Synthesis of iron-doped zinc oxide nanoparticles by simple heating: influence of precursor...

18 Int. J. Materials Engineering Innovation, Vol. 6, No. 1, 2015

Copyright © 2015 Inderscience Enterprises Ltd.

Synthesis of iron-doped zinc oxide nanoparticles by simple heating: influence of precursor composition and temperature

Sampa Chakrabarti* Department of Chemical Engineering, 92, Acharya P.C. Road, Kolkata 700 009, India and Centre for Research in Nanoscience & Nanotechnology, University of Calcutta, India Email: [email protected] Email: [email protected] *Corresponding author

Xin Liu and Changning Li Department of Chemical and Biological Engineering, University at Buffalo (SUNY), 310 Furnas Hall, Buffalo, New York, 14260-4200, USA Email: [email protected] Email: [email protected]

Prantik Banerjee Department of Environmental Science, University of Calcutta, 35 Ballygunge Circular Road, Kolkata – 700 029, India Email: [email protected]

Saikat Maitra Government College of Engineering and Ceramic Technology, 73, Abinash Chandra Banerjee Lane, Kolkata – 700 010, India Email: [email protected]

Mark T. Swihart Department of Chemical and Biological Engineering, University at Buffalo (SUNY), 310 Furnas Hall, Buffalo, New York, 14260-4200, USA Email: [email protected]

Synthesis of iron-doped zinc oxide nanoparticles by simple heating 19

Abstract: We demonstrate a general single-pot heating method for preparing iron-doped zinc oxide nanocrystals from acetyl acetonate precursors in non-aqueous solvents. The particles were characterised by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), UV-visible (UV-Vis) and Fourier transform infrared (FTIR) optical absorbance spectroscopies. The dependences of the size of the nanocrystals and doping level on the synthesis temperature and precursor composition were elucidated and modelled.

Keywords: crystal structure; nanostructures; semiconductors; chemical synthesis; X-ray diffraction.

Reference to this paper should be made as follows: Chakrabarti, S., Liu, X., Li, C., Banerjee, P., Maitra, S. and Swihart, M.T. (2015) ‘Synthesis of iron-doped zinc oxide nanoparticles by simple heating: influence of precursor composition and temperature’, Int. J. Materials Engineering Innovation, Vol. 6, No. 1, pp.18–31.

Biographical notes: Sampa Chakrabarti earned her BSc (Chemistry, 1984), BTech (1987), MTech (1989) and PhD (2006) in Chemical Engineering from the University of Calcutta. She has 11 years of working experience in engineering consultancy organisations before pursuing her PhD in the field of application of chemical engineering for environmental remediation. Since 2004, she has about 50 papers published in high impact international peer reviewed journals and conference proceedings. She has over 500 citations. At present, she is an Associate Professor in the Department of Chemical Engineering, University of Calcutta, India and has about 13 years of teaching and research experience.

Xin Liu earned his BS in Chemical Engineering from Tianjin University and recently completed his PhD in the research group of Prof. Mark. T. Swihart at The University at Buffalo. He has published more than a dozen peer reviewed papers.

Changning Li earned his BS in Chemistry from Peking University and is pursuing his MS in the research group of Prof. Mark. T. Swihart at the University at Buffalo (SUNY).

Prantik Banerjee has completed his Masters in Environmental Science from the University of Calcutta in 2008. He was appointed as a Senior Research Fellow (by the Council for Scientific and Industrial Research, India) in the Department of Chemical Engineering, University of Calcutta and registered as a PhD student in the Department of Environmental Science in the same university. He has publications in both peer-reviewed journals and as conference proceedings and is also involved as a reviewer with an Elsevier-published journal.

Saikat Maitra received his BSc (Chemistry, 1985), BTech (1988), MTech (1990) and PhD in Chemical Technology (Ceramic) from the University of Calcutta. He has a good number of publications in national and international peer-reviewed journals. He has teaching experience in UTP-Malaysia and research experience in reputed research institutes in India. He has supervised a good number of students for PhD. At present, he is a Professor and Officer-in-Charge of the Government College of Engineering and Ceramic Technology, Government of West Bengal, India.

