Crystallinity Research Articles

Tunable Synthesis of Metal-Rich and Phosphorus-Rich Nickel Phosphides and Their Comparative Evaluation as Hydrogen Evolution Electrocatalysts.

Flexible synthetic routes to crystalline metal-rich to phosphorus-rich nickel phosphides are highly desired for comparable electrocatalytic HER studies. This report details solvent-free, direct, and tin-flux-assisted synthesis of five different nickel phosphides from NiCl2 and phosphorus at moderate temperatures (500 °C). Direct reactions are thermodynamically driven via PCl3 formation and tuned through reaction stoichiometry to produce crystalline Ni-P materials from metal-rich (Ni2P, Ni5P4) to phosphorus-rich (cubic NiP2) compositions. A tin flux in NiCl2/P reactions allows access to monoclinic NiP2 and NiP3. Intermediates in tin flux reactions were isolated to help identify phosphorus-rich Ni-P formation mechanisms. These crystalline micrometer-sized nickel phosphide powders were affixed to carbon-wax electrodes and investigated as HER electrocatalysts in acidic electrolyte. All nickel phosphides show moderate HER activity in a potential range of -160 to -260 mV to achieve current densities of 10 mA/cm2 ordered as c-NiP2 ≥ Ni5P4 > NiP3 > m-NiP2 > Ni2P, with NiP3 activity showing some particle size influence. Phosphorus-rich c/m-NiP2 appears most stable under acidic conditions during extended reactions. The HER activity of these different nickel phosphides appears influenced by a combination of factors such as particle size, phosphorus content, polyphosphide anions, and surface charge.

New Insights into the Surfactant-Assisted Liquid-Phase Exfoliation of Bi2S3 for Electrocatalytic Applications

During water electrolysis, adding an electrocatalyst for the hydrogen evolution reaction (HER) is necessary to reduce the activation barrier and thus enhance the reaction rate. Metal chalcogenide-based 2D nanomaterials have been studied as an alternative to noble metal electrocatalysts because of their interesting electrocatalytic properties and low costs of production. However, the difficulty in improving the catalytic efficiency and industrializing the synthetic methods have become a problem in the potential application of these species in electrocatalysis. Liquid-phase exfoliation (LPE) is a low-cost and scalable technique for lab- and industrial-scale synthesis of 2D-material colloidal inks. In this work, we present, to the best of our knowledge, for the first time a systematic study on the surfactant-assisted LPE of bulk Bi2S3 crystalline powder to produce nanosheets (NSs). Different dispersing agents and LPE conditions have been tested in order to obtain colloidal low-dimensional Bi2S3 NSs in H2O at optimized concentrations. Eventually, colloidally stable layered nano-sized Bi2S3 suspensions can be produced with yields of up to ~12.5%. The thus obtained low-dimensional Bi2S3 is proven to be more active for HER than the bulk starting material, showing an overpotential of only 235 mV and an optimized Tafel slope of 125 mV/dec. Our results provide a facile top-down method to produce nano-sized Bi2S3 through a green approach and demonstrate that this material can have a good potential as electrocatalyst for HER.

Using Nicotine in A Silica-Exposed Mouse Model to Promote Lung Epithelial-Mesenchymal Transition.

Smoking and exposure to silica are common among occupational workers, and silica is more likely to injure the lungs of smokers than non-smokers. The role of nicotine, the primary addictive ingredient in cigarettes, in silicosis development is unclear. The mouse model employed in this study was simple and easily controlled, and it effectively simulated the effects of chronic nicotine ingestion and repeated exposure to silica on lung fibrosis through epithelial-mesenchymal transition in human beings. In addition, this model can help in the direct study of the effects of nicotine on silicosis while avoiding the effects of other components in cigarette smoke. After environmental adaptation, mice were injected subcutaneously with 0.25 mg/kg nicotine solution into the loose skin over the neck every morning and evening at 12 h intervals over 40 days. Additionally, crystalline silica powder (1-5 µm) was suspended in normal saline, diluted to a suspension of 20 mg/mL, and dispersed evenly using an ultrasonic water bath. The isoflurane-anesthetized mice inhaled 50 µL of this silica dust suspension through the nose and were awoken via chest massage. Silica exposure was administrated daily on days 5-19. The double-exposed mouse model was exposed to nicotine and then silica, which matches the exposure history of workers who are exposed to both harmful factors. In addition, nicotine promoted pulmonary fibrosis through epithelial-mesenchymal transformation (EMT) in mice. This animal model can be used to study the effects of multiple factors on the development of silicosis.

