Methods for the determination of ship fuel sulphur content and NOx emission factors based on remote measurements have been compared in the harbour of Rotterdam and compared to direct stack emission ...measurements on the ferry Stena Hollandica. The methods were selected based on a review of the available literature on ship emission measurements. They were either optical (LIDAR, Differential Optical Absorption Spectroscopy (DOAS), UV camera), combined with model-based estimates of fuel consumption, or based on the so called "sniffer" principle, where SO2 or NOx emission factors are determined from simultaneous measurement of the increase of CO2 and SO2 or NOx concentrations in the plume of the ship compared to the background. The measurements were performed from stations at land, from a boat and from a helicopter. Mobile measurement platforms were found to have important advantages compared to the land-based ones because they allow optimizing the sampling conditions and sampling from ships on the open sea. Although optical methods can provide reliable results it was found that at the state of the art level, the "sniffer" approach is the most convenient technique for determining both SO2 and NOx emission factors remotely. The average random error on the determination of SO2 emission factors comparing two identical instrumental set-ups was 6 %. However, it was found that apparently minor differences in the instrumental characteristics, such as response time, could cause significant differences between the emission factors determined. Direct stack measurements showed that about 14% of the fuel sulphur content was not emitted as SO2. This was supported by the remote measurements and is in agreement with the results of other field studies. S, 1984, Notes on Heavy Fuel Oil
We have investigated the complexation of the luminescent Nd3+, Eu3+, Gd3+, Tb3+, Er3+, and Yb3+ ions by a polylysin dendrimer containing 21 amide groups in the interior and, in the periphery, 24 ...chromophoric dansyl units which show an intense fluorescence band in the visible region. Most of the experiments were performed in 5:1 acetonitrile/dichloromethane solution at 298 K. On addition of the lanthanide ions to dendrimer solutions, the fluorescence of the dansyl units is quenched; in Nd3+, Er3+, and Yb3+, a sensitized near-infrared emission of the lanthanide ion is observed. At low metal ion concentrations, each dendrimer hosts only one metal ion and when the hosted metal ion is Nd3+ or Eu3+, the fluorescence of all the 24 dansyl units of the dendrimer is quenched with unitary efficiency. Quantitative measurements were performed in a variety of experimental conditions, including protonation of the dansyl units and measurements in rigid matrix at 77 K where a sensitized Eu3+ emission could also be observed. The results obtained have been interpreted on the basis of the energy levels and redox potentials of dendrimer and metal ions.
Recent advances in the field of photoactive dendrimers containing metal complexes are reviewed. Dendrimers with Ru(bpy)
3
2+ as a core exhibit the characteristic Ru(bpy)
3
2+-type luminescence that ...can be (i) protected from external quenchers by the dendrimer branches and (ii) sensitized by chromophoric groups contained in the periphery of the dendrimer (antenna effect). Several examples of dendrimers fully based on transition metal complexes (i.e., containing a metal at each branching point of the dendrimer structure) have been investigated with the purpose of light harvesting. Dendrimers containing one or more free base and metal porphyrin units have been investigated for light harvesting and for a variety of other purposes.
Scattered examples of other types of photoactive dendrimers are also reviewed.
An eosin molecule encapsulated into the dendrimer shown in the picture collects electronic energy from all 64 chromophoric units of the dendrimer, which comprises three different types of ...chromophore. Efficient intramolecular (within the dendrimer) and intermolecular (dendrimer‐host→eosin‐guest) energy‐transfer processes by a Förster type mechanism, as suggested by the strong overlap between the emission and absorption spectra of the relevant donor and acceptor units.
Plastics are ubiquitous in our daily life. Large quantities of plastics leak in the environment where they weather and fragment into micro- and nanoparticles. This potentially releases additives, but ...rarely leads to a complete mineralization, thus constitutes an environmental hazard. Plastic pollution in agricultural soils currently represents a major challenge: quantitative data of nanoplastics in soils as well as their effects on biodiversity and ecosystem functions need more attention. Plastic accumulation interferes with soil functions, including water dynamics, aeration, microbial activities, and nutrient cycling processes, thus impairing agricultural crop yield. Plastic debris directly affects living organisms but also acts as contaminant vectors in the soils, increasing the effects and the threats on biodiversity. Finally, the effects of plastics on terrestrial invertebrates, representing major taxa in abundance and diversity in the soil compartment, need urgently more investigation from the infra-individual to the ecosystem scales.
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•Research on micro and nanoplastic must consider environmentally realistic scenarios.•Our knowledge of impacts and fate of plastics in the environment must be improved.•More research revealing the small-sized plastics on living organisms are required.•Scaling the impacts at different organizational levels is critically needed.
