Emission Mode Research Articles

Unleashing the glow: upconverting nanoparticles recharge persistent luminescent materials – applications in 3D-printing and optical coding

In this study, composite materials composed of LiYbF4:Tm3+@LiYF4 and SrAl2O4:Eu2+ or ZnGa2O4:Cr3+ compounds were used for 3D-printed polymer items for optical coding operating in the afterglow and upconversion emission modes.

Photo-emission electron gun and electron optical simulation for ultrafast scanning electron microscope

Ultrafast scanning electron microscope (USEM) integrates pump-probe technique with microscopic imaging, enabling the visualizing of photon-induced surface charge dynamics with high spatial and temporal resolution. This capability is crucial for high-resolution detection of semiconductor surface states and optoelectronic devices. This work discusses the parametric design of a thermionic emission electron gun that has been modified into a photoemission electron gun, based on a home-built ultrafast scanning electron microscope. Given that the dose of the photoemitting electron beam is usually much lower than that of thermionic emission, the transition to photoemission requires the removal of the self-bias voltage function of the original electron microscope power supply to ensure the normal operation of the Wehnelt electrode. We quantitatively analyze the dependence of bias voltage, cathode, Wehnelt electrode, and anode on the position, size and divergence angle of crossover, which helps to improve the parameter adjustment of the modified electron gun. The analysis results indicate that if the distance between the Wehnelt electrode and the anode is adjusted from 8 to 23 mm, the distance between the filament and wehnelt can be changes from 0.65 to 0.45 mm to cooperate with the bias adjustment, so that the normal use of high-resolution thermionic emission mode, low voltage mode and photoemission mode can be realized. Subsequently, the effect of the mirror’s position on the electron optical path is analyzed. It is found that when the anode is raised 1.4 mm above the mirror, the influence on the electron optical path can be ignored. Additionally, the zero-of-time and temporal broadening of the photo-electron pulse are further simulated. The results indicate that with the increase of bias voltage, the time zero of photoemission will be delayed and the temporal broadening will become larger. This study lays a foundation for the future development of ultrafast electron microscope and the design of photoemission electron sources.

Microfluidic-driven short peptide hydrogels with optical waveguiding properties

Supramolecular hydrogels of DLeu–LPhe–LPhe tripeptide were prepared employing microfluidics, resulting in fibrillar structures with optical waveguiding ability in conjunction with dyes, which enable emission modulation across spectral regions.

Joint decisions on selling mode choice and emission reduction investment under cap-and-trade regulation

Consumers' growing awareness of environmental protection and carbon regulations enacted by the government based on strengthened environmental pressure are forcing manufacturers to curb carbon emissions. This paper considers a manufacturer investing in green technology to reduce carbon emissions under the cap-and-trade regulation, selling products to consumers through a direct channel and an online retail platform. The platform could choose to operate either in an agency mode or a reselling mode. A three-stage game is constructed to examine the interactions between the manufacturer's investment and the platform's operation mode under the cap-and-trade regulation, as well as the influences of the regulation on the interactions, and the supply chain coordination. The findings suggest that green technology investment in either operation mode leads to Pareto improvement in profits of both the platform and the manufacturer, and the investment induces the platform to prefer the reselling mode. Besides, the cap-and-trade regulation encourages the platform to opt for the agency mode, while the investment could mitigate the influence of the regulation on the platform's mode choice, with greater investment efficiency resulting in better mitigation. Furthermore, the investment could induce supply chain coordination under two modes through two different contracts.

Surface Modification of ZnO Nanotubes by Ag and Au Coatings of Variable Thickness: Systematic Analysis of the Factors Leading to UV Light Emission Enhancement.

