Single Crystal Host Research Articles

Probing the in-plane dipole moment vector between ground and excited state of single molecules by the Stark effect.

Single molecules, embedded inside a well-defined insertion site of a single-crystalline host matrix, are sensitive probes of electric field via the induced Stark shift on their lifetime-limited electronic transition. Though the response of molecules to electric field has been shown to be relatively homogeneous, crystal symmetry allows for several, spectroscopically-indistinguishable, orientations of the net permanent dipole moment between the ground and excited state - the dipole vector - and this is problematic for measuring field orientation and magnitude. In this work, we measure for each terrylene molecule, embedded inside a new host matrix, the dipole vector independently by an electric field that we can rotate in the plane of the crystal. This single crystal host matrix, called [1]BenzoThieno[3,2-b]BenzoThiophene, induces a moderate symmetry breaking of the embedded centrosymmetric terrylene molecule, and gives rise to a net dipole moment of 0.28±0.09 Debye. Based on quantum chemistry calculations we propose an insertion site that best matches the experimental findings.

Photoluminescence and energy transfer mechanisms of Tm3+ doped Y2O3 laser crystals: experimental and theoretical insights.

Rare-earth thulium (Tm3+) doped yttrium oxide (Y2O3) host single crystals are promising "eye-safe" laser materials. However, the mechanisms of photoluminescence and energy transfer in Tm3+ doped Y2O3 crystals are not yet understood at the fundamental level. Here, we synthetize a series of Y2O3:Tm3+ samples by the sol-gel method. Our experimental results show that the most intensive absorption line of the 3H6 → 1D2 transition occurs at 358 nm, and the strongest emission line of the 1D2 → 3F4 transition is located at 453 nm, which are in good agreement with the calculations of 363 nm and 458 nm, respectively. By using the CALYPSO structural search method, the ground state structure of Y2O3:Tm3+ with P2 space group symmetry is uncovered. The complete energy levels, including free-ion LS terms and crystal-field LSJ multiplet manifolds, of Y2O3:Tm3+ are obtained based on our developed WEPMD method. The present findings show that our WEPMD method can be used in experiments to elucidate the underlying mechanisms of photoluminescence and energy transfer in Tm3+ doped Y2O3 crystals, which offer insights for further understanding of other rare-earth doped laser materials.

Polymer-Inorganic Crystalline Nanocomposite Materials via Nanoparticle Occlusion.

Efficient occlusion of guest nanoparticles into host single crystals opens up a straightforward and versatile way to construct functional crystalline nanocomposites. This new technique has attracted increasing research interest because it enables the composition, structure, and properties of the resulting nanocomposites to be well-controlled. This review aims to provide a comprehensive summary of nanoparticle occlusion within inorganic crystals. First, recently-developed strategies for the occlusion of various colloidal particles (e.g., diblock copolymer nanoparticles, polymer-modified inorganic nanoparticles, oil droplets, etc.) within host crystals (e.g., CaCO3 , ZnO, or ZIF-8) are summarized. Second, new results pertaining to spatially-controlled occlusion and the physical mechanism of nanoparticle occlusion are briefly discussed. Finally, the physicochemical properties and potential applications of various functional nanocomposite crystals constructed via nanoparticle occlusion are highlighted and the perspective on the likely future for this research topic is also offered.

Initializing 214 Pure 14-Qubit Entangled Nuclear Spin States in a Hyperpolarized Molecular Solid.

Quantum entanglement has been realized on a variety of physical platforms such as quantum dots, trapped atomic ions, and superconductors. Here we introduce specific molecular solids as promising alternative platforms. Our model system is triplet pentacene in a host single crystal at level anticrossing (LAC) conditions. First, a laser pulse generates the triplet state and initiates entanglement between an electron spin and 14 hyperfine coupled proton spins (quantum bits or qubits). This gives rise to large nuclear spin polarization. Subsequently, a resonant high-power microwave (mw) pulse disentangles the electron spin from the nuclear spins. Simultaneously, high-dimensional multiqubit entanglement is formed among the proton spins. We verified the initialization of 214 pure 14-qubit entangled nuclear spin states with an average degree of entanglement of Eav = 0.77 ± 0.03. These results pave the way for large-scale quantum information processing with more than 10 000 multiqubit entangled states corresponding to computational (Hilbert) space dimensions of dim >1053.

