Addressing Chirality in the Structure and Synthesis of [18 F]5-Fluoroaminosuberic Acid ([18 F]FASu).

An increasing number of positron emission tomography (PET) radiotracers are being developed that are modelled on various amino acids to better understand disease in a manner that is complementary to traditional glycolysis-targeting [18 F]-fluorodeoxyglucose. Since chiral centers are ubiquitous in amino acids, generating an optically pure radiolabeled amino acid is important for patient dose, image quality and understanding the physiology behaviour. Past studies on the radiosynthesis of amino acid radiotracers seldom address the impact of reaction conditions on their chirality. The amino acid PET tracer, [18 F]5-fluoroaminosuberic acid ([18 F]FASu), has two chiral centers at the 2- and 5-positions and is being developed as a specific tracer for the cystine transporter (system xC- ), a biomarker for oxidative stress. Herein we report a method for synthesizing pure 2S,5R/S-FASu. We have resolved the 5-position configuration by applying Mosher's method combined with 2D NMR, which has enabled the synthesis of 18 FASu with fully known configuration. Our study serves as an example of a systematic method to identify and characterize amino acid tracers with chiral centers.

Comparing the net-energy balance of standalone photovoltaic-coupled electrolysis and photoelectrochemical hydrogen production.

Photovoltaic-coupled electrolysis (PV-E) and photoelectrochemical (PEC) water splitting are two options for storing solar energy as hydrogen. Understanding the requirements for achieving a positive energy balance over the lifetime of facilities using these technologies is important for ensuring sustainability. While neither technology has yet reached full commercialisation, they are also at very different technology readiness levels and scales of development. Here, we model the energy balance of standalone large-scale facilities to evaluate their energy return on energy invested (ERoEI) over time and energy payback time (EPBT). We find that for average input parameters based on present commercialised modules, a PV-E facility shows an EPBT of 6.2 years and ERoEI after 20 years of 2.1, which rises to approximately 3.7 with an EPBT of 2.7 years for favourable parameters using the best metrics amongst large-scale modules. The energy balance of PV-E facilities is influenced most strongly by the upfront embodied energy costs of the photovoltaic component. In contrast, the simulated ERoEI for a PEC facility made with earth abundant materials only peaks at 0.42 after 11 years and about 0.71 after 20 years for facilities with higher-performance active materials. Doubling the conversion efficiency to 10% and halving the degradation rate to 2% for a 10-year device lifetime can allow PEC facilities to achieve an ERoEI after 20 years of 2.1 for optimistic future parameters. We also estimate that recycling the materials used in hydrogen production technologies improves the energy balance by 28% and 14% for favourable-case PV-E and PEC water splitting facilities, respectively.

Macroporous Vanadium Oxide Ion Storage Films Enable Fast Switching Speed and High Cycling Stability of Electrochromic Devices.

Compared to the significant effort dedicated toward developing efficient electrochromic materials for the working electrodes of electrochromic (EC) devices, the attention paid to developing ion storage counter electrode materials for EC devices has been trivial. Herein, we report that a macroporous crystalline V2O5 film as an ion storage layer paired with a WO3 working electrode results in an EC device with high performance. The macroporous vanadium oxide films are prepared by a simple template-free photodeposition method that allows us to tune the thickness and crystallinity of the film, thus giving access to a full EC device with optimal EC performance: short response time of about 2 s, high electrochromic cycling stability up to 10,000 times, long memory effect over 24 h, and an exceedingly high coloration efficiency of 189 cm2/C that are superior to the state-of-the-art performance of solution-processed vanadium oxide based EC devices. The extraordinary EC performance can be attributed to the macroporous structure, high crystallinity, and optimized thickness of the vanadium oxide films that boost the charge-balancing capability of the films. The easy and controllable preparation and the efficient charge-balancing capability of the macroporous vanadium oxide film make it a promising ion storage material for developing high-performance EC devices.

Solution-Deposited Solid-State Electrochromic Windows.

Commercially available electrochromic (EC) windows are based on solid-state devices in which WO3 and NiOx films commonly serve as the EC and counter electrode layers, respectively. These metal oxide layers are typically physically deposited under vacuum, a time- and capital-intensive process when using rigid substrates. Herein we report a facile solution deposition method for producing amorphous WO3 and NiOx layers that prove to be effective materials for a solid-state EC device. The full device containing these solution-processed layers demonstrates performance metrics that meet or exceed the benchmark set by devices containing physically deposited layers of the same compositions. The superior EC performance measured for our devices is attributed to the amorphous nature of the NiOx produced by the solution-based photodeposition method, which yields a more effective ion storage counter electrode relative to the crystalline NiOx layers that are more widely used. This versatile method yields a distinctive approach for constructing EC windows.