A novel binary solid-liquid biphasic functionalized ionic liquids for efficient CO2 capture: Reversible polarity and low energy penalty

Ionic liquids (ILs) solid-liquid biphasic solvents for CO2 capture have the advantages of high CO2 loading and low energy consumption, and their phase change behavior was regulated via phase separation agents. However, phase separator agents exhibit bottlenecks in terms of volatility loss and high-rich phase viscosity. A novel “reversible polarity” functionalized ionic liquids (isophorone diamine-imidazole, [IPDAH][Im]) was innovatively proposed in this work, which featured solid-liquid phase change behavior upon CO2 absorption in water in the absence of a phase separation agent. After saturated absorption, CO2 products were enriched into the lower phase and precipitated as a white crystalline powder with 91 % of the total CO2 loading (1.15 mol mol−1) but only 60 % of the total volume. Products after thermal desorption (393.15 K), maintaining 80 % of its initial loading after the sixth regeneration cycle. Based on the results of experimental characterization and theoretical calculation, [IPDAH][Im] possessed reversible polarity, and its initial polarity was consistent with that of water. After absorption, [IPDAH][Im] interacted with CO2 to form products whose polarity diminishes, resulting in the associated phase transition; after desorption, the high polarity is restored. The products existed as ion pairs (ILsCOO−-ILsH+), as evidenced by strong van der Waals interaction, and electrostatic attraction. Strong hydrogen bonding forces between the products and the Hansen solubility parameter, as well as the high lattice energy, led to the self-agglomeration formation of the products in water, resulting in the development of a solid powder product. The heat duty of [IPDAH][Im]–H2O was 1.23 GJ ton−1 CO2, which was approximately 67 % less than that of monoethanolamine (MEA; 3.77 GJ ton−1 CO2), signifying a major potential for application in CO2 capture.

Softness of hydrated salt crystals under deliquescence

Deliquescence is a first-order phase transition, happening when a salt absorbs water vapor. This has a major impact on the stability of crystalline powders that are important for example in pharmacology, food science and for our environment and climate. Here we show that during deliquescence, the abundant salt sodium sulfate decahydrate, mirabilite (Na2SO4·10H2O), behaves differently than anhydrous salts. Using various microscopy techniques combined with Raman spectroscopy, we show that mirabilite crystals not only lose their facets but also become soft and deformable. As a result, microcrystals of mirabilite simultaneously behave crystalline-like in the core bulk and liquid-like at the surface. Defects at the surface can heal at a speed much faster than the deliquescence rate by the mechanism of visco-capillary flow over the surface. While magnesium sulfate hexahydrate (MgSO4⋅6H2O) behaves similarly during deliquescence, a soft and deformable state is completely absent for the anhydrous salts sodium chloride (NaCl) and sodium sulfate thenardite (Na2SO4). The results highlight the effect of crystalline water, and its mobility in the crystalline structure on the observed softness during deliquescence. Controlled hydrated salts have potential applications such as thermal energy storage, where the key parameter is relative humidity rather than temperature.

Viagra exposure effects on learning and memory, some neurotransmitters and oxidative indices in male mice

BackgroundViagra is a white crystalline powder, with a molecular weight of 666.7, covered with a blue shell and takes the shape of a diamond or a rhombus. Male Swiss white mice were used to study the effect of Viagra on learning behavior, some neurotransmitters, and indicators of oxidative stress. In the Shuttle box, Water-maze, and T-Maze tests, Viagra -treated males showed decreased body weight and improved learning behavior. AimThe purpose of this study is to determine the effect of Viagra oral administration on learning behavior, neurotransmitters, and oxidative markers in male mice. MethodsIn this study, Dopamine (DA), 5-hydroxyanisole (5-HA) and acetylcholinesterase (AchE) were all downregulated. Biochemical assays such as glutathione (GSH) and enzyme activity of Glutathione S Transferase (GST), Catalase (CAT), and superoxide dismutase (SOD) and Thiobarbituric acid relative substances (TBARS) was studied. ResultsThe results of this study show that the shuttle box test, Viagra exposure, water maize test, and t-maize test were all associated (p < 0.05). Exposure to Viagra decreased DA, 5-HT, AChE, GSH, GST, CAT, and SOD, although TBARS was significantly (p < 0.001) increased compared to their control groups. ConclusionThis study contained the necessary explanations that explain the causes of the effect of Viagra on learning and other data, depending on the results obtained and other previous studies in this field. In general, Viagra still needs more studies to detect its harmful effects on other aspects of human and animal health.

