RESUMO
In this paper, a simple, label-free and ultrasensitive resonance light scattering (RLS) method for ultratrace protein detection was investigated using graphene quantum dots (GQDs) as probes. Due to the electrostatic interaction between GQDs and protein, the RLS intensity was gradually enhanced as the protein was added into the GQDs solution. Through a series of optimization experiments, the optimal detection conditions of the GQDs solution were as follows: pH = 7.4, 2 M ion concentration and 60 µM GQDs. Under the optimized conditions, the linear correlation between the GQDs and the concentration of protein was observed from 10 µM to 60 µM with the correlation coefficient (R2) of 0.9978, and the limit of detection (LOD) was 2.4 µM. Time-resolved fluorescence spectrum showed that the electron transition channel was not affected by the protein self-assembled on the surface of GQDs, which indicated that the interaction between GQDs and protein was mainly the electrostatic interaction. The proposed method revealed that the RLS enhancement effect from the self-assembled GQDs-protein hybrid nano-system provided a green and simple method to establish ultrasensitive biosensors.
RESUMO
Metamaterial of dual-square array is proposed to design a dual-band circular polarizer. The novel design of asymmetric unit cell and layout of duplicate arrays significantly enhances the coupling between electric and magnetic fields. Simulation and measurement results show that the polarizer presents wide angle circular dichroism and circular birefringence. Moreover, the polarization conversion of the proposed metamaterial changes with frequency, incident angle, and polarization of incident waves. The fundamental mechanism behind is concluded to be the angle-dependent chirality and dispersion of our novel design.
