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Summary High-throughput manufacturing of hybrid halide perovskite solar cells is the next challenge before they enter the market. An anti-solvent bath is generally required to control the perovskite film assembly starting from precursors in solution. Although an anti-solvent bath has proven feasible for roll-to-roll deposition, it implies an undoubted increased complexity of the manufacturing line, meaning enhanced costs for the process itself and anti-solvent disposal. Here, we take advantage of the use of a starch polymer as a rheological modifier in perovskite precursor solutions to avoid the anti-solvent bath. Starch allows for control of the perovskite growth process in one step and reach of required viscosities for gravure-printing technique with ∼50% less of the raw precursor materials. This combined with simplified processing conditions are expected to drastically lower the costs of perovskite material production. We demonstrate that this approach can be upscaled to roll-to-roll gravure printing of flexible solar cells, reaching a maximum power conversion efficiency close to 10%.

The industrialization of perovskite solar cells relies on solving intrinsic-to-material issues. To reach record efficiencies perovskite deposition needs to be finely adjusted by multi-step processes, in a humidity free glove-box environment and by means of hardly scalable techniques often associated with toxic solvents and anti-solvent dripping/bath. Herein, the use of polymeric material is proposed to deposit perovskite layers with easy processability. To the scope, a starch-polymer/perovskite composite is developed to suit slot-die coating technique requirement, allowing the deposition of hybrid halide perovskite material in a single straightforward step without the use of toxic solvents, and in uncontrolled humid environment (RH up to 70 %). The starch-polymer increases the viscosity of the perovskite precursor solutions and delays the perovskite crystallization that results in the formation of perovskite films at mild temperature (60 degrees C) with good morphology. These innovative inks enables the fabrication of flexible solar cells with p-i-n configuration featured by a power conversion efficiency higher than 3 %. . Overall, this approach can be exploited in the future to massively reduce perovskite manufacturing costs related to keeping the entire fabrication line at high-temperature and under nitrogen or dry conditions.

[Y(O 2 CNBu 2 ) 3 ], has been prepared by extraction of the Y 3+ ions from aqueous solution into heptane by the NHBu 2 /CO 2 system. Exhaustive hydrolysis of [Y(O 2 CNBu 2 ) 3 ] produced the yttrium carbonate [Y 2 (CO 3 ) 3 ⋅n H 2 O] (n = 2–3), that was converted to Y 2 O 3 by thermal treatment at 550 °C for 12 h. The exhaustive hydrolysis of [Y(O 2 CNBu 2 ) 3 ] and [Al(OBu) 3 ] (Y/Al molar ratio = 3/5) carried out at room temperature yielded an intermediate mixed carbonate, that, upon heating at 950 °C for 12 h, was converted to Y 3 Al 5 O 12 . The exhaustive hydrolysis of [Y(O 2 CNBu 2 ) 3 ] and [Al(OBu) 3 ] was repeated in the presence of [Nd(O 2 CNBu 2 ) 3 ] (Nd/Y molar ratio = 0.07;(Nd + Y)/Al molar ratio = 3:5). The neodymium doped garnet Nd:Y 3 Al 5 O 12 was obtained, through the intermediate formation of a mixed hydroxo-carbonate. For comparison, the neodymium doped garnet was prepared also starting from N,N -dialkylcarbamato complexes of all three metals, [Y(O 2 CNBu 2 ) 3 ], [Nd(O 2 CNBu 2 ) 3 ] and [Al 2 (O 2 CN i Pr 2 ) 6 ] (Nd/Y molar ratio = 0.07;(Nd + Y)/Al molar ratio = 3:5). Also in this case the intermediate mixed hydroxo-carbonate, after heating at 950 °C for 12 h, evolved to Nd:Y 3 Al 5 O 12 . FTIR, XRD, SEM, TGA measurements were used for the characterization of the obtained materials. Preliminary studies of the photoluminescent emission properties were carried out on Nd:Y 3 Al 5 O 12 . Photoluminescence dynamics have been investigated by means of femtosecond laser pulses and nanosecond temporal resolution up to the millisecond range after excitation. All the luminescence traces have shown a decay time of the order 200 microseconds indicating its potential as a laser medium for infrared emission at 1064 nm.

Aiming at clarifying the interplay on TiO2 photoactivity between particle morphology and surface fluorination, the photocatalytic performance of anatase nanocrystals, characterized by a pseudo-spherical shape or a nanosheet structure, is investigated in both a reduction and an oxidation reaction, either in the absence or in the presence of added fluoride anions. Cr(VI) photocatalytic reduction is strongly favored by a large exposure of anatase {001} facets; however, surface fluorination leads in this case to a morphology-independent photoactivity decrease, due to the decreased adsorption of the reaction substrate. More interestingly, a beneficial synergistic effect between the platelet-like anatase morphology and TiO2 surface fluorination is clearly outlined in Rhodamine B photocatalytic degradation, possibly resulting from the intrinsic ability of fluorinated {001} anatase facets of boosting •OH radical mediated oxidation paths, due to their larger amount of surface –OH groups, as revealed using Fourier-transform infrared spectroscopy.

