Halide Matrix Research Articles

Achieving Near-Infrared Highly Sensitive Temperature Sensing in Lanthanide-Doped Lead-Free Double Perovskite NaLaMgWO6 with Significant Thermal Enhancement.

The significant temperature response of lanthanide-doped up-conversion luminescent materials is typically characterized by a severe thermal quenching of the luminescence intensity at elevated ambient temperatures, which severely restricts materials' capability in temperature sensing. Herein, the influence of matrix phonon properties on the remarkable thermal enhancement effect in the thermosensitive material NaLaMgWO6:Yb3+/Nd3+ is reported. It is elucidated that achieving a significant thermal enhancement of Nd3+ with a higher phonon energy oxide matrix is easier than a halide matrix, which has lower phonon energy by comparison with previous findings. Interestingly, the emission of thermally related levels gets enhanced to various extents through phonon-assisted thermal population. In light of this, a three-model thermometer is constructed based on luminescence intensity ratio (LIR) technology. Given that Sr and ΔE possess a positive correlation, it is feasible to acquire greater temperature monitoring sensitivity Sr in Nd3+, which has a larger ΔE. At 313 K, this thermometry model may achieve a maximum sensitivity of 2.84%·K-1. This work not only provides guidance for the selection of efficient near-infrared up-conversion material but also opens up a prospect for the realization of ultrasensitive thermally coupled luminescent thermometers.

Halide Perovskites-Based Diffusive Memristors for Artificial Mechano-Nociceptive System.

Numerous efforts for emulating organ systems comprised of multiple functional units have driven substantial advancements in bio-realistic electronics and systems. The resistance change behavior observed in diffusive memristors shares similarities with the potential change in biological neurons. Here, the diffusive threshold switching phenomenon in Ag-incorporated organometallic halide perovskites is utilized to demonstrate the functions of afferent neurons. Halide perovskites-based diffusive memristors show a low threshold voltage of ≈0.2V with little variation, attributed to the facile migration of Ag ions uniformly dispersed within the halide matrix. Based on the reversible and reliable volatile threshold switching, the memristors successfully demonstrate fundamental nociceptive functions including threshold firing, relaxation, and sensitization. Furthermore, to replicate the biological mechano-nociceptive phenomenon at a system level, an artificial mechano-nociceptive system is built by integrating a diffusive memristor with a force-sensing resistor. The presented system is capable of detecting and discerning the detrimental impact caused by a heavy steel ball, effectively exhibiting the corresponding sensitization response. By further extending the single nociceptive system into a 5 × 5 array, successful stereoscopic nociception of uneven impulses is achieved in the artificial skin system through array-scale sensitization. These results represent significant progress in the field of bio-inspired electronics and systems.

Imbedded Perovskite Nanocrystals in Metal Halide Microcrystal: Synthesis and Heterostructure

AbstractLead halide perovskite nanocrystals and other metal halides have received considerable attention due to their unique optoelectronic properties. A combined perovskite nanocrystal‐metal halide heterostructure can achieve desirable properties for enriched applications. However, the construction of such a heterostructure is challenging. In this study, a CsPbBr3/Cs2ZnBr4 heterostructured microcrystal with perovskite nanocrystals embedded in a metal halide matrix is successfully synthesized using a facile ultrasound‐assisted post‐processing method. The heterostructure of the perovskite‐metal halide composite materials is fully deciphered through ab initio calculations and multiscale characterizations. The heterostructure‐induced variation in optical properties is elucidated based on micro‐nano spectral and luminescence kinetic behaviors. This study provides new insights into the design of perovskite nanocrystal‐based heterostructured materials, improving the understanding of metal halides and extending their applications.

Efficient, Multicolored, and Stable Room‐Temperature Phosphorescence Doped Materials Based on a Lead Halide Matrix: A Coordination‐Driven Doping Strategy

AbstractRoom temperature phosphorescence (RTP) materials have wide applications, and guest/host doping is an important method to achieve RTP. Although weak host–guest interactions (such as hydrogen bonding and π–π stacking) are considered to play a key role in inducing RTP in most doped systems (DSs), stronger and facile coordination bonds can achieve RTP more effectively and are believed to do so in DSs in related research. However, there is a lack of solid experimental evidence. Herein a new stable ligand‐modified lead halide (PCB) is synthesized and used as matrix to prepare RTP NA/PCB DSs with naphthalene derivatives (NA) as guests. Remarkably, a coordination bond between host and guest is experimentally demonstrated and revealed to play a decisive role in the generation of efficient RTP. On this basis, a coordination‐driven doping strategy is proposed to achieve efficient, multicolored, and long‐lived RTP of the DSs. In addition, NA/PCB shows excellent RTP stability and can be used in advanced security encryption, white light emitting diodes, and phosphorescent temperature sensors. This work not only proves the important role of coordination bonds in the RTP DSs, but also shows the potential of the ligand‐modified lead halide matrix as the host material of RTP.

