Qianqian Lv

Metabolic profiling of myrislignan by UPLC-ESI-QTOFMS-based metabolomics

Myrislignan (MRL) is a bioactive 8-O-4′-neolignan distributed in nutmeg that is an official Traditional Chinese Medicine used for the treatment of gastrointestinal diseases in China. In the present study, the metabolic map of MRL was determined in mouse by ultra-performance chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOFMS)-based metabolomics. A total of 23 MRL metabolites (19 were newly identified) were determined in both in vivo and in vitro metabolism of MRL. It was found that hydroxylation and demethylation were the major metabolic pathways for MRL metabolism in vitro and in vivo, respectively. Recombinant cytochrome P450s (CYPs) screening revealed that CYP3A4 and CYP3A5 played a crucial role in the metabolism of MRL. Interestingly, MRL and its metabolites were prone to generate the high abundance ions of Na+ adducts due to one 8-O-4′ type bond in their molecular structures. Taken together, these data reveal the metabolic map of MRL, contributing to the understanding of the metabolism and disposition of 8-O-4′-neolignans in nutmeg.

Metabolic profiling of dehydrodiisoeugenol using xenobiotic metabolomics

HighlightsMetabolic map of dehydrodiisoeugenol from nutmeg was determined by metabolomics.Of the total 13 metabolites generated from dehydrodiisoeugenol, 7 are found to be novel.CYP1A1 plays the crucial role in the metabolism of dehydrodiisoeugenol.Two gut microbiota metabolites were elevated in mice urine after DDIE exposure. Abstract Dehydrodiisoeugenol (DDIE), a representative and major benzofuran‐type neolignan in Myristica fragrans Houtt., shows anti‐inflammatory and anti‐bacterial actions. In order to better understand its pharmacological properties, xenobiotic metabolomics was used to determine the metabolic map of DDIE and its influence on endogenous metabolites. Total thirteen metabolites of DDIE were identified through in vivo and in vitro metabolism, and seven of them were reported for the first time in the present study. The identity of DDIE metabolites was achieved by comparison of the MS/MS fragmentation pattern with DDIE using ultra‐performance chromatography electrospray ionization quadrupole time‐of‐flight mass spectrometry (UPLC‐ESI‐ QTOFMS). Demethylation and ring‐opening reaction were the major metabolic pathways for in vivo metabolism of DDIE. Recombinant cytochrome P450 s (CYPs) screening revealed that CYP1A1 is a primary enzyme contributing to the formation of metabolites D1‐D4. More importantly, the levels of two endogenous metabolites 2,8‐dihydroxyquinoline and its glucuronide were significantly elevated in mouse urine after DDIE exposure, which explains in part its modulatory effects on gut microbiota. Taken together, these data contribute to the understanding of the disposition and pharmacological activities of DDIE in vivo.

Design and fabrication of multi-channel photodetector array monolithic with arrayed waveguide grating

We have provided optical simulations of the evanescently coupled waveguide photodiodes integrated with a 13-channels AWGs. The photodiode could exhibit high internal efficiency by appropriate choice of layers geometry and refractive index. Aseamless joint structure has been designed and fabricated for integrating the output waveguides of AWGs with the evanescently coupled waveguide photodiode array. The highest simulation quantum efficiency could achieve 92% when the matching layer thickness of the PD is 120 nm and the insertion length is 2 μm. The fabricated PD with 320-nm-thick matching layer and 2-μm-length insertion matching layer present a responsivity of 0.87 A/W.

A Low Dark Current Mesa-Type InGaAs/InAlAs Avalanche Photodiode

A top-illuminated three-mesa-type InGaAs/InAlAs separate absorption, grading, charge, and multiplication avalanche photodiode with a mesa larger than P contact mesa to reduce surface electric field, which achieves simultaneously the low dark current of planar type device and fabrication-simplicity and reproducibility of the mesa type one, is demonstrated. A high responsivity of 0.77 A/W (M = 1, without AR) at 1.55 μm and high multiplication gain of more than 100 is achieved, whereas the dark current at 0.9 Vb is as low as 6 nA at room temperature (with 55-μm active region diameter). The dark current of devices of this structure is analyzed and proved to be mainly composed of surface leakage current and is significantly reduced compared with typical mesa structure devices with the same active region size while the capacitance is similar to that of typical mesa structure devices.

