Interfacial Charge Transfer Induced Electronic Property Tuning of MoS_2 by Molecular Functionalization

The modulation of electrical properties of MoS_2 has attracted extensive research interest because of its potential applications in electronic and optoelectronic devices.Herein,interfacial charge transfer induced electronic property tuning of MoS_2 are investigated by in situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy measurements.A downward band-bending of MoS_2-related electronic states along with the decreasing work function,which are induced by the electron transfer from Cs overlayers to MoS_2,is observed after the functionalization of MoS_2 with Cs,leading to n-type doping.Meanwhile,when MoS_2 is modified with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F_4-TCNQ),an upward band-bending of MoS_2-related electronic states along with the increasing work function is observed at the interfaces.This is attributed to the electron depletion within MoS_2 due to the strong electron withdrawing property of F_4-TCNQ,indicating p-type doping of MoS_2.Our findings reveal that surface transfer doping is an effective approach for electronic property tuning of MoS_2 and paves the way to optimize its performance in electronic and optoelectronic devices.

Accurate quantification of TiO_(2)(B)'s phase purity via Raman spectroscopy

Bronze phase titanium dioxide(TiO_(2)(B))could be a promising high-power anode for lithium ion battery.However,TiO_(2)(B)is a metastable material,so the as-synthesized samples are inevitably accompanied by the existence of anatase phases.It has been found that the TiO_(2)(B)'s purity is positively correlated with its electrochemical performance.Herein,we have established an accurate quantification of the TiO_(2)(B)/anatase ratio,by figuring out the function between the purity of TiO_(2)(B)phase in the high purity range and its Raman spectra features in combination of the calibration by the synchrotron radiation X-ray diffraction(XRD).Compared with the time-consuming electrochemical method,the rapid,sensitive and non-destructive features of Raman spectroscopy have made it a promising candidate for determining the purity of TiO_(2)(B).Further,the correlations developed in this work should be instructive in synthesizing pure TiO_(2)(B)and furthermore optimizing its electrochemical charge storage properties.

Theoretical Study on Electronic and Charge Transfer Properties of Oligo[8]thiophene and Its Circular,Hooped,and Helical Derivatives

The novel linear, circular, hooped, and helical molecules based on oligo[8]thio- phene were theoretically studied for the applications of charge transfer devices. To investigate the influence of topology for oligo[8]thiophene derivatives, the geometry structures, frontier molecular orbital （FMO） energies, charge transport properties, and stability property were predicted by density functional theory methods. The calculated results reported herein show that the oligo[8]thiophene derivative with linear structure has smaller energy gap, and fused oligo[8]thiophene derivative with circular structure has the smallest reorganization energy among the designed molecules. We have also studied the stability properties of the designed molecules, and oligo[8]thiophene derivatives are more stable tharJ the fused oligo[8]thiophene derivatives.

Rational Design of Star-shaped Molecules with Benzene Core and Naphthalimide Derivatives End Groups as Organic Light-emitting Materials

A series of star-shaped molecules with benzene core and naphthalimides derivatives end groups have been designed to explore their optical,electronic,and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes（OLEDs）. The frontier molecular orbitals（FMOs） analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer（ICT）. The calculated results show that the optical and electronic properties of star-shaped molecules are affected by the substituent groups in N-position of 1,8-naphthalimide ring. Our results suggest that star-shaped molecules with n-butyl（1）,benzene（2）,thiophene（3）,thiophene S？,S？-dioxide（4）,benzo[c][1,2,5]thiadiazole（5）,and 2,7a-dihydrobenzo[d]thiazole（6） fragments are expected to be promising candidates for luminescent and electron transport materials for OLEDs. This study should be helpful in further theoretical investigations on such kind of systems and also to the experimental study for charge transport and/or luminescent materials for OLEDs.

A STUDY ON THE INTERACTION BETWEEN CH_3OH AND H_2CO MOLECULES IN TERMS OF THE PROPERTIES OF CHARGE DENSITY DISTRIBUTIONS

Two possible complexes formed by the interaction of CH_3OH and H_2CO,one hydrogen-bonded (Ⅰ)and one donor-acceptor complex(Ⅱ),have been reported in the previous paper.Based on the ab initio 6-31G basis set calculations,the properties of the charge density for the complexeshave been analyzed using the theory of atoms in molecules.The nature of the complex formation has been discussed in terms of the properties of the charge density distributions.