Solution growth of millimeter‐scale Na2SiF6 single crystals for Mn4+‐doping as red phosphor

AbstractThe cation exchange method has been demonstrated to be efficient in doping Mn4+ ions into various fluorides to synthesize the red‐emitting LED phosphors. This paper, however, reports the challenge in using this method to dope Mn4+ into the Na2SiF6 single crystals, to prepare the fluoride phosphor in single‐crystal form, a state‐of‐the‐art study in the white LED lighting field. The millimeter‐sized Na2SiF6 single crystals with a uniform columnar morphology (2–3 mm in length) were successfully grown in solution by a slow cooling process after optimizing the precursors. Then, the crystals were soaked in the HF solution dissolved with K2MnF6 to implement Mn4+‐doping via the cation exchange process. Evaluation of the Mn4+‐doping behavior reveals that the Mn4+ ↔ Si4+ cation exchange is less efficient in the case of single crystal host compared with the polycrystalline powdery ones and by‐reactions also occur which generates new phases. The Na2SiF6 single crystals doped with Mn4+ exhibit a series of discrete sharp peaks with intense zero phonon line emission at 617 nm under 450 nm blue irradiation. This study may trigger the exploration of new single crystal fluoride phosphor.

Incorporation of nanogels within calcite single crystals for the storage, protection and controlled release of active compounds.

Nanocarriers have tremendous potential for the encapsulation, storage and delivery of active compounds. However, current formulations often employ open structures that achieve efficient loading of active agents, but that suffer undesired leakage and instability of the payloads over time. Here, a straightforward strategy that overcomes these issues is presented, in which protein nanogels are encapsulated within single crystals of calcite (CaCO3). Demonstrating our approach with bovine serum albumin (BSA) nanogels loaded with (bio)active compounds, including doxorubicin (a chemotherapeutic drug) and lysozyme (an antibacterial enzyme), we show that these nanogels can be occluded within calcite host crystals at levels of up to 45 vol%. Encapsulated within the dense mineral, the active compounds are stable against harsh conditions such as high temperature and pH, and controlled release can be triggered by a simple reduction of the pH. Comparisons with analogous systems – amorphous calcium carbonate, mesoporous vaterite (CaCO3) polycrystals, and calcite crystals containing polymer vesicles – demonstrate the superior encapsulation performance of the nanogel/calcite system. This opens the door to encapsulating a broad range of existing nanocarrier systems within single crystal hosts for the efficient storage, transport and controlled release of various active guest species.

Measuring the Magnetic Dipole Transition of Single Nanorods by Spectroscopy and Fourier Microscopy

Rare-earth doped nanocrystals possess optical transitions with significant either electric or magnetic dipole characters. They are of considerable interest for understanding and engineering light-matter interactions at the nanoscale with numerous applications in nanophotonics. Here, we study the ${}^{5}{D}_{0}{\ensuremath{\rightarrow}}^{7}{F}_{1}$ transition dipole vector in individual ${\mathrm{NaYF}}_{4}:{\mathrm{Eu}}^{3+}$ nanorod crystals by Fourier and confocal microscopies. A single-crystal host matrix leads to narrow emission lines at room temperature that permit separation of the Stark sublevels resulting from the crystal-field splitting. We observe a fully magnetic transition and low variability of the transition dipole orientation over several single nanorods. We estimate the proportion of the dipole transitions for the Stark sublevels. We also determine an effective altitude of the rod with respect to the substrate. The narrow emission lines characteristic of ${\mathrm{NaYF}}_{4}:{\mathrm{Eu}}^{3+}$ ensure well-defined electric or magnetic transitions, and are thus instrumental for probing locally their electromagnetic environment by standard confocal microscopy.

