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Supercritical antisolvent precipitation route was employed for the first time to prepare Gd-doped ZnO photocatalysts to be tested in the photocatalytic degradation of atrazine under visible light. Physical-chemical characterization data show that the addition of Gd does not change the crystalline structure of ZnO and that Gd3+ ions are successfully introduced into the semiconductor lattice, leading to a decrease of band gap energy value and inducing the formation of oxygen vacancies inside the ZnO framework. The photocatalytic performances of the as-prepared samples are determined by analyzing the degradation of atrazine under visible light irradiation. The doped photocatalyst with a Gd loading of 0.7 mol% exhibits the highest photocatalytic activity under visible light irradiation compared to the other prepared photocatalysts. The possible reaction mechanism of the optimized photocatalyst is also discussed.

In this study, P-doped TiO2 photocatalysts with different molar percentages (in the range 0.071–1.25 mol %) of the non-metallic element were prepared and their photocatalytic activity under visible light irradiation was tested. All achieved samples were characterized by XRD, Raman, UV–Vis DRS and SEM–EDX techniques. XRD and Raman analysis showed that all doped photocatalysts were in anatase phase and evidenced that P ions were successfully incorporated into the TiO2 crystal lattice, affecting also the crystallinity degree of the P-doped TiO2 photocatalysts. Noticeably, the UV–Vis DRS spectra evidenced that the highest redshift in absorption edge was observed for the photocatalyst with the lowest P content (0.071PT), which showed also the lowest bandgap (2.9 eV). The photocatalytic performances of all P-doped TiO2 samples were compared with that of commercial TiO2 by evaluating the decolorization of methylene blue (MB) dye under visible light irradiation. Results showed that phosphorus doping strongly promoted photocatalytic activity in the presence of visible light. Furthermore, the most active photocatalyst in visible light tests (0.071PT) also showed better photocatalytic activity than commercial TiO2 in the decolorization of MB under simulated sunlight irradiation. Finally, 0.071PT photocatalyst was preliminarily tested against Escherichia coli (E. coli) under simulated solar light, showing an inactivation efficiency of 90% after 2 h of treatment time. Graphical abstract

The increasingly intense consumption of plastics and, above all, their improper disposal in the environment are causing serious environmental concerns. Great efforts have been made for the development of new methods aimed at facilitating and speeding up the identification and sorting of different materials in the plastic recycling process. In this field, new strategies based on fluorescent tagging have been developed. This work concerns the synthesis and characterization of new fluorescent copolymers of polyethylene (PE) and polystyrene (PS), which are among the most produced and consumed plastic materials. The synthesized copolymers are potentially suitable for use as fluorescent markers of PE and PS. Ethylene-co-N-pentenyl carbazole (P(E-co-PK)) and styrene-co-4-(N-carbazolyl)methyl styrene (P(S-co-SK)) copolymers were prepared by Ziegler–Natta and free radical polymerization, respectively. If excited at 300 nm, both P(E-co-PK)s and P(S-co-SK)s give fluorescence emissions resulting in them being optically active. Moreover, due to the low amount of fluorescent units, they show chemico-physical properties such as those of their corresponding homopolymers (PE and PS). P(E-co-PK)s and P(S-co-SK)s have been also tested as fluorescent markers of PE and PS. The experimental results demonstrate that from PE/P(E-co-PK) and PS/P(S-co-SK) blends prepared using only 1% by weight of fluorescent copolymer, distinguishable fluorescent emissions can be still detected.

