Double Crystal Research Articles

In situ hydrothermal growth of Zeolite-A membrane on polysulfone hollow fibers

Zeolite-A hollow-fiber membranes with a high surface area are explored to address the present demands of high-productivity bioethanol manufacturing. Herein, we prepared Zeolite-A membranes on polymeric hollow-fiber support via double hydrothermal crystallization. The first hydrothermal crystallization from the solution yielded zeolite A crystals anchored on the polysulfone support. This transformation of the hollow fiber's skin layer into an organic-inorganic interface layer, as observed through SEM-EDX elemental analysis. This interface layer with penetrated Zeolite-A provides nucleation sites for further Zeolite-A membrane formation during the second hydrothermal crystallization and simultaneously enhanced interphase adhesion of Zeolite-A with the polymer support. The duration of the first and second cycles of hydrothermal crystallization was systematically studied to obtain continuous, crack-free, and pure Zeolite-A membranes on polysulfone hollow-fiber support. The membrane exhibited fluxes of 3.8 and 9.75 kg m−2 h−1 at 25 °C and 75 °C, respectively, with >99.9 wt% water separated through pervaporation of the 90/10 wt % ethanol/water mixture.

Highly efficient, self-powered UV photodiodes based on leadfree perovskite nanocrystals through interfacial engineering

Double perovskite crystals are promising alternatives for lead-based perovskites that has potential to address toxicity and instability issues. In this study, Cs2AgBiCl6 nanocrystals (NCs) with high absorption coefficients were synthesized by hot-injection method. The bandgap engineering was realized by tuning the halide composition in Cs2AgBiCl6 to Cs2AgBiBr6. Both NCs were used as light-absorbing layers in lead-free perovskite photodiodes that exhibit wavelength-selectivity for UV–visible light operatable even at a bias voltage of 0 V. Cs2AgBiBr6-based photodiode exhibits a characteristic detection peak at 340 nm with a responsivity of 3.21 mA W−1, a specific detectivity up to 8.91 × 1010 Jones and a fast response speed with a rise/fall time of 30/35 ms. The excellent performance of self-driven photodiodes lights up the prospect of lead-free perovskite NCs in highly efficient optoelectronic devices.

Versatile Double Bandgap Photonic Crystals of High Color Saturation.

Double bandgap photonic crystals (PCs) exhibit significant potential for applications in various color display-related fields. However, they show low color saturation and inadequate color modulation capabilities. This study presents a viable approach to the fabrication of double bandgap photonic inks diffracting typical secondary colors and other composite colors by simply mixing two photonic nanochains (PNCs) of different primary colors as pigments in an appropriate percentage following the conventional RGB color matching method. In this approach, the PNCs are magnetically responsive and display three primary colors that can be synthesized by combining hydrogen bond-guided and magnetic field (H)-assisted template polymerization. The as-prepared double bandgap photonic inks present high color saturation due to the fixed and narrow full-width at half-maxima of the parent PNCs with a suitable chain length. Furthermore, they can be used to easily produce a flexible double bandgap PC film by embedding the PNCs into a gel, such as polyacrylamide, facilitating fast steady display performance without the requirement of an external magnetic field. This research not only presents the unique advantages of PNCs in constructing multi-bandgap PCs but also establishes the feasibility of utilizing PNCs in practical applications within the fields of anti-counterfeiting and flexible wearable devices.

Synthesis and Optimization of Cs2B'B″X6 Double Perovskite for Efficient and Sustainable Solar Cells.

Hybrid perovskite materials with high light absorption coefficients, long diffusion lengths, and high mobility have attracted much attention, but their commercial development has been seriously hindered by two major problems: instability and lead toxicity. This has led to lead-free halide double perovskite becoming a prominent competitor in the photovoltaic field. For lead-free double perovskites, Pb2+ can be heterovalent, substituted by non-toxic metal cations as a double perovskite structure, which promotes the flexibility of the composition. However, the four component elements and low solubility in the solvent result in synthesis difficulties and phase impurity problems. And material phase purity and film quality are closely related to the number of defects, which can limit the photoelectric performance of solar cells. Therefore, based on this point, we summarize the synthesis methods of Cs2B'B″X6 double perovskite crystals and thin films. Moreover, in the application of solar cells, the existing research mainly focuses on the formation process of thin films, band gap adjustment, and surface engineering to improve the quality of films and optimize the performance of devices. Finally, we propose that Cs2B'B″X6 lead-free perovskites offer a promising pathway toward developing highly efficient and stable perovskite solar cells.

