about

50

nm

and

lengths

of

300

nm.

Fig.

2

(i–k)

exhibits

the

FE-
SEM

images

of

nanoparticle-decorated

ZnO

pigment.

The

surface
of

ZnO

pigment

was

decorated

by

nanoparticles

with

diameters
of

approximately

20–50

nm.

The

decorated

surface

of

pigment
was

led

to

increase

specific

surface

area

and

surface

roughness
of

particles

and

consequently,

increase

the

light

scattering

effi-
ciency

[16,20].

N
2
adsorption–desorption

results

further

confirmed
Fig.

2.

Low-

and

high-magnification

FE-SEM

images

of

ZnO

structures:

(a,

b)

Scale-like,

(c,

d)

submicrorods,

(e,

f)

microrods,

(g,

h)

nanorods

and

(i,

j,

k)

nanoparticle-decorated
ZnO.
36 N.

Kiomarsipour

et

al.

/

Applied

Surface

Science

270 (2013) 33–

38
Fig.

2.

(Continued).
the

porous

surface

feature

of

the

nanoparticle-decorated

ZnO

pig-
ment.

The

representative

isotherm

of

the

ZnO

pigment

is

shown

in
Fig.

3.

The

N
2
isotherm

plot

belongs

to

the

type

IV

isotherm

in

the
Brunauer

classification

[21].

A

hysteresis

loop

observed

at

higher
relative

pressures

(P/P
0
=

0.5–0.9)

is

associated

with

the

filling

and
emptying

of

mesoporous

(10–30

nm

in

diameter)

by

capillary

con-
densation.

According

to

the

IUPAC

classifications,

the

observed

loop
0
20

40
60
0

0.5

1
Va/cm3(STP) g-1
p/p
0
ADS

DES
Fig.

3.

Typical

N
2
adsorption–desorption

isothermal

of

the

nanoparticle-decorated

ZnO

pigment.
indicates

the

H
3
type,

implying

the

presence

of

mesoporous

[21].
The

BET

surface

area

of

the

nanoparticle-decorated

ZnO

pigment
was

calculated

to

be

only

6.3712

m
2
/g.

The

surface

of

the

particles
was

decorated

by

nanoparticles

with

diameters

of

approximately
20–50

nm,

on

which

mesoporous

with

diameter

ranging

from

10
to

30

nm

were

formed

among

nanoparticles

simultaneously.
The

experimentally

measured

specular-included

UV/VIS/NIR
reflectance

spectra

of

ZnO

pigments

are

shown

in

Fig.

4.

It

can

be
seen

that

the

optical

property

was

greatly

affected

by

morphology
and

particle

size

of

pigments.

The

particle

size

of

the

pigment

plays
an

important

role

in

light

scattering

efficiency

[15,22,23].
Wave

theories

of

light

account

for

bending

phenomena

which
give

rise

to

scattering.

Light

scattering

by

this

mechanism

increases

with

decreasing

particle

size

until

an

optimum

is

reached

at
approximately

half

the

wavelenght

of

light.

Optimal

particle

size
for

scattering

can

be

calculated,

and

also

depends

on

wavelength
[24].

The

scattering

efficiency

is

extremely

dependent

upon

the

par-
ticle

size

distribution

of

the

pigment.

It

is

well

known

from

Mie
scattering

theory

that

as

the

pigment

particle

diameter

approaches
approximately

one-half

that

of

the

incident

radiation

wavelength,
scattering

is

increased

dramatically.

The

results

of

the

modeling
indicated

that

an

optimum

particle

size

of

distribution

would

be
between

between

0.25

and

0.45

␮m,

and

particles

greater

than
1.5

␮m

provide

very

little

Mie

scattering

contributions

[22,23].

It
is

quite

evident

from

the

contour

plot

that

ZnO

particle

diameter
greater

than

approximately

1.5

␮m

do

not

scatter

light

efficiency
at

any

wavelength

[15].

When

particle

sizes

are

large

(greater

than
1.5

␮m),

reflectance

is

relatively

low.

As

particle

size

decreases,
reflectance

increases

as

the

number

of

first-surface

reflections

and

the

amount

of

multiple

scattering

increases.

