Recent Advances in Organic Dyes for Application in Dye-Sensitized Solar Cells under Indoor Lighting Conditions.

Among the emerging photovoltaic (PV) technologies, Dye-Sensitized Solar Cells (DSSCs) appear especially interesting in view of their potential for unconventional PV applications. In particular, DSSCs have been proven to provide excellent performances under indoor illumination, opening the way to their use in the field of low-power devices, such as wearable electronics and wireless sensor networks, including those relevant for application to the rapidly growing Internet of Things technology. Considering the low intensity of indoor light sources, efficient light capture constitutes a pivotal factor in optimizing cell efficiency. Consequently, the development of novel dyes exhibiting intense absorption within the visible range and light-harvesting properties well-matched with the emission spectra of the various light sources becomes indispensable. In this review, we will discuss the current state-of-the-art in the design, synthesis, and application of organic dyes as sensitizers for indoor DSSCs, focusing on the most recent results. We will start by examining the various classes of individual dyes reported to date for this application, organized by their structural features, highlighting their strengths and weaknesses. On the basis of this discussion, we will then draft some potential guidelines in an effort to help the design of this kind of sensitizer. Subsequently, we will describe some alternative approaches investigated to improve the light-harvesting properties of the cells, such as the co-sensitization strategy and the use of concerted companion dyes. Finally, the issue of measurement standardization will be introduced, and some considerations regarding the proper characterization methods of indoor PV systems and their differences compared to (simulated) outdoor conditions will be provided.

Orange/Red Benzo[1,2-b:4,5-b']dithiophene 1,1,5,5-Tetraoxide-Based Emitters for Luminescent Solar Concentrators: Effect of Structures on Fluorescence Properties and Device Performances.

Luminescent solar concentrators (LSCs) are a class of optical devices able to harvest, downshift, and concentrate sunlight, thanks to the presence of emitting materials embedded in a polymer matrix. Use of LSCs in combination with silicon-based photovoltaic (PV) devices has been proposed as a viable strategy to enhance their ability to harvest diffuse light and facilitate their integration in the built environment. LSC performances can be improved by employing organic fluorophores with strong light absorption in the center of the solar spectrum and intense, red-shifted emission. In this work, we present the design, synthesis, characterization, and application in LSCs of a series of orange/red organic emitters featuring a benzo[1,2-b:4,5-b']dithiophene 1,1,5,5-tetraoxide central core as an acceptor (A) unit. The latter was connected to different donor (D) and acceptor (A') moieties by means of Pd-catalyzed direct arylation reactions, yielding compounds with either symmetric (D-A-D) or non-symmetric (D-A-A') structures. We found that upon light absorption, the compounds attained excited states with a strong intramolecular charge-transfer character, whose evolution was greatly influenced by the nature of the substituents. In general, symmetric structures showed better photophysical properties for the application in LSCs than their non-symmetric counterparts, and using a donor group of moderate strength such as triphenylamine was found preferable. The best LSC built with these compounds presented photonic (external quantum efficiency of 8.4 ± 0.1%) and PV (device efficiency of 0.94 ± 0.06%) performances close to the state-of-the-art, coupled with a sufficient stability in accelerated aging tests.

Prostate-specific antigen kinetics parameters are predictive of positron emission tomography features worsening in patients with biochemical relapse after prostate cancer treatment with radical intent: Results from a longitudinal cohort study.

