Quantum-confined bismuth iodide perovskite nanocrystals in mesoporous matrices.

Bismuth iodide perovskite nanocrystals are considered a viable alternative to the Pb halide ones due to their reduced toxicity and increased stability. However, it is still challenging to fabricate nanocrystals with a small and controlled size, and their electronic properties are not well understood. Here, we propose the growth of Bi iodide perovskite nanocrystals using different mesoporous silica with ordered pores of controlled diameter as templates. We obtain a series of confined Cs3Bi2I9 and MA3Bi2I9 perovskites with diameters of 2.3, 3.7, 7.4, and 9.2 nm, and precise size control. The complex absorption spectra of the encapsulated perovskites cannot be properly fitted using classical Tauc or Elliott formalisms. By fitting the spectra with a modified Elliott formula, the bandgap values and exciton binding energies (70-400 meV) could be extracted. The calculated bandgaps scale with the pore sizes. Using a combined experimental and theoretical approach, we demonstrate for the first time quantum confinement in 0D Bi-iodide perovskite nanocrystals.

TiO2-SiO2 Self-Standing Materials bearing Hierarchical Porosity: MUB-200(x) Series toward 3D-Efficient VOC Photoabatement Properties.

Three-dimensional photoactive self-standing porous materials have been synthesized through the integration of soft chemistry and colloids (emulsions, lyotrope mesophases, and P25 titania nanoparticles). Final multiscale porous ceramics bear 700-1000 m2 g-1 of micromesoporosity depending on the P25 nanoparticle contents. The applied thermal treatment does not affect the P25 anatase/rutile allotropic phase ratio. Photonic investigations correlated with the foams' morphologies suggest that the larger amount of TiO2 that is introduced, the larger the walls' density and the smaller the mean size of the void macroscopic diameters, with both effects inducing a reduction of the photon transport mean free path (lt) with the P25 content increase. A light penetration depth in the range of 6 mm is reached, thus depicting real 3D photonic scavenger behavior. The 3D photocatalytic properties of the MUB-200(x) series, studied in a dynamic "flow-through" configuration, show that the highest photoactivity (concentration of acetone ablated and concentration of CO2 formed) is obtained with the highest monolith height (volume) while providing an average of 75% mineralization. These experimental results validate the fact that these materials, bearing 3D photoactivity, are paving the path for air purification operating with self-standing porous monolith-type materials, which are much easier to handle than powders. As such, the photocatalytic systems can now be advantageously miniaturized, thereby offering indoor air treatment within vehicles/homes while drastically limiting the associated encumbrance. This volumetric counterintuitive acting mode for light-induced reactions may find other relevant advanced applications for photoinduced water splitting, solar fuel, and dye-sensitized solar cells while both optimizing photon scavenging and opening the path for the miniaturization of the processes where encumbrance or a foot-print penalty would be advantageously circumvented.

Heterogeneous Photoredox Catalysis Based on Silica Mesoporous Material and Eosin Y: Impact of Material Support on Selectivity of Radical Cyclization.

Heterogenization of the photocatalyst appears to be a valuable solution to reach sustainable processes. Rapid and efficient synthesis of supported photocatalyst is still a remaining challenge and the choice of the support material is crucial. The present study aims at preparing a new generation of hybrid inorganic/organic photocatalysts based on silica mesoporous material and Eosin Y. These results highlight the influence of non-covalent interactions between the material support and the reagent impacting the selectivity of the reaction.

Natural water defluoridation by adsorption on Laponite clay.

Safe drinking water is a necessity for every human being, but clean water is scarce and not easily available due to natural geochemical factors or industrial pollutant activity. Many issues involving water quality could be greatly improved using clays as adsorbents. We highlight for the first time, the uptake of fluoride from natural water by Laponite, synthetic hectorite clay, in raw and modified state. A series of batch adsorption experiments were carried out to evaluate the adsorption potential of the different parameters. The optimized parameters were: contact time, adsorbent dose and pH. It was found that fluoride uptake from natural water was better using raw Laponite and inorganic-modified Laponite than using organic-modified Laponite clays. Adsorbents were characterized before and after fluoride adsorption by X-ray diffraction, X-ray fluorescence, FTIR, thermo gravimetric analyses and 19F solid state NMR spectroscopy. The experimental data showed that both Langmuir and Freundlich models fitted an adsorption isotherm well. Thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated. These parameters indicated that fluoride adsorption onto Laponite was nonspontaneous and endothermic in temperature range between 25 and 45 °C.

