Latest ArticlesFurazan and furoxan represent fascinating explosophoric units with intriguing structures and unique properties. Compared with other nitrogen-rich heterocycles, most poly furazan and furoxan-based heterocycles demonstrate superior energetic performances due to the higher enthalpy of formation and density levels. A large variety of advanced energetic materials have been achieved based on the combination of furazan and furoxan moieties with different kinds of linkers and this review provides an overview of the development of energetic poly furazan and furoxan structures during the past decades, with their physical properties and detonation characteristics summarized and compared with traditional energetic materials. Various synthetic strategies towards these compact energetic structures are highlighted by covering the most important cyclization methods for construction of the hetercyclic scaffolds and the following modifications such as nitrations and oxidations. Given the synthetic availabilities and outstanding properties, energetic materials based on poly furazan and furoxan structures are undoubtedly listed as a promising candidate for the development of new-generation explosives, propellants and pyrotechnics.
Understanding the unique characteristics of continuous-flow photochemistry will lead to a paradigm shift in the way we enhance sustainability and wellbeing. In this mini-review, we first provide a succinct overview of working principles of this technique and discuss several recent synthetic protocols. Then, emphasis is given to those representative examples which address environmental issues such as indoor air pollutants and water contamination. Finally, recent progress made using this technique to deal with rising CO2 emission, solar energy utilization and biomedical equipment is described. It is believed that this mini-review could inspire more chemists to utilize this technique in their research, either in the academic or industrial field.
Eleven new fluorine-containing FDA-approved drugs have been profiled and details of their discovery and preparation are discussed. Therapeutic areas include schizophrenia, migraine, multiple sclerosis, insomnia, rheumatoid arthritis, anti-tuberculosis, breast cancer, lymphoma kinase inhibitor, serotonin receptor antagonist. New pharmaceuticals feature four examples of aromatic fluorine, three aromatic CF3 group, three aliphatic CF3 and one compound with aromatic CF3O group. Furthermore, among the new compounds, six are chiral and seven are derived from tailor-made amino acids.
In recent decades, the properties and behaviors of nanofluidic devices have been widely explored in varied subjects such as engineering, physics, chemistry, and biology. Among the rich properties of nanofluidics, ionic current rectification (ICR) is a unique phenomenon arising from asymmetric nanofluidic devices with electric double layer (EDL) overlapped. The ICR property is especially useful in applications including energy conversion, mass separation, sea water purification and bioanalysis. In this review, the ICR property in nanofluidics as well as the underlying mechanism is demonstrated. The influencing factors concerning to the ICR property are systematically summarized. The asymmetric geometry as well as the charge distribution is in charge of the ICR behavior occurring in nanofluidic devices. This review is aimed at readers who are interested in the fundamentals of mass transport in nanofluidics in general, as well as those who are willing to apply nanofluidics in various research fields.
Direct infusion mass spectrometry (DIMS) is a powerful technique in clinical diagnosis for screening neonatal amino acid metabolic disorders from dried blood spots (DBS). However, DIMS sometimes generated false-positive results for analysis of amino acids. In this work, we utilized a stable isotope derivatization method, combining with liquid chromatography tandem mass spectrometry (SID-LC-MS), to improve the specificity for screening amino acids in DBS specimens. A pair of isotope reagents, p-(dimethylamino)phenyl isothiocyanate (DMAP-NCS) and 4-isothiocyanato-N, N-bis(methyl-[2H2])aniline ([2H4]DMAP-NCS), was synthesized and used to label amino acids in DBS specimens. The [2H4]DMAP-NCS labelled amino acid standards were used as internal standards to compensate the matrix effect. This method was validated by measuring linearity, recovery and accuracy. The results showed that the developed SID-LC-MS method can be used for sensitive and selective determination of 12 diagnostically important amino acids in DBS specimens.
A colorimetric and fluorometric dual probe based on a water-soluble polythiophene derivative (PMTPBA) was designed and synthesized. It can be applied to determination of picric acid (PA) in 100% aqueous solution. The approach relies on the formation of supramolecular polythiophene assemblies in the presence of PA through electrostatic, charge transfer and π-π stacking interactions. This probe could be utilized for the rapid and visual detection of PA both in aqueous solution and solid support with high specificity and sensitivity. The detection limit of this sensor is as low as 5.0×10-8 mol/L.