Application of Thermochemical Method to Determine the Crystallinity Degree of Cellulose Materials

Currently, to characterize the crystallinity of cellulose, such an estimated parameter as the crystallinity index is used, measured by various methods and techniques. The main purpose of this article was to develop a thermochemical method for determining the real degree of crystallinity (X) of cellulose based on the measurement of the enthalpy of wetting. Various cellulose samples, such as MCC, pure cotton cellulose, bleached wood pulps, mercerized celluloses, and viscose rayon fibers, were used. For these samples, the exothermic wetting enthalpy (ΔHw), the maximum amount of sorbed moisture (Ao), as well as the X-ray index of crystallinity (CrI) were studied. The dependence of ΔHw on Ao was linear and can be expressed by the equation: ΔHw = k Ao, where the coefficient k = −336 (J/g). After substituting the theoretical value Ao,a = 0.5 (g/g) into this equation, the numerical value of maximum wetting enthalpy ΔHw,a = −168 (J/g) for completely amorphous cellulose was obtained. As a result, the equation for calculating the real crystallinity degree (X) expressed in mass fractions was derived: X = 1 − (ΔHw/ΔHw,a). Analysis of the obtained results showed that only the X parameter can characterize the real content of crystallites in cellulose samples, instead of the approximate CrI parameter.

Crystalline and vitreous Na3.89Ca0.67Al0.23Ti0.77(PO4)3 : Synthesis, crystal structure, vibrational and UV–Visible spectra

Na3.89Ca0.67Al0.23Ti0.77(PO4)3 phosphate exists in both crystalline and vitreous forms. It has been synthesized as microcrystalline powder, single crystals and glass. The structure of the crystalline form, belonging to Nasicon family with M(1)M(2)3A2(PO4)3 formula, was solved by single crystal X-ray diffraction (Space group R32, Z = 6, ah = 8.9976(1) Å, ch = 21.8312(3) Å, R1 = 0.03, wR2 = 0.06). A Rietveld refinement was also performed. The structure is formed by a 3D network of PO4 tetrahedra and AO6 (A= Na/Ca and Al/Ti) octahedra sharing corners. One of the two positions of A sites is statistically occupied by Na+ and Ca2+, the other position is statistically occupied by Al3+ and Ti4+. The remaining sodium atoms occupy totally M(1) and partially M(2) interstitial sites. Raman and infrared spectra show for the crystalline powder, broad peaks attributed principally to monophosphate PO4 modes. The structure of the glass contains PO4 and P2O7 groups and short -Ti-O-Ti-O- chains. UV–Visible spectra consist of strong bands at high energy assigned to O-Ti and O-Al electronic charge transfers.

Removal of copper from aqueous solutions by biosorption onto pine sawdust

Untreated Pinus radiata sawdust was investigated for the removal of Cu+2 ions from aqueous solutions. The biomass was characterized by Inductively Coupled Plasma-Mass (ICP-MS) spectrometry and by Scanning Electron Microscopy with an Energy Dispersive X-ray spectroscopy (SEM-EDX), X-Ray crystalline powder Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy, before and after adsorption. The influence of contact time (up to equilibrium), adsorbent dose (1–50 g/L), initial metal ion concentration (5–300 mg/L) and pH (2–8) on copper sorption efficiency was studied through batch experiments. The results demonstrated that adsorption equilibrium is reached in less than 2 h and the best conditions (Cu+2 removal percentage, 93.4% and adsorption capacity, 0.82 mg/g) were achieved by increasing the adsorbent dose up to 5 g/L and the solution pH up to 7, and decreasing the initial metal concentration to 5 mg/L. The adsorption was optimized by means of a Doehlert experimental design analyzing the influence of adsorbent dose (5–15 g/L) and copper initial concentration (5–45 mg/L) on adsorption efficiency. Kinetic data were satisfactorily fitted to the second-order kinetic model. Intraparticle diffusion model demonstrated that different stages are involved in the adsorption process. Langmuir isotherms fitted satisfactorily the copper bioadsorption equilibrium data. Desorption studies achieved high efficiencies up to 94.5% and the possibility of sawdust regeneration was studied with four adsorption-desorption cycles. Thus, this study evidenced that sawdust is a promising efficient, renewable and economic adsorbent for metal removal and its use for that purpose constitutes an alternative for its management and valorization.

