TiO2@C core-shell nanoparticles formed by polymeric nano-encapsulation

Abstract

TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e., the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolysis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent.

TiO2@Carbon Photocatalysts: The Effect of Carbon Thickness on Catalysis

“…42,48 The second step is the in situ chain growth/encapsulation process on the TiO 2 surface via RAFT polymerization. 41,[47][48][49][50] As the RAFT polymerization is a well-controlled polymerization process, the chains of the RAFT dispersant are extended upon adding monomers, and the chain length of the final block copolymers can be easily tuned by varying the amount of added monomers. The RAFT dispersant is adsorbed at the surface of the TiO 2 , therefore, the second block of the polymer effectively forms a continuous polymer shell around the TiO 2, resulting in a complete engulfing of the TiO 2 NBs by a polymeric shell.…”

Triple Axial Coelectrospun Multifunctional Double-Shell TiO2@ZnO Carbon Hollow Nanofibrous Mat Transformed to C-Attached TiO2 Brush-Like Nanotube Arrays: An Mo6+ Adsorbent Nonwoven Mat

“…Furthermore, the Raman peaks of ZnO overlapped with that of the rutile TiO 2 at 333 cm -1 , 376 cm -1 , 427 cm -1 and 542 cm -1 represent the E 2 (highlow), A 1 (TO), E 2 (high) and E 2 (high+low) modes, respectively (inset in Figure 3a as well as the bands in the range of 1000-1300 cm -1 support the graphitization of PAN during a two-step heat treatment process 59 . The broad absorption peak about 3391 cm -1 , and the band at 1598 cm -1 are correspond to the surface absorbed water and the hydroxyl groups 58 .…”

“…However, only four peaks at 144 cm -1 (B 1 g), 249 cm -1 (Eg), 440 cm -1 (Eg), and 606 cm -1 (A 1 g) can be observed in the Raman spectra of C-attached TiO 2 nanostructures, which are well consistent with that of reported rutile TiO 2 . The peaks D and G at around 1280-1318 cm -1 and 1536-1555 cm −1 respectively, correspond to sp 2 carbon atoms in a disordered environment and to carbons in extended p-conjugated graphite-like arrangements (graphite carbon)[58][59][60][61] . The peak intensity ratio of D-band and G-band (I D /I G ) is found to be 2.0 for the C-attached TiO 2 hollow nanofibers compared with the I D /I G value of TiO 2 @ZnO/C (about 2.7), supporting higher graphite values of the C-attached rutile TiO 2 than TiO 2 @ZnO/C.…”

Fabrication of core–shell nanocomposites with enhanced photocatalytic efficacy

“…First, the two monomers are transformed to ph‐NH 3 + Cl − salts (phenyl salts) in aqueous acidic conditions. When the suspension of TiO 2 nanoparticles in water is added to the acidic reaction solution, it is anticipated that it is positively charged . Subsequently, an electrostatic interaction originates between the phenyl salts and the positively charged TiO 2 surface.…”