Multimodal Emission Research Articles

Study of multimodal light emissions from Pr3+/Yb3+ doped NaLa(MoO4)2 phosphors for optoelectronic devices and plant-growth applications.

Recent advancements in materials design have driven the scientific community to explore phosphor materials for multifunctional applications. This study presents the multimodal light emission (downshifting - DS, quantum cutting - QC, and upconversion - UC) from Pr3+/Yb3+ activated NaLa(MoO4)2 phosphors for multifunctional applications. Under blue (449 nm) and NIR (980 nm) excitation, co-doped phosphors emit visible light through DS and UC processes caused by different f-f transitions of Pr3+ ions. Additionally, when the co-doped samples are excited with blue light, they emit a near-infrared (NIR) light band ranging from 900 to 1050 nm. This is caused by the f-f transition of Yb3+ resulting from energy transfer from a single Pr3+ ion to a pair of Yb3+ ions through the QC process. Concurrently, in-depth investigations were conducted to understand the concentration and thermal quenching mechanism. Firstly, the applicability of phosphors in optical thermometry using the luminescence intensity ratio (LIR) technique was explored, with the maximum relative sensitivity of 0.41% K-1 (448 K). A phosphor-coated LED (pc-LED) was constructed by coupling NaLa0.97Pr0.03(MoO4)2 with a blue LED chip (InGaN). Furthermore, based on the observed optical properties of the prepared phosphor, its application in improving the photovoltaic performance of solar cells and indoor plant applications is systematically discussed.

The POINTER Imaging baseline cohort: Associations between multimodal neuroimaging biomarkers, cardiovascular health, and cognition.

The U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (U.S. POINTER) is evaluating lifestyle interventions in older adults at risk for cognitive decline and dementia. Here we characterize the baseline data set of the POINTER Imaging ancillary study. Participants underwent health and cognitive assessments and neuroimaging with multimodal positron emission tomography (PET) (beta-amyloid [Aβ] and tau) and magnetic resonance imaging (MRI). Framingham risk score (FRS) was used to quantify cardiovascular disease (CVD) risk. A total of 1052 participants (31% from underrepresented ethnoracial groups) were enrolled. Compared to Aβ-, Aβ+ (29%) participants were older, had higher apolipoprotein E (APOE) ε4 carriage rate and white matter hyperintensity volume, and greater temporal tau. FRS was related to MRI measures, but not AD biomarkers. FRS and tau had independent effects on cognition. In this heterogenous, at-risk cohort, CVD risk was related to more abnormal brain structure and poorer cognition, representing a putative non-AD (Alzheimer's disease) pathway to brain injury and cognitive decline. ·The U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (U.S. POINTER) cohort is enriched for cardiovascular disease (CVD) and poor lifestyle ·POINTER Imaging collected multimodal neuroimaging data in this unique, at-risk cohort ·Amyloid burden was related to age, apolipoprotein E (APOE) ε4 carriage, and measures of disease progression ·Associations between amyloid and tau, and tau and cognition, were relatively weak ·CVD risk and tau pathology were independently related to memory.

Machine learning based damage identification in SiC/SiC composites from acoustic emissions using autoencoders

Developing the ability to leverage machine learning (ML) to identify damage mechanisms in heterogeneous materials from their acoustic emissions (AE) has wide-reaching ramifications for multi-modal experimentation. It would allow researchers to augment damage triangulation, lifetime prediction, and high-resolution optical studies with complementary mechanism-informed data streams. However, developing this capability hinges on the collection of ground truth acoustic libraries from damage in realistic geometries. Due to time and monetary considerations, there is a dearth of ground truth libraries which can be used to robustly characterize ML mechanism identification frameworks. Addressing this gap, we present a multi-modal acoustic emission and x-ray computed tomography study where AE is gathered, and subsequently labeled, from SiC/SiC unidirectional composites under monotonic tension. This library is used to demonstrate that acoustic signals from early fiber breaks are obscured by matrix cracking. A first-order micromechanical model is used to explain the origin of this obscuring effect, and identify fundamental limitations of unsupervised frameworks. An autoencoder-based anomaly detector approach is used for the first time to overcome these limitations, additionally demonstrating that the frequency distribution of fiber break acoustic signals is narrow. Implications of these findings for enhanced multi-modal testing and online health monitoring are discussed, and strategies for implementation of supervised damage mechanism identification frameworks are proposed.

