Room-temperature phosphorescent materials that emit light in the visible (red, green, and blue; from 400 to 700 nm) have been a major focus of research and development during the past decades, due to ...their applications in organic light-emitting diodes (OLEDs), light-emitting electrochemical cells, photovoltaic cells, chemical sensors, and bio-imaging. In recent years, near-infrared (NIR) phosphorescence beyond the visible region (7002500 nm) has emerged as a new, promising, and challenging research field with potential applications toward NIR OLEDs, telecommunications, night vision-readable displays. Moreover, NIR phosphorescence holds promise for
in vivo
imaging, because cells and tissues exhibit little absorption and auto-fluorescence in this spectral region. This review describes the overall progress made in the past ten years on NIR phosphorescent transition-metal complexes including Cu(
i
), Cu(
ii
), Cr(
iii
), Re(
i
), Re(
iii
), Ru(
ii
), Os(
ii
), Ir(
iii
), Pt(
ii
), Pd(
ii
), Au(
i
), and Au(
iii
) complexes, with a primary focus on material design complemented with a selection of optical, electronic, sensory, and biologic applications. A critical comparison of various NIR phosphorescent materials reported in the literature and a blueprint for future development in this field are also provided.
An overview of the latest developments and applications in the field of room-temperature near-infrared phosphorescent transition-metal complexes is given.
In most safety-critical domains the need for traceability is prescribed by certifying bodies. Trace links are generally created among requirements, design, source code, test cases and other ...artifacts, however, creating such links manually is time consuming and error prone. Automated solutions use information retrieval and machine learning techniques to generate trace links, however, current techniques fail to understand semantics of the software artifacts or to integrate domain knowledge into the tracing process and therefore tend to deliver imprecise and inaccurate results. In this paper, we present a solution that uses deep learning to incorporate requirements artifact semantics and domain knowledge into the tracing solution. We propose a tracing network architecture that utilizes Word Embedding and Recurrent Neural Network (RNN) models to generate trace links. Word embedding learns word vectors that represent knowledge of the domain corpus and RNN uses these word vectors to learn the sentence semantics of requirements artifacts. We trained 360 different configurations of the tracing network using existing trace links in the Positive Train Control domain and identified the Bidirectional Gated Recurrent Unit (BI-GRU) as the best model for the tracing task. BI-GRU significantly out-performed state-of-the-art tracing methods including the Vector Space Model and Latent Semantic Indexing.
Air pollution in transportation cabins has recently become a public concern. However, few studies assessed the exposure levels of suspected air pollutants including Volatile Organic Compounds (VOCs). ...This paper studied the exposure levels of in-carriage VOCs (benzene, toluene, ethylbenzene, xylene, styrene, formaldehyde, acetaldehyde, acetone and acrolein) in Shanghai, China and estimated the health risk in different conditions. The results indicated that VOCs concentrations in metro carriages varied from different train models, due to the difference in carriage size and ventilation system. The concentrations of aromatic VOCs in old metro carriage were 1–2 times higher than the new ones, as better paintings were used in new trains. Poor air circulation and ventilation in the underground track was likely to be the cause of higher VOCs levels (~10%) than the above-ground track. Lower aromatic compounds levels and higher carbonyls levels were observed in metro carriages at suburban areas than those at urban areas, likely due to less aromatic emission sources and more carbonyls emission sources in suburban areas. Acetone and acrolein were found to increase from 7.71 to 26.28μg/m3 with number of commuters increasing from 40 to 200 in the carriages. According to the acceptable level proposed by the World Health Organization (1×10−6–1×10−5), the life carcinogenic risk of commuters by subway (8.5×10−6-4.8×10−5) was little above the acceptable level in Shanghai. Further application of our findings is possible to act as a reference in facilitating regulations for metro systems in other cities around world, so that in-carriage air quality might be improved.
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•The VOCs concentration in different metro carriages under different route conditions were analyzed.•The VOCs exposure levels inside metro carriages in Shanghai, China were calculated.•The health risk of commuters' exposure to VOCs inside subway was estimated.
A series of colorful Salen-type Schiff bases derived from the different diamine bridges including 1,2-ethylenediamine (Et1–Et3), 1,2-cyclohexanediamine (Cy1–Cy3), 1,2-phenylenediamine (Ph1–Ph4), ...dicyano-1,2-ethenediamine (CN1–CN3), phenazine-2,3-diamine (Phen1–Phen3), and naphthalene-2,3-diamine (Naph1 and Naph2) have been designed and prepared. The presence of electron-accepting substituents, electron-donating substituents, donor–acceptor (DA) systems, and/or π-extended systems leads to not only full absorption and emission spectra (300–700 nm) in the visible region but also high fluorescence quantum yields up to 0.83 in solution. The experimental results and density functional theory (DFT) calculations have proved that the highest occupied molecular orbital (HOMO) levels, the lowest unoccupied molecular orbital (LUMO) levels, and consequently the energy gaps of these Salen ligands can be well tuned. The LUMO levels of these Salen ligands are mainly affected by the diamine bridges, whereas both the HOMO and LUMO levels are influenced by the phenol fragments. Adding Cu2+ and Co2+ to CN1 solution leads to a drastic color change from pink into brownish red and purple, respectively, which is useful not only for the ratiometric detection but also for rapid visual sensing even by the naked eye. Moreover, the properties of the cis–trans isomer of CN1 are examined. The Salen ligands have coordination chemistry similar to other well-known tetradentate porphyrin ligands as well as much easier preparation and rich photophysical properties.