Fe–Pr co-doped TiO2 photocatalysts are synthetized by sol–gel method using titanium tetraisopropoxide, praseodymium nitrate and iron acetylacetonate as precursors of titania, praseodymium and iron, respectively. The chemical-physical properties of all prepared samples are analysed by X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), photoluminescence (PL) spectroscopy and N2 adsorption at −196 °C. XRD patterns show the main peaks of anatase phase in all photocatalysts and evidence that Fe and Pr ions are effectively introduced into the TiO2 lattice. UV–vis DRS spectra indicate the reduction of the band gap value of Fe-Pr co-doped TiO2 with respect to TiO2 and Pr-doped TiO2 thank to co-doping of TiO2 with Pr and Fe ions. The photocatalytic performances of all prepared samples are investigated for the degradation of Acid Orange 7 azo dye (AO7) and also of phenol under visible light irradiation. Photocatalytic efficiency obtained using Fe–Pr co-doped TiO2 markedly increases compared to un-doped TiO2, Pr-doped TiO2 and Fe-doped TiO2 photocatalysts. Fe-Pr co-doped TiO2 prepared with 8.5 mg of praseodymium nitrate gave the best photocatalytic activity. The enhanced photocatalytic activity should be associated with the simultaneous doping of TiO2 with Pr3+ and Fe3+ ions that induces a marked decrease of band gap value together with an enhanced generation of oxygen vacancies, which can trap electrons, and therefore reducing their recombination with photogenerated positive holes. Indeed, using the optimized Fe-Pr co-doped TiO2, the dye discoloration and mineralization is about 87 and 80 %, respectively, after 60 min of LEDs visible light irradiation, underlining the best performances of the optimized Fe–Pr co-doped TiO2 in terms of treatment time. Finally, the optimized Fe-Pr co-doped TiO2 is tested for visible light degradation of phenol in aqueous solution, confirming the absence of possible sensitization phenomena of photocatalyst surface by the AO7 dye.

This mini review summarizes the preparation and testing of polymeric composites with a N-doped TiO2 photocatalyst to effectively design a photocatalytic system for water pollutant degradation under visible light. In detail, the various N-doped TiO2/polymer composites reported in the literature are briefly discussed along with some examples dealing with the use of N-doped TiO2 particles, both supported on the external surface of polymers and dispersed within the structure of visible-light-transparent polymeric aerogels. Finally, the scope for future works and challenges for the commercialization of such materials are highlighted.

The production of L-lactide from L-lactic acid involves a substantial formation of meso-lactide as an impurity, and, upon polymerization with the industrial catalyst tin octanoate, results in poly(L-lactic acid) of reduced crystallinity due to stereoerrors randomly distributed along the polymer chains. We describe a new approach wherein, instead of avoiding stereoerrors by removing the meso-lactide prior to polymerization, the stereoerrors in the polymer are tolerated, by crowding them in a stereogradient copolymer. A zirconium complex of an amine tris(phenolate) ligand is found to exhibit very high syndioselectivity in the ring opening polymerization catalysis of meso-lactide at room temperature, and gives rise to stereogradient copolymers in the polymerization of mixtures of meso-lactide/L-lactide in the melt at 180 °C. Relative to the stereo-random copolymers obtained with tin octanoate, the stereogradient copolymers exhibit enhanced crystallinities manifested in lower solubilities and higher melting temperatures and enthalpies.