Synthesis of Hierarchical Zeolites with Morphology Control: Plain and Hollow Spherical Beads of Silicalite-1 Nanosheets.

Binderless pure silica zeolites (zeosils) spheres and hollow spheres with a diameter of 20 µm composed of silicalite-1 nanosheets particles were prepared by pseudomorphic transformation of spherical silica beads using different temperatures (110, 130, and 150 °C) and treatment times (1-5 days) in order to adapt the local dissolution rate of silica to the crystallization rate of silicalite-1 nanosheets allowing to preserve the initial morphology of the silica beads. Fully crystalline beads of 20 µm were obtained at 110 °C for 5 days, whereas hollow spheres similar in size were synthesized at higher temperatures. The crystallization process seems to begin at the outer surface of the amorphous silica beads and spreads with the time in the interior of the beads leading to a dissolution of the inner amorphous part of the beads to create zeosil hollow spheres for the highest treatment temperatures (130 and 150 °C). The dissolution rate of the inner amorphous part of the beads increases by increasing the hydrothermal treatment temperature from 130 to 150 °C. The silicalite-1 beads synthesized at 110 °C for 5 days showed to be promising for rapid molecular decontamination by adsorbing n-hexane in larger amount than the silicalite-1 conventional big crystals in powder forms.

Synthesis and characterization of mesoporous SBA-15 and SBA-16 as carriers to improve albendazole dissolution rate.

Albendazole (ABZ, anti-parasitic active pharmaceutical ingredient) is a crystalline low water-soluble drug, thus the dissolution rate in gastrointestinal fluids is limited. Consequently, the improvement of the water solubility and dissolution rate of ABZ implies a great challenge for a more efficient treatment of hydatidosis. In this context, SBA-15 and SBA-16 ordered mesoporous silica materials were synthetized and loaded with ABZ. X-ray diffraction, FT-IR spectroscopy, nitrogen physisorption manometry, particle size distribution and scanning electronic microscopy were used to characterize unloaded and loaded materials (ABZ/SBA-15 and ABZ/SBA-16). The loaded ABZ amount in the carriers was estimated by elemental analysis. For the loaded materials, the drug solubility and release profile were evaluated. In addition, mathematical models were compared to explain the dissolution kinetics of ABZ from mesoporous solids. ABZ was successfully loaded into the mesopores. The amorphous state of the adsorbed ABZ was confirmed by differential scanning calorimetry that resulted in a notable increment in the dissolution rate compared to crystalline ABZ. Drug release behaviors were well simulated by the Weibull model for ABZ/SBA-15 and by the Gompertz function for pure ABZ and ABZ/SBA-16. The SBA-15 carrier exhibited the highest drug loading and dissolution rate becoming a promising material to improve ABZ bioavailability.

Amorphous mesostructured zirconia with high (hydro)thermal stability.

Here, combining the evaporation-induced self-assembly (EISA) method and the liquid crystal templating pathway, mesostructured amorphous zirconium oxides have been prepared by a soft templating method without addition of any heteroelement to stabilize the mesopore framework. The recovered materials have been characterized by SAXS measurements, nitrogen adsorption-desorption analysis and X-ray diffraction (XRD). The obtained mesostructured zirconia exhibits a high thermal stability. An in situ XRD study performed as a function of temperature shows that the amorphous ZrO2, obtained after removal of the pore templating agent (pluronic P123), begins to crystallize in air from 420 °C. Amorphous mesostructured ZrO2 also presents a high hydrothermal stability; these materials are not degraded after 72 hours in boiling water.

