查看更多>>摘要：The Sm3+, Eu3+ single doped, and Sm3+/Eu3+ co-doped lithium bismuth alumino borosilicate (LiBiAlBSi) glasses were prepared by using the melt quenching method and studied photoluminescence (PL) excitation, PL emission, and PL decay to have a better insight into their utility as red emission element for white LEDs. Sm3+ doped LiBiAlBSiSm05 glasses exhibit admirable emission features in the reddish-orange region under n-UV excitation (402 nm). Sm3+/Eu3+ co-doped LiBiAlBSi glasses can be adeptly excited by the blue and n-UV region which is confirmed from the excitation spectrum. In the Sm3+/Eu3+ co-doped LiBiAlBSi glasses, the PL decay lifetime for the Sm3+ emitting level (4G5/2) declines and the energy transfer efficiency increases with an upsurge in Eu3+ ion content, which suggests the energy transfer (ET) process occurs from Sm3+ to Eu3+ ions. The ET process from Sm3+ to Eu3+ ions is also suggested by Dexter's ET method and Reisfeld's approximation by using emission spectra due to non-radiative dipole-dipole (d-d) interaction. The calculated values of CIE chromaticity coordinate for the as-prepared glasses under n-UV excitation shifted from reddish-orange to the red spectral part with the upsurge in Eu3+ concentration. The temperature-dependent PL studies of the optimized LiBiAlBSiSE10 glass revealed its superior thermal stability. All the results obtained finally suggest that, the Sm3+/Eu3+ co-doped LiBiAlBSi glass with 0.5 mol% of Sm3+ ions and 1.0 mol% of Eu3+ ions is a thermally stable candidate to produce intense red color needed to fabricate white LEDs under n-UV and blue excitation through the downshifting process.
查看更多>>摘要：Strong photooxidative activity of dichloroP(V)tetrakis(4-chlorophenyl)porphyrin via electron transfer was expected. To control the activity of this P(V)porphyrin, bis(6-quinolinoxy)P(V)tetrakis(4-chlorophenyl)porphyrin (QuinP(V)TClPP), was synthesized. The pK(a) of a protonated quinoline moiety, the electron donor, was estimated to be 4.6. The singlet excited state of QuinP(V)TClPP was quenched via intramolecular electron transfer under neutral condition. Under an acidic condition, the fluorescence intensity and the singlet oxygen (O-1(2)) generation yield by photoexcited QuinP(V)TClPP were significantly increased through protonation of the quinoline moiety. The photosensitized damage of human serum albumin by QuinP(V)TClPP through O-1(2) generation and electron transfer mechanisms was effectively enhanced under an acidic condition.
查看更多>>摘要：Using ab initio calculations in combination with the quantum theory of atoms in molecules (QTAIM) we investigate the molecular complex between the auride ion and borane. QTAIM indicates that about 1/3 of the negative charge of Au- is transferred to borane to establish a shared interaction mainly covalent in character. The replacement of BH3 by BF3 decreases the interaction strength. A similar trend is observed in the isoelectronic complexes with mercury which are stabilized by much weaker interactions. The interaction of AuBH3- with alkali metal ions (Li+ to Cs+) yields neutral complexes which are stabilized by electrostatic effects.
查看更多>>摘要：Carbon quantum dots/titanium dioxide (CQDs/TiO2) nanocomposites were synthesized with TEMPO oxidized cellulose as carbon source via a facile method. In this eco-friendly system, the photocatalytic activity of CQDs/ TiO2 were evaluated through photo-degradation of methylene blue (MB) under visible light. The results show that CQDs/TiO2 composites possess high photocatalytic degradation efficiency up to 92%. The enhanced degradation efficiency of MB was probably attributed to that the photoelectrical properties of CQDs can lead to effective separation of photo-generated electrons-holes pairs. Moreover, the TEMPO oxidized cellulose has abundant amino groups, which can significantly improve the photophysical properties of CQDs.
