The synthesis of hybrid nano-composites in which an inorganic layer is grown on a polymeric surface via chemical bonds, is a challenging goal for many applications from photocatalysis, to sensing and optoelectronics. Herein, we describe on the growth of ZnO nanostructures by an Atomic Layer Deposition (ALD) technique on polyetherimide (poly(2,2′-bis(3,4-dicarboxyphenoxy)phenylpropane)-2-phenylendiimide ULTEM® 1000) substrates. A surface modification consisting of a thermal photo-oxidization process, applied for different exposure times, has been properly performed on the polymer to promote the production of ALD suitable functionalities as reactive surface-sites. The chemical anchoring of the inorganic species from the gas-phase is demonstrated by spectroscopy and mass analyses to exclusively occur on the pre-oxidized films, whilst the ZnO growth does not occur in the untreated ULTEM® films in the operative ALD conditions. Notably, we demonstrate that two different regimes of growth take place in the oxidized polymer as a function of the photo-exposure time. In particular, the formation of a nanostructured coating of ZnO on the polyetherimide surface is found in the case of short-time photo-exposed polyetherimide (ALD-like regime), whilst an intermixed organic/polymer layer is found on the long-time oxidized films (Vapor Phase Infiltration, VPI-like regime). The photocatalytic activity of the synthesized materials has been tested through the degradation of methylene blue dye in aqueous solution under UV light irradiation, to give a proof of concept of a possible application of the nano-composites.

Silicon nanowires (Si-NWs) have been extensively studied for their numerous applications in nano-electronics. The most common method for their synthesis is the vapor–liquid–solid growth, using gold as catalyst. After the growth, the metal remains on the Si-NW tip, representing an important issue, because Au creates deep traps in the Si band gap that deteriorate the device performance. The methods proposed so far to remove Au offer low efficiency, strongly oxidize the Si-NW sidewalls, or produce structural damage. A physical and chemical characterization of the as-grown Si-NWs is presented. A thin shell covering the Au tip and acting as a barrier is found. The chemical composition of this layer is investigated through high resolution transmission electron microscopy (TEM) coupled with chemical analysis; its formation mechanism is discussed in terms of atomic interdiffusion phenomena, driven by the heating/cooling processes taking place inside the eutectic-Si-NW system. Based on the knowledge acquired, a new efficient etching procedure is developed. The characterization after the chemical etching is also performed to monitor the removal process and the Si-NWs morphological characteristics, demonstrating the efficiency of the proposed method and the absence of modifications in the nanostructure.

Electrochemically induced phase transformations often dictate the charge-transfer behavior of metal-oxide electrodes; however, their impact on the charge-storage remains largely unexplored, particularly for Bi-based systems. In this work, we investigate the charge-storage mechanisms governing the battery-like behavior of films based on the Bi-oxide/Bi0 redox couple, prepared without any carbon-based additives or binders. In particular, we compared the performances of electrochemically activated BiOx(NO3)y(OH)z xerogel—used without thermal treatment—with those of materials annealed in forming gas, consisting of β-Bi2O3/Bi0 crystalline domains. The electro-activated xerogels exhibit nearly constant specific capacitances across the investigated current-density range (∼115 F g−1 at 0.5 A g−1 to ∼80 F g−1 at 3 A g−1) in 1 M KOH. Annealed samples show higher specific capacitances at low current-density values (∼320 F g−1 at 0.5 A g−1) with lower values (∼50 F g−1 at 3 A g−1) at higher current densities. A multitechnique characterization reveals that charge storage in the electro-activated xerogel is predominantly governed by the surface Bi ↔ BiO2− reaction. Conversely, in the annealed films, the behavior is largely diffusion-controlled. In these systems, the initial β-Bi2O3 phase undergoes an electrochemically driven transformation into monoclinic α-Bi2O3, giving rise to an additional charge-storage pathway associated with the internal α-Bi2O3 ↔ Bi0 redox process.