Emission Channels Research Articles

Cooperation of ICT and intramolecular spirocyclization: Construction of versatile fluorescent probe visualizing triple organelles in three distinct channels

The cooperation and interplay among multiple organelles play essential roles in a variety of crucial biological and pathological procedures. Fluorescent probes enabling discriminative visualization of triple organelles with different emission colors were promising molecular tools to investigate organelles interaction network, which however were rarely reported. Herein, by cooperating the polarity-sensitive intramolecular charge transfer (ICT) mechanism and pH-responsible intramolecular reversible cyclization reaction, we have constructed a fluorescent probe to distinguish lipid droplets (LDs), mitochondria, and lysosomes in three distinct channels without crosstalk emission. The probe (Triorg) presented in ring-open form in lysosomes to emit red fluorescence, while kept in ring-close form in LDs and mitochondria but distinguish the two organelles based on their different polarity. As a result, Triorg discriminated LDs, mitochondria, and lysosomes with blue, green, and red emission channels, respectively. Particularly, Triorg enabled visualizing LDs accumulation and consumption with blue emission, and detecting mitochondrial dysfunction and lysosomal damages with decreased green and red emission, respectively. The lysosomal damage and LDs consumption induced by chlorpromazine (a drug) and phenylarsine oxide (a toxic substance) have been revealed. The amount, morphologies, and three-dimension distribution of the three organelles in live tissues were also successfully visualized with Triorg.

Combined dual-channel fluorescence depth sensing of indocyanine green and protoporphyrin IX kinetics in subcutaneous murine tumors.

Fluorescence sensing within tissue is an effective tool for tissue characterization; however, the modality and geometry of the image acquisition can alter the observed signal. We introduce a novel optical fiber-based system capable of measuring two fluorescent contrast agents through 2cm of tissue with simple passive electronic switching between the excitation light, simultaneously acquiring fluorescence and excitation data. The goal was to quantify indocyanine green (ICG) and protoporphyrin IX (PpIX) within tissue, and the sampling method was compared with wide-field surface imaging to contrast the value of deep sensing versus surface imaging. This was achieved by choosing filters for specific wavelengths that were mutually exclusive between ICG and PpIX and coupling these filters to two separate detectors, which allows for direct swapping of the excitation and emission channels by switching the on-time of each excitation laser between 780- and 633-nm wavelengths. This system was compared with two non-contact surface imaging systems for both ICG and PpIX, which revealed that the fluorescence depth sensing system was superior in its ability to resolve kinetics differences in deeper tissues that would normally be dominated by strong signals from skin and other surface tissues. Specifically, the system was tested using pancreatic adenocarcinoma tumors injected into murine models, which were imaged at several time points throughout tumor growth to its diameter. This demonstrated the system's capability to track longitudinal changes in ICG and PpIX kinetics that result from tumor growth and development, with larger tumors showing sluggish uptake and clearance of ICG, which was not observable with surface imaging. Similarly, PpIX was quantified, which showed slower kinetics over different time points, and was further compared with the wide-filed imager. These results were further validated through depth measurements in tissue phantoms and model-based interpretation. This fluorescence depth sensing system can be used to sample the interior blood flow characteristics by ICG sensing of tissue as deep as 20mm into the tissue with sensitivity to kinetics that are superior to surface imaging and may be combined with other imaging modalities such as ultrasound to provide guided deep fluorescence measurements.

S-curve bias optimization of navigation signals based on a pre-distortion method

Abstract Nonideal radio-frequency (RF) emission channels directly affect the quality of navigation signals. In particular, the deviation in the pseudo-range, caused by differences among the RF channels of multiple satellites, can decrease user positioning accuracy. Previous studies have primarily focused on designing pre-distortion filters to improve the performance of non-ideal RF channels in navigation signal generators. However, this study shows that using a pre-distortion filter alone limits the improvement of the S-curve bias because the constant-envelope character is compromised, and the nonlinearity of the high-power amplifier (HPA) becomes more pronounced. Applications that require better accuracy require require a smaller S-curve bias. This study proposes a method to compensate for the nonideal RF channel by using pre-distortion that considers both the nonlinear HPA and nonideal filter characteristics. The proposed method is validated through numerical analysis and simulations. The results show that the proposed method can reduce the S-curve bias across different receiver configurations. This study is a useful reference for improving the quality of navigation signals, particularly in terms of correcting the S-curve bias.

