Liming Xie

Identifying the Crystalline Orientation of Black Phosphorus Using Angle‐Resolved Polarized Raman Spectroscopy

An optical anisotropic nature of black phosphorus (BP) is revealed by angle-resolved polarized Raman spectroscopy (ARPRS), and for the first time, an all-optical method was realized to identify the crystal orientation of BP sheets, that is, the zigzag and armchair directions. We found that Raman intensities of Ag(1), B2g, and Ag(2) modes of BP not only depend on the polarization angle α, but also relate to the sample rotation angle θ. Furthermore, their intensities reach the local maximum or minimum values when the crystalline orientation is along with the polarization direction of scattered light (es). Combining with the angle-resolved conductance, it is confirmed that Ag(2) mode intensity achieves a relative larger (or smaller) local maximum under parallel polarization configuration when armchair (or zigzag) direction is parallel to es. Therefore, ARPRS can be used as a rapid, precise, and nondestructive method to identify the crystalline orientation of BP layers.

Solvatochromic Effect on the Photoluminescence of MoS2 Monolayers

The effect of surrounding solvents on the photoluminescence (PL) of MoS2 monolayers on Si/SiO2 substrates is studied. A redshift (up to -60 meV) is observed for MoS2 monolayers with nonhalogenated solvent surroundings. A blueshift (up to 60 meV) and intensity increase (2-50 times) are observed for monolayers with halogenated solvent surroundings.

Quantitative study of protein coronas on gold nanoparticles with different surface modifications

AbstractProtein coronas provide the biological identity of nanomaterials in vivo. Here we have used dynamic light scattering (DLS) and transmission electron microscopy (TEM) to investigate the adsorption of serum proteins, including bovine serum albumin (BSA), transferrin (TRF) and fibrinogen (FIB), on gold nanoparticles (AuNPs) with different surface modifications (citrate, thioglycolic acid, cysteine, polyethylene glycol (PEG, Mw = 2 k and 5 k)). AuNPs with PEG(5 k) surface modification showed no protein adsorption. AuNPs with non-PEG surface modifications showed aggregation with FIB. AuNPs with citrate and thioglycolic acid surface modifications showed 6–8 nm thick BSA and TRF coronas (corresponding to monolayer or bilayer proteins), in which the microscopic dissociation constants of BSA and TRF protein coronas are in the range of 10−8 to 10−6 M.

Anisotropic Spectroscopy and Electrical Properties of 2D ReS2(1–x)Se2x Alloys with Distorted 1T Structure

2D black phosphorus (BP) and rhenium dichalcogenides (ReX2 , X = S, Se) possess intrinsic in-plane anisotropic physical properties arising from their low crystal lattice symmetry, which has inspired their novel applications in electronics, photonics, and optoelectronics. Different from BP with poor environmental stability, ReX2 has low-symmetry distorted 1T structures with excellent stability. In ReX2 , the electronic structure is weakly dependent on layer numbers, which restricts their property tunability and device applications. Here, the properties are tuned, such as optical bandgap, Raman anisotropy, and electrical transport, by alloying 2D ReS2 and ReSe2 . Photoluminescence emission energy of ReS2(1-x) Se2x monolayers (x from 0 to 1 with a step of 0.1) can be continuously tuned ranging from 1.62 to 1.31 eV. Polarization behavior of Raman modes, such as ReS2 -like peak at 212 cm-1 , shifts as the composition changes. Anisotropic electrical property is maintained in ReS2(1-x) Se2x with high electron mobility along b-axis for all compositions of ReS2(1-x) Se2x .

Nanoparticles' interference in the evaluation of in vitro toxicity of silver nanoparticles

The biological safety of nanomaterials is a worldwide concern considering the extensive usage of nanoparticles in daily life as well as in medical care. However, toxicity evaluation of nanomaterials has met difficulties because of unique properties of nanomaterials. Here, we have investigated the interference of nanoparticles on the toxicity evaluations. Silver nanoparticles (AgNPs) with different sizes and surface coatings were used as model materials. Several widely used assays, such as lactate dehydrogenase (LDH) release, MTS assay and nitric oxide (NO) measurement, have been investigated in our study. Our results showed that 20 nm PVP-coated AgNPs with a concentration of 42.8 μg mL−1 affected LDH detection by about 50%, while citrate-coated 20 nm AgNPs with a concentration of 42.8 μg mL−1 affected LDH detection by about 70%. Moreover, 20 nm AgNPs with a concentration of 42.8 μg mL−1 disturbed MTS assay and NO measurement by less than 20% and 10%, respectively. Based on our results, nanoparticles with higher concentrations gave more interference. Therefore, for accurate toxicity evaluation of nanoparticles, it is very necessary to limit particle concentrations or choose other approaches free from the interference.

Growth of two-dimensional materials on hexagonal boron nitride (h-BN)

With its atomically smooth surface yet no dangling bond, chemical inertness and high temperature sustainability, the insulating hexagonal boron nitride (h-BN) can be an ideal substrate for two-dimensional (2D) material growth and device measurement. In this review, research progress on the chemical growth of 2D materials on h-BN has been summarized, such as chemical vapor deposition and molecular beam epitaxy of graphene and various transition metal dichalcogenides. Further, stacking of the as-grown 2D materials relative to h-BN, thermal expansion matching between the deposited materials and h-BN, electrical property of 2D materials on h-BN have been discussed in detail.

A Plasmon-Enhanced Fluorescence Protein Microchip with High-Sensitivity for Multiple Islet Autoantibodies Measurements in Autoimmune Diabetes Diagnosis

Correct classification diagnosis of diabetes is critical for timely and appropriate treatment, which partially depends on the multiple islet autoantibodies measurement and combined analysis. This study reports plasmon-enhanced fluorescence protein microchip method, a fast, high-throughput, and high sensitive method, to measure circulating islet autoantibodies. This method can achieve islet autoantibodies combined analysis within a few hours by using a few microliters of serum. Combined islet autoantibodies analysis improved discriminatory ability, especially the diagnostic sensitivity. Furthermore, by applying this method, we found 4 out of 6 diabetes atypical patients who were clinically highly suspected of having autoimmune diabetes but had a negative result of glutamic acid decarboxylase antibody and insulinoma-associated protein 2 antibody by enzyme-linked immunosorbent assay were positive at least 1 out of 4 islet autoantibodies, largely reducing the rate of missed diagnosis of autoimmune diabetes and further validating its clinical value. This study shows the great clinical potentials of plasmon-enhanced fluorescence protein microchips.

Chemical Growth of 1T-TaS2 Monolayer and Thin Films: Robust Charge Density Wave Transitions and High Bolometric Responsivity

Ultrathin two-dimensional (2D) charge density wave (CDW) materials, with sharp resistance change at the phase-transition temperature, yet with ultrathin thickness, hold great potential for electrical device applications. However, chemical synthesis of high-quality samples and observation of the CDW states down to the monolayer limit is still of great challenge. Chemical vapor deposition of 1T-TaS2 sheets on hexagonal boron nitride (h-BN) with robust CDW states even down to the monolayer extreme is reported here. Further, based on the near commensurate CDW to incommensurate CDW phase transition with a high temperature coefficient of resistance (TCR), highly responsive room-temperature bolometers are fabricated by suspending the as-grown 1T-TaS2 sheets.