微波辅助合成促进铬酸铋晶体的光生电荷分离

为了将可再生太阳能转化为化学物质,探索具有宽光谱响应的光催化剂用于光催化分解水越来越受到人们的关注。作为铋基层状金属氧化物的一员,铬酸铋(Bi_(2)CrO_(6))的带隙约为1.9 eV,在利用大范围太阳光谱方面具有潜力。然而,Bi_(2)CrO_(6)较差的电荷分离性能限制了其在光催化中的应用。本文采用微波辅助水热合成方法制备了具有规则形貌的Bi_(2)CrO_(6)晶体,该晶体具有结晶度高、形貌均匀的优点。与传统制备方法相比,微波辐照实现了体系的快速加热,极大地加速了成核和生长的化学反应,从而在几分钟内形成了Bi_(2)CrO_(6)晶体。微波辅助合成的Bi_(2)CrO_(6)晶体在光催化和光电化学测试中表现出更好的光生电荷分离以及水氧化活性。此外实验中观察到光生电子和空穴在Bi_(2)CrO_(6)晶体的不同晶面之间发生空间分离,通过进一步在不同晶面上光沉积选择性负载还原和氧化助催化剂,显著增强了光催化活性。这项工作为制备高效太阳能转换的半导体光催化剂提供了一种可行的解决方案。

Analysis of the Relationship between Mechanical Properties and Pore Structure of MSW Incineration Bottom Ash Fine Aggregate Concrete after Freeze-Thaw Cycles Based on the Gray Theory

The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles,and the relationship between the mechanical properties and pore structure of concrete with fine aggregate from municipal solid waste(MSW)incineration bottom ash after freeze-thaw cycles is analyzed under the degree of freeze-thaw hazard variation.In this paper,the gray correlation method is used to calculate the correlation between the relative dynamic elastic modulus,compressive strength,and microscopic porosity parameters to speculate on the most important factors affecting their changes.The GM(1,1)model was established based on the compressive strength of the waste incineration ash aggregate concrete,the relative error between the simulated and actual values in the model was less than 5%,and the accuracy of the model was level 1,indicating that the GM(1,1)model can well reflect the change in the compressive strength of the MSW incineration bottom ash aggregate concrete during freeze-thaw cycles.Using the gray correlation method,the correlation between the relative dynamic elastic modulus,compressive strength,air content,specific surface area,pore spacing coefficient,and pore average chord length was calculated,and the pore spacing coefficient and pore average chord length were determined to be highly correlated with each other.This determination can help analyze and infer the deterioration mechanism of concrete subject to freeze-thaw cycles.These results can provide a theoretical basis for guiding the engineering practice of concrete with fine aggregates of household bottom ash in the northern cold region.

The remarkable effect of amino hydrogen on membrane permeability and organelle staining of 1,8-naphthalimide dyes

Membrane permeability and intracellular diffusion of fluorescent probes determine staining selectivity of intracellular substructures.However,the relationship between the molecular structure of fluorescent probes and their membrane permeability and intracellular distribution is poorly understood.In this paper,we reported a series of 1,8-naphthalimide dyes and carried out cell imaging experiments,and found that the presence of amino hydrogen in these dyes played a crucial role in their cell membrane permeability and intracellular distribution.The secondary amino group containing compounds 1-4 show excellent membrane permeability and strong fluorescence in living cells.While the tertiary amine containing dyes 5 and 6 can hardly permeate the cell membrane though they show extremely similar structure with compounds 2-4.Compound 1 can selectively image lipid droplets by selecting the wavelength of excitation light.With the specificity for lysosomes,2 and 4 have been used in long-term time-lapses imaging of lysosomal dynamics and tracking the process of lysosome-lysosome interaction,fusion and movement.The effect of hydrogen-containing amino substituent on the cell membrane permeability of fluorescent molecules is promising for the development of better biocompatible probes.

Incorporation sodium ions into monodisperse lead-free double perovskite Cs_(2)AgBiCl_(6) nanocrystals to improve optical properties

Lead-free double perovskite nanocrystals(NCs)have emerged as a promising candidate in the optical field,owing to their non-toxic,good moist heat and chemical stability.However,their poor optical properties limited their application.To improve the optical properties of lead-free double perovskite NCs,metal ion doping or alloying had been suggested as a promising strategy.Here,we prepared monodisperse,uniformly sized,cubic morphology of Cs_(2)AgBiCl_(6)NCs with different Na^(+)incorporation amounts via a simple hot-injection method.The Na^(+)incorporation broke the parity-forbidden transition by reducing the inversion symmetry of the electron wave function at the Ag site,which changed the parity of the self-trapped exciton wave function and thus allowed radiative recombination.As a result,the photoluminescence quantum yield(PLQY)of Na^(+)-alloyed Cs_(2)AgBiCl_(6)NCs(12.1%)was higher than that of Cs_(2)AgBiCl_(6)NCs(2.4%),and the exciton lifetime of Na^(+)-alloyed Cs_(2)AgBiCl_(6)NCs increased to 36.98 ns from 17.58 ns for Cs_(2)AgBiCl_(6)NCs.By adjusting the amount of Na^(+)incorporation,the band gap of Cs_(2)AgBiCl_(6)NCs can be significantly tuned from~2.90 eV to~3.50 eV.Furthermore,the temperature-dependent photoluminescence spectra indicated that the Na^(+)-alloyed Cs_(2)AgBiCl_(6)NCs possessed higher longitudinal optical phonon energy and exciton binding energy compared to Cs_(2)AgBiCl_(6)NCs.This suggested that there were strong exciton-phonon interactions during exciton recombination,a reduced probability of non-radiative processes,and excellent thermal stability.It offers a promising strategy for improving the optical properties of lead-free double perovskite NCs,and have the potential to replace traditional lead halide perovskite NCs in future optoelectronic applications.

Tailoring morphology symmetry of bismuth vanadate photocatalysts for efficient charge separation

Although spatial charge separation between different facets of semiconductor crystals has been recognized as a general strategy in photocatalysis, the vital role of crystal morphology symmetry in charge separation properties still remains elusive. Herein,taking monoclinic bismuth vanadate(BiVO_(4)) as a platform, we found distinct charge separation difference via rationally tailoring the morphology symmetry from octahedral to truncated octahedral crystals. For octahedral BiVO_(4), photogenerated electrons and holes can be separated between edges and quasi-equivalent facets. However, as for truncated octahedral crystals,photogenerated electrons tend to transfer to {010} facets while photogenerated holes prefer to accumulate on {120} facets, thus realizing the spatial separation of photogenerated charge between different facets. Morphology tailoring of BiVO_(4) crystals leads to a significantly improved photogenerated charge separation efficiency and photocatalytic water oxidation activity. The built-in electric field for driving the separation of photogenerated electrons and holes is considered to be modulated by tuning the morphology symmetry of BiVO_(4) crystals. This work discloses the significant roles of morphology symmetry in photogenerated charge separation and facilitates the rational design of artificial photocatalysts.

Aniline as a TICT rotor to derive methine fluorogens for biomolecules:A curcuminoid-BF2 compound for lighting up HSA/BSA

The unique structure of fluorescent proteins in which the fluorophore is encapsulated by the protein shell to restrict rotation and emit light inspired the screening of chromophores that selectively bind to biomolecules to generate fluorescence. In this paper, we report a curcuminoid-BF2-like fluorescent dye NBF2containing 4-dimethylaniline as an electron-donating group. When this dye is combined with HSA or BSA, the fluorescence is enhanced 90/112-fold, and the fluorescence quantum yield increases from <0.001to 0.16/0.19. Such a large change in fluorescence enhancement is due to the encapsulation of N-BF2in the protein cavity by HSA/BSA, which inhibits the intramolecular rotation of the aniline moiety caused by charge transfer after the fluorophore is excited by light. N-BF2has fast and strong binding to HSA or BSA and was found to be reversible in solution and intracellularly. Since N-BF2also has the ability to target lipid droplets, the complex of N-BF2/HSA realizes the regulation of reversible lipid droplet staining in cells.

Constructing D-π-A-π dye to obtain red-emission fluorescent probe for structured illumination microscopy imaging of lipid droplet dynamics

Lipid droplets(LDs)are dynamic organelles interacting with a variety of intracellular organelles.Tracking intracellular LD dynamics employing synthetic small molecules is crucial for biological studies.Fluorescence imaging in the red and near infrared(NIR)region is more suitable for biological imaging due to its low phototoxicity and high signal-to-noise ratio.However,available LD-dyes in the red region with remarkable environmental sensitivity,selectivity for LDs staining are limited.Here,we constructed a red-emission D-π-A-π type LDdye LD 688P with higher environmental sensitivity and suitable“calculated log P”(Clog P)for LDs dynamic imaging.LD 688P was proved to be highly selective and photostable for tracing LD fusion including multiple consecutive fusions and fusions in a centrosymmetric manner by super-resolution microscopy.We believe that the D-π-A-π skeleton would be an efficient strategy to construct red and even NIR-emission dyes.

Enhanced reductive degradation of carbon tetrachloride by carbon dioxide radical anion-based sodium percarbonate/ Fe（ll）/formic acid system in aqueous solution

The performance of sodium percarbonate （SPC） activated with ferrous ion （Fe（Ⅱ） with the addition of formic acid （FA） to stimulate the degradation of carbon tetrachloride （CT） was investigated. Results showed that CT could be entirely reduced within 15 min in the system at a variety of SPC/Fe（Ⅱ）/FA/CT molar ratios in experimental level. Scavenging tests indicated that carbon dioxide radical anion （CO2-） was the dominant reactive oxygen species responsible for CT degradation. CT degradation rate, to a large extent, increased with increasing dosages of chemical agents and the optimal molar ratio of SPC/Fe（Ⅱ）/FAJCT was set as 60/60/60/1. The initial concentration of CT can hardly affect the CT removal, while CT degradation was favorable in the pH range of 3.0-9.0, but apparently inhibited at pH 12. C1- and HCO3 of high concentration showed negative impact on CT removal. Cl- released from CT was detected and the results confirmed nearly complete mineralization ofCT. CT degradation was proposed by reductive C-C1 bond splitting. This study demonstrated that SPC activated with Fe（Ⅱ） with the addition of FA may be promising technique for CT remediation in contaminated groundwater.

Anomalous phonon softening in the topological insulator Sn-doped Bi1.1Sb0.9Te2S

Investigations into the phonon behavior provide important information on interactions between different excitations in quantum materials.We perform a detailed study of the phonon behavior in the topological insulator Sn-doped Bi1.1Sb0.9Te2S using infrared spectroscopy.We observe two IR-active phonon modes at about 64 and 165 cm^1,which are labeled withαandβ,respectively.While the evolution of theβmode with temperature can be well described by the expected anharmonic decay process,theαmode shifts to lower frequencies with decreasing temperature.Such an anomalous softening of theαmode may arise from the charged-phonon effect due to the coupling between this mode and the topological surface states in Sn-doped Bi1.1Sb0.9Te2S.

Enhanced carbon tetrachloride degradation by hydroxylamine in ferrous ion activated calcium peroxide in the presence of formic acid

Hydroxyl radicals(HO*)show low reactivity with perchlorinated hydrocarbons,such as carbon tetrachloride(CT),in conventional Fenton reactions,therefore,the generation of reductive radicals has attracted increasing attention.This study investigated the enhancement of CT degradation by the synergistic effects of hydroxylamine(HA)and formic acid(FA)(initial[CT]=0.13 mmol/L)in a Fe(il)activated calcium peroxide(CP)fenton process.CT degradation increased from 56.6%to 99.9%with the addition of 0.78 mmol/L HA to the CP/Fe(II)/FA/CT process in a molar ratio o f 12/6/12/1.The results also showed that the presence of HA enhanced the regeneration of Fe(II)from Fe(III),and the production of HO*increased one-fold when employing benzoic acid as the HO*probe.Additionally,FA slightly improves the production of HO*.A study of the mechanism confirmed that the carbon dioxide radical(C02·),a strong reductant generated by the reaction between FA and HO*,was the dominant radical responsible for CT degradation.Almost complete CT dechlorination was achieved in the process.The presence of humic acid and chloride ion slightly decreased CT removal,while high doses of bicarbonate and high pH inhibited CT degradation.This study helps us to better understand the synergistic roles of FA and HA for HO·and C02·^-generation and the removal of perchlorinated hydrocarbons in modified Fenton systems.

Quantitative assessment of rhodamine spectra

With the development of single-molecule detection and super-resolution fluorescence imaging,rhodamine dyes gain new life.Through the modification of the N-substituents a nd the replacement of the oxygen atom in xanthene,the wavelength and brightness can be effectively changed.However,the spectra of rhodamine,especially due to the balance between ring-closed non-fluorescent lactone and ring-opened fluorescent zwitterion/cation,are sensitive to interference from various environmental facto rs,In this way,the spectral data of various rhodamines repo rted by different re search groups under different test conditions lacked comparability,sometimes even lacked accuracy.In order to meet the requirements for the accuracy and uniformity of spectral data in the research of single molecule imaging and dye structure-fluorescence relationship study,we have tested the spectra of fifteen rhodamine dyes that cover the visible and near-infrared regions under exactly the same conditions.By studying the dependence of the spectra on dye concentrations,it was confirmed that 1 μmol/L was ideal fo r detection less from the interference of dye molecule aggregation.We provide compre hensive and reliable spectral data of these fifteen dyes,which are expected to be used as references for future research.And the direct comparison of different rhodamine spectra would help to understand the structure-fluorescence relationship of rhodamines.