Here, we demonstrate our extended effort to extensively study the structural properties and, in particular, the photocatalytic application of these hybrid nanocatalysts. Methods A modified microwave method was used to synthesise the TiO2/MWCNTs hybrid nanocatalysts. Initially, a 3.5-cm hole was drilled through the top of a household microwave oven. A reflux condenser was subsequently installed in the microwave oven to enable continuous synthesis at ambient pressures. Since the microwave has a wavelength of 12 cm, there will be no escaped radiation through the hole. As additional protection purpose, the microwave
was operated inside a fume hood. Commercial MWCNTs (Cheap Tubes Inc., Brattleboro, VT, USA) with an outer buy Torin 2 diameter of 10 to 30 nm, an inner diameter of 5 nm, a surface area of 110 m2/g and lengths up to 50 μm were used in this work. Due to electrostatic interactions and van der Waals forces between the individual nanotubes, the MWCNTs exhibit a strong tendency to agglomerate. This agglomeration
leads to poor solubility of the MWCNTs in most aqueous and organic solvents. Thus, to achieve a stable aqueous suspension of MWCNTs, functionalisation processes are necessary due to the presence of a large ISRIB in vivo amount of functional groups on the nanotubes’ surface. The presence of these functional groups on the MWCNTs’ surface imparts negative charges and thus generates repulsion forces, which inhibit agglomeration. These negative charges can also function as anchor sites and thereby enable the in situ attachment of synthesised nanoparticles onto the MWCNTs’ surface. For this purpose, the MWCNTs were first functionalised by being
sonicated for 3 h in a 65% TPX-0005 solution of concentrated HNO3. The suspended MWCNTs were then placed in the modified microwave oven (Sharp model R-369 T) and irradiated for 20 min at a power of 550 W. Afterwards, the product was rinsed with deionised water six times and then completely dried at 80°C. old The MWCNTs were denoted as functionalised MWCNTs (f-MWCNTs) after this process. The surface areas of the f-MWCNTs dramatically increased to 357.6 m2/g after the functionalisation process. Greater MWCNT surface area recorded after functionalisation has been associated with the increase of functional groups on the nanotube surface [39]. Preparation of TiO2/MWCNTs nanocatalysts involved the dispersion of f-MWCNTs in ethanol (pH = 2) and sonicated for 1 h. Then, approximately 561 μL of titanium isopropoxide (TTIP) was added dropwise to the suspension over a period of 20 min under vigorous stirring. Notably, under acidic conditions, the TiO2 surface contains positive charges due to the presence of ≡Ti-OH2 + groups [40], which enhance the adhesion characteristics on the MWCNTs’ surface. The amount of TTIP precursor represented a TiO2/f-MWCNT weight ratio of 50%.