Simultaneous dual-colour labelling of mitochondria and lysosomes: An indolium-based approach

Fluorescence is a valuable tool for understanding mitochondria-lysosome interactions, which is central for unveiling their roles in health and disease. Herein, we describe novel indolium-based molecules for labelling mitochondria and lysosomes simultaneously with organelle-specific fluorescence properties. These probes readily enable clear distinction of mitochondria and lysosomes by combining confocal and two-photon fluorescence microscopy. Our results show that this unique behaviour relies on aggregation. The functioning of these probes is not compromised by mitophagy, allowing the visualisation of these organelles in separate emission channels by using a single fluorescent marker under all scenarios. Their enhanced experimental simplicity compared to using multiple dyes makes these novel compounds well-suited for automated screening applications within living cells.

Novel Colorimetric and Near-Infrared Ratiometric Fluorescent Probe for Sensing Cysteine in Food Samples, Plants, and Living Cells.

Cysteine (Cys) is a crucial biothiol that acts a significant function in food samples and biological systems, including plant roots and living cells. Hence, we developed a novel colorimetric and near-infrared ratiometric fluorescent probe (CT), composed of coumarin and tetrahydroacridine-conjugated indole salt, for the detection of Cys. Upon reaction with Cys, the probe undergoes a specific N-substitution reaction, resulting in a notable colorimetric change and a significant ratiometric fluorescent response in both visible and near-infrared emission channels. These dual-channel ratiometric fluorescence changes are completely independent, enabling the probe to obtain great selectivity, sensitivity, and exceptional detection accuracy. Leveraging these attributes, the probe was employed to provide accurate quantitative analysis of Cys in food samples. Furthermore, confocal imaging demonstrated that the probe could monitor both exogenous and endogenous Cys levels in living cells and track Cys changes in plant roots under heavy metal stress. This work presents a dependable and accurate imaging solution for tracking and identifying Cys of real food, plants, and living cells.

Emission spectrum and photon statistics in cavity-QED system under incoherent pumping

The emission spectrum is an important tool for studying the properties and interactions of matter. By comparing analytical and numerical solutions, we validate the applicability and limitations of the low-excitation approximation. Here we show that even with a moderate pumping rate, rich multiple peaks can be observed in the emission spectrum which is the result of excitation of higher dressed rungs. Moreover, we find distinct photon distributions in the steady state under different pumping and coupling conditions and the physical mechanisms behind these phenomena are also illustrated. Additionally, we also show that the interference between the emission channels of the emitter and cavity can result in asymmetry of the emission spectrum of the whole system even if the emitter is resonant with the cavity field. Our findings can help in understanding the nonlinear characteristics and photon statistics in the cavity-QED systems.

Transient Leakage Electroluminescence of Quantum-Dot Light-Emitting Diodes.

Parasitic emission or leakage emission caused by electron leakage to a hole transport layer in quantum-dot light-emitting diodes (QLEDs) critically impacts device efficiency and operational stability. The buildup dynamics of such emission channels, however, was insufficiently researched. Herein, we investigate transient electroluminescence dynamics of leakage emission in red/green/blue (R/G/B) QLEDs and reveal notable contrast for R and G. In RQLEDs, leakage emission exhibits delayed turning-on than primary emission, which is attributed to much slower filling up from lower-energy electron states and the initial quenching by nonradiative recombination with trapped holes. For GQLEDs, leakage emission turns on much more concurrently, and emission preferably starts from higher energy states. For R/G QLEDs, under varied offset voltage modulation, the current efficiency of primary emission is invert-correlated to leakage emission, reconfirming leakage emission as a loss indicator.

