Qin Wei's research while affiliated with Shandong University of Traditional Chinese Medicine and other places

Graphene field‐effect transistors (G‐FETs) have attracted widespread attention in disease diagnosis, benefiting from these advantages of high sensitivity, label‐free, easy integration, and direct detection of nucleic acids (NAs) in liquid environments. However, the problem of nonspecific signals in G‐FETs is not fundamentally solved due to a lack of systematic theoretical research to support the development of effective solutions. Thus, researchers have to rely on speculative mechanisms to minimize nonspecific signals in experiments as much as possible. Herein, the nonspecific signal mechanism caused by eight types of π–π interaction paths mediated by aromatic rings is theoretically determined. Based on theoretical simulation results, the feasibility of blocking nonspecific signal paths through Nafion functionalization methods is experimentally verified. Experiments confirm that Nafion‐modified G‐FETs (NMG‐FETs) have excellent performance in avoiding nonspecific signals compared to traditional G‐FETs. Furthermore, the NMG‐FET achieves ultra‐sensitive detection of Down syndrome–related DNA down to 1 aM and severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) RNA down to 5 aM, and shows good specificity in base recognition. This study is expected to promote the theoretical advancement of the nonspecific signal mechanism in G‐FET NA detection and offer a practical strategy for improving signal purity and accuracy.

The output power in ultrafast fiber lasers is usually limited due to the lack of a versatile saturable absorber with high damage threshold and large modulation depth. Here we proposed a more efficient strategy to improve the output energy of erbium-doped fiber laser based on indium selenide (In 2 Se 3 ) prepared by using the physical vapor deposition (PVD) method. Finally, stable mode-locked bright pulses and triple-wavelength dark–bright pulse pair generation were obtained successfully by adjusting the polarization state. The average output power and pulse energy were 172.4 mW/101 nJ and 171.3 mW/100 nJ, which are significantly improved compared with the previous work. These data demonstrate that the PVD-In 2 Se 3 can be a feasible nonlinear photonic material for high-power fiber lasers, which will pave a fresh avenue for the high-power fiber laser.

Three-dimensional layered silver nanoflowers/graphene (AgNFs/Graphene) nanohybrids were firstly proposed and fabricated for the sensitive flexible biosensors. Flexible bio-friendly graphene films, which are beneficial for the Ag adatom absorption, can be used not only as the growth platform to form the AgNFs nanostructures, but also as the nano-spacer to form the layered AgNFs/Graphene nanohybrids. The growth mechanism and the horizon-vertical (H-V) coupling effects of the porous AgNFs/Graphene layers were studied by using VASP and COMSOL simulation. Electromagnetic intensity can be easily enhanced by the horizontal coupling on the AgNFs nanostructures surfaces and the vertical coupling on the layered AgNFs/Graphene nanohybrids. Rhodamine 6 G (R6 G), CV, lysozyme, and DNA molecules can be easily detected by our proposed flexible biosensors.

In this work, we report about high energy and various solitons’ operation by using high-efficiency topological insulator bismuth telluride ( ${\rm Bi}_2{\rm Te}_3$ B i 2 T e 3 ) nanofilms as broadband saturable absorbers in the passively mode-locked Er-doped fiber laser. The ${\rm Bi}_2{\rm Te}_3$ B i 2 T e 3 film was successfully synthesized by chemical vapor deposition (CVD). Excellent characteristics of the dark–bright pulse pairs, bright pulses, and multiharmonics have been investigated experimentally by adjusting the polarization state. At the same time, the maximum average output power was 40.18 mW, and the single-pulse energy was 20.91 nJ. As we all know, it is the various solitons of the first generation with large pulse energy in an Er-doped fiber laser with ${\rm Bi}_2{\rm Te}_3$ B i 2 T e 3 as saturable absorber. The experimental results show that CVD ${\rm Bi}_2{\rm Te}_3$ B i 2 T e 3 can be used as an excellent candidate in mode-locked fiber lasers.

We demonstrated a passively mode-locked Er-doped fiber laser by a high-efficiency Bismuth Telluride (Bi2Te3) as passive saturable absorber. The Bi2Te3 thin film was grown by chemical vapor deposition (CVD). The maximum average output power and pulse energy were as high as 40.74 mW and 23.9 nJ under the pump power of 659 mW, which are much higher than the results obtained previously. The signal to noise ratio was observed to be more than 60 dB, which indicates the stability of the generated pulse. Our results proved that CVD-Bi2Te3 was an excellent candidate for demonstrating large-energy pulse operations on mode-locked Er-doped fiber laser.

There dimensional (3D) metallic nanohybrids have attracted attentions for the applications in nanophotonic devices, catalysis and biosensor. Here, the 3D suspended Ag nanoparticles/Carbon nanotubes (AgNPs/CNTs) nanohybrids, obtained by self-aggregating AgNPs onto the suspended CNT networks, are synthesized and used for the SERS application. The electric field distribution with the near-field and far-field coupling can be obtained by the optimization of the nanogaps of the AgNPs. Such suspended AgNPs/CNTs nanohybrids are studied to be used as the ultra-sensitive SERS biosensor, benefiting from the bio-compatibility and chemical absorption of the CNT networks and the EM enhancement of the 3D denser “hotspots”. R6G molecules with a concentration as low as 10⁻¹⁵ M can be clearly detected, demonstrating their excellent Raman enhancement.

A novel and efficient surface enhanced Raman scattering (SERS) substrate has been presented based on Gold@silver/pyramidal silicon 3D substrate (Au@Ag/3D-Si). By combining the SERS activity of Ag, the chemical stability of Au and the large field enhancement of 3D-Si, the Au@Ag/3D-Si substrate possesses perfect sensitivity, homogeneity, reproducibility and chemical stability. Using R6G as probe molecule, the SERS results imply that the Au@Ag/3D-Si substrate is superior to the 3D-Si, Ag/3D-Si and Au/3D-Si substrate. We also confirmed these excellent behaviors in theory via a commercial COMSOL software. The corresponding experimental and theoretical results indicate that our proposed Au@Ag/3D-Si substrate is expected to develop new opportunities for label-free SERS detections in biological sensors, biomedical diagnostics and food safety.