Hydrothermal synthesis of zinc oxide nanoparticles using rice as soft biotemplate
© Ramimoghadam et al.; licensee Chemistry Central Ltd. 2013
Received: 24 April 2013
Accepted: 25 July 2013
Published: 6 August 2013
Rice as a renewable, abundant bio-resource with unique characteristics can be used as a bio-template to synthesize various functional nanomaterials. Therefore, the effect of uncooked rice flour as bio-template on physico-chemical properties, especially the morphology of zinc oxide nanostructures was investigated in this study.
The ZnO particles were synthesized through hydrothermal-biotemplate method using zinc acetate-sodium hydroxide and uncooked rice flour at various ratios as precursors at 120°C for 18 hours.
The results indicate that rice as a bio-template can be used to modify the shape and size of zinc oxide particles. Different morphologies, namely flake-, flower-, rose-, star- and rod-like structures were obtained with particle size at micro- and nanometer range. Pore size and texture of the resulting zinc oxide particles were found to be template-dependent and the resulting specific surface area enhanced compared to the zinc oxide synthesized without rice under the same conditions. However, optical property particularly the band gap energy is generally quite similar.
Pure zinc oxide crystals were successfully synthesized using rice flour as biotemplate at various ratios of zinc salt to rice. The size- and shape-controlled capability of rice to assemble the ZnO particles can be employed for further useful practical applications.
KeywordsZinc oxide nanoparticles Rice Biotemplate Soft templating Starch Hydrothermal method
Remarkable improvements have been made using bio-inspired approach for materials synthesis due to possible control of physico-chemical properties. A technique that employs natural materials as biotemplates to synthesize micro- and nano-scaled materials with morphologies and structures resemble to those of the biotemplate is called as biomorphic mineralization . These kinds of works keep on growing and contributing to a new interdisciplinary areas, especially with the synthesis, self-assembly and processing of the organized inorganic materials .
Biotemplating approach is an impressive strategy to achieve the morphology-controllable materials with structural specialty, complexity and relevant fascinating functions. The advantages of applying biotemplates are that they are relatively cheap, economical, environmentally benign and renewable . A series of natural biotemplates that were utilized in the fabrication of functional materials includes DNA , proteins , viruses , bacteria , diatoms , pollen grains , shell membrane, wood  and cellulose fibers .
Application of metal oxides materials have extensively arisen throughout human civilization and the uses of nano-sized particles are even more significant. Among them, ZnO nanoparticles are always in the center of attention due to their fascinating properties and extensive application. Bio-inspired synthesis of ZnO nanoparticles has been achieved using environmentally and eco-friendly accepted systems. Several studies have been investigated the use of natural materials for ZnO nanoparticles synthesis such as DNA , silk , albumen , orange juice , pea starch , peptide structures  and etc. The use of nanoparticles derived from noble metals has spread in many areas involving medical fields, electronics, antibacterial textiles, etc. As a matter of fact, orientation, size and physical properties of nanoparticles affect the performance and reproducibility of a potential device. Thus the synthesis and assembly of shape- and size-controlled nanocrystals are essential components for any practical applications.
Agricultural materials particularly those containing cellulose indicate potential metal bio-sorption capacity. The basic components of the agricultural materials include hemi-cellulose, lignin, extractives, lipids, proteins, etc. . Rice is an agricultural bio-resource which can be used as non-metalic bio-precursor to synthesize functional materials . The main component of rice is starch which is one of the most fascinating bioresource that can be used for nanotechnology application. The carbohydrate polymeric chains build up from glucose units and parted in linear amylase and branched amylopectin. These peculiarities are representing the key structural elements for the synthesis of new functional nanomaterials . Starch-based oxides with biocompatible and non-toxic features, grant a new class of functional nanomaterials with potential application in various industries. Therefore using rice as a soft biotemplate appears to be a promising way to synthesize zinc oxide nanoparticles. In our study, rice was chosen to be used as a soft template material due to its high porous structure, special components and relatively low cost. Lots of studies have been conducted to investigate the use of rice husk [1, 19] and starches [20, 21] for the synthesis of various functional materials. However, to the best of our knowledge, no such study on the synthesis of ZnO nanoparticles using rice as biotemplate is found in the open literature. Therefore, this study will contribute some input to the body of knowledge and worth to be carried out. The main objective of this research is to determine the effects of uncooked rice as a biotemplate on ZnO physico-chemical properties, particularly its morphology and surface properties. Due to easy controlling of the size, shape and water solubility of ZnO, then the biocompatibility and functionality of ZnO nanomaterials could be further improved by surface modification .