Plastics are a heterogeneous class of synthetic compounds that, due to their unique characteristics find numerous applications both in industrial and civil fields. However, despite the great advantages that these materials brought in everyday life, the plastic wastes resulting from their massive use represent one of the main environmental problems at the global level. Once released, plastics persist for a long time and are subjected both to biotic and abiotic processes leading to the formation of small particles, known as micro and to nanoplastics, that interact with organisms, accumulating inside tissues and risking to enter in the trophic chain. Among the different types of plastic, polypropylene (PP) is one of the diffused, widely exploited in food and textile industries for disposable packaging and to produce surgical masks. Owing to the huge distribution and the resultant abundant presence of PP waste products, it results necessary investigate the possible toxicity on living organisms. For these reasons, here we analyzed the effects of PP micro and nanoplastics dispersed in freshwater, using the medicinal leech Hirudo verbana as invertebrate model. To better follow the plastics fate, fluorescent particles, labeled with a fluorophore, have been used. Animals were examined at various timings after plastics exposure and results were analyzed by means of microscopy, immunofluorescent and molecular biology analyses. After assessing the entrance of PP fragments into leech tissues, the activation of the innate immune response was evaluated. The results show that the presence of micro and nanoplastics induces an initial physical protection that consists in the secretion of mucus, followed by an increase of blood vessels and the recruitment of immune cells, in particular macrophages. Moreover, macrophages were directly involved in both phagocytic and encapsulation processes, as demonstrated by acid phosphatase (ACP) histoenzymatic and Thioflavin-T assays, expressing specific pro-inflammatory factors, such as HvRNASET2 and HmAIF-1, as demonstrated by immunolocalization and qPCR experiments. Finally, the expression levels of genes related to oxidative stress-induced enzymes have been investigated, in order to evaluate the possible increase in reactive oxygen species (ROS), due to the entry into the leech tissues of PP micro and nanoplastics. This work allows deepening the current knowledge of the possible harmful effects on human health deriving from micro and nanoplastics dispersion, leading new insight about freshwater ecosystems that often represent the first environments interested in plastic pollution.

Fluorescent polypropylenes for the detection of PP-derived microplastic pollutants in organic tissues.

We describe alkoxo-aluminum catalysts of chiral bipyrrolidine-based salan ligands that follow the dual-stereocontrol mechanism wherein a given combination of stereogeneities at the metal site and the proximal center of the last inserted lactidyl ("match") is active towards lactide having a proximal stereogenic center of the opposite configuration, while the diastereomeric combination of stereogeneities ("mismatch") is inactive towards any lactide. Polymerization of rac-LA by the enantiomerically pure catalysts was sluggish and gave stereoirregular poly(lactic acid) (PLA) because selective insertion to a match diastereomer gives a mismatch diastereomer. The racemic catalysts showed higher activity and led to highly heterotactic PLA following polymeryl exchange between two mismatched catalyst enantiomers. A succession of match diastereomers in selective meso-LA insertions led to syndiotactic PLAs reaching a syndiotacticity degree of α=0.96. This polymer featured a Tm of 153 °C matching the highest reported value, and the highest crystallinity (ΔHm =56 J g-1 ) ever reported for syndiotactic PLA.

The analysis of FT-IR spectra of isotactic and syndiotactic poly(N-pentenylcarbazole) (i-PPK and s-PPK) amorphous film samples are reported in the present paper. A comparison with FT-IR spectrum of a non stereoregular polyvinylcarbazole (PVK) commercial sample is also presented. Calculated vibration spectra of both i-PPK and s-PPK are obtained through the Density Functional Theory (DFT) method. Theoretical results are interpreted in terms of potential energy distribution (PED) analysis, and compared with i-PPK and s-PPK FT-IR experimental spectra. Only a few differences, due to the conformational constrain imposed by tacticity, are detected between the two fully amorphous polymer stereoisomers. Moreover, the observed differences between PPKs and PVK spectra are attributed to the presence of the alkylene linker (-(CH2)3-) in PPK samples, distancing the carbazole groups to the main chain. The alkylene linker allows more flexibility to both the side and main chain of PPK samples, giving rise to new vibrational mixed modes which are not detected in PVK.

The most recent results concerning the stereospecific synthesis and the microstructural, chemico-physical and optical characterization of polymers containing pendant carbazolyl groups are reviewed for the first time. Stereoregular poly(N-alkenyl-carbazole)s, poly(4-(Ncarbazolyl) methyl styrene), poly(ω-(N-carbazolyl)alkyl acrylate)s and poly(ω-(N-carbazolyl)alkyl metacrylate)s are considered in this review, with a particular focus on the influence of polymer stereochemistry on photophysical behavior. Potential applications of these materials in light-emitting diodes (LEDs), electrochromic devices, electrophotography and holographic memories are also discussed. Among these, we show the appealing results of our experiments, concerning the color tuning in organic LEDs based on poly(N-pentenyl-carbazole) by means of the polymer chain stereoregularity.

