Preparation and Crystal Modification of Ibuprofen-Loaded Solid Lipid Microparticles

An emulsion-congealing technique is used to prepare solid lipid microparticles （SLM） containing ibuprofen with glyceryl behenate, tripalmitin and beewax as excipients. The difference of the solubility parameters between the excipients and ibuprofen are used to analyze their compatibility. Both the solubility parameter analysis and the experimental results show that glyceryl behenate is the best among the three excipients. The solid particles disperse well in aqueous phase when the drug loading reaches 10% （relative to lipid only）. Glycerides exhibit marked polymorphism and their rapid rates of crystallization accelerate the formation of metastable crystal modification. The metastable crystal modification characterizes high drug loading capacity but less stability. Increasing the content of lipophilic drug in a lipid matrix facilitates the transformation of excipients to more stable polymorphic forms.

Continuous-flow synthesis and crystal modification of Pigment Red 53

In this study,a continuous-flow procedure containing four steps has been developed to synthesize Pigment Red 53 and modify its crystal structure.This process avoided the problems of conveying highly insoluble reaction intermediates by removing intermediate operating steps.After optimization,the overall yield of Pigment Red 53:1 reached 97.1%in the total residence time of 80 s by this diazotizationcoupling-laking-crystal transition process.From batch to continuous flow,the purity of products increased from 97.1%to 98.2%and the median diameter of pigment particles decreased from 14μm to 1.9μm.This process achieved a similar crystal transition effect in 18 s as in batch,producingα,δandνcrystals of Pigment Red 53:2 as expected.In conclusion,this continuous-flow procedure displays advantages in both synthesis and crystal transition,indicating another potential use for industrial application.

Effect of Solvent Annealing Temperature on Crystal Modifications and Phase Transition Behavior of Regioregular Poly(3-octylthiophene)

In present study, the effect of the solvent annealing temperature on the crystal modifications and the phase transition behavior of the subsequently dried poly（3-octylthiophene） （P3OT） film has been investigated by the combination of DSC, WAXD and FTIR techniques. When chloroform is employed as the solvent, it is unexpectedly found that form I and form II crystal modifications of P3OT could be respectively obtained by room temperature and low temperature annealing. Comparing to the mostly used solvent reported for preparing form II, i.e. carbon disulfide （CS2） which is toxic and corrosive, chloroform is less toxic and corrosive and more suitable for solution processing of P3OT. Therefore, this finding provides an alternative way to obtain form II. By temperature dependent IR spectroscopy, the structural evolution of P3OT during the form II to form I phase transition process has also been studied in detail.

Heterogeneous crystallization of Chlorzoxazone for modulating the physicochemical properties of crystals Author links open overlay panel

The polymer on modulating the crystal's habit is an evolving research in pharmaceutical crystallization.This study demonstrates the crystal habit modification of chlorzoxazone(CHZ)by heterogeneous crystallization(HC)in the binary solvent acetonitrile-ethanol(A-E(1:1))in the presence of polyvinylpyrrolidine(PVP)at concentrations of 0.50,0.75,and 1.00 wt%.The A-E(1:1)and PVP in HC experiments influenced to change the shape of crystals from needle to plate shape and reduced the crystal size producing a lower aspect ratio(in the range of 1.5-2.3).In the presence of PVP,the CHZ size distribution is 65-78μm which tends to enhance the powder flow-ability of CHZ crystals and as the PVP concentration increases,the nucleation rate decreases.The solubility of size-reduced CHZ crystals at different pH is found to be improved by 1.2-1.4 times.Hence,HC is deemed effective in modifying the physicochemical attributes of CHZ.

Absorption modification by laser irradiation in DKDP crystals

Laser-induced modification at 355 nm of deuterated potassium dihydrogen phosphate（DKDP） crystals following exposure to nanosecond（ns） and sub-ns laser irradiation is investigated in order to probe the absorption mechanism in damage initiation. Laser damage resistance is greatly improved by sub-ns laser conditioning,whereas only a little improvement occurred after ns laser conditioning at the same laser fluence. Moreover, scattering and transmittance variations after the two types of laser conditioning indicate similar reduction of linear absorption. However, by contrast, large differences on nonlinear absorption modification are discovered using Z-scan measurement. This characteristic absorption modification by laser irradiation provides evidence that a nonlinear absorption mechanism plays a key role in damage initiation at 355 nm.

Preparation and upconversion luminescence modification of YbPO4:Er3+inverse opal heterostructure

Photonic crystal heterostructures composed of YbPO4：Er^（3＋） inverse opal and polystyrene opal were prepared via a template-assisted process, which exhibited two photonic band gaps. The microstructure,phase and optical properties of photonic crystal heterostructures were investigated by x-ray diffraction,scanning electron microscopy, fluorescence spectroscopy, absorption spectroscopy, fluorescence lifetime,etc. The upconversion emission suppression caused by single photonic band gap from the following YbPO4：Er^（3＋） inverse opal or the upper opal was observed. The upconversion luminescence was strongly suppressed due to the two photonic band gap overlapping effect caused by the following YbPO4：Er^（3＋） inverse opal or the upper opal. The modified mechanisms of upconversion luminescence were discussed by the upconversion luminescence lifetime of YbPO4：Er^（3＋） photonic crystal heterostructures. The results demonstrated the modified upconversion luminescence is attributed to the photon trapping caused by Bragg reflection of photonic crystal heterostructures.