Herein, we report on a two‐step bichromatic synthesis of coumarins involving UV‐A and UV‐C light. The first step is a UV‐A‐photoinduced ruthenium‐catalyzed cross‐metathesis (CM) reaction of 2‐nitrobenzyl‐protected 2‐hydroxystyrenes with acrylates, using an external solution of 1‐pyrenecarboxaldehyde as a UV filter. Irradiation in the absence of the filter permanently inhibits the light‐activated catalyst due to photocleavage of the photolabile protecting group (PPG) and ensuing phenolate chelation to the ruthenium. The simple removal of the external filter after CM allows further photochemical reactions with UV‐C light to achieve more complex architectures, such as the coumarins presented in this work.
A novel visible light‐mediated, copper‐catalysed aerobic oxidation of the C≡C bond in ynamides/ynamines at room temperature by using molecular oxygen as an oxidant is described. Overall, 23 examples were demonstrated with substrates having a wide range of functional groups. The current protocol can be readily scaled up to a preparative (1–2 g) scale with high yields (78–92%), high atom efficiency, and reaction mass efficiency. The mechanistic study shows that in‐situ formation of a copper(I)‐coordinated π‐complex (λ max=460 nm) is most probably the key light absorbing species responsible for the visible light‐induced oxidation of ynamides and ynamines. This sustainable oxidation approach allows the direct synthesis of potentially important novel α‐ketoimide/α‐ketoamide skeletons without the need of external oxidants (organic/inorganic oxidants) and generation of stoichiometric amounts of wastes.
Recently, micro‐TAS (Micro Total Analysis Systems) that performs genetic testing on devices containing microfluidics has been actively studied. In micro‐TAS, a micromixer and a microreactor provided on a microfluidic device are driven by feeding reagents with micropumps. Various micropumps were developed and studied: for example, displacement pumps, electro‐osmotic pumps, chemically actuated micropumps. The diaphragm type, which is a general pump, has the problem that reagents stagnation flow on the microfluidic device due to pulsation. Focusing on gas generation technology based on photochemical reaction, we thought that gas generation by light irradiation could be used for micropumps. Here we reported the basic concept for the photochemical actuated micropump and characterized performance of the device. 相似文献
The photochemistry of anthracene, a new class of photoresist for direct laser writing, is used to enable visible‐light‐gated control over the mechanical properties of 3D microstructures post‐manufacturing. The mechanical and viscoelastic properties (hardness, complex elastic modulus, and loss factor) of the microstructures are measured over the course of irradiation via dynamic mechanical analysis on the nanoscale. Irradiation of the microstructures leads to a strong hardening and stiffening effect due to the generation of additional crosslinks through the photodimerization of the anthracene functionalities. A relationship between the loss of fluorescence—a consequence of the photodimerization—and changes in the mechanical properties is established. The fluorescence thus serves as a proxy read‐out for the mechanical properties. These photoresponsive microstructures can potentially be used as “mechanical blank slates”: their mechanical properties can be readily adjusted using visible light to serve the demands of different applications and read out using their fluorescence. 相似文献
Lead halide perovskite nanocrystals (NCs) have demonstrated great potential as appealing candidates for advanced optoelectronic applications. However, the toxicity of lead and the intrinsic instability toward moisture hinder their mass production and commercialization. Herein, to solve such thorny problems, novel lead‐free Cs2AgBiBr6 double perovskite NCs fabricated via a simple hot‐injection method are reported, which exhibit impressive stability in moisture, light, and temperature. Such materials are then applied into photocatalytic CO2 reduction, achieving a total electron consumption of 105 µmol g?1 under AM 1.5G illumination for 6 h. This study offers a reliable avenue for Cs2AgBiBr6 perovskite nanocrystals preparation, which holds a great potential in the further photochemical applications. 相似文献
The induction of electrohydrodynamic instabilities in nematic liquid crystals through light illumination are reported. For this purpose, a photochromic spiropyran is added to the liquid crystal mixture. When an electrical field is applied in the absence of UV light, the homeotropic liquid crystal reorients perpendicular to the electrical field driven by its negative dielectric anisotropy. Upon exposure to UV light, the nonionic spiropyran isomerizes to the zwitterionic merocyanine form inducing electrohydrodynamic instabilities which turns the cell from transparent into highly scattering. The reverse isomerization to closed‐ring spiropyran form occurs thermally or under visible light, which stops the electrohydrodynamic instabilities and the cell becomes transparent again. It is demonstrated that the photoionic electrohydrodynamic instabilities can be used for light regulation. Local exposure, either to drive the electrohydrodynamics or to remove them enables the formation of colored images. 相似文献
The possibility to impart surface properties to any polymeric substrate using a fast, reproducible, and industrially friendly procedure, without the need for surface pretreatment, is highly sought after. This is in particular true in the frame of antibacterial surfaces to hinder the threat of biofilm formation. In this study, the potential of aryl‐azide polymers for photofunctionalization and the importance of the polymer structure for an efficient grafting are demonstrated. The strategy is illustrated with a UV‐reactive hydrophilic poly(2‐oxazoline) based copolymer, which can be photografted onto any polymer substrate that contains carbon–hydrogen bonds to introduce antifouling properties. Through detailed characterization it is demonstrated that the controlled spatial distribution of the UV‐reactive aryl‐azide moieties within the poly(2‐oxazline) structure, in the form of pseudogradient copolymers, ensures higher grafting efficacy than other copolymer structures including block copolymers. Furthermore, it is found that the photografting results in a covalently bound layer, which is thermally stable and causes a significant antiadherence effect and biofilm reduction against Escherichia coli and Staphylococcus epidermidis strains while remaining noncytotoxic against mouse fibroblasts. 相似文献