Multicomponent solid solution with pyrochlore structure

Multicomponent oxide with pyrochlore structure (A2B2O7), containing 7 different A-site cations and 3 B-site cations in equiatomic amounts, was synthesized. Powders with nominal composition (La1/7Sm1/7Nd1/7Pr1/7Y1/7Gd1/7Yb1/7)2(Sn1/3Hf1/3Zr1/3)2O7 were fabricated through a reaction of metal nitrates (A-site) and metal chlorides (B-site) with sodium hydroxide during the solid state displacement reaction. Room temperature synthesis initially resulted in the obtainment of amorphous powders, which crystallized after subsequent calcination to form single crystalline compounds. Crystalline high-entropy ceramic powders formation took place at temperatures as low as 750°C. During calcination, defective fluorite (F-A2B2O7) and crystal pyrochlore (Py-A2B2O7) structures coexist. A large number of cations induce the obtainment of stable high-entropy pyrochlores. Results showed that sintering at 1650°C lead to pure crystalline single-phase pyrochlore formation. High-density ceramic, free of additives, was obtained after powders were compacted and subjected to pressureless sintering at 1650°C. Multicomponent pyrochlore structure was investigated using the theoretical and experimental multi-methodological approach.

Formation and Structural Characterization of Spinel‐Phase Zn2TiO4 Synthesized in a High‐Temperature Solution Approach

AbstractSpinel phase Zn2TiO4 powders were prepared by high‐temperature solution, which is a kind of molten salt (such as KCl melt). The effect of Zn2TiO4 synthesis was explored under different holding time, preparation temperature and the mass ratio of salt to raw material in KCl melt. Through experimental analysis, the synthesis temperature range of Zn2TiO4 phase in KCl molten salt system was from 800 to 1000 °C. Compared with the traditional solid‐state reaction, the stable temperature range of Zn2TiO4 phase in KCl molten salt system was wider. The HRTEM image analysis of calcined product was consistent with the XRD result. The TEM analysis showed that the average particle size of Zn2TiO4 powder was 200 nm. The crystallinity of Zn2TiO4 increased with increasing sintering time and Zn/Ti molar ratio. Compared with LiCl+KCl and LiCl melts, the crystallinity of Zn2TiO4 powder synthesized in KCl molten salt system was better. It is determined that the high‐temperature solution (KCl melt) can be successfully applied for large‐scale synthesis of spinel phase Zn2TiO4.

An investigation of fuel precursors and calcination temperature to obtain mayenite (Ca12Al14O33) powders by solution combustion synthesis

The influence of the fuel (glycine, urea, citric acid and sucrose) and calcination temperature used to obtain calcium aluminate in the mayenite phase assisted by solution combustion synthesis (SCS) is the central point of this work. Thermal gravimetric analysis helps to establish the calcination temperatures used (1100, 1200 and 1300 °C). Using the X-ray diffraction technique (XRD) and complementary analyses, such as Raman spectroscopy, the specific surface area and laser granulometry, it was possible to elucidate the behavior and relationship of the fuel and heat treatment on the phase formation, crystallite size and powder crystallinity. Glycine showed better performance than other fuels, with the lowest calcination temperature, obtaining pure mayenite with nanometric crystallite size in all calcination ranges. Thus, it was observed that the type of fuel has an influence on obtaining pure mayenite, as well as the calcination temperature, and glycine reveals the best performance.

Access and Capture of Layered Double Perovskite Polytypic Phase through High-Pressure Engineering

Engineering halide perovskites through external pressure is as an effective means to tune the crystal structure, thus optoelectronic properties of the material. In this work, we studied the structural and optical property evolutions of Cs4MIIBi2Cl12 (MII: Cd, Cd0.8Mn0.2, Mn) layered double perovskite (LDP) crystalline powders under high pressure. A novel polytypic phase transition was observed featuring lateral interlayer sliding of the Bi–MII–Bi trilayer units, resulting in a new LDP-12R phase. Importantly, this high-pressure induced LDP-12R crystal phase can be preserved after complete decompression and captured at ambient conditions. Moreover, the LDP samples showed a pressure-dependent photoluminescence property. Our findings exemplified a new perovskite polytype that can be accessed and captured through high-pressure processing, advocating the uniqueness of LDP materials with soft and transformable crystal lattices.

Improving the Bioactivity of Norfloxacin with Tablets Made from Paper.