Interference between multipolar two-photon transitions in quantum emitters near plasmonic nanostructures

In the vicinity of plasmonic nanostructures that support highly confined light fields, spontaneous emission processes, such as two-photon spontaneous emission (TPSE), exhibit higher-order multipolar emission pathways beyond the dipolar one. These multipolar emission channels occur simultaneously and can interfere with each other. We develop a novel framework that computes these interference effects for TPSE of a quantum emitter close to an arbitrary nanostructure. The model is based on the computation of Purcell factors that can be calculated with conventional electromagnetic simulations, which avoids complex analytic calculations for the environment. For a transition of a hydrogen-like emitter close to a graphene nanotriangle, we demonstrate a breakdown of the dipolar selection rule in the TPSE process. This breakdown is due to a huge enhancement of the two-electric dipole (2ED) and of the two-electric quadrupole (2EQ) transitions. We observe an important interference between these multipolar transitions, as it increases the total rate by 67%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$67 \\, \\%$$\\end{document}. In the end, our framework is a complete tool to design emitters and nanostructures for TPSE, where the exploitation of previously ignored interference effects provides an additional degree of freedom, for example to boost desired transitions and to supress undesirable ones.

Aggregation-induced emission sensors based on sulfide-containing naphthalimides for imaging latent fingerprints

Aggregation-induced emission luminogens have attracted extensive attention due to their wide applications. In this work, two naphthalimide derivatives (NIS1 and NIS2) were designed and synthesized which could be used as the solid imaging agents for their AIE effects. In both molecules, V-shape structures were introduced to construct de-planar conjugated systems using O and N atoms as the centers. The center atoms tune the emissions of these molecules in deep blue (411∼436 nm, NIS1) and yellow-green (521∼540 nm, NIS2) regions in organic solvents with different polarity. NIS1 and NIS2 exhibit AIE-active fluorescence in their aqueous solutions (545 nm for NIS1 and 600 nm for NIS2). Further studies on their photophysical properties indicate that the introduction of methylmercapto group (-SCH3) can enhance the AIE intensities compared to their mimic. DFT calculation was performed to explore the different transitions occurred in these compounds. At last, NIS1 and NIS2 were successfully fabricated as the solid imaging agents and applied to the latent fingerprints imaging on varied substances. A highlight in this work is these imaging agents can work well on the scene with high background fluorescence by optimizing the excitation wavelength and selecting suitable emission channel.

Modulation of AIE and Intramolecular Charge Transfer of a Pyrene-Based Probe for Discriminatory Detection and Imaging of Oligomers and Amyloid Fibrils.

Oligomers and amyloid fibrils formed at different stages of protein aggregation are important biomarkers for a variety of neurodegenerative diseases including Alzheimer's and Parkinson's diseases. The development of probes for the sensitive detection of oligomeric species is important for early stage diagnosis of amyloidogenic diseases. Many small molecular dyes have been developed to probe the dynamic growth of amyloid fibrils. However, there is a lack of discriminatory detection strategies to monitor the dynamics of both oligomers and amyloid fibrils based on the differential modulation of the photophysical properties of a single dye. Here we report a pyrene-based intramolecular charge transfer (ICT) dye with large Stokes shifted red-emitting aggregation induced emission (AIE) for monitoring the dynamic populations of both oligomers and fibrils during the aggregation of hen egg white lysozyme (HEWL) protein. At the early stage of protein aggregation, the accumulation of HEWL oligomers results in a rapid and substantial increase in the red AIE intensity at 660 nm. Later, as the oligomers transform into mature fibrils, the dye exhibits a distinct photophysical change. Binding of the dye to HEWL fibrils strongly suppresses the red AIE and enhances ICT emission. This is evidenced by a gradual decrease in the AIE intensity (∼660 nm) and an increase in LE (∼490 nm) and ICT (∼540 nm) emission intensities during the later stages of protein aggregation. Thus, the dye provides simultaneous measurements of the population dynamics of both HEWL oligomers and fibrils during protein aggregation based on the discriminatory modulation of AIE and ICT of the dye. The dye also enables imaging of both HEWL oligomers and fibrils simultaneously using different emission channels in super-resolution confocal fluorescence microscopy.

