Synthesis and Characterization of Lignin-Silver Nanoparticles

Metal nanoparticle synthesis via environmentally friendly methods is gaining interest for their potential advantages over conventional physico-chemical approaches. Herein, we propose a robust green synthesis route for lignin-modified silver nanoparticles, utilizing the recovery of lignin as a renewable raw material and exploring its application in valuable areas. Through a systematic approach combining UV-Vis spectroscopy with AAS and DLS, we identified repeatable and scalable reaction conditions in an aqueous solution at pH 11 for homogeneous silver nanoparticles with high uniformity. The TEM median sizes ranged from 12 to 15 nm with circularity between 0.985 and 0.993. The silver nanoparticles yield exceeded 0.010 mol L-1, comparable with traditional physico-chemical methods, with a minimal loss of silver precursor ranging between 0.5 and 3.9%. Characterization by XRD and XPS revealed the presence of Ag-O bonding involving lignin functional groups on the pure face-centered cubic structure of metallic silver. Moreover, the lignin-modified silver nanoparticles generated a localized thermal effect upon near-infrared laser irradiation (808 nm), potentially allowing for targeted applications in the biomedical field. Our study showcases the potential of lignin as a renewable reducing and capping agent for silver nanoparticle synthesis, addressing some shortcomings of green synthesis approaches and contributing to the development of suitable nanomaterials.

Aspect Ratio Modulation of Sucralose through {002}/{011} Preferred Orientation in Antisolvent Crystallization

The aspect ratio modulation in the alcoholysis process is highly significant for the production of high-quality sucralose. In this work, antisolvent crystallization (ASC) accompanied by preferred orientation was first adopted in the sucralose separation, based on which simultaneous modulations on aspect ratio, solubility, and stability have been realized. In detail, after the alcoholysis process in methanol, four antisolvents bearing different functional groups were used in ASC, i.e., isopentanol (IPN), isovaleraldehyde (IVD), isovaleric acid (IVA), and isobutyl propionate (IBP). To our interest, when IVA was used as the antisolvent, the highest separation efficiency (49.33%), fastest crystallizing rate (5.64%/h), lowest aspect ratio (1.55), and solubility (9.28 wt %) and good thermal stability (131.65 °C) of sucralose were achieved. Single crystal structures of sucralose using different antisolvents have been determined. Sucralose using IVA as the antisolvent exhibits the greatest molecular distortion and strongest intermolecular C-H···Cl hydrogen bonds; thus, the preferred growth along {002}/{011} directions has occurred and accounted for its lower aspect ratio, worse solubility, and better stability. The strongest methanol···IVA interactions due to the presence of a carboxyl group can accelerate the formation of the emulsion, resulting in the fastest crystallizing rate. The antisolvent screening and the discovery about relative mechanisms will provide a theoretical guide for the production of high-quality sucralose.

On the solubility of sucrose in technical solutions – molasses revisited

This manuscript covers two aspects of the subject area described in the title. In order to improve the understanding and control of sucrose solubility in molasses it is believed that it is necessary to firstly gather experimentally detailed and consistent solubility and composition data. Secondly, the mathematical description of sucrose solubilities in molasses should be reconsidered. In the contribution data on 49 different molasses are described. The data show significant variation in both the sucrose solubility and the composition of the nonsucrose components. Current models to describe the solubility are discussed in light of thermodynamical considerations and their success in representing the data gathered.

Particle crystallization by supercritical antisolvent processing techniques: the case of Retama raetam powder for pharmaceutical purposes

In this work, the Supercritical AntiSolvent process has been used to generate micronized crystals of Retama raetam. The process was performed using ethanol and CO2 as solvent and antisolvent, respectively. Recrystallization was made at various temperatures (30–50 °C) and pressures (8–12 MPa) using a constant flow rate of supercritical CO2 (2 kg/h). We have been also varied the solution flow rate and its volume to identify conditions leading to spheroidal powder morphology. Size and morphology have been characterized by scanning electron microscopy and ImageJ software. The spraying of the supercritical solution directing the flow towards the precipitator results in the deposition of fine particles with uniform morphology at the bottom, and of a porous film adhering to the precipitator wall. For that reason, thermodynamic and hydrodynamic aspects are discussed so as to rationalize the powder and spongious film characteristics and provide a new way to control the SAS process applied to plant derivatives.

