Nanotechnology has grown tremendously in the past few years, and the importance of this type of technology in industry and society could not be denied. This is due to the fact that this technology can contribute to almost every aspect of life, from transportation to food and from medical to agriculture. Nanotechnology can be taken as the manipulation of matter at the scale size of 1–100 nm, which promises invention of new materials; especially, nanomaterials and devices. One of the advantages of nanomaterials is that they could be designed according to a specific use. Lately, nanotechnology has been attracting much more attention due to its growing importance in industry and academia [1–3]. Significant achievements in this area of research could be referred in literatures for nanoscience and nanotechnology, which has proven to have widespread applications [4–6].
One type of nanomaterials that is subjected to intense research lately is inorganic layered material; especially, layered double hydroxide (LDH). LDH can be used as the host for the formation of organic–inorganic nanohybrid material. A variety of organic moieties can be intercalated into the LDH interlayers, which makes them extremely promising for the purposes of drug delivery and gene therapy [7, 8], controlled release of plant growth regulator and herbicides [9–11], contaminants remover , polymer composite material with enhanced thermal stability  and various other applications. Research in the area of organic–inorganic nanohybrids often lead to formation of new materials with enhanced properties such as physico-mechanical, thermal, water swelling, electrical properties, etc. .
LDH is classified as layered anionic material formed by the positively charged layers with two or more types of metallic cations and exchangeable hydrated gallery anions. The general formula of LDH is
where MII represents divalent cations (Mg2+, Mn2+, Fe2+, Co2+, Cu2+, Ni2+, Zn2+, Ca2+, etc.), MIII represents trivalent cations (Al3+, Cr3+, Mn3+, Fe3+, Co3+, La3+) and Am− represents anions (CO32−, SO42−, NO3−, PO43−, Cl−) in the interlayer region . The ability of LDH to undergo anion exchange process that occurs in the interlayer domain makes it flexible to incorporate or intercalate beneficial anion for the target use.
Intercalation that involves insertion or incorporation of beneficial agent has gained overwhelming interests lately due to its unique physicochemical properties. The research on new and improved properties of intercalation product appears to be very interesting, because it gives rise to an almost unlimited set of new compounds, the so-called nanohybrid materials with a large spectrum of known and unknown properties [16–20]. Various types of intercalation method could be adopted such as anion exchange of a precursor LDH, direct synthesis by co-precipitation, rehydration of a calcined LDH precursor and thermal reaction . One of the beneficial agents that can be intercalated into LDH is agrochemical; for example, 2,4-dichlorophenoxyacetic acid (2,4-D).
2,4-Dichlorophenoxyacetic acid is widely used in agriculture sector. It is a systemic hormone-type selective herbicide , where at low concentration it can act as an auxin analogue, promoting plant growth but lethal to plants at high concentrations. Therefore, 2,4-D is also used as an herbicide against broad-leafed and woody plants [23–25]. It was also reported that 2,4-D can be used as latex stimulant for Hevea Brasiliensis, but the use of 2,4-D was later partially discontinued due to the introduction of an ethylene producing compound into the market . Concern on agrochemicals contamination in the environment has recently risen due to the potential hazards. As an example, 2,4-D can easily be transferred into water body due to its high solubility  and entering the human and animal food chains, and finally causing serious health problems. Formation of such intercalated compound or controlled release formulation of agrochemicals is one of the methods to solve this problem.
Apart from LDHs, many other matrices can also be used as the hosts for controlled release formulations. Previous works show that nanoporous, silicified phospholipids and stimuli–responsive magnetic nanoparticles can also be used as the hosts for glycolic acid and 4-diamino-6-mercaptopyrimidine, respectively [29, 30]. It was found that both the hosts and the intercalated guests play important role in determining the controlled release property of the resulting controlled release formulations.
Here, we describe the synthesis and the controlled release property of 2,4-D, a latex stimulant agent, in which the 2,4-D is intercalated into Zn–Al-LDH for the formation of the nanohybrid. The release was studied using single, binary and ternary systems. To our knowledge, no controlled release study of 2,4-D from its LDH nanohybrid in various aqueous media has intensively been carried out. The Zn–Al–2,4-D nanohybrid material is expected to inherit the same property of 2,4-D, which is to affect the physiological process of rubber plant in order to improve the quality and to increase the latex yield, but the release of 2,4-D is in a controlled manner. Further understanding of the role of controlled release behavior of 2,4-D on the latex output from the rubber tree could lead to the application of 2,4-D in the form of slow release formulation. It is hoped that the associated process is safe and environmentally friendly as the 2,4-D is not exposed directly to the user and the environment, and, therefore, could prevent the associated problems.