Photophysical Properties of Submicrometer Ultrathin Perovskite Single-Crystal Films.

Organic-inorganic hybrid perovskite (OIHP) has attracted a great deal of interest with respect to diverse optoelectronic devices. However, the photophysical properties of the OIHP require further understanding because most of the investigations have been conducted with polycrystalline perovskites, which contain high-density structural defects. Here, diverse photophysical properties, including structural characterization, spectroscopic features, and photoexcited products, are studied in submicrometer CH3NH3PbBr3 ultrathin single-crystal (UTSC) films. Unlike polycrystalline films and large single crystals, the UTSC film provides a unique platform for studying spectroscopic characteristics of single-crystal perovskites. Compared with the polycrystalline film, the UTSC film presents an atomically flat morphology and near-perfect lattice with a lower defect density, leading to an isotropic system that can be applied in the construction of high-performance optoelectronic devices. Furthermore, a long lifetime emissive channel assigned to the trion is indicated, which is scarcely found in perovskite polycrystalline films. Our results profoundly improve our understanding of their photophysical properties and expand the horizons for perovskite materials in photonic applications.

Mass Cycle and Dynamics of a Virtual Quiescent Prominence

The mass cycle of solar prominences or filaments is still not completely understood. Researchers agree that these dense structures form by coronal in situ condensations and plasma siphoning from the underlying chromosphere. In the evaporation–condensation model siphoning arises due to evaporation of chromospheric plasma from localized footpoint heating, but this is challenging to justify observationally. Here, we simulate the reconnection–condensation model at extreme resolutions down to 20.8 km within a three-dimensional (3D) magnetohydrodynamic coronal volume. We form a draining, quiescent prominence and associated coronal rain simultaneously. We show that thermal instability—acting as a trigger for local condensation formation—by itself drives siphoning flows from the low corona without the need of any localized heating. In addition, for the first time, we demonstrate through a statistical analysis along more than 1000 magnetic field lines that cold condensations give rise to siphoning flows within magnetic threads. This siphoning arises from the strong pressure gradient along field lines induced by thermal instability. No correlation is found between siphoning flows and the prominence mass, making thermal instability the main in situ mass-collection mechanism. Our simulated prominence drains by gliding along strongly sheared, asymmetric, dipped magnetic arcades, and develops natural vertical fine structure in an otherwise horizontal magnetic field due to the magnetic Rayleigh–Taylor instability. By synthesising our data, our model shows remarkable agreement with observations of quiescent prominences such as its dark coronal cavity in extreme-ultraviolet emission channels, fine-scale vertical structure, and reconnection outflows, which, for the first time, have been self-consistently obtained as the prominence evolves.

Method for Assessing Noise Quality Based on Entropy Quality Factor

The work analyzes the existing approaches to solving the problem of a comprehensive study of the qualitative characteristics of side electromagnetic emission generators. In addition, methods and means of information leakage through the channels of side electromagnetic emission are considered, which make it possible to evaluate the effectiveness of noise generators. Electromagnetic emission can propagate in almost all environments. Side electromagnetic emission is one of the effective ways to protect computer equipment from information leakage through the channel of side electromagnetic emissions and interference. The masking noise is generated by the noise generator, and the quality factor of the masking noise is the quality factor of the entropy noise. In addition, measurements of masking noise interference using a spectrum analyzer and an oscilloscope are carried out and a method for estimating the entropy noise quality coefficient (ENQC) is proposed. The calculated value of the entropy noise quality factor is compared with the normalized value set for this type of noise generator. The novelty of the work is the development of a new method for assessing the quality of masking noise interference, based on the calculation of the entropy quality coefficient, as well as the development of software for automating the calculation. The study of the quality characteristics of the noise generator (NG) taking into account the design of a mock-up sample of the device, which is a complex work. In turn, based on the results obtained, it is possible to develop specialized automated tools for assessing the quality of masking noise interference.

