High-Throughput Screening of Nanoparticle-Stabilizing Ligands:Application to Preparing Antimicrobial Curcumin Nanoparticles by Antisolvent Precipitation

Water-dispersible curcumin nanoparticles were prepared by bottom-up antisolvent precipitation approach. A new high-throughput screening technique was developed for selecting appropriate ligands stabilizing the nanoparticles in aqueous medium and improving their performance. The initial set of twenty-eight potential stabilizing ligands was evaluated based on their capacity to improve curcumin dispersibility in aqueous medium. The performance of four promising ligands(amino acid proline, polyphenol tannic acid, polycation Polyquaternium 10, and neutral polymer polyvinylpyrrolidone) was tested in ultrasound-aided antisolvent precipitation trials. Using the selected stabilizing ligands diminished the average particle size from ca. 1,200 to 170–230 nm, reduced their dispersity, improved stability, and allowed reaching curcumin concentration of up to 1.4 m M in aqueous medium. Storage stability of the aqueous nanodispersions varied from 2 days to 2 weeks, depending on stabilizing ligand. Studying the effects of ionic strength and pH on size and f-potential of the particles suggested that electrostatic forces and hydrophobic interactions could be the major factors affecting their stability. The ligand-protected nanoparticles showed minimal inhibitory concentration of 400 or500 μM toward Escherichia coli. We suggest that the presented screening approach may be useful for preparing nanoparticles of various poorly water-soluble bioactive materials.

Controlling the Molecular Weight and Molecular Weight Distribution using Compressed CO_2 Antisolvent

Effect of CO2 dissolved in tetrahydrofuran (THF) on the polymerization of styrene in THF was studied at 333.2 K and different pressures. It was found that the molecular weight (MW) and MW distribution of the polystyrene (PS) could be controlled by pressure.

Green antisolvent additive engineering to improve the performance of perovskite solar cells

High-quality perovskite films with larger grain size and fewer defects is a prerequisite for highperformance perovskite solar cells(PSCs).Antisolvent-assisted crystallization is an effective approach to obtain compact and uniform perovskite films;however,the majority of antisolvents currently applied have strong toxicity,and the control of perovskite crystallization is not easy through single antisolvent.In this work,a green antisolvent of ethyl acetate(EA)with acetylacetone(AA)additive is used to fine-tune perovskite crystallization and passivate defect,which produces uniform and compact CH;NH;PbI;perovskite films having larger grain and fewer grain boundaries and reduced defect density.Meanwhile,the interfacial hydrophobic characteristic of the perovskite films is enhanced.At the optimized concentration of AA in EA,the power conversion efficiency(PCE)of the CH;NH;PbI;PSCs was improved from 19.2%to 21.1%and their stability in air was also enhanced.These results present a green antisolvent additive engineering strategy to enhance the crystallinity,passivate defects,and fabricate efficient and stable PSCs.

Controlling solid form and crystal habit of triphenylmethanol by antisolvent crystallization in a microfluidic device

Crystal habit and crystal form are critical elements in determining product properties and functions. In this work, we developed a microfluidic antisolvent crystallization technique to rapidly screen and accurately control the solid form and crystal habit of triphenylmethanol(Ph_(3)COH). This advanced technique separates the primary mixing of solutions from crystal formation(nucleation and growth) by introducing the microfluidic device, avoiding clogging in microchannels to obtain high-quality crystals. The results show that we can achieve controllable preparation of pure 2Ph_(3)COH·DMSO(DMSO solvate), pure Ph_(3)COH(form β), and mixed crystals with different mass ratios. Moreover, the microscale can prompt the DMSO solvate to grow into hexagonal sheet-like and bulk crystals. We can regulate the aspect ratio of hexagonal sheet-like crystals in binary solvents and control the crystal habit of the form β to transition between long needle-like shapes and short hexagonal prisms in DMF-H_(2)O. Meanwhile, we revealed that the solvent ratio, the antisolvent flow rate, and the initial concentration of Ph_(3)COH are the main factors affecting the solid form selectivity and morphology transition. Such a novel method would be considered as a promising technique to be extended to screen and control key crystallization parameters of other substances.