(1) Background: Many drugs possess poor bioavailability, and many strategies are available to overcome this issue. In this study, smartFilm technology, i.e., a porous cellulose matrix (paper), in which the active compound can be loaded onto in an amorphous state was utilised for oral administration to improve the solubility and bioactivity of a poorly soluble BSC class IV antibiotic. (2) Methods: Norfloxacin was used as the model drug and loaded into commercially available paper. The resulting norfloxacin-loaded smartFilms were transformed into smartFilm granules via wet granulation and the resulting norfloxacin-loaded smartFilm granules were transformed into norfloxacin-loaded tablets made from paper, i.e., smartFilm tablets. The crystalline state of norfloxacin was investigated, as well as the pharmaceutical properties of the granules and the tablets. The bioactivity of the smartFilm tablets was assessed in vitro and ex vivo to determine the antibacterial activity of norfloxacin. The results were compared to a physical mixture tablet that contained non-loaded paper granules and equal amounts of norfloxacin as a crystalline powder. (3) Results: Norfloxacin-loaded smartFilm granules and norfloxacin-loaded smartFilm tablets contained norfloxacin in an amorphous state, which resulted in an improved and faster release of norfloxacin when compared to the physical mixture tablet. The bioactivity was up to three times higher when compared to the physical mixture tablet. The ex vivo model was demonstrated to be a useful tool that allows for a fast and cost-effective discrimination between "good" and "bad" formulations. It provides realistic physiological conditions and can therefore yield meaningful, additional biopharmaceutical information that cannot be assessed in classical in vitro experiments. (4) Conclusions: smartFilm tablets are a promising, universal, industrially feasible and cost-effective formulation strategy for improved solubility and enhanced bioactivity of poorly soluble drugs.

Spectral properties inspired image enhancement for crystalline polymer powder impurity detection

Crystalline polymer powder inevitably incorporates certain impurities, including decomposed polymers or foreign particles. An essential criterion for assessing the quality of polymers is the quantity of contaminants in the powder. However, it is challenging to discern powder contaminants through machine vision due to the poor quality of images taken at production sites. Inspired by the spectral properties of crystalline polymers, this paper proposes an efficient image-based impurity detection method, which seeks to precisely and robustly detect contaminant content. Based on the changes in absorbance during polymer decomposition, a highly selective channel-weighted image enhancement approach is designed to emphasize the difference between impurities and normal particles. Then, using the prior information on the powder’s attributes, an adaptive thresholding method is employed to categorize pixels belonging to impurities. Finally, a dataset of 119 12-megapixel photos from a chemical facility, where the average size of contaminants in images is 43 pixels, is used to evaluate the performance of the proposed algorithm. The results of the detection demonstrate that the proposed strategy for image enhancement has better selectivity to impurities than typical image enhancement methods.

Remediation of Cu Contaminated Soil by Fe78Si9B13AP Permeability Reaction Barrier Combined with Electrokinetic Method

Iron-based amorphous crystalline powder Fe78Si9B13AP is used as a permeability reaction barrier (PRB) combined with an electrokinetic method (EK-PRB) to study the removal rate of Cu in contaminated soil. After treating Cucontaminated soil for 5 days under different voltage gradients and soil water content, the soil pH is between 3.1 and 7.2. The increase of voltage gradient and soil water content can effectively promote the movement of Cu2+ to the cathode. The voltage gradient is 3 V/cm, and the water content of 40% is considered to be an optional experimental condition. Therefore, under this condition, the effects of Fe78Si9B13AP and zero-valent iron (ZVI) as PRB on the removal rate of total Cu in soil and the transformation of chemical forms of Cu are studied. Compared with ZVI, Fe78Si9B13AP as PRB has a better remediation effect. EK-Fe78Si9B13AP can remove 80.3% of total Cu in soil, and the biologically available Cu is reduced to 3.6%, which effectively reduces the environmental risk of contaminated soil.

Spin crossover in mixed-anion Fe(NH2trz)3(BF4)(SiF6)0.5 crystalline rod-shaped particles: the strength of the solid-liquid post synthetic modification.

A pure mixed-anion Fe(NH2trz)3(BF4)(SiF6)0.5 spin crossover complex is obtained implementing a solid-liquid post synthetic modification approach from the Fe(NH2trz)3(BF4)2 parent complex. This method allows obtaining highly crystalline powder samples incorporating homogeneous micrometric (1 μm long) rod-shaped particles. This compound presents an abrupt spin crossover behaviour with a narrow (10 K) hysteresis loop centred just above room temperature (320 K) which makes it very interesting for future integration into devices for various applications.

