Formation Of Microcrystals Research Articles

Early Stages of Crystallization of Lanthanum-Borogermanate Glass by a Femtosecond Laser Beam

Regions in the bulk of lanthanum borogermanate glass modified by a femtosecond laser beam were studied by means of optical microscopy and confocal Raman scattering (RS) spectroscopy. The obtained data show that, at the stages preceding the formation of an LaBGeO5 microcrystal, upon irradiation by a femtosecond beam in a certain interval of laser pulse energy germanium nanocrystals precipitate in the zone of local heating. The correlation between the conditions of laser irradiation leading to the appearance of germanium nanocrystals and the conditions ensuring with high probability the crystallization of phases of the low-temperature modification of lanthanum borate and stillwellite-like lanthanum borogermanate suggest that germanium nanocrystals can serve as nuclei for heterogeneous crystallization of LaBO3 and LaBGeO3.

Pharmaceutical Microcrystal Formation by Supersaturation Control with an Electrolyte

Pharmaceutical Microcrystal Formation by Supersaturation Control with an Electrolyte

Forced dried droplet method for MALDI sample preparation

A forced dried droplet method (FDD) is developed to overcome the drawbacks of the conventional dried-droplet (DD) method for matrix assisted laser desorption/ionization (MALDI) sample preparation. The crystals produced by the DD method are heterogeneous and irregularly distributed, and thus many methods have tried to solve the problems. However, most of them spend more time or need additional instruments to generate homogeneous microcrystals. The FDD sample preparation method can produce uniform microcrystals with homogeneous size distribution in few minutes without additional instruments. Stirring the sample spot solution (an agitation process) with a pipette tip can change the crystal size distribution which is observed by the microscope. Mass spectrometric analysis shows that the smaller the crystal size is, the better the ion signal intensity is. The formation of microcrystals can be explained with the effective rate of secondary nucleation. The relative standard deviation (RSD) of the FDD method is ∼16% which is comparable to the two-layer (TL) method and is better than the DD method.

Anti-Transforming Growth Factor β IgG Elicits a Dual Effect on Calcium Oxalate Crystallization and Progressive Nephrocalcinosis-Related Chronic Kidney Disease.

Crystallopathies are a heterogeneous group of diseases caused by intrinsic or environmental microparticles or crystals, promoting tissue inflammation and scarring. Certain proteins interfere with crystal formation and growth, e.g., with intrarenal calcium oxalate (CaOx) crystal formation, a common cause of kidney stone disease or nephrocalcinosis-related chronic kidney disease (CKD). We hypothesized that immunoglobulins can modulate CaOx microcrystal formation and crystal growth and that therefore, biological IgG-based drugs designed to specifically target disease modifying proteins would elicit a dual effect on the outcome of CaOx-related crystallopathies. Indeed, both the anti-transforming growth factor (TGF)β IgG and control IgG1 antibody impaired CaOx crystallization in vitro, and decreased intrarenal CaOx crystal deposition and subsequent CKD in mice on an oxalate-rich diet compared to oxalate-fed control mice. However, the TGFβ-specific IgG antibody showed nephroprotective effects beyond those of control IgG1 and substantially reduced interstitial fibrosis as indicated by magnetic resonance imaging, silver and α-smooth muscle actin staining, RT-qPCR, and flow cytometry for pro-fibrotic macrophages. Suppressing interstitial fibrosis slowed the decline of glomerular filtration rate (GFR) compared to treatment with control IgG1 [slope of m = −8.9 vs. m = −14.5 μl/min/100 g body weight (BW)/day, Δ = 38.3%], an increased GFR at the end of the study (120.4 vs. 42.6 μl/min/100 g BW, Δ = 64.6%), and prolonged end stage renal disease (ESRD)-free renal survival by 10 days (Δ = 38.5%). Delayed onset of anti-TGFβ IgG from day 7 was no longer effective. Our results suggest that biological drugs can elicit dual therapeutic effects on intrinsic crystallopathies, such as anti-TGFβ IgG antibody treatment inhibits CaOx crystallization as well as interstitial fibrosis in nephrocalcinosis-related CKD.

Hydrogen Bond Dynamics of Cellulose through Inelastic Neutron Scattering Spectroscopy.