Results and discussion
Morphology and size
Figure 2g and h indicate the FESEM images of ZnO sample synthesized using 1 g UR. Very unique star-like structure can be clearly observed at low to high magnification. The star-like structure contains small flakes with denticulated edges which attach to other similar flakes in the center. A closer look shows that the lateral flake act as a substrate for other flakes to grow on the surface and form star-like structure. Similar structure was also reported in literature, confirming that the branched pattern for soft templates, starch, revealing that the semicrystalline granules of starch are made from concentric rings in which the amylose and amylopectin, basic components are aligned perpendiculary to the growth rings and to the granule surface . Figure 2g and h shows that the size of the star-like ZnO particles decreased in comparison with the previous lower amount of uncooked rice.
In the case of ZnO crystals synthesized at 2 g UR, increasing the amount of biotemplate resulted in different morphologies of ZnO particles produced. It formed lots of agglomerated toothed-edge flakes which become a secondary unit for bigger particles. The star-like shape of the particles can be perceived in some areas but aggregation seems to be dominant and prevented clearer observation of the particles as they really are.
Figure 2k and l show FESEM images for as-synthesized ZnO particles synthesized using 4 g UR. The ZnO morphology changed to flower-like structures, mostly rose-like shapes. Detailed view on flower-like particles reveals that their flakes have largest diameter compared to other samples. In the case of ZnO synthesized using 8 g UR, a new morphology, different from other and control samples was observed. The ZnO crystals show mostly rods with around 100 nm size. Moreover, agglomerated without any specific shape particles coexisted with nanorods in the structure of ZnO synthesized using 8 g UR.
The rice main component is carbohydrates which is polysaccharides. In synthesis of nanosized oxide-based materials, carbohydrate can play multiple roles, namely coating/capping, functionalizing, stabilizing, poring and/or coordinating agent. In one hand, polymeric structure of starch with helical-shaped carbonaceous matrix which carrying multiple polyol groups create a protective and functionalized surrounding shield for metal ions which plays a structure-directing role. The hydroxyl groups of amylopectin could be involved both in intra- and/or intermolecular supramolecular association. They are able to coordinate transition metal ions, maintaining the nanoparticles highly aggregated [18, 23]. Rice granules swell in aqueous solution and their semi-crystalline structure is lost as the smaller amylose molecules start leaching out of the granule. The small amylose molecules can form complexes with Zn2+ because of their high number of coordinating functional groups. It is likely that the majority of the zinc ions are closely associated with the starch molecules, so nucleation and initial crystal growth might preferentially occur within regions of both high starch concentration and high Zn2+ concentration . The Van der Waals interactions between the surface molecules of the nanocrystallites form the driving force for self-assembly, and then ZnO nanocrystals can be assembled to form larger ZnO crystals , which explain the basis of the growth mechanism of zinc oxide crystals when raw rice was used as template.
Generally, the volume absorbed for samples synthesized using 0.25, 0.5, 1 and 2 g UR is higher than that of ZnO synthesized without UR. It is notable that maximum volume absorbed is observed for the sample synthesized using 0.25 g UR with value of 98 cm3/g. The decreasing trend for volume absorbed value for rest of the samples can be clearly observed from Figure 7. These dramatic changes in the adsorption behavior are often caused by surface modifications, which manifested itself in a significant decrease in the amount adsorbed . The desorption branches of the isotherms are also in good agreement with this result. The desorption branches of samples are quite different due to the modification has occurred in their pore’s texture.
In addition, H3 hysteresis usually indicates loosely assembled aggregated plate-like particles forming slit-like pores. However, changes can be observed from hysteresis loops. In the case of the sample synthesized using 8 g UR, an almost horizontal desorption branch with least volume adsorbed can be observed. Therefore this shows that modification in the pore texture of ZnO samples synthesized at different concentrations of UR has been occurred.