Surface modification by plasmonic metals is one of the most promising ways to increase the band-to-band excitonic recombination in zinc oxide (ZnO) nanostructures. However, the metal-induced modulation of the UV light emission depends strongly on the production method, making it difficult to recognize the mechanism responsible for charge/energy transfer between the semiconductor and a metal. Therefore, in this study, the ZnO/Ag and Au hybrids were produced by the same, fully controlled experimental approach. ZnO nanotubes (NTs), fabricated by a template-assisted ALD synthesis, were coated by metals of variable mass thickness (1-6.5 nm thick) using the electron beam PVD technique. The deposited Ag and Au metals grew in the form of island films made of metallic nanoparticles (NPs). The size of the NPs and their size distribution decreased, while the spacing between the NPs increased as the mass of the deposited Ag and Au metals decreased. Systematic optical analysis allowed us to unravel a specific role of surface defects in ZnO NTs in the processes occurring at the ZnO/metal interface. The enhancement of the UV emission was observed only in the ZnO/Ag system. The phenomena were tentatively ascribed to the coupling between the defect-related (DL) excitonic recombination in ZnO and the localized surface plasmon resonance (LSPR) at the Ag NPs. However, the enhancement of UV light was observed only for a narrow range of Ag NP dimensions, indicating the great importance of the size and internanoparticle spacing in the plasmonic coupling. Moreover, the enhancement factors were much stronger in ZnO NTs characterized by robust DL-related emission before metal deposition. In contrast to Ag, Au coatings caused quenching of the UV emission from ZnO NTs, which was attributed to the uncoupling between the DL and LSP energies in this system and a possible formation of the ohmic contact between the Au metal and the ZnO.

10,600 nm High Level-Laser Therapy Dosimetry in Management of Unresponsive Persistent Peripheral Giant Cell Granuloma to Standard Surgical Approach: A Case Report with 6-Month Follow-Up.

Peripheral giant cell granuloma (PGCG) is a non-neoplastic, tumour-like reactive lesion that exclusively involves the gingiva and/or the alveolar crest. The surgical approach with a scalpel has been the golden standard of treatment for PGCG, but the scientific literature reports a high rate of lesion recurrence. Hence, this unique case report aimed to evaluate the efficacy of λ 10,600 nm high-level laser therapy (HLLT) in eradicating persistent, aggressive, and recurrent PGCG that failed to respond to standard surgical treatment. A fit and healthy thirty-four-year-old Caucasian male presented with a two-month history of recurrent episodes of an oral mucosal lesion involving the buccal and lingual interdental papillae between the lower right second premolar (LR5) and lower right first molar (LR6), which was surgically excised with a scalpel three times previously. A λ 10,600 nm-induced HLLT was chosen as a treatment modality at a lower peak power of 1.62 W, measured with a power metre, emitted in gated emission mode (50% duty cycle), whereby the average output power reaching the target tissue was 0.81 W. The spot size was 0.8 mm. Ninety seconds was the total treatment duration, and the total energy density was 7934.78 J/cm2. Patient self-reporting outcomes revealed minimal to no post-operative complications. Initial healing was observed on the 4th day of the post-laser treatment, and a complete healing occurred at two-weeks post-operatively. The histological analysis revealed PGCG. This unique case report study demonstrated the efficacy of λ 10,600 nm-induced HLLT and its superiority to eradicate persistent aggressive PGCG over the standard surgical approach with minimal to no post-operative complications, accelerating wound healing beyond the physiological healing time associated with no evidence of PGCG recurrence at the six-month follow-up timepoint. Based on the significant findings of this unique study and the results of our previous clinical studies, we can confirm the validity and effectiveness of our standardised λ 10,600 nm laser dosimetry-induced HLLT and treatment protocol in achieving optimal outcomes. Randomised controlled clinical trials with large data comparing λ 10,600 nm with our dosimetry protocol to the standard surgical treatment modality at long follow-up timepoints are warranted.

An evaluation of photobiomodulation effects on human gingival fibroblast cells under hyperglycemic condition: an in vitro study.