This work explores the dynamics of hydrogen bond networks in cellulose through inelastic neutron scattering (INS) and periodic CASTEP calculations. Estimated spectra were based on the crystal structure of cellulose Iα and Iβ and replicate the INS spectrum of cellulose samples with remarkable similarity, allowing a reliable assignment of INS bands to vibrational modes of cellulose. Comparison of cellulose samples from varied sources, from bacterial to kraft pulp, allows the identification of characteristic INS bands, arising from C2-OH torsional motions, which easily identify which allomorph-Iα or Iβ-is prevalent. A high crystallinity index is revealed by the presence of well-defined INS bands associated with highly cooperative CH bending modes along the chain. Hydrating kraft cellulose samples clearly affects those INS bands related with the hydroxymethyl group, identified as the preferred binding site for water molecules. At high humidity content level, a significant proportion of the water molecules is aggregated in clusters within the amorphous cellulose domains. The formation of ice microcrystals leads to a partial disruption of the hydrogen-bond network, as can be concluded from the observed red-shift of the torsional OH vibrational modes. The full assignment and interpretation of cellulose's INS spectra herein provided is a sound basis for future use of INS spectroscopy in the characterization of functionalized cellulose fibers and composite materials.

Brittle deformation during Alpine basal accretion and the origin of seismicity nests above the subduction interface

Geophysical observations on active subduction zones have evidenced high seismicity clusters at 20–40 km depth in the fore-arc region whose origin remains controversial. We report here field observations of pervasive pseudotachylyte networks (interpreted as evidence for paleo-seismicity) in the now-exhumed Valpelline continental unit (Dent Blanche complex, NW. Alps, Italy), a tectonic sliver accreted to the upper plate at c. 30 km depth during the Paleocene Alpine subduction. Pre-alpine granulite-facies paragneiss from the core of the Valpelline unit are crosscut by widespread, mm to cm-thick pseudotachylyte veins. Co-seismic heating and subsequent cooling led to the formation of Ti-rich garnet rims, ilmenite needles, Ca-rich plagioclase, biotite microliths and hercynite micro-crystals. 39Ar–40Ar dating yields a 51–54 Ma age range for these veins, thus suggesting that frictional melting events occurred near peak burial conditions while the Valpelline unit was already inserted inside the duplex structure. In contrast, the base of the Valpelline unit underwent synchronous ductile and brittle, seismic deformation under water-bearing conditions followed by a re-equilibration at c. 40 Ma (39Ar–40Ar on retrograded pseudotachylyte veins) during exhumation-related deformation. Calculated rheological profiles suggest that pseudotachylyte veins from the dry core of the granulite unit record upper plate micro-seismicity (Mw 2–3) formed under very high differential stresses (>500 MPa) while the sheared base of the unit underwent repeated brittle–ductile deformation at much lower differential stresses (<40 MPa) in a fluid-saturated environment. These results demonstrate that some of the seismicity clusters nested along and above the plate interface may reflect the presence of stiff tectonic slivers rheologically analogous to the Valpelline unit acting as repeatedly breaking asperities in the basal accretion region of active subduction zones.

Supersaturation-controlled microcrystallization and visualization analysis for serial femtosecond crystallography

Time-resolved serial femtosecond crystallography with X-ray free electron laser (XFEL) holds the potential to view fast reactions occurring at near-physiological temperature. However, production and characterization of homogeneous micron-sized protein crystals at high density remain a bottleneck, due to the lack of the necessary equipments in ordinary laboratories. We describe here supersaturation-controlled microcrystallization and visualization and analysis tools that can be easily used in any laboratory. The microcrystallization conditions of the influenza virus hemagglutinin were initially obtained with low reproducibility, which was improved by employing a rapid evaporation of hanging drops. Supersaturation-controlled microcrystallization was then developed in a vapor diffusion mode, where supersaturation was induced by evaporation in hanging drops sequentially for durations ranging from 30 sec to 3 min, depending on the protein. It was applied successfully to the microcrystal formation of lysozyme, ferritin and hemagglutinin with high density. Moreover, visualization and analysis tools were developed to characterize the microcrystals observed by light microscopy. The size and density distributions of microcrystals analyzed by the tools were found to be consistent with the results of manual analysis, further validated by high-resolution microscopic analyses. Our supersaturation-controlled microcrystallization and visualization and analysis tools will provide universal access to successful XFEL studies.

Multiple yet Controllable Photoswitching in a Single AIEgen System.

