Search

The absorption and photoluminescence (PL) spectra of negatively photodoped ZnO nanocrystals dispersed in ethanol are measured under a stepwise photodoping process at room temperature. The spectra are measured almost simultaneously at each photodoping level and compared in detail to discuss the origin of the spectral change. The redshift of the PL spectrum and the increase of its intensity are clearly observed in the early stage of photodoping and are attributed to the trion luminescence. The PL spectrum is found to split into two peaks for highly photodoped nanocrystals. The cause of the splitting is discussed in terms of its dependence on the nanocrystal size. [ABSTRACT FROM AUTHOR]

Single particle level microscopy of immobilized FAPbBr3 nanocrystals (NCs) has elucidated the involvement of different processes in their photoluminescence (PL) intermittency. Four different blinking patterns are observed in the data from more than 100 NCs. The dependence of PL decays on PL intensities brought out in fluorescence lifetime intensity distribution (FLID) plots is rationalized by the interplay of exciton- and trion-mediated recombinations along with hot carrier (HC) trapping. The high intensity-long lifetime component is attributed to neutral exciton recombination, the low intensity-short lifetime component is attributed to trion assisted recombination, and the low intensity-long lifetime component is attributed to hot carrier recombination. Change-point analysis (CPA) of the PL blinking data reveals the involvement of multiple intermediate states. Truncated power law distribution is found to be more appropriate than power law and lognormal distribution for on and off events. Probability distributions of PL trajectories of single NCs are obtained for two different excitation fluences and wavelengths (λex = 400, 440 nm). Trapping rate (kT) prevails at higher power densities for both excitation wavelengths. From a careful analysis of the FLID and probability distributions, it is concluded that there is competition between the HC and trion assisted blinking pathways and that the contribution of these mechanisms varies with excitation wavelength as well as fluence. [ABSTRACT FROM AUTHOR]

It has been shown theoretically that a strong quantum confinement regime in Si nanocrystals promotes highly efficient simultaneous excitation of two electron–hole pairs (biexciton) by a single photon. The rate (inverse lifetime) of biexciton generation has been calculated analytically as a function of the nanocrystal radius. The size-dependence of the rate in Si nanocrystal turns out to be sharp enough—in fact, it is inversely proportional to the sixth power of the radius. At radii values approaching a nanometer, the lifetime of biexciton generation falls into the nanosecond range. The threshold energy of this process in Si nanocrystals is exactly equal to twice the nanocrystal gap in contrast to the case of nanocrystals formed of direct-bandgap semiconductors, where the direct photon-induced creation of a biexciton with such an energy is, in fact, suppressed. [ABSTRACT FROM AUTHOR]

The use of semiconductor nanocrystals in scalable quantum technologies requires characterization of the exciton coherence dynamics in an ensemble of electronically isolated crystals in which system–bath interactions are nevertheless strong. In this communication, we identify signatures of Fano-like interference between excitons and photocarriers in the coherent two-dimensional photoluminescence excitation spectral lineshapes of mixed lead-halide perovskite nanocrystals in dilute solution. Specifically, by tuning the femtosecond-pulse spectrum, we show such interference in an intermediate coupling regime, which is evident in the coherent lineshape when simultaneously exciting the exciton and the free-carrier band at higher energy. We conclude that this interference is an intrinsic effect that will be consequential in the quantum dynamics of the system and will thus dictate decoherence dynamics, with consequences in their application in quantum technologies. [ABSTRACT FROM AUTHOR]

Halide perovskite nanocrystals are at the forefront of materials research due to their remarkable optoelectronic properties and versatile applications. While their lattice structure and optical properties have been extensively investigated for the structure–property correlation, their lattice dynamics, the physical link between the lattice structure and optoelectronic properties, has been much less visited. We report the evolution of structural dynamics of a series of cesium lead halide perovskite nanocrystals whose size and morphology are systematically varied by synthesis temperature. Low-frequency Raman spectroscopy uncovers the nanocrystals' structural dynamics, including a relaxational spectral continuum from ligand librations and a phonon spectrum evolving with nanocrystal size. As the size of nanocrystals increases, their phonon spectrum becomes more intense, and their spectral weights redistribute with new first- and second-order modes being activated. The linewidth of the observed phonon modes generally broadens as the nanocrystal grows larger, an interesting deviation from the established phonon confinement model. We suggest that strong confinement and truncation of the lattice and ligands anchoring on the surface might lead to pinning of the lattice dynamics at nanoscale. These findings offer new insights into the bulk–nano-transition in halide perovskite soft semiconductors. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots are of increasing interest for mid-infrared detection and emission, but device performances will vastly benefit from reducing the non-radiative recombination. Empirically, the photoluminescence quantum yield decreases exponentially toward the mid-infrared, which appears similar to the energy gap law known for molecular fluorescence in the near-infrared. For molecules, the mechanism is electron–vibration coupling and fast internal vibrational relaxation. Here, we explore the possible mechanisms for inorganic quantum dots. The primary mechanism is assigned to an electric dipole near-field energy transfer from the quantum dot electronic transitions to the infrared absorption of surface organic ligands and then to the multiphonon absorption of the quantum dot inorganic core or the surrounding inorganic matrix. In order to obtain luminescent quantum dots in the 3–10 μm range, we motivate the importance of using inorganic matrices, which have a higher infrared transparency compared to organic materials. At longer wavelengths, inter-quantum dot energy transfer is noted to be much faster than radiative relaxation, indicating that bright mid-infrared colloidal quantum dot films might then benefit from dilution. [ABSTRACT FROM AUTHOR]

Functionalization of perovskite nanocrystal surfaces with thiocyanate anions presents a transformative approach to enhancing stability and photoluminescence quantum yield (PLQY) through surface defect passivation. This study investigates the role of thiocyanate ligands in modifying the optoelectronic properties of CsPbBr3 nanocrystals. We employed ultrafast two-dimensional infrared spectroscopy to investigate the nature of the dynamic interaction of thiocyanate ligands with nanocrystal surfaces, providing insights into the mechanisms underlying the observed increase in PLQY and stability. Our analysis reveals that the thiocyanate ligands efficiently passivate the surface defects, thereby enhancing the PLQY and the stability of the treated nanocrystals. The spectroscopic evidence supports a model where thiocyanate binds to under-coordinated lead atoms, contributing to a stable nanocrystal surface with enhanced optoelectronic performance. This ligand-induced passivation mechanism advances our understanding of surface chemistry's role in optimizing nanomaterials for solar cell and LED applications. [ABSTRACT FROM AUTHOR]

Semiconductor nanocrystals (NCs) can function as efficient gain materials with chemical versatility because of their surface ligands. Because the properties of NCs in solution are sensitive to ligand–environment interactions, local chemical changes can result in changes in the optical response. However, amplification of the optical response is technically challenging because of colloidal instability at NC concentrations needed for sufficient gain to overcome losses. This paper demonstrates liquid lasing from plasmonic lattice cavities integrated with ligand-engineered CdZnS/ZnS NCs dispersed in toluene and water. By taking advantage of calcium ion-induced aggregation of NCs in aqueous solutions, we show how lasing threshold can be used as a transduction signal for ion detection. Our work highlights how NC solutions and plasmonic lattices with open cavity architectures can serve as a biosensing platform for lab-on-chip devices. [ABSTRACT FROM AUTHOR]

