Boosting the efficiency of transient photoluminescence microscopy using cylindrical lenses.

Transient Photoluminescence Microscopy (TPLM) allows for the direct visualization of carrier transport in semiconductor materials with sub nanosecond and few nanometer resolution. The technique is based on measuring changes in the spatial distribution of a diffraction limited population of carriers using spatiotemporal detection of the radiative decay of the carriers. The spatial resolution of TPLM is therefore primarily determined by the signal-to-noise-ratio (SNR). Here we present a method using cylindrical lenses to boost the signal acquisition in TPLM experiments. The resulting asymmetric magnification of the photoluminescence emission of the diffraction limited spot can increase the collection efficiency by more than a factor of 10, significantly reducing acquisition times and further boosting spatial resolution.

Nanoengineering Triplet-Triplet Annihilation Upconversion: From Materials to Real-World Applications.

Using light to control matter has captured the imagination of scientists for generations, as there is an abundance of photons at our disposal. Yet delivering photons beyond the surface to many photoresponsive systems has proven challenging, particularly at scale, due to light attenuation via absorption and scattering losses. Triplet-triplet annihilation upconversion (TTA-UC), a process which allows for low energy photons to be converted to high energy photons, is poised to overcome these challenges by allowing for precise spatial generation of high energy photons due to its nonlinear nature. With a wide range of sensitizer and annihilator motifs available for TTA-UC, many researchers seek to integrate these materials in solution or solid-state applications. In this Review, we discuss nanoengineering deployment strategies and highlight their uses in recent state-of-the-art examples of TTA-UC integrated in both solution and solid-state applications. Considering both implementation tactics and application-specific requirements, we identify critical needs to push TTA-UC-based applications from an academic curiosity to a scalable technology.

Correction: Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(II) complexes.

Correction for 'Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(II) complexes' by Philipp Dierks et al., Chem. Commun., 2021, 57, 6640-6643, https://doi.org/10.1039/D1CC01716K.

Triplet Fusion Upconversion Nanocapsule Synthesis.

Triplet fusion upconversion (UC) allows for the generation of one high energy photon from two low energy input photons. This well-studied process has significant implications for producing high energy light beyond a material's surface. However, the deployment of UC materials has been stymied due to poor material solubility, high concentration requirements, and oxygen sensitivity, ultimately resulting in reduced light output. Toward this end, nanoencapsulation has been a popular motif to circumvent these challenges, but durability has remained elusive in organic solvents. Recently, a nanoencapsulation technique was engineered to tackle each of these challenges, whereupon an oleic acid nanodroplet containing upconversion materials was encapsulated with a silica shell. Ultimately, these nanocapsules (NCs) were durable enough to enable triplet fusion upconversion-facilitated volumetric three-dimensional (3D) printing. By encapsulating upconversion materials with silica and dispersing them in a 3D printing resin, photopatterning beyond the surface of the printing vat was made possible. Here, video protocols for the synthesis of upconversion NCs are presented for both small-scale and large-scale batches. The outlined protocols serve as a starting point for adapting this encapsulation scheme to multiple upconversion schemes for use in volumetric 3D printing applications.

Triplet fusion upconversion nanocapsules for volumetric 3D printing.

Three-dimensional (3D) printing has exploded in interest as new technologies have opened up a multitude of applications1-6, with stereolithography a particularly successful approach4,7-9. However, owing to the linear absorption of light, this technique requires photopolymerization to occur at the surface of the printing volume, imparting fundamental limitations on resin choice and shape gamut. One promising way to circumvent this interfacial paradigm is to move beyond linear processes, with many groups using two-photon absorption to print in a truly volumetric fashion3,7-9. Using two-photon absorption, many groups and companies have been able to create remarkable nanoscale structures4,5, but the laser power required to drive this process has limited print size and speed, preventing widespread application beyond the nanoscale. Here we use triplet fusion upconversion10-13 to print volumetrically with less than 4 milliwatt continuous-wave excitation. Upconversion is introduced to the resin by means of encapsulation with a silica shell and solubilizing ligands. We further introduce an excitonic strategy to systematically control the upconversion threshold to support either monovoxel or parallelized printing schemes, printing at power densities several orders of magnitude lower than the power densities required for two-photon-based 3D printing.

Ion Mobility Studies of Pyrroloquinoline Quinone Aza-Crown Ether-Lanthanide Complexes.