Seeking new methods to obtain elaborate artificial on-demand photoswitching with multiple functionalities remains challenging. Most of the systems reported so far possess only one specific function and their nonemissive nature in the aggregated state inevitably limit their applications. Herein, a tailored cyanostilbene-based molecule with aggregation-induced emission characteristic was synthesized and was found to exhibit efficient, multiple and controllable photoresponsive behaviors under different conditions. Specifically, three different reactions were involved: (i) reversible Z/E isomerization under room light and thermal treatment in CH3CN, (ii) UV-induced photocyclization with a concomitant dramatic fluorescence enhancement, and (iii) regio- and stereoselective photodimerization in aqueous medium with microcrystal formation. Experimental and theoretical analyses gave visible insights and detailed mechanisms of the photoreaction processes. Fluorescent 2D photopattern with enhanced signal-to-background ratio was fabricated based on the controllable "turn-on" and "turn-off" photobehaviors in different states. The present study thus paves an easy yet efficient way to construct smart multiphotochromes for unique applications.

Selective area formation of arsenic oxide-rich octahedral microcrystals during photochemical etching of n-type GaAs

We demonstrate how to spatially localize the formation of octahedral arsenic oxide microcrystals in selective areas of highly doped n-type GaAs substrates during rapid digital projection photochemical (PC) etching with sulfuric acid. We captured a time lapse video that shows that these crystal-like octahedral structures grow to various sizes ranging from 5 µm to 100 µm. By conducting a series of different studies, we identified the etch rate, the area of illumination, the acid type, and the substrate quality as major factors that affect crystal formation. In particular, we observed that the structures only formed in the high etch rate illuminated regions of the wafer. Moreover, they only formed when the area of illumination was adequately large. The structures formed but then partially dissolved when hydrochloric acid was used. Lastly, we observed the growth of individual microcrystals for prime grade wafers but the formation of a network of microcrystalline features for mechanical grade wafers.

Reversible Thermochromic Polymeric Thin Films Made of Ultrathin 2D Crystals of Coordination Polymers Based on Copper(I)‐Thiophenolates

AbstractA one‐pot reaction between Cu(BF4)2·xH2O and 4‐mercaptobenzoic acid in acetone or methanol gives rise to the formation of lamellar microcrystals of two Cu(I)‐thiophenolate‐based coordination polymers (CPs) with the formulas [CuCT] n (1) (CT = 4‐carboxy‐thiophenolate) and [CuMCT]n (2) (MCT = 4‐methoxycarbonyl‐thiophenolate). Both 1 and 2 show a reversible luminescent thermochromic behavior upon cooling, changing their color from pale yellow to green to orange in the case of 1, and from pale orange to green in the case of 2. It is shown that the lamellar character of these crystals, which exhibit micrometer lateral dimensions and sub‐micrometer/nanometer thicknesses, allows processing them with an organic polymer such as polyvinylidene difluoride (PVDF) to form thermochromic 1@PVDF and 2@PVDF thin films. These thermal stimuli‐responsive thin films are freestanding, free of macroscopic defects, and robust under mechanical bending stress, opening up the possibility to use them in, for example, 2D imaging sensor films.

Calcium Microcrystal Formation in Recurrent Herniation Patients After Autologous Disc Cell Transplantation.

Autologous disc cell transplantation (ADCT) is a cell-based therapy aiming to initiate regeneration of intervertebral disc (IVD) tissue, but little is known about potential risks. This study aims to investigate the presence of structural phenomena accompanying the transformation process after ADCT treatment in IVD disease. Structural phenomena of ADCT-treated patients (Group 1, n=10) with recurrent disc herniation were compared to conventionally-treated patients with recurrent herniation (Group 2, n=10) and patients with a first-time herniation (Group 3, n=10). For ethical reasons, a control group of ADCT patients who did not have a recurrent disc herniation was not possible. Tissue samples were obtained via micro-sequestrectomy after disc herniation and analyzed by micro-computed tomography, scanning electron microscopy, energy dispersive spectroscopy, and histology in terms of calcification zones, tissue structure, cell density, cell morphology, and elemental composition. The major differentiator between sample groups was calcium microcrystal formation in all ADCT samples, not found in any of the control group samples, which may indicate disc degradation. The incorporation of mineral particles provided clear contrast between the different materials and chemical analysis of a single particle indicated the presence of magnesium-containing calcium phosphate. As IVD calcification is a primary indicator of disc degeneration, further investigation of ADCT and detailed investigations assessing each patient's Pfirrmann degeneration grade following herniation is warranted. Structural phenomena unique to ADCT herniation prompt further investigation of the therapy's mechanisms and its effect on IVD tissue. However, the impossibility of a perfect control group limits the generalizable interpretation of the results.