This work presents the influence of host defect centers on the photoluminescence characteristics of Mg 1 − x Er x Al 2 O 4 (x = 0.005, 0.01, and 0.03) nanocrystals under UV and near-infrared (NIR) excitations. The spinel-structured nanocrystals are synthesized through the combustion method. The Rietveld refinement and nuclear magnetic resonance analyses estimated the Er 3 + ion occupancy at octahedral and other random sites of the MgAl 2 O 4 lattice, and the existence of various lattice defects. Diffuse reflectance spectra showed broad bands attributed to oxygen vacancies as well as antisite defects and sharp peaks attributed to f–f transitions of Er 3 + ions. The upconversion luminescence spectra consisted of sharp emission lines, ascribed to Er 3 + ions, in the green and red wavelength regions, which overlapped over the broad curve attributed to intrinsic defects. Further, the UV excited downconversion luminescence spectra showed two broad emission bands in blue–violet and red-NIR regions with a very weak Er 3 + ion emission feature. This up- and downconversion emission revealed energy transfer between host and Er 3 + ions via intrinsic defects. As a result, the emission color changes from bluish purple to white by varying the excitation wavelength from UV to NIR. This rare earth activated luminescence from MgAl 2 O 4 nanocrystals would exhibit potential applications in display devices and solid-state lighting. [ABSTRACT FROM AUTHOR]

Lead halide perovskite nanocrystals (NCs) have superior luminescence properties compared to classical semiconductor NCs and they are considered promising materials for next-generation emitters. In this work, we measured the size and temperature dependence of the luminescence decay curve in CsPbBr 3 NCs. To reproduce the experimental results, a simple model including one and two-phonon transitions between the exciton fine structures is introduced. It is found that the temperature dependence of the decay rates in small NCs is better reproduced by the two-phonon model rather than by the one-phonon model. However, the one-phonon process becomes more important for large NCs as the bright-dark splitting decreases. [ABSTRACT FROM AUTHOR]

The graphene-based electromagnetic wave absorption materials have attracted extensive attention due to their lightweight, strong absorption, broadband, and thin thickness. In this work, graphene hollow microspheres anchored with FeNi-coupled nanocrystal (GHMs@FeNi3/NiFe2O4) were synthesized using water-in-oil (W/O) emulsification and high-temperature calcination. The GHMs@FeNi3/NiFe2O4 microspheres have a homogeneous spherical morphology and a pronounced hollow structure, and the FeNi-coupled nanocrystals are homogeneously embedded in a spongy shell assembled by rGO nanosheets. Owing to the optimized impedance matching and enhanced attenuation, the GHMs@FeNi3/NiFe2O4 composites exhibit outstanding microwave absorption ability, particularly in the Ku band. The minimum reflection loss (RLmin) value can reach −58.96 dB at 14.43 GHz with a matching thickness of 2.25 mm, and the effective absorption bandwidth (lower than −10 dB) is up to 6.29 GHz (11.71–18 GHz) covering the whole Ku band. We believe that our work provides an idea for the design of high-performance absorbing composite materials. [ABSTRACT FROM AUTHOR]

The cooperative emission of interacting nanocrystals is an exciting topic fueled by recent reports of superfluorescence and superradiance in assemblies of perovskite nanocubes. Several studies estimated that coherent coupling is localized to a small fraction of nanocrystals (10−7–10−3) within the assembly, raising questions about the origins of localization and ways to overcome it. In this work, we examine single-excitation superradiance by calculating radiative decays and the distribution of superradiant wave function in two-dimensional CsPbBr3 nanocube superlattices. The calculations reveal that the energy disorder caused by size distribution and large interparticle separations reduces radiative coupling and leads to the excitation localization, with the energy disorder being the dominant factor. The single-excitation model clearly predicts that, in the pursuit of cooperative effects, having identical nanocubes in the superlattice is more important than achieving a perfect spatial order. The monolayers of large CsPbBr3 nanocubes (LNC = 10–20 nm) are proposed as model systems for experimental tests of superradiance under conditions of non-negligible size dispersion, while small nanocubes (LNC = 5–10 nm) are preferred for realizing the Dicke state under ideal conditions. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals have been under intense investigation for their promise in optoelectronic devices due to their remarkable physics, such as liquid/solid duality. This liquid/solid duality may give rise to their defect tolerance and other such useful properties. This duality means that the electronic states are fluctuating in time, on a distribution of timescales from femtoseconds to picoseconds. Hence, these lattice induced energy fluctuations that are connected to polaron formation are also connected to exciton formation and dynamics. We observe these correlations and dynamics in metal halide perovskite nanocrystals of CsPbI3 and CsPbBr3 using two-dimensional electronic (2DE) spectroscopy, with its unique ability to resolve dynamics in heterogeneously broadened systems. The 2DE spectra immediately reveal a previously unobserved excitonic splitting in these 15 nm NCs that may have a coarse excitonic structure. 2D lineshape dynamics reveal a glassy response on the 300 fs timescale due to polaron formation. The lighter Br system shows larger amplitude and faster timescale fluctuations that give rise to dynamic line broadening. The 2DE signals enable 1D transient absorption analysis of exciton cooling dynamics. Exciton cooling within this doublet is shown to take place on a slower timescale than within the excitonic continuum. The energy dissipation rates are the same for the I and Br systems for incoherent exciton cooling but are very different for the coherent dynamics that give rise to line broadening. Exciton cooling is shown to take place on the same timescale as polaron formation, revealing both as coupled many-body excitation. [ABSTRACT FROM AUTHOR]

Copper phosphide (Cu3-xP) nanocrystals are promising materials for nanoplasmonics due to their substoichiometric composition, enabling the generation and stabilization of excess delocalized holes and leading to localized surface plasmon resonance (LSPR) absorption in the near-IR. We present three Cu-coupled redox chemistries that allow postsynthetic modulation of the delocalized hole concentrations and corresponding LSPR absorption in colloidal Cu3-xP nanocrystals. Changes in the structural, optical, and compositional properties are evaluated by powder X-ray diffraction, electronic absorption spectroscopy, 31P magic-angle spinning solid-state nuclear magnetic resonance spectroscopy, and elemental analysis. The redox chemistries presented herein can be used to access nanocrystals with LSPR energies of 660-890 meV, a larger range than has been possible through synthetic tuning alone. In addition to utilizing previously reported redox chemistries used for copper chalcogenide nanocrystals, we show that the largest structural and LSPR modulation is achieved using a divalent metal halide and trioctylphosphine. Specifically, nanocrystals treated with zinc iodide and trioctylphosphine have the smallest unit-cell volume (295.2 Å3) reported for P63cm Cu3-xP, indicating more Cu vacancies than have been previously observed. Overall, these redox chemistries present valuable insight into controlling the optical and structural properties of Cu3-xP.

Self-assembly of colloidal nanocrystals (NCs) into superlattices (SLs) is an appealing strategy to design hierarchically organized materials with promising functionalities. Mechanistic studies are still needed to uncover the design principles for SL self-assembly, but such studies have been difficult to perform due to the fast time and short length scales of NC systems. To address this challenge, we developed an apparatus to directly measure the evolving phases in situ and in real time of an electrostatically stabilized Au NC solution before, during, and after it is quenched to form SLs using small-angle X-ray scattering. By developing a quantitative model, we fit the time-dependent scattering patterns to obtain the phase diagram of the system and the kinetics of the colloidal and SL phases as a function of varying quench conditions. The extracted phase diagram is consistent with particles whose interactions are short in range relative to their diameter. We find the degree of SL order is primarily determined by fast (subsecond) initial nucleation and growth kinetics, while coarsening at later times depends nonmonotonically on the driving force for self-assembly. We validate these results by direct comparison with simulations and use them to suggest dynamic design principles to optimize the crystallinity within a finite time window. The combination of this measurement methodology, quantitative analysis, and simulation should be generalizable to elucidate and better control the microscopic self-assembly pathways of a wide range of bottom-up assembled systems and architectures.

