review on multi-dimensional zinc oxide nanostructures€¦ · thin films are good examples of 2-d...

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( Received 30 June 2020; Accepted 21 July 2020; Date of Publication 22 July 2020 )

WSN 147 (2020) 140-165 EISSN 2392-2192

Review on Multi-dimensional Zinc Oxide Nanostructures

Sarani Acharyya1, Swarnali Acharyya2, Pijus Kanti Samanta3,*

1Department of Physics, Sahid Matangini Hazra Government College for Women, Tamluk, Purba Medinipur, West Bengal, India

2Department of Physics, Panskura Banamali College (Autonomous), Panskura, Purba Medinipur, West Bengal, India

3Department of Physics (PG & UG), Prabhat Kumar College, Contai - 721404, West Bengal, India

*E-mail address: [email protected]

ABSTRACT

Nanostructured materials are being widely investigated due to their versatile properties leading to

promising applications in various areas starting from electronics to environment and medical science.

Amongst the various investigated nanostructures, Zinc Oxide (ZnO) is very important because of its

versatile properties like high and direct band gap, optical transparency, room temperature

ferromagnetism, piezoelectric property and gas sensing property. This mini review article is focused on

the morphological study of various ZnO nanostructures starting from hierarchical nanostructures to

quantum dots.

Keywords: Zinc Oxide, Semiconductor, Band-gap, Morphology

1. INTRODUCTION

Nanomaterials are in the forefront of modern research because of their unique properties

compared to their bulk counterpart. In a bulk material the electrons can move over a large

distance (few hundreds of unit cells) within the material. Hence, the electrons suffer multiple

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World Scientific News 147 (2020) 140-165

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scattering and collisions with the lattice ions, phonons, impurities and defects of the material

[1, 2]. In nanoscale materials, one or more dimensions being very small (only few tens of unit

cells) the motion of the electrons is very much restricted. As a result, the scattering and

collisions of electrons with the lattice ions, phonons, impurities and defects of the material is

very less. This will result in enormous change in the electrical, optical, thermal, magnetic and

dielectric properties of the material [3-8].

Amongst the various studied metal-oxides, zinc oxide (ZnO) is very popular because of

is semiconducting nature with high and direct band gap of 3.4 eV [9-11]. Besides, it has a very

high exciton binding energy of 60 meV [12-15]. Due to this large excitonic binding energy ZnO

may generate stable lasing emission upon suitable optical excitation. Huang et al. had reported

UV lasing from ZnO nanorods grown on GaN substrate [16]. Being a high band gap

semiconductor, UV emission is the characteristics emission from ZnO nanostructures and may

reports are available in the literature [17-20]. However, at low temperature, chemically grown

ZnO nanocrystals contain several defects like Zn-vacancy, O-vacancy, Zn- and O-interstitials

and ionized oxygen vacancy [21-25]. The energy levels of these defect states have been

calculated by many researchers [26-31]. It reveals that due to lower energy, any transition

associated with these defect states lead to visible photoluminescence from ZnO nanostructures.

Visible photoluminescence (red, yellow, green, blue, and violet) from various types of ZnO

nanostructures are already reported in literature [32-35]. Mai et al. had reported the synthesis

of ZnO/PMMA nanocomposite by sol-gel method along with ultrasound. The synthesized

nanostructure shown enhanced red photoluminescence peaked at ~ 600 nm owing to interfacial

band-bending effect [36].

Besides, optical emission property, ZnO exhibit room temperature ferromagnetism as

reported by many researchers [37, 38]. Optical transparency with room temperature

ferromagnetism may explore applications of ZnO towards fabricating various spintronic

devices [39]. ZnO crystal is non-centrosymmetric and thus exhibit permanent dipole moment

directed along its c-axis. This leads to occurrence of piezoelectric property in the material.