A series of TiO2–based photocatalysts obtained by deposition of Pt nanoparticles (NPs) has been tested in the photocatalytic decomposition of aqueous ammonia under UVA irradiation. Two main deposition routes were employed, i.e. (i) the deposition of surfactant-stabilized preformed metal NPs and (ii) a modified version of the well-known deposition-precipitation technique, employing urea as precipitating agent. The effects that the deposition route and the amount of deposited metal have on both ammonia conversion (XNH3) and selectivity (SY) towards the different N-containing products (Y = N2, NO2−, NO3−) have been investigated systematically, in relation to the morphological distribution of NPs on TiO2, as evidenced by HR-TEM analysis. The combination of Pt (0.8 wt.%) with a relatively low amount of Ru NPs (0.1 wt.%) as co-catalysts, both deposited on TiO2 under optimized conditions, results in an exceptional stabilization of nitrite ions (SNO2− ∼ 70%), from which N2, the most desired ammonia oxidation product, might subsequently be obtained catalytically.

Hematite represents the most common burning rate modifier used in propellant production. The tuning of burning rate is obtained even for amounts ranging below 1 wt% of the total composition. Different studies have evidenced a role in ammonium perchlorate dissociation while there are not enough literature documents to clearly support or oppose its capability to enhance binder decomposition. The acceptance of such ingredient in an industrial environment is based mostly on the verification of few parameters, relevant to catalytic action (namely, particle size, specific surface area). The complexity of the iron oxide family shows a wide set of features, neglected in standard quality check but important for a detailed characterization. Such properties assist in defining a unique fingerprint of the material and can be used for detailed identification of batch-to-batch reproducibility, for new supplier qualification, or for improvement of basic knowledge. The present paper is an extract of a detailed characterization activity performed on different batches of nominally identical propellant-grade hematite. Reported results show peculiar properties of the ingredients and characterization methodologies specifically employed for the scope, proposing an end-to-end batch analysis for full ingredient back-trace capability in the supply chain.

A promising, yet challenging, route towards renewable production of hydrogen is the direct conversion of solar energy at a simple and low cost semiconductor/water junction. Despite the theoretical simplicity of such a photoelectrochemical device, different limitations among candidate semiconductor materials have hindered its development. After many decades of research on inorganic semiconductors, a conclusive solution still appears out of reach. Here, we report an efficient hybrid organic–inorganic H2 evolving photocathode, consisting of a donor/acceptor blend sandwiched between charge-selective layers and a thin electrocatalyst layer. The role and stability of the different interfaces are investigated, and the conductive polymer is proven to be an efficient material for a semiconductor/liquid PEC junction. The best performing electrodes show high performances with a photocurrent of 3 mA cm−2 at 0 V vs. RHE, optimal process stability with 100% faradaic efficiency during electrode's lifetime, excellent energetics with +0.67 V vs. RHE onset potential, promising operational activity of several hours and by-design compatibility for implementation in a tandem architecture. This work demonstrates organic semiconductors as a radically new option for efficient direct conversion of solar energy into fuels, and points out the route towards high performance organic photoelectrochemical water splitting.

The time-resolved photoluminescence (PL) in the nanosecond time scale of TiO2 materials undoped or codoped with nitrogen and fluorine (N,F-doping) and modified by noble metals (NM, i.e. Au or Pt) nanoparticles (NPs) photodeposition has been systematically investigated in relation to their photocatalytic activity in hydrogen production. The main aim of the study is to elucidate the origin of the NM-dependent synergistic effects in photoactivity produced by N,F-doping of TiO2 and NM NPs deposition on the oxide surface. While TiO2 doping with fluorine and nitrogen introduces new stabilized luminescent defective trap states below the conduction band revealed by long-living PL components, the presence of NM NPs on the TiO2 surface produces a PL intensity suppression, which is more relevant for Au rather than for Pt-NPs containing materials. Time-resolved PL analysis indicates that the electron transfer occurring at the TiO2/metal interface is affected by both the defective structure of anatase N,F-doped TiO2 and the type of NM (Au or Pt). In particular, Au rather than Pt NPs appear to strongly interact with the charge carriers trapped at surface defect sites, gold NPs being expected to preferentially grow on such sites during photodeposition. Furthermore, plasmonic gold NPs excitation upon PL light absorption is evidenced by the PL spectral shape variation observed only in the case of Au/TiO2. Thus, the larger synergistic effect on photocatalytic hydrogen production observed upon Au NPs photodeposition on N,F-doped TiO2 results from the opening of a new efficient electron transfer path from luminescent defective trap states on doped TiO2 to Au NPs, where proton reduction occurs.