Controlled synthesis and photoluminescence properties of In2O3 rods with dodecahedron In2O3 microcrystals on top

In2O3 rods with dodecahedron In2O3 microcrystals on top were synthesized in an electrical furnace via Au‐catalyzed vapor transport process. A catalyst‐assisted selective vapor‐solid (VS) growth was proposed to explain the formation of the dodecahedron In2O3 microcrystal, while the self‐catalytic VS growth mechanism dominated the subsequent one‐dimensional (1D) growth of the In2O3 rod underneath the In2O3 microcrystal. The structural evolution of these structures was carefully examined during the synthesis process by controlling the growth parameters. The morphologies, crystalline structures and surface chemistry were characterized by scanning electron microscopy (SEM), X‐ray diffraction technique (XRD), and X‐ray photoelectron spectroscopy (XPS), respectively. The photoluminescence (PL) spectrum at room temperature of the as‐grown In2O3 structures exhibited both UV and blue luminescence emission under one excitation at 260 nm, which may be related to the existence of oxygen vacancies. The synthesized multifaceted In2O3 microcrystal has shown to contain a large number of vertices and may find many applications in developing three‐dimensional (3D) resonators. This work will not only enrich the synthesis science but also will open doors for applications of such structures in optical devices.

Synthesis of [Fe(Leq)(Lax)] n coordination polymer nanoparticles using blockcopolymer micelles.

Spin-crossover compounds are a class of materials that can change their spin state from high spin (HS) to low spin (LS) by external stimuli such as light, pressure or temperature. Applications demand compounds with defined properties concerning the size and switchability that are maintained when the compound is integrated into composite materials. Here, we report the synthesis of [Fe(Leq)(Lax)]n coordination polymer (CP) nanoparticles using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) micelles as template. Variation of the solvent (THF and toluene) and the rigidity of the axial ligand Lax (Lax = 1,2-di(pyridin-4-yl)ethane) (bpea), trans-1,2-di(pyridin-4-yl)ethene (bpee), and 1,2-di(pyridin-4-yl)ethyne) (bpey); Leq = 1,2-phenylenebis(iminomethylidyne)-bis(2,4-pentanedionato)(2−)) allowed the determination of the preconditions for the selective formation of nanoparticles. A low solubility of the CP in the used solvent and a high stability of the Fe–L bond with regard to ligand exchange are necessary for the formation of composite nanoparticles where the BCP micelle is filled with the CP, as in the case of the [FeLeq(bpey)]n@BCP. Otherwise, in the case of more flexible ligands or ligands that lead to high spin complexes, the formation of microcrystals next to the CP–BCP nanoparticles is observed above a certain concentration of [Fe(Leq)(Lax)]n. The core of the nanoparticles is about 45 nm in diameter due to the templating effect of the BCP micelle, independent of the used iron complex and [Fe(Leq)(Lax)]n concentration. The spin-crossover properties of the composite material are similar to those of the bulk for FeLeq(bpea)]n@BCP while pronounced differences are observed in the case of [FeLeq(bpey)]n@BCP nanoparticles.

In Vitro Bioactivity Behavior of some Borate Glasses and their Glass-Ceramic Derivatives Containing Zn2+, Ag+ or Cu2+ by Immersion in Phosphate Solution and their Anti-Microbial Activity

Some soda lime borate glasses containing sele- cted Zn2+, Ag+ or Cu2+ ions or all of them were prepared together with their glass ceramic derivatives by thermal heat-treatment two step regime. X-ray diffraction measurement was utilized to identify the precipitated crystalline phases upon thermal treatment. Fourier Transformer infrared (FTIR) spectra analyses were carried out for the parent glasses and glass-ceramics before and after immersion in phosphate solution for two weeks. The FTIR spectra indicate the presence of IR peaks characteristic for the formation of calcium phosphate (hydroxyapatite) after the immersion process. Scanning Electron Microscope (SEM) studies confirm the formation of characteristic rounded or nodular micro-crystals due to hydroxyapatite indicating the bioactivity behavior of the prepared glasses and glass ceramics. The glasses and glass-ceramics were investigated for their antibacterial and antifungal efficiency and the results were observed to be varied with the constituting additional introduced dopant oxides and with the degree of crystallinity in the glass-ceramic samples.

Kinetics of the electron beam induced crystallization of amorphous ZrO2 films obtained via ion-plasma and laser sputtering

The structure and electron beam induced crystallization kinetics of amorphous ZrO2 films obtained via ion-plasma and laser sputtering were compared. The studies were performed by electron diffraction and transmission electron microscopy with recording video films in situ. The effect of an electron beam on an amorphous film in a vacuum was accompanied by the formation of zirconia microcrystals with an FCC lattice. For laser evaporation, the density of crystallization nuclei was β ~ 109 cm–2, and the characteristic length unit was D0 ~ 0.48 μm. For ion-plasma evaporation, β ~ 1010 cm–2, and D0 ~ 0.06 μm. The kinetic curves of the crystallization of amorphous films were analyzed using the β-variant of the Kolmogorov model as a basis.

