Xiao Huang

Submonolayered Ru Deposited on Ultrathin Pd Nanosheets used for Enhanced Catalytic Applications.

Ultrathin Pd nanosheets (NSs) coated with submonolayered Ru, referred to as Pd@Ru NSs, are synthesized via a seed-mediated growth method. The underpotential deposition can be the driving force for the formation of Pd@Ru NSs. The Pd@Ru NSs exhibit superior catalytic properties in the reduction of 4-nitrophenol and the semihydrogenation of 1-octyne, compared to the pure Pd NSs and Ru NSs.

Preparation of Cobalt Sulfide Nanoparticle‐Decorated Nitrogen and Sulfur Co‐Doped Reduced Graphene Oxide Aerogel Used as a Highly Efficient Electrocatalyst for Oxygen Reduction Reaction

A novel 3D cobalt sulfide (CoS) nanoparticle-decorated nitrogen and sulfur co-doped reduced graphene oxide aerogel (NSGA), referred to as CoS/NSGA, is prepared via three sequential processes, i.e., freeze-drying, annealing, and sulfidization. The obtained CoS/NSGA exhibits excellent electrocatalytic performance in the alkaline solution.

Two-dimensional transition metal dichalcogenide nanomaterials for biosensing applications

Biosensors are powerful tools used to monitor biological and biochemical processes, ranging from clinical diagnosis to disease therapy. The huge demands for bioassays greatly promote the development of new nanomaterials as sensing platforms. Two-dimensional (2D) nanomaterials with superior properties, such as large surface areas and excellent conductivities, are excellent candidates for biosensor applications. Among them, single- or few-layered transition metal dichalcogenide (TMD) nanomaterials represent an emerging class of 2D nanomaterials with unique physical, chemical, and electronic properties. In this mini-review, we summarize the recent progress in 2D TMD nanomaterial-based biosensors for the sensitive detection of various kinds of targets, including nucleic acid, proteins, and small biomolecules, based on different sensors like optical sensors and electrochemical sensors, and bioelectronic sensors. Finally, the challenges and opportunities in this promising field are also proposed.

Orientation controlled preparation of nanoporous carbon nitride fibers and related composite for gas sensing under ambient conditions

Creating pores in suprastructures of two-dimensional (2D) materials while controlling the orientation of the 2D building blocks is important in achieving large specific surface areas and tuning the anisotropic properties of the obtained functional hierarchical structures. In this contribution, we report that arranging graphitic carbon nitride (g-C3N4) nanosheets into one-dimensional (1D) architectures with controlled orientation has been achieved by using 1D oriented melem hydrate fibers as the synthetic precursor via a polycondensation process, during which the removal of water molecules and release of ammonia gas led to the creation of pores without destroying the 1D morphology of the oriented structures. The resulting porous g-C3N4 fibers with both meso- and micro-sized pores and largely exposed edges exhibited good sensing sensitivity and selectivity towards NO2. The sensing performance was further improved by hybridization of the porous fibers with Au nanoparticles (Au NPs), leading to a detection limit of 60 ppb under ambient conditions. Our results suggest that the highly porous g-C3N4 fibers and the related hybrid structures with largely exposed graphitic layer edges are excellent sensing platforms and may also show promise in other electronic and electrochemical applications.

Optical thickness identification of transition metal dichalcogenide nanosheets on transparent substrates

Transparent and flexible devices based on two-dimensional (2D) materials hold great potential for many electronic/optoelectronic applications. The direct and fast thickness identification of 2D materials on transparent substrates is therefore an essential step in such applications, but remains challenging. Here, we present a simple, rapid and reliable optical method to identify the thickness of 2D nanosheets on transparent substrates, such as polydimethylsiloxane, glass, and coverslip. Under reflection and transmission light, 1-20L MoS2 and 1-14L WSe2 nanosheets can be reliably identified by measuring the optical contrast difference between the 2D nanosheets and substrates in color, red, green or blue channels. Meanwhile, the values of all the measured contrast differences as a function of layer number can be well fitted with the Boltzmann function, indicating the generalizability and reliability of our optical method. Our method will not only facilitate the fundamental study of the thickness-dependent properties of 2D nanosheets, but will also expand their potential applications in the field of flexible/transparent electronics and optoelectronics.

Transforming Monolayer Transition-Metal Dichalcogenide Nanosheets into One-Dimensional Nanoscrolls with High Photosensitivity

One-dimensional (1D) nanoscrolls derived from two-dimensional (2D) nanosheets own unusual physical and chemical properties that arise from the spiraled 1D morphology and the atomic thin 2D building blocks. Unfortunately, preparation of large-sized nanoscrolls of transition-metal dichalcogenides (TMDCs) remains a big challenge, which greatly restricts the fabrication of single-scroll devices for their fundamental studies and further applications. In this work, we report a universal and facile method, by making use of the evaporation process of volatile organic solvent, to prepare TMDC (e.g., MoS2 and WS2) nanoscrolls with lengths of several tens to one hundred micrometers from their 2D precursors presynthesized by chemical vapor deposition on Si/SiO2. Both atomic force microscopy and electron microscopy characterizations confirmed the spirally rolledup structure in the resulting nanoscrolls. An interlayer spacing of as small as ∼0.65 nm was observed, suggesting the strong coupling between adjacent layers, which was further evidenced by the emergence of new breathing mode peaks in the ultralow frequency Raman spectrum. Importantly, compared with the photodetector fabricated from a monolayer MoS2 or WS2 nanosheet, the device based on an MoS2 or WS2 nanoscroll showed the much enhanced performance, respectively, with the photosensitivity greatly increased up to 2 orders of magnitude. Our work suggests that turning 2D TMDCs into 1D scrolls is promising in achieving high performances in various electronic/optoelectronic applications, and our general method can be extended to the preparation of large-sized nanoscrolls of other kinds of 2D materials that may bring about new properties and phenomena.

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Recently, it has been reported that physisorbed adsorbates can be trapped between the bottom surface of two-dimensional (2D) materials and supported substrate to form 2D confined films. However, the influence of such 2D confined adsorbates on the properties of 2D materials is rarely explored. Herein, we combined atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM) and Raman spectroscopy especially the ultralow frequency (ULF) Raman spectroscopy to explore the influence of 2D confined organic adlayer thickness on the ULF breathing modes of few-layer MoS2 and WSe2 nanosheets. As the thickness of organic adlayers increased, red shift, coexistence of blue and red shifts as well as blue shift of ULF breathing mode was observed. KPFM measurement confirmed the enhanced n-doping and p-doping behaviors of organic adlayers as their thickness increased, respectively. Our results will provide new insights into the interaction between 2D confined adsorbates and bottom surface of 2D nanosheets, which could be useful for modulating properties of 2D materials.摘要在二维材料下表面与衬底之间的受限空间中, 物理吸附物如水分子和有机分子等可形成二维吸附层. 然而, 这类吸附层如何影响其上层二维材料的性能尚未被探究. 本文中, 我们结合原子力显微镜、 开尔文力显微镜以及超低波拉曼光谱仪来探究有机分子吸附层对其上的少层二硫化钼及二硒化钨纳米薄片性质的影响. 随吸附层厚度增加, 纳米薄片的超低波呼吸模式拉曼峰发生红移、 红移和蓝移共存以及仅有蓝移的现象. 此外, 纳米薄片的掺杂程度也逐渐增强. 理解有机分子吸附层与二维材料下表面之间的相互作用, 有望对二维材料性质的调节提供帮助.