Performance of surfactant-modified *BEA-type zeolite nanosponges for the removal of nitrate in contaminated water: Effect of the external surface.

Hierarchical *BEA-type nanosponges zeolite with a high external surface area (116 m2.g-1) and small crystal size, synthesized in the presence of a dual-porogenic organic compound, were modified with a cationic surfactant (HDTMA+Br-: hexadecyltrimethyl ammonium bromide) in order to create a new anion exchanger system: the surfactant-modified zeolite nanosponges (SMZNS). For comparison, two other surfactant-modified *BEA-type zeolite materials, SMZMC and SMZNC, were obtained by modifying the synthesized conventional micron-size microcrytals and nanocrystals *BEA-type zeolite with HDTMA+Br-, respectively. Textural and structural properties were determined for the three prepared materials using N2 adsorption/desorption analysis, XRD, SEM, and TEM. Nitrate adsorption isotherms were drawn in a large concentration range [0.8-24.2 mmol.L-1] and fitted with Langmuir isotherm model. The maximum nitrate removal capacity (1338 mmol.Kg-1/83 mg.g-1) was obtained for SMZNS material. This value is the highest ever observed for nitrate removal using surfactant-modified zeolite. The nitrate removal kinetics were fitted with the pseudo second-order model for both materials SMZNS and SMZNC.

Synthesis of Binderless ZK-4 Zeolite Microspheres at High Temperature.

Binderless zeolite macrostructures in the form of ZK-4 microspheres were prepared using anion-exchange resin beads as shape-directing macrotemplates. The particles were synthesized under hydrothermal conditions at different temperatures and treatment times. The influence of the different synthesis parameters was investigated by X-ray diffraction, scanning electron microscopy, fluorescence X, nitrogen adsorption measurements and 29Si solid-state NMR. Fully crystalline spheres similar in size and shape to the original resin beads were obtained by a hydrothermal treatment at the highest temperatures (150⁻180 °C) for a short treatment time of 24 h. The synthesized microspheres showed to be promising in the molecular decontamination of volatile organic compounds (VOCs).

Manufacture and optimization of low-cost tubular ceramic supports for membrane filtration: application to algal solution concentration.

Low-cost tubular macroporous supports for ceramic membranes were elaborated using the extrusion method, followed by curing, debinding, and sintering processes, from a powder mixture containing kaolin, starch, and sand. The obtained substrates were characterized using mercury intrusion porosimetry, water absorption test, water permeability, scanning electron microscopy, and three-point bending test to evaluate the effects of the additives on the relevant characteristics. According to experimental results, adding the starch ratio to the kaolin powder shows a notable impact on the membrane porosity and consequently on the water permeability of the tubular supports, whereas their mechanical strength decreased compared to those prepared from kaolin alone. It has been shown that the addition of an appropriate amount of starch to the ceramic paste leads to obtaining membrane supports with the desired porosity. Indeed, the water permeability increased significantly from 20 to 612 L h-1 m-2 bar-1 for samples without and with 20 wt% of starch, respectively, as well as the open porosity, the apparent porosity, and the pore size distribution. The bending strength decreased slightly and reached about 4 MPa for samples with the highest starch amounts. On the other hand, the incorporation of sand in a mixture of kaolin + 10 wt% starch increased the mechanical strength and the water permeability. The samples containing 3 wt% of sand exhibited a bending strength four times higher than the supports without sand; the water permeability measured was about 221 L h-1 m-2 bar-1. These elaborated tubular supports for membrane are found to be suitable for solution concentration; they were applied for algal solution and are also easily cleaned by water.

Insights into the Formation and Properties of Templated Dual Mesoporous Titania with Enhanced Photocatalytic Activity.

The one pot synthesis of dual mesoporous titania (2.3 and 7.7 nm) has been achieved from a mixture of fluorinated and Pluronic surfactants. The small and large mesopore networks are templated, respectively, by a fluorinated-rich liquid crystal and a Pluronic-rich liquid crystal, which are in equilibrium. After calcination at 350 °C, the amorphous walls are transformed into semicrystalline anatase preserving the mesoporous structure. Results concerning the photodegradation of methyl orange using the calcined photocatalysts highlight that the kinetic rate constant (k) determined for the dual mesoporous titania is 2.6 times higher than the k value obtained for the monomodal ones.