查看更多>>摘要：Study on the redistribution mechanism of preparing dichlorodimethylsilane (M2) by the ZnCl2/MIL-53(Al) catalyst (configurations a and b) was performed by using the density functional theory (DFT) method. The redistribution mechanism was confirmed by the intrinsic reaction coordinates (IRC) method, vibrational analysis of the transition states, and related qualitative analysis of the bond orders, electronic localization function (ELF) and localized orbital locator (LOL). The results showed that the ZnCl2/MIL-53(Al) catalysts (configurations a and b) were in favor of the redistribution reaction and activation energies of the rate determining steps (RDSs) in the main reaction were 115 and 88 kJ.mol(-1), respectively. As compared to the activation energies of the ZnCl2 and MIL-53(Al) catalysts, the ZnCl2/MIL-53(Al) catalyst (configuration b) possesses the better catalytic activity. It is suggested that post-modified with Lewis acid plays a vital role on the redistribution synthesis.
查看更多>>摘要：Lead toxicity is the never-ending and everyday growing problem of the world. It is reported to be a life threatening poison for infants and children. Although the number of receptors are reported in the literature the wildness of toxicity is intense, which is somewhat like the ever-increasing gap between demand and supply. The C1 (2-[(5-Bromo-2-hydroxy benzylidene)-amino]-3-(1H-imidazol-4-yl)-propionic acid) and C2 (2-Amino-5[N'-(5-bromo-2-hydroxy-benzylidene)-guanidino]-pentanoic acid) were prepared to test their capability as lead (Pb) sensors. The probes C1 and C2 were synthesized by treating bromo salicylaldehyde with amino acids histidine and arginine at room temperature. The Schiff bases formed show significant binding with Pb2+ions in the aqueous medium. The lowest detection limit is 20 ng/ml of both sensors. As lead toxicity is fatal to infants and kids and both amino acids viz., arginine and histidine are a common component of total parental nutrition in infants and kids. Thus, amino acids substituted C1-C2 probes are of great significance for the development of molecular drugs to treat lead poisoning especially in infants, and extensively for the human body.
Liang, Julia J. J.Pitsillou, EleniVerveris, KatherineGuallar, Victor...
8页
查看更多>>摘要：The SARS-CoV-2 papain-like (PLpro) protease is essential for viral replication. We investigated potential antiviral effects of hypericin relative to the well-known noncovalent PLpro inhibitor GRL-0617. Molecular dynamics and PELE Monte Carlo simulations highlight favourable binding of hypericin and GRL-0617 to the naphthalene binding pocket of PLpro. Although not potent as GRL-0617 (45.8 vs 1.6 mu M for protease activity, respectively), in vitro fluorogenic enzymatic assays with hypericin show concentration-dependent inhibition of both PLpro pro-tease and deubiquitinating activities. Given its use in supplementations and the FDA conditional approval of a synthetic version, further evaluation of hypericin as a potential SARS-CoV-2 antiviral is warranted.
查看更多>>摘要：The catalytic conversion of carbon dioxide into clean fuel and value-added chemicals is one of best ways to resolve the issues of greenhouse-gas emission and worldwide energy shortage and to benefit sustainable development of society. Our DFT calculations demonstrate that group 3 metal silylamides are able to accomplish the CO2 reduction reaction, where the scandium one bears the best catalytic activity. It requires very small positive free energy to capture CO2. The subsequent hydrogenation reactions are thermodynamically and kinetically favored, where the transition state (*CO2H2)(#) costs 4.7 kcal/mol energy. Comparatively, the water elimination requires to absorb less energy.
查看更多>>摘要：Interfacial charge-transfer transitions (ICTTs) between organic compounds and inorganic semiconductors enable the absorption of visible light with colourless organic molecules and direct charge separation for their potential applications in photoenergy conversions and chemical sensing. TiO2 nanocomplexes with aromatic carboxylic acids are one of the most important ICTT systems for photoenergy conversions. Here, we report the aromatic-ring dependence of ICTT in TiO2 nanocomplexes with benzoic acid, naphthalene-2-carboxylic acid, and anthrancene2-carboxylic acid. Our research reveals the significant red-shift of ICTT by expanding the pi-conjugated system from the benzene to anthracene ring and elucidates the mechanism.
NSTL
Elsevier