Flash Nanoprecipitation Research Articles

Development of an In Vitro Release Assay for Low-Density Cannabidiol Nanoparticles Prepared by Flash NanoPrecipitation.

Nanoparticle encapsulation is an attractive approach to improve the oral bioavailability of hydrophobic therapeutics. The high specific surface area of nanoparticle formulations, combined with the thermodynamically driven increased solubility of an amorphous drug core, promotes rapid drug dissolution. However, the physicochemical properties of the hydrophobic therapeutic can present obstacles to in vitro characterization of nanoparticle formulations. Namely, drugs with low density and high membrane binding affinity frustrate traditional analytical methods to monitor release kinetics from nanoparticles. In this work, cannabidiol (CBD) was encapsulated into nanoparticles with low polydispersity and high drug loading via Flash NanoPrecipitation (FNP), a scalable self-assembly process. Hydroxypropyl methylcellulose acetate succinate (HPMCAS) and lecithin were employed as amphiphilic particle stabilizers during the FNP process. However, the low density and high membrane binding affinity of the amorphous CBD nanoparticle core prevented the characterization of in vitro release kinetics by conventional methods. Released CBD could not be separated from intact nanoparticles by filtration or centrifugation. To address this challenge, an alternative approach is described to coencapsulate 6 nm hydrophobic Fe3O4 colloids with CBD during FNP. The Fe3O4 colloids were added at 33% by mass (approximately 20% by volume) to increase the density of the nanoparticles, resulting in particles with an average diameter of 160 nm (CBD-lecithin-Fe3O4) or 280 nm (CBD-HPMCAS-Fe3O4). This densification enabled the centrifugal separation of dissolved (released) CBD from unreleased CBD during the in vitro assay while avoiding the losses associated with a filtration step. The resulting nanoparticle formulations provided more rapid and complete in vitro dissolution kinetics than bulk CBD, representing a 6-fold improvement in dissolution compared to crystalline CBD. The coencapsulation of high-density Fe3O4 colloids to enable the separation of nanoparticles from release media is a novel approach to measuring in vitro release kinetics of nanoencapsulated low-density, hydrophobic drug molecules.

High throughput onion-like liposome formation with efficient protein encapsulation under flash antisolvent mixing

Achieving a high encapsulation efficiency and loading capacity of proteins in lecithin-based liposomes has always been a challenge. Here, we use Flash Nano-Precipitation (FNP) to produce liposomes and investigated the encapsulation of model protein (Bovine Serum Albumin, BSA). Through rapid turbulent mixing, we obtained liposomes with small size, low polydispersity, and good batch repeatability at a high production rate. We demonstrated that the bilayer of liposomes prepared solely using lecithin was defective, which led to the fusion, and increased size and polydispersity. When cholesterol was added to reach a lecithin-to-cholesterol molar ratio of 5:3, a compact bilayer formed to effectively inhibit liposome fusion. The encapsulation efficiency and loading capacity of BSA was as high as ∼ 68% and ∼ 6% in lecithin-cholesterol liposome, respectively, far exceeding the values reported in the literature. Further study by Quartz Crystal Microbalance with Dissipation (QCM-D) revealed that the highly effective encapsulation was due to the rapid mutual adsorption between BSA and defective/curved lecithin double layers during the liposome formation. Such rapid mutual adsorption leads to the layer-by-layer assembly and formation of onion-like compact liposome structure as revealed by Cryo-TEM. This simple FNP method provides a scalable manufacturing approach for liposomes with efficient protein encapsulation. The revealed adsorption mechanism between protein and lecithin bilayers could also serve as a guide for similar studies.

Fabrication of polysaccharide-stabilized zein nanoparticles by flash nanoprecipitation for doxorubicin sustained release

The effective fabrication of biocompatible and robust delivery carriers is an ongoing challenge in the nanomedicine for cancer treatments. Zein has proven Generally Recognized as Safe (GRAS) for clinical uses. However, its poor solubility and stability in aqueous media limits the broad applications of zein-based nanoparticles (NPs). In this study, a novel flash nanoprecipitation (FNP) was utilized to fabricate polysaccharide-stabilized zein NPs (polysaccharide/zein NPs) with small size and good stability over two weeks. The physicochemical properties of NPs were determined by the concentration and polysaccharides/zein weight ratio. FNP preparation at lower concentration (0.5 mg/mL) of polysaccharides and zein as well as the weight ratio of 1:1 led to the formation of smaller NPs with lower polydispersity. Alginate-stabilized zein NPs (AlgZ) exhibited excellent drug encapsulation efficiency (∼77.9%) and loading capacity up to ∼ 16.3% when they were used as carriers for doxorubicin (DOX). Specifically, DOX-loaded AlgZ showed sustained release of DOX, which enables the significantly prolonged cancer cell-killing and inhibits the burst release of DOX, thus exhibited great potential in the sustainable delivery of hydrophobic drugs.

Small-volume in vitro lipid digestion measurements for assessing drug dissolution in lipid-based formulations using SAXS

Lipid-based formulations improve the absorption capacity of poorly-water-soluble drugs and digestion of the formulation is a critical step in that absorption process. A recent approach to understanding the propensity for drug to dissolve in digesting lipid-based formulations couples an in vitro pH-stat lipolysis model to small-angle X-ray scattering (SAXS) by means of a flow-through capillary. However, the conventional pH-stat apparatus used to measure the extent of lipid digestion during such experiments requires digest volumes of 15–30 mL and drug doses of 50–200 mg, which is problematic for scarce compounds and can require excessive amounts of formulation reagents. This manuscript describes an approach to reduce the amount of material required for in vitro lipolysis experiments coupled to SAXS, for use in instances where the amount of drug or formulation medium is limited. Importantly, this was achieved while maintaining the pH stat conditions, which is critical for maintaining biorelevance and driving digestion to completion. The digestibility of infant formula with the poorly-water-soluble drugs halofantrine and clofazimine dispersed into it was measured as an exemplar paediatric-friendly lipid formulation. Halofantrine was incorporated in its powdered free base form and clofazimine was incorporated both as unformulated drug powder and as drug in nanoparticulate form prepared using Flash NanoPrecipitation. The fraction of triglyceride digested was found to be independent of vessel size and the incorporation of drug. The dissolution of the two forms of clofazimine during the digestion of infant formula were then measured using synchrotron SAXS, which revealed complete and partial solubilisation over 30 min of digestion for the powdered drug and nanoparticle formulations, respectively. The main challenge in reducing the volume of the measurements was in ensuring that thorough mixing was occurring in the smaller digestion vessel to provide uniform sampling of the dispersion medium.

Regulated preparation of celastrol-loaded nanoparticle by flash nanoprecipitation

Active components in Chinese medicine have shown great effects in treating various illness covering inflammation, obesity, diabetes and cancer. However, most of the active components, e.g. celastrol, suffer from the poor solubility and severe toxicity which limit their practical applications. One of the promising strategies is to load drugs in polymeric nanoparticles (NPs). While so far, most of the drug-loaded NPs were prepared by anti-solvent assembly or precipitation, which is a spontaneous and time-consuming process that provides thermodynamic equilibrium NPs with typically low particle yield and drug loading content. Herein, we apply a kinetically controlled method, namely Flash Nanoprecipitation (FNP), to construct celastrol-loaded NPs. Specifically, solvent streams containing celastrol and biodegradable Dextran-b-PLGA are mixed with anti-solvent streams in a multi-inlet vortex mixer. The fast mixing and co-precipitation provide NPs with well-defined particle radius (80–160 nm, PDI <0.2) and structure, high celastrol loading content (11–63%) and tunable release as well. The regulation is achieved by manipulating the drug concentration and stream velocity (defined as Reynolds number). Moreover, the obtained NPs display efficient inhibition of A549 lung cancer cells, whereas notably reduced cytotoxicity to HL-7702 normal liver cell lines. Our study validates advantages of FNP method on preparing Chinese medicine drug-loaded NPs, and the achieved regulation on particle properties show great potential for boosting the application of Chinese medicine active components.

SANS Study of PPPO in Mixed Solvents and Impact on Polymer Nanoprecipitation.

We investigate the conformation of poly(2,6-diphenyl-p-phenylene oxide) (PPPO) in good and mixed solvents by small-angle neutron scattering (SANS) across its ternary phase diagram. Dichloromethane was selected as a “good” solvent and heptane as a “poor” solvent whose addition eventually induces demixing and polymer precipitation. Below the overlap concentration c*, the polymer conformation is found to be well described by the polymer-excluded volume model and above by the Ornstein–Zernike expression with a correlation length ξ which depends on the concentration and solvent/nonsolvent ratio. We quantify the decrease in polymer radius of gyration Rg, increase in ξ, and effective χ parameter approaching the phase boundary. Upon flash nanoprecipitation, the characteristic particle radius (estimated by scanning electron microscopy, SEM) is found to scale with polymer concentration as well as with nonsolvent content. Significantly, the solution volume per precipitated particle remains nearly constant at all polymer concentrations. Overall, our findings correlate ternary solution structure with the fabrication of polymer nanoparticles by nonsolvent-induced phase separation and precipitation.

Enhanced oxygen reduction reaction performance of Co@N–C derived from metal-organic frameworks ZIF-67 via a continuous microchannel reactor

Traditional methods of preparing metal-organic frameworks (MOFs) compounds have the disadvantages such as poor dispersion, inefficient and discontinuous process. In this work, microchannel reactor is used to prepare MOFs-derived zeolite-imidazole material via flash nanoprecipitation to form ZIF-67 + PEI(FNP), which reduces the MOF synthesis time down to millisecond time interval while keeping the synthesized ZIF-67 + PEI(FNP) highly dispersed. The Co@N–C(FNP)catalyst obtained by flash nanoprecipitation and carbonization has a higher Co content and thus more active sites for oxygen reduction reaction than the Co@N–C(DM) catalyst prepared by direct mixing method. Electrochemical tests show that the Co@N–C(FNP) catalyst prepared by this method has excellent oxygen reduction performance, good methanol resistance and high stability. The onset potential and half-wave potential of Co@N–C(FNP) are 0.92 VRHE and 0.83 VRHE, respectively, which are higher than that of Co@N–C(DM) (Eonset = 0.90 VRHE and E1/2 = 0.83 VRHE). Moreover, the Zn-air battery assembled with Co@N–C(FNP) as the cathode catalyst has high open circuit voltage, high power density and large specific capacity. The performance of these batteries has been comparable to that of Pt/C assembled batteries. Density functional theory (DFT) calculations confirm that the Co (220) crystal plane present in Co@N–C(FNP) have stronger adsorption energy than that of Co (111) crystal plane in Co@N–C(DM), leading to better electrocatalytic performance of the former.

Antioxidant Response Activating nanoParticles (ARAPas) localize to atherosclerotic plaque and locally activate the Nrf2 pathway.

Atherosclerotic disease is the leading cause of death world-wide with few novel therapies available despite the ongoing health burden. Redox dysfunction is a well-established driver of atherosclerotic progression; however, the clinical translation of redox-based therapies is lacking. One of the challenges facing redox-based therapies is their targeted delivery to cellular domains of redox dysregulation. In the current study, we sought to develop Antioxidant Response Activating nanoParticles (ARAPas), encapsulating redox-based interventions, that exploit macrophage biology and the dysfunctional endothelium in order to selectively accumulate in atherosclerotic plaque. We employed flash nanoprecipitation (FNP) to synthesize bio-compatible polymeric nanoparticles encapsulating the hydrophobic Nrf2 activator drug, CDDO-Methyl (CDDOMe-ARAPas). Nuclear factor erythroid 2-related factor 2 (Nrf2)-activators are a promising class of redox-active drug molecules whereby activation of Nrf2 results in the expression of several antioxidant and cyto-protective enzymes that can be athero-protective. In this study, we characterize the physicochemical properties of CDDOMe-ARAPas as well as confirm their in vitro internalization by murine macrophages. Drug release of CDDOMe was determined by Nrf2-driven GFP fluorescence. Moreover, we show that these CDDOMe-ARAPas exert anti-inflammatory effects in classically activated macrophages. Finally, we show that CDDOMe-ARAPas selectively accumulate in atherosclerotic plaque of two widely-used murine models of atherosclerosis: ApoE-/- and LDLr-/- mice, and are capable of increasing gene expression of Nrf2-transcriptional targets in the atherosclerotic aortic arch. Future work will assess the therapeutic efficacy of intra-plaque Nrf2 activation with CDDOMe-ARAPas to inhibit atherosclerotic plaque progression. Overall, our present studies underline that targeting of atherosclerotic plaque is an effective means to enhance delivery of redox-based interventions.

Polymer Concentration Maximizes Encapsulation Efficiency in Electrohydrodynamic Mixing Nanoprecipitation

Encapsulation in self-assembled block copolymer (BCP) based nanoparticles (NPs) is a common approach to enhance hydrophobic drug solubility, and nanoprecipitation processes in particular can yield high encapsulation efficiency (EE). However, guiding principles for optimizing polymer, drug, and solvent selection are critically needed to facilitate rapid design of drug nanocarriers. Here, we evaluated the relationship between drug-polymer compatibility and concentration ratios on EE and nanocarrier size. Our studies employed a panel of four drugs with differing molecular structures (i.e., coumarin 6, dexamethasone, vorinostat/SAHA, and lutein) and two BCPs [poly(caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) and poly(styrene)-b-poly(ethylene oxide) (PS-b-PEO)] synthesized using three nanoprecipitation processes [i.e., batch sonication, continuous flow flash nanoprecipitation (FNP), and electrohydrodynamic mixing-mediated nanoprecipitation (EM-NP)]. Continuous FNP and EM-NP processes demonstrated up to 50% higher EE than batch sonication methods, particularly for aliphatic compounds. Drug-polymer compatibilities were assessed using Hansen solubility parameters, Hansen interaction spheres, and Flory Huggins interaction parameters, but few correlations were EE observed. Although some Hansen solubility (i.e., hydrogen bonding and total) and Flory Huggins interaction parameters were predictive of drug-polymer preferences, no parameter was predictive of EE trends among drugs. Next, the relationship between polymer: drug molar ratio and EE was assessed using coumarin 6 as a model drug. As polymer:drug ratio increased from &amp;lt;1 to 3–6, EE approached a maximum (i.e., ∼51% for PCL BCPs vs. ∼44% PS BCPs) with Langmuir adsorption behavior. Langmuir behavior likely reflects a formation mechanism in which drug aggregate growth is controlled by BCP adsorption. These data suggest polymer:drug ratio is a better predictor of EE than solubility parameters and should serve as a first point of optimization.

Clofazimine-Loaded Mucoadhesive Nanoparticles Prepared by Flash Nanoprecipitation for Strategic Intestinal Delivery.

This study was undertaken to develop novel mucoadhesive formulations of clofazimine (CFZ), a drug candidate for the treatment of cryptosporidiosis, with the aim of strategic delivery to the small intestine, the main site of the disease parasites. CFZ-loaded nanoparticles (nCFZ) coated with non-biodegradable anionic polymer (nCFZ/A) and biodegradable anionic protein complex (nCFZ/dA) were prepared by Flash NanoPrecipitation (FNP) and evaluated for their physicochemical and biopharmaceutical properties. The mean diameters of nCFZ/A and nCFZ/dA were ca. 90 and 240nm, respectively, and they showed narrow size distributions and negative ζ-potentials. Both formulations showed higher solubility of CFZ in aqueous solution than crystalline CFZ. Despite their improved dispersion behaviors, both formulations exhibited significantly lower diffusiveness than crystalline CFZ in a diffusion test using artificial mucus (AM). Quartz crystal microbalance analysis showed that both formulations clearly interacted with mucin, which appeared to be responsible for their reduced diffusiveness in AM. These results suggest the potent mucoadhesion of nCFZ/A and nCFZ/dA. After the oral administration of CFZ samples (10mg-CFZ/kg) to rats, nCFZ/dA and nCFZ/A exhibited a prolongation in Tmax by 2 and >9h, respectively, compared with crystalline CFZ. At 24h after oral doses of nCFZ/A and nCFZ/dA with mucoadhesion, there were marked increases in the intestinal CFZ concentration (4-7 fold) compared with Lamprene®, a commercial CFZ product, indicating enhanced CFZ exposure in the small intestine. The use of FNP may produce mucoadhesive CFZ formulations with improved intestinal exposure, possibly offering enhanced anti-cryptosporidium therapy.

Sustained IGF-1 delivery ameliorates effects of chronic denervation and improves functional recovery after peripheral nerve injury and repair

Functional recovery following peripheral nerve injury is limited by progressive atrophy of denervated muscle and Schwann cells (SCs) that occurs during the long regenerative period prior to end-organ reinnervation. Insulin-like growth factor 1 (IGF-1) is a potent mitogen with well-described trophic and anti-apoptotic effects on neurons, myocytes, and SCs. Achieving sustained, targeted delivery of small protein therapeutics remains a challenge. We hypothesized that a novel nanoparticle (NP) delivery system can provide controlled release of bioactive IGF-1 targeted to denervated muscle and nerve tissue to achieve improved motor recovery through amelioration of denervation-induced muscle atrophy and SC senescence and enhanced axonal regeneration. Biodegradable NPs with encapsulated IGF-1/dextran sulfate polyelectrolyte complexes were formulated using a flash nanoprecipitation method to preserve IGF-1 bioactivity and maximize encapsulation efficiencies. Under optimized conditions, uniform PEG-b-PCL NPs were generated with an encapsulation efficiency of 88.4%, loading level of 14.2%, and a near-zero-order release of bioactive IGF-1 for more than 20 days in vitro. The effects of locally delivered IGF-1 NPs on denervated muscle and SCs were assessed in a rat median nerve transection-without- repair model. The effects of IGF-1 NPs on axonal regeneration, muscle atrophy, reinnervation, and recovery of motor function were assessed in a model in which chronic denervation is induced prior to nerve repair. IGF-1 NP treatment resulted in significantly greater recovery of forepaw grip strength, decreased denervation-induced muscle atrophy, decreased SC senescence, and improved neuromuscular reinnervation.

Nanostructure Controlled by Flash Nanoprecipitation and Application on Agriculture

Nanostructure Controlled by Flash Nanoprecipitation and Application on Agriculture

Control and Preparation of Quaternized Chitosan and Carboxymethyl Chitosan Nanoscale Polyelectrolyte Complexes Based on Reactive Flash Nanoprecipitation.

Nanoscale polyelectrolyte complex materials have been extensively investigated for their promising application in protocell, drug carriers, imaging, and catalysis. However, the conventional preparation approach involving positive and negative polyelectrolytes leads to large size, wide size distribution, instability, and aggregation due to the nonhomogeneous mixing process. Herein, we employ reactive flash nanoprecipitation (RFNP) to control the mixing and preparation of the nanoscale polyelectrolyte complex. With RFNP, homogeneous mixing complexation between oppositely charged chitosan derivatives could be achieved, resulting in stable nanoscale complexes (NCs) with controllable size and narrow size distribution. The smallest size of NCs is found at specific pH due to the maximum attraction of positive and negative molecules of chitosan. The size can be modulated by altering the volumetric flow rates of inlet streams, concentration, and charge molar ratio of two oppositely charged chitosan derivatives. The charge molar ratio is also tuned to create NCs with positive and negative shells. There is no significant variation in the size of NCs produced at different intervals of time. This method allows continuous and tunable NC production and could have the potential for fast, practical translation.

Preparation of Aspirin Nanosuspension by Antisolvent Precipitation Method

Preparation of Aspirin Nanosuspension by Antisolvent Precipitation Method

Precision Polymer Particles by Flash Nanoprecipitation and Microfluidic Droplet Extraction

We comparatively review two versatile approaches employed in the precise formation of polymer particles, with length scales from 10s of nm to to 100s μm, from ternary polymer(s), solvent and nonsolvent mixtures. Flash nanoprecipitation (FNP) utilizes an opposing jet arrangement to mix a dilute polymer solution and a nonsolvent in confinement, inducing a rapid (∼millisecond) chain collapse and eventual precipitation of nanoparticles (NPs) of 10–1000 nm diameters. FNP of polymer mixtures and block copolymers can yield a range of multiphase morphologies with various functionalities. While droplet solvent extraction (DSE) also involves the exposure of a polymer solution to a nonsolvent, in this case the polymer solution is templated into a droplet prior to solvent extraction, often using microfluidics, resulting in polymer particles of 1–1000 μm diameter. Droplet shrinkage and solvent exchange are generally accompanied by a series of processes including demixing, coarsening, phase inversion, skin formation, and kinetic arrest, which lead to a plethora of possible internal and external particle morphologies. In the absence of external flow fields, DSE corresponds effectively to nonsolvent induced phase separation (NIPS) in a spherical geometry. In this review, we discuss the requirements to implement both approaches, detailing consequences of ternary solution phase behavior and the interplay of the various processes underpinning particle formation and highlighting the similarities, differences, and complementarity of FNP and DSE. In addition to reviewing previous work in the field, we report comparative experimental results on the formation of polystyrene particles by both approaches, emphasizing the importance of solution phase behavior in process design.

Preparation and characterization of nanoparticles from field pea starch by batch versus continuous nanoprecipitation techniques

Starch nanoparticles (SNPs) were produced by batch nanoprecipitation (BNP) and continuous techniques such as flash nanoprecipitation (FNP) and microfluidic nanoprecipitation (MNP). Water and absolute ethanol were used as solvent (S) and antisolvent (AS), respectively, while they can be mixed either dropwise or direct mixing at once. The effects of processing parameters on SNPs properties were investigated including antisolvent/solvent (AS/S) ratio, starch concentration, mixing technique and flow rate. Field emission scanning electronic microscopy (FE-SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectrophotometry were used to characterize the nature of molecular interactions and structure within SNP. The results indicated that BNP can be successfully achieved in a shorter time with a smaller particle size and narrower particle size distribution, even at AS/S ratio as low as 1:1, using direct mixing at once method than the dropwise technique. Increasing the starch concentration at a fixed AS/S ratio of 1:1, initially decreased the average particle size from 135 (2.5 mg/mL) to 123 nm (10 mg/mL), and then increased to ~430 nm (50 mg/mL). Based on the optimized conditions for BNP, continuous methods (FNP and MNP), were investigated in the commercial prospective for potential scale up processing. Under the same conditions, FNP involving confined impinging jet mixer (CIJM) at an overall flow rate of 60 mL/min, had a uniform spherical shape with particle size of ~100 nm, which was superior to all other techniques investigated. Regardless of the techniques used, all SNPs had an amorphous structure with short-range molecular order.

Pi-stacking Enhances Stability, Scalability of Formation, Control over Flexibility and Circulation Time of Polymeric Filaments.

Self-assembling filomicelles (FM) are of great interest to nanomedicine due to their structural flexibility, extensive systemic circulation time, and amenability to unique "cylinder-to-sphere" morphological transitions. However, current fabrication techniques for FM self-assembly are highly variable and difficult to scale. Here, we demonstrate that tetrablock copolymers composed of poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) diblocks linked by a pi-stacking perylene bisimide (PBI) moiety permit rapid, scalable, and facile assembly of FM via the flash nanoprecipitation (FNP) method. Co-assembling the tetrablocks and PEG-b-PPS diblocks at different molar ratios resulted in mixed PBI-containing FM (mPBI-FM) with tunable length and flexibility. The flexibility of mPBI-FM can be optimized to decrease uptake by macrophages in vivo, leading to increased circulation time versus (-)PBI-FM without PBI tetrablocks after intravenous administration in mice. While PEG-b-PPS diblocks form FM within a narrow range of hydrophilic weight fractions, incorporation of pi-stacking PBI groups expanded this range to increase favorability of FM assembly. Furthermore, the aggregation-dependent fluorescence of PBI shifted during oxidation-induced "cylinder-to-sphere" transitions of mPBI-FM into micelles, resulting in a distinct emission wavelength for filamentous versus spherical nanostructures. Thus, incorporation of pi-stacking allows for rapid, scalable assembly of FM with tunable flexibility and stability for theranostic and nanomedicine applications.

Facile controlling internal structure of β-carotene-loaded protein nanoparticles by Flash Nanoprecipitation

As one of the most significant carotenoids, β-carotene is applied widely in human nutrition and reducing incidence of chronic diseases, due to its highest provitamin A activity. The nano-carrier technology has been used to prepare β-carotene-loaded nanoparticle to improve bioavailability in functional food and beverage, as β-carotene is high hydrophobic. However, the control of the internal structure of β-carotene-loaded nanoparticle is not investigated and the relationship between internal structure and release have not been well understood. Here, we report a kinetic-controlled method, Flash Nanoprecipitation, which allows to control the internal structure of β-carotene-loaded nanoparticle, from compact core-shell structure with high packing density to loose structure with low packing density. The different structures show obviously different release behavior: loose structure associates with high release of β-carotene, while compact structure associates with slight release. TEM and dynamic-static light scattering are employed to characterize the morphology and internal structure, respectively. The developed strategy could be helpful for practical application of β-carotene nanoparticles with tunable properties.

Modification of NiFe layered double hydroxide by lanthanum doping for boosting water splitting

Electrolysis of water can directly produce hydrogen and oxygen, providing the possibility to expand the production of high purity hydrogen. It consists of two half reactions: anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER). Developing electrocatalysts is an effective way to improve the efficiency of water splitting. Two-dimensional layered double hydroxides (LDHs), as abundant, cheap and bifunctional catalysts, have the similar electrocatalytic performance as precious metals, thereby receiving pretty much attention. Here, a facile flash nano-precipitation (FNP) synthetic strategy is presented to acquire NiFe LDH. Based on it, La-NiFe LDH is obtained by adding rare earth element lanthanum (La) with different contents using mechanical method. Owing to the synergistic effect between La and laminate metal, La-NiFe LDH shows an excellent water splitting performance, where the overpotential of OER activity is 340 mV and HER performance is 57 mV at the current density of 10 mA∙cm−2. Combined with characterization, performance and theoretical calculation, it is confirmed that the electronic structure of LDH laminates can be adjusted by La doping, reducing the Gibbs free energy in the reaction accordingly, which is beneficial to the water splitting reaction. In general, an easy-to-implement and rapid preparation method provides a convenient and green way to obtain water splitting catalyst with enhanced performance.

Engineering Nanoparticulate Organic Photocatalysts via a Scalable Flash Nanoprecipitation Process for Efficient Hydrogen Production

AbstractDirectly converting sunlight into hydrogen fuels using particulate photocatalysts represents a sustainable route for clean energy supply. Organic semiconductors have emerged as attractive candidates but always suffer from optical and exciton recombination losses with large exciton “dead zone” inside the bulk material, severely limiting the catalytic performance. Herein, we demonstrate a facile strategy that combines a scalable flash nanoprecipitation (FNP) method with hydrophilic soluble polymers (PC‐PEG5 and PS‐PEG5) to prepare highly efficient nanosized photocatalysts without using surfactants. Significantly, a 70‐fold enhancement of hydrogen evolution rate (HER) is achieved for nanosized PC‐PEG5, and the FNP‐processed PS‐PEG5 shows a peak HER rate of up to 37.2 mmol h−1 g−1 under full‐spectrum sunlight irradiation, which is among the highest results for polymer photocatalysts. A scaling‐up production of nanocatalyst is demonstrated with the continuously operational FNP.