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Doping semiconductor nanomaterials with manganese ion (Mn2+) introduce a well‐defined photoactive d‐d level within the band structure, paving the way for diverse applications. Although Mn doping in single‐layer 2D hybrid perovskites (n = 1) has been extensively studied, limited research has been conducted on doping with modulation of the layer thickness. Herein, Mn2+ doping in hybrid 2D perovskite nanoplatelets (NPLs), L2An‐1[Pb1‐xMnx]nBr3n+1 (where L = butylammonium, A = methylammonium), with variations in Mn concentration (x = 0–0.60) and layer thickness (n = 1–3) is reported. Substitutional doping of Mn significantly increases the photoluminescence quantum yield as well as the rate of energy transfer efficiency, which strongly depends on the layer thickness of NPLs. The Mn concentration in 2D NPLs determines the rate of forward and backward energy transfer. Low‐temperature emission spectra allow to determine thickness‐dependent exciton binding energy for Mn‐doped 2D NPLs (x = 0.5) with values of 410 ± 11 meV (n = 1), 188 ± 9 meV (n = 2), and 151 ± 17 meV (n = 3). The faster dissociation of band‐edge excitons into free carriers at Mn2+ sites results in high brightness with an excellent CRI of 89.2 for the white light‐emitting diode. [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]

Quantum dot light emitting devices (QLEDs) show promise for displays, with polyethylenedioxythiophene:polystyrene (PEDOT:PSS) commonly used as a hole injection layer (HIL) due to its high conductivity and work function. However, PEDOT:PSS-based QLEDs face an energy barrier, reducing efficiency. Herein, in this work, we used the rapid thermal annealing (RTA) process to improve the conductivity by controlling the RTA processing time which reduced the interfacial resistance. This improves charge balance and long-term stability by preventing electron leakage. The optimized V2O5/PEDOT:PSS-based QLED, with an EQE of 18%, CE of 77 cd A−1 and maximum luminance of 23 242 cd m−2, outperforms the PEDOT:PSS-based counterpart. This highlights the strategic superiority of V2O5 HIL in our QLED. [ABSTRACT FROM AUTHOR]

Zero‐dimensional (0D) 5s2‐metal halide (MH) materials offer potential for use in solid‐state lighting, optical thermography, and scintillation applications. The organic components of most highly luminescent materials are inherently unstable under moisture and thermal stress, which restricts their practical use in advanced applications. Hence, highly luminescent and stable inorganic luminescent materials are required. In this work, to the best of current knowledge, a 0D completely inorganic luminescent member of K2SbCl5 that exhibits orange emission at 610 nm with an 80% photoluminescence quantum yield (PLQY) is reported for the first time. Density functional theory calculations reveal that the [SbCl5]2‐ square pyramidal units are the only optically active emission centers in K2SbCl5. The white light‐emitting device utilizing K2SbCl5 demonstrates impressive performance metrics, boasting a substantial color rendering index (CRI) of 94 and an exceptional luminous efficacy of 118.1 lm W−1. Hence, this isolated [SbCl5]2−square pyramidal environment serves as a design principle for the development of highly efficient inorganic Sb3+‐based luminescent materials for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

Classical theories of dielectric friction make two critical assumptions: (i) friction due to van der Waals (vdW) forces is described by hydrodynamic drag and is independent of the ionic charge and (ii) vdW and electrostatic forces are statistically independent. Both assumptions turn out to be incorrect when tested against simulations of anions and cations with varying charge magnitude dissolved in water. Both the vdW and electrostatic components of the force variance scale linearly with the ionic charge squared. The two components are strongly anticorrelated producing simple relations for the total force variance in terms of self-variances. The inverse diffusion constant scales linearly with the charge squared. Solvation asymmetry between cations and anions extends to linear transport coefficients. [ABSTRACT FROM AUTHOR]

