Experimental and DFT Studies of Au Deposition Over WO_(3)/g-C_(3)N_(4) Z-Scheme Heterojunction

A typical Z-scheme system is composed of two photocatalysts which generate two sets of charge carriers and split water into H2 and O2 at different locations.Scientists are struggling to enhance the efficiencies of these systems by maximizing their light absorption,engineering more stable redox couples,and discovering new O2 and H2 evolutions co-catalysts.In this work,Au decorated WO3/g-C3N4 Z-scheme nanocomposites are fabricated via wet-chemical and photo-deposition methods.The nanocomposites are utilized in photocatalysis for H2 production and 2,4-dichlorophenol(2,4-DCP)degradation.It is investigated that the optimized 4Au/6%WO3/CN nanocomposite is highly efficient for production of 69.9 and 307.3μmol h−1 g−1 H2 gas,respectively,under visible-light(λ>420 nm)and UV–visible illumination.Further,the fabricated 4Au/6%WO3/CN nanocomposite is significant(i.e.,100%degradation in 2 h)for 2,4-DCP degradation under visible light and highly stable in photocatalysis.A significant 4.17%quantum efficiency is recorded for H2 production at wavelength 420 nm.This enhanced performance is attributed to the improved charge separation and the surface plasmon resonance effect of Au nanoparticles.Solid-state density functional theory simulations are performed to countercheck and validate our experimental data.Positive surface formation energy,high charge transfer,and strong non-bonding interaction via electrostatic forces confirm the stability of 4Au/6%WO3/CN interface.

Fe-N-C nanostick derived from 1D Fe-ZIFs for electrocatalytic oxygen reduction

The slow oxygen reduction process at the cathode and the scarcity of platinum-based metals lead to limited applications in fuel cells and metal-air cells.Recently,transition metal and nitrogen co-doped carbon-based catalysts(M–N–C)are regarded as the most prospective non-precious metal catalysts for future fuel cell applications.It is verified theoretically and experimentally that the metal and nitrogen coordination structure is the main catalytic activity center of oxygen reduction reaction(ORR),so constructing M–N–C materials with high available surface area and structural stability is an effective way to accelerate ORR.Herein,we deliberately synthesize a one-dimensional ZIF structure to fabricate one-dimensional porous Fe–N–C nanostick via two-step pyrolysis.Excitingly,the as-synthesized exhibited an outstanding ORR activity in alkaline medium(E_(1/2)of 0.928 V),as well as superior stability(only changed 7 mV after 10,000 cycles in alkaline medium).Our results show that the reduction of electrocatalyst dimensionality can promote mass transport and increase the accessibility of active sites,thus optimizing their performance in ORR.This work is a good demonstration of the importance of a rational design of catalyst structure for efficient ORR.

Tetravalent Terbium Chelates: Stability Enhancement and Property Tuning

Coordination chemistry of rare-earth elements has been dominated by the+3 oxidation state.Complexes with higher-valence lanthanide ions are synthetically challenging but are of fundamental research interest and significance as advanced molecular materials.Herein,four tetravalent terbium complexes(2-5)of the common formula[Tb(OSiPh3)4L](L=ethylene glycol dimethyl ether(DME),2,2’-bipyridine(bpy),2,2’-bipyrimidine(bpym),and 1,10-phenanthroline(phen))are reported.Crystallographic analyses reveal in each of these complexes a hexacoordinate Tb(IV)ion situated in a distorted octahedral coordination environment formed by four triphenylsi-loxido ligands and a bidentate chelating ligand.The use of chelating ligands enhances the stability of the resulting complexes over their THF solvate precursor.More significantly,the aromatic N-chelating ligands have been found to tune effectively the electronic structures of the complexes,as evidenced by the sizable potential shifts observed for the quasi-reversible redox Tb(IV/III)process and by the changes in their absorption spectra.The experimental findings are augmented with quantum theoretical calculations in which the ligandπ-donation to the 5d orbitals of the Tb(IV)center is found to be primarily responsible for stability enhancement and the corresponding changes of physical properties observed.Magnetic measurements and results from electron paramagnetic resonance studies produced small absolute values of zero-field splittings of these complexes,ranging from 0.1071(22)to 1.1484(112)cm-1 and comparable to the values reported for analogous Tb(IV)complexes.