Ammonium and potassium removal from swine liquid manure using clinoptilolite, chabazite and faujasite zeolites.

This study concerns cationic exchanges performed in order to remove ammonium and potassium cations from manure by using various zeolites: clinoptilolite, chabazite and NaX faujasite. First, the effect of temperature (25 °C and 40 °C) on the exchange rate between zeolites and an ammonium chloride solution was investigated. Then, cationic exchanges were performed on these three zeolites using on one side a mixed ammonium and potassium chloride solution reproducing the chemical composition of a swine manure and on the other side the corresponding liquid manure. No significant difference was observed on the exchange rate and the trapping of ammonium cations by changing the temperature (25 or 40 °C). Clinoptilolite showed a good selectivity towards ammonium cations using model (NH4Cl, and mixed NH4Cl/KCl) solutions but is less efficient with the liquid manure. Chabazite and faujasite were found more efficient than clinoptilolite for trapping ammonium cations. However, NaX faujasite enables trapping 3 times more ammonium cations than chabazite from manure (60 and 20 mg/g, respectively). Moreover, chabazite allowed to trap the same amount of potassium cations than NaX faujasite (33 and 35 mg/g, respectively).

In Situ Small-Angle X-ray Scattering Investigation of the Formation of Dual-Mesoporous Materials.

The formation of a 2D-hexagonal (p6m) silica-based hybrid dual-mesoporous material is investigated in situ by using synchrotron time-resolved small-angle X-ray scattering (SAXS). The material is synthesized from a mixed micellar solution of a nonionic fluorinated surfactant, R(F) 8 (EO)9 (EO=ethylene oxide) and a nonionic triblock copolymer, P123. Both mesoporous networks, with pore dimensions of 3.3 and 8.5 nm respectively, are observed by nitrogen sorption, transmission electron microscopy (TEM), and SAXS. The in situ SAXS experiments reveal that mesophase formation occurs in two steps. First the nucleation and growth of a primary 2D-hexagonal network (N1), associated with mixed micelles containing P123, then subsequent formation of a second network (N2), associated with micelles of pure R(F) 8 (EO)9 . The data obtained from SAXS and TEM suggest that the N1 network is used as a nucleation center for the formation of the N2 network, which would result in the formation of a grain with two mesopore sizes. Understanding the mechanism of the formation of such materials is an important step towards the synthesis of more-complex materials by fine tuning the porosity.

Evaluation of paraclinical tests in the diagnosis of cervicogenic dizziness.

OBJECTIVE: To assess the utility of the paraclinical tests in patients presenting with clinical diagnosis of cervicogenic dizziness. STUDY DESIGN: Case controlled. SETTING: Otolaryngology clinic of a tertiary referral hospital center. PATIENTS: Twenty-five subjects with cervicogenic dizziness and 25 subjects with benign paroxysmal positional vertigo. MAIN OUTCOME MEASURES: Symptoms description, Dizziness Handicap Inventory-short form (DHI), Trait anxiety score, cervical joint position error, the smooth pursuit neck torsion and cervical torsion tests on videonystagmography, and standing balance test (timed 10-meter walk with head turns). RESULTS: The results showed differences in reported symptoms, in mean cervical joint position error (p = 0.001), and cervical torsion test (p = 0.001) between the two groups. There was no between-group difference for DHI scores (p = 0.137), trait anxiety scores (p = 0.240), and walking test: time (p = 0.797), steps (p = 0.963). The Youden index is 0.60 for the predictive value of the cervical joint position error, and the smooth pursuit and the cervical torsion tests. CONCLUSION: This study showed differences in sensorimotor disturbances between the two groups, particularly in the control of head and eye movements and cervical proprioception. Patients with cervicogenic dizziness were more likely to (1) have a sensation of drunkenness and lightheadedness, (2) have pain induced during the physical examination of the upper cervical vertebrae, (3) have an elevated joint position error of 4.5 degrees during the cervical relocation test, and (4) exhibit more than 2 degrees per second nystagmus during the cervical rotation test. The walking test was not able to differentiate the two groups.

