Xiaotian Sun

Facile, Large-Quantity Synthesis of Stable, Tunable-Color Silicon Nanoparticles and Their Application for Long-Term Cellular Imaging

We herein introduce a facile, low-cost photochemical method capable of rapid (<40 min) and large-quantity (∼10 g) production of highly fluorescent (quantum yield: 25%) silicon nanoparticles (SiNPs) of tunable optical properties (peak emission wavelength in the range of 470-560 nm) under ambient air conditions, by introducing 1,8-naphthalimide as a reducing agent and surface ligands. The as-prepared SiNPs feature robust storage stability and photostability preserving strong and stable fluorescent during long-term (>3 h) high-power UV irradiation, in contrast to the rapid fluorescence quenching within 2 h of conventional organic dyes and II-VI quantum dots under the same conditions. The as-prepared SiNPs serving as photostable nanoprobes are workable for cellular imaging in long-term manners. Our findings provide a powerful method for mild-condition and low-cost, large-quantity production of highly fluorescent and photostable SiNPs for various promising applications.

Mechanism of graphene oxide as an enzyme inhibitor from molecular dynamics simulations.

Graphene and its water-soluble derivative, graphene oxide (GO), have attracted huge attention because of their interesting physical and chemical properties, and they have shown wide applications in various fields including biotechnology and biomedicine. Recently, GO has been shown to be the most efficient inhibitor for α-chymotrypsin (ChT) compared with all other artificial inhibitors. However, how GO interacts with bioactive proteins and its potential in enzyme engineering have been rarely explored. In this study, we investigate the interactions between ChT and graphene/GO by using molecular dynamics (MD) simulation. We find that ChT is adsorbed onto the surface of GO or graphene during 100 ns MD simulations. The α-helix of ChT plays as an important anchor to interact with GO. The cationic and hydrophobic residues of ChT form strong interactions with GO, which leads to the deformation of the active site of ChT and the inhibition of ChT. In comparison, the active site of ChT is only slightly affected after ChT adsorbed onto the graphene surface. In addition, the secondary structure of ChT is not affected after it is adsorbed onto GO or graphene surface. Our results illustrate the mechanism of the interaction between GO/graphene and enzyme and provide guidelines for designing efficient artificial inhibitors.

The Selective Interaction between Silica Nanoparticles and Enzymes from Molecular Dynamics Simulations

Nanoscale particles have become promising materials in many fields, such as cancer therapeutics, diagnosis, imaging, drug delivery, catalysis, as well as biosensors. In order to stimulate and facilitate these applications, there is an urgent need for the understanding of the interaction mode between the nano-particles and proteins. In this study, we investigate the orientation and adsorption between several enzymes (cytochrome c, RNase A, lysozyme) and 4 nm/11 nm silica nanoparticles (SNPs) by using molecular dynamics (MD) simulation. Our results show that three enzymes are adsorbed onto the surfaces of both 4 nm and 11 nm SNPs during our MD simulations and the small SNPs induce greater structural stabilization. The active site of cytochrome c is far away from the surface of 4 nm SNPs, while it is adsorbed onto the surface of 11 nm SNPs. We also explore the influences of different groups (-OH, -COOH, -NH2 and CH3) coated onto silica nanoparticles, which show significantly different impacts. Our molecular dynamics results indicate the selective interaction between silicon nanoparticles and enzymes, which is consistent with experimental results. Our study provides useful guides for designing/modifying nanomaterials to interact with proteins for their bio-applications.

Induce magnetism into silicene by embedding transition-metal atoms

Embedding transition-metal (TM) atoms into nonmagnetic nanomaterials is an efficient way to induce magnetism. Using first-principles calculations, we systematically investigated the structural stability and magnetic properties of TM atoms from Sc to Zn embedded into silicene with single vacancy (SV) and double vacancies (DV). The binding energies for different TM atoms correlate with the TM d-shell electrons. Sc, Ti, and Co show the largest binding energies of as high as 6 eV, while Zn has the lowest binding energy of about 2 eV. The magnetic moment of silicene can be modulated by embedding TM atoms from V to Co, which mainly comes from the 3d orbitals of TM along with partly contributions from the neighboring Si atoms. Fe atom on SV and Mn atom on DV have the largest magnetic moment of more than 3 μB. In addition, we find that doping of N or C atoms on the vacancy site could greatly enhance the magnetism of the systems. Our results provide a promising approach to design silicene-based nanoelectronics and spintronics device.