Precise, reliable, and remote measurement of dissolved oxygen in aqueous media is of great importance for many industrial, environmental, and biological applications. In particular, photoelectrochemical sensors working in differential mode have recently demonstrated promising properties, in terms of stability, sensitivity, and application potential. Here, a new approach is presented, combining visible light sensitivity, efficient photocurrent generation, and solution-processed fabrication methods of conjugated polymers, with charge carriers selectivity, energetic alignment favorable to efficient interfacial charge transfer and high surface area achievable by using metal oxide nanostructures. Extensive characterization and optimization of the hybrid organic/inorganic system are carried out, leading to the realization of an oxygen sensor device, based on nanostructured palladium oxide/poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole]/[6,6]phenyl-C61-butyric acid methyl ester (PdO/APFO-3:PCBM) as materials of choice. State-of-the-art sensitivity, amounting at −5.87 μA cm−2 ppm−1, low background signal, in the order of −4.85 μA cm−2, good electrochemical stability for more than 2 h of continuous functioning and high reproducibility of the signal over the pH 1 to 10 range, are reported, making the hybrid device suitable for several practical uses. The results fully validate the mixed organic/inorganic approach for photoelectrochemical applications, and pave the way for its further exploitation in fields like waste water treatment, environmental monitoring, and water splitting.

Arrays of hyperbranched high aspect ratio mesostructures are grown by pulsed laser deposition through a self-assembly process from the gas phase. These hierarchical arrays are successfully used as photoanodes for the photoelectrochemical splitting of water, exhibiting an onset potential as low as 0.4 V vs. RHE and saturation current densities up to 1.85 mA cm−2 at 0.8 V vs. RHE. While the latter is similar to the state of the art values for WO3 nanostructured photoanodes, both the onset and saturation voltages are significantly lower than any other reported values. This peculiar behavior is attributed to the hyperbranched structure and to its excellent optical and electronic properties.

The controlled shaping of nanoparticles' morphology is one of the pillars of nanotechnology. Here, we demonstrate that photocatalytic lithography, a technique already proved to be useful in materials science, can act as a dry etching technique for noble metal nanoparticles. Triangular silver nanoprisms are self-assembled on titanium dioxide films and photocatalytically shaped into discoidal particles upon irradiation with near-UV light. The obtained patterned surfaces show a dramatically different surface-enhanced Raman scattering response, suggesting the utility of our approach for the development of sensors. The photocatalytic nature of the particle shaping is demonstrated and a plausible mechanism drawn by performing photocatalysis in different configurations (direct and remote) and by irradiating in different solvents.

Grafting-from is the technique of choice to obtain polymer brushes. It is based on the growth of polymer chains directly from an initiator-functionalized surface, and its development gained momentum thanks to recent advances in controlled polymerization techniques. However, despite the great amount of work that has been performed on this subject, the influence exerted by the initiator layer on the characteristics of the resulting brushes has been almost completely overlooked. Our group has already demonstrated that positron annihilation spectroscopy (PAS) is a valuable analytical tool for the study of polymer brushes. Here, we applied this technique to show that differences in the organization of the initiator layer dramatically reflect on the characteristics of polymer brushes. Brushes made by surface-initiated atom transfer radical polymerization (ATRP) of a pH-responsive polymer, poly(dimethylaminoethyl methacrylate) (PDMAEMA), were investigated also in terms of the effects of protonation and of the incorporation of silver nanoparticles inside the brushes, shining a new light on the internal structure of such complex, fascinating systems.

Nano-sized aluminum (nAl) particles have several features that make them interesting for energetic applications. Compared to micron-sized aluminum (μAl) higher reactivity, lower ignition temperature and condensed combustion products of reduced size can be achieved. This work focuses on the pre-burning characterization of nAl. In the analysis, different features of various powders (passivated by air or organic compounds, and eventually coated by hydrocarbons and fluorohydrocarbons) are investigated focusing on the application in energetic systems. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (SSA) measurement, and volumetric techniques are considered for an extensive characterization of the powder morphology (particle size, shape, and texture), structure, and composition (active metal content). The reactivity of nAl is investigated at low- and high-heating rates. The behavior of powder suspensions is analyzed by a plate–plate rheometer considering hydroxyl-terminated polybutadiene (HTPB) as the suspending medium. The effects of the nAl passivation/coating layer on the viscosity of HTPB-based slurries are discussed. This information is crucial for an effective evaluation of the nanomaterial dispersion in the HTPB matrix and for the identification of possible limitations in the propellant/fuel manufacturing process. The presented results enable a comprehensive understanding of the relationships between nanosized additives morphology/structure, oxidative reactivity, and propellant/fuel rheological behavior.