20 S. Chakrabarti et al.

Mark T. Swihart earned his BS (1992) from Rice University and PhD (1997) from the University of Minnesota, both in Chemical Engineering. He is a Professor of the Department of Chemical and Biological Engineering at the University at Buffalo (UB), the Director of the UB2020 Strategic Initiative in Integrated Nanostructured System at UB, and the co-Director of the New York State Center of Excellence in Materials Informatics at UB. He has co-authored more than 125 refereed journal publications.

1 Introduction

Semiconductor nanoparticles (NPs) have been investigated widely for applications in areas including displays, photocatalysis, spintronics and cosmetics (Rao and Raveau, 1998). Zinc oxide (ZnO) is a low cost and environmentally safe semiconductor with a wide band-gap of 3.37 eV at room temperature (Maldonado et al., 2001; Nandi et al., 2012). The optical and electronic properties of semiconductor nanocrystals, including ZnO, depend upon the nanocrystal size, shape, and composition (Smith and Nie, 2010). One approach for tuning these properties in ZnO is doping with transition metal elements. Incorporation of transition metal dopant atoms introduces new states into the semiconductor band structure and thereby affects the optical and electronic properties (Behnajady et al., 2009). Doping of ZnO with transition metals like iron (Fe), manganese (Mn) or cobalt (Co) has been shown to decrease the band-gap energy of the semiconductor which eventually enhances its performance as a photocatalyst or dilute magnetic semiconductor (DMS) (Pearton et al., 2007). Ba-Abbad et al. (2013) synthesised Fe-doped ZnO NPs via a sol-gel method from Zn-acetate and Fe(III) nitrate precursors without any capping agent. As the Fe3+ concentration increased from 0.25 wt.% to 1 wt.%, the crystal size decreased relative to the undoped ZnO NPs. This was accompanied by a red-shift of the absorption edge with doping. Photocatalytic property was likewise enhanced by doping (Ba-Abbad et al., 2013). Fe is the most popular dopant for ZnO owing to its compatibility with Zn2+ ion as per Hume-Rothery rule, due to its abundance and low cost, as well as its non-toxicity, which maintains the biocompatibility of ZnO particles (Smith, 1993). It can impart ferromagnetism to the semiconductor as well (Pearton et al., 2007; Sato and Katayama-Yoshida, 2001).

There are several protocols for synthesising Fe-doped ZnO NPs, including sol-gel processes, solid-state reactions, co-precipitation and pulsed laser deposition. Saleh et al. (2012) studied the influence of Fe-doping on the structural, magnetic and optical properties of nanocrystalline ZnO particles. They have synthesised Fe-doped ZnO NPs from ZnSO4 and FeCl2 hydrate solutions by co-precipitation using NaOH in water at room temperature under continuous ultrasonic stirring for 2 hours. A quasi-hexagonal morphology was observed. They investigated the amount of Fe incorporated as a function of the initial cation ratio in solution. They observed an upper limit for incorporation of Fe in ZnO of approximately 21%. They have also established an inverse correlation between extent of Fe-incorporation and the band-gap energy. Magnetic measurement showed ferromagnetism for all doped samples. Reddy et al. (2012) synthesised Fe-doped ZnO-NP by solution combustion at 300°C, using Zn(NO3)2 as oxidiser, oxyalyl dihydrazide as fuel and Fe(NO3)3 as dopant. They observed a decrease in particle-size


