Multiband Emissions Research Articles

Energy transfer enabled multiemission KBaLu(BO3)2:Ce3+,Mn2+,Tb3+ phosphors for ratiometric thermometers and WLED

Phosphors with multiband emissions have unique applications in thermometers and white LED, which can be readily realized by energy transfer. In this work, the energy transfers from Ce3+ to Mn2+/Tb3+ have been successfully constructed to achieve multiband emission in the KBaLu(BO3)2 (KBLBO) phosphors. KBLBO:Ce3+ can be efficiently excited by the near-ultraviolet light and shows a broad emission band at 453 nm. On the basis of the energy transfer from the Ce3+ to Mn2+/Tb3+ ions, KBLBO:Ce3+,Mn2+/Tb3+ exhibits a multiband emission consists of blue and red bands/green bands. The KBLBO:0.02Ce3+,0.03Mn2+ phosphor can function as a ratiometric thermometer with high temperature sensing performance by taking use of the differences in the thermal quenching behavior between the Ce3+ and Mn2+ ions. Moreover, a single-phase white light emitting phosphor KBLBO:0.02Ce3+,0.03Mn2+,0.01 Tb3+ was obtained. Meanwhile, the as-prepared WLED device exhibits CRI of 87.1 and CCT of 5090 K. Our work not only reveals the multifunctionality of the new KBLBO phosphors, but also points out the design and utilization strategies of multiband emission phosphors based on energy transfer.

Realizing Red Mechanoluminescence of ZnS: Mn2+ Through Ferromagnetic Coupling

AbstractSelf‐recoverable mechanoluminescence (ML) is becoming a novel technology widely used in the fields of sensing, display, and artificial intelligence. The dominant ML material, ZnS: Mn2+, is reported to solely present a yellow emission color, which limits the applications of self‐recoverable ML materials to a large extent. Herein, an effective strategy to extend the ML emission range of ZnS: Mn2+ by the ferromagnetic coupling of Mn2+ ions are reported. Under the thermal carbon‐reduction atmosphere (TCRA), the emission ranges of ML, photoluminescence (PL), and persistent luminescence spectra of ZnS: Mn2+ phosphors are all successfully broadened from yellow to red. Furthermore, as for the PL and ML intensities of ZnS: Mn2+, they are intensified to 1.76 and 3.23 folds larger under the TCRA treatment than those in pure nitrogen, respectively. Various spectra and magnetic test results reveal that the red emission bands of ZnS: Mn2+ @TCRA phosphors originate from the ferromagnetic coupling of Mn2+ ions. This study is the first to realize strong red emission and tunable multicolor luminescence in the conventional ZnS‐based phosphors, which introduces opportunities for discovering the multiband emissions of Mn2+ ion in other compounds. Brightly multicolored ZnS: xMn2+ @TCRA elastic films have been fabricated to demonstrate their anti‐counterfeiting and security applications.

Multi-band optical variability on diverse timescales of blazar 1E 1458.8+2249

Abstract This study presents an analysis of the optical variability of the blazar 1E 1458.8+2249 on diverse timescales using multi-band observations, including observations in the optical BVRI bands carried out with the T60 and T100 telescopes from 2020 to 2023 and ZTF gri data from 2018 to 2023. On seven nights, we searched for intraday variability using the power-enhanced F-test and the nested ANOVA test, but no significant variability was found. The long-term light curve shows a variability behaviour in the optical BVRI bands with amplitudes of $\sim$ 100% and in the gri bands with amplitudes of $\sim$ 120%, including short-term variability of up to $\sim$ 1.1 mag. Correlation analysis revealed a strong correlation between the optical multi-band emissions without any time lag. From 62 nightly spectral energy distributions, we obtained spectral indices between 0.826 and 1.360, with an average of $1.128\pm0.063$ . The relationships of both spectral indices and colour with respect to brightness indicate a mild BWB trend throughout the observation period, both intraday and long-term. We also performed a periodicity search using the weighted wavelet Z-transform and Lomb–Scargle methods. A recurrent optical emission pattern with a quasi-periodicity of $\sim$ 340 days is detected in the combined V- and R-band light curves. The observational results indicate that the blazar 1E 1458.8+2249 has a complex variability, while emphasising the need for future observations to unravel its underlying mechanisms.

