化学•材料最新文献

Self-powered broadband photodetection has evoked increased interest in next-generation photoelectronic devices. However, realizing self-powered broadband photodetection in a single material is still a challenge because of the harsh requirements, including powerful built-in field, excellent charge transport behaviors, as well as the broad absorption. Herein, we first realize broadband photodetection in the range from X-ray to UV-vis light in a polar two-dimensional perovskite (2-FBA)₂MAPb₂I₇ (2-FBA = 2-fluorobenzylamine, MA = methylamine) by incorporating an aromatic spacer into a three-dimensional prototype. As a result, (2-FBA)₂MAPb₂I₇ exhibited a superior response to UV-vis light (377 to 637 nm) without voltage bias. Specifically, a high switching ratio of 1.05 × 10⁴, an outstanding responsivity (R) of 1420 mA W^-1, and detectivity (D*) of 1.59 × 10¹³ Jones were achieved under light illumination at 520 nm. Moreover, (2-FBA)₂MAPb₂I₇ achieved a high sensitivity of 46.4 μC Gy^-1 cm^-2 without voltage bias, two times higher than that of a commercial α-Se film detector (20 μC Gy^-1 cm^-2). The sensitivity can be further improved to 3316 μC Gy^-1 cm^-2 at a 50 V bias. These results give insight into the design of 2D perovskites for self-powered broadband photodetection.

Natural manganese (Mn) oxide coatings, resulting from the heterogeneous nucleation on foreign substances, have garnered interest based on their importance in the reaction with organic substances and in environmental systems. However, the heterogeneous nucleation of the natural Mn oxide coatings still remains elusive. Here, via fast photochemical oxidation of Mn²⁺(aq), we show that Mn(IV) oxide nuclei form and aggregate on quartz in three distinct successive stages: (i) a nanocrystalline film of unaligned grain forms, (ii) nanoislands develop on the film, and (iii) nanorods form on the nanoislands. Each stage has different crystalline structures and forms by aligned attachment of nanoscale precursors on the preceding surface. Crystal lattice analyses confirm the crystalline development, from the short-range order of the Mn oxide film to the long-range order of the nanorods. Also, the heterogeneous nucleation observed in this work produced groutellite-like tunnel structures of Mn oxide on quartz. This revealed pathway of the heterogeneous nucleation can offer a new perspective on the variety of poorly crystalline structures of natural Mn oxides found in the environment, which can affect elemental redox cycles, contaminant sequestration and removal, and soil carbon storage.

Reverse intersystem crossing (RISC) has become possible by minimizing the energy gap between the first excited singlet (S₁) and triplet state (T₁), which facilitates the thermally activated delayed fluorescence (TADF). Due to the small singlet-triplet energy gap, the S₁ and T₁ states exhibit comparable redox reactivity, leading organic TADF compounds to be potent photocatalysts. Here, we report such TADF compounds with multiple donor units designed as an efficient photocatalyst for the direct C(sp³)-H carbamoylation of saturated aza-heterocycles. The results obtained by photophysical investigations and chemical calculations confirm that both the S₁ and T₁ states are involved in the photocatalysis cycle, with the fast spin-flip from the S₁ to triplet states being a crucial factor in the enhancement of catalytic performance. The findings will be beneficial for the design of novel, efficient organic photocatalysis with TADF characteristics and aid in the development of organic photocatalysis.

The effects of methyl substitution on the ultrafast internal conversion from the S₂(¹B_1u, ππ*) state to the S₀ state of benzene were studied using ultrafast extreme-ultraviolet photoelectron spectroscopy and electronic structure calculations. The quantum yield of the internal conversion to the S₀ state reached ∼0.69 in benzene, while lower values of 0.35 and 0.12 were obtained for toluene and o-xylene, respectively. These results indicate that methyl substitution makes the conical intersections less accessible to the nuclear wave packet.

Oxidized lipids arising from oxidative stress are associated with many serious health conditions, including cardiovascular diseases. For example, KDdiA-PC and KOdiA-PC are two oxidized phosphatidylcholines (oxPC) directly linked to atherosclerosis, which precipitate heart failure, stroke, aneurysms, and chronic kidney disease. These oxPCs are well-characterized in small particles such as low-density lipoprotein, but how their presence affects the biophysical properties of larger bilayer membranes is unclear. It is also unclear how membrane mediators, such as cholesterol, affect lipid bilayers containing these oxPCs. Here, we characterize supported lipid bilayers (SLBs) containing POPC, KDdiA-PC, or KOdiA-PC, and cholesterol. We used a quartz crystal microbalance with dissipation monitoring (QCM-D), fluorescence microscopy, and all-atom molecular dynamics (MD) to examine the formation process, biophysical properties, and specific lipid conformations in simulated bilayers. Experimentally, we show that liposomes containing either oxPC form SLBs by rupturing on contact with SiO₂ substrates, which differs from the typical adsorption-rupture pathway observed with nonoxidized liposomes. We also show that increasing the oxPC concentration in SLBs results in thinner bilayers that contain defects. Simulations reveal that the oxidized sn-2 tails of KDdiA-PC and KOdiA-PC bend out of the hydrophobic membrane core into the hydrophilic headgroup region and beyond. The altered conformations of these oxPC, which are affected by cholesterol content and protonation state of the oxidized functional groups, contribute to trends of decreasing membrane thickness and increasing membrane area with increasing oxPC concentration. This combined approach provides a comprehensive view of the biophysical properties of membranes containing KDdiA-PC and KOdiA-PC at the molecular level, which is crucial to understanding the role of lipid oxidation in cardiovascular disease and related immune responses.

