Kinds Of Acceptors Research Articles

Study on the structure–performance relationship of nonlinear optical chromophores with different donors, bridges, and acceptors

Three series of high performance nonlinear optical chromophores based on triphenylamine or N,N-bis-(4-methoxyphenyl)arylamine as donors and three kinds of acceptors were synthesized and investigated.

Benzothiadiazole-based non-fullerene acceptors

The power conversion efficiencies (PCEs) of organic solar cells (OSCs) have been greatly improved with the rapid development of non-fullerene acceptors (NFAs) in recent five years. Among a great deal of electron-accepting units (A units), benzothiadiazole (BT) is the most important one and has been widely used to construct high-efficiency NFAs due to its unique electron-withdrawing properties, plane rigidity and structural adjustability. The optoelectronic properties of BT-based small molecules can be efficiently modulated with the location of BT unit in the molecular backbone. Typically, BT unit is used as an A 1 unit to construct A 2 -D-A 1 -D-A 2 and A 2 -A 1 -D-A 1 -A 2 type acceptors. Furthermore, DA’ D -type fused BT-units can be utilized as a central segment to design A-DA’D-A type NFAs, which promote the rapid progress of OSCs from 2019. Judicious molecular engineering can finetune the energy levels of frontier molecular orbitals, absorption spectra, and the π-π staking properties of these materials. In turn, high-efficiency photovoltaic devices can be obtained by combining these BT-based NFAs with suitable p-type polymers. The highest PCE of OSC reached up to 18%, which could be mainly attributed to the emerge of the fused-BT-based molecule Y6. This review firstly made a precise classification of BT-based NFAs, and then summarized the relationship of chemical structures, molecular properties, and device performance. Finally, we looked forward to the challenges and design directions of this kind of molecules in the future. Benzothiadiazole (BT) is the most important electron-accepting (A) unit and has been widely used to construct high-efficiency non-fullerene acceptors (NFAs). This review firstly made a precise classification of BT-based NFAs: single-BT, double-BT, multiple-BT and ring-fused BT. Then, we summarized the relationship of chemical structures, molecular properties, energy loss and photovoltaic performance. Finally, the challenges and design directions of this kind of molecules are prospected. • A comprehensive review on the development of BT-based non-fullerene acceptors (NFAs) was made. • BT-based acceptor is an eximious material to obtain power conversion efficiency of more than 18%. • This kind of acceptor has been systematically classified and the structure-property relationships were deeply summarized. • An innovative prospect for the future development and the direction of industrialization of BT-based acceptors was made.

In Situ Spectrophotometric Investigation of Charge Transfer Complexes Between Triamterene, a Management of Hypertension Drug, and Four Kinds of Nitro Acceptors in Different Organic Solvents

A UV–Vis spectrophotometric method was used to confirm the intermolecular charge-transfer complexes of the drug triamterene (TM) donor with four nitro π-acceptors (2,4,6-trinitrophenol (PA), 4-nitrophenol (4-NP), 4-nitroacetophenone (4-NAP) and m-dinirobenzene (m-DNB)) in methanol, ethanol, acetone, acetonitrile, chloroform, dichloromethane, and dichloroethane at 25 °C. The spectra showed chemical shifts upon the addition of TM to solutions of the nitro acceptors in the solvents. The appearance of new bands or hyper- and hypo-chromic effects confirmed the presence of charge-transfer complexes. The spectra of the complexes of TM and nitro π-acceptors show different absorption bands at different wavelengths for different solvents. The molar ratio method showed a result of 1:1 for the TM–PA system and 1:2 for the TM–4-NP, TM–4NAP, and TM–m-DNB charge-transfer complexes. The physical spectroscopic parameters were calculated, including the formation constant (KCT), molar extinction coefficient (eCT), oscillator strengths (f), ionization potential (Ip), resonance energy (RN), and Gibbs energy (ΔG°). The optical band gap of the TM-nitro charge-transfer complexes was estimated, and there was clearly a relationship between the different kinds of acceptors and their optical band gaps.

Cellulose–chitin hybrids: synthesis of branched amino polysaccharides by regioselective introduction of (N-acetyl-)d-glucosamine branches into cellulose

Cellulose–chitin hybrid-type branched polysaccharides, β-1,4-d-glucans having amino sugar branches at the C-6 position, have been synthesized through a series of site-specific modification reactions. Cellulose was first transformed to two kinds of acceptors having a reactive group only at C-6. Glycosylation reactions of these acceptors with an oxazoline donor derived from d-glucosamine resulted in the introduction of amino sugar branches into cellulose. An acceptor carrying the O-trimethylsilyl group at C-6 was particularly suitable for glycosylation in solution to form branched celluloses with various degrees of substitution up to about 0.5 per pyranose unit in a controlled manner. Deprotection of the product afforded the cellulose having N-acetyl-d-glucosamine or d-glucosamine branches depending on the reaction conditions. The deprotected nonnatural branched polysaccharides were readily soluble in neutral water as well as common organic solvents and would be promising as a new type of water-soluble amino polysaccharides.

Divacancy complexes induced by Cu diffusion in Zn-doped GaAs

Positron annihilation spectroscopy was applied to investigate the nature and thermal behavior of defects induced by Cu diffusion in Zn-doped p-type GaAs crystals. Cu atoms were intentionally introduced in the GaAs lattice through thermally activated diffusion from a thin Cu capping layer at 1100 °C under defined arsenic vapor pressure. During isochronal annealing of the obtained Cu-diffused GaAs in the temperature range of 450−850 K, vacancy clusters were found to form, grow and finally disappear. We found that annealing at 650 K triggers the formation of divacancies, whereas further increasing in the annealing temperature up to 750 K leads to the formation of divacancy-copper complexes. The observations suggest that the formation of these vacancy-like defects in GaAs is related to the out-diffusion of Cu. Two kinds of acceptors are detected with a concentration of about 1016 − 1017 cm−3, negative ions and arsenic vacancy copper complexes. Transmission electron microscopy showed the presence of voids and Cu precipitates which are not observed by positron measurements. The positron binding energy to shallow traps is estimated using the positron trapping model. Coincidence Doppler broadening spectroscopy showed the presence of Cu in the immediate vicinity of the detected vacancies. Theoretical calculations suggested that the detected defect is V Ga V As-2CuGa.

Energy band and acceptor binding energy of GaN and Al xGa 1− xN

The hole effective-mass Hamiltonian for the semiconductors of wurtzite structure is established, and the effective-mass parameters of GaN and Al x Ga 1− x N are given. Besides the asymmetry in the z and x, y directions, the linear term of the momentum operator in the Hamiltonian is essential in determining the valence band structure, which is different from that of the zinc-blende structure. The binding energies of acceptor states are calculated by solving strictly the effective-mass equations. The binding energies of donor and acceptor for wurtzite GaN are 20 and 131, 97 meV, respectively, which are inconsistent with the recent experimental results. It is proposed that there are two kinds of acceptors in wurtzite GaN. One kind is the general acceptor such as C, substituting N, which satisfies the effective-mass theory, and the other includes Mg, Zn, Cd etc., the binding energy of which deviates from that given by the effective-mass theory. Experimentally, wurtzite GaN was grown by the MBE method, and the PL spectra were measured. Three main peaks are assigned to the DA transitions from the two kinds of acceptor. Some of the transitions were identified as coming from the cubic phase of GaN, which appears randomly within the predominantly hexagonal material. The binding energy of acceptor in AlN is about 239, 158 meV, that in Al x Ga 1− x N alloys ( x≈0.2) is 147, 111 meV, close to that in GaN.

Energy bands and acceptor binding energies of GaN

The energy bands of zinc-blende and wurtzite GaN are calculated with the empirical pseudopotential method, and the pseudopotential parameters for Ga and N atoms are given. The calculated energy bands are in agreement with those obtained by the ab initio method. The effective-mass theory for the semiconductors of wurtzite structure is established, and the effective-mass parameters of GaN for both structures are given. The binding energies of acceptor states are calculated by solving strictly the effective-mass equations. The binding energies of donor and acceptor are 24 and 142 meV for the zinc-blende structure, 20 and 131, and 97 meV for the wurtzite structure, respectively, which are consistent with recent experimental results. It is proposed that there are two kinds of acceptor in wurtzite GaN. One kind is the general acceptor such as C, which substitutes N, which satisfies the effective-mass theory. The other kind of acceptor includes Mg, Zn, Cd, etc., the binding energy of these acceptors is deviated from that given by the effective-mass theory. In this report, wurtzite GaN is grown by the molecular-beam epitaxy method, and the photoluminescence spectra were measured. Three main peaks are assigned to the donor-acceptor transitions from two kinds of acceptors. Some of the transitions were identified as coming from the cubic phase of GaN, which appears randomly within the predominantly hexagonal material.

P-Type co-doping study of GaN by photoluminescence

Photoluminescence measurements were performed on p-type co-doping effects of C, As, and Mg in GaN. The dopants were incorporated into GaN by ion implantation performed at 77 K. We find that the 3.42 eV luminescence line is sensitive to hole concentration, and propose that after careful calibration the 3.42 eV line may be used as a probe to measure hole concentration in GaN. Simply doping one kind of acceptors will not result in holes, while co-doping can substantially improve p-type doping efficiency. As+C and As+Mg co-doping induce an acceptor level of 180 meV above the valence band. Mg+C co-doping is the most promising method for p-type doping, the related acceptor level is determined to be as shallow as 130 meV. The improvement of the doping efficiency by co-doping is probably due to the decrease of the acceptor ionization energy.

Hydrogen bonds in molecular assemblies of natural, synthetic and ‘designer’ peptides

The initial folding of the backbone of peptides and the subsequent arrangement of the molecules into a supramolecular assembly is primarily associated with NH⋯OC hydrogen bonds where the N⋯O distance is 2.8–3.0 Å and to a lesser extent with water molecules that act as donors and acceptors for hydrogen bonds, both within a peptide molecule and between peptide molecules. In helical peptides, the transition between 3 10-helices (with 10 atoms in a hydrogen-bond ring) and α-helices (with 13 atoms in a hydrogen bond ring) merely requires a shift from one CO to an adjacent CO and is often quite facile. Among examples to be presented are two crystal structures of a heptapeptide wherein the helices are the 3 10-type when the amino end group is Boc and the α-type when the amino end is Ac. A new type of regular helix was synthesized and characterized by x-ray diffraction analysis using β-amino acid residues, rather than α-amino acid residues. The new helix was named β-foldamer and it is characterized by 14-atom hydrogen-bond rings rather than the 13-atom rings present in α-helices. An NH group will not always form a hydrogen bond with any CO (or H 2O) that is present in a crystal. Examples are shown in which the N⋯O distance is > 3.30 A ̊ and also examples of structures in which there is no O acceptor or any other kind of acceptor within possible reach of an available NH. Assemblies with ‘free’ NH groups are presented in which there is no possibility for a ‘cooperative hydrogen bond’ between NH and the center of a phenyl group, although other structures with a close NH⋯phenyl approach will be discussed.

Evidence of two kinds of acceptors in undoped semi-insulating GaAs: Positron trapping at gallium vacancies and negative ions.

Positron-lifetime experiments have been performed in Zn-doped p-type and undoped semi-insulating GaAs in the temperature range 20--300 K to investigate native point defects. In p-type materials with hole concentrations of ${10}^{15}$--${10}^{19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, no evidence of positron trapping is observed. The temperature dependence of the positron lifetime can be explained in terms of lattice expansion associated with positron-phonon coupling. Therefore, we ascribe it to delocalized positrons. In semi-insulating GaAs, two kinds of acceptors are detected with concentrations in the range ${10}^{15}$--${10}^{17}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$: gallium vacancies and negative ions. The temperature dependence of the positron trapping at the Ga vacancy exhibits a slope break at about 130 K. A weakly bound Rydberg-like precursor state is invoked to explain this temperature dependence.

Conducting organic complexes using dumbbell-shaped donors (BTFE-X); X=B, DMB, DMtB, DCB

Novel dumbbell-shaped donors, (BTFE-X): 1,4 bis [2-(tetrathiafulvalene-2-yl)ethylenyl]-2,5- X ; X =benzene, dimethylbenzene(DMB), dimetoxybenzene, and dichlorobenzene were synthesized and their complexes were made with several kinds of acceptors. Some complexes showed high conductivity more than 1S/cm at room temperature. Most conducting complexes, (BTFE-DMB)iodide, have three different types of crystal structures and showed corresponding temperature dependence of the conductivity. Compacting pellets consisting of (BTFE-DMB)I 3 powder crystals having a certain crystal structure exhibited pressure induced-resistive anomaly around 175K under 0.1GPa.

Comparison of strontium-induced and oxygen-induced holes in La2CuO4.

The Hall coefficient, dc conductivity, and hence the mobility, as well as the ac conductivity and the dielectric constant in the ${\mathrm{CuO}}_{2}$ planes are reported for single crystals of ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ containing \ensuremath{\sim}0.2 mole % holes introduced by doping with oxygen or strontium. In general, the transport properties are quite similar for the two kinds of acceptors. A smaller value of the binding energy is found for the Sr acceptor than the oxygen acceptor. In addition, the in-plane dielectric constant is found to be larger in the Sr-doped sample, and the characteristic temperature for variable-range hopping is smaller. The latter observations indicate that the radius of the hole's orbit when bound to the acceptor is larger for Sr than for O, consistent with the smaller binding energy. Despite these differences in the bound states of the acceptors, the holes introduced by O and Sr appear to affect the antiferromagnetic order in the same way since the two crystals have the same N\'eel temperature. The temperature dependencies of the in-plane mobility for the two systems are very similar, and are well-described by a simple model combining polar optical phonon scattering and the scattering of charged impurities. The quantitative agreement with theory for the optical phonon scattering confirms the polaronic nature of the charge carriers.

Kinetic Properties and Acceptor Substrate Preferences of Two Kinds of Gal.beta.1,3GalNAc .alpha.2,3-Sialyltransferase from Mouse Brain

The cDNAs encoding two kinds of Gal beta 1,3GalNAc alpha 2,3-sialytransferases (ST3GalA.1 and ST3GalA.2) have been cloned from mouse brain, both of which could synthesize the NeuAc alpha 2,3Gal beta 1,-3GalNAc sequence of gangliosides as well as O-glycosidically linked oligosaccharides of glycoproteins [Lee et al. (1993) Eur. J. Biochem. 216, 377-385; Lee et al. (1994) J. Biol. Chem. (in press)]. Kinetic analysis of the two sialyltransferases using Gal beta 1,3GalNAc, asialoGM1, or asialofetuin revealed that ST3GalA.1 exhibits the highest Km value for asialoGM1 (Km = 1.25 mM) and the lowest one for asialofetuin (Km = 0.10 mM), whereas the Km values of ST3GalA.2 for the substrates are very similar (Km approximately 0.5 mM). The synthesis of GM1b from asialoGM1 by ST3GalA.1 was clearly inhibited in the presence of Gal beta 1,3GalNAc or asialofetuin, but that by ST3GalA.2 was not at all. On the other hand, the activity of ST3GalA.2 toward Gal beta 1,3GalNAc or asialofetuin was inhibited by asialoGM1 or GM1. The results of acceptor competition experiments involving asialoGM1, Gal beta 1,3GalNAc, and asialofetuin indicated that ST3GalA.2 exhibits noncompetitive inhibition between asialoGM1 and Gal beta 1,3GalNAc or between asialoGM1 and asialofetuin, whereas ST3GalA.1 exhibits competitive inhibition between all kinds of acceptors. These results strongly indicate that acceptor preference of ST3GalA.1 is different from that of ST3GalA.2, although their acceptor substrate specificities are the same; i.e., gangliosides serve as predominant acceptors for the latter over O-glycosidically linked oligosaccharides of glycoproteins, which are much better acceptors for the former.

Origin of donor and acceptor species in undoped ZnSe grown by low-pressure metalorganic chemical vapor deposition

Effects of the [H2 Se]/[Dimethylzinc] source ratio on the electrical properties in the temperature range of 15–300 K and on the cathodoluminescence properties at 77 K have been investigated for undoped ZnSe films grown in one deposition run on (100)GaAs substrates at 350 °C by metalorganic chemical vapor deposition. The properties correlated with each other and depended on the degrees of deviation from stoichiometry. The dominant donor is identified with selenium vacancy from the dependence of donor concentration on the ratio and on the film thickness. Two kinds of acceptors were introduced according to the deviation from stoichiometry. They are tentatively associated with NSe and NaZn . Extended lattice defects which reduce the electron mobility are favored at the high ratios and they seem a principal factor of the high-resistive property of this material.

Photoluminescence on oxygen-rich acceptor-doped silicon

Oxygen-related centres in silicon containing the acceptors boron, aluminium, gallium or indium, were studied by photoluminescence. Only the O band showed a dependence on the kind of acceptor. In acceptor-implanted material the formation of the P luminescence was enhanced and a new photoluminescence line was observed at 1.117 eV, which was attributed to a boron-oxygen complex.

Transfer of solvated electrons to some aliphatic halides in ethanol at 77 K. The role of Franck-Condon factors

Electron transfer probabilities of solvated electrons were determined by optical absorption measurements in ethanol at 77 K. Large variations in the electron transfer probabilities were recognized for various kinds of acceptors, being related to the activation energy of the dissociative electron attachments in gases. These were ascribed to the effects of the nuclear contributions of the acceptors, namely, Franck-Condon factors. Treating the nonadiabatic electron transfer process with the Fermi golden rule instead of the simple barrier penetration model, the Franck-Condon factors were calculated in the same manner developed in the theory of predissociation. Using Morse potentials obtained in the gas phase, relationships among the transfer of solvated electrons and dissociative electron attachments in gases and liquids were clarified. 2 tables, 5 figures.

Optical Properties of GaN Light Emitting Diodes

Gallium nitride light emitting diodes (LED's) fabricated on {11̅02} oriented sapphire substrates are found to emit only green light independent of Zn concentration during the i‐layer growth of i‐n structures, while LED's on {0001} substrates are found to be able to emit blue to yellow light by controlling the Zn concentration. In investigating the temperature dependence of electroluminescence and photoluminescence spectra, it was found that the spectra consist of two components: blue emission and yellow or green emission. The relative intensity of the blue emission increased with the decrease in temperature. On the other hand, the yellow and green emissions were found to increase in their relative intensities when the temperature was raised to room temperature. These results imply that two kinds of acceptors are formed by doping with Zn into a crystal. The acceptor contributing to the blue emission is located at 0.4 eV above the valence band. The other acceptor responsible for the yellow and green emissions is an impurity band situated at a position higher than 0.8 eV above the valence band.

Formic acid and saturated hydrocarbons as alarm pheromones for the ant Formica rufa

Releasers for the most intense, the fast-running, phase of the alarm behaviour were studied in worker ants of the formicine ant Formica rufa. The investigation was performed with a new technique in which the intensity and the duration of the behaviour pattern were measured in an objective and automatic way. Workers of formicine ants eiect a mixture of formic acid and the secretion from Dufour's gland against an enemy. The secretion from this gland in F. rufa consists of a great number of substances, 39 of which have been identified. The dominating substances form a homologous series of aliphatic, saturated hydrocarbons. Some of these hydrocarbons as well as the formic acid are alarm pheromones. The behavioural threshold value for one of these compounds, decane, was lower than 5.10 13 molecules cm −3 air. The threshold value for formic acid was estimated to 7.10 15 molecules cm −3 air. Formic acid and undecane are shown to belong to different reaction groups. The hydrocarbons, on the other hand, seem to affect the same kind of acceptor or receptor. The total intensity and duration of the alarm behaviour released by formic acid and one hydrocarbon are additive if the two substances are combined in a stimulus. A combination of two hydrocarbons and formic acid release a stronger behaviour than one hydrocarbon with formic acid even when the two stimuli contain the same number of molecules. The hydrocarbons have a combined effect and their relative concentrations regulate the intensity and duration of the alarm behaviour.

Étude de l'activité de transfert de glucose, à partir d'UDP‐glucose, dans les membranes microsomiques des hépatocytes de rat

Microsomal preparations from rat liver mediate transfer of glucosyl units from UDP-glucose to three different kinds of acceptors: an endogenous glycoprotein, exogenous glycogen and collagen. Both glucosyl transferases work at acidic pH, 6.5 for transfer on endogeneous acceptor and glycogen and at pH 5.5 for transfer on collagen. None of these enzymes require divalent cations for activity. While transfers on endogenous acceptor and glycogen are inhibited by the presence of a non-ionic detergent, Triton X-100, the transfer on collagen is activated by the same detergent. Glycogen-synthase activity requires glucose 6-phosphate at an optimal concentration of 1 mM. The Km values for UDP-glucose are respectively: 0.5 mM, 0.33 mM, and 1 mM for transfer on endogenous acceptor, glycogen and collagen. Characterisation of the product indicates that a protein-bound alpha1-4 glucan is formed when no primer is added. Enzymatic and acidic hydrolyses of radioactive glycogen and collagen show only glucose as a radioactive sugar identified by thin layer chromatography on cellulose. Pre-treatment of microsomal membranes by alpha-amylase demonstrates that glucosyltransferases are not adsorbed on endogenous glycogen and seem to be really membranous enzymes.

ChemInform Abstract: FLUORESCENCE DEPOLARIZATION STUDY OF HYDROGEN BONDED 1‐ANTHROL

Rotaional depolarization of 1-anthrol fluorescence was studied in liquid paraffin. The molecular volume of 1-anthrol becomes large when it forms a hydrogen bonded complex. The molecular volume of the complex depends on the concentration of acceptor as well as the kind of acceptor. The molecular volume obtained by extrapolation to nil acceptor concentration increases with increasing size of acceptor molecule and is appreciably larger for amines than for ethers. The emitting species in the case of amines is 1-anthrolate ion pair whose strong dipolar nature may cause further interaction with excess amine molecules. It is probable that more than one molecule of amine participate in the rotating unit, leading to a large molecular volume. The rotational relaxation time was evaluated and found to depend on acceptor concentration. Two competitive effects occur by the increase in acceptor concentration, one shortening the relaxation time because of reduction of viscosity, and the other lengthening it because of mo...