BET surface area, BJH pore size diameter and pore volume of ZnO nano- microstructures synthesized at different concentrations of UR
BET surface area (m2/g)
BJH pore diameter (nm)
BJH pore volume (cm3/g)
All chemicals used in this work were of analytical reagent grade and used as received without any further purification. All aqueous solutions were prepared using deionized water. The raw rice was purchased from a local market and then ground into powder form in a milling machine, Fritsch Pulverisette 6 type planetary monomill, Germany.
In a typical procedure, 1 g of zinc acetate (Zn(Ac)2.2H2O) and 0.8 g sodium hydroxide (NaOH) were dissolved in 25 mL distilled water under constant stirring (Zn2+:OH- = 1: 4). The measured pH was 13. After 1 hour stirring, different concentrations of rice powder 0, 0.25, 0.5, 1, 2, 4 and 8 g were introduced into the solution (the ratio of zinc acetate to rice powder was chosen at i.e. 1:0, 1:0.25, 1:0.5, 1:1, 1:2, 1:4 and 1:8 w/w%) and stirring was continued until the rice powder was completely dissolved. The solutions with lower concentrations of rice powder were easily dissolved and the color of solution remained white. In higher concentrations of rice powder, yellowish solutions after longer time of stirring were observed. Attempt has been made to use higher concentrations of rice, 16 g, but the resulting solution was very difficult of dissolve and therefore the experiment was discarded. Finally the mentioned solution was transferred into a Teflon-lined stainless steel autoclave, 50 mL and hydrothermal growth was carried out at 120°C for 18 h. After treatment, the autoclaves were allowed to cool down and the precipitates were collected, centrifuged at 40,000 × g for 10 min and supernatant was discarded. The obtained particles were washed three times with ethanol and distilled water in order to remove impurities and dried at 60°C for 24 h.
Powder X-ray diffraction (PXRD) analysis was performed on a Shimadzu diffractometer, XRD-6000 (Tokyo, Japan) equipped with CuKα radiation. The morphology of the micro- and nanostructures were characterized by field emission scanning electron microscopy (FESEM) a JOEL JSM-6400 (Tokyo, Japan). Surface characterization of the material was carried out using nitrogen gas adsorption–desorption technique at 77 K using a Micromeritics ASAP 2000 (Norcross, GA, USA). Thermogravimetric and differential thermogravimetric analysis (TGA-DTG) were carried out using a Mettler Toledo instrument (Greifensee, Switzerland) using a heating rate of 10°C/min, in the range of 25–1000°C under nitrogen atmosphere. Fourier transform infrared spectra were recorded over the 280–4000 cm−1 range using a Perkin-Elmer 100 spectrophotometer (Waltham, MA, USA) under standard conditions. The UV-VIS-NIR spectrophotometer UV-3600 SHIMADZU was used to determine the optical properties.
Uncooked rice, a bioresource can be used as biotemplate for morphology directing agent for the synthesis of ZnO micro- and nanostructures by hydrothermal method. The effects of uncooked rice on ZnO properties were investigated. Various ratios of rice were used and was found to change the morphology and size of the resulting ZnO crystals with different structures; flower-, flake-, rose-, star- and rod-like. The growth mechanism of ZnO crystals is possibly directed by conjugated and/or competing chemical/supramolecular interaction between zinc ions and the main component of the rice, carbohydrates. Surface modification of rice on the resulting ZnO was observed through pore texture and specific surface area.
Differential thermogravimetric analysis
Band gap energy
Field emission scanning electron microscopy
Fourier transform infrared
International union of pure and applied chemistry
Joint committee on powder diffraction standards
The authors are gratefully acknowledged the Ministry of Higher Education of Malaysia (MOHE) for financial support under grant No. FRGS/1/11/SG/UPM/01/2 (Vot No. 5524165).