Lanthanide-dependent enzymes and their biomimetic complexes have arisen as an interesting target of research in the past decade. These enzymes, specifically, pyrroloquinoline quinone (PQQ)-bearing methanol dehydrogenases, efficiently convert alcohols to the respective aldehydes. To rationally design bioinspired alcohol dehydrogenation catalysts, it is imperative to understand the species involved in catalysis. However, given the extremely flexible coordination sphere of lanthanides, it is often difficult to assess the number and nature of the active species. Here, we show how such questions can be addressed by using a combination of ion mobility spectrometry, mass spectrometry, and quantum-chemical calculations to study the test systems PQQ and lanthanide-PQQ-crown ether ligand complexes. Specifically, we determine the gas-phase structures of [PQQH2]-, [PQQH2+H2O]-, [PQQH2+MeOH]-, [PQQ-15c5+H]+, and [PQQ-15c5+Ln+NO3]2+ (Ln = La to Lu, except Pm). In the latter case, a trend to smaller collision cross sections across the lanthanide series is clearly observable, in line with the well-known lanthanide contraction. We hope that in the future such investigations will help to guide the design and understanding of lanthanide-based biomimetic complexes optimized for catalytic function.

Halide Mixing Inhibits Exciton Transport in Two-dimensional Perovskites Despite Phase Purity.

Halide mixing is one of the most powerful techniques to tune the optical bandgap of metal-halide perovskites. However, halide mixing has commonly been observed to result in phase segregation, which reduces excited-state transport and limits device performance. While the current emphasis lies on the development of strategies to prevent phase segregation, it remains unclear how halide mixing may affect excited-state transport even if phase purity is maintained. Here, we study exciton transport in phase pure mixed-halide 2D perovskites of (PEA)2Pb(I1-x Br x )4. Using transient photoluminescence microscopy, we show that, despite phase purity, halide mixing inhibits exciton transport. We find a significant reduction even for relatively low alloying concentrations. By performing Brownian dynamics simulations, we are able to reproduce our experimental results and attribute the decrease in diffusivity to the energetically disordered potential landscape that arises due to the intrinsic random distribution of alloying sites.

Cardiovascular Events After Partner Bereavement, What is the Role of Low Dose Aspirin and Beta-Blockers?

Bereavement due to loss of a partner is one of the most stressful life events, often leading to adverse physiological responses. Spousal loss has been associated with an increased morbidity and mortality, particularly from cardiovascular disease. Use of aspirin and/or beta adrenergic blockers have previously been suggested to play a role in cardiovascular risk associated with early bereavement. However, the available literature regarding this topic is limited. In this review article, we explore the potential beneficial role of aspirin and beta blockers in early bereavement. Our systematic review suggests that most studies have found aspirin and beta blockers to be beneficial in preventing adverse cardiovascular outcomes associated with early bereavement. Further randomized controlled long-term studies are warranted with adequate sample size to clearly establish the role of these medications on cardiovascular disease in late bereavement.

Bright Luminescence by Combining Chiral [2.2]Paracyclophane with a Boron-Nitrogen-Doped Polyaromatic Hydrocarbon Building Block.

Novel BN-doped compounds based on chiral, tetrasubstituted [2.2]paracyclophane and NBN-benzo[f,g]tetracene were synthesized by Sonogashira-Hagihara coupling. Conjugated ethynyl linkers allow electronic communication between the π-electron systems through-bond, whereas through-space interactions are provided by strong π-π overlap between the pairs of NBN-building blocks. Excellent optical and chiroptical properties in racemic and enantiopure conditions were measured, with molar absorption coefficients up to ϵ=2.04×105  M-1 cm-1 , fluorescence quantum yields up to ΦPL =0.70, and intense, mirror-image electronic circular dichroism and circularly polarized luminescence signals of the magnitude of 10-3 for the absorption and luminescence dissymmetry factors. Computed glum,calcd. values match the experimental ones. Electroanalytical data show both oxidation and reduction of the ethynyl-linked tetra-NBN-substituted paracyclophane, with an overlap of two redox processes for oxidation leading to a diradical dication.

Efficient interlayer exciton transport in two-dimensional metal-halide perovskites.