Red Sm:KGd(WO4)2 laser at 649 nm.

We report on the first laser operation of a Sm3+-doped monoclinic KGd(WO4)2 double tungstate crystal in the red spectral range. Pumped by a frequency-doubled optically pumped semiconductor laser (2ω-OPSL) at 479.1 nm, the 0.8 at.% Sm:KGd(WO4)2 laser generated an output power up to 17.6 mW at 649.1 nm (the 4G5/2 → 6H9/2 transition) with a slope efficiency of 16.9%, a laser threshold down to 29 mW and a linear polarization. The laser exhibited a self-pulsing behavior, delivering µs-long pulses with a repetition rate of a few kHz. The polarized spectroscopic properties of Sm3+ ions were determined as well.

Thermal and molecular characteristics of novel water-soluble polysaccharide from the Pteridium aquilinum and Dryopteris filix-mas

Novel water-soluble complex polysaccharides (CPS) were obtained from Pteridium aquilinum and Dryopteris filix-mas. The yield of CPS was determined to be 4.161%-5.677%. As a result of the physicochemical composition, the CPS contained 12.10–13.65% moisture, 1.983–2.686% protein, 0.123–0.916% lipids and 12.06–21.52% ash. In HPLC analysis, sugar components of the samples (glucose+fructose+saccharose+maltose+lactose) ranged between 35.85–40.98%. Peaks of the fingerprint region specific for polysaccharides were identified during FT-IR analysis. DSC analysis showed that the glassy transition temperature of the DFR sample was higher than in the other three samples. A double cold crystallization peak was detected in all samples. During TGA analysis, the CPS samples exhibited a small amount of mass loss (1.2–1.85%) between 0 and 100 °C, and the DTGmax.p1 region continued up to 215–230 °C. These findings indicate that the four types of polysaccharides have excellent thermal stability (up to 230 °C) and are applicable to high-temperature food processing.

White light emitting diodes based on lanthanide ions doped Cs2NaInCl6 double perovskites

Lead-free halide double perovskites are widely used for phosphors converted light emitting diode (pc-LED) devices. However, it remains a challenge to modulate their spectra to meet different application requirements. Herein, Cs2NaInCl6:Sb3+ double perovskite crystals with excellent blue emission of self-trapped excitons (STEs) were prepared and a lanthanide ions (Ln3+) doping strategy was employed to enable multicolor emissions in this system. The emission colors can be continuously adjusted in a wide range by altering the Ln3+ ions doping levels. Especially, white light emissions with tunable correlated color temperature were obtained in Tb3+, Ho3+ ions codoped samples. Outstanding photoluminescence quantum yields of the samples are ascribed to the sensitization effect of Sb3+ ions and the efficient energy-transfer from STEs to Ln3+ ions. LED devices were further fabricated to demonstrate the great application potentials of the prepared phosphors. These findings provide deep insights for the designing of multicolor double perovskite phosphors.

Excited State Dynamics of Undoped and Eu3+-doped TbAl3(BO3)4 Crystals

The room temperature luminescence spectra and emission decay curves of undoped and Eu3+-doped TbAl3(BO3)4 crystals, grown using the flux growth technique, are presented and discussed. The experimental results show that excitation of the Tb3+ levels gives rise to 5D0 emission from the Eu3+ ion, and therefore non-radiative energy transfer is operative involving the two ions. Analysis of the experimental data indicates that the excitation of the Tb3+ donor ion gives rise to diffusion limited migration of the energy in the 5D4 level of the Tb3+ subset of cations, followed by the energy transfer process populating the 5D0 level of Eu3+. Upon increasing the concentration of the Eu3+ acceptor, the mainly green emission intensity and the decay time of the 5D4 level decrease, whilst the red emission of 5D0 becomes dominant. The experimental data are interpreted on the basis of the trigonal huntite-type structure of the double borate crystals under investigation.