PbS semiconductor nanocrystals (NCs) have been heavily explored for infrared optoelectronics but can exhibit visible-wavelength quantum-confined optical gaps when sufficiently small (⌀ = 1.8–2.7 nm). However, small PbS NCs traditionally exhibited very broad ensemble absorption linewidths, attributed to poor size-heterogeneity. Here, harnessing recent synthetic advances, we report photophysical measurements on PbS ensembles that span this underexplored size range. We observe that the smallest PbS NCs pervasively exhibit lower brightness and anomalously accelerated photoluminescence decays—relative to the idealized photophysical models that successfully describe larger NCs. We find that effects of residual ensemble size-heterogeneity are insufficient to explain our observations, so we explore plausible processes that are intrinsic to individual nanocrystals. Notably, the anomalous decay kinetics unfold, surprisingly, over hundreds-of-nanosecond timescales. These are poorly matched to effects of direct carrier trapping or fine-structure thermalization but are consistent with non-radiative recombination linked to a dynamic surface. Thus, the progressive enhancement of anomalous decay in the smallest particles supports predictions that the surface plays an outsized role in exciton–phonon coupling. We corroborate this claim by showing that the anomalous decay is significantly remedied by the installation of a rigidifying shell. Intriguingly, our measurements show that the anomalous aspect of these kinetics is insensitive to temperature between T = 298 and 77 K, offering important experimental constraint on possible mechanisms involving structural fluctuations. Thus, our findings identify and map the anomalous photoluminescence kinetics that become pervasive in the smallest PbS NCs and call for targeted experiments and theory to disentangle their origin. [ABSTRACT FROM AUTHOR]

Incorporating magnetic ions into semiconductor nanocrystals has emerged as a prominent research field for manipulating spin-related properties. The magnetic ions within the host semiconductor experience spin-exchange interactions with photogenerated carriers and are often involved in the recombination routes, stimulating special magneto-optical effects. The current account presents a comparative study, emphasizing the impact of engineering nanostructures and selecting magnetic ions in shaping carrier–magnetic ion interactions. Various host materials, including the II–VI group, halide perovskites, and I–III–VI2 in diverse structural configurations such as core/shell quantum dots, seeded nanorods, and nanoplatelets, incorporated with magnetic ions such as Mn2+, Ni2+, and Cu1+/2+ are highlighted. These materials have recently been investigated by us using state-of-the-art steady-state and transient optically detected magnetic resonance (ODMR) spectroscopy to explore individual spin-dynamics between the photogenerated carriers and magnetic ions and their dependence on morphology, location, crystal composition, and type of the magnetic ion. The information extracted from the analyses of the ODMR spectra in those studies exposes fundamental physical parameters, such as g-factors, exchange coupling constants, and hyperfine interactions, together providing insights into the nature of the carrier (electron, hole, dopant), its local surroundings (isotropic/anisotropic), and spin dynamics. The findings illuminate the importance of ODMR spectroscopy in advancing our understanding of the role of magnetic ions in semiconductor nanocrystals and offer valuable knowledge for designing magnetic materials intended for various spin-related technologies. [ABSTRACT FROM AUTHOR]

Anion exchange is a facile, post-synthetic method to tune the emission wavelength of colloidal cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals. While colloidal nanocrystals can exhibit size-dependent phase stability and chemical reactivity, the role of size in the mechanism of anion exchange in CsPbX3 nanocrystals has not been elucidated. We used single-particle fluorescence microscopy to monitor the transformation of individual CsPbBr3 nanocrystals to CsPbI3. By systematically varying the size of the nanocrystals and the concentration of substitutional iodide, we observed that smaller nanocrystals exhibit longer transition times in their fluorescence trajectories, while larger nanocrystals undergo a more abrupt transition during anion exchange. Monte Carlo simulations were used to rationalize the size-dependent reactivity, in which we varied how each exchange event affects the probability for further exchange. Greater cooperativity for simulated ion exchange leads to shorter transition times to complete the exchange. We propose that size-dependent miscibility between CsPbBr3 and CsPbI3 at the nanoscale controls the reaction kinetics. Smaller nanocrystals maintain a homogeneous composition during anion exchange. As the nanocrystal size increases, variations in the octahedral tilting patterns of the perovskite crystals lead to different structures for CsPbBr3 and CsPbI3. Thus, an iodide-rich region must first nucleate within larger CsPbBr3 nanocrystals, which is followed by rapid transformation to CsPbI3. While higher concentrations of substitutional anions can suppress this size-dependent reactivity, the inherent differences in reactivity between nanocrystals of different sizes are important to consider when scaling up this reaction for applications in solid-state lighting and biological imaging. [ABSTRACT FROM AUTHOR]

The field of 2D nanomaterials is ever-growing with a myriad of synthetic advancements that have been used to obtain such materials. There are top-down, as well as bottom-up, fabrication methods for obtaining 2D nanomaterials; however, synthesis of 2D nanomaterials from solution offers a simple scalable way to control size, shape, and surface. This review outlines the recent advances in colloidal polyol synthesis of 2D nanomaterials and provides perspectives on the similarities and differences in various syntheses. Various materials classes are presented and discussed, including metals, oxides, chalcogenides, and halides, that can be synthesized as 2D nanomaterials via a polyol process. Throughout the literature, polyol media is demonstrated to be versatile not only as a solvent and reducing agent for metal precursors but also as a binding and shape-directing agent for many 2D nanomaterials. Polyols also offer the ability to dissolve various surfactants and additives that can further control the morphology and composition of various nanomaterials. In this review, we outline the various 2D materials that have been realized via the solution polyol route. [ABSTRACT FROM AUTHOR]

Converting carbon dioxide into formic acid with formate dehydrogenase (FDH) as a catalyst is a gentle and eco‐friendly process that not only conserves energy and reduces emissions but transforms waste into valuable resource. Enzyme immobilization is a common strategy for improving the stability and recyclability of enzyme, however, the procedures are usually complicated that include surface modification and binding reactions in order to form reliable linkages. Co‐deposition of polydopamine (PDA) with polyethyleneimine (PEI) is a popular surface modification approach in versatile fields, but their co‐deposition with enzymes is rarely reported. Herein, one‐pot immobilization of FDH on SiO2 nanoparticles based on catechol chemistry was attempted for the first time with or without PEI, and the resultant immobilized enzymes, FDH/PDA/PEI‐SiO2 and FDH/PDA‐SiO2, were characterized, and the effects of the composition and deposition conditions on the catalytic performance were investigated. FDH/PDA‐SiO2 exhibited a higher apparent specific activity than FDH/PDA/PEI‐SiO2, which was separately 0.167 and 0.136 mM/h/mg. The activity recovery rate was 464% and 378% of that of free enzyme. After 5 cycles, their relative activity was 82.3% and 87.4%. This research is significant in presenting a simple and high‐efficient one‐pot immobilization method that can be extended to other kinds of enzymes. [ABSTRACT FROM AUTHOR]

