Narrow Emission Research Articles

SDSS1335+0728: The awakening of a ∼106 M⊙ black hole

Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼106 M⊙ black hole (BH) that is currently in the process of “turning on”. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1 − W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼106 M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGN observed in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour.

Final Moments. II. Observational Properties and Physical Modeling of Circumstellar-material-interacting Type II Supernovae

We present ultraviolet/optical/near-infrared observations and modeling of Type II supernovae (SNe II) whose early time (δ t < 2 days) spectra show transient, narrow emission lines from shock ionization of confined (r < 1015 cm) circumstellar material (CSM). The observed electron-scattering broadened line profiles (i.e., IIn-like) of H i, He i/ii, C iv, and N iii/iv/v from the CSM persist on a characteristic timescale (t IIn) that marks a transition to a lower-density CSM and the emergence of Doppler-broadened features from the fast-moving SN ejecta. Our sample, the largest to date, consists of 39 SNe with early time IIn-like features in addition to 35 “comparison” SNe with no evidence of early time IIn-like features, all with ultraviolet observations. The total sample includes 50 unpublished objects with a total of 474 previously unpublished spectra and 50 multiband light curves, collected primarily through the Young Supernova Experiment and Global Supernova Project collaborations. For all sample objects, we find a significant correlation between peak ultraviolet brightness and both t IIn and the rise time, as well as evidence for enhanced peak luminosities in SNe II with IIn-like features. We quantify mass-loss rates and CSM density for the sample through the matching of peak multiband absolute magnitudes, rise times, t IIn, and optical SN spectra with a grid of radiation hydrodynamics and non-local thermodynamic equilibrium radiative-transfer simulations. For our grid of models, all with the same underlying explosion, there is a trend between the duration of the electron-scattering broadened line profiles and inferred mass-loss rate: tIIn≈3.8[Ṁ/ (0.01 M ⊙ yr−1)] days.

Tunable Narrowband to Wideband emission of Mn2+, Eu2+ Co-doped GdMgAl11O19 for multifunctional applications

As the widespread application of white light-emitting diodes (WLEDs) in lighting field and liquid crystal display (LCD) backlight, the development of phosphors toward multifunctional applications is considered to be an inevitable tendency. In this work, multi-color light emissions have been realized in Eu2+ and Mn2+-activated magnetoplumbite-type GdMgAl11O19 (GMAO) along with adjustable photoluminescence properties. Significantly, a promising narrow-band green light emission can be achieved by Mn2+-activated GMAO with the full width at half maximum (FWHM) of 27 nm, and such narrow emission band makes the as-prepared WLED device reach 121 % of National Television Standards Committee (NTSC), which can act as an ideal LCD backlight. On the other hand, the broad cyan light can be achieved in Eu2+-activated GMAO. Moreover, multi-color light emissions have been realized in Eu2+ and Mn2+ co-doped GMAO, and the energy transfer from Eu2+ to Mn2+ ions was established. Benefitting from the broad band cyan light emission of Eu2+ ion, a promising WLED device with high color rendering index (CRI) of 90 has been fabricated by using Eu2+ and Mn2+ co-doped sample. The result indicates the multifunctional applications of the GMAO modulated by Eu2+ and Mn2+ activators.

Fusion of Selenium‐Embedded Multi‐Resonance Units Toward Narrowband Emission and Fast Triplet‐Singlet Exciton Conversion

AbstractDeveloping multi‐resonance thermally activated fluorescence (MR‐TADF) emitters with both fast reverse intersystem crossing (RISC) rate and narrow emission bandwidth still remains a formidable challenge. Herein, a design strategy of fused MR skeleton containing heavy chalcogen (sulfur or selenium) for high‐performance MR‐TADF molecules is developed. Impressively, Se‐embedded emitter (DSeBN) shows extremely narrow full width at half maximum (FWHM) value of 16 nm and ultrafast RISC rate constant up to 2.0 × 106 s−1. The organic light‐emitting diode (OLED) based on this emitter exhibits excellent performance parameters with extremely narrow FWHM of 17 nm and high external quantum efficiency (EQE) of 35.31%. Significantly, much suppressed efficiency roll‐off is achieved, in which the EQE still stayed at 32.47% and 25.05% at the luminance of 100 and 1000 cd m−2, respectively. These results represent the state‐of‐the‐art device performance in terms of efficiency and FWHM, shedding new light on the development of practical MR‐TADF emitters.

A mega-electron volt emission line in the spectrum of a gamma-ray burst.

A long gamma-ray burst (GRB) is observed when the collapse of a massive star produces an ultrarelativistic outflow pointed toward Earth. Gamma-ray spectra of long GRBs are smooth, typically modeled by joint power-law segments describing a continuum, with no detected spectral lines. We report a significant (>6σ) narrow emission feature at ~10 mega-electron volts (MeV) in the spectrum of the bright GRB 221009A. Over 80 seconds, it evolves in energy (~12 to ~6 MeV) and in luminosity (~1.1 to <0.43 × 1050 erg second-1) but has a constant width of ~1 MeV. We interpret this feature as a blueshifted spectral line produced by the annihilation of electron-positron pairs, potentially in the same location responsible for emitting the brightest GRB pulses.

Bright and Fast Emission from Robust Supramolecular J-Aggregate Nanostructures through Silica-Encapsulation.

We introduce a two-step silica-encapsulation procedure to optimize both the optical efficiency and structural robustness of 5,5',6,6'-tetrachloro-1,1'-diethyl-3,3'-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC), a two-dimensional sheet-like J-aggregate. We report a fluorescence quantum yield of ∼98%, the highest quantum yield recorded for any J-aggregate structure at room temperature, and a fast, emissive lifetime of 234 ps. Silica, as an encapsulating matrix, provides optical transparency, chemical inertness, and robustness to dilution, while rigidifying the J-aggregate structure. Our in situ encapsulation process preserves the excitonic structure in TDBC J-aggregates, maintaining their light absorption and emission properties. The homogeneous silica coating has an average thickness of 0.5-1 nm around J-aggregate sheets. Silica encapsulation permits extensive dilutions of J-aggregates without significant disintegration into monomers. The narrow absorbance and emission line widths exhibit further narrowing upon cooling to 79 K, which is consistent with J-type coupling in the encapsulated aggregates. This silica TDBC J-aggregate construct signifies (1) a bright, fast, and robust fluorophore system, (2) a platform for further manipulation of J-aggregates as building blocks for integration with other optical materials and structures, and (3) a system for fundamental studies of exciton delocalization, transport, and emission dynamics within a rigid matrix.

The fast transient AT 2023clx in the nearby LINER galaxy NGC 3799 as a tidal disruption of a very low-mass star

We present an extensive analysis of the optical and ultraviolet (UV) properties of AT 2023clx, the closest optical/UV tidal disruption event (TDE) to date ($z=0.01107$), which occurred in the nucleus of the interacting low-ionization nuclear emission-line region (LINER) galaxy, NGC 3799. After correcting for the host reddening ($ h $ = 0.179 mag), we find its peak absolute $g$-band magnitude to be $-18.03 0.07$ mag, and its peak bolometric luminosity to be L_ pk $. AT 2023clx displays several distinctive features: first, it rose to peak within $10.4 days, making it the fastest rising TDE to date. Our SMBH mass estimate of $ M BH ---estimated using several standard methods--- rules out the possibility of an intermediate-mass BH as the reason for the fast rise. Dense spectral follow-up reveals a blue continuum that cools slowly and broad Balmer and He II lines as well as weak He I emission features that are typically seen in TDEs. The early, broad (width $ $) profile of Halpha matches theoretical expectations from an optically thick outflow. A flat Balmer decrement ($L_ H alpha $/$L_ H beta 1.58$) suggests that the lines are collisionally excited rather than being produced via photoionisation, in contrast to typical active galactic nuclei. A second distinctive feature, seen for the first time in TDE spectra, is a sharp, narrow emission peak at a rest wavelength of sim 6353 This feature is clearly visible up to 10\,d post-peak; we attribute it to clumpy material preceding the bulk outflow, which manifests as a high-velocity component of Halpha ($-9\,584 $). Its third distinctive feature is the rapid cooling during the first sim 20 days after peak, reflected as a break in the temperature evolution. Combining these findings, we propose a scenario for AT 2023clx involving the disruption of a very low-mass star ($ with an outflow launched in our line of sight and with disruption properties that led to efficient circularisation and prompt accretion disc formation, observed through a low-density photosphere.

The power of spectrally enhanced artificial night-time lights data: Assessing NTL risks along the urban-natural interface

Artificial night-time lights (NTL) have long been known for their adverse effects on humans and the environment. Recent studies report that the severity of NTL impact on organisms is associated not only with its intensity but also a spectrum. The spectral resolution of freely available satellite NTL data is restricted to red, green, and blue sub-spectra, which are significantly wider than the ranges of vulnerability, reported by laboratory studies for various species. The present study is the first attempt to overlap spectrum-specific NTL data, describing the intensities of light emitted by different lamp types with relatively narrow emission peaks, with the sites where species vulnerable to specific NTL sub-spectra were detected. We overlap those light intensity maps with increasingly detailed maps of natural areas located along the urban-natural interface of the Haifa region. We analyze light pollution in the ecological corridors, which host numerous species with different, but unknown, spectrum-specific effects of NTL (a coarse-level analysis), and in the sites of several species, with either known or unknown spectrum-specific effects of NTL (a fine-level analysis). We show that a considerable part of the ecological corridors is polluted by metal halide and high-pressure sodium lamps which may negatively influence plants, bees, sea turtles, birds, and mammals. One habitat site of the Near Eastern fire salamander (Salamandra infraimmaculata) is polluted by lamps with green-light emission peaks which may explain the low reproductive success of this population. Despite the study limitations, related to the region-specific NTL data of spectrum-specific resolution and scarcity of evidence about the spectrum-specific NTL harmful effects on organisms, we believe that the obtained results would contribute to the elaboration of more informed fine-tuned artificial lighting policies which would diminish the burden of urban built-up zones on their neighboring natural areas.

Crystal Field Engineering Inducing Transformation from Narrow Band of Eu3+ to Broadband of Eu2.

The complete transformation from narrow peak emission of Eu3+ to broadband emission of Eu2+ was first realized in La1-xSr2+xAl1-xSixO5:Eu series solutions relying on crystal field engineering and adjustment of synthesis parameters. The original red phosphor La0.97Sr2AlO5:0.03Eu3+peaks at 703 nm originated from 5D0 →7F4 transition of Eu3+ under 395 nm excitation. As the x value regularly increased, Sr2SiO4-type green phosphor La0.17Sr2.8Al0.2Si0.8O5:0.03Eu2+ was synthesized at x = 0.8, which can be efficiently excited by UV/blue light chips. Moreover, when x > 0.975, Sr3SiO5:Eu2+ type broadband orange phosphor Sr2.945Al0.025Si0.975O5:0.03Eu2+ with excellent thermal stability (91.3% peak intensity at 150 °C) was obtained. Variations in the crystal structure, phase, and luminescence properties were studied in detail. We hope this work can provide a reference that solid solution between distinct but structurally related systems is a strategy to explore the possible phosphors for phosphor-converted light-emitting diodes.

Oligocarbazole modified hybridized local and charge transfer emitters for efficient solution-processed deep blue organic light-emitting diodes

Herein, two new blue solution-processable hybridized local and charge transfer (HLCT) fluorophores (pCTPI and mCTPI) were designed and synthesized by incorporating oligocarbazole fragment into the HLCT luminogenic triphenylamine-phenanthroimidazole (TPI) molecule. Their HLCT and photoluminescence properties were experimentally and theoretically probed by the solvation effect and density functional theory calculations. These materials exhibited an intense blue emission (440 nm) with a good solution-processed film-forming quality and decent hole mobility (3.98–4.55 × 10−6 cm2 V−1s−1), resulting in a successful utilization as non-doped emissive layers in simple solution-processed organic light-emitting diodes (OLEDs). The devices showed deep blue emission (430 nm) with excellent electroluminescence (EL) performance and narrow EL emission as compared to the TPI-based device. Notably, pCTPI-based solution-processed OLED achieved a luminance of 4938 cd m−2 and an external quantum efficiency of 6.35 %.

Unity quantum yield of InP/ZnSe/ZnS quantum dots enabled by Zn halide-derived hybrid shelling approach

Environment-benign indium phosphide (InP) quantum dots (QDs) show great promise as visible emitters for next-generation display applications, where bright and narrow emissivity of QDs should be required toward high-efficiency, high-color reproducibility. The photoluminescence (PL) performance of InP QDs has been consistently, markedly improved, particularly owing to the exquisite synthetic control over core size homogeneity and core/shell heterostructural variation. To date, synthesis of most high-quality InP QDs has been implemented by using zinc (Zn) carboxylate as a shell precursor that unavoidably entails the formation of surface oxide on InP core. Herein, we demonstrate synthesis of superbly bright, color-pure green InP/ZnSe/ZnS QDs by exploring an innovative hybrid Zn shelling approach, where Zn halide (ZnX2, X = Cl, Br, I) and Zn oleate are co-used as shell precursors. In the hybrid Zn shelling process, the type of ZnX2 is found to affect the growth outcomes of ZnSe inner shell and consequent optical properties of the resulting heterostructured InP QDs. Enabled by not only the near-complete removal of the oxide layer on InP core surface through the hybrid Zn shelling process but the controlled growth rate of ZnSe inner shell, green InP/ZnSe/ZnS QDs achieve a record quantum yield (QY) up to unity along with a highly sharp linewidth of 32 nm upon growth of an optimal ZnSe shell thickness. This work affords an effective means to synthesize high-quality heterostructured InP QDs with superb emissive properties.

Crystal-Rigidifying Strategy in Hybrid Manganese Halide to Achieve Narrow Green Emission and High Structural Stability.

Although organic-inorganic hybrid Mn2+ halides have advanced significantly, achieving high stability and narrow-band emission remains enormously challenging owing to the weak ionic nature and soft crystal lattice of the halide structure. To address these issues, we proposed a cationic engineering strategy of long-range cation π···π stacking and C-H···π interactions to simultaneously improve the crystal structural stability and rigidity. Herein, two organic zero-dimensional (0D) manganese halide hybrids of (BACQ)2MnX4 [BACQ = 4-(butylamino)-7-chloroquinolin-1-ium; X = Cl and Br] were synthesized. (BACQ)2MnX4 display strong green-light emissions with the narrowest full width at half-maximum (fwhm) of 39 nm, which is significantly smaller than those of commercial green phosphor β-SiAlON:Eu2+ and most of reported manganese halides. Detailed Hirshfeld surface analyses demonstrate the rigid environment around the [MnX4]2- units originating from the interactions between [BACQ]+. The rigid crystal structure weakens the electron-phonon coupling and renders narrow fwhm of these manganese halides, which is further confirmed by temperature-dependent emission spectra. Remarkably, (BACQ)2MnX4 realizes outstanding structural and luminescence stabilities in various extreme environments. Benefiting from the excellent performance, these Mn2+ halides are used to assemble light-emitting diodes with a wide color gamut of 105% of the National Television System Committee 1931 standard, showcasing the advanced applications in liquid-crystal-display backlighting.

In-situ passivation and anchoring of perovskite quantum dots on KSF:Mn phosphor for liquid crystal display

Perovskite quantum dots (PQDs) hold immense potential for application in backlight liquid crystal display (LCD) owing to their narrow emission spectra, tunable luminous wavelength along with high photoluminescence quantum yield. However, their poor stability severely impedes the practical application of PQDs in optoelectronic devices. Here, we prepare KSF@PQDs composites by in-situ generation of green-emitting MAPbBr3 PQDs on the surface of treated KSF:Mn red phosphors. The surface treatments on KSF:Mn are employed for realization of in-situ passivation and anchoring of MAPbBr3 through chemical interaction between the NH2 group on KSF:Mn and Pb2+ on PQDs, which enables high luminescence intensity, narrow spectral width and simultaneously high photostability of PQDs. Moreover, the ratio of green-to-red emission intensity in KSF@PQDs can be easily modulated by changing APTES content during the surface treatment of KSF:Mn. Further, white light-emitting diode devices consisting of InGaN chip and KSF@PQDs composite achieve luminous efficiency of 41.6 lm·W−1, as well as wide color gamut of 116.6 % for National Television Systems Council standard and 87.2 % for Rec.2020 standard, which paves the way for the application of high stability PQDs in wide color gamut LCD.

Ultraviolet-B Resonant-Cavity Light-Emitting Diodes with Tunnel Junctions and Dielectric Mirrors.

We demonstrate the first electrically injected AlGaN-based ultraviolet-B resonant-cavity light-emitting diode (RCLED). The devices feature dielectric SiO2/HfO2 distributed Bragg reflectors enabled by tunnel junctions (TJs) for lateral current spreading. A highly doped n++-AlGaN/n++-GaN/p++-AlGaN TJ and a top n-AlGaN current spreading layer are used as transparent contacts, resulting in a good current spreading up to an active region mesa diameter of 120 μm. To access the N-face side of the device, the substrate is removed by electrochemically etching a sacrificial n-AlGaN layer, leading to a smooth underetched surface without evident parasitic etching in the n- and n++-doped layers of the device. The RCLEDs show a narrow emission spectrum with a full width at half-maximum (FWHM) of 4.3 nm compared to 9.4 nm for an ordinary LED and a more directional emission pattern with an angular FWHM of 52° for the resonance at 310 nm in comparison to ∼126° for an LED. Additionally, the RCLEDs show a much more stable emission spectrum with temperature with a red-shift of the electroluminescence peak of about ∼18 pm/K and a negligible change of the FWHM compared to LEDs, which shift ∼30 pm/K and show spectrum broadening with temperature. The demonstration of those devices, where a highly reflective mirror is spatially separated from an ohmic metal contact, opens up a new design space to potentially increase the poor light extraction efficiency in UV LEDs and is an important step toward electrically injected UV vertical-cavity surface-emitting lasers.

Excellent Electroluminescent Property of Eu3+-Induced Polystyrene-co-poly(acrylic acid) Aggregates (EIPAs) in Polymeric Light-Emitting Diodes.

Eu3+-induced polystyrene-co-poly(acrylic acid) aggregates (EIPAs) were synthesized using a self-assembly approach, and their structures and photophysical characteristics were examined to achieve effective monochromatic red emission in polymer light-emitting diodes (PLEDs). By adjusting the monomer ratio in RAFT polymerization, the size of Eu3+-induced block copolymer nanoaggregates can be regulated, thereby modulating the luminescence intensity. High-performance bilayer polymer light-emitting devices were fabricated using poly(9,9-dioctylfluorene) (PFO) and 2-(tert-butylphenyl)-5-biphenylyl-1,3,4-oxadiazole (PBD) as the host matrix, with EIPAs as the guest dopant. The devices exhibited narrow red emission at 615 nm with a full width at half-maximum (fwhm) of 15 nm across doping concentrations of 1, 3, 5, and 10 wt %. At a doping concentration of 3 wt %, the device achieved a maximum brightness of 1864.48 cd/m2 at 193.82 mA/cm2 and an external quantum efficiency of 3.20% at a current density of 3.5 mA/cm2. These results indicate that incorporating polystyrene-co-poly(acrylic acid) with Eu3+ complexes enhances the excitation and emission intensity, as well as the structural stability of the emitting layer in PLEDs, thereby improving the device performance.

Probing the Shock Breakout Signal of SN 2024ggi from the Transformation of Early Flash Spectroscopy

We present early-time, hour-to-day cadence spectroscopy of the nearby Type II supernova (SN II) 2024ggi, which was discovered at a phase when the SN shock had just emerged from the red supergiant (RSG) progenitor star. Over the first few days after the first light, SN 2024ggi exhibited prominent narrow emission lines formed through intense and persistent photoionization of the nearby circumstellar material (CSM). In the first 63 hr, spectral lines of He, C, N, and O revealed a rapid rise in ionization as a result of the progressive sweeping up of the CSM by the shock. The duration of the IIn-like spectra indicates a dense and relatively confined CSM distribution extending up to ∼4 × 1014 cm. Spectral modeling reveals that a CSM mass-loss rate at this region exceeding 5 × 10−3 M ⊙ yr−1 is required to reproduce low-ionization emissions, which dramatically exceeds that of an RSG. Analyzing the Hα emission shift implies the velocity of the unshocked outer CSM to be between 20 and 40 km s−1, matching the typical wind velocity of an RSG. The differences between the inner and outer layers of the CSM and an RSG progenitor highlight a complex mass-loss history before the explosion of SN 2024ggi.