Ultrathin lanthanide oxides nanomaterials： synthesis, properties and applications

Over the past decade, ultrathin lanthanide oxides(Ln_2O_3, Ln = La to Lu) nanomaterials have been intensively studied in the fields of rare earth materials science. This unique class of nanomaterials has shown many unprecedented properties(big surface area, high surface effect, physical and chemical activities) and is thus being explored for numerous promising applications. In this review, a brief introduction of ultrathin Ln_2O_3 nanomaterials was given and their unique advantages were highlighted. Then, the typical synthetic methodologies were summarized and compared(thermal decomposition, solvothermal, soft template, co-precipition and microwave etc.). Due to the high surface effect, some promising applications of ultrathin Ln_2O_3 nanomaterials, such as drug delivery and catalysis of CO oxidation, were reviewed. Finally, on the basis of current achievements on ultrathin Ln_2O_3 nanomaterials, personal perspectives and challenges on future research directions were proposed.

Mn–Co–Ni–O thin films prepared by sputtering with alloy target

The thin film of heat-sensitive materials has been widely concerned with the current trend of miniaturization and integration of sensors.In this work,Mn1.56 Co0.96 Ni0.48 O4(MCNO)thin films were prepared on Si O2/Si substrates by sputtering with Mn–Co–Ni alloy target and then annealing in air at different temperatures(650–900℃).The X-ray diffraction(XRD)and field emission scanning electron microscopy(FE-SEM)analysis indicated that the main crystalline phase of MCNO thin films was spinel crystal structure;the surface of the thin films was very dense and uniform.The electrical properties of the thin films were studied in the temperature range of–5–50℃.The MCNO thin film with a low room temperature resistance R25 of 71.1 kΩand a high thermosensitive constant B value of 3305 K was obtained at 750℃.X-ray photoelectron spectroscopy(XPS)analysis showed that the concentration of Mn3+and Mn4+cations in MCNO thin films is the highest when annealing temperature is 750℃.The complex impedance analysis revealed internal conduction mechanism of the MCNO thin film and the resistance of the thin film was dominated by grain boundary resistance.

Organic–inorganic hybrid perovskite scintillators for mixed field radiation detection

Sensitive and fast detection of neutrons and gamma rays is vital for homeland security,high-energy physics,and proton therapy.Fast-neutron detectors rely on light organic scintillators,andγ-ray detectors use heavy inorganic scintillators and semiconductors.Efficient mixed-field detection using a single material is highly challenging due to their contradictory requirements.Here we report hybrid perovskites(C_(8)H_(12)N)_(2)Pb(Br_(0.95)Cl_(0.05))_(4)that combine light organic cations and heavy inorganic skeletons at a molecular level to achieve unprecedented performance for mixed-field radiation detection.High neutron absorption due to a high density of hydrogen,strong radiative recombination within the highly confined[PbX_(6)]^(4-)layer,and sub-nanometer distance between absorption sites and radiative centers,enable a light yield of 41000 photons/MeV,detection pulse width of 2.97 ns and extraordinary linearity response toward both fast neutrons andγ-rays,outperforming commonly used fast-neutron scintillators.Neutron energy spectrum,time-of-flight based fast-neutron/γ-ray discrimination and neutron yield monitoring were all successfully achieved using(C_(8)H_(12)N)_(2)Pb(Br_(0.95)Cl_(0.05))_(4)detectors.We further demonstrate the monitoring of reaction kinetics and total power of a nuclear fusion reaction.We envision that molecular hybridized scintillators open a new avenue for mixed-field radiation detection and imaging.

Atomic-level correlation between the electrochemical performance of an oxygen-evolving catalyst and the effects of CeO_(2) functionalization

Herein,we prepared a bimetallic layered double hydroxide(FeCo LDH)featuring a dandelion-like structure.Anchoring of CeO_(2)onto FeCo LDH produced interfaces between the functionalizing CeO_(2)and the parent LDH.Comparative electrochemical studies were carried out.Onset potential,overpotential,and Tafel slope point to the superior oxygen-evolving performance of CeO_(2)-FeCo LDH with respect to FeCo LDH,therefore,demonstrating the merits of CeO_(2)functionalization.The electronic structures of Fe,Co,and Ce were analyzed by X-ray photoelectron spectroscopy(XPS)and electron energy loss spectroscopy(EELS)from which the increase of Co^(3+)and the concurrent lowering of Ce^(4+)were established.With the use of CeO_(2)-FeCo LDH,accelerated formation at a sizably reduced potential of Co-OOH,one of the key intermediates preceding the release of O_(2)was observed by in situ Raman spectroscopy.We now have the atomic-level and location-specific evidence,the increase of the active Co^(3+)across the interface to correlate the enhanced catalytic performance with CeO_(2)functionalization.

