Oxidation kinetics and non-Marcusian charge transfer in dimensionally confined semiconductors

Electrochemical reactions represent essential processes in fundamental chemistry that foster a wide range of applications. Although most electrochemical reactions in bulk substances can be well described by the classical Marcus-Gerischer charge transfer theory, the realistic reaction character and mechanism in dimensionally confined systems remain unknown. Here, we report the multiparametric survey on the kinetics of lateral photooxidation in structurally identical WS2 and MoS2 monolayers, where electrochemical oxidation occurs at the atomically thin monolayer edges. The oxidation rate is correlated quantitatively with various crystallographic and environmental parameters, including the density of reactive sites, humidity, temperature, and illumination fluence. In particular, we observe distinctive reaction barriers of 1.4 and 0.9 eV for the two structurally identical semiconductors and uncover an unusual non-Marcusian charge transfer mechanism in these dimensionally confined monolayers due to the limit in reactant supplies. A scenario of band bending is proposed to explain the discrepancy in reaction barriers. These results add important knowledge into the fundamental electrochemical reaction theory in low-dimensional systems.Comment: 20 pages, 4 figure

Holocene vegetational and climatic history of the Xuguo Co catchment in the central Tibetan Plateau

A 101-cm core was taken from a large lake in the central Tibetan Plateau. Its pollen and loss-on-ignition analyses provide a Holocene vegetational, climatic, and environmental history of the lake catchment. Pollen analysis shows that: dense steppe dominated regional vegetation in the early Holocene (9,200–8,000 cal. yr BP); regional vegetation coverage gradually decreased in the middle Holocene (8,000–4,100 cal. yr BP); and marsh meadow grew on the lake edge and sparse steppe occupied the lake catchment after 4,100 cal. yr BP. Our result also reveals that: 9,200–8,000 cal. yr BP witnessed summer temperature, monsoonal rainfall, and lake-level maxima, as well as few winter and spring aeolian activities and frequent wildfires; 8,000–4,100 cal. yr BP saw a nonlinear decline in temperature, rainfall, lake level, and wildfires; and modern climatic and environmental conditions were established after 4,100 cal. yr BP. Three major monsoon-weakening events at ca. 6,700, 5,800, and 4,100 cal. yr BP were detected by pollen signals and proxies of the climate and environment

Non-invasive digital etching of van der Waals semiconductors

The capability to finely tailor material thickness with simultaneous atomic precision and non-invasivity would be useful for constructing quantum platforms and post-Moore microelectronics. However, it remains challenging to attain synchronized controls over tailoring selectivity and precision. Here we report a protocol that allows for non-invasive and atomically digital etching of van der Waals transition-metal dichalcogenides through selective alloying via low-temperature thermal diffusion and subsequent wet etching. The mechanism of selective alloying between sacrifice metal atoms and defective or pristine dichalcogenides is analyzed with high-resolution scanning transmission electron microscopy. Also, the non-invasive nature and atomic level precision of our etching technique are corroborated by consistent spectral, crystallographic and electrical characterization measurements. The low-temperature charge mobility of as-etched MoS$_2$ reaches up to $1200\,$cm$^{2}\cdot$V$^{-1}\cdot$s$^{-1}$, comparable to that of exfoliated pristine counterparts. The entire protocol represents a highly precise and non-invasive tailoring route for material manipulation.Comment: 46 pages, 4 figures, with S

Non-invasive digital etching of van der Waals semiconductors

The capability to finely tailor material thickness with simultaneous atomic precision and non-invasivity would be useful for constructing quantum platforms and post-Moore microelectronics. However, it remains challenging to attain synchronized controls over tailoring selectivity and precision. Here we report a protocol that allows for non-invasive and atomically digital etching of van der Waals transition-metal dichalcogenides through selective alloying via low-temperature thermal diffusion and subsequent wet etching. The mechanism of selective alloying between sacrifice metal atoms and defective or pristine dichalcogenides is analyzed with high-resolution scanning transmission electron microscopy. Also, the non-invasive nature and atomic level precision of our etching technique are corroborated by consistent spectral, crystallographic, and electrical characterization measurements. The low-temperature charge mobility of as-etched MoS2 reaches up to 1200 cm2 V−1s−1, comparable to that of exfoliated pristine counterparts. The entire protocol represents a highly precise and non-invasive tailoring route for material manipulation

Pex3 peroxisome biogenesis proteins function in peroxisome inheritance as class V myosin receptors

Pex3 links peroxisome formation and inheritance. By binding to class V myosin, biogenesis protein Pex3 also directs the organelles into daughter cells

Study of the Synergistic Effect of Induction Heating Parameters on Heating Efficiency Using Taguchi Method and Response Surface Method

This work designed an intercalation internal induction heating coil in a mold and drew a plate-type steel for the heating mold (size: 300 mm × 200 mm × 40 mm). First, to explore the influence rule of special-shaped coils on induction heating effects, the temperature rise curve on the mold surface was simulated at different heating depths, currents, and frequencies. Next, the extent to which these three factors affect the maximum mean temperature and temperature uniformity was discussed using the Taguchi method and the analysis of variance (ANOVA). Results show that heating depth and current are important factors influencing the target results, while frequency only has a small impact. The maximum mean temperature reaches its peak level when the heating depth, current, and frequency are at the respective values of 5 mm, 1200 A, and 40 KHz and the optimal temperature uniformity can be achieved when these values are 7 mm, 800 A, and 20 KHz, respectively. Finally, the synergistic effect of different factors on target results was analyzed using the response surface method (RSM)

Delocalized surface state in epitaxial Si(111) film with spontaneous √3 x √3 superstructure

The multilayer silicene films were grown on Ag(111), with increasing thickness above 30 monolayers (ML). Scanning tunneling microscopy (STM) observations suggest that the multilayer silicene is indeed a bulk-like Si(111) film with a (√ 3 x √ 3)R30° honeycomb superstructure on surface. The possibility for formation of Si(111)(√ 3 x √ 3)R30°-Ag reconstruction on the surface can be distinctively ruled out by peeling off the surface layer with the STM tip. On this surface, delocalized surface state as well as linear energy-momentum dispersion was observed from quasiparticle interference patterns. Our results indicate that a bulklike silicon film with diamondlike structure can also host delocalized surface state, which is even more attractive for potential applications, such as new generation of nanodevices based on Si