Mobility of ions in polar liquids is diminished when the ionic charge is increased. This phenomenon, known as dielectric friction, is caused by the retarded response of the liquid's dipoles to the charge movement. Linear response theories predict linear scaling of the inverse diffusion coefficient with the squared ionic charge. This prediction is analyzed here by molecular dynamics simulations of model ions with fractional charge q in the simple point charge water and by microscopic theory formulated in terms of the dynamic electric-field susceptibility of the solvent. The results of the analytical theory, and of its dielectric continuum limit, are in excellent agreement with simulations at sufficiently small charges q < 0.5 when linear response holds. At higher ionic charges, the hydration shell contracts, resulting in deviations from linear response in both static and dynamic properties of the electric field produced by water at the ion. Nevertheless, dielectric friction continues to rise in the nonlinear regime, resulting in an overall factor of 3.7 slower diffusion upon placing a single charge q = 1 on the solute. An approximately linear scaling of the inverse diffusion coefficient with the squared ionic charge comes from a mutual compensation between nonlinear solvation and correlations between non-electrostatic and electrostatic forces. Mobility of common electrolyte ions in water is predicted to occur in the regime of nonlinear dielectric friction. [ABSTRACT FROM AUTHOR]

White‐light‐emitting single‐component materials are in high demand for lighting applications. However, achieving white light in single‐doped metal halide materials remains a challenge. Herein, for the first time, zero‐dimensional Cs3ScCl6:Sb3+(CSC:Sb3+) nanocrystals (NCs) are reported that exhibit bright white‐light emission, which is a result of combination of the excessive blue and yellow emissions of carbon dots and spin‐forbidden electronic transitions of Sb3+ ions. CSC:Sb3+ NCs exhibit a high photoluminescence quantum yield of 48%. Furthermore, they retain 75% of their original photoluminescence efficiency at 100 °C. This high thermal stability is mainly attributed to its lower dimensionality and high exciton binding energy as they facilitate the creation of stable white light at elevated temperatures. A single‐component white‐light‐emitting diode fabricated using CSC:Sb3+ NCs exhibits a high‐color rendering index and luminous efficacy values of 90 and 23 lm W−1 at a high flux current of 200 mA. Therefore, the findings may pave the way for developing the next generation of white‐light‐emitting devices using a single component of white‐light‐emitting material. [ABSTRACT FROM AUTHOR]

We consider a new class of model systems to study systematically the role of molecular shape in the transport properties of dense liquids. Our model is a liquid binary mixture where both the molecules are non-spherical and characterized by a collection of parameters. Although in the real world most of the molecules are non-spherical, only a limited number of theoretical studies exist on the effects of molecular shapes and hardly any have addressed the validity of the hydrodynamic predictions of rotational and translational diffusion of these shapes in liquids. In this work, we study a model liquid consisting of a mixture of prolate and oblate (80:20 mixture) ellipsoids with interactions governed by a modified Gay-Berne potential for a particular aspect ratio (ratio of the length and diameter of the ellipsoids), at various temperature and pressure conditions. We report calculations of transport properties of this binary mixture by varying temperature over a wide range at a fixed pressure. We find that for the pressure-density conditions studied, there is no signature of any phase separation, except transitions to the crystalline phase at low temperatures and relatively low pressure (the reason we largely confined our studies to high pressure). We find that for our model binary mixture, both stick and slip hydrodynamic predictions break down in a major fashion, for both prolates and oblates and particularly so for rotation. Moreover, prolates and oblates themselves display different dynamical features in the mean square displacement and in orientational time correlation functions. [ABSTRACT FROM AUTHOR]

We examine the separation distance dependence of the hydrophobic force by systematically varying the distance (d) between twowalls. The hydrophobic force exhibits a distance mediated crossover from a liquid-like to a gas-like behavior at around d ~ 12 Å for 1 atm pressure. The distance dependence can be fitted to a bi-exponential form, with the longer distance part displaying a correlation length of 20 Å. In addition, the crossover is found to be accompanied by a divergent-like growth of the local relative number fluctuation of the water molecules confined between the two surfaces. Furthermore, at a fixed separation (d = 20 Å), we observe a pressure induced structural modification of confined water at high pressure. The confined water is found to form an ordered structure at high pressure (10 000 atm) and room temperature, in agreement with the experimental study [ABSTRACT FROM AUTHOR]