A Review of Transition Metal Oxygen-Evolving Catalysts Decorated by Cerium-Based Materials:Current Status and Future Prospects

Non-noble metal catalysts are suitable for the oxygen evolution reaction(OER)owing to their original oxidation states and oxygen coordination environments,which can regulate the adsorption of OH−at the active sites to facilitate the formation of oxygencontaining intermediates.However,the difficulties encountered in the conversion of intermediates(M–OH,M–O,and M–OOH)lead to low efficiency.Decorations of transition metal catalysts with foreign elements are regarded effective solutions,among which decoration with Ce-based materials(CeBM)is the most prominent.This review investigates the current status and future prospects of CeBM-decorated transition metal electrocatalysts.By presenting a thorough account of the latest development,we aim to set a common ground for the research community for a deeper understanding of the roles of CeBM that originate from its unique electronic structure and abundant oxygen vacancies.Moreover,we wish to provide our own perspectives as to how to further the design of Ce-based OER electrocatalysts and where such catalysts may be applied in fields beyond electrocatalysis.

N-doped carbon shell encapsulated PtZn intermetallic nanopartides as highly efficient catalysts for fuel cells

The high cost and poor durability of Pt nanoparticles(NPs)have always been great challenges to the commercialization of proton exchange membrane fuel cells(PEMFCs).Pt-based intermetallic NPs with a highly ordered structure are considered as promising catalysts for PEMFCs due to their high catalytic activity and stability.Here,we reported a facile method to synthesize N-doped carbon encapsulated PtZn intermetallic(PtZn@NC)NPs via the pyrolysis of Pt@Zn-based zeolitic imidazolate framework-8(Pt@ZIF-8)composites.The catalyst obtained at 800℃(10%-PtZn@NC-800)was found to exhibit a half-wave potential(Ev2)up to 0.912 V versus reversible hydrogen electrode(RHE)for the cathodic oxygen reduction reaction in an acidic medium,which shifted by 26 mV positively compared to the benchmark Pt/C catalyst.Besides,the mass activity and specific activity of 10%-PtZn@NC-800 at 0.9 V versus RHE were nearly 3 and 5 times as great as that of commercial Pt/C,respectively.It is worth noting that the PtZn@NC showed excel Ient stability in oxygen reducti on reacti on(ORR)with just 1 mV of the Ev2 loss after 5,000 cycles,which is superior to that of most reported PtM catalysts(especially those disordered solid solutions).Furthermore,such N-doped carb on shell encapsulated PtZn intermetallic NPs showed significa ntly enha need performances towards the anodic oxidation reaction of organic small molecules(such as methanol and formic acid).The synergistic effects of the N doped carbon encapsulation structure and intermetallic NPs are responsible for outstanding performances of the catalysts.This work provides us a new engineering strategy to acquire highly active and stable multifunctional catalysts for PEMFCs.

A smart post-synthetic route towards[Fe_(2)Co_(2)]molecular capsules with electron transfer and bidirectional switching behaviors

Aldehyde groups were intentionally equipped on the cyanide-bridged[Fe_(2)Co_(2)]square molecules:{[(Tp*)Fe(CN)_(3)Co(bpy^(CHO))_(2)]_(2)-[PF_(6)]_(2)}·4MeOH(1,Tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate;bpy^(CHO)=4-formyl-4′-methyl-2,2′-bipyridine),thus providing chemical-active windows for post-modification towards desired functions.In this contribution,by taking advantage of efficient Schiff-base condensation between the aldehyde-substituted bipyridine derivative(bpyCHO)and alkyl diamines(H_(2)N-(CH_(2))_(n)NH_(2)),two discrete[Fe_(2)Co_(2)]compounds{[(Tp∗)Fe(CN)_(3)Co(bpy^(C=N(CH_(2))_(n)N=C)bpy)]2[PF_(6)]_(2)}⋅6DMF(2,n=5;3,n=7)were prepared,where the cyanide-bridged[Fe_(2)Co_(2)]square cores were encapsulated by the flexible alkyl chains.Variable-temperature single-crystal X-ray diffraction and magnetic studies revealed complete thermo(T_(1/2)=233 K(2)and 237 K(3))and photo-induced electron transfer event accompanying spin transition between the diamagnetic[Fe^(Ⅱ)_(LS2)Co^(Ⅲ)_(LS2)]state and the paramagnetic[Fe^(Ⅲ)_(LS2)Co^(Ⅱ)_(HS2)]state(LS,low spin;HS,high spin).In addition,the bidirectional switching between the two states was achieved with alternating laser irradiation at 808 and 532 nm at 10 K.

Formic Acid Dehydrogenation for Hydrogen Production Promoted by Grubbs and Hoveyda-Grubbs Catalysts

In this work,we screened three Grubbs catalysts and two Hoveyda-Grubbs catalysts for the production of H_(2) by dehydrogenation of formic acid(FA).The best results were achieved with the use of a first-generation Hoveyda-Grubbs catalyst.With a catalyst loading of mere 0.5μmol, a maximum TON of 36356 was obtained within 3 h.Two key intermediates were identified by using 1H NMR and high-resolution electrospray ionization mass spectroscopy(HRESI-MS),based on which a mechanism possibly responsible for the observed catalysis was proposed.

