In this work we report the design and synthesis of high-surface-area photocatalysts by coating TiO2 on fibrous nanosilica (KCC-1) using atomic layer deposition (ALD). Our developed catalyst showed enhanced photocatalytic activity, better than that of the well-known MCM-41- and SBA-15-supported TiO2 catalysts using ALD as well as that of other silica-supported TiO2 catalysts reported in the literature to date. This work shows how one can tune the photocatalytic activity of supported TiO2 catalysts by simply tuning the morphology of the support. In addition to extensive characterization of materials using various techniques, comprehensive mechanistic insight into ALD TiO2 coating on KCC-1 fibers was gained using solid-state NMR and UV-DRS. For the first time, we also observed the formation of small and monodispersed TiO2 nanoparticles after heat treatment of these ALD-coated samples of KCC-1. Notably, we observed size quantization effects in these TiO2 nanoparticles, which was confirmed by band gap shift measurements and the Brus effective mass approximation method. We believe that the combination of the unique textural properties and morphology of KCC-1 and TiO2 nanoparticle formation and their size quantization is the reason behind the enhanced photocatalytic activity of KCC-1/TiO2 catalysts.

We report a facile protocol for the synthesis of fibrous nano-silica (KCC-1) with controllable size and fiber density. In this work, we have shown that the particle size, fiber density, surface area and pore volume of KCC-1 can be effectively controlled and tuned by changing various reaction parameters, such as the concentrations of urea, CTAB, 1-pentanol, reaction time, temperature, solvent ratio, and even outside stirring time. For the first time, we were able to control the particle size ranging from as small as 170 nm to as large as 1120 nm. We were also able to control the fiber density from low to medium to very dense, which consequently allowed the tuning of the pore volume. We were able to achieve a pore volume of 2.18 cm3/g, which is the highest reported for such a fibrous material. Notably we were even able to increase the surface area up to 1244 m2/g, nearly double the previously reported surface area of KCC-1. Thus, one can now synthesize KCC-1 with various degrees of size, surface area, pore volume, and fiber density.

We report a dendritic fibrous nano-silica supported gold nanoparticles (DFNS/Au) as peroxidase like artificial enzyme. This study indicates the unique role of fibrous morphology of DFNS for enhancement in enzymatic activity. A solvent dependent selectivity towards a two-electron oxidation product, TMB-diamine, has also been observed.

A new method has been developed to fabricate active TiO photocatalysts by tuning the morphology of the catalyst support. A sustainable solution-phase TiO deposition on dendritic fibrous nanosilica (DFNS) protocol is developed, which is better than the complex and expensive atomic layer deposition technique. In general, catalytic activity decreases with an increased TiO loading on conventional mesoporous silica because of the loss of the surface area caused by the blocking of pores. Notably, in the case of the dendritic fibrous nanosilica KCC-1 as a support, because of its open fibrous morphology, even at the highest TiO loading, a relatively large amount of surface area remained intact. This improved the accessibility of active sites, which increased the catalytic performance of the KCC-1/TiO photocatalyst. KCC-1-supported TiO is a superior photocatalyst in terms of H generation (26.4 mmol gTiO2 h ) under UV light. This study may provide a new direction for photocatalyst development through the morphology control of the support.

Although the range of photocatalysts with controllable size, shape and morphology has developed in recent years with a large number of silica-supported TiO 2 catalysts, the details of photocatalytic interfaces between nanosilica and TiO 2 them and the mechanisms of TiO 2 functionalization of silica surfaces are not yet well understood. It is worth mentioning that the understanding of a mechanism from a molecular point of view has always been a challenge in the field of materials science. Here, we probe interfaces in (dendritic fibrous nano-silica (DFNS) supported TiO 2 photocatalysts as well as propose and prove the formation mechanism of the photocatalyst, DFNS/TiO 2 , by ammoniaassisted functionalization of DFNS by titanium butoxide (TBOT). The proposed formation mechanism includes the following steps: i) the deprotonation of silica surface (silanols) by ammonia and the hydrolysis of TBOT to titanium hydroxide [Ti(OH) 4 ], ii) the donation of electron lone pair from ammonia to the Ti 4 + ion of Ti(OH) 4 , iii) the release of hydroxide ions, followed by hetero-condensation of dehydroxylated titanium ions with the deprotonated silanols, generating SiÀOÀTi oxobridges, iv) the formation of oxy-anion of titanols and its reaction with another molecule of ammonia-activated titanium hydroxide to generate TiÀOÀTi oxobridges, and v) the continuation of the above cycle of steps until the titanium hydroxide precursor is consumed to produce silica supported titanium hydroxide. During thermal treatment, the titanols condense, yielding DFNS/TiO 2 photocatalysts. To prove this mechanism, detailed solid-state 1 H, 29 Si, 47,49 Ti NMR and in situ FTIR studies were carried out, based on which different surface species formed during TiO 2 growth on DFNS were identified. This has led to fundamental insights into the reaction of TBOT with DFNS silica surface and interfaces between DFNS and TiO 2 .[a] R.