An in vitro study was designed to evaluate the effects of photobiomodulation (PBM) with 915-nm diode laser on human gingival fibroblast (HGF) cells under hyperglycemic condition. The HGF cells were cultured in Dulbecco's modified eagle medium (DMEM) medium containing 30mM glucose concentration for 48h to mimic the hyperglycemic condition. Subsequently, the cells received three sessions of PBM (915nm, continuous emission mode, 200 mW, energy density values of 3.2, 6, and 9.2J/cm2). Twenty-four hours post-irradiation, cell proliferation, expression of interleukin 6 (IL-6), and vascular endothelial growth factor (VEGF) were assessed with MTT and real-time polymerase chain reaction (PCR) tests, respectively. Also, reactive oxygen species (ROS) production was measured using CM-H2DCFDA fluorimetry. No changes were detected in the cell proliferation rate between the high glucose control group and laser-treated cells, while VEGF and IL-6 gene expression levels increased significantly after PBM in the high glucose-treated cells group. ROS level was significantly decreased in the irradiated cells in high-glucose medium compared with the high glucose control group. Our study revealed the inductive role of 915-nm-mediated PBM on VEGF and the inflammatory response while concurrently reducing reactive oxygen species production in HGF cells in hyperglycemic conditions.

Performance seeking control method for minimum pollutant emission mode for turbofan engine

The research shows that the impact of aero-engine pollutant emission on the environment cannot be ignored. In addition to fuel type and combustor structure, aero-engine exhaust pollutants are also related to engine operating conditions and control systems. In this context, taking CO and NOx as the main exhaust pollutants of the engine as the research object, a performance optimization control method of the minimum pollutant emission mode of the engine is proposed. Firstly, the CO and NOx emission characteristics of the engine under different operating conditions at sea level are calculated by CFD numerical simulation method, and the engine component-level model applicable to all flight envelope and all conditions is established according to the characteristic data. Secondly, in order to improve computational efficiency, an airborne model with high accuracy and real-time performance is established through the deep neural network. Compared to the component-level model, the average relative error of each performance parameter is less than 0.5 %, and the real-time performance is improved by about 12 times. Finally, the optimization principle of the minimum pollutant emission mode is discussed. The feasible sequential quadratic programming (FSQP) algorithm is selected, and the fuel quantity and throat area of the tail nozzle are taken as control variables. Numerical simulations are performed in the typical mission envelope. Simulation results show that the CO emission index decreases by 5 % and the NOx emission index decreases by more than 6.5 % through performance optimization control of the minimum pollutant emission mode under the premise of ensuring constant engine thrust and meeting other constraints.

Study on the modes transformation and emission characteristics of Ionic Liquid Electrospray Thrusters

Ionic Liquid Electrospray Thrusters (ILETs) exhibit distinct emission characteristics when operating in different emission mode under different conditions, which can significantly impact their performance. Therefore, to optimize the performance of ILETs and make them suitable for a wide range of space missions, it is necessary to investigate the emission mode characteristics of ILETs. In this study, the ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-Im) was used to conduct experiments at varying supply voltage and flow rate conditions. The emitted current was measured and the liquid surface was imaged using a high-speed camera. The emission mode was estimated using algebraic calculations. Experimental results revealed that ILETs operate in the Ion-droplet Mixed mode at low flow rates, while the emission mode transforms into the Droplet mode as the flow rate increases. Similarly, as the supply voltage increases, the emission mode transforms from the Droplet mode to the Ion-droplet Mixed mode. The liquid surface height decreased with the supply voltage increase in each mode, and it increased with the flow rate in the Droplet mode. Notably, the liquid surface height in the Ion-droplet Mixed mode was similar to that in the Droplet mode at the lowest flow rate. Furthermore, the ion ratio significantly affected the thrust and specific impulse of ILETs.

Smart-Responsive HOF Heterostructures with Multiple Spatial-Resolved Emission Modes toward Photonic Security Platform.