Characterization of quantum dot-like emitters in programmable arrays of nanowrinkles of 1L-WSe2

When combined with nanostructured substrates, two-dimensional semiconductors can be engineered with strain to tailor light–matter interactions on the nanoscale. Recently, room-temperature nanoscale exciton localization with controllable wrinkling in 1L-WSe2 was achieved using arrays of gold nanocones. Here, the characterization of quantum dot-like states and single-photon emitters in the 1L-WSe2/nanocone system is reported. The nanocones induce a wide range of strains, and as a result, a diverse ensemble of narrowband, potential single-photon emitters is observed. The distribution of emitter energies reveals that most reside in two spectrally isolated bands, leaving a less populated intermediate band that is spectrally isolated from the ensembles. The spectral isolation is advantageous for high-purity quantum light emitters, and anti-bunched emission from one of these states is confirmed up to 25 K. Although the spatial distribution of strain is expected to influence the orientation of the transition dipoles of the emitters, multimodal emission polarization anisotropy and atomic force microscopy reveal that the macroscopic orientation of the wrinkles is not a good predictor of dipole orientation. Finally, the emission is found to change with thermal cycling from 4 to 290 K and back to 4 K, highlighting the need to control factors such as temperature-induced strain to enhance the robustness of this quantum emitter platform. The initial characterization here shows that controlled nanowrinkles of 1L-WSe2 generate quantum light in addition to uncovering potential challenges that need to be addressed for their adoption into quantum photonic technologies.

The single near-infrared upconversion luminescence of a novel KYb (MoO4)2: Er3+ phosphor for the temperature sensing

The rare earth doping upconversion luminescence (UCL) materials exhibit multimodal emission, which has huge potential applications. However, it is still a difficult problem to obtain a single emission by modulating UCL, especially the modulation of single red light and single near-infrared light. In this work, we report a novel UCL KYb (MoO4)2: Er3+ phosphor, which can achieve a single near-infrared emission (804 nm) under rare earth Er3+ doping. Its pure phase was successfully prepared by high-temperature solid-state method, and its optimal Er3+ doping concentration was found to be 0.1 %. Excited at 980 nm laser, KYb (MoO4)2: Er3+ exhibit a single near-infrared UCL attributed to the 4I9/2 → 4I15/2 transition of Er3+ ions. To further explain its UCL mechanism, the power dependence, ultraviolet-visible-near-infrared absorption spectrum, excitation spectrum and emission spectrum of KYb (MoO4)2: Er3+ was measured. Due to the excellent near-infrared emission, the temperature-dependent UCL properties of the KYb (MoO4)2: Er3+ material is investigated in the temperature range from 298 K to 673 K. The linear relationship between the UCL and the temperature, And the sensitivity of KYb (MoO4)2: Er3+ phosphor reaches the maximum value at 673 K, which is 0.0078 K−1. The single near-infrared luminescence with good penetrability and large sensitivity makes KYb (MoO4)2: Er3+ have a promising application prospect in the fields of non-contact temperature sensing and bioimaging.

Dynamic manipulation of multimodal emission in Er3+-activated non-core–shell structure for optical thermometry and information security

Dynamic manipulation of multimodal emission in Er3+-activated non-core–shell structure for optical thermometry and information security

Focal acetylcholinergic modulation of the human midcingulo-insular network during attention: Meta-analytic neuroimaging and behavioral evidence.