Visualizing the toughening origins of gel-grown calcite single-crystal composites

Biogenic single crystals have been widely demonstrated to incorporate macromolecules to achieve extra damage tolerance, spurring investigations on their synthetic analogs with enhanced mechanical properties as well as the enhancement mechanism(s) behind. And the investigations rely on both rational design of the single-crystal composites and, equally importantly, nanoscale and in-situ characterization strategy. Here, composite structures are constructed inside the calcite single-crystal host by incorporating guest materials of agarose fibers, multi-walled carbon nanotubes (MWCNTs), and graphene oxide (GO), through crystallization in agarose gel media. Further, transmission electron microscopy-scanning probe microscopy (TEM-SPM) method, coupling compression measurements with nanoscale imaging, shows that the obtained single-crystal composites exhibit improved toughness, compared to the solution-grown pure single crystals. Particularly, the rupture time increases by 1.25 times after the gel-networks and MWCNTs are incorporated. More importantly, the in-situ observation of the crystal deformation suggests that the guest incorporation toughens the single-crystal host by the shielding effect of nanofiber on crack-bridging at nanoscale. As such, this work may have implications for understanding the damage tolerance of biominerals as well as towards the development of new mechanically reinforced single-crystal composite materials.

Polymer-Directed Assembly of Single Crystal Zinc Oxide/Magnetite Nanocomposites under Atmospheric and Hydrothermal Conditions

Within the field of crystal growth it is recognized that secondary species can sometimes be occluded within a growing crystal according to the crystallization conditions and pairing of the additive and host crystal. This article takes inspiration from this phenomenon to create multifunctional inorganic nanocomposites with unique structures: inorganic single crystals containing embedded inorganic nanoparticles. Using magnetite (Fe3O4)/ZnO as a suitable test system, ZnO crystals are precipitated from aqueous solution at 90 °C and atmospheric pressure in the presence of Fe3O4 nanoparticles functionalized with anionic diblock copolymers. Analysis of product nanocomposite crystals using atomic absorption spectroscopy shows that the Fe3O4 nanoparticles are embedded within the ZnO single crystal hosts at levels of approximately 10 wt %, and TEM analysis shows that there is no apparent discontinuity between the nanoparticles and host crystal matrix. Importantly, we then demonstrate that this occlusion approach ca...

Top Seeded Solution Growth, Structural and Vibrational Analyses of K1−x Na x Gd(WO4)2 (0.0 ≤ x ≤ 0.2) Single Crystals

Laser host single crystals of K1−xNaxGd(WO4)2 (0.0 ≤ x ≤ 0.2) have been grown by high temperature top seeded solution with low viscus K2WO4 as flux. The powder x-ray diffraction pattern of the synthesised charge confirmed the crystalline quality and possible incorporation of sodium in the KGd(WO4)2 (KGW) matrix. Estimated lattice parameters of the grown crystals revealed that there were no anomalous structural changes due to the incorporation of sodium in the KGW matrix. The change in structural phase transition and its thermal stability due to addition of sodium ions have been studied through differential thermal analysis. The homogeneous distribution of sodium and other metal ions in the matrix were qualitatively studied from energy-dispersive x-ray spectroscopy measurements. The Raman and Fourier transform infrared spectroscopy analyses have shown the influence of vibrational changes due to the incorporation of sodium ions in KGW. The optical absorption studies have shown the broad absorption band in the near-ultra violet region corresponding to the W6+ to O2− charge transfer band. These results suggest that incorporation of sodium in a KGW matrix appear to have modulated the physical properties of the grown crystals.

Epifluorescence microscopy: a sensitive tool for studying the morphology and oriented growth of europium precipitates in KI single-crystal hosts.