Deep-red laser operation of cleaved single-crystal plates of Eu:CsGd(MoO4)2 molybdate.

We report on the first deep-red laser operation of a heavily Eu3+-doped cesium gadolinium double molybdate crystal with a perfect cleavage. A 17 at. % Eu:CsGd(MoO4)2 laser based on cleaved single-crystal plates generated a maximum continuous-wave output power of 212 mW at 703.1 nm (5D0 → 7F4 transition) with a slope efficiency of 30.1%, a low laser threshold of 51 mW, linear polarization, and a beam quality factor M2 = 1.6-1.7. This monoclinic crystal is promising for deep-red microchip lasers.

Tunable and Efficient Photoluminescence of Lanthanide-Doped Cs2NaScCl6 Double Perovskite Single Crystals toward Multifunctional Light-Emitting Diode Applications.

Lead-free halide double perovskite, as one of the promising candidates for lead halide perovskite materials, shows great potential in light-emitting diodes (LEDs), benefiting from its environmental friendliness and high chemical stability. However, the poor regulation of the emission spectra severely limits its application range. Herein, various lanthanide ions were successfully doped in Cs2NaScCl6 double perovskite single crystals (DPSCs) to yield effective and stable emissions spanning from visible to near-infrared (NIR) regions. Notably, efficient energy transfer from the host to the dopants enables tunable emissions with good chromaticity, which is rarely reported in the field of lead-free double perovskite. Moreover, density functional theory calculations reveal that the high local electron density around the [LnCl6]3- octahedron in DPSCs plays a key role in the improvement of photoluminescence quantum yields (PLQYs). The optimal PLQYs are up to 84%, which increases around 3 times over that of the undoped sample. Finally, multicolor and NIR LEDs based on Ln3+-doped Cs2NaScCl6 DPSCs were fabricated and had different application functions. Specifically, the single-composite white LED shows adjustable coordinates and correlated color temperatures, while the NIR LED shows good night vision imaging. This work provides new inspiration for the application of efficient multifunctional LEDs based on lead-free double perovskite materials.

Vibration response characteristics of the 2nd-crystal system with cross-spring pivot in a monochromator

The 2nd-crystal systems based on the single-axis hinge or optimized cross-spring pivot are compared by theoretical analysis, finite element calculation and experimental test. To improve the vibration stability of the monochromator in synchrotron radiation, the overall vibration response characteristics and their effects on the crystal performance are analyzed. Results show (a) the cross-spring pivot provide better axial stability and higher axial stiffness than the single-axis hinge, (b) the first-order natural frequency of the angle adjustment mechanism with cross-spring pivot is increased by a factor of approximately 3.1, and (c) the first-order natural frequency of the whole 2nd-crystal system is increased by 45 %. The RMS value of the relative pitch angle vibration of the double crystals without cooling is improved by 12.6%, and is 83.6 nrad under liquid nitrogen cooling. The vibration stability of the 2nd-crystal system with cross-spring pivot is greatly improved, which provides a new research basis for further optimization of the 2nd-crystal system and monochromator.

Real‐Time Quantification of Cell Mechanics and Functions by Double Resonator Piezoelectric Cytometry – Theory and Study of Cellular Adhesion of HUVECs

AbstractCell mechanics is closely associated with cellular structure and function. However, the inability to measure both cellular force and viscoelasticity of statistically significant number of cells noninvasively remains a challenge for quantitative characterizations of various cellular functions and practical applications. Here a double resonator piezoelectric cytometry (DRPC), using AT and BT cut quartz crystals of the same frequency and surface morphology is developed to simultaneously quantify the cells‐generated forces (ΔS) and viscoelastic moduli (G′, G″) of a population of isolated single cells or cells with different degrees of cell‐cell interactions in a non‐invasive and real time manner. DRPC captures the dynamic mechanical parameters ΔS and G′, G″ during the adhesions of human umbilical vein endothelial cells (HUVECs) under different ligand densities of adhesion molecules fibronectin or Arg‐Gly‐Asp (RGD) modified on the gold surfaces of 9 MHz AT and BT cut quartz crystals, and different seeding densities of HUVECs. It is found that both the ligand density and cell seeding density affect the magnitudes of ΔS and G′, G″ and their correlations are revealed for the first time by DRPC. The validity of DRPC is further verified by mechanical changes of the cells in response to treatments with cytoskeleton regulators.