The basal forebrain cholinergic neurons provide acetylcholine to the cortex via large projections. Recent molecular imaging work in humans indicates that the cortical cholinergic innervation is not uniformly distributed, but rather may disproportionately innervate cortical areas relevant to supervisory attention. In this study, we therefore reexamined the spatial relationship between acetylcholinergic modulation and attention in the human cortex using meta-analytic strategies targeting both pharmacological and non-pharmacological neuroimaging studies. We found that pharmaco-modulation of acetylcholine evoked both increased activity in the anterior cingulate and decreased activity in the opercular and insular cortex. In large independent meta-analyses of non-pharmacological neuroimaging research, we demonstrate that during attentional engagement these cortical areas exhibit (1) task-related co-activation with the basal forebrain, (2) task-related co-activation with one another, and (3) spatial overlap with dense cholinergic innervations originating from the basal forebrain, as estimated by multimodal positron emission tomography and magnetic resonance imaging. Finally, we provide meta-analytic evidence that pharmaco-modulation of acetylcholine also induces a speeding of responses to targets with no apparent tradeoff in accuracy. In sum, we demonstrate in humans that acetylcholinergic modulation of midcingulo-insular hubs of the ventral attention/salience network via basal forebrain afferents may coordinate selection of task relevant information, thereby facilitating cognition and behavior.

Tailor Traps in Bi3+-Doped NaGdGeO4 Phosphors by Introducing Eu3+ Ions to Switch Multimodal Phosphorescence Emission.

Featured with a tunable excitation/emission wavelength and excellent physicochemical stability, inorganic fluorescent materials are widely used in the fields of anti-counterfeiting. Here, we design a multi-stimuli-responsive dynamic fluorescence and phosphorescence anti-counterfeiting material by introducing Eu3+ ions in NaGdGeO4: Bi3+ to tailor the trap structure. The photoluminescence (PL), long persistent luminescence (LPL), and photo-stimulated luminescence (PSL) colors of NaGdGeO4: Bi3+, Eu3+ can be switched by varying the excitation modes (ultraviolet, near infrared, and X-ray light). Especially, the LPL and PSL colors of NaGdGeO4: Bi3+, Eu3+ vary with increasing decay and stimulation times. In addition, X-ray excitation ensures the specificity of the luminescence of NaGdGeO4: Bi3+, Eu3+ compared with ultraviolet excitation. This rapidly-changing-color fluorescent material offers the possibility of sophisticated anti-counterfeiting applications in the future.

Multimode Emission from Lanthanide‐Based Metal–Organic Frameworks for Advanced Information Encryption

AbstractAlthough remarkable progress on luminescent materials is made in advanced optical information storage and anti‐counterfeiting applications, many challenges still remain in these fields. Currently, most luminescent materials are based on a single photoluminescent model that can be easily imitated by substitutes. In this work, a series of multimodal emission lanthanide‐based metal–organic frameworks (MOFs) are developed, where they emit red and green light originating from Eu3+ and Tb3+ under ultraviolet light irradiation. Meanwhile, under 980 nm near‐infrared laser irradiation, these MOFs show cyan upconversion cooperative luminescence derived from Yb3+ and characteristic upconversion luminescence from lanthanide activators (Eu3+, Tb3+, or Ho3+), respectively. Based on the integrated optical functionality, the functional information storage applications are successfully designed, which indicates that multimodal emission features can be easily detected under ultraviolet lamps (254 or 393 nm) or 980 nm near‐infrared laser. And, the unique optical features show a high level of security in the advanced information storage application, which would be sufficiently complex to be forged.

Probing multimodal light emission from Tb3+/Yb3+-doped garnet nanophosphors for lighting applications.

Herein we report the solution-combustion-method-synthesized Tb3+- and Tb3+/Yb3+-doped Gd3Ga5O12 nanophosphors, which possess luminescent and magnetic properties. The phase formation/crystal structure, and morphology of the prepared nanophosphors are studied using X-ray diffraction (XRD)/Raman spectroscopy and a field emission scanning electron microscope (FE-SEM), respectively. Tb3+/Yb3+-doped phosphor samples exhibit green emission with an intense band around 544 nm through downshifting (DS) and upconversion (UC) processes because of the 5D4 → 7F5 transition of Tb3+. In addition to this visible emission, these samples also show a NIR emission band around 1024 nm via the quantum cutting (QC) process due to the 2F5/2 → 2F7/2 transition of Yb3+. Emission decay measurements of the 5D4 → 7F5 transition of Tb3+ are performed to obtain the rate of energy transfer from Tb3+ to nearby Yb3+. Furthermore, using this energy transfer, the quantum cutting efficiencies were estimated. For their practical application, a selected sample was used to fabricate a LED device by combining the sample with a UV-C LED (274 nm). The obtained results, such as the activation energy (∼0.20 eV) and the high CRI value (78), suggest that the prepared sample can be utilized as a green-light-emitting agent in phosphor-coated (pc) WLEDs.

