Semiconductor nanocrystals with uniform morphology and composition are expected to show consistent responses during light-matter interactions. However, microscopy reveals significant variations in their photoluminescence blinking patterns, even under identical experimental conditions. This discrepancy arises from differences in crystal defects and nonradiative trap states. As a result, heterogeneous blinking patterns serve as valuable indicator of material quality, uncovering several concealed features through statistical analysis of large datasets. Nonetheless, efficient segregation and analysis of numerous blinking trajectories remain a challenge due to laborious calculations, computational bottlenecks, and manual intervention. In this study, we introduce a robust unsupervised machine learning (UML) assisted module to cluster high-dimensional blinking patterns in near-real-time, while calculating category-wise power spectral densities (PSD) to investigate active traps. Furthermore, we explore the impact of data preprocessing on clustering performance. The 'clustering-segregation-analysis' (UML-PSD) methodology demonstrates versatility, paving a way to advance contemporary (micro)spectroscopy, specifically for rapid and cost-effective optical characterization of semiconductor nanocrystals.

Significant efforts have been devoted to optimizing the postsynthesis processing of all-inorganic colloidal CsPbBr3 nanocrystals (NCs) to achieve stable and ultrapure green emission. However, these NCs harbor a variety of compositional, structural, and surface defects, which undergo dynamic changes during nonsolvent purification. Despite recent advances, the mechanisms underlying degradation during purification and their effects on the photophysical properties of CsPbBr3 NCs remain unclear. In this study, we examine how the polarity of nonsolvents influences the structural integrity, packing behavior, defects formation, as well as optical properties of the resultant NCs, i.e., photoluminescence (PL) blinking, and charge-carrier recombination dynamics. Using synchrotron-based in situ small-angle X-ray scattering, we show that ligand-shell removal during purification induces NC aggregation through a hierarchical, turbostratically stacked assembly process. Ex situ grazing-incidence X-ray scattering further reveals the atomic and nanoscale orientational ordering in NC thin films. Transmission electron microscopy demonstrates that ketone-based washing results in rapid, disordered aggregation and planar defect formation, whereas ester-based washing leads to slower aggregation without stacking faults. Moreover, single-particle PL microscopy indicates pronounced blinking in ketone-treated NCs, attributed to nonradiative structural defect formation. Finally, our findings suggest that ketone-processed NCs exhibit poor electroluminescence performance, whereas ester-processed NCs retain structural integrity and achieve external quantum efficiencies of up to ∼17.6% in light-emitting diodes.

Metal halide perovskites have emerged as promising semiconductors for high-performance photodetectors and X-ray sensors due to their high-Z composition, excellent charge transport, and intrinsic defect tolerance. However, scalable fabrication of thick, pinhole-free films with controlled crystallinity and long-term stability remains challenging, limiting their device performance. Here, we demonstrate the chemical vapor deposition of large-grain, phase-pure CsPbBr3 films with thicknesses of ∼3 µm and grain sizes up to 35 µm, an order of magnitude larger than those obtained by conventional spin coating. By optimizing deposition parameters and substrate selection, we achieve smooth, uniform films with prolonged carrier decay times and enhanced charge transport, as evidenced by time-resolved photoluminescence and Drude-like behavior in terahertz photoconductivity measurements. Photodetectors based on these films exhibit ultralow dark currents (<1 pA cm- 2 at 0 V), high switching ratios (∼104), responsivities up to 0.176 A W- 1, and detectivities of 8.4 × 101 2 Jones, while maintaining exceptional operational and ambient stability over one year. X-ray sensitivity measurements further confirm the potential of these devices for low-dose detection applications. This work establishes CVD as a reproducible, solvent-free route to high-quality halide perovskite films, providing a clear pathway to next-generation photodetectors and X-ray sensors with superior performance and long-term stability.

Two-dimensional (2D) lead halide perovskites have emerged as a promising alternative to their three-dimensional counterparts, offering superior ambient stability and enhanced moisture resistance. Additionally, A-site multi-cation perovskites have gained attention for their ability to improve stability and enhance optoelectronic device performance. Despite these advantages, the synthesis of multi-cation 2D perovskites has traditionally been limited by complex and time-intensive methods, hindering their broader application potential. In this work, we demonstrate the use of a ligand-assisted reprecipitation synthesis approach to produce high-quality 2D formamidinium-guanidinium lead iodide perovskites. By varying the ratio of surface capping ligands, aspect-ratio-tuned nanowires (NWs) were obtained. Phase-pure NWs were confirmed from grazing-incidence wide-angle X-ray scattering and 4D scanning transmission electron microscopy. A single particle optical study pointed out that these confined structures of 2D perovskites were shown to exhibit non-linear optical (NLO) anisotropy in the form of third-harmonic generation and two-photon photoluminescence along the growth direction of the NWs. To demonstrate practical applicability, flexible photodetectors based on these NWs were fabricated, exhibiting a two-order-of-magnitude increase of conductance under UV illumination (405 nm) upon increasing the irradiance from 1 mW cm-2 to 1 W cm-2, with sub-50 µs response times. Power-dependent photoconductivity measurements further revealed that photo-carrier generation is limited by a bimolecular recombination process originating from band-to-band recombination, highlighting the intrinsic charge transport dynamics of the system.

