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Structural prediction of thiolate-protected gold nanoclusters (AuNCs) with diverse charge states can enrich the understanding of this species. Untill now, the number of anion AuNCs is still deficient. In this work, a series of gold nanoclusters with negative total charge, including [Au28(SR)17]−, [Au35(SR)20]−, [Au42(SR)23]−, [Au49(SR)26]−, and [Au56(SR)29]−, are designed. Following a crystallized [Au23(SR)16]− prototype structure, the inner core of the newly predicted clusters is obtained through packing crossed Au7. Next, proper protecting thiolate ligands are arranged to fulfill the duet rule to obtain Au3(2e) and Au4(2e). Extensive analysis indicates that these clusters own high stabilities. Molecular orbital analysis shows that the orbitals for the populations of the valence electron locate at each Au3(2e) and Au4(2e), which demonstrates the reliability of the grand unified model. This work should be helpful for enriching the structural diversity of AuNCs. [ABSTRACT FROM AUTHOR]

In the process of oilfield development, the reservoir of oil wells were polluted due to well flushing and pump inspection, which resulted in long recovery period of oil well production after operation, or even difficult recovery of production. According to the states mentioned above, researchers developed XST and XSK series multifunctional flushing fluid, which had the function of anti-swelling, anti-pollution, as well as cleaning functions. The laboratory experiments showed that the oil washing efficiency ≥80%, anti-swelling rate ≥70%, as well as the damage value of reservoir permeability ≤30%. The above formula was applied in J902 oil well, which achieved great success. Not only the fishing tools went in smoothly, but also the recovery period after the well flushing operation was shortened to 4 days, which effectively reduced the impact of the well flushing operation on the well production.

In the process of oilfield development, the reservoir can be polluted by well cleaning, pump inspection and other operations. And that will lead to a long recovery period of oil well production after operation, and even the production is difficult to recover. In recent years, unplugging transformation and other technologies have been researched and applied, and certain results have been achieved. However, there is a lack of systematic evaluation and analysis on the applicability, advantages and disadvantages of various technologies. For this reason, the application effect of the existing technology is systematically analyzed and evaluated in terms of the formula of unplugging agent, unplugging process, damage mechanism, oil-water well relationship, production layer and other aspects by means of combination of geology and engineering. The adaptability of this technology is obtained, and it is used as the principle of well selection for subsequent technical application to further improve the effect of measures.

Understanding the excited state behavior of isomeric structures of thiolate-protected gold nanoclusters is still a challenging task. In this paper, based on grand unified model and ring model for describing thiolate-protected gold nanoclusters, we have predicted four isomers of Au24(SR)16 nanoclusters. Density functional theory calculations show that the total energy of one of the predicted isomers is 0.1 eV lower in energy than previously crystallized isomer. The nonradiative relaxation dynamics simulations of Au24(SH)16 isomers are performed to reveal the effects of structural isomerism on relaxation process of the lowest energy states, in which that most of the low-excited states consist of core states. In addition, crystallized isomer possesses the shorter e–h recombination time, whereas the most stable isomer has the longer recombination time, which may be attributed to the synergistic effect of nonadiabatic coupling and decoherence time. Our results could provide practical guidance to predict new gold nanoclusters for future experimental synthesis, and stimulate the exploration of atomic structures of same sized gold nanoclusters for photovoltaic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study presents thorough structural insights into the stability of crystallized Au22(SAdm)16 (HSAdm = 1-adamantanethiol) nanocluster. With the recently developed Ring Model for describing the interaction between inner gold cores and outer protecting ligands in thiolate-protected gold nanoclusters, the experimental spontaneous transformation from the crystallized Au22(SAdm)16 to Au21(SAdm)15 could be well understood as structurally unfavorable for the current Au22(SAdm)16 and could also be attributed to the weaker aurophilic interaction between the inner Au4 core and the surrounding rings in Au22(SAdm)16 over that in Au21(SAdm)15. Furthermore, with the Ring Model and the grand unified model, two new Au22(SCH3)16 isomers with evident lower energies, higher HOMO–LUMO gaps as well as distinct optical properties over the available crystallized isomer were obtained. This study deepens the current knowledge on the structure of the Au22(SR)16 cluster from a new structural point of view and also confirms the validity as well as practicability of the Ring Model in understanding and predicting the stable structures of thiolate-protected gold nanoclusters. [ABSTRACT FROM AUTHOR]

Opiate analgesics are widely used and abused drugs. Individual differences in opiate sensitivity can hamper effective pain treatments and increase risks of drug abuse. Although genetic factors might affect individual differences in opiate sensitivity, scientific evidence for specific genetic mechanisms that underlie these differences has been sparse. Recent studies using inbred and knockout mice have revealed that the mu opioid peptide (MOP) receptor encoded by the Oprm1 gene has a mandatory role in the analgesic and addictive properties of opiate drugs. Increasing evidence suggests that differences in Oprm1 gene sequences affect the amount of Oprm1 mRNA and sensitivity to opiates, and > 100 polymorphisms have been identified in the human OPRM1 gene, some of which are related to vulnerability to drug dependence in some populations. Rapid advances in this research field are leading to improved understanding of the relationships between gene polymorphisms and opiate sensitivities that will enable more-accurate prediction of the opiate sensitivity and opiate requirements in individual patients.

Precise mono-doping of metal atom into metal particles at a specific particle position (e.g., the central site) in a highly controllable manner is still a challenge. In this work, we develop a highly controllable strategy for exchanging a single Ag atom into the central gold site of Au13Ag12(PPh3)10Cl8 (Ph = phenyl) nanoclusters. Interestingly, a "pigeon-pair" cluster of {[Au13Ag12(PPh3)10Cl8]·[Au12Ag13(PPh3)10Cl8]}2+ is obtained and confirmed by electrospray ionization mass spectrometry (ESI-MS), thermogravimetric analysis (TGA) and single crystal X-ray diffraction (SCXRD) analysis. The experimental results and density functional theory (DFT) calculations suggest that the single-metal-atom exchanging from [Au13Ag12(PPh3)10Cl8]+ to [Au12Ag13(PPh3)10Cl8]+ occurs at the central position through the side entry of the μ3-bridging Cl atoms. Finally, the effects on the electronic structure and properties caused by the single-atom exchange at the central site are shown by the enhancement of fluorescence and catalytic activity in the photocatalytic oxidation of ethanol. [ABSTRACT FROM AUTHOR]