Dark current modeling of thick perovskite X‑ray detectors

Metal halide perovskites(MHPs)have demonstrated excellent performances in detection of X-rays and gamma-rays.Most studies focus on improving the sensitivity of single-pixel MHP detectors.However,little work pays attention to the dark current,which is crucial for the back-end circuit integration.Herein,the requirement of dark current is quantitatively evaluated as low as 10^(−9)A/cm^(2)for X-ray imagers integrated on pixel circuits.Moreover,through the semiconductor device analysis and simulation,we reveal that the main current compositions of thick perovskite X-ray detectors are the thermionic-emission current(J_(T))and the generation-recombination current(J_(g-r)).The typical observed failures of p-n junctions in thick detectors are caused by the high generation-recombination current due to the band mismatch and interface defects.This work provides a deep insight into the design of high sensitivity and low dark current perovskite X-ray detectors.

Metal-organic frameworks of lanthanide iminodiacetates and tartrates:Synthesis,structural characterization and luminescence properties——Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

Two series of lanthanide-containing metal-organic frameworks(Ln-MOFs)of the general formula{[Ln(HIDA)_(2)H_(2)O]ClO_(4)·H_(2)O}_n(Ln=La(1),Nd(2),Eu(3),Gd(4),Tb(5),Eu:Tb(6);H_(2)IDA=iminodiacetic acid)and[Ln(TT)(HTT)(H_(2)O)_3]_n(Ln=Eu(7),Gd(8),Tb(9),Dy(10),and Eu:Tb(11);H_(2)TT=tartaric acid)were synthesized by reacting Ln(ClO_(4))_3 with iminodiacetic acid and L-tartaric acid,respectively.All compounds were structurally characterized by single-crystal X-ray diffraction.Elemental analyses are co nsistent with the corre sponding crystallographically generated formulas.Mo reover,the luminescence properties of both the single and mixed-lanthanide complexes were studied.Near infrared,red,and green emissions that are characteristic of Nd(Ⅲ),Eu(Ⅲ),and Tb(Ⅲ)are observed for 2,3/7,and 5/9,respectively.For the two mixed-lanthanide complex systems 6 and 11,depending on the relative amount of Eu(Ⅲ)and Tb(Ⅲ),the color of emission can be fine-tuned.It is found that a small amount of Eu(Ⅲ)is adequate for the observation of the most intense transition of Eu(Ⅲ).This is believed to be a result of energy transfer from Tb(Ⅲ)to Eu(Ⅲ)within the same complex-a conclusion supported by the significantly shortened lifetime of Tb(Ⅲ)and the accompanying enhanced lifetime of Eu(Ⅲ)in the mixedlanthanide complex with respect to the corresponding values for the pure Tb(Ⅲ)and Eu(Ⅲ)complexes with the same ligand.

Secondary Metal Coordination Using a Tetranuclear Complex as Ligand Leading to Hexanuclear Complexes with Enhanced Thermal Barriers for Electron Transfer

Postsynthesis of the paramagnetic square-shaped complex{[(Tp*Me)Fe(μ-CN)_(2)(CN)][Co(dmbpy)_(2)]}_(2)(BPh_(4))_(2)·6MeCN·H2O[1,Tp*Me=tris(3,4,5-trimethylpyrazole)-borate;dmbpy=4,4′-dimethyl-2,2′-bipyridine)]by grafting transition metal(II)thiocyanates via its terminal cyano groups afforded three hexanuclear[Fe_(2)Co_(2)M_(2)]clusters(M=Zn,2;Co,3;Cd,4).The peripheral metal-complex units serving as excellent electron acceptors were found to help stabilize the low-temperature state of Fe^(II,LS)–Co^(III,LS) within the complex core.

Hybrid Bioelastomer Reinforced by Ultrathin Nanowires of Lanthanide Hydroxycarbonates for Promising Biomedical Applications

Hybrids composed of biocompatible polymers reinforced with inorganic nanomaterials are useful for many biomedical applications including implantation and tissue regeneration and engineering.In this work,we report a new type of hybrid prepared by doping ultrathin nanowires of lanthanide hydroxycarbonates into classical biocompatible poly(citrates-siloxane).The doping of the inorganic nanowires imparts the hybrids with excellent miscibility with the polymeric matrix,producing hybrids with high elasticity and high tensile strength.The hybrids containing Eu(III)and Gd(III)display their respective luminescence and magnetic properties and thus,offer opportunities to monitor the fate of such hybrids when used in vivo.Insignificant degradation and excellent biocompatibility of these hybrids have also been demonstrated.Together,these favorable traits portend useful applications of the newly developed hybrid elastomers.