The effect of Er3+ concentration on the kinetics of multiband upconversion in NaYF4:Yb/Er microcrystals.

In Yb-Er co-doped upconversion (UC) nanomaterials, upconversion luminescence (UCL) can be modulated to generate multiband UCL emissions by changing the concentration of activator Er3+. Nonetheless, the effect of the Er3+ concentrations on the kinetics of these emissions is still unknown. We here study the single β-NaYF4:Yb3+/Er3+ microcrystal (MC) doped with different Er3+ concentrations by nanosecond time-resolved spectroscopy. Interestingly, different Er3+ doping concentrations exhibit different UCL emission bands and UCL response rates. At low Er3+ doping concentrations (1mol%), multiband emission in β-NaYF4:Yb3+/Er3+ (20/1mol%) MCs could not be observed and the response rate of UCL was slow (5-10μs) in β-NaYF4:Yb3+/Er3+. Increasing the Er3+ doping concentration to 10mol% can shorten the distance between Yb3+ ions and Er3+ ions, which promotes the energy transfer between them. β-NaYF4:Yb3+/Er3+ (20/10mol%) can achieve obvious multiband UCL and a quick response rate (0.3µs). However, a further increase in the Er doping concentration (80mol%) makes MCs limited by the CR process and cannot achieve the four-photon UC process (4F5/2 → 2K13/2 and 2H9/2 → 2D5/2). Therefore, the result shows that changing the Er3+ doping concentration could control the energy flow between the different energy levels in Er3+, which could affect the response time and UCL emission of the Yb/Er doped rare earth materials. Our work can facilitate the development of fast-response optoelectronics, optical-sensing, and display industries.

A novel M2Ga2GeO7:N3+ (M = Ca, Ba, Sr; N = Cr, Nd, Er) sub-micron phosphor with multiband NIR emissions: preparation, structure, properties, and LEDs

Near-infrared (NIR) emission materials can be widely applied in various fields, such as food detection, imaging, treatment, electronic products. With the trend of miniaturization of equipment, smaller materials are needed. In this work, we successfully synthesized a series of M2Ga2GeO7:N3+ (M = Ca, Ba, Sr; N = Cr, Nd, Er) samples and then focused on the study of Nd3+ doped Sr2Ga2GeO7 (SGGO). A series of SGGO:xNd3+ sub-micron phosphors were prepared via a microwave-assisted sol–gel process combined with subsequent calcination at 750 ℃, and the structural information and luminescent properties were systematically studied. SGGO is a representative tetragonal crystal and belonging to the space group of P21m (113). The Nd3+ ions occupy eight-coordinated Sr2+ sites in the crystal lattice. From SEM analysis, the average particle size distribution is 219.7 ± 41.4 nm. The sub-micron phosphors have rich excitation spectra ranging from 350 nm to 850 nm and can produce multiband NIR emissions of 1331, 1056, and 905 nm when excited by ultraviolet and NIR light. The maximum emission intensity was obtained by optimizing the doping ratio of Nd3+ ions. A commercial chip was then utilized to fabricate light-emitting diodes (LEDs) to verify its application potential in NIR-II mini-LEDs. Compared with blue light LEDs, the as-prepared LEDs had good imaging penetration depth and could be clearly observed under 10 mm of chicken breast coverage. The maximum imaging penetration depth can be 33 mm.

Enhanced core–shell CeO2:Er,Yb@W18O49 heterojunction H2 generation by multiband emissions of Er ions

The core–shell CeO2:Er,Yb@W18O49 heterojunction is successfully synthesized via the facile solvothermal method. The octahedral CeO2:Er,Yb nanocrystal’s core exhibits green (2H11/2, 4S3/2 → 4I15/2), red (4F9/2 → 4I15/2) and NIR (4I11/2 → 4I15/2 and 4I13/2 → 4I15/2) emission under 980 nm laser diode excitation, and the multiband emissions are absorbed by the W18O49 nanowire’s shell, re-exciting its higher energy localized surface plasmon resonances (LSPR). With the excitation of 980 nm, the photocatalytic property of CeO2:Er,Yb@W18O49 for hydrogen (H2) evolution from ammonia borane (BH3NH3), a three-fold increase compared to W18O49, is researched. The application of natural sunlight for the production of H2 is studied, and an obvious H2 production enhancement compared to the use of W18O49 (two-fold) is also observed. This remarkable enhancement in the catalytic activity of CeO2:Er,Yb@W18O49 heterostructures is ascribed to the re-excitation of LSPR by multiband emissions of CeO2:Er,Yb.

