Question

What are the instruments that have been utilized for the review article discussions?
1. Introduction In recent years, nanoclays have been the object of particular interest for many scientists and researchers in chemistry, physics, engineering and biology due to their excellent properties as well as their sustain- ability [1-3]. For instance, they represent the starting point to the de velopment of smart materials for drug delivery (4-9), food packaging [10-12), environmental remediation and wastewater treatment [13], cultural heritage [14–17and additives for enhancing the performances of polymers [18,19). Due to the large demand of applications, the physico-chemical properties of nanoparticles, and nanoclays particu- larly, have been manipulated in order to improve their stability in aqueous media 20,21]. Since the discovery of carbon nanotubes in 1991 [22], the tubular structure has been widely investigated in other types of particles including metal nanotubes 23,24), oxide nanotubes [25,26], semiconducting nanotubes [27), nitride nanotubes [28,29] and natural clay nanotubes, which have gained interest in the material science and nanotechnology for their large specific surface, high por- osity and tunable surface chemistry. This review will be focused on the strategies to prepare stable dis- persions of halloysite clay nanotubes (HNTS) that are naturally-occur- ring two-layered aluminosilicate characterized by a hollow tubular structure with a spiral conformation (Fig. 1) and unit formula (Absi20 (OH)4 NH30) [1]. The inter layer distance depends on the hy- dration state being 0.7 nm and 1 nm for n = 0 and n = 2 respectively [1] The HNTs size depends on the deposit and varies from 50 to 70 nm in external diameter, and from 10 to 20 nm diameter for the lumen [18,31). The tubes' lengths range with in 0.5-1.5 um. The extemal surface of HNTs is composed of silicon oxygen tetrahedron mean while the internal lumen consists of alumina oxygen octahedrons (32), so the outer surface is distributed mainly with Si-O-si group and the inner surface is composed of Al-OH (30,33]. Because of the multilayer structure, most of the hydroxyl groups exist within the lumen and only a few in the outer surface [34]. Considering the different chemistry in the inner/outer surface, the former is positively charged and the latter is negatively charged in water in a pH range between 2 and 8. More over, as a widely used environmentally friendly clay material, HNTS have a good biocompatibility [35] and they are non-toxic as evidenced by in vivo [36] and in vitro tests [37]. These characteristics make HNTS excellent vehicles for carrying numerous types of cargos, when nega- tively charged molecules are sacked into the tube's lumen and positive ones adsorbed on the tube's outer surface. The colloidal stability of HNTs is a key point that has been deeply investigated, in order to im- prove the nanoparticles manageability trough the several possible uses that could be made [38]. For instance, when stable colloidal dispersions are reached, both a higher specific surface and a greater cavity area of halloysite nanotubes could be obtained and extensively used in nano- catalysis (39-45), nanotemplate [46] and biological controlled release [47-49). This purpose was pursued by some different strategies of

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Answer 1

From the review paper the instrument that has been used in the review are

1) Isothermal titration colorimetry(ITC)

2) Turbidimetry

3) Small angle neutron scattering (SANS)

4) Doppler interferometry

5) Tensiometer

6) Polarized Dynamic Light scattering

7) Derivative Thermogravimetry (DTG )

8) Transmission Electron Microscopy (TEM)

As they have not mention about TEM but the size of Halloysite clay nanotubes is in nano range according to paper so they had performed TEM amalysis for the size determination..