Recently, lanthanide‐based 0D metal halides have garnered considerable attention owing to their applications in light–emitting diodes (LEDs), X‐ray imaging, and photodetectors. Among these materials, 0D Cs3TbCl6 (CTC) nanocrystals (NCs) have demonstrated promising performance in X‐ray imaging and light‐emitting diodes. However, a considerable drawback of CTC NCs is their limited absorption coefficient in the UV‐A region (315–380 nm). To address this limitation and enhance the absorption coefficient in the UV‐A region, Ce3+ is incorporated into CTC NCs—advantageous owing to the high absorption coefficient of Ce3+ in the UV‐A region, attributed to—4f‐5d orbital coupling. In addition, Ce3+ ions sensitize the luminescence of CTC NCs and enhance the photoluminescence quantum yield from 75% to 87%. Energy transfer from Ce3+ to Tb3+ is investigated at different dopant ratios. Furthermore, Cs3CeTbCl6 (CCTC) NCs have been utilized in white LED devices. Understanding such competitive energy transfer in lanthanide‐based perovskite‐inspired metal halides will facilitate the development of novel luminescent metal halides for lighting applications. [ABSTRACT FROM AUTHOR]

The commonly used automotive head‐up display (HUD) technology is confronted with the problems of poor stability in organic resin counterpart and the unsatisfactory display effect of projection lighting source. To solve these issues, developing state‐of‐the‐art materials and designing new HUD schemes with a wide color gamut is of necessity. Herein, a series of pure red/green/blue (R/G/B) upconverting (UC) nano‐glass‐ceramics (GCs) containing lanthanide‐doped NaLuF4 nanocrystals (NCs) are synthesized in a cost‐effective, environment‐friendly, and scalable manner, simultaneously achieving high crystallinity (≈45.44%) and high transparency (>80%). Yb3+ is chosen as the sensitizer to Tm3+ (blue UC)/Ho3+ (green UC), due to its large absorption cross section from ground state 2F7/2 to excited state 2F5/2; meanwhile Er3+, Tm3+ co‐doped into NCs can obtain pure red UC emission via promoting the population of Er3+ red‐emitting 4F9/2 state. Consequently, the as‐prepared materials exhibit high R/G/B color purity of > 80% owing to the energy transfer between different lanthanide ions (Yb3+, Tm3+, Ho3+, and Er3+) upon 980 nm near‐infrared (NIR) laser excitation, and possess superior thermal reversibility/water resistivity. Remarkably, two unprecedented HUD prototypes are constructed to demonstrate the application feasibility of developed pure R/G/B UC GCs. [ABSTRACT FROM AUTHOR]

Constructing an S-scheme system with highly active catalysts is a significant approach for improving the separation of photoinduced carriers to solve the related environmental aggravation. In this study, a well-designed S-scheme AgVO3/CaIn2S4 photocatalyst was synthesized for water purification by in situ growing CaIn2S4 nanocrystals on AgVO3 nanorod surfaces. The optimized AgVO3/CaIn2S4 heterostructure demonstrates an enhanced photocatalytic efficiency (94.1%) toward tetracycline hydrochloride (TCH) degradation compared with bare AgVO3 (42.6%) and CaIn2S4 (81.6%). The significant enhancement of photocatalytic activity is attributed to the S-scheme charge transfer mechanism in the AgVO3/CaIn2S4 heterostructure, which effectively directs photogenerated charge migration, boosts charge transfer, and preserves the high redox capacity of photoexcited electrons and holes on different active sites. This study is expected to offer insights into strategically designing and preparing S-scheme heterojunction photocatalysts to improve water purification. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: We present a facile synthetic strategy to create mesoporous Cu2O nanocrystals with tunable pore structures and surface functional groups of amine derivatives for efficient and preferable electrochemical conversion of CO2 into ethylene. The structural characteristics of these Cu2O nanocrystals can be manipulated using a set of amine derivatives, such as pyridine, 4,4'‐bipyridine, and hexamethylenetetramine, during the oxidative etching process of Cu nanocrystals by bubbling gaseous oxygen in N,N‐dimethylformamide solution. These amine derivatives not only serve as surface functional groups but also significantly affect the resulting pore structures. The synergistic effect of pore structure confinement and surface amine functionalization leads to the superb Faradaic efficiency (FE) of 51.9% for C2H4, respectively, together with the C2H4 partial current density of –209.4 mA·cm−2 at –0.8 V vs. reversible hydrogen electrode (RHE). The relatively high selectivity towards C2H4 was investigated using DFT simulations, where 4,4'‐bipyridine functionalized Cu2O seemed to favor the C2H4 formation with the low free energy of the intermediates. This study provides a feasible strategy to manipulate the pore structure and surface functionalization of mesoporous Cu2O nanocrystals by regulating the oxidative etching process, which sheds light on the rational preparation of high‐performance CO2RR electrocatalysts. [ABSTRACT FROM AUTHOR]

This paper presents the preparation and characterization of transparent oxyfluoride glass ceramics (GCs) that contain nanocrystals of K 3 YF 6 co-doped with Dy3+ and Sm3+. The study investigates the luminescence characteristics, the process of energy transfer (ET) and the behavior of the ratio-metric temperature sensing. The formation of well-defined nanocrystals of K 3 YF 6 in the glass substrate was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By varying Sm3+ concentration, a tunable emission ranging from pale yellow to orange-red was observed. Energy transfer from Dy3+ to Sm3+ ions was confirmed through fluorescence spectra and decay curves. Sample K 3 YF 6 , containing 0.5 mol%Dy3+/1.2 mol%Sm3+, showed an absolute sensitivity (S a) of 0.635 % K−1 and relative sensitivity (S r) of 0.401 % K−1. These findings underscore the promising applications of K 3 YF 6 : Dy3+, Sm3+ GCs in multicolor displays and high-performance temperature sensing devices. [ABSTRACT FROM AUTHOR]

The primary obstacle faced by researchers in the field of luminescent metal-halide perovskites is their inherent instability, prompting a shift in focus towards enhancing the stability of perovskite nanocrystals (PNCs). One of the promising approaches to address this challenge involves the utilization of metal-organic frameworks (MOFs) to fabricate PNCs@MOF composites. The present study reports a facile and low-cost colloidal strategy to prepare (Et 3 NH)PbBr 3 PNCs followed by their encapsulation within UiO-67 to enhance their photoluminescence (PL) emission stability. The PNCs and modified UiO-67 were prepared separately via simple and efficient ligand-assisted reprecipitation (LARP) and hydrothermal methods, respectively. After modification of the UiO-67, the pore sizes experienced a substantial increase from 1.90 to 28.84 nm which significantly facilitated the localization of PNCs within the porous matrix. Under a full survey of experimental conditions, the resulting (Et 3 NH)PbBr 3 @UiO-67 composite exhibited a bright deep-blue emission at around 410 nm with an emission quantum yield of 52 %. The emission durability of the fabricated PNCs@MOF composites was assessed against temperature and long-time of storage, confirming the superior advantages of MOF even at elevated temperatures of up to 100 °C. The stable and luminous deep-blue emission displayed by the PNCs@MOF composites in this investigation, offers a promising advancement in materials development for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Transparent glass‐ceramics (GCs) are promising for applications that require both optical clarity and superior mechanical strength, such as high‐performance displays and ballistic armor. However, achieving this combination typically involves a trade‐off, as crystallization processes that enhance mechanical properties often compromise transparency. This study investigates the optimization of mechanical properties in transparent and translucent MgO‐Al2O3‐SiO2 (MAS) GCs. We examine the heat treatment conditions necessary for achieving various levels of transparency and evaluate the influence of crystal size and volume fraction on Vickers hardness, indentation crack resistance, and fracture toughness (KIc). Our findings indicate that, depending on the composition and heat treatment conditions, even nanocrystals smaller than 100 nm can diminish transparency, rendering the GCs translucent. Translucent and opaque samples exhibit superior mechanical performance due to higher crystallized fractions and larger crystals. However, specific thermal protocols were identified to produce transparent GCs (visible light transmittance > 80% for 1.5 mm thick samples) with at least a 30% increase in KIc compared to their parent glasses. This study demonstrates the feasibility of balancing transparency and mechanical strength in MAS GCs through careful optimization of processing parameters. [ABSTRACT FROM AUTHOR]