Photocatalysis is the most promising and cheap route for water purification. In this work, we demonstrate the degradation of organic pollutants, such as picric acid and methylene blue, by an efficient, reusable Bi2CuO4/BiPO4 heterojunction photocatalyst. The Bi2CuO4/BiPO4 heterojunction was fabricated using a solvothermal method followed by sonication. The Bi2CuO4/BiPO4 heterojunction shows enhanced photocatalytic degradation of picric acid and methylene blue dye under ultraviolet‐visible (UV/Vis) light compared to its individual constituents as well as compared to the previously reported Bi2CuO4‐based photocatalyst. The high photocatalytic activity of the Bi2CuO4/BiPO4 heterojunction can be attributed to the enhanced separation efficiency of the photogenerated electron and hole pairs. The photocatalytic activity of the Bi2CuO4 nanostructures, which is generally weak due to faster recombination of the electron and hole, is enhanced by means of heterojunction formation with BiPO4 nanocrystals. Interestingly, the hydroxyl radical, which was found to be the primary active species, is not generated at the valence band due to thermodynamic constraints. In contrast, experiments carried out under controlled conditions unequivocally confirm that their generation is related to oxygen reduction at the conduction band. Let′s split: A Bi2CuO4/BiPO4 heterojunction shows enhanced photocatalytic degradation of picric acid and methylene blue dye under UV/Vis light compared to its individual constituents and also compared to previously reported Bi2CuO4‐based photocatalysts. The high photocatalytic activity of the Bi2CuO4/BiPO4 heterojunction can be attributed to the enhanced separation efficiency of photogenerated electron and hole pairs. [ABSTRACT FROM AUTHOR]

In this communication we report the observation of intense near infrared (NIR) emissions in the 900 nm to 2000 nm range from colloidal water dispersible lanthanide (Ln3+) doped GdVO4 nanocrystals (Ln = Sm3+, Nd3+, Dy3+, Tm3+, Er3+ and Ho3+). Observing strong NIR emission, particularly from aqueous medium, is a challenge as the luminescence is more prone to non-radiative relaxation. The observed intense NIR emissions from Ln3+-doped GdVO4 nanocrystal ions are attributed to the efficient sensitization of the Ln3+ excited levels via a GdVO4 host matrix. The GdVO4 matrix shows intense and broad absorbance in the ultraviolet (UV) region resulting from the charge transfer from the 2p orbital of oxygen to the d orbital of V5+ ions of the VO4− group. Upon UV excitation, GdVO4 absorbs the light and efficiently transfers the energy to the excited state of the Ln3+ ions, which emit in the NIR region. The calculated energy transfer efficiencies for most of the studied Ln3+ ions are about 90%. In fact, the observed enhancement in the NIR emission intensity varies between 3 (for Sm3+) and 53 fold (Nd3+) compared to direct excitation. The combination of high aqueous stability and intense NIR emission can be advantageous for applications like NIR bioimaging. In addition, these colloidal nanocrystals can easily be incorporated into sol–gel or glass matrices for the fabrication of devices such as optical amplifiers, fiber optics for telecommunications, etc. [ABSTRACT FROM AUTHOR]