Highly flexible dual-mode anti-counterfeiting designs based on tunable multi-band emissions and afterglow from chromium-doped aluminates

Dual-mode anti-counterfeiting design based on fluorescence and afterglow.

Constraining the Environmental Properties of FRB 131104 Using the Unified Dynamical Afterglow Model

Abstract Multiband observations of the fast radio burst (FRB) 131104 show that this burst may be associated with a gamma-ray transient entitled Swift J0644.5−5111. Follow-up observations for potential X-ray and radio counterparts of FRB 131104/Swift J0644.5−5111 got null results and provided the upper limits of the emission flux at 5.5 GHz, 7.5 GHz, U-band, and X-ray band. By assuming this association and using these upper limits, environmental properties (the fraction of energy in a magnetic field ε B and the number density n) of the progenitor system of FRB 131104/Swift J0644.5−5111 were constrained in the context of the standard afterglow model that neglects the nonrelativistic effect and jet effect by several groups. In this paper, we adopt a unified afterglow model that takes into account the nonrelativistic effect and jet effect and use the upper limits of four bands (5.5 GHz, 7.5 GHz, U-band, and X-ray) to obtain more stringent constraints on the parameter space spanned by ε B and n. We thus suggest that FRB 131104/Swift J0644.5−5111 might originate from a black hole–neutron star merger event. Moreover, we calculate multiband emissions from a kilonova powered by the radioactivity of r-process elements synthesized in the ejected neutron-rich material and find that the U-band emission from the putative kilonova is significantly lower than the upper limit of the observations.

Occurrence features of simultaneous H+- and He+-band EMIC emissions in the outer radiation belt

As an important loss mechanism of radiation belt electrons, electromagnetic ion cyclotron (EMIC) waves show up as three distinct frequency bands below the hydrogen (H+), helium (He+), and oxygen (O+) ion gyrofrequencies. Compared to O+-band EMIC waves, H+- and He+-band emissions generally occur more frequently and result in more efficient scattering removal of <∼5 MeV relativistic electrons. Therefore, knowledge about the occurrence of these two bands is important for understanding the evolution of the relativistic electron population. To evaluate the occurrence pattern and wave properties of H+- and He+-band EMIC waves when they occur concurrently, we investigate 64 events of multi-band EMIC emissions identified from high quality Van Allen Probes wave data. Our quantitative results demonstrate a strong occurrence dependence of the multi-band EMIC emissions on magnetic local time (MLT) and L-shell to mainly concentrate on the dayside region of L = ∼4–6. We also find that the average magnetic field amplitude of H+-band waves is larger than that of He+-band waves only when L < 4.5 and AE∗ < 300 nT, and He+-band emissions are more intense under all other conditions. In contrast to 5 events that have average H+-band amplitude over 2 nT, 19 events exhibit >2 nT He+-band amplitude, indicating that the He+-band waves can be more easily amplified than the H+-band waves under the same circumstances. For simultaneous occurrences of the two EMIC wave bands, their frequencies vary with L-shell and geomagnetic activity: the peak wave frequency of H+-band emissions varies between 0.25 and 0.8 fcp with the average between 0.25 and 0.6 fcp, while that of He+-band emissions varies between 0.03 and 0.23 fcp with the average between 0.05 and 0.15 fcp. These newly observed occurrence features of simultaneous H+- and He+-band EMIC emissions provide improved information to quantify the overall contribution of multi-band EMIC waves to the loss processes of radiation belt electrons.

Laboratory unraveling of matter accretion in young stars.

Accretion dynamics in the formation of young stars is still a matter of debate because of limitations in observations and modeling. Through scaled laboratory experiments of collimated plasma accretion onto a solid in the presence of a magnetic field, we open a first window on this phenomenon by tracking, with spatial and temporal resolution, the dynamics of the system and simultaneously measuring multiband emissions. We observe in these experiments that matter, upon impact, is ejected laterally from the solid surface and then refocused by the magnetic field toward the incoming stream. This ejected matter forms a plasma shell that envelops the shocked core, reducing escaped x-ray emission. This finding demonstrates one possible structure reconciling current discrepancies between mass accretion rates derived from x-ray and optical observations, respectively.