Recently emerging perovskite nanocrystals (PNCs) have drawn considerable attention due to the superior optoelectronic performances. However, the terrible stability of red emissive PNCs (r‐PNCs) limits their broader application in aqueous media. Despite various encapsulation methods are proposed, the preparation of aqueous r‐PNCs with facile operation and excellent durability is still challenging. Herein, aqueous green emissive PNCs (g‐PNCs) by employing water as an external stimulus to treat oleyamine‐capped CsPbBr3 PNCs are synthesized initially, and then aqueous‐stable pure red emissive PNCs by anion‐exchange reaction and subsequently thiocyanate (SCN‐) passivation treatment (SCN‐r‐PNCs) are prepared. The obtained aqueous‐stable SCN‐r‐PNCs display high brightness, outstanding stability, and extended photoluminescence lifetime. Moreover, by combining aqueous r‐PNCs and portable smartphones, a fluorescence chemosensor for the detection of aqueous SCN− ions is constructed, which exhibits simple operation, high sensitivity, high selectivity, low detection limit, and visualized sensing. This work not only provides a new and facile strategy to prepare aqueous‐stable red emissive PNCs, but also further extends the application of red emissive PNCs in aqueous‐based fields. [ABSTRACT FROM AUTHOR]

Introduction: Silver nanoparticles have a diversity of applications both in biological and technological areas. More recently, studies conducted in the Nano/Bio interface have demonstrated that chiral nanocrystals grew in chiral templates, and nanostructures functionalized with chiral molecules present specific properties. These properties apply to advanced materials, energy, medicine, and pharmacology. Methodology: The present study synthesized silver nanoparticles on silver seeds using D- and L-histidine as templates and borohydride as a reducing agent. Results and Discussion: The nanoparticles were characterized by UV-visible spectroscopy and presented surface plasmon resonance (SPR) bands around 415 nm. CD spectra showed signals in the region of the SPR band, indicating the growth of nanocrystals with chiral distortion. Synthesized silver nanoparticles were also characterized by high-resolution transmission electron microscopy (HRTEM), which evidenced the presence of histidine corona. The silver nanoparticles were functionalized with prolyl-oligopeptidase (POP), a prolinespecific endopeptidase expressed in the brain. This enzyme cleaves neuroactive peptides involved in memory, learning, and neurodegeneration. The enzyme POP was expressed with a His-tag to provide competitive binding affinity to silver nanoparticles covered by D- and L-histidine. Considering the biological importance, POP was chosen as a model for studying the functionalization of chiral silver nanoparticles regarding the chiral discrimination for binding affinity and stabilization. [ABSTRACT FROM AUTHOR]

Self-assembly of colloidal particles into 3D lattices, with potential applications as single crystals with promising optical properties, has received considerable attention. The superior bandgap properties of open colloidal lattices over their more easily self-assembling close-packed counterparts make them more demanding for this purpose. However, due to the mechanical instability of low-coordination open lattices, their self-assembly has proven to be challenging. Here, we employ a model of triblock Janus nanoparticles, which includes their surface chemistry (hydrophobic patches at the poles and surface charges in the equator) to simulate their self-assembly to three-dimensional nanocrystals. The solvent is explicitly included in the simulation, and hydrodynamic interactions are taken into account by dissipative particle dynamics. Biased sampling simulations are conducted to drive the simulations between different phases. The phase diagrams represent a competition between the liquid phase, open (pyrochlore, perovskite, and diamond), and close-packed [body-centered cubic (bcc) and face-centered cubic (fcc)] nanocrystals, whose stabilities depend on the patch width, temperature, and density. Patch widths allowing for three contacts per patch stabilize the pyrochlore nanocrystal at low densities and the fcc phase at high densities, and those allowing four contacts per patch stabilize the perovskite nanocrystal at low densities, the bcc lattice at higher densities, and upon further compression, the fcc lattice. The diamond nanocrystal is stabilized by wide enough patches that provide strong enough bonding between nanoparticles. Increasing the density converts the diamond nanocrystal to bcc and, subsequently, to a higher-density fcc lattice. The calculated free energies for conversion of liquid to crystalline phases reveal that the barrier height for nucleation of open lattices (within their stability domains) is lower than that for denser lattices. [ABSTRACT FROM AUTHOR]

Ultrathin two-dimensional (2D) nanostructures, with superhigh exposure of the under-coordinated metal atoms relative to large-sized quasi-spherical particles or bulk counterparts, have shown enormous potential to enhance various heterogeneous catalytic reactions. The creation of in-plane holes and rational assembling of ultrathin 2D nanosheets into 3D hierarchical architectures can prevent the restacking issue of nanosheets, thereby providing more active sites by hampering atomic diffusion, nearby nanosheet aggregation, and thermodynamic structural reform. Herein, we report the stepwise construction of ultrathin CuAuAg nanosheet-assembled 3D nanoflowers (NFs). The synthesis involves the conversion of Au@CuxO mesoporous nanospheres into CuAg NFs, followed by a controlled galvanic replacement reaction with chloroauric acid to create holes and manipulate the atomic ratio between Cu, Au, and Ag. With strong broad-spectrum light absorption across the UV–vis region, the current CuAuAg NFs exhibited satisfactory photothermal conversion under Xe lamp irradiation. When serving as HER electrocatalysts, the Cu10.5Au58.4Ag31.1 NFs displayed the optimized performance in terms of overpotential and activity, surpassing the Cu71.4Ag28.6 NFs and Au NCs, which is supported by DFT simulations, showcasing the multimetallic coupling advantage for HER. This study presents a viable route to construct trimetallic 3D hierarchical nanostructures and validates their application in photothermal conversion and electrocatalytic HER, guiding the design of high-performance photosensitizers and electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g‐C3N4) has received much attention as a metal‐free photocatalyst for dye degradation and sterilization. However, the low photocatalytic bactericidal activity and the difficulty in recycling have limited its applications. Here, oxidatively modified g‐C3N4 grafted with polyethyleneimine (PEI) nanofiber membranes (PVA/PEI‐OCN) was reported to enhance the photocatalytic activity. The modification by PEI grafting could reduce the recombination rate of photogenerated carriers and lead to more electrons for the photocatalytic reaction. In addition, electron spin resonance (ESR) results showed that the generation of reactive oxygen species (˙OH, ˙O2− and 1O2) were significantly enhanced in photocatalysis, leading to the significant enhancement of photocatalytic bactericidal activity and dye degradation. Furthermore, the PVA/PEI‐OCN nanofiber membranes prepared by electrospinning had smooth surfaces and uniform fiber formation, with an average diameter of 380 ± 60 nm. The tensile strength was about 73.5% higher than that of PVA nanofiber membranes. The inhibition diameter of PVA/PEI‐OCN‐4 against Escherichisa coli (E. coil) could reach 20 ± 0.2 mm, and the maximum degradation efficiency of methylene blue solution (10 mg/L) could reach 92.8% within 120 min. This work provided an effective paradigm for the rational design of metal‐free photocatalytic materials for elimination of bacterial and dye contamination. [ABSTRACT FROM AUTHOR]