A Simple Population Balance Model for Crystallization of L-Lactide in a Mixture of n-Hexane and Tetrahydrofuran

In this contribution, crystallization was performed to assess the kinetics of nucleation and crystal growth of L-lactide. In most common solvents, this compound shows very high solubility even at low temperatures, which could be challenging for crystallization process design. In the first part of this paper, the anti-solvent effects of n-hexane on solutions of L-lactide in tetrahydrofuran (THF) were investigated through studying the influence of solvent compositions on the solubility. Thanks to these effects, the solubility of the interested compound can be adjusted to desired degrees of supersaturation by adding suitable amounts of the anti-solvent. In the second part, a solvent composition at a mass ratio of 45/55 (n-hexane/THF) was chosen, and an isothermal seeded crystallization process was implemented. The evolution of the particle sizes and changes in the solute concentration profile of this process were monitored. Based on the obtained data, a widely used model, i.e., the population balance equation (PBE), was then utilized to model the crystal size distribution (CSD). Reasonable assumptions were made to reduce the mathematical complexity of the PBE. In the simplified model, only crystal growth and secondary nucleation were considered for model formulation, with assumptions of the size-independent growth rate and negligible size of nuclei. The kinetic parameters were estimated by using the seed and final-time crystal density functions in combination with variations in the concentration of the mother liquor. Indeed, the numerical solution for the one-dimensional problem of the L-lactide crystallization based on the estimated parameters gained a relatively good agreement with the determined CSD. Furthermore, the obtained model also correlated well with the variations in the solute concentration of the mother liquor. In short, this simple approach can be used for predicting the productivity and CSD of the L-lactide crystallization.

Directing Crystallization Outcomes of Conformationally Flexible Molecules: Polymorphs, Solvates, and Desolvation Pathways of Fluconazole

Control over polymorphism and solvatomorphism in API assisted by structural information, e.g., molecular conformation or associations via hydrogen bonds, is crucial for the industrial development of new drugs, as the crystallization products differ in solubility, dissolution profile, compressibility, or melting temperature. The stability of the final formulation and technological factors of the pharmaceutical powders further emphasize the importance of precise crystallization protocols. This is particularly important when working with highly flexible molecules with considerable conformational freedom and a large number of hydrogen bond donors or acceptors (e.g., fluconazole, FLU). Here, cooling and suspension crystallization were applied to access polymorphs and solvates of FLU, a widely used azole antifungal agent with high molecular flexibility and several reported polymorphs. Each of four polymorphic forms, FLU I, II, III, or IV, can be obtained from the same set of alcohols (MeOH, EtOH, isPrOH) and DMF via careful control of the crystallization conditions. For the first time, two types of isostructural channel solvates of FLU were obtained (nine new structures). Type I solvates were prepared by cooling crystallization in Tol, ACN, DMSO, BuOH, and BuON. Type II solvates formed in DCM, ACN, nPrOH, and BuOH during suspension experiments. We propose desolvation pathways for both types of solvates based on the structural analysis of the newly obtained solvates and their desolvation products. Type I solvates desolvate to FLU form I by hydrogen-bonded chain rearrangements. Type II solvates desolvation leads first to an isomorphic desolvate, followed by a phase transition to FLU form II through hydrogen-bonded dimer rearrangement. Combining solvent-mediated phase transformations with structural analysis and solid-state NMR, supported by periodic electronic structure calculations, allowed us to elucidate the interrelations and transformation pathways of FLU.

Impurity incorporation in solution crystallization: diagnosis, prevention, and control

This work highlights recent advances in the diagnosis, prevention, and control of impurity incorporation during solution crystallization.

Emulsions of miscible solvents: the origin of anti-solvent crystallization

Emulsions of miscible solvents: the origin of anti-solvent crystallization. We demonstrate that emulsions in a miscible solvents system could provide the opportunity to explain an accurate mechanism of anti-solvent crystallization before nucleation.