Lanthanide (Ln)-doped nanocrystals generally display low luminescence quantum efficiency due to forbidden nature of the 4f–4f transition besides possessing low absorption cross sections (∼10 M−1 cm−1). Considering the demand for these materials, particularly for light emission and bioimaging applications, it is very important to improve their quantum efficiency. This work demonstrates a strategy to enhance Si solar cell efficiency via sensitization of Eu3+ ions luminescence from colloidal nanocrystals. We have for the first time developed a simple ligand exchange approach to attach 4,4,4-trifluoro-1-phenyl-1,3 butanedione (TPB) to the surface of Eu3+-doped LiYF4 nanocrystals (NCs). Owing to the good overlap between the emission of the TPB ligands and the energy levels of Eu3+ ions, an efficient energy transfer takes place from the ligand to Eu3+ ions upon ultraviolet (UV) excitation of the ligand, leading to intense red emission. The sensitization of Eu3+ ions greatly enhanced the quantum yield of Eu3+ ions (∼31%) compared to the ∼5% obtained via direct excitation of Eu3+ ions (λexi = 394 nm) in Eu3+-doped LiYF4 NCs. A device was fabricated by embedding the nanocrystals on a Si solar cell to capture the UV photons and convert them into visible ones, which subsequently creates charge carriers inside the cell. Upon exposure to UV light, the nanocrystal embedded Si solar cell shows overall enhancement in the photocurrent upon excitation under UV radiation. [ABSTRACT FROM AUTHOR]

The formation of orthorhombic-phase GdF3 nanocrystals (thermodynamically controlled product) requires higher activation energy than that necessary for the formation of hexagonal-phase GdF3 nanocrystals (kinetically controlled product). As a result, whenever a reaction is carried out at higher temperatures, formation of the orthorhombic-phase GdF3 is generally preferred. However, the thermodynamic product is always more stable than the kinetic one at lower temperatures. Here, we report a simple microwave-assisted method to synthesize stable, hexagonal-phase, polyvinylpyrrolidone (PVP) functionalized Eu3+-doped GdF3 nanocrystals at higher temperatures (up to 220 °C). This is achieved by tuning the viscosity of the solvents as well as using KF as fluoride source. Both the morphology and the size of the GdF3 nanocrystals can also be varied by tuning the reaction conditions. Functionalization of the nanocrystals with PVP makes them water-dispersible. The Eu3+-doped GdF3 nanocrystals show intense red emission and longer luminescence lifetimes. The high luminescence efficiency of the Eu3+-doped GdF3 nanocrystals together with their high dispersibility in water can make them suitable for use in bioimaging and MRI imaging applications. [ABSTRACT FROM AUTHOR]

We report the enhancement of both visible and near infrared (NIR) emissions from Nd3+ ions via Ce3+ sensitization in colloidal nanocrystals for the first time. This is achieved in citrate capped Nd3+-doped CeF3 nanocrystals under ultraviolet (UV) irradiation (λex = 282 nm). The lasing transition (4F3/2→4I11/2) at 1064 nm from Nd3+-doped CeF3 nanocrystals has much higher emission intensity via Ce3+ ion sensitization compared to the direct excitation of Nd3+ ions. The nanocrystals were prepared using a simple microwave irradiation route. Moreover, the study has been extended to Sm3+-doped CeF3 nanocrystals which show strong characteristic emissions of Sm3+ ions via energy transfer from Ce3+ ions. The energy transfer mechanism from Ce3+ to Nd3+ and Sm3+ ions is proposed. [ABSTRACT FROM AUTHOR]

Local heterogeneity is ubiquitous in natural aqueous systems. It can be caused locally by external biomolecular subsystems like proteins, DNA, micelles and reverse micelles, nanoscopic materials etc., but can also be intrinsic to the thermodynamic nature of the aqueous solution itself (like binary mixtures or at the gas–liquid interface). The altered dynamics of water in the presence of such diverse surfaces has attracted considerable attention in recent years. As these interfaces are quite narrow, only a few molecular layers thick, they are hard to study by conventional methods. The recent development of two dimensional infra-red (2D-IR) spectroscopy allows us to estimate length and time scales of such dynamics fairly accurately. In this work, we present a series of interesting studies employing two dimensional infra-red spectroscopy (2D-IR) to investigate (i) the heterogeneous dynamics of water inside reverse micelles of varying sizes, (ii) supercritical water near the Widom line that is known to exhibit pronounced density fluctuations and also study (iii) the collective and local polarization fluctuation of water molecules in the presence of several different proteins. The spatio-temporal correlation of confined water molecules inside reverse micelles of varying sizes is well captured through the spectral diffusion of corresponding 2D-IR spectra. In the case of supercritical water also, we observe a strong signature of dynamic heterogeneity from the elongated nature of the 2D-IR spectra. In this case the relaxation is ultrafast. We find remarkable agreement between the different tools employed to study the relaxation of density heterogeneity. For aqueous protein solutions, we find that the calculated dielectric constant of the respective systems unanimously shows a noticeable increment compared to that of neat water. However, the ‘effective’ dielectric constant for successive layers shows significant variation, with the layer adjacent to the protein having a much lower value. Relaxation is also slowest at the surface. We find that the dielectric constant achieves the bulk value at distances more than 3 nm from the surface of the protein. [ABSTRACT FROM AUTHOR]