Excited-state absorption and upconversion pumping of Tm3+-doped potassium lutetium double tungstate.

We report on a bulk thulium laser operating on the 3H4 → 3H5 transition with pure upconversion pumping at 1064 nm by an ytterbium fiber laser (addressing the 3F4 → 3F2,3 excited-state absorption (ESA) transition of Tm3+ ions) generating 433 mW at 2291 nm with a slope efficiency of 7.4% / 33.2% vs. the incident / absorbed pump power, respectively, and linear laser polarization representing the highest output power ever extracted from any bulk 2.3 µm thulium laser with upconversion pumping. As a gain material, a Tm3+-doped potassium lutetium double tungstate crystal is employed. The polarized ESA spectra of this material in the near-infrared are measured by the pump-probe method. The possible benefits of dual-wavelength pumping at 0.79 and 1.06 µm are also explored, indicating a positive effect of co-pumping at 0.79 µm on reducing the threshold pump power for upconversion pumping.

Binary mixtures formed between methyl malonic acid and alkyloxy benzoic acids: optical and thermal investigations

Double hydrogen bond liquid crystals (MM + nBOA) are prepared from Methyl Malonic acid (MM) and p-n alkyloxy benzoic acid (nBOA, whose carbon chain length varies from pentyl to dodecyl) treated with dimethyl form amide. MM + 7BOA and MM + 9BOA mesogenic complexes are preferred as chemical ingredients for preparing binary mixtures as they exhibit rich phase polymorphism. MM + 7BOA is treated as X component while MM + 9BOA is treated as Y component. Appropriate molar ratio (0.1X to 0.9X and 0.1Y to 0.9Y) variation leads to formation of nine binary mixtures. Chemical, optical and thermal investigations are performed for fitting the binary mixtures to applicational viability.

Highly efficient visible and near-infrared luminescence of Sb3+, Tm3+ co-doped Cs2NaYCl6 lead-free double perovskite and light emitting diodes

Near-infrared (NIR) luminescent materials have been widely used in biomedicine, optical communication and other fields due to their unique photophysical properties. However, the development of efficient NIR luminescent materials is still a challenge. Herein, Sb3+, Tm3+ co-doped Cs2NaYCl6 double perovskite single crystals (SCs) have been synthesized. Benefiting from the crystal structure and rare earth lattice of rare earth-based double perovskite host, lanthanide ions can be doped effectively, and the optimal NIR photoluminescence quantum yield (PLQY) of Cs2NaYCl6:Sb3+, Tm3+ SCs is up to 20.2%. The energy transfer mechanism was systematically surveyed by steady-state spectroscopy. Furthermore, a compact visible and NIR light emitting diode was fabricated by coating Cs2NaYCl6:Sb3+, Tm3+ SCs on a commercial 320 nm LED chip. This light source has a promising application prospect in multifunctional lighting.

Modulating the afterglow time of Mn2+ doped double perovskites by size tuning and its applications in dynamic information display.

Mn2+ doped lead-free double perovskites are emerging afterglow materials that can avoid the usage of rare earth ions. However, the regulation of the afterglow time is still a challenge. In this work, the Mn doped Cs2Na0.2Ag0.8InCl6 crystals with afterglow emission at about 600 nm are synthesized by a solvothermal method. Then, the Mn2+ doped double perovskite crystals are crushed into different sizes. As the size decreases from 1.7 mm to 0.075 mm, the afterglow time decreases from 2070 s to 196 s. Steady-state photoluminescence (PL) spectra, time resolved PL, thermoluminescence (TL) reveal the afterglow time monotonously decreases due to the enhanced nonradiative surface trapping. The modulation on afterglow time will greatly promote their applications in various fields, such as bioimaging, sensing, encryption, and anti-counterfeiting. As a proof of concept, dynamic display of information is realized based on different afterglow times.

