Modest exciton diffusion lengths dictate the need for nanostructured bulk heterojunctions in organic photovoltaic (OPV) cells; however, this morphology compromises charge collection. Here, we reveal ...rapid exciton diffusion in films of a fused-ring electron acceptor that, when blended with a donor, already outperforms fullerene-based OPV cells. Temperature-dependent ultrafast exciton annihilation measurements are used to resolve a quasi-activationless exciton diffusion coefficient of at least 2 × 10–2 cm2/s, substantially exceeding typical organic semiconductors and consistent with the 20–50 nm domain sizes in optimized blends. Enhanced three-dimensional diffusion is shown to arise from molecular and packing factors; the rigid planar molecular structure is associated with low reorganization energy, good transition dipole moment alignment, high chromophore density, and low disorder, all enhancing long-range resonant energy transfer. Relieving exciton diffusion constraints has important implications for OPVs; large, ordered, and pure domains enhance charge separation and transport, and suppress recombination, thereby boosting fill factors. Further enhancements to diffusion lengths may even obviate the need for the bulk heterojunction morphology.
We report a simple, low‐symmetry 2‐(1‐(pyridine‐4‐methyl)‐1H‐1,2,3‐triazol‐4‐yl)pyridine ligand that has both monodentate and bidentate binding sites. With platinum(II) and/or palladium(II) ions, two ...examples of a new nona‐nuclear metallo‐assembly have been accessed. These complexes were characterized by NMR spectroscopy, electrospray mass spectrometry (ESI‐MS), and in key cases, X‐ray crystallography. The cages possess three clefts comprised of planar cationic panels. This structural feature enables the binding of planar aromatic guests such as anthracene. More interestingly, the heterometallic assembly was able to catalyze the light‐induced 4+2 cycloaddition of anthracene with singlet oxygen.
A catalytic donut: A heterometallic (PdII/PtII) nona‐nuclear metallo‐cage binds anthracene molecules and catalyzes their conversion into endoperoxides through singlet oxygen production in the presence of light.
Metallosupramolecular architectures are beginning to be exploited for a range of applications including drug delivery, catalysis, molecular recognition, and sensing. For the most part these ...achievements have been made with high-symmetry metallosupramolecular architectures composed of just one type of ligand and metal ion. Recently, considerable efforts have been made to generate metallosupramolecular architectures that are made up of multiple different ligands and/or metals ions in order to obtain more complex systems with new properties. Herein we show that the addition of an electron-rich 2-amino-substituted tripyridyl ligand, 2,6-bis(pyridin-3-ylethynyl)pyridine (2A-tripy), to a solution of the Pd2(tripy)4(4+) cage resulted in the clean generation of a heteroleptic Pd2(tripy)2(2A-tripy)2(4+) architecture. The formation of the mixed-ligand cage Pd2(tripy)2(2A-tripy)2(4+) was confirmed using (1)H NMR spectroscopy, diffusion-ordered spectroscopy, and rotating-frame nuclear Overhauser effect spectroscopy and high-resolution electrospray ionization mass spectrometry. Density functional theory calculations suggested the cis isomer was more stable that the trans isomer. Additionally, the calculations indicated that the heteroleptic palladium(II) cages are kinetically metastable intermediates rather than the thermodynamic product of the reaction. Competition experiments supported that finding and showed the cages are long-lived in solution at room temperature. Finally, it was shown that the addition of 2A-tripy to a range of preformed Pd2(Ltripy)4(4+) cages cleanly generated the mixed-ligand systems. Three other systems displaying different exo and endo functionalities within the cage assembly were generated, suggesting that this method could be applied to synthesize a range of highly functionalized heteroleptic cis-Pd2(La)2(Lb)2(4+) cages.
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Low-frequency Raman (LFR) spectroscopy probes vibrational modes related to long-range order (i.e., crystallinity) that can provide unique information on the solid-state/structural ...characteristics among other properties. Furthermore, the recent advancements in instrumentation (most notably, narrow wavelength band filters) and data analysis has allowed to overcome some of the previous limitations of this technique. In fact, LFR spectroscopy has now enjoyed a surge in popularity with applications found in many research areas. This mini-review article provides a comprehensive summary of established and exciting new LFR applications for pharmaceutical analysis. Aspects of the underlying theory, instrumentation and data analysis (including application of chemometric and computational techniques) are also discussed in detail.
Solid state of inhalable high dose powders Adhikari, Bishal Raj; Gordon, Keith C.; Das, Shyamal C.
Advanced drug delivery reviews,
October 2022, 2022-10-00, 20221001, Letnik:
189
Journal Article
Recenzirano
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•Preparation techniques play an important role in defining solid state of powders.•Amorphous powders exhibit both poor physical and chemical stability.•The impact of solid state on ...aerosolization of high dose powder is still unclear.•Aerosolization stability of amorphous powders can be improved via surface enrichment or co-amorphization with hydrophobic excipient/API.•Solid dispersions, mesoporous systems, or co-amorphous systems might be prepared to stabilize amorphous states.
High dose inhaled powders have received increased attention for treating lung infections. These powders can be prepared using techniques such as spray drying, spray-freeze drying, crystallization, and milling. The selected preparation technique is known to influence the solid state of the powders, which in turn can potentially modulate aerosolization and aerosolization stability. This review focuses on how and to what extent the change in solid state of high dose powders can influence aerosolization. It also discusses the commonly used solid state characterization techniques and the application of potential strategies to improve the physical and chemical stability of the amorphous powders for high dose delivery.
