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Cylindrical waveguides have a wide range of applications in photonic integrated circuits because of lower transmission losses. This paper proposes a directional coupler composed of a cylindrical silicon nanowire waveguide and a metal-based cylindrical hybrid plasmon waveguide. The coupling characteristics of the coupler are analyzed theoretically and are also simulated using the finite-difference time-domain method. The results show that the coupler can operate effectively with a relatively short coupling length, displaying low insertion loss, and a high coupling efficiency and extinction ratio. This study also shows how the TM mode in the plasmon waveguide can be excited with the TE mode of the dielectric waveguide. This directional coupler has a potential application in signal exchanging and mode switching between the dielectric and plasmon waveguides in photonic integrated circuits.

By performing first-principle quantum transport calculations, we investigate the effects of connected position and B/N doping on the transport properties of a single cruciform diamine molecule connected to zigzag graphene nanoribbon leads. The negative differential resistance behaviors are found in I V characteristics of the undoped molecular device. The peak-to-valley current ratio can be modulated obviously by changing the connected position. Then, we find the B/N doped effects are sensitive to doping site in the connected region. The replacement of B/N atom on R1 (carbon atom in connected region close to the zigzag graphene nanoribbon) seldom affects the transmission spectrum around Fermi level. But, the replacement of B/N atom on R2 (carbon atom in connected region close to the molecule) can raise the transmission coefficient around Fermi level markedly leading to the large growth of the current at the low biases. In addition, the replacement of N atom on R2 can induce a negative differential resistance behavior in I V curve at low bias region.

The extraction conditions of water-soluble polysaccharides from pomelo peels were optimized by response surface methodology. The optimum polysaccharide extraction parameters were determined using a Box-Behnken design as follows: liquid-solid ratio of 34 mL/g, extraction temperature of 87ºC, extraction time of 2 h and extraction frequency of 2. Under these conditions, the corresponding yield of polysaccharides was 8.73%, which was consistent with the predicted value of 8.78%. The in vitro antioxidant assays revealed that pomelo peels polysaccharides exhibited higher scavenging activity to 1,1-diphenyl-2-picrylhydrazyl radicals, whereas relatively lower scavenging activities to superoxide anions and hydroxyl radical. Taken together, these results suggested that pomelo peels polysaccharides had the potential to be antioxidants in pharmaceutical industries and functional foods.

By performing first-principle quantum transport calculations, we investigated the effects of the edge types and edge defects on the electronic and transport properties of phosphorene nanoribbons (PNRs). The calculated band structures show the PNRs with the zigzag and cliff edges are all metallic. The conductance of the cliff phosphorene nanoribbon (CPNR) is higher than that of the zigzag phosphorene nanoribbon (ZPNR). The low bias negative differential resistance behavior is only found in the ZPNR and the peak-to-valley current ratio is up to 102. More over, we found the carrier transport channels under low bias of ZPNR and CPNR mainly locate on the edges. The current-voltage characteristics show the defects induced by removing the phosphorus atoms from the edge can decrease the conductance of the ZPNR and CPNR obviously. The low bias negative differential resistance behavior of the ZPNR also can be weakened or removed by the edge defects.

We have studied the effects of stretching and compression on the electronic properties of 7-alkanedithiol covalently linked to two Au electrodes. Results show a progressive increase in conductivity upon molecule compression and decrease with molecule stretching. The notable conductance increase at high compression is attributed to a significant modification of HOMO and LUMO orbitals of the junction, which enhances electron delocalization and promotes tunneling across the junction. More important, the current switching ratios between the various stages of compressed/extended geometries almost maintain the constant values on the bias region from 0 V to 2 V. In other word, the mechanically-induced conductance enhancement and weakening are stable within a large bias voltage range.

By applying nonequilibrium Green's functions in combination with the density-functional theory, we investigate the electron transport properties of the salicylideneaniline molecule sandwiched between two armchair graphene nanoribbon (AGNR) electrodes. It shows that the width of the AGNR electrodes plays a significant role in the transport properties of the salicylideneaniline molecular junctions. The current–voltage characteristics of the salicylideneaniline molecule sandwiched between 8AGNR electrodes can perform a stable conductance switching behavior at the bias region [1.2 V, 1.6 V] when the molecule translates between the trans -enol form and the trans -keto form. When the electrodes change to 7AGNR, a remarkable negative differential resistance behavior can be found in the salicylideneaniline molecular device at the trans -keto form. That means the salicylideneaniline molecule can perform different functions when it connects to the different AGNR electrodes.