Search Results (10)

Background/Objectives: Selective laser sintering (SLS) is one of the most promising 3D printing techniques for pharmaceutical applications as it offers numerous advantages, such as suitability to work with already approved pharmaceutical excipients, the elimination of solvents, and the ability to produce fast-dissolving, porous dosage forms with high drug loading. When the powder mixture is exposed to elevated temperatures during SLS printing, the active ingredients can be converted from the crystalline to the amorphous state, which can be used as a strategy to improve the dissolution rate and bioavailability of poorly soluble drugs. This study investigates the potential application of SLS 3D printing for the fabrication of tablets containing the poorly soluble drug carvedilol with the aim of improving the dissolution rate of the drug by forming an amorphous form through the printing process. Methods: Using SLS 3D printing, eight tablet formulations were produced using two different powder mixtures and four combinations of experimental conditions, followed by physicochemical characterization and dissolution testing. Results: Physicochemical characterization revealed that at least partial amorphization of carvedilol occurred during the printing process. Although variations in process parameters were minimal, higher temperatures in combination with lower laser speeds appeared to facilitate a greater degree of amorphization. Ultimately, the partial conversion to the amorphous form significantly improved the dissolution of carvedilol compared to its pure crystalline form. Conclusions: Obtained results suggest that the SLS 3D printing technique can be effectively used to convert poorly water-soluble drugs to their amorphous state, thereby improving solubility and bioavailability. Full article

Electromagnetic waves (EMWs) have become an integral part of our daily lives, but they are causing a new form of environmental pollution, manifesting as electromagnetic interference (EMI) and radio frequency signal leakage. As a result, the demand for innovative, eco-friendly materials capable of blocking EMWs has escalated in the past decade, underscoring the significance of our research. In the realm of modern science, the creation of new materials must consider the starting materials, production costs, energy usage, and the potential for air, water, and soil pollution. Herein, we utilized biowaste materials generated during the distillation of fruit schnapps. The biowaste from apple and quince schnapps distillation was used as starting material, mixed with KOH, and carbonized at 850 °C, in a nitrogen atmosphere. The structure of samples was investigated using various techniques (infrared, Raman, energy-dispersive X-ray, X-ray photoelectron spectroscopies, thermogravimetric analysis, BET surface area analyzer). Encouragingly, these materials demonstrated the ability to block EMWs within a frequency range of 8 to 12 GHz. Shielding efficiency was measured using waveguide adapters connected to ports (1 and 2) of the vector network analyzer using radio-frequency coaxial cables. At a frequency of 10 GHz, carbonized biowaste blocks 78.5% of the incident electromagnetic wave. Full article

A lack of strategies for the utilization of harvest residues (HRs) has led to serious environmental problems due to an accumulation of these residues or their burning in the field. In this study, wheat and corn HRs were used as feedstock for the production of microcrystalline cellulose (MCC) by treatment with 2–8% sodium hydroxide, 10% hydrogen peroxide and further hydrolysis with 1–2 M hydrochloric acid. The changes in the FT-IR spectra and PXRD diffractograms after chemical treatment confirmed the removal of most of the lignin, hemicellulose and amorphous fraction of cellulose. A higher degree of crystallinity was observed for MCC obtained from corn HRs, which was attributed to a more efficient removal of lignin and hemicellulose by a higher sodium hydroxide concentration, which facilitates the dissolution of amorphous cellulose during acid hydrolysis. MCC obtained from HRs exhibited lower bulk density and poorer flow properties but similar or better tableting properties compared to commercial MCC (Ceolus^TM PH101). The lower ejection and detachment stress suggests that MCC isolated from HRs requires less lubricant compared to commercial MCC. This study showed that MCC isolated from wheat and corn HRs exhibits comparable tableting behaviour like commercial sample, further supporting this type of agricultural waste utilization. Full article