Structures, mobility and electronic properties of point defects in arsenene, antimonene and an antimony arsenide alloy

Defects are unavoidable during the synthesis of materials, especially for two-dimensional (2D) nanomaterials. They are usually seen as detrimental to device properties, but sometimes bring about new beneficial effects. In order to clarify the influence of defects on the structural and electronic properties, we have performed first-principles calculations to systematically investigate the structural stability, mobility and electronic properties of typical point defects in 2D arsenene (h-As), antimonene (h-Sb) and antimony arsenide (h-AsSb), including the Stone–Wales defects, single vacancies (SVs), double vacancies (DVs) and adatoms. To provide visual guidance for experimental observations, scanning tunnelling microscopy (STM) images are simulated. Compared to defects in graphene and silicene, these defects form more easily with lower formation energies, and SVs can diffuse very quickly to the edges with a lower diffusion barrier of less than 1 eV. Monolayer arsenene, antimonene and antimony arsenide are indirect band gap semiconductors, and the defective structures significantly reduce the band gaps. Most of the SV and adatom defects carry magnetic moments due to the dangling bonds resulting from the absent or extra atom. Our present results have demonstrated that the point defects induce significant effects on the electronic properties of pristine arsenene, antimonene and the antimony arsenide alloy, which should be considered in their future applications.

Structural stability and band gap tunability of single-side hydrogenated graphene from first-principles calculations

Based on density functional theory (DFT) calculations, we have constructed and investigated different types of single-side hydrogenated graphene (SSHG) structures from their structural motifs. The structural stability and electronic properties of these SSHG structures are extensively analyzed and compared with the reported structures. The single-side hydrogenation causes a severe bending in graphene at high H coverage, which leads to a greater formation energy with increasing H coverage. Among the SSHG structures that we have considered, the configurations with H attached along the armchair direction show the lowest formation energies due to a relatively small buckling compared to other configurations. Moreover, only the armchair hydrogenated graphene opens a band gap near the Fermi level, and the band gap can be modulated from zero to 1.44 eV by varying the H coverage from zero to 50%. Our results suggest an efficient way to prepare graphene-based materials and devices with suitable band gaps.

The structures and properties of Si/SiO2 core/shell quantum dots studied by density-functional tight-binding calculations

Si/SiO2 core/shell quantum dots (QDs) have been shown with wavelength-tunable photoluminescence in addition to their inert, nontoxic, abundant, low-cost, biocompatible advantages. Due to their big size, here, we apply density-functional tight-binding (DFTB) method to perform calculations to study their structures and properties. We systematically investigate the effects of surface passivation, thickness of SiO2 shell, and Si/O ratio on the structures and properties of Si/SiO2 core/shell quantum dots. We find that hydroxyl passivated Si/SiO2 core/shell quantum dots are able to stabilize the quantum dots compared with hydrogen passivated Si/SiO2 core/shell quantum dots. By using DFTB method, we are able to study Si/SiO2 core/shell quantum dots of big size (3u2009nm) and we find that, in Si/SiO2 core/shell quantum dots, there are competing effects between quantum confinement (blueshift) and oxidation (redshift) with the decrease of the size of Si core. The transition point is when Si/SiO2 ratio is around 1:1. Th...

High performance single In 2 Se 3 nanowire photodetector

The single In 2 Se 3 nanowire photodetectors were fabricated and the performance characteristics of the NW devices were systematically investigated. The single In 2 Se 3 NW photodetectors show high and stable photoresponse at wide light wavelength (254–800 nm) and temperature range (7–300 K). The spectra response curve indicates the absorption coefficient of the In2Se3 NWs at certain wavelength dominates the performance of the devices. The good linearity of the photocurrents with the incident irradiation over a wide wavelength range has been obtained, indicating the In 2 Se 3 nanowire photodetector works under a typical light dependent resistor mode.

Sub-5 nm Monolayer Arsenene and Antimonene Transistors

Novel two-dimensional (2D) semiconductors arsenene and antimonene are promising channel materials for next-generation field effect transistors (FETs) because of the high carrier mobility and stability under ambient conditions. Stimulated by the recent experimental development of sub-5 nm 2D MoS2 FETs, we investigate the device performance of monolayer (ML) arsenene and antimonene in the sub-5 nm region by using accurate ab initio quantum transport simulation. We reveal that the optimized sub-5 nm double-gate (DG) ML arsenene and antimonene metal-oxide-semiconductor FETs (MOSFETs) can fulfill the low power requirements of the International Technology Roadmap for Semiconductors in 2028 until the gate length is scaled down to 4 nm. When the gate length is scaled down to 1 nm, the performances of the DG ML arsenene and antimonene MOSFETs are superior to that of the DG ML MoS2 MOSFETs in terms of the on-current. Therefore, 2D arsenene and antimonene are probably more suitable for ultrascaled FETs than 2D MoS2 in the post-silicon era.