No abstract

No abstract

No abstract

Size‐dependent optical absorption of semiconductive (2H) layered molybdenum disulfide (MoS2), exhibiting great discrimination abilities to single‐ and double‐stranded DNA (ssDNA) and (dsDNA), is studied. In the presence of high concentration of salt, layered MoS2 trends to aggregate rapidly, leading to the increases of sizes in both vertical and lateral dimensions of the nanosheets, which results from the interplay between van der Waals attraction and electrical double‐layer repulsion. Meanwhile, the aggregation behavior of layered MoS2 is remarkably inhibited by the synergistic effects of DNA oligonucleotides. ssDNA can adsorb on the surface of layered MoS2, resulting in a great dispersion, even in the presence of high concentration of salt, while the dispersion behavior is weakened when ssDNA is replaced by dsDNA. Whereas compared to graphene with zero bandgap energy, layered MoS2, with semiconductive properties, exhibits great characteristic optical absorption in visible wavelength region devoted to exploring the aggregation behavior of layered MoS2. Therefore, DNA oligonucleotides induced size control of layered MoS2, contributing to the regular change of its characteristic absorption in visible region, is considered a label‐free bioassay for the detection of single‐nucleotide polymorphism. Due to its easy operation and high specificity, it is expected that the proposed assay holds great promise for further applications.

No abstract

Phytic acid (IP6) and its salts are promising reagents to alleviate corrosion of metals, which are environmentally friendly and highly efficient, compared to some traditional inhibitors toxic to environment. This paper reports the studies of the structure and anticorrosion features of two kinds of the self-assembled monolayers (SAMs) of IP6 at the silver surface under various pH values, 1.27 and 13, by using electrochemical and surface enhanced Raman scattering (SERS) spectroelectrochemical measurements. On the basis of recorded ex situ SERS spectra, different adsorption modes of both resulted SAMs of IP6 at the silver surfaces have been postulated. In addition, based on in situ SERS electrochemical measurements, a tentative explanation for the difference in corrosion potentials of two kinds of the silver surfaces in the presence of SAMs formed from completely protonated or deprotonated IP6 molecules has also been presented.

The emergence of a rich variety of layered materials has attracted considerable attention in recent years because of their exciting properties. However, the applications of layered materials in optoelectronic devices are hampered by the low light absorption of monolayers/few layers, the lack of p-n junction, and the challenges for large-scale production. Here, we report a scalable production of β-InSe/Si heterojunction arrays using pulsed-laser deposition. Photodetectors based on the as-produced heterojunction array are sensitive to a broadband wavelength from ultraviolet (370 nm) to near-infrared (808 nm), showing a high responsivity (5.9 A/W), a decent current on/off ratio (∼600), and a superior detectivity (4.9 × 10 jones), simultaneously. These figures-of-merits are among the best values of the reported heterojunction-based photodetectors. In addition, these devices can further enable the detection of weak signals, as successfully demonstrated with weak light sources including a flashlight, lighter, and fluorescent light. Device physics modeling shows that their high performance is attributed to the strong light absorption of the relatively thick β-InSe film (20.3 nm) and the rational energy band structures of β-InSe and Si, which allows efficient separation of photoexcited electron-hole pairs. These results offer a new insight into the rational design of optoelectronic devices from the synergetic effect of layered materials as well as mature semiconductor technology.

A photodetector based on 2D non‐layered materials can easily utilize the photogating effect to achieve considerable photogain, but at the cost of response speed. Here, a rationally designed tunneling heterojunction fabricated by vertical stacking of non‐layered In2S3 and Te flakes is studied systematically. The Te/In2S3 heterojunctions possess type‐II band alignment and can transfer to type‐I or type‐III depending on the electric field applied, allowing for tunable tunneling of the photoinduced carriers. The Te/In2S3 tunneling heterojunction exhibits a reverse rectification ratio exceeding 104, an ultralow forward current of 10−12 A, and a current on/off ratio over 105. A photodetector based on the heterojunctions shows an ultrahigh photoresponsivity of 146 A W−1 in the visible range. Furthermore, the devices exhibit a response time of 5 ms, which is two and four orders of magnitude faster than that of its constituent In2S3 and Te. The simultaneously improved photocurrent and response speed are attributed to the direct tunneling of the photoinduced carriers, as well as a combined mechanism of photoconductive and photogating effects. In addition, the photodetector exhibits a clear photovoltaic effect, which can work in a self‐powered mode.