Layered VOPO₄·2H₂O is synthesized by the sonochemical method. An X-ray powder diffraction is used to examine the crystal structure, while scanning electron microscopy is used to reveal the morphology of the powder. The crystal structure refinement is performed in the P4/nmmZ space group. The electrochemical intercalation of several cations (Na⁺, Mg²⁺, Ca²⁺, and Al³⁺) in saturated nitrate aqueous solutions is investigated. The most notable reversible activity is found for the cycling in aluminium nitrate aqueous solution in the voltage range from −0.1 to 0.8 V vs. SCE. During the preparation of the electrode, it is observed that the structure is prone to changes that have not been recorded in the literature so far. Namely, the use of conventional binder PVDF in NMP solution deteriorates the structure and lowers the powder’s crystallinity, while the use of Nafion solution causes the rearrangement of the atoms in a new crystal form that can be described in the monoclinic P2₁/c space group. Consequently, these structural changes affect electrochemical performances. The observed differences in electrochemical performances are a result of structural rearrangements. Full article

Lanthanide ions possess various emission channels in the near-infrared region that are well known in bulk crystals but are far less studied in samples with nanometric size. In this work, we present the infrared spectroscopic characterization of various Nd-doped fluoride and sesquioxide nanocrystals, namely Nd:Y₂O₃, Nd:Lu₂O₃, Nd:Sc₂O₃, Nd:YF₃, and Nd:LuF₃. Emissions from the three main emission bands in the near-infrared region have been observed and the emission cross-sections have been calculated. Moreover, another decay channel at around 2 μm has been observed and ascribed to the ⁴F_3/2→⁴I_15/2 transition. The lifetime of the ⁴F_3/2 level has been measured under LED pumping. Emission cross-sections for the various compounds are calculated in the 1 μm, 900 nm, and 1.3 μm regions and are of the order of 10⁻²⁰ cm² in agreement with the literature results. Those in the 2 μm region are of the order of 10⁻²¹ cm². Full article

The impact of rare earth oxide (REO) concentration on the deposition process and selective recovery of the metal being deposited from a molten fluoride salt system was investigated by applying deposition of Nd and Pr and varying the concentration of REO added to the electrolyte. A ternary phase diagram for the liquidus temperature of the NdF₃-PrF₃-LiF system was constructed to better predict the optimal electrolyte constitution. Cyclic voltammetry was used to record three redox signals, reflecting the processes involving Nd(III)/Nd and Pr(III)/Pr transformations. A two-step red/ox process for Nd(III) ions and a single-step red/ox process for Pr(III) ions were confirmed by square-wave voltammetry. The cyclic voltammetry results indicated the possibility of neodymium and praseodymium co-deposition. In order to sustain higher co-deposition rates on the cathode and to avoid increased production of PFC greenhouse gases on the anode, a low-overpotential deposition technique was used for Nd and Pr electrodeposition from the electrolyte with varying Nd₂O₃ and Pr₆O₁₁ concentrations. Co-deposited neodymium and praseodymium metals were characterized by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) analysis. After electrodeposition, concentration profiles of neodymium and praseodymium were recorded, starting from the cathode surface towards the electrolyte bulk. The working temperature of 1050 °C of the molten fluoride salt basic electrolyte, in line with the constructed phase diagram, was validated by improved co-deposition and led to a more effective deposition process. Full article

Electrodeposition processes of neodymium and praseodymium in molten NdF₃ + PrF₃ + LiF + 1 wt.%Pr₆O₁₁ + 1 wt.%Nd₂O₃ and NdF₃ + PrF₃ + LiF + 2 wt.%Pr₆O₁₁ + 2 wt.%Nd₂O₃ electrolytes at 1323 K were investigated. Cyclic voltammetry, square wave voltammetry, and open circuit potentiometry were applied to study the electrochemical reduction of Nd(III) and Pr(III) ions on Mo and W cathodes. It was established that a critical condition for Nd and Pr co-deposition in oxyfluoride electrolytes was a constant praseodymium deposition overpotential of ≈−0.100 V, which was shown to result in co-deposition current densities approaching 6 mAcm⁻². Analysis of the results obtained by applied electrochemical techniques showed that praseodymium deposition proceeds as a one-step process involving exchange of three electrons (Pr(III)→Pr(0)) and that neodymium deposition is a two-step process: the first involves one electron exchange (Nd(III)→Nd(II)), and the second involves an exchange of two electrons (Nd(II)→Nd(0)). X-ray diffraction analyses confirmed the formation of metallic Nd and Pr on the working substrate. Keeping the anodic potential to the glassy carbon working anode low results in very low levels of carbon oxides, fluorine and fluorocarbon gas emissions, which should qualify the studied system as an environmentally friendly option for rare earth metal deposition. The newly reported data for Nd and Pr metals co-deposition provide valuable information for the recycling of neodymium-iron-boron magnets. Full article