OBJECTIVE: The aim of this study was to identify prostate-specific antigen (PSA) kinetics parameters predictive of [(18)F]fluorocholine positron emission tomography/computed tomography ((18)FC PET/CT) features worsening in a cohort of patients with biochemical failure after prostate cancer treatment. MATERIAL AND METHODS: This longitudinal cohort study comprised 103 consecutive patients. All patients underwent two (18)FC PET/CT scans: one at baseline (PET1) and one after 6 months (PET2). Total PSA (tPSA), PSA velocity (vPSA), PSA doubling time (PSAdt), absolute variation in PSA values between PET2 and PET1 (ΔPSA), and percentage variation in PSA between the two PSA measurements (PSA%) were measured in each patient. Progression of disease on (18)FC PET/CT findings was compared with the PSA kinetics parameters. The major outcome measure was disease progression at PET2. RESULTS: (18)FC PET/CT progression between PET1 and PET2 was reported in 64 patients (62.1%), while in 39 cases it remained unvaried. The following PSA kinetic parameters correlated with worsened (18)FC PET/CT findings: ΔPSA >5 ng/ml [odds ratio (OR = 6.44, 95% confidence interval (CI) 1.04-39.6; p = 0.04], vPSA >6 ng/ml/month (OR = 5.2, 95% CI 0.9-29.8; p = 0.05) and PSAdt <6 months (OR = 5.2, 95% CI 0.4-5.4; p = 0.03). From receiver operating characteristics (ROC) analysis, the combination with the three PSA kinetics parameters for predicting worsened (18)FC PET/CT findings resulted in a sensitivity of 86% (95% CI 77-92%) and specificity of 77% (95% CI 65-85%). CONCLUSION: PSA kinetics is strictly related to (18)FC PET/CT findings. In patients with biochemical relapse, ΔPSA >5 ng/ml, PSAdt <6 months and vPSA >6 ng/ml/month are highly predictive of (18)FC PET/CT features worsening, independently from the treatment received.

SBP ratio in exercise stress testing: validation by perfusion imaging.

AIMS: The 3-min SBP ratio (SBPR) was proposed to detect significant coronary artery disease (CAD), but its relationship with abnormalities detected by myocardial perfusion-gated single-photon emission computed tomography (SPECT) was never examined. METHODS: In 156 consecutive patients submitted to resting and exercise gated SPECT for suspect CAD, perfusion scores, ejection fraction and transient ischemic dilatation (TID) were evaluated and compared with SBPR. RESULTS: There were weak correlations between SBPR and summed stress score (ρ = 0.232, P < 0.004), and summed difference score (SDS) (ρ = 0.228, P < 0.004). According to receiver operating characteristic analysis, SBPR was poorly effective for identifying patients with inducible ischemia (SDS ≥ 2): area under curve = 0.64, (P < 0.002), sensitivity = 82%, specificity = 40%. No relationship was registered between SBPR and postexercise ejection fraction drop, and the relationship with TID was poor (ρ = 0.263, P < 0.001). CONCLUSION: In patients submitted to gated SPECT for suspect CAD, SBPR appears poorly effective for the detection of significant CAD, and does not show any valuable relationship with exercise-induced functional abnormalities.

Prognostic implications of post-stress ejection fraction decrease detected by gated SPECT in the absence of stress-induced perfusion abnormalities.

PURPOSE: The prognostic meaning of a post-stress ejection fraction (EF) decrease detected by perfusion gated SPECT is still unclear.We therefore followed up patients with post-stress EF decrease in the absence of stress-induced perfusion abnormalities. METHODS: We prospectively enrolled 57 consecutive patients with post-stress EF drop ≥ 5 EF units and summed difference score (SDS) ≤ 1. They were followed up for more than 1 year and their outcome was compared with a group of sex- and age-matched controls with the same SDS but without EF decrease. RESULTS: During follow-up there were 13 events (1 cardiac death, 1 non-fatal myocardial infarction, 1 congestive heart failure and 10 late revascularizations). In the control group we registered six events. There was a significant difference (p<0.0001) between the event-free survival curves of the two groups. CONCLUSION: The event rate of patients with post-stress EF decrease ≥ 5 EF units is relatively high and is significantly worse than that of a control group of patients with similarly normal SDS but without EF changes. Therefore, a post-stress EF decrease without stress-induced perfusion abnormalities should be cautiously interpreted.