## 1 Introduction  
In recent years, the controlled synthesis of inorganic particles and their morphologies are of strong interests due to the fact they have very important potential as optical, sensor, catalytic, and electrical materials [1; 2; 3; 4]. Among those, zinc oxide ZnO has been used as a useful candidate for various applications due to their unique optical and electrical properties, which renders it suitable in many application fields from optoelectronics to energy conversion, hydrophobic and electrowettable surfaces, piezoelectric, nanogenerators, gas sensing, and photocatalytic systems [5; 6; 7; 8; 9; 10; 11; 12]. It is well known that the physical properties of ZnO are strongly dependent on its morphology and size [13]. Numerous researchers have paid considerable attention to the micro/nano-structures systems, especially three-dimensional hierarchical superstructures that are assembled by nanoscale building blocks such as nanoplates, nanowires, nanosheets and nanorods [14; 15]. Therefore, considerable efforts have been devoted to design of effective methods to synthesize ZnO with tunable size and morphology. Over the past decades, various methods have been developed to synthesize ZnO with various morphologies such as physical and chemical vapor deposition, thermal evaporation, metal-organic chemical vapor deposition and wetting chemical synthesis, template-assisted growth and solution-based approaches [16; 17; 18]. During the last decades, various studies concerning the control of the nucleation and the growth of ZnO nano/microstructures embedded in polymeric matrices have been reported, with a special emphasis on the particles morphological control and its influence on their physical properties [19; 20]. In this context, [PERSON] _et al._ have developed a method to fabricate a mem-sensor in which ZnO wires embedded in a polymeric matrix are ordered to create morphological anisotropy by means of dielectrophoresis [21]. For these reasons, several works were performed in order to tune the shape and the size of ZnO structures using different capping agents capable of stabilizing a particular crystal facet by adsorption and alter the growth rate in different crystal planes [22; 23]. Moreover, different soft templates/capping agents such as water-soluble polymers [24; 25; 26], citrate salts [27; 28], surfactants [29; 30; 31], a mixture of sodium citrate and alkylamine [23], citric acid [25], ethylene diamine [32], and amino acids [33] have been successfully used in wet-chemical methods. In this context, [PERSON] _et al._ have developed a method to fabricate novel flower-like 3D ZnO superstructures in aqueous solution and using trisodium citrate dihydrate as a surfactant to enhance the nucleation-growth process implied in the formation of such hierarchical superstructures [34]. Multilayered ZnO nanosheets with porous structures were synthetized by simple calcination of the hydroxide zinc carbonate at 400 \({}^{\circ}\)C in air ambient to be used as acetone sensors [35]. [PERSON] _et al._ have developed a simple method to fabricate a coral-shaped porous ZnO nanostructure by room temperature sputtering processes [36]. [PERSON] _et al._ also reported the formation of novel ZnO hierarchical nanowires for high efficiency dye-sensitized solar cells [37]. Moreover, using a solvothermal approach in an aqueous solution of ethylene diamine, [PERSON] _et al._ prepared ZnO hierarchical micro/nanostructures possessing enhanced photocatalytic performance [38]. Prism-like and flower-like ZnO structures with good photocatalytic activities were synthetized through a hydrothermal route in the presence of amino acid [39]. [PERSON] _et al._ also developed novel ZnO nanorod-assembled hollow superstructures for photoluminescence and catalysis applications using hydrothermal reaction via sodium carboxymethyl cellulose (CMC) assistance [40].