Circularly polarized luminescence and nonlinear optical harmonic generation based on chiral zinc halides.

Chiral hybrid metal halides have grabbed extensive attention in linear and nonlinear chiroptics. Herein, 0D chiral zinc halides, (R-/S-2-MP)ZnCl4, have been fabricated, which demonstrate high efficiency second-order nonlinear optical responses. Incorporating Sb3+ into the chiral zinc halide matrix triggers the circularly polarized luminescence effectively with a balance between quantum yield and luminescence dissymmetry factor.

Room Temperature Halide-Eutectic Solid Electrolytes with Viscous Feature and Ultrahigh Ionic Conductivity.

A viscous feature is beneficial for a solid electrolyte with respect to assembling solid-state batteries, which can change the solid-solid contacts from point to face. Here, novel halide-based deep eutectic solid electrolytes (DESEs) prepared by a facile ball milling method is reported. The mixture of halides triggers the deep eutectic phenomena by intermolecular interactions, leading to diverse morphologies and viscous statuses in terms of composition. Chemical- and micro-structure analyses via the cryogenic technique reveal that the LiCl and LiF nanoparticles are dispersed in an amorphous halide matrix, which endow freely mobile ions for fast ion transport. The optimized DESE thus achieves low activation energy and high ionic conductivity of 16 mS cm-1 at room temperature, one of the highest values among various electrolytes so far. By integrating with the active materials to form a composite cathode, the viscous DESE yields a super-dense composite pellet which possesses intensively enhanced ionic conductivity in contrast to those formed by the sulfide-based electrolyte additives, demonstrating an attractive application prospect.

Quantitative modelling towards trace spectroanalysis of dielectrics by sliding spark plasma

A consistent theme in trace analytical atomic spectroscopy is the search for methods of efficient atomization and excitation of sample matrices in solid form – so-called direct analysis. The technique reported here – the sliding spark – is a special pulsed plasma specularly discharging on a dielectric surface enforced between a pair of electrodes in air at atmospheric pressure. Although the sliding spark is characterized by complex emission spectra with very few lines that are optically thin and interference-free, the plasma has potential for spectroanalysis of dielectric materials as the excited species in the plasma which are at low concentration compared to those in the ground or metastable states may be quantified via their spectral line intensities. The challenge is how to conceptualize an analytical model from first principles and develop from it a calibration strategy for trace quantitative analysis in a form that can be expressed mathematically. We describe the sliding spark technique and the utility of halide matrix modifiers to increase sensitivity, as well as the feasibility of developing, for selected spectral lines, a conceptual scheme with semi-empirical models for trace quantitative spectroscopy of heavy metals spiked in pelletized dielectric samples. The proposed quantitative models demonstrate that the sliding spark plasma spectra are useful for simple, affordable, and rapid direct trace spectroscopy of dielectrics, a ubiquitous theme in industrial, environmental and medical analyses.

Dopant-Assisted Matrix Stabilization Enables Thermoelectric Performance Enhancement in n-Type Quantum Dot Films.

Efficient thermoelectric generators require further progress in developing n-type semiconductors that combine low thermal conductivity with high electrical conductivity. By embedding colloidal quantum dots (CQDs) in a metal halide matrix (QDMH), the metal halide matrix can enhance phonon scattering, thus suppressing thermal transport; however, simultaneously achieving high electrical conductivity in such systems has previously been limited by the deleterious impact of a large density of interfaces on charge transport. Therefore, new strategies are needed to improve charge carrier transport without sacrificing matrix-enabled low thermal transport. Here, we report the use of chemical doping in the solution state to improve electron transport while maintaining low thermal transport in QDMH films. By incorporating cesium carbonate (Cs2CO3) salts as a dopant prior to matrix formation, we find that the dopant stabilizes the matrix in colloidal inks and enables efficient n-type doping in QDMH films. As a result, this strategy leads to an enhanced n-type thermoelectric behavior in solution-processed QDMH films near room temperature, with a thermal conductivity of 0.25 W m-1 K-1-significantly lower than in prior films based on organic-ligand-cross-linked CQD films (>0.6 W m-1 K-1) and spark-plasma-sintered CQD systems (>1 W m-1 K-1). This study provides a pathway to developing efficient n-type thermoelectric materials with low thermal conductivity using single-step deposition and low-temperature processing.