Luminescent hydrogen-bonded organic frameworks (HOFs) with the unique dynamics and versatile functional sites hold great potential application in information security, yet most of responsive HOFs focus on the single-component framework with restrained emission control, limiting further applications in advanced confidential information protection. Herein, the first smart-responsive HOF heterostructure with multiple spatial-resolved emission modes for covert photonic security platform is reported. The HOF heterostructures are prepared by integrating different HOFs into a single microwire based on a hydrogen-bond-assisted epitaxial growth method. The distinct responsive behaviors of HOFs permit the heterostructure to simultaneously display the thermochromism via the framework transformation and the acidichromism via the protonation effect, thus generating multiple emission modes. The dual stimuli-controlled spatial-resolved emission modes constitute the fingerprint of a heterostructure, and enable the establishment of the smart-responsive photonic barcode with multiple convert states, which further demonstrate the dynamic coding capability and enhanced security in anticounterfeiting label applications. These results offer a promising route to design function-oriented smart responsive HOF microdevices toward advanced anticounterfeiting applications.

A flexible electrochromic device with variable infrared emissivity based on W18O49 nanowire cathode and MXene infrared transparent conducting electrode

Electrochromism with tunable infrared (IR) responses has emerged as an intriguing technology for adaptive IR camouflage and radiative thermal management. Its current development is however hindered by low IR emissivity modulation and unsatisfactory cycle life. Herein, a flexible IR electrochromic device with large IR emissivity modulation and high stability is fabricated by combining an oxygen-deficient W18O49 nanowire cathode and a MXene-based IR transparent conducting electrode. The nanowire structure and abundant oxygen vacancies of W18O49 works in synergy with the high IR transparence of the MXene conducing electrode, to provide the IR emissivity to vary from 0.8 to 0.4 within 3–5 μm (△ε = 0.4), and from 0.77 to 0.3 within 8–14 μm (△ε = 0.47). A long cycle life of more than 2000 cycles was also verified, which could be attributed to the high stability of W18O49 and no material phase transition during cycling. This work demonstrates a viable pathway to design and build high performance flexible IR electrochromic devices for adaptive thermal management.

Terahertz imaging through emissivity control

Electromagnetic radiation in the terahertz (THz) frequency band has unique potential for future communication and imaging applications. However, the adoption of THz technologies is hindered by the lack of cost-effective THz sources. Here we demonstrate a way to generate and control THz radiation, via spatio-temporal emissivity modulation. By patterning the optical photoexcitation of a surface-passivated silicon wafer, we locally control the free-electron density, and thereby pattern the wafer’s emissivity in the THz part of the electromagnetic spectrum. We show how this unconventional source of controllable THz radiation enables a form of incoherent computational THz imaging. We use it to image various concealed objects, demonstrating that this scheme has the penetrating capability of other THz imaging approaches, without the requirement of femtosecond pulsed laser sources. Furthermore, the incoherent nature of thermal radiation also ensures the obtained images are free of interference artifacts. Our spatio-temporal emissivity control could enable a family of long-wavelength structured illumination, imaging, and spectroscopy systems.

Stepless IR Chromism in Ti3 C2 Tx MXene Tuned by Interlayer Water Molecules.

Real-time control over infrared (IR) radiation of objects is highly desired in a variety of areas such as personal thermal regulation and IR camouflage. This requires the dynamic modulation of IR emissivity in a stepless manner over a wide range (>50%), which remains a daunting challenge. Here, an emissivity modulation phenomenon is reported in stacked 2D Ti3 C2 Tx MXene nanosheets, from 12% to 68% as the intercalation/discharging of water molecules within the interlayers. The intercalation of water molecules dynamically changes the electronic properties and the complex permittivity in IR frequencies of Ti3 C2 Tx . This emissivity modulation is a stepless and reversible process without the assistance of any external energy input. Further, intercalating cellulose nanofibers into the Ti3 C2 Tx interlayers makes this dynamic process highly repeatable. Last, a sweat-responsive adaptive textile that can improve thermal comfort of human body under changes in metabolic rates and environmental conditions is demonstrated, showing great potential of this mechanism in passive on-demand radiation modulation.