A comparative study was conducted to investigate the gamma and neutron radiation shielding properties of composites made from iron metal (micro and nano) dispersed within natural rubber (NR). The aim was to attenuate neutron and γ‐rays. The study utilized the gamma spectroscopy technique and the Monte Carlo FLUKA code. To assess the gamma ray shielding, a 3×3 Nal (Tl) detector and radioactive point sources were employed. Two comparative studies were carried out, one using Fe loaded NR (Fe/NR) composites in microsize and the other using Fe/NR composites in nanosize. The objective was to determine the impact of iron nanoparticles on the shielding ability of the composites. The findings revealed that the Fe/NR composites in nanosize exhibited superior gamma radiation shielding ability compared with the Fe/NR composites in microsize. These results were supported by the FLUKA Monte Carlo code, which demonstrated good agreement with both the experimental and theoretical XCOM data. [ABSTRACT FROM AUTHOR]

Fluorescence/luminescence bioimaging, utilizing rare‐earth doped nanocrystals (RENCs) within the NIR‐IIb (1500–1700 nm) sub‐window, has drawn interest for its deep penetration depth and superior resolution. Herein, Er3+/Yb3+ couple is rationally designed in topologically arranged RENCs that facilitate a boosted 1530 nm emission of Er3+ via premeditated Yb3+‐mediated energy transfer processes under 808 nm excitation. To maximize this modulation effect for boosting 1530 nm emission, a regional active ions concentration and spatial regulation strategy is explored in the optimized concentration and core–shell–shell structure (NaErF4:20%Yb@NaYbF4:20%Er@NaYF4 with a quantum yield of 16.46% in NIR‐IIb region). Leveraging the superior emission and multi‐wavelength excitation characteristics of the as‐obtained nanocrystals, a NIR‐IIb‐based ratiometric fluorescence imaging measurement is achieved under 808 and 980 nm excitation, which cannot only show the 2D distribution of probes but also provide spatial depth information (range from 0 to 2.8 mm with a tissue depth resolution of 66 µm). The findings hold significant potential for advancing both vascular science and clinical medicine. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF) nanofillers have attracted significant attention recently for high-temperature proton exchange membrane fuel cell (HT-PEMFC) applications because of their excellent effectiveness for enhancing the performance of proton exchange membranes (PEMs) based on phosphoric acid–doped polybenzimidazole (PBI). Universitetet i Oslo-66 (UiO-66) is one of the most used zirconium-based MOFs. In this study, we synthesized amine-functionalized UiO-66, imidazole-functionalized UiO-66, and sulfonated UiO-66 as nanofillers for adjusting the interfacial compatibility of PBI-based nanocomposite membranes. The results demonstrated that incorporating functionalized UiO-66 nanocrystals simultaneously improved tensile strength, oxidative stability, and proton conductivity of the membranes. Moreover, the imidazole-functionalized UiO-66 nanofiller exhibited optimal interfacial compatibility with polybenzimidazole and more significantly improved membrane properties than the other nanofillers. The PEM containing 10 wt% imidazole-functionalized UiO-66 achieved a 113% increase in proton conductivity at 170°C (0.0418 S/cm) and a 249% increase in the maximum power density of the fuel cell (406.1 mW/cm2). [Display omitted] • Functionalization of zirconium-based metal-organic framework nanofillers. • Imidazole-functionalized nanofillers obtained better interfacial compatibility. • Imidazole-functionalized nanofillers enhanced membrane properties most. • A 113% increase in the proton conductivity of the proton exchange membrane. • A 249% increase in the maximum power density of fuel cell was demonstrated. [ABSTRACT FROM AUTHOR]

Structural modelling of operando pair distribution function (PDF) data of complex functional materials can be highly challenging. To aid the understanding of complex operando PDF data, this article demonstrates a toolbox for PDF analysis. The tools include denoising using principal component analysis together with the structureMining, similarityMapping and nmfMapping apps available through the online service 'PDF in the cloud' (PDFitc, https://pdfitc.org/). The toolbox is used for both ex situ and operando PDF data for 3 nm TiO2‐bronze nanocrystals, which function as the active electrode material in a Li‐ion battery. The tools enable structural modelling of the ex situ and operando PDF data, revealing two pristine TiO2 phases (bronze and anatase) and two lithiated LixTiO2 phases (lithiated versions of bronze and anatase), and the phase evolution during galvanostatic cycling is characterized. [ABSTRACT FROM AUTHOR]

Herein we report the existence of room temperature ferromagnetic ordering in pristine cuprous oxide nanocrystals mediated by native point defects present in the material. To demonstrate defect‐induced magnetism, cuprous oxide nanocrystals were synthesized in a simple and sustainable route employing hydroxylamine as the reducing agent. The crystalline phase of the as‐synthesized nanocrystals was investigated and was found to have crystallized in cuprite crystal structure. The optical absorption characteristics exhibits absorption features in the visible region between 400 and 600 nm signifying the presence of optically active defects. The morphology of the sample was examined, which reveals the shape to be corner‐truncated rhombic dodecahedral and the size to be in the range of 200–250 nm. The field‐dependent magnetization measurement at room temperature indicates the presence of collective ferromagnetism with hysteresis behavior (Ms = 210 memu g−1, Mr = 43 memu g−1, Hc = 16.37 mT) due to exchange interaction between the uncompensated spin moments present on the surface of the material. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters and defect structures are theoretically studied for the substitutional Mn2+ at the core of CdSe nanocrystals and in the bulk materials from the perturbation calculations of spin Hamiltonian parameters for trigonal tetrahedral 3d5 clusters. Both the crystal‐field and charge transfer contributions are taken into account in the calculations from the cluster approach. The impurity‐ligand bond angles are found to be about 1.84° larger and 0.10° smaller in the CdSe:Mn2+ nanocrystals and bulk materials, respectively, than those (≈109.37°) of the host Cd2+ sites. The quantitative criterion of occupation (at the core or surface) for Mn2+ in CdX (X = S, Se, Te) nanocrystals is presented for the first time based on the inequations of hyperfine structure constants (HSCs). This criterion is well supported by the experimental HSCs data of Mn2+ in CdX nanocrystals. The previous assignments of signals SI as Mn2+ at the core of CdS nanocrystals are renewed as Mn2+ at the surface based on the above criterion. The present studies would be helpful to achieve convenient determination of occupation for Mn2+ impurities in CdX semiconductor nanocrystals by means of spectral (e.g., HSCs) analysis. [ABSTRACT FROM AUTHOR]