- Yang D, Fan T, Zhou H, Ding J, Zhang D: Biogenic hierarchical TiO2/SiO2 derived from rice husk and enhanced photocatalytic properties for dye degradation. PLoS One. 2011, 6 (9): e24788-10.1371/journal.pone.0024788.View ArticleGoogle Scholar
- Qinglei L, Fan T, Ding J, Guo Q: Bio-inspired functional materials templated from nature materials. kona powder and particle journal. 2010, 28 (28): 116-130.Google Scholar
- Zhou H, Fan T, Zhang D: Biotemplated materials for sustainable energy and environment: current status and challenges. Chem Sus Chem. 2011, 4 (10): 1344-87. 10.1002/cssc.201100048.View ArticleGoogle Scholar
- Seeman NC: DNA in a material world. Nature. 2003, 421 (6921): 427-31. 10.1038/nature01406.View ArticleGoogle Scholar
- McMillan RA, Paavola CD, Howard J, Chan SL, Zaluzec NJ, Trent JD: Ordered nanoparticle arrays formed on engineered chaperonin protein templates. Nat Mater. 2002, 1 (4): 247-52. 10.1038/nmat775.View ArticleGoogle Scholar
- Fowler C, Shenton W: Tobacco mosaic virus liquid crystals as templates for the interior design of silica mesophases and nanoparticles. Adv Mater. 2001, 37235 (3): 1266-1269.View ArticleGoogle Scholar
- Davis S, Patel H: Brittle bacteria: a biomimetic approach to the formation of fibrous composite materials. Chem Phys Lett. 1998, 10: 2516-2524.Google Scholar
- Payne EK, Rosi NL, Xue C, Mirkin CA: Sacrificial biological templates for the formation of nanostructured metallic microshells. Angew Chem Int Ed Engl. 2005, 44 (32): 5064-7. 10.1002/anie.200500988.View ArticleGoogle Scholar
- Hall SR, Bolger H, Mann S: Morphosynthesis of complex inorganic forms using pollen grain templates Porous micron-sized particles of silica, calcium carbonate or by template-directed synthesis employing intact pollen. Chem Commun (Camb). 2003, 44: 2784-2785.View ArticleGoogle Scholar
- Gao X, Matsui H: Peptide-based nanotubes and their applications in bionanotechnology. Adv Mater. 2005, 17 (17): 2037-2050. 10.1002/adma.200401849.View ArticleGoogle Scholar
- He J, Kunitake T, Nakao A: Facile in situ synthesis of noble metal nanoparticles in porous cellulose fibers. Chem Mater. 2003, 15 (23): 4401-4406. 10.1021/cm034720r.View ArticleGoogle Scholar
- Cai A-J, Wang Y-L, Xing S-T, Du L-Q, Ma Z-C: Tuned morphologies of DNA-assisted ZnO struggling against pH. Ceram Int. 2013, 39 (1): 605-609. 10.1016/j.ceramint.2012.06.071.View ArticleGoogle Scholar
- Han J, Su H, Xu J, Song W, Gu Y, Chen Y, Moon W-J, Zhang D: Silk-mediated synthesis and modification of photoluminescent ZnO nanoparticles. Journal of Nanoparticle Research. 2012, 14 (2): 726-View ArticleGoogle Scholar
- Nouroozi F, Farzaneh F: Synthesis and characterization of brush-like ZnO nanorods using albumen as biotemplate. J Braz Chem Soc. 2011, 22 (3): 484-488. 10.1590/S0103-50532011000300011.View ArticleGoogle Scholar
- Jha AK, Kumar V, Prasad K: Biosynthesis of metal and oxide nanoparticles using orange juice. Journal of Bionanoscience. 2011, 5 (2): 162-166. 10.1166/jbns.2011.1053.View ArticleGoogle Scholar
- Yu J, Yang J, Liu B, Ma X: Preparation and characterization of glycerol plasticized-pea starch/ZnO-carboxymethylcellulose sodium nanocomposites. Bioresour Technol. 2009, 100 (11): 2832-41. 10.1016/j.biortech.2008.12.045.View ArticleGoogle Scholar
- Tomczak MM, Gupta MK, Drummy LF, Rozenzhak SM, Naik RR: Morphological control and assembly of zinc oxide using a biotemplate. Acta Biomater. 2009, 5 (3): 876-82. 10.1016/j.actbio.2008.11.011.View ArticleGoogle Scholar
- Visinescu D, Patrinoiu G, Tirsoaga A, Carp O, et al: Polysaccharides route: a new green strategy for metal oxides synthesis. Environmental Chemistry for a Sustainable World. vol. 1: Nanotechnology and Health Risk. Edited by: Lichtfouse E. 2012, Netherlands: Springer, 119-169.View ArticleGoogle Scholar