Anteverted internal auditory canal as an inner ear anomaly in patients with craniofacial microsomia.

Craniofacial microsomia involves structure of the first and second branchial arches. A wide range of ear anomalies, affecting external, middle and inner ear, has been described in association with this condition. We report three cases of anteverted internal auditory canal in patients presenting craniofacial microsomia. This unique internal auditory canal orientation was found on high-resolution computed tomography of the temporal bones. This internal auditory canal anomaly is yet unreported in craniofacial anomalies.

Updates on the diagnosis and treatment of intracranial nerve malignant peripheral nerve sheath tumors.

BACKGROUND: Malignant peripheral nerve sheath tumors (MPNSTs) are rare entities and MPNSTs of intracranial nerves are even more sporadic. MPNSTs present diagnosis and treatment challenges since there are no defined diagnosis criteria and no established therapeutic strategies. METHODS: We reviewed literature for MPNST-related articles. We found 45 relevant studies in which 60 cases were described. RESULTS: We identified 60 cases of intracranial nerve MPNSTs. The age ranged from 3 to 75 years old. Male to female ratio was 1.5:1. The most involved cranial nerves (CNs) were CN VIII (60%), CN V (27%), and CN VII (10%). Most of the MPNSTs reported (47%) arose sporadically, 40% arose from a schwannoma, 8% arose from a neurofibroma, and 6% arose from an unspecified nerve tumor. Twenty patients had a history of radiation exposure, four patients had neurofibromatosis type 1 (NF1), four patients had neurofibromatosis type 2 (NF2), and NF2 was suspected in two other patients. Twenty-two patients were treated with radiotherapy and presented a higher survival rate. Seventy-two percent of patients died of their disease while 28% of patients survived. One-year survival rate was 33%. Forty-five percent of tumors recurred and 19% of patients had metastases. CONCLUSION: MPNSTs involving CNs are very rare. Diagnosis is made in regards to the histological and pathological findings. Imaging may help orient the diagnosis. A preexisting knowledge of the clinical situation is more likely to lead to a correct diagnosis. The mainstay of treatment is radical surgical resection with adjuvant radiotherapy. Since these tumors are associated with a poor prognosis, a close follow-up is mandatory.

Ecodesign of ordered mesoporous silica materials.

Characterized by a regular porosity in terms of pore size and pore network arrangement, ordered mesoporous solids have attracted increasing interest in the last two decades. These materials have been identified as potential candidates for several applications. However, more environmentally friendly and economical synthesis routes of mesoporous silica materials were found to be necessary in order to develop these applications on an industrial scale. Consequently, ecodesign of ordered mesoporous silica has been considerably developed with the objective of optimizing the chemistry and the processing aspects of the material synthesis. In this review, the main strategies developed with this aim are presented and discussed.

Block copolymer self-assembly in mesostructured silica films revealed by real-time FTIR and solid-state NMR.

Over the past ten years, understanding the self-assembly process within mesostructured silica films has been a major concern. Our characterization approach relies on two powerful and complementary techniques: in situ time-resolved FTIR spectroscopy and ex situ solid-state NMR. As model systems, three silica/surfactant films displaying various degrees of mesostructuration were synthesized using an amphiphilic block copolymer (PEO-b-PPO-b-PEO) via a UV light induced self-assembly process. The key idea is that the hydration state of the hydrophobic PPO chain is expected to be different depending upon whether the sample is amorphous (blend) or mesostructured (segregated). With real-time FTIR experiments, we show that the methyl deformation mode can act as a signature for the PPO microenvironment so as to trace the progressive copolymer self-association throughout the irradiation time. In (1)H solid-state NMR, the dependence of the (1)H chemical shift on the PPO hydration state has been exploited to evidence the extent of mesostructuration.