It is well known that two metal oxides can form depletion layers at the interface by constructing heterojunctions due to the different Fermi energy levels of each metal oxide, which can improve the carrier mobility and provide significant advantages for gas sensing. In this work, NdFeO 3 nanoparticles were grown on ZnO with hexagonal cone structure by secondary hydrothermal method to successfully construct n-ZnO/p-NdFeO 3 heterojunctions, and the crystal structures, oxygen vacancies, microstructures, optical properties, and gas-sensing properties of the ZnO/NdFeO 3 composites were investigated. The ZnO/NdFeO 3 sensors showed good ethanolamine (EA) The response characteristics of the ZnO/NdFeO 3 sensor to ethanolamine (EA) with a concentration of 100 ppm EA at 240 °C (R g /R a) is about 25, which improves the response by a factor of 1.6 and 1.32 compared with that of NdFeO3 and ZnO. Meanwhile, it has excellent selectivity, good cyclic reproducibility, and durable long-term stability with response/recovery times of 19 s/49 s. The improved EA sensing performance of NdFeO 3 -modified ZnO, in addition to its large specific surface area due to its unique rough inhomogeneous structure, is also related to the higher concentration of oxygen vacancies at the ZnO/NdFeO 3 interface after the composite. In addition, the construction of ZnO/NdFeO 3 heterostructure brings more efficient carrier migration, which is favorable to the surface reaction and diffusion of EA molecules, and lowers the ZnO operating temperature, thus reducing the energy consumption. The ZnO/NdFeO 3 composite sensor based on n-p heterojunction provides a valuable strategy for the detection of volatile organic compounds. [ABSTRACT FROM AUTHOR]

Metal halide perovskite (MHPs) nanocrystals (NCs) have recently emerged as promising materials for optoelectronic applications due to their exceptional photophysical properties. A comprehensive understanding of the underlying principles and key challenges associated with controlling the hot carrier (HC) cooling dynamics in MHPs is pivotal for the design of efficient perovskite‐based optoelectronic applications. This review highlights the general carrier cooling mechanism and identifies influencing crucial controlling parameters for carrier dynamics. The discussion includes strategies for manipulating HC cooling dynamics through carrier‐phonon and carrier‐carrier interactions. Notably, recent advancements in HC extraction with suitable acceptors are explored, as efficient HC extraction is imperative for the advancement of optoelectronic applications. The objective of this review is to outline potential pathways for strategically modifying carrier cooling processes to align with specific optoelectronic applications. A profound comprehension of charge carrier dynamics in MHPs NCs will pave the way for the development of highly efficient optoelectronic applications. [ABSTRACT FROM AUTHOR]

The walnut shell is an agro-waste that could be used as nanocellulose source. In the literature, different methods were used to isolate nanocrystals and depending on the method used, spherical or rod like nanocrystals were obtained. The novelty of the current study is the characterization of the crystallinity index, the thermal stability, and the chemical composition, in addition to the geometrical features, of rod like nanocrystals isolated from the walnut shell of "Juglans regia". The AFM images corroborated that rod like nanocrystals can be isolated using the procedures proposed in the current study. Furthermore, when alkali solution pretreatments were used and the subsequent acid hydrolysis, the isolated CNC showed lower amount of non-cellulosic compounds, and superior L/D and crystallinity index values than CNC isolated directly from walnut shells by acid hydrolysis. The aspect ratio and thermal stability of nanocrystals isolated in the current work are higher than the reported in the literature for other nanocrystals isolated from walnut shells. Finally, the properties of isolated nanocrystals were compared with a commercial cellulose nanocrystal and other nanocrystals reported in the literature. [ABSTRACT FROM AUTHOR]

Piezochromic materials refer to a class of matters that alter their photoluminescence (PL) colors in response to the external stimuli, which exhibit promising smart applications in anti‐counterfeiting, optoelectronic memory and pressure‐sensing. However, so far, most reported piezochromic materials have been confined to organic materials or hybrid materials containing organic moieties with limited piezochromic range of less than 100 nm in visible region. Here, we achieved an intriguing piezochromism in all‐inorganic zero‐dimensional (0D) Cs3Cu2Cl5 nanocrystals (NCs) with a considerable piezochromic range of 232 nm because of their unique inorganic rigid structure. The PL energy shifted from the lowest‐energy red fluorescence (1.85 eV) to the highest‐energy blue fluorescence (2.83 eV), covering almost the entire visible wavelength range. Pressure‐modulated self‐trapped exciton emission between different energy levels of self‐trapped states within Cs3Cu2Cl5 NCs was the main reason for this piezochromism property. Note that the quenched emission, which is over five times more intense than that in the initial state, is retained under ambient conditions upon decompression. This work provides a promising pressure indicating material, particularly used in pressure stability monitoring for equipment working at extreme environments. [ABSTRACT FROM AUTHOR]

With their exceptional optoelectronic properties, CsPbBr3 perovskite nanocrystals (NCs) are promising materials for light‐emitting devices. Elucidating their stimulated emission mechanisms is fundamental to grasp the limitations hindering their use as electrically pumped lasers. In particular, two questions remain open: why the Amplified Spontaneous Emission (ASE) band is significantly shifted from the fluorescence one, and why the former seems to suddenly emerge from, and coexist with, the latter. Here, these questions are addressed through experimental ASE measurements, combined with numerical simulations and a comprehensive assessment of the performance of different analytical expressions used in the literature to retrieve the optical gain from these experiments. This multi‐facet study shows that the ASE behavior in CsPbBr3 NCs thin films stems from four distinctive processes: reabsorption due to a large overlap between the absorption and fluorescence spectra, a strong contribution of excited state absorption within the fluorescence window, the excitation of differently polarized waveguide modes, and the coexistence of short‐ and long‐lived localized excitons. The results in this work delineate the best practices to analyze the optical gain in perovskite samples, help to understand their ASE mechanisms, and provide insights to boost their lasing efficiency. [ABSTRACT FROM AUTHOR]

Weak luminescence of the small‐sized lanthanide‐doped nanoparticles has limited their applications long. In recent years, there is a growing interest in luminescence thermal enhancement in small‐sized upconversion nanoparticles (UCNPs). The mitigation of surface quenching effects and the improvement of energy transfer (ET) are two convincing explanations for this phenomenon. A systematical investigation on the luminescence dynamics of Yb3+ is implemented. ET rate and then the proportion of ET increases greatly with rising temperatures in Yb3+/Tm3+ codoped system, while an alternative trend can be summarized in Yb3+/Er3+ one. Based on these findings, therefore it can be concluded that the surface quenching mitigation related to the desorption of water molecules on the surface is a common mechanism of the luminescence thermal enhancement. But ET related to the thermally‐activated surface phonons is a special case, it does play a positive role in Yb3+/Tm3+ system. These findings not only explain the upconversion luminescence thermal enhancement in Yb3+/Tm3+ system is more significant but also help to understand thermal enhancement and benefit highly‐sensitive temperature probe design. [ABSTRACT FROM AUTHOR]

Construction of self‐healing materials with improved mechanical performance is a great challenge. A strong and tough self‐healing composite is fabricated via in situ growth of zeolitic imidazole framework‐8 (ZIF‐8) nanocrystals in imidazole‐containing polymer networks. By adjusting the stoichiometric ratio of the zinc salt to 2‐methylimidazole, composites with various mechanical performances are obtained. The existence of ZIF‐8 nanocrystals via in situ growth in the polymer networks is confirmed by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The zinc–imidazole interactions between the ZIF‐8 nanocrystals and the polymer are confirmed by attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy. The composites can repair themselves under mild conditions owing to dynamic zinc–imidazole interactions. The self‐healing efficiency of composites can reach up to 91% under the condition of 60 °C for 48 h. In contrast to the pure zinc cation crosslinking system, the composite containing ZIF‐8 nanocrystals prepared via in situ growth exhibited enhanced tensile strength and toughness by 43% and 100%, respectively. This study proves that incorporating the metal‐organic frameworks (MOFs) materials into a self‐healing system via an in situ growth strategy is highly promising for designing self‐healing materials with improved mechanical performance. [ABSTRACT FROM AUTHOR]