Strategy to probe multimodal light emissions from Eu3+/Yb3+ activated garnet nanophosphors for LED devices and solar cell applications.

This study investigates multimodal light emission from an Eu3+/Yb3+ activated Y3Ga5O12 (YGG) nanophosphor synthesized using a low temperature solution combustion method. The prepared sample possesses a cubic phase and an Ia3̄d space group and this is confirmed with X-ray diffraction and Rietveld refinement analysis. The synthesized sample shows orange-red emission bands because of the f-f transitions of Eu3+ under UV (393 nm) and NIR (980 nm) excitations via downshifting (DS) and upconversion (UC) processes, respectively. Upon UV (393 nm) excitation of the sample, the Eu3+ ions absorb this energy and then transfer it to a neighboring pair of Yb3+ ions giving NIR emission (900-1100 nm) corresponding to the 2F5/2 → 2F7/2 transition of Yb3+. The energy transfer from a single Eu3+ ion to a pair of Yb3+ ions is possible because of the quantum cutting (QC) process and this energy transfer efficiency is found to increase with the increasing concentration of the Yb3+. The quantitative estimation of energy transfer and internal quantum cutting efficiency is determined by measuring the decay kinetics. An activation energy of 0.25 eV indicates the good thermal stability of the sample. Furthermore, samples are suitable for use in practical applications in lighting devices by combining them with the near-ultraviolet (NUV; InGaN) chip. The fabricated LED device shows stability with the driving current flow values. Studies indicate that the present nanophosphor could be useful for display devices, and in enhancing the spectral conversion efficiency of the solar cells.

Acoustic emission monitoring and damage evaluation of bi-adhesive joint patch-repaired composites

Tensile behavior and failure modes of the bonding interface of the repaired composite were investigated in combination with nondestructive testing techniques. The carbon nanotube-modified two-sided adhesive repair method improved the repair effect, while different failure modes of patch fracture and patch debonding were observed. The condition monitoring and damage pattern identification of the composites were performed in a non-destructive manner using acoustic emission and digital image correlation techniques. Analysis of acoustic emission signals was used to discriminate between matrix/patch cracking and bonding layer failure. The clustering analysis of the characteristic parameters is corroborated with the time-frequency domain analysis of the signal waveform to discriminate the interfacial damage of the patch debonding damage behavior. It was found that the double adhesive repair with the modified adhesive layer placed at the edge showed better repair results. In contrast, the repair pattern with the modified adhesive layer in the middle is relatively poor, and the patch debonding behavior corresponding to the multimodal acoustic emission signal at the high peak frequency is observed.

Multi-modal tomographic imaging system for poolside characterization of nuclear test fuels: Design considerations and studies

Testing and qualification of advanced nuclear fuels involve an iterative process of prototyping, in-pile irradiation testing, and in/ex situ examination. Fuel restructuring and fission product migration during burnup are among the most important aspects of fuel evolution and affect several important performance characteristics (e.g., heat removal, accident tolerance, and fission product retention). Poolside nondestructive characterization techniques provide fuel developers with tools to understand fuel evolution at different time points of burnup. A design for a compact, submersible, and multi-modal (transmission and emission) gamma-ray tomography system for imaging irradiated nuclear fuel is presented herein. Detector selection, collimator geometry and fabrication, mechanical design, imaging protocol, and acquisition protocol are discussed. Modeling calculations showed that sub-millimeter resolution could be achieved in a matter of hours in both transmission and emission tomography images. Several design compromises and fabrication challenges are discussed to further the development of future submersible gamma-ray tomography instruments.