SPR in Cesium Halide Thin Films Due to Embedded Elliptic Cesium Metal Nano-Particles

Cesium nanorods embedded in cesium halides (CsCl, CsBr, and CsI) show surface plasmon resonance (SPR) absorption peaks. The size and shape of these cesium nanorods in the cesium halide matrix evolve with time, which gives some uncontrollable data for comparing with the theory. The theory used here was developed by R. Gans. It leads to the good match between experiment and theory for Cs–Cs halide nanocomposites.

Ab initio calculation of stressed cesium iodide lattices and resulting surface plasmon resonance peak shifts

Alkali halides have received attention due to their potential application as detector coating. This is due to the appearance of Surface Plasmon Resonance (SPR) absorption peaks in their absorption spectrum. The formation of SPR peaks is due to the formation of cesium metal clusters within the cesium halide matrix. Experimental work on cesium iodide explained the formation of cesium clusters in cesium iodide films. It was experimentally seen that when iodine atom escapes from the cesium iodide unit cell, then the newly created cubic unit cell of cesium exerts force on neighboring cesium iodide unit cells. This force results in cesium iodide taking up a tetragonal lattice structure. The aim of this paper is to theoretically investigate the tetragonal cesium iodide’s band structure and dielectric constant using ab initio calculations. The results indicate that both the band structure and the dielectric constant of cesium iodide in tetragonal phase show a systematic variation with changes in the lattice constant. This alteration in dielectric constant or variation in refractive index of cesium iodide, which acts as the surrounding media for the cesium metal clusters, induces a shift in the SPR peak position. The calculated dielectric constants were used for Gan model calculations of the extinction coefficient and evaluation of SPR peak position ([Formula: see text]). A redshift in [Formula: see text] was seen with increasing dielectric constant that appears with stress acting on cesium iodide’s lattice. These results were found to be in agreement with experimental results reported earlier by us.

Methodological effects in Fourier transform infrared (FTIR) spectroscopy: Implications for structural analyses of biomacromolecular samples

A set of experimental data obtained by Fourier transform infrared (FTIR) spectroscopy (involving the use of samples ground and pressed with KBr, i.e. in a polar halide matrix) and by matrix-free transmission FTIR or diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic methodologies (involving measurements of thin films or pure powdered samples, respectively) were compared for several different biomacromolecular substances. The samples under study included poly-3-hydroxybutyrate (PHB) isolated from cell biomass of the rhizobacterium Azospirillum brasilense; dry PHB-containing A. brasilense biomass; pectin (natural carboxylated heteropolysaccharide of plant origin; obtained from apple peel) as well as its chemically modified derivatives obtained by partial esterification of its galacturonide-chain hydroxyl moieties with palmitic, oleic and linoleic acids. Significant shifts of some FTIR vibrational bands related to polar functional groups of all the biomacromolecules under study, induced by the halide matrix used for preparing the samples for spectroscopic measurements, were shown and discussed. A polar halide matrix used for preparing samples for FTIR measurements was shown to be likely to affect band positions not only per se, by affecting band energies or via ion exchange (e.g., with carboxylate moieties), but also by inducing crystallisation of metastable amorphous biopolymers (e.g., PHB of microbial origin). The results obtained have important implications for correct structural analyses of polar, H-bonded and/or amphiphilic biomacromolecular systems using different methodologies of FTIR spectroscopy.