The chemical modification of biomaterials (i.e., polyesters, polysaccharides) can offer the opportunity to develop multifunctional platforms characterized by a combination of suitable properties and useful for biomedical applications. Polydopamine (PDA) is a mussel-inspired polymer with excellent properties such as adsorption ability, high hydrophilicity, electrical properties and numerous functional groups for immobilizing biomolecules. Due to high adhesion properties to almost all kinds of substrates PDA it has been largely used as coating for surface modification of material to modulate cellular responses, including cell spreading, migration, proliferation, and differentiation. In order to develop bio-functionalized systems, PDA was proposed as coating of biomaterials differently processed in form of sub-micrometric fibres, microgels and foams. Starting by a dopamine precursor solution, PDA coating deposition on substrates was performed by exploring different methodologies. In particular, poly-e-caprolactone (PCL) electrospun fibres coated with PDA by electrofluidodynamic process was reported as possible bio-conductive interfaces. Preliminary results, in terms of synthesis conditions, structural characterization, and in vitro cell studies suggested that polymerization/oxidation reactions can be properly optimized to guide PDA self-assembly in order to control surface properties, and ultimately, influence cell materials interactions.

The zinc complexes 1 and 2 bearing chelating phosphorous based pincer ligands were found to catalyze the ring-opening copolymerization of L-lactide and ε-caprolactone in the melt at 110 °C to obtain a series of random copolymers in which the monomer distributions were coherent with the monomer ratio in the feed. All the obtained copolymers showed high molecular masses with monomodal and moderately narrow distributions. The thermal properties of the achieved copolymers (Tg, glass transition temperature, and Tm, melting temperature) were strongly dependent on their composition. A linear dependence of Tg with molar percentage of lactide in the copolymers was observed over a temperature range from -59 °C (pure polycaprolactone) to 55 °C (pure polylactide)., Polyesters; ROP; Zinc catalyst; Biodegradable; Copolymers.

The tetradentate dianionic {ONNO}-type salanol ligands featuring phenolate and alcoholate arms and a chiral-bipyrrolidine core are introduced. The diastereoselectively-formed {ONNO}-Al-OBn complexes catalyze the ring-opening polymerization of rac-lactide and meso-lactide by either the dual stereocontrol or the chain-end stereocontrol mechanisms to give PLAs of all possible tacticities.

The coordination chemistry and the activities in the ring-opening polymerization catalysis of racemic lactide (LA) of magnesium complexes of a series of {ONNN}-type sequential monoanionic ligands are described. All ligands include pyridyl and substituted-phenolate as peripheral groups. The ligands bearing either chiral or meso-bipyrrolidine cores led to single diastereomeric complexes, whereas the ligands bearing a diaminoethane core led to diastereomer mixtures. All {ONNN}Mg-X complexes [X=Cl, HMDS (hexamethyldisilazide)] led to highly active and isoselective catalysts. The complexes bearing the chiral bipyrrolidine core exhibited the highest activities (full consumption of 5000 equiv. of rac-LA at RT within 5 min) and highest isoselectivities (Pm =0.91), as well as a living character. The complexes of the meso-bipyrrolidine based ligands were almost as active and slightly less stereoselective, while those of the diaminoethane based ligands exhibited reduced activities and isoselectivities.

Contaminants of emerging concern (CECs) occur in the environment on a global scale and encompass a huge number of life style compounds, ranging from organic and inorganic compounds to nanoparticles, released into the environment because of human activities with the potential to harm biota and health. Owing to their extensive application, their continuous occurrence and release in wastewaters, sewage sludge, surface water and groundwaters, landfills, and waste have become an emerging issue to consider control measures for them. Urban Wastewater Treatment Plants are one of the main point sources of CECs to the environment as UWWTPs are usually not designed to effectively remove them. Although improvement of analytical techniques allowed the identification of widespread CECs in reduced concentrations (μg to ng/L) and in various environmental compartments, we are still far away from a complete classification of many CECs and their potential harmful effects. Therefore, providing data on occurrence, sources, and fate of CECs is essential for prioritizing and regulating them.