A molecular‐level abacus‐like system driven by light inputs has been designed in the form of a 2rotaxane, comprising the π‐electron‐donating macrocyclic polyether bis‐p‐phenylene‐34‐crown‐10 ...(BPP34C10) and a dumbbell‐shaped component that contains 1) a RuII polypyridine complex as one of its stoppers in the form of a photoactive unit, 2) a p‐terphenyl‐type ring system as a rigid spacer, 3) a 4,4′‐bipyridinium unit and a 3,3′‐dimethyl‐4,4′‐bipyridinium unit as π‐electron‐accepting stations, and 4) a tetraarylmethane group as the second stopper. The synthesis of the 2rotaxane was accomplished in four successive stages. First of all, the dumbbell‐shaped component of the 2rotaxane was constructed by using conventional synthetic methodology to make 1) the so‐called “west‐side” comprised of the RuII polypyridine complex linked by a bismethylene spacer to the p‐terphenyl‐type ring system terminated by a benzylic bromomethyl function and 2) the so‐called “east‐side” comprised of the tetraarylmethane group, attached by a polyether linkage to the bipyridinium unit, itself joined in turn by a trismethylene spacer to an incipient 3,3′‐dimethyl‐4,4′‐bipyridinium unit. Next, 3) the “west‐side” and “east‐side” were fused together by means of an alkylation to give the dumbbell‐shaped compound, which was 4) finally subjected to a thermodynamically driven slippage reaction, with BPP34C10 as the ring, to afford the 2rotaxane. The structure of this interlocked molecular compound was characterized by mass spectrometry and NMR spectroscopy, which also established, along with cyclic voltammetry, the co‐conformational behavior of the molecular shuttle. The stable translational isomer is the one in which the BPP34C10 component encircles the 4,4′‐bipyridinium unit, in keeping with the fact that this station is a better π‐electron acceptor than the other station. This observation raises the question—can the BPP34C10 macrocycle be made to shuttle between the two stations by a sequence of photoinduced electron transfer processes? In order to find an answer to this question, the electrochemical, photophysical, and photochemical (under continuous and pulsed excitation) properties of the 2rotaxane, its dumbbell‐shaped component, and some model compounds containing electro‐ and photoactive units have been investigated. In an attempt to obtain the photoinduced abacus‐like movement of the BPP34C10 macrocycle between the two stations, two strategies have been employed—one was based fully on processes that involved only the rotaxane components (intramolecular mechanism), while the other one required the help of external reactants (sacrificial mechanism). Both mechanisms imply a sequence of four steps (destabilization of the stable translational isomer, macrocyclic ring displacement, electronic reset, and nuclear reset) that have to compete with energy‐wasteful steps. The results have demonstrated that photochemically driven switching can be performed successfully by the sacrificial mechanism, whereas, in the case of the intramolecular mechanism, it would appear that the electronic reset of the system is faster than the ring displacement.
Un 2rotassano potenzialmente adatto a funzionare come pallottoliere molecolare azionato da stimoli luminosi è stato progettato e sintetizzato. Esso è costituito da un etere corona π elettron donatore (BPP34C10) e da un componente lineare contenente 1) un complesso polipiridinico di RuII come unità fotoattiva e “stopper” per il macrociclo, 2) uno spaziatore p‐terfenilico rigido, 3) un gruppo 4,4′‐dipiridinio ed uno 3,3′‐dimetil‐4,4′‐dipiridinio come “stazioni” π elettron accettrici e 4) un gruppo tetraarilmetano come secondo “stopper”. La sintesi del 2rotassano è stata ottenuta in quattro passaggi successivi. In primo luogo è stato preparato il componente lineare; mediante metodologie sintetiche convenzionali sono state ottenute 1) la cosiddetta “regione occidentale”, che comprende il complesso di RuII legato allo spaziatore p‐terfenilico, funzionalizzato con un gruppo bromobenzilico, e 2) la “regione orientale”, costituita dal gruppo tetraarilmetano legato all'unità 4,4′‐dipiridinio, a sua volta connessa ad un gruppo precursore dell'unità 3,3′‐dimetil‐4,4′‐dipiridinio. In seguito, 3) la regione occidentale e quella orientale sono state fuse mediante una reazione di alchilazione, ottenendo così il componente lineare desiderato; infine, 4) esso è stato fatto reagire con il macrociclo BPP34C10 sotto controllo termodinamico allo scopo di preparare il 2rotassano. La struttura del rotassano è stata caratterizzata mediante spettrometria di massa e spettroscopia NMR; tali esperimenti hanno anche messo in evidenza, assieme a misure di voltammetria ciclica, il suo comportamento co‐conformazionale. L'isomero traslazionale stabile del rotassano è quello in cui il macrociclo BPP34C10 si trova sull'unità 4,4′‐dipiridinio, in accordo con il fatto che questa unità possiede proprietà π elettron accettrici migliori di quella 3,3′‐dimetilata. Il quesito cruciale, a questo punto, è: si può spostare il macrociclo BPP34C10 da una stazione all'altra utilizzando una sequenza fotoindotta di processi di trasferimento elettronico? Per rispondere a questa domanda sono state studiate le proprietà elettrochimiche, fotofisiche e fotochimiche (con eccitazione sia continua che pulsata) del 2rotassano, dei suoi componenti molecolari e di alcuni composti modello per le unità fotoattive ed elettroattive in questione. Sono state esplorate due strategie allo scopo ottenere il movimento fotoindotto del macrociclo da una stazione all'altra del componente lineare: la prima basata su processi coinvolgenti soltanto i componenti del rotassano (meccanismo intramolecolare), la seconda, invece, assistita dall'intervento di reagenti esterni (meccanismo sacrificale). Entrambi i meccanismi implicano una sequenza di quattro eventi (destabilizzazione dell'isomero traslazionale stabile, spostamento del macrociclo, ripristino elettronico e ripristino nucleare), che debbono competere con processi dissipativi. I risultati dimostrano che questo congegno molecolare può essere effettivamente azionato dalla luce utilizzando il meccanismo sacrificale; nel caso del meccanismo intramolecolare, invece, sembra che il ripristino elettronico del sistema sia più rapido dello spostamendo del macrociclo.
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