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"photochemistry"
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Photo-Activated Sludge : a novel algal-bacterial biotreatment for nitrogen removal from wastewater
Ammoniumrijk afvalwater wordt veelal geproduceerd door gemeentelijk, industrieel en landbouwafval, en effluent uit anaerobe afvalwaterzuiveringsmethoden. Dit vormt een risico voor het milieu vanwege de hoge concentratie aan voedingsstoffen (stikstof en fosfor), wat eutrofièering in waterpartijen kan bevorderen en daarmee de kwaliteit van ecosystemen kan aantasten. Als innovatieve oplossing hierop is een nieuw biologisch verwerkingsmechanisme genaamd Photo-Activated Sludge (PAS) geèevalueerd, wat gebruik maakt van een consortium van microalgen en bacterièen voor de zuivering van ammoniumrijk afvalwater.
Book
In Situ Photochemistry on a Benchtop Nmr Spectrometer with pH₂ Hyperpolarisation
High-resolution benchtop NMR spectrometers are uniquely suited for reaction monitoring applications, owing to their portability and accessibility, but the low inherent sensitivity of the approach can limit the observation of low-concentration transient species. In this work, a hyperpolarisation technique called parahydrogen induced polarisation (PHIP) was employed to overcome this limitation and observe both thermal and photochemical reactivity. The developed PHIP hyperpolarised reaction monitoring procedure enabled quantitative analysis of the oxidative addition of H2 to trans-[IrCl(CO)(PPh3)2], with a k2 rate constant of (0.89 ± 0.03) dm3 mol-1 s-1 showing excellent consistency with established literature. The method was validated against several key experimental parameters (including temperature and relaxation) to establish it as a robust route to accurately monitor reactions at low-field. Through integration of low-cost ex situ and in situ photochemistry setups that utilise broadband UV sources, the photochemistry of metal dihydrides (M = Ir, Ru) was explored on a benchtop NMR spectrometer for the first time. Implementation of a photochemical pump - NMR probe method with the in situ photochemistry setup allowed observation of photochemistry on the micro-to-millisecond timescale enabling the observation of short-lived hyperpolarised cis-[Ru(H)2(dppe)2] (with a hyperpolarised T1 of (250 ± 20) ms). This setup was employed to detect coherent magnetic evolution of metal complexes formed from addition of parahydrogen which has only been observed previously using a laser within a high-field NMR setup. Magnetic evolution was observed for cis-[Ru(H)2(dppe)2], [Ru(H)2(CO)2(dpae)], [Ir(H)2(CO)(PPh3)2I] and [Ir(H)2(13CO)(PPh3)2I] indicating the viability of a low-cost, benchtop NMR alternative to currently established practices.
Dissertation
Direct observation of ultrafast symmetry reduction during internal conversion of 2-thiouracil using Coulomb explosion imaging
The photochemistry of heterocyclic molecules plays a decisive role for processes and applications like DNA photo-protection from UV damage and organic photocatalysis. The photochemical reactivity of heterocycles is determined by the redistribution of photoenergy into electronic and nuclear degrees of freedom, initially involving ultrafast internal conversion. Most heterocycles are planar in their ground state and internal conversion requires symmetry breaking. To lower the symmetry, the molecule must undergo an out-of-plane motion, which has not yet been observed directly. Here we show using the example of 2-thiouracil, how Coulomb explosion imaging can be utilized to extract comprehensive information on this molecular deformation, linking the extracted deplanarization of the molecular geometry to the previously studied temporal evolution of its electronic properties. Particularly, the protons of the exploded molecule are well-suited messengers carrying rich information on its geometry at distinct times after electronic excitation. We expect that our new analysis approach centered on these peripheral protons can be adapted as a general concept for future time-resolved studies of complex molecules in the gas phase.