In this work, composite monolithic aerogels based on syndiotactic polystyrene (s-PS) and N-doped TiO2 (NdT) photocatalyst characterized by high surface areas (up to 280 m2/g) and low density (0.1 g cm−3) are presented. These aerogels are obtained by supercritical carbon dioxide extraction of NdT/s-PS gels prepared by s-PS dissolution with NdT in suitable organic solvent. X-ray diffraction measurements and SEM analysis showed that a highly efficient dispersion of NdT nanoparticles can be achieved in the composite aerogels avoiding thus the aggregation phenomena that typically occur when the photocatalyst is used in slurry reactors. The optimization of NdT amount dispersed in s-PS was evaluated using phenol as model pollutant both under UV and visible light irradiation. The photoactivity of NdT/s-PS samples increased with increase of the amount of NdT dispersed in aerogel matrix up to NdT/s-PS weight ratio equal to 10/90 (10NdT/s-PS), for which the highest phenol degradation and TOC removal were achieved both under UV and visible light irradiation. Moreover, the photocatalytic activity of the optimized photocatalyst 10NdT/s-PS did not change significantly after several reuses underlining that any NdT particles are removed from the polymeric matrix.

Crystalline films of syndiotactic polystyrene (s-PS), a commercially available thermoplastic polymer, having a highly hydrophilic amorphous phase, were achieved by using a mild solid-state sulfonation procedure. Despite the used mild process conditions, an easy and uniform sulfonation of the phenyl rings of the amorphous phase is obtained. The crystallinity of the polymer was not affect by the sulfonation degree (S), at least at S less than 20%, and the obtained polymer films show the nanoporous crystalline form of s-PS. As widely reported in literature, the nanoporous nature of the polymer crystalline phase gives to these materials the ability to absorb and release organic molecules of appropriate size and polarity. This property, coupled to transparency, makes these materials potentially useful intraocular lens (IOLs) and contact lens applications. Sulfonation procedure and sulfonated film samples characterization by using wide-angle X-ray diffraction (WAXD), Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy techniques and water sorption tests were reported. Furthermore, the biocompatibility study demonstrated no cytotoxicity and appropriate cell interaction properties for the specific applications.

Fe0 (ZVI) is one of the most effective reactants for treatment of water contaminated with chlorinated hydrocarbons, pollutants recalcitrant to degradation. Unfortunately, ZVI use is limited by corrosion and loss of reactivity over time. In order to suppress oxidation and passivation phenomena of iron, in this study ZVI was coupled to a suitable semiconductor (ZnS). Under UV light, electrons in the valence band of ZnS are promoted in the conducting band (ECB = − 1.04 eV vs NHE) and are able to reduce Fe2+ to Fe0 (E0 = − 0.44 eV vs NHE). The ZnS_ZVI composite was simply prepared by coating commercial ZnS with Fe0 obtained by reducing Fe (II) salt with sodium borohydride. The achieved ZnS_ZVI catalytic system was characterized by FESEM, WAXD, Raman and N2 adsorption at −196 °C, with the aim to analyze morphology and crystalline structure of both components of the ZnS_ZVI system. Catalytic activity tests showed that ZnS_ZVI is effective in degrading probe molecules, eriochrome black T dye (EBT) and chlorobenzene (PhCl), from aqueous solutions under UV light irradiation. The experimental results show that in both cases the reductive action of Fe0 on the N = N bond of EBT and C-Cl of PhCl is synergistically coupled to the oxidative action of ZnS towards by-products. OH radicals, generated by the reaction between the electron holes in the valence band of ZnS and H2O (OH−), were indeed confirmed by photoluminescence analysis. Recyclability tests indicate that ZnS_ZVI is highly stable since its catalytic activity, on both probe molecules, remains unchanged even after several cycles of reuse under UV irradiation. ZnS_ZVI catalytic behavior towards EBT has been carefully analyzed and a possible mechanism of EBT degradation has been proposed, which involves the formation of a Fe2+-EBT complex whose structure has also been suggested.