with increasing Fe concentration. Samples with higher Fe-concentration were also more porous. Band-gap energy decreased with increasing Fe-concentration. Thermo-luminescence was observed for all Fe-ZnO samples. Liu et al. (2012) synthesised Zn(1–x)FexO [x = 0 – 0.05] NPs from ZnSO4, CO(NH2)2 and metallic Fe at 80°C using a two-step solid-liquid chemical route, followed by annealing at 300°C. From the XRD analysis, they observed that the crystallinity of ZnO decreased as the extent of Fe-doping increased. At higher concentration of Fe, a minor spinel phase of ZnFe2O4 was detected. However, the crystal growth of ZnO was suppressed with increased Fe-loading. In this case, the band-gap energy increased slightly with increasing Fe-doping. The maximum degree of ferromagnetism was observed for Zn0.99Fe0.01O. Singhal et al. (2008) synthesised colloidal Fe-doped ZnO from a mixed solution of Zn-acetylacetonate and Fe-acetylacetonate at 200°C in hexadecylamine. The amine acts as a solvent as well as a capping agent. In that study, the particles were not further annealed. FTIR confirmed the presence of amine-ligand near the surface of nanocrystals. Cell-volume increased with increasing Fe-concentration. No secondary phase was detected. Ferromagnetism was observed at room temperature. Cu, Fe and Mn-doped ZnO NPs were synthesised by Jung using both a solid-sate reaction method and a co-precipitation method from inorganic precursors at low temperature in an aqueous medium (Jung, 2010). The NPs were annealed to 900°C and 600°C respectively before they were used for photocatalytic degradation of 1,4-dichlorobenzene under visible light irradiation. XRD showed that no secondary phase was present below 5 mol % Fe. The band gap decreased with increasing substitution, and the decrease was the lowest in case of Fe-doping. However, Mn-substituted ZnO was found to be the most efficient photocatalyst. Mishra and Das (2010) synthesised ZnO:Fe with different proportions of Zn and Fe. XRD and TEM confirmed the phase purity and indicated a reduction in particle-size with increase in the dopant. Zhang et al. (2013) synthesised Fe-doped ZnO nanowires and used the same for degradation of DCB and MO. Doped nanowires showed enhanced photocatalytic activity (Zhang et al., 2013).

In this report, we demonstrate a single-pot heating protocol for synthesising Fe-doped ZnO NPs starting from the acetyl-acetonate precursors of both of the metals. The same protocol has been followed by Liu and Swihart (2013) for synthesis of undoped pure ZnO NPs. The temperature of synthesis is relatively low. Due to the simplicity of the process it is amenable for scaling-up using batch or continuous reactors in industry. It is interesting to control the physical, optical and electronic properties of the NPs during their synthesis and crystallisation. In this study, we also report the influence of the composition of the precursor-mixture as well as of the temperature on the size, crystal structure and band-gap energy of the synthesised ZnO NPs. The NPs were characterised by TEM, EDX, XRD and UV-Vis spectrometry. The novelty of the work lies in reporting the crystal dimensions (average and along the major planes) as function of composition and temperature. Proposing an approximate mathematical model is also a unique approach.

2 Materials and methods

2.1 Materials

Chemicals used in this study were zinc (II) acetyl-acetonate (AR grade, 25% Zn, Acros Organics), Fe (III) acetyl-acetonate (99% pure, AR grade, Aldrich), benzyl ether (99%


pure, AR grade, Aldrich), oleylamine (AR grade, Aldrich), oleic acid (AR grade, Aldrich) and 1-hexadecanol (AR grade, Aldrich). HPLC grade ethanol, chloroform and hexanol (Fisher) were used for washing and suspension.

2.2 Procedure of synthesis

A total of 1 mmol of Zn(acac)2 and Fe(acac)3 at varying molar ratios was dissolved in 10 mL benzyl ether in a 100 mL round-bottomed flask. 1 mL oleic acid, 1.4 mL oleylamine and 1.8 g (1.5 mmol) of 1-hexadecanol were added to the flask and the mixture was heated in a heating mantle under a nitrogen atmosphere at a desired temperature, which was controlled using a J-KEM temperature controller. After a few minutes of heating, the mixture became translucent and the colour turned to light yellow. After a few more minutes of heating, the mixture reached the set point temperature and was kept at that temperature for 8 to 10 minutes, until it became slightly turbid. It was then allowed to cool slowly by removing the heater. Then the NPs were centrifuged at approximately 8,000 × g after adding ethanol as an antisolvent, which decreases their colloidal stability. They were finally re-dispersed in hexane or chloroform.