There is report of excellent piezoelectric properties of ZnO by Wang et al. [40]. The nanorods

were grown on c-plane–oriented α-Al2O3 substrate, using Au particles as a catalyst synthesized

ZnO using vapor-liquid-solid (VLS) method. When the nanorods were bent, a strain field is

generated. Separation of charges across the nanowires ccurs under the combined atiocn of

piezoelectric and semiconducting properties of ZnO. A current is also generaed when a

Schottky contact is created between the metal tip and the nanorods. It was reported that the

efficiency of the nanowire based piezoelectric power generator varies from 17 to 30%.

Here, in this mini review article we shall focus towards studying ZnO nanostructures of

different morphological architecture. This will help in understanding the structure property

relationship of the material which is very much essential in for fabricating ZnO based devices.

2. CRYSTAL STRUCTURE

ZnO usually crystallizes in wurtzite form with space group p63mc and lattice parameters

𝑎 = 3.296 Å and 𝑐 = 5.2065Å [41]. The crystal has small deviation from centro-symmetric structure leading to the polar nature of the crystal [42]. The wurtzite structure of ZnO is formed

by alternative stacking of planes along c-axis terminated with Zn2+ and O2− ion which are

tetrahedrally coordinated [41] (see Figure 1).


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Figure 1. Wurtzite structure of ZnO (yellow spheres are zinc and grey spheres are oxygen

ions respectively). Reproduced from [43].

Figure 2. Various lattice planes of ZnO (reproduced from [44]).


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The structure lacks of centre of inversion leading to pyroelectric and piezoelectric

properties in the material. The basal plane is (0001) which is polar in nature. One side of this

plane is terminated by the Zn2+ ions while the other side is terminated with O2− ions. This leads

to the development of dipole directed along c-axis of the crystal. Due to high surface energy,

the poar surfaces allow massive surface reconstruction to get a stable form. However, (0001)

surfaces are automatically flat and have high stability without any surface reconstructions. The

other facets {21̅1̅0} and {011̅0} are non-polar with lower surface energy than {0001} facets [41]. Various planes of ZnO are shown in Figure 2.

3. METHODOLOGIES OF SYNTHESIS

Synthesis methodologies of nanomaterials can be broadly classified into two categories-

(a) Top-down approach and (b) Bottom-up approach. The top down processes are- mechanical

and ball milling, lithography technique. There are many processes of growing nanostructures

by bottom up process. These are – (a) Vapour phase process-thermal evaporation, electron

beam evaporation, sputtering (dc and ac), chcemical vapour deposition, vapour-liquid-solid

mehod, vacuum arc deposition, pulsed laser deposition and molecular beam epitaxy; (b) Liquid

phse growth- wet chemical method / sol-gel method, closed bath deposition, hydrothermal

method, electrochemcial method and laser ablation. Each methods have its advantages and

limitations. The controll parameters are also different in different methods. So the researchers

can choose any method of growing nanostructures as per their convenience and need.

4. HIERARCHICAL THREE-DIMENSIONAL ZnO NANOSTRUCTURES

Figure 3. Hierarchical ZnO nanostructures grown on silicon substrate. Reproduced from [45].


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In three dimensional (3D) nanostructures all the dimensions of the nanostructure are much

larger than few hundred nanometer. The quantum confinement of electrons in these structures

is very weak. There are varieties of hierarchical ZnO nanostructures synthesized by researchers

and reported in the literature.

Liu et al. have reported the synthesis of hierarchical ZnO nanostructures by thermo-

evaporation method [45]. The thermo-evaporation unit consists of a tubular furnace with an

arrangement of flow of carrier gas. Pure zinc powder (99.9%) without any catalysts was used

as the source material. The material was heated to 550 ◦C at a rate of heating ~ 25 °C/min.

Oxugen gas was slowly pourges into the furnace to supply oxygen for the formation of ZnO

from Zn. A Si substrate was places inside the furnace as the substrate. After the desired growth

of the ZnO nanostructures, the source of oxygen was first cut off and ultrapure nitrogen gas was

ntroduced into the furnace.