We present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19, during the LIGO–Virgo–KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered ∼14% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz, where we assume the gravitational-wave emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1 × 10 −4 M ⊙ c 2 and luminosity 2.6 × 10 −4 M ⊙ c 2 s −1 for a source emitting at 82 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.08, at frequencies above 1200 Hz, surpassing past results.

We present results from a search for X-ray/gamma-ray counterparts of gravitational-wave (GW) candidates from the third observing run (O3) of the LIGO-Virgo-KAGRA network using the Swift Burst Alert Telescope (Swift-BAT). The search includes 636 GW candidates received with low latency, 86 of which have been confirmed by the offline analysis and included in the third cumulative Gravitational-Wave Transient Catalogs (GWTC-3). Targeted searches were carried out on the entire GW sample using the maximum-likelihood Non-imaging Transient Reconstruction and Temporal Search pipeline on the BAT data made available via the GUANO infrastructure. We do not detect any significant electromagnetic emission that is temporally and spatially coincident with any of the GW candidates. We report flux upper limits in the 15-350 keV band as a function of sky position for all the catalog candidates. For GW candidates where the Swift-BAT false alarm rate is less than 10(-3) Hz, we compute the GW-BAT joint false alarm rate. Finally, the derived Swift-BAT upper limits are used to infer constraints on the putative electromagnetic emission associated with binary black hole mergers.

Metal halide perovskites (MHPs) are emerging as promising materials for optoelectronic and photovoltaic applications due to their favorable electronic properties, including a tunable bandgap. However, achieving high stability for these materials remains a critical challenge, particularly for CsPbI3, whose photoactive phases spontaneously convert into a nonphotoactive yellow orthorhombic δ-phase under ambient conditions. This transformation results in a significant increase in bandgap and a loss of photoactive functionality. In this study, we investigate the impact of Zn2+ and Cd2+ dopants on the phase stability of CsPbI3 nanocrystals (NCs), emphasizing the formation of Ruddlesden-Popper (RP) planar defects, which are frequently observed during compositional tuning. Using transmission electron microscopy (TEM), we follow the temporal evolution of the phase transformation, where black-phase NCs agglomerate and form elongated microtubes with a yellow-phase crystal structure. Our observations demonstrate that doped samples are significantly more stable, while the dopants are key factors in the formation of the RP-like defects with specific atomic arrangements. Using a combination of quantitative TEM and molecular dynamics (MD) simulations we characterize the structure and composition of as-found RP-like defects and elucidate their role in stabilizing the photoactive phases of CsPbI3 through decreased phase transition kinetics.

Semiconductor materials capable of broadband photodetection, spanning X‐rays to near‐infrared (NIR), are essential for applications in medical imaging, industrial inspection, security, and telecommunications. Conventional photodetectors like Si, Ge, InGaAs, and amorphous Se (a‐Se) often encounter tradeoffs in efficiency or cost‐effectiveness. Halide perovskites (HPs) offer competitive or superior optoelectronic properties with low‐cost, solution‐based processing. However, lead‐based HPs pose toxicity and stability challenges, while lead‐free tin‐based HPs suffer from Sn2+ oxidation and structural degradation. The lead‐free double perovskite Cs2AgBiBr6 has emerged as a stable, nontoxic alternative for X‐ray and visible‐light photodetection. Despite its advantages, its high bandgap (≈1.9 eV) limits NIR absorption. This study explores doping Cs2AgBiBr6 with noble metal cations (Au3+, Pd2+, and Ir3+) to lower its absorption onset and enhance its photodetection capabilities across a broad spectrum. The results demonstrate that noble metal doping can overcome the intrinsic limitations of pristine Cs2AgBiBr6, enabling efficient photodetection from X‐rays to the NIR range. This approach highlights a viable pathway for developing next‐generation broadband photodetectors that combine nontoxicity, stability, and wide‐spectrum sensitivity.