- Rahman MM, Hasnida N, Wan Nik WB: Preparation of zeolite Y using local Raw material rice husk as a silica source. J Sci Res. 2009, 1 (2): 2-8.Google Scholar
- Zhang G, Shen X, Yang Y: Facile synthesis of monodisperse porous ZnO spheres by a soluble starch-assisted method and their photocatalytic activity. J Phys Chem C. 2011, 115 (15): 7145-7152. 10.1021/jp110256s.View ArticleGoogle Scholar
- Taubert A, Wegner G: Formation of uniform and monodisperse zincite crystals in the presence of soluble starch. J Mater Chem. 2002, 12 (4): 805-807. 10.1039/b110424c.View ArticleGoogle Scholar
- Gidley M: Starch structure/function relationships: achievements and challenges. Starch: advances in structure and function. Special publication-royal society of chemistry. 2001, Great Britain: Food Chemistry Group, 1-7.View ArticleGoogle Scholar
- Paraschiv C, Tudose M: Green synthetic strategies of oxide materials: polysaccharides-assisted synthesis. Rev Roum Chim. 2010, 55: 1017-1026.Google Scholar
- Mazloumi M, Taghavi S, Arami H, Zanganeh S, Kajbafvala A, Shayegh MR, Sadrnezhaad SK: Self-assembly of ZnO nanoparticles and subsequent formation of hollow microspheres. J Alloys Compd. 2009, 468 (1–2): 303-307.View ArticleGoogle Scholar
- Chittofrati A, Matijevic E: Uniform particles of zinc oxide of different morphologies. Colloids and Surfaces. 1990, 48: 65-78.View ArticleGoogle Scholar
- Ascough PL, Bird MI, Francis SM, Lebl T: Alkali extraction of archaeological and geological charcoal: evidence for diagenetic degradation and formation of humic acids. J Archaeol Sci. 2011, 38 (1): 69-78. 10.1016/j.jas.2010.08.011.View ArticleGoogle Scholar
- Zheng Y, Chen C, Zhan Y, Lin X, Zheng Q, Wei K, Zhu J, Zhu Y: Luminescence and photocatalytic activity of ZnO nanocrystals: correlation between structure and property. Inorg Chem. 2007, 46 (16): 6675-82. 10.1021/ic062394m.View ArticleGoogle Scholar
- Meskinfam M: Synthesis and characterization of surface functionalized nanobiocomposite by nano hydroxyapatite. International Journal of chemical and Biological Engineering. 2012, 6: 192-195.Google Scholar
- Ma X, Yu J, He K, Wang N: The effects of different plasticizers on the properties of thermoplastic starch as solid polymer electrolytes. Macromol Mater Eng. 2007, 292 (4): 503-510. 10.1002/mame.200600445.View ArticleGoogle Scholar
- Qian J, Wang J, Jin Z: Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal. Mater Sci Eng A. 2004, 371 (1–2): 229-235.View ArticleGoogle Scholar
- Kizil R, Irudayaraj J, Seetharaman K: Characterization of irradiated starches by using FT-Raman and FTIR spectroscopy. J Agric Food Chem. 2002, 50 (14): 3912-8. 10.1021/jf011652p.View ArticleGoogle Scholar
- Khamthong P, Lumdubwong N: Effects of heat-moisture treatment on normal and waxy rice flours and production of thermoplastic flour materials. Carbohydr Polym. 2012, 90: 340-347. 10.1016/j.carbpol.2012.05.049.View ArticleGoogle Scholar
- Ciesielski W, Tomasik P: Thermal properties of complexes of amaranthus starch with selected metal salts. Thermochim Acta. 2003, 403 (2): 161-171. 10.1016/S0040-6031(02)00509-9.View ArticleGoogle Scholar
- Kruk M, Jaroniec M: Gas adsorption characterization of ordered organic–inorganic nanocomposite materials. Chem Mater. 2001, 13 (10): 3169-3183. 10.1021/cm0101069.View ArticleGoogle Scholar
- Yu J, Yu H, Cheng B, Zhao X, Zhang Q: Preparation and photocatalytic activity of mesoporous anatase TiO2 nanofibers by a hydrothermal method. Journal of Photochemistry and Photobiology A: Chemistry. 2006, 182 (2): 121-127. 10.1016/j.jphotochem.2006.01.022.View ArticleGoogle Scholar
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