2.3 Instruments and methods for characterisation

The NPs produced at various temperatures and precursor ratios were characterised by the following techniques:

• XRD: Powder X-ray diffraction (XRD, Bruker Ultima IV with Cu Kα X-ray) was used to characterise the crystal structure of Fe-doped ZnO NPs. Samples were prepared by drop-casting high-concentration dispersions of Fe-doped ZnO NPs onto glass slides.

• TEM: Fe-doped ZnO NPs were characterised by transmission electron microscopy (TEM) using a JEOL JEM-2010 microscope at a working voltage of 200 kV. Selected area electron diffraction (SAED) patterns were obtained in the same instrument.

• EDX: Quantitative elemental analysis of Fe-doped ZnO NPs was performed using an Oxford Instruments X-Max® 20 mm2 Energy Dispersive X-ray Spectrometer (EDS) detector, in a Zeiss Auriga scanning electron microscope.

• UV-Vis: Optical absorbance of Fe-doped ZnO NPs was measured using a Shimadzu 3600 UV–Visible-NIR scanning spectrophotometer.

• FTIR: Fourier transformed infrared spectroscopy was done in a Jasco FTIR-6300 instrument.


3 Results and discussions

3.1 Formation of NPs

The mechanism of formation of oxide nanocrystals from organic precursors in non-aqueous media has been discussed in several reports (Song et al., 2009; Pérez-Mirabet et al., 2013; Ambrožič et al., 2011; Patterson, 1939). A major problem of the sol-gel process for the synthesis of NPs is the uncontrolled reaction rate at the hydrolysis and condensation steps. We did not use any species that could generate excess hydroxyl ion in the system, hence there was no hydrolysis. The entire dissociation was facilitated by long-chain amines and alcohols present in the system in a complex process. A mixture of zinc (II) and Fe (III) acetyl acetonate precursor probably reacts with oleylamine to form a complex of relatively low stability. Thermal decomposition of these complexes produces ZnO NPs upon heating. Rapid nucleation followed by controlled, relatively slow growth results in the formation of nano particles with narrow size distribution. Moreover the acetyl acetonate precursors act as templates to grow the ZnO NPs in a hexagonal arrangement (Music and Sarie, 2012). By forming complexes with the acetyl acetonate precursors, olelyamine and oleic acid can modulate the reactivity of the zinc and Fe sources. Poly-condensation continued with time under controlled nitrogen atmosphere forming capped (Zn-O-Zn)n and (Zn-O-Fe)n layers and subsequent controlled decomposition of these layers yielded nano-sized ZnO and ZnO doped with Fe.

3.2 Characterisation of the synthesised NPs

Figure 1(a) shows TEM images of the NPs produced at 220 to 230°C with a Zn:Fe molar ratio of 1:0.096. The average size of the particles is about 20 nm, and they are hexagonal platelets, reflecting the hexagonal wurtzite ZnO crystal structure. Unlike undoped ZnO [Figure 1(b)], overlapping nanocrystals exhibit Moiré-patterns created by interference between the crystal lattices of the two stacked nanocrystals. This provides particularly clear evidence that the hexagonal platelets are flat and have a common crystal orientation. EDX (Table 1) shows that this particular sample was doped to 9.2 wt% Fe (molar Zn: Fe = 1:0.13). It may be noted that relative to zinc, Fe has been preferentially incorporated in the particles. The Fe to zinc ratio in the particles exceeds that in the precursor mixture. EDX also indicates that the particles are deficient in oxygen. Because the synthesis was performed with organo-metallic precursors in organic solvent, no excess source of oxygen was present. Table 1 EDX data for Fe-doped ZnO NPs

Element Weight% Atomic%

O K 8.92 28.24 Fe K 9.22 8.36 Zn K 81.86 63.40 Totals 100.00 100.00


Figure 1 (a) Tem images of the Fe-doped zinc oxide nanoparticles (b) TEM images of the undoped zinc oxide nanoparticles

(a) (b)

Decomposition of organic solvent and ligands can create a reducing atmosphere that leads to the oxygen deficiency in the particles.

XRD (Figure 2) showed that the particles had the hexagonal wurtzite crystal structure, corresponding to the ZnO mineral zincite. No secondary phase of any Fe(III)-oxide was detected. This indicates inclusion of Fe into the ZnO lattice. Crystallite sizes were calculating using Reitveld refinement, allowing for arbitrary crystallite shape and orientation. Because the crystals are hexagonal platelets rather than rods, their thickness along the [002] direction was typically less than the dimensions along the [100] and [101] directions. The UV-Vis spectrum of this sample is given in Figure 3. The band-gap energy of this sample is calculated as 2.75 eV which is significantly lower than that of pure ZnO. Hence, we suggest that the Fe-doped ZnO NPs are potentially more active photocatalysts at visible wavelengths, compared to pure ZnO.

Figure 2 X-ray diffraction pattern for Fe-doped zinc oxide nanoparticles


Figure 3 UV-Vis spectrum of Fe-doped zinc oxide nanoparticles

Figure 4 FTIR spectrum for Fe-doped zinc oxide nanoparticles (see online version for colours)

FTIR spectroscopy (Figure 4) of the ZnO-NP provides information on the functional groups present on the surface as well as on the structure of the material. Strong peaks around 450 to 600 cm–1 correspond to M-O-M’, M-O-M, M-O or M’-O bond stretching where M = Zn and M’ = Fe. This is consistent with the wurtzite crystal structure of ZnO (Ambrožič et al., 2010). One strong band at 3,952 cm–1 is also indicative of Zn-OH bonding. Another strong peak at 730 cm–1 indicates C = C double bond which has been attributed to the oleic acid and oleylamine on the surface used as surfactant or stabiliser. The presence of amine is further confirmed by the strong peak at 1,091 cm–1 (Liu et al., 2012).


3.3 Influence of the composition of precursors on the characteristics of the NPs

We expected that the characteristics of the NPs may be influenced by the ratio of the precursors taken in the initial mixture. To examine this, NPs were synthesised with varying molar ratio of Zn and Fe precursors under the otherwise identical experimental conditions. The crystallite size was calculated from the powder XRD patterns which were fit using Rietveld refinement. Table 2 Influence of precursor composition on properties of Fe-doped ZnO NPs

Crystal dimensions (nm) Sl. no.

Composition (mmol)

Zn(acac)2: Fe(acac)3

Grain thickness (nm) [100] [101] [002]

Band gap energy

(eV)

Composition as per EDX atomic

% Fe

1 1: 0.053 22.9 27.1 22.9 17.4 2.80 4.8 2 1: 0.096 22.8 28.0 23.9 19.0 2.75 16.0 3 1: 0.111 22.5 33.9 25.4 12.1 2.70 12.6 4 1: 0.176 13.8 19.3 15.5 10.3 2.70 5.0

The NPs thus synthesised were characterised and the results are tabulated in Table 2. The grain thickness calculated from Scherrer equation (Patterson, 1939) remained approximately unchanged with increasing Fe-precursor concentration up to a certain extent. A small decrease was noted and could be attributed to the grain-boundary compression by deposition of Fe-oxide at the grain boundary. As a result of this, after a critical value, the grain thickness decreased significantly (Figure 5). Crystal dimensions along [100], [101] and [002] planes increased up to 0.111 mmol of Fe-precursor and after that a sharp fall. This may be due to incorporation of cubic close-packed Fe-oxide inside hexagonal ZnO. The bandgap energy decreased with increase in the Fe-precursor up to a particular composition. After that composition, it remained unchanged. This suggests that within the range of experimental conditions considered here, the minimum band-gap energy achievable is 2.7 eV. The physical appearances of the NPs are shown in Figure 6.

Figure 5 Influence of precursor composition on crystal dimension


Figure 6 Colour of the suspension darkens with increase in the Fe-precursor (see online version for colours)

The colour of the suspension darkens with increase in the Fe-precursor, reflecting the decrease in band gap energy and corresponding increase in absorbance at visible wavelengths. The XRD patterns from the Fe-doped ZnO resemble those of pure ZnO crystals in terms of the angles and d-values. The lattice parameters decrease with increase in Fe-concentration.

3.4 Influence of the temperature of synthesis on the characteristics of the NPs

The crystallisation process is impacted by kinetic factors, two of which are concentration and temperature. There exists a critical radius above which the formed nucleus can be stabilised. Such critical radius relates to Gibbs free energy (∆G) and the surface energy (γ). Assuming no dramatic change of surface energy, we can correlate equation (1) with equation (2). It shows r* is inversely proportional both to concentration of monomer and temperature. This is consistent with the observation that there exists a minimum activation temperature and critical precursor concentration to form stable nuclei upon which nanocrystals grow.

0Δ ln

ΩKT CG

C= − (1)

*

Δγ

rG

= − (2)

To examine this, NPs were synthesised varying the temperature of synthesis under otherwise identical experimental conditions. The NPs thus produced with molar composition of precursor as 1: 0.053 (mmol of Zn(acac)2: Fe(acac)3) were characterised and the results are tabulated in Table 3.

Table 3 shows that both cell volume and wt% of Fe decreases with increase in temperature. We suggest that at higher temperature, crystallinity increases and there is a tendency to form perfect crystals rejecting impurities like Fe; hence the crystal of ZnO


rejects Fe atom (or Fe3+ ion) to enter the crystal lattice. Decrease in cell volume supports equation (2) indirectly. Lattice parameters decreased with increase in temperature. Table 3 Influence of synthesis temperature on properties of Fe-doped ZnO NPs

Crystal dimensions (nm) Sl. no.

Synthesis temperature

range °C

Grain thickness

(nm) [100] [101] [002]

Cell volume

(Å)3

Bandgap energy

(eV)

Composition as per EDX

Wt% Fe

1 200–210 21.9 25.6 22.1 18 55.03 2.8 5.54 2 220–230 22.9 27.1 22.9 17.4 55.11 2.8 4.798 3 240–250 27.6 33.8 31.3 28.5 55.00 2.6 4.177

Crystallite size increased linearly (Figure 7) with increase in temperature as a result of enhanced mass transport at higher temperature because of the increase in crystallinity, following the equation as:

( )20.1425 8.6417 0.88sg T R= − = (3)

where gs = grain size in nm from fitting of the powder XRD pattern.

Figure 7 Influence of temperature on crystal dimensions

Xu et al. (2001) also observed the same phenomenon. At 240 to 250°C, the crystals seemed to be nano-rods rather than platelets since there was an intense peak at [002] plane and the dimension at [002] plane is comparable to those of the planes [100] and [101] (Table 3).

The lattice parameters, a and c did not change much and hence the cell volume remained nearly unchanged. However band-gap energy decreased with the increase in temperature. This may result from the formation of composite oxide of ZnO and Fe2O3 in the form of ZnFe2O4 at the surface of ZnO particles which affected the energy level of the crystals rather than doped NPs.

Figure 8 shows the linear fitting of the atomic percent of Fe obtained from EDX with the reaction temperature. Fitting of data led to the following linear relationship:

2W 0.034 12.67 with regression coefficient 0.999p T R= − + = (4)


where pW = weight percent of Fe obtained from EDX and T is the maximum temperature of synthesis in °C.

Figure 8 Extent of doping with reaction temperature

4 Conclusions

Fe-doped ZnO NPs have been synthesised in the presence of surfactants and capping agents (ligands) at different temperature and composition of acetyl acetonate precursors. Characterisation with XRD and EDX shows that in all cases, Fe has been incorporated within the ZnO crystal structure. However some amount of Fe-oxides has also been deposited at the grain boundaries. The band-gap energy has been reduced to a particular value by doping and hence the doped particles can be more easily excited by visible light or any such lower energy. Hence doped ZnO NPs are expected to be better photocatalysts than the undoped ones, especially under visible light. Grain sizes calculated from XRD peak broadening remained almost unchanged with increase in Fe-precursor and after a critical value it decreased significantly. With increase in the synthesis-temperature, grain sizes increased whereas the extent of doping decreased. In both cases, linear relationships were proposed.

Acknowledgements

The authors would like to thank Prof. Arup Mukherjee, Centre for Research in Nanoscience and Nanotechnology for FTIR.

References Ambrožič, G., Škapin, S. D., Žigon, M. and Orel, Z.C. (2010) ‘The synthesis of zinc oxide

nanoparticles from zinc acetylacetonate hydrate and 1-butanol or isobutanol’, Journal of Colloid and Interface Science, Vol. 346, No. 2, pp.317–323.

Ambrožič, G., Škapin, S.D., Žigon, M. and Orel, Z.C. (2011) ‘The formation of zinc oxide nanoparticles from zinc acetylacetonate hydrate in tert-butanol: a comparative mechanistic study with isomeric C4 alcohols as the media’, Materials Research Bulletin, Vol. 46, No. 12, pp.2497–2501.


Ba-Abbad, M.M., Kadhum, A.A.H., Mohamad, A.B., Takriff, M.S. and Sopian, K. (2013) ‘Visible light photocatalytic activity of Fe3+-doped ZnO nanoparticle prepared via sol-gel technique’, Chemosphere, Vol. 91, No. 2, pp.1604–1611.

Behnajady, M.A., Modirshahla, N., Shokri, M., Zeininezhad, A. and Zamani, H.A. (2009) ‘Enhancement photocatalytic activity of ZnO nanoparticles by silver doping with optimization of photodeposition method parameters’, Journal of Environmental Science and Health, Part A. Toxic/Hazardous Substances and Environmental Engineering, Vol. 44, No. 7, pp.666–672.

Jung, D. (2010) ‘Syntheses and characterizations of transition metal-doped ZnO’, Solid State Science, Vol. 12, No. 4, pp.466–470.

Liu, C., Meng, D., Pang, H., Wu, X., Xie, J., Chen, L. and Liu, X. (2012) ‘Influence of Fe-doping on the structural, optical and magnetic properties of ZnO nanoparticles’, Journal of Magnetism and Magnetic Materials, Vol. 324, No. 20, pp.3356–3360.

Liu, X. and Swihart, M.T. (2013) ‘A general single-pot heating method for morphology, size and luminescence-controllable synthesis of colloidal ZnO nanocrystals’, Nanoscale, Vol. 5, No. 5, pp.8029–8036.

Maldonado, A., Olvera, M.L., Asomoza, R. and Tirado-Guerra, S. (2001) ‘Chromium doped ZnO thin films deposited by chemical spray: chromium effect’, Journal of Vacuum Science & Technology A, Vol. 18, Nos. 1–3, pp.2097–2101.

Mishra, A.K. and Das, D. (2010) ‘Investigation on Fe-doped ZnO nanostructures prepared by a chemical route’, Materials Science and Engineering: B, Vol. 171, No. 7, pp.5–10.

Music, S. and Sarie, S., (2012) ‘Formation of hollow zinc oxide particles by simple hydrolysis of zinc acetyl acetonate’, Ceramic International, Vol. 8, No. 5, pp.6047–6052.

Nandi, I., Mitra, P., Banerjee, P., Chakrabarti, A., Ghosh, M. and Chakrabarti, S. (2012) ‘Ecotoxicological impact of sunlight assisted photoreduction of hexavalent chromium present in wastewater with zinc oxide nanoparticles on common Anabaena flos-aquae’, Ecotoxicology and Environmental Safety, 1 December, Vol. 86, pp.7–12.

Patterson, A.L. (1939) ‘The Scherrer formula for X-ray particle size determination’, Physical Review Letters, Vol. 56, No. 10, pp.978–982.

Pearton, S.J., Norton, D.P., Ivill, M.P., Hebard, A.F., Zavada, J.M., Chen, W.M. and Buyanova, I.A. (2007) ‘ZnO doped with transition metal ions’, IEEE Transactions on Electron Devices, Vol. 54, No. 5, pp.1040–1048.

Pérez-Mirabet, L., Solano, E., Martínez-Julián, F., Guzmán, R., Arbiol, J., Puig, T., Obradors, X., Pomar, A., Yáñez, R., Ros, J. and Ricart, S. (2013) ‘One-pot synthesis of stable colloidal solutions of MFe2O4 nanoparticles using oleylamine as solvent and stabilizer’, Materials Research Bulletin, Vol. 48, No. 3, pp.966–972.

Rao, C.N.R. and Raveau, B. (1998) Transition Metal Oxides, 2nd ed., Wiley Interscience, New York.

Reddy, J.A., Kokila, M.K., Nagabhushana, H., Sharma, S.C., Rao, J.L., Nagabhushana, B.M., Chakradhar, R.P.S. and Shivakumara, C. (2012) ‘Structural, EPR, photo and thermoluminescence properties of ZnO:Fe nanoparticles’, Materials Chemistry and Physics, Vol. 133, Nos. 2–3, pp.876–883.

Saleh, R., Prakoso, S.P. and Fishli, A. (2012) ‘The influence of Fe doping on the structural, magnetic and optical properties of nanocrystalline ZnO particles’, Journal of Magnetism and Magnetic Materials, Vol. 324, No. 5, pp.665–670.

Sato, K. and Katayama-Yoshida, H. (2001) ‘Stabilization of ferromagnetic states by electron doping in Fe-, Co- or Ni-doped ZnO’, Japanese Journal of Applied Physics, Vol. 40, pp.L334–L336.

Singhal, A., Acharya, S.N., Tyagi, A.K., Manna, P.K. and Yusuf, S.M. (2008) ‘Colloidal Fe-doped ZnO nanocrystals: facile low temperature synthesis, characterization and properties’, Materials Science and Engineering: B, Vol. 153, Nos. 1–3, pp.47–52.

Smith, A.M. and Nie, S. (2010) ‘Semiconductor nanocrystals: structure, properties, and band gap engineering’, Accounts of Chemical Research, Vol. 43, No. 2, pp.190–200.


Smith, W.F. (1993) Foundations of Materials Science and Engineering, McGraw-Hill, New York. Song, J.Y., Jang, H.K. and Kim, B.S. (2009) ‘Biological synthesis of gold nanoparticles using

Magnolia kobus and Diopyros kaki leaf extracts’, Process Biochemistry, Vol. 44, No. 10, pp.1133–1138.

Xu, X.L., Lau, S.P.L., Chen, J.S., Sun, Z., Tay, B.K. and Chai, J.W. (2001) ‘Dependence of electrical and optical properties of ZnO films on substrate temperature’, Materials Science in Semiconductor Processing, Vol. 4, No. 6, pp.617–620.

Zhang, Y., Ram, M.K., Stefanakos, E.K. and Goswami, D.Y. (2013) ‘Enhanced photocatalytic activity of iron doped zinc oxide nanowires for water decontamination’, Surface & Coatings Technology, 25 February, Vol. 217, pp.119–123.

Synthesis of iron-doped zinc oxide nanoparticles by simple heating: influence of precursor...

Documents

Transcript of Synthesis of iron-doped zinc oxide nanoparticles by simple heating: influence of precursor...