Figure 4. FESEM micrographs of ZnO hierarchical nanostructures composed of a hexagonal

trunk decorated with two sets of mutually intercalated paddle blades, each set with its own

threefold rotational symmetry, and being rotated for 60 • with respect to each other. (a) Top,

(b) side, and (c) bottom views, respectively. (d) High magnification image showing the flat

hexagonal cross sections of the blades. The dashed lines in (d) serve as guides to the eye.

Reproduced under CCBY 3 lisence from [45].


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Finally the temperature was reduced gradually. By this method they were able to obtain

hierarchical nanostructures of ZnO in the form of hexagonal trunk decorated with two sets of

mutually intercalated paddle blades. Figure 3 and 4 shows the FESEM images of the

nanostructure reported in [45]. The TEM image of the nanostructures shown in Figure 5 shows

the orientation of lattice planes.

Figure 5. (Color online) Microstructural analysis of the ZnO propellers composed of a main

trunk with layers of paddle blades. (a) Bright field TEM image, with the boxed region further

enlarged in (b). (c) HRTEM image of the boxed Hierarchical ZnO nanostructures grown on

silicon substrate. Reproduced under CCBY 3 lisence from [45]


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There is also report of hierarchical ZnO nanostructures by Rani et al. [46]. They used zinc

nitrate as precursor in hydrothermal synthesis method. It was revealed from their results that

the precursor concentration plays an important role in determining the morphology of the

nanostructures (see Figure 6).

Kim et al. had also reported porous nanoflowers and hierarchical ZnO nanostructures (see

Figure 7) by chemical method [47]. In brief, Zn(NO3)2·6H2O aquash solution of appropriate

stoichiometry was mixed with NaOH solution and the mixture was heated at 90 °C for 1 h. The

resulting precipitate was then heat treated to get the final product.

Figure 6. FESEM image of ZnO nanorod prepared using zinc nitrate with different

concentration annealed at 200 °C: 0.05 M (a), 0.1 M (b) and 0.4 M (c) and annealed at 500 °C:

0.05 M (d), 0.1 M (e) and 0.4 M (f). Reproduced under CCBY license from [46].

5. TWO-DIMENSIONAL ZnO NANOSTRUCTURES

2-D nanostructures are usually extended in a plane while its thickness is very small up to

few layers of atoms. This indicates that the motion of electrons in these structures is restricted

in the plane of the film while they have restricted motion along the film thickness. This leads

to the quantization of energy along only one direction only. The degree of freedom in these 2-

D nanostructures is 2. Thin films are good examples of 2-D nanostructures. The film thickness

may vary from few atomic layers to few hundreds of atomic layers in case of thick film.

Depending of this thickness the property of the thin film materials will change.

Two-dimensional thin film nanostructures can be fabricated easily by both solution phase

methods (hydrothermal, chemical, electrochemical, sol-gel) and also by vapour phase growth


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processes (chemical and physical vapour deposition, sputtering, molecular beam epitaxy and

vapour-liquid-solid method).

Figure 7. (a-c) SEM images of as-prepared H-NS precursors; (d-f) SEM images of heat-treated

H-NS ZnO nanostructures; (g-i) TEM images of heat-treated H-NS ZnO nanostructures.

Reproduced under CCBY license from [47]

Ultrafine ZnO nanosheet synthesis is reported by Kim et al. [48]. The fabricated structure

exhibit excellent piezoelectric property. The FESEM and TEM images of the synthesized

product are shown in Figure 8. In chemical growth process the morphology of the


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nanostructures depends on the current flowing through the electrode, type of electrodes,

concentration of the electrolyte, temperature of growth, pH of the electrolyte and the growth

duration.

Figure 8. (a) Plan-view FE-SEM image of the ZnO nanosheets network grown on Al.

(b) Cross-sectional TEM image of the ZnO nanosheets network, formation of LDH at the

interface between the ZnO nanosheets and the Al electrode is highlighted. Reproduced under

CCBY license from [48].