Effect of Hydrogen Charging on the Tensile and Constant Load Properties of an Austenitic Stainless Steel Weldment

The effect of cathodic hydrogen charging on the tensile and constant load properties was deter- mined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base metal and a 308L filler steel as a weld metal. Part of the 304L solution treated steel was separately given additional sensitization treatment to simulate the microstructure that would develop in the heat affected zone. Tests were performed at room temperature on notched round bar specimens. Hydrogen charging resulted in a pronounced embrittlement of the tested materials. This was manifested mainly as a considerable loss in the ductility of tensile specimens and a decrease in the time to failure and threshold stress of constant load specimens. The 308L weld metal exhibited the highest, and the 304L solution treated steel the lowest, resistance to hydrogen embrittlement. Hydrogen embrittlement was associated with the formation of strain induced martensite as well as a transition from brittle to ductile fracture morphology onwards the centre of the specimens.

A Quantum Chemical Screening of Two Imidazole-Chalcone Hybrid Ligands and Their Pd, Pt and Zn Complexes for Charge Transport and Nonlinear Optical (NLO) Properties: A DFT Study

A quantum chemical screening of two imidazole-based chalcone ligands: 2- [1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol and 2-[1-(3-(1H- imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol (hereinafter referred to as HL1 and HL2 respectively) and their Pd, Pt and Zn chelates for charge transport and nonlinear optical (NLO) properties, is reported via dispersion- corrected density functional theory (DFT-D3) and time-dependent DFT (TD- DFT) methods. From our results, Pd and Pt complexes have been observed to show excellent hole-transport properties, owing to their very small reorganization energies. The light extraction efficiency of the HL1-Pt complex was deduced to be particularly impressive, thus suitable for the manufacture of hole transport layer in violet light emitting diodes (LEDs). Moreover, redox potentials and chemical stability studies have enabled us to validate the greater stability in moisture (towards oxidation), of HL2 complexes compared to their HL1 counterparts. The first and second hyperpolarizabilities of both ligands and their complexes have been found to be outstandingly higher than those of the push-pull prototypical, para-nitroaniline by factors of up to 12 in the case of HL2. These compounds, with the exception of the HL2-Pt complex, are thus interesting candidates having wide transparency tradeoffs for NLO efficiency in the manufacture of optoelectronic and photonic devices capable of second and third-order NLO response. Finally, metal chelation has been established to enhance the NLO response of all the chalcone-based imidazole ligands investigated as a result of metal-ligand charge transfer and ligand- metal charge transfer electronic transitions identified in the resulting complexes with the exception of the zinc complexes.

Surface charge property governing co-transport of illite colloids and Eu(Ⅲ) in saturated porous media

The transport of colloids and radionuclides is sophisticated because of the variety of charge properties between colloidal particles and host subsurface media, which causes great difficulty in establishing a reliable model of radionuclides migration by taking the colloid phase into consideration. In this work,the co-transport of illite colloids(IC) and Eu(Ⅲ) in the quartz sand and iron-coated sand porous media was investigated by column experiments to address the predominant mechanism of charge properties on co-transport. Results showed that Eu(Ⅲ) transport was driven by the illite colloids and electrostatic interaction was critical in governing the co-transport patterns. The promotion of Eu(Ⅲ) transport by IC was attenuated in the iron-coated sand systems;more IC-Eu(Ⅲ) complexes were retained uniformly in the column. The pore throat shrinkage caused by electrostatic attachment between aggregated IC and iron oxides exacerbated the physical straining and size exclusion effect of IC-Eu(Ⅲ) complexes. An aggravated irreversible retention of IC-Eu(Ⅲ) was detected in iron-coated sand column due to the electrostatic attraction of IC-Eu(Ⅲ) to host media. The findings are essential for improving the understanding on the potential transport, retention and release risk of colloids associated radionuclides, and imply that the positively charged permeable reactive barrier is an effective strategy to reduce the transport risk of colloid associated radionuclides.

Cocrystal engineering:towards high-performance near-infrared organic phototransistors based on donor-acceptor charge transfer cocrystals

Near-infrared organic phototransistors have wide application prospects in many fields.The active materials with the high mobility and near-infrared response are critical to building high-performance near-infrared organic phototransistors,which are scarce at present.Herein,a new charge transfer cocrystal using 5,7-dihydroindolo[2,3-b]carbazole(5,7-ICZ)as the donor and 2,2’-(benzo[1,2-b:4,5-b’]dithiophene-4,8-diylidene)dimalononitrile(DTTCNQ)as the acceptor is properly designed and prepared in a stoichiometric ratio(D:A=1:1),which not only displays a high electron mobility of 0.15 cm^(2)V^(-1)s^(-1) and very low dark current,but also can serve as the active layer materials in the region of near-infrared detection due to the narrowed band gap and good charge transport properties.A high photosensitivity of 1.8×10^(4),the ultrahigh photoresponsivity of 2,923 A W-1and the high detectivity of 4.26×10^(11)Jones of the organic near-infrared phototransistors are obtained.

