Photochemical Degradation of Phenols in Water Using Flavin-based Photosensitizers

A slightly modified method for 10-ethyl flavin was developed in the present study. The synthetic product was characterized by nuclear magnetic resonance(NMR) and mass spectrometry, and used to catalyze the photocatalytic degradation of phenol, 2, 4-dichlorophenoxyacetic acid, p-nitrophenol, 4-chlorophenol, 4-methoxyphenol, 4-chloro-2-methyl-phenoxyacetic acid and2, 4, 5-trichloro-phenoxyacetic acid. Both HPLC(high performance liquid chromatography) and GC-MS data suggested that all phenols were degraded in the presence of either flavin at micromolar concentrations under direct sun light. A rapid breakdown of the phenols was observed. The degradation efficiency was clearly dependent on phenol type. In a decreasing order of degradation efficiency over a 2-h period, the phenols were 4-chlorophenol and 4-methoxyphenol(-80%) > phenoxyacetic acids(60%-65%) > nitrophenol and phenol(-35%).

Weak-value amplification for the optical signature of topological phase transitions

We show that weak measurements can be used to measure the tiny signature of topological phase transitions.The signature is an in-plane photonic spin Hall effect,which can be described as a consequence of a Berry phase.It is also parallel to the propagation direction of a light beam.The imaginary part of the weak value can be used to analyze ultrasmall longitudinal phase shifts in different topological phases.These optical signatures are related to the Chern number and bandgaps;we also use a preselection and postselection technique on the spin state to enhance the original signature.The weak amplification technique offers a potential way to determine the spin and valley properties of charge carriers,Chern numbers,and topological phases by direct optical measurement.

Radiative cooling and cold storage for concentrated solar power plants

Concentrated solar power(CSP)plants are generally located in solar-abundant yet hot and water-stressed loca-tions.In such circumstances,efficient but water-intensive once-through wet cooling and water-free but inefficient air cooling are both unfavorable.Considering both thermal efficiency and water availability/temperature,recir-culating evaporative cooling is a better alternative.However,evaporative cooling still loses large amounts of water into the atmosphere and thus requires a nonstop water supply.Therefore,simultaneously reducing water loss and maintaining thermal efficiency requires efficient means of supplemental cooling for CSP plants.Follow-ing our previous work on scalable radiative cooling films and a kW-scale radiative cooling system,we explore the potential of consumptive water use reduction in recirculating wet-cooled CSP plants by integrating supplemental radiative cooling and cold storage.Through modeling of a reference CSP plant with a supplemental radiative cooling system as large as the plant solar field,the results show that 40%-60%of the annual consumptive water use can be potentially reduced in the hot southwestern U.S.region with daytime-only radiative cooling,whereas the annual potential water saving can be as much as 65%-85%if the radiative cooling system works both day and night with cold storage.