Distribution characteristics and controlling factors of typical heavy metals in Huanghe River estuary,China

The geochemical characteristics and potential controlling factors of colloidal Zn,Cd,and Pb in Huanghe(Yellow)River estuary(HRE),China were investigated.The three metals were highly variable over a range of spatiotemporal scales,comprehensively forced by various physical and biological processes.Total dissolved Zn,Cd,and Pb varied from 200.1 to 321.7,2.6 to 4.1,and 0.5 to 1.0 nmol/L,respectively.Only one near-estuarine station of Zn had contamination factor values>1,which indicate the lower contaminant levels.Five dissolved species of Zn,Cd and Pb were fractionated,namely<1 kDa,1-3 kDa,3-10 kDa,10-100 kDa,and 100 kDa-0.45μm.The<1 kDa truly dissolved phase was the main fraction of the three dissolved metals(50%-62%),while the 100-kDa-0.45-μm high molecular weight colloidal fraction was dominant in their respective colloidal phase.Territorial input and sediment acted as important sources of strong ligands and natural colloids for the HRE water system.<3-kDa Zn and Pb were susceptible to the dissolved oxygen,the behaviors of colloidal Zn and 3-10-kDa Pb were related to dissolved organic carbon(DOC).However,no significant correlation between each dissolved fraction of Cd and salinity,pH,temperature,colloidal organic carbon,and DOC was found in this study.Overall,these findings,completed by the evaluation of the dissolved species of Zn,Cd,and Pb at 10 sites over the river-sea mixing zone,provided new insights into the colloidal heterogeneity that affect metals geochemical features,migration and fate in estuaries.

Effects of Ni substitution on multiferroic properties in Bi_(5)FeTi_(3)O_(15) ceramics

The single-phase multiferroic Bi_(5)Fe_(1−x)NixTi_(3)O_(15)(BFNT-x,x=0,0.1,0.2,0.3,0.4,and 0.5)ceramics were synthesized by a sol-gel auto-combustion method,and their microstructures,ferroelectric,magnetic,and dielectric properties were investigated in detail.All samples belong to layer-perovskited Aurivillius phase containing four perovskite units sandwiched between two Bi-O layers.Ni substitution can not only improve ferroelectricity but also enhance the magnetic properties.The BFNT-0.2 sample shows the largest remnant polarization(2Pr∼11.6µC/cm^(2))and the highest remnant magnetization(2Mr∼0.244 emu/g).The enhancement of the magnetic properties may mainly originate from the spin canting of Fe/Ni-O octahedra via Dzyaloshinskii-Moriya(DM)interaction.In order to explore the influence of valance state of magnetic ions on the properties,the x-ray photoelectron spectroscopy was carried out.Furthermore,structural,ferroelectric,and magnetic transitions were also investigated.

Synergistic modulation of spin and fluorescence signals in a nano-Saturn assembled by a metallofullerene and cycloparaphenylene nanohoop

Spin-based interdisciplinary research has attracted considerable attention,and various applications in magnetic memory,quantum science,and precision measuring technology have been reported.In this study,we induced a fluorescence property in a spin-active molecule by supramolecular assembly and realized a synergistic modulation of its spin and fluorescence properties.A Saturn-shaped supramolecular complex was synthesized using a spin-active metallofullerene Sc_(3)C_(2)@C80 with a fluorescent nanohoop of tetra-benzothiadiazole-based[12]cycloparaphenylene(TB[12]CPP),and its spin and fluorescence properties were comprehensively investigated.Temperature-dependent electron paramagnetic resonance(EPR)spectroscopy and fluorescence analyses were conducted.Synchronous changes in the EPR signals and fluorescence peaks were discovered in the temperature range of 170–290 K.Based on nuclear magnetic resonance observations and theoretical calculations,a temperature-dependent host–guest interaction between Sc_(3)C_(2)@C_(80)and a nanohoop was demonstrated,which explained the synchronous changes in the EPR signals and fluorescence peaks for Sc_(3)C_(2)@C_(80)⊂TB[12]CPP.The application of Sc_(3)C_(2)@C_(80)as a molecular spin system to probe the host–guest interaction was also evaluated.These results show that the supramolecular assembly can be used to design advanced spin systems coupled with optical and magnetic behaviors based on paramagnetic and luminescent molecules.

Zirconium nitride as a highly efficient nitrogen source to synthesize the metal nitride clusterfullerenes

Metal nitride clusterfullerenes(NCFs)have significant applications in molecular electronics,biomedical imaging,and nonlinear optical devices due to their unique structures.However,their wide applications are limited by the production quantity.In this work,the yields of metal nitride clusterfullerenes M3N@C80(M=Y,Sc,Gd)were greatly enhanced by utilizing zirconium nitride(Zr N)as an efficient nitrogen source for the arc-discharge method.Compared with the traditional synthetic route using N2gas as nitrogen source,the Zr N inside graphite tube can be vaporized simultaneously with metal and graphite,and then afford the high concentration of nitrogen atoms in the arc region,which will promote the formation of metal nitride clusterfullerenes finally.The Zr N can promote the yields of Y3N@C80,Sc3N@C80and Gd3N@C80,revealing the universal applicability of Zr N as a highly efficient nitrogen source.Specifically,the yield of Sc3N@C80was greatly improved when adding Zr N,and it shows over double yield compared to traditional synthetic route using N2gas.In addition,Zr N can also enhance the yields of paramagnetic azametallofullerene M2@C79N due to the high concentration of nitrogen atoms in the arc region.This new method enhances the production quantity of metal nitride clusterfullerenes and azametallofullerenes,and it will greatly promote the research and application of these molecular carbon materials.

A molecular brake hoop for the motion of metal atoms inside fullerene cage

Molecular machines have attracted extensive attention due to their fancy concept and their potential to influence the science and technology.The dynamic motion of encapsulated metallic clusters is a distinctive character for endohedral metallofullerenes.For the development of molecular rotors based on metallofullerenes,the most challenging issue is how to control the motion of untouchable metallic cluster inside fullerene cage.In this work,we report a molecular brake hoop for the motion of metal atoms inside fullerene cage.A cycloparaphenylene of[12]CPP was employed to hoop the metallofullerene and produce two supramolecular complexes of Sc_(3)N@C_(80)⊂[12]CPP and Sc_(2)C_(2)@C_(82)⊂[12]CPP.Moreover,the temperature-dependent ^(45)Sc nuclear magnetic resonance spectroscopy(NMR)was employed to detect the motion of internal Sc_(3)N and Sc_(2)C_(2) clusters.^(45)Sc NMR results reveal that the[12]CPP can slow down the rotation of internal metallic cluster through host-guest interaction,and thus the[12]CPP can be considered as a molecular brake hoop for the internal metal motion of metallofullerenes.Furthermore,by means of this molecular brake hoop,the motion of metal atoms inside fullerene cage have expanded range of velocity.In addition,theoretical calculations on Sc_(3)N@C_(80)⊂[12]CPP were executed to illustrate the molecular orientation as well as internal Sc_(3)N rotation.This study would promote the research of endohedral metallofullerene as a molecular rotor.

Ferroelectric,magnetic,and optical properties of Aurivillius compound Bi_(5)FeTi_(2.5)Co_(0.5)O_(15)

Bi_(5)FeTi_(2.5)Co_(0.5)O_(15)(BFTC)ceramics was successfully synthesized using the sol-gel method.It exhibits simultaneously visible-light response,ferroelectric and weak ferromagnetic orders at room temperature.The narrow band gap of 2.06 eV was determined via the UVevis diffuse absorption spectrum.The x-ray photoelectron spectroscopy results show that the Fe ions in the samples is 3 t and 2 t valence states while the doped Co ions is 2 t valence state.The BFTC sample undergoes a ferromagnetic-like transition at~552 K.Weak ferromagnetism is mainly due to spin-canting of Fe-based and Co-based sublattices via Dzyaloshinskii-Moriya(DM)interaction.Dielectric loss and dielectric modulus exhibit the characteristics of dielectric relaxation,which can be ascribed to oxygen/vacancy hopping.These results reveal many potentially useful physical phenomena and open a new avenue to design of novel solar-energy conversion devices and multiferroic applications.