Pradhan et al. had reported thin ZnO nanosheets assembly by simple electrochemical

deposition method [49]. The FESEM images of the synthesized structure are shown in Figure

9.

ZnO nanosheets can also be fabricated by pulsed laser ablation. Ryu et al had reported a

simple pulsed laser ablation method of synthesizing ZnO nanoflakes [50]. In brief,

predetermined amount of ZnCl2, NH4OH and hexamethylenetetramine (HMTA) were dissolved

in de-ionised water and stirred well in a magnetic stirrer. The solution was then put in a Teflon-

lined stainless-steel autoclave.

The autoclave was heated at 150 °C for 5 h. The precipitate was then processed and

calcined at 350 °C for 2 h for further use. In the second step of the process, this ZnO powder

and carbon nanotube were dispersed in 400 mL ethanol with weight ration 10:1. The mixture

was then undergone ultrasonication. Nd:YAG laser (Q-switch type) system was used for the

ablation process.

The SEM image of the obtained product is shown in figure 10 [50]. This picture clearly

shows the 2-D ZnO nanosheets of size ~ 1×1 μm2.


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Figure 9. SEM images of (a, b) ZnO nanowalls, (c, d) nanodisks, (e, f) nanospikes, and (g, h)

nanopillars grown on ITO-glass at 70 °C with 0.1 M KCl solution and varying Zn(NO3)2·6H2O

concentrations of 0.1, 0.05, 0.01, and 0.001 M, respectively. Insets show the corresponding

cross-sectional images Reproduced under CCBY license from [49].


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Figure 10. FESEM image of ZnO Nanosheets. Reproduced under CCBY license from [50].

6. ONE-DIMENSIONAL ZnO NANOSTRUCTURES

Figure 11. Scanning electron microscope (SEM) (top and side views, respectively): (a,b) Seed;

(c,d) ZnO nanorods (ZNRs) fabricated using the ACG method; (e,f) ZNRs fabricated using the

MAG method; (g,h) ZnO debris on the surface of vertical ZNRs. Reproduced under CCBY

license from [55].


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Now let us consider one dimensional nanostructure where two of the dimensions are in

nanoscale while the third one in extended to few microns. Nanorods, nanotubes, Nanopencils

are very good examples of 1-D nanostructures. In these nanostructures the motion of the

electrons is restricted along one dimension and thus have only one degree of freedom. The

energy gets quantized along two confined direction while continuous along the rest one

direction.

Chemical synthesis and microwave assisted growth method are very cost-effective and

popular method of growing ultra-long nanorods especially of metal oxides and sulphides. There

are several reports on the synthesis of ZnO nanorods by this method [51-55]. Figure 11 shows

the SEM images of ZnO nanorods synthesized by chemical and microwave methods as reported

by Rana et al. [55]. The schematic set-up is also shown in Figure 12 [55].

Rana et al. had followed a simple chemical and microwave assisted process of growing

ZnO nanorods [55].

They used aquash solution of zinc nitride hexahydrate [Zn(NO3)2·6H2O] and

methenamine [C6H12N4] as the precursors. The mixed solution was undergone a thermal

treatment and microwave treatment respectively.

Figure 12. Heating profile for (a) aqueous chemical growth (ACG) and (b) microwave-assisted

growth (MAG) methods. Reproduced under CCBY license from [55].

According to the report of Rana et al., aquash solution of ammonium hydroxide

[NH4OH], zinc nitride hexahydrate and methenamine solution reaction produce ZnO nuclides

[55]. A seeded substrate when kept in this solution, the growth of flower-like ZnO

nanostructures are formed.

A schematic of the growth process and the SEM images of the product are shown in figure

13. Detail of the methodology is available elsewhere in [55].


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Figure 13. (a–f) Process flow for ZnO nanoflowers (ZNFs) growth using the ACG and MAG

methods, (g) SEM image of ZNF using the ACG method, and (h) SEM image of ZNF using the

MAG method. Reproduced under CCBY license from [55].


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Figure 14. SEM images of ZnO nanotubes (ZNTs) (inset: magnified image), formed via defect-

centric etching of ZNRs grown with (a) ACG and (b) MAG methods; (c) Etching mechanism

for ACG and MAG ZNRs. Reproduced under CCBY license from [55].

Figure 14 (a-b) shows the SEM images of ZnO nanotubes reported in [55]. The

transformation of the nanorods into nanotubes via etching mechanism is also shown

schematically in Figure 14 (c-d).

Chemical synthesis of ZnO nanorods is also reported by Samanta et al. [56]. In brief, zinc

nitrate hexahydrate (Zn(NO3)2·6H2O) sodium hydroxide (NaOH) aquash solution was put

under constant stirring maintaining the temperature at 34 °C.


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Figure 15. FESEM images of the a as synthesized ZnO nanorods, and ZnO nanorods annealed

at b 200 °C, c 400 °C, and d 800°C, respectively. Reproduced under CCBY license from [56].

Figure 16. (a) Plan-view SEM image of a patterned template for ZnO NR growth. (b)–(d) 30°

tilted SEM images of the growth results on the template with the growth durations of 10, 30,

and 180 min, respectively, when the concentration of the growth solution is 0.08 M and the

growth temperature is 80 °C Reproduced under CCBY license from [57].


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Figure 17. SEM top view of the nanotubes obtained in an etching solution containing:

(a) 0.75 wt% of NH3(aq) and 1.5 wt% of CTAB; (b) 0.75 wt% NH3(aq) and 0.25 wt% of CTAB.

Reproduced under CCBY license from [58].

Figure 18. SEM images of ALD TiO2 coated TiO2 nanotube layers soaked in water for 28 days.

All scale bars are 100 nm. Reproduced under CCBY license from [59].


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The pH of the solution was maintained at 11. At the end of the reaction, the precipitate

was filtered, washed using distilled water annealed at 200, 400, and 800 °C respectively. It was

observed that by varying the growth temperature, the nanorods transformed into Nanopencils

like structure (see Figure 15) [56]. Similar hexagonal ZnO nanorods is also reported by Yao et

al. using hydrothermal method (see Figure 16) [57]

Solution phase growth of ZnO nanotubes are also reported elsewhere in [58, 59]. The

corresponding SEM images are also shown in Figure 17 and Figure 18 respectively.

7. ZnO QUANTUM DOTS

Quantum dots (QDs) are of great interest because of their efficient and intense

photoluminescence leading their potential from electronic display to biomedical imaging. As

the name suggests, QDs are very small size nanostructure consisting of few atoms only. Thus,

the electrons are confined from all three direction. Hence the energy is completely quantized in

all three directions.

There are several models that describes the relation between the QDs size and its band

gap L. E. Brus first put forward a theoretical calculation of band gap in semiconductor

nanoparticles/quantum dots (using CdS and CdSe as examples) based on “effective mass

approximation” (EMA) [60].

𝐸𝑔𝑄𝐷 = 𝐸𝑔

𝑏𝑢𝑙𝑘 +ℎ2

8𝑅2(

1

𝑚𝑒∗+

1

𝑚ℎ∗ ) −

1.8𝑒2

𝜖𝑜𝜖𝑟𝑅

Here, 𝐸𝑔𝑄𝐷

and 𝐸𝑔𝑏𝑢𝑙𝑘 are the band gap of the semiconductor in the bulk state and quantum dots

respectively and R is radius of the quantum dots. The 2nd term in the right-hand side is called

the quantum localization term (kinetic energy term) which varies with 𝑅−2. The third term appears due to the screened Coulombic interaction between the electrons and holes and varies

with 𝑅−1. Y. Kayanuma modified Brus equation by considering the electron-hole spatial correlation

effect and the band gap of the quantum dot is given by [61]

𝐸𝑔𝑄𝐷 = 𝐸𝑔

𝑏𝑢𝑙𝑘 +ℎ2

8𝑚0𝑅2(

1

𝑚𝑒∗+

1

𝑚ℎ∗ ) −

1.8𝑒2

𝜖𝑅− 0.248

4𝜋2𝑒4𝑚0

2(4𝜋𝜖)2ℎ2 (1

𝑚𝑒∗+

1𝑚ℎ

∗ )

The last term arises due to salvation energy loss (spatial correlation effect) and is

independent of R. this term is significant only when the semiconductor materials have very low

dielectric constant. Thus, the last term is usually neglected.

Chemical method is a very popular technique to synthesize ultra-fine QDs. Bera et al. had

reported the sol-gel synthesis of ZnO QDs using zinc acetate and NaOH [62]. In their synthesis

process, predetermined amount of Zn acetate and NaOH were dissolved in ethanol and

maintained at 70 °C. Then, 10 ml of 0.5 M OH solution and 0.08 M zinc acetate solution was

put under vigorous stirring in an ice bath. ZnO QDs after formation, get precipitated from the

solution. In this method they have been able to produce ZnO QDs of size 3-8 nm.


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A modified sol-gel method has been reported by Ding et al. to synthesized ZnO quantum

dots [63]. In this method polyvinyl alcohol (PVA) was used to form an ink-absorbing coating

with ultraviolet shielding performance on poly (ethylene terephthalate) (PET) films. In this

method ethanolic solution of zinc acetate and NaOH were used in suitable molar ratio. The

reaction was initiated by mixing these two solutions for different time duration (20 min, 40 min,

60 min, 80 min, 100 min, and 120 min) to obtain ZnO QDs.

Zinc acetate-based sol-gel method of synthesis of ZnO QDs is also reported by Ye et al.

[64]. In this method predetermined zinc acetate dihydrate (ZnAc2·2H2O) anhydrous ethanolic

solution was put under vigorous stirring for 40 min. Then, PEG-400 with n(PEG400): n(Zn2+)

= 1:1 was also added to the acetate solution. This results in the formation of ZnAc2/PEG-

400/ethanol solution. Then LiOH ethanolic solution was added and stirred further form 30 min.

On addition of 1 mL Oleic acid (OA) and successive stirring for 1 min yield precipitate of PEG-

400/OA-modified ZnO QDs. After aging for 2 h, the solution was centrifuged for 5 min at a

rate 4000 rpm. During this centrifuging, ethanol was added to shatter agglomerated white

precipitate. The procedure was repeated further two times to obtain PEG-400/OA modified ZnO

QDs. It was then dispersed in n-hexane by ultrasonication for 5 min at 0 °C. This results in the

formation of ZnO QD/n-hexane solution. It was also observed that in this process, reactants

concentration, material ratio and reaction time play important role in determining the size of

the QDs.

The growth equation in this process are as follows [64, 65]

The other possible reaction mechanisms are [64, 65]

Spray combustion is also a unique method of synthesizing ultra-fine ZnO QDs. Mädler

has reported spray combustion of Zn on Si to prepare ZnO QDs of size ~ 1.5 nm [66]. In those

growth technique Si plays an important role in controlling the growth and stabilization of ZnO

QDs. It was further observed in their research that the band gap decreases with increasing size

of the QDs.

Microwave assisted non-aqueous method is also a popular technique to synthesize ZnO

QDs. In a report by Asok et al., hydrolysis of zinc acetate by lithium hydroxide in ethanol

medium with the aid of microwave heating produces ZnO QDs [67]. This method offers the

production of ZnO QDs of high stability. As discussed in [67], Zn(OAc)2 and LiOH were used


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as the precursors in the synthesis process. Absolute ethanol was used as the solvent. The

alcoholic solution of Zn(OAc)2 and LiOH of predetermined stoichiometry was mixed in a

sealed vessel in an ice bath. This prevent the reaction during mixing. Under magnetic stirring,

microwave was irradiated over the system by a CEM Discover reactor. The sample was heated

up to 75 °C and kept fixed. High magnetic stirring was set up for one minute after which the

microwave was switched off. The solution was then cooled down to room temperature