Highly efficient quantum dot near-infrared light-emitting diodes

Embedding quantum dots in a perovskite matrix yields efficient light emitters. Colloidal quantum dots (CQDs) are emerging as promising materials for constructing infrared sources in view of their tunable luminescence, high quantum efficiency and compatibility with solution processing1. However, CQD films available today suffer from a compromise between luminescence efficiency and charge transport, and this leads to unacceptably high power consumption. Here, we overcome this issue by embedding CQDs in a high-mobility hybrid perovskite matrix. The new composite enhances radiative recombination in the dots by preventing transport-assisted trapping losses; yet does so without increasing the turn-on voltage. Through compositional engineering of the mixed halide matrix, we achieve a record electroluminescence power conversion efficiency of 4.9%. This surpasses the performance of previously reported CQD near-infrared devices two-fold, indicating great potential for this hybrid QD-in-perovskite approach.

A Method for Polarizing More Number of Impurity-Vacancy Dipoles

Free rotating impurity-vacancy (IV) dipoles in an alkali halide matrix are polarized to the extent of 1/3 of the total number of IV dipoles. An experimental procedure is suggested in this article which will help in the polarization of IV dipoles to the extent of 2/3 of the total number of IV dipoles. In the suggested experimental procedure, the electric field will be applied at first in one direction and then will be applied in succession in opposite direction. Ionic thermocurrent technique is employed to ascertain the increase in polarization of IV dipoles.

Preparation, characterization and ionic conductivity studies of ZrO 2 dispersed mixed halide matrix (KCl) 0.9–(NaCl) 0.1

Composite electrolytes in the system [(KCl) 0.9:(NaCl) 0.1] 1− y :(ZrO 2) y were prepared and their ionic conductivities were studied. In our previous study on the mixed halide system (KCl) 1− x :(NaCl) x , maximum conductivity (∼50 times that of the base KCl matrix) was found when x=0.1. The matrix (KCl) 0.9:(NaCl) 0.1 was dispersed with different concentration of ZrO 2 (powder) for the preparation of composites and their conductivities were determined. The maximum conductivity was developed for the composite having composition y=0.5. The matrices were prepared by melt-quench technique and the dispersion of ZrO 2 was carried out in liquid medium. The conductivity measurements of the composites were carried out by impedance spectroscopy technique. The composite [(KCl) 0.9:(NaCl) 0.1] 0.5:(ZrO 2) 0.5 was characterized by X-ray diffraction (XRD) analysis, differential thermal analysis (DTA), thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The conductivity of the composite [(KCl) 0.9:(NaCl) 0.1] 0.5:(ZrO 2) 0.5 as a function of temperature was also studied. The conductivity increase in the composite could be attributed to enhancement of defect concentration in the space charge region created at the interface between the host halide and the dispersoid.

Combustion Synthesis of Molybdenum Disilicide (MoSi2) Fine Powders

The combustion characteristics of a MoO3+SiO2+Mg system diluted with sodium chloride have been studied in order to synthesize molybdenum disilicide (MoSi2) fine powders. The effect of processing variables, including the sodium chloride content and the reactants proportion on the phase composition and microstructure of the final products, was obtained. Both the combustion temperature and the wave velocity decreased with an increase in the amount of sodium chloride. With the appropriate processing parameters, the reacted product consisted of solid crystalline MoSi2, and an MgO phase was prepared in the molten sodium halide matrix at 1100°–1350°C. The final product purification resulted in MoSi2 powder with a particle size of 100–500 nm. The mechanism of the MoSi2 formation in the sodium chloride matrix is discussed by analyzing the phase evaluation in the extinguished combustion wave.

Infrared spectra of amino acid zwitterions isolated in alkali halide matrices

A new spray sampling method (DSD) exploited in the measurement of infrared absorption of amino acids and dipeptides has resulted in a third category of spectra. They display qualitative similarities to the resolved bands obtained in the vapor and low-temperature inert-gas isolated matrix, and on the other hand have some common vibrational frequencies with the solution and alkali halide pressed pellet spectra. Comparisons of group frequencies obtained by the DSD and pellet methods, and presented for a number of amino acids and dipeptides, are informative of structural differences in the molecules obtained by the two methods. As well, results are presented for the measured and predicted dependence on the alkali halide matrix. It is argued that the sum of evidence presented supports the conclusion that zwitterions isolated as monomers are produced by the DSD sampling method. The method is not exclusive to the amino acids. Other applications include purine and water.