The morphology and oriented growth of europium precipitates in well-annealed Eu²⁺-doped KI single crystals are investigated by epifluorescence microscopy using the proper doping ions as fluorochromes. To make this, electronic spatial reconstructions of some fields of precipitates and of some individual precipitates were built from epifluorescence microscope images of different optical cross-sections of these objects. The building procedures are carefully explained. Previously, the KI:Eu²⁺ system was characterized by fluorescence spectrophotometry and the KI-host long-range translational order was tested by single-plate X-ray diffraction. Precipitates are shaped as plates, with their broad faces being parallel to host lattice planes of either {100}- or {110}-forms (the {100}- or {110}-plates, respectively) and as rods lying along host lattice <100>-directions. The {100}-plates have rhomboidal broad faces with a side lying along a <100>-direction, an internal angle of about 45°, as measured on the corresponding {100}-plane, and, consequently, another side (the {100}<110>-side) lying along a <110> direction on this plane. The {110}-plates have rectangular broad faces with a side lying along a <100>-direction and with another side (the {110}<110>-side) lying along a <110>-direction on the corresponding {110}-plane. Spatial reconstructions of a typical precipitate field, a typical {100}-plate, a typical {110}-plate and a typical rod are described in detail. Precipitates were measured in their different dimensions and the measuring procedures are explained. The plate thicknesses and rod diameters are into a common narrow range of values (0.5-0.2 μm) which contains also the inferior limits of the obtained length ranges for the {100}<110>- and {110}<110>-sides (5.1-0.3 and 4.9-0.3 μm, respectively). It is discussed that that three different europium precipitation states are responsible for the studied precipitation and that plates grew from rods during annealing.

Reversible crystal deformation of a single-crystal host of copper(II) 1-naphthoate-pyrazine through crystal phase transition induced by methanol vapor sorption.

A novel microporous single crystal of [Cu(II)2(1-NA)4(pyz)]n (1-NA: 1-naphthoate, pyz: pyrazine) exhibited bending and straightening action on a macroscopic scale during the first-order crystal phase transition induced by methanol vapor sorption.

Encapsulation of nanoparticles into single-crystal ZnO nanorods and microrods.

One-dimensional single crystal incorporating functional nanoparticles of other materials could be an interesting platform for various applications. We studied the encapsulation of nanoparticles into single-crystal ZnO nanorods by exploiting the crystal growth of ZnO in aqueous solution. Two types of nanodiamonds with mean diameters of 10 nm and 40 nm, respectively, and polymer nanobeads with size of 200 nm have been used to study the encapsulation process. It was found that by regrowing these ZnO nanorods with nanoparticles attached to their surfaces, a full encapsulation of nanoparticles into nanorods can be achieved. We demonstrate that our low-temperature aqueous solution growth of ZnO nanorods do not affect or cause degradation of the nanoparticles of either inorganic or organic materials. This new growth method opens the way to a plethora of applications combining the properties of single crystal host and encapsulated nanoparticles. We perform micro-photoluminescence measurement on a single ZnO nanorod containing luminescent nanodiamonds and the spectrum has a different shape from that of naked nanodiamonds, revealing the cavity effect of ZnO nanorod.

Superposition model analysis of zero field splitting for Mn2+ in some host single crystals

The Newman superposition model has been used to investigate the substitution of Mn2+ for Zn2+ site in ammonium tetra flurozincate dihydrate and for Co2+ site in cobalt ammonium phosphate hexahydrate and cobalt potassium phosphate hexahydrate single crystals. The calculated values of zero field splitting parameter b20 at room temperature fit the experimental data with average intrinsic parameters \( \overline{b}_{2} \) (F) = −0.0531 cm−1 for fluorine and \( \overline{b}_{2} \) (O) = −0.0280 cm−1 for oxygen, taken t2 = 7 for Mn2+ doped in ammonium tetra fluorozincate dihydrate single crystals. The values of \( \overline{b}_{2} \) determined for Mn2+ doped in cobalt ammonium phosphate hexahydrate are −0.049 cm−1 for site I and −0.045 cm−1 for site II and in cobalt pottasium phosphate hexahydrate single crystals it is found to be \( \overline{b}_{2} \) = −0.086 cm−1. We find close agreement between theoretical and experimental values of b20.