Structural Inhomogeneities and Nonlinear Phenomena in Charge Transfer under Cold Field Emission in Individual Closed Carbon Nanotubes

The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the I-V characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the I-V characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim (F-N) function by one to three orders of magnitude. The I-V characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the I-V characteristics have distinct regions of negative differential conductivity.

Theoretical simulation and mechanisms of SmNiO3-based phase change metamaterial for mid-infrared dynamic thermal control

Dynamic thermal emission control has gained increasing attention across diverse fields. Among phase change materials (PCMs), SmNiO3 has attracted many interests because of its fast phase transition and non-volatile properties. However, constructing an emissivity modulation metamaterial with angle stability performance is still rather challenging. In this work, we propose three kinds of SmNiO3-based metamaterials for mid-infrared emissivity dynamic modulation, specifically a trapezoidal metamaterial consisting of alternating SmNiO3 and Si multi-layer thin films and two modified grating metastructures, realizing an average emissivity modulation Δεaver of 0.42–0.45 in 5–16 µm. It is confirmed that the magnetic resonance stimulated inside the metamaterial is because of the slow-light effect. This work provides theoretical fundamentals for the design of dynamic thermal control metamaterials and benefits applications in the fields of infrared emission modulation.

X-ray excited optical luminescence at Carnaúba, the Sirius X-ray nanoprobe beamline

This work presents the developments and initial results obtained using X-ray excited optical luminescence (XEOL) at the Carnaúba, the nanoprobe beamline from Sirius, the Brazilian 4th generation synchrotron source. XEOL is a highly important tool to study luminescence mechanisms and identify optical channels in various types of materials under X-ray irradiation. Using this capability combined with a nanoprobe, one can probe optical channels, for example, in heterogenous materials, and directly correlate them with chemical composition, oxidizing state of absorbers, structure and/or morphology in simultaneous studies. Carnaúba is composed by two experimental station and at the Tarumã station, the first entering in operation, it has been possible to investigate XEOL in the integrated and emission modes, and 2D images in hyperspectral mapping with submicrometric resolution. Herein, it is showed some examples of studies combining excitation energy, emission wavelength and emission intensity in 3D spectra, 2D imaging, and XEOL emission on the study of very sensitive samples that can be easily damaged by the probe. This work also highlights some of the upcoming developments that include the time-resolved and in situ experiments, this last one using microfluidic cells, and the improvement of the covered emission wavelength up to 1700 nm, which will open new opportunities for studying optical materials.

ICE modes with high wave numbers

This work deals with high-k modes of the ion cyclotron emission (ICE)—the modes with frequencies close to ion cyclotron harmonics and wave numbers well exceeding those of fast magnetoacoustic modes (FMM). These modes exist due to finite Larmor radius of the ions. They are responsible for the ICE recently observed in the DIII-D tokamak [N. A. Crocker et al., Nucl. Fusion 62, 026023 (2022)]. The work is aimed at knowing the radial structure of high-k eigenmodes. Its analysis is relied on a comprehensive study carried out by employing a general dispersion equation for traveling waves, which allowed to group modes and determine conditions of their existence. Differential equations for various eigenmodes (standing waves) were obtained and analyzed. In particular, electrostatic modes and electromagnetic modes with various ratios of the longitudinal phase velocity to the electron thermal velocity were considered. A numerical code solving these equations was developed. It is found that high-k modes with sufficiently large poloidal mode numbers are located at the plasma periphery, and their amplitudes in the plasma core are very small. It is concluded that high-k modes are not an exceptional case, although presumably FMMs can explain most ICE experiments. They exist in plasmas with various magnitudes of β, representing different wave branches associated with finite Larmor radius of the ions. The mentioned experiment on DIII-D is discussed.

Mode Changing in PSR B0844-35 and PSR B1758-29 with Enhanced Emission at the Profile Centers

We have studied the single pulse emission from two pulsars, PSR B0844-35 and PSR B1758-29, over a wide frequency range of 300–750 MHz using the upgraded Giant Metrewave Radio Telescope. The two pulsars have relatively wide profiles with multiple components, which are a result of the line of sight traversing near the center of the emission beam. In both pulsars, the single pulse sequences show the presence of two distinct emission states, where the profiles become much brighter at the center, with prominent core components during one of the modes, while in the other mode the single pulses show odd–even subpulse drifting with a periodicity of around 2P, P being the rotation period of the pulsar. The centrally bright mode was seen for 10% of the observing duration in PSR B0844-35, which usually lasted for short durations of around 10 pulses, but had two longer sequences of around 100 pulses. On the contrary, the centrally bright mode was dominant in PSR B1758-29 and was seen for around 60% of the observing duration. PSR B1758-29 also showed period amplitude modulations of 60P–70P in both modes. The mode changing in these two pulsars facilitates investigation of the sparking process in the inner acceleration region, dominated by nondipolar magnetic fields. The change in the surface magnetic field configurations likely results in the emission mode change.

Colloidal Nanoplatelets‐Based Soft Matter Technology for Photonic Interconnected Networks: Low‐Threshold Lasing and Polygonal Self‐Coupling Microlasers

AbstractSoft matter‐based microlasers are widely regarded as excellent building blocks for realizing photonic interconnected networks in optoelectronic chips, owing to their flexibility and functional network topology. However, the potential of these devices is hindered by challenges such as poor lasing stability, high lasing threshold, and gaps in knowledge regarding cavity interconnection characteristics. In this study, the first demonstration of a high‐quality, low‐threshold nanoplatelets (NPLs)‐based polymer microfiber laser fabricated using capillary immersion techniques and its photonic interconnected networks are presented. CdSe/CdS@Cd1‐xZnxS core/buffer shell@graded‐shell NPLs with high optical gain characteristics are adopted as the gain medium. The study achieves a lasing threshold below 14.8 µJ cm−2, a single‐mode quality (Q)‐factor of ≈5500, and robust lasing stability in the fabricated NPLs‐based microfibers. Furthermore, the study pioneers the exploration of polygonal self‐coupling microlasers and the optical characteristics of their interconnected fiber network. Based on the signal generation mechanism observed in the photonic networks, an interconnected NPLs‐based fiber network structure achieving single‐mode lasing emission and laser mode modulation is successfully designed. The work contributes a novel method for realizing microlasers fabricated via soft‐matter technologies and provides a key foundation and new insights for unit design and programming for future photonic network systems.

Investigating the multidrifting behaviour of subpulses in PSR J2007 + 0910 with the FAST

ABSTRACT The multidrifting subpulse behaviours in PSR J2007 + 0910 have been studied carefully with the high sensitivity observations of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at 1250 MHz. We found that there are at least six different single emission modes in PSR J2007 + 0910 are observed, four of which show significant subpulse drifting behaviours (modes A, B, C, and D), and the remaining two (modes E1 and E2) show stationary subpulse structures. The subpulse drifting periods of modes A, B, C, and D are P3,A = 8.7 ± 1.6P, P3,B = 15.8 ± 1.2P, P3,C = 21.6 ± 1.3P, and P3,D = 32.3 ± 0.9P, respectively, where P represents the pulse period of this pulsar. The subpulse separation is almost the same for all modes P2 = 6.01 ± 0.18°. Deep analysis suggests that the appearance and significant changes in the drifting period of multidrifting subpulse emission modes for a pulsar may originate from the aliasing effect. The observed non-drifting modes may be caused by the spark point move with a period ∼P2. Our statistical analysis shows that the drift mode of this pulsar almost always switches from slower to faster drifts in the mode change. The interesting subpulse emission phenomenon of PSR J2007 + 0910 provides a unique opportunity to understand the switching mechanism of multidrift mode.