Catalytic systems for methane combustion, with Rh and Pt in a BaZrO3-based perovskite, were synthesized at the University of L'Aquila and tested at close to industrial conditions at the KTH Energy ...

Different chemical routes for obtaining nanostructured WO 3 on transparent conductive oxides have been tried by considering the Santato-Augustynski recipe as a main guideline. The preparation started from tungstate salts as precursors and involved different organic dispersing agents. Calcination in air at 550 °C produced the final oxide. Aim of this work is to test the oxide materials as photoanodes for the photo-electrochemical water splitting. WO 3 is a wide bandgap semiconductor, able to transport photogenerated carriers under irradiation, provided that it has a good crystalline structure. The morphology and the crystal size of the obtained WO 3 nanoparticles have been investigated by SEM and XRD. This work shows that the particle size of the WO 3 film decreases with increase in molecular weight of the organic dispersing agents. The current–voltage characteristic curves of WO 3 -based electrodes have been obtained by biasing a photo-electrochemical cell with an external voltage ramp, both in the dark and under simulated solar irradiation. Results showed that under incident irradiance a noticeable photocurrent density is obtained with a reasonably steep current–voltage slope and with a plateau current of the order of 1.6–1.8 mA/cm 2 under incident 0.14 W/cm 2 AM 1.5 irradiation.

Syndiotactic polystyrene (SPS), a thermoplastic polymer that exhibits a high T m in some crystalline forms, can be conveniently processed by a cold-compaction technique. Processing temperatures in the range of 150-210°C, well below the T m , v gives rise to physicomechanical properties comparable and even better than those obtained by thermal compression or injection molding. The optimum treatment temperature seems to fall around 175°C. X-ray diffraction analysis, thermal analysis, and density measurements suggest that such behavior is connected to phase transitions of SPS and favored by the presence of styrene included in the crystalline fraction.

Anodically grown WO(3) photoelectrodes prepared in an N-methylformamide (NMF) electrolyte have been investigated with the aim of exploring the effects induced by anodization time and water concentration in the electrochemical bath on the properties of the resulting photoanodes. An n-type WO(3) semiconductor is one of the most promising photoanodes for hydrogen production from water splitting and the electrochemical anodization of tungsten allows very good photoelectrodes, which are characterized by a low charge-transfer resistance and an increased spectral response in the visible region, to be obtained. These photoanodes were investigated by a combination of steady state and transient photoelectrochemical techniques and a correlation between photocurrent produced, morphology, and charge transport has been evaluated.

The catalytic combustion technology still lacks of catalytic systems stable at high temperatures, such as those of the gas turbine inlet in the last turbine generation. In this paper we tried to solve this problem by fitting transition metals inside a crystal structure which is known to be very stable. Several oxides have been synthesised by a modified citrate method and investigated in the catalytic combustion of methane. Synthesised catalysts consist of a solid solutions with a perovskite structure of formula BaZr (1− x ) Me x O 3 , where Me = Rh, Pd, Mn, Ni, Ru, Pt, Co. The goal of the work has been to provide the physicochemical, structural and morphological characterisation and the activity of these catalysts containing different amounts of transition metals, by means of BET, XRD profile fitting and TPC reactivity tests, respectively. The synthesised powders showed a very limited hysteresis between the increasing and decreasing temperature curves and therefore should display no oscillations in working conditions. These systems could be a high temperature alternative to the hexa-aluminates and could avoid the homogeneous post combustion volumes typical of the hybrid and XONON combustors.

The loading of pre-treated amorphous silica with platinum or palladium was carried out by using the molecular precursors Pt2(micro-Cl)2Cl2(CO)2, or Pd2(micro-Cl)2Cl2(CO)2, respectively, which contain the required amount of coordinated CO to carry out the formation of the metal particles upon contact with moisture. The reactivity of the well-soluble mononuclear platinum complex cis-PtCl2(CO)2 with stoichiometric amounts of water was investigated either under N2 or CO. The metal nanoparticles produced on the silica matrix have been characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalytic performance of the silica-supported metals thus produced was evaluated in the hydrogenation of cyclohexene.

The first solvent-free crystal structure of PCBM, an organic semiconductor widely used in solvent-free nanocrystalline films in plastic solar cells, is reported and its relevance to structure-property relationships discussed. The PCBM structure, obtained from o-dichlorobenzene solvates by solvent abstraction, was solved using powder diffraction, demonstrating this possibility for functionalized fullerenes.