Further

decreases

in
particle

size

result

in

an

improvement

of

the

reflectance.

As

parti-
cle

size

decreases

such

that

the

size

is

less

than

the

wavelength,

the
particle

as

a

whole

interacts

with

a

wavelength

of

light

[25].
N.

Kiomarsipour

et

al.

/

Applied

Surface

Science

270 (2013) 33–

38 37
0
20
40
60
80
100
0 50

0 100

0 150

0 200

0 250

0

Reflectance (%)
Wavelenght

(nm)
Nanop

article-decorated Z

nO
Scale-li

ke ZnO
Submic

rorod

s ZnO
Microrods ZnO
Nanorods Z

nO
Fig.

4.

Experimental

specular-included

UV/VIS/NIR

reflectance

spectra

of

as-synthesized

ZnO

pigments.
From

Fig.

4,

it

can

be

observed

that

the

spectral

reflectances

of
nanorod

and

microrod

ZnO

pigments

are

lower

than

the

others.
Because

of

the

particle

sizes

of

nanorod

and

microrod

ZnO

pig-
ments

are

smaller

and

greater

than

the

optimal

particle

size

range
of

0.25–1.5

␮m,

respectively,

hence

do

not

scatter

light

efficienty
at

any

wavelength

[15].

The

observed

high

light

absorption

in

UV
region

(at

wavelengths

below

366

nm)

indicated

in

Fig.

4

is

due

to
ZnO

band

gap

and

this

phenomenon

is

one

of

the

most

important
ZnO

characteristics

[14].

The

particle

sizes

of

scale-like

and

submi-
crorod

ZnO

pigments

are

in

the

optimum

range

of

0.25–0.45

␮m,
and

their

UV/VIS/NIR

reflectance

spectra

have

the

suitable

amount
for

pigmentation

applications.

Consequently,

the

decorated

surface
of

new

ZnO

pigment

led

to

higher

light

reflectance.

The

decorated
surface

with

nanoparticles

led

to

increasing

of

special

surface

area
and

consequently

increasing

the

light

scattering.

The

presence

of
nanoparticles

on

the

surface

of

pigment

caused

increase

surface
roughness

and

more

chance

for

light

to

be

refracted.

The

higher
reflectance

of

new

morphology

also

can

be

attributed

to

more

dif-
ference

between

the

refractive

indices

ZnO

and

air-voids

in

pigment
mesoporous

structure

(between

in

particles).

The

nanoparticle-
decorated

ZnO

pigments

similar

to

particles

containing

air

voids
led

to

higher

reflectance

index

due

to

much

difference

between
the

refractive

indices

of

ZnO

and

air

voids

and

hence

increased

the
light

scattering

[26].
The

AFM

images

of

scale-like

and

nanoparticle-decorated

ZnO
pigments

are

presented

in

Fig.

5.

As

can

be

seen

in

this

figure

(Fig.

5),

the

surface

roughness

of

nanoparticle-decorated

ZnO

is

higher

and
more

uniform

than

scale-like

ZnO.
The

scattering

of

light

by

small

particles

is

determined

not

only
by

the

composition

of

the

incident

light

and

the

optical

properties
of

the

particles

and

the

medium

but

also

by

the

size,

shape,

con-
centration,

surface

roughness,

spatial

arrangement

of

the

particles,
etc.

Many

studies

had

shown

that

surface

roughness

can

indeed
play

an

important

role

on

the

light

scattering

pattern

under

certain
conditions

[27–30].

The

initial

theoretical

studies

and

subsequent
experimental

studies

of

multiple-scattering

effects

were

carried
out

for

randomly

rough

surfaces

characterized

by

rms

heights

of
the

order

of

5–10

nm,

and

transverse

correlation

lengths

of

the
order

of

100

nm,

i.e.

surfaces

with

nanoscale

roughness.

Subse-
quent

experimental

and

theoretical

work

was

devoted

to

the

study
of

surfaces

that

were

significantly

rougher

than

these,

e.g.

surfaces
with

microscale

roughness.

This

is

because

some

of

the

methods
Fig.

5.

AFM

images

of:

(a)

nanoparticle-decorated

and

(b)

scale-like

ZnO

pigments.
38 N.