Conventional photovoltaic (PV)‐photodetectors are hard to detect fainted signals, while photomultiplication (PM)‐capable devices indispensable for detecting weak light and are prone to degrade under strong light illumination and large bias, and it is urgent to realize highly efficient integrated detecting system with both PM and PV operation modes. In this work, one lead‐free Cs3Cu2I5 nanocrystals with self‐trapping exciton nature was introduced as interfacial layer adjacent to bulk and layer‐by‐layer heterojunction structure, and corresponding organic photodetectors with bias‐switchable dual modes are demonstrated. The fabricated device exhibits low operating bias (0 V for PV mode and 0.8 V for PM mode), high specific detectivity (~1013 Jones), fast response speed as low as 1.59 μs, large bandwidth over 0.2 MHz and long‐term operational stability last for 4 months in ambient condition. This synergy strategy also validated in different materials and device architectures, providing a convenient and scalable production process to develop highly efficient bias‐switchable multi‐functional organic optoelectrical applications. [ABSTRACT FROM AUTHOR]

Element substitution in Cu2ZnSnS4‐like chalcogenides offers the potential to create alternative low‐cost photovoltaic and thermoelectric materials with tunable properties. In this work, the “green” synthesis of colloidal cation‐substituted Cu–Ni–Sn–S nanocrystals (CNTS NCs) in aqueous solutions using thioglycolic acid as a stabilizer is reported for the first time. The structural and optical properties of CNTS NCs are studied in colloidal solutions and thin films, and are compared with those of Cu–Zn–Sn–S (CZTS) NCs obtained under similar conditions. The NC sizes of both compounds are estimated to be in the range of 1.5–2.5 nm. Both NCs exhibit strongly non‐stoichiometric composition and a structure corresponding to cationically disordered kesterite Cu2ZnSnS4, which are common features of such quaternary metal‐based chalcogenides. The phonon Raman spectra of CNTS and CZTS NCs exhibit very similar lineshapes, but the CNTS phonon band has a larger width and lower frequency, presumably due to stronger cation disorder. The absorption of both types of NCs extends continuously through the visible range with an estimated bandgap of ≈2.2 eV and sub‐bandgap absorption due to an Urbach tail. The absorption coefficient of CNTS is determined to be α > 102 cm−1 at 700 nm and α > 104 cm−1 at 400 nm. [ABSTRACT FROM AUTHOR]

With the rapid development of social industrialization, energy crisis and environmental problems are becoming increasingly serious. Therefore, there is an urgent need to synthesize multi-mode nanocatalysts for general application. In this paper, a h-Fe3O4@Pd/PDA nanocatalyst with Pd nanocrystals sandwiched between a h-Fe3O4 hollow sphere and a polydopamine (PDA) shell was prepared by a simple redox-oxidative polymerization method. The catalytic activity of h-Fe3O4@Pd/PDA hollow spheres was evaluated using selective reduction hydrogenation of 4-nitrostyrene, reduction of 4-nitrophenol and oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) as catalytic models. h-Fe3O4@Pd/PDA has reduction kinetics of 4-nitrophenol up to 0.77 min−1 mg−1. Importantly, the rate of 4-nitrophenol reduction catalyzed by h-Fe3O4@Pd/PDA was enhanced by 1.43 times under near infrared light (NIR, 808 nm) irradiation. In addition, NIR laser can induce the selective reduction of 4-nitrostyrene to 4-aminostyrene by h-Fe3O4@Pd/PDA with a selectivity of 84.8%. Under different reaction scenarios, h-Fe3O4@Pd/PDA hollow spheres could be recycled by magnetic recovery, and the catalytic reaction activity was above 70% after six cycles. As a result, owing to the simple fabrication, good magnetic separation and high NIR-enhanced catalytic properties, h-Fe3O4@Pd/PDA exhibited a wide range of potential in nanocatalysis. [ABSTRACT FROM AUTHOR]

The effect of Al3+ ions in the AlF 3 compound on the reduction process of Yb3+ to Yb2+ ions in SiO 2 –AlF 3 –BaF 2 –TiO 2 –LaF 3 (SABTL) transparent silicate glass-ceramics was investigated. The valence states of the elements in the raw materials mixture existing in the transparent silicate glass-ceramics were determined using X-ray photoelectron spectroscopy (XPS) spectrum analysis. The transparent silicate glass-ceramics SABTL containing Ba 2 LaF 7 nanocrystals and Silver (Ag) nanoparticles (AgNPs) were identified through X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) image. With the increase of Al3+ ions molar concentration, the self-reduction process of Yb3+ to Yb2+ ions was enhanced and thus significantly affected the optical bandgaps and upconversion (UC)-, near-infrared (NIR)- emissions of Nd3+/Yb3+ co-doped in SABTL containing Ba 2 LaF 7 nanocrystals and AgNPs under excitation of 980 nm laser diode (LD). The optimal molar concentration ratio between SiO 2 and AlF 3 compound was determined such that the NIR bandwidth flatness of Nd3+/Yb3+ co-doped in SABTL containing Ba 2 LaF 7 nanocrystals in the wavelength range of 1000–1200 nm was the flattest. In addition, the CIE 1931 (x, y) color coordinates for UC- and visible (VIS)- emissions of Nd3+/Yb3+ co-doped SABTL-0.5Nd2Yb-xAg (x = 0, 2, 3, 4, and 5) glass-ceramics samples are also calculated and determined the color region for light-emitting diode (LED) application. [ABSTRACT FROM AUTHOR]

Luminescence imaging in the second near-infrared (NIR-II) window, particularly within the NIR-IIb (1500–1700 nm) sub-window, has been utilized for both fundamental research and clinical applications due to its exceptional spatiotemporal resolution. Nevertheless, efficient contrast agents designed for NIR-IIb imaging are still scarce. Herein, a multilayered rare-earth nanocrystal (NaYF 4 :Yb,Er,Ce@NaYF 4 :Yb,Nd@NaYF 4) with strong NIR-IIb luminescence was designed and synthesized. The doping of Ce3+ ions in the core effectively suppresses the upconversion and boosts the downconversion luminescence by populating the Er 4I 13/2 level. Additionally, by separating the sensitizer (Nd3+) and the activator (Er3+) in different layers, we are able to maximize the light absorption around 800 nm and reduce the cross relaxations between rare-earth elements, which leads to a strong downconversion emission around 1530 nm under 808 nm excitation. After passivation with NaYF 4 shell and phase transfer with highly PEGylated mesoporous silica layer, the nanocomposites with excellent colloidal stability and bright NIR-IIb emission were obtained. With long blood circulation time in vivo, the fabricated nanocomposites enable high resolution and contrast luminescence imaging of the blood vessels and tumors in living mice. Moreover, the rare-earth nanocrystals with superior optical properties also hold great promise for various applications in optical sensing and biomedical imaging. [Display omitted] [ABSTRACT FROM AUTHOR]