An emerging class of two-dimensional (2D) layered perovskites with alternating cations in the interlayer space (ACI) offers tunable dimensionality and enhanced chemical stability, furnishing new opportunities for perovskite-based optoelectronic devices. In order to optimize the macroscopic device performance, a fundamental understanding of the fate and dynamics of photogenerated charge carriers (e.g., free carriers or excitons) is essential. Terahertz spectroscopy unveils unique intrinsic features of distinct ultrafast processes involving photoexcited states. Our study focused on the dynamics of charge carriers in 2D ACI perovskites with varying layers (n). Our results reveal photogenerated charge carrier transitions from excitons to free carriers mediated by increasing the thickness of the interlayer space cation, going from ACI-1 (n = 1) to ACI-3 (n = 3) structures. Further, we examine the transport of photogenerated charge carriers. While n = 1 exhibits a strong excitonic character, a remarkable high charge carrier mobility was recorded with a layer of n ≥ 2.

Metal halide perovskites constitute a promising area of research for application in light-emitting diodes (LEDs), given the successful demonstration of high external quantum efficiency (EQE) devices across the visible to the near-infrared window. Nevertheless, the ionic crystal structure, significantly impacted by internal defects and ionic migration, poses a challenge to the long-term stability of perovskite materials. This limitation stands as a pivotal hurdle impeding further commercialization of perovskite LEDs (PeLEDs). Two-dimensional (2D) perovskite-based materials strive to enhance the operational stability of PeLED devices by refining the crystal structure and passivating the film defects. To this end, we have successfully developed high-quality 2D perovskite thin films using 1,4-butanediammonium (BDA) and methylammonium as alternating cations in the interlayer space (ACI) for efficient LEDs with improved operational stability. Our best-performing device demonstrates an EQE of 4.3% at a high current density (J) of 130 mA/cm2 and remains above 3.3% for a J up to 510 mA/cm2, leading to a high radiance of 138 W/Sr·m2 when driven at 6 V. More importantly, this device shows impressive operational stability, retaining ∼80% of its initial performance operating at 25 mA/cm2 for 9 h. The utilization of ACI perovskites in PeLEDs demonstrates their potential for balancing both high stability and high efficiency.

Mixed cation quasi-2D tin iodide perovskites are promising materials for deep-red to NIR emitting light-emitting diode (LED) applications. However, phase purity remains the major concern to avoid mixed emissions from two or more wavelengths. This work presents the evolution of pure deep red electroluminescence (EL) centred at ≈700 nm corresponding to the emission of pure n = 2 2D crystalline phase. However, structural and optical studies evidenced the formation of mixed-phase heterostructures consisting of n = 1, n = 2, and n = ∞ phase (i.e., FASnI3). It is observed that altering the mixed cation ratio, phase distribution is modified, affecting the EL behavior, causing the observation or absence of the n = 1 2D phase EL emission peak. Selective charge transport and their cascade mechanism illustrates the pure color EL evolution with the support from transient absorption spectroscopic studies. In this regard, a case study is provided along with the supportive rationalities behind the exceptional evolution of pure deep red EL even from the mixed-phase perovskite, reported for the first time in case of quasi-2D tin iodide perovskite.

In this study, we report the first observation of a near-infrared (NIR) emission band from all-inorganic CsPbBr3 and CsPb(Br/Cl)3 perovskite microcrystals. By means of temperature- and power-dependent NIR and visible luminescence spectroscopy, we demonstrate that a fraction of the excited states in these materials relax through radiative transitions involving traps located deep within the band gap, leading to broadband NIR emission. The quantum yield of this deep trap emission is quantitatively determined for the first time and amounts to approximately 0.3% at room temperature. Furthermore, by examining the picosecond-to-nanosecond dynamics of the excited states, using time-resolved luminescence spectroscopy, we observe that the population of NIR initial states occurs on a 660 ps time scale, consistent with the capture of free carriers by deep trap sites. Hence, this work deepens our fundamental understanding of previously unexplored recombination channels in metal halide perovskite microcrystals.

Dearomatization of indoles through a charge transfer complex constitutes a powerful tool for synthesizing three-dimensional constrained structures. However, the implementation of this strategy for the dearomatization of tryptamine-derived isocyanides to generate spirocyclic scaffolds remains underdeveloped. In this work, we have demonstrated the ability of tryptamine-derived isocyanides to form aggregates at higher concentration, enabling a single electron transfer step to generate carbon-based-radical intermediates. Optical, HRMS and computational studies have elucidated key aspects associated with the photophysical properties of tryptamine-derived isocyanides. The developed protocol is operationally simple, robust and demonstrates a novel approach to generate conformationally constrained spirocyclic scaffolds, compounds with high demand in various fields, including drug discovery.