Kiomarsipour

et

al.

/

Applied

Surface

Science

270 (2013) 33–

38
developed

for

treating

scattering

from

surfaces

with

this

larger
scale

of

roughness,

especially

computational

methods,

can

also
be

used

in

the

study

of

scattering

from

surfaces

with

nanoscale
roughness,

and

some

of

the

results

obtained

in

studies

of

sur-
faces

with

the

larger

scale

roughness

also

apply

to

surfaces

with
nanoscale

roughness

[31].

Another

study

indicated

that

a

good
correlation

was

between

the

surface

roughness

from

AFM

and

opti-
cal

reflection

measurements.

In

addition,

angle-resolved

reflection
measurements

gave

an

account

on

the

decrease

in

optical

scat-
tering

after

polishing

the

sample

surface.

In

this

case,

the

angular
reflection

distribution

is

similar

to

that

of

a

thin

sample

with

low
surface

roughness

and

shows

that

the

measured

optical

scattering
is

mainly

determined

by

the

surface

roughness

[32].

On

the

other
hand,

it

is

evident

that

increasing

surface

roughness

strongly

affects
the

scattering

properties

of

ice

particles

[33].

The

higher

surface
roughness

of

nanoparticle-decorated

ZnO

led

to

multiple

scatter-
ing

and

increasing

of

the

reflectance.

Presence

of

nanoparticles

on
the

pigment

surface

enhanced

the

multiple

scattering

for

whole

of
wavelength

range

[34,35].
4.

Conclusions
Well-dispersed

five

different

morphologies

of

ZnO

pigment
was

synthesized

by

a

simple

hydrothermal

method.

Evaluation

of
their

optical

properties

indicated

that

the

spectral

reflectance

was
strongly

affected

by

particle

shape

and

size.

Nanorod

and

microrod
ZnO

pigments

had

shown

the

lower

reflectance

spectra,

because
their

particle

size

were

not

in

the

optimum

range

and

they

do
not

scatter

light

efficiently

at

any

wavelength.

Scale-like

and

sub-
microrod

ZnO

pigments

had

shown

mean

reflectance.

The

novel
nanoparticle-decorated

ZnO

pigment

showed

the

highest

spectral
reflectance

and

it

is

promising

to

be

applied

in

paint

coatings

due
to

its

excellent

VIS/NIR

reflectance

property.

The

higher

surface
roughness

of

nanoparticle-decorated

ZnO

pigment

led

to

higher
multiple

scattering

and

higher

reflectance.
References
[1]

S.K.

Dhoke,

A.S.

Khanna,

T.J.

Mangal

Sinha,

Effect

of

nano-ZnO

particles

on

the
corrosion

behavior

of

alkyd-based

waterborne

coatings,

Progress

in

Organic
Coatings

64

(2009)

371–382.
[2]

S.H.

Ko,

I.

Park,

H.

Pan,

N.

Misra,

M.S.

Rogers,

ZnO

nanowire

network

transistor
fabrication

on

a

polymer

substrate

by

low-temperature,

all-inorganic

nanopar-
ticle

solution

process,

Applied

Physics

Letters

92

(2008)

154102–154103.
[3]

Y.

Khan,

S.K.

Durrani,

M.

Mehmood,

J.

Ahmad,

M.R.

Khan,

S.

Firdous,

Low

tem-
perature

synthesis

of

fluorescent

ZnO

nanoparticles,

Applied

Surface

Science
257

(2010)

1756–1761.
[4]

Y.F.

Zhu,

W.Z.

Shen,

Synthesis

of

ZnO

compound

nanostructures

via

a

chem-
ical

route

for

photovoltaic

applications,

Applied

Surface

Science

256

(2010)
7472–7477.
[5]

L.

Feng,

A.

Liu,

J.

Wei,

M.

Liu,

Y.

Ma,

B.

Man,

Synthesis,

characterization

and

opti-
cal

properties

of

multipod

ZnO

whiskers,

Applied

Surface

Science

255

(2009)
8667–8671.
[6] J.

Wang,

H.

Zhuang,

J.

Li,

P.

Xu,

Synthesis,

morphology

and

growth

mechanism

of
brush-like

ZnO

nanostructures,

Applied

Surface

Science

257

(2011)

2097–2101.
[7]

C.C.

Lin,

Y.Y.

Li,

Synthesis

of

ZnO

nanowires

by

thermal

decomposition

of

zinc
acetate

dihydrate,

Materials

Chemistry

and

Physics

113

(2009)

334–337.
[8]

Y.

Wang,

X.

Chen,

J.

Zhang,

Z.

Sun,

Y.

Li,

K.

Zhang,

B.

Yang,

Fabrication

of
surface-patterned

and

free-standing

ZnO

nanobowls,

Colloids

and

Surfaces

A
329

(2008)

184–189.
[9]

W.S.

Chiu,

P.S.

Khiew,

D.

Isa,

M.

Cloke,

S.

Radiman,

R.A.

Shukor,

M.H.

Abdullah,
N.M.

Huang,

Synthesis

of

two-dimensional

ZnO

nanopellets

by

pyrolysis

of

zinc
oleate,

Chemical

Engineering

Journal

142

(2008)

337–343.
[10]

H.

Zhao,

X.

Su,

F.

Xiao,

J.

Wang,

J.

Jian,

Synthesis

and

gas

sensor

properties

of
flower-like

3D

ZnO

microstructures,

Materials

Science

and

Engineering

B

176
(2011)

611–615.
[11]

J.

Huang,

Y.

Wu,

C.

Gu,

M.

Zhai,

Y.

Sun,

J.

Liu,

Fabrication

and

gas-sensing

prop-
erties

of

hierarchically

porous

ZnO

architectures,

Sensors

an

Actuators

B

155
(2011)

126–133.
[12]

S.M.

Peng,

Y.K.

Su,

L.W.

Ji,

S.J.

Young,

C.N.

Tsai,

W.C.

Chao,

Z.S.

Chen,

C.Z.

Wu,
Semitransparent

field-effect

transistors

based

on

ZnO

nanowire

networks,

IEEE
Electron

Device

Letters

32

(2011)

533–535.
[13] O.

Akhavan,

M.

Mehrabian,

K.

Mirabbaszadeh,

R.

Azimirad,

Hydrothermal

syn-
thesis

of

ZnO

nanorod

arrays

for

photocatalytic

inactivation

of

bacteria,

Journal
of

Physics

D:

Applied

Physics

42

(2009)

225305.
[14]

G.

Buxbaum,

Industrial

Inorganic

Pigments,

Second

ed.,

Wiley-VCH

Verlag
GmbH,

D-69469,

Weinheim,

1998.
[15]

J.A.

Johnson,

J.J.

Heidenreich,

R.A.

Mantz,

P.M.

Baker,

M.S.

Donley,

A

multiple-
scattering

model

analysis

of

zinc

oxide

pigment

for

spacecraft

thermal

control
coatings,

Progress

in

Organic

Coatings

47

(2003)

432–442.
[16] C.

Li,

G.W.

Kattawar,

P.

Yang,

Effects

of

surface

roughness

on

light

scattering

by
small

particles,

Journal

of

Quantitative

Spectroscopy

and

Radiative

Transfer

89
(2004)

123–131.
[17] J.

Krc,

M.

Zeman,

O.

Kluth,

F.

Smole,

M.

Topic,

Effect

of

surface

roughness

of
ZnO:Al

films

on

light

scattering

in

hydrogenated

amorphous

silicon

solar

cells,
Thin

Solid

Films

426

(2003)

296–304.
[18]

N.

Kiomarsipour,

R.

Shoja

Razavi,

Characterization

and

optical

property

of

ZnO
nano-,

submicro-

and

microrods

synthesized

by

hydrothermal

method

on

a
large-scale,

Superlattices

and

Microstructures

52

(2012)

704–710.
[19]

N.

Kiomarsipour,

R.

Shoja

Razavi,

Hydrothermal

synthesis

and

optical

prop-
erty

of

scale-like

and

spindle-like

ZnO,

Ceramics

International

39

(2013)
813–818.

[20]

J.E.

Van

Nostrand,

R.

Cortez,

Z.P.

Rice,

N.C.

Cady,

M.

