Evaluation of cell-free DNA approaches for multi-cancer early detection.

In the Circulating Cell-free Genome Atlas (NCT02889978) substudy 1, we evaluate several approaches for a circulating cell-free DNA (cfDNA)-based multi-cancer early detection (MCED) test by defining clinical limit of detection (LOD) based on circulating tumor allele fraction (cTAF), enabling performance comparisons. Among 10 machine-learning classifiers trained on the same samples and independently validated, when evaluated at 98% specificity, those using whole-genome (WG) methylation, single nucleotide variants with paired white blood cell background removal, and combined scores from classifiers evaluated in this study show the highest cancer signal detection sensitivities. Compared with clinical stage and tumor type, cTAF is a more significant predictor of classifier performance and may more closely reflect tumor biology. Clinical LODs mirror relative sensitivities for all approaches. The WG methylation feature best predicts cancer signal origin. WG methylation is the most promising technology for MCED and informs development of a targeted methylation MCED test.

Improving the mass transport of copper-complex redox mediators in dye-sensitized solar cells by reducing the inter-electrode distance.

In this work, we study the influence of the distance between electrodes on the performance of dye-sensitized solar cells based on TiO2 using the organic dye LEG4 and a Cu(dmp)2 redox couple (dmp = dimethyl phenantroline). The solar cells are characterized by a large open circuit voltage of up to 1.03 V, and an efficiency of 8.2% has been achieved for a 5.3 µm thick TiO2 film using an epoxy resin-based sealed cell configuration with a minimal separation between electrodes. Transient short-circuit photocurrent measurements up to an intensity of 3 Suns show a significant decay in photocurrent after an initial peak current upon switching on the light for larger distance, resulting in a lower steady state photocurrent. For the smaller distance cells, the steady state photocurrent is linear with light intensity up to 2 Suns. Charge extraction measurements under short-circuit conditions show that reducing the distance between electrodes increases the electron collection efficiency and thus, the attainable photocurrent. Recombination losses increase with larger electrode separation distance and higher light intensity due to mass transport limitation of the redox mediator. Electrochemical impedance measurements confirm the effect of electrode distance on the redox couple transport, showing an additional loop with increasing distance. For the configuration where the TiO2 film is in very close proximity to the PEDOT-covered counter electrode, inductive behavior is observed at low frequencies. The inductive behavior disappears with the incorporation of an insulating porous ZrO2 layer. The equivalent circuit for the solar cell has been expanded to include this effect.

Chemical and Physical Reduction of High Valence Ni States in Mesoporous NiO Film for Solar Cell Application.

The most common material for dye-sensitized photocathodes is mesoporous NiO. We transformed the usual brownish NiO to be more transparent by reducing high valence Ni impurities. Two pretreatment methods have been used: chemical reduction by NaBH4 and thermal reduction by heating. The power conversion efficiency of the cell was increased by 33% through chemical treatment, and an increase in open-circuit voltage from 105 to 225 mV was obtained upon heat treatment. By optical spectroelectrochemistry, we could identify two species with characteristically different spectra assigned to Ni3+ and Ni4+. We suggest that the reduction of surface Ni3+ and Ni4+ to Ni2+ decreases the recombination reaction between holes on the NiO surface with the electrolyte. It also keeps the dye firmly on the surface, building a barrier for electrolyte recombination. This causes an increase in open-circuit photovoltage for the treated film.

A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells.

Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy-by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte-to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system.

Development of high efficiency 100% aqueous cobalt electrolyte dye-sensitised solar cells.

In this study we report the application of three cobalt redox shuttles in 100% aqueous electrolyte dye-sensitised solar cells (DSCs). By using chloride as a counter-ion for cobalt bipyridine, cobalt phenanthroline and cobalt bipyridine pyrazole, the redox shuttles were made water soluble; no surfactant or further treatment was necessary. A simple system of merely the redox shuttles and 1-methylbenzimidazole (MBI) in water as an electrolyte in combination with an organic dye and a mesoporous PEDOT counter electrode was optimised. The optimisation resulted in an average efficiency of 5.5% (record efficiency of 5.7%) at 1 sun. The results of this study present promising routes for further improvements of aqueous cobalt electrolyte DSCs.