A two-step formal (4 + 1) annulation-dehydration reaction offers a convenient route to C2-arylated indoles and benzofurans. This reaction exploits the bifunctional reactivity of electron-deficient benzyl chlorides with N-sulfonyl-2-aminobenzaldehydes or salicylaldehyde derivatives. The reaction tolerates both electron-withdrawing and donating groups on the substituted aldehydes, as well as variation of electron-withdrawing groups at the para position of the benzyl chloride reagent. This work also identifies interesting byproducts resulting from the self-reaction of these benzyl chlorides under basic conditions.

This review highlights important research on anion coordination chemistry for materials applications over the last decade. This field has numerous applications in various areas, such as the environment, industry, and medicine. Despite its enormous potential, real-world applicability is still pending. However, there has been a new trajectory in the field recently, with rapid advancement in designing sophisticated molecular systems for various materials applications. To keep track of this dynamic advancement, we have discussed some outstanding research work with enormous potential for materials applications in the near future.

An iron-catalyzed nitrene transfer reaction for the rapid synthesis of sulfinamidines from readily available sulfenamides is reported. This method features mild conditions, short reaction times, and a broad substrate scope, allowing the preparation of a variety of sulfinamidines in good to excellent yields. The synthetic utility of the sulfinamidine products was further demonstrated through their conversion to other valuable sulfur(VI) compounds, such as sulfondiimidoyl fluorides, sulfinamidiate esters, and sulfonimidamides. Preliminary efforts in the development of an asymmetric variant showed moderate enantioselectivity.

Biogenic volatile organic compounds (BVOCs) contribute to the formation of secondary organic aerosol (SOA) through atmospheric oxidation. Previously detected SOA-markers in northern hemisphere ice cores from Alaska, Greenland, Russia, and Switzerland indicate the transportation of isoprene and monoterpene oxidation products from their forestry sources to these glacial regions. Antarctica is geographically further removed from the BVOC's source, indicating significantly lower SOA-marker concentrations are likely in southern hemisphere ice cores. The aim of this study was to develop a sensitive mass-spectrometric method to detect and quantify low-abundance SOA-markers of isoprene and monoterpenes in ice core samples. Employment of a triple quadrupole HPLC-MS method enabled limit of detections in the range of 0.4-10 ppt for nine terrestrial SOA-markers and a marker of biomass burning, levoglucosan. Quantification was conducted in the multiple reaction monitoring mode with two specific transitions monitored for each target compound. Application of the developed method onto a section of a Jurassic ice core from Antarctica revealed the presence of seven of the target compounds: 2-methylerythritol, 2-methylglyceric acid, cis-pinonic acid, 3-methyl-1,2,3-butanetricarboxylic acid, pinolic acid, cis-norpinonic acid, and pinic acid. Repeatability ranged between 2.2% and 6.2%. This is the first time that such SOA-markers have been discovered and quantified in Antarctic ice.

Recent advances in local electron correlation approaches have enabled the relatively routine access to CCSD(T) [that is, coupled cluster (CC) with single, double, and perturbative triple excitations] computations for molecules of a hundred or more atoms. Here, approaching their complete basis set (CBS) limit becomes more challenging due to extensive basis set superposition errors, often necessitating the use of large atomic orbital (AO) basis sets with diffuse functions. Here, we study a potential remedy in the form of non-atom-centered or floating orbitals (FOs). FOs are still rarely employed even for small molecules due to the practical complication of defining their position, number, exponents, etc. The most frequently used FO method thus simply places a single FO center with a large number of FOs toward the middle of noncovalent dimers; however, a single FO center for larger complexes can soon become insufficient. A recent alternative uses a grid of FO centers around the monomers with a single s function per center, which is currently applicable only for H, C, N, and O atoms. Here, we build on the above advantages and mitigate some drawbacks of previous FO approaches by using a layer of FO centers and 4-9 FOs/center for each monomer. Thus, a double layer of FOs is placed between the interacting subsystems. When extending the double-ζ AO basis with this double layer of FOs, the quality of conventional augmented double-ζ or conventional triple-ζ AO bases can be reached or surpassed with less orbitals, leading to few tenths of a kcal/mol basis set errors for medium-sized dimers. This good performance extends to larger molecules (shown here up to 72 atoms), as efficient local natural orbital (LNO) CCSD(T) computations with only double-ζ AO and 4 FOs/center FO bases match our LNO-CCSD(T)/CBS reference within ca. 0.1 kcal/mol. These developments introduce FO methods to the accurate modeling of large molecular complexes without limitations to atom types by further accelerating efficient correlation calculations, like LNO-CCSD(T).