Spectra of surface-enhanced Raman scattering of nanocluster NaXe

The integrated ultraviolet (UV)-micro-laser-matrix can be expected, if the novel nanomaterial with a matrix distribution can emit UV radiation and easily inverses the population between its ground and excited states. Solid NaXe nanoclusters should belong to such a nanomaterial. Metallic Na colloids of nanometer size have been formed as the results of the aggregations of F centers in heavily irradiated NaCl [1]. It has been indicated by the measurements of transmission electron microscopy (TEM) that alkali atoms, including Na and K, in alkali metal colloids retain their original face centered cubic (fcc) positions within the alkali halide matrix and that their lattice parameters are not far different from their host matrix [2]. It has been also evidenced by TEM and selected-area electron diffraction experiments that noblegas ions implanted into metals and magnesium oxide can be trapped and solid noble-gas inclusion can be formed [3]. Their positions have been found to be fccs in fcc matrix [3]. It has been also demonstrated by our former experiments [4, 5] that the novel solid NaXe can be prepared under the appropriate conditions of xenon ion implantation into NaCl samples and a strong 355 nmUV-radiation emission can be observed. In this paper, the surface-enhanced Raman scattering (SERS) spectra of nanocluster NaXe in NaCl are measured at room temperature and their characteristics are discussed. In the experiment, pure NaCl powder, in which the grain diameters are smaller than 53 µm, is pressed to disks as samples. Xenon ions are implanted at 10 −6 Torr by using an accelerating voltage of 200 kV. The xenon ion flux is 5×10 17 ions/cm 2 . Under this implantation condition, solid NaXe nanoclusters with blue color are formed through the interaction between solid Xe and metallic Na colloids in xenon-ion–implanted NaCl samples. The sizes of solid NaXe nanoclusters are measured to be within 80 nm by scanning electron microscopy (Hitachi S-3500N). The Raman-scattering is often enhanced by the colloids formed on the surface of the sample. This process is called SERS [6]. These SERS spectra can provide information about the nature and geometry of the colloids in samples. Therefore, low-frequency Raman-scattering spectra are used to study the colloidal structure in our ∗ Author to whom all correspondence should be addressed.

The FT-IR spectra of glycine and glycylglycine zwitterions isolated in alkali halide matrices

The infrared absorption spectra of glycine and the dipeptide glycylglycine have been measured using a novel spray-sampling technique which leads to better resolved spectra than the traditional crystal and solution methods. Spectra were recorded for a number of different alkali halide matrices. Theoretical predictions of the spectra have been undertaken using the self-consistent reaction field Onsager continuum model, without the inclusion of specific solute solvent interactions. Good agreement has been achieved between measured and predicted structures and spectra. For the glycine zwitterion in alkali halide matrices, the measured spectra suggest a trans structure about the NC bond, while for the dipeptide the conformation about the peptide bond is trans as in the crystal. The DSD spectra showed little dependence on the alkali halide matrix used to isolate the amino acid zwitterions in support of the theoretical approach adopted.

Magnetic resonance in micro- and nanostructures

GaAs/AlAs and GaAs/AlGaAs quantum wells and superlattices were grown by molecularbeam epitaxy and self-organized oriented silver halide micro- and nanocrystals were embedded in crystalline alkali halide matrix. We report the results of the application of optically detected magnetic resonance (ODMR) and level anticrossing (LAC) spectroscopy for the investigations of these two classes of nanostructures. ODMR and LAC spectroscopy are shown to be very suitable for obtaining important physical parameters of low-dimensional systems and for a local diagnostics of nanostructures.

Thermal studies on the polymorphic modifications of (R,S) propranolol hydrochloride

The polymorphism of (R,S) propranolol hydrochloride was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray powder diffractometry (XRPD) and thermomicroscopy (HSM) coupled with FT-IR spectroscopy. Propranolol hydrochloride existed in three different crystalline forms, denoted as forms I, II and III, according to their decreasing melting temperatures. Modification II was the commercial product. The forms I and III were obtained by melting form II in different experimental conditions. Form III was obtained only by solidification of the melt in the presence of an alkali halide matrix (as a crystalline film on an alkali halide window or as powder dispersion in a KBr pellet). Forms I and II were also obtained by crystallization from 95% aqueous ethanol and acetone, respectively. The three forms were easily differentiated by their IR spectra in the 3400–2000 cm −1 range. The different crystalline structures of forms I and II were characterized by means of their X-ray powder diffraction patterns.