Fast Solvent Evaporation Research Articles

Synthesis, Characterization, and Stability Optimization of Ibuprofen Cocrystals eEploying Various Hydrophilic Polymers.

Cocrystals are an efficient way for the delivery of low soluble drugs but when dissolved they rapidly disproportionate. To formulate the cocrystals in tablets, cocrystals must be stabilized. In this study ibuprofen-nicotinamide (IBU-NIC) cocrystals were synthesized initially by slow solvent evaporation and for bulk production by fast solvent evaporation techniques. The cocrystals were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectrophotometer (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and optical microscopy. The ibuprofen cocrystals showed greater solubility compared to the parent drug. Intrinsic dissolution data was utilized for efficacious screening of tablet formulations. Using hydrophilic polymers at a ratio of 6:1 (polymer to IBU-NIC cocrystal ratio), hydroxypropyl methylcellulose (F1), polyvinylpyrrolidone (PVP) K-30 (F2) and PVP K-90 (F3), three tablet formulations were prepared that stabilized cocrystals during dissolution. The drug release profiles after 60 minutes from formulations F1 (92.30), F2 (98.54), F3 (99.88) were all higher compared to the marketed brand BRUFEN® F, (79.61%) in a simulated intestinal media (p<0.001). Significant increase in the dissolution rate of cocrystal was observed with no phase change in all formulations.

Ordered mesoporous nanofibers mimicking vascular bundles for lithium metal batteries.

Hierarchical self-assembly with long-range order above centimeters widely exists in nature. Mimicking similar structures to promote reaction kinetics of electrochemical energy devices is of immense interest, yet remains challenging. Here, we report a bottom-up self-assembly approach to constructing ordered mesoporous nanofibers with a structure resembling vascular bundles via electrospinning. The synthesis involves self-assembling polystyrene (PS) homopolymer, amphiphilic diblock copolymer, and precursors into supramolecular micelles. Elongational dynamics of viscoelastic micelle solution together with fast solvent evaporation during electrospinning cause simultaneous close packing and uniaxial stretching of micelles, consequently producing polymer nanofibers consisting of oriented micelles. The method is versatile for the fabrication of large-scale ordered mesoporous nanofibers with adjustable pore diameter and various compositions such as carbon, SiO2, TiO2 and WO3. The aligned longitudinal mesopores connected side-by-side by tiny pores offer highly exposed active sites and expedite electron/ion transport. The assembled electrodes deliver outstanding performance for lithium metal batteries.

Fast solvent evaporation of phase pure CuBi2O4 photocathodes for photoelectrocatalytic water splitting

P-type metal oxide semiconductor CuBi2O4 exhibits excellent energy band structures and photoelectric response characteristics, which are critical for photoelectrocatalytic water splitting. However, the photocurrent densities are still well below the theoretical limit due to poor charge carrier separation and transport properties. In this work, we report a synthetic method for the preparation of phase-pure CuBi2O4 photocathode films via spray pyrolysis by adjusting the evaporation rate of the atomized droplets. An increase in the evaporation rate of the solvent may fix the structure of the deposited film faster and decrease the time available for the establishment of the segregation gradient, thus producing phase-pure semiconductor films. This method reduces process complexity and cost, and the applicability of spray pyrolysis for the preparation of phase-pure CuBi2O4 films is also confirmed. In addition, the photoelectrochemical evaluation of the samples prepared under different treatment conditions reveals that hole transport critically affects the photoelectrocatalytic performance of CuBi2O4 photocathodes. CuO can be used as a hole transport layer to promote the collection and transfer of holes and reduce the recombination of photogenerated carriers.

Influence of the Volatility of Solvent on the Reproducibility of Droplet Formation in Pharmaceutical Inkjet Printing

Drop-on-demand (DOD) inkjet printing enables exact dispensing and positioning of single droplets in the picoliter range. In this study, we investigate the long-term reproducibility of droplet formation of piezoelectric inkjet printed drug solutions using solvents with different volatilities. We found inkjet printability of EtOH/ASA drug solutions is limited, as there is a rapid forming of drug deposits on the nozzle of the printhead because of fast solvent evaporation. Droplet formation of c = 100 g/L EtOH/ASA solution was affected after only a few seconds by little drug deposits, whereas for c = 10 g/L EtOH/ASA solution, a negative affection was observed only after t = 15 min, while prominent drug deposits form at the printhead tip. Due to the creeping effect, the crystallizing structures of ASA spread around the nozzle but do not clog it necessarily. When there is a negative affection, the droplet trajectory is affected the most, while the droplet volume and droplet velocity are influenced less. In contrast, no formation of drug deposits could be observed for highly concentrated, low volatile DMSO-based drug solution of c = 100 g/L even after a dispensing time of t = 30 min. Therefore, low volatile solvents are preferable to highly volatile solvents to ensure a reproducible droplet formation in long-term inkjet printing of highly concentrated drug solutions. Highly volatile solvents require relatively low drug concentrations and frequent printhead cleaning. The findings of this study are especially relevant when high droplet positioning precision is desired, e.g., drug loading of microreservoirs or drug-coating of microneedle devices.

