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•Submicrometric TiO2 coatings by Plasma Electrolytic Oxidation.•TiO2 high photoactivity in the UV range.•Low temperature oxidation.•Short processing times with respect to traditional ...anodic oxidation.
The effect of synthesis conditions on the properties of nanoporous TiO2 coatings obtained by PEO in refrigerated electrolytes have been investigated. Linear sweep voltammetry was carried out on the TiO2 coatings, in dark and under UV-C irradiation, in order to assess the photoelectrochemical behavior of samples. The largest photocurrents (0.18mA/cm2) were measured on TiO2 coatings obtained by PEO in refrigerated aqueous solutions. UV–vis spectra revealed that lowering the processing temperature from 20 to −3.5°C induced a blue-shift of the absorption band of the TiO2 coatings from 3.05 to 3.42eV. The main advantage of PEO in refrigerated aqueous solutions over current approaches, based on anodic oxidation and thermal treatments, is that the synthesis of photoactive TiO2 coatings can be carried out in a relatively easy, quick and reproducible way, without annealing pre- and post-treatments. Furthermore, by controlling the solution temperature in PEO process, the photocurrent of the resulting TiO2 coating reaches quite high values.
Graphene is a zero‐gap, semiconducting 2D material that exhibits outstanding charge‐transport properties. One way to open a band gap and make graphene useful as a semiconducting material is to ...confine the electron delocalization in one dimension through the preparation of graphene nanoribbons (GNR). Although several methods have been reported so far, solution‐phase, bottom‐up synthesis is the most promising in terms of structural precision and large‐scale production. Herein, we report the synthesis of a well‐defined, helically coiled GNR from a polychlorinated poly(m‐phenylene) through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction. The structure of the helical GNR was confirmed by 1H NMR, FT‐IR, XPS, TEM, and Raman spectroscopy. This Riemann surface‐like GNR has a band gap of 2.15 eV and is highly emissive in the visible region, both in solution and the solid state.
Nano‐Luftschlangen: Helicen‐artige Graphen‐Nanobänder (HGNR) wurden durch regioselektive photochemische Cyclodehydrochlorierung aus einer polychlorierten Polyphenylen‐Vorstufe hergestellt.
Since the early 70s, printed circuit boards (PCBs) are firmly entrenched in all electronic branches, from the consumer electronics to scientific and medical equipment, culminating later in the ...personal computer industry. Electroless nickel immersion gold (ENIG) process is one of the most used selective finishing in PCBs production. It involves two different electroless deposition mechanisms: (1) NiP autocatalytic deposition and (2) gold galvanic immersion plating in which displacement reactions are involved. Because during ENIG process, NiP is dissolved from the electrode surface into the solution, it can be considered as a controlled corrosion process of the metal substrate: selection of the complexing agents in solution is thus crucial. Since they are the most used complexing agents, EDTA and citric acid have been investigated. In order to understand their effects on the NiP surface during the immersion plating, open circuit potential (Voc) and linear sweep voltammetry (LSV) measurements have been performed. Furthermore, to establish which complexes are adsorbed on the electrode surface during the plating process, in situ Raman spectroscopy was carried out showing EDTA to be the most effective Ni cations chelating agent. To assess the effect of Cu contamination, accountable of reddish gold failure mode, the electrochemical and in situ spectroscopic analyses on both immersion gold solution and polluted revealed that the adsorption of C u ( C N ) 2 − and/or C u ( C N ) 3 2 − complexes is competitive with Au ( CN ) 2 − . To evaluate the effects of copper contamination on gold nucleation and growth FE-SEM and AFM were carried out, while gold layer solderability has been evaluated according to NF-A-89 400 standard.