Finely Tuned Electron/Hole Transport Preference of Thiazoloisoindigo-based Conjugated Polymers by Incorporation of Heavy Chalcogenophenes

A series of copolymers of thiazoloisoindigo (Tzll) with different chalcogenophene trimers were synthesized to systematicllyinvestigate the chalcogen effect on their charge transport propertes.When only the middlethiophene ring of terthiphene(T-T-T)is replaced byheavier chalcogenophenes,a preference(expressed by the ratio of μe/μh)towards electron transport was observed descending from T-T-Tto T-Se-Tthen to T-Te-T(Se and Te stand for selenophene and tellurophene,respectively).On the other hand,with the increased number of heavierchalcogenophenes,a preference toward hole transport was observed descending from Se-T-Se to Se-Se-se then to Se-Te-Se.This phenomenon iswellexplained by the balance between the aromatic resonance energy of the chalcogenophenes and the electronegativity of the chalcogens.Specifically,P(TZll-T-Se-T)displayed relatively balanced ambipolar property(μh^(max)andμe^(max) of 3.77 and 1.59 cm^(2)·v^(-1)·s^(-1)with aμe/μh of 0.42).while P(Tll-Se-Te-Se)exhibited the best preference to hole transfer with a u.u,of 0.09.P(Tzll-T-Te-T)exhibited the best preference to electrontransfer with aμe/μl,of 16 and theμe^(max)of 0.64 cm^(2)·v^(-).s^(-1)which is the highest electron mobility among the known conjugated polymerscontaining tellurophenes.

Tax distortions in cross-border flows of intangible assets

The phenomenon of global fragmented production and associated trade in intermediate products,including intangible assets,has changed how economists study globalization and how new public policies are shaped.Understanding cross-border flows of disembodied knowledge,often associated with intellectual property(IP),is essential for analyzing how modern economies operate.Available data to document these international IP-related knowledge flowsdnamely cross-border payments for IPdare distorted by various factors.Tax planning by multinational enterprises has seriously distorted the measurement of cross-border IP flows,affecting national measurements of imports,exports,GDP,and productivity.The tax-induced mismeasurement could be more than 35% of global charges for use of intellectual property,and greater for individual countries,particularly high-taxrate countries.International initiatives to address the effects of tax base erosion,profit shifting,and other statistical initiatives on global value chains will improve future measurements of cross-border IP flows,improving the understanding of both the creation and uses of IP.

Simultaneous studies of pressure effect on charge transport and photophysical properties in organic semiconductors:A theoretical investigation

High-mobility and strong luminescent materials are essential as an important component of organic photodiodes,having received extensive attention in the field of organic optoelectronics.Beyond the conventional chemical synthesis of new molecules,pressure technology,as a flexible and efficient method,can tune the electronic and optical properties reversibly.However,the mechanism in organic materials has not been systematically revealed.Here,we theoretically predicted the pressure-depended luminescence and charge transport properties of high-performance organic optoelectronic semiconductors,2,6-diphenylanthracene(DPA),by first-principle and multi-scale theoretical calculation methods.The dispersion-corrected density functional theory(DFT-D)and hybrid quantum mechanics/molecular mechanics(QM/MM)method were used to get the electronic structures and vibration properties under pressure.Furthermore,the charge transport and luminescence properties were calculated with the quantum tunneling method and thermal vibration correlation function.We found that the pressure could significantly improve the charge transport performance of the DPA single crystal.When the applied pressure increased to 1.86 GPa,the hole mobility could be doubled.At the same time,due to the weak exciton coupling effect and the rigid flat structure,there is neither fluorescence quenching nor obvious emission enhancement phenomenon.The DPA single crystal possesses a slightly higher fluorescence quantum yield~0.47 under pressure.Our work systematically explored the pressure-dependence photoelectric properties and explained the inside mechanism.Also,we proposed that the exte rnal pressure would be an effective way to improve the photoelectric perfo rmance of organic semiconductors.