P. Davide Cozzoli

Heterostructuring colloidal nanocrystals into multicomponent modular constructs, where domains of distinct metal and semiconductor phases are interconnected through bonding interfaces, is a consolidated approach to advanced breeds of solution‐processable hybrid nanomaterials capable of expressing richly tunable and even entirely novel physical‐chemical properties and functionalities. To meet the challenges posed by the wet‐chemical synthesis of metal‐semiconductor nanoheterostructures and to overcome some intrinsic limitations of available protocols, innovative transformative routes, based on the paradigm of partial chemicalization, have recently been devised within the framework of the standard seeded‐growth scheme. These techniques involve regiospecific replacement reactions on preformed nanocrystal substrates, thus holding great synthetic potential for programmable configurational diversification. This review article illustrates achievements so far made in the elaboration of metal‐semiconductor nanoheterostructures with tailored arrangements of their component modules by means of conversion pathways that leverage on spatially controlled partial chemicalization of mono‐ and bi‐metallic seeds. The advantages and limitations of these approaches are discussed within the context of the most plausible mechanisms underlying the evolution of the nanoheterostructures in liquid media. Representative physical‐chemical properties and applications of chemicalization‐derived metal‐semiconductor nanoheterostructures are emphasized. Finally, prospects for developments in the field are outlined.

Thin films of titanium dioxide (TiO2) nanocrystals, widely acknowledged for their unique physical-chemical properties and functionalities, are used in disparate technological fields, including photovoltaics, sensing, environmental remediation and energy storage. In this paper, the preparation of thin films consisting of anatase-phase TiO2 nanorods deposited using the matrix-assisted pulsed laser evaporation (MAPLE) technique and their characterization in terms of morphology, elemental composition and wettability are presented and discussed. Particular attention is paid to the effects of the laser fluence, varied over a broad range (F = 25, 50, 100 mJ/cm2), and to the role of the capping surfactants bound to the surface of the nanorod precursors. Whereas increasing fluence favored a partial removal of the surface-bound surfactants, a post-growth UV-light-driven photocatalytic treatment of the films was found to be necessary to reduce the incorporated fraction of organics to a further substantial extent. It was noteworthy that, under our experimental conditions, the distinctive surface patterns and roughness that commonly degrade the morphology of films deposited using the MAPLE technique were not observable. This previously unreported experimental evidence was rationalized on the basis of the interaction dynamics between solvent/solute droplets ejected from the laser-irradiated target and the rough surfaces of the growing film.