Computational screening of multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules for lasing application

Multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules charactering large emission oscillator strengths, effective reverse intersystem crossing (RISC), and narrow emission spectral width, have great potential as laser materials. We propose a molecular descriptor for quick screening MR-TADF molecules as laser candidate materials, A =ΔESTσeffnet,opt, namely, the product of singlet-triplet energy gap and the optical pumping net stimulated emission cross section. These quantities can be calculated by combining quantum chemistry package Gaussian and our own MOMAP program. Through extensive computations benchmarked with existing experiments, we suggest that A value should be larger than 0.311 ⨉ 10−17 cm2 eV for promising lasing molecules. We virtually designed 119 molecules with MR-TADF property, and based on our theoretical protocol by considering descriptor A, we are able to select 10 molecules as lasing molecules. We then further screen out 2 molecules through analyzing the spectral overlap, indicating that only eight molecules are prospective candidates for laser materials. Particularly, we find that ADBNA-Me-BPy molecule possesses large radiative decay rate and large reverse intersystem crossing rate, 1.90 × 106 s−1 and 1.01 × 108 s−1, respectively, implying a low lasing threshold, promising for electrically pumped lasing.

Recent Development and Advancement in Quantum Dots in Pharmaceutical and Biomedical Fields for the Delivery of Drugs

Abstract: Nanoscale semiconductors known as quantum dots (QDs) are essential for drug testing because they bridge the gap between nanotechnology and the testing of drugs. QDs are a valuable tool in theranostics and treatment because of their unique physicochemical features. Due to their photoluminescence and electronic properties, including broad and continuous absorption spectra, narrow emission spectra from visible to near-infrared wavelengths, and long-lasting and high brightness, they are suitable probe materials for use in (bio)sensing (immunological) platforms. Several studies use QDs due to their optical, magnetic, electrical, photochemical, and biological features that allow them to be employed in various scientific domains. When utilized in drug delivery systems, fluorescent markers, such as QDs, can track the metabolism of drugs in the human body. Many medicinal applications, such as disease diagnosis and medication research, can benefit from these fluorescent tests. In this review article, the application of QD in drug delivery and immunoassay sensing has been described in detail.

Highly stable deep-blue emitting CsPbBr3 nanoplatelets with modified zwitterionic surface passivation

Two-dimensional CsPbBr3 nanoplatelets (NPLs) with narrow emission line width are one of the most promising materials for lighting and display applications. Nevertheless, it has been difficult to successfully synthesize deep-blue emitting CsPbBr3 NPLs with long-term stability and high photoluminescence quantum yield (PLQY), which prevents their widespread application in the field of lighting. The use of ligands engineering strategy has demonstrated an increase in the PLQY and stability. Herein, a method employing in situ formation of modified zwitterionic surface ligands is proposed to successfully synthesize high-quality CsPbBr3 NPLs. Zwitterionic passivation strategy can produce deep blue emission of CsPbBr3 NPLs at ∼ 461 nm, achieving a near-unity quantum yield and excellent stability for long-term storage at room-temperature, heat treatment, and ultraviolet irradiation. This enhancement can be attributed to the strong chelation between the modified zwitterions and the surface of CsPbBr3 NPLs, which can effectively immobilize surface halide ions and passivate surface defects. This work provides a flexible way to achieve high PLQY and improve the stability issues in perovskite NPLs.

Do new-type urbanisation pilots narrow urban household carbon emission differences between cities? A temporal-spatial within-between decomposition analysis

The relationship between urbanisation and carbon emissions has been widely discussed. However, whether new-type urbanisation, which aims to achieve green development, helps reduce urban household carbon emissions (UHC), remains unclear. By expanding the temporal-spatial within-between refined Laspeyres index decomposition model with data from 236 Chinese cities from 2015 to 2021, this study investigated the differences in UHC between pilot and non-pilot cities under the new-type urbanisation pilot policy and further explored the drivers of these differences. The temporal decomposition results highlighted the changes and their drivers in UHC between pilot and non-pilot cities. UHC have increased in both types of cities, with the increase linked to higher urbanisation rates, greater carbon intensity, and rising incomes. However, the energy intensity and the urban-rural income gap effects helped curb the extent of the increase. Although a higher level of UHC existed in the pilot cities, the new-type urbanisation pilot policy helped narrow the gap in UHC between pilot and non-pilot cities, thus curbing UHC. The spatial decomposition results further explored the causes of the UHC gap between pilot and non-pilot cities. The within-between decomposition results suggested that, for pilot cities, those with higher UHC than the pilot-group average should close the gap with the group average, whereas those with lower UHC than the national average should close the gap with the national average. The findings present a useful reference for balancing urbanisation with a low-carbon household sector.