Ground‐Based Far Infrared Emissivity Measurements Using the Absolute Radiance Interferometer

AbstractFar infrared (FIR) emission from the Earth's polar regions has become an area of increasing scientific interest and value. FIR emission is important for understanding Earth's radiative balance and improving global climate models, especially in rapidly changing Arctic conditions. Far‐infrared emission from Earth is not currently being monitored from space, except as part of broadband emission channels of Earth radiation budget measurements like those from the CERES project, and only limited measurements in the FIR spectrum exist. The Absolute Radiance Interferometer (ARI), developed as a prototype of the infrared spectrometer for CLARREO at the University of Wisconsin‐Madison, Space Science and Engineering Center, measures absolute spectrally resolved infrared (IR) radiance from 200 to 2,000 cm−1 (or 5–50 μm) at 0.5 cm−1 resolution with high accuracy (<0.1 K 3‐sigma brightness temperature at scene temperature). This instrument was taken into the field in Madison, Wisconsin, USA, during the winters of 2021 and 2022, where the weather can reach polar‐like conditions to measure high spectral resolution radiances of various sample types. Sample materials included water, snow, ice, evergreen leaves, dry grass, and sand, all characteristic of high latitude regions. Radiances collected from both a sky view and the sample view in clear‐sky conditions were used to retrieve FIR emissivity. This paper describes the ARI instrument configuration and capability for ground‐based measurements in the FIR region, and documents retrieved emissivities of various analyzed samples. The retrieved emissivity results are publicly available, and comparisons are made to simulated emissivity estimates.

Structural formation yield of GeV centers from implanted Ge in diamond

In order to study the structural formation yield of germanium-vacancy (GeV) centers from implanted Ge in diamond, we have investigated its lattice location by using the β − emission channeling technique from the radioactive isotope 75Ge (t 1/2 = 83 min) produced at the ISOLDE/CERN facility. 75Ge was introduced via recoil implantation following 30 keV ion implantation of the precursor isotope 75Ga (126 s) with fluences around 2 × 1012–5 × 1013 cm−2. While for room temperature implantation fractions around 20% were observed in split-vacancy configuration and 45% substitutional Ge, following implantation or annealing up to 900 °C, the split-vacancy fraction dropped to 6%–9% and the substitutional fraction reached 85%–96%. GeV complexes thus show a lower structural formation yield than other impurities, with substitutional Ge being the dominant configuration. Moreover, annealing or high-temperature implantation seem to favor the formation of substitutional Ge over GeV. Our results strongly suggest that GeV complexes are thermally unstable and transformed to substitutional Ge by capture of mobile carbon interstitials, which is likely to contribute to the difficulties in achieving high formation yields of these optically active centers.

Dual‐Mode Thermal Responses in Red and Near‐Infrared Emission Channels via Manipulating Cross Relaxations

AbstractLead‐free double perovskites with multi‐mode emission characters are highly desired for optoelectronic devices. Herein, dual‐mode thermal responses with low thermal quenching in the red emission channel and high thermal quenching in the near‐infrared (NIR) channel are achieved in a holmium‐based double perovskite (Cs2NaHoCl6). The temperature‐dependent emission is modulated by manipulating three cross relaxations of CR1 (5F4, 5I7) → (5F5, 5I6), CR2 (5S2, 5I8) → (5F5, 5I7), and CR3 (5F5, 5F5) → (5I7, 5G4) through adjusting the concentration of Ho3+. The difference in thermal response between the red and NIR emissions becomes more pronounced with a higher concentration of Ho3+ up to 100%, while the two emissions show almost the same thermal quenching behavior when the Ho3+ concentration is below 20%. To demonstrate their applications, a thermal‐responsive dual‐mode information encryption system and a NIR emitting LED with night vision capacity are fabricated using the prepared samples. This study provides a new approach for thermal quenching regulation in rare‐earth‐based lead‐free perovskites and illustrates their potential in lighting, anti‐counterfeiting, and sensing applications.