Synthesis and luminescent properties of lanthanide-doped ScVO4 microcrystals

High quality and monodispersed ScVO4 microcrystals were successfully synthesized via a mild hydrothermal route using NH4VO3 as vanadium source. The X-ray power diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) results indicated that the size, shape, and phase formation of the ScVO4 microcrystals could be tuned by altering the reaction temperature, reaction time, and pH value of the initial solution. Furthermore, the down- and upconversion luminescence of ScVO4:Ln (Ln=Eu, Dy, Sm, Yb/Ho, Yb/Er, and Yb/Tm) microcrystals were characterized and the respective energy transfer processes were also discussed. The experimental results demonstrated that reactions at 200 °C, 24 h, and pH=6 could generate perfect ScVO4 microcrystals, which were then used for luminescence studies.

Aerogels containing 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin with controlled state of aggregation

Aerogels made of chitosan and chondroitin sulfate, and containing 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin have been synthesized. The aerogels presented a microstructure made of microfibers and microsheets, with porosity higher than 99%. The dispersion and state of aggregation of the dye in the solids have been controlled with the aid of aromatic polyelectrolytes able to produce aromatic-aromatic interactions. Thus, non-homogenous dispersions of the dye as J-aggregates and formation of microcrystals on the microsheet surface were observed in the absence of the aromatic polymers; on the contrary, well dispersed H-aggregates of the dye were observed in the presence of poly(decylviologen), and well dispersed complexed monomeric dye molecules were found in the presence of a polyketone derivatized with hystamine, thus presenting imidazolium pendant groups. The same state of aggregation has been observed in solution for the respective complexes, highlighting the potential of aromatic-aromatic interactions to achieve a control of the state of aggregation of dyes in solution and further transfer to the solid state keeping their photophysical properties, and furnishing means for a good dispersion of the dyes in solid materials.

Biosorption and reduction of Au (III) to gold nanoparticles by thiourea modified alginate

In this study, modified alginate biosorbent has shown a remarkably selective adsorption of Au (III) ions from multi-metallic solutions containing equal moles of Au (III), Pd (II), Pt (IV), Co (II), Ni (II) and Cu (II) ions under acidic conditions. The maximum uptake capacity of Au (III) was found to be 8.47mmolg−1 at 323.15K. Adsorption of Au (III) by modified alginate biosorbent was accompanied by chemical reduction of Au (III), leading to the formation of gold nanocrystals and microcrystals. Biosorption and reduction of Au (III) in acidic media are mediated by the electrostatic and covalent interactions between Au (III) and hydroxyl, carboxyl, amino and CS functional groups of modified alginate adsorbent.

Morphological evolution of hexapod Cu2O microcrystals by a rapid template-free autoclaving technique

Morphologically tuned Cu2O micro-crystals were synthesized by one-pot autoclaving method at 150°C for a shorter reaction time in the presence of copper nitrate and di-methyl formamide (DMF) without using any external templating agents. Powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) showed the formation of phase pure Cu2O in the as-prepared samples. Morphological analysis indicated the formation of hexapod Cu2O with twenty four {111} facets at 150°C/2h. The hydrolysis product of DMF, i.e., di-methyl amine (Me2NH) and formic acid (HCOOH) played a significant role as growth controller and reducing agent, respectively for the formation of Cu2O micro-crystals. A proposed formation mechanism was illustrated.

Light-Assisted Solvothermal Chemistry Using Plasmonic Nanoparticles.

Solvothermal synthesis, denoting chemical reactions occurring in metastable liquids above their boiling point, normally requires the use of a sealed autoclave under pressure to prevent the solvent from boiling. This work introduces an experimental approach that enables solvothermal synthesis at ambient pressure in an open reaction medium. The approach is based on the use of gold nanoparticles deposited on a glass substrate and acting as photothermal sources. To illustrate the approach, the selected hydrothermal reaction involves the formation of indium hydroxide microcrystals favored at 200 °C in liquid water. In addition to demonstrating the principle, the benefits and the specific characteristics of such an approach are investigated, in particular, the much faster reaction rate, the achievable spatial and time scales, the effect of microscale temperature gradients, the effect of the size of the heated area, and the effect of thermal-induced microscale fluid convection. This technique is general and could be used to spatially control the deposition of virtually any material for which a solvothermal synthesis exists.