Very strong Eu3+ luminescence is achieved via sensitization by carbon dots (C-dots) in Eu3+-doped LaF3C-dot nanocomposites for the first time. This energy transfer via C-dots leads to the broadband excitation of Eu3+ ions which can have potential use in phosphor based LEDs. [ABSTRACT FROM AUTHOR]

In this article, we report for the first time the use of Ln3+-doped nanocrystals to detect aromatic amino acids (AAs) up to nanomolar concentration. Detection of AAs is important for several reasons. For instance, increased levels of AAs are detected in the early phase of gastric carcinogenesis in gastric juice samples. In this work, we have shown that the highly efficient energy transfer between Ce3+ and Tb3+ ions in Ce3+/Tb3+-doped CaMoO4 nanocrystals is selectively altered by the addition of AAs, thus providing a simple resonance energy transfer (RET) approach to detect AAs in the nanomolar (nM) range. This is achieved as the absorption spectrum of AAs overlaps with the emission spectrum of the Ce3+/Tb3+-doped CaMoO4 nanocrystals, thus reducing the energy transfer efficiency between the Ce3+ and Tb3+ ions. This selective energy transfer process leads to the quenching of the Tb3+ emission from the nanocrystals. The high selectivity was verified by the addition of essential or non-essential amino acids, and some metal ions and molecules that generally coexist with AAs in our body. Moreover, the selective quenching of the Tb3+ ion emission can be easily reversed by the addition of ninhydrin; 90% of the initial luminescence intensity is recovered during the reversal process. This process was repeated for more than five cycles with only a slight decrease in the sensing ability. The study was also extended to 2D surfaces where the nanocrystals are strongly attached to a positively charged surface, which, upon dipping into the AA solution, leads to the quenching of the luminescence exhibited by the Tb3+ ions. The signal can be easily recovered after ninhydrin treatment. [ABSTRACT FROM AUTHOR]

In this article, we discuss the microwave synthesis of sodium dodecyl sulphate (SDS) stabilized Ln3+-doped CaMoO4 nanocrystals (Ln3+ = Eu3+, Er3+/Yb3+). The nanocrystals are quite monodispersed with an average size close to 100 nm. FTIR and TGA analyses suggest strong binding of the SDS molecules to the CaMoO4 nanocrystals surface. The high dispersibility of the nanocrystals in water implies that SDS stabilizes the nanocrystals as a bilayer structure. The SDS coating also assists in the easy dispersion of the nanocrystals in toluene without any additional surface chemistry. The Eu3+ ions doped in the CaMoO4 nanocrystals display very strong red luminescence with a quantum yield close to 40%. Under 980 nm excitation, Er3+/Yb3+-doped CaMoO4 nanocrystals display Er3+ emissions at 550 and 650 nm. In addition, interestingly, a NIR peak at around 833 nm is observed, which occurred via a three photon process. Furthermore, the CaMoO4 nanocrystals exhibit photocatalytic activity which is studied through the degradation of Rhodamine B (RhB) dye in neutral conditions. The RhB dye is significantly degraded by ∼80% under UV illumination within 4 h and the rate of degradation is comparable to that observed for well known ZnO nanoparticles. The high luminescence quantum efficiency and strong photocatalytic activity of the Ln3+-doped CaMoO4 nanocrystals make them a potential material for dual applications such as bio-imaging and photocatalysis. [ABSTRACT FROM AUTHOR]