Controlling the bandwidth of high harmonic emission peaks with the spectral polarization of the driver.

We demonstrate a high harmonic-generation scheme that offers control over the bandwidth of the spectral peaks. The scheme uses a vectorial two-color driver with close central frequencies, generated by spectrally splitting a linearly polarized input femtosecond-duration laser pulse and subsequently recombining the two halves after their polarizations are made cross-elliptical and counter-rotating. This results in the generation of new emission channels that coalesce into broad odd-integer HHG peaks, the bandwidth of each being proportional to the frequency difference between the two colors, to the harmonic order and inversely proportional to the driver fields' ellipticities. Peak broadening to the extent that a supercontinuum is formed is also demonstrated. This source will find use in HHG applications benefiting from high-flux broadband extreme ultraviolet radiation, such as attosecond transient absorption spectroscopy.

Bias-Free Access to Orbital Angular Momentum in Two-Dimensional Quantum Materials.

The demonstration of a topological band inversion constitutes the most elementary proof of a quantum spin Hall insulator (QSHI). On a fundamental level, such an inverted band gap is intrinsically related to the bulk Berry curvature, a gauge-invariant fingerprint of the wave function's quantum geometric properties in Hilbert space. Intimately tied to orbital angular momentum (OAM), the Berry curvature can be, in principle, extracted from circular dichroism in angle-resolved photoemission spectroscopy (CD-ARPES), were it not for interfering final state photoelectron emission channels that obscure the initial state OAM signature. Here, we outline a full-experimental strategy to avoid such interference artifacts and isolate the clean OAM from the CD-ARPES response. Bench-marking this strategy for the recently discovered atomic monolayer system indenene, we demonstrate its distinct QSHI character and establish CD-ARPES as a scalable bulk probe to experimentally classify the topology of two-dimensional quantum materials with time reversal symmetry.

A triphenylamine-thiophene-based fluorescent probe for the dual-channel detection and imaging of hypochlorite and viscosity in live cells

In this research, a new triphenylamine-thiophene-based fluorescent probe, denoted as TTD, was constructed for simultaneous detection of viscosity and hypochlorite (ClO−) with dual-response signals. The hindrance of intramolecular bond rotation within TTD in a high-viscosity environment turns on the probe’s emission at 600 nm, resulting in strong red fluorescence. Simultaneously, the oxidation of the imine moiety to the aldehyde product, induced by ClO−, leads to substantial emission enhancement at 460 nm, generating vivid blue fluorescence. As a result, TTD can be employed for the dual-color visualization of changes in viscosity and ClO− levels, demonstrating good selectivity. TTD has been applied to image the elevated level of viscosity induced by nystatin, rotenone or erastin as well as exogenously introduced ClO− in living cells. Importantly, from two independent emission channels, TTD is capable of monitoring both ClO− and viscosity fluctuations within live cells during the inflammatory response triggered by lipopolysaccharide (LPS).

Extreme mass-ratio inspirals as probes of fundamental dipoles

Even if globally neutral, in various scenarios compact objects can have a nonvanishing dipole moment. Examples include neutron stars with magnetic dipoles, black-hole microstates in the string-theory fuzzball scenario, and classical black holes in modified theories of gravity with spin-induced scalarization or Lorentz-violating terms. A fundamental dipole moment would give rise to rich phenomenology, for example, to intrinsic precession and extra emission channels in binary systems. We show that extreme mass-ratio inspirals (EMRIs) detectable by future gravitational-wave interferometers allow us to study a fundamental dipole on the secondary object in a model-agnostic fashion. By developing a general model for a fundamental scalar dipole, we compute the extra flux associated with it. This effect is suppressed by the square of the mass ratio relative to the case of fundamental charges, making its detection with EMRIs very challenging for the typical dipole moments predicted in various models. On the other hand, for the same reason, the impact of an extra dipole for constraints on extra fundamental charges is likely negligible, making the latter constraints more robust. Published by the American Physical Society 2024