Catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles were fabricated using a combination of sol–gel chemistry and coaxial electrospinning technique. We report the fabrication of catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles (AuNPs) using a combination of sol–gel chemistry and coaxial electrospinning technique. The coaxial electrospinning involved the use of a mixture of poly(vinyl pyrrolidone) (PVP) and titania sol as the shell forming component, whereas a mixture of poly(4-vinyl pyridine) (P4VP) and pre-synthesized AuNPs constituted the core forming component. The core–shell nanofibers were calcined stepwise up to 600 °C which resulted in decomposition and removal of the organic constituents of the nanofibers. This led to the formation of porous and hollow titania nanofibers, where the catalytic AuNPs were embedded in the inner wall of the titania shell. The catalytic activity of the prepared Au@TiO₂ porous nanofibers was investigated using a model reaction of catalytic reduction of 4-nitrophenol and Congo red dye in the presence of NaBH₄. The Au@TiO₂ porous and hollow nanofibers exhibited excellent catalytic activity and recyclability, and the morphology of the nanofibers remained intact after repeated usage. The presented approach could be a promising route for immobilizing various nanosized catalysts in hollow titania supports for the design of stable catalytic systems where the added photocatalytic activity of titania could further be of significance.

We investigated the micellar behavior of a series of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers in different P4VP-selective alcoholic solvents. The micellar behavior was further correlated with the spectroscopic ellipsometry results obtained on swelling of PS and P4VP polymer films in the corresponding solvent vapors. The time-resolved (in situ) dynamic light scattering (DLS) measurements, in combination with (ex situ) electron microscopy imaging, revealed information about the aggregation state of PS-b-P4VP BCP in different alcohols and the effect of heat treatment. The ellipsometry measurements allowed us to estimate the difference in solvent selectivity toward PS/P4VP pair. Both DLS and ellipsometric studies suggested that less polar alcohols (i.e., 1-propanol, 1-butanol, and 1-pentanol) are likely to be close to each other in terms of their selectivity toward PS/P4VP pair, whereas more polar ethanol and methanol show the highest and the lowest affinity toward P4VP, respectively.

Fabrication of block copolymer (BCP) template-assisted nano-catalysts has been a subject of immense interest in the field of catalysis and polymer chemistry for more than two decades now. Different methods, such as colloidal route, on-substrate methods, bulk self-assembly approaches, combined approaches, and many others have been used to prepare such nano-catalysts. The present review focuses on the advances made in this direction using diblock, triblock, and other types of BCP self-assembled structures. It will be shown how interestingly, researchers have exploited the features of tunable periodicity, domain orientation, and degree of lateral orders of self-assembled BCPs by using fundamental approaches, as well as using different combinations of simple methods to fabricate efficient catalysts. These approaches allow for fabricating catalysts that are used for the growth of single- and multi-walled carbon nanotubes (CNTs) on the substrate, size-dependent electrooxidation of the carbon mono oxide, cracking of 1,3,5-triisopropylbenzene (TIPB), methanol oxidation, formic acid oxidation, and for catalytic degradation of dyes and water pollutants, etc. The focus will also be on how efficient and ease-of-use catalysts can be fabricated using different BCP templates, and how these have contributed to the fabrication of different nano-catalysts, such as nanoparticle array catalysts, strawberry and Janus-like nanoparticles catalysts, mesoporous nanoparticles and film catalysts, gyroid-based bicontinuous catalysts, and hollow fiber membrane catalysts.

The present paper reports the fabrication of novel types of hybrid fibrous photocatalysts by combining block copolymer (BCP) templating, sol-gel processing, and coaxial electrospinning techniques. Coaxial electrospinning produces core-shell nanofibers (NFs), which are converted into hollow porous TiO₂ NFs using an oxidative calcination step. Hybrid BCP micelles comprising a single plasmonic nanoparticle (NP) in their core and thereof derived silica-coated core-shell particles are utilized as precursors to generate yolk-shell type particulate inclusions in photocatalytically active NFs. The catalytic and photocatalytic activity of calcined NFs comprising different types of yolk-shell particles is systematically investigated and compared. Interestingly, calcined NFs comprising silica-coated yolk-shells demonstrate enhanced catalytic and photocatalytic performance despite the presence of silica shell separating plasmonic NP from the TiO₂ matrix. Electromagnetic simulations indicate that this enhancement is caused by a localized surface plasmon resonance and a confinement effect in silica-coated yolk-shells embedded in porous TiO₂ NFs. Utilization of the coaxially electrospun TiO₂ NFs in combination with yolk-shells comprising plasmonic NPs reveals to be a potent method for the photocatalytic decomposition of numerous pollutants. It is worth noting that this study stands as the first occurrence of combining yolk-shells (Au@void@SiO₂) with porous electrospun NFs (TiO₂) for photocatalytic purposes and gaining an understanding of plasmon and confinement effects for photocatalytic performance. This approach represents a promising route for fabricating highly active and up-scalable fibrous photocatalytic systems.