Fast solvent evaporation by experimental optimization using central composite design for one-step fabrication of superhydrophobic polypropylene surface

Fast solvent evaporation by experimental optimization using central composite design for one-step fabrication of superhydrophobic polypropylene surface

Characterization, stability and solubility of co-amorphous systems of glibenclamide and L-arginine at different pH

Purpose: To investigate the stability and solubility of co-amorphous systems of glibenclamide (GBC) with L-arginine (L-Arg) at different pH values.&#x0D; Methods: Three co-amorphous solids of GBC and L-Arg were obtained by fast solvent evaporation using 2:1, 1:1 and 1:2 stoichiometries. All co-amorphous systems were characterized by XRPD, FTIR, RAMAN and NMR-solid state as well as thermal techniques such as DSC and TGA. The stability of coamorphous systems was evaluated by indicative stability and stability in relevant physiological media was measured at different pH values.&#x0D; Results: The chemical characterization suggest that there was no proton transference between L-Arg and GBC indicative of co-amorphous solids. Stability studies showed that all the co-amorphous solids are unstable under humid conditions and only the co-amorphous system of GBC: L-Arg 1:2 was stable in all the pH values tested. Solubility studies at different pH values showed that the co-amorphous GBC: L-Arg 1:1 and 1:2, showed increasing solubility values even at pH &lt; 7 (0.6468 mg/mL at pH 1.2 for coamorphous GBC: L-Arg 1:2 at the first hour) where free GBC was not soluble.&#x0D; Conclusion: Co-amorphous systems of GBC and L-Arg, is an interesting strategy to increase the solubility of poorly-soluble drugs at acidic pH values&#x0D; Keywords: Co-amorphous; Glibenclamide; L-Arginine; Solubility; Stability

Large-Area Uniaxial-Oriented Growth of Free-Standing Thin Films at the Liquid-Air Interface with Millimeter-Sized Grains.

Manipulating materials at the atomic scale and assembling them into macroscopic structures with controlled dimensionalities and single-crystal quality are grand scientific challenges. Here, we report a general solvent evaporation method to synthesize large-area uniaxial-oriented growth of free-standing thin films at the liquid-air interface. Crystals nucleate at the solution surface and rotate into the same orientation under electrostatic interaction and then merge as large crystals and grow laterally into a large-area uniform thin film with millimeter-sized grains. The lateral dimension is confined only by the size of containers. The film thickness can be tuned by adjusting solvent evaporation rate (R) and solute diffusivity (D), and a characteristic length, , was derived to estimate the film thickness. Molecular dynamic (MD) simulations reveal a concentration spike at the liquid-air interface during fast solvent evaporation, leading to the lateral growth of thin films. The large-area uniaxial oriented films are demonstrated on both inorganic metal halides and hybrid metal halide perovskites. The solvent evaporation approach and the determination of key parameters enabling film thickness prediction are beneficial to the high throughput and scalable production of single crystal-quality thin film materials under controlled evaporation conditions.

Gaining Insight into the Role of the Solvent during Spray Drying of Amorphous Solid Dispersions by Studying Evaporation Kinetics.

Spray drying is one of the most commonly used manufacturing techniques for amorphous solid dispersions (ASDs). During spray drying, very fast solvent evaporation is enabled by the generation of small droplets and exposure of these droplets to a heated drying gas. This fast solvent evaporation leads to an increased viscosity that enables kinetic trapping of an active pharmaceutical ingredient (API) in a polymer matrix, which is favorable for the formulation of supersaturated, kinetically stabilized ASDs. In this work, the relation between the solvent evaporation rate and the kinetic stabilization of highly drug-loaded ASDs was investigated. Accordingly, thermal gravimetric analysis (TGA) was employed to study the evaporation kinetics of seven organic solvents and the influence of solutes, i.e., poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA), fenofibrate (FNB), and naproxen (NAP), on the evaporation behavior. At 10 °C below the boiling point of the respective solvent, methanol (MeOH) had the lowest evaporation rate and dichloromethane (DCM) had the highest. PVPVA decreased the evaporation rate for all solvents, yet this effect was more pronounced for the relatively faster evaporating solvents. The APIs had opposite effects on the evaporation process: FNB increased the evaporation rate, while NAP decreased it. The latter might indicate the presence of interactions between NAP and the solvent or NAP and PVPVA, which was further investigated using Fourier transform-InfraRed (FT-IR) spectroscopy. Based on these findings, spray drying process parameters were adapted to alter the evaporation rate. Increasing the evaporation rate of MeOH and DCM enabled the kinetic stabilization of higher drug loadings of FNB, while the opposite trend was observed for ASDs of NAP. Even when higher drug loadings could be kinetically stabilized by adapting the process parameters, the improvement was limited, demonstrating that the phase behavior of these ASDs of FNB and NAP immediately after preparation was predominantly determined by the API-polymer-solvent combination rather than the process parameters applied.