The Al-V alloys were synthetized by potentiostatic electrodeposition onto a glassy carbon electrode from equimolar AlCl₃ + NaCl bath containing vanadium ions at 200 °C. The alloy deposits were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The deposits were identified as Al₃V and AlV₃ alloys. It was found that intermetallic alloys were synthetized during aluminium underpotential deposition onto vanadium metal that was previously deposited on the glassy carbon electrode by diffusion-controlled overpotential deposition. Alloys were the result of solid-state interdiffusion between the initially deposited vanadium and the subsequently deposited aluminium. As a source to secure a constant concentration of vanadium in the electrolyte during deposition, vanadium anodic dissolution, and VCl₃ melt addition were studied. The effect of vanadium ion concentration in the electrolyte on the composition and the surface morphology of the obtained deposits was investigated. The results indicate that controlled vanadium and aluminium codeposition could be a further step to the successful development of an advanced technology for Al₃V and AlV₃ alloy synthesis. Full article

Neodymium was electrochemically deposited from NdF₃–LiF–Nd₂O₃ molten salt electrolyte onto the Mo electrode at temperatures close to 1273 K. Cyclic voltammetry and chronoamperometry measurements were the applied electrochemical methods. Metallic neodymium is obtained by potentiostatic deposition. The optical microscopy and XRD were used to analyze the electrolyte, the working electrode surface, and the deposit on the electrode. It was established that Nd(III) ions were reduced to Nd metals in two steps: Nd(III) + e⁻ → Nd(II) at potential ≈−0.55 V vs. W and Nd(II) + 2e⁻ → Nd(0) at ≈−0.83 V vs. W. Both of these processes are reversible and under mass transfer control. Upon deposition under the regime of relatively small deposition overpotential of −0.10 V to −0.20 V, and after the electrolyte was cooled off, Nd metal was observed at the surface of the Mo electrode. CO and CF₄ were gases registered as being evolved at the anode. CO and CF₄ evolution were observed in quantities below 600 ppm and 10 ppm, respectively. Full article

The emission of Er³⁺ provides three combinations of emission bands suitable for ratiometric luminescence thermometry. Two combinations utilize ratios of visible emissions (²H_11/2→⁴I_15/2 at 523 nm/ ⁴S_3/2→⁴I_15/2 at 542 nm and ⁴F_7/2→⁴I_15/2 at 485 nm/ ⁴S_3/2→⁴I_15/2 at 545 nm), while emissions from the third combination are located in near-infrared, e.g., in the first biological window (²H_11/2→⁴I_13/2 at 793 nm/ ⁴S_3/2→⁴I_13/2 at 840 nm). Herein, we aimed to compare thermometric performances of these three different ratiometric readouts on account of their relative sensitivities, resolutions, and repeatability of measurements. For this aim, we prepared Yb³⁺,Er³⁺:YF₃ nanopowders by oxide fluorination. The structure of the materials was confirmed by X-ray diffraction analysis and particle morphology was evaluated from FE-SEM measurements. Upconversion emission spectra were measured over the 293–473 K range upon excitation by 980 nm radiation. The obtained relative sensitivities on temperature for 523/542, 485/542, and 793/840 emission intensity ratios were 1.06 ± 0.02, 2.03 ± 0.23, and 0.98 ± 0.10%K⁻¹ with temperature resolutions of 0.3, 0.7, and 1.8 K, respectively. The study showed that the higher relative temperature sensitivity does not necessarily lead to the more precise temperature measurement and better resolution, since it may be compromised by a larger uncertainty in measurement of low-intensity emission bands. Full article