Spirohypatone A (1), a spirocyclic PPAP (polycyclic polyprenylated acylphloroglucinol) bearing an unprecedented hexahydro-1'H-spiro [cyclohexane-1, 2'-pentalene]-2, 4, 6-trione core and a new homologue (spirohypatone B, 2) were isolated from Hypericum patulum together with two known biosynthetic precursors. Compound 1 represents the first spirocyclic PPAP possessing a 5/5/6 carbon ring system, biogenetically derived from the intermediate 3 (attack from C-3 to C-12), which was differed from normal spirocyclic PPAPs (attack from C-3 to C-11). In addition, through extensive spectroscopic analysis, an interconversion mechanism of keto-enol of 1 was postulated and confirmed by its methylated reaction. The structures and absolute configurations of 1 and 2 were determined by comprehensive spectroscopic and chemical derivatized methods and X-ray crystallography. Compounds 1, 2, and 4 were tested to exhibit cytotoxic activities against several cancer cell lines.
Alloy and small size nanostructures are favorable to catalytical performance, but not to surface-enhanced Raman spectroscopy (SERS) applications. Integrating SERS and catalytic activity into the nanocrystals with both alloy and small size structures is of great interest in fabrication of SERS platform to in situ monitor catalytical reaction. Herein, we report a facile method to synthesize Au@AgPd trimetallic nanoflowers (Au@AgPd NFs) with both SERS and catalytic activities, through simultaneous selective growth of Ag and Pd on Au core to form highly-branched alloy shell. These nanocrystals have the properties of small sizes, defects abundance, and highly-dispersed alloy shell which offer superior catalytic activity, while the merits of monodisperse, excellent stability, and highly-branched shell and core/alloy-shell structure promise the enhanced SERS activity. We further studied their growth mechanisms, and found that the ratio of Ag to Pd, sizes of Au core, and surfactant cetyltrimethylammonium bromide together determine this special structure. Using this as-synthesized nanocrystals, a monolayer bifunctional platform with both SERS and catalytical activity was fabricated through selfassembly at air/water interface, and applied to in situ SERS monitoring the reaction process of Pd-catalyzed hydrogenation of 4-nitrothiophenol to 4-aminothiophenol.
Nanobubble is a rising research field, which attracts more and more attentions due to its potential applications in medical science, catalysis, electrochemistry and etc. To better implement these applications, it is urgent to understand one of the most important mechanisms of nanobubbles, the evolution. However, few attentions have been paid in this aspect because of the methodology difficulties. Here we successfully used dark-field microscopy to study the evolution process of single nanobubbles generated from formic acid dehydrogenation on single Pd-Ag nanoplates. We found some of the nanobubbles in this system can exhibit three distinct states representing different sizes, which can transform among each other. These transitions are not direct but through some intermediate states. Further kinetic analysis reveals complicated mechanisms behind the evolution of single nanobubbles. The results acquired from this study can be applicable to nanobubble systems in general and provide insights into the understanding of mechanisms affecting the stability of nanobubbles and their applications.
Facile achievement of gold nanorods (AuNRs) with controllable longitudinal surface plasmon resonance (LSPR) is of great importance for their applications in various fields. The LSPR of AuNRs is sensitive to their aspect ratio, which is still hard to be precisely tuned by direct synthesis. In this work, we report a simple approach for end-selective etching of AuNRs by a rapid oxidation process with Au(Ⅲ) in cetyltrimethylammonium bromide (CTAB) solution at a mild temperature. The LSPR wavelength and the length of AuNRs blue shifted linearly as a function of the amount of Au(Ⅲ), while the diameter of AuNRs remained nearly constant. The oxidative rate is temperature dependent, and the oxidative process for a desired LSPR can be accomplished within 15 min at 60 ℃. Further investigations indicated that Br- determine the occurrence of the oxidation between AuNRs and Au(Ⅲ), and a small amount of surfactant chain (CTA+) is crucial for stabilizing AuNRs. This method presents a quick but robust strategy for acquiring AuNRs with an arbitrary intermediate LSPR wavelength using the same starting AuNRs, and can be a powerful tool for subsequent applications.
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