Journal Article
Photochemistry and photophysics of polymer materials
Presents the state of the technology, from fundamentals to new materials and applications Today's electronic devices, computers, solar cells, printing, imaging, copying, and recording technology, to name a few, all owe a debt to our growing understanding of the photophysics and photochemistry of polymeric materials. This book draws together, analyzes, and presents our current understanding of polymer photochemistry and photophysics. In addition to exploring materials, mechanisms, processes, and properties, the handbook also highlights the latest applications in the field and points to new developments on the horizon. Photochemistry and Photophysics of Polymer Materials is divided into seventeen chapters, including: Optical and luminescent properties and applications of metal complex-based polymers Photoinitiators for free radical polymerization reactions Photovoltaic polymer materials Photoimaging and lithographic processes in polymers Photostabilization of polymer materials Photodegradation processes in polymeric materials Each chapter, written by one or more leading experts and pioneers in the field, incorporates all the latest findings and developments as well as the authors' own personal insights and perspectives. References guide readers to the literature for further investigation of individual topics. Together, the contributions represent a series of major developments in the polymer world in which light and its energy have been put to valuable use. Not only does this reference capture our current state of knowledge, but it also provides the foundation for new research and the development of new materials and new applications.
eBook
Applying plasmonics to a sustainable future
Plasmonic technologies may form components of a future clean and sustainable society Chemistry is fundamental for powering our society. A flurry of very promising experiments demonstrate that plasmonics may have a transformative impact on the way we will drive, manipulate, enhance, and monitor chemical processes in the future. Plasmonics offers the ultimate spatial and temporal control over light and photochemistry, with the help of metallic nanostructures capable of concentrating electromagnetic energy into nanoscale volumes. Surface plasmons (SPs) are charge-density oscillations at the surface of a conducting material and decay by reemission of a photon or through the creation of highly energetic (“hot”) electrons and holes. The subsequent equilibration of hot carriers with lattice phonons can lead to appreciable local heating.
Journal Article
Autonomous mobile robots for exploratory synthetic chemistry
Autonomous laboratories can accelerate discoveries in chemical synthesis, but this requires automated measurements coupled with reliable decision-making
1
,
2
. Most autonomous laboratories involve bespoke automated equipment
3
–
6
, and reaction outcomes are often assessed using a single, hard-wired characterization technique
7
. Any decision-making algorithms
8
must then operate using this narrow range of characterization data
9
,
10
. By contrast, manual experiments tend to draw on a wider range of instruments to characterize reaction products, and decisions are rarely taken based on one measurement alone. Here we show that a synthesis laboratory can be integrated into an autonomous laboratory by using mobile robots
11
–
13
that operate equipment and make decisions in a human-like way. Our modular workflow combines mobile robots, an automated synthesis platform, a liquid chromatography–mass spectrometer and a benchtop nuclear magnetic resonance spectrometer. This allows robots to share existing laboratory equipment with human researchers without monopolizing it or requiring extensive redesign. A heuristic decision-maker processes the orthogonal measurement data, selecting successful reactions to take forward and automatically checking the reproducibility of any screening hits. We exemplify this approach in the three areas of structural diversification chemistry, supramolecular host–guest chemistry and photochemical synthesis. This strategy is particularly suited to exploratory chemistry that can yield multiple potential products, as for supramolecular assemblies, where we also extend the method to an autonomous function assay by evaluating host–guest binding properties.
A modular autonomous platform for general exploratory synthetic chemistry uses mobile robots to integrate an automated synthesis platform and two analysis platforms.
Journal Article
Photodegradation of bisphenol A in water and ice: identification of products using three photosensitizers
Bisphenol A (BPA) is a widespread organic micro-pollutant, found in most environments, including alpine and Arctic regions, and several matrices such as waters and aerosols. Polar regions are characterized by periods of intense irradiation with no sunset due to the continuous sunlight, while alpine areas, despite following the day-night cycle of mid-latitudes, also undergo strong irradiation. For such conditions, it is possible that a fraction of the BPA present in snow may degrade through direct photolysis, producing other unknown species with different environmental mobility and possible ecotoxic effects. Furthermore, the snowpack is rich in species (known as photosensitizers) that facilitate indirect photodegradation processes through reactions involving hydroxyl radicals
, singlet oxygen (
O
), excited triplet states of the organic fraction (
CDOM*), and nitrite/nitrate. In this study, we investigated both direct and indirect photodegradation of BPA in the presence of specific photosensitizers producing
,
O
,
CDOM*, and NO
to specifically explore the products of the reaction. The study was conducted in both liquid water and ice, under light and dark conditions. Results, obtained by HPLC-HRMS, revealed that the matrix in which the reaction takes place, in addition to the photosensitizer used, may influence the degradation by-products. This allows for the possibility of distinguishing the reaction environment based on the identified product.
Journal Article