Minimizing the Heat Effect of Photodynamic Therapy Based on Inorganic Nanocomposites Mediated by 808 nm Near-Infrared Light.

Photodynamic therapy (PDT) based on photosensitizers (PSs) constructed with nanomaterials has become popular in cancer treatment, especially oral carcinoma cell. This therapy is characterized by improved PS accumulation in tumor regions and generation of reactive oxygen species (ROS) for PDT under specific excitation. In the selection of near-infrared (NIR) window, 808 nm NIR light because it can avoid the absorption of water is particularly suitable for the application in PDT. Hence, multiband emissions under a single 808 nm near-infrared excitation of Nd3+ -sensitized upconversion nanoparticles (808 nm UCNPs) have been applied for the PDT effect. 808 nm UCNPs serve as light converter to emit UV light to excite inorganic PS, graphitic carbon nitride quantum dots (CNQDs), thereby generating ROS. In this study, a nanocomposite consisting UCNPs conjugated with poly-l-lysine (PLL) to improve binding with CNQDs is fabricated. According to the research results, NIR-triggered nanocomposites of 808 nm UCNP-PLL@CNs have been verified by significant improvement in ROS generation. Consequently, 808 nm UCNP-PLL@CNs exhibit high capability for ROS production and efficient PDT in vitro and in vivo. Moreover, the mechanism of PDT treatment by 808 nm UCNP-PLL@CNs is evaluated using the cell apoptosis pathway.

Modeling multiband emissions from two young SNRs with a time-dependent magnetic field

The nonthermal components in hard X-rays have been detected in two young supernova remnants (SNRs): SN 1006 and Kepler's SNR. Various theoretical models showed that the amplification of the magnetic field was crucial to explain their multiband emission properties. We investigate the evolution of the magnetic field and model the multiband emissions from these two young SNRs with a time-dependent injection model. The results indicate that (1) the radio and X-ray emissions are reproduced by synchrotron radiation of the injected electrons, while the γ-rays can be explained as inverse Compton scattering of the relativistic electrons and proton-proton interaction of the high-energy protons; and (2) the amplification of the magnetic field spontaneously happens with reasonable parameters.

A New Coordination Polymer of Zn(II)-btc (H3btc = Benzene-1,3,5-tricarboxylic acid) with Protonated Acridine: Synthesis, Crystal Structure and Spectroscopic Properties

A new Zn(II)-btc coordination polymer 1 (H3btc = benzene-1,3,5-tricarboxylic acid) containing protonated acridines was synthesized by hydrothermal reaction at 165 °C for 3 days and characterized by FT-IR, UV–Vis, Fluorescence, TGA measurements and single-crystal/powder X-ray crystallography. The crystallographic data for 1: monoclinic, P21/n, a = 11.0100(5), b = 16.7104(7), c = 11.7492(5) A, β = 98.735(2), V = 2136.56(16) A3, Z = 4, T = 130(2) K, Dc = 1.572 g cm−3, F(000) = 1036, μ(Mo Kα) = 1.205 mm−1, GOF = 1.005. R 1 = 0.0427, wR 2 = 0.1410 [I > 2σ(I)]. Structural analysis also revealed that the btc3− ligands bridge four-coordinate Zn(II) centres to form a 2-D grid-like layer network on the bc plane. The protonated acridines fill up the cavities formed between adjacent layers and combine the 2-D layers to generate a non-interpenetrating 3-D supramolecular framework through the hydrogen bondings and π···π packing interactions. The fluorescence investigation disclosed that 1 shows multiband emissions over a wide range. A non-interpenetrating 3-D supramolecular framework, built from Zn(II) ions and benzene-1,3,5-tricarboxylate ligands, encapsulates the protonated acridines and exhibits multiband fluorescence emissions over a wide range.

Intrinsic single-band upconversion emission in colloidal Yb/Er(Tm):Na3Zr(Hf)F7 nanocrystals

Novel Yb/Er(Tm):Na(3)MF(7) (M = Zr, Hf) nanocrystals with intrinsic single-band upconversion emission, in contrast to the routine lanthanide-doped fluoride nanocrystals which show typical multi-band upconversion emissions, are reported for the first time. Specifically, the red upconversion intensity of the Yb/Er:Na(3)ZrF(7) nanocrystals is about 5 times as high as that of the hexagonal Yb/Er:NaYF(4) ones with a similar crystal size.

