Structural and photoelectrochemical properties of porous TiO2 nanofibers decorated with Fe2O3 by sol-flame

The hybrid structure of Fe2O3 nanoparticles/TiO2 nanofibers (NFs), combines the merits of large surface areas of TiO2 NFs and absorption in ultraviolet light–visible light range. This structure can be used for many applications such as photoelectrochemical water splitting and photo-catalysis. Here, a sol-flame method is used for depositing Fe2O3 on TiO2 NFs that were prepared by hydrothermal on Ti sheets. The obtained materials were characterized by XRD, SEM, UV/Vis diffuse reflectance, Raman, and XPS. The results revealed the formation of rutile and anatase crystalline phases together with Fe2O3. This process moves the absorption threshold of TiO2 NFs support into visible spectrum range and enhances the photocurrent in comparison to bare TiO2 NFs, although no hole scavenger was used. The impedance measurement at low and high frequencies revealed an increase in series resistance and a decrease in resistance of charge transfer with sol-flame treatment time. A mechanism for explaining the charge transfer in these TiO2 NFs decorated with Fe2O3 nanoparticles was proposed.

Modification of Hematite Electronic Properties with Trimethyl Aluminum to Enhance the Efficiency of Photoelectrodes

The electronic properties of hematite were investigated by means of synchrotron radiation photoemission (SR-PES) and X-ray absorption spectroscopy (XAS). Hematite samples were exposed to trimethyl aluminum (TMA) pulses, a widely used Al-precursor for the atomic layer deposition (ALD) of Al2O3. SR-PES and XAS showed that the electronic properties of hematite were modified by the interaction with TMA. In particular, the hybridization of O 2p states with Fe 3d and Fe 4s4p changed upon TMA pulses due to electron inclusion as polarons. The change of hybridization correlates with an enhancement of the photocurrent density due to water oxidation for the hematite electrodes. Such an enhancement has been associated with an improvement in charge carrier transport. Our findings open new perspectives for the understanding and utilization of electrode modifications by very thin ALD films and show that the interactions between metal precursors and substrates seem to be important factors in defining their electronic and photoelectrocatalytic properties.

Acoustic properties of porous concrete made from arlite and vermiculite lightweight aggregates

The use of sustainable materials is becoming a common practice for noise abatement in building and civil engineering industries. In this context, many applications have been found for porous concrete made from lightweight aggregates. This work investigates the acoustic properties of porous concrete made from arlite and vermiculite lightweight aggregates. These natural resources can still be regarded as sustainable since they can be recycled and do not generate environmentally hazardous waste. The experimental basis used consists of different type specimens whose acoustic performance is assessed in an impedance tube. Additionally, a simple theoretical model for granular porous media, based on parameters measurable with basic experimental procedures, is adopted to predict the acoustic properties of the prepared mixes. The theoretical predictions compare well with the absorption measurements. Preliminary results show the good absorption capability of these materials, making them a promising alternative to traditional porous concrete solutions.

Influence of alkylphosphonic acid grafting on the electronic and magnetic properties of La2/3Sr1/3MnO3 surfaces

Self-assembled monolayers (SAMs) are highly promising materials for molecular engineering of electronic and spintronics devices thanks to their surface functionalization properties. In this direction, alkylphosphonic acids have been used to functionalize the most common ferromagnetic electrode in organic spintronics: La2/3Sr1/3MnO3 (LSMO). However, a study on the influence of SAMs grafting on LSMO electronic and magnetic properties is still missing. In this letter, we probe the influence of alkylphosphonic acids-based SAMs on the electronic and magnetic properties of the LSMO surface using different spectroscopies. We observe by X-ray photoemission and X-ray absorption that the grafting of the molecules on the LSMO surface induces a reduction of the Mn oxidation state. Ultraviolet photoelectron spectroscopy measurements also show that the LSMO work function can be modified by surface dipoles opening the door to both tune the charge and spin injection efficiencies in organic devices such as organic light-emitting diodes.