Landau theory of ferroelectric transition in long cylindrical nanoparticles

Using a phenomenological Landau theory, the size dependence on ferroelectric transition for free-standing long cylindrical nanoparticles is discussed. We derive the size dependence of the transition temperature, polarization profile as well as the static susceptibility. The transition temperature vanishes below a critical size where the static susceptibility shows divergence obeying Curie-Weiss law. In order to make this result compared with experiments, the average polarization and the susceptibility is computed with a Gaussian particle size distribution. The average polarization in such a case shows smearing with respect to the particle size whereas the divergence in the susceptibilty gets rounded. This might correspond to a size dependent soft mode which can be observed in Raman measurement.     

Cleavage of C(aryl)−CH3 Bonds in the Absence of Directing Groups under Transition Metal Free Conditions

Organic chemists now can construct carbon–carbon σ‐bonds selectively and sequentially, whereas methods for the selective cleavage of carbon–carbon σ‐bonds, especially for unreactive hydrocarbons, remain limited. Activation by ring strain, directing groups, or in the presence of a carbonyl or a cyano group is usually required. In this work, by using a sequential strategy site‐selective cleavage and borylation of C(aryl)?CH₃ bonds has been developed under directing group free and transition metal free conditions. Methyl groups of various arenes are selectively cleaved and replaced by boryl groups. Mechanistic analysis suggests that it proceeds by a sequential intermolecular oxidation and coupling of a transient aryl radical, generated by radical decarboxylation, involving a pyridine‐stabilized persistent boryl radical.     

A Concise Total Synthesis of (−)‐Himalensine A

The daphniphyllum alkaloids are a structurally fascinating and remarkably diverse family of natural products. General strategies for the chemical synthesis of their challenging architectures are highly desirable for efficiently accessing these intriguing alkaloids and addressing their pharmaceutical potential. Herein, a concise strategy designed to provide general and diversifiable access to various daphniphyllum alkaloids is described and utilized in the asymmetric synthesis of (?)‐himalensine A, which was accomplished in 14 steps. Key features of this strategy include a Cu‐catalyzed nitrile hydration, a Heck reaction to construct the challenging 2‐azabicyclo[3.3.1]nonane motif, a Meinwald rearrangement reaction, six, pot‐economic reactions, and the minimal use of protecting groups, which significantly improved the overall synthetic efficiency.     

Tuning the In Vivo Transport of Anticancer Drugs Using Renal‐Clearable Gold Nanoparticles

Precise control of in vivo transport of anticancer drugs in normal and cancerous tissues with engineered nanoparticles is key to the future success of cancer nanomedicines in clinics. This requires a fundamental understanding of how engineered nanoparticles impact the targeting‐clearance and permeation‐retention paradoxes in the anticancer‐drug delivery. Herein, we systematically investigated how renal‐clearable gold nanoparticles (AuNPs) affect the permeation, distribution, and retention of the anticancer drug doxorubicin in both cancerous and normal tissues. Renal‐clearable AuNPs retain the advantages of the free drug, including rapid tumor targeting and high tumor vascular permeability. The renal‐clearable AuNPs also accelerated body clearance of off‐target drug via renal elimination. These results clearly indicate that diverse in vivo transport behaviors of engineered nanoparticles can be used to reconcile long‐standing paradoxes in the anticancer drug delivery.     

Making JP‐10 Superfuel Affordable with a Lignocellulosic Platform Compound

The synthesis of renewable jet fuel from lignocellulosic platform compounds has drawn a lot of attention in recent years. So far, most work has concentrated on the production of conventional jet fuels. JP‐10 is an advanced jet fuel currently obtained from fossil energy. Due to its excellent properties, JP‐10 has been widely used in military aircraft. However, the high price and low availability limit its application in civil aviation. Here, we report a new strategy for the synthesis of bio‐JP‐10 fuel from furfuryl alcohol that is produced on an industrial scale from agricultural and forestry residues. Under the optimized conditions, bio‐JP‐10 fuel was produced with high overall carbon yields (≈65 %). A preliminary economic analysis indicates that the price of bio‐JP‐10 fuel can be greatly decreased from ≈7091 US$/ton (by fossil route) to less than 5600 US$/ton using our new strategy. This work makes the practical application of bio‐JP‐10 fuel forseeable.     

A Dual‐Surface Amidoximated Halloysite Nanotube for High‐Efficiency Economical Uranium Extraction from Seawater

By chemical cross‐linking the amidoxime group onto dual‐surfaces of natural ore materials, namely halloysite nanotubes (HNTs), an efficient adsorbent, AO‐HNTs, is developed. AO‐HNTs show high uranium adsorption capacity of 456.24 mg g^?1 in 32 ppm uranium‐spiked simulated seawater. In natural seawater, AO‐HNTs reach the high uranium extraction capacity of 9.01 mg g^?1 after 30 days’ field test. The dual‐surface amidoximated hollow nanotubular AO‐HNTs exhibit more coordination active sites for uranium adsorption, which is attributed to the high and fast uranium adsorption capacity. Because of the stable natural ore structure, AO‐HNTs also show long service life. Benefiting from the low cost of HNTs, the cost for uranium extraction from seawater is close to the uranium price in the spot uranium market, suggesting that AO‐HNTs could be used for economical extraction of uranium from the oceans.     

Theranostic Nanoplatform with Hydrogen Sulfide Activatable NIR Responsiveness for Imaging‐Guided On‐Demand Drug Release

NIR light responsive nanoplatforms hold great promise for on‐demand drug release in precision cancer medicine. However, currently available systems utilize “always‐on” photothermal transducers that lack target specificity, and thus inaccurately differentiate tumors from normal tissues. Developed here is a theranostic nanoplatform featuring H₂S‐mediated in situ production of NIR photothermal agents for imaging‐guided and photocontrolled drug release. The system targets H₂S‐rich cancers. This nanoplatform shows H₂S‐activatable NIR‐II emission and NIR light controllable release of the drug Camptothecin‐11. Upon administering the system to HCT116 tumor‐bearing mice, the tumor is greatly suppressed with minimal side effects, arising from the synergy of the cancer‐specific and NIR light activated therapy. This theranostic nanoplatform thus sheds light on precision medicine with guidance through NIR‐II imaging.