Combustion-generated carbon nanoparticles exhibit a variety of optical and physicochemical properties. Therefore, when applying laser diagnostic tools for monitoring purpose, it is important to ...consider the different response of the particles with varying properties as well as the impact of laser irradiation on these properties. In this work, we analyze the possible modification of particle optical and physicochemical properties by coupling extinction measurements with FT-IR and Raman spectroscopy. The aim is to retrieve optical, chemical, and structural properties of the particles under analysis. To our knowledge, the approach proposed in this work has not yet been performed on irradiated particles. Particles are sampled from a premixed flame at two heights above the burner, representing two different aging stages. While extinction measurements are carried out in-flow, FT-IR and Raman spectroscopy are performed on particles collected for ex-situ analysis. Moreover, the analysis is conducted on both pristine and irradiated nanoparticles with one and ten laser shots. While nascent particles do not exhibit relevant modification under laser irradiation, heating mature particles with one or more laser pulses of relatively high energy density is observed to significantly affect absorption properties, particle structures and specific surface functionalities. The presence of oxygenated species in mature particles and in particular the structures spectroscopically correlated with graphene oxide indicates that specific chemical reaction pathways can occur under laser irradiation, likely promoted in the ambient condition under analysis.
•Application of on-line extinction measurements and off-line FT-IR and Raman spectroscopy to laser-irradiated soot particles.•Analysis performed on nascent and mature particles irradiated with a single and 10 laser shots.•Complex modification of the particles under analysis, resulting in an increase in the amorphous carbon amount.•Presence of oxygenated groups similar to those observed in graphene oxide spectra.•Under laser irradiation, soot particles exhibit an increasing tendency to undergo chemical reactions.
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•Immobilized, high surface area TiO2 films were obtained via anodizing.•A plug-flow reactor for gas-phase photocatalysis was developed.•A high degradation efficiency was achieved for ...medium–low toluene concentration.•Photocatalyst deactivation was recovered through a simple reactivation.
In this study, a novel annular plug flow reactor (PFR) with built-in nanotubular TiO2 obtained via anodizing was tested for the photocatalytic degradation of toluene. The oxide was grown directly on a titanium substrate by anodizing, as this method implies no risk of nanoparticles release in the environment during or after the photocatalytic process. Experiments were carried out in presence of an UV-A light source by modulating relative humidity, gas concentration and flow rate, to evaluate possible applications in indoor and industrial environments.
The photocatalytic system demonstrated high photodegradation efficiency up to 90% for an inlet toluene concentration of 10 ppm, thus showing potential applications in mildly polluted environments, such as homes, offices and up to more severely polluted ones like offset printing plants, automobile manufacturing industries or even professional kitchens, where the exposure to cooking oil fumes is significant. In case of high toluene concentration, the initial degradation percentage falls in a range between 60 and 70%; subsequently, the instant degradation shows a gradual decrease ascribed to photocatalyst deactivation, which occurred due to the accumulation of recalcitrant by-products on the adsorption sites, thus highlighting some limitations for industrial applications when selected VOCs are present; nonetheless, the photocatalyst regained its initial activity through a simple photocatalyst reactivation process, leading to a maximum instant degradation percentage up to 90% for an inlet toluene concentration of 20 ppm.
Lung toxicity of carbon nanotubes (CNTs) is matter of concern since very long time. However, their mechanism of toxicity is still not yet well defined. In this work, the role of structural defects as ...organic stressors of CNTs able to trigger their potential toxicity is investigated. Four commercial CNTs, with different carbon purity grade, are morphologically characterized by transmission electron microscopy (TEM) and the relative amount of structural defects are estimated through Raman spectroscopy, by measuring the intensity ratio D/G (ID/IG). The oxidative potential of CNTs is evaluated with cytochrome-C assay and reactive oxygen species (ROS) detection. Data show that CNTs with larger amounts of structural defects (higher ID/IG ratio) induce an increased ROS generation and consequent cytotoxicity and cellular damage, shown by TEM images of CNTs-cells interaction. Raman analyses of cells exposed to CNTs point out that the spectra of the CNTs inside the cells show no differences with respect of the signal recorded for cell-free CNTs, evidencing their biopersistence in lung cells. Raman spectra cannot provide direct indication of the existence of metals as impurity. It follows that the intensity ratio ID/IG can be taken as a predictive marker of the toxicity of a given CNT.
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•Inhalation of CNTs can lead to the development of the adverse outcome lung fibrosis.•Raman spectroscopy quantifies the relative amount of CNTs' structural defects.•CNT structural defects act as stressors and early predictive markers of CNT toxicity.•In vitro lung cytotoxicity is associated to the extent of structural disorder of CNTs.•CNTs do not change their structure once inside the lung cells environment.