Single-Component Color-Tunable Smart Organic Emitters with Simultaneous Multistage Stimuli-Responsiveness and Multimode Emissions.

Achieving color-tunable emission in single-component organic emitters with multistage stimuli-responsiveness is of vital significance for intelligent optoelectronic applications, but remains enormously challenging. Herein, we present an unprecedented example of a color-tunable single-component smart organic emitter (DDOP) that simultaneously exhibits multistage stimuli-responsiveness and multimode emissions. DDOP based on a highly twisted amide-bridged donor-acceptor-donor structure has been found to facilitate intersystem crossing, form multimode emissions, and generate multiple emissive species with multistage stimuli-responsiveness. DDOP pristine crystalline powders exhibit abnormal excitation-dependent emissions from a monomer-dominated blue emission centered at 470 nm to a dimer-dominated yellow emission centered at 550 nm through decreasing the ultraviolet (UV) excitation wavelengths, whereas DDOP single crystals show a wide emission band with a main emission peak at 585 nm when excited at different wavelengths. The emission behaviors of pristine crystalline powders and single crystals are different, demonstrating emission features that are closely related to the aggregation states. The work has developed color-tunable single-component organic emitters with simultaneous multistage stimuli-responsiveness and multimode emissions, which is vital for expanding intelligent optoelectronic applications, including multilevel information encryption, multicolor emissive patterns, and visual monitoring of UV wavelengths.

The mechanochemically prepared compositions of skin care substances with silicates for medicinal and cosmetic applications

Introduction: The active biological substances used in medicinal and cosmetic applications, are mainly organic acids. The local contact effect of the protons located on the surface of their crystallites can irritate the mucous membranes of the stomach and esophagus (medicines), or skin of the face (cosmetics). The irritating effect of protons can be weakened either by grinding crystalline acid powders to nanoscale sizes, or by neutralizing them. Organic acids are polymerized due to hydrogen bonds, which does not allow them to be dispersed to nanometric sizes by traditional methods. It was previously shown that during the mechanical activation of silicates, short-lived hydroxyl groups become available. Objective: The purpose of this work is to study the possibility of neutralization of protons of organic acids during their mechanochemical interaction with silicates. Methods: The IR spectroscopy, X-ray analysis and electron microscopy methods were used for research. Results: It was shown by that organic acid is "grafted" to the silicate surface due to neutralization of organic acid protons by hydroxyl groups of layered silicates, opened during mechanical activation. This makes it possible to form highly dispersed composite structures "organic acid/layered silicate" in dicarboxylic (carboxylic, aromatic, amino) acids - talc (pyrophyllite, kaolinite) systems. Conclusions: Such mechanochemically synthesized composites, in which acid is grafted to an inert carrier, in addition to high dispersion, provide a decrease in the acidity of the resulting product. In the case of mechanochemical interaction of SiO2 with organic acids, the basic centers mainly work on the surface of SiO2 , which is opened during mechanical activation. Organic acids (hydroxo acids, dicarboxylic, carboxylic, aromatic) are distributed in an extremely thin layer on the surface of silicon oxide due to the "SiO2 — adsorption water — acid" bond. This allows to change the pharmacokinetics and avoid ulcerogenic action and reduce the irritating effect of organic acids on the skin.

Crystallization-Enhanced Emission and Room-Temperature Phosphorescence of Cyclic Triimidazole-Monohexyl Thiophene Derivatives

The development of organic room-temperature phosphorescent (ORTP) materials represents an active field of research due to their significant advantages with respect to their organometallic counterparts. Two cyclic triimidazole (TT) derivatives bearing one and three hexyl-thiophene moieties, TT-HThio and TT-(HThio)3, have been prepared and characterized. Both compounds display enhanced quantum yields in their crystalline form with respect to those in a solution state, revealing crystallization-enhanced emissive (CEE) behavior. Importantly, while single fluorescence is observed in solution, crystalline powders also feature dual ORTP, whose respective molecular and aggregate origins have been disclosed through X-ray diffraction analysis and DFT/TDDFT calculations. The relation between the photophysical properties of TT-HThio and its crystallinity degree has been confirmed by a decrease in photoluminescent quantum yield (Φ) and loss of vibronic resolution when its crystals are ground in a mortar, revealing mechanochromic behavior and confirming CEE features.