Photocatalytic activity of Eu-doped ZnO prepared by supercritical antisolvent precipitation route:When defects become virtues

The aim of this work is to determine the structural and optical properties of Eu-doped ZnO powders prepared by supercritical antisolvent precipitation route(SAS)and to correlate the physico-chemical features with the photocatalytic activity under UV light.Raman and EPR spectroscopy highlight the introduction of novel defects(mainly singly and doubly ionized oxygen vacancies,and oxygen interstitials)on the Eu-doped ZnO samples,which confer higher hydrophilicity to the doped samples with respect to bare ZnO,as evidenced by FT-IR analysis.Additionally,photoluminescence spectra show that the presence of Eu^(3+) totally quenches the visible light emission typical of bare ZnO,which mainly results from the recombination of photogenerated holes at defective sites.The prepared samples were tested both for the photocatalytic degradation of crystal violet dye(CV)and for the partial oxidation of ferulic acid under UV irradiation.The photocatalytic activity results evidence of a higher ability of Eu-doped photocatalysts to degrade CV and ferulic acid,while higher selectivity values towards vanillin are obtained in the presence of bare ZnO.The higher activity of Eu-doped ZnO photocatalysts is linked to the stabilization of photogenerated holes and to their higher hydrophilicity,both brought by the generation of defective sites induced by the presence of Eu^(3+) ions within the ZnO lattice.

PURIFICATION OF BILIRUBIN AND MICRO-PARTICLE FORMATION WITH SUPERCRITICAL FLUID ANTI-SOLVENT PRECIPITATION

1 INTRODUCTIONA supercritical fluid is one existing at temperatures and pressures above its criticalpoint values(T_c,p_c) [1].Supercritical fluid has unconventional thermophysical prop-erties,exhibiting higher density,greater compressibility,lower viscosity between the gasand liquid extremes.Its solute binary diffusion coefficient is considerably higher thanthat in liquids[2-4].Supercritical fluid extraction(SFE)has been suggested as a viablealternative to other separation technologies.

Strategies and methods for fabricating high quality metal halide perovskite thin films for solar cells

With the development of human society,the problems of environmental deterioration and energy shortage have become increasingly prominent.In order to solve these problems,metal halide perovskite solar cells(PSCs)stand out because of their excellent properties(i.e.,high optical absorption coefficient,long carrier lifetime and carrier diffusion length,adjustable band gap)and have been widely studied.PSCs with low cost,high power conversion efficiency and high stability are the future development trend.The quality of perovskite film is essential for fabricating PSCs with high performance.To provide a full picture of realizing high performance PSCs,this review focuses on the strategies for preparing high quality perovskite films(including antisolvent,Lewis acid-base,additive engineering,scaleable fabrication,strain engineering and band gap adjustment),and therefore to fabricate high performance PSCs and to accelerate the commercialization.

Estimation of secondary nucleation kinetics of benzoic acid in batch crystallizer

The nucleation and growth kinetics of benzoic acid were determined in a population balance model,describing the seeded batch antisolvent crystallization process.The process analytical technologies(PATs)were utilized to record the evolution of chord length distributions(CLDs)in solid phase together with the concentration decay in liquid phase,which provided essential experimental information for parameter estimation.The model was solved using standard method of moments based on the moments calculated from CLDs and solute concentration.A developed model,incorporating the nucleation and crystal growth as functions of both supersaturation and solvent composition,has been constructed by fitting the zeroth moment of particles and concentration trends.The determined kinetic parameters were consequently validated against a new experiment with a different flow rate,indicating that the developed model predicted crystallization process reasonably well.This work illustrates the strategy in construct a population balance model for further simulation,model-based optimization and control studies of benzoic acid in antisolvent crystallization.

Improving Ultraviolet Stability of Perovskite Solar Cells via Singlet Fission Down-Conversion

The instability of perovskite materials under continuous ultraviolet(UV)light irradiation and high sensitivity in humid environments remain obstacles to future commercialization.Especially,the photovoltaic performance of perovskite solar cells(PVSCs)is prone to decline under UV light exposure for sustained periods of time.However,in conventional methods,preventing UV light from entering PVSCs usually comes at the expense of reducing short circuit photocurrent(Jsc).Herein,the UV stability of PVSCs is modified by in-troducing a singlet fission down-conversion layer 6,13-bis(triisopropylsilylethynyl)pentacene(TIPS-PEN)via one-step anti-solvent method without sacrificing device efficiency.The introduction of down conversion layer can not only improve the Jsc by converting UV light into multiple excitons,but also enhance the open-circuit voltage(Voc)owing to a better matched energy level alignment at the perovskite/spiro-OMeTAD interface.Consequently,the TIPS-PEN incorporated PVSCs attain the champion power conversion effi-ciency(PCE)up to 22.92%accompanied with dramatically increased UV photostability which can retain 80%of its primitive PCE un-der continuous UV light soaking for 150 h.Moreover,the unencapsulated PVSCs with TIPS-PEN exhibit remarkable moisture stability which can sustain over 80%of the initial value under air conditions(50%relative humidity,25℃)after 1000 h.