Charge carriers in the soft and polar perovskite lattice form so-called polaron quasiparticles, charge carriers dressed with a lattice deformation. The spatial extent of a polaron is governed by the material's electron-phonon interaction strength, which determines charge carrier effective mass, mobility, and the so-called Mott polaron density, that is, the maximum stable density of charge carriers that a perovskite can support. Despite its significance, controlling polaron dimensions has been challenging. Here, experimental substantial tuning of polaron dimensions is reported by lattice engineering, through Pb/Sn substitution in CH3NH3SnxPb1-xI3. The polaron dimension is deduced from the Mott polaron density, which can be composition-tuned over an order of magnitude, while charge carrier mobility occurs through band transport, and remains substantial across all compositions, ranging from 10 s to 100 s cm2 V s-1 at room temperature. The effective modulation of polaron size can be understood by considering the bond asymmetry after carrier injection as well as the random spatial distribution of Pb/Sn ions. This study underscores the potential for tailoring polaron dimensions, which is crucial for optimizing applications prioritizing either high charge carrier density or high mobility.

The ligand passivation is considered an attractive strategy to prepare high-quality perovskite nanocrystals (PNCs) with improved photophysical features in polar media. However, the long-term stabilization of PNCs in these environments is still challenging, being pivotal to understanding the protection mechanism given by prominent surface ligands and avoiding material deterioration in polar solvents. In this work, how the nature of diverse alkylammonium bromides used during surface passivation influences the photophysical properties and quality of CsPbX3 PNCs fully dispersed in alcohol environments, exhibiting stability up to 10 months are investigated. By adding didodecyldimethylammonium benzyldodecyldimethylammonium and tetrabutylammonium bromides (DDAB, BDAB, and TBAB, respectively), DDAB and BDAB promote a suitable and partial surface coverage are observed, respectively, suppressing defect sites in the nanocrystals. Conversely, TBAB shows poor surface protection, decreasing the PL features of PNCs. The presence of DDAB and BDAB favors the fabrication of color converters, and efficient light-emitting diodes (LEDs) with external quantum efficiencies (EQE) of approximate to 23%. Interestingly, significant device stability with BDAB capping shows an LED half-life of 20-fold longer than for DDAB. This contribution offers a promising approach for preparing highly luminescent and stable alcohol-dispersed PNCs, useful for fabricating efficient optoelectronic devices.

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass $M>70$ $M_\odot$) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities $0 < e \leq 0.3$ at $0.33$ Gpc$^{-3}$ yr$^{-1}$ at 90\% confidence level.

The magnetar SGR 1935+2154 is the only known Galactic source of fast radio bursts (FRBs). FRBs from SGR 1935+2154 were first detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB and the Survey for Transient Astronomical Radio Emission 2 in 2020 April, after the conclusion of the LIGO, Virgo, and KAGRA Collaborations' O3 observing run. Here, we analyze four periods of gravitational wave (GW) data from the GEO600 detector coincident with four periods of FRB activity detected by CHIME/FRB, as well as X-ray glitches and X-ray bursts detected by NICER and NuSTAR close to the time of one of the FRBs. We do not detect any significant GW emission from any of the events. Instead, using a short-duration GW search (for bursts <= 1 s) we derive 50% (90%) upper limits of 10(48) (10(49)) erg for GWs at 300 Hz and 10(49) (10(50)) erg at 2 kHz, and constrain the GW-to-radio energy ratio to <= 10(14)-10(16). We also derive upper limits from a long-duration search for bursts with durations between 1 and 10 s. These represent the strictest upper limits on concurrent GW emission from FRBs.

(Micro)spectroscopy often generates various output signals due to intrinsic inhomogeneity of material arrangement at low dimensions or machinery drift, albeit the bulk composition and experimental parameters remain constant. In fact, such diversity can be harnessed to measure material’s purity, unveiling various concealed features via statistical inspection of heterogeneous signals acquired from several microscopy scans. However, the approach requires efficient categorization of a substantial number of signals, which is currently encumbered by laborious calculations, computational hurdles, and manual intervention. This necessitates a programmed interface to perform time-efficient big data analytics, lack of which has perpetually widened the schism between laboratory and industrial-scale microscopy-based assessment of nanomaterials. We present a robust technique - an unsupervised machine learning driven module for automatic clustering and class-wise power spectral density calculation of real-time microscopy signals. Our methodology has been tested across different aspects of wide-field fluorescence imaging and scanning tunnelling spectroscopy, demonstrating the versatility. Additionally, we investigated the impact of data-processing on the clustering efficiency and optimized the methodology. We anticipate that our futuristic workflow package for contemporary microscopes is the initial endeavor toward fast data analytics and instant material characterization, spanning a diverse spectrum of interests.

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for $U(1)_{B-L}$ gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the $U(1)_{B-L}$ gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM.