Extreme weather events recorded by daily to hourly resolution biogeochemical proxies of marine giant clam shells.

Paleoclimate research has built a framework for Earth's climate changes over the past 65 million years or even longer. However, our knowledge of weather-timescale extreme events (WEEs, also named paleoweather), which usually occur over several days or hours, under different climate regimes is almost blank because current paleoclimatic records rarely provide information with temporal resolution shorter than monthly scale. Here we show that giant clam shells (Tridacna spp.) from the tropical western Pacific have clear daily growth bands, and several 2-y-long (from January 29, 2012 to December 9, 2013) daily to hourly resolution biological and geochemical records, including daily growth rate, hourly elements/Ca ratios, and fluorescence intensity, were obtained. We found that the pulsed changes of these ultra-high-resolution proxy records clearly matched with the typical instrumental WEEs, for example, tropical cyclones during the summer-autumn and cold surges during the winter. When a tropical cyclone passes through or approaches the sampling site, the growth rate of Tridacna shell decreases abruptly due to the bad weather. Meanwhile, enhanced vertical mixing brings nutrient-enriched subsurface water to the surface, resulting in a high Fe/Ca ratio and strong fluorescence intensity (induced by phytoplankton bloom) in the shell. Our results demonstrate that Tridacna shell has the potential to be used as an ultra-high-resolution archive for paleoweather reconstructions. The fossil shells living in different geological times can be built as a Geological Weather Station network to lengthen the modern instrumental data and investigate the WEEs under various climate conditions.

All-printed organic photodetectors with metal electrodes enabled by one-step solvent-mediated transfer printing technology.

A one-step solvent-mediated transfer printing technology (sTPT) is proposed to fabricate printable silver (Ag) electrodes. This simple approach can realize the residuals in the active layer serving as the mediator due to the capillary action without the use of any additional solvent. The as-cast polydimethylsiloxane (PDMS) was used as the stamp in the fabrication process. The residual solvent and the as-cast PDMS stamps simplified the fabrication process, while the transfer-printed Ag electrodes presented favorable conductivity and improved hydrophobicity due to the presence of residual PDMS on the surface of Ag, indicating the superiority as the top electrode for organic photodetectors (OPDs). Compared to the devices with the top Ag electrodes fabricated by the conventional evaporation method, we demonstrated that the OPDs with transfer-printed Ag electrodes presented better performance than that of the reference devices, including suppressed dark current, enlarged linear dynamic range, shortened response time, and optimized durability. These improved performances can be attributed to the fewer traps at the interface between the active layer and Ag electrodes. The sTPT may be a promising method for the fabrication of OPDs owing to the simplified fabrication process and enhanced device performance.

Reconstruction of ENSO variability using the standardized growth index of a Tridacna shell from Yongshu Reef, South China Sea.

El Niño-Southern Oscillation (ENSO) is the strongest signal of global interannual climate anomaly and reconstructing past ENSO variations using high-resolution paleoclimate archives can improve our understanding of ENSO variability, as well as improve our ability to predict future climate changes. Here, a daily resolution standardized growth index (SGI) was established using a giant clam (Tridacna spp.) shell specimen MD2 (life span: 1994-2013 CE), collected from the Yongshu Reef, southern South China Sea (SCS). The cross-spectral and correlation analysis indicated that the SGI variation of MD2 was strongly influenced by ENSO variability on an interannual timescale. Tridacna spp. is in symbiosis with zooxanthellae, and its growth index is usually modulated by the photosynthetic efficiency of zooxanthellae. During the El Niño (La Niña) period, the convective anomalies stimulated in western Pacific would increase (decrease) the effective solar radiation on Yongshu Reef, and in turn influence the photosynthesis rate of zooxanthellae and enzyme activity for the calcification site and thus the SGI of giant clam MD2. The SGI can explain 54.7 % of ENSO variance, demonstrating the potential for Tridacna SGI in ENSO reconstruction. Compared with conventional ENSO reconstruction using high-resolution geochemical proxies, the method of giant clam SGI is rapid and economical.

Physical Properties of an Ultrathin Al2O3/HfO2 Composite Film by Atomic Layer Deposition and the Application in Thin-Film Transistors.

A high-quality ultrathin dielectric film is important in the field of microelectronics. We designed a composite structure composed of Al2O3/HfO2 with different Al2O3/HfO2 cycles prepared by atomic layer deposition (ALD) to obtain high-quality ultrathin (1-12 nm) dielectric films. Al2O3 protected HfO2 from interacting with the Si substrate and inhibited the crystallization of the HfO2 film. High permittivity material of HfO2 was adopted to guarantee the good insulating property of the composite film. We investigated the physical properties as well as the growth mode of the composite film and found that the film exhibited a layer growth mode. The water contact angle and grazing-incidence small-angle X-ray scattering analyses revealed that the film was formed physically at 3 nm, while the thickness of the electrically stable film was 10 nm from grazing-incidence wide-angle X-ray scattering and dielectric constant analyses. The composite film was applied as a dielectric layer in thin-film transistors (TFTs). The threshold voltage was decreased to 0.27 V compared to the organic field-effect transistor with the single HfO2 dielectric, and the subthreshold swing was as small as 0.05 V/dec with a carrier mobility of 49.2 cm2/V s. The off-current was as low as 10-11 A, and the on/off ratio was as high as 5.5 × 106. This ALD-prepared composite strategy provides a simple and practical way to obtain the high-quality dielectric film, which shows the potential application in the field of microelectronics.

Biomimetic Superhydrophobic Films with an Extremely Low Roll-Off Angle Modified by F16CuPc via Two-Step Fabrication.

Superhydrophobicity is the phenomenon of which the water contact angle (WCA) of droplets on a solid surface is greater than 150°. In the present paper, we prepare a superhydrophobic film with a structure similar to the surface of a lotus leaf, which is composed of polydimethylsiloxane (PDMS), zinc oxide (ZnO), a molecular sieve (MS) and 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluorophthalocyanine copper(II) (F16CuPc). The F16CuPc was used as the modifier to reduce the surface energy of the biomimetic micro-nanostructure. With the introduction of F16CuPc, the superhydrophobic properties of the surface were enhanced so that the WCA and water roll-off angle could reach 167.1° and 0.5°, respectively. Scanning electron microscopy, X-ray energy spectrometry, and X-ray photoelectron spectroscopy analyses verified that the enhanced superhydrophobic properties of the film were mainly attributed to the modification of F16CuPc. Finally, thermal, mechanical, and chemical stability studies, as well as the influences of UV and underwater immersion on the superhydrophobic film were investigated. This developed two-step fabrication method may be a potential direction for superhydrophobic surface fabrication due to its simple process, excellent superhydrophobic property, and favorable stability.