Crystal structures and electronic properties of solid fluorine under high pressure

As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction patterns, the space group of fluorine at ambient pressure is in controversy. We successfully obtain its thermodynamically stable low-pressure phase, which shares the same structure as the earlier known C2/c. Further investigations on phonon spectra reveal the instability of the C2/m structure with imaginary frequency in the Brillouin zone and confirm the dynamically stable property of the C2/c structure at the same time. Compressing fluorine up to 8 GPa, the C2/c phase is found to undergo a phase transition to a new structure with a space group of Cmca. Electronic energy band structures indicate the insulating feature of C2/c and Cmca with no bands across the Fermi level. The infrared (IR) and Raman spectra of C2/c and Cmca at selected pressures are calculated to provide useful information to future experiments.

High-responsivity InGaAs/InP photodetectors integrated on silicon-on-insulator waveguide circuits

This paper presents a high responsivity InGaAs / InP PIN photodetector bonded on silicon-on-insulator (SOI) waveguide circuit with a Si waveguide width of 2000 nm. Divinyltetramethyldisiloxane-benzocyclobutene (DVS-BCB) is used to integrate the InGaAs/InP film epitaxial layers onto the silicon waveguide wafer. A grating coupler is adopted to couple light from the fiber to the Si waveguide. Light in the Si photonic waveguide is evanescently coupled into the InP ridge waveguide and can finally be absorbed in the absorption layer. The simulation results show that the detection efficiency can reach 95%. The measured detector responsivity is 0.87 A/W (excluding the coupling loss between the fiber and the grating coupler and the silicon propagation loss) at a wavelength of 1550nm and a bias voltage of -3V.

Photoconductive multi-layer graphene photodetectors fabricated on etched silicon-on-insulator substratesr*

Recently, graphene-based photodetectors have been rapidly developed. However, their photoresponsivities are generally low due to the weak optical absorption strength of graphene. In this paper, we fabricate photoconductive multi-layer graphene (MLG) photodetectors on etched silicon-on-insulator substrates. A photoresponsivity exceeding is obtained, which enables most optoelectronic application. In addition, according to the analyses of the high photoresponsivity and long photoresponse time, we conclude that the working mechanism of the device is photoconductive effect. The process of photons conversion into conducting electrons is also described in detail. Finally, according to the distinct difference between the photoresponses at 1550 nm and 808 nm, we estimate that the position of the trapping energy is somewhere between 0.4 eV and 0.76 eV, higher than the Fermi energy of MLG. Our work paves a new way for fabricating the graphene photoconductive photodetectors.

Bolometric effect in a waveguide-integrated graphene photodetector

Graphene is an alternative material for photodetectors owing to its unique properties. These include its uniform absorption of light from ultraviolet to infrared and its ultrahigh mobility for both electrons and holes. Unfortunately, due to the low absorption of light, the photoresponsivity of graphene-based photodetectors is usually low, only a few milliamps per watt. In this letter, we fabricate a waveguide-integrated graphene photodetector. A photoresponsivity exceeding 0.11 AW−1 is obtained which enables most optoelectronic applications. The dominating mechanism of photoresponse is investigated and is attributed to the photo-induced bolometric effect. Theoretical calculation shows that the bolometric photoresponsivity is 4.6 AW−1. The absorption coefficient of the device is estimated to be 0.27 dBμm−1.

Design and Fabrication of an Array of 8 Evanescently Coupled Uni-Traveling-Carrier Photodiodes

Optical transmission from a diluted waveguide to an evanescently coupled uni-traveling carrier photodiode is optimized. The fabricated array of 8 photodiodes each shows a −3dB bandwidth of 17GHz and linear photocurrent to 20mA.

Optical design of the high-responsivity evanescently coupled photodiodes integrated with the output waveguides of AWGS

We have provided optical simulations of the evanescently coupled waveguide photodiodes integrated with a 10 channels AWGs. The photodiode could exhibit high internal efficiency by appropriate choice of layers geometry and refractive index. Two structures have been designed for integrating the output waveguides of AWGs with the evanescently coupled waveguide photodiode array : One is a seamless joint between the AWGs output waveguide and the photodiode; the other one has a shallow trench between the AWGs top cladding layer and the photodiode p-doped layer. The simulation results show that the photodiodes have quantum efficiencies as high as 87% and 64%, respectively, at 1.55μm wavelength.