We report our systematic studies of novel, simple, selective, and sensitive optical (both colorimetric and fluorescent) chemosensors for detecting Al3+ based on transmetalation reactions (metal ...displacement or exchange reactions) of a series of K(I), Ca(II), Zn(II), Cu(II), and Pt(II) complexes containing different ligands of salen-based Schiff bases. Both the chemical structure of the salen ligand and the identity of the central metal ion have a tremendous impact on the sensing performance, which is mainly determined by the stability constant of the complex. Moreover, the selectivities of the salen-complex-based chemosensors are much better than those of the corresponding free salen ligands because of the shielding function of the filled-in metal ion in the complex. Therefore, the present work potentially provides a new and simple way to design optical probes via complex-based transmetalation reactions.
The quantitative determination of oxygen concentration is essential for a variety of applications ranging from life sciences to environmental sciences. Optical oxygen sensing allows non-invasive ...measurements with biological objects, parallel monitoring of multiple samples, and imaging. In general, ratiometric optical oxygen sensing is more desirable, due to its advantages of selectivity, insensitivity to ambient or scattered light, and elimination of instrumental fluctuation. Moreover, it can provide the perceived colour change, which would be useful not only for the ratiometric method of detection but also for rapid visual sensing. Mainly focusing on material design for ratiometric measurement, this review describes the overall progress made in the past ten years on ratiometric optical ground-state triplet oxygen sensing and offers a critical comparison of various methods reported in the literature. It also provides a development blueprint for ratiometric optical oxygen sensing.
Overview of the latest developments in the field of ratiometric optical oxygen sensing.
Security constrained unit commitment (SCUC) is one of the most important daily tasks that independent system operators (ISOs) or regional transmission organizations (RTOs) must accomplish in daily ...electric power market. Security constraints have long been regarded as difficult constraints for unit commitment problems. If the inactive security constraints can be identified and eliminated, the SCUC problem can be greatly simplified. In this paper, a necessary and sufficient condition for a security constraint to be inactive is established. It is proved that all inactive constraints can be identified by solving a series of small-scale mixed integer linear programming (MILP) problems. More importantly, an analytical sufficient condition is established and most of the inactive constraints can be quickly identified without solving MILP or linear programming (LP) problems. A very important feature of the conditions obtained is that they are only related to the load demands and parameters of the transmission network. Numerical testing is performed for three power grids and the results are impressive. Over 85% of the security constraints are identified as inactive and the crucial transmission lines affecting the total operating cost are among those associated with the remaining security constraints, providing useful information for transmission planning.
The First Symposium on Software Engineering for Machine Learning Applications (SEMLA) aimed to create a space in which machine learning (ML) and software engineering (SE) experts could come together ...to discuss challenges, new insights, and practical ideas regarding the engineering of ML and AI-based systems. Key challenges discussed included the accuracy of systems built using ML and AI models, the testing of those systems, industrial applications of AI, and the rift between the ML and SE communities. This article is part of a theme issue on software engineering's 50th anniversary.
Three binuclear cyclometalated PtII complexes, (ppy)Pt(µ‐SA)Pt(ppy) (ppy = 2‐phenylpyridine, SA: salicylaldehyde azine), have been synthesized and characterized. Owing to the blockage of the ...intramolecular rotation of the bridging SA ligands, all three complexes exhibit propeller‐type enantiomers and aggregation‐induced phosphorescence (AIP). Interestingly, one complex with –NEt2 groups instead of long alkyl chains, amide, urea peptides, cholesterol, sugar, or steroidal groups was found to show strong phosphorescence enhancement gated by the gelation process. This unusual gelation behavior is rarely encountered, as the metallogel has no intermolecular hydrogen bonding or Pt–Pt interactions. We attribute the driving force of this gelation‐induced phosphorescence (GIP) to the propeller‐type structure, optimally balanced solubility of –NEt2 groups, enantiomer‐induced π–π stacking interactions, and strong multiple intermolecular H–C, H–O, and H–H interactions.
Propeller‐type binuclear PtII enantiomers without any intermolecular hydrogen bonding or Pt–Pt interaction exhibit unusual aggregation/gelation‐induced phosphorescence through strong multiple intermolecular H–C, H–Pt, H–O, and H–H interactions. The intermolecular π–π stacking interactions between two enantiomers can be well tuned by their chemical structures to induce the formation of gels.
Natural products are usually non-conjugated and chiral, but organic luminescent materials are commonly polycyclic aromatic molecules with extended π-conjugation. In the present work, we combine with ...the advantages of non-conjugation and chirality to prepare a series of novel and simple salen ligands (41 samples), which have a non-conjugated and chiral ( S , S ) and ( R , R ) cyclohexane or 1,2-diphenylethane bridge but display strong blue, green, and red aggregation-induced emission (AIE) with large Stokes shifts (up to 186 nm) and high fluorescence quantum yields (up to 0.35). Through hydrogen and halogen bonds, these flexible salen ligands can be used as universal anion probes and chiral receptors of unprotected amino acids (enantiomeric selectivity up to 0.11) with fluorescence quantum yields up to 0.29 and 0.27, respectively. Moreover, the effects of different chiral bridges on the molecule arrangement, AIE, and anion and chiral recognition properties are also explored, which provide unequivocal insights for the design of non-conjugated chiral and soft fluorescent materials.
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