Stability analysis of an angle trimmer mechanism applied to a double crystal monochromator

Double crystal monochromator is the core device of the synchrotron light source beamline, for the application of double crystal monochromator trimmer mechanism not only needs a high angular adjustment resolution, but also needs a high inherent frequency to ensure its stability. In this paper, we have analyzed the inherent frequency of an angle-trimming mechanism applied to a biocrystal monochromator by the energy method, established the relationship equation between its inherent frequency and each parameter of the mechanism, and analyzed the influence of each parameter on its inherent frequency. And we establish the simulation model according to the actual installation situation to carry out finite element analysis. The results prove that the mechanism has excellent stability performance and meets the requirements of light source use.

Binary mixtures of double hydrogen bond liquid crystals: chemical, optical, thermal investigations

Binary mixtures of double hydrogen bond liquid crystals are investigated by chemical, optical and thermal studies. These binaries exhibiting rich phase polymorphism, in which hydrogen bond is formed between Methyl Malonic acid (MM), heptyloxy benzoic acid (7BOA), and decyloxy benzoic acid (10BOA) abbreviated as MM + 7BOA and MM + 10BOA. MM + 7BOA (X) is considered as one of the variants while MM + 10BOA (Y) is considered as other variant. Appropriate molar ratio (0.1X to 0.9X and 0.1Y to 0.9Y) variation in the precursors leads to formation of nine binary mixtures.

Lattice Dynamics and Electron-Phonon Coupling in Double Perovskite Cs2NaFeCl6.

Phonon-phonon and electron/exciton-phonon coupling play a vitally important role in thermal, electronic, as well as optical properties of metal halide perovskites. In this work, we evaluate phonon anharmonicity and coupling between electronic and vibrational excitations in novel double perovskite Cs2NaFeCl6 single crystals. By employing comprehensive Raman measurements combined with first-principles theoretical calculations, we identify four Raman-active vibrational modes. Polarization properties of these modes imply Fm3̅m symmetry of the lattice, indicative for on average an ordered distribution of Fe and Na atoms in the lattice. We further show that temperature dependence of the Raman modes, such as changes in the phonon line width and their energies, suggests high phonon anharmonicity, typical for double perovskite materials. Resonant multiphonon Raman scattering reveals the presence of high-lying band states that mediate strong electron-phonon coupling and give rise to intense nA 1g overtones up to the fifth order. Strong electron-phonon coupling in Cs2NaFeCl6 is also concluded based on the Urbach tail analysis of the absorption coefficient and the calculated Fröhlich coupling constant. Our results, therefore, suggest significant impacts of phonon-phonon and electron-phonon interactions on electronic properties of Cs2NaFeCl6, important for potential applications of this novel material.

Growth of Robust Carbon Nitride Films by Double Crystallization with Exceptionally Boosted Electrochemiluminescence for Visual DNA Detection

AbstractElectrochemically generated chemiluminescence (ECL) has attracted significant interest over the past decades, ranging from fundamental studies on highly efficient electron‐to‐photon interconversion to practical bioassays. Nonetheless, the ECL efficiency (ΦECL) of most emitters is low, which significantly hampers further development. Herein, this work reports a highly robust carbon nitride film with unusually enhanced ECL efficiency (2256 times higher than that of the reference Ru(bpy)3Cl2/K2S2O8). Double crystallization, which provides the primary interaction of carbon nitride with the substrate and subsequent growth, plays a crucial role in the preparation. The improved ECL efficiency is ascribed to little pinholes suppressing futile co‐reagent reduction, maintenance of more orbit‐delocalized heptazine subunits improving ECL kinetics, and high transparency avoiding self‐absorption. As a potential application, an ultrasensitive visual DNA biosensor by the naked eye is further successfully developed with a linear detection range of 100 pmto 1 µmand limit of detection of 27 pm(S/N = 3).