This article develops a kind of core-shell structure with optical magnetic properties and conjugates it with fluorescent labels to synthesize nanocomposite particles. For the pure Fe3O4 nanoferrofluid prepared by chemical co-precipitation method, its average particle size is 25nm, and a layer of zinc sulfide shell is absorbed on the surface of Fe3O4 nanoparticles. Inspection by ξ-potentialmeter shows that the surface of Fe3O4 particles carries positive charge, thus increasing the efficiency of its conjugation with oligonucleotide. The prepared Fe3O4∕ZnS core-shell nanocomposite particles are conjugated with two groups of oligonucleotide and a bridge oligonucleotide primer with different sequences, and then they are mixed. These three groups of oligonucleotide primer base with different sequences are designed to be partially complementary and are mutually conjugated together through the hybridization of DNAs. As supported by colormetric reporter gene, the hybridization technology for different sequences of DNA developed by this article is proved successful.

In this letter, we successfully demonstrated a AlGaN/GaN high-electron mobility transistor on silicon substrate with high product of maximum oscillation frequency (f max ) and gate length (L G ) by reducing the gate resistance (R g ) using a thick, high aspect ratio rectangular gate (R-gate) structure with an L G of 265 nm and thickness of 315 nm which was fabricated using a thick polymethyl methacrylate lift-off process. The maximum drain current is over 1 A/mm, and the peak transconductance is 291 mS/mm. The values of cutoff frequency and f max are 43.7 GHz and 126.5 GHz at a drain voltage (V d ) of 12 V, respectively. R g is extracted through the small-signal model, and the value is given as 0.21 -mm which is comparable to devices with the T-gate structure. This low R g results in a high f max and high f max × L G product of 33.52 GHz-µm, comparable to previously reported GaN-on-Si transistors for both R-gate and T-gate structures.INDEX TERMS AlGaN/GaN, high-electron mobility transistor (HEMT), silicon substrate, power-gain cutoff frequency (f max ), rectangular gate, f max × L G .

No abstract