ISA-Net: Improved spatial attention network for PET-CT tumor segmentation

Background and Objective: Achieving accurate and automated tumor segmentation plays an important role in both clinical practice and radiomics research. Segmentation in medicine is now often performed manually by experts, which is a laborious, expensive and error-prone task. Manual annotation relies heavily on the experience and knowledge of these experts. In addition, there is much intra- and interobserver variation. Therefore, it is of great significance to develop a method that can automatically segment tumor target regions. Methods: In this paper, we propose a deep learning segmentation method based on multimodal positron emission tomography-computed tomography (PET-CT), which combines the high sensitivity of PET and the precise anatomical information of CT. We design an improved spatial attention network(ISA-Net) to increase the accuracy of PET or CT in detecting tumors, which uses multi-scale convolution operation to extract feature information and can highlight the tumor region location information and suppress the non-tumor region location information. In addition, our network uses dual-channel inputs in the coding stage and fuses them in the decoding stage, which can take advantage of the differences and complementarities between PET and CT. Results: We validated the proposed ISA-Net method on two clinical datasets, a soft tissue sarcoma(STS) and a head and neck tumor(HECKTOR) dataset, and compared with other attention methods for tumor segmentation. The DSC score of 0.8378 on STS dataset and 0.8076 on HECKTOR dataset show that ISA-Net method achieves better segmentation performance and has better generalization. Conclusions: The method proposed in this paper is based on multi-modal medical image tumor segmentation, which can effectively utilize the difference and complementarity of different modes. The method can also be applied to other multi-modal data or single-modal data by proper adjustment.

Electron–phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots

Due to the complex core–shell structure and variety of surface functional groups, the photoluminescence (PL) mechanism of carbon dots (CDs) remain unclear. o-Phenylenediamine (oPD), as one of the most common precursors for preparing red emissive CDs, has been extensively studied. Interestingly, most of the red emission CDs based on oPD have similar PL emission characteristics. Herein, we prepared six different oPD-based CDs and found that they had almost the same PL emission and absorption spectra after purification. Structural and spectral characterization indicated that they had similar carbon core structures but different surface polymer shells. Furthermore, single-molecule PL spectroscopy confirmed that the multi-modal emission of those CDs originated from the transitions of different vibrational energy levels of the same PL center in the carbon core. In addition, the phenomenon of “spectral splitting” of single-particle CDs was observed at low temperature, which confirmed these oPD-based CDs were unique materials with properties of both organic molecules and quantum dots. Finally, theoretical calculations revealed their potential polymerization mode and carbon core structure. Moreover, we proposed the PL mechanism of red-emitting CDs based on oPD precursors; that is, the carbon core regulates the PL emission, and the polymer shell regulates the PL intensity. Our work resolves the controversy on the PL mechanism of oPD-based red CDs. These findings provide a general guide for the mechanism exploration and structural analysis of other types of CDs.

Single-Mode Emission in InP Microdisks on Si Using Au Antenna.

An important building block for on-chip photonic applications is a scaled emitter. Whispering gallery mode cavities based on III–Vs on Si allow for small device footprints and lasing with low thresholds. However, multimodal emission and wavelength stability over a wider range of temperature can be challenging. Here, we explore the use of Au nanorod antennae on InP whispering gallery mode lasers on Si for single-mode emission. We show that by proper choice of the antenna size and positioning, we can suppress the side modes of a cavity and achieve single-mode emission over a wide excitation range. We establish emission trends by varying the size of the antenna and show that the far-field radiation pattern differs significantly for devices with and without antenna. Furthermore, the antenna-induced single-mode emission is dominant from room temperature (300 K) down to 200 K, whereas the cavity without an antenna is multimodal and its dominant emission wavelength is highly temperature-dependent.

Fabrication of a Microcavity Prepared by Remote Epitaxy over Monolayer Molybdenum Disulfide.

Advances in epitaxy have enabled the preparation of high-quality material architectures consisting of incommensurate components. Remote epitaxy based on lattice transparency of atomically thin graphene has been intensively studied for cost-effective advanced device manufacturing and heterostructure formation. However, remote epitaxy on nongraphene two-dimensional (2D) materials has rarely been studied even though it has a broad and immediate impact on various disciplines, such as many-body physics and the design of advanced devices. Herein, we report remote epitaxy of ZnO on monolayer MoS2 and the realization of a whispering-gallery-mode (WGM) cavity composed of a single crystalline ZnO nanorod and monolayer MoS2. Cross-sectional transmission electron microscopy and first-principles calculations revealed that the nongraphene 2D material interacted with overgrown and substrate layers and also exhibited lattice transparency. The WGM cavity embedding monolayer MoS2 showed enhanced luminescence of MoS2 and multimodal emission.

Altered Default Mode Network Is Associated With Cognitive Impairment in CADASIL as Revealed by Multimodal Neuroimaging.

Background and Purpose: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy caused by mutations in the NOTCH3 gene is a hereditary cerebral small vessel disease, manifesting with stroke, cognitive impairment, and mood disturbances. Functional or structural changes in the default mode network (DMN), which plays important role in cognitive and mental maintenance, have been found in several neurological and mental diseases. However, it remains unclear whether DMN is altered in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).Methods: Multimodal imaging methods, including MRI and positron emission tomography (PET), were applied to evaluate the functional, structural, and metabolic characteristics of DMN in 25 patients with CADASIL and 42 healthy controls.Results: Compared with controls, patients with CADASIL had decreased nodal efficiency and degree centrality of the dorsal medial pre-frontal cortex and hippocampal formation within DMN. Structural MRI and diffusion tensor imaging (DTI) showed decreased gray matter volume and fiber tracks presented in the bilateral hippocampal formation. Meanwhile, PET imaging showed decreased metabolism within the whole DMN in CADASIL. Furthermore, correlation analyses showed that these nodal characteristics, gray matter volume, and metabolic signals of DMN were related to cognitive scores in CADASIL.Conclusions: Our results suggested that altered network characteristics of DMN might play important roles in cognitive deficits of CADASIL.

Multi-Modal Co-Learning for Liver Lesion Segmentation on PET-CT Images.

Liver lesion segmentation is an essential process to assist doctors in hepatocellular carcinoma diagnosis and treatment planning. Multi-modal positron emission tomography and computed tomography (PET-CT) scans are widely utilized due to their complementary feature information for this purpose. However, current methods ignore the interaction of information across the two modalities during feature extraction, omit the co-learning of the feature maps of different resolutions, and do not ensure that shallow and deep features complement each others sufficiently. In this paper, our proposed model can achieve feature interaction across multi-modal channels by sharing the down-sampling blocks between two encoding branches to eliminate misleading features. Furthermore, we combine feature maps of different resolutions to derive spatially varying fusion maps and enhance the lesions information. In addition, we introduce a similarity loss function for consistency constraint in case that predictions of separated refactoring branches for the same regions vary a lot. We evaluate our model for liver tumor segmentation using a PET-CT scans dataset, compare our method with the baseline techniques for multi-modal (multi-branches, multi-channels and cascaded networks) and then demonstrate that our method has a significantly higher accuracy ( ) than the baseline models.

Broadband multimodal emission in Sb-doped CaZnOS-layered semiconductors

Mechanoluminescent (ML) smart materials are expected to be used in stress sensors, new displays, and advanced flexible optoelectronic devices, because of their unique mechanical-to-light energy conversion properties. However, the narrow-range ML emission characteristics of single materials limit their application scope. In this work, we report on the broadband multimodal emission in Sb-doped CaZnOS layered semiconductors. A series of CaZnOS layer-structured powders with different Sb3+ doping concentrations were synthesised using a high-temperature solid-phase method. The CaZnOS:Sb3+ phosphor achieved a wide range of ML spectra (400–900 nm), adjustable photoluminescence with double luminescent peaks located at 465 and 620 nm, and the X-ray-induced luminescence characteristics were systematically studied. We have also achieved ultra-broad warm white light ML emission of Sb3+ and Bi3+ co-doped samples. Therefore, it can be expected that these ML phosphors will be used in smart lighting, displays, visible stress sensors, and X-ray imaging and detections.