This work is focused on the study of the correlation between the photocatalytic activity of N-doped TiO2 particles, achieved by a designed synthesis, and their degree of aggregation in aqueous suspension. N-doped TiO2 photocatalyst particles, suspended in bidistilled water, presented a trimodal (in the nano-micro metric range) aggregate size distribution. This distribution resulted monomodal, in the nanometric range, when in the aqueous solution was added an organic dispersing agent (azulene). This behavior was associated to the presence, on the N-doped TiO2 particle surfaces, of an organic phase which was detected by thermal and infrared analysis. This organic phase was assumed to have a stabilizing function for nanoparticles. The influence of aggregate size of N-doped TiO2 photocatalyst on the photocatalytic degradation of methylene blue has been studied. The aggregate size distribution of photocatalyst influenced the amount of methylene blue adsorbed on catalyst surface and increased the photocatalytic activity. The influence of operating parameters such as the amount of dispersing agent and the amount of photocatalyst in aqueous suspensions has also been examined.

Monolithic aerogels of poly(2,6-dimethyl-1,4-phenylene)oxide (an industrially relevant polymer generally known as polyphenyleneoxide or PPO), have been prepared and characterized. These aerogels obtained by supercritical carbon dioxide extraction of thermoreversible gels of high molecular weight PPO present an apparent porosity typically in the range 70%–95% and high surface area values up to 750 m 2 /g. Moreover these aerogels are characterized by an excellent sorption uptake of organic pollutants at low vapor pressure and good recyclability by thermal regeneration. Good mechanical properties and dimensional stability of PPO monoliths is due to the polymer high molecular weight which ensures formation of a fibrillar morphology, already in the precursor gel. Sorption capacity and recyclability of PPO aerogels are mostly due to their crystalline phase: (i) its nanoporous-crystalline structure assures high specific surface areas; (ii) its high melting temperature assures a high thermal monolith stability as well as easy and cheap recovery of absorbed guest molecules by thermal treatments rather than by solvent extractions.

Enantiopure poly(lactic acid) (PLA) can form stereocomplexes when enantiomeric PLA chains are mixed in equivalent amounts. Such materials provide interesting features that might be suitable for numerous applications. Despite several advantages, the main drawback of PLA is its narrow window of processing, thus limiting its use for industrial applications. Reported herein are achiral iron complexes, that are highly active, productive, and stereoselective under mild reaction conditions for the ring-opening polymerization of lactide. The corresponding catalytic systems enable the production of stereoblock polymers with high molecular weights, allowing the formation of thermally stable and industrially relevant stereocomplexes.

Highly porous monolithic aerogels based on ZnO photocatalyst and syndiotactic polystyrene (s-PS) were obtained by supercritical CO2 treatment of ZnO/s-PS gels. The prepared aerogels were characterized and their photocatalytic activity was evaluated using phenol and toluene as water pollutant models. The s-PS nanoporous crystalline phase, able to absorb pollutant molecules, was proven to be necessary to ensure high photocatalytic efficiency as the aerogel acts not only as a support, but also as pollutant pre-concentrator. The reusability of ZnO/s-PS aerogels is also strong showing no decrease in photocatalytic activity after six consecutive degradation trials. Finally, the aerogel matrix prevents ZnO dissolution occurring under acidic conditions and promotes a selective removal of the pollutants. The synergy between the photocatalyst and the innovative polymeric support provides the composite system with robustness, chemical stability, easy recovery after treatment, high efficiency of pollutant removal with a marked selectivity which make these materials promising for large scale applications.