Two-dimensional (2D) metal-halide perovskites are attractive for use in light harvesting and light emitting devices, presenting improved stability as compared to the more conventional three-dimensional perovskite phases. Significant attention has been paid to influencing the layer orientation of 2D perovskite phases, with the charge-carrier transport through the plane of the material being orders of magnitude more efficient than the interlayer transport. Importantly though, the thinnest members of the 2D perovskite family exhibit strong exciton binding energies, suggesting that interlayer energy transport mediated by dipole-dipole coupling may be relevant. We present transient microscopy measurements of the interlayer energy transport in the (PEA)2PbI4 perovskite. We find efficient interlayer exciton transport (0.06 cm2 s-1), which translates into a diffusion length that exceeds 100 nm and a sub-ps timescale for energy transfer. While still slower than the in-plane exciton transport (0.2 cm2 s-1), our results show that excitonic energy transport is considerably less anisotropic than charge-carrier transport for 2D perovskites.

Ultrafast and long-time excited state kinetics of an NIR-emissive vanadium(iii) complex I: synthesis, spectroscopy and static quantum chemistry.

In spite of intense, recent research efforts, luminescent transition metal complexes with Earth-abundant metals are still very rare owing to the small ligand field splitting of 3d transition metal complexes and the resulting non-emissive low-energy metal-centered states. Low-energy excited states decay efficiently non-radiatively, so that near-infrared emissive transition metal complexes with 3d transition metals are even more challenging. We report that the heteroleptic pseudo-octahedral d2-vanadium(iii) complex VCl3(ddpd) (ddpd = N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine) shows near-infrared singlet → triplet spin-flip phosphorescence maxima at 1102, 1219 and 1256 nm with a lifetime of 0.5 µs at room temperature. Band splitting, ligand deuteration, excitation energy and temperature effects on the excited state dynamics will be discussed on slow and fast timescales using Raman, static and time-resolved photoluminescence, step-scan FTIR and fs-UV pump-vis probe spectroscopy as well as photolysis experiments in combination with static quantum chemical calculations. These results inform future design strategies for molecular materials of Earth-abundant metal ions exhibiting spin-flip luminescence and photoinduced metal-ligand bond homolysis.

Vacancy control in acene blends links exothermic singlet fission to coherence.

The fission of singlet excitons into triplet pairs in organic materials holds great technological promise, but the rational application of this phenomenon is hampered by a lack of understanding of its complex photophysics. Here, we use the controlled introduction of vacancies by means of spacer molecules in tetracene and pentacene thin films as a tuning parameter complementing experimental observables to identify the operating principles of different singlet fission pathways. Time-resolved spectroscopic measurements in combination with microscopic modelling enables us to demonstrate distinct scenarios, resulting from different singlet-to-triplet pair energy alignments. For pentacene, where fission is exothermic, coherent mixing between the photoexcited singlet and triplet-pair states is promoted by vibronic resonances, which drives the fission process with little sensitivity to the vacancy concentration. Such vibronic resonances do not occur for endothermic materials such as tetracene, for which we find fission to be fully incoherent; a process that is shown to slow down with increasing vacancy concentration.

Strongly Red-Emissive Molecular Ruby [Cr(bpmp)2]3+ Surpasses [Ru(bpy)3]2.

Gaining chemical control over the thermodynamics and kinetics of photoexcited states is paramount to an efficient and sustainable utilization of photoactive transition metal complexes in a plethora of technologies. In contrast to energies of charge transfer states described by spatially separated orbitals, the energies of spin-flip states cannot straightforwardly be predicted as Pauli repulsion and the nephelauxetic effect play key roles. Guided by multireference quantum chemical calculations, we report a novel highly luminescent spin-flip emitter with a quantum chemically predicted blue-shifted luminescence. The spin-flip emission band of the chromium complex [Cr(bpmp)2]3+ (bpmp = 2,6-bis(2-pyridylmethyl)pyridine) shifted to higher energy from ca. 780 nm observed for known highly emissive chromium(III) complexes to 709 nm. The photoluminescence quantum yields climb to 20%, and very long excited state lifetimes in the millisecond range are achieved at room temperature in acidic D2O solution. Partial ligand deuteration increases the quantum yield to 25%. The high excited state energy of [Cr(bpmp)2]3+ and its facile reduction to [Cr(bpmp)2]2+ result in a high excited state redox potential. The ligand's methylene bridge acts as a Brønsted acid quenching the luminescence at high pH. Combined with a pH-insensitive chromium(III) emitter, ratiometric optical pH sensing is achieved with single wavelength excitation. The photophysical and ground state properties (quantum yield, lifetime, redox potential, and acid/base) of this spin-flip complex incorporating an earth-abundant metal surpass those of the classical precious metal [Ru(α-diimine)3]2+ charge transfer complexes, which are commonly employed in optical sensing and photo(redox) catalysis, underlining the bright future of these molecular ruby analogues.

Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(II) complexes.

Two closely related FeII complexes with 2,6-bis(1-ethyl-1H-1,2,3-triazol-4yl)pyridine and 2,6-bis(1,2,3-triazol-5-ylidene)pyridine ligands are presented to gain new insights into the photophysics of bis(tridentate) iron(ii) complexes. The [Fe(N^N^N)2]2+ pseudoisomer sensitizes singlet oxygen through a MC state with nanosecond lifetime after MLCT excitation, while the bis(tridentate) [Fe(C^N^C)2]2+ pseudoisomer possesses a similar 3MLCT lifetime as the tris(bidentate) [Fe(C^C)2(N^N)]2+ complexes with four mesoionic carbenes.

Rare-earth coordination polymers with multimodal luminescence on the nano-, micro-, and milli-second time scales.

We present a coordination polymer based on rare-earth metal centers and carboxylated 4,4'-diphenyl-2,2'-bipyridine ligands. We investigate Y3+, Lu3+, Eu3+, and a statistical mixture of Y3+ with Eu3+ as metal centers. When Y3+ or Lu3+ is exclusively present in the coordination polymer, biluminescence from the ligand is observed: violet emission from the singlet state (417 nm, 0.9 ns lifetime) and orange emission from the triplet state (585 nm, 76 ms (Y3+) and 31 ms (Lu3+)). When Eu3+ is present in a statistical mixture with Y3+, red emission from the Eu3+ (611 nm, ∼ 500 µs ) is observed in addition to the ligand emissions. We demonstrate that this multi-mode emission is enabled by the immobility of singlet and triplet states on the ligand. Eu3+ only receives energy from adjacent ligands. Meanwhile, in the broad inhomogeneous distribution of ligand energies, higher energy states favor singlet emission, whereas faster intersystem crossing in the more stabilized ligands enhances their contribution to triplet emission.

Chronic Systemic Inflammatory Skin Disease as a Risk Factor for Cardiovascular Disease.

Chronic systemic skin disease and cardiovascular disease are multisystem disorders which have been associated with each other for centuries. Recent research has strengthened this association, particularly in systemic inflammatory disease. Here we explore the current literature on psoriasis, hidradenitis suppurativa, lupus erythematosus, acanthosis nigricans, atopic dermatitis, and bullous pemphigoid. Psoriasis is a chronic inflammatory disorder that has been labeled as a risk-modifier for hyperlipidemia and coronary artery disease by the American College of Cardiology ACC lipid guidelines. Cardiovascular disease is also found at a significantly higher rate in patients with hidradenitis suppurativa and lupus erythematosus. Some associations have even been noted between cardiovascular disease and acanthosis nigricans, atopic dermatitis, and bullous pemphigoid. While many of these associations have been attributed to a shared underlying disease process such as chronic systemic inflammation and shared underlying risk factors, these dermatologic manifestations can help to identify patients at higher risk for cardiovascular disease.

Invasive Strategies for the Treatment of Pulmonary Embolism. Where Are We in 2020?

Pulmonary Embolism (PE) is the third most common cause of cardiovascular mortality in the United States, with 60,000-100,000 deaths per year following myocardial infarction and stroke. During the past 5 years, there has been an introduction of novel interventions as a result of a renewed interest in optimizing PE management, particularly among those individuals with more severe disease of hemodynamic significance. The cornerstone treatment for PE is anticoagulation. More aggressive alternatives have been considered for patients with intermediate and high-risk PE. In general, these options can be grouped into 3 different categories: systemic thrombolysis, catheter-directed interventions, and surgical embolectomy. Systemic thrombolysis has shown statistical benefit in several randomized trials for intermediate- and high-risk PE, however, this benefit has been offset by an elevated risk of major bleeding and intracerebral hemorrhage, limiting their use in clinical practice. Catheter-directed thrombolysis refers to catheter-directed injection of a thrombolytic drug directly into the pulmonary artery. Three interventional devices (EKOSonic endovascular system, FlowTriever embolectomy device and the Indigo thrombectomy system) have recently been cleared by the US Food and Drug Administration for marketing, and several others are in various stages of development. As of today, catheter-based interventions are limited to small randomized trials and single arm-prospective studies focused on short-term surrogate endpoints. Although single arm studies carry some value establishing the preliminary safety and effectiveness of these devices, they are not sufficient to stratify risk and guide clinical practice. Furthermore, no trials have been performed with enough power to assess potential mortality benefit with the use of catheter-directed thrombolysis or catheter-based embolectomy devices, hence treatment decisions continue to be influenced by individual risk of bleeding, the location of thrombus and operator expertise until additional evidence becomes available.