Concentration dependence study of VUV–UV–visible luminescence of Nd3+ and Gd3+ in LuLiF4

An overview of absorption and luminescence characteristics of Nd3+ and Gd3+ centers in a LiLuF4 single crystal host is provided. Single crystals doped with the above rare earth ions were prepared by micro-pulling-down technique in the form of rods a few cm long with a diameter of about 2mm. Excitation and emission spectra and fast decay kinetics in VUV and UV spectral regions were measured at room temperature. The observed absorption and emission peaks are due to the 5d–4f and 4f–4f optical transitions of Nd3+ and Gd3+ centers. Concentration dependence of the decay kinetics is also discussed.

VUV-UV-visible luminescence of Nd3+, Er3+ and Tm3+ and energy distribution in LiLuF4 single crystal host

It is the aim of this contribution to provide an overview of luminescence spectra and decay characteristics of Nd3+, Er3+ and Tm3+ centers in LiLuF4 single crystal including possible energy transfer mechanisms towards and away from the Nd3+ 5d excited state. Single crystal doped with the mentioned RE ions were prepared by micro-pulling-down technique. Excitation and emission spectra and fast decay kinetics in VUV spectral region are completed with radio-and photoluminescence spectra and decay kinetics in UV-visible region.

Dynamic gas separation on a flexible single-crystal host

Dynamic gas separation on a flexible single-crystal host

VUV-UV-visible luminescence of Nd3+, Er3+ and Tm3+ in LiLuF4 single crystal host

Abstract An overlook of absorption and luminescence characteristics of Nd3+, Er3+ and Tm3+ centers in LiLuF4 single crystal is provided. Single crystal doped with the mentioned RE ions were prepared by micro-pulling-down technique in the form of few cm long rods with the diameter of about 2 mm. Excitation and emission spectra and fast decay kinetics in VUV spectral region were measured at SUPERLUMI station at synchrotron DESY, Hamburg and characterization was further completed in UV-visible region at conventional spectrophotometers. Observed absorption and emission peaks are ascribed to the 5d–4f and 4f–4f optical transitions in the doped rare earth ions. Concentration dependence of the decay kinetics is discussed.

Switch of channel geometry by 1D component slide responding to slight structural stimuli of adsorbed guest

The adsorption behavior of a flexible single-crystal host [Cu2(bza)4(pyz)]n was studied for a planar triangular molecule and investigated for large host structural changes including a switch of channel geometry responding to included guest molecules.

Acetonitrile vapour inclusion in single-crystal adsorbents [MII2(bza)4(pyz)]n (MII = Rh, Cu)

We studied acetonitrile vapour inclusion behaviour for flexible single-crystal hosts [M2(bza)4(pyz)]n (M = Rh2+ (1), Cu2+ (2); bza = benzoate, pyz = pyrazine) by adsorption experiments and single-crystal X-ray analysis of the inclusion state. Independent of metal ions, the flexible single-crystal hosts smoothly and reversibly adsorbed acetonitrile molecules up to ca. 2 molecules per M2 unit through an adsorption leap, which indicated the change of crystal phase transformations. The results showed that the acetonitrile inclusion crystals were isostructural with including acetonitrile molecules aligned in a head-to-tail fashion in a 1D channel. The acetonitrile molecules were densely included in the channel compared with those in an acetonitrile crystal, indicating that the flexible hosts provide a suitable field for observing the acetonitrile inclusion structure. While the inclusion crystal structure was independent of metal ions, the adsorption behaviour has a difference in the critical pressure and amount of the adsorption leap, depending on the metal ions in the host skeletons.