Characterization of Silver Nanowire-Based Transparent Electrodes Obtained Using Different Drying Methods.

Metal-based transparent top electrodes allow electronic devices to achieve transparency, thereby expanding their application range. Silver nanowire (AgNW)-based transparent electrodes can function as transparent top electrodes, owing to their excellent conductivity and transmittance. However, they require a high-temperature drying process, which damages the bottom functional layers. Here, we fabricated two types of AgNW-based electrodes using the following three drying methods: thermal, room-temperature, and vacuum. Thereafter, we investigated the variation in their morphological, electrical, and optical characteristics as a function of the drying method and duration. When the AgNW-exposed electrode was dried at room temperature, it exhibited a high surface roughness and low conductivity, owing to the slow solvent evaporation. However, under vacuum, it exhibited a similar electrical conductivity to that achieved by thermal drying because of the decreased solvent boiling point and fast solvent evaporation. Conversely, the AgNW-embedded electrodes exhibited similar roughness values and electrical conductivities regardless of the drying method applied. This was because the polymer shrinkage during the AgNW embedding process generated capillary force and improved the interconnectivity between the nanowires. The AgNW-based electrodes exhibited similar optical properties regardless of the drying method and electrode type. This study reveals that vacuum drying can afford transparent top electrodes without damaging functional layers.

3D MXene Sponge: Facile Synthesis, Excellent Hydrophobicity, and High Photothermal Efficiency for Waste Oil Collection and Purification

Photothermally assisted superhydrophobic sponges play a vital role in the fields of waste oil collection, oil purification, and solar desalination. However, the widely reported superhydrophobic sponges with photothermal efficiency usually suffer from a post-/premodification process of harmful materials, high loading content of photothermal agents, and low photothermal efficiency. Herein, an MXene-based melamine sponge (MS) was facilely fabricated by hydrogen bonding interaction between the amino groups on the skeleton of the MS and the polar groups on the surface of the as-exfoliated 2D MXene Ti3C2Tx nanosheets. Interestingly, the as-fabricated MXene sponge exhibits excellent hydrophobicity and high photothermal efficiency under an extremely low loading of MXene Ti3C2Tx nanosheets (0.1 wt %). Moreover, the highly hydrophobic sponge also possesses a high oil absorption capacity as high as 176 times of its own weight and keeps stable under multiple absorption/desorption cycling tests. Surprisingly, the surface temperature of the MXene sponge can quickly reach 47 °C under illumination and has good reproducibility during multiple light on/off cycles. The excellent photothermal performance and large oil absorption capacity of the MXene sponge endow the highly hydrophobic sponge with fast solvent evaporation speed and high-purity waste oil collection (99.7 wt % dichloromethane) under illumination, which holds great promise for oil/water separation, leaked oil collection, and photo-driven waste oil collection and purification applications. It is envisioned that this work can open a new strategy for new designs of 3D multifunctional sponges for high-performance waste oil collection and purification.

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

(Invited) Rational Strategies for Efficient Perovskite Solar Cells

The past decade has witnessed tremendous advances in organometal halide perovskite solar cells (PSCs) due largely to the stellar set of optoelectronic properties of perovskites such as high absorption coefficient, long carrier diffusion length, and low electron–hole recombination rate constant. Notably, the organolead halide PSC has reached a certified champion power conversion efficiency (PCE) of 25.2%. Rapid progress in PCE has been realized by structure design, materials chemistry, process engineering, and device physics. In this talk, I will first introduce a meniscus-assisted solution printing method (MASP) towards large-grained perovskite films for morphology and crystallinity control. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparted the diffusion of perovskite solutes, thus facilitating the growth of micrometer-scale perovskite grains, leading to perovskite film with good crystallization and preferred orientation. This robust MASP strategy may in principle be easily extended to craft other solution-printed perovskite-based optoelectronics. Secondly, I will demonstrate an interesting interface engineering approach with 2D ambipolar black phosphorene (BP) for high-efficiency and stable PSCs. BP carries a stellar set of physical properties such as conveniently tunable bandgap and extremely high ambipolar carrier mobility. Concurrently enhanced carrier extraction at both electron transport layer/perovskite and perovskite/hole transport layer interfaces was achieved through judicious design and position of BP with tailored thickness as dual-functional nanomaterials. Thirdly, a spatial poling approach will be introduced for perovskite recrystallization towards preferred orientation, crystallinity, and morphology. Finally, the challenges facing the future development and commercialization of PSCs will be summarized and provided.

Fabrication of PVDF/PES nanofibers with unsmooth fractal surfaces by electrospinning: A general strategy and formation mechanism

Smaller fibers are welcome in many applications due to larger surface area, but there is a threshold for smallest fibers for a fixed spinning system. In order to further improve surface area, hierarchical structure is considered in this paper using electrospinning. A bi-solvent system is used in our experiment for fast solvent evaporation. Unsmooth nanofibers are obtained, and the formation mechanism is elucidated.

Structural variations of two-dimensional networks of 2,4,6-tris(4-bromophenyl)-1,3,5-triazine on Au(111) surface from solutions

Monolayers of 2,4,6-tris-(4-bromophenyl)-1,3,5-triazine (TBPT) on Au(111) surfaces were formed via solvent evaporation at different temperatures, and the molecular arrangement and intermolecular association type of these monolayers were probed by scanning tunneling microscopy. Intermolecular Br–N interactions were dominant in the phase formed at 70 °C (phase A), while phases with dominant Br–Br interactions were observed at higher temperatures, with a further temperature increase leading to dimerization. The additional heating of different monomer assemblies of the phase formed at 80 °C in air afforded phase A, which was thus concluded to be the most stable phase. These results suggest that the dimerization or polymerization of TBPT occurs through metastable phases other than phase A and requires fast solvent evaporation.

A Study of the Optical Properties and Fabrication of Coatings Made of Three-Dimensional Photonic Glass

Photonic crystals employ optical properties based on optical, physical, chemical, and material science. Nanosilica particles have a high specific surface area and are widely used in nanotechnology research and biomedical applications. In this study, nanosilica particles were fabricated by sol–gel methods, and the particle sizes of the silica nanoparticles were 280, 232, and 187 nm, based on dynamic light scattering. The silica nanoparticle suspension solution was heated to boiling for fast evaporation processing for self-assembly to fabricate three-dimensional photonic glass for structural color coatings. The sample had an adjustable structural color (red: 640 nm, green: 532 nm, and blue: 432 nm). The microstructures of various structure-colored samples were arranged, but there was a disordered solid arrangement of silica nanoparticles. These were not perfect opal-based photonic crystals. Compared to opal-based photonic crystals, the arrangement of silica nanoparticles was a glassy structure with a short-range order. Due to the accumulation of silica nanoparticle aggregates, samples displayed a stable colloidal film, independent of the viewing angle. In our study, the fast solvent evaporation in the self-assembly process led to the formation of a colloidal amorphous array, and it fitted the requirement for non-iridescence. Non-iridescent photonic glass with various colors was obtained. This type of color coating has wide potential applications, including reflective displays, colorimetric sensors, textiles, and buildings.

Effects of surface morphology of electrospun polystyrene fiber on its air filtration performance

A series of membranes, made from polystyrene microfibers and with different morphologies, were fabricated via electrospinning method in this study. In addition, not only porous fibers but also beaded fibers were obtained by adjusting the experimental temperature in a reasonable and appropriate way. Assisted by a high-speed camera, the images of jet behaviors at different experimental temperatures were captured for the purpose of in-depth and comprehensive understanding of formation mechanism of different fiber morphologies. Mono-disperse sodium chloride aerosol particles with different sizes and cigarette smoke were used, for the attainment of the objective of evaluation on the filtration performance of fabricated membranes. The experimental results showed that straight fiber with narrow pores on its surface can be obtained at 20°C spinning temperature because of the rapid jet motion and solvent evaporation, and also, beaded fibers can be fabricated in the situation of spinning temperature higher than 25°C due to the sudden change of surface tension resulted from the fast solvent evaporation. The porous straight fibers exhibited excellent filtration performance to cigarette smoke and aerosol containing particles of all sizes (99.76%, 99.92%, and 99.99% filtration efficiency for particles with sizes of 0.3 µm, 0.5 µm, and 1 µm, respectively).

Electrospinning and Mechanotropic Phenomena in Polymer Solutions

AbstractThe mechanism of electrospinning traditionally is related to fast evaporation of solvent from thin liquid jets of polymer solution observed in high‐voltage electric fields. Another mechanism, called mechanotropic spinning, is more reasonable for polymer solutions in solvents having low vapor pressure and high boiling temperature, that is, dimethylacetamide (DMAc), DMF, dimethyl sulfoxide (DMSO). Under elongation, the solution undergoes phase separation as a result of high‐speed stretching and the solvent reveals on the surface of the fiber without its complete evaporation. Microfibers obtained by mechanotropic spinning as well as by electrospinning of PAN solutions in DMSO and polyamidbenzamidazol in DMAc have stable droplets of the solvent on the fiber surface.

Rubbery nanofibers by co-electrospinning of almost immiscible NBR and PCL blends

The paper presents a simple method for producing rubbery nanofibers without additional crosslinking required. Electrospinning's fast solvent evaporation is able to induce in liquid NBR/PCL pairs thermoplastic elastomeric (TPE) structure that holds stable over time without any further processing. The slight relative solubility of the polymers pair promotes a homogeneous blend formation with low Tg regions of blended NBR/PCL, avoiding phase separation. Such nanofibers show also a PCL-like crystal phase that is surprisingly higher than plain PCL nanofibrous counterpart and seemingly promoted by NBR/PCL interaction at molecular scale. The obtained nanofibrous-TPE morphology is reproducible, stable with time up to at least two years and is detected in a wide range of blend compositions (up to 80%wt NBR). Such a morphology reflects in good mechanical properties, which are analysed with a fitting model taking into account nanofibrous structure. Its impressive fitting ability helps interpretation of tensile tests behavior, carried out via normalization of force data with respect to sample mass, highlighting the contribution of liquid rubber in improving both elastic modulus and properties at failure. Such rubbery nanofibers represent a cost-effective powerful tool for the production of advanced self-damping composite materials with improved overall mechanical properties.

The Nature of Conformational Polymorphism in the Crystals of Ph3Sb(O2CCH2–CH=CH2)2

Crystallization of the Ph3Sb(O2CCH2−CH=CH2)2 complex upon fast solvent (benzene) evaporation gives monoclinic crystals (I), whereas in the case of slow evaporation, triclinic crystals are formed (II). Also, monoclinic crystals are spontaneously transformed into triclinic crystals within 6 months. It was shown that the presence of voids near one carboxylate ligand in the monoclinic phase of Ph3Sb-(O2CCH2−CH=CH2)2 decreases the energy of intermolecular interactions and, as a consequence, leads to a conformational transition with a noticeable decrease in the crystal lattice energy. Thus, the presence of voids in the monoclinic phase crystal allows the formation of a thermodynamically more favorable conformation of the molecule in the crystal. Several structural models were determined for the Ph3Sb(O2CCH2−CH=CH2)2 complex (CIF files no. 1887561 (IIAM), model of non-interacting atoms; 1887562 (I), multipole model; 1887563 (IIIAM), model of non-interacting atoms; 1887564 (II), multipole model).

Scalable Fabrication of Highly Crystalline Organic Semiconductor Thin Film by Channel-Restricted Screen Printing toward the Low-Cost Fabrication of High-Performance Transistor Arrays.

Control over the morphology and crystallinity of small-molecule organic semiconductor (OSC) films is of key importance to enable high-performance organic optoelectronic devices. However, such control remains particularly challenging for solution-processed OSC devices because of the complex crystallization kinetics of small-molecule OSC materials in the dynamic flow of inks. Here, a simple yet effective channel-restricted screen-printing method is reported, which uses small-molecule OSCs/insulating polymer to yield large-grained small-molecule OSC thin-film arrays with good crystallization and preferred orientation. The use of cross-linked organic polymer banks produces a confinement effect to trigger the outward convective flow at two sides of the channel by the fast solvent evaporation, which imparts the transport of small-molecule OSC solutes and promotes the growth of small-molecule OSC crystals parallel to the channel. The small-molecule OSC thin-film array produced by screen printing exhibits excellent performance characteristics with an average mobility of 7.94 cm2 V-1 s-1 and a maximum mobility of 12.10 cm2 V-1 s-1 , which are on par with its single crystal. Finally, screen printing can be carried out using a flexible substrate, with good performance. These demonstrations bring this robust screen-printing method closer to industrial application and expand its applicability to various flexible electronics.