Radio frequency atmospheric pressure micro-plasma technique is a unique very rarely

reported in literature to synthesize QDs. Jain et al. has reported the synthesis of ZnO QDs of

size 1.9 nm by this method [68]. Further no ligands are required in controlling the size of the

QDs. The details of the experimental set up is available elsewhere in [68]. Figure 19 shows the

schematic of the experimental set up. The plasma chamber consists of a stainless-steel

cylindrical tube along with a quartz capillary tube of external diameter 1 mm and internal

diameter 0.7 mm). The tube contains a thin Zn-wire of diameter ~0.25 mm. This Zn-wire acts

as the ground electrode as shown in figure. A copper power electrode wounds surrounding the

tube. A radio frequency source of frequency 13.56 MHz was used to supply power of 40 W to

the electrodes. Flow of argon gas at rate of 150 sccm was also used in the system. On application

of the rf voltage, the plasma is generated between the power electrode and the Zn-wire. The

collector (which is usually a solid substrate) was kept at a distance of 1.5 cm from the capillary.

The growth process was continued for 30 min. SEM images of the resulting quantum dots

are shown in Figure 20.

Figure 19. Experimental set-up of the RF plasma reactor used for ZnO QDs synthesis.

Reproduced from [68].


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Figure 20. Scanning electron microscope image of particle deposition at 40 W with 150 sccm

of Ar flow. Reproduced from [68].

The SEM image produced by this method is shown in Figure 21 [68]. The TEM images

of the synthesized ZnO QDs are also shown in Figure 19. The selected area diffraction and

particle size distribution are shown in Figure 22.

Figure 21. Transmission electron microscope images of ZnO QD. Reproduced from [68].


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Figure 22. SAED pattern (left) and particle size analysis (right). Reproduced from [68].

8. CONCLUSIONS

Multi-dimensional ZnO nanostructures have been described in detail with morphological

features. Various methods like, chemical method, electrochemical method and microwave

assisted chemical method have been deployed to fabricate these nanostructures like -

hierarchical nanostructures, nanosheets, nanorods, nanotubes, nanopencils and quantum dots.

The reports suggest that various experimental parameters like, precursor concentrations, pH of

the solution, type of solvent, growth duration, type of electrode (in case of electrochemical

method) plays important role in determining the morphology of the nanostructures. These ZnO

nanostructures will be very useful in the field of nanoelectronics, gas and chemical sensors,

conducting electrode and various biological applications.

BIOGRAPHY

Sarani Acharyya is a 6th semester undergraduate student of Physics

(Honours) from Sahid Matangini Hazra Government College for Women,

located in the East Midnapore district, West Bengal, India. Her research

interest includes processing of nanomaterials and their biological

applications. She is presently engaged in synthesizing various compound

semiconductor nanostructures including CdS, CdSe, ZnO, CuO, MgO.


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Swarnali Acharyya is a 2nd semester undergraduate student of Physics

(Honours) from Panskura Banamali College (Autonomous), located in the

East Midnapore district, West Bengal, India. Her research interest includes

processing of nanomaterials for optoelectronic applications. She is presently

engaged in synthesizing various metal oxide nanostructures including ZnO,

CuO and TiO2

Dr. Pijus Kanti Samanta dis M.Sc. and Ph.D. in Physics from Indian Institute

of Technology Kharagpur. His research interest includes synthesis and

characterization of nanomaterials for opto- and nano-electronic, and

biomedical applications. He is also working on the toxicological study of

nanomaterials for their use towards sustainable environmental development.

He has published more than 60 papers in international journals of high repute

and 5 monographs. He was affiliate member of IUPAC, USA (2012-2013),

and life member of International Association of Advanced Materials, Sweden.

Presently he is Assistant Professor of Physics at Prabhat Kumar College,

Contai, WB.

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review on multi-dimensional zinc oxide nanostructures€¦ · thin films are good examples of 2-d...

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