One of the challenges in drug development today is that many new drug candidates are poorly water-soluble, and one of the approaches to overcome this problem is to transfer a crystalline drug into ...its amorphous form, thus increasing dissolution rate and apparent solubility of the compound. In this study, a coamorphous drug/drug combination between the two nonsteroidal anti-inflammatory drugs, naproxen and γ-indomethacin, was prepared and investigated. At molar ratios of 2:1, 1:1 and 1:2, the drugs were quench cooled in order to obtain a coamorphous binary phase. Physical stability was examined at 277.15 and 298.15 K under dry conditions (phosphorus pentoxide) and analyzed with X-ray powder diffraction (XRPD). Intrinsic dissolution testing was carried out to identify dissolution advantages of the coamorphous form over its crystalline counterparts or amorphous indomethacin. Fourier transform infrared spectroscopy (FTIR) was used for analyses at the molecular level to detect potential molecular interactions. Differential scanning calorimetry (DSC) thermograms were employed to assess the glass transition temperatures (T g), and the results were compared with predicted T gs from the Gordon–Taylor equation. Results showed that naproxen could be made amorphous in combination with indomethacin while this was not possible with naproxen alone. Peak shifts in the FTIR spectra indicated molecular interactions between both drugs, and it is suggested that the two drugs formed a heterodimer. Therefore, samples at the 1:2 and 2:1 ratios showed recrystallization of the excess drug upon storage whereas the 1:1 ratio samples remained amorphous. Intrinsic dissolution testing showed increased dissolution rate of both drugs in the coamorphous form as well as a synchronized release for the 1:1 coamorphous blend. All T gs displayed negative deviations from the Gordon–Taylor equation with the 1:1 ratio showing the largest deviation. In a novel approach of predicting the glass transition temperature, the 1:1 drug ratio was inserted as an individual component in the Gordon–Taylor equation with the excess drug representing the second compound. This approach resulted in a good fit to the experimentally determined T gs.
Moving Droplets in 3D Using Light Xiao, Yang; Zarghami, Sara; Wagner, Klaudia ...
Advanced materials,
August 29, 2018, Letnik:
30, Številka:
35
Journal Article
Recenzirano
Odprti dostop
The emulation of the complex cellular and bacterial vesicles used to transport materials through fluids has the potential to add revolutionary capabilities to fluidic platforms. Although a number of ...artificial motile vesicles or microdroplets have been demonstrated previously, control over their movement in liquid in 3D has not been achieved. Here it is shown that by adding a chemical “fuel,” a photoactive material, to the droplet, it can be moved in any direction (3D) in water using simple light sources without the need for additives in the water. The droplets can be made up of a range of solvents and move with speeds as high as 10.4 mm s−1 toward or away from the irradiation source as a result of a light‐induced isothermal change in interfacial tension (Marangoni flow). It is further demonstrated that more complex functions can be accomplished by merging a photoactive droplet with a droplet carrying a “cargo” and moving the new larger droplet to a “reactor” droplet where the cargo undergoes a chemical reaction. The control and versatility of this light‐activated, motile droplet system will open up new possibilities for fluidic chemical transport and applications.
The light‐controlled isothermal 3D movement in water of organic droplets containing a photoactive material is demonstrated. The droplets can be moved toward or away from light and can be merged with other droplets to pick up “cargo” that can undergo a chemical reaction through droplet–droplet interactions.
Low-frequency peaks in the Raman spectra of amorphous poly(ether ether ketone) (PEEK) were investigated. An amorphous sample with zero crystallinity, as confirmed by wide-angle X-ray diffraction, was ...used in this study. In a previous study, two peaks were observed in the low-frequency Raman spectra of the crystallized samples. Among these, the peaks at 135 cm−1 disappeared for the amorphous sample. Meanwhile, for the first time, the peak at 50 cm−1 was observed in the crystallized sample. Similar to the peak at 135 cm−1, the peak at 50 cm−1 disappeared in the amorphous state, and its intensity increased with increasing crystallinity. The origins of the two peaks were associated with the Ph-CO-Ph-type intermolecular vibrational modes in the simulation. This suggests that the Ph-CO-Ph vibrational mode observed in the low-frequency region of PEEK was strongly influenced by the intermolecular order.
Raman mapping of pharmaceuticals Gordon, Keith C.; McGoverin, Cushla M.
International journal of pharmaceutics,
09/2011, Letnik:
417, Številka:
1
Journal Article
Recenzirano
A review of several pharmaceutical applications of Raman mapping for distributional assessment of various drug delivery systems.
Raman spectroscopy may be implemented through a microscope to provide ...fine scale axial and lateral chemical maps. The molecular structure of many drugs makes Raman spectroscopy particularly well suited to the investigation of pharmaceutical systems. Chemometric methods currently used to assess bulk Raman spectroscopic data are typically applied to Raman mapping data from pharmaceuticals; few reports exist where the spatial information inherent to a mapped dataset is used for the calculation of chemical maps. Both univariate and multivariate methods have been applied to Raman mapping data to determine the distribution of active pharmaceutical ingredients (APIs) in tablets, solid dispersions for increased solubility and controlled release devices. The ability to axially (depth) profile using Raman mapping has been used in studies of API penetration through membranes, cellular uptake of drug delivery liposomes, and initial API distribution and subsequent elution from coatings of medical devices. New instrumental developments will increase the efficiency of Raman mapping and lead to greater utilisation of Raman mapping for analyses of pharmaceutical systems.
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