Ligand exchange engineering of FAPbI_(3) perovskite quantum dots for solar cells

Formamidinium lead triiodide(FAPbI_(3))perovskite quantum dots(PQDs)show great advantages in photovoltaic applications due to their ideal bandgap energy,high stability and solution processability.The anti-solvent used for the post-treatment of FAPbI_(3) PQD solid flms signifcantly afects the surface chemistry of the PQDs,and thus the vacancies caused by surface ligand removal inhibit the optoelectronic properties and stability of PQDs.Here,we study the efects of diferent anti-solvents with diferent polarities on FAPbI_(3) PQDs and select a series of organic molecules for surface passivation of PQDs.The results show that methyl acetate could efectively remove surface ligands from the PQD surface without destroying its crystal structure during the post-treatment.The benzamidine hydrochloride(PhFACl)applied as short ligands of PQDs during the post-treatment could fll the A-site and X-site vacancies of PQDs and thus improve the electronic coupling of PQDs.Finally,the PhFACl-based PQD solar cell(PQDSC)achieves a power conversion efciency of 6.4%,compared to that of 4.63%for the conventional PQDSC.This work provides a reference for insights into the surface passivation of PQDs and the improvement in device performance of PQDSCs.

Manipulating the film morphology evolution toward green solvent-processed perovskite solar cells

High-performance perovskite solar cells(PVSCs)with low energy consumption and green processing are highly desired,but constrained by the difficulty in morphology control and the poor understanding on morphology evolution mechanisms.To address this issue,here we studied the effect of antisolvents on the perovskite film formation.We found that both the antisolvents and the perovskite composition affect the perovskite film morphology greatly via influencing the intermediate phase,and different perovskite compositions require different antisolvents to reach the optimal morphology.This provides the opportunity to achieve high-performance PVSCs with green antisolvent,that is,isopropanol(iPA)by changing the perovskite compositions,and leads to a powerconversionefficiency(PCE)of 21.50% for PVSCs based on MA_(0.6)FA_(0.4)PbI_(3).Further,we fabricated“fully green”PVSCs with all layers prepared by green sol-vents,and the optimal PCE can reach 19%,which represents the highest among PVSCs with full-green processing.This work provides insight into the perovskite morphology evolution and paves the way toward“green”processing PVSCs.

Supercritical fluids:Clean solvents for green chemistry

Supercritical fluids are becoming increasingly attractive as environmentally acceptable replacement for organic solvents in chemical reactions and material processing. This paper highlights some of the properties of supercritical fluids, especially supercritical CO2, which offer particular advantages for the handling of polymers, metal complexes and the environmentally more friendly synthesis and manufacture of chemicals. The paper includes same of the researches in University of Nottingham and a number of recent reviews which together provide a comprehensive introduction.

Supersaturation-driven self-assembly formation of ceftriaxone sodium spherulites:From amorphous form to spherulites

Drug particles with spherical morphology possess amazing advantages in terms of particle flowability,mechanical properties,drug solubility,and bioavailability.The growth mechanism of drug spherulite is of great importance for the preparation and regulation of spherulites.Herein,ceftriaxone sodium spherulites were fabricated by the antisolvent crystallization method using dropwise addition of ceftriaxone sodium solution to acetone.Online observation of the whole crystallization process combined with electron microscopy technique revealed the spherical growth process from amorphous form to spherulites.As the supersaturation of the crystallization system was adjusted,the ceftriaxone sodium crystals transformed from amorphous form to spherulites.In the process of antisolvent crystallization with acetone as antisolvent,when the theoretical supersaturation degree S was higher than 2.62,the crystallization system tended to appear amorphous form;when S was between 2.57 and 2.62,the amorphous form transformed into clustered spherulites;when S was less than 2.57,the surface of spherulites will be covered with flaky crystal,which transformed into urchin-like type.With the understanding of the spherical growth mechanism,the ceftriaxone sodium spherulites prepared in this research with modified supersaturation control had a low residue of antisolvent acetone,and the flowability was significantly improved.