Bergkvist,

Local

transport
properties,

morphology,

microstructure

and

transport

properties

of

ZnO

deco-
rated

SiO
2
nanoparticles,

Nanotechnology

21

(2010)

415602,

IOP

Publishing.
[21]

L.

Zhang,

J.

Zhao,

J.

Zheng,

L.

Li,

Z.

Zhu,

Hydrothermal

synthesis

of

hierarchical

nanoparticle-decorated

ZnO

microdisks

and

the

structure-enhanced

acetylene
sensing

properties

at

high

temperatures,

Sensors

and

Actuators

B

158

(2011)
144–150.
[22]

J.A.

Johnson,

A.I.

Haines,

L.A.

Bedrossian,

M.T.

Kenny,

Development

of

improved
thermal

control

coatings

for

space

assets,

AFRL-ML-WP-TP-2004-411,

2004.
[23]

E.S.

Berman,

J.A.

Johnson,

R.A.

Mantz,

P.S.

Meltzer,

Spacecraft

materials

develop-
ment

programs

for

thermal

control

coatings

and

space

environmental

testing,
The

AMPTIAC

Quarterly

8

(2004)

58–66.
[24]

R.

Lambourne,

T.A.

Strivens,

Paint

and

Surface

Coatings:

Theory

and

Practice,
Second

ed.,

William

Andrew

Publishing,

Cambridge,

1999.
[25] J.F.

Mustard,

J.E.

Hays,

Effects

of

hyperfine

particles

on

reflectance

spectra

from
0.3

to

25

␮m,

Icarus

125

(1997)

145–163.
[26]

N.

Kiomarsipour,

R.

Shoja

Razavi,

K.

Ghani,

Improvement

of

spacecraft

white
thermal

control

coatings

using

the

new

synthesized

Zn-MCM-41

pigment,

Dyes
and

Pigments

96

(2013)

403–406.
[27] K.

Nelson,

Y.

Deng,

Effect

of

polycrystalline

structure

of

TiO2

particles

on

the
light

scattering

efficiency,

Journal

of

Colloid

and

Interface

Science

319

(2008)
130–139.
[28] R.D.

Geil,

M.

Mendenhall,

R.A.

Weller,

B.R.

Rogers,

Effects

of

multiple

scatter-
ing

and

surface

roughness

on

medium

energy

backscattering

spectra,

Nuclear
Instruments

and

Methods

in

Physics

Research

Section

B

256

(2007)

631–637.
[29]

B.R.

Nag,

M.

Das,

Scattering

potential

for

interface

roughness

scattering,

Applied
Surface

Science

182

(2001)

357–360.
[30]

M.

Kahnert,

T.

Nousiainen,

M.A.

Thomas,

J.

Tyynelä,

Light

scattering

by

parti-
cles

with

small-scale

surface

roughness:

comparison

of

four

classes

of

model
geometries,

Journal

of

Quantitative

Spectroscopy

and

Radiative

Transfer

113
(2012)

2356–2367.
[31]

A.A.

Maradudin,

Light

scattering

and

nanoscale

surface

roughness,

in:

Nano-

structure

Science

and

Technology,

National

Research

Council

of

Canada,
Ottawa,

2007.
[32] R.

Bruggemann,

P.

Reinig,

M.

Hölling,

Thickness

dependence

of

optical

scat-
tering

and

surface

roughness

in

microcrystalline

silicon,

Thin

Solid

Films

427
(2003)

358–361.
[33]

M.I.

Mishchenko,

L.D.

Travis,

Scattering,

Absorption

and

Emission

of

Light

by
Small

Particles,

Revised

electronic

edition,

Goddard

Institute

for

Space

Studies,
New

York,

2004.
[34]

R.T.

Zaera,

J.

Elias,

C.L.

Clément,

ZnO

nanowire

arrays:

optical

scattering

and
sensitization

to

solar

light,

Applied

Physics

Letters

93

(2008)

233119.
[35]

E.

Pál,

V.

Hornok,

A.

Oszkó,

I.

Dékány,

Hydrothermal

synthesis

of

prism-like
and

flower-like

ZnO

and

indium-doped

ZnO

structures,

Colloids

and

Surfaces
A:

Physicochemical

and

Engineering

Aspects

340

(2009)

1–9.