The Face Is the Mirror of the Soul. The Cardiovascular Physical Exam Is Not Yet Dead!

Cardiac pathology can be congenital or acquired with underlying genetic predispositions. In this era of medicine there is a concern that the comprehensive physical examination doctors prided themselves on is becoming a lost art. Research studies have also revealed a decline in physical examination skills. The full clinical cardiovascular examination is indeed quite complex and does take significant time to master. It is critical that physicians be competent in the physical exam. Not identifying subtle clinical findings leading to missed or delayed diagnosis which can lead to significant morbidity and mortality. In this paper we intend to highlight the clinical cardiovascular findings that may be detected on patients even before initiating the physical exam. The head and neck visual examination may be quite revealing.

Can Computed Fractional Flow Reserve Coronary CT Angiography (FFRCT) Offer an Accurate Noninvasive Comparison to Invasive Coronary Angiography (ICA)? "The Noninvasive CATH." A Comprehensive Review.

Invasive coronary angiography (ICA) serves as a very important tool in the diagnosis of coronary artery disease (CAD) and provides information for further intervention. Fractional Flow Reserve (FFR) at the time of ICA is the gold standard to analyze the hemodynamic and physiologic significance of moderate coronary stenosis. The dawn of coronary CT angiography (CTA) has helped in visualizing the anatomy of coronary arteries. Computed Fractional Flow Reserve (FFRCT) from such an imaging study shows promise in providing valuable data about physiology on top of the anatomy noninvasively; which can guide decision-making process for revascularization. This manuscript aims to review the accuracy of FFRCT obtained from a coronary CTA in the diagnosis of hemodynamically significant coronary artery stenosis and ruling out nonsignificant coronary artery stenosis when compared to the Gold standard of FFR obtained during ICA. We conducted a Medline search using various combinations of "FFRCT," "ICA" "noninvasive," "significant stenosis," and "CAD" to identify pivotal randomized trials published before May 1, 2020, for inclusion in this review. Concurrently, major practice guidelines, trial bibliographies, and pertinent reviews were examined to ensure inclusion of relevant trials. A consensus among the authors was used to choose items for narrative inclusion. The following section reviews data from pivotal trials to determine a noninvasive strategy in appropriate patients to accurately detect functionally significant stenosis. For these trials, the sensitivity, specificity, and accuracy are compared. Trials reviewed: CTA, FFRCT, ICA, CT-myocardial perfusion imaging. FFRCT is a novel noninvasive modality which localizes significant "ischemia-causing" stenosis (≤0.80) by means of crystal fluid dynamics eliminating the need for vasodilators. The analysis of FFRCT by DISCOVER FLOW, DeFACTO, NXT trials revealed high sensitivity, negative predictive value, and good accuracy. The ADVANCE registry showed significantly lower events of CV death or myocardial infarction with a negative FFRCT (>0.80 study). The PLATFORM trial showed significant reduction in negative ICA with negative FFRCT, thus ultimately reducing the number of unnecessary percutaneous coronary intervention. Decrease in healthcare costs was noted with FFRCT, decreasing downstream testing, and invasive procedures. FFRCT is a novel modality for analyzing significant stenosis in CAD noninvasively. The high sensitivity of this modality could make it a good rule out tool to avoid unnecessary intervention in physiologically insignificant lesions. Limitations of this modality include low specificity, double exposure to contrast, turnaround time, and upfront costs. Further query into this matter is warranted.

Unexpected discovery of calcium cryptates with exceptional stability.

A 2,2'-bipyridine-N,N'-dioxide-based cryptand has been found to exhibit exceptional apparent complex stability for Ca2+ and unusually shows very high selectivity for Ca2+ over trivalent lanthanoid cations. The calcium cryptate is kinetically inert to an extent that it even withstands competition experiments with a 77-fold excess of free DOTA ligand, which is currently the chelator with the highest formation constant for calcium.