Herein we describe the synthesis, structure, and properties of chiral peropyrenes. Using p-terphenyl-2,2″,6,6″-tetrayne derivatives as precursors, chiral peropyrenes were formed after a 4-fold alkyne ...cyclization reaction promoted by triflic acid. Due to the repulsion of the two aryl substituents within the same bay region, the chiral peropyrene adopts a twisted backbone with an end-to-end twist angle of 28° that was unambiguously confirmed by X-ray crystallographic analysis. The chiral peropyrene products absorb and emit in the green region of the UV–visible spectrum. Circular dichroism spectroscopy shows strong Cotton effects (Δε = ±100 M–1 cm–1 at 300 nm). The Raman data shows the expected D-band along with a split G-band that is due to longitudinal and transversal G modes. This data corresponds well with the simulated Raman spectra of chiral peropyrenes. The chiral peropyrene products also display circularly polarized luminescence. The cyclization reaction mechanism and the enantiomeric composition of the peropyrene products are explained using DFT calculations. The inversion barrier for racemization was determined experimentally to be 29 kcal/mol and is supported by quantum mechanical calculations.
Phototautomerism in the excited states of free-base 5, 10, 15, 20-tetrakis(4-sulfonatophenyl) porphyrin (H
2
TPPS
4−
) has been investigated combining, for the first time, advanced Electron ...Paramagnetic Resonance (EPR) with fluorescence and Raman spectroscopy. Triplet EPR spectroscopy, performed in protic and deuterated solvents and in the presence of photoselection, confirms the occurrence of phototautomerization and additionally suggests the formation of the
cis
tautomer as a minor component. The zero-field splitting parameters and triplet sublevel populations indicate that the process is slow in the triplet state. The results obtained by EPR combined with photoselection and fluorescence anisotropy have been interpreted within a model which accounts for a fast
trans–trans
tautomerization promoted by a spin-vibronic coupling mechanism for intersystem crossing, with an even distribution of the two
trans
tautomers at liquid nitrogen temperatures for H
2
TPPS
4−
.
Graphical abstract
We propose the use of surface plasmon resonance (SPR) as a distinctive marker for real-time monitoring in reaction conditions of gold nanoparticles supported on α-Al2O3. The study leverages the SPR ...shape-and-size dependency to monitor metal nanoparticles in reaction conditions, evidencing an influence of both dimensions and agglomerations on the SPR peak position. Operando measurements, coupling UV-vis spectroscopy and catalytic testing, allows to follow the dynamics during nanoparticle formation (Au3+ to Au0 reduction) and during the reverse water gas shift reaction (CO2 + H2 → CO + H2O). The catalyst structure and stability in reaction conditions was further confirmed by operando X-ray spectroscopy and PXRD data. Overall, this approach enables the direct acquisition of information on the structure–activity relationship of metal-based supported catalysts under actual reaction conditions.
We propose the use of surface plasmon resonance (SPR) as a distinctive marker for real-time monitoring in reaction conditions of gold nanoparticles supported on α-Al
2
O
3
. The study leverages the ...SPR shape-and-size dependency to monitor metal nanoparticles in reaction conditions, evidencing an influence of both dimensions and agglomerations on the SPR peak position.
Operando
measurements, coupling UV-vis spectroscopy and catalytic testing, allows to follow the dynamics during nanoparticle formation (Au
3+
to Au
0
reduction) and during the reverse water gas shift reaction (CO
2
+ H
2
→ CO + H
2
O). The catalyst structure and stability in reaction conditions was further confirmed by
operando
X-ray spectroscopy and PXRD data. Overall, this approach enables the direct acquisition of information on the structure-activity relationship of metal-based supported catalysts under actual reaction conditions.
Surface plasmon resonance peak probed by
operando
UV-vis diffuse reflectance spectroscopy allows for the monitoring of metal nanoparticles formation on an Au/α-Al
2
O
3
catalyst and for the evaluation of their size and stability in reaction conditions.
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