Modified super-wide-angle Sagnac imaging interferometer based on LCoS for atmospheric wind measurement

The modified super-wide-angle Sagnac imaging interferometer (MSASII) based on liquid crystals on silicon (LCoS) is proposed as a novel device for the detection of the upper atmospheric wind field. This device employs the phase-only modulation (POM) of LCoS coupled with the MSASII, and can measure phase changes in multi-band emissions without moving mirror. It can be used to replace the conventional Michelson’s interferometer with step-moving mirror device. The optical path difference (OPD) equation of MSASII-LCoS is derived, and the four compensation conditions (field, chromatics, thermal and achromaticity of thermal compensations) are discussed within the scope of wind measurement. The real parameters of LCoS and optical glasses are selected for numerical simulation and analysis. Three aurora lines (732.0, 630.0 and 557.7 nm) are considered, and their phase variations are 3.61, 2.02 and 0.15 fringes at the same incident angle of 3°, respectively. The rate of change of OPD with temperature is the magnitude of 10 −6 cm/K, and the corresponding phase variations are within 0.09 fringes. The accuracy of phase modulation can be 0.614×10 −2 rad when LCoS of 10-bits is used. The novel model MSASII-LCoS shows its advantage for atmospheric wind measurement in the aspects of the overall structure, anti-vibration, operational flexibility and detection accuracy.

Multifrequency emission analysis of TeV blazars H 2356–309 and 1ES 1218+304

The multiband nonthermal emissions in radio, X-ray, and very high-energy (VHE) γ-ray bands from two distant blazars, H 2356–309 and 1ES 1218+304, have been detected, and, especially from recent observations with the Suzaku, MAGIC and VERITAS telescopes, clearly reveal nonthermal power-law spectra. We study the broadband nonthermal spectra of the two sources by using a combination of a one-zone homogeneous synchrotron self-Compton (SSC) model and an inhomogeneous conical jet model, where the new external background light (EBL) model is taken into account. The results show that (1) the nonthermal emissions of the two blazars, ranging from X-rays to VHE γ-rays, are from the homogeneous zone whereas the emissions in the radio bands can be explained as the radiation from the inhomogeneous conical jet; (2) a strict lower-limit EBL model can be used to explain their observed spectra well.

The relation between Type-IV solar radio bursts and associated phenomena and white light flares : XIE Rui-xiang & WANG Min Yunnan Observatory, CAS, Kunming 650011

Based on a qualitative analysis of the data of the type IV radio burst and accompanying phenomena (post flare loops, radio pulsation in the decaying phase, multi-band emissions and mass ejection etc.) associated with the white light flare (WLF) of 1991 June 6, it is proposed that the WLF and radio burst come from the same electron accelerating area in the low corona. The energy transfer of the WLF may be a two-step process, the energy of nonthermal electrons from the corona is precipitated in the chromosphere, producing compression waves or a downward radiative field, and then the temperature of the upper photosphere is increased and the WLF is initiated. Moreover, the post-flare loops and radio fine structures may be the counterparts of the WLF.

Equatorial electromagnetic emission with discrete spectra near harmonics of oxygen gyrofrequency during magnetic storm

Equatorial electromagnetic ELF emissions at a frequency range around the oxygen ion gyrofrequency were observed in the low altitude plasmasphere (L = 1.5∼2.5) during magnetic storms with high activity of the ring current by triaxial search coil and single component electric field instruments on board the Akebono satellite. We find that a particular type of the ELF emissions occur with a multi‐band spectral structure around the local gyrofrequency (Fo+) of the oxygen ion (O+) during the main phase of magnetic storm. Our finding includes the following; The multi‐band emissions are localized in the morning sector and often consist of several spaced frequency bands closely related the local gyro‐harmonics of oxygen ion (O+) with a fundamental frequency of Fo+ or 2Fo+. The frequency of each band is dependent on the local magnetic field variation along the satellite orbit and the spacing between the bands is almost equal to Fo+ or 2Fo